The 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.

This 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.

Based 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.

Simulation 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.

The 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.

The 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.

This 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.

A 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.

Experimental 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.

This proposed method improvesisolation between amplitude and phase, effectively eliminating phase differences between the output and sampled waveforms.

The 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.

This study aims to extract the SSRF (Shanghai Synchrotron Radiation Facility) electron beam parameters based on the laser Compton scattering (LCS) techniques.

Under 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.

The 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.

Results 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.

Rubber-based nanocomposites have become a research focus in the nuclear industry due to their wide application in wearable radiation protection devices.

This study aims to explore the γ-ray shielding mechanism of composite material of Bi₂WO₆ nanoparticles and natural rubber (NR), so as to provide theoretical support for the further materials preparation of low toxicity, light weight and high efficiency radiation shielding.

Bismuth tungstate (Bi₂WO₆) nanoparticles synthesized via hydrothermal process, additionally, WO₃ and Bi₂O₃ particles were prepared by ball milling method. Then, these particles were filled into natural rubber (NR) at the mass fraction of 30% to fabricate three composites: NR/Bi₂WO₆, NR/WO₃ and NR/Bi₂O₃. Finally, laser particle size analyzer, X-ray diffraction analysis (XRD) and field emission scanning electron microscope (FE-SEM), etc., were employed to access the mechanical properties of NR/Bi₂WO₆, and the γ-ray shielding effect was evaluated on the basis of the γ-ray shielding effects of Bi₂WO₆, WO₃ and Bi₂O₃.

The results show that the NR/Bi₂WO₆ nanocomposites achieves a γ-ray shielding factor of 13.6% for 59.5 keV (²⁴¹Am point source), which is significantly higher than NR/WO₃ (7.4%) and NR/Bi₂O₃ (9.2%). Furthermore, a comparison of WO₃ and Bi₂O₃ indicates that the interlayer effect of the Bi₂O₂²⁺ and WO₄^2- layers in the Bi₂WO₆ cell is conducive to increasing the probability of collisions between γ photons and extranuclear electrons.

The γ-ray shielding performance of NR/Bi₂WO₆ composites is significantly improved by the boundary complementary effect of both K and L layer absorption edges of W and Bi elements existed in Bi₂WO₆ nanoparticles, which enhances the attenuation efficiency of NR/Bi₂WO₆ to the γ-ray.

Due to high energy resolution and position sensitivity features, the multi-electrode high purity germanium (M-HPGe) detector is widely applied in rare event physics for events extraction.

This study aims to make use of pulse shape in M-HPGe detector as a useful reference to optimize the performance of gamma spectrometry, rare events detection and signal/background discrimination of M-HPGe detector in other scenarios.

The pulse shape of inductive charge at different readout electrodes in M-HPGe detector was simulated by joint calling process of Monte Carlo simulation process and single point position energy deposition pulse waveform simulation. Then, the pulse shape in M-HPGe detector was estimated through the distribution of the internal electric field, the weighting potential inside the detector, the carrier track and the inductive charge at the readout electrode.

Simulation results of pulse shape in M-HPGe detector show that the collector electrodes along the electrodes distribution induces significantly different inductive signals, and weak mirror signals are induced by the adjacent electrodes. This indicates that the M-HPGe detector has position resolution feature along the electrodes distribution.

This method can be used to support the research on the physical mechanism of the gamma track reconstruction discrimination method, and it can also simulate and evaluate the application effect of the track reconstruction discrimination method.

Radioactivity measurement is widely used in various fields of nuclear technology application. The measurement uncertainty, confidence interval and detection limit are important parameters in radioactive measurement. Different calculation methods may get different results, and the calculation results directly affect some important and relevant decisions.

This study aims at the calculation method of parameters in α particle radioactivity measurement that is used properly.

Both the partial derivative method and Monte Carlo method were applied to determinate the important parameters of α particle radioactivity measurement in this study. Firstly, based on the measurement of α activity concentration in gas using Passivated Implanted Planar Silicon (PIPS) detector, the sources of uncertainty for the measurement results were analyzed in details. Then, measurement uncertainty, confidence limits, decision threshold and detection limit of α particle activity concentration under different input modes were derived and calculated by partial derivative and Monte Carlo methods, singly and jointly. Finally, calculation results were compared analyzed.

The results show that when the input uncertainty is higher than 10%, the relative deviation between confidence interval and uncertainty results obtained by the two calculation methods is greater than 15%. When the relative uncertainty of the input is small, the detection limit is about 2 times of the decision threshold.

The partial derivative method is widely used without consideration of the probability distribution of the input, hence not suitable for complex and special input models. Under this circumstances, Monte Carlo method can be used to obtain more reliable calculation results. The two approaches can be applied jointly in complementary ways.

Developing electronic devices, such as metal oxide semiconductor field effect transistor (MOSFET) amplifiers with high radiation resistance, is crucial for robots working in nuclear environments.

This study aims to test the irradiation resistance performance of commercial MOSFET amplifiers and reveal the corresponding irradiation failure mechanism.

An in-situ gamma rays irradiation experiment platform was employed to conduct irradiation test on three trench MOSFET amplifiers using a ⁶⁰Co source. Response to different doses, and the electrical properties of these MOSFET amplifiers were investigated before and after irradiation. The failure analysis methods including electrical characteristics tests, thermal emission microscopy (EMMI) for failure location determination, focused ion beam (FIB) sample preparation, scanning electron microscope (SEM), and transmission electron microscope (TEM) characterization were employed to reveal the irradiation failure mechanism.

Experimental results showed that the three MOSFET amplifiers failed after irradiation by absorbed doses of 982.6 Gy, 986.2 Gy, and 1 082.4 Gy, respectively. The drain-source breakdown voltage BV_DSS of the MOSFET decreases from 110.5 V to 0.96 V, while the gate-source drive current I_GSS increases from 2.9 nA to 81.3 mA, as well as the threshold voltage V_GS(th) is not be detected due to the short circuit.

When the MOSFET amplifiers are irradiated in a charged operating state, the accumulation of captured charges in the gate oxide will lead to a decrease in the threshold voltage and breakdown voltage. Electron-hole pairs generated by high-energy and high-dose gamma-ray irradiation may continue to accumulate under the action of the circuit electric field, resulting in local high electric fields and high heat areas. The superposition of these high electric fields and high heat areas will cause the source aluminum metal to melt and ablate, causing a short circuit between the gate and the source.

In order to enhance the detection sensitivity of HPGe detectors for measuring the low-level activity of radionuclides, samples are usually measured as close to the detector as possible to improve the detection efficiency, which inevitably leads to serious coincidence-summing effects in return and affects the accuracy of measured activity.

This study aims to conduct efficiency simulation and coincidence-summing correction for HPGe detectors.

First of all, the peak efficiency of the HPGe detector was simulated by Geant4 and the internal geometry of the HPGe detector was optimized by comparing the simulated results with the experimental results of the mixed standard calibration source. Then, the total efficiency of the detector with various dead layer thickness was calibrated and the coincidence-summing correction factors were calculated. Finally, "Proficiency Test Exercise (PTE) 2021" conducted by the Provisional Technical Secretariat (PTS) of Comprehensive Nuclear Test Ban Treaty (CTBT) was applied to the correction of the measured activity.

Measurement results show that the relative deviation between the corrected activity and the reference result is less than 3%.

Results of this study demonstrate that the efficiency simulation and coincidence-summing correction for HPGe detector solves problems of limited calibration point source and high experimental cost, lays a foundation for measuring activities of nuclides in the sample accurately.

Uranium-molybdenum (U-Mo) alloy, which is applied in the heat-pipe cooled reactor (referred as heat-pipe reactor), has the advantages of high thermal conductivity, high density of uranium and excellent irradiation performance. At the same time, U-Mo alloy has significantly thermal expansion and irradiation swelling whilst the high temperature will aggravate the irradiation swelling of U-Mo alloy and reduce the performance of the material. Hence research on swelling under high temperature of U-Mo alloy is essential in the design of this fuel.

The study aims to comprehensively evaluate the effect of fuel swelling under high temperature of U-Mo alloy on reactor core structure.

Firstly, based on the irradiation data of U-Mo alloy under high temperature, a new type of swelling model considering the effect of high temperature was established. Secondly, a three-dimensional (3D) thermal-mechanical coupling analysis model of U-Mo alloy fuel was set up using finite element analysis (FEA) software COMSOL Multiphysics (referred to as COMSOL). Thirdly, a thermal-mechanical coupling analysis was carried out with concern of the thermal expansion effect to verify the validity of the 3D FEA model. Finally, this swelling model was used to study the fuel swelling effect of reactor core by considering the irradiation swelling of U-Mo alloy at high temperature, and the stress and deformation analysis under different burnup were carried out to evaluate the effect of fuel swelling on the core structural stability.

Under steady-state operating conditions, the core fuel of 1 kWe Kilopower heat-pipe reactor has a large deformation at the end of life (EOL) due to thermal expansion and irradiation swelling, and the maximum deformation reaching 5.28 mm. The maximum stress caused by deformation is 57.4 MPa, which is concentrated on the wall where the heat pipe is connected to the core fuel. Thermal expansion is the main factor that causes stress and deformation of fuel. As the burnup continues to deepen, the irradiation swelling of U-Mo alloy at high temperature leads to greater deformation and greater stress of the fuel. The maximum deformation of the fuel is 6.63 mm when the burnup is 0.4%, which increases by 1.69 mm compared with the calculation results considering only thermal expansion. The maximum core fuel stress reaches 85.1 MPa, which is close to the yield limit of U-Mo alloy. And the stability of fuel structure may be threatened.

The results of this study indicate that the swelling effect of U-Mo alloy at high temperature leads to more severe deformation and greater stress on the fuel. The influence of thermal expansion and irradiation swelling on the structural stability of the core at high temperature and high burnup needs to be considered in reactor fuel design. In addition, it is necessary to accelerate the irradiation test of U-Mo alloy at high temperature to optimize the irradiation behavior model.

Molten salt reactors have been selected as one of the promising candidate Generation IV reactor technologies, due to the advantages of inherent safety and high economic efficiency. The small modular molten salt reactor (SM-MSR), which utilizes low-enriched uranium and thorium fuels, is regarded as a wise development path to speed deployment time. Uncertainty and sensibility analysis of accidents possess a great guidance in nuclear reactor design and safety analysis that can be performed to obtain the safety boundary and through sensitivity analysis, thereafter to obtain the correlation of the accident consequence and input parameters. Reactivity insertion transient accident represents a type of hypothetical accidents of SM-MSR, and the study of reactivity insertion transient accident can offer useful information to improve physics thermohydraulic and structure designs.

This study aims to investigate the uncertainty and sensibility of MSR reactivity insertion accident and provide supports for the design and safety analysis of the small modular molten salt reactor.

RELAP5-TMSR code was employed to establish a transient behavior analysis model for SM-MSR, and the model consisted of four coupled parts, including the primary circuit, 2nd circuit, air cooling system modules and passive residual heat removal system. Then, propagation of input uncertainty approach on the basis of Monte Carlo methods was employed to analyze the uncertainty of reactivity insertion transient accident consequence. Uncertain parameters for the reactivity insertion transient accident were selected by the phenomena identification and ranking table (PIRT). Subsequencely, a list of input parameters along with their associated density functions was adopted by using a probabilistic methodology to establish the code run times and sets of uncertain input parameters that was propagated through the RELAP5-TMSR code, and then obtain the upper and lower uncertainty bands of the reactivity insertion transient consequence. Finally, the sensibility of input parameters was analyzed by performing Multiple Linear Regression (MLR) method, and the F-test was used to assess whether the MLR models comply with statistical laws. If the linear model was strong collinear, a significance test of the semi-partial correlation coefficient (SPC) was used for the ranking of input uncertainty parameters, otherwise, the standardized regression coefficient (SRC) would be used for the significance test.

The uncertainty analysis results show that the maximum fuel salt temperature of SM-MSR is 727.4 ℃ which is lower than the acceptance criteria (800 ℃). Through statistical analysis, the maximum value of reactor outlet fuel salt temperature is normally distributed.

The molten salt reactor has good safety characteristics, and the 5 important parameters are density of fuel salt, local resistance coefficient of reactor core, reactor power, local resistance coefficient of primary circuit and reactor shutdown margin.

The heat pipe reactor (HPR) is characterized by inherent safety and a compact structure, which making it widely applicable. The thermoelectric conversion system (TEC) is a key system in the HPR that converts thermal energy to electrical energy. Its form and operational principles significantly impact the accident safety characteristics and dynamic response of the HPR. A self-developed analysis code TAPIRS-D for HPR systems has already incorporated stirling cycle with semiconductor thermoelectric conversion system at the Nuclear Safety and Operations Research Laboratory of Xi'an Jiaotong University, China.

This study aims to develop a new dynamic thermoelectric conversion module suitable for open Brayton cycle on the basis of the TAPIRS-D code.

Firstly, an open Brayton TEC model was developed for code TAPIRS-D, making it capable of analyzing heat pipe reactor system coupled with different thermoelectric conversion systems, such as stirling cycle, open Brayton TEC as well as semiconductor thermoelectric conversion system. Then, maximum relative errors in temperature prediction, pressure prediction and maximum flowrate prediction were obtained by comparison between the calculated results of the newly developed open Brayton TEC model and the experimental data to confirm the rationality of the model. Finally, the upgraded TAPIRS-D were applied to evaluate the reactivity insertion accident of SAIRS-C reactor concept, and the transient performance of SAIRS-C coupling with different thermoelectric conversion system were analyzed and compared.

Comparison results show that the newly developed open Brayton TEC model has a maximum relative error of 2% in temperature prediction, a maximum relative error of 3% in pressure prediction and maximum relative error of 15% in flowrate prediction. Under the same accident conditions involving the introduction of reactivity, the calculation results indicate that the reactor using the Stirling conversion system has the smallest change in core power after an accident while the temperature rise of the Stirling machine's hot end is relatively high.

Results of this study demonstrate that the output power of open Brayton cycle and thermoelectric conversion system has a similar variation change, which are both larger than that of stirling conversion system whilst heat pipe reactor system coupling with semiconductor thermoelectric conversion system has the largest cycle efficiency gain. However, special attention should be pay on the circuit load of semiconductor thermoelectric conversion system under reactivity insertion accident.

Liquid lead-bismuth eutectic (LBE) corrosion and dissolution of structural materials pose significant challenges in the application of lead-bismuth-cooled fast reactors (LFRs). The use of oxygen as an inhibitor emerges as a promising approach to mitigate the corrosion of structural materials by liquid LBE. The oxidative corrosion in LFRs is influenced by various physical parameters within the reactor, including temperature, oxygen concentration, and time. Concurrently, the growth of the oxide layer on the cladding surface exacerbates the heat transfer between the cladding and the coolant, thereby influencing the thermal-hydraulic and neutron physics parameters of the core. Understanding the corrosion protection of structural materials and multi-physics characteristics is crucial issue for LFRs.

This study aims to investigate the coupled mechanisms of neutron physics, thermal-hydraulics, and oxidative corrosion, along with the distribution of the oxide layer in lead-bismuth reactors.

A neutronics-thermal-hydraulics-material coupling framework was developed to investigate the variations in multi-physics parameters and oxide layer distribution in the LFR fuel rod under oxidative corrosion conditions. First of all, based on the Multiphysics Object-Oriented Simulation Environment (MOOSE), the framework was developed to couple three modules: neutron physics, thermal-hydraulics, and oxidative corrosion, and conduct simulation calculations. Thereafter, various lead-bismuth reactor oxide layer growth-removal models were encompassed into a MOOSE-based oxidative corrosion module, named Seal, and the Martinelli model was adopted in subsequent simulations after comparison with experimental values. Then, the neutron physics module was solved by the open-source neutron diffusion equation solver Moltres and the thermal-hydraulics module calculation was performed by MOOSE's Navier-Stokes and Heat Conduction modules. Two coupling relationships in the coupling framework, i.e., (1) the neutron physics module for transferring power distribution to the thermal-hydraulics module, and the thermal-hydraulics module transferring temperature distribution to the neutron physics module; (2) the thermal-hydraulics module transferring temperature field and flow field to the oxidative corrosion module, and the oxidative corrosion module transferring oxide layer thickness distribution to the thermal-hydraulics module, were investigated. Finally, the approach of simultaneously solving the coupled equations under the same mesh was employed for coupled calculations, with the control equations of the three modules solved simultaneously to achieve synchronized convergence of physical quantities. And the developed coupled framework was applied to perform benchmark calculations and sensitivity analysis of oxygen concentration for a lead-bismuth reactor fuel rod.

The results indicate that: (1) after 10 000 h of oxidative corrosion under benchmark conditions, the average thickness of the oxide layer is approximately 10 μm, the maximum fuel temperature rise is 16 K, and keff decreases by 10^-4; (2) an increase in oxygen concentration effectively inhibits magnetite dissolution but has a relatively minor promoting effect on the growth of Fe-Cr spinel.

This study demonstrates that the increase in oxygen concentration has a positive effect on the protection and self-healing ability of the oxide layer. It has both theoretical and practical significance for the development, design, and safety evaluation of LFR in China.

Oscillatory conditions significantly affect the thermal-hydraulic characteristics of floating reactors, leading to changes in the growth of chalk river unidentified deposit (CRUD).

This study aims to investigates CRUD growth on fuel rod bundles under oscillatory conditions.

Firstly, based on the data exchange method, the one-dimensional system program RELAP5 and the CFD (Computational Fluid Dynamics) program ANSYS Fluent were coupled to simulate the primary loop, and mathematical models of coolant flow and corrosion product deposition growth under oscillatory conditions were added to the simulation. Then, CRUD growth calculations and coolant flow mathematical models under oscillatory conditions were embedded into the multiscale simulation. Finally, the influences of oscillatory conditions on flow characteristics in rod bundle channels, fuel rod wall temperature, and CRUD growth were analyzed.

The simulation outcomes reveal that oscillation induces periodic variations in both the coolant flow rate and outer wall temperature of the rods. At lower axial heights, CRUD grows thicker on the rods near the peripheral wall. At higher axial heights, the CRUD distribution pattern tends to be consistent across all rods. The CRUD thickness distribution in the circumferential direction of the fuel rods tends to form an elliptical pattern in polar coordinates.

Fluctuations in flow rate and temperature can enhance erosion in the tangential direction of oscillation, diminish the deposition process, and result in varied CRUD distribution patterns at distinct positions.

Stepper motor driver is the main equipment of the cabinet of Absorption Sphere Shutdown System (ASSS) of High Temperature Gas-Cooled Reactor Pebble-Bed Modules (HTR-PM), which can control the stepper motor to act according to the preset value. If ASSS works abnormally due to the influence of interference, it will cause the stepper motor to run unexpectedly, which may cause the risk of the absorption sphere falling or refusing to fall by mistake and affect normal operation or nuclear safety of HTR-PM.

This study aims to formulate a scientific and reasonable anti-interference, so as to effectively reduce the pollution and impact of power grid and grounding system caused by pulse width modulation (PWM) mechanism, and avoid abnormal operation of stepper motor driver.

Through theoretical calculations and practical tests, the transmission path, mechanism and influence degree of interference caused by PWM were investigated, and customized optoelectronic isolation equipment was designed. Dedicated reactor and filter were installed on the transmission paths of the corresponding interference sources, hence effectively blocking the propagation interference and suppressing its impact, which was in the line with the unique working environment of the cabinet of the absorption sphere shutdown drive mechanism.

The anti-interference design scheme of drive cabinet in absorption sphere shutdown system effectively suppresses the impact of interference on the system, ensures the accurate and stable operation of the stepper motor driver, and realizes the angle deviation of the stepper motor within 1° for every 20 cycles operation, which effectively prevents the risk of malfunction of the stepper motor and improves the reliability of the system operation.

This design scheme has a good guiding significance for the anti-interference design of various control systems of the same type, and has certain promotion significance.

In the aftermath of a high-altitude nuclear explosion, the delayed γ-rays emanating from the debris undergo a complex ionization process while traversing the non-uniform high-altitude atmosphere. This process results in a significant augmentation of the electron number density in the ionosphere, thereby affecting radio communication links traversing the ionosphere.

This study aims to develop a comprehensive modeling and simulation framework that accurately captures the temporal and spatial evolution of delayed γ-ray sources and their corresponding atmospheric ionization effects.

Firstly, a hydrodynamic model was established to simulate the debris motion resulting from a high-altitude nuclear explosion. Subsequently, a hierarchical equivalent model of delayed γ-ray sources was formulated based on the debris parameters. Then, the Monte Carlo method was utilized to simulate the ionization effect of these delayed γ-rays in the non-uniform high-altitude atmosphere. Finally, given the dynamic evolution of the debris shape, a stratified sampling approach was employed to determine the initial positions of the delayed γ-rays. Various conditions such as 4 Mt equivalent explosion at a height of 40 km, 4 Mt equivalent at a height of 80 km, 100 kt equivalent at a height of 40 km, and 100 kt equivalent at a height of 80 km, the fragment cloud was evenly divided into 10 layers according to their respective proportions. MCATNP code was used to calculate the distribution of electron production rates formed by the ionization of the atmosphere by delayed γ-rays generated by the debris different times after the explosion. Furthermore, considering the exponential decay of atmospheric density with height, the mass thickness sampling method was adopted to simplify the computational model.

The results indicate that the ionization intensity and range of delayed γ-rays are significantly influenced by the debris shape. In the case of a megaton-level high-altitude nuclear explosion, the ionization range of delayed γ-rays can extend to over a thousand kilometers. Specifically, with a constant explosion height, an increase in the equivalent yield leads to an augmentation in the debris height and horizontal radius, thereby enhancing the ionization range and intensity. Conversely, when the burst height is increased while maintaining a constant equivalent yield, the debris height and horizontal radius increase, leading to an expansion in the ionization range but a reduction in ionization intensity.

In nuclear radiation measurement, pulse distortion is inevitable due to the interference of the measurement system itself and the measurement environment. If the parameters of such pulses cannot be accurately estimated, the resolution performance of the energy spectrum will be reduced.

This study aims to accurately estimate the height of distorted pulses using neural network model.

Firstly, six lightweight neural network models, i.e., LeNet5, LSTM, GRU, UNet, CNN-GRU, CNN-LSTM, were applied to parameter prediction of distorted nuclear pulses, including pulse amplitude parameters and distortion time parameters. Then, based on the distorted pulses generated by predefined mathematical models, the dataset required for model training was obtained through digital triangulation shaping. Finally, parameter prediction performances of those neural network models on test set with additional white noise, Gaussian noise and flicker noise were compared with each other, as well as with the traditional digital forming method.

When evaluating the parameter prediction performance of six neural network models, the UNet model achieves the lowest relative error on the test set, with a relative error of approximately 0.57% for amplitude parameters and 3.51% for time parameters. In the signal-to-noise ratio experiment, noise is superimposed on the test set to obtain noise test sets with different signal-to-noise ratios.

The results of this study show that the proposed models can achieve accurate estimation of the parameters of distorted pulses.

With the increasingly strict requirements of the fourth-generation synchrotron radiation light source on the brightness and emittance of the beam, the impact of micro-vibration on the beam quality has gradually become prominent. However, there is still no unified standard for comprehensive testing and evaluating the impact of ground-based micro-vibrations, making the effective management and control of micro-vibration particularly difficult.

This study aims to evaluate the random characteristics of ground vibration and analyze the vibration sources in detail.

A spectral estimation-based model was developed for vibration data processing, and a method based on probability statistics was proposed to evaluate the displacement of ground micro-vibration. Then, triaxial force feedback velocity sensor (seismometer) was employed to test the micro vibration of foundation of Wuhan Advanced Light Source (WALS) pre-research site, and the vibration root mean square (RMS) displacement was comprehensively and objectively assessed by aforementioned approach.

The results indicate that the vertical vibration average RMS displacement of the isolated foundation in the experimental hall of WALS within the pre-research zone of WALS is 8.08 nm, with a σ value of 4.55 nm. It is noted that the vertical vibration displacement (ave RMS+3σ) reaches about 21.73 nm, which satisfies the 40 nm requirement.

This vibration data processing method proposed in this study is appropriate for evaluating the vibrations of the original background and isolated treatment foundation, as well as for analysis of vibration sources at the component level.