Hybrid four-beam ion accelerator

Abstract

The invention relates to the technical field of synchronous accelerators, in particular to a mixed four-beam ion accelerator which comprises an ion source, a radio frequency quadrupole field accelerator, a focusing device and a target chamber which are arranged in sequence, and the ion source is used for continuously generating N kinds of ion beams with different mass-to-charge ratios; the radio frequency quadrupole field accelerator is provided with N beam hole channels and is used for accelerating the N ion beams with different mass-to-charge ratios at the same time; the focusing and bunching device is provided with a conical solenoid so as to converge the N accelerated ion beams with different mass-to-charge ratios into one beam to form an ion beam mixed with different mass-to-charge ratios; the target chamber is used for placing a target material and injecting the mixed ion beam; the ion source of the ion accelerator can generate ion beams with different mass-to-charge ratios, and enables the beams with different mass-to-charge ratios to realize different acceleration effects to obtain beams with different energies, and the beams are converged and hit into the target chamber, so that the flexibility is higher.

Description

Technical Field

[0001] The present application relates to the technical field of synchrotron accelerators, and in particular to a hybrid four-beam ion accelerator. Background Art

[0002] Ion implantation is a method of doping semiconductors and surface treating metals. Impurities are ionized into ions and focused into an ion beam. After being accelerated in an electric field to obtain extremely high kinetic energy, they are injected into the material to achieve doping.

[0003] Existing ion accelerators mostly use serial and electrostatic acceleration methods, and are composed of multiple accelerators and ion sources. Their beam intensity is relatively low, and there are certain limitations in the selection of ion types. Summary of the invention

[0004] Based on the above technical problems, the present application provides a hybrid four-beam ion accelerator, which can inject ions with different mass-to-charge ratios and has high flexibility.

[0005] The technical solution provided by this application is:

[0006] A hybrid four-beam ion accelerator comprises an ion source, a radio frequency quadrupole accelerator, a focusing device and a target chamber which are arranged in sequence, wherein:

[0007] An ion source, used for continuously generating N ion beams with different mass-to-charge ratios;

[0008] A radio frequency quadrupole accelerator is provided with N beam channels for simultaneously accelerating N ion beams of different mass-to-charge ratios;

[0009] A focusing and bunching device is provided with a conical solenoid to converge the N accelerated ion beams of different mass-to-charge ratios into one beam to form an ion beam mixed with different mass-to-charge ratios;

[0010] The terminal target chamber is used to place the target material and inject the mixed ion beam.

[0011] In an optional embodiment, a radio frequency quadrupole accelerator is provided with an accelerating cavity, M stem-ring electrodes and N rod electrode groups, each rod electrode group is provided with four rod electrodes, and the four rod electrodes are arranged correspondingly to form a beam channel, the M stem-ring electrodes are respectively distributed at equal intervals along the beam channel, and each stem-ring electrode is connected to the accelerating cavity, and N through openings are symmetrically opened in the stem-ring electrode, each through opening is corresponding to a rod electrode group passing through, and each rod electrode group is respectively connected to the stem-ring electrode.

[0012] In an optional embodiment, the energy change of a particle after one acceleration unit in a radio frequency quadrupole accelerator follows the following expression:

[0013] ΔW=qE0 TI 0 (κa)l cosφ s ;

[0014]

[0015] Where T is the transit time factor, φ s is the synchronization phase, E 0 is the average value of the electric field peak in an accelerating unit, V is the inter-electrode voltage, A is the parameter representing the accelerating ability of the RF quadrupole field, m is the electrode modulation parameter, a is the minimum aperture of the beam channel, βλ is the modulation period, and λ is the RF wavelength.

[0016] In an optional embodiment, the accelerating cavity is provided with a plurality of groups of tuner assemblies distributed at equal intervals, each group of tuner assemblies is provided with two couplers, and the two couplers are symmetrically arranged on both sides of the accelerating cavity.

[0017] In an optional embodiment, a cooling water circuit is symmetrically provided on the surface of the accelerating cavity.

[0018] In an optional embodiment, the ion source is provided with N laser ion sources, one laser ion source is correspondingly arranged at the entrance of one beam channel, and the mass-to-charge ratios of ions excited by the N laser ion sources are different.

[0019] In an optional embodiment, each laser ion source includes an inner target chamber, a laser, a first plane mirror, a second plane mirror, a plano-convex lens, a target material surface and a drift pipe. The laser and the first plane mirror are arranged outside the inner target chamber to direct the laser beam into the inner target chamber. The second plane mirror, the plano-convex lens and the target surface are arranged in the inner target chamber. After passing through the second plane mirror and the plano-convex lens, the laser beam is focused on the target material surface to generate plasma. The drift pipe is arranged at the entrance of the beam channel to allow the plasma to drift to the entrance of the beam channel.

[0020] In an optional embodiment, the inlet of the conical solenoid is connected to the outlet of the beam channel.

[0021] The beneficial effects of this technical solution are as follows:

[0022] The ion source of the ion accelerator can generate ions of different valence states, and the mass-to-charge ratios (M / q) of ion beams of different valence states are different, that is, they can be composed of ions of any element, which provides flexibility for the composition combination of the final ion beam; the radio frequency quadrupole field accelerator is provided with N beam channels in the cavity, each beam channel corresponds to accelerating an ion beam, and multiple beam channels can respectively accelerate ion beams of different mass-to-charge ratios, and at the same time, beams of different mass-to-charge ratios can achieve different acceleration effects, and beams of different energies are obtained, and the beam intensity can reach the milliampere level. In other words, each ion beam is accelerated and preliminarily and individually bunched and focused in the corresponding beam channel of the radio frequency quadrupole field accelerator; N kinds of ion beams enter the focusing and bunching device at the same time, and the N kinds of ion beams are mixed into one beam in the structure of the focusing and bunching device, and focusing and bunching are achieved in the structure, similar to the ion beam of a "cocktail beam", and finally the ion beam line of the mixed "cocktail beam" is injected into the target chamber through the outlet end of the conical solenoid to achieve ion implantation or material irradiation of related materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the structure of an ion accelerator according to an embodiment of the present application;

[0024] Figure 2 A schematic diagram of the structure of a laser ion source according to an embodiment of the present application;

[0025] Figure 3 A schematic diagram of the three-dimensional structure of a radio frequency quadrupole field accelerator according to an embodiment of the present application;

[0026] Figure 4 A schematic diagram of a longitudinal cross-sectional structure of a radio frequency quadrupole field accelerator according to an embodiment of the present application;

[0027] Figure 5 This is a schematic diagram of the transverse cross-sectional structure of the radio frequency quadrupole field accelerator according to an embodiment of the present application.

[0028] Explanation of the reference numerals: ion source 1, laser ion source 110, inner target chamber 111, laser 112, first plane mirror 113, second plane mirror 114, plano-convex lens 115, target surface 116, drift pipe 117, radio frequency quadrupole accelerator 2, accelerating cavity 210, stem-ring electrode 220, rod electrode group 230, rod electrode 231, tuner assembly 240, coupler 241, cooling water loop 250, focusing and beam-forming device 3, conical solenoid 310, terminal target chamber 4. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0030] In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other. For ease of description, the concepts of "first", "second", etc. mentioned in this application are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence of the functions performed by these devices, modules or units. The modifications of "one" and "multiple" mentioned in this application are illustrative and non-restrictive, and those skilled in the art should understand that unless otherwise clearly stated in the context, it should be understood as "one or more".

[0031] The specific implementation of the present application is described in detail below with reference to the accompanying drawings.

[0032] refer to Figure 1 The embodiment of the present application provides a hybrid four-beam ion accelerator, comprising an ion source 1, a radio frequency quadrupole field accelerator 2, a focusing device and a target chamber 4 arranged in sequence, wherein:

[0033] An ion source 1, used for continuously generating N ion beams with different mass-to-charge ratios; in this embodiment, there are four ion beams;

[0034] A radio frequency quadrupole field accelerator 2 is provided with N beam channels for simultaneously accelerating N ion beams with different mass-to-charge ratios;

[0035] The focusing and bunching device 3 is provided with a conical solenoid 310 to converge the N accelerated ion beams with different mass-to-charge ratios into one beam to form an ion beam mixed with different mass-to-charge ratios;

[0036] The terminal target chamber 4 is used to place the target material and inject the mixed ion beam.

[0037] Compared with the prior art, the ion source 1 of the ion accelerator of the embodiment of the present application can generate ions of different valence states, and the mass-to-charge ratio (M / q) of ion beams of different valence states is different, that is, it can be composed of ions of any element, which provides flexibility for the composition combination of the final ion beam; the radio frequency quadrupole accelerator 2 is provided with N beam channels in the cavity, each beam channel corresponding to the acceleration of an ion beam, and multiple beam channels can accelerate ion beams of different mass-to-charge ratios respectively, and at the same time, beams of different mass-to-charge ratios can achieve different acceleration effects, and beams of different energies can be obtained. The beam intensity can reach the milliampere level. In other words, each ion beam is accelerated and preliminarily and individually bunched and focused in the corresponding beam channel of the radio frequency quadrupole accelerator 2; N kinds of ion beams enter the focusing and bunching device 3 at the same time, and in the structure of the focusing and bunching device 3, the N kinds of ion beams are mixed into one beam, and focusing and bunching are achieved in the structure, similar to the ion beam of a "cocktail beam". Finally, the ion beam line of the mixed "cocktail beam" is injected into the target chamber 4 through the outlet end of the conical solenoid 310 to achieve ion implantation or material irradiation of the relevant materials. The "cocktail beam" in the embodiment of the present application can be seen in FIG. Figure 1 The conical solenoid part in the middle shows the shape of the ion beam. Beams of various different mass-to-charge ratios are introduced from the inlet end of the conical solenoid 310 , and then converge into one beam at the outlet end under the action of the conical solenoid 310 and enter the target chamber 4 .

[0038] like Figure 1 As shown, the focusing and bunching device 3 is made of a conical solenoid 310. In this structure, four ion beams are injected into the solenoid, focused, and converged to a point at the end of the solenoid. The entrance of the conical solenoid 310 is connected to the exit of the beam channel. In the embodiment of the present application, N is 4. Four ion beams with different charge-to-mass ratios converge into one beam at the end of the focusing system to form a mixed ion beam. Finally, the focused mixed ion beam hits the target.

[0039] like Figure 3 , Figure 4 and Figure 5 It is shown that the radio frequency quadrupole accelerator 2 in the embodiment of the present application is provided with an accelerating cavity 210, M stem-ring electrodes 220 and N rod electrode 231 groups 230, each rod electrode 231 group 230 is provided with four rod electrodes 231, and the four rod electrodes 231 are correspondingly arranged to form a beam channel, the M stem-ring electrodes 220 are respectively distributed at equal intervals along the beam channel, and each stem-ring electrode 220 is connected to the accelerating cavity 210, and the stem-ring electrode 220 is symmetrically provided with N through openings, each through opening correspondingly allows a rod electrode 231 group 230 to pass through, and each rod electrode 231 group 230 is respectively connected to the stem-ring electrode 220.

[0040] It should be noted that the radio frequency quadrupole accelerator 2 uses symmetrically placed rod electrodes 231, and applies equal and opposite alternating voltages to the relative electrodes and the adjacent electrodes, respectively, to form beam channels for accelerating ion beams. Multiple beam channels are evenly distributed in the stem-ring electrode 220, and the symmetrical structure reduces cavity detuning. M and N are both positive integers, and M can be set according to the acceleration requirements, such as Figure 5 As shown, in the embodiment of the present application, N is 4, and 4 beam channels are also designed, that is, the radio frequency quadrupole accelerator 2 is designed with 4 beam channels in one cavity, which can accelerate 4 ion beams with different charge-to-mass ratios at the same time.

[0041] Further explanation, according to the acceleration principle of the radio frequency quadrupole accelerator 2 in the embodiment of the present application, the energy change of the particle after one acceleration unit in the radio frequency quadrupole accelerator follows the following expression:

[0042] ΔW=qE 0 TI 0 (κa)l cosφ s ;

[0043]

[0044] Among them, ΔW is the energy change of the particle after one acceleration unit, T is the transit time factor, φ s is the synchronization phase, E 0 is the average value of the electric field peak value in an accelerating unit, V is the inter-electrode voltage, A is the parameter representing the acceleration capability of the RF quadrupole field, m is the electrode modulation parameter, a is the minimum aperture of the beam channel, βλ is the modulation period, λ is the RF wavelength, and I 0 () is the zero-order Bessel function, q is the charge number of the particle (that is, the charge number of the ion), and l is the length of an acceleration unit.

[0045] In the above formula, l = β s λ / 2,β s is the speed of the synchronization particle, and λ is the radio frequency wavelength.

[0046] In the design of the radio frequency quadrupole accelerator 2 in the embodiment of the present application, the electrode modulation parameter m, the minimum beam aperture a and the synchronization phase φ s It is an adjustable parameter, and other parameters will be determined at the beginning of the design. Therefore, following the above formula, before the equipment is operated, it is determined to adjust different electrode modulation parameters, beam aperture and synchronization phase to obtain different longitudinal acceleration parameters, and combine beams with different charge-to-mass ratios to achieve different acceleration effects and obtain beams with different energies.

[0047] The derivation process of the parameter A of the radio frequency quadrupole field (RFQ) acceleration capability in the above embodiment of the present application can be seen as follows:

[0048] The potential function of the RFQ accelerator in the embodiment of the present application is crucial for solving the geometry of the equipotential surfaces of the electrodes and the inter-electrode electric field. The electromagnetic field distribution between the modulated electrodes in the RFQ accelerator can be described by Maxwell's equations:

[0049]

[0050] in, is the electric field strength, is the magnetic induction intensity, is the electric vector displacement, is the magnetic field strength, is the current density, and ρ is the charge density. When the distance between the electrode and the beam axis is less than the RF wavelength, the distribution of the electromagnetic field can be regarded as a quasi-static approximation, that is, The quasi-static approximation method can be used to simplify Maxwell's equations into two independent equations containing only the electric field and the magnetic field. Since only the electric field distribution is of concern in RFQ, when studying beam dynamics, it is only necessary to solve One equation is sufficient, which greatly simplifies the calculation process. Using the cylindrical coordinate system, the potential U can be expressed as Among them, u(r,θ,z) is the potential function, ω is the angular frequency of the potential change, is the initial phase, according to the relationship between electric field and potential It can be obtained that u(r,θ,z) satisfies the Laplace equation:

[0051]

[0052] This equation in cylindrical coordinates can be written as:

[0053] By solving the Laplace equation, the expression of the potential function can be obtained as follows:

[0054]

[0055] Where n+s=2q+1(q=0,1,2……). The above equation is called the general potential function, I 2s (nkr) is called the modified Bessel function of the 2s order. This potential function can be used to calculate the electric field near the beam. This equation contains all high-order terms. Although it can reflect the electric field distribution formed by an electrode cross section of any shape, it is very troublesome to solve the coefficients of the high-order terms. In actual solutions, only the first few terms are needed to meet the accuracy requirements. The most commonly used potential binomial potential function is used. Taking s = 0 and n = 1, the expression of the RFQ binomial potential function is:

[0056] u(r,θ,z)=A 01 r 2cos(2θ)+A 10 I 0 (kr)cos(kz);

[0057] The first term is independent of z and reflects the transverse focusing effect of the electrode, while the second term reflects the longitudinal acceleration effect of the electrode. The zero-order Bessel function I 0 (v)~1+v 2 / 4. Constant A 01 and A 10 Determined by the geometric shape of the electrodes, two boundary conditions can be obtained by using the fact that the potentials of the horizontal and vertical electrodes are the same in magnitude and opposite in polarity;

[0058] (1) When z = 0, if the potential of the horizontal electrode u = V 0 / 2, we can get:

[0059]

[0060] (2) When z = 0, the potential of the vertical electrode is u = -V 0 / 2, we can get:

[0061]

[0062] Solving the two together yields:

[0063]

[0064]

[0065] So: X and A satisfy the following relationship:

[0066] X+AI 0 (ka) = 1; the stronger the longitudinal electric field used for acceleration, the weaker the transverse focusing electric field, and the larger the modulation coefficient m, the stronger the longitudinal acceleration effect. The above obtains the parameter A of the radio frequency quadrupole field acceleration capability of the embodiment of the present application.

[0067] like Figure 4 and Figure 5As shown, the accelerating cavity 210 implemented in the present application is provided with a plurality of groups of tuner assemblies 240 distributed at equal intervals, each group of tuner assemblies 240 is provided with two couplers 241, and the two couplers 241 are symmetrically arranged on both sides of the accelerating cavity 210, so that the structure is more reasonable and compact. The surface of the accelerating cavity 210 is symmetrically provided with cooling water loops 250, and the accelerator is dissipated by cooling water treatment through the cooling water loops 250. When passing the cooling water, it is possible to pay attention to whether each channel is fully circulated, and to detect the flow rate of the water channel to see whether the water flow rate requirement is met, so as to avoid cavity deformation and cavity detuning due to the large amount of heat generated by the pipeline when accelerating the beam.

[0068] There are many ways for the ion source 1 to continuously generate N ion beams with different mass-to-charge ratios. One way is to use a laser ion source, and another way is to use an electron cyclotron resonance ion source. In usage scenarios with more stringent requirements on simultaneity, a laser ion source is preferably used. The embodiment of the present application uses a laser ion source.

[0069] like Figure 2 As shown, the ion source 1 is provided with N laser ion sources 110, one laser ion source 110 is correspondingly arranged at the entrance of a beam channel, and the mass-to-charge ratios of the ions generated by the N laser ion sources 110 are different. The laser ion source 110 focuses a high-power laser beam onto the surface of a solid target material, so that laser targeting produces a high-temperature and high-density plasma. Once the plasma is formed, it expands within a certain cone angle range along the normal direction of the target surface under the action of the density gradient to form an ion beam. The laser ion source 110 has the characteristics of high current, high charge state, and short pulse. Combined with Figure 5 The ion source 1 of the embodiment of the present application is provided with four laser ion sources 110. The four laser ion sources 110 simultaneously excite and generate ions, which enter the corresponding beam channels for acceleration.

[0070] refer to Figure 2 Each laser ion source 110 includes an inner target chamber 111, a laser 112, a first plane mirror 113, a second plane mirror 114, a plano-convex lens 115, a target surface 116 and a drift pipe 117. The laser 112 and the first plane mirror 113 are arranged outside the inner target chamber 111 to inject the laser beam into the inner target chamber 111. The second plane mirror 114, the plano-convex lens 115 and the target surface are arranged in the inner target chamber 111. After the laser beam passes through the second plane mirror 114 and the plano-convex lens 115, it is focused on the target surface 116 to generate plasma. The drift pipe 117 is arranged at the entrance of the beam channel to make the plasma drift to the entrance of the beam channel. The laser beam of the embodiment of the present application is incident at a certain angle, and is focused on the target surface by the plano-convex lens 115 to generate plasma. The plasma passes through a section of the drift pipe 117 at the front end of the inner target chamber 111, and drifts to the entrance of the electrode of the beam channel, and is then led out.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A hybrid four-beam ion accelerator, characterized in that: The invention comprises an ion source, a radio frequency quadrupole field accelerator, a focusing device and a target chamber which are arranged in sequence, wherein: An ion source, used for continuously generating N ion beams with different mass-to-charge ratios; A radio frequency quadrupole accelerator is provided with N beam channels for simultaneously accelerating N ion beams of different mass-to-charge ratios; A focusing and bunching device is provided with a conical solenoid to converge the N accelerated ion beams of different mass-to-charge ratios into one beam to form an ion beam mixed with different mass-to-charge ratios; The terminal target chamber is used to place the target material and inject the mixed ion beam.

2. The ion accelerator according to claim 1, characterized in that: The radio frequency quadrupole accelerator is provided with an accelerating cavity, M stem-ring electrodes and N rod electrode groups, each rod electrode group is provided with four rod electrodes, and the four rod electrodes are arranged correspondingly to form a beam channel, the M stem-ring electrodes are distributed at equal intervals along the beam channel, and each stem-ring electrode is connected to the accelerating cavity, and N through openings are symmetrically opened in the stem-ring electrode, each through opening is corresponding to a rod electrode group passing through, and each rod electrode group is connected to the stem-ring electrode.

3. The ion accelerator according to claim 2, characterized in that: The energy change of a particle after one acceleration unit in a radio frequency quadrupole accelerator follows the following expression: Δw=qE0TI0(ka)lcosφ s ; Where T is the transit time factor, φ s is the synchronization phase, E0 is the average value of the electric field peak in an accelerating unit, V is the inter-electrode voltage, A is the parameter representing the accelerating ability of the RF quadrupole field, m is the electrode modulation parameter, a is the minimum aperture of the beam channel, βλ is the modulation period, and λ is the RF wavelength.

4. The ion accelerator according to claim 2, characterized in that: The accelerating cavity is provided with a plurality of groups of tuner components which are equally spaced, each group of tuner components is provided with two couplers, and the two couplers are symmetrically arranged on both sides of the accelerating cavity.

5. The ion accelerator according to claim 2, characterized in that: The surface of the accelerating cavity tube is symmetrically provided with cooling water circuits.

6. The ion accelerator according to claim 1, characterized in that: The ion source is provided with N laser ion sources, one laser ion source is correspondingly arranged at the entrance of a beam channel, and the mass-to-charge ratios of ions excited by the N laser ion sources are different.

7. The ion accelerator according to claim 6, characterized in that: Each laser ion source includes an inner target chamber, a laser, a first plane mirror, a second plane mirror, a plano-convex lens, a target surface and a drift pipe. The laser and the first plane mirror are arranged outside the inner target chamber to project the laser beam into the inner target chamber. The second plane mirror, the plano-convex lens and the target surface are arranged in the inner target chamber. After passing through the second plane mirror and the plano-convex lens, the laser beam is focused on the target surface to generate plasma. The drift pipe is arranged at the entrance of the beam channel to make the plasma drift to the entrance of the beam channel.

8. The ion accelerator according to claim 1, characterized in that: The inlet of the conical solenoid is connected to the outlet of the beam channel.

9. The ion accelerator according to claim 1, characterized in that: The mixed multiple ion beams are a "cocktail" ion beam.

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