A time stretched drift tube and ultrafast diagnostic system

Abstract

The application discloses a time stretching drift tube and an ultrafast diagnosis system, and relates to the technical field of ultrafast diagnosis. The time stretching drift tube comprises the following in sequence: a photocathode, a first grid, a second grid, a microchannel plate, a third grid and an anode arranged in a vacuum device; the photocathode and the first grid constitute a front-end acceleration zone, the first grid and the second grid constitute a deceleration zone, and the second grid and the microchannel plate constitute a drift zone; the microchannel plate and the third grid constitute a rear-end first acceleration zone, and the third grid and the anode constitute a rear-end second acceleration zone; a magnetic lens is arranged outside the vacuum device region corresponding to the drift zone to exert radial constraint on the electrons passing through the drift zone. The time stretching drift tube can meet the linear stretching condition and has high time stretching precision at a large stretching ratio.

Description

Technical Field

[0001] This invention relates to the field of ultrafast diagnostic technology, and in particular to a time-stretch drift tube and an ultrafast diagnostic system. Background Technology

[0002] With the continuous advancement of science and technology, such as the rapid development of quantum computing, nanotechnology, and biotechnology, increasingly higher requirements are being placed on the time resolution capability of ultrafast diagnostic equipment.

[0003] In existing technologies, there are two main approaches to improving the time resolution of ultrafast diagnostic equipment: one is to improve the equipment's structure or components to enhance its time resolution; the other is to use time stretching techniques to spatially broaden electrons, thereby improving time resolution. Due to structural limitations in existing ultrafast diagnostic equipment, the first approach is unlikely to achieve significant improvements in time resolution. Therefore, the second approach is currently commonly used to enhance the time resolution of ultrafast diagnostic equipment. Time stretching techniques primarily utilize the velocity dispersion of electrons in a time-stretching drift tube to stretch electrical signals over long timescales.

[0004] However, existing time-stretching drift tubes cannot strictly meet the requirements of linear stretching and have low time-stretching accuracy of electrons at large stretching ratios. Summary of the Invention

[0005] Therefore, it is necessary to provide a time-stretch drift tube and an ultrafast diagnostic system to address the above-mentioned technical problems. This time-stretch drift tube has high time stretching accuracy at a large stretching ratio.

[0006] The present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a time-stretching drift tube, comprising: a photocathode, a first grid, a second grid, a microchannel plate, a third grid, and an anode sequentially disposed in a vacuum device;

[0008] The photocathode and the first grid form a front-end acceleration zone, the first grid and the second grid form a deceleration zone, and the second grid and the microchannel plate form a drift zone; the microchannel plate and the third grid form a rear-end first acceleration zone, and the third grid and the anode form a rear-end second acceleration zone.

[0009] A photocathode is used to receive incident light and convert it into electrons that enter the acceleration region.

[0010] A constant electric field is applied to the acceleration zone so that electrons entering the acceleration zone at different times enter the deceleration zone with the same axial velocity.

[0011] A time-varying electric field is applied to the deceleration region so that electrons entering the deceleration region at different times enter the drift region with different axial velocities.

[0012] The drift region is an equipotential region, which stretches electrons entering the drift region at different axial velocities over time. A magnetic lens is placed outside the vacuum device region corresponding to the drift region to apply radial constraint to the electrons passing through the drift region.

[0013] The first acceleration zone at the back end is used to reduce the time dispersion of electrons emitted through the microchannel plate;

[0014] The second acceleration zone at the back end is used to further reduce electron time dispersion and prevent interference caused by induced current signals at the anode. It also converts electrons into electrical pulse signals through the anode so that they can be received by an external high-frequency oscilloscope.

[0015] In one embodiment, the time-stretch drift tube further includes a DC control module and a pulse control circuit; the DC control module applies a constant potential to the photocathode, the first grid, the second grid, the input and output surfaces of the microchannel plate, the third grid, and the anode; the DC control module or the pulse control circuit applies current to the magnetic lens; the pulse control circuit applies a pulse current to the first grid and keeps the voltage difference between the photocathode and the first grid constant.

[0016] In one embodiment, the lengths of the front acceleration zone, deceleration zone, rear first acceleration zone, and rear second acceleration zone are less than or equal to a first preset length, the length of the drift zone is less than or equal to a second preset length, and the first preset length is less than the second preset length; the difference between the lengths of the front acceleration zone and deceleration zone and the length of the drift zone is greater than a third preset length.

[0017] In one embodiment, the material of the photocathode is determined based on the incident light wavelength.

[0018] In one embodiment, the formula for calculating the transit time of electrons through the front-end acceleration region is:

[0019] d1 = v0t + a z t 2 / 2;

[0020]

[0021] a z =V pc e / md1;

[0022] Where d1 is the length of the front acceleration region, v0 is the initial axial velocity of the electron, t is the transit time of the electron through the front acceleration region, and a z Let V be the axial acceleration, E0 be the initial axial energy of the electron, m be the electron mass, e be the charge of a single electron, and V be the initial axial acceleration.pc This refers to the pressure difference in the front-end acceleration zone.

[0023] In one embodiment, the linear stretching condition of the drift region is:

[0024]

[0025] in, Let t be the change of the potential of the first grid with time t, M be the linear stretching factor of the drift region, U1(t) be the potential difference of the front acceleration region, U2(t) be the potential difference of the deceleration region, L be the length of the drift region, m be the electron mass, and e be the charge of a single electron.

[0026] In one embodiment, the formula for signal inversion using a time-stretch drift tube is expressed as:

[0027]

[0028] in, Let Ψ(t′) represent the intensity distribution of the input signal to the time-stretched drift tube, Ψ(t′) represent the signal intensity distribution after time stretching through the drift region, and M(t) represent the linear stretching factor of the drift region.

[0029] The present invention provides an ultrafast diagnostic system, which includes the time-stretch drift tube described in any of the embodiments of the first aspect above.

[0030] The above-mentioned at least one technical solution adopted in this invention can achieve the following beneficial effects:

[0031] In this invention, by setting a grid structure, electrons have better transmittance, and by applying radial constraint to electrons in the drift region through a magnetic lens, electrons are stretched axially without radial expansion, thus improving time stretching accuracy. Furthermore, after electrons undergo time stretching in the drift region, they are passed through the first and second acceleration regions at the rear end, reducing time dispersion caused by electrons exiting the drift region and further improving time stretching accuracy. In addition, setting a third grid between the microchannel plate and the anode can effectively prevent the induced current formed by electrons exiting the microchannel plate at the anode, improving the anti-interference capability of the rear end and effectively enhancing the accuracy of the electrical signal received by the anode. Attached Figure Description

[0032] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0033] Figure 1 This is a schematic diagram of the structure of a time-stretching drift tube provided by the present invention;

[0034] Figure 2 A schematic diagram of the applied voltage of each component in a time-stretching drift tube provided by the present invention;

[0035] Figure 3 A schematic diagram of electronic time stretching in the drift region of a time-stretched drift tube provided by the present invention.

[0036] Figure 4 This invention provides a schematic diagram of the derivation and inversion of pulse signal changes.

[0037] Figure 5 This invention provides a schematic diagram of the current curves collected at the anode at different triggering times.

[0038] Explanation of reference numerals in the attached figures:

[0039] 101. Vacuum device; 102. Photocathode; 103. First grid; 104. Second grid; 105. Microchannel plate; 106. Third grid; 107. Anode; 108. Magnetic lens. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0041] The Compton effect refers to the scattering of incident high-energy photons through inelastic collisions with electrons in atoms. High-energy photons (such as gamma rays) transfer some energy to electrons, causing them to detach from the atom and become recoil electrons, thus changing the photon's energy and direction of motion. Inverse Compton scattering is similar to Compton scattering, both being scattering phenomena between photons and free electrons, but the energy transfer is in the opposite direction. In Compton scattering, energy is transferred from photon to electron, while inverse Compton scattering, energy is transferred from electron to photon.

[0042] Time stretching technology mainly utilizes the velocity dispersion of electrons in a vacuum drift tube to stretch electrical signals over a long time scale. This method can convert ultrashort pulse time scales into longer time scales.

[0043] Therefore, to address the demand for ultrafast diagnostic equipment in various ultrafast radiation detection fields such as inverse Compton scattering sources, laser plasma, and Betatron radiation sources—specifically, the need to extract as much comprehensive physical information as possible, including spatial and intensity information, during reaction processes on nanosecond or even sub-nanosecond timescales—a miniature time-stretching drift tube for ultrafast diagnostic systems is proposed. This time-stretching drift tube features a novel structure that achieves linear stretching while significantly improving the accuracy of the detection signal.

[0044] The technical solutions provided by the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0045] Figure 1 This is a schematic diagram of the structure of a time-stretch drift tube according to the present invention. The time-stretch drift tube specifically includes: a photocathode 102, a first grid 103, a second grid 104, a microchannel plate 105, a third grid 106, and an anode 107, which are sequentially arranged in a vacuum device 101.

[0046] The photocathode 102 and the first grid 103 form a front-end acceleration region, the first grid 103 and the second grid 104 form a deceleration region, and the second grid 104 and the microchannel plate 105 form a drift region; the microchannel plate 105 and the third grid 106 form a rear-end first acceleration region, and the third grid 106 and the anode 106 form a rear-end second acceleration region; a magnetic lens 108 is provided outside the vacuum device area corresponding to the drift region to apply radial constraint to electrons passing through the drift region.

[0047] The photocathode receives incident light and converts it into electrons that enter the acceleration region. A constant electric field is applied to the front acceleration region to ensure that electrons entering the acceleration region at different times enter the deceleration region with the same axial velocity. A time-varying electric field is applied to the deceleration region to ensure that electrons entering the deceleration region at different times enter the drift region with different axial velocities. The drift region is an equipotential region, which stretches the electrons entering the drift region with different axial velocities over time. The rear first acceleration region reduces the time dispersion of electrons emitted through the microchannel plate. The rear second acceleration region further reduces electron time dispersion while preventing interference from the anode caused by induced current signals. The anode converts electrons into electrical pulse signals for reception by an external high-frequency oscilloscope. The anode is the electron receiving electrode.

[0048] Specifically, the time-stretching principle of this time-stretching tube is as follows: Visible light (incident light) irradiates the photocathode, generating photoelectrons. These photoelectrons are accelerated by the cathode and the first grid M1 before entering a deceleration region (from the first grid M1 to the second grid M2) with a time-varying electric field. Between the first grid M1 and the second grid M2, the photoelectrons are subjected to the time-varying electric field. Photoelectrons generated at different times enter the drift region (from the second grid M2 to the input surface of the microchannel plate, MCP) with different axial velocities. Since the drift region is an equipotential region, the electrons move at a uniform speed axially. The distance between electrons with different axial velocities is increased, thus achieving time stretching. Time stretching technology can effectively reduce the time resolution requirements of diagnostic equipment during ultrafast diagnostics. That is, the source signal only needs to cross the ramp interval of the ramp loading signal to achieve a fixed stretching ratio, without needing to determine the specific loading time, greatly simplifying the physical system design and making signal synchronization easier. Furthermore, the stretched signal only needs to undergo two steps—signal linear compression and amplification—to easily obtain the source signal.

[0049] The physical process of electron motion in the time-stretched drift tube of this invention is as follows: The photocathode receives incident light radiation, converts photons into electrons, and retains their time-intensity information. The electrons generated by the photocathode are axially accelerated through the front acceleration region (loaded with an electrostatic field, i.e., constant voltage) and then enter the deceleration region. The deceleration region is loaded with a time-varying electric field, so that the electrons entering the region first experience less axial deceleration than the electrons entering the region later. Therefore, electrons in the electron beam at different times will experience velocity dispersion and enter the drift region. The drift region is the main area of ​​time stretching, which allows the electron beam to be fully stretched on the time scale. The stretched electron beam bombards the MCP input surface and, after electron multiplication, is output from the MCP output surface and enters the rear-end first-stage acceleration region (rear-end first acceleration region). Then it enters the rear-end second-stage acceleration region (rear-end second acceleration region) and bombards the anode, converting it into an electrical pulse signal that is detected by an external high-frequency oscilloscope. Therefore, the photoelectrons generated by the photocathode successively experience the front acceleration region, deceleration region, drift region, MCP electron multiplication, rear-end first-stage acceleration region, and rear-end second-stage acceleration region.

[0050] In this time-stretching drift tube, all components except the magnetic lens are in a high-vacuum environment, i.e., within a vacuum device. The high-vacuum state inside the vacuum device is approximately 10... -5 Pa. The magnetic lens is a long magnetic lens, and there may be two long magnetic lenses, which are placed on the upper and lower sides outside the drift region, respectively.

[0051] Optionally, the material of the photocathode is determined based on the incident light wavelength. Incident light irradiates the photocathode, generating photoelectrons through the external photoelectric effect. The material of the photocathode can be selected according to the incident light wavelength, including materials such as gold, potassium-sodium-cesium-antimony compounds (KNaCsSb), or gallium arsenide (GaAs). Similarly, the photocathode is fabricated on the inner surface of the input window. For example, different input window materials selectively transmit different wavelengths of light; quartz glass transmits ultraviolet light, but ordinary glass does not. The input window material must be selected according to the incident light wavelength, such as leaded glass or quartz glass.

[0052] After being stretched, the electron beam is multiplied by the MCP element and accelerated by the two-stage acceleration zone at the rear end before bombarding the anode (the anode material can be a metal such as aluminum or gold). The beam is then acquired by an external high-frequency oscilloscope. The function of the third grid M3 at the rear end is to provide the rear-end accelerating electric field and shield the induced current signal of the anode receiving stage, thereby improving the accuracy of the acquired signal and reducing interference.

[0053] The overall size of this time-stretch drift tube is approximately Ф75mm×150mm, which is much smaller than traditional pulse broadening tubes and other diagnostic equipment.

[0054] By studying the first and last electrons in the emitted electron beam, the entire generation and transport process of electrons in the time-stretched drift tube is analyzed, including the acceleration of electrons emitted from the photocathode in the front acceleration zone, the deceleration in the deceleration zone, the stretching in the drift zone, the multiplication in the MCP device, the acceleration of electrons in the first acceleration zone at the rear end, and the acceleration of electrons in the second acceleration zone at the rear end, which bombard the metal anode to form an electrical pulse signal that is detected and recorded by an external high-frequency oscilloscope.

[0055] A constant electric field is applied between the photocathode and M1, which can effectively reduce the time dispersion caused by the axial energy distribution of electrons emitted from the photocathode. This allows electrons entering the deceleration zones of M1 and M2 at different times to have nearly the same axial velocity. At the same time, based on the grid structure, the ramp pulse can effectively pass through the core region of electron motion, forming an effective time-varying deceleration electric field, thereby creating velocity dispersion.

[0056] The time-stretch drift tube also includes a DC control module and a pulse control circuit; the DC control module applies a constant potential to the photocathode, the first grid, the second grid, the input and output surfaces of the microchannel plate, the third grid, and the anode; the DC control module or the pulse control circuit applies current to the magnetic lens; the pulse control circuit applies a pulse current to the first grid and keeps the voltage difference between the photocathode and the first grid constant.

[0057] Keeping the voltage difference between the photocathode and the first grid constant, a time-varying decelerating electric field is generated between the first grid and the second grid. In this field, the axial acceleration of electrons in the front acceleration region is consistent and does not change with the time of electron generation. It is only related to the axial component of the initial energy distribution of the electrons.

[0058] Optionally, such as Figure 2 As shown, a constant voltage of -2V can be applied to the photocathode via a DC control module, a constant voltage of -1V can be applied to the input surfaces of the first grid, the second grid, and the microchannel plate, a constant voltage of 0V can be applied to the output surface of the microchannel plate, a constant voltage of 1V can be applied to the third grid, and a constant voltage of 2V can be applied to the anode. A current can be applied to the magnetic lens via a DC control module or a pulse control circuit. The magnetic lens can determine the current based on the applied current and the number of windings to ensure that the magnetic field strength is 120 Gauss. The pulse control circuit applies a ramp pulse current to the first grid.

[0059] Furthermore, in this invention, the first grid, the second grid, and the third grid adopt a grid structure with a grid width of 10um+ / -0.5um and a grid size of 40um+ / -0.5um. This ensures that the electron transmittance reaches more than 60% while effectively guaranteeing the formation of the electric field.

[0060] A constant electric field is applied between the photocathode and the first grid M1, which effectively reduces the time dispersion caused by the axial energy distribution of electrons emitted from the photocathode. This ensures that electrons entering the deceleration regions of the first grid M1 and the second grid M2 at different times have nearly the same axial velocity. Simultaneously, based on the grid structure, the ramp pulse can effectively pass through the core region of electron motion, forming an effective time-varying deceleration electric field, thus creating velocity dispersion. When the ramp pulse propagates on the second grid M2, a good time-varying electric field is also generated in the central region through which the electrons pass.

[0061] The time stretching of the electron beam is mainly concentrated in the drift region, and the electron transit time is also mainly concentrated in the drift region, on the order of nanoseconds. Therefore, a radial constraint needs to be applied to the electron beam. Otherwise, the electron beam spot will expand radially due to space charge effects, etc., and the electron beam spot acting on the anode signal receiving electrode will become larger, that is, the electron transit time will become more diffuse, resulting in a larger error in the detection result. Therefore, a magnetic lens is set outside the drift region to apply radial constraint to the electrons passing through the drift region, thereby improving the accuracy of time stretching in the time stretching drift tube.

[0062] Microchannel plates (MCPs) are used for electrical signal enhancement; therefore, the time-stretch drift tube of the present invention can be used for weak signal detection.

[0063] The advantages of setting the third grid M3 are: ① Based on the energy distribution of MCP emitted electrons, most of them are low-energy electrons, so their axial emission velocity is low, which will lead to an increase in time dispersion. The existence of the M3 structure plays a post-acceleration role, which is used to reduce the accuracy of the detection results caused by the time dispersion of MCP emitted electrons; ② The existence of M3 can effectively prevent the induced current formed by MCP emitted electrons at the anode, that is, it has anti-interference capability and can effectively improve the accuracy and sensitivity of the electrical signal received by the receiving electrode.

[0064] In one embodiment, the lengths of the front acceleration zone, deceleration zone, rear first acceleration zone, and rear second acceleration zone are less than or equal to a first preset length, the length of the drift zone is less than or equal to a second preset length, and the first preset length is less than the second preset length; the difference between the lengths of the front acceleration zone and deceleration zone and the length of the drift zone is greater than a third preset length.

[0065] Furthermore, the lengths of the front acceleration and deceleration zones should be much shorter than the length of the drift zone. For example, the difference between the lengths of the front acceleration and deceleration zones and the drift zone can be set to be greater than a third preset length. The third, second, and third preset lengths can all be set according to requirements. For example, the lengths of the front acceleration zone, deceleration zone, and the first and second rear acceleration zones should all be no greater than 2mm, and the length of the drift zone should be no greater than 120mm.

[0066] In one embodiment, the formula for calculating the transit time of electrons through the front-end acceleration region is:

[0067] d1 = v0t + a z t 2 / twenty one)

[0068]

[0069] a z =V pc e / md1 (3)

[0070] Where d1 is the length of the front acceleration region, v0 is the initial axial velocity of the electron, t is the transit time of the electron through the front acceleration region, and a z Let V be the axial acceleration, E0 be the initial axial energy of the electron, m be the electron mass, e be the charge of a single electron, and V be the initial axial acceleration. pc This refers to the pressure difference in the front-end acceleration zone.

[0071] In one embodiment, the linear stretching condition of the drift region is:

[0072]

[0073] in, Let t be the change of the potential of the first grid with time t, M be the linear stretching factor of the drift region, U1(t) be the potential difference of the front acceleration region, U2(t) be the potential difference of the deceleration region, L be the length of the drift region, m be the electron mass, and e be the charge of a single electron.

[0074] Specifically, the derivation process of the linear stretching condition in the drift region is as follows:

[0075] Compared to the drift region, the lengths of the acceleration and deceleration regions at the front are much shorter than the drift region, and the velocity difference between the electrons at the beginning and end of the electron beam cluster does not reach its maximum. Therefore, the main stretching region of the electron beam is the drift region. An analysis of the linear stretching in the drift region is conducted, as follows... Figure 3 As shown, Figure 3 This is a schematic diagram of electron time stretching in the drift region. dt is the time difference between the first and last electrons when the electron beam enters the drift region. The drift time of the first electron in the electron beam from entering the drift region to completely leaving the drift region is t0, and the drift time of the last electron is t1. M is the time stretching factor of the drift region.

[0076] Among them, t i The time when an electron entering the drift region from the second grid M2 reaches the input surface of the microchannel plate MCP is t′. i Then we have:

[0077]

[0078] Where L is the length of the drift region, eV(t) i ) for t i The axial energy of the incident electron at time t, neglecting the effect of the electron's space charge, is given. The axial velocity of the electron entering the drift region is related to its axial energy. For any two times t... a , t b (t a <t b The time stretching factor when electrons emitted from M2 reach the MCP input surface is:

[0079]

[0080] Taking the limit of both sides of formula (8), if we want M(t) to be equal to... a , t b If ) is a constant, i.e., linear stretching, then:

[0081]

[0082] Inferred:

[0083]

[0084] Solve the differential equation:

[0085] [V(t)′] 2 =K 2 V(t) 3 (11)

[0086]

[0087] V(t) is the voltage value of the first grid M1.

[0088] Calculated using the initial condition V(0) = 1kV, U1(t) = 1kV, M2 potential Finally, the potential of M1 is obtained. for:

[0089]

[0090] Substituting M = 50 and formula (13) back into formula (10), we get K ≈ 5.8 × 10⁻⁶. 8 To obtain the linear tensile condition:

[0091]

[0092] In one embodiment, the formula for signal inversion using a time-stretch drift tube is expressed as:

[0093]

[0094] in, Let Ψ(t′) represent the intensity distribution of the input signal to the time-stretched drift tube, Ψ(t′) represent the signal intensity distribution after time stretching through the drift region, and M(t) represent the linear stretching factor of the drift region.

[0095] If it is an ideal linear stretching process, then the inverted signal will be the accurate source signal. Let the source signal at time t... a To t b The time interval enters the drift region, and the intensity distribution is as follows: The time interval during which the signal reaches the end of the drift region after being stretched is t′. a to t′ b The corresponding intensity distribution is Ψ(t′). a →t′ b According to the law of conservation of charge and t′ b -t′ a / t b -t a =M(t), taking the limit of both sides, we get formula (15).

[0096] In an exemplary embodiment, a Gaussian reference source signal is defined with a full width at half maximum (FWHM) of 10 ps, ​​a standard deviation (σ) of 4.25 ps, and a μ of 20 ps. The derivation and inversion of pulse signals, such as Figure 4 As shown, the reference source signal is as follows Figure 4 As shown in Figure (a), the anode collector signal was obtained using Computer Simulation Technology (CST) software under the conditions of a photocathode voltage of 1 kV, drift region length L = 100 mm, and signal trigger time ttrig = 20 ps. The source signal obtained after inversion is shown in Figure (a). Figure 4 As shown in Figure (b), the curve obtained after inversion is basically consistent with the curve of the reference source signal.

[0097] Considering single-pulse cases with different trigger times, the pulse generation time falls within the time window of a linearly stretched electrical pulse, such as... Figure 5 As shown, the anode and collector current curves were obtained at different trigger times, ranging from 0 ps to 100 ps, ​​with an interval of 10 ps. Figure 5 It can be seen that the current curve waveforms between 10ps and 40ps are relatively consistent, and the stretching factor is relatively stable.

[0098] This invention provides a miniature time-stretch drift tube for use in ultrafast diagnostic systems, aiming to meet the needs of more efficient detection and lower system construction costs in ultrafast testing and diagnostics of devices such as inverse Compton scattering sources, laser plasmas, and Betatron radiation sources, simplifying system design. Based on the time-stretching principle, this miniature time-stretch drift tube utilizes linear stretching conditions. The source signal only needs to cross the ramp interval of the ramp loading signal to achieve a fixed stretching ratio, eliminating the need to determine the specific loading time. This greatly simplifies the physical system design and makes signal synchronization easier. Furthermore, the stretched signal only requires two steps—linear signal compression and amplification—to easily obtain the source signal. This invention reduces costs, shrinks size (miniaturization), and improves the integration of beam diagnostics, providing an innovative solution for experimental research and industrial applications in related fields.

[0099] Based on the principle of time stretching, this invention calculates the motion state of electrons in a spatial field, conducts physical design of a small time stretching drift tube, and then obtains detailed linear stretching conditions through numerical calculation. It can also inversely derive the original signal based on the electrical pulse pattern received by the anode, thus realizing the detection of picosecond and even femtosecond pulse rays at a large stretching ratio.

[0100] The present invention proposes a small time-stretch drift tube for use in ultrafast diagnostic systems. Its time stretching characteristic is linear time stretching, which simplifies the physical design of the corresponding diagnostic system and facilitates the inversion of source signal information.

[0101] In one exemplary embodiment, an ultrafast diagnostic system is provided, which includes the time-stretch drift tube described in any of the above embodiments.

[0102] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this invention.

Claims

1. A time-stretching drift tube, characterized in that, include: A photocathode, a first grid, a second grid, a microchannel plate, a third grid, and an anode are sequentially arranged in a vacuum device. The photocathode and the first grid form a front-end acceleration zone, the first grid and the second grid form a deceleration zone, and the second grid and the microchannel plate form a drift zone; the microchannel plate and the third grid form a rear-end first acceleration zone, and the third grid and the anode form a rear-end second acceleration zone. The photocathode is used to receive incident light and convert the incident light into electrons that enter the front-end acceleration region; A constant electric field is applied to the front-end acceleration zone so that electrons entering the front-end acceleration zone at different times enter the deceleration zone with the same axial velocity. The deceleration zone is loaded with a time-varying electric field so that electrons entering the deceleration zone at different times enter the drift zone with different axial velocities. The drift region is an equipotential region, which stretches electrons entering the drift region at different axial velocities over time; a magnetic lens is provided outside the vacuum device region corresponding to the drift region to apply radial constraint to the electrons passing through the drift region. The first acceleration zone at the rear end is used to reduce the time dispersion of electrons emitted through the microchannel plate; The second acceleration zone at the rear end is used to further reduce electron time dispersion and prevent the anode from being interfered with by the induced current signal, and to convert electrons into electrical pulse signals through the anode so that they can be received by an external high-frequency oscilloscope. The linear stretching condition of the drift region is: ； ； ； in, The potential of the first grid over time t Changes, M The linear stretching factor of the drift region. The potential difference in the front-end acceleration region. The potential difference in the deceleration zone. The length of the drift region, For electronic quality, The charge of a single electron. K It is a constant. .

2. The time-stretching drift tube according to claim 1, characterized in that, The time-stretch drift tube also includes a DC control module and a pulse control circuit; the DC control module applies a constant potential to the photocathode, the first grid, the second grid, the input and output surfaces of the microchannel plate, the third grid, and the anode; and the DC control module or the pulse control circuit applies current to the magnetic lens. The pulse control circuit applies a pulse current to the first grid while maintaining a constant voltage difference between the photocathode and the first grid.

3. The time-stretching drift tube according to claim 1, characterized in that, The lengths of the front acceleration zone, the deceleration zone, the rear first acceleration zone, and the rear second acceleration zone are less than or equal to a first preset length, the length of the drift zone is less than or equal to a second preset length, and the first preset length is less than the second preset length; the difference between the lengths of the front acceleration zone and the deceleration zone and the length of the drift zone is greater than a third preset length.

4. The time-stretching drift tube according to claim 1, characterized in that, The photocathode is made of gold, potassium sodium cesium antimony compounds, or gallium arsenide.

5. The time-stretching drift tube according to claim 1, characterized in that, The formula for calculating the transit time of electrons through the aforementioned front-end acceleration region is as follows: ； ； ； in, The length of the front-end acceleration area. Let be the initial axial velocity of the electron. The transit time of electrons through the aforementioned front-end acceleration region. For axial acceleration, Let be the initial axial energy of the electron. For electronic quality, The charge of a single electron. This refers to the pressure difference in the front-end acceleration zone.

6. The time-stretching drift tube according to claim 1, characterized in that, The formula for signal inversion using the time-stretch drift tube is expressed as follows: ； in, The intensity distribution of the input signal to the time-stretched drift tube. The signal strength distribution after time stretching through the drift region. This represents the linear stretching factor of the drift region.

7. An ultrafast diagnostic system, characterized in that, The system includes a time-stretch drift tube as described in any one of claims 1-6.

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