CN113630951B - Liquid helium-free radio frequency superconducting accelerator - Google Patents
Liquid helium-free radio frequency superconducting accelerator Download PDFInfo
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- CN113630951B CN113630951B CN202110895550.4A CN202110895550A CN113630951B CN 113630951 B CN113630951 B CN 113630951B CN 202110895550 A CN202110895550 A CN 202110895550A CN 113630951 B CN113630951 B CN 113630951B
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
- H05H7/00—Details of devices of the types covered by groups H05H9/00, H05H11/00, H05H13/00
- H05H7/14—Vacuum chambers
- H05H7/18—Cavities; Resonators
- H05H7/20—Cavities; Resonators with superconductive walls
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- H—ELECTRICITY
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- H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
- H05H7/00—Details of devices of the types covered by groups H05H9/00, H05H11/00, H05H13/00
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
- H05H7/00—Details of devices of the types covered by groups H05H9/00, H05H11/00, H05H13/00
- H05H7/001—Arrangements for beam delivery or irradiation
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
- H05H7/00—Details of devices of the types covered by groups H05H9/00, H05H11/00, H05H13/00
- H05H7/02—Circuits or systems for supplying or feeding radio-frequency energy
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
- H05H7/00—Details of devices of the types covered by groups H05H9/00, H05H11/00, H05H13/00
- H05H7/02—Circuits or systems for supplying or feeding radio-frequency energy
- H05H2007/025—Radiofrequency systems
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Abstract
The invention relates to a liquid helium-free radio frequency superconducting accelerator, wherein charged particle beams are generated and led out through an injection system and are led into an acceleration module through a beam transmission system, a power source system supplies radio frequency power to the acceleration module, a low-level and control system monitors operation, maintains stable electromagnetic field amplitude and phase in a superconducting cavity, and charged particles are led into an application terminal through the beam transmission system after being accelerated in the acceleration module. According to the invention, the superconducting cavity is cooled in a solid conduction mode, so that the superconducting cavity stably operates at a low temperature, charged particle beam current is accelerated, a cooling mode that the current radio frequency superconducting accelerating cavity can only be soaked in liquid helium is eliminated, a liquid helium soaking and cooling thermostat with a complex structure and a liquid helium low-temperature station with a large cost occupation scale are omitted, and the advantages of low price, small occupied area, simple structure, compact layout, convenience in operation and maintenance and the like are achieved, the application difficulty of the radio frequency superconducting accelerator can be remarkably reduced, and the application range of the radio frequency superconducting accelerator is greatly expanded.
Description
Technical Field
The invention relates to a superconducting accelerator, in particular to a liquid helium-free radio frequency superconducting accelerator based on solid conduction cooling, and belongs to the technical field of superconduction.
Background
Charged particle accelerators are an indispensable research tool in the fields of high-energy physics, atomic molecular physics, life and material science, nuclear physics, radionuclide research, and the like. Due to the extremely low surface resistance of the radio frequency superconducting accelerating cavity (superconducting cavity), compared with a normal temperature accelerator, the superconducting accelerator has the advantage of being capable of working in a high duty ratio or even in a continuous wave mode, and radio frequency superconducting is one of core technologies of modern particle accelerators.
The superconducting cavity is the core acceleration component of the superconducting accelerator. At present, the superconducting cavity is mainly made of low-temperature superconducting material metal niobium, and is required to be soaked in liquid helium with the temperature of 2K-4K to realize cooling. However, the liquid helium soaking cooling mode results in a complex structure of the refrigerating system, high manufacturing cost and high-specialized low-temperature refrigerating operation and maintenance team, which severely restricts the application range of the current superconducting accelerator taking the pure niobium superconducting cavity as the core. Therefore, how to get rid of the constraint of liquid helium is a key for reducing the complexity of the superconducting accelerator, the operation and maintenance difficulty and expanding the application range of the superconducting accelerator.
On the one hand, has a high superconducting transition temperature (T c ) Nb in high overheat magnetic field 3 Sn、MgB 2 Radio frequency superconducting materials such as NbN, nbTiN, iron-based superconductors and the like, and the radio frequency performance of the radio frequency superconducting materials at 4.2K or even higher temperature can reach the niobium-based superconducting cavity 2KA lower level; on the other hand, the current industrial refrigerator has a cooling power of 2W at 4.2K low temperature, and the cooling power increases with the temperature, and is driven by Nb by solid conduction cooling mode 3 Sn、MgB 2 The capability of stable operation of superconducting cavities of high-temperature superconducting materials such as NbN, nbTiN, iron-based superconductors and the like.
Disclosure of Invention
Aiming at the problems, the invention aims to provide a liquid helium-free radio frequency superconducting accelerator based on solid conduction cooling, so that the working mode that a traditional superconducting cavity is soaked in liquid helium for cooling is eliminated, and the application difficulty of a radio frequency superconducting technology is reduced.
In order to achieve the above purpose, the present invention adopts the following technical scheme: a liquid helium-free radio frequency superconducting accelerator comprises a charged particle injection system, a beam transmission system, an acceleration module system, a power source system, a low level and control system and an application terminal; the input end and the output end of the acceleration module system are respectively connected with the output end of the charged particle injection system and the input end of the application terminal through the beam transmission system; the charged particle injection system is configured to generate a charged particle beam of a specific energy, a specific species, a specific intensity of flow, a specific parameter; the beam transmission system is configured to guide the charged particle beam led out from the charged particle injection system into the superconducting cavity of the acceleration module system to be accelerated, and guide the accelerated charged particle beam led out from the superconducting cavity of the acceleration module system to be transmitted to the application terminal according to a specified track; the power source system is connected with the superconducting cavity of the acceleration module system and is configured to provide radio frequency power for the superconducting cavity of the acceleration module system so as to establish a radio frequency electromagnetic field in the superconducting cavity, and the charged particle beam is accelerated under the action of the electromagnetic field in the superconducting cavity; the low level and control system is respectively and electrically connected with the charged particle injection system, the beam transmission system, the acceleration module system and the application terminal, and is configured to monitor the running state of the accelerator and maintain the stable amplitude and phase of the electromagnetic field in the superconducting cavity by collecting and processing the temperature, vacuum degree, radio frequency, beam position, beam energy and beam emittance signals of the accelerator.
The liquid helium-free radio frequency superconducting accelerator preferably comprises: a superconducting cavity configured to provide energy to a beam of charged particles; a cryogenic unit configured to provide a desired cryogenic environment to the superconducting cavity; and the vacuum unit is connected with the superconducting cavity and is configured to provide a cavity vacuum environment and an interlayer vacuum environment required by operation for the superconducting cavity.
The liquid helium-free radio frequency superconducting accelerator preferably comprises a power source and a coupler, wherein the coupler is connected with a coupling port of the superconducting cavity, and is configured to feed radio frequency power output by the power source into the superconducting cavity.
The liquid helium-free radio frequency superconducting accelerator preferably comprises a beam pipeline, a magnet element and a beam diagnosis element, wherein the beam pipeline is processed by stainless steel and is in butt joint with a pipeline of the acceleration module system, the beam pipeline is vacuumized, the vacuum degree is lower than 1e-5Pa, and the connection parts of the beam pipeline are all sealed by metal to ensure high vacuum; the beam pipeline is provided with beam diagnostic elements for measuring the position, energy, intensity and emittance of the charged particle beam, and the beam pipeline is also provided with a diode magnet for deflection of the charged particle beam, a solenoid and a quadrupole magnet for focusing the charged particle beam, a hexapole magnet for dispersion elimination, a scanning magnet for irradiation and other magnet elements required according to application requirements.
Preferably, the charged particles generated by the charged particle injection system of the liquid helium-free radio frequency superconducting accelerator comprise electrons, protons, carbon ions or the like.
The liquid helium-free radio frequency superconducting accelerator, preferably, the cryogenic unit comprises: a cold shield disposed outside the superconducting cavity, the cold shield configured to reduce static heat loss of the superconducting cavity; a magnetic shielding layer disposed in a space between the cold shield and the superconducting cavity, the magnetic shielding layer configured to shield an earth ambient magnetic field, reducing magnetic flux trapping of the superconducting cavity; the cooling guide blocks are arranged in the heating area of the superconducting cavity, and the inner surfaces of the cooling guide blocks are attached to the outer surfaces of the superconducting cavity; the secondary cooling plates are arranged above the cold guide blocks, and one sides of the secondary cooling plates are respectively connected with a plurality of groups of the cold guide blocks through flexible cold chains; the refrigerator is arranged above the secondary cold plates, and the secondary cold heads of the refrigerator are connected with the other side of the secondary cold plates through flexible cold chains.
In the liquid helium-free radio frequency superconducting accelerator, preferably, the cold guide block is in a half hoop form, and the half hoops of the cold guide block are all fastened and connected through screws and nuts; meanwhile, indium sheets are uniformly distributed on the contact interface of the cold guide block and the superconducting cavity and the joint of the half anchor ear; temperature sensors are arranged on the outer surface of the heating area of the superconducting cavity, the cold guide block, the secondary cold plate and the secondary cold head and used for monitoring the temperature change of the superconducting cavity; meanwhile, a high-precision heater is arranged on the secondary cold head and is used for matching a temperature controller and a temperature sensor, so that the conditions that the cooling rate is stable between 30K and 15K and is continuously adjustable between 1min/K and 5min/K are realized, and the temperature gradient of the superconducting cavity in the axial direction is ensured to be less than or equal to 0.025K/cm; and a fluxgate probe is arranged on the outer surface of the superconducting cavity, and the fluxgate probe can accurately measure the magnetic field intensity which is less than or equal to 10 and mGs and is used for measuring and monitoring residual magnetism.
The liquid helium-free radio frequency superconducting accelerator, preferably, the vacuum unit comprises: a vacuum enclosure disposed outside the cold shield, the vacuum enclosure configured to form an interlayer vacuum environment between the vacuum enclosure and the superconducting cavity for reducing static heat loss; one ends of the two groups of vacuum pipelines are respectively connected with two beam flow pipelines of the superconducting cavity through vacuum angle valves, and the other ends of the two groups of vacuum pipelines penetrate out of the vacuum cover and then are connected with the vacuum pump group so as to form a cavity vacuum environment for accelerating charged particles in a superconducting cavity-pipeline system formed by the superconducting cavity and the vacuum pipelines.
In the liquid helium-free radio frequency superconducting accelerator, preferably, the vacuum cover is made of stainless steel, and the inner surface and the outer surface of the vacuum cover are polished; the top of the vacuum cover is provided with an opposite port of the refrigerator, the side face of the vacuum cover is provided with an opposite port of the vacuum pipeline, and the bottom of the vacuum cover is provided with an opposite port of the coupler; a temperature sensor wall penetrating piece is reserved on the vacuum cover and is used for butt joint of data wires of the temperature sensor; a magnetic probe sensor wall penetrating piece is reserved on the vacuum cover and is used for butt joint of data wires of the fluxgate probe; the vacuum cover is reserved with a backfill opening for high-purity nitrogen inflation to recover vacuum and cleaning a pipeline.
The liquid helium-free radio frequency superconducting accelerator preferably further comprises a shock absorber arranged at the top of the vacuum cover, and the refrigerator is arranged on the shock absorber; meanwhile, vibration of the refrigerator is effectively prevented from being transmitted to the superconducting cavity through a flexible cold chain between a secondary cold head of the refrigerator and the superconducting cavity; the superconducting cavity is supported in the vacuum cover through a supporting structure made of non-magnetic materials, and fine tuning rods are arranged on the supporting structure.
Due to the adoption of the technical scheme, the invention has the following advantages:
the charged particle beam is generated and led out by the injection system and is led into the acceleration module by the beam transmission system, the power source system supplies high-frequency power to the acceleration module, the low-level and control system monitors operation, maintains stable electromagnetic field amplitude and phase in the superconducting cavity, and the charged particles are led into the application terminal by the beam transmission system after being accelerated in the acceleration module. Because the superconducting cavity is cooled by a solid conduction mode based on a commercial refrigerator, the superconducting cavity stably operates at a low temperature, the charged particle beam is accelerated, the cooling mode that the current radio frequency superconducting accelerating cavity can only be soaked in liquid helium is eliminated, a liquid helium soaking and cooling thermostat with a complex structure and a liquid helium low-temperature station with a large cost and occupation area are omitted, and the radio frequency superconducting accelerator has the advantages of low price, small occupation area, simple structure, compact layout, convenient operation and maintenance and the like, can obviously reduce the application difficulty of the radio frequency superconducting accelerator, and greatly expands the application range of the radio frequency superconducting accelerator.
Drawings
FIG. 1 is a schematic diagram of a liquid helium free RF superconducting accelerator according to one embodiment of the present invention;
fig. 2 is an axial cross-sectional view of an acceleration module system according to the embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the description of the present invention, it should be noted that the azimuth or positional relationship indicated by the terms "upper", "lower", "inner", "outer", etc. are based on the azimuth or positional relationship shown in the drawings, and are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the system or element referred to must have a specific azimuth, be configured and operated in a specific azimuth, and thus should not be construed as limiting the present invention. Moreover, the use of the terms first, second, etc. to define elements is merely for convenience in distinguishing the elements from each other, and the terms are not specifically meant to indicate or imply relative importance unless otherwise indicated.
In the description of the present invention, it should be noted that, unless explicitly stated and limited otherwise, the terms "mounted," "disposed," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
The invention provides a liquid helium-free radio frequency superconducting accelerator, which comprises a charged particle injection system, a beam transmission system, an acceleration module system, a power source system, a low level and control system and an application terminal; the input end and the output end of the acceleration module system are respectively connected with the output end of the charged particle injection system and the input end of the application terminal through the beam transmission system; the charged particle injection system is configured to generate a charged particle beam of a specific energy, a specific species, a specific intensity of flow, a specific parameter; the beam transmission system is configured to guide the charged particle beam led out from the charged particle injection system into the superconducting cavity of the acceleration module system to be accelerated, and guide the accelerated charged particle beam led out from the superconducting cavity of the acceleration module system to be transmitted to the application terminal according to a specified track; the power source system is connected with the superconducting cavity of the acceleration module system and is configured to provide radio frequency power for the superconducting cavity of the acceleration module system so as to establish a radio frequency electromagnetic field in the superconducting cavity, and the charged particle beam is accelerated under the action of the electromagnetic field in the superconducting cavity; the low level and control system is respectively and electrically connected with the charged particle injection system, the beam transmission system, the acceleration module system and the application terminal, and is configured to monitor the running state of the accelerator by collecting and processing the temperature, vacuum degree, radio frequency, beam position, beam energy and beam emittance signals of the accelerator so as to maintain the amplitude and phase stability of the electromagnetic field in the superconducting cavity. According to the invention, the superconducting cavity is cooled in a solid conduction mode, so that the superconducting cavity stably operates at a low temperature, charged particle beam current is accelerated, a cooling mode that the current radio frequency superconducting accelerating cavity can only be soaked in liquid helium is eliminated, a liquid helium soaking and cooling thermostat with a complex structure and a liquid helium low-temperature station with a large cost occupation scale are omitted, and the advantages of low price, small occupied area, simple structure, compact layout, convenience in operation and maintenance and the like are achieved, the application difficulty of the radio frequency superconducting accelerator can be remarkably reduced, and the application range of the radio frequency superconducting accelerator is greatly expanded.
The liquid helium-free radio frequency superconducting accelerator provided by the invention is described in detail below with reference to the accompanying drawings.
As shown in fig. 1, the liquid helium-free rf superconducting accelerator provided in this embodiment includes a charged particle injection system 10, a beam transport system 20, an acceleration module system 30, a power source system 40, a low level and control system 50, and an application terminal 60. The input end and the output end of the acceleration module system 30 are connected with the output end of the charged particle injection system 10 and the input end of the application terminal 60 through the beam transmission system 20, respectively. The charged particle injection system 10 is configured to generate a charged particle beam of a specific energy, a specific kind, a specific intensity of flow, a specific parameter, the beam transport system 20 is configured to guide the charged particle beam extracted from the charged particle injection system 10 into the superconducting cavity of the acceleration module system 30 to be accelerated, and to guide the accelerated charged particle beam extracted from the superconducting cavity of the acceleration module system 30 to be transported to the application terminal 60 according to a specified trajectory; the power source system 40 is connected with the superconducting cavity of the acceleration module system 30, and the power source system 40 is configured to provide radio frequency power to the superconducting cavity of the acceleration module system 30 so as to establish a radio frequency electromagnetic field in the superconducting cavity, so that the charged particle beam is accelerated by the electromagnetic field in the superconducting cavity; the low level and control system 50 is electrically connected to the charged particle injection system 10, the beam delivery system 20, the acceleration module system 30 and the application terminal 60, respectively, and the low level and control system 50 is configured to monitor the operation state of the accelerator by acquiring and processing signals such as temperature, vacuum, radio frequency, beam position, beam energy, beam emittance, etc. of the accelerator, so as to maintain the electromagnetic field amplitude and phase stability in the superconducting cavity.
In the above embodiment, the acceleration module system 30 preferably includes: a superconducting cavity 1 configured to provide energy to a beam of charged particles; a cryogenic unit 2 configured to provide a desired cryogenic environment to the superconducting cavity 1; and a vacuum unit 3 connected to the superconducting cavity 1, the vacuum unit 3 being configured to provide the superconducting cavity 1 with a cavity vacuum environment and a sandwich vacuum environment required for operation.
In the above embodiment, the power source system 40 preferably mainly includes a power source (not shown in the drawings) and a coupler 4, the coupler 4 is connected to the coupling port of the superconducting cavity 1, and the coupler 4 is configured to feed radio frequency power output from the power source into the superconducting cavity 1. In the embodiment, the power source is a solid-state power source, the working frequency is 1.3GHz, and the output power is 10kW; the operating frequency of the coupler 4 is 1.3GHz and the maximum operating power is 5kW.
In the above-described embodiment, the beam delivery system 20 preferably includes a beam conduit, various types of magnet elements, and various beam diagnostic elements of the charged particle beam. The beam pipeline is processed by 304 stainless steel and is in butt joint with a pipeline of the acceleration module system 30, the connection part of the beam pipeline is completely sealed by metal to ensure high vacuum, the beam pipeline is vacuumized by an oil-free dry pump, a molecular pump or an ion pump, and the vacuum degree is lower than 1e-5Pa; the beam pipeline is provided with beam diagnostic elements for measuring properties such as charged particle beam position, energy, intensity, emittance and the like, and is also provided with a diode magnet for deflection of the charged particle beam, a solenoid and a quadrupole magnet for focusing the charged particle beam, a hexapole magnet for dispersion elimination, a scanning magnet for irradiation and other magnet elements required according to application requirements.
In the above embodiment, the low level and control system 50 preferably adopts a digital low level control system based on FPGA, mainly including frequency synthesis, FPGA digital signal processing platform and upper communication software, in which the power stability requirement is less than or equal to 0.3% and the phase control accuracy requirement is less than or equal to 0.3 0 。
In the above embodiment, preferably, the charged particles generated by the charged particle injection system 10 are electrons (may also be protons or carbon ions, etc.), the average current intensity of the charged particle beam is 1-5 mA, the energy is 300KeV or more, the charge quantity of the beam cluster is 1pC-100pC, the micro pulse repetition frequency is 54.17MHz, the macro pulse repetition frequency is 1/2/5/10/20Hz, and the macro pulse width is 10 us-1 ms.
In the above embodiment, preferably, the low temperature unit 2 includes: a cold shield 2-1 provided outside the superconducting cavity 1, the cold shield 2-1 being configured to reduce static heat loss of the superconducting cavity 1; a magnetic shielding layer (not shown) disposed in the space between the cold shield 2-1 and the superconducting cavity 1, the magnetic shielding layer being configured to shield the earth's ambient magnetic field, reducing magnetic flux trapping of the superconducting cavity 1; the three groups of cold guide copper blocks 2-2 are respectively arranged in the equatorial region and the beam pipeline regions on two sides of the superconducting cavity 1 along the circumferential direction, and the inner surfaces of the cold guide copper blocks 2-2 are attached to the equatorial region of the superconducting cavity 1 and the outer surfaces of the beam pipeline regions; the secondary cold plate 2-3 is arranged above the cold-conducting copper blocks 2-2, and one side of the secondary cold plate 2-3 is respectively connected with the three groups of cold-conducting copper blocks 2-2 through the flexible cold chain 2-4; and the refrigerating machines 2-5, at least one refrigerating machine 2-5 is arranged above the secondary cold plate 2-3, and the secondary cold head 2-6 of the refrigerating machine 2-5 is connected with the other side of the secondary cold plate 2-3 through the flexible cold chain 2-4. Therefore, the heat generated by the inner wall of the superconducting cavity 1 is transferred to the secondary cold plate 2-3 through the flexible cold chain 2-4 by the cold-conducting copper block 2-2 and then transferred to the secondary cold head 2-6 of the refrigerator 2-5 through the flexible cold chain 2-4, so that the superconducting cavity 1 is maintained in a low-temperature superconducting working state. It should be noted that, the three groups of cold-conducting copper blocks 2-2 are respectively arranged in the equatorial region and the beam pipeline regions at two sides of the superconducting cavity 1 along the circumferential direction, only for the case that the superconducting cavity 1 is a single ellipsoidal cavity (i.e. an accelerating unit), but if the superconducting cavity 1 comprises a plurality of accelerating units, the required quantity of the cold-conducting copper blocks 2-2 is determined according to application requirements; and, if the shape of the superconducting cavity 1 is not an ellipsoidal cavity, it is necessary to dispose the cold-conducting copper block 2-2 in the heat-generating region of the superconducting cavity 1.
In the above embodiment, preferably, the cold-conducting copper block 2-2 is in a form of half hoops, and the half hoops of the cold-conducting copper block 2-2 are fastened and connected by screws and nuts; meanwhile, indium sheets (not shown in the figure) are uniformly distributed on the contact interface of the cold-conducting copper block 2-2 and the superconducting cavity body 1 and at the joint of the half hoops so as to strengthen heat conduction; in order to reduce the residual magnetism of the space where the superconducting cavity 1 is located and effectively fasten, the screw is a 316L stainless steel screw, the nut is a silicon bronze nut, and the gasket is a stainless steel spring pad; further, the tightening torque of the screw and the nut is 115N.m, and the thermal resistance of the tightening joint is ensured to be lower than 1 multiplied by 10 -4 Km 2 /W。
In the above embodiment, preferably, temperature sensors (not shown in the figure) are arranged on the outer surface of the equatorial region of the superconducting cavity 1, on the three groups of cold-conducting copper blocks 2-2, the secondary cold plates 2-3, the secondary cold heads 2-6, and the like, for monitoring the temperature change of the superconducting cavity 1; meanwhile, a high-precision heater (not shown in the figure) is arranged on the secondary cold head 2-6 and is used for matching a temperature controller and a temperature sensor, so that the conditions that the cooling rate is stable between 30K and 15K and is continuously adjustable between 1min/K and 5min/K are realized, and the temperature gradient of the superconducting cavity 1 in the axial direction is ensured to be less than or equal to 0.025K/cm.
In the above embodiment, preferably, flux gate probes (not shown) capable of accurately measuring the magnetic field strength of 10mGs or less are disposed on the outer surfaces of the equatorial region and the outer surfaces of the beam pipe regions on both sides of the superconducting cavity 1 for remanence measurement and monitoring.
In the above embodiment, preferably, the vacuum unit 3 includes: a vacuum cover 3-1 provided outside the cold shield 2-1, the vacuum cover 3-1 being configured to form an interlayer vacuum environment for reducing static heat loss between the vacuum cover 3-1 and the superconducting cavity 1; one end of each of the two groups of vacuum pipelines 3-2 is connected with two bundles of flow pipelines of the superconducting cavity 1 through a vacuum angle valve 3-3, and the other end of each of the two groups of vacuum pipelines 3-2 penetrates out of the vacuum cover 3-1 and then is connected with a vacuum pump group (not shown in the figure) so as to form a cavity vacuum environment for accelerating charged particles in the superconducting cavity-pipeline system formed by the superconducting cavity 1 and the vacuum pipelines 3-2.
In the embodiment, preferably, the leak rate of the cavity vacuum environment is less than or equal to 5e-10mbar L/S at normal temperature, and the vacuum degree of the cavity vacuum environment is less than or equal to 5e-5Pa at normal temperature; the leak rate is less than or equal to 5e-8mbar L/S at normal temperature in the interlayer vacuum environment, and the vacuum degree is less than or equal to 5e-3Pa at normal temperature in the interlayer vacuum environment.
In the above embodiment, preferably, the vacuum cover 3-1 is made of stainless steel, and the inner and outer surfaces are polished to reduce gas adsorption; the top of the vacuum cover 3-1 is provided with a butt joint of the refrigerator 2-5, the side surface is provided with a butt joint of the refrigerator and the vacuum pipeline 3-2, and the bottom is provided with a butt joint of the coupler 4; a temperature sensor wall penetrating piece 3-4 is reserved on the vacuum cover 3-1 and is used for butt joint of data wires of the temperature sensor; the vacuum cover 3-1 is provided with a magnetic probe sensor wall penetrating piece 3-5 for butt joint of data wires of the fluxgate probe; the vacuum cover 3-1 is reserved with a backfill port for high-purity nitrogen gas inflation to recover vacuum and cleaning a pipeline, so that the cleanliness of the device is ensured.
In the above embodiment, preferably, since the cavity wall loss of the superconducting cavity 1 is very small, the bandwidth is very narrow, and the cavity vibration may cause the frequency detuning of the superconducting cavity, so in order to avoid that the vibration of the refrigerator 2-5 is transmitted to the superconducting cavity 1 to affect the stable operation of the superconducting cavity, the liquid helium-free radio frequency superconducting accelerator further comprises a shock absorber 5 arranged at the top of the vacuum cover 3-1, and the refrigerator 2-5 is arranged on the shock absorber 5, so that the vibration amplitude of the secondary cold head 2-6 of the refrigerator 2-5 in butt joint with the superconducting cavity 1 is greatly reduced; meanwhile, the flexible cold chain 2-4 between the secondary cold head 2-6 of the refrigerator 2-5 and the superconducting cavity 1 can effectively prevent the vibration of the refrigerator 2-5 from being transmitted to the superconducting cavity 1.
In the above embodiment, preferably, the superconducting cavity 1 is supported in the vacuum cover 3-1 by the support structure 6 made of non-magnetic material, and the support structure 6 is provided with a fine tuning rod, so that the position of the superconducting cavity can be finely tuned with high precision, so as to meet the collimation requirement of the superconducting cavity 1 of the accelerator.
In the above embodiment, it is preferable that the inner surface of the superconducting cavity 1 is formed with a thin film of a high temperature superconducting material, that is, a material having a superconducting transition temperature higher than 15K at zero magnetic field and a superheated magnetic field higher than 150mT at 4K temperature, such as Nb 3 Sn、MgB 2 NbN, iron-based superconducting materials, and the like. The shape and operating frequency of the superconducting cavity 1 are determined by parameters such as the type of charged particles to be accelerated, energy, etc., and may be a transverse magnetic wave (TM) superconducting cavity, a transverse electromagnetic wave (TEM) superconducting cavity, or other superconducting cavity structures.
It should be understood by those skilled in the art that the drawings and implementations of the present invention are for convenience only and the principles of the present invention and the examples of the liquid helium-free rf superconducting accelerator and the method of using the same are set forth herein for one shape of superconducting cavity, rather than for indicating or implying that the superconducting cavity and the solid conductive cooling structure design must have specific shape, size and material limitations, and therefore should not be taken as limiting the scope of the present invention. All applications of using a refrigerator drive to accelerate charged particles based on solid conduction cooling should be within the scope of the present invention.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (8)
1. The liquid helium-free radio frequency superconducting accelerator is characterized by comprising a charged particle injection system (10), a beam transmission system (20), an acceleration module system (30), a power source system (40), a low-level and control system (50) and an application terminal (60);
wherein the input end and the output end of the acceleration module system (30) are respectively connected with the output end of the charged particle injection system (10) and the input end of the application terminal (60) through the beam transmission system (20);
the charged particle injection system (10) is configured to generate a charged particle beam of a specific energy, a specific species, a specific intensity, a specific parameter;
the beam transport system (20) is configured to direct a beam of charged particles exiting the charged particle injection system (10) into the superconducting cavity of the acceleration module system (30) to be accelerated, and to direct the accelerated beam of charged particles exiting the superconducting cavity of the acceleration module system (30) to be transported to the application terminal (60) according to a specified trajectory;
the power source system (40) is connected with the superconducting cavity of the acceleration module system (30), and the power source system (40) is configured to provide radio frequency power to the superconducting cavity of the acceleration module system (30) so as to establish a radio frequency electromagnetic field in the superconducting cavity, so that charged particle beams are accelerated under the action of the electromagnetic field in the superconducting cavity;
the low-level and control system (50) is respectively and electrically connected with the charged particle injection system (10), the beam transmission system (20), the acceleration module system (30) and the application terminal (60), and the low-level and control system (50) is configured to monitor the running state of the accelerator by collecting and processing the temperature, the vacuum degree, the radio frequency, the beam position, the beam energy and the beam emittance signals of the accelerator so as to maintain the electromagnetic field amplitude and the phase stability in the superconducting cavity;
the acceleration module system (30) includes: a superconducting cavity (1) configured to provide energy to a beam of charged particles; -a cryogenic unit (2) configured to provide a desired cryogenic environment to the superconducting cavity (1); a vacuum unit (3) connected to the superconducting cavity (1), the vacuum unit (3) being configured to provide the superconducting cavity (1) with a cavity vacuum environment and a sandwich vacuum environment required for operation;
the cryogenic unit (2) comprises: a cold shield (2-1) covering the outside of the superconducting cavity (1), the cold shield (2-1) being configured to reduce static heat loss of the superconducting cavity (1); a magnetic shielding layer arranged in a space between the cold shield (2-1) and the superconducting cavity (1), the magnetic shielding layer being configured to shield an earth ambient magnetic field, reducing magnetic flux trapping of the superconducting cavity (1); the cooling guide blocks (2-2) are arranged in the heating area of the superconducting cavity (1), and the inner surfaces of the cooling guide blocks (2-2) are attached to the outer surfaces of the superconducting cavity (1); the secondary cooling plates (2-3) are arranged above the cold guide blocks (2-2), and one sides of the secondary cooling plates (2-3) are respectively connected with a plurality of groups of the cold guide blocks (2-2) through flexible cold chains (2-4); the refrigerating machine (2-5), at least one refrigerating machine (2-5) is arranged above the secondary cold plate (2-3), and the secondary cold head (2-6) of the refrigerating machine (2-5) is connected with the other side of the secondary cold plate (2-3) through a flexible cold chain (2-4).
2. The liquid helium free radio frequency superconducting accelerator according to claim 1, wherein the power source system (40) comprises a power source and a coupler (4), the coupler (4) being connected to a coupling port of the superconducting cavity (1), the coupler (4) being configured to feed radio frequency power output by the power source into the superconducting cavity (1).
3. The liquid helium-free radio frequency superconducting accelerator according to claim 2, wherein the beam transmission system (20) comprises a beam pipeline, a magnet element and a beam diagnosis element, the beam pipeline is processed by stainless steel and is in butt joint with a pipeline of the acceleration module system (30), the beam pipeline is vacuumized, the vacuum degree is lower than 1e-5Pa, and the connection parts of the beam pipeline are all sealed by metal to ensure high vacuum; the beam pipeline is provided with a beam diagnosis element for measuring the position, energy, intensity and emittance of the charged particle beam, and the beam pipeline is also provided with a diode magnet for deflection of the charged particle beam, a solenoid and a quadrupole magnet for focusing the charged particle beam, a hexapole magnet for eliminating chromatic dispersion, and a scanning magnet for irradiation.
4. The liquid helium-free radio frequency superconducting accelerator according to claim 1, wherein the charged particles generated by the charged particle injection system (10) comprise electrons, protons or carbon ions.
5. The liquid helium-free radio frequency superconducting accelerator according to claim 2, wherein the cold guide block (2-2) is in a half hoop form, and the half hoops of the cold guide block (2-2) are all fastened and connected through screws and nuts;
meanwhile, indium sheets are uniformly distributed on the contact interface of the cold guide block (2-2) and the superconducting cavity (1) and at the joint of the half anchor ear;
temperature sensors are uniformly distributed on the outer surface of the heating area of the superconducting cavity (1), the cold guide block (2-2), the secondary cold plate (2-3) and the secondary cold head (2-6) and are used for monitoring the temperature change of the superconducting cavity (1);
meanwhile, a high-precision heater is arranged on the secondary cold head (2-6) and is used for matching a temperature controller and a temperature sensor, so that the conditions that the cooling rate is stable between 30K and 15K and is continuously adjustable between 1min/K and 5min/K are realized, and the temperature gradient of the superconducting cavity (1) in the axial direction is ensured to be less than or equal to 0.025K/cm;
and a fluxgate probe is arranged on the outer surface of the superconducting cavity (1), and the fluxgate probe can accurately measure the magnetic field intensity which is less than or equal to 10 and mGs and is used for measuring and monitoring residual magnetism.
6. The liquid helium free radio frequency superconducting accelerator according to claim 5, wherein the vacuum unit (3) comprises:
-a vacuum enclosure (3-1) being provided outside the cold shield (2-1), the vacuum enclosure (3-1) being configured to form an interlayer vacuum environment between the vacuum enclosure (3-1) and the superconducting cavity (1) for reducing static heat loss;
one end of each vacuum pipeline (3-2) is connected with two bundles of flow pipelines of the superconducting cavity (1) through a vacuum angle valve (3-3), and the other end of each vacuum pipeline (3-2) penetrates out of the vacuum cover (3-1) and then is connected with a vacuum pump set so as to form a cavity vacuum environment for accelerating charged particles in a superconducting cavity-pipeline system formed by the superconducting cavity (1) and the vacuum pipeline (3-2).
7. The liquid helium-free radio frequency superconducting accelerator according to claim 6, wherein the vacuum cover (3-1) is made of stainless steel, and the inner and outer surfaces are polished; the top of the vacuum cover (3-1) is provided with a butt joint of the refrigerator (2-5), the side surface of the vacuum cover is provided with a butt joint of the vacuum pipeline (3-2), and the bottom of the vacuum cover is provided with a butt joint of the coupler (4); a temperature sensor wall penetrating piece (3-4) is reserved on the vacuum cover (3-1) and is used for butt joint of data wires of the temperature sensor; a magnetic probe sensor wall penetrating piece (3-5) is reserved on the vacuum cover (3-1) and is used for butt joint of data wires of the fluxgate probe; the vacuum cover (3-1) is reserved with a backfill port for high-purity nitrogen inflation to recover vacuum and cleaning a pipeline.
8. The liquid helium free radio frequency superconducting accelerator according to claim 6, further comprising a shock absorber (5) provided on top of the vacuum enclosure (3-1), the refrigerator (2-5) being provided on the shock absorber (5);
meanwhile, vibration of the refrigerator (2-5) is effectively prevented from being transmitted to the superconducting cavity (1) through a flexible cold chain (2-4) between a secondary cold head (2-6) of the refrigerator (2-5) and the superconducting cavity (1);
the superconducting cavity (1) is supported in the vacuum cover (3-1) through a supporting structure (6) made of a non-magnetic material, and a fine tuning rod is arranged on the supporting structure (6).
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