Single / double-module energy-adjustable superconducting electron accelerator device, medical isotope production system and method

Abstract

The invention provides a single / double-module energy-adjustable superconducting electron accelerator device, a medical isotope production system and a medical isotope production method, and the device comprises an injection system which is used for generating an electron beam current with certain energy and current intensity; the acceleration module system comprises single or double parallel acceleration modules, and each acceleration module comprises a superconducting cavity and a low-temperature unit; the low-temperature unit comprises a refrigerator, a high-thermal-conductivity cold chain, and a cold shield and a vacuum shell which sequentially cover the periphery; the radio frequency system is used for feeding microwave power into the superconducting cavity, maintaining the amplitude and phase stability of an electromagnetic field and accurately compensating the frequency deviation of the superconducting cavity; and the electron motion trail control system is used for guiding the electron beam to pass through the acceleration module and the plurality of circulating transmission pipelines with the corner radiuses sequentially enlarged for multiple times. The technical problems that an existing accelerator is limited by serious heating and cannot achieve high-flow-intensity and high-energy operation, a low-temperature cooling system is complex, so that the operation and maintenance cost is high, high energy and high flow intensity cannot be considered at the same time, and medical isotope production is difficult to meet are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of superconducting accelerators, in particular to a single / dual-module energy-adjustable superconducting electron accelerator device, a medical isotope production system and a method. BACKGROUND

[0002] Medical isotopes play an important role in the fields of early diagnosis, precise treatment, drug research, and pathological research in modern medicine. In recent years, the annual growth rate of medical isotope consumption has maintained at about 10%, and the supply gap is expected to be large in the future.

[0003] The traditional production method has problems such as low product purity and high radiation risk. The production of isotopes using electron accelerators has the advantages of high purity and strong flexibility. However, the existing room temperature electron accelerators are limited by severe heating and can only work in low duty cycle mode with insufficient current; at the same time, the current superconducting accelerator requires a complex low-temperature system for cooling, which has high operation and maintenance costs; moreover, the existing electron accelerators do not solve the demand for high-energy (>10 MeV) electron beams, and are not suitable for medical isotope production.

[0004] In addition, the existing accelerators mostly use a single acceleration path, and due to the inherent contradiction between “energy increase depending on path lengthening” and “transmission loss and system load increase under high current”, it is difficult to balance the demand for high energy and high current, which limits the production efficiency of medical isotopes. SUMMARY

[0005] The present application aims to provide a single / dual-module energy-adjustable superconducting electron accelerator device, a medical isotope production system and a method, which solves the technical problem that the existing accelerators are limited by severe heating and cannot achieve high-current and high-energy operation, the complex low-temperature cooling system results in high operation and maintenance costs, and the high energy and high current cannot be balanced, thereby failing to meet the technical requirements of medical isotope production.

[0006] To solve the above technical problems, the technical solutions of the present application are as follows: In a first aspect, the present invention provides a single / dual-module energy-tunable superconducting electron accelerator device, comprising: an injection system for generating an electron beam with an energy of not less than 300 keV and an average current intensity of not less than 2 mA; an acceleration module system connected to the injection system, comprising a single acceleration module or dual parallel acceleration modules; each acceleration module comprising a superconducting cavity and a cryogenic unit; the superconducting cavity having multiple acceleration units connected in series, with its two ends being an input beam pipe and an output beam pipe, respectively; the cryogenic unit comprising multiple refrigerators, a high thermal conductivity cold chain, and a system sequentially encased within the multiple acceleration modules. The cryostat consists of a cold shield and a vacuum shell surrounding both the cold end of the cryostat and the superconducting cavity. The cryostat is connected to the cold shield and the outer surface of the superconducting cavity via high thermal conductivity cold chains. The radio frequency system is used to feed microwave power into the superconducting cavity of each acceleration module, maintain the stability of the electromagnetic field amplitude and phase, and accurately compensate for the frequency deviation of the superconducting cavity. The electron motion trajectory control system is used to guide the electron beam to pass through a single acceleration module or dual parallel acceleration modules multiple times, and sequentially pass through multiple loop transmission channels with progressively increasing corner radii, so that the beam is transmitted and output according to a specified trajectory.

[0007] Furthermore, the outer surface of the superconducting cavity is provided with a solid conductive cooling structure, which is connected to the high thermal conductivity cold chain through through holes arranged thereon.

[0008] Furthermore, the solid conductive cooling structure adopts a niobium metal cooling ring. The niobium metal cooling ring is disposed on the outer surface of each acceleration unit of the superconducting cavity and is symmetrically arranged around the vertical equator. Multiple through holes are evenly distributed on each cooling ring. The through holes of adjacent cooling rings are staggered by a certain circumferential angle difference, which is used to uniformly connect the corresponding high thermal conductivity cold chain through fasteners.

[0009] Furthermore, the high thermal conductivity cold chain uses high thermal conductivity materials, including oxygen-free copper or high-purity aluminum, and indium sheets are installed at its connection points to enhance thermal conductivity.

[0010] Furthermore, the radio frequency system includes: a power source unit: a solid-state power source or a vacuum electronic device type, used to generate the microwave power required to establish a microwave electromagnetic field within the superconducting cavity; a transmission line unit, used to transmit microwave power to the coupler, the form of which is selected according to the operating frequency; a coupler: used to feed microwave power into the superconducting cavity; a tuner: used to accurately compensate for frequency deviations caused by factors such as vibration, Lorentz force, beam load, and microphone effect in the superconducting cavity, so that the resonant frequency of the superconducting cavity is always locked at the operating frequency of the signal source, thereby ensuring the stability of the accelerating field and the beam quality; and a control unit: used to acquire and process multi-parameter signals of the accelerator to monitor its operating status and maintain the stability of the amplitude and phase of the electromagnetic field within the superconducting cavity.

[0011] Furthermore, the electronic motion trajectory control system includes: a transmission pipeline unit, comprising a straight pipeline and a corner bend; the straight pipeline is used to connect with the injection system pipeline, the acceleration module pipeline, and the application terminal pipeline, and is connected to the corner bend to form the circulating transmission pipeline; a magnet unit, mounted on the transmission pipeline unit, is used to focus the electron beam and deflect it to guide it to move along a preset circulating transmission trajectory; and a beam diagnostic unit is used to monitor the current intensity, position, and bundle length information of the electron beam in real time.

[0012] Furthermore, the annular portion of the multiple cyclic transmission trajectories of the single acceleration module is waist-shaped, and only the straight-line portion of the trajectory on the side where the acceleration module is located overlaps. The two ends of the overlapping trajectory are the input straight-line trajectory and the output straight-line trajectory, which can be used as the initial input end and the final output end, respectively. The annular portion of the multiple cyclic transmission trajectories of the dual parallel acceleration module is a rounded rectangle, and the long straight-line portion of the trajectory on the side where the two acceleration modules are located overlaps. Among them, the two ends of the overlapping trajectory are an input straight-line trajectory and an output straight-line trajectory, which can be used as the initial input end and the first final output end, respectively. The magnet unit includes a focusing magnet and a deflecting magnet, and each trajectory is equipped with a corresponding magnet on the transmission pipe unit according to physical requirements.

[0013] Furthermore, the annular portion of the multiple cyclic transmission trajectories of the dual parallel acceleration module is a rounded rectangle, and the long straight-line portion of the trajectory on the side where the two acceleration modules are located overlaps. One end of the trajectory on the other overlapping side is another output straight-line trajectory, which is set in parallel with an input straight-line trajectory and extends in the opposite direction, and can be used as a second final output end.

[0014] Secondly, the present invention also provides a medical isotope production system, including an isotope production system and a single / dual-module energy-tunable superconducting electron accelerator device as described in any of the above claims; the isotope production system is connected to the output end of the device as an application terminal, and generates gamma rays by bombarding a heavy metal target with an accelerated electron beam, and generates medical isotopes through photonuclear reactions.

[0015] Thirdly, the invention also provides a method for producing medical isotopes, applied to the aforementioned medical isotope production system, comprising the following steps: providing an electron beam through an injection system, wherein the energy of the electron beam is not less than 300 keV and the average current intensity is not less than 2 mA; introducing the electron beam into the acceleration module system for acceleration, so that the final energy of the electron beam reaches not less than 10 MeV; bombarding a heavy metal target with the accelerated electron beam to generate high-energy gamma rays through bremsstrahlung; bombarding the target material with the high-energy gamma rays to trigger a photonuclear reaction that releases neutrons and generates medical isotopes; and water-cooling the heavy metal target and the target material to maintain the stability of the target material.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: This invention provides an electron beam with an energy of no less than 300 keV and an average current intensity of no less than 2 mA through an injection system. By coordinating an acceleration module system and an electron motion trajectory control system, the electron beam is guided to traverse a single or dual parallel acceleration module multiple times. Combined with a cyclic transmission pipeline design, continuous acceleration of the electron beam is achieved, ultimately reaching an energy no less than the set value. This overcomes the limitations of traditional single acceleration paths and meets the high-energy and high-current requirements of medical isotope production. Furthermore, the stable control of the electromagnetic field amplitude and phase by the radio frequency system, and the precise guidance of beam transmission by the electron motion trajectory control system, ensure the stability and efficiency of the accelerator operation, providing reliable support for the efficient production of medical isotopes.

[0017] The acceleration module of this invention adopts a solid conductive cooling structure (such as a niobium conductive cooling ring) that connects the cold screen and the superconducting cavity through a high thermal conductivity cold chain. Combined with the vacuum shell and cold screen design, it simplifies the cryogenic cooling system, reduces operation and maintenance costs, and ensures that the superconducting cavity is stably in a superconducting state.

[0018] In this invention, each accelerating unit of the superconducting cavity has multiple niobium cooling rings fixed on its outer surface, symmetrically arranged around the vertical equator. These cooling rings have evenly distributed through-holes, with adjacent rings having their through-holes offset at a certain circumferential angle. This structure allows for uniform connection to a high-thermal-conductivity cold chain. This unique cooling ring design achieves more efficient heat transfer, ensuring temperature uniformity across the superconducting cavity, effectively reducing temperature differences, suppressing thermal current, preventing additional magnetic flux pinning heat loss, and increasing operational thermal stability. This, in turn, ensures the accelerator stably accelerates the electron beam, meeting the high-energy electron beam requirements for medical isotope production.

[0019] This invention utilizes accelerated electron beams to bombard a heavy metal target to generate gamma rays, which are then used to generate medical isotopes through photonuclear reactions. Furthermore, water cooling is used to maintain the stability of the target material, overcoming the problems of low product purity and high radiation risk associated with traditional production methods. This invention can better meet the growing demand for medical isotopes. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 is a schematic diagram of the structural principle of the medical isotope production system provided in this embodiment, wherein... Figure 1 a To use a single acceleration module,Figure 1 b To employ dual parallel acceleration modules; Figure 2 This is a schematic diagram of the structure of the ellipsoidal superconducting cavity with multiple acceleration units connected in series, as provided in this embodiment. Figure 3 This is a schematic axial cross-sectional view of the cooling acceleration module system provided in this embodiment; Figure 4 This is a record of the stable operation of the conductive cooling acceleration module that has been built in this embodiment; Figure 5 Electron beam acceleration recording of the constructed conductive cooling acceleration module provided in this embodiment.

[0022] icon: 1-Input beam pipe; 2-Acceleration unit; 3-Output beam pipe; 4-Cooling ring; 5-Equatorial position; 6-Vacuum shell; 7-Cold shield; 8-Pipe vacuum unit; 9-Secondary cold head; 10-First-stage cold head; 11-Vacuum shell base plate; 12-Bracket; 13-Coupler; 14-Refrigerator; 15-First layer magnetic shield; 16-Second layer magnetic shield. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0025] Example 1 This embodiment provides a single / dual-module energy-tunable superconducting electron accelerator device, as shown in Figures 1-3, comprising: an injection system for generating an electron beam with an energy of not less than 300 keV and an average current intensity of not less than 2 mA; an acceleration module system connected to the injection system, including a single acceleration module or dual parallel acceleration modules; each acceleration module including a superconducting cavity and a cryogenic unit; the superconducting cavity having multiple acceleration units 2 connected in series, with its two ends being an input beam pipe 1 and an output beam pipe 3, respectively; the cryogenic unit including multiple refrigerators 14, a high thermal conductivity cold chain, and a system sequentially encased within the multiple acceleration units 14. The refrigerator 14 has a cold shield 7 and a vacuum shell 6 surrounding both the cold end and the superconducting cavity. The refrigerator 14 is connected to the cold shield 7 via a high thermal conductivity cold chain, and its primary cold head 10 is connected to the cold shield 7, and its secondary cold head 9 is connected to the outer surface of the superconducting cavity. The radio frequency system is used to feed microwave power into the superconducting cavity of each acceleration module, maintain the stability of the electromagnetic field amplitude and phase, and accurately compensate for the frequency deviation of the superconducting cavity. The electron motion trajectory control system is used to guide the electron beam to pass through a single acceleration module or a dual parallel acceleration module multiple times, and during this process, it passes through multiple loop transmission channels with progressively increasing corner radii, so that the beam is transmitted and output according to a specified trajectory.

[0026] In this embodiment, the injection system is used to provide an electron beam that meets the physical requirements of the acceleration module system. The electron gun used in the injection system is not limited to any type, but must meet the following requirements: the generated electron beam energy is not less than 300 keV, and the average current intensity is not less than 2 mA; before being injected into the acceleration module, the ratio between the transverse cross-sectional dimension of the electron beam cluster and the diameter of the beam transmission channel of the acceleration module is not higher than 0.1, and the ratio between the longitudinal time length of a single electron beam cluster and the working microwave period of the superconducting cavity of the acceleration module is not higher than 0.05, to ensure that there is no beam loss during the acceleration and transmission of the electron beam cluster in the acceleration module.

[0027] Specifically, in this embodiment, the injection system can use a thermionic cathode electron gun to generate an electron beam. The electron beam energy generated by the injection system can reach 1 MeV (1 MeV = 1000 keV), the average electron beam current can reach 10 mA, the transverse cross-sectional dimension of the electron beam cluster is ≤2 mm, and the longitudinal length of the electron beam cluster is less than 10 ps. These parameters are required, on the one hand, to leverage the high-current acceleration advantage of the superconducting accelerator of this invention and improve the production efficiency of medical isotopes; on the other hand, to ensure that there is no beam loss during the transmission and acceleration of the electron beam within the acceleration module, preventing any impact on the thermal stability of the acceleration module.

[0028] More specifically, the electron gun is the source of the electron beam, and its performance plays a crucial role in the initial energy and current intensity of the electron beam. Thermionic cathode electron guns, field emission electron guns, or photocathode electron guns can be selected. Thermionic cathode electron guns heat the cathode material, enabling electrons to gain sufficient energy to overcome the work function and be emitted. By precisely controlling the heating current and voltage of the cathode, the amount of electrons emitted can be effectively adjusted, thereby controlling the electron beam current intensity. Simultaneously, optimizing the accelerating electric field design of the electron gun, such as changing the voltage between the anode and cathode, can adjust the extraction energy of the electron beam. Adjusting the current and voltage of the magnet power supply can change the focusing magnetic field, thus adjusting the lateral cross-sectional size of the electron beam current generated by the injection system. Changing the magnitude of the electron gun grid suppression voltage can adjust the longitudinal length of the electron beam cluster in the injection system. Field emission electron guns utilize a strong electric field to cause electrons to quantum tunnel from the cathode surface. The emitted electron beam has high brightness and low emissivity, which is beneficial for obtaining high-energy and high-current electron beams. By adjusting the electric field strength of the field emission cathode and the structural parameters of related electrodes, the energy and current intensity of the electron beam can be controlled.

[0029] In this embodiment, the acceleration module system includes one or two parallel acceleration modules. The acceleration module system serves two purposes: firstly, to provide the superconducting cavity with the cryogenic environment required to maintain its superconducting state; and secondly, to accelerate the electron beam and increase its energy. Specifically, it includes a cryogenic unit and a superconducting cavity. The cryogenic unit is configured to provide the superconducting cavity with the cryogenic environment required to maintain its superconducting state, and the superconducting cavity is configured to accelerate the electron beam and increase its energy.

[0030] The cryogenic unit includes a cryostat 14, a vacuum shell 6, a cold shield 7, a magnetic shield, and a high thermal conductivity cold chain. The vacuum shell 6 is the outermost layer, providing a vacuum environment. The cold shield 7 is inside the vacuum shell 6 and covers the outside of the superconducting cavity, reducing system radiative heat leakage. The magnetic shield is set on the inner surfaces of the cold shield 7 and the vacuum shell 6, shielding the Earth's magnetic field. The cryostat 14 is a small, commercially available mass-produced cryostat, installed as a cold source on the outer wall of the vacuum shell 6. The first-stage cold head 10 of the cryostat 14 is connected to the cold shield 7 of the acceleration module via a high thermal conductivity cold chain, and the second-stage cold head 9 of the cryostat 14 is connected to the outer surface of the superconducting cavity via the same high thermal conductivity cold chain, so that the heat generated on the inner surface of the superconducting cavity during operation can be cooled in time through the cold chain. In this invention, the refrigerator 14 can be a Gifford-McMahon (GM) type refrigerator 14, a Pulse Tube (PT) type refrigerator 14, or other types of refrigerator 14, and the cooling capacity of the refrigerator 14 at 4.2K is not less than 1W.

[0031] Specifically, in this embodiment, each acceleration module can use 10 GM refrigerators 14, all of which are mounted on the outer surface of the module vacuum shell base plate 11. The vacuum shell 6 is made of stainless steel. The vacuum shell base plate 11 has interfaces for the 10 GM refrigerators 14, temperature sensor through-wall interfaces, magnetic probe sensor through-wall interfaces, and lead wire through-wall interfaces for the high-precision heater of the secondary cold head 9. It also has interfaces on the sides for docking with the vacuum pump group and interfaces on the front and rear sides for docking with the transmission pipeline. The cold shield 7 is located in the inner space of the vacuum shell 6, covering the superconducting cavity and the magnetic shield.

[0032] In this embodiment of the invention, the cold screen 7 is made of copper, a metal with good thermal conductivity. A high thermal conductivity cold chain connects the first-stage cold head 10 of 10 GM refrigerators 14 to the cold screen 7, keeping the cold screen 7 at approximately 40K during operation. This reduces radiative heat leakage from the superconducting cavity and static heat loss at low temperatures in the accelerator module. The magnetic shield is configured to shield the Earth's ambient magnetic field, reducing magnetic flux pinning in the superconducting cavity (a physics term; in radio frequency superconducting accelerators, magnetic fields can be "trapped" by defects in the superconducting material, a phenomenon known as pinning; pinned magnetic fields oscillate and generate heat under the influence of radio frequency electromagnetic fields, resulting in additional heat loss).

[0033] In this embodiment of the invention, two layers of magnetic shielding are arranged. The first layer of magnetic shielding 15 is attached to the inner wall of the vacuum shell 6 to shield and reduce the magnetic field of the Earth's environment inside the vacuum shell 6 in the first stage. The second layer of magnetic shielding 16 is attached to the inner wall of the cold screen 7 to shield and reduce the environmental magnetic field inside the cold screen 7 and around the superconducting cavity in the second stage. Both layers of magnetic shielding in this embodiment of the invention are made of permalloy with a thickness of 1.0 mm. After shielding by the two magnetic shields, the target environmental magnetic field around the superconducting cavity is reduced to below 10 mGs.

[0034] The high thermal conductivity cold chain provides a rapid channel for heat transfer within the acceleration module. In this invention, the high thermal conductivity cold chain is a braided tape made of high thermal conductivity materials such as oxygen-free copper or high-purity aluminum. On one hand, the braided tape securely connects the primary cold heads 10 of the 10 GM refrigerators 14 to 10 locations on the cold screen 7 using screws. During operation, the primary cold heads 10 effectively cool the cold screen 7, maintaining its temperature at approximately 40K. On the other hand, the braided tape securely connects the secondary cold heads 9 of the 10 GM refrigerators 14 to the through holes of the cooling niobium rings on the outer surface of the superconducting cavity using screws. During operation, the secondary cold heads 9 effectively cool the superconducting cavity, reducing its temperature to below 4.2K and placing it in a superconducting state. Indium sheets are arranged at the connections between the braided tape and the primary cold heads 10, secondary cold heads 9, cold screen 7, and cooling niobium rings of the refrigerators 14 to enhance thermal conductivity.

[0035] Furthermore, temperature sensors and high-precision heaters are installed at the secondary cold heads 9 of the aforementioned 10 GM refrigerators 14. These sensors are used to control the secondary cold heads 9 of the 10 GM refrigerators 14 to achieve synchronous, controllable, slow, and stable cooling when crossing the sensitive temperature range of 18K. The cooling rate is continuously adjustable between 2 min / K and 60 min / K. Additionally, a fluxgate probe is positioned in the center of the superconducting cavity for remanence measurement and monitoring. Figure 3 This diagram shows an axial cross-sectional view of the acceleration module system provided in this embodiment of the invention.

[0036] The superconducting cavity is a microwave resonant cavity with a superconducting material on its inner surface. During operation, a microwave electromagnetic field of a certain intensity and frequency is established inside the cavity. The electron beam is accelerated and energized by the microwave electromagnetic field as it passes through the superconducting cavity. A thin film or bulk of superconducting material is formed on the inner surface of the superconducting cavity. The superconducting material refers to a material with a superconducting transition temperature higher than 13K under zero magnetic field and a superheated magnetic field higher than 100mT at 4K temperature, including but not limited to Nb3Sn, MgB2, NbN, NbTiN, iron-based superconductors, etc.

[0037] Specifically, this invention employs one or two parallel-placed acceleration modules, each containing a superconducting cavity of type 1.3 GHz 9-cell ellipsoidal cavity. In this embodiment, an Nb3Sn thin film is grown on the inner surface of the superconducting cavity. The superconducting transition temperature of Nb3Sn reaches 18.3 K under zero magnetic field, while the overheating magnetic field at 4 K temperature approaches 400 mT. Each acceleration unit 2 of the superconducting cavity has four niobium cooling rings 4 symmetrically arranged around the equatorial position 5 welded to its outer surface. Each cooling ring 4 has six sets of through holes evenly distributed (the circumferential spacing between adjacent sets of through holes is 60 degrees; each set can use two through holes and connect to a high thermal conductivity cold chain; each high thermal conductivity cold chain connector has two holes, which correspond to each set of through holes for secure connection). The through holes of adjacent cooling rings 4 are staggered by a 30° circumferential orientation. A cooling ring 4 is welded to the outer surface of both the input and output beam pipes 3 of the superconducting cavity, and each cooling ring 4 is also provided with a through hole. Figure 2 This illustrates the 1.3 GHz 9-cell ellipsoidal Nb3Sn thin-film superconducting cavity used in this embodiment of the invention.

[0038] Furthermore, the electron beam gains energy when passing through the accelerator module, the magnitude of which is related to the working gradient of the superconducting cavity within the accelerator module. This invention controls the trajectory of the electron beam to allow it to pass through one or two parallel accelerator modules multiple times, enabling continuous acceleration and energy enhancement of electrons. The final energy of the electron beam is determined by the number of times it passes through the accelerator modules.

[0039] In this embodiment, the radio frequency system is used on the one hand to feed a microwave power source into the superconducting cavity within the acceleration module and establish a microwave electromagnetic field within the superconducting cavity; on the other hand, it is used to control the stability of the amplitude and phase of the microwave electromagnetic field within the superconducting cavity; simultaneously, it is used to accurately compensate for frequency deviations caused by factors such as vibration, Lorentz force, beam load, and microphone effect in the superconducting cavity, ensuring that the resonant frequency of the superconducting cavity is always locked at the operating frequency of the signal source, thereby guaranteeing the stability of the acceleration field and beam quality. Specifically, it includes a power source unit, a transmission line unit, a coupler 13, a tuner (not shown in the figure), and a control unit.

[0040] The power source unit is used to generate the microwave power required to establish a microwave electromagnetic field in the superconducting cavity. It can be a solid-state power source or a vacuum electronic device such as a klystron or magnetron. Its operating frequency covers the operating frequency of the superconducting cavity, and its output power is determined by the electron beam power, which is determined by the electron beam intensity and the energy boost obtained in the acceleration module.

[0041] The transmission line unit is used for directional transmission of microwave power. The form of the transmission line is mainly determined by the operating frequency. When the operating frequency is not higher than 650MHz, the coaxial line form can be selected, and when the operating frequency is higher than 650MHz, the waveguide form can be selected.

[0042] The coupler 13 unit is used to feed microwave power into the superconducting cavity. One end of the coupler 13 is connected to the power source through a transmission line, and the other end of the coupler 13 is connected to the superconducting cavity.

[0043] The tuner is used to precisely compensate for the frequency deviation of the superconducting cavity, so that the resonant frequency of the superconducting cavity is always locked at the operating frequency of the signal source.

[0044] The control unit is used to collect, transmit and process signals such as temperature, vacuum and radio frequency of the accelerator, monitor the operating status of the accelerator, and maintain the stability of the electromagnetic field amplitude and phase in the superconducting cavity. The specific requirements for the stability of the electromagnetic field amplitude and phase in the superconducting cavity are determined by the application requirements.

[0045] Specifically, in this embodiment of the invention, the electron beam current is 10mA, the maximum energy gain of the electron beam within the acceleration module is above 10MeV, and the newly gained beam power is above 100kW. This embodiment of the invention employs one or two parallel-placed acceleration module systems. Each acceleration module has the same structure and radio frequency system. The power source is a solid-state power source with a frequency of 1.3GHz and a rated power ≥150kW. Coupler 13 includes a fundamental mode main coupler 13 and a higher-order mode coupler. The main coupler has a transmission frequency of 1.3GHz, a dual-window coaxial structure, one end connected to the power source via a transmission line, and the other end connected to the main coupling port of the superconducting cavity. It is configured to feed microwave power into the superconducting cavity. The higher-order mode coupler is located outside the beam channel downstream of the superconducting cavity and is configured to absorb the higher-order modes induced by the electron beam within the superconducting cavity, preventing the higher-order mode fields from interfering with the normal acceleration and transmission of the electron beam within the superconducting cavity. In this embodiment, the superconducting cavity operates at a frequency of 1.3 GHz. Therefore, the power transmission line adopts a WR650 waveguide structure and is configured to guide the directional transmission of microwave power. The transmission line includes a straight waveguide for transmission along a straight direction and a bent waveguide for changing the transmission direction. The tuner has a tuning range of ≤1 MHz and a tuning accuracy of ≤10 Hz, including both slow and fast tuning methods. The slow tuning module is used to compensate for the one-time slow frequency change caused by the cooling process. The frequency change of the superconducting cavity caused by factors such as Lorentz force, microphone effect, and beam load is a fast change process that accompanies the operation of the superconducting cavity and ranges from several hundred Hz. This will be compensated by the fast tuning module. In this embodiment, the control unit is configured to collect, transmit, and process the temperature, vacuum, and radio frequency signals of the accelerator to monitor the operating status of the accelerator and maintain the stability of the electromagnetic field amplitude and phase within the superconducting cavity. This invention adopts an FPGA-based digital low-level control system, which mainly includes frequency synthesis, an FPGA digital signal processing platform, and upper-layer communication software.

[0046] In this embodiment, the electron motion trajectory control system guides the electron beam to travel along a specified trajectory. When a single acceleration module is used, the electron beam's trajectory is controlled to allow it to traverse the single acceleration module multiple times, achieving continuous acceleration and energization. When dual parallel acceleration modules are used, the system primarily guides the electron beam from the injection system into acceleration module 1 for initial acceleration. After acceleration, the beam leaves acceleration module 1 and enters acceleration module 2 via a corner trajectory for further acceleration. It then re-enters acceleration module 1 via another corner trajectory, repeating this process multiple times. The electron beam is continuously accelerated through acceleration modules 1 and 2, and along multiple corner trajectories, ultimately guiding the beam to its target energy level along a specified trajectory to the medical isotope production terminal. The final energy of the electron beam is determined by the number of times it traverses the acceleration modules. The electron motion trajectory control system mainly includes a transmission channel unit, a magnet unit, and a beam guide unit.

[0047] The transmission pipeline unit connects with the injection system pipeline, the acceleration module pipeline, and the isotope production system pipeline to provide a transmission path for the electron beam. The transmission pipeline is made of 304 stainless steel. In this embodiment, the inner diameter of the pipeline is set according to actual needs (e.g., 35mm). All beam pipeline connections are sealed with metal to ensure high vacuum. The beam pipeline is evacuated using an oil-free dry pump, a molecular pump, and an ion pump, with a vacuum level below 1e-5 Pa.

[0048] The magnet units are installed on the transmission pipes. Taking a dual-parallel acceleration module as an example, they are specifically installed on the transmission pipes at the injection system outlet, the two acceleration module inlet transmission pipes, the two acceleration module outlet transmission pipes, the isotope production system transmission pipe, and the transmission pipes along each corner and bend. These include deflection magnets, focusing magnets, and other functional magnets configured according to application requirements. After the electron beam exits the injection system and before entering acceleration module 1 and acceleration module 2, it needs to be laterally focused by the focusing magnet to ensure that the lateral cross-sectional dimension of the electron beam entering acceleration module 1 and acceleration module 2 is ≤2mm. This prevents the electron beam from bombarding the inner walls of the superconducting cavities of acceleration modules 1 and 2, causing heat deposition and affecting the overall thermal stability of the device. After the electron beam passes through acceleration modules 1 and 2, is accelerated, and leaves the two acceleration modules, it needs to be laterally focused by the focusing magnet to ensure that the electron beam does not diverge and bombard the inner walls of the transmission pipes, causing beam loss. After the electron beam passes through acceleration modules 1 and 2 and is accelerated, it needs to be deflected by deflecting magnets and guided into the transmission pipes of each corner and bend trajectory, and the quality of the electron beam is adjusted according to physical requirements.

[0049] Specifically, when using a single acceleration module, the embodiments of this invention have three corner trajectories, and the electron beam can be accelerated continuously four times by the same acceleration module. The magnetic field strength and corner radius of each corner trajectory need to be precisely adjusted so that the acceleration gradient, acceleration phase, and acceleration trajectory experienced by electron beams transmitted along different trajectories after entering the acceleration module remain consistent. Each corner trajectory requires the placement of corresponding focusing magnets and deflecting magnets according to physical requirements. By extracting electron beams transmitted along different corner trajectories, electron beam currents of different energies can be obtained. Finally, when the energy of the electron beam reaches the target value, the electron beam will be guided to the isotope production system for target firing and production of medical isotopes.

[0050] When using dual parallel acceleration modules, after the electron beam is first accelerated along a straight trajectory and leaves acceleration module 1, it is guided along a corner trajectory 1 into acceleration module 2 for further acceleration and energization. Then, the electron beam is guided along a corner trajectory 2 back into acceleration module 1 for further acceleration and energization. Subsequently, the electron beam is guided along multiple corner trajectories and repeatedly transmitted into acceleration modules 1 and 2 for continuous acceleration and energization. In this embodiment, there are a total of 6 corner trajectories, allowing the electron beam to be accelerated a maximum of 4 times by acceleration module 1 and a maximum of 3 times by acceleration module 2. In this embodiment, acceleration modules 1 and 2 have isotope production systems 1 and 2 respectively at their exit directions. By extracting electron beams transmitted along different corner trajectories, electron beams of different energies can be obtained. Once the energy of the electron beam reaches the target value, the electron beam can be drawn from the outlet of the acceleration module 1 and transmitted to the isotope production system 1 for target firing and production of medical isotopes, or the electron beam can be drawn from the outlet of the acceleration module 2 and transmitted to the isotope production system 2 for target firing and production of medical isotopes.

[0051] Each corner trajectory consists of a series of independent magnets and beam transmission channels. Each trajectory transmits an electron beam with different energy; the magnetic field strength and corner radius of each trajectory are also different. This is used to guide electron beams of specific energy accurately along specific trajectories, avoid mutual interference between electron beams in different trajectories, and ensure accurate re-entry into the acceleration module for continuous acceleration and energy enhancement. The magnetic field strength and corner radius of each corner trajectory need to be precisely adjusted to ensure that the acceleration gradient, acceleration phase, and acceleration trajectory experienced by electron beams from different trajectories remain consistent after entering the acceleration module. Each corner trajectory requires the placement of corresponding focusing magnets and deflecting magnets according to physical requirements.

[0052] The beam diagnostic unit is used to monitor information such as the electron beam current intensity, position, and bundle length to determine the state of the electron beam during acceleration and propagation. In this embodiment, a Fast Current Transformer (FCT) is used to measure the electron beam current intensity, a Beam Position Monitor (BPM) is used to measure the electron beam position, and a Fast Sampling Oscilloscope (FSO) is used to measure the electron beam bundle length.

[0053] In this embodiment, the vacuum system is configured to provide the vacuum environment required for the operation of the accelerator, and mainly includes a pipeline vacuum unit 8, an acceleration module vacuum unit, and a vacuum pump unit.

[0054] The vacuum of the "superconducting cavity-transmission pipeline" system, which consists of the transmission pipeline and the superconducting cavity of the acceleration module, is called pipeline vacuum unit 8. The leakage rate of the pipeline vacuum at room temperature is required to be ≤5e-10mbarL / S, and the vacuum degree of the pipeline vacuum at room temperature is required to be lower than 1e-5Pa. The pipeline vacuum is used to provide a vacuum environment for the transmission of the electron beam and to prevent the electron beam from colliding with the residual gas molecules in the pipeline, causing beam loss.

[0055] Among them, the acceleration module vacuum is the interlayer vacuum between the module vacuum cover and the superconducting cavity, which is used to reduce static heat loss. The interlayer vacuum requires a leakage rate of ≤5e-8mbarL / S at room temperature and a vacuum degree of ≤5e-3Pa at room temperature.

[0056] The vacuum pump set is used to extract gas from the transmission pipeline and the acceleration module, maintaining the vacuum environment of the transmission pipeline and the acceleration module. The vacuum pump set is an oil-free pump set, including oil-free dry pumps, oil-free molecular pumps, and ion pumps. Taking the dual parallel acceleration module as an example, a pump set is set between the electron beam extraction system and acceleration module 1, a pump set is set at the inlet of acceleration module 2, a pump set is set at each of the first, second, third, fourth, fifth, and sixth bends, a pump set is set at the outlet of acceleration module 1 and acceleration module 2, and a pump set is set at each of isotope production system 1 and isotope production system 2. All of the above pump sets are used to maintain the pipeline vacuum. The vacuum shell 6 of acceleration module 1 and acceleration module 2 are each equipped with a pump set to maintain the interlayer vacuum of the acceleration module system.

[0057] Example 2 This embodiment also provides a medical isotope production system, as shown in Figures 1-3, including an injection system, an acceleration module system, a radio frequency system, an electron motion trajectory control system, a vacuum system, and an isotope production system. The input and output terminals of the acceleration module system are connected to the output terminal of the injection system and the input terminal of the isotope production system, respectively, via the electron motion trajectory control system. The injection system is configured to generate an electron beam with specific energy, specific flux intensity, and specific parameters. The acceleration module system is configured to provide the superconducting cavity with the cryogenic environment required to maintain superconducting operation and to accelerate the electron beam to increase its energy; specifically, it includes a cryogenic unit and a superconducting cavity. The radio frequency system is configured to feed a microwave power source into the acceleration module and establish a microwave electromagnetic field within the superconducting cavity; and to control the stability of the amplitude and phase of the microwave electromagnetic field within the superconducting cavity. Simultaneously, it is used to precisely compensate for frequency deviations in the superconducting cavity, ensuring that the resonant frequency of the superconducting cavity is always locked at the operating frequency of the signal source; specifically, it includes a power source unit, a transmission line unit, a coupler 13, a tuner, and a control unit. The electron trajectory control system is configured to guide the electron beam along a specified trajectory and includes a magnet unit, a beam guide unit, and a transmission pipe unit. The vacuum system is configured to provide the vacuum environment required for accelerator operation and mainly includes a pipe vacuum unit 8, an acceleration module vacuum unit, and a vacuum pump unit. The isotope production system is configured to produce medical isotopes by bombarding the terminal target with the accelerated electron beam.

[0058] Specifically, the isotope production system utilizes an accelerated electron beam to bombard a terminal target to produce medical isotopes, primarily involving two processes. First, the electron beam bombards a heavy metal target, generating high-energy gamma rays through bremsstrahlung physics. Then, these high-energy gamma rays undergo photonuclear reactions with the atomic nuclei in the target material, releasing a neutron and thus generating the desired medical isotope. The material of the target is determined by the target medical isotope to be produced. In this embodiment, the heavy metal target used for generating high-energy gamma rays by electron beam irradiation is tantalum, and the target material used for generating medical isotopes by high-energy gamma ray irradiation is molybdenum-100 with a purity of over 99.9%; the type of medical isotope generated through photonuclear reactions is molybdenum-99. In this embodiment, because a large amount of heat deposition occurs during the electron beam bombardment of the heavy metal tantalum and the high-energy gamma ray irradiation of the molybdenum-100 target, both the heavy metal tantalum and molybdenum-100 are water-cooled to maintain the stability of the target material.

[0059] Example 3 This embodiment also provides a method for producing medical isotopes, applied to the aforementioned medical isotope production system, comprising the following steps: providing an electron beam through an injection system, wherein the energy of the electron beam is not less than 300 keV and the average current intensity is not less than 2 mA; introducing the electron beam into the acceleration module system for acceleration, so that the final energy of the electron beam reaches not less than 10 MeV; bombarding a heavy metal target with the accelerated electron beam to generate high-energy gamma rays through bremsstrahlung; bombarding the target material with the high-energy gamma rays to trigger a photonuclear reaction that releases neutrons and generates medical isotopes; and water-cooling the heavy metal target and the target material to maintain the stability of the target material.

[0060] Prototype setup and verification Figure 4 The diagram shows the record of the conductive cooling acceleration module built by the applicant using the technology in this embodiment operating stably for 40 minutes under a peak surface electric field of 15.0 MV / m. Figure 5 The results demonstrate that the conductive cooling (Nb3Sn radio frequency superconducting) electron accelerator module built by the applicant using the technology in this embodiment achieved stable acceleration for 1 hour under conditions of electron beam energy of 4.4 MeV and average current in macropulse (mA) of 170 mA. This fully illustrates the feasibility of the technical route of the present invention.

[0061] It should be noted that when using a single acceleration module, this embodiment has three corner trajectories, and the electron beam can be continuously accelerated four times by the same acceleration module, producing molybdenum-99 as the medical isotope. Firstly, by changing the operating gradient of the superconducting cavity within the acceleration module or the number of corner trajectories, electron beams with other target energies can be obtained. Secondly, by changing the target material of the isotope production system, medical isotopes of other target types can be produced. Furthermore, this invention is also applicable to superconducting cavities made of other materials with a superconducting transition temperature higher than 15K under zero magnetic field and a superheated magnetic field higher than 150mT at 4K.

[0062] When using dual parallel acceleration modules, this embodiment has 6 corner trajectories. The electron beam can be accelerated a maximum of 4 times by acceleration module 1 and a maximum of 3 times by acceleration module 2, producing molybdenum-99 as the medical isotope. First, by changing the operating gradient of the superconducting cavity within the acceleration module or the number of corner trajectories, electron beams with other target energies can be obtained. Second, by changing the target material of the isotope production system, other types of medical isotopes can be produced. Furthermore, this invention is also applicable to superconducting cavities made of other materials with a superconducting transition temperature higher than 15K under zero magnetic field and an overheating magnetic field higher than 150mT at 4K.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A single / dual-module energy-tunable superconducting electron accelerator device, characterized in that, include: An injection system is used to generate an electron beam with an energy of not less than 300 keV and an average current intensity of not less than 2 mA. An acceleration module system, connected to the injection system, includes a single acceleration module or dual parallel acceleration modules; each acceleration module includes a superconducting cavity and a cryogenic unit; the superconducting cavity has multiple acceleration units (2) connected in series, with an input beam pipe (1) and an output beam pipe (3) at its two ends respectively; the cryogenic unit includes multiple refrigerators (14), a high thermal conductivity cold chain, and a cold screen (7) and a vacuum shell (6) sequentially covering the cold ends of the multiple refrigerators (14) and the superconducting cavity; the refrigerators (14) are connected to the cold screen (7) via a high thermal conductivity cold chain, and the cold screen (9) is connected to the outer surface of the superconducting cavity via a high thermal conductivity cold chain; The radio frequency system is used to feed microwave power into the superconducting cavity of each acceleration module, maintain the stability of electromagnetic field amplitude and phase, and accurately compensate for the frequency deviation of the superconducting cavity. The electronic motion trajectory control system is used to guide the electron beam through a single acceleration module or dual parallel acceleration modules multiple times, and during this process, it sequentially passes through multiple loop transmission channels with progressively increasing corner radii, so that the beam is transmitted and output according to a specified trajectory.

2. The single / dual-module energy-tunable superconducting electron accelerator device according to claim 1, characterized in that, The outer surface of the superconducting cavity is provided with a solid conductive cooling structure, which is connected to the high thermal conductivity cold chain through through holes arranged thereon.

3. The single / dual-module energy-tunable superconducting electron accelerator device according to claim 2, characterized in that, The solid conductive cooling structure adopts a niobium metal cooling ring (4). The niobium metal cooling ring (4) is set on the outer surface of each acceleration unit (2) of the superconducting cavity and is symmetrically arranged around the vertical equatorial position (5). Multiple through holes are evenly distributed on each cooling ring (4). The through holes of adjacent cooling rings (4) are staggered by a certain circumferential angle difference, which is used to uniformly connect the corresponding high thermal conductivity cold chain through fasteners.

4. The single / dual-module energy-tunable superconducting electron accelerator device according to claim 1, characterized in that, The high thermal conductivity cold chain uses high thermal conductivity materials, including oxygen-free copper or high-purity aluminum, and indium sheets are installed at the joints to enhance thermal conductivity.

5. The single / dual-module energy-tunable superconducting electron accelerator device according to claim 1, characterized in that, The radio frequency system includes: Power source unit: a solid-state power source or vacuum electronic device type, used to generate the microwave power required to establish a microwave electromagnetic field in the superconducting cavity; Transmission line unit, used to transmit microwave power to coupler (13), the form of which is selected according to the operating frequency; Coupler (13): used to feed microwave power into the superconducting cavity; Tuner: Used to precisely compensate for the frequency deviation of the superconducting cavity, so that the resonant frequency of the superconducting cavity is always locked at the operating frequency of the signal source; Control unit: Used to acquire and process multi-parameter signals of the accelerator to monitor its operating status and maintain the stability of the electromagnetic field amplitude and phase within the superconducting cavity.

6. The single / dual-module energy-tunable superconducting electron accelerator device according to claim 1, characterized in that, The electronic motion trajectory control system includes: The transmission pipeline unit includes a straight pipeline and a corner bend; the straight pipeline is used to connect with the injection system pipeline, the acceleration module pipeline and the application terminal pipeline, and is connected with the corner bend to form the circulating transmission pipeline; The magnet unit, mounted on the transmission pipe unit, is used to focus the electron beam and deflect it to guide it to move along a preset cyclic transmission trajectory. The beam diagnostic unit is used to monitor the current intensity, position, and bundle length of the electron beam in real time.

7. The single / dual-module energy-tunable superconducting electron accelerator device according to claim 6, characterized in that, The annular portion of the multiple cyclic transmission trajectories of a single acceleration module is waist-shaped, and only the straight portion of the trajectory on the side where the acceleration module is located overlaps. The two ends of the overlapping trajectory are the input straight trajectory and the output straight trajectory, which can be used as the initial input end and the final output end. The annular portion of the multiple cyclic transmission trajectories of the dual parallel acceleration modules is a rounded rectangle, and the long straight-line portion of the trajectories on the side where the two acceleration modules are located overlaps; wherein, the two ends of the overlapping trajectory are an input straight-line trajectory and an output straight-line trajectory, which can be used as the initial input end and the first final output end, respectively. The magnet unit includes a focusing magnet and a deflecting magnet, and each trajectory is equipped with a corresponding magnet on the transmission pipe unit according to physical requirements.

8. The single / dual-module energy-tunable superconducting electronic accelerator device according to claim 7, wherein the annular portion of the multiple cyclic transmission trajectories of the dual parallel acceleration modules is a rounded rectangle, and the long straight-line portions of the trajectories on the sides where the two acceleration modules are located overlap, characterized in that... One end of the other overlapping trajectory is another output straight line trajectory, which is set in parallel with an input straight line trajectory and extends in the opposite direction, and can be used as a second final output end.

9. A medical isotope production system, characterized in that, Including isotope production systems and the single / dual-module energy-tunable superconducting electron accelerator device as described in any one of claims 1-8; The isotope production system is connected to the output of the device as an application terminal. It uses an accelerated electron beam to bombard a heavy metal target to generate gamma rays, and then generates medical isotopes through photonuclear reactions.

10. A method for producing medical isotopes, characterized in that, The medical isotope production system according to claim 9 comprises the following steps: An electron beam is provided by an injection system, wherein the energy of the electron beam is not less than 300 keV and the average current intensity is not less than 2 mA. The electron beam is introduced into the acceleration module system for acceleration, so that the final energy of the electron beam reaches not less than 10MeV; High-energy gamma rays are generated by bombarding a heavy metal target with an accelerated electron beam and bremsstrahlung. The high-energy gamma rays are used to bombard the target material, triggering a photonuclear reaction that releases neutrons and generates medical isotopes. Water cooling is used to maintain the stability of the heavy metal target and the target material.

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