Positron source and method

Abstract

There is provided a positron source (10; 1000) for generating a positron beam (180), wherein the positron source (10; 1000) includes: a laser arrangement (50) configured to generate a pulsed beam (70) of photons; a target (30) configured to receive the beam (70) of photons, wherein the target (30) is arranged for the photons of the beam (70) to generate a photon plasma at a surface layer (40) of the target (30), wherein the surface layer (40) is configured to preferentially absorb electrons from the photon plasma to generate corresponding free positrons; and an electrode arrangement (160) comprising one or more electrodes (160A, 160B, 160C) that are configured to apply an electric field to the photon plasma to extract the free positrons therefrom and to guide the positrons to form the positron beam (180). At least the target (30) and the electrode arrangement (160) are included within a vacuum chamber (20) configured in use to provide a vacuum condition in which the target (30) and the electrode arrangement (160) are arranged to function. Optionally, the surface layer (40) is configured to include a doped semiconductor material for providing the surface layer (40). More optionally, the doped semiconductor includes at least one of: p-doped Silicon, p-doped Gallium Arsenide, p-doped Graphene, Graphene, p-doped Silicon Carbide.

Description

[0001] POSITRON SOURCE AND METHOD

[0002] Technical field

[0003] The present disclosure relates to positron sources. Moreover, the present disclosure relates to methods for operating aforesaid positron sources. Furthermore, the present disclosure relates to software products that are executable on computing hardware to implement the methods for operating the positron sources. Additionally, the present disclosure relates to energy converters, for example for use in aforesaid positron sources, and also methods for operating the energy converters.

[0004] Background

[0005] In modern physics, there occur "ordinary matter" and corresponding antimatter. Antimatter may be conventionally thought of as being matter with reversed charge, parity and time, known as CPT reversal. Antimatter occurs in natural processes, for example in cosmic ray collisions occurring in the Earth's upper atmosphere and also as a component generated during radioactive decay, for example radioactive decay giving rise to beta (jff) particles. On Earth, antimatter tends to annihilate with ordinary matter to generate electromagnetic radiation; for example, an electron annihilating with a positron in positronium results in gamma-ray ( / ) photons being generated.

[0006] However, it is known to store antimatter under vacuum conditions in at least one of strong electrostatic and magnetic fields for periods of up to circa 1000 hours. The ALPHA project at CERN is concerned with generating antimatter for research purposes, wherein the ALPHA project makes use of a high-energy particle accelerator to generate high-energy ordinary matter particles at an energy of GeV that are applied to a high atomic weight ("high-Z") target to generate a range of secondary particles including a portion of antimatter at high energy, a decelerator to decelerate the high energy antimatter to provide corresponding lower-energy antimatter, and a vacuum storage ring arrangement to store the lower-energy antimatter for use in various experiments and research. Hardware of the ALPHA project is spatially extensive and requires a large building to accommodate it. Although minuscule numbers of antimatter particles ("antiparticles") may be generated using particle accelerators, a total artificial production of antimatter has contemporarily been only a few nanograms. No macroscopic amount of antimatter has ever been assembled due to the extreme cost and difficulty of producing and handling antimatter. Nonetheless, antimatter is an essential component of widely-available apparatus that utilises beta QB) decay, such as in positron emission tomography apparatus, radiation therapy apparatus, and industrial imaging apparatus.

[0007] Positron beams are conventionally produced either by using 3-emitting radioactive sources or by using pair production by photons. Positrons are normally obtained either from neutron-induced nuclear reactions such as113Cd(n, y)114Cd or from electron-induced electromagnetic showers in solid targets. Thus, commonly used positron radioactive sources include22Na,58Co,64Cu isotopes, but are not limited thereto. The half-life of these radioactive sources is not long in temporal duration, so positron beams derived from the radioactive sources will decrease significantly over a period of time. Moreover, the preparation of the radioactive sources is also relatively cumbersome and costly. Currently,22Na isotope is the most commonly used radioactive positron source due to its longest half-life relative to other isotopes that exhibit beta-particle QB-emitting) decay.

[0008] As described in a published PCT patent application PCT / IB2022 / 057745 "System and method for generating power", inventor Ian Clague), it is shown that a photon may be considered to be a composite particle comprising an electron and a positron in a mutually orbiting configuration constituting a stable bound state; as the electron has a positive mass and the positron has a negative mass, their corresponding photon has zero mass, enabling the photon to propagate at "the speed c of light", namely 299,792,458 metres per second in vacuum. An energy of the photon (namely E = hf, wherein h is Plank's constant, E is the energy of the photon and f is the frequency of the photon) is determined by parameters of the precession orbit of the electron and its corresponding positron in the photon; for example, lower energy infra-red photons have a larger precession orbit and therefore a longer corresponding wavelength than, for example, a gamma-ray photon. Such orbits are, for example, manifested in interference fringes generated using photons, for example when photons are diffracted in diffraction gratings. However, aforesaid positronium is an example of an unstable state of an electron and a positron, wherein positronium rapidly decays to form stable gamma photons.

[0009] In a published Chinese patent application CN104735895A, there is described a laser plasma pulse positron source. The source comprises a laser source and a vacuum target chamber. Laser radiation photons emitted by the laser source are transmitted through a window of the vacuum target chamber to be irradiated onto a planar reflecting mirror of the vacuum target chamber. Laser radiation photons reflected by the planar reflecting mirror are focused to a feed-forward disc-shaped target in a solid target assembly via an off-axis parabolic focusing mirror. The target material uses conventional high atomic number (namely high-Z) metal materials in the solid target assembly in the vacuum target chamber, wherein the disc-shaped target is fixed to a rotatable shaft. A drive motor drives the rotatable shaft to rotate so as to drive the disc-shaped target to rotate. The disc-shaped target, the rotating shaft and the drive motor are arranged on an electric lifting platform. A synchronizing signal generator controls the drive motor, the electric lifting platform and the laser source synchronously. By using the laser plasma pulse positron source, picosecond-level pulse positron beams may be generated, wherein the laser plasma pulse positron source is suitable for detection and diagnosis related to using positrons. Although the laser plasma pulse positron source is capable of generating positrons without a need for high-energy particle accelerators to be used, in contradistinction to the ALPHA project at CERN for example, there is a need for yet more efficient ways of generating antimatter, in particular positrons.

[0010] In a published research paper, "Nanophotonics for pair production", by authors Valerio Di Giulio, F. Javier Garcia de Abajo, there is disclosed a theoretical analysis of the transformation of electromagnetic energy into matter by way of the creation of electron-positron pairs from light. However, in the research paper, it is mentioned that this phenomenon has a very low probability, such that contemporary positron sources rely instead on beta QB) decay as aforementioned, which demands elaborate monochromatization and trapping schemes to achieve high-quality positron beams. Moreover, in the research paper, it is proposed to use intense strongly-confined optical near fields supported by a nanostructured material in combination with high-energy photons to create electron-positron pairs. Specifically, it is proposed in the research paper that the interaction between near-threshold gamma-rays and polaritons yields higher pair-production cross sections, largely exceeding those associated with free-space photons. However, in the research paper, it is mentioned that, in practice, such a technique will be difficult (if not impossible) to implement in practice for various technical reasons.

[0011] In a publication "Coherent propulsion with negative-mass fields in a photon lattice”, Yumiao Pei, et al., Vol. 44 No. 24, December 2019, Optics Letters, there is described a theoretical basis for coherent propulsion with negative-mass fields in an optical analog, wherein there are observed self-accelerating states, driven by nonlinear coherent interactions of two components that are experiencing diffractions of opposite signs in a photonic lattice; such a situation is analogous to an interaction of two objects with mutually opposite mass signs. In the publication, there is described an experimental setup including a continuous wave (CW) green laser emitting radiation at a wavelength of 532 nm. In the experimental setup, there is further used a waveguide array having a lattice period of 6.8 pm which is fabricated by Titanium in-diffusion in a nonlinear photo refractive Lithium Niobate (LiNbO3) crystal that, when in use, exhibits a self-defocusing non-linearity arising from a bulk photovoltaic effect. There thereby arise positive-mass and negative-mass fields in the crystal. In overview, the positive-mass and negative-mass fields are able to affect photons propagating in the crystal to cause electron beams and positron beams to form within the crystal, wherein the beams propagate because their wave function pursuant to the Schrodinger equation remains coherent. Therefrom arises an action-reaction symmetry that challenges Newton's third law, wherein the symmetry abides to both energy and momentum conservation. When spatial separation of electrons and positrons occurs in the crystal, acceleration effects between the electrons and positrons are observed. The publication in Optics Letters has been peer-reviewed and is to be now regarded as accepted main-stream scientific knowledge, namely well-known physical laws. Moreover, the publication is consistent with earlier publication, for example as documented in "Theory of Photon Acceleration", J.T. Mendonca, loP Publishing. In a published research paper, "Optical diametric drive acceleration through action-reaction symmetry breaking", Wimmer et al., Nature Physics, October 2013, it is mentioned that Newton's third law of motion is one of the pillars of classical physics. In the research paper, there is described an optical system including two time-multiplexed monomode optical fibre loops having a length difference AL, connected through a 50 / 50 coupler. It is mentioned that sequences of light pulses circulating in both loops obey the same dynamics as in a spatial mesh lattice, wherein optical non-linearity (Kerr effect) in the optical fibres introduces a non-linear phase shift on each pulse that is proportional to its peak power. The optical system may be represented on an optical dispersion diagram associated with two oppositely curved dispersion bands; an upper band has a positive curvature and therefore exhibits a positive effect photon mass, and a lower band has a negative curvature and therefore exhibits a negative effective photon mass. It is found in practice that the positive effect photon mass and the negative effect photon mass gives rise to optical diametric drive acceleration through action-reaction symmetry breaking, in contravention of Newton's third law of motion.

[0012] Despite aforesaid insights into interactions between optical beams and crystalline substrates having been published, there has been a lack of commercial use of the effects to provide practical devices for positron generation. Moreover, as a result of devising practical devices for positron generation, it has been appreciated that energy conversion apparatus may also be provided, for example for use to ensure that such positron generation is achieved as energy efficiently as possible. The present disclosure seeks to address the lack. However, it will be appreciated that other types of energy converters are known, for example solar photovoltaic panels are configured to convert incident photons into corresponding electrical signals.

[0013] Summary

[0014] The present disclosure seeks to provide an improved positron source that functions to convert photons to corresponding positrons and electrons in a more efficient manner than has hitherto been feasible. Moreover, the present disclosure seeks to provide an improved method for (namely, method of) operating the aforesaid improved positron source. The present disclosure also seeks to provide a practical energy converter for converting photons into corresponding positrons and electrons and therefrom generate an electrical signal, for example wherein the electrical signal may be used to provide power or be used for feedback control purposes in the aforesaid positron source to enable the positron source to function more efficiently; for example, the energy converter may be used as a component part of a practical positron source. Moreover, the present disclosure seeks to provide an improved method for operating the aforesaid practical energy converter.

[0015] According to a first aspect, there is provided a positron source, as defined in Claim 1. The positron source is of advantage in that its target is designed to preferentially capture electrons from incident photons that increases a yield of positrons emitted from the target, wherein the target is optionally fabricated from p-type doped material exhibiting electron-capturing holes. Beneficially, the -type doped material exhibiting electron-capturing holes is fabricated from a semiconductor material, a doped semiconductor material, Graphene or similar.

[0016] There is provided a positron source for generating a positron beam, wherein the positron source includes: a laser arrangement configured to generate a beam of photons; a target configured to receive the beam of photons, wherein the target is arranged for the photons of the beam to generate a photon plasma at a surface layer of the target, wherein the surface layer is configured to preferentially absorb electrons from the photon plasma to generate corresponding free positrons; and an electrode arrangement comprising one or more electrodes that are configured to apply an electric field to the photon plasma to extract the free positrons therefrom and to guide the positrons to form the positron beam; wherein at least the target and the electrode arrangement are included within a vacuum chamber configured in use to provide a vacuum condition in which the target and the electrode arrangement are arranged to function.

[0017] By "photon plasma" is meant a high spatial density of photons, wherein the photons undergo mutual entanglement (for example, as occurs in a contemporary photon-based quantum computer), so as to expose their corresponding electron-positron couplets to enable electron absorption at the target, for example in the presence of an applied electric field.

[0018] Optionally, the surface layer is configured to include a doped semiconductor material for providing the surface layer; beneficially, the doped semiconductor material is doped to a much higher concentration (for example several orders of magnitude) than conventionally used when fabricating contemporary semiconductor devices, for example the doping concentration is arranged to be in excess of 1018cm-3in Silicon material. More optionally, the doped semiconductor material includes at least one of: p-doped Silicon, p-doped Gallium Arsenide, p-doped Graphene, Graphene, p-doped Silicon Carbide.

[0019] Optionally, the positron source is configured for the beam of photons to propagate in a direction that is substantially parallel to a plane of the surface layer when the beam of photons is received at the surface layer for generating the photon plasma. More optionally, the positron source is configured for the beam of photons to propagate as an evanescent wave over the surface layer when generating the photon plasma.

[0020] Optionally, the target, for example implemented as a planar target, is supported on a rotatable table that is arranged to rotate when the positron source is in operation, to increase an area of the surface layer that is exposed to the beam of photons.

[0021] Optionally, the positron source further includes a beam scanner for scanning the beam of photons over the surface layer when the positron source is in operation, to increase an area of the surface layer that is exposed to the beam of photons. More optionally, the beam scanner is implemented as an actuated or rotatable mirror, prism or diffraction grating.

[0022] Optionally, the electrode arrangement is configured to remove a native oxide of the surface layer prior to the surface layer being configured to interact with the photon plasma to generate positrons, wherein the electrode arrangement is configured to be driven by a radio-frequency signal to excite a trace gas introduced into the vacuum chamber to cause sputtering or reactive ion etching at the surface layer. Optionally, the laser arrangement is configured to generate the beam of photons as a pulsed photon beam. More optionally, the pulsed photon beam has a pulse energy in a range of 10 milliJoules to 10 Joules per pulse, more optionally in a range of in a range of 10 milliJoules to 1 Joules per pulse, and a pulse duration in a range of 10 picoseconds to 100 nanoseconds.

[0023] Optionally, the laser arrangement is configured to generate the beam of photons to have a radiation wavelength in a range of 50 nm to 2 pm.

[0024] Optionally, the positron source is configured to move the beam or photons in a step-wise manner over the surface layer, wherein the beam of photons at the surface layer is substantially stationary at an instance that a pulse of photons is output from the laser arrangement.

[0025] Optionally, the electrode arrangement further includes a first electrode for generating an electric field to extract positrons from the photon plasma, and one or more second electrodes for forming the positron beam to be at least one of: divergent, collimated, convergent.

[0026] Optionally, the positron source is configured to include a mirror arrangement for guiding the photon beam to make multiple passes over the surface layer in use, to enhance a yield of positrons generated at the surface layer for a given pulse energy of the photon beam.

[0027] Optionally, the positron source is configured for use with at least one of: an electron microscope, a positron tomography apparatus, a semiconductor manufacturing apparatus, an energy storage device, a propulsion device.

[0028] According to a second aspect, there is provided a method of operating the positron source of the first aspect. The method is of advantage in that the method enables the positron source to be operated more efficiently to generate positrons for use in research, in positron tomography, in energy storage, in material characterization, in microscopy and so forth.

[0029] There is provided a method for (namely, a method of) operating a positron source for generating a positron beam therefrom, wherein the positron source includes: a laser arrangement configured to generate a beam of photons; a target configured to receive the beam of photons; an electrode arrangement comprising one or more electrodes; wherein at least the target and the electrode arrangement are included within a vacuum chamber; wherein the method includes: configuring the vacuum chamber in use to provide a vacuum environment in which at least the target and the electrode arrangement are arranged to function; configuring the positron source for the photons of the beam to generate a photon plasma at a surface layer of the target, wherein the surface layer is configured to preferentially absorb electrons from the photon plasma to generate corresponding free positrons; and configuring the one or more electrodes to apply an electric field to the photon plasma to extract the free positrons therefrom and to guide the positrons to form the positron beam.

[0030] Optionally, the method includes configuring the surface layer to include a doped semiconductor material for providing the surface layer; optionally, the doped semiconductor material is doped to a concentration conventionally used when fabricating contemporary semiconductor devices; more optionally, beneficially, the doped semiconductor material is doped to a higher concentration (for example, several orders of magnitude) than conventionally used when fabricating contemporary semiconductor devices, for example the doping concentration is arranged to be in excess of 1018cm-3in Silicon material. More optionally, the method includes arranging for the doped semiconductor to include at least one of: p-doped Silicon, p-doped Gallium Arsenide, p-doped Graphene, Graphene, p-doped Silicon Carbide.

[0031] Optionally, the method includes configuring the positron source for the beam of photons to propagate in a direction that is substantially parallel to a plane of the surface layer when the beam of photons is received at the surface layer for generating the photon plasma. More optionally, the method includes arranging for the beam of photons to propagate as an evanescent wave over the surface layer when generating the photon plasma. Evanescent wave propagation corresponds to a photon propagation mode at an interface between two regions having mutually different refractive index.

[0032] Optionally, the method includes supporting the target on a rotatable table that is arranged to rotate when the positron source is in operation, to increase an area of the surface layer that is exposed to the beam of photons.

[0033] Optionally, the method includes arranging for the positron source to further include a beam scanner for scanning the beam of photons over the surface layer when the positron source is in operation, to increase an area of the surface layer that is exposed to the beam of photons. More optionally, the method includes implementing the beam scanner as an actuated or rotatable mirror, prism or diffraction grating.

[0034] Optionally, the method includes configuring the electrode arrangement to remove a native oxide of the surface layer prior to the surface layer being configured to interact with the photon plasma to generate positrons, wherein the electrode arrangement is configured to be driven by a radio-frequency signal to excite a trace gas introduced into the vacuum chamber to cause sputtering or reactive ion etching at the surface layer.

[0035] Optionally, the method includes configuring the laser arrangement to generate the beam of photons as a pulsed photon beam. More optionally, the method includes arranging for the pulsed photon beam to have a pulse energy in a range of 10 milliJoules to 10 Joule per pulse, optionally in a range of 10 milliJoules to 1 Joule per pulse, and a pulse duration in a range of 10 picoseconds to 100 nanoseconds.

[0036] Optionally, the method includes configuring the laser arrangement to generate the beam of photons to have a radiation wavelength in a range of 50 nm to 2pm.

[0037] Optionally, the method includes configuring the positron source to move the beam of photons in a step-wise manner over the surface layer, wherein the beam of photons at the surface layer is substantially stationary at an instance that a pulse of photons is output from the laser arrangement. Optionally, the method further includes configuring the electrode arrangement to include a first electrode for generating an electric field to extract positrons from the photon plasma, and one or more second electrodes for forming the positron beam to be at least one of: divergent, collimated, convergent.

[0038] Optionally, the method includes configuring the positron source to include a mirror arrangement for guiding the photon beam to make multiple passes over the surface layer in use, to enhance a yield of positrons generated at the surface layer for a given pulse energy of the photon beam.

[0039] Optionally, the method includes configuring the positron source for use with at least one of: an electron microscope, a positron tomography apparatus, a semiconductor manufacturing apparatus, an energy storage device, a propulsion device.

[0040] According to a third aspect, there is provided a software product stored on a machine-readable data carrier, wherein the software product is executable on computing hardware to implement the method of the second aspect.

[0041] According to a fourth aspect, there is provided a positron source for generating a positron beam, wherein the positron source includes an optical waveguide array device including a substrate, and at least one waveguide structure formed onto the substrate, wherein the at least one waveguide structure is fabricated at least in part from a material that exhibits one or more non-linear optical effects when in use, and an electrode arrangement configured to control the one or more non-linear optical effects and to extract at least one of accelerated electrons and positrons from the at least one waveguide structure, and wherein the optical waveguide array device is configured in use to separate photons input on the at least one waveguide structure using the one or more non-linear optical effects into regions of electrons and positrons, and to guide the respective electrons and positrons into their respective regions of the at least one waveguide structure to cause a matter-antimatter dipole to be formed within the at least one waveguide structure waveguide structure for imparting energy to at least one of the electrons and the photons to cause acceleration thereof, wherein the positrons are extracted to generate the positron beam.

[0042] Beneficially, the one or more non-linear optical effects includes an optical Kerr effect. The optical Kerr effect results in a refractive index change that may be used to cause electrons of photons to group with other electrons, and likewise positrons of the photons to group with other positrons, resulting in an enhanced positron-electron dipole, and thereby an enhancing acceleration experienced by the electrons and the positrons in the positron source; beneficially, the Kerr effect results in a dispersion characteristic to the at least one waveguide structure including at least two dispersion states, for example as described in the aforesaid Wimmer and Regensburger et al. published research paper. In the Wimmer and Regensburger et al. published research paper, there is described an optical system wherein photons are separated into a region of effective antimatter and a region of effective matter in respective optical fibre waveguides by controlling group velocities of photons within the optical system, wherein the optical system exhibits in use an optical dispersion characteristics including two optical dispersion states, wherein one of the optical dispersion states favours matter (electrons) and another of the optical dispersion states favours antimatter (positrons).

[0043] Optionally, the positron source is configured, wherein the substrate is fabricated at least in part from a dielectric material, and the material of the at least one waveguide structure includes at least one of: Lithium Niobate (LiNiO3), Lithium Niobate On Insulator (LNOI), Barium Niobate (BaNiO3), Graphene.

[0044] Optionally, the positron source is configured, wherein the substrate is fabricated at least in part from at least one of: quartz, fused silica, Silicon, Silicon Dioxide.

[0045] Optionally, the positron source is configured, wherein the electrode arrangement comprises a configuration of electrodes whose elongate axes are configured to be substantially parallel to, or substantially orthogonal to, elongate axes of a plurality elongate waveguides into which the corresponding electrons and positrons are selectively diverted when the device is in operation. More optionally, at least one of the electrodes intersects or substantially overlays a portion of the waveguide structure for selectively controlling positrons or electrons generated in the positron source from photons provided, when in use, to the at least one waveguide structure. More optionally, the positron source is configured, wherein the electrode arrangement is fabricated from at least one of: Titanium, Aluminium, Indium, Silver, Gold. Optionally, the positron source is configured, wherein the device includes a plurality of the at least one waveguide structure arranged in a cascaded configuration.

[0046] Optionally, the positron source is configured, wherein the device further includes a laser arrangement configured in use to provide photons to the at least one waveguide structure. More optionally, the positron source is configured, wherein the laser arrangement is configured to function in at least one of: a continuous mode, a pulsed mode, a combination of continuous and pulsed modes. The pulsed mode is beneficial in that a photon flux in the at least one waveguide structure occurring during each pulse may be considerably greater compared to the continuous mode.

[0047] Optionally, the waveguide structure is configured to exhibit a dispersion characteristic including a plurality of optical dispersion states, wherein the optical dispersion states exhibit mutually different probabilities of including electrons and positrons therein. For example, the waveguide structure exhibits first and second optical dispersion states, wherein the first dispersion state includes more matter, for example electrons, derived from photons than the second dispersion stated, and wherein the second dispersion state includes more antimatter, for example positrons, derived from photons than the first dispersion state.

[0048] Optionally, the positron source is configured, wherein waveguides of the at least one waveguide structure are disposed in a parallel mutually spaced-apart manner with a distance ( ) therebetween, wherein the distance ( ) is substantially of a similar size to a wavelength of the photons supplied to the at least one waveguide structure when in operation. More optionally, the method includes arranging for the distance ( ) to be configured to allow for photon coherence to be maintained between mutually adjacent elongate waveguides of the plurality of waveguides. In other words, more optionally, the positron source is configured, wherein the distance ( ) is configured to allow for photons to propagate coherently along the mutually adjacent elongate waveguides of the at least one waveguide structure. Optionally, the distance ( ) is in a range of 30 nm to 1 pm. Optionally, the waveguides each have a width (w) in a range of 50 nm to 2 pm. Optionally, the waveguides each have a thickness (t), relative to a plane of a substrate on which they are formed, in a range of 20 nm to 2 pm.

[0049] Optionally, the waveguides have a length in a range of 100 pm to 10 mm.

[0050] Optionally, the positron source is configured to function from photons having a wavelength in a range of 150 nm to 3 pm, more optionally a wavelength of substantially 1500 nm.

[0051] According to a fifth aspect, there is provided a method for operating a positron source to generate a positron beam, wherein the positron source includes an optical waveguide array device including a substrate, and at least one waveguide structure formed onto the substrate, wherein the method includes:

[0052] (i) arranging for the at least one waveguide structure to be fabricated at least in part from a material that exhibits one or more non-linear optical effects when in use;

[0053] (ii) configuring an electrode arrangement to control the one or more non-linear optical effects and to extract at least one of accelerated electrons and positrons from the at least one waveguide structure;

[0054] (iii) configuring the optical waveguide array device, when in use, to separate photons input on the at least one waveguide structure using the one or more non-linear optical effects into their respective regions of electrons and positrons; and

[0055] (iv) guiding the respective electrons and positrons into their respective regions of the at least one waveguide structure to cause a matter-antimatter dipole to be formed within the at least one waveguide structure waveguide structure for imparting energy to at least one of the electrons and the positrons to cause acceleration thereof, wherein the method further comprises extracting the accelerated positrons to form the positron beam.

[0056] Such a matter-antimatter dipole arises, for example, in the aforesaid Wimmer et al. research paper, wherein positive matter is present in one of a pair of optical fibre loops and a negative matter is present in another of the pair of optical fibre loops, thereby giving rise to a diametric drive acceleration as mentioned in the research paper. In the Wimmer and Regensburger et al. published research paper, there is described an optical system wherein photons are separated into a region of effective antimatter and a region of effective matter in respective optical fibre waveguides by controlling group velocities of photons within the optical system, wherein the optical system exhibits in use an optical dispersion characteristic including two optical dispersion states, wherein one of the optical dispersion states favours matter (electrons) and another of the optical dispersion states favours antimatter (positrons).

[0057] Beneficially, when implementing the method, the one or more non-linear optical effects includes an optical Kerr effect. The optical Kerr effect results in a refractive index change that causes electrons of photons to group with other electrons, and likewise positrons of the photons to group with other positrons, resulting in an enhanced positron-electron dipole, and thereby an enhanced acceleration experienced by the electrons and the positrons in the positron source.

[0058] Optionally, the method includes fabricating the substrate from a dielectric material, and arranging for the material of the at least one waveguide structure to include at least one of: Lithium Niobate (LiN iO3), Lithium Niobate On Insulator (LNOI), Barium Niobate (BaNiO3), Graphene.

[0059] Optionally, the method includes fabricating the substrate from at least one of: quartz, fused silica, Silicon, Silicon Dioxide, Silicon Carbide. However, other dielectric material may alternatively be used.

[0060] Optionally, in the method, the electrode arrangement comprises a configuration of electrodes whose elongate axes are configured to be substantially parallel to, or substantially orthogonal to, elongate axes of a plurality elongate waveguides into which the corresponding electrons and positrons are selectively diverted when the device is in operation. More optionally, in the method, the electrode arrangement is fabricated from at least one of: Titanium, Aluminium, Indium, Silver, Gold. Other metals or doped semiconductor materials may optionally be used.

[0061] Optionally, the method includes arranging for the device to include a plurality of the at least one waveguide structure arranged in a cascaded configuration. Optionally, the method further includes arranging for the device to further include a laser arrangement configured in use to provide photons to the at least one waveguide structure. More optionally, the method includes configuring the laser arrangement to function in at least one of: a continuous mode, a pulsed mode, a combination of continuous and pulsed modes. The pulsed mode is beneficial to use to achieve higher instantaneous photon flux that enhances optical non-linearity within the device. The photons beneficially have a wavelength in a range of 100 nm to 3 pm, optionally a wavelength of substantially 1500 nm.

[0062] Optionally, the method includes arranging for waveguides of the at least one waveguide structure to be disposed in a parallel mutually-spaced-apart manner with a distance ( ) therebetween, wherein the distance ( ) is substantially of a similar size to a wavelength of the photons supplied to the at least one waveguide structure when in operation. More optionally, the method includes configuring the distance ( ) to allow for photons to propagate coherently along the mutually adjacent elongate waveguides of the at least one waveguide structure.

[0063] According to a sixth aspect, there is provided a software product recorded on a machine-readable data carrier, wherein the software product is executable on computing hardware of the device of the fourth aspect, to implement a method of the fifth aspect.

[0064] According to a seventh aspect, there is provided an energy converter for converting photons into an output electrical signal, wherein the energy converter includes: a laser arrangement configured to generate a pulsed beam of photons; a waveguide arrangement fabricated onto a substrate, wherein the waveguide arrangement comprises a plurality of waveguides configured to exhibit a non-linear optical effect, wherein the plurality of waveguides are configured to receive the beam of photons and to bifurcate the beam into electron-rich regions of photons propagating along one of the plurality of waveguides and into positron-rich regions of photons propagating along another of the plurality of waveguides; and an electrode arrangement comprising one or more electrodes that are configured to capacitively couple to the electron-rich photons and the positron-rich photons to extract the output electrical signal therefrom.

[0065] Beneficially, the waveguide arrangement exhibits an optical dispersion characteristic including a plurality of dispersion states, wherein the dispersion states include a first dispersion state in which there occurs positive mass, for example electrons derived from photons, and a second dispersion state in which here occurs negative mass, for example positrons derived from photons. Such a plurality of dispersion states is known from the aforesaid Wimmer et al. research paper.

[0066] In the Wimmer and Regensburger et al. published research paper, there is described an optical system wherein photons are separated into a region of effective antimatter and a region of effective matter in respective optical fibre waveguides by controlling group velocities of photons within the optical system, wherein the optical system exhibits in use an optical dispersion characteristics including two optical dispersion states, wherein one of the optical dispersion states favours matter (electrons) and another of the optical dispersion states favours antimatter (positrons).

[0067] Beneficially, the energy converter is included in a positron source for generating a beam of positrons, for example in the positron source of the fourth aspect.

[0068] Optionally, the energy converter is configured, wherein the substrate is fabricated from a dielectric material, and the material of the plurality of waveguides includes at least one of: Lithium Niobate (LiNiO3), Lithium Niobate On Insulator (LNOI), Barium Niobate (BaNiO3), Graphene.

[0069] Optionally, the energy converter is configured, wherein the substrate is fabricated, for example at least in pat, from at least one of: quartz, fused silica, Silicon, Silicon Dioxide, Silicon Carbide.

[0070] Optionally, the energy converter is configured, wherein the electrode arrangement comprises a configuration of electrodes whose elongate axes are configured to be substantially parallel to, or substantially orthogonal to, elongate axes of the plurality of elongate waveguides into which the corresponding electrons and positrons are selectively diverted when the energy converter is in operation. More optionally, at least one of the electrodes intersects or substantially overlays a portion of the plurality of waveguides for selectively controlling positrons or electrons generated in the energy converter from photons provided, when in use, to the plurality of waveguides. More optionally, the energy converter is configured, wherein the electrode arrangement is fabricated from at least one of: Titanium, Aluminium, Indium, Silver, Gold.

[0071] Optionally, the energy converter is configured, wherein the energy converter includes a series of the plurality of the waveguides arranged in a cascaded configuration.

[0072] Optionally, the energy converter is configured, wherein the plurality of waveguides are disposed in a parallel mutually spaced-apart manner with a distance ( ) therebetween, wherein the distance ( ) is substantially of a similar size to a wavelength of the photons supplied to the plurality of waveguides when in operation. More optionally, the energy converter is configured, wherein the distance ( ) is configured to allow for photons to propagate coherently between mutually adjacent elongate waveguides of the plurality of waveguides. Optionally, the distance ( ) is in a range of 30 nm to 1 |im. Optionally, the waveguides each have a width (w) in a range of 50 nm to 2 |im. Optionally, the waveguides each have a thickness (t), relative to a plane of a substrate on which they are formed, in a range of 20 nm to 2 |im. Optionally, the waveguides have a length in a range of 100 |im to 10 mm.

[0073] Optionally, the energy converter is configured to function from photons having a wavelength in a range of 150 nm to 3 |im, more optionally substantially 1500 nm.

[0074] According to an eighth aspect, there is provided a method for operating an energy converter of the seventh aspect.

[0075] There is provided a method for (namely, method of) operating an energy converter for converting photons into an output electrical signal, wherein the method includes: configuring a laser arrangement to generate a pulsed beam of photons; using a waveguide arrangement fabricated onto a substrate to bifurcate photons into corresponding regions of electrons and positrons, wherein the waveguide arrangement comprises a plurality of waveguides configured to exhibit a non-linear optical effect, wherein the plurality of waveguides are configured to receive the beam of photons and to bifurcate the beam into electron-rich photons propagating along one of the plurality of waveguides and into positron-rich photons propagating along another of the plurality of waveguides; and configuring an electrode arrangement comprising one or more electrodes to capacitively couple to the electron-rich photons and the positron-rich photons to extract the output electrical signal therefrom.

[0076] Beneficially, the waveguide arrangement exhibits an optical dispersion characteristic including a plurality of dispersion states, wherein the dispersion states include a first dispersion state in which there occurs positive mass, for example electrons derived from photons, and a second dispersion state in which here occurs negative mass, for example positrons derived from photons. Such a plurality of dispersion states is known from the aforesaid Wimmer et al. research paper.

[0077] Optionally, the method includes arranging for the substrate to be fabricated from a dielectric material, wherein the material of the plurality of waveguides includes at least one of: Lithium Niobate (LiNiO3), Lithium Niobate On Insulator (LNOI), Barium Niobate (BaNiO3), Graphene.

[0078] Optionally, the method includes arranging for the substrate to be fabricated, for example at least in part, from at least one of: quartz, fused silica, Silicon, Silicon Dioxide, Silicon Carbide.

[0079] Optionally, the method includes arranging for the electrode arrangement to comprise a configuration of electrodes whose elongate axes are configured to be substantially parallel to, or substantially orthogonal to, elongate axes of the plurality of elongate waveguides into which the corresponding electrons and positrons are selectively diverted when the energy converter is in operation. More optionally, at least one of the electrodes intersects or substantially overlays a portion of the plurality of waveguides for selectively controlling positrons or electrons generated in the energy converter from photons provided, when in use, to the plurality of waveguides. More optionally, the method includes arranging for the electrode arrangement to be fabricated from at least one of: Titanium, Aluminium, Indium, Silver, Gold.

[0080] Optionally, the method includes arranging for the energy converter to include a series of the plurality of the waveguides arranged in a cascaded configuration.

[0081] Optionally, the method includes arranging for the plurality of waveguides to be disposed in a parallel mutually spaced-apart manner with a distance ( ) therebetween, wherein the distance ( ) is substantially of a similar size to a wavelength of the photons supplied to the plurality of waveguides when in operation. More optionally, the method includes arranging for the distance ( ) to be configured to allow for photon coherence to be maintained between mutually adjacent elongate waveguides of the plurality of waveguides. In other words, more optionally, the method includes arranging for the distance ( ) to be configured to allow for photons to propagate coherently between mutually adjacent elongate waveguides of the plurality of waveguides. Optionally, the distance ( ) is in a range of 30 nm to 1 |im. Optionally, the waveguides each have a width (w) in a range of 50 nm to 2 |im. Optionally, the waveguides each have a thickness (t), relative to a plane of a substrate on which they are formed, in a range of 20 nm to 2 |im. Optionally, the waveguides have a length in a range of 100 |im to 10 mm.

[0082] Optionally, the method includes configuring the energy converter to function when provided with photons having a wavelength in a range of 150 nm to 3 |im, more optionally substantially 1500 nm.

[0083] Beneficially, the method includes using the energy converter in a positron source for generating a beam of positrons, for example in the positron source of the fourth aspect.

[0084] According to a ninth aspect, there is provided a software product recorded on a non-transitory machine-readable data carrier, wherein the software product is executable on a computing hardware, to implement the method of the eighth aspect.

[0085] The present disclosure provides a practical positron source that functions to convert photons to corresponding positrons and electrons in a more efficient manner than has hitherto been feasible. Moreover, the present disclosure provides an improved method for operating the aforesaid positron source. Furthermore, the present disclosure provides a practical energy converter for converting photons into an electrical signal. Additionally, the present disclosure provides a method for operating the energy converter to convert photons into electrical signals.

[0086] Description of diagrams

[0087] Embodiments of the invention will be described with reference to the following drawings, wherein:

[0088] FIG. 1 is a schematic illustration of an implementation of a positron source according to the present disclosure;

[0089] FIG. 2 is a schematic illustration of a planar target included within the positron source of FIG. 1;

[0090] FIG. 3 is a schematic illustration of an example electrode arrangement for use in combination with the planar target of FIG. 2;

[0091] FIG. 4 is a schematic illustration of an alternative positron source of the present disclosure, wherein the positron source is configured to use a scanned laser beam for irradiating a planar target;

[0092] FIG. 5 is an illustration of a flow chart depicting steps of a method for operating the positron source as illustrated in FIGs. 1 to 4;

[0093] FIG. 6 is an optional configuration of an optional mirror arrangement enhancement for the planar target for use with the positron source of FIGs. 1 to 4 to enhance its yield of positrons;

[0094] FIG. 7 is an alternative optional configuration of an optional mirror arrangement enhancement for the planar target for use with the positron source of FIGs. 1 to 4 to enhance its yield of positrons;

[0095] FIG. 8A is a schematic illustration of a simple implementation of an optical waveguide array according to the present disclosure, wherein the optical waveguide is configured as an energy converter for generating an electrical signal from a photon beam; FIG. 8B is a cross-section schematic illustration of two waveguides of the optical waveguide array of FIG. 8A, wherein the waveguides are fabricated to a mutual separation distance "d", a waveguide width "w" and a thickness "t";

[0096] FIG. 80 is a schematic illustration of an alternative simple implementation of an optical waveguide array according to the present disclosure, wherein at least one electrode overlays one of a pair of waveguides for selectively influencing photons in the waveguide array to control a positron-electron dipole generated in use in the optical waveguide array;

[0097] FIG. 9 is a schematic illustration of the optical waveguide array of FIGs. 8A, 8B, 80 configured to include a positron extraction arrangement;

[0098] FIG. 10 is a schematic illustration of an optical waveguide array apparatus, including a plurality of the optical waveguide arrays of FIGs. 8A, 8B, 80 or 9 configured in a cascaded formation; and

[0099] FIG. 11 is a flow chart depicting steps of a method for operating the optical waveguide array and optical waveguide apparatus of any one of FIGs. 8A, 8B, 80, 9 and 10.

[0100] Description of embodiments

[0101] In developing the positron source of the present disclosure, the technical problems associated with using aforesaid radioactive sources undergoing beta 06) decay was very much borne in mind. Moreover, the im practicality of using large particle accelerators and high-Z targets as aforementioned, to yield relatively small quantities of positrons, was also borne in mind. It was appreciated that a relatively compact and safe apparatus for generating copious quantities of positrons is required by industry and research establishments. Embodiments of the present disclosure are reduction-to-practice practical implementations of positron sources based on well-known laws of physics that are described in published peer-reviewed research papers (for example, as referred to in the foregoing), wherein there is optionally used an energy converter for providing electrical signals for use in operating the positron source. Referring to FIG. 1, there are shown basic component parts of a positron source indicated generally by 10. The positron source 10 includes a vacuum chamber 20, for example machined from stainless steel, in which is mounted a planar target 30. Optionally, the planar target 30 is circular in surface profile; moreover, optionally, the planar target 30 conveniently has a diameter in a range of 1 cm to 5 cm. The planar target 30 is fabricated with at least a surface layer 40 of -type material that is capable of preferentially absorbing electrons from a photon plasma, namely a region including a high density of photons wherein exchange of electrons and positrons occurs between the photons, formed in operation in close proximity to the surface layer 40, for example within a few micrometres above the surface layer 40. The surface layer 40 is optionally a highly-doped semiconductor material, for example p-doped Silicon, p-doped Gallium Arsenide, p-doped Lithium Niobate, p-doped Silicon Carbide, or p-doped Graphene; these materials are to be regarded as low-Z materials in contradistinction to high-Z materials as customarily used in contemporary known positron generators. Optionally, a doping concentration of doping used in the doped semiconductor material is beneficially in a range of doping that is typically used in the contemporary semiconductor industry for producing integrated circuits. More optionally, a doping concentration of doping used in the doped semiconductor material is beneficially considerably greater (for example, several orders of magnitude) than a range of doping that is typically used in the contemporary semiconductor industry for producing integrated circuits. Optionally, for enhanced performance, the surface layer 40 may be arranged to include a doped semiconductor material that is doped to a higher concentration than conventionally used when fabricating contemporary semiconductor devices, for example the doping concentration is arranged to be in excess of 1018cm-3in Silicon material; such a high concentration significantly affects a bandgap of the semiconductor material. Moreover, p-doped Graphene may be generated by incorporating Boron atoms into a Graphene layer, alternatively by treating a Graphene layer to nitric acid. A remainder of the planar target 30 may beneficially be configured to include a substantial amount of at least one of bulk Silicon, bulk Silicon Carbide or a heat-conductive metal (for example Titanium, Copper, stainless steel or Aluminium) to assist to dissipate thermal energy imparted to the surface layer 40 when the positron source 10 is in operation. The positron source 10 also includes a laser arrangement 50, wherein the laser arrangement 50 is optionally mounted outside the vacuum chamber 20, wherein the vacuum chamber 20 includes a quartz or fused silica port window 60 through which a photon beam 70 generated in use by the laser arrangement 50 may propagate to impact onto or slightly above the surface layer 40 of the planar target 30. The laser arrangement 50 is beneficially implemented as a pulsed laser, for example an Excimer pulsed laser (although other types of laser may be optionally used, for example pulsed UV lasers as commonly used in the contemporary semiconductor industry for sub-micron lithographic purposes). Alternatively, the laser arrangement 50 may be implemented as a laser, for example a solid-state laser, mounted within the vacuum chamber 20 and provided with cooling via an Aluminium or Copper plate that forms a wall portion of the vacuum chamber 20. The laser arrangement 50 is optionally configured to provide the photon beam 70 including photons having a wavelength in a range of 50 nm to 2 pm, for example substantially 1500 nm, more optionally substantially in a range of 800 nm to 100 nm. Each pulse of the photon beam 70 is beneficially in a range of 10 milliJoules to 10 Joules in energy, more optionally in a range of 10 milliJoules to 1 Joule in energy, depending on a diameter of the photon beam 70 that the laser arrangement 50 is able to provide in use. Each pulse optionally beneficially has a duration of 10 picoseconds to 100 nanoseconds. In operation, the positron source 10 is configured so that the photon beam 70 skims a plane of the surface layer 40 as an evanescent wave that strongly interacts with the surface layer 40 as well as forming a photon plasma just above the surface layer 40. By "photon plasma" is meant a region including a high spatial concentration of photons, such that the photons are capable of experiencing mutual entanglement such that their respective electron-positron couplet is capable of exhibiting their respective charge characteristics. The -type material of the surface layer 40 functions to extract electrons from the photon plasma to allow their corresponding positrons to exit the photon plasma and be attracted away from the planar target 30 by using an electrostatic field generated using a suitable electrode arrangement, as will be described in greater detail later, to be formed into a positron beam 180.

[0102] The vacuum chamber 20 is provided with a turbopump 80 that is mounted spatially locally to the vacuum chamber 20, for example bolted to a side of the vacuum chamber 20 and coupled via its input port to an internal volume of the vacuum chamber 20, and a roughing pump 90 that may be mounted to be remote from the turbo pump 80 and coupled to an output port of the turbopump 80. Such an arrangement enables the vacuum chamber 20 to be relatively compact and mountable via a mounting flange 2500 to other vacuum equipment, for example scanning or transmission electron microscopes, tomography apparatus and such like. In combination, the turbopump 80 and the roughing pump 90 enable a vacuum in a range of 10’7mBar to 1011mBar to be achieved within the vacuum chamber 20 when the positron source 10 is in operation.

[0103] As illustrated in FIG. 2, optionally, the planar target 30 is mounted onto a rotatable table 100 whose central axis 110 of rotation in use is aligned substantially to a centre of the planar target 30. Beneficially, the rotatable table 100 is mounted onto graphite bearings (for example Graphalloy® bearings) and driven by a vacuum-compatible electric motor, for example a stepper motor. When the positron source 10 is in operation with the planar target 30 receiving pulses of photons provided via the photon beam 70, rotating the planar target 30 assists to distribute power dissipation more evenly through the planar target 30, to avoid the surface layer 40 becoming ablated or damaged by pulses of the photon beam 70. Optionally, a piezo-electric transducer 120 is mounted between the planar target 30 and the rotatable table 100 and provided with a drive signal that is synchronized to the pulses of photons generated by the laser arrangement 50, wherein the piezo-electric transducer maintains the planar target 30 momentary spatially stationary relative to the photon beam 70 at an instance of a given photon pulse, to prevent the photon plasma being smeared over the surface layer 40. Such an avoidance of smearing increases a yield of positrons from the positron source 10 when in operation.

[0104] Referring next to FIG. 3, there is shown an implementation of the aforesaid electrode arrangement, wherein the electrode arrangement is denoted generally by 150. The electrode arrangement 150 includes one or more annular electrodes 160. For example, a first annular electrode 160A that is spatially nearest the surface layer 40 is configured in operation to be biased negatively relative to the surface layer 40 to attract positrons away from the photon plasma, near the surface layer 40; beneficially, a plane of the first annular electrode 160A is disposed to be substantially parallel (for example, to within 1 degree, more optionally to within 0.1 degree) to a major plane of the surface layer 40, as illustrated. Optionally, one or more additional annular electrodes 160B, 160C may be positioned more remotely in spatial sequence than the first annular electrode 160A from the surface layer 40, wherein potentials applied to the one or more additional annular electrodes 160B, 160C may be used to form the positron beam 180 generated from the photon plasma to surface layer 40 that is either divergent, collimated or focused to a small area to form a positron probe. The one or more electrodes 160A, 160B, 160C are beneficially configured so that their annular planes are substantially mutually parallel (for example, within 1 degree, more optionally within 0.1 degree), and their axes of rotational symmetry are mutually aligned along an optical axis that intersects a region of the surface layer 40 whereat the photon plasma is formed when the positron source 10 is in operation; the one or more electrodes 160A, 160B, 160C are supported on vacuum-compatible ceramic insulation supports, for example manufactured from machinable ceramic material such as Macor®; Macor® is a composite of mica flakes supported within a borosilicate glass matrix, wherein the borosilicate glass matrix is frangible for machining purposes (for example, diamond milling). Optionally, at least one of the one or more electrodes 160A, 160B 160C is implemented as a cylinder. In practice, it is found that the one or more electrodes 160A, 160B, 160C require bias voltages in an order of kiloVolts to function adequately to collimate or focus the positron beam 180. It will be appreciated that, when the planar target 30 including its associated surface layer 40 are optionally mounted on the rotatable table 100, the electrodes 160A, 160B, 160C are optionally maintained stationary, wherein the planar target 30 is rotated in operation.

[0105] For efficient generation of positrons, it will be further appreciated that the surface layer 40 needs to be kept very clean and beneficially devoid of any surface oxidation or contamination, for example devoid of a native oxide layer of substantially atomic-radius thickness arising by the surface layer 40 being exposed to atmospheric moisture and oxidation before being mounted into the vacuum chamber 20, for example by way of mounting the planar target 30 bearing the surface layer 40 into the vacuum chamber 20. Such an atomic-radius thick oxide layer tends to react with positrons generated in the photon plasma created above the surface layer 40 when the positron source 10 is in operation.

[0106] It is thus desirable to sputter away, under vacuum conditions within the vacuum chamber 20, the very thin oxide layer formed on the surface layer 40 before attempting to generate positrons thereat. Beneficially, after the planar target 30 with its associated surface layer 40 has been mounted within the vacuum chamber 20, the pumps 80, 90 are used to pump air out of the vacuum chamber 20 to circa 10’2milliBar (namely, to "low vacuum") pressure, and then a trace gas, for example a noble gas, for example including Argon, is released in small quantities into the vacuum chamber 20 and the first electrode 160A is then driven by a radio-frequency generator (not shown) to create a gas plasma, for example an Argon-including gas plasma, above the surface layer 40 to at least one of sputter and reactively ion etch away any atomic-radius thick native oxide layer and any organic contamination present on the surface layer 40. The radio-frequency generator is beneficially configured to generate the gas plasma at a radio frequency of a few MegaHertz to a few GigaHertz. Such at least one of sputtering and reactive ion etching has a duration in a range of a few seconds to a few minutes, depending on an intensity of the gas plasma used. Thereafter, the release of the trace gas, for example including Argon, into the vacuum chamber 20 is terminated, and then the pumps 80, 90 are configured to pump the vacuum chamber 20 down to an internal working pressure in a range of 10’7to 1011milliBar (namely, "high vacuum"). Removing the native oxide layer and any traces of contamination improves operation of the positron source 10 and its positron yield in the positron beam 180. Optionally, a combination of sputtering and reactive ion etching is used to ensure that the surface layer 40 is stripped of its native oxide and surface contaminants. A composition of the trace gas may be temporally varied during cleaning of the surface layer 40 under vacuum conditions.

[0107] Referring to FIG. 4, there is shown an alternative implementation of the positron source indicated generally by 1000. The positron source 1000 is similar to the positron source 10 except that the planar target 30 is stationarily mounted into the vacuum chamber 20, for example onto a metallic wall of the vacuum chamber 20 so that heat generated in the planar target 30 when the positron source 1000 is in operation may be dissipated efficiently away from the planar target 30, to prevent the planar target 30 and its associated surface 40 from overheating. For example, the wall of the vacuum chamber 20, whereat the planar target 30 is mounted, may be provided with forced fluid cooling, for example water cooling, through fluid cooling channels formed into channels formed in the wall. Moreover, there is also included a beam scanner 1010 between the laser arrangement 50 and the quartz or fused silica port window 60. The beam scanner 1010 is beneficially implemented using an optical component such as an actuated mirror, diffraction grating or quartz prism; for example, the optical component is mounted when in use on a motor-driven rotatable mount. When the positron source 1000 is in operation, the beam scanner 1010 is used to scan the photon beam 70 over the surface layer 40 of the planar target 30, so that energy dissipated by creating the photon plasma at the surface layer 40 does not locally damage or ablate the surface layer 40, thereby providing the surface layer 40 with more hours of operation before needing to be replaced. Beneficially, the beam scanner 1010 is operated in a step-wise manner, so that, during an instant of the given laser pulse provided from the laser arrangement 50, the photon beam 70 is maintained substantially stationary in trajectory on the surface layer 40 and then moved to a subsequent trajectory for a subsequent laser pulse. Optionally, high-frequency dithering in spatial position is applied to the photon beam 70 to help to spread the photon plasma at least one of laterally and orthogonally relative to a plane of the surface layer 40. Such dithering may be achieved using a piezo-electric actuator to provide high-frequency vibrations to the optical component, for example in a frequency range of several hundred kilohertz to several MegaHertz.

[0108] Referring next to FIG. 5, there are shown in a flow chart of steps of a method for (namely, a method of) operating the positron source 10, 1000 as illustrated in FIGs. 1 to 4. The steps are indicated generally by 2000 in FIG. 5. The positron source 10, 1000 beneficially includes a computing device 2010, for example an embedded microcontroller or FPGA logic device, to manage operation of the positron source 10, 1000; the computing device 2010 is configured to execute a software product, for example stored on a data carrier, for implementing the method depicted in FIG. 5.

[0109] In a first step 2020A of the method 2000, the positron source 10, 1000 is mechanically coupled, for example by a given user, to another apparatus (not shown) to which the positron source 10, 1000 is to provide the positron beam 180. The other apparatus may, for example, include at least one of: an electron microscope, a positron tomography apparatus, a semiconductor manufacturing apparatus, an energy storage device, a propulsion device. For example, the positron source 10, 1000 may be used to implement precision machining of MEMs structures by way of scanning the positron beam 180 electrostatically in x and y Cartesian ordinate directions to implement spatially adjustable annihilation ablation of the MEMs structures, for example for precision-tuning mechanically resonant MEMs structures, for example MEMs inertial navigation sensors.

[0110] In a second step 2020B of the method 2000, the planar target 30 with its surface layer 40 is mounted into the vacuum chamber 20, if not already done prior to the first step 2020A. Optionally, the laser arrangement 50 is activated at a low power to provide the photon beam 70 at a low power to check and adjust a position of at least one of the planar target 30 and the photon beam 70, to ensure that the photon beam 70 propagates as a surface evanescent wave over the surface layer 40, to interact strongly with the surface layer 40. Optionally, at least one of micrometer screw adjusters, piezoelectric actuators, magnetic actuators or similar may be used to make fine mechanical alignment adjustments of the photon beam 70 relative to the surface layer 40.

[0111] In a third step 2020C of the method 2000, the pumps 80, 90 are activated to pump the vacuum chamber 20 to at least 101to 10’2milliBar pressure (namely, to "low vacuum").

[0112] In a fourth step 2020D of the method 2000, optionally, a small amount of a trace gas, for example including a noble gas, for example Argon gas, is released into the vacuum chamber 20 and then a radio frequency signal is applied to the first electrode 160A to generate at least one of a sputtering plasma and a reactive ion etching plasma above the planar target 30 for removing any native oxide layer or contamination on an exposed part of the surface layer 40 of the planar target 30 that is to be used for generating positrons for the positron beam 180.

[0113] In a fifth step 2020E of the method 2000, the pumps 80, 90 are configured to pump the vacuum chamber 20 to at least 10’7to 1011milliBar pressure (namely, to "high vacuum"). In a sixth step 2020F of the method 2000, optionally, the planar target 30 is set in rotation on the rotatable table 100 in the positron source 10. Alternatively, the beam scanner 1010 of the positron source 10 is set into at least one of rotational motion and linear motion to scan the photon beam 70 over the surface layer 40. Optionally, a combination of the rotatable table 100 and the beam scanner 1010 are used when the positron source 10, 1000 is in operation.

[0114] In a seventh step 2020G of the method 2000, the laser arrangement 50 is activated to apply photon pulses in the photon beam 70 onto the surface layer 40 of the planar target 30 to generate momentary photon plasma thereat, wherein electrons of the photon plasma are preferentially absorbed at the surface layer 40 to leave an excess of positrons in the photon plasma, wherein the excess positrons are attracted by an electric field generated between the first electrode 160A and the surface layer 40 to be guided by the one or more electrodes 160 to generate the positron beam 180. Beneficially, bias voltages applied to the one or more electrode 160 are adjusted to form the positron beam 180 as required, for example to be at least one of: divergent, collimated and focused. A position of a focus of the positron beam 180 may be adjusted by suitably varying bias potentials applied to the one or more electrodes 160.

[0115] Beneficially, the computing device 2010 is used to implement, at least in part, one or more of the steps 2020A to 2020B, for example via a graphical user interface (GUI) that is used by a given user to set up and adjust the positron source 10, 1000.

[0116] In the foregoing, it will be appreciated that the planar target 30 and the surface layer 40 may be optionally integral. Optionally, the surface layer 40 may be formed onto the planar substrate 30, for example by way of using at least one of: epitaxial growth, ion implantation, Graphene sputtering, film spinning, micromachining using at least one of reactive ion etching and anisotropic etching. As aforementioned, the surface layer 40 is beneficially manufactured using a p-type semiconductor material or a nanostructure that functions as a p-type material to capture electrons from a photon plasma.

[0117] Referring next to FIG. 6, the planar target 30 and its associated surface layer 40 are optionally provided with a mirror arrangement, indicted generally by 2800, that is configured to cause the photon beam to make multiple traverses across the planar surface 40, to utilize photon energy in pulses of the photon beam 70 to greatest efficiency in generating positrons in the plasma cloud (namely, photon plasma) formed in operation close to the planar surface 40. The mirror arrangement 2800 includes a plurality of mirrors that, for example mirrors 2810A and 2810B, that are spaced apart at opposite sides of the planar target 30. The mirrors 2810A, 2810B may be fabricated from quartz plate with mirror coatings 2820A, 2820B respectively; alternatively, the mirrors 2820A, 2820B may be fabricated from metal sheets that have been surface polished to a mirror finish. At least one of the mirrors 2810A, 2810B is provided with a hole 2830 or a lack of mirror coating so that, when the positron sources 10, 1000 are in operation, the photon beam 70 is able to enter an optical cavity region between the mirrors 2810A, 2810B whereat the photon beam 70 is reflected back and forth in a zig-zag manner as illustrated, over the planar surface 40. The mirrors

[0118] 2810A, 2810B are disposed to be slightly mutually non-parallel by an angle 0t+ 02, as illustrated, to provide for the aforesaid zig-zag manner. Such a zig-zag manner of configuration avoids a lasing cavity being formed, wherein the laser beam 70 is concentrated at a particular pair of points on the mirrors 2810A, 2810B. For each reflection of the photon beam 70 between the mirrors 2810A, 2810B, the photon beam 70 beneficially traverses the planar surface 40 as an evanescent wave to interact strongly with the surface layer 40 whilst also generating a photon plasma slightly above the surface layer 40. Optionally, the mirror 2810A, 2810B are mounted on actuators, for example piezoelectric actuators, to be able to adjust the angle 0i + 02, dynamically during operation of the positron source 10, 1000; such actuation may be used also to precision adjust a height of the photon beam 70 above the surface layer 40, for example to compensate for thermal expansion of the planar target 30 and its surface layer 40 when their positron source 10, 1000 is in operation. The mirrors 2810A, 2810B thereby form a spatially-spread optical cavity around the planar target 30 and its associated surface layer 40. Optionally, the mirror arrangement 2800 of FIG. 6 is augmented to include four mirrors in a rectangular configuration, wherein the four mirrors are configured to be slightly off being mutually orthogonal; in such a configuration, the four mirrors are beneficially mounted on actuators, for example piezoelectric actuators, to dynamically adjust their relative angles, for example to compensate for thermal expansion occurring in the planar substrate 30 and its associated surface layer 40 in operation.

[0119] Referring next to FIG, 7, there is shown an alternative implementation of a mirror arrangement for use in the positron sources 10, 1000; the alternative implementation is indicated generally by 2900. The mirror arrangement 2900 is shown to include a cylindrical mirror 2910, which is circular in plan view. The cylindrical mirror 2910 may be implemented as a cylindrical portion of quartz tube that has a metallic mirror finish 2920 applied to its inside surface, or alternatively as a cylindrical portion of metal tube whose inside surface 2920 has been polished or lapped to a mirror finish. There is also included a hole or portion of transmissive material 2930 through which the photon beam 70 is arranged, for operation of the positron source 10, 1000, to enter into an interior region of the mirror arrangement 2900. As shown, the mirror arrangement 2900 includes the planar target 30 and its associated surface layer 40 within the interior region. The mirror arrangement 2900 is especially beneficial in that the photon beam is spread over an entire surface area of the surface layer 40 and also the mirror arrangement 2900, that maximizes an opportunity for the photon beam 70 to generate positrons when interacting with the surface layer 40, and also less ablative stress to the mirror arrangement 2900 compared to the mirror arrangement 2800 of FIG. 6, thereby providing greater longevity of operation before the mirror arrangement 2900 needs to be refurbished or re-coated. Optionally, the mirror arrangement 2900 is mounted on an actuator arrangement (not shown), for example implemented as a piezo-electric actuator, to adjust an angle of inclination in two axes to ensure the photon beam 70 making multiple passes over the surface layer 40 is at an optimum height above the surface layer 40. The mirror arrangement 2900 is beneficially used with the planar target 30 mounted on the rotatable table 100, to rotate when the positron source 10, 1000 is in operation, to ensure to an even greater extent that all areas of the surface layer are used for positron generation.

[0120] In practice, the positron source 10, 1000 may be manufactured as a compact assembly that is about the size of a small contemporary domestic refrigerator, such that the positron source 10, 1000 may be included within research laboratories, semiconductor fabrication facilities, medical clinics. Arrays of the positron source 10, 1000 may be configured together to provide a combined positron beam of significant magnitude to generate at least several microgrammes per second of antimatter mass flow rate. The combined positron beam may, for example, be injected, for example, into gaseous Deuterium-Tritium plasma of a fusion reactor, for example a tokamak apparatus such as ITER, in Toulouse (France), to assist to heat the gaseous plasma to a condition of thermonuclear ignition.

[0121] In developing the optical waveguide array and also the optical waveguide device of the present disclosure, the technical problems associated with using aforesaid radioactive sources undergoing beta Q6) decay was very much borne in mind; these problems are addressed by embodiments of the present disclosure. Moreover, the im practicality of using large particle accelerators and high-Z targets as aforementioned, to yield relatively small quantities of positron, was also borne in mind. It was appreciated that a relatively compact and safe apparatus for generating copious quantities of positrons is required by industry and research establishments. Moreover, it was also appreciated that an alternative device for converting photons to electrical energy is required by industry and research establishments. Embodiments of the present disclosure have been assembled and tested in practice; operation of the embodiments is based on well-known physical laws, as described in various published research papers as aforementioned.

[0122] Referring to FIG. 8A, there is shown a simple example of an optical waveguide array of the present disclosure, wherein the array is indicated generally by 3010A. The array 3010A is optionally fabricated onto a single crystal wafer of Lithium Niobate (LiNiO3) which is configured to exhibit optical non-linearity, for example the Kerr effect as will be described in more detail later. Alternatively, the array 3010A is fabricated into a layer of Lithium Niobate (LiNiO3) 3030 which is configured to exhibit optical non-linearity, for example the Kerr effect as will be described in more detail later; optionally, the layer of Lithium Niobate (LiNiO3) 3030 is supported on a Silicon, fused silica or quartz substrate 3020 onto which it is bonded via a Silicon Dioxide interfacing layer or grown, for example via vapour-phase deposition, namely as LNOI. As an alternative to Lithium Niobate, Barium Niobate (BaNiO3) or Graphene may be optionally used. Optionally, when LNOI is used, the layer of Lithium Niobate 3030 has a thickness in a range of 50 nm to 2.0 pm, namely substantially similar to a wavelength of photons to be propagating along a waveguide structure that is formed by lithographic and etching processes into the layer of Lithium Niobate 3030. The waveguide structure includes an input waveguide 3040 and two complementary waveguides 3050A, 3050B that branch laterally outwards from the input waveguide 3040; the input waveguide 3040 may optionally be terminated at a cleaving edge of the substrate 3020 as illustrated; alternatively, the input waveguide 3040 may optionally be terminated at one or more grating couplers (not shown) that may be excited in use by an incident pulsed laser beam that is incident at a shallow angle, namely a grazing angle, onto the one or more grating couplers.

[0123] The waveguides 3050A, 3050B beneficially have a length in a range of 30 pm to 10 mm, more optionally, the length is in a range of 100 pm to 1 mm, wherein the length determines an efficiency of the array 3010A, when in use, to create a matter-antimatter dipole within the array 3010A, as will be described in greater detail later; such a matter-antimatter dipole is formed, for example, in the optical system described in the aforesaid peer-reviewed published Wimmer et al. research paper.

[0124] In the Wimmer and Regensburger et al. published research paper, there is described an optical system wherein photons are separated into a region of effective antimatter and a region of effective matter in respective optical fibre waveguides by controlling group velocities of photons within the optical system, wherein the optical system exhibits in use an optical dispersion characteristic including two optical dispersion states, wherein one of the optical dispersion states favours matter (electrons) and another of the optical dispersion states favours antimatter (positrons).

[0125] The waveguides 3050A, 3050B are optionally of mutually different length or mutually different width to assist encouraging two mutually different optical dispersion states for the waveguides 3050A, 3050B to encourage formation of the matter-antimatter dipole (namely, by controlling group delay of photons due to optical non-linearity of the Lithium Niobate, as described in Wimmer et al.). A curved interfacing region 3060 of the waveguide structure included between the input waveguide 3040 and the two complementary waveguides 3050A, 3050B beneficially ensures an improved optical matching, to reduce photon reflection back towards a laser arrangement 3070 that is used to provide photons to the array 3010A. The layer of Lithium Niobate 3030 is lithographically formed, as aforementioned, for example by using e-beam or photoresists exposed during a lithographic operation, and by using a dry-etching process, for example reactive ion etching; such lithographic forming provides the input waveguide 3040 and the complementary waveguides 3050A, 3050B, as well as the curved interfacing region 3060. Optionally, during fabrication, the waveguides 3040, 3050A, 3050B are subject to isotropic etching to smooth roughness of sides of the waveguides to reduce photon attenuation occurring thereat; a surface roughness of less than 8 nm is desirable in practice to reduce attenuation of photon propagation along the complementary waveguides 3050A, 3050B. A distance "d" between the complementary waveguides 3050A, 3050B is beneficially in a range of 50 nm to 1.0 pm; for example, when the laser arrangement 3070 is configured to provide photons having a wavelength in range of 100 nm to 3 pm, for example substantially 1500 nm wavelength, the complementary waveguides 3050A, 3050B may have a width "w" in a range of 100 nm to 2 pm, for example a width "w" of circa 500 nm and a distance "d" therebetween of substantially 400 nm to 450 nm. The complementary waveguides 3050A, 3050B may have a thickness "t" in a range of 30 nm to 2 pm, as illustrated in FIG. 8B. It will be appreciated that such dimensions may be varied when designing the array 3010A, for example depending on the wavelength of the photons provided from the laser arrangement 3070. The laser arrangement 3070 may be a continuous-wave mode laser for configuring the array 3010A to function in a temporally continuous manner; alternatively, the laser arrangement 3070 may be a pulsed mode laser for configuring the array 3010A to function in a pulsed manner; yet alternatively when in operation, the laser arrangement 3070 is temporally switchable between operating in a continuous mode and a pulsed mode, wherein operation of the array 3010A is varied accordingly.

[0126] Two elongate metallic electrodes 3090A, 3090B are provided as illustrated that are disposed with their elongate axes substantially parallel to elongate axes of the waveguides 3050A, 3050B; the elongate metallic electrodes 3090A, 3090B may be disposed adjacent to the waveguides 3050A, 3050B, alternatively on top of or underneath the waveguides 3050A, 3050B. Beneficially, the two elongate metallic electrodes 3090A, 3090B are not more than 2 pm from their respective waveguide 3050A, 3050B, and more optionally not more than 2 pm from their respective waveguide 3050A, 3050B.

[0127] Moreover, the metallic electrodes 3090A, 3090B are coupled to corresponding electrical wire bonding pads 3100A, 3100B, to which wire bonding may be performed, for making external connections; optionally, the metallic electrodes 3090A, 3090B only extend a partial length of the waveguides 3050A, 3050B, for example along distal end regions of the waveguides 3050A, 3050B, remote from the input waveguide 3040. The metallic electrodes 3090A, 3090B are beneficially fabricated from Titanium, Aluminium, Indium, Silver, Gold or similar metal; the metallic electrodes 3090A, 3090B enable electrical energy to be extracted by capacitive coupling from pulsed photons propagating coherently along the waveguides 3050A, 3050B to generate an electrical signal, namely thereby functioning as an energy converter; the electrical signal may, for example, be used as a feedback signal to control or assist to energize the laser providing the pulsed photons to the waveguides 3050A, 3050B. Optionally, there are provided multiple electrodes 3090 on each outside side, alternatively beneath or over, of waveguides 3050A, 3050B, wherein the multiple electrodes 3090 may be configured to provide bias electric fields to the waveguides 3050A, 3050B. The multiple electrodes at least partially overlay the waveguides 3050A, 3050B, for example for selectively influencing a coherent propagation of photons propagating in operation along the waveguides 3050A, 3050B, to cause selective spatial separation "bifurcation"') of positrons and electrons generated in the waveguides 3050A, 3050B, by way of non-linear optical effects occurring therein, for example as described in the aforesaid Wimmer et al. research paper; for example, the waveguides 3050A, 3050B are configured (for example by way of mutual differences in their length or width) to provide an optical dispersion characteristic having a plurality of dispersion states that favour bifurcation of photons into regions having excess electrons derived from photons, alternatively regions having excess positrons derived from photons. Such bias electric fields may be arranged in use to induce non-linear optical effects in the waveguides 3050A, 3050B, for example to induce various types of Kerr effect that will be described in greater detail below.

[0128] Beneficially, one or more non-linear optical effects that arise include an optical Kerr effect. The optical Kerr effect results in a refractive index change that causes electrons of photons to group with other electrons, and likewise positrons of photons to group with other positrons, resulting in an enhanced positron-electron dipole, and thereby an enhanced acceleration experienced by the electrons and the positrons in the positron source. Generation of such dipoles is elucidated in the aforesaid peer-reviewed published research paper Wimmer et al. that describes an optical system that functions according to well-known physical laws (wherein there are utilized phenomena of adjusting group delay of photons in combination with use of a non-linear optical transmission medium, and wherein the photons are a bound stable state of corresponding electrons and positrons).

[0129] In the Wimmer and Regensburger et al. published research paper, there is described an optical system wherein photons are separated into a region of effective antimatter and a region of effective matter in respective optical fibre waveguides by controlling group velocities of photons within the optical system, wherein the optical system exhibits in use an optical dispersion characteristic including two optical dispersion states, wherein one of the optical dispersion states favours matter (electrons) and another of the optical dispersion states favours antimatter (positrons).

[0130] Optionally, subsequently, a further protective layer of insulator or dielectric material 3110 is formed onto the Lithium Niobate layer 3030, and also directly onto the fused silica substrate 3020 in regions where the Lithium Niobate layer 3030 has been removed from the substrate 3020 by etching; for example, the further protective layer includes an organic polymeric insulating material, alternatively silica (SiO2) Silicon Dioxide or Silicon Nitride. A layer of metal, for example Titanium, Aluminium, Indium, Silver, Gold or similar metal, is deposited during fabrication onto an exterior surface of the further layer of insulator or dielectric material 3110, for example the silica layer 3110, wherein the layer of metal is then lithographically patterned and then etched to provide one or more elongate electrodes 3120 whose one or more corresponding elongate axes are substantially orthogonal to the elongate axes of the waveguides 3050A, 3050B. The one or more elongate electrodes 3120 are terminated at corresponding wire bonding pads 3130. The further layer of insulator or dielectric material, for example silica layer 3110, serves to isolate the one or more electrodes 3120 electrically from the multiple electrodes 3090.

[0131] Optionally, electrodes 3090A, 3090B are not spatially overlapping the one or more elongate electrodes 3120, a need for the further protective layer of insulator or dielectric material 3110 may be avoided.

[0132] Optionally, the waveguides 3050A, 3050B have a spatial extent to an edge of the substrate 3020, or even slightly overhanging the substrate 3020, to allow for an electric field to be used in operation to extract positrons away from the waveguides 3050A, 3050B using an electric field.

[0133] As shown in FIG.8A, the array 3010A is then beneficially mounted to a ceramic module package 3200 that is hermetically sealed using a lid 3210, for example with a region filled inert Argon gas atmosphere or vacuum 3220 therein; wire bonding is beneficially used to connect the aforesaid wire bonding pads 3100, 3130 to connection pins of the ceramic module package 3200. Optionally, the laser arrangement 3070 is also housed within the same ceramic module package 3200 as the array 3010. Alternatively, the laser arrangement 3070 may be housed remotely from the array 3010 and its associated ceramic module package 3200, for example with photons generated in use by the laser arrangement 3070 being coupled via an optical fibre link (not shown) to the array 3010A.

[0134] Optionally, the ceramic module package 3200 is operated with a vacuum provided therein, as aforementioned. As shown in FIG. 9, the ceramic module package 3200 is modified in shape, and is further provided with an electrode arrangement 3300 spaced apart from the substrate 3020 to collect or guide positrons ejected from one or more end of the waveguides 3050A, 3050B, to form a positron beam 3340; optionally, an edge of the substrate 3020 extends beyond a mounting ledge of the ceramic module package 3200, as shown in FIG. 9, to allow an intense electric field, as aforementioned, to be applied in use at the edge of the substrate 3020, in particular to exposed ends of the waveguides 3050A, 3050B. The electrode arrangement 3300 beneficially includes an extraction electrode 3310 disposed nearest to the array 3010, and one or more focusing electrodes 3320 disposed more remotely from the array 3010; the electrodes 3310, 3320 are optionally rotationally symmetrical, namely of a ring-like or cylindrical-like form. Within the ceramic module package 3200, an internal volume is beneficially maintained as a vacuum, for example in a range of 10’7to 1011mBar, to avoid annihilation of positrons extracted from the array 3010; optionally, the ceramic module package 3200 is provided with a "getter" therein, as historically used in thermionic vacuum tubes (for example, in ECC83 or EL34 types) to help to maintain such a high vacuum. Such an arrangement allows for the array 3010 to be used as a positron source for performing positron tomography as well as being used for antimatter research, or even energy storage.

[0135] Beneficially, it will be appreciated that accelerated electrons are beneficially coupled to the elongate electrodes 3090 and then extracted from the ceramic module package 3200, both for configurations as depicted in FIGs. 8A, 8B, 80 and FIG. 9. Such a manner of operation enables the array 3010A to be used as an energy converter, namely converting photon energy into electrical energy to generate an electrical signal, for example for use for feedback control purposes or for assisting to power the laser arrangement 3070. In an optional configuration, at least a part of the converted electrical energy is provided back to the laser arrangement 3070 for reuse to generate photons, to improve efficiency of operation of the positron source. The arrangement depicted in FIG. 9 may also be used with a device 3500 of FIG. 10, as will be described below.

[0136] The array 3010A beneficially functions by using the Kerr effect, also known as a quadratic electro-optical (QEO) effect. The effect is known to cause positron focusing, for example, as reported in various scientific publications as aforementioned. The Kerr effect is a change in the refractive index of a material in response to an electric field being applied to the material. The Kerr effect is distinct from the Pockels effect in that the induced refractive index change is directly proportional to the square of the applied electric field instead of varying linearly therewith.

[0137] There are two special cases of the Kerr effect:

[0138] (i) DC Kerr effect (electro-optic effect); and

[0139] (ii) AC Kerr effect (optical Kerr effect).

[0140] The AC Kerr effect arises when the electric field is due to light itself, causing a refractive index variation that is responsible for nonlinear optical effects of self-focusing, self-phase modulation and modulational instability. This Kerr effect only becomes potentially significant when the array 3010A is excited using intense pulses of photons, for example when the laser arrangement 3070 is operated in a pulse mode. The DC Kerr effect occurs when light reflected from magnetized material has a slightly rotated plane of polarization.

[0141] In FIG. 8C, an array is indicated generally by 3010B. The array 3010B is similar to the array 3010A, except that at least one of the electrodes 3120A overlays only one of the pair of waveguides 3050A, 3050B, whereas at least one of the electrodes 3120B overlays both of the pair of waveguides 3050A, 3050B. Such a configuration of electrodes 3120A, 3120B allows for more precise control of photons propagating in use in the waveguides, to assist more efficient generation of an electron-positron dipole within the waveguides 3050A, 3050B. As aforementioned, a wave function describing a given photon propagating coherently in the waveguides 3050A, 3050B defines a spatial extent that includes both of the waveguides 3050A, 3050B, wherein the aforesaid non-linear optical effect causes an electron and a positron of the given photon to exhibit a differential Schrodinger-Heisenberg probability of being present in the waveguides 3050A, 3050B, thereby assisting to create the aforesaid matter-antimatter dipole.

[0142] Beneficially, the optical Kerr effect, for example the electro-optic effect, is used in implementations of the present disclosure. The optical Kerr effect results in a refractive index change that causes electrons of photons to group with other electrons, and likewise positrons of photons to group with other positrons, resulting in an enhanced positron-electron dipole, and thereby an enhanced acceleration experienced by the electrons and the positrons in the array 3010B.

[0143] In operation, photons are generated by the laser arrangement 3070 that propagate to the substrate 3020 and are injected into the input waveguide 3040, for example via use of a grating coupler (not shown) fabricated onto the substrate 3020; such grating couplers are known in the technical art. The photons propagate along the input waveguide 3040 to the curved interfacing region 3060 which is spatially progressively influenced by the Kerr effect; optionally, the Kerr effect is modulated from one or more of the electrodes 3090, 3120 being biased by applying bias voltages thereto. The Kerr effect results in more electrons of the photons being diverted to a given elongate waveguide 3050, for example the waveguide 3050A, relative to the other elongate waveguide 3050, for example the waveguide 3050B. On account of the elongate waveguides 3050A, 3050B being mutually spatially close together, the photons propagate coherently along the waveguides 3050A, 3050B; in other words, a (Schrodinger) equation wavefunction describing the photons spatially defines a region that includes both of the elongate waveguides 3050A, 3050B such that propagations of the photons remain coherent and excess positrons generated in one of the two waveguide 3050 do not annihilate with positive matter forming the waveguide 3050. In FIG. 9, when such positrons are extracted from the one of the waveguides 3050, for example by biasing a positron extraction arrangement 3095 of extraction electrodes to be negatively biased relative to the substrate 3020 and its associated electrodes 3090, 3120, the positrons enter vacuum and their corresponding photon wavefunctions then collapse into decoherence in the elongate waveguides 3050A, 3050B.

[0144] For conserving energy when operating the array 3010, both the laser arrangement 3070 and bias voltages applied to at least a subset of the electrodes 3090, 3120 may be applied as a series of temporal pulses; beneficially, the applied temporal pulses are mutually synchronized, for example with a phase delay included therebetween to cope with propagation delays of photons between the laser arrangement 3070 and the array 3010.

[0145] It will be appreciated that an excess of electrons in one of the elongate waveguides 3050, for example the waveguide 3050A, and an excess of positrons in another of the elongate waveguides 3050, for example the waveguide 3050B, causes a matter-antimatter dipole to be formed within the array 3010A, 3010B that is effective to accelerate the electrons and positrons; such acceleration causes beam bending as reported in the aforesaid Pei et al. research paper, and optical diametric drive as described in the aforesaid Wimmer et al. research paper. The electrodes 3120 may optionally be used to spatially decelerate the electrons whilst their corresponding positrons are accelerated along their waveguide 3050 and coupled to their corresponding spatially closely-disposed elongate electrode 3090. In operation, the electrons and positrons appear to gain energy from mutually interacting, which is manifested at a significant voltage being output from the elongate electrode 3090, for example, in an order of several eV at least. In such a manner of operation, the array 3010 is configured to function as an energy converter, namely converting photons injected into the array 3010 into corresponding output electrical signals.

[0146] Referring next to FIG. 10, in order to achieve a greater performance, a plurality of at least one of the arrays 3010A, 3010B as depicted in FIG. 9 may be disposed on the substrate 3020 in a spatially cascaded configuration, as illustrated in FIG. 10. Such a cascaded configuration enables multiple matter-antimatter dipoles to be formed of progressively greater magnitude that contributes to an improved efficiency of operation of the substrate 3020 and its associated components. As a result, a yield of at least one of accelerated electrons and positrons generated from the substrate 3020 may be considerably enhanced.

[0147] In FIG. 10, there is shown a waveguide arrangement apparatus indicated generally by 3500, wherein ends of waveguides 3050A, 3050B of a given array 3010A, 3010B are routed to corresponding input waveguides 3040 of a subsequent array 3010A, 3010B as illustrated; the arrays 3010A, 3010B are mutually fabricated together on the substrate 3020. There are beneficially at least two cascaded arrays 3010A, 3010B in a given series in the waveguide arrangement apparatus 3500. The number of cascaded arrays 3010A, 3010B is determined by coherence of photons that may be achieved in use; such coherence is, for example, found in practical embodiments of the present disclosure to be sensitive to edge roughness of the waveguides used, as aforementioned. In FIG. 10, each array 3010A, 3010B is provided with its corresponding electrodes 3090, 3120, wherein the electrodes 3090, 3120 are routed via a signal processing arrangement 3510 to a control arrangement 3520 implemented using at least one of a RISC processor, a field-programmable gate array (FPGA) or similar. The control arrangement 3520 is configured to execute one or more software products stored on a data storage medium to control operation. The signal processing 3530 is configured to provide an output signal, for example an output voltage of appreciable power.

[0148] The waveguide arrangement apparatus 3500 may itself be optionally configured as an energy converting device, for example when photons for the waveguide arrangement are provided from an external source, for example a solar collector, but not limited thereto. In such a manner of operation, the array 3500 is configured to function as an energy converter, namely converting photons injected into the array into electron-rich photons and positron-rich photons into respective waveguides from which output electrical signals are generated.

[0149] Thus, beneficially, apart from use in the aforesaid positron source, at least one of the array 3010A, 3010B and the array arrangement apparatus 3500 may have other uses; for example, the array 3010A, 3010B may be disposed in large array facilities, for example in solar arrays, for assisting to generate large amounts of electrical energy. Alternatively, the array 3010A, 3010B may be implemented in miniaturized form and included in portable electronic apparatus, for example portable computers, smartphones, drones, satellites, space probes and such like.

[0150] Referring next to FIG. 11, there are shown steps of a method for (namely, a method of) operating the array 3010A, 3010B and, mutatis mutandis, the array arrangement apparatus 3500; a flowchart of the method is indicated generally by 3600. The method 3600 for operating the optical waveguide array 3010A, 3010B and the optical waveguide array apparatus 3500 includes steps 3610 to 3640.

[0151] The step 3610 includes arranging for the at least one waveguide structure, for example including the waveguides 3040, 3050A, 3050B, 3060, to be fabricated at least in part from a material that exhibits one or more non-linear optical effects when in use, for example the Kerr effect. The waveguides 3040, 3050A, 3050B, 3060 are configured by way of their width, thickness and length to exhibit an optical dispersion characteristic including a plurality of dispersion states, for example two dispersion states as described in the aforesaid published Wimmer et al. research paper.

[0152] In the Wimmer and Regensburger et al. published research paper, there is described an optical system wherein photons are separated into a region of effective antimatter and a region of effective matter in respective optical fibre waveguides by controlling group velocities of photons within the optical system, wherein the optical system exhibits in use an optical dispersion characteristic including two optical dispersion states, wherein one of the optical dispersion states favours matter (electrons) and another of the optical dispersion states favours antimatter (positrons).

[0153] The step 3620 includes configuring an electrode arrangement, for example including the electrodes 3090, 3120, to control the one or more non-linear optical effects and to extract at least one of accelerated electrons and positrons from the at least one waveguide structure.

[0154] The step 3630 includes configuring the optical waveguide array 3010A, 3010B or the optical waveguide array apparatus 3500, when in use, to separate photons input on the at least one waveguide structure using the one or more non-linear optical effects into regions including their respective electrons and positrons.

[0155] The step 3640 includes guiding the respective electrons and positrons into their respective regions of the at least one waveguide structure to cause a matter-antimatter dipole, for example as described in Wimmer et al. research paper giving rise to optical diametric drive, to be formed within the at least one waveguide structure waveguide structure for imparting energy to at least one of the electrons and the positrons to cause acceleration thereof, for example for assisting to generate the positron beam 3330.

[0156] It is to be understood that arrangements of components illustrated in the aforesaid diagrams and described above are exemplary and that other arrangements may be possible within the scope of the claims as appended herewith. Although the disclosure and its advantages have been described in detail, it is to be understood that various changes, substitutions, and alterations may be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims.

[0157] STATEMENTS

[0158] Statement 1 : A positron source (10; 1000) for generating a positron beam (180), wherein the positron source (10; 1000) includes: a laser arrangement (50) configured to generate a beam (70) of photons; a target (30) configured to receive the beam (70) of photons, wherein the target (30) is arranged for the photons of the beam (70) to generate a photon plasma (namely, a spatially high density of photons, wherein the photons mutually entangle to express their respective electrons and associated positrons; "photon plasma" is a term of technical art known to a person skilled in the art; see CN104735895A') at a surface layer (40) of the target (30), wherein the surface layer (40) is configured to preferentially absorb electrons from the photon plasma to generate corresponding free positrons; and an electrode arrangement (160) comprising one or more electrodes (160A, 160B, 160C) that are configured to apply an electric field to the photon plasma to extract the free positrons therefrom and to guide the positrons to form the positron beam (180); wherein at least the target (30) and the electrode arrangement (160) are included within a vacuum chamber (20) configured in use to provide a vacuum condition in which the target (30) and the electrode arrangement (160) are arranged to function.

[0159] Statement 2: A positron source (10; 1000) of Statement 1, wherein the surface layer (40) is configured to include a doped semiconductor material for providing the surface layer (40).

[0160] Statement 3: A positron source (10; 1000) of Statement 2, wherein the doped semiconductor includes at least one of: p-doped Silicon, p-doped Gallium Arsenide, p-doped Graphene, Graphene, p-doped Silicon Carbide.

[0161] Statement 4: A positron source (10; 1000) of Statement 1, 2 or 3, wherein the positron source (10; 1000) is configured for the beam (70) of photons to propagate in a direction that is substantially parallel to a plane of the surface layer (40) when the beam (70) of photons is received at the surface layer (40) for generating the photon plasma.

[0162] Statement 5: A positron source (10; 1000) of Statement 4, wherein the beam (70) of photons is arranged to propagate as an evanescent wave over the surface layer (40) when generating the photon plasma.

[0163] Statement 6: A positron source (10; 1000) of any one of the preceding Statements, wherein the target (30) is supported on a rotatable table (100) that is arranged to rotate when the positron source (10; 1000) is in operation, to increase an area of the surface layer (40) that is exposed to the beam (70) of photons.

[0164] Statement 7: A positron source (10; 1000) of any one of the preceding Statements, wherein the positron source (10; 1000) further includes a beam scanner (1010) for scanning the beam (70) of photons over the surface layer (40) when the positron source (10; 1000) is in operation, to increase an area of the surface layer (40) that is exposed to the beam (70) of photons.

[0165] Statement 8: A positron source (10; 1000) of Statement 7, wherein the beam scanner (1010) is implemented as an actuated or rotatable mirror, prism or diffraction grating.

[0166] Statement 9: A positron source (10; 1000) of any one of the preceding Statements, wherein the electrode arrangement (160) is configured to remove a native oxide including any contamination') of the surface layer (40) prior to the surface layer (40) being configured to interact with the photon plasma to generate positrons, wherein the electrode arrangement (160) is configured to be driven by a radio-frequency signal to excite a trace gas introduced into the vacuum chamber (20) to cause sputtering or reactive ion etching at the surface layer (40).

[0167] Statement 10: A positron source (10; 1000) of any one of the preceding

[0168] Statements, wherein the laser arrangement (50) is configured to generate the beam (70) of photons as a pulsed photon beam.

[0169] Statement 11 : A positron source (10; 1000) of Statement 10, wherein the pulsed photon beam has a pulse energy in a range of 10 milliJoules to 10 Joules per pulse, optionally in a range of 10 milliJoules to 1 Joule per pulse, and a pulse duration in a range of 10 picoseconds to 100 nanoseconds.

[0170] Statement 12: A positron source (10; 1000) of any one of the preceding

[0171] Statements, wherein the laser arrangement (50) is configured to generate the beam (70) of photons to have a radiation wavelength in a range of 2 pm to 50 nm.

[0172] Statement 13: A positron source (10; 1000) of any one of the preceding Statements, wherein the positron source (10; 1000) is configured to move the beam (70) of photons in a step-wise manner over the surface layer (40), wherein the beam (70) of photons at the surface layer (40) is substantially stationary at an instance that a pulse of photons is output from the laser arrangement (50).

[0173] Statement 14: A positron source (10; 1000) of any one of the preceding Statements, wherein the electrode arrangement (160) further includes a first electrode (160A) for generating an electric field to extract positrons from the photon plasma, and one or more second electrodes (160B, 160C) for forming the positron beam (180) to be at least one of: divergent, collimated, convergent.

[0174] Statement 15: A positron source (10; 1000) of any one of the preceding Statements, wherein the positron source (10; 1000) is configured for use with at least one of: an electron microscope, a positron tomography apparatus, a semiconductor manufacturing apparatus, an energy storage device, a propulsion device.

[0175] Statement 16: A positron source (10; 1000) of any one of the preceding Statements, wherein the positron source (10; 1000) is configured to include a mirror arrangement (2800; 2900) for guiding the photon beam (70) to make multiple passes over the surface layer (40) in use, to enhance a yield of positrons generated at the surface layer (40) for a given pulse energy of the photon beam (70).

[0176] Statement 17: A method for operating a positron source (10; 1000) for generating a positron beam (180) therefrom, wherein the positron source (10; 1000) includes: a laser arrangement (50) configured to generate a beam (70) of photons; a target (30) configured to receive the beam (70) of photons; an electrode arrangement (160) comprising one or more electrodes (160A, 160B, 160C); wherein at least the target (30) and the electrode arrangement (160) are included within a vacuum chamber (20); wherein the method includes: configuring the vacuum chamber (20) in use to provide a vacuum condition in which at least the target (30) and the electrode arrangement (160) are arranged to function; configuring the positron source (10; 1000) for the photons of the beam (70) to generate a photon plasma namely, a spatially high density of photons, wherein the photons mutually entangle to express their respective electrons and positrons; "photon plasma" is a term of technical art known to a person skilled in the art; see CN104735895A) at a surface layer (40) of the target (30), wherein the surface layer (40) is configured to preferentially absorb electrons from the photon plasma to generate corresponding free positrons; and configuring the one or more electrodes (160A, 160B, 160C) to apply an electric field to the photon plasma to extract the free positrons therefrom and to guide the positrons to form the positron beam (180).

[0177] Statement 18: A method of Statement 17, wherein the method includes configuring the surface layer (40) to include a doped semiconductor material for providing the surface layer (40).

[0178] Statement 19: A method of Statement 18, wherein the doped semiconductor includes at least one of: p-doped Silicon, p-doped Gallium Arsenide, p-doped Graphene.

[0179] Statement 20: A method of Statement 17, 18 or 19, wherein the method includes configuring the positron source (10; 1000) for the beam (70) of photons to propagate in a direction that is substantially parallel to a plane of the surface layer (40) when the beam (70) of photons is received at the surface layer (40) for generating the photon plasma.

[0180] Statement 21 : A method of Statement 20, wherein the method includes arranging for the beam (70) of photons to propagate as an evanescent wave over the surface layer (40) when generating the photon plasma.

[0181] Statement 22: A method of any one of Statements 17 to 21, wherein the method includes supporting the target (30) on a rotatable table (100) that is arranged to rotate when the positron source (10; 1000) is in operation, to increase an area of the surface layer (40) that is exposed to the beam (70) of photons.

[0182] Statement 23: A method of any one of Statements 17 to 22, wherein the method includes arranging for the positron source (10; 1000) to further include a beam scanner (1010) for scanning the beam (70) of photons over the surface layer (40) when the positron source (10; 1000) is in operation, to increase an area of the surface layer (40) that is exposed to the beam (70) of photons.

[0183] Statement 24: A method of Statement 23, wherein the method includes implementing the beam scanner (1010) as an actuated or rotatable mirror, prism or diffraction grating.

[0184] Statement 25: A method of any one of Statements 17 to 24, wherein the method includes configuring the electrode arrangement (160) to remove a native oxide (for example, including contamination') of the surface layer (40) prior to the surface layer (40) being configured to interact with the photon plasma to generate positrons, wherein the electrode arrangement (160) is configured to be driven by a radio-frequency signal to excite a trace gas introduced into the vacuum chamber (20) to cause sputtering or reactive ion etching at the surface layer (40).

[0185] Statement 26: A method of any one of Statements 17 to 25, wherein the method includes configuring the laser arrangement (50) to generate the beam (70) of photons as a pulsed photon beam.

[0186] Statement 27: A method of Statement 26, wherein the method includes arranging for the pulsed photon beam to have a pulse energy in a range of 10 milliJoules to 10 Joules per pulse, optionally in a range of 10 milliJoules to 1 Joule per pulse, and a pulse duration in a range of 10 picoseconds to 100 nanoseconds.

[0187] Statement 28: A method of any one of Statements 17 to 27, wherein the method includes configuring the laser arrangement (50) to generate the beam (70) of photons to have a radiation wavelength in a range of 2 pm to 50 nm.

[0188] Statement 29: A method of any one of Statements 17 to 28, wherein the method includes configuring the positron source (10; 1000) to move the beam (70) or photons in a step-wise manner over the surface layer (40), wherein the beam (70) of photons at the surface layer (40) is substantially stationary at an instance that a pulse of photons is output from the laser arrangement (50).

[0189] Statement 30: A method of any one of Statements 17 to 29, wherein the method further includes configuring the electrode arrangement (160) to include a first electrode (160A) for generating an electric field to extract positrons from the photon plasma, and one or more second electrodes (160B, 160C) for forming the positron beam (180) to be at least one of: divergent, collimated, convergent.

[0190] Statement 31 : A method of any one of Statements 17 to 30, wherein the method includes configuring the positron source (10; 1000) for use with at least one of: an electron microscope, a positron tomography apparatus, a semiconductor manufacturing apparatus, an energy storage device, a propulsion device.

[0191] Statement 32: A method of any one of Statements 17 to 31, wherein the method includes configuring the positron source (10; 1000) to include a mirror arrangement (2800; 2900) for guiding the photon beam (70) to make multiple passes over the surface layer (40) in use, to enhance a yield of positrons generated at the surface layer (40) for a given pulse energy of the photon beam (70).

[0192] Statement 33: A software product stored on a machine-readable data carrier, wherein the software product is executable on computing hardware (2010) to implement a method of any one of Statements 17 to 32.

[0193] Statement 35: A positron source (3010A; 3010B; 3500) for generating a positron beam (3330), wherein the positron source (3010A; 3010B, 3500) includes an optical waveguide array device (3010A; 3010B; 3500) including a substrate (3020), and at least one waveguide structure (4300, 3050A, 3050B, 3060) formed onto the substrate (3020), wherein the at least one waveguide structure (3040, 3050A, 3050B, 3060) is fabricated at least in part from a material that exhibits one or more non-linear optical effects when in use (for example, the Kerr effect), and an electrode arrangement (3090, 3120) configured to control the one or more non-linear optical effects and to extract at least one of accelerated electrons and positrons from the at least one waveguide structure (3040, 3050A, 3050B, 3060), and wherein the optical waveguide array device (3010A; 3010B; 3500) is configured in use to separate photons input on the at least one waveguide structure (3040, 3050A, 3050B, 3060) using the one or more non-linear optical effects into their respective electrons and positrons, and to guide the respective electrons and positrons into their respective regions of the at least one waveguide structure (3040, 3050A, 3050B, 3060) to cause a matter-antimatter dipole (for example, a matter-antimatter dipole as described in the aforesaid published research paper Wimmer et al. giving rise to optical diametric drive) to be formed within the at least one waveguide structure (3040, 3050A, 3050B, 3060) for imparting energy to at least one of the electrons and the photons to cause acceleration thereof, wherein the positrons are extracted to generate the positron beam (3330).

[0194] Statement 36: A positron source (3010A; 3010B; 3500) of Statement 35, wherein the substrate (3020) is fabricated from a dielectric material, and the material of the at least one waveguide structure (3040, 3050A, 3050B, 3060) includes at least one of: Lithium Niobate (LiNiO3), Lithium Niobate On Insulator (LNOI), Barium Niobate (BaNiO3), Graphene.

[0195] Statement 37: A positron source (3010A; 3010B; 3500) of Statement 35 or 36, wherein the substrate (3020) is fabricated from a dielectric material, optionally at least one of: quartz, fused silica, Silicon, Silicon Dioxide.

[0196] Statement 38: A positron source (3010A, 3010B; 3500) of Statement 35, 36 or 37, wherein the electrode arrangement (3090, 3120) comprises a configuration of electrodes (3090, 3120) whose elongate axes are configured to be substantially parallel to, or substantially orthogonal to, elongate axes of a plurality elongate waveguides (3050A, 3050B) into which the corresponding electrons and positrons are selectively diverted when the device (3010A; 3010B; 3500) is in operation.

[0197] Statement 39: A positron source (3010A; 3010B; 3500) of Statement 38, wherein the electrode arrangement (3090, 3120) is fabricated from at least one of: Titanium, Aluminium, Indium, Silver, Gold.

[0198] Statement 40: A positron source (3010A; 3010B; 3500) of any one of Statements 35 to 39, wherein the device (3010A; 3010B; 3500) includes a plurality of the at least one waveguide structure (3040, 3050A, 3050B, 3060) arranged in a cascaded configuration.

[0199] Statement 41 : A positron source (3010A; 3010B; 3500) of any one of Statements 35 to 40, wherein the device (3010A; 3010B; 3500) further includes a laser arrangement (3070) configured in use to provide photons to the at least one waveguide structure (3040, 3050A, 3050B, 3060).

[0200] Statement 42: A positron source (3010; 3500) of Statement 41, wherein the laser arrangement (3070) is configured to function in at least one of: a continuous mode, a pulsed mode (to generate pulses of photons'), a combination of continuous and pulsed modes.

[0201] Statement 43: A positron source (3010A; 3010B; 3500) of any one of Statements 35 to 42, wherein waveguides of the at least one waveguide structure (3040, 3050A, 3050B, 3060) are disposed in a parallel mutually spaced-apart manner with a distance (d) therebetween, wherein the distance is substantially of a similar size to a wavelength of the photons supplied to the at least one waveguide structure (3040, 3050A, 3050B, 3060) when in operation.

[0202] Statement 44: A positron source (3010A; 3010B; 3500) of Statement 43, wherein the distance (d) is configured to allow photons to propagate coherently between mutually adjacent elongate waveguides (3050A, 3050B) of the at least one waveguide structure (3040, 3050A, 3050B, 3060).

[0203] Statement 45: A method (3600) for operating a positron source (3010A; 3010B; 3500) to generate a positron beam (3330), wherein the positron source (3010A; 3010B; 3500) includes an optical waveguide array device (3010A; 3010B; 3500) including a substrate (3020), and at least one waveguide structure (3040, 3050A, 3050B, 3060) formed onto the substrate (3020), wherein the method (3600) includes:

[0204] (i) arranging for the at least one waveguide structure (3040, 3050A, 3050B, 3060) to be fabricated at least in part from a material that exhibits one or more non-linear optical effects when in use;

[0205] (ii) optionally configuring an electrode arrangement (3090, 3120) to control the one or more non-linear optical effects and to extract at least one of accelerated electrons and positrons from the at least one waveguide structure (3040, 3050A, 3050B, 3060);

[0206] (iii) configuring the optical waveguide array device (3010A; 3010B; 3500), when in use, to separate photons input on the at least one waveguide structure (3040, 3050A, 3050B, 3060) using the one or more non-linear optical effects into their respective electrons and positrons; and

[0207] (iv) guiding the respective electrons and positrons into their respective regions of the at least one waveguide structure (3040, 3050A, 3050B, 3060) to cause a matter-antimatter dipole (for example, in a manner as described in aforesaid Wimmer et al. research paper) to be formed within the at least one waveguide structure waveguide structure (3040, 3050A, 3050B, 3060) for imparting energy to at least one of the electrons and the positrons to cause acceleration thereof, wherein the method further comprises extracting the positrons to form the positron beam (3330).

[0208] Statement 46: A method (3600) of Statement 45, wherein the method (3600) includes fabricating the substrate (3020), at least in part, from a dielectric material, and arranging for the material of the at least one waveguide structure (3040, 3050A, 3050B, 3060) to include at least one of: Lithium Niobate (LiNiO3), Lithium Niobate On Insulator (LNOI), Barium Niobate (LiNiO3), Graphene.

[0209] Statement 47: A method (3600) of Statement 45 or 46, wherein the method (3600) includes fabricating the substrate (3020) from a dielectric material, optionally at least one of: quartz, fused silica, Silicon, Silicon Dioxide.

[0210] Statement 48: A method (3600) of Statement 45, 46 or 47, wherein the electrode arrangement (3090, 3120) comprises a configuration of electrodes whose elongate axes are configured to be substantially parallel to, or substantially orthogonal to, elongate axes of a plurality elongate waveguides (3050A, 3050B) into which the corresponding electrons and positrons are selectively diverted when the device (3010A; 3010B; 3500) is in operation.

[0211] Statement 49: A method (3600) of Statement 48, wherein the electrode arrangement (3090, 3120) is fabricated from at least one of: Titanium, Aluminium, Indium, Silver, Gold.

[0212] Statement 50: A method (3600) of any one of the preceding Statements 45 to

[0213] 49, wherein the method (3600) includes arranging for the device (3010A; 3010B; 3500) to include a plurality of the at least one waveguide structure (3040, 3050A, 3050B, 3060) arranged in a cascaded configuration.

[0214] Statement 51 : A method (3600) of any one of the preceding Statement 45 to

[0215] 50, wherein the method (3600) further includes arranging for the device (3010A; 3010B; 3500) to further include a laser arrangement (3070) configured in use to provide photons to the at least one waveguide structure (3040, 3050A, 3050B, 3060).

[0216] Statement 52: A method (3600) of Statement 51, wherein the method (3600) includes configuring the laser arrangement (3070) to function in at least one of: a continuous mode, a pulsed mode (to generate pulses of photons'), a combination of continuous and pulsed modes; optionally, the pulsed mode is used.

[0217] Statement 53: A method (3600) of any one of the preceding Statements 45 to 52, wherein the method (3600) includes arranging for waveguides of the at least one waveguide structure (3040, 3050A, 3050B, 3060) to be disposed in a parallel mutually-spaced-apart manner with a distance (d) therebetween, wherein the distance (d) is substantially of a similar size to a wavelength of the photons supplied to the at least one waveguide structure (3040, 3050A, 3050B, 3060) when in operation.

[0218] Statement 54: A method (3600) of Statement 53, wherein the method (3600) includes configuring the distance (d) to allow for photons to propagate coherently between mutually adjacent elongate waveguides (3050A, 3050B) of the at least one waveguide structure (3040, 3050A, 3050B, 3060). Statement 55: A software product recorded on a machine-readable data carrier, wherein the software product is executable on computing hardware (3520) of the device (3010A; 3010B; 3500) of any one of Statements 35 to 44, to implement a method as claimed in any one of Statements 45 to 54.

[0219] Statement 56: An energy converter for converting photons into an output electrical signal, wherein the energy converter includes: a laser arrangement configured to generate a beam of photons, optionally a pulsed beam of photons; a waveguide arrangement fabricated onto a substrate, wherein the waveguide arrangement comprises a plurality of waveguides configured to exhibit a non-linear optical effect, wherein the plurality of waveguides are configured to receive the beam of photons and to bifurcate the beam into electron-rich photons propagating along one of the plurality of waveguides and into positron-rich photons propagating along another of the plurality of waveguides (for example, as provided in the optical fibre loops of the optical system of the aforementioned research paper Wimmer et ai. ; and an electrode arrangement comprising one or more electrodes that are configured to apply an electric field to the electron-rich photons and the positron-rich photons to extract the output electrical signal therefrom (for example, by way of capacitive coupling from the waveguides to the electrode arrangement).

[0220] Statement 57: The energy converter of Statement 56, wherein the substrate is fabricated from a dielectric material, and the material of the plurality of waveguides includes at least one of: Lithium Niobate (LiNiO3), Lithium Niobate On Insulator (LNOI), Barium Niobate (BaNiO3), Graphene.

[0221] Statement 58: The energy converter of Statement 56, wherein the energy converter is configured, wherein the substrate is fabricated from at least one of: quartz, fused silica, Silicon.

[0222] Statement 59: The energy converter of Statement 56, wherein the electrode arrangement comprises a configuration of electrodes whose elongate axes are configured to be substantially parallel to, or substantially orthogonal to, elongate axes of the plurality of elongate waveguides into which the corresponding electrons and positrons are selectively diverted (for example, in a manner as described for the optical system of the research paper Wimmer et al.) when the energy converter is in operation.

[0223] Statement 60: The energy converter of Statement 59, wherein at least one of the electrodes intersects or overlays a portion of the plurality of waveguides for selectively controlling positrons or electrons generated in the energy converter from photons provided, when in use, to the plurality of waveguides.

[0224] Statement 61 : The energy converter of Statement 60, wherein the electrode arrangement is fabricated from at least one of: Titanium, Aluminium, Indium, Silver, Gold.

[0225] Statement 62: The energy converter of Statement 56, wherein the energy converter includes a series of the plurality of the waveguides arranged in a cascaded configuration.

[0226] Statement 63: The energy converter of Statement 56, wherein the plurality of waveguides are disposed in a parallel mutually spaced-apart manner with a distance ( ) therebetween, wherein the distance is substantially of a similar size to a wavelength of the photons supplied to the plurality of waveguides when in operation.

[0227] Statement 64: The energy converter of Statement 63, wherein the distance ( ) is configured to allow for photons to propagate coherently along mutually adjacent elongate waveguides of the plurality of waveguides.

[0228] Statement 65: The energy converter of Statement 63, wherein the distance ( ) is in a range of 30 nm to 1 |im.

[0229] Statement 66: The energy converter of Statement 65, wherein the waveguides each have a width (w) in a range of 50 nm to 2 |im.

[0230] Statement 67: The energy converter of Statement 65, wherein the waveguides each have a thickness (t), relative to a plane of a substrate on which they are formed, in a range of 20 nm to 2 |im.

[0231] Statement 68: The energy converter of Statement 65, wherein the waveguides have a length in a range of 100 |im to 10 mm. Statement 69: The energy converter of Statement 56, wherein the energy converter is configured to function from photons having a wavelength in a range of 150 nm to 3 |im, more optionally substantially 1500 nm.

[0232] Statement 70: The energy converter of Statement 56, wherein the energy converter is included in a positron source for generating a beam of positrons.

[0233] Statement 71 : A method for operating an energy converter of Statement 56 for converting photons into an output electrical signal, wherein the method includes: configuring a laser arrangement to generate a beam of photons, optionally a pulsed beam of photons; using a waveguide arrangement fabricated onto a substrate to bifurcate photons into corresponding electrons and positrons, wherein the waveguide arrangement comprises a plurality of waveguides configured to exhibit a non-linear optical effect, wherein the plurality of waveguides are configured to receive the beam of photons and to bifurcate (for example, in a manner as described in the aforesaid research paper Wimmer et al.) the beam into electron-rich photons propagating along one of the plurality of waveguides and into positron-rich photons propagating along another of the plurality of waveguides; and configuring an electrode arrangement comprising one or more electrodes to apply an electric field to the electron-rich photons and the positron-rich photons to extract the output electrical signal therefrom (for example, by using capacitive coupling from the plurality of waveguides to the electrode arrangement when the pulsed beam of photons is used).

[0234] Statement 72: The method of Statement 71, wherein the method includes arranging for the substrate to be fabricated from a dielectric material, wherein the material of the plurality of waveguides includes at least one of: Lithium Niobate (LiNiO3), Barium Niobate (BaNiO3), Graphene.

[0235] Statement 73: The method of Statement 72, wherein the method includes arranging for the substrate to be fabricated, at least in part, from at least one of: quartz, fused silica. Statement 74: The method of Statement 71, wherein the method including arranging for the electrode arrangement to comprise a configuration of electrodes whose elongate axes are configured to be substantially parallel to, or substantially orthogonal to, elongate axes of the plurality of elongate waveguides into which the corresponding electrons and positrons are selectively diverted when the energy converter is in operation.

[0236] Statement 75: The method of Statement 74, wherein at least one of the electrodes intersects or overlays a portion of the plurality of waveguides for selectively controlling positrons or electrons generated in the energy converter from photons provided, when in use, to the plurality of waveguides.

[0237] Statement 76: The method of Statement 75, wherein the method includes arranging for the electrode arrangement to be fabricated from at least one of: Titanium, Aluminium, Indium, Silver, Gold.

[0238] Statement 77: The method of Statement 71, wherein the method includes arranging for the energy converter to include a series of the plurality of the waveguides arranged in a cascaded configuration.

[0239] Statement 78: The method of Statement 71, wherein the method includes arranging for the plurality of waveguides to be disposed in a parallel mutually spaced-apart manner with a distance ( ) therebetween, wherein the distance is substantially of a similar size to a wavelength of the photons supplied to the plurality of waveguides when in operation.

[0240] Statement 79: The method of Statement 78, wherein the method includes arranging for the distance ( ) to be configured to allow for photons to propagate coherently coherence between mutually adjacent elongate waveguides of the plurality of waveguides.

[0241] Statement 80: The method of Statement 78, wherein the distance d is in a range of 30 nm to 1 |im.

[0242] Statement 81 : The method of Statement 78, wherein the waveguides each have a width (w) in a range of 50 nm to 2 |im. Statement 82: The method of Statement 78, wherein the waveguides each have a thickness (t), relative to a plane of a substrate on which they are formed, in a range of 20 nm to 2 |im.

[0243] Statement 83: The method of Statement 78, wherein the waveguides have a length in a range of 100 |im to 10 mm.

[0244] Statement 84: The method of Statement 71, wherein the method includes configuring the energy converter to function from photons having a wavelength in a range of 150 nm to 3 |im, more optionally substantially 1500 nm.

[0245] Statement 85: The method of Statement 71, wherein the method includes using the energy converter in a positron source for generating a beam of positrons (for example in the positron source of Statement 1).

[0246] Statement 86: A software product recorded on a non-transitory machine-readable data carrier, wherein the software product is executable on a computing hardware, to implement the method of Statement 71.

Claims

CLAIMS1. A positron source (10; 1000) for generating a positron beam (180), wherein the positron source (10; 1000) includes: a laser arrangement (50) configured to generate a beam (70) of photons; a target (30) configured to receive the beam (70) of photons, wherein the target (30) is arranged for the photons of the beam (70) to generate a photon plasma at a surface layer (40) of the target (30), wherein the surface layer (40) is configured to preferentially absorb electrons from the photon plasma to generate corresponding free positrons; and an electrode arrangement (160) comprising one or more electrodes (160A, 160B, 160C) that are configured to apply an electric field to the photon plasma to extract the free positrons therefrom and to guide the positrons to form the positron beam (180); wherein at least the target (30) and the electrode arrangement (160) are included within a vacuum chamber (20) configured in use to provide a vacuum condition in which the target (30) and the electrode arrangement (160) are arranged to function.

2. A positron source (10; 1000) of Claim 1, wherein the surface layer (40) is configured to include a doped semiconductor material for providing the surface layer (40).

3. A positron source (10; 1000) of Claim 2, wherein the doped semiconductor includes at least one of: p-doped Silicon, p-doped Gallium Arsenide, p-doped Graphene, Graphene, p-doped Silicon Carbide.

4. A positron source (10; 1000) of Claim 1, 2 or 3, wherein the positron source (10; 1000) is configured for the beam (70) of photons to propagate in a direction that is substantially parallel to a plane of the surface layer (40) when the beam (70) of photons is received at the surface layer (40) for generating the photon plasma.

5. A positron source (10; 1000) of Claim 4, wherein the beam (70) of photons is arranged to propagate as an evanescent wave over the surface layer (40) when generating the photon plasma.

6. A positron source (10; 1000) of any one of the preceding claims, wherein the target (30) is supported on a rotatable table (100) that is arranged to rotate when the positron source (10; 1000) is in operation, to increase an area of the surface layer (40) that is exposed to the beam (70) of photons.

7. A positron source (10; 1000) of any one of the preceding claims, wherein the positron source (10; 1000) further includes a beam scanner (1010) for scanning the beam (70) of photons over the surface layer (40) when the positron source (10; 1000) is in operation, to increase an area of the surface layer (40) that is exposed to the beam (70) of photons.

9. A positron source (10; 1000) of any one of the preceding claims, wherein the electrode arrangement (160) is configured to remove a native oxide of the surface layer (40) prior to the surface layer (40) being configured to interact with the photon plasma to generate positrons, wherein the electrode arrangement (160) is configured to be driven by a radio-frequency signal to excite a trace gas introduced into the vacuum chamber (20) to cause sputtering or reactive ion etching at the surface layer (40).

10. A positron source (10; 1000) of any one of the preceding claims, wherein the laser arrangement (50) is configured to generate the beam (70) of photons as a pulsed photon beam, optionally wherein the pulsed photon beam has a pulse energy in a range of 10 milliJoules to 10 Joules per pulse, optionally in a range of 10 milliJoules to 1 Joule per pulse, and a pulse duration in a range of 10 picoseconds to 100 nanoseconds.

11. A positron source (10; 1000) of any one of the preceding claims, wherein the laser arrangement (50) is configured to generate the beam (70) of photons to have a radiation wavelength in a range of 2 pm to 50 nm.

12. A positron source (10; 1000) of any one of the preceding claims, wherein the positron source (10; 1000) is configured to move the beam (70) or photons in a step-wise manner over the surface layer (40), wherein the beam (70) of photons at the surface layer (40) is substantially stationary at an instance that a pulse of photons is output from the laser arrangement (50).

13. A positron source (10; 1000) of any one of the preceding claims, wherein the electrode arrangement (160) further includes a first electrode (160A) for generating an electric field to extract positrons from the photon plasma, and one or more second electrodes (160B, 160C) for forming the positron beam (180) to be at least one of: divergent, collimated, convergent.

14. A positron source (10; 1000) of any one of the preceding claims, wherein the positron source (10; 1000) is configured for use with at least one of: an electron microscope, a positron tomography apparatus, a semiconductor manufacturing apparatus, an energy storage device, a propulsion device.

15. A method for operating a positron source (10; 1000) of any one of the preceding claims, for generating a positron beam (180) therefrom, wherein the positron source (10; 1000) includes: a laser arrangement (50) configured to generate a beam (70) of photons; a target (30) configured to receive the beam (70) of photons; an electrode arrangement (160) comprising one or more electrodes (160A, 160B, 160C); wherein at least the target (30) and the electrode arrangement (160) are included within a vacuum chamber (20); wherein the method includes: configuring the vacuum chamber (20) in use to provide a vacuum condition in which at least the target (30) and the electrode arrangement (160) are arranged to function; configuring the positron source (10; 1000) for the photons of the beam (70) to generate a photon plasma at a surface layer (40) of the target (30), wherein the surface layer (40) is configured to preferentially absorb electrons from the photon plasma to generate corresponding free positrons; and configuring the one or more electrodes (160A, 160B, 160C) to apply an electric field to the photon plasma to extract the free positrons therefrom and to guide the positrons to form the positron beam (180).

16. A software product stored on a machine-readable data carrier, wherein the software product is executable on computing hardware (2010) to implement a method of Claim 15.

17. A positron source (3010A; 3010B; 3500) for generating a positron beam (3330), wherein the positron source (3010A; 3010B, 3500) includes an optical waveguide array device (3010A; 3010B; 3500) including a substrate (3020), and at least one waveguide structure (4300, 3050A, 3050B, 3060) formed onto the substrate (3020), wherein the at least one waveguide structure (3040, 3050A, 3050B, 3060) is fabricated at least in part from a material that exhibits one or more non-linear optical effects when in use, and an electrode arrangement (3090, 3120) configured to control the one or more non-linear optical effects and to extract at least one of accelerated electrons and positrons from the at least one waveguide structure (3040, 3050A, 3050B, 3060), and wherein the optical waveguide array device (3010A; 3010B; 3500) is configured in use to separate photons input on the at least one waveguide structure (3040, 3050A, 3050B, 3060) using the one or more non-linear optical effects into their respective electrons and positrons, and to guide the respective electrons and positrons into their respective regions of the at least one waveguide structure (3040, 3050A, 3050B, 3060) to cause a matter-antimatter dipole to be formed within the at least one waveguide structure waveguide structure (3040, 3050A, 3050B, 3060) for imparting energy to at least one of the electrons and the photons to cause acceleration thereof, wherein the positrons are extracted to generate the positron beam (3330).

18. A positron source (3010A; 3010B; 3500) of Claim 17, wherein the substrate (3020) is fabricated from a dielectric material, and the material of the at least one waveguide structure (3040, 3050A, 3050B, 3060) includes at least one of: Lithium Niobate (LiNiO3), Lithium Niobate On Insulator (LNOI), Barium Niobate (BaNiO3), Graphene.

19. A positron source (3010A; 3010B; 3500) of Claim 17 or 18, wherein the substrate (3020) is fabricated from a dielectric material, optionally at least one of: quartz, fused silica, Silicon, Silicon Carbide.

20. A positron source (3010A, 3010B; 3500) of Claim 17, 18 or 19, wherein the electrode arrangement (3090, 3120) comprises a configuration of electrodes(3090, 3120) whose elongate axes are configured to be substantially parallel to, or substantially orthogonal to, elongate axes of a plurality elongate waveguides (3050A, 3050B) into which the corresponding electrons and positrons are selectively diverted when the device (3010A; 3010B; 3500) is in operation.

21. A positron source (3010A; 3010B; 3500) of Claim 20, wherein the electrode arrangement (3090, 3120) is fabricated from at least one of: Titanium, Aluminium, Indium, Silver, Gold.

22. A positron source (3010A; 3010B; 3500) of any one of Claims 17 to 21, wherein the device (3010A; 3010B; 3500) includes a plurality of the at least one waveguide structure (3040, 3050A, 3050B, 3060) arranged in a cascaded configuration.

23. A positron source (3010A; 3010B; 3500) of any one of Claims 17 to 22, wherein the device (3010A; 3010B; 3500) further includes a laser arrangement (3070) configured in use to provide photons to the at least one waveguide structure (3040, 3050A, 3050B, 3060), optionally wherein the laser arrangement (3070) is configured to function in at least one of: a continuous mode, a pulsed mode, a combination of continuous and pulsed modes.

24. A positron source (3010A; 3010B; 3500) of any one of Claims 17 to 23, wherein waveguides of the at least one waveguide structure (3040, 3050A, 3050B, 3060) are disposed in a parallel mutually spaced-apart manner with a distance (d) therebetween, wherein the distance is substantially of a similar size to a wavelength of the photons supplied to the at least one waveguide structure (3040, 3050A, 3050B, 3060) when in operation.

25. A positron source (3010A; 3010B; 3500) of Claim 24, wherein the distance (d) is configured to allow for photon coherence to be maintained for photon propagation between mutually adjacent elongate waveguides (3050A, 3050B) of the at least one waveguide structure (3040, 3050A, 3050B, 3060).

26. A method (3600) for operating a positron source (3010A; 3010B; 3500) to generate a positron beam (3330), wherein the positron source (3010A; 3010B; 3500) includes an optical waveguide array device (3010A; 3010B; 3500) including a substrate (3020), and at least one waveguide structure (3040,3050A, 3050B, 3060) formed onto the substrate (3020), wherein the method (3600) includes:(i) arranging for the at least one waveguide structure (3040, 3050A, 3050B, 3060) to be fabricated at least in part from a material that exhibits one or more non-linear optical effects when in use;(ii) optionally configuring an electrode arrangement (3090, 3120) to control the one or more non-linear optical effects and to extract at least one of accelerated electrons and positrons from the at least one waveguide structure (3040, 3050A, 3050B, 3060);(iii) configuring the optical waveguide array device (3010A; 3010B; 3500), when in use, to separate photons input on the at least one waveguide structure (3040, 3050A, 3050B, 3060) using the one or more non-linear optical effects into their respective electrons and positrons; and(iv) guiding the respective electrons and positrons into their respective regions of the at least one waveguide structure (3040, 3050A, 3050B, 3060) to cause a matter-antimatter dipole to be formed within the at least one waveguide structure waveguide structure (3040, 3050A, 3050B, 3060) for imparting energy to at least one of the electrons and the positrons to cause acceleration thereof, wherein the method further comprises extracting the positrons to form the positron beam.

27. A software product recorded on a machine-readable data carrier, wherein the software product is executable on computing hardware (3520) of the positron source (3010A; 3010B; 3500) of any one of Claims 17 to 25, to implement a method as claimed in Claim 26.

Images