Ion implanter

Abstract

The application relates to an ion implanter, comprising at least one ion source, a radio frequency quadrupole accelerator and a cross finger magnetic type drift tube linear accelerator arranged in sequence along a beam transmission direction, a low-energy transmission line is arranged between the ion source and the radio frequency quadrupole accelerator, a matching section is arranged between the radio frequency quadrupole accelerator and the cross finger magnetic type drift tube linear accelerator, and the cross finger magnetic type drift tube linear accelerator comprises four cavities, and a focusing section is arranged between any two adjacent cavities. The ion implanter adopts a higher working frequency, and through optimized beam dynamics design and structure design, miniaturization and high efficiency of the ion implanter are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of particle accelerator technology, and more particularly to an ion implanter. BACKGROUND

[0002] Multi-ion particle therapy is the most advanced tumor radiotherapy technology at present, which needs to use a charged particle accelerator to accelerate different kinds of heavy ions.

[0003] The existing ion implanter mainly includes an ion source system, a radio frequency quadruple accelerator (RFQ) and a drifting tube linac (DTL), generates ions through the ion source system, then accelerates and leads out the ions to the RFQ, the RFQ accelerates the ions, and then the ions enter the DTL for acceleration to obtain the required ion beam.

[0004] The working frequency of the existing ion implanter is concentrated in 100-217MHz, the frequency is low, and the existing ion implanter is large in size. SUMMARY

[0005] The present application aims to provide an ion implanter which is small in size and high in working frequency.

[0006] In order to achieve the above purpose, the present application provides an ion implanter, which comprises at least one ion source and a radio frequency quadruple accelerator and a cross-finger magnetic type drifting tube linac arranged in sequence along the beam transmission direction, a low-energy transmission line is arranged between the ion source and the radio frequency quadruple accelerator, a matching section is arranged between the radio frequency quadruple accelerator and the cross-finger magnetic type drifting tube linac, and the cross-finger magnetic type drifting tube linac comprises four cavities, and a focusing section is arranged between any two adjacent cavities.

[0007] Further, the matching section comprises four fourth quadrupole irons arranged in sequence, a third beam measuring device is arranged between the first fourth quadrupole iron and the second fourth quadrupole iron, and the matching section is arranged so that the phase space distribution of the passing beam becomes consistent, and the motion trend is focusing.

[0008] Further, the focusing section is composed of three fifth quadrupole irons arranged in sequence, and the focusing section is arranged so that the motion trend of the passing beam in two directions returns to focusing.

[0009] Further, each cavity of the cross-finger magnetic type drifting tube linac corresponds to a KONUS period, two bunching sections are arranged in each cavity, and the two bunching sections are arranged in negative phase to control the length of the beam.

[0010] Further, the at least one ion source comprises a first ion source for generating C 4+ ion beam, a second ion source for generating H3 + ion beam, and a third ion source for generating 3 He + and O 6+ ion beam.

[0011] Further, the number of the ion sources is plural, the low-energy transport line comprises a deflection magnet for deflecting the heavy ion beam, and the deflection magnet is arranged downstream of each ion source.

[0012] Further, the low-energy transport line comprises a first solenoid, a first beam measuring device, a first correction magnet, a first quadrupole, a deflection magnet, a second correction magnet, three second quadrupoles, a dipole, a second beam measuring device, three third quadrupoles, and a second solenoid arranged in sequence along the beam transport direction, the dipole, the second beam measuring device, the three third quadrupoles, and the second solenoid are shared by the plural ion sources, and the first solenoid, the first beam measuring device, the first correction magnet, the first quadrupole, the deflection magnet, the second correction magnet, and the three second quadrupoles are arranged downstream of each ion source.

[0013] Further, the pole tip radius of the radio frequency quadrupole accelerator varies along the beam transport direction.

[0014] Further, the downstream of the interdigital drift tube linear accelerator is further provided with a medium-energy transport line for transporting the heavy ion beam accelerated by the interdigital drift tube linear accelerator into a main accelerator.

[0015] Further, the medium-energy transport line comprises a fourth beam measuring device, three sixth quadrupoles, a third correction magnet, a beam spreader, three seventh quadrupoles, an eighth quadrupole, a fourth correction magnet, and a stripper arranged in sequence along the beam transport direction.

[0016] The ion implanter of the present application, IH-DTL, adopts a segmented design, which includes four cavities, the phase and power of each cavity are independently adjustable, the distance between adjacent cavities is not affected by the beam phase, which can effectively shorten the length of IH-DTL, and the segmented independent adjustable operation mode is helpful for the pre-operation beam debugging, and the segmented design is also convenient for the subsequent maintenance and upgrading during operation; two bunching sections are arranged in each cavity, which can improve the transmission efficiency and effectively increase the length of the acceleration section in the KONUS period, which is beneficial to improve the average acceleration gradient and thus reduce the length of IH-DTL; the drift tube and the cavity of IH-DTL can be integrally processed, thereby eliminating assembly errors, improving beam quality, and at the same time making the processing and assembly more convenient and fast; multiple ion sources are adopted, which can generate different types of heavy ion beams, thereby realizing the rapid switching of different types of particles and meeting the requirements of multi-particle treatment, and when any ion source fails, it can be replaced by other ion sources; the RFQ adopts a variable focusing factor, which effectively reduces the beam loss, allows the acceleration section to have a higher acceleration gradient, and realizes the miniaturization and high efficiency of the RFQ. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 FIG. 1 is a structural schematic diagram of an ion implanter according to an embodiment of the present application;

[0018] Figure 2 FIG. 4 is a schematic diagram of the variation of the pole tip shape of the RFQ of the ion implanter according to the embodiment of the present application along the beam transmission direction;

[0019] Figure 3 FIG. 5 is a schematic diagram of the cross section of the pole tip of the RFQ of the ion implanter according to the embodiment of the present application. DETAILED DESCRIPTION

[0020] The preferred embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0021] As Figure 1As shown, the present application provides an ion implanter, which comprises at least one ion source 100, an RFQ 200 and an IH-DTL (Interdigital H-mode Drifting Tube Linac) 300 arranged in sequence along the beam transmission direction, and a low energy beam transport (LEBT) 400 arranged between the ion source 100 and the RFQ. The ion source 100 is used to generate a heavy ion beam (i.e. beam), and the LEBT 400 is used to distribute and focus the beam so that the beam meets the emittance requirement of the entrance of the RFQ 200. The heavy ion beam is transmitted to the RFQ 200 through the LEBT 400, and the RFQ 200 accelerates the heavy ion beam. A matching section 500 is arranged between the RFQ 200 and the IH-DTL 300, which is used to make the phase space distribution of the heavy ion beam consistent so as to meet the injection requirement of the IH-DTL 300. The IH-DTL 300 comprises four cavities 310, which are used to accelerate the heavy ion beam. A focusing section 320 is arranged between any two adjacent cavities 310.

[0022] In some embodiments, a medium energy beam transport (MEBT) 600 is further arranged downstream of the IH-DTL 300, which is used to transmit the heavy ion beam accelerated by the IH-DTL 300 to other accelerators (e.g. main accelerator).

[0023] The ion source 100 can be an ECR (Electron Cyclotron Resonance) ion source. A gas is introduced into the ECR ion source through a gas inlet, and a microwave power is fed into the ECR ion source through a microwave input port. The gas forms a plasma at the position of the electrode, and then the heavy ions are separated by a high extraction voltage and extracted from the ECR ion source. The extraction voltage can be 50kV.

[0024] In some embodiments, the ion source 100 can be arranged as three, one of which is used to generate C 4+ ion beam, one is used to generate H3 + ion beam, and the last one is used to generate He 3 ion beam and O + ion beam, and serves as a backup for the first two ion sources 100. 6+

[0025] The LEBT 400 can comprise a deflection magnet 405. When the ion source 100 is working, ions with different mass-to-charge ratios are generated, and the turning radii of these ions are different when passing through the deflection magnet 405. Therefore, the deflection magnet 405 can be used to select ions with a specific mass-to-charge ratio to enter the RFQ 200. In this embodiment, C 4+ , H3 + , O 6+ and He 3 ions need to be selected. + ions need to be selected.​

[0026] In an exemplary embodiment, the LEBT 400 comprises a first solenoid 401, a first beam measurement device 402, a first corrector magnet 403, a first quadrupole 404, a deflection magnet 405, a second corrector magnet 406, three second quadrupoles 407 connected in series, a dipole 408, a second beam measurement device 409, three third quadrupoles 410 connected in series, and a second solenoid 411 arranged in sequence along the beam transmission direction; wherein the solenoid is used for transverse focusing of the heavy ion beam; the beam measurement device is used for measuring various parameters of the heavy ion beam, determining whether the beam meets the design requirements, and adjusting the beam according to the measurement results; the corrector magnet is used to eliminate the offset of the beam center; the quadrupole is used for transverse focusing and controlling the transverse size of the beam; and the dipole 408 is used for deflecting the heavy ion beam generated by different ion sources.

[0027] When there are multiple ion sources 100, a deflection magnet 405 needs to be arranged downstream of each ion source 100 to select the ions generated by the ion source 100. In some embodiments, the dipole 408, the second beam measurement device 409, the three third quadrupoles 410, and the second solenoid 411 can be shared by multiple ion sources 100, and the first solenoid 401, the first beam measurement device 402, the first corrector magnet 403, the first quadrupole 404, the deflection magnet 405, the second corrector magnet 406, and the three second quadrupoles 407 need to be arranged downstream of each ion source 100. In this way, the heavy ion beams generated by different ion sources 100 can all pass through the dipole 408, the second beam measurement device 409, the three third quadrupoles 410, and the second solenoid 411 after being deflected by the deflection magnet 405, and then enter the RFQ 200.

[0028] RFQ is an accelerating structure invented for the characteristics of low-energy particle beams. It mainly generates strong focusing effect by four electrodes, solves the problem of the increase of the emittance of low-energy particle beams, and adds modulation on the pole head to generate acceleration effect. RFQ mainly has two types, four-bar type and four-wing type, the main difference is the shape of the electrode. The electrode of four-bar type RFQ is rod-shaped, which is connected to the support plate alternately through the metal plate to form positive and negative voltage; the electrode of four-wing type RFQ is directly connected to the cavity wall to realize positive and negative voltage through the circumferential phase difference. According to the characteristics of the modulation of the RFQ pole head, the RFQ can be divided into four sections: radial matching section, shaping section, bunching section and acceleration section. In the radial matching section, the focusing force increases from 0 to the maximum value in a short distance, and the beam is matched with the time-varying focusing force without loss; in the shaping section, the synchronous phase and the longitudinal electric field begin to be modulated, the synchronous phase increases from-90°, and the longitudinal electric field increases from 0, which preliminarily shapes the beam shape and prepares for bunching; in the bunching section, the synchronous phase and the modulation coefficient further increase to the final value; in the acceleration section, the synchronous phase and the modulation coefficient no longer change, and the maximum acceleration electric field is reached to accelerate the beam to the final energy.

[0029] The heavy ion beam at the entrance of the RFQ 200 is in the state of continuous beam. As shown in Figure 2 , the distance between the solid line and the dotted line is the aperture, as shown in Figure 3 , there are multiple pole heads 210 in the RFQ 200, the cross-sectional shape of the front end of the pole head 210 is a circular arc, the radius of the circular arc is the pole head radius, the pole head radius of the RFQ 200 changes along the beam transmission direction, and the focusing factor also changes. The heavy ion beam first enters the radial matching section of the RFQ 200, where the aperture of the RFQ 200 rapidly narrows, and the modulation of the transverse shape of the beam allows the RFQ 200 to capture more particles. In the shaping section, the focusing factor reaches the maximum value, the modulation of the pole head 210 starts to increase slowly from 0, and the continuous beam also starts to form bunches slowly. In the bunching section, the modulation of the pole head 210 further increases to the maximum value, and the beam is further bunched, and the transverse and longitudinal phase space distributions are both periodically oscillating. Finally, the beam enters the acceleration section, the focusing factor decreases, and the modulation coefficient reaches the maximum value, and the pole head remains unchanged, which is mainly used for accelerating the beam. The beam is accelerated to more than 600keV / u in the length of 2 meters through the RFQ 200.

[0030] The phase space distribution of the beam at the exit of the RFQ 200 is opposite in the horizontal and vertical directions, which cannot meet the injection requirements of the IH-DTL 300, and thus a matching section 500 is needed. The matching section 500 includes four fourth quadrupole magnets 510 arranged in sequence. After passing through the matching section 500, the phase space distribution of the beam becomes consistent, and the movement trend is focusing. In some embodiments, a third beam measurement device 520 can be arranged between the first fourth quadrupole magnet 510 and the second fourth quadrupole magnet 510, for measuring the parameters of the heavy ion beam accelerated by the RFQ 200.

[0031] In the present embodiment, the RFQ 200 uses shorter shaping sections and bunching sections than the prior art, and the synchronous phase and modulation coefficient increase faster in the shaping sections and bunching sections, effectively reducing the length of the RFQ 200.

[0032] A DTL is an accelerator structure composed of drift tubes and accelerating gaps. A conventional DTL, i.e., an Alvarez DTL, has a large volume, a low accelerating gradient, a long length for accelerating the same energy, and needs to add permanent quadrupole magnets in the drift tubes, which is difficult to process and may cause large errors, and is difficult to adjust after processing. The IH-DTL is a new type of DTL, which has the advantages of high accelerating gradient, can greatly reduce the length of the DTL, and does not need to install magnets in the drift tubes, which reduces the process difficulty and has a wider range of choices for magnets, which can be selected as electromagnetic quadrupole magnets, and can be adjusted for errors during actual debugging and operation. The IH-DTL mainly has two different designs, one is the KONUS (Kombinierte Null Grad Struktur) beam dynamics design, and the other is the APF (Alternating Phase Focusing) beam dynamics design. The average accelerating gradient of the APF scheme IH-DTL is low, the entrance acceptance is low, and it is not suitable for large beam current, and the requirements for processing errors and operation stability are extremely high. Once the entrance beam parameters deviate or the structure has errors, the exit beam parameters will have a large error, which cannot meet the requirements.

[0033] In the embodiment, the IH-DTL 300 adopts the KONUS beam dynamics design, which includes four cavities 310, i.e., four segments, and thus has four KONUS periods, each cavity corresponding to one KONUS period. Due to the space charge effect and the influence of the focusing magnet, the length of the beam is elongated after passing through the matching segment, and thus a bunching segment is needed to compress the length of the beam. Two bunching segments are designed for each KONUS period, and after passing through the first bunching segment, the beam enters the 0-phase acceleration segment, which is the main acceleration part. Due to the obvious space charge effect of the heavy ion beam, the length of the beam is elongated after passing through the acceleration segment, and thus a second bunching segment is designed to control the length of the beam. After the beam is accelerated through one period, the movement trend of the beam in the horizontal and vertical directions both become defocusing, and thus a focusing segment is needed to change the transverse phase space distribution thereof. The focusing segment 320 between each cavity 310 can be composed of three fifth quadrupole magnets 321, and after the focusing and adjustment of the magnets, the movement trend of the beam in the two directions returns to focusing, and enters the first bunching segment of the next KONUS period, that is, the focusing segment 320 is arranged to make the movement trend of the passing beam in the two directions return to focusing. After being accelerated through the four KONUS periods, the energy of the beam reaches 7 MeV / u or above.

[0034] In some embodiments, the RFQ 200 and the IH-DTL 300 are both fed with power into the cavities through coaxial couplers, wherein the four cavities 310 of the IH-DTL 300 can be fed with power by four couplers respectively, so that independent power and phase adjustment can be achieved. In this way, the length between each cavity 310 of the IH-DTL 300 can be made more flexible, without being limited by the requirement of the beam phase.

[0035] C 4+ , H3 + , and 3 He + has a mass-to-charge ratio of 1 / 3, and O 6+ has a mass-to-charge ratio of 3 / 8, and the mass-to-charge ratios are different, and the acceleration under the same electric field is different, in order to ensure that ions with different mass-to-charge ratios obtain the same acceleration effect, it is necessary to adjust the electric field size in the RFQ 200 and the IH-DTL 300 in proportion, which can be achieved by adjusting the feeding power of the RFQ 200 and the IH-DTL 300 to change the electric field size excited in the cavities, so as to accelerate heavy ion beams with different mass-to-charge ratios by one injector.

[0036] In the embodiment, the RFQ 200 and the IH-DTL 300 can both adopt a working frequency of 325 MHz, which is higher than that of the existing ion injectors. A higher working frequency can make the cavities of the RFQ 200 and the DTL 300 smaller, and allow a larger electric field to be generated in the cavities, greatly reducing the length and volume of the ion injector.

[0037] In the above embodiment, all the quadrupole electromagnets can be electromagnetic quadrupole electromagnets.

[0038] The MEBT 600 includes a debuncher 604 for reducing the energy spread of the beam so that more beam can enter the main accelerator.

[0039] In some embodiments, the MEBT 600 can include, in sequence along the beam transmission direction, a fourth beam diagnostic device 601, three sixth quadrupole electromagnets 602, a third corrector magnet 603, the debuncher 604, three seventh quadrupole electromagnets 605, an eighth quadrupole electromagnet 606, a fourth corrector magnet 607, and a stripper 608. Since the long-distance drift of the beam will cause its transverse size to increase continuously, the beam is mainly focused by the quadrupole electromagnets in the MEBT 600. Since the MEBT transmits multiple heavy ion beams, the beam parameters will change, and therefore more flexible electromagnetic electromagnets are used. The beam entering the main accelerator also uses the stripper 608 to strip it to improve the specific charge of the heavy ions, which is conducive to improving the acceleration efficiency of the main accelerator. After the MEBT, the beam intensity in the energy spread ± 7 keV / u range is more than 70% of the input beam.

[0040] The ion implanter of the embodiment of the present application, the IH-DTL 300 adopts a segmented design, which includes four cavities 310, the phase and power of each cavity 310 are independently adjustable, the distance between adjacent cavities is not affected by the phase of the beam, which can effectively shorten the length of the IH-DTL 300, and the segmented and independently adjustable operation mode is helpful for the beam debugging before operation, and the segmented design is also convenient for the subsequent maintenance and upgrading during operation; two bunching sections are arranged in each cavity 310, which can improve the transmission efficiency and effectively increase the length of the acceleration section in the KONUS period, which is conducive to improving the average acceleration gradient and thus reducing the length of the IH-DTL 300; the drift tube and the cavity of the IH-DTL 300 can be integrally machined, thereby eliminating assembly errors and improving beam quality, and at the same time making the machining and assembly more convenient and fast; a plurality of ion sources 100 are adopted, which can generate different types of heavy ion beams, thereby realizing the rapid switching of different types of particles and meeting the requirements of multi-particle therapy, and when any ion source fails, it can be replaced by other ion sources; the RFQ 200 adopts a variable focusing factor, thereby effectively reducing the beam loss, allowing the acceleration section to have a higher acceleration gradient, and realizing the miniaturization and high efficiency of the RFQ 200.

[0041] The above merely describes preferred embodiments of the present application, and is not intended to limit the scope of the present application. The above-described embodiments of the present application can be variously changed. That is, simple, equivalent changes and modifications made in accordance with the content of the claims and the specification of the present application are intended to fall within the scope of the present application. The present application is not limited by the above-described embodiments.

Claims

1. An ion implanter, characterized in that, The device includes at least one ion source and a radio frequency quadrupole accelerator and an interdigitated drift tube linear accelerator arranged sequentially along the beam transmission direction. A low-energy transmission line is provided between the ion source and the radio frequency quadrupole accelerator. A matching section is provided between the radio frequency quadrupole accelerator and the interdigitated drift tube linear accelerator. The interdigitated drift tube linear accelerator includes four cavities. The phase and power of each cavity are set to be independently adjustable. A focusing section is provided between any two adjacent cavities.

2. The ion implanter according to claim 1, characterized in that, The matching section includes four fourth quadrupole irons arranged in sequence. A third beam measuring device is set between the first and second fourth quadrupole irons. The matching section is configured to make the phase space distribution of the passing beams consistent, and the motion trend is focused.

3. The ion implanter according to claim 1, characterized in that, The focusing section consists of three fifth quadrupole irons arranged in sequence, and the focusing section is configured to bring the motion trend of the passing beam in both directions back to focus.

4. The ion implanter according to claim 1, characterized in that, Each cavity of the cross-finger drift tube linear accelerator corresponds to one KONUS cycle. Each cavity is equipped with two beam-focusing sections, both of which are set to negative phase to control the beam length.

5. The ion implanter according to claim 1, characterized in that, At least one ion source includes a first ion source, a second ion source, and a third ion source, wherein the first ion source is used to generate C 4+ Ion beam, the second ion source is used to generate H3 + An ion beam, wherein the third ion source is used to generate an ion beam. 3 He + and O 6+ Ion beam.

6. The ion implanter according to claim 1, characterized in that, The number of ion sources is multiple, and the low-energy transmission line includes deflecting magnets for deflecting the heavy ion beam. One deflecting magnet is disposed downstream of each ion source.

7. The ion implanter according to claim 6, characterized in that, The low-energy transmission line includes a first solenoid, a first beam measurement device, a first correction magnet, a first quadrupole, a deflection magnet, a second correction magnet, three second quadrupoles, a dipolar magnet, a second beam measurement device, three third quadrupoles, and a second solenoid arranged sequentially along the beam transmission direction. The dipolar magnet, the second beam measurement device, the three third quadrupoles, and the second solenoid are shared by multiple ion sources. A set of the first solenoid, the first beam measurement device, the first correction magnet, the first quadrupole, the deflection magnet, the second correction magnet, and the three second quadrupoles is provided downstream of each ion source.

8. The ion implanter according to claim 1, characterized in that, The radius of the pole head of the radio frequency quadrupole accelerator varies along the beam propagation direction.

9. The ion implanter according to claim 1, characterized in that, A medium-energy transmission line is also provided downstream of the interdigitated drift tube linear accelerator to transmit the heavy ion beam accelerated by the interdigitated drift tube linear accelerator to the main accelerator.

10. The ion implanter according to claim 9, characterized in that, The medium-energy transmission line includes a fourth beam measuring device, three sixth quadrupole magnets, a third correction magnet, a beam diffuser, three seventh quadrupole magnets, an eighth quadrupole magnet, a fourth correction magnet, and a stripper arranged sequentially along the beam transmission direction.

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