Superconducting electron linear accelerator device for isotope production

Abstract

The utility model provides a superconducting electron linear accelerator device for isotope production, which comprises an injector, a superconducting acceleration module and an irradiation target area which are arranged in sequence, and the superconducting acceleration module is connected with a low-temperature cooling system, a radio frequency driving system and a control system; the superconducting acceleration module comprises a low-beta-value Ni3Sn superconducting cavity and five standard Ni3Sn superconducting cavity modules, the low-beta-value superconducting cavity is an SRF acceleration cavity of a 2-cell cavity with beta = 0.7, and each standard superconducting cavity module consists of four SRF acceleration cavities of the 2-cell cavity with beta = 1 which are connected in series; and the input end of the standard superconducting cavity module adopts a symmetrical double-input coupler. According to the linear accelerator device provided by the utility model, the Ni3Sn superconducting cavity adopts a 2-cell and double-input coupler structure, so that the power requirement of high-power input coupling can be reduced under high flow intensity, a high-power electron beam is generated at lower cost, and efficient and economic production of isotopes is realized.

Description

Technical Field

[0001] This utility model belongs to the field of accelerator technology, and specifically relates to a superconducting electron linear accelerator device for isotope production. Background Technology

[0002] Medical isotopes play a crucial role in the diagnosis and treatment of various diseases. Currently, the production of medical isotopes primarily relies on nuclear reactors. While the technology for producing isotopes using nuclear reactors is mature, it suffers from high operating costs, generates large amounts of radioactive waste, and has stringent safety requirements. Furthermore, as reactors age or are decommissioned, their isotope supply capacity decreases. In contrast, accelerator-based methods for producing isotopes have lower construction and operating costs, generate less radioactive waste, and pose no risk of nuclear proliferation.

[0003] Compared to other accelerators, using electron linear accelerators to produce radioactive isotopes offers several advantages. Linear accelerators feature high beam intensity and low beam loss. The energy of the electron beam is adjustable, allowing for the production of multiple isotopes simply by altering the irradiation of the target material. Furthermore, isotopes produced using electron accelerators exhibit high purity with minimal impurity nuclides, simplifying the purification system structure and reducing costs.

[0004] Most existing applied electron accelerators operate at room temperature, and due to significant cavity wall losses, the average power of the electron beam is typically limited to tens of kilowatts, making it difficult to meet the demands of efficient isotope production. In recent years, superconducting electron accelerator technology has gradually emerged, offering advantages such as low heat loss, high energy efficiency, and high repetition rate, and is capable of providing high-intensity electron beams.

[0005] However, current superconducting accelerators primarily use pure niobium materials for large-scale scientific installations. The liquid helium immersion cooling method for pure niobium cavities, due to its reliance on complex cryogenic systems and high maintenance costs, limits the widespread adoption of superconducting accelerators. In recent years, niobium-tritin (Nb3Sn) has emerged as a new superconducting material to replace pure niobium. Its superior performance at 4.2K, characterized by a high quality factor and low heat loss, allows for direct cooling of the superconducting cavity using a small 4K cryostat, eliminating the need for a liquid helium system. This offers advantages such as compact structure, easy maintenance, and low operating costs, significantly simplifying the cooling system of superconducting accelerators. Nb3Sn superconducting cavities typically require the formation of a Nb3Sn thin film on the inner wall of the pure niobium cavity via tin diffusion, which places extremely high demands on temperature control, annealing time, and film thickness.

[0006] Currently, linear accelerators have been designed for applications such as wastewater treatment, irradiation production of nanoscale wood materials, and medical isotope production. However, international research on niobium-tritin superconducting accelerators remains in the conceptual design stage, with no successful application cases, especially for high-power electron beam applications in isotope production. For isotope production, the only existing international application is a conceptual design of a 1.3 GHz 3-cell TESLA-type niobium-tritin accelerator, without any related experiments. Multi-cell niobium-tritin superconducting cavities are still in the technology and process development stage.

[0007] For the application requirement of isotope production, the yield of isotopes is directly proportional to the current of the electron beam intensity. Under the premise of economy, the electron beam current intensity is required to be high enough. Therefore, it is necessary to design a practically applicable electron linear accelerator based on a niobium-tin superconducting cavity to generate an electron beam with high beam intensity to meet the needs of efficient isotope production. Utility Model Content

[0008] The purpose of this invention is to provide a superconducting electron linear accelerator device for isotope production, so as to achieve efficient and economical isotope production.

[0009] To achieve the above objectives, this utility model provides a superconducting electron linear accelerator device for isotope production, comprising an injector, a superconducting accelerator module, and an irradiation target area arranged sequentially. The superconducting accelerator module is connected to a cryogenic cooling system, a radio frequency drive system, and a control system. The superconducting accelerator module includes a low-β niobium-tritin superconducting cavity and five standard niobium-tritin superconducting cavity modules. The low-β niobium-tritin superconducting cavity is composed of a 2-cell SRF accelerator cavity with β = 0.7, and each standard niobium-tritin superconducting cavity module is composed of four 2-cell SRF accelerator cavities with β = 1 connected in series. The input terminals of the standard niobium-tritin superconducting cavity modules and the input terminals of the low-β niobium-tritin superconducting cavity are coupled with symmetrical dual-input couplers.

[0010] Each 2-cell SRF accelerating cavity operates at a frequency of 1.3 GHz and uses a standardized superconducting accelerating cavity from the German TESLA project; the superconducting accelerating module is used to accelerate the electron beam to a beam energy of 40 MeV.

[0011] The injector includes a fast gate pulser and a thermionic gate-controlled DC electron gun connected thereto. The pulse signal of the fast gate pulser is applied to the control gate of the thermionic gate-controlled DC electron gun, which serves as the electron source for the superconducting acceleration module.

[0012] The injector also includes three injector solenoids and a focusing cavity disposed downstream of the hot cathode grid-controlled DC electron gun; and a superconducting cavity solenoid is provided between the low β-value niobium tritin superconducting cavity and the first standard niobium tritin superconducting cavity module.

[0013] The cryogenic cooling system uses a GM miniature refrigerator for conductive cooling of the superconducting cavity; the radio frequency drive system uses a 1.3 GHz L-band radio frequency source to provide a stable power source for the superconducting accelerator module; and the control system is used to monitor and adjust the operating status of the superconducting accelerator module.

[0014] The irradiation target area includes a converter and a target material; the converter is composed of a high-Z material and is used to convert the electron beam accelerated by the superconducting acceleration module into a high-energy gamma-ray photon beam, and the target material is used to absorb the high-energy gamma rays generated by the converter and produce target isotopes through photonuclear reactions.

[0015] The commercially available GM miniature refrigerator has a power of 4.5W and an operating temperature of 4K, and the low-β niobium-tritin superconducting cavity and the standard niobium-tritin superconducting cavity module can operate at a temperature of 4.2K.

[0016] The superconducting electron linear accelerator device is optimized by using a multi-objective genetic algorithm to optimize the beam current parameters of the electron beam at the exit of the superconducting electron linear accelerator device. The beam current parameters of the electron beam include the energy, average current intensity, transverse beam spot size, and energy dispersion of the electron beam at the accelerator exit.

[0017] The optimization variables of the multi-objective genetic algorithm include the magnetic field strength of the three injector solenoids, the phase of the focusing cavity, the acceleration amplitude and phase shift of the low-β niobium-tin superconducting cavity, the magnetic field strength and position of the superconducting cavity solenoid, the acceleration amplitude of each 2-cell cavity in the five standard niobium-tin superconducting cavity modules, the position of the first 2-cell cavity in the first standard niobium-tin superconducting cavity module, and the phase shift of each 2-cell cavity in the first and second standard niobium-tin superconducting cavity modules.

[0018] This invention relates to a superconducting electron linear accelerator device for isotope production. Its niobium-tin superconducting cavity adopts a 2-cell and dual-input coupler structure. Under high current intensity, it can reduce the power requirements of high-power input coupling and generate a high-power electron beam with an accelerator exit electron energy of 40MeV and an average current intensity of 10mA at a lower cost, thereby achieving efficient and economical isotope production.

[0019] This invention combines Nb3Sn material with a 2-cell TESLA cavity for medical isotope production, improving the feasibility of the manufacturing process. The 2-cell cavity is more conducive to the transmission of high-current electron beams. Furthermore, the dual-input coupler structure reduces the power requirements for high-power input coupling under high current conditions. This invention, employing a 2-cell Nb3Sn cavity and a dual-input coupler structure, satisfies the stability requirements of the SRF cavity and the load-bearing capacity requirements of the coupler under high-current electron beam conditions.

[0020] This invention uses a multi-objective genetic algorithm (MOGA) to jointly optimize the beam performance of the injector and accelerator section, which differs from existing segmented optimization methods. This invention integrates the injector and accelerator sections as a whole, considering the joint optimization of the solenoid, focusing cavity, and SRF accelerator cavity. Attached Figure Description

[0021] Figure 1 This is a structural block diagram of the superconducting linear electron accelerator for isotope production according to this utility model.

[0022] Figure 2 This is a layout diagram of the superconducting electron linear accelerator section of this utility model. The total length of the electron accelerator, injector section, and superconducting acceleration module section is approximately 15 meters. The injector section consists of a hot cathode DC electron gun, three solenoids, and a focusing cavity. After passing through the injection section, the electron beam is accelerated to 40 MeV through a superconducting 2-cell resonant unit cavity with β<1 and five superconducting modules (each module consists of four 2-cell TESLA standard cavities).

[0023] Figure 3 This is a schematic diagram illustrating the principle of isotope generation by an electron beam irradiating the target area in this invention.

[0024] Figures 4A-4B This is a schematic diagram of the structure and axial electric field distribution of a 2-cell TESLA cavity.

[0025] Figures 5A-5F This is a schematic diagram illustrating the simulation results of the superconducting linear electron accelerator of this invention. Wherein, Figures 5A-5C The longitudinal and transverse particle distribution of the electron beam at the injector exit is shown: Figure 5A This represents the distribution of electron energy with respect to the longitudinal position z. Figure 5B It is a transverse phase space distribution of x-x'. Figure 5C It has a horizontal xy distribution. Figure 5D-5F The longitudinal and transverse particle distribution of the electron beam exiting the superconducting module is shown: Figure 5D This represents the distribution of electron energy with respect to the longitudinal position z. Figure 5E It is a transverse phase space distribution of x-x'. Figure 5F It has a horizontal xy distribution.

[0026] Figures 6A-6C This is a schematic diagram showing the parameter variations of the superconducting linear electron accelerator of this invention. Figure 6A To increase the beam energy during the acceleration process of the superconducting module, Figure 6B This represents the change in the RMS transverse beam spot size during acceleration in the superconducting module. Figure 6C This represents the change in relative energy dissipation during acceleration. Detailed Implementation

[0027] The embodiments of this utility model are given below with reference to the accompanying drawings and described in detail.

[0028] like Figure 1 As shown, this utility model provides an electron linear accelerator based on a niobium-tritin (Nb3Sn) superconducting radio frequency cavity. This electron linear accelerator is installed in an isotope production system and can provide an electron beam with a beam energy of 40MeV and an average current intensity of 10mA. Its main structure includes an injector 1, a superconducting acceleration module 2 and an irradiation target area 6 arranged in sequence. The superconducting acceleration module 2 is connected to a cryogenic cooling system 3, a radio frequency drive system 4 and a control system 5.

[0029] The technical parameters of this invention include a maximum acceleration gradient of 2.0 MV / m for the 2-cell cavity, a beam current of 10 mA, and a corresponding input power of 20 kW. By using dual-input couplers, the power requirement of a single input coupler can be reduced by 50%, from 20 kW to 10 kW. These designs, based on physical calculations, improve the engineering feasibility of constructing the overall accelerator and reduce the difficulty of engineering implementation.

[0030] Among them, the injector 1, the superconducting acceleration module 2 and the irradiation target area 6 are arranged sequentially along the direction of incident electron beam transmission and are located in the same vertical plane.

[0031] The cryogenic cooling system 3 is connected to the superconducting cavity of the superconducting accelerator module 2 via a cooling conductor. The control system 5 extracts different types of signals from the superconducting accelerator module 2 to monitor and adjust the operating status of the superconducting cavity. The radio frequency drive system 4 inputs radio frequency signals into the superconducting cavity of the superconducting accelerator module 2 via a power coupler.

[0032] The injector 1 includes a fast gate pulser and a thermionic grid-controlled DC electron gun 11 connected thereto. The pulse signal of the fast gate pulser is applied to the control gate of the thermionic grid-controlled DC electron gun to modulate the emission of the electron beam. The thermionic grid-controlled DC electron gun serves as the electron source of the superconducting acceleration module 2, providing a stable electron beam with a high repetition rate.

[0033] During operation, the cathode of the thermionic grid-controlled DC electron gun is typically under a constant negative high voltage, continuously generating electrons. A fast gate pulse modulates the frequency of electron beam emission. The pulse signal applied by the fast gate pulse controls the gate potential, thereby determining the frequency of electron beam emission. When a negative bias voltage is applied to the gate pulse, electron emission is suppressed; when a positive signal is applied, the electron beam is released, causing the electron beam to output according to the set frequency and duty cycle, thus forming a high repetition rate electron beam.

[0034] like Figure 2 As shown, the injector 1 also includes three injector solenoids 12 and a focusing cavity 13 disposed downstream of the hot cathode grid-controlled DC electron gun 11. The three solenoids are used to laterally focus the electron beam and maintain the lateral dimension of the electron beam; the focusing cavity is used to compress the length of the electron beam.

[0035] In this embodiment, the accelerating voltage between the cathode and anode of the hot cathode gate-controlled DC electron gun is approximately 87 kV. To synchronize the 1.3 GHz radio frequency of the fast gate pulser and the electron linear accelerator, the pulse signal of the fast gate pulser is a 130 MHz radio frequency signal to periodically modulate electron emission, forming an electron bundle with a charge of 77 pC. Therefore, the hot cathode gate-controlled DC electron gun 11 can stably output a current of 10 mA. The focusing cavity 13 employs a 650 MHz focusing cavity, compressing the electron bundle to an RMS beam length of less than 20 ps.

[0036] The superconducting acceleration module 2 accelerates the electron beam using a niobium-tritin (Nb3Sn) superconducting radio frequency cavity. It includes a low-β niobium-tritin superconducting cavity 21 (β < 1) and five standard niobium-tritin superconducting cavity modules 22. The accelerating cavities in each standard niobium-tritin superconducting cavity module 22 are all niobium-tritin superconducting cavities with a β = 1. The superconducting acceleration module 2 is used to accelerate the electron beam to a beam energy of 40 MeV, and the accelerated electron beam is then guided into the irradiation target area.

[0037] The physical meaning of the β value is the ratio of electron velocity to the speed of light. Low-β superconducting cavities also use niobium-tin alloy, but their cavity design differs from the standard (β=1) niobium-tin superconducting cavity. In this embodiment, both the low-β niobium-tin superconducting cavity 21 and the standard niobium-tin superconducting cavity module 22 of the superconducting acceleration module 2 adopt a 2-cell SRF (superconducting radio frequency) acceleration cavity. Each 2-cell SRF acceleration cavity operates at a frequency of 1.3 GHz and uses the standardized superconducting acceleration cavity from the German TESLA (TeV-Energy Superconducting Linear Accelerator) project. Furthermore, the input terminals of the standard niobium-tin superconducting cavity module 22 and the low-β niobium-tin superconducting cavity 21 employ symmetrical dual-input couplers, which reduces the power requirements for high-power input coupling under high current conditions. A 2-cell cavity indicates that the accelerating cavity consists of two tandemly connected cell units. A 2-cell cavity is more advantageous for the transmission of high-current electron beams (with a current intensity of 10 mA). Compared to a 3-cell structure, this invention employs a TESLA-type 2-cell cavity combined with a symmetrical dual-input coupler in an Nb3Sn superconducting cavity, a structure even more suitable for high-current transmission.

[0038] The low-β niobium-tritin superconducting cavity 21 consists of a 2-cell SRF accelerating cavity with β = 0.7, and each standard niobium-tritin superconducting cavity module 22 consists of four tandem 2-cell SRF accelerating cavities with β = 1. Figure 2 As shown, a superconducting cavity solenoid 23 is provided between the low-β niobium-tritin superconducting cavity 21 and the first standard niobium-tritin superconducting cavity module 22 to control the lateral dimension of the electron beam. As shown in Figure 4, each 2-cell cavity consists of four half-bowl-shaped structures, with two half-bowl-shaped structures forming one cell unit of the 2-cell cavity. Along the direction of electron beam propagation, the half-bowl-shaped structures in each 2-cell cavity correspond to the first half-bowl-shaped structure Half-cell1, the dumbbell (formed by two half-bowl-shaped structures back to back), and the second half-bowl-shaped structure Half-cell2, respectively. Specific parameters are shown in Table 1. The beam tube length at the end of the first half-bowl-shaped structure Half-cell1 is 141.6 mm, and the beam tube length at the end of the second half-bowl-shaped structure Half-cell2 is 105.6 mm. The total length of each 2-cell cavity is 475.6 mm, and the acceleration length is 228.4 mm. In addition, the distance between adjacent 2-cell TESLA cavities in the same standard niobium-tin superconducting cavity module 22 is 115.4 mm, corresponding to half a microwave wavelength, and the distance between two adjacent modules is 475.6 mm.

[0039] Table 1: Specific structural parameters of the 2-cell cavity

[0040] Cavity shape parameters Half-cell1 Dumbbell Half-cell2 <![CDATA[Length xlen2]]> 57 57.7 56 <![CDATA[Equatorial radius r2]]> 103.3 103.3 103.3 <![CDATA[Iris radius r1]]> 39 35 39 <![CDATA[Horizontal semi-axis length rx1]]> 10 12 9 <![CDATA[Vertical semi-axis length ry1]]> 13.5 19 12.8 <![CDATA[Radius rx2 and ry2]]> 40.3 42 42

[0041] In the Nb3Sn-based superconducting accelerator module, the energy gain of each 2-cell SRF accelerating cavity is approximately 1.93 MeV. The accelerating length of each 2-cell SRF accelerating cavity is 228.4 mm. The effective accelerating gradient of the low-β Nb3Sn superconducting cavity 21 and the standard Nb3Sn superconducting cavity module 22 is calculated to be 8.5 MV / m. This effective accelerating gradient is below 10 MV / m, ensuring stable operation of both the low-β Nb3Sn superconducting cavity 21 and the standard Nb3Sn superconducting cavity module 22.

[0042] Therefore, the injection energy of the electron beam is relatively low (~87 keV), and the electron velocity is not close to the speed of light. In the non-relativistic region, a low-β niobium-tritin superconducting cavity 21 with a β value of 0.7 is first used to accelerate the electrons, achieving phase matching for the acceleration of low-energy electrons. After passing through a solenoid 23 located downstream of the low-β niobium-tritin superconducting cavity 21 with a β value of 0.7, the lateral dimension of the electron beam is controlled between 1 and 3 mm. In this embodiment, the lateral dimension of the electron beam after passing through the solenoid is 2.8 mm. The electron beam then passes through an SRF accelerating cavity consisting of five modules, each module consisting of four tandem 2-cell cavities. Figure 6A The results show that after acceleration by the superconducting module, the electron beam energy continuously increases, eventually reaching an average energy of 41.15 MeV. After acceleration, the electron beam is extracted to the irradiation target area 6.

[0043] like Figure 3 As shown, the irradiation target area 6 includes a converter 61 and a target 62. The converter 61 converts the electron beam accelerated by the superconducting acceleration module 2 into a high-energy gamma (γ) ray photon beam. The target 62 is used to induce photonuclear reactions, absorb the high-energy gamma rays generated by the converter 61, and produce target isotopes through photonuclear reactions (γ,n) or (γ,p).

[0044] Therefore, as Figure 3 As shown, the accelerated electron beam bombards the converter 61, and the electron beam passes through the converter 61 to generate a high-energy gamma-ray photon beam through bremsstrahlung radiation. Then, the high-energy gamma-ray photons irradiate the target material 62, and the photons interact with the atomic nuclei on the target material 62, thereby inducing photonuclear reactions (γ,n) or (γ,p), which are used to produce... 99 Mo、 67 Cu、 225 The target isotopes are Ac and others. In the first stage, photons are absorbed by the atomic nucleus, transferring their kinetic energy to the nucleus and raising it to an excited state. In the second stage, the excited nucleus then releases nucleons, converting the original nuclide into an isotope.

[0045] The converter 61 is composed of high-Z materials, typically tungsten (Wt, melting point 3422℃), platinum (Pt, melting point 1768℃), tantalum (Ta, melting point 3017℃), iridium (Ir, melting point 2446℃), etc. These materials have high atomic numbers and high melting points.

[0046] The target material 62 absorbs the high-energy gamma rays generated by the converter 61 and produces the target isotope through photonuclear reactions (γ,n) or (γ,p). The target material 62 is enriched with the target isotope's corresponding target material. Different target material materials can be used to produce different target isotopes, for example: molybdenum-100 (…). 100 Mo) target material → Production of molybdenum-99 (Mo) target material through (γ,n) reaction. 99 Mo); Zinc-68( 68 Zn) target material → Copper-67 produced through (γ,n) reaction ( 67 Cu); Radium-226 226 Ra) target material → Production of Actinium-225 via (γ,n) reaction ( 225 Ac).

[0047] The cryogenic cooling system 3 employs a GM (Gifford-Mcmahon) miniature refrigerator for conductive cooling of all low-β niobium tritin superconducting cavities 21 and standard niobium tritin superconducting cavity modules 22 in the superconducting accelerator module 2. Specifically, thermally conductive metal is connected around the equator of both the low-β niobium tritin superconducting cavities 21 and the standard niobium tritin superconducting cavity modules 22. This thermally conductive metal is directly connected to the secondary cold head of the GM miniature refrigerator. The primary cold head of the GM miniature refrigerator is connected to the thermal shielding layer and coupler of the superconducting accelerator module 2 to cool it to 50K. Calculations show that the cavity wall loss of each 2-cell cavity in the standard niobium tritin superconducting cavity module 22 is approximately 1.7W. Since the commercially available GM miniature refrigerator has a power of 4.5W and an operating temperature of 4K, and both the low-β niobium tritin superconducting cavity 21 and the standard niobium tritin superconducting cavity module 22 can operate at 4.2K, two GM miniature refrigerators are required for each standard niobium tritin superconducting cavity module 22.

[0048] The radio frequency drive system 4 uses a 1.3 GHz L-band radio frequency source to provide a stable power source for all the low β value niobium tritin superconducting cavities 21 and the first standard niobium tritin superconducting cavity module 22 of the superconducting acceleration module 2, meeting the radio frequency power requirements of the entire accelerator system.

[0049] Since the input of the standard niobium-tin superconducting cavity module 22 uses a symmetrical dual-input coupler, and the maximum input power of each 2-cell cavity is about 20kW, the maximum input power of each coupler of the symmetrical dual-input coupler is only 10kW. This not only easily meets the power performance requirements of the couplers for current high-power L-band RF sources, but also has the potential to operate at higher acceleration gradients, reducing the power requirements of high-power input coupling.

[0050] The control system 5 is used to monitor and adjust the operating status of the superconducting accelerator module 2. The control system 5 includes a low-level control system for controlling the cavity pressure and phase of the low-β niobium-tritin superconducting cavity 21 and the standard niobium-tritin superconducting cavity module 22 of the superconducting accelerator module 2, and also includes a monitoring and interlocking safety protection system.

[0051] The superconducting electron linear accelerator device is optimized using a multi-objective genetic algorithm, which optimizes the beam parameters of the electron beam at the accelerator exit, including the energy, average current intensity, transverse beam spot size, and energy dispersion of the electron beam at the accelerator exit, thereby improving the yield of isotopes.

[0052] To optimize the electron beam parameters, the optimization variables of the multi-objective genetic algorithm include the magnetic field strength of the three injector solenoids 12, the phase of the focusing cavity 13, the acceleration gradient and phase shift of the low-β niobium-tin superconducting cavity 21 and the standard niobium-tin superconducting cavity module 22.

[0053] The optimization objectives using the multi-objective genetic algorithm include (1) minimizing the energy dispersion of the electron beam at the linear accelerator exit; (2) minimizing the transverse beam spot size at the linear accelerator exit (based on being greater than 0.85 mm); (3) controlling the maximum value of the RMS beam spot size during transmission to avoid beam loss; and (4) achieving the target energy of 40 MeV at the accelerator exit.

[0054] In this embodiment, the input data of the multi-objective genetic algorithm is a set of optimization variables, a total of 18 optimization variables, including: (1) the magnetic field strength of the first injector solenoid 12; (2) the magnetic field strength of the second injector solenoid 12; (3) the phase of the focusing cavity 13; (4) the magnetic field strength of the third injector solenoid 12; (5) the acceleration amplitude Max(E) of the low β value niobium-tritin superconducting cavity 21; (6) the phase shift of the low β value niobium-tritin superconducting cavity 21; (7) the magnetic field strength of the superconducting cavity solenoid 23; (8) the position of the superconducting cavity solenoid 23; (9) the acceleration amplitude of each 2-cell cavity in the five standard niobium-tritin superconducting cavity modules 22; (10) the position of the first 2-cell cavity in the first standard niobium-tritin superconducting cavity module 22; (11-18) the phase shift of each 2-cell cavity in the first and second standard niobium-tritin superconducting cavity modules 22. The phase shift of the other niobium-tin superconducting cavity modules 22 does not need to be set. As the electron beam energy increases during the acceleration process, the various beam parameters of the electron beam tend to stabilize. The phase of the niobium-tin superconducting cavity modules 22 can be kept at the maximum acceleration phase.

[0055] Multi-objective genetic algorithms are an effective optimization method for solving complex problems with multiple competing objectives. The multi-objective genetic algorithm used in this invention can be any existing multi-objective genetic algorithm.

[0056] In this embodiment, the implementation process of the multi-objective genetic algorithm is as follows:

[0057] Step S1: Starting with population initialization, randomly generate an initial solution for a set of optimization variables, such as including 200 different parameter combinations.

[0058] Step S2: Use the electron beam dynamics simulation software PARMELA and ASTRA to calculate the key indicators of energy, average current intensity, transverse beam spot size and energy dissipation for each individual in order to evaluate the fitness of each individual.

[0059] The energy of the electron beam is adjusted by the acceleration amplitude, variables (5) and (9); the average current intensity is determined by the charge of a single bundle and the repetition frequency of the electron gun and the fast gate pulser; the fitness function is related to the transverse beam size and energy dispersion, and the specific expression is f(1) = ΔE / E; (relative energy dispersion) f(1) = w1*sigx + w2*max(sigx); where sigx is the transverse beam size at the accelerator exit, max(sigx) is the maximum transverse beam size during acceleration, w1 and w2 are weights, w1 = 30, w2 = 1.

[0060] Step S3: Based on the fitness of each individual, perform selection, crossover, and mutation operations to generate offspring individuals. Specifically, the population can be non-dominated and sorted according to fitness, excluding individuals with large sequences and retaining those with small sequences. A subset of individuals with high fitness are selected for the next generation. Subsequently, through simulated binary crossover, the parameters of two superior individuals are combined to generate a new optimized scheme. Simultaneously, some individuals are mutated with a certain probability to increase the search range and avoid getting trapped in local optima.

[0061] Step S4: Repeat steps S2 and S3 to continuously generate new individuals until the termination condition is met. The termination condition includes continuously generating individuals for 100 generations, or the optimization objective converges. At this point, the final output is a set of optimal parameters that satisfy the optimization objective.

[0062] This invention presents a multi-objective genetic algorithm that uses both PARMELA and ASTRA simulation software for combined optimization, integrating the optimization objectives of the injection and accelerator sections into a single simulation calculation. This allows for control of the transverse beam size and energy dispersion at the accelerator exit. Unlike existing segmented optimization methods, this invention utilizes a multi-objective genetic algorithm (MOGA) to jointly optimize the entire beam performance of the injector + accelerator section. It considers the joint optimization of the solenoid, focusing cavity, and SRF accelerating cavity as a whole.

[0063] Table 2 shows the design parameters of the superconducting electronic linear accelerator and the optimized simulated final beam parameters. It can be seen that the final optimization result is close to the optimization target.

[0064] Table 2: Design and simulation parameters of the superconducting electron linear accelerator

[0065]

[0066] Figures 5A-5C The electron beam distribution at the injector outlet is shown, illustrating the effects of the solenoid and focusing cavity, and the longitudinal electron beam length (e.g., Figure 5A (as shown) and the transverse dimensions of the electron beam (e.g.) Figure 5C (As shown) it was brought under control. Figures 5D-5F To illustrate the electron beam distribution at the accelerator exit, it is necessary to demonstrate that the local energy dispersion of the electron beam is small and the longitudinal beam length is within a reasonable range (e.g., Figure 5D As shown), the transverse dimension of the electron beam is small (e.g. Figure 5F As shown in the figure, it meets the design requirements for isotope production.

[0067] Figure 6AThe process of accelerating the electron beam energy in the superconducting module involves an electron energy of approximately 40 MeV at the accelerator exit. This range of approximately 40 MeV is suitable for electron beam energy in isotope production. Too low an energy will reduce the yield of isotopes, while too high an energy will lead to the production of more unnecessary radioactive isotopes. Figure 6B The variation of the transverse beam size during the acceleration process of the superconducting module demonstrates that the beam size is reduced after optimization. A smaller electron beam helps to generate a more concentrated photon beam, which has a higher probability of hitting the target, thereby improving the efficiency of photonuclear reaction. Figure 6C To mitigate the changes in energy dispersion during acceleration, the energy dispersion at the exit point is optimized, ultimately suppressing it to below 3%. Lower energy dispersion results in fewer impurity nuclides. Furthermore, from the perspective of electron beam transmission, to prevent beam loss during transmission, excessive energy dispersion should also be controlled. The electron beam parameters at the accelerator exit—beam energy, beam spot size, and energy dispersion—meet the design requirements for isotope production.

[0068] In summary, the superconducting electron linear accelerator device for isotope production of this utility model adopts a 2-cell and dual-input coupler structure in its niobium-tin superconducting cavity. Under high current intensity, the power requirements of high-power input coupling can be reduced, and a high-power electron beam with an accelerator exit electron energy of 40MeV and an average current intensity of 10mA can be generated at a lower cost, thereby realizing efficient and economical isotope production.

[0069] In this invention, the efficiency of isotope production is improved in the following two aspects: ① A 2-cell Nb3Sn superconducting cavity is used. Compared with the traditional Nb cavity, the Nb3Sn superconducting electron beam cavity has a higher quality factor Q and lower surface resistivity, which can provide a higher acceleration gradient under the same input power, thereby reducing energy loss and improving the overall energy conversion efficiency of the accelerator. In addition, the niobium-tin cavity has a higher critical temperature, which allows it to maintain excellent performance at higher temperatures (e.g., it can operate stably at 4.2K), while the existing pure niobium superconducting cavity requires a lower operating temperature of 2K to achieve similar performance, thereby reducing the complexity of the cooling system and operating costs. ② A higher electron beam flux can increase the yield of isotopes. The 10mA electron beam generated by this invention can increase the yield of isotopes and achieve the high efficiency requirements of isotope production.

[0070] Improving the economics of isotope production can be achieved in the following ways: ① Using a 4K GM refrigerator reduces cooling costs and avoids the high consumption of liquid helium systems, resulting in lower operating costs and simpler maintenance for the accelerator. The GM miniature refrigerator can be used for conductive cooling, avoiding the high costs associated with liquid helium cooling systems in superconducting accelerators. This also reduces operating costs and maintenance complexity, and allows for a more compact accelerator structure. ② This invention employs a symmetrical dual-input coupler, distributing the power load across the two couplers. This reduces the limitations of high-power input, enabling the superconducting cavity to operate more stably in a high-current mode with an average current of 10mA, improving beam transmission efficiency, reducing equipment failure rates, and thus lowering long-term operating and maintenance costs. The average current is significantly higher than that of traditional room-temperature accelerators (typically with beam currents only in the μA range), and the higher current of the electron beam can increase the yield of medical isotopes. ③ This invention employs a multi-objective genetic algorithm to optimize the beam parameters at the electron accelerator exit, and combines a solenoid and a superconducting acceleration module to control the lateral dimensions and energy dissipation of the electron beam. This maintains parameters such as beam energy, beam intensity, lateral dimensions, and energy dissipation within the design range (as shown in Table 2), ensuring optimal parameters when the electron beam enters the irradiation target area, reducing the generation of impurity nuclides, increasing isotope yield and purity, and reducing post-processing costs. ④ The electron beam energy is adjustable. By changing the target material in the irradiation target area, different medical target isotopes can be produced. One device can be used for… 99 Mo、 67 Cu、 225 The production of various medical isotopes such as Ac has broad market prospects and economic value.

[0071] This invention combines Nb3Sn material with a 2-cell TESLA cavity for medical isotope production, improving the feasibility of the manufacturing process. The 2-cell cavity is more conducive to the transmission of high-current electron beams. Furthermore, the dual-input coupler structure reduces the power requirements for high-power input coupling under high current conditions. This invention, employing a 2-cell Nb3Sn cavity and a dual-input coupler structure, satisfies the stability requirements of the SRF cavity and the load-bearing capacity requirements of the coupler under high-current electron beam conditions.

[0072] The above description is merely a preferred embodiment of this utility model and is not intended to limit the scope of this utility model. Various variations can be made to the above embodiments of this utility model. All simple and equivalent changes and modifications made based on the claims and description of this utility model application fall within the protection scope of the claims of this utility model patent. Any aspects not described in detail in this utility model are conventional technical content.

Claims

1. A superconducting electron linear accelerator device for isotope production, characterized in that, It includes an injector, a superconducting acceleration module, and an irradiation target area arranged in sequence. The superconducting acceleration module is connected to a cryogenic cooling system, a radio frequency drive system, and a control system. The superconducting acceleration module includes a low-β niobium-tritin superconducting cavity and five standard niobium-tritin superconducting cavity modules. The low-β niobium-tritin superconducting cavity consists of a 2-cell SRF acceleration cavity with β = 0.7, and each standard niobium-tritin superconducting cavity module consists of four 2-cell SRF acceleration cavities with β = 1 connected in series. The input terminals of the standard niobium-tritin superconducting cavity modules and the input terminals of the low-β niobium-tritin superconducting cavity adopt symmetrical dual-input couplers.

2. The superconducting electron linear accelerator device for isotope production according to claim 1, characterized in that, Each 2-cell SRF accelerating cavity operates at a frequency of 1.3 GHz and uses a standardized superconducting accelerating cavity from the German TESLA project; the superconducting accelerating module is used to accelerate the electron beam to a beam energy of 40 MeV.

3. The superconducting electron linear accelerator device for isotope production according to claim 1, characterized in that, The injector includes a fast gate pulser and a thermionic gate-controlled DC electron gun connected thereto. The pulse signal of the fast gate pulser is applied to the control gate of the thermionic gate-controlled DC electron gun, which serves as the electron source for the superconducting acceleration module.

4. The superconducting electron linear accelerator device for isotope production according to claim 3, characterized in that, The injector also includes three injector solenoids and a focusing cavity disposed downstream of the hot cathode grid-controlled DC electron gun; and a superconducting cavity solenoid is provided between the low β-value niobium tritin superconducting cavity and the first standard niobium tritin superconducting cavity module.

5. The superconducting electron linear accelerator device for isotope production according to claim 1, characterized in that, The cryogenic cooling system uses a GM miniature refrigerator for conductive cooling of the superconducting cavity; the radio frequency drive system uses a 1.3 GHz L-band radio frequency source to provide a stable power source for the superconducting accelerator module; and the control system is used to monitor and adjust the operating status of the superconducting accelerator module.

6. The superconducting electron linear accelerator device for isotope production according to claim 1, characterized in that, The irradiation target area includes a converter and a target material; the converter is composed of a high-Z material and is used to convert the electron beam accelerated by the superconducting acceleration module into a high-energy gamma-ray photon beam, and the target material is used to absorb the high-energy gamma rays generated by the converter and produce target isotopes through photonuclear reactions.

7. The superconducting electron linear accelerator device for isotope production according to claim 5, characterized in that, The GM miniature refrigerator has a power of 4.5W and an operating temperature of 4K, and the low-β niobium-tritin superconducting cavity and the standard niobium-tritin superconducting cavity module can operate at a temperature of 4.2K.

8. The superconducting electron linear accelerator device for isotope production according to claim 4, characterized in that, The superconducting electron linear accelerator device is optimized by using a multi-objective genetic algorithm to optimize the beam current parameters of the electron beam at the exit of the superconducting electron linear accelerator device. The beam current parameters of the electron beam include the energy, average current intensity, transverse beam spot size, and energy dispersion of the electron beam at the accelerator exit. The optimization variables of the multi-objective genetic algorithm include the magnetic field strength of the three injector solenoids, the phase of the focusing cavity, the acceleration amplitude and phase shift of the low-β niobium-tin superconducting cavity, the magnetic field strength and position of the superconducting cavity solenoid, the acceleration amplitude of each 2-cell cavity in the five standard niobium-tin superconducting cavity modules, the position of the first 2-cell cavity in the first standard niobium-tin superconducting cavity module, and the phase shift of each 2-cell cavity in the first and second standard niobium-tin superconducting cavity modules.

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