Vol.33,

The Hefei Advanced Light Facility (HALF) proposed by the National Synchrotron Radiation Laboratory (NSRL) is a Diffraction Limited Storage Ring (DLSR), which plans to use a full energy linac as the injector. To ensure injection efficiency, the injection beam needs to have low emittance. Therefore, a photocathode radio frequency (RF) gun was developed in the HALF R&D project. The gun is designed to deliver high-quality electron bunches with a typically 0.5 nC charge and ∼ 4.5 MeV energy with low emittance. The initial system commission with an electron beam was completed at the end of 2020, and a stable 1.2 –1.4 mm ⋅ mrad emittance with a bunch charge of 500 pC was demonstrated. In this paper, we report the experimental results and experience obtained during the commission, including the RF gun, drive laser system, and beam diagnostics.

511

A database system, known as the large PMT characterization and instrumentation database system (LPMT-CIDS), was designed and implemented for the Jiangmen Underground Neutrino Observatory (JUNO). The system is based on a Linux + Apache + MySQL + PHP (LAMP) server and focuses on modularization and architecture separation. It covers all the testing stages for the 20-inch photomultiplier tubes (PMTs) at JUNO and provides its users with data storage, analysis, and visualization services. Based on the successful use of the system in the 20-inch PMT testing program, its design approach and construction elements can be extended to other projects.

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639

The neutron count rate fluctuation reaches six orders of magnitude between the ohmic plasma scenario and high power of auxiliary heating on an experimental advanced superconducting tokamak (EAST). The measurement result of neutron flux monitoring (NFM) is a significant feedback parameter related to the acquisition of radiation protection-related information and rapid fluctuations in neutron emission induced by plasma magnetohydrodynamic activity. Therefore, a wide range and high time resolution are required for the NFM system on EAST. To satisfy these requirements, a digital pulse signal acquisition and processing system with a wide dynamic range and fast response time was developed. The present study was conducted using a field-programmable gate array (FPGA) and peripheral component interconnect extension for instrument express (PXIe) platform. The digital dual measurement modes, which are composed of the pulse-counting mode and AC coupled square integral’s Campbelling mode, were designed to expand the measurement range of the signal acquisition and processing system. The time resolution of the signal acquisition and processing system was improved from 10 ms to 1 ms owing to utilizing high-speed analog-to-digital converter (ADC), a high-speed PXIe communication with a direct memory access (DMA) mode, and online data preprocessing technology of FPGA. The signal acquisition and processing system was tested experimentally in the EAST radiation field. The test results showed that the time resolution of NFM was improved to 1 ms, and the dynamic range of the neutron counts rate was expanded to more than 10⁶ counts per second. The Campbelling mode was calibrated using a multipoint average linear fitting method; subsequently, the fitting coefficient reached 0.9911. Therefore, the newly developed pulse signal acquisition and processing system ensures that the NFM system meets the requirements of high-parameter experiments conducted on EAST more effectively.

564

The influence of combined total ionization dose (TID) and radiated electromagnetic interference (EMI) in a commercial analog-to-digital converter (ADC) was studied. The degradation of the direct-current response, the static parameters, and the dynamic parameters caused by the TID and EMI separately and synergistically are presented. The experimental results demonstrate that the increase in TID intensifies data error and the signal-to-noise ratio (SNR) degradation caused by radiated EMI. The cumulative distribution function of EMI failure with respect to data error and SNR with different TIDs was extracted. The decreasing trend of the threshold was acquired with a small sample size of five for each TID group. The result indicates that the ADC is more sensitive in a compound radiation environment.

450

The high-altitude detection of astronomical radiation (HADAR) experiment is a new Cherenkov observation technique with a wide field of view (FoV), aimed at observing the prompt emissions of GRBs. The bottleneck for this type of experiment can be found in determining how to reject the high rate of night-sky background (NSB) noise from random stars. In this work, we propose a novel method for rejecting noise, which considers the spatial properties of GRBs and the temporal characteristics of Cherenkov radiation. In space coordinates, the map between the celestial sphere and the fired photomultiplier tubes (PMTs) on the telescope's camera can be expressed as f(δ(i,j))=δ'(i',j'), which means that a limited number of PMTs is selected from one direction. On the temporal scale, a 20-ns time window was selected based on the knowledge of Cherenkov radiation. This allowed integration of the NSB for a short time interval. Consequently, the angular resolution and effective area at 100 GeV in the HADAR experiment were obtained as 0.2° and 10⁴ m², respectively. This method can be applied to all wide-FoV experiments.

634

Cerebral perfusion computed tomography (PCT) is an important imaging modality for evaluating of cerebrovascular diseases and stroke symptoms. With widespread public concern about the potential cancer risks and health hazards associated with cumulative radiation exposure in PCT imaging, considerable research has been conducted to reduce the radiation dose in X-ray-based brain perfusion imaging. Reducing the dose of X-rays causes severe noise and artifacts in PCT images. To solve this problem, we propose a deep learning method called NCS-Unet. The exceptional characteristics of non-subsampled contourlet transform (NSCT) and the Sobel filter are introduced into NCS-Unet. NSCT decomposes the convolved features into high- and low-frequency components. The decomposed high-frequency component retains image edges, contrast imaging traces, and noise, whereas the low-frequency component retains the main image information. The Sobel filter extracts the contours of the original image and the imaging traces caused by the contrast agent decay. The extracted information is added to NCS-Unet to improve its performance in noise reduction and artifact removal. Qualitative and quantitative analyses demonstrated that the proposed NCS-Unet can improve the quality of low-dose cone-beam CT perfusion reconstruction images and the accuracy of perfusion parameter calculations.

398

Thin Layer Activation is a nuclear technique that has key advantages over other wear measuring techniques for mechanical systems, especially for in site experiments on equipment important to safety in nuclear plants. Still, it incurs radioactive dose and, thus, must be proved radiologically safe before use, otherwise the utilization of this technique may be hindered inviable. Proving said technique is safe previous to any operational/monetary cost is key, providing a methodology for this early assertion is the main contribution of this work - here, only non-occupationally exposed individuals are considered. This work offers a methodology, through a case study, to ascertain the Thin Layer Activation parameters to obtain safe levels of radioactive dose while maintaining statistically reliable results. This methodology consists of using simulations, through the Monte Carlo Method, to obtain the floors and ceilings for the previously mentioned activation parameters based on operation and work conditions in site.

333

Compact accelerator-based neutron source (CANS) facilities are garnering attention and play an important and expanding role in material and engineering sciences, as well as in neutron science education and training. Neutrons are produced by bombarding a low-energy proton beam onto a beryllium or lithium target. In such an accelerator-based neutron source, a radio frequency quadrupole (RFQ) is usually utilized to accelerate a high-intensity proton beam to a few MeV. This study mainly covers the high-frequency structure design optimizations of a 4-vane RFQ with Pi-mode Stabilizer Loops (PISLs) and its RF stability analysis. A 176 MHz RFQ accelerator is designed to operate at a 10% duty factor and could accelerate an 80 mA proton beam from 65 keV to 2.5 MeV within a length of 5.3 m. The adoption of PISLs ensures high RF stability, eases the operation of the accelerator, and implies less stringent alignment and machining tolerances.

385

To predict the thermal-hydraulic (T/H) parameters of the reactor core for liquid-metal-cooled fast reactors (LMFRs), especially under flow blockage accidents, we developed a subchannel code called KMC-FB. This code uses a time-dependent, four-equation, single-phase flow model together with a 3D heat conduction model for the fuel rods, which is solved by numerical methods based on the finite difference method with a staggered mesh. Owing to the local effect of the blockage on the flow field, low axial flow, increased forced cross flow, and backflow occur. To more accurately simulate this problem, we implemented a robust and novel solution method. We verified the code with a low-flow (~0.01 m/s) and large-scale blockage case. For the preliminary validation, we compared our results with the experimental data of the NACIE-UP BFPS blockage test and the KIT 19ROD blockage test. The results revealed that KMC-FB has sufficient solution accuracy and can be used in future flow blockage analyses for LMFRs.

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In the present work, a new transient calculation method for parameters that can be used to evaluate the ability of oxygen control in a non-isothermal lead-bismuth eutectic (LBE) loop with solid-phase oxygen control was proposed. It incorporates the dissolution process of PbO particles and the oxygen mass transfer process, and an optimized method was used for finding out the optimized oxygen mass transfer coefficient. In numerical terms, three mass transfer models were simultaneously applied, and comparisons of calculated and experimental results from the CRAFT loop indicated that the optimized calculation method and these new oxygen mass transfer models were correct and applicable to other LBE loops. Through this calculation method, we aimed to optimize prediction of the distribution of oxygen and iron concentrations, time taken to establish the steady state of oxygen, and maximum dissolution/precipitation rates of corrosion products and corrosion depth across the entire LBE loop. We hope that this work will provide a potential reference for designing a more intelligent oxygen control system in future.

433

The control rod drive mechanism (CRDM) is an essential part of the control and safety protection system of pressurized water reactors. Current CRDM simulations are mostly performed collectively using a single method, ignoring the influence of multiple motion units and the differences in various features among them, which strongly affect the efficiency and accuracy of the simulations. In this study, we constructed a flow field fusion simulation method based on model features by combining key motion unit analysis and various simulation methods and then applied the method to the CRDM simulation process. CRDM performs motion unit decomposition through the structural hierarchy of function-movement-action (FMA) method, and the key meta-actions are identified as the nodes in the flow field simulation. We established a fused feature-based multimethod simulation process and processed the simulation methods and data according to the features of the fluid domain space and the structural complexity to obtain the fusion simulation results. Compared to traditional simulation methods and real measurements, the simulation method provides advantages in terms of simulation efficiency and accuracy.

661

Discussions pertaining to enhancement in the luminous efficiency of cesium iodide (CsI) detectors doped with sodium (Na) abound. In this study, the defect structure of one Cs atom replaced by one Na atom is calculated using the ab initio method. Subsequently, the electronic band structures, densities of states, optical absorption spectra, phonons, and transport properties of CsI in perfect and defective structures are investigated. The absorption spectra of CsI with and without Na impurities are compared. It is discovered that the impurity levels in the forbidden band are generated from the shell electron distributions of the impurity atoms, not from lattice distortions. Furthermore, it is discovered that the optical absorption can be enhanced by doping CsI with Na.

521

A prototype beam monitor was designed to provide tracking information for heavy-ion projectiles for the Cool Storage Ring (CSR) External-Target Experiment (CEE) at the Heavy Ion Research Facility in Lanzhou (HIRFL). High granularity and direct charge sensing are the main features of this device. It measures the beam position in a two-dimensional (2D) plane transverse to the beam direction on an event-by-event basis. The current design consists of two field cages inside a single vessel that operates independently and has electrical drift fields in orthogonal directions. Preliminary tests of the prototype were performed using a ²⁴¹Am α source. The results show that a spatial resolution of less than 40 μm and a time resolution of less than 600 ns can be achieved.

427

The number-of-constituent-quark (NCQ) scaling behavior of the elliptic flow of identified particles produced in A+A collisions is studied quantitatively using an empirical function that fits the experimental v₂ data available from the RHIC and LHC. The most common approach for NCQ scaling involves (1) doing a scaling of the experimental v₂ data of an identified particle with its NCQ, (2) doing the same to its transverse momentum or energy, then (3) combining all the scaled data and identifying the NCQ behavior by intuitively looking (since the measured experimental data are discrete). We define two variables (d₁, d₂) to describe NCQ scaling quantitatively and simultaneously, and identify the approximate region where the NCQ scaling holds. This approach could be applied to study NCQ or other scaling phenomena in future experiments.

369

The effects of additional oxidants, such as NaNO₃, Na₂S₂O₃, KClO₄, and K₂Cr₂O₇, on the supercritical water oxidation (SCWO) of tributyl phosphate (TBP) were studied. The coupling of an ionic oxidant with SCWO can effectively enhance the oxidative degradation ability of the system, thus increasing its organic-matter-removal efficiency at a reduced reaction temperature. Moreover, the addition of NaNO₃, KClO₄, or K₂Cr₂O₇ could improve this efficiency at a reaction temperature of 500 °C compared with that of the original system at 550 °C. Additionally, based on the conditions adopted in this study, the addition of either of these oxidants could reduce the final total organic carbon (TOC) of the effluent from ~500 to <100 ppm. Concurrently, the ionic oxidants could effectively improve the processing capacity of the SCWO system to reduce the scale of the equipment, as well as the amount of produced wastewater. Compared with KClO₄ and Na₂S₂O₃, the addition of 10 mmol/L NaNO₃ and K₂Cr₂O₇ to the organic feed could increase the processing capacity of the system from 4% to 10% while maintaining the TOC removal at >99%. The effects of the ionic oxidants on the gas products, including CO₂, CO, H₂, and CH₄, as well as other organic gases, have also been studied. Among these gas products, CO₂ accounted for the main gas product with a proportion of more than half. At <500 °C, temperature significantly affected the as products (CO, H₂, CH₄, and other organic gases). However, the gas product was mainly CO₂ when the temperature was increased to ≥500 °C. This study initially revealed the enhancement effect of ionic oxidants on SCWO, which still requires further research.

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