BackgroundBipolar magnet power supplies using switching techniques are commonly used to provide stable excitation current for correction magnet coils. Specification of the Shenzhen Superconductive Soft-X-ray Free Electron Laser (S3FEL) project requires enhanced magnetic field stability of correction magnets. However, when switching power supplies are used for correction magnets at low currents, the very narrow pulse width of the power switch leads to poor stability in the output current.PurposeThis study aims to propose a method involving a series controllable bidirectional impedance circuit to improve the stability of low current output from the correction magnet power supply.MethodsFirstly, the characteristics of a controllable bidirectional impedance was identified when connected in series from the power supply to the correction magnet, and a Bode diagram was applied to analyzing its features. Then, a controllable bidirectional impedance circuit was designed on the basis of simulation analysis. Finally, experimental validation was conducted using the correction magnet and power supply from Shanghai Synchrotron Radiation Facility (SSRF).ResultsThe experimental results demonstrate that serially connecting controllable bidirectional impedances not only improves low current stability but also allows for smooth switching between MOSFETs and controllable bidirectional impedances.ConclusionsThe circuit design proposed in this study is simple and proves to be effective to improve the stability of bipolar magnet power supply under low current condition.

BackgroundBoron neutron capture therapy (BNCT) is a new type of binary targeted radiotherapy that is gradually entering the commercial stage. The accelerator-based boron neutron capture therapy (AB-BNCT) neutron sources used in hospitals are inevitably accompanied by neutron leakage and gamma-ray contamination during equipment operation and patient treatment.PurposeThis study aims to analyze the radiation safety of public during the operation of BNCT using Monte Carlo geometric splitting variance reduction technique.MethodsFirstly, based on a 10 mA 2.8 MeV proton accelerator neutron source, the International Commission on Radiological Protection (ICRP) and the basic standard for ionizing radiation protection and radiation source safety in China, GB 18871?2002 was taken as the reference standard for the annual effective dose limit of 1 mSv for the public. This dose limit was conservatively estimated to be equivalent to a dose rate limit of 0.5 μSv·h-1. Then, a water model with the size of 100 cm×30 cm×80 cm was placed at the outlet of beam shaping assembly (BSA) after neutron beam moderation and collimation, and the shielding calculations of AB-BNCT treatment room were conducted by Monte Carlo programs with various techniques. Finally, these results were comparatively analyzed to give shielding scheme design of the AB-BNCT treatment room, and the optimization design was carried out according to the weak link of the shielding.ResultsThe simulation results indicate that the variance reduction techniques of geometric splitting and Russian roulette for shielding simulation calculations has higher efficiency and achieve more accurate calculation results. After optimizing the shielding design of the BNCT treatment room, the conservative calculation results prove that the total dose rate at the corridor outside the treatment room is less than 0.5 μSv·h-1 when the shielding body is 60 cm thick boron containing heavy concrete, which meets the design requirements. In addition, the thickness range of the boron containing heavy concrete shielding wall required for radioactive workers is given to be 45~50 cm when the dose rate limit is less than 2.5 μSv·h-1.ConclusionsThe shielding design of BNCT treatment room using Monte Carlo geometric splitting variance reduction technique in this study is safe and reliable, providing a theoretical basis for the commercial development of BNCT.

BackgroundThere are a large number of Cloisonné enamel in the Palace Museum, among which there are many problems in the screening of the manufacture process and background information of the enamel with "Jingtai". X-ray technology can be applied to non-destructive test of the structure and composition of enamel, and help researchers to acquire the information behind cultural relics.PurposeThis study aims to apply X-ray techniques to the investigation of Cloisonné enamel in the Palace Museum for analyzing their period, glaze and structure.MethodsFirstly, two pieces of enamel inscribed with "Jingtai" in the Palace Museum were selected as the research object. Then, the X-ray Computed Tomography (CT), X-ray Fluorescence (XRF) and Raman spectroscopy techniques were applied to investigating the period, glaze, structure and composition of these two Cloisonné enamels. Finally, comparative analysis of these identified characteristics was conducted to infer the differences in different parts of Cloisonné enamels.ResultsAnalysis results indicate that both of two Cloisonné enamels are old utensils made by changing their shapes with recombination of the old pieces, thus forming a new piece of enamel with "Jingtai" engraved on the bottom.ConclusionsThrough the mutual verification between the results of scientific and technical means, a clear conclusion is obtained, which provides a new idea and solution for the subsequent research on the modified enamel.

BackgroundThe Shanghai soft X-ray Free Electron Laser (SXFEL) and the Shanghai High repetition rate XFEL and Extreme light facility (SHINE) are equipped with various high-power microwave components, including traveling wave accelerating tubes, deflection cavities, pulse compressors, etc.PurposeThis study aims to develop two high-power stainless steel absorbing loads, so as to meet the testing and operational requirements of these components at high power levels.MethodsFirstly, an initial load model was designed through simulation methods, and the microwave parameters were optimized. Then, the convection heat transfer coefficient in the waterway was calculated using theoretical calculations. Based on this information, thermal analysis was conducted on the mechanical model of the load to determine its temperature distribution under working conditions. Finally, the loads were manufactured and their RF parameters were measured using a vector network analyzer both in the clamping state and after welding.ResultsThe two X-band loads feature a waveguide structure with periodic grooves, and are operated at 11.424 GHz and 11.988 GHz respectively. The simulation results show that the bandwidth of two loads below -20 dB near the center frequency reaches over 100 MHz. The experimental test results are in good agreement with the simulation calculation results, meeting the design requirements.ConclusionsThe developed high power X-band dry loads described in this study satisfy operating requirements for SXFEL and SHINE.

BackgroundBoron neutron capture therapy (BNCT) is a highly promising and precise cancer treatment technique with substantial application prospects worldwide. The neutron transport process directly influences beam characteristics and accuracy of treatment planning.PurposeThis study aims to use the advanced Monte Carlo software, NECP-MCX, to investigate the neutron transport in an accelerator-driven BNCT (AB-BNCT) device.MethodsThe advanced Monte Carlo software, NECP-MCX, was used to investigate the neutron transport in an AB-BNCT device and calculate the beam parameters at the exit of the beam-shaping assembly (BSA), and results were compared with that calculated using the mainstream Monte Carlo software MCNP software. The relative biological dose deposition in Snyder head phantoms using various databases was calculated using both NECP-MCX and MCNP for comparative analysis. [Results andConclusions] The results show that in the design of the designated beam-shaping assembly, the neutron beam parameters obtained from NECP-MCX simulations minimally deviated from those calculated using the mainstream Monte Carlo software. The values satisfy the specifications of the International Atomic Energy Agency, confirming the applicability of NECP-MCX for neutron transport simulation in AB-BNCT. Regarding the Snyder head phantom, the relative biological dose parameters obtained by matching NECP-MCX with different databases satisfy clinical treatment standards, providing a foundation for selecting databases in the biological-based treatment planning system.

BackgroundEfficiency calibration is an important prerequisite for γ-spectroscopy measurement, and its accuracy directly affects the reliability of measurement results. The commonly used efficiency calibration methods are active efficiency calibration based on experimental measurement and passive efficiency calibration based on Monte Carlo (MC) simulations.PurposeThis study aims to propose a sourceless efficiency calibration method for γ spectrum based on numerical analysis.MethodsBased on theoretical analysis and numerical calculation, a passive efficiency calibration method based on numerical analysis was established, and applied to a constructed geometric model for typical cylindrical LaBr3(Ce) and NaI(Tl) detector with a diameter and length of 3.8 cm. The γ-ray path trajectory inside the detector, relative position of the source and detector, and peak-to-total ratio were comprehensively analyzed. Efficiency formulas for radioactive point, surface, and volume radioactive sources were formulated. Then, a numerical integration program based on Simpson's algorithm was implemented in MATLAB to solve the numerical analytical formula, and applied to the calculation of detection efficiencies of the 3.8 cm cylindrical LaBr3(Ce) and NaI(Tl) detectors for isotropic 137Cs point, surface, and volume sources. The calculation was performed again by changing the position of the point source and the size of the surface and volume sources. Simultaneously, the Monte Carlo (MC) simulation software MCNP5 was employed to establish the physical model of the detector, and the F8 pulse amplitude card was used to calculate the detection efficiency of the detector for specific energy γ-rays. Finally, detection efficiency obtained by numerical calculation was compared with that of MC simulation to verify the efficiency of proposed sourceless efficiency calibration method for γ spectrum.ResultsCompared with the MC simulation results, the maximum error of numerical calculation does not exceed 3.5%, and the maximum relative errors of the point source efficiency, surface source efficiency and volume source efficiency are 3.26%, 3.33% and 3.36%, repectively, which proves the reliability and accuracy of the numerical analysis method in calculating the detection efficiency.ConclusionsThe passive efficiency calibration method proposed in this study is accurate and fast, avoids complicated MC simulation software, which tends to be difficult to understand and operate. Additionally, this work can be extended to the efficiency calibration of nuclear radiation detectors with different shapes, providing a new pathway for the efficiency calibration of detectors.

BackgroundPhotonuclear reactions and compact neutron sources have emerged as promising tools for the production of medical isotopes, providing alternatives to conventional reactor-based high-enriched uranium methods. East China University of Technology (ECUT) is currently constructing an electron accelerator-driven photoneutron source (ECANS) for medical isotope production research.PurposeThis study aims to investigate the photonuclear reaction with 100Mo isotope and utilize the generated neutrons for isotopic production.MethodsFirstly, the photonuclear reactions of 100Mo was analyzed in details. The neutron spectrum and activation yield of 99Mo within a high purity 100Mo target were investigated. Then, a new model to produce medical isotopes was established on the basis of the ECANS photonuclear source, comprising neutron energy modulation layer and neutron reflection layer. Finally, the production yields of 99Mo, 177Lu, and 90Y in various natural oxides were calculated and the feasibility of using photonuclear sources for medical isotope production was assessed. The content of radioactive impurities in natural oxides under irradiation conditions was also analyzed.ResultsSimulation results demonstrate that photo-nuclear reactions can effectively produce medical isotopes such as 99Mo, 177Lu, and 90Y, with respective activities of 0.64 TBq·d-1, 0.67 TBq·d-1, and 2.11 TBq·d-1. And in the high purity 100Mo target, the daily output of 99Mo reaches 2.00 TBq·d-1.ConclusionsThis study demonstrates the feasibility of using the photodisintegration reaction of 100Mo as a neutron source for secondary production of medical isotopes, offering the potential to enhance the economic viability of isotope production. The approach of this study provides preliminary insights for subsequent separation and purification processes, hence has certain reference value for the development of tools for radioactive isotope production.

BackgroundWith the development of materials science and technology, more and more novel neutron shielding materials have been studied and prepared. The test of thermal neutron shielding performance of materials is an important measure of evaluating the shielding performance of novel neutron shielding materials, and provides important guidance for the improvement and application of materials. Special attention has been paid to the thermal neutron shielding properties of some thin materials, such as radiation protection fibers, shielding coatings, radiation protection rubber, composites with thermal neutron absorbers. At present, it is not easy to obtain pure thermal neutron field based on isotope neutron source, and the commonly used thermal neutron detector has a wide energy response range, and there is no unified test standard, hence the accuracy of the test results of thermal neutron shielding performance of materials needs to be further improved.PurposeThis study aims to propose an accurate method for testing the thermal neutron shielding properties of materials and to design a corresponding test platform.MethodsA thermal neutron shielding performance testing method based on the "cadmium filter method" was proposed and a corresponding testing platform was established. Firstly, the platform was based on a 252Cf isotope neutron source and a 3He proportional counter, with the design principle of minimizing errors. Then, Monte Carlo simulation method was used to optimize the materials and dimensions of the radiation shield, neutron moderator, collimator, and detector shield of the platform. The system error caused by the testing principle was reduced by further optimizing the cadmium filter method, and a collimating neutron beam launcher was designed to improve the collimation effect of the neutron beam, increase the thermal neutron fluence rate and thermal neutron share, and reduce the random error and the system error caused by the system design. Finally, the thermal neutron shielding performance of the materials commonly used in the nuclear field were tested and corresponding simulation calculations were carried out to verify the feasibility and accuracy of the test method. Five factors affecting shielding performance testing, i.e., detector type, neutron source intensity, distance to detector, detection system centerline offset, and neutron source type were analyzed simultaneously.ResultsThe actual test results are in good agreement with the simulation results, with excellent repeatability and reproducibility under different influencing factors.ConclusionsThis study provides an effective means to accurately evaluate the thermal neutron shielding properties of materials.

BackgroundThe exploration of mineral resources and geological structures is crucial for the sustainable development of the economy, society, and environment. Cosmic ray muons, a type of natural background radiation, can be utilized in muon transmission imaging which is based on density differences of transmitted target.PurposeThis study aims to enable non-contact, long-range, and non-destructive imaging of target objects, making it a powerful complement to traditional exploration methods for mineral resources.MethodsThe Geant4 software was utilized to simulate the physical processes of cosmic ray muons with materials of varying densities, and the shallow and deep geological structures were explored using a "telescope" configuration for muon transmission imaging. Firstly, the discriminability of muon imaging technology for substances with varying percentage density differences in rocks. For the simulation of, a volcanic model was constructed and four muon detectors was employed for simulating the imaging of the shallow geological structures from different angles, ensuring coverage of the entire mountain. Then, muon detectors located 600 m underground were utilized to extend exploration above unexplored areas with varying scales of undiscovered gold ore to obtain deep geological structures. Muons with energy lower than the minimum penetrating energy along their paths were absorbed by objects whilst muons that reached the detectors carried information about the materials along their paths. Meanwhile, the collected ray information was utilized to establish a density inversion model to obtain the minimum penetrating energy for each path, enabling the deduction of opacity distribution. Finally, the density distribution of volcanic model was determined by combining the geometric structure of the detected object, and individual detection points enabled two-dimensional monitoring whilst multiple detection points allowed for three-dimensional monitoring.ResultsThe imaging results of simulation show that the muon transmission imaging method can differentiate between different geological structures when the density difference exceeds 5%. In deep geological exploration, due to the low muon flux, imaging requires more time to accumulate sufficient muon events. Muon transmission imaging technology can effectively identify mineral deposits within deep rock formations when the difference in opacity between the path of muon penetration through the gold ore and the surrounding rock is greater than 4%.ConclusionsResults of his study demonstrate that the cosmic ray muon transmission imaging technology can be applied to geological exploration to achieve non-destructive exploration and obtain higher imaging accuracy when there is a reasonable density difference in the mineral resources and geological structures of the exploration area.

BackgroundThe defects generated during the working process of metal materials have a significant impact on their performance. For example, the radiation-induced embrittlement and hardening of reactor pressure vessel (RPV) steels are a factor of concern, which hinders the life extension of the RPV. Annealing treatment is applied to alleviating irradiation-induced precipitates and defects and recover RPV's mechanical properties in the past few decades to extend the in-service lifetime of the RPV. Unfortunately, this conventional method generally requires a high treatment temperature and long operation time, inevitably wasting considerable energy due to the huge size of the RPV. Recently, as a more convenient and energy-saving method, the repair of metal defects by electropulsing treatment (EPT) has been developed.PurposeThis study aims to design and construct a device for EPT processing of samples, and investigate the repairs of defects in electron irradiated and deformed iron and RPV steel after EPT by using positron lifetime spectroscopy.MethodsElectron irradiated pure iron and RPV steel samples were prepared and subjected to multi parameter EPT device developed in laboratory, and the changes in defects of the samples with EPT were characterized by positron lifetime spectroscopy. In addition, the mechanical properties of pure iron tensile samples were characterized by micro Vickers hardness, and the defect information was characterized by positron lifetime spectroscopy to explore the relationship between macroscopic properties and microstructure.ResultsThe defects introduced by electron irradiation in pure iron and RPV steel samples gradually recover after EPT and exhibit similar patterns to annealing treatment. After stretching, the number of defects in pure iron samples increases, leading to an increase in Vickers hardness. EPT can restore defect and reduce Vickers hardness.ConclusionsThe defects generated by irradiation or deformation in pure iron and RPV steel can be partially repaired through EPT. The effect of defect repair is not only related to the initial state of the sample, but also to EPT's parameters. As a new non-destructive testing method, positron annihilation is expected to provide a criterion for material damage or defect repair under the action of pulse current, which can conveniently, quickly, and sensitively detect the defect state of actual working components.

BackgroundThe use of controlled X-ray sources instead of 137Cs radioactive sources in density logging has become a new trend. The intensity of the X-ray source is substantially influenced by the high voltage on the target substrate, and the density measurement uncertainty can be maintained at 0.01 g·cm-3 when the high voltage is 350 kV.PurposeThis study aims to analyze the parameters of the shielding material and thickness suitable for the 350 kV high-voltage X-ray density logging instrument.MethodsThe Monte Carlo method was used to analyze the energy spectrum and counting rate of X-rays passing through different materials and thicknesses. By comparing the correlation between the 0~0.15 MeV and 0.15~0.35 MeV energy windows, the reasons for the difference between the X-ray attenuation and detector count rate in different energy windows were determined. In addition, combined with the actual instrument model construction of the four-detector X-ray density logging instrument, the influence of the three parts of particles on the detector was primarily considered. The placement mode and optimal thickness of each part of the shield for detectors were analyzed and designed using Monte Carlo N-particle (MCNP) simulation.ResultsThe simulation results show that the attenuation of X-rays in high- and low-energy windows increases with increase of atomic number and thickness of shielding materials. When tungsten nickel iron alloy is selected as the shielding material for the four-detector X-ray density logging instrument model, the suitable thickness of the shield between the base and the near-source detector is 1.75 cm. Meanwhile, to maintain the high voltage of X-ray generator at 350 kV, a shield layer with a thickness of 0.2 cm is placed between each detector, and a shield layer with a thickness of 0.35 cm is added to the back of the detector.ConclusionsThis study provides the design theory and key parameters for shielding materials and structures in the development of X-ray density logging tool.

BackgroundThe 1.2 MeV/10 mA electron accelerator, as one of electron irradiation sources for comprehensive irradiation test chamber in Space Environment Simulation and Research Infrastructure (SESRI), can provide electron beams on the millimeter scale. However, the electron beam, as the electron irradiation source in space environment ground simulation experiment for aerospace, must be uniformly irradiated on large objects. Therefore, a well-suited irradiated technique is significant.PurposeThis study aims to obtain beam scanning with less than 10% of inhomogeneity for 0.6 MeV, 1.0 MeV, 1.2 MeV electron beam for SESRI.MethodsBased on the overall irradiation requirements, a specific beam-scanning system, including the scanning magnet with customized design, digital power supply and a dedicated apparatus for beam uniformity measurement, was developed. Particularly, in order to eliminate the influence of 45° incidence of electron beam upon scanning uniformity, an asymmetric and non-standard triangular waveform for the magnetic field excitation current was employed and implemented. The measurements for the beam non-uniformity were carried out on field experiments.ResultsExperimental results show that the scanning area of this electron accelerator reaches 1 000 mm×1 000 mm, and the scanning nonuniformity is less than 10% for variable beam energy from 0.6 MeV to 1.2 MeV, achieving the design goal and satisfying the irradiation requirements of SESRI.ConclusionsA specific beam-scanning system developed for SESRI is verified in this study, offering a good reference for any similar beam-scanning scenarios.

BackgroundShanghai HIgh repetitioN rate XFEL and Extreme light facility (SHINE) is a large-scale scientific facility under construction in China. Due to 1 MHz repetition rate and thousands of kilometers length of SHINE, the accelerator interlock system should be a large system with response speed in microsecond magnitude and capable of processing tens of thousands of signals simultaneously.PurposeThis study aims to design and implement fast interlock system integrated with the conventional slow interlock system for SHINE accelerator.MethodThrough the analysis of SHINE requirements, FPGA (Field Programmable Gate Array) technology, distributed control technology, and network communication technology were adopted to complete the design of the fast interlock system. The integration of fast interlock system and slow interlock system on the same platform was achieved through programmable control technology and interface program development. The interface development software for the control system was designed and developed using PyDM, and the massive data exchange between large-scale interlock system was solved by using FL-net technology. Finally, based on Experimental Physics and Industrial Control System (EPICS), the design of operation mode, system architecture and data transmission were implemented and deployed.ResultsThe accelerator interlocking system developed in this study enables data exchange and expansion between fast and slow interlocks, as well as between any station. The average response time for multiple sites connected by a 1 m cable is 903.32 ns, and the average response time for multiple sites connected by an 800 m cable is 5.33 μs.ConclusionsAll the functions of fast interlock system are implemented and verified, and the system have been put into online operation for SHINE injector. The response time test results meet the SHINE operation requirements, and remote control of the system has been implemented based on the EPICS.

BackgroundCompared with commercial X-ray tubes, Betatron can emit MeV-level X-rays and its penetration capability is better than that of keV-level X-rays, which can be used for non-destructive testing (NDT) of large workpieces.PurposeThis study aims to design and build a 2D/3D X-ray imaging platform for NDT of large workpieces by using a compact Betatron as the X-ray source.MethodsFirstly, the hardware of the imaging platform was designed. It consisted of the compact Betatron with X-ray energy of 2.50/7.50 MeV, a high-energy X-ray line array detector with GGAG(Gd3Ga2Al3O12) scintillator and a two-axis mobile platform. Then, based on the principle and image correction algorithm of the 2D imaging system, the stripe noise characteristics in both the pixel direction and time direction were analyzed, and the blank pixel correction method was employed to correct the two-dimensional image. Its two-dimensional imaging performance test was conducted on a 6 cm square steel workpiece. Finally, three-dimensional image reconstruction of the workpiece was achieved by rotating the workpiece to obtain projection values at different angles, and the spatial resolution of 3D imaging was calculated using logistic function fitting method. Results of different tomographic reconstruction algorithms were compared and analyzed to obtain important 3D imaging system parameters.ResultsMeasurement results show that the thickness of the stainless-steel half-value layer of the system is 24.94 mm, the 2D imaging spatial resolution is 2.12 mm, and the tomographic reconstruction image spatial resolution is 1.00 mm.ConclusionsCompared with the keV-level X-ray imaging system, this system can complete the non-destructive testing of larger workpieces.

BackgroundBoron Neutron Capture Therapy (BNCT) is a binary radiation therapy with strong targeting and high energy transfer line density at the cellular scale. It has the advantages of short treatment cycle and minimal damage to surrounding healthy tissues, making it a promising cancer treatment method.PurposeThis study aims to design beam shaping assembly (BSA) to make the neutron beam of D-Be neutron source suitable for BNCT and ensure neutron directionality.MethodsThe Monte Carlo simulation programs GEANT4 and FLUKA were employed to simulate the generation of 9Be(d,n)10B reaction neutron sources and subsequent neutron moderation. Then, a scheme design for BSA was carried out using a 1.45 MeV, 30 mA deuterium beam to bombard a 9 μm thin beryllium target, and set a basis BSA model with a cylindrical structure as a whole.ResultsThe simulation results show that using a 20 cm thick BiF3 and 30 cm thick MgF2 combined slowing layer, a 30 cm thick Pb reflector layer, a 9 cm thick MgF2 supplementary slowing layer, and a 0.2 mm thick Cd thermal neutron absorption layer, the outlet is ensured to γ and fast neutron composition, Φepi/Φth, Φepi/Φfast meets the recommended values of the IAEA (International Atomic Energy Agency).ConclusionsThis study obtained the neutron spectra and BSA specific design scheme of low-energy deuterium beams and thin beryllium targets, providing data reference for the slowing shaping of neutrons in D-Be neutron sources and supporting subsequent research on D-Be sources.

BackgroundThe non-destructive indirect measurement of accelerator electron beam parameters is a challenging task. Both the traditional X-ray pinhole imaging methods on storage rings and optical diffraction radiation (ODR) from a slit techniques on linear accelerators have their shortcomings. The laser Compton scattering (LCS) device is a new light source that uses relativistic electrons and low-energy photons to collide with each other to produce high-energy γ beams.PurposeThis study aims to extract the SSRF (Shanghai Synchrotron Radiation Facility) electron beam parameters based on the laser Compton scattering (LCS) techniques.MethodUnder the condition of controllable laser parameters, the electron beam parameters of LCS could be determined by the γ beam measurement. Firstly, simulation spectra reconstructed by self-developed Monte Carlo program based on Geant4 were selected by those best matched with the experimentally measured energy spectra. Then, the corresponding parameters of electron beam, including beam spot size in horizontal direction, electron energy and emittance, were extracted. Finally, the consistency of the gamma energy spectra at different colliding angles measured on the Shanghai Laser Electron Gamma Source (SLEGS) beamline station of SSRF was verified.ResultsThe extracted electron beam parameters of the SSRF storing ring are in good agreement with the theoretical values. The electron beam energy at SSRF storage ring BL03SSID interaction point is (3 511.44±0.11) MeV, the transverse (horizontal) dimension of the electron beam is (316.60±0.15) μm, and the emittance of the electron beam is (4.56±0.01) nm·rad, with relative deviations of 0.33%, 1.6%, 8.1%, respectively.ConclusionResults of this study demonstrate that LCS is an effective and non-destructive way to determine the electron beam parameters indirectly and lays a stable foundation for the extraction of other parameters of the electron beam.

BackgroundThe RF output amplitude of the Low Level Radio Frequency (LLRF) system in Shanghai Soft X-ray Free-electron Laser (SXFEL) exhibits oscillations during the search for the maximum accelerating phase, compromisingthe stability of the entire device.PurposeThis study aims to develope a multi-variable estimation-based calibration technology for the Vector Modulator (VM) to stabilize the RF output amplitude and reduce the crosstalk between the amplitude and phase loops in closed-loop control.MethodsA non-ideal model of the VM was analyzed and established to address output amplitude stabilization in the LLRF system's microwave power source. The parameters of this model were estimated using real input and output data from the VM. A calibration algorithm was then designed and implemented to mitigate the adverse effects caused by non-ideal factors.ResultsExperimental results demonstrate that the proposed method reduces the impact of phase setpoint changes on the VM's output amplitude from 4.0% Root Mean Square (RMS) to 0.19% RMS after calibration. Furthermore, the error between the phase setpoint and measured phase was reduced to within 0.18° RMS.ConclusionsThis proposed method improvesisolation between amplitude and phase, effectively eliminating phase differences between the output and sampled waveforms.

BackgroundThe Multilayer Ionization Chamber (MLIC) is an instrument in rapidly measuring the proton depth dose distribution, which is crucial for enhancing the efficiency of beam commissioning and daily quality assurance in treatment rooms.PurposeThis study aims to investigate the impact of the Water Equivalent Ratio (WER) energy dependence of various absorber materials on MLIC measurements, thereby improving the accuracy of depth dose distribution measurements.MethodsBased on the fixed beam source parameters in the beam therapy room of Shanghai Advanced Proton Facility (SAPT), a physical model of MLIC was constructed using Monte-Carlo method. The simulation environment was validated by comparison of the measured and simulated integrated depth dose curve. The WER for three absorber materials i.e., Aluminum, PMMA, and FR-4, was calculated by simulation across different energies and thicknesses. Then, proton pencil beams of varying energies were simulated incident on MLIC, and the depth dose distribution of MLIC made from these materials was analyzed whilst the MLIC composed of water absorber was served as a reference.ResultsSimulation results show that the energy dependence of WER significantly influences the range parameters of the depth dose distribution, which was measured by MLIC within the clinical proton radiotherapy energy spectrum, with an impact exceeding 60%, and has a lower effect on the width and the distal dose falling region length of the Bragg peak. By adopting the appropriate WER values, the disparities in depth dose distribution parameters between MLIC made from different absorber materials and that composed of water absorber can be greatly reduced. Notably, for PMMA (Polymethylmethacrylate), the range discrepancy is minimized to 0.220 mm.ConclusionsThe depth dose distribution measured by MLIC is notably affected by the energy dependence of WER, underscoring the importance of considering WER's energy dependence in clinical proton therapy. The study is valuable for guiding experiment tests and optimized design of MLIC.

BackgroundThe Super Tau Charm Facility (STCF) is a new generation electron-positron colliders at the forefront of high precision, and its high brightness requirements pose a major challenge to accelerator technology. Resonant cavity-based monitors utilize characteristic mode signals for non-intercepting, high signal-to-noise ratio measurements, hence may meet the online high-resolution measurement requirements of various high-quality linear accelerators.PurposeThis study aims to address the challenges posed by the short lifetime and the small dynamic aperture of the storage ring beams in the STCF by developing high-resolution monitoring techniques for bunch length and charge to ensure efficient injection and precise measurement of these parameters.MethodsAccording to the beam parameters and measurement requirements of the STCF injector, the physical design and simulation of the resonator bunch length and charge monitor were carried out. Two Pill-Box cavities were designed by using Computer Simulation Technology (CST) modeling, and their structures were optimized. Subsequently, the beam load in the CST particle studio for simulation was conducted to analyze influences of beam tilt and lateral offset on the measurement accuracy, and the measuring resolutions of bunch length and charge were evaluated using cavity beam position monitor (CBPM).ResultsSimulation results show that the measurement errors of bunch length and charge are 3.3% and 0.02%, respectively. According to the online test results of the same type monitor, it is estimated that the resolution of bunch length of the monitor is expected to reach 100 fs@1.5 nC, and the relative resolution of charge measurement is better than 0.07%.ConclusionsThe currently designed monitor meets the diagnostic requirements of bunch length and charge of STCF, it will be manufactured in future for online testing.

BackgroundMulti-Wires detector (MW) is widely used in beam profile measurements. However, wire deformation and even wire broken have also happened frequently during the MW operation due to beam power deposition on the wire under high beam power environment.PurposeThis study aims to investigate the influences of the beam parameters and detector design, especially wire tension structure, on the wire temperature and wire deformation arising therefrom.MethodsFirstly, based on the backward Euler method with adaptive steps, a numerical algorithm was developed to conduct temperature simulation of MW. Then, verification experiments with various beam parameters and detector design of MW were performed in an ion source platform at Institute of Modern Physics (IMP), Chinese Academy of Sciences, and the wire deformation caused by temperature was reproduced and observed at HIMMWW (Heavy Ion Medical Machine at WuWei city, China) complex. Finally, comparative analysis was conducted on the relevant results to find the appropriate beam parameters and detector design.Results & ConclusionsExperimental results show that temperature plays an essential role on wire deformation if none tension mechanism is implemented on wire structure. Based on numerical simulations, experiments verifications and operation experiences, a fixed wire tension maintained by welding is appropriate while the wire temperature is below 1 300 K, which also provides a simple construction and a low cost. After exceeding 1 300 K, pre-tensioning by a spring is essential to support the wire with a constant tension to avoid deformation.

BackgroundIn the process of nuclear fuel generation, neutron poisons are added to enhance performance of nuclear fuel. Erbium is a common neutron poison, and its content needs to be measured and analyzed during the production of such nuclear fuels. The traditional methods have limited penetration and can only analyze the surface of the samples, unable to penetrate the bulk nuclear fuel materials for internal component analysis. Prompt Gamma-ray Neutron Activation Analysis (PGNAA) is a non-destructive testing technique, which is suitable for detecting large samples.PurposeThis study aims to explore the feasibility of determining the erbium in large samples based on PGNAA technology.MethodsFirstly, a deuterium-tritium (D-T) neutron generator and a high-purity germanium (HPGe) detector were employed to establish a measurement platform. Erbium oxide was selected as the sample, and measurements were conducted utilizing the 815.9 keV peak emitted from the reaction of fast neutrons with erbium. Then, the neutron yield of D-T neutron generator was calculated using copper foil activation and Monte Carlo simulations, and the neutron spectrum at sample position was calculated using Monte Carlo simulation for observing the thermal and fast neutron fluxes. Finally, the calibration curve and mass detection limit were analyzed.ResultsMeasurement results show that the neutron yield of D-T neutron generator is (2.34±0.01)×106 s-1 and the fast neutron flux at sample position is 106 cm-2?s-1. Analysis results demonstrate that there is a good linear relationship between the 815.9 keV peak counts and the mass of erbium. The mass detection limit for erbium is 28 g. In addition, there is no interference between the intrinsic gamma ray of 238U and the 815.9 keV Er peak.ConclusionsThis study veri?es the feasibility of PGNAA technology for the erbium determination, which can be used for further analysis of erbium in nuclear fuel.

Compared with turn-by-turn beam diagnostic techniques widely used in electron storage ring, bunch-by-bunch diagnostic technology allows the measurement and analysis of each bunch, offering a more comprehensive understanding of the internal state of the electron beam with results that are closer to the true physical model. Recent advancements in data acquisition equipment and signal processing algorithms have laid the foundation for the continuous development of bunch-by-bunch diagnostic techniques. This article provides an overview of the basic principles and architecture of bunch-by-bunch diagnostics, summarizes exploratory work and research achievements in this field by major domestic and international research groups, highlights the research approach, latest findings, and technological applications explored by the Shanghai Synchrotron Radiation Facility (SSRF) team. The future research directions worth attention and development trends are discussed, offering valuable insights for researchers dedicated to the field of beam measurements.