CN108566721A - Linear accelerator and synchrotron - Google Patents

Abstract

A linear accelerator, comprising: an acceleration cavity; a magnet cavity shell, located inside the acceleration cavity and connected to the inner wall of the acceleration cavity; a core tube for particle beams to pass through the magnet cavity shell, and a At least three quadrupole magnets connected in series inside the magnet chamber shell are used to focus the particle beam, and each of the at least three quadrupole magnets includes a central through hole, and the core tube passes through the central through hole. A synchrotron, characterized in that the synchrotron uses the above-mentioned linear accelerator as an injector.

Description

Linear accelerators and synchrotrons

technical field

The present invention relates to the related fields of particle accelerators, in particular to a linear accelerator and a synchrotron.

Background technique

Accelerator is a device that increases the kinetic energy of charged particles, which can be used in nuclear experiments, radiological medicine, radiochemical, radioactive isotope manufacturing, non-destructive flaw detection, etc. The current mainstream heavy ion proton accelerators are divided into three categories, namely linear accelerators, cyclotrons and synchrotrons. Linear accelerators and cyclotrons are suitable for medium and low energy protons and heavy ions, and can be used in the fields of medium and low energy material irradiation and ion implantation; synchrotrons are suitable for higher energy protons and heavy ions, generally used for cancer radiotherapy or medium High energy material irradiation field. Due to the limitation of its own structure, the beam transmission efficiency of cyclotron is very low. The injection and extraction structure of the linear accelerator itself is simple, the transmission efficiency is close to 100%, and it can accelerate a very strong beam. Due to its principle, the synchrotron must have an injector to accelerate the beam from several keV/u to several MeV/u energy, and the linear accelerator can be used as the injector of the synchrotron.

In traditional linear accelerators, the focusing magnet is generally placed outside the high-frequency accelerating cavity, and even if it is placed inside the accelerating cavity, a single magnet is packaged. Placing the focusing magnet outside the acceleration cavity is not conducive to the compactness of the entire linear accelerator, and it will make it more difficult to match the particle beam in the longitudinal direction. Usually, part of the acceleration performance will be sacrificed to achieve the longitudinal matching of the beam. In this way, the accelerator with the same energy It will become longer, and the space occupied by the accelerator will be larger. In addition, the newly added acceleration cavity must be equipped with a high-frequency power source and a level control system, so that the construction cost of the entire accelerator will be greater. However, placing a single packaged focusing magnet inside the acceleration cavity is not conducive to the lateral spatial matching of the particle beam in the linear accelerator. If a separately packaged focusing magnet is used inside the cavity, a large number of focusing magnets need to be placed inside the high-frequency acceleration cavity to meet the requirements for lateral matching of the particle beam. The inserted magnet will cause a sharp increase in the capacitive load of the high-frequency accelerating cavity. In this case, in order to achieve the same accelerating electric field, the power fed into the high-frequency accelerating cavity will increase by ten to dozens of times, which will make the accelerator The construction cost of the accelerator increases sharply, and the heating problem caused by high power will make the operation of the accelerator more difficult.

Contents of the invention

In view of the above problems, it is necessary to propose a new accelerator structure that can accelerate the beam in the high-frequency acceleration cavity and achieve lateral focus at the same time.

As an aspect of the present invention, a kind of linear accelerator is proposed, comprising:

acceleration cavity;

A magnet chamber shell, located inside the acceleration chamber and connected to the inner wall of the acceleration chamber;

a core tube for the passage of the particle beam located inside the magnet chamber housing, and

At least three quadrupole magnets connected in series inside the magnet chamber shell are used to focus the particle beam, and each of the at least three quadrupole magnets includes a central through hole, and the core tube passes through the central through hole hole.

In some embodiments, the at least three quadrupole magnets include three quadrupole magnets, and the polarities of adjacent magnets are opposite.

In some embodiments, an adjustment device and a positioning device are also arranged in the magnet housing, for adjusting or locking the positions of the three magnets.

In some embodiments, each magnet is configured with a magnet coil, and the magnet coil is arranged in a structure of an outer square and an inner circle.

In some embodiments, the magnet chamber shell has a double-layer structure, and a water channel for circulating cooling water is arranged between the two layers of the double-layer structure.

In some embodiments, the linear accelerator further includes a support cavity shell, one end of the support cavity shell is connected to the magnet cavity shell, and the other end of the support cavity shell is connected to the inner wall of the acceleration cavity.

In some embodiments, it is characterized in that, the inside of the support cavity shell includes a water circuit and an electric circuit, the water channel in the support cavity shell communicates with the water channel in the magnet cavity shell and the magnet coil, and the circuit communicates with the magnet coil. The magnet coil is connected.

In some embodiments, the support cavity shell includes a conical portion and a cylindrical portion, the conical portion is connected to the magnet cavity shell, and the cylindrical portion is connected to the inner wall of the acceleration cavity.

In some embodiments, the support chamber shell is connected to the inner wall of the acceleration chamber through a mounting flange, and the mounting flange includes a high-frequency sealing structure and a vacuum sealing structure.

Another aspect of the present invention provides a synchrotron, characterized in that the synchrotron uses the above-mentioned linear accelerator as an injector.

Based on the above technical solution, it can be seen that the present invention has achieved at least one of the following beneficial effects:

The linear accelerator and synchrotron provided by the present invention can make the linear accelerator more compact and economical in structure, and can realize lateral focusing while the beam is accelerated inside the high-frequency accelerating cavity, so that the linear accelerator can be significantly improved and enhanced. The quality of the medium and low energy particle beams drawn out by the accelerator device can further improve the performance of the synchrotron using the linear accelerator as the injector.

Description of drawings

Fig. 1 is a partial structural schematic view of a linear accelerator according to an embodiment of the present invention;

Fig. 2 is a structural diagram of an interdigitated drift tube linear accelerator according to a practical example of the present invention.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below. Apparently, the described embodiments are some, not all, embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the usual meanings understood by those skilled in the art to which the present invention belongs.

Fig. 1 is a partial structural schematic diagram of a linear accelerator according to an embodiment of the present invention. As shown in Fig. 1, described linear accelerator comprises: acceleration cavity 14; Magnet cavity shell 2, is positioned at acceleration cavity 14 inside and is connected with the inner wall of acceleration cavity 14; , and three quadrupole magnets 1 connected in series inside the magnet chamber shell 2 are used to focus the particle beam. The three quadrupole magnets 1 all include a central through hole, and the core tube 5 passes through the central through hole. The cross section of the acceleration cavity 14 can be in the shape of a square, a square with rounded corners, a circle or an ellipse. The magnet cavity housing 2 can adopt any suitable shape that is easy to assemble and connect with the acceleration cavity, for example, it can be cylindrical or square. Although it is shown in Fig. 1 that a magnet cavity shell 2 is placed inside the acceleration cavity 14, the embodiment of the present invention is not limited thereto, and a plurality of magnet cavity shells 2 can be placed inside the acceleration cavity 14 as required, and each magnet cavity shell 2 packages three magnets.

Through the above-mentioned structure, the linear accelerator can be made more compact and economical in structure than the existing linear accelerator, and at the same time, it also takes into account the high-frequency performance of the linear accelerator cavity and the lateral focusing ability of the beam, so the linear accelerator can be significantly improved and enhanced. The quality of the medium and low energy particle beams drawn out by the device.

According to some embodiments, the linac is a drift tube linac. The drift tube linear accelerator accelerates the charged particles along the forward direction of the beam with the high-frequency electric field generated between the electrodes of the drift tube.

According to some embodiments, among the three quadrupole magnets, adjacent magnets have opposite polarities. The quadrupole magnet includes four symmetrically distributed magnetic pole heads, and between adjacent quadrupole magnets, the N pole corresponds to the S pole, and the S pole corresponds to the N pole. In this application, the three series-connected quadrupole magnets 1 packaged together in the magnet chamber shell 2 are simply referred to as three-in-one quadrupole magnets. In order to make the ion beam with uniform phase space distribution in the horizontal and vertical directions produce the same phase shift in the horizontal and vertical directions, at least three quadrupole magnets are required. A single quadrupole magnet will turn the symmetrical beam (horizontal and vertical phase space consistent) into an asymmetric beam, that is, focus in one direction and defocus in the other direction, resulting in a larger beam envelope after the beam passes through the quadrupole magnet Small. Symmetrical beam matching is also not possible with two consecutive quadrupole magnets of opposite polarity. Therefore, the three-in-one quadrupole magnet focusing structure not only has excellent performance in principle, but also is more economical in cost.

The existing single packaged quadrupole magnet can only produce one transverse direction (such as horizontal direction) focusing on the particle beam passing through it, and will produce unfavorable dispersion in another direction (such as vertical direction) to the beam transmission. coke effect. This leads to the need to install a quadrupole magnet on each drift tube inside the acceleration chamber, so as to ensure that the beam current will not diverge and be lost during the transmission and acceleration process. The disadvantages of this scheme include: 1. A large number of magnets must be installed inside the acceleration cavity, and each magnet must be powered by a separate DC power supply, which will greatly increase the construction cost of the accelerator; Installing a quadrupole magnet will greatly increase the high-frequency power loss of the accelerating cavity, thereby greatly increasing the operating cost of the accelerator, and at the same time increasing the difficulty of cooling the accelerating cavity. Furthermore, the use of a series of quadrupole magnets packaged in a single unit will make the particle beam always in an asymmetric spatial distribution in the acceleration gap of the drift tube, which will produce a coupling phenomenon in the axisymmetric accelerating electric field, resulting in beam current The equivalent emittance increases.

A single quadrupole magnet produces different phase shifts in the horizontal and vertical directions of the beam, while adjacent quadrupole magnets with opposite polarities can produce the same phase shift in the horizontal and vertical directions of the beam. Therefore, the built-in three-in-one quadrupole magnet structure in the high-frequency acceleration cavity in the embodiment of the present invention can focus the particle beam in the horizontal and vertical directions simultaneously, so that the beam is always in axisymmetric distribution in the acceleration gap, and its The coupling phenomenon can be avoided in the symmetrical accelerating electric field. In addition, the focusing structure in the embodiment of the present invention can make the phase shift of the horizontal and vertical directions of the beam sufficiently large, so as to avoid placing too many focusing structures in the accelerating cavity, thereby reducing the loss of the high-frequency accelerating cavity power.

According to some embodiments, an adjustment device and a positioning device are also arranged in the magnet cavity housing 2 for adjusting or locking the positions of the three magnets. For example, as shown in FIG. 1 , a longitudinal adjustment mechanism 6 , a lateral adjustment mechanism 7 and a magnet spacing adjustment mechanism 8 may be included.

Specifically, the longitudinal adjustment mechanism 6 and the lateral adjustment mechanism 7 are used for longitudinal positioning support and lateral positioning support between the magnet 1 and the magnet cavity shell 2, and the magnet spacing adjustment mechanism 8 is used for controlling the coaxiality and spacing between the magnets 1 . For example, if the inner diameter of the magnet chamber shell 2 is consistent with the outer diameter of the magnet 1, the lateral adjustment mechanism 7 of the magnet 1 and the magnet chamber shell 2 can be realized by nesting and matching the circumferential contour of the magnet 1 and the circumferential contour of the magnet chamber shell 2; The inner diameter of the magnet chamber shell 2 is greater than the outer diameter of the magnet 1, and the lateral adjustment mechanism 7 can cooperate with the V-shaped groove on the magnet chamber shell 2 inner layer and the A-shaped boss (tip cut flat) processed on the magnet 1 iron yoke to realize. The longitudinal adjustment mechanism 6 between the end magnet 1 and the magnet cavity shell 2 can be realized by the hollow cylindrical structure of the inner layer of the magnet cavity shell 2 and the cylindrical structure processed on the end magnet 1 . The coaxiality between the magnets 1 is achieved by inserting four cylindrical rods with threads at both ends into the cylindrical holes of each magnet 1. A cylindrical sleeve with a specific length is used to control the distance between the magnets 1, and finally the two ends of the cylindrical rods are fixed with nuts. The machining accuracy of the magnet yoke structure is required to be 0.02mm. The adjustment device and positioning device are measured and corrected during the assembly process, and the final magnet assembly accuracy (including the position and spacing of all magnets) is required to reach 0.05mm.

According to some embodiments, the three magnets 1 are all equipped with magnet coils 4 , and the magnet coils 4 can be arranged in a structure of outer square and inner circle, so as to cool the magnet coils through cooling water while energizing.

As shown in Figure 1, the magnet cavity shell 2 can be a double-layer structure, and a water channel 3 for circulating cooling water is arranged between the two layers of the double-layer structure to take away the high frequency on the outer surface of the magnet cavity shell 2. Heat generated by electromagnetic fields. Also, it is not necessary to occupy extra space in the magnet cavity housing 2 .

According to some embodiments, the linear accelerator further includes a supporting cavity shell, one end of which is in communication with the magnet cavity shell 2 , and the other end is connected with the inner wall of the accelerating cavity 14 . Preferably, as shown in FIG. 1 , the support chamber shell includes a conical portion 9 and a cylindrical portion 10 , the conical portion 9 is connected to the magnet chamber shell 2 , and the cylindrical portion 10 is connected to the inner wall of the acceleration chamber 14 . The external waterway 12 and the external water/circuit 13 are introduced from the support cavity shell, the external waterway 12 communicates with the waterway 3 in the magnet cavity shell 2 , and the external water/circuit 13 communicates with the magnet coil 4 . Preferably, the support chamber shell is connected to the inner wall of the acceleration chamber 14 through a mounting flange 11, and the mounting flange 11 includes a high-frequency sealing structure and a vacuum sealing structure.

In the embodiment of the present invention, each quadrupole magnet 1 needs to be energized and cooled, and these waterways and circuits need to be drawn out from the magnet chamber shell 2 to the outside of the acceleration chamber 14, which requires a channel , the support structure of the magnet chamber shell 2 housing in the structure of the present invention can not only realize the function of support, but also serve as the lead-out channel of the waterway and the circuit. The magnet coil 4 is made of an oxygen-free copper material with a hollow structure with an outer side and an inner circle, and deionized water can be fed into the magnet coil 4 to cool the magnet coil 4 while being energized. In order to utilize the space inside the magnet chamber housing 2 as much as possible, the iron yoke of the quadrupole magnet 1 generally occupies the space of the housing in the lateral direction, so that the housing is also used for lateral positioning of the magnet. The outgoing wire of the magnet coil 4 can only be drawn out from the gap between the adjacent magnets 1 . In this way, the cylindrical diameter of the supporting structure of the housing should cover the range of the gap between two adjacent magnets. However, the large diameter of the shell support structure is not conducive to the high-frequency performance of the drift tube linear accelerator, so firstly the conical part 9 is used to convert the large diameter into a smaller diameter, and then the cylindrical part 10 with a smaller diameter is used to extend to accelerate The casing of the chamber 14 is sealed and connected with the casing of the acceleration chamber 14 through the mounting flange 11 .

With the above settings, the power consumption of the high-frequency accelerating cavity of the drift tube linac will be very low, because it will not significantly increase the capacitance between the drift tubes. In this way, the power consumption of the drift tube linear accelerator can be controlled within 100kW; after the above-mentioned water cooling structure design, the accelerator can work in the continuous wave mode. Compared with other types of drift tube linear accelerators with a power consumption above 1MW, which can only work in a low duty cycle pulse mode, the current intensity of the average particle beam of the drift tube linear accelerator of the present invention will be much greater.

In addition, the high-gradient (high magnetic field strength) three-in-one quadrupole magnet built into the high-frequency acceleration cavity can simultaneously achieve symmetrical beam-to-symmetrical beam matching at its entrance and exit. A particle beam with consistent horizontal and vertical envelopes can be called a symmetrical beam. The electric field felt by a symmetrical beam during acceleration and transmission in an axisymmetric high-frequency electromagnetic field is always symmetrical, and the beam transmission behavior will also maintain This symmetry. If the present invention is not used to laterally focus the beam current in the drift tube linear accelerator, the beam current can only form an asymmetric envelope in the acceleration gap, that is, the horizontal and vertical envelopes differ greatly, and the axial symmetry felt by the beam current The electric field will generate a nonlinear force on the asymmetrically distributed beam, thereby deteriorating the quality of the beam.

As shown in FIG. 2, FIG. 2 is a schematic diagram of a partially cut-away structure of an interdigitated (IH) type drift tube linear accelerator according to a practical example of the present invention. In the acceleration chamber 14 , the charged particles are accelerated along the forward direction of the beam by the high-frequency electric field generated between the electrodes of the drift tube 15 , and are focused in the magnet chamber shell 2 .

Therefore, when the above structure is applied to an IH (interdigital H-type structure) or CH (cross-bar H-type structure) type drift tube linear accelerator, not only the length of the drift tube linear accelerator can be significantly reduced, but also the drift tube can be The dynamics scheme of the linear accelerator is more excellent, because the longitudinal emittance growth of the beam can be minimized through the above settings.

Another aspect of the present invention provides a synchrotron using the above linear accelerator as an injector. Applying the linear accelerator provided by the present invention as the injector of the synchrotron can greatly increase the flow intensity and beam quality of the injection beam of the synchrotron.

The linear accelerator and the synchrotron provided by the embodiments of the present invention can make the linear accelerator more compact and economical in structure, and at the same time can significantly improve and improve the quality of the low- and medium-energy particle beams drawn by the linear accelerator device, and can further improve the The linear accelerator is used as the performance of the synchrotron of the injector; the present invention can be applied to the fields of basic nuclear physics application research, medical accelerator device, aerospace and industrial irradiation, and also provides a more powerful means for nuclear physics, atomic and molecular physics experimental research in addition .

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. Within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

Claims (10)

1. A linear accelerator, comprising: acceleration cavity; A magnet chamber shell, located inside the acceleration chamber and connected to the inner wall of the acceleration chamber; a core tube for the passage of the particle beam located inside the magnet chamber housing, and At least three quadrupole magnets connected in series inside the magnet chamber shell are used to focus the particle beam, and each of the at least three quadrupole magnets includes a central through hole, and the core tube passes through the central through hole hole. 2. The linear accelerator according to claim 1, wherein the at least three quadrupole magnets comprise three quadrupole magnets, and the polarities of adjacent magnets are opposite. 3 . The linear accelerator according to claim 1 , wherein an adjusting device and a positioning device are arranged in the magnet chamber housing, for adjusting or locking the positions of the at least three magnets. 4 . 4 . The linear accelerator according to claim 1 , wherein each magnet is equipped with a magnet coil, and the magnet coil is arranged in a structure of an outer square and an inner circle. 5 . The linear accelerator according to claim 1 , wherein the magnet housing is a double-layer structure, and a water channel for circulating cooling water is arranged between the two layers of the double-layer structure. 6 . 6. The linear accelerator according to claim 5, characterized in that, the linear accelerator further comprises a support cavity shell, one end of the support cavity shell is connected to the magnet cavity shell, and the other end of the support cavity shell is connected to the magnet cavity shell. The inner walls of the acceleration chamber are connected. 7. The linear accelerator according to claim 6, characterized in that, the inside of the support chamber shell includes a waterway and an electric circuit, the waterway in the support chamber shell communicates with the waterway in the magnet chamber shell and the coil, and the An electrical circuit communicates with the magnet coil of the magnet. 8. The linear accelerator according to claim 6, wherein the support cavity shell comprises a conical portion and a cylindrical portion, the conical portion is connected with the magnet cavity shell, and the cylindrical portion is connected with the magnet cavity shell. The inner wall of the acceleration chamber is connected. 9 . The linear accelerator according to claim 6 , wherein the support chamber shell is connected to the inner wall of the acceleration chamber through a mounting flange, and the mounting flange includes a high-frequency sealing structure and a vacuum sealing structure. 10. A synchrotron, characterized in that the synchrotron uses the linear accelerator according to any one of claims 1-9 as the injector.