Vol.32,

The soft X-ray polarimeter (SXP) is a detector with a wide energy range, large area, and large field of view. A SXP will be mounted on the Chinese Space Station and will mainly focus on detecting the polarization of transient soft X-ray (210) sources, especially gamma-ray bursts (GRBs). In this work, a polarimeter detector unit is taken as an example, and Geant4 and Garfield++ software are used to simulate the detection efficiency and track production. An improved track reconstruction algorithm is proposed and used to reconstruct two-dimensional images of the tracks. In this method, the initial emission angle of photoelectrons is reconstructed from the initial part of the track by shortening or extending the initial part of the track until the remaining track is straight, and the number of pixels is within an adjustable threshold. The modulation factor of the photoelectronic tracks after reconstruction reaches approximately 57% in the photon energy range of 7 keV to 10 keV.

488

Positron sources are one of the most important components of the injector of a circular electron positron collector (CEPC). The CEPC is designed as an e⁺e^- collider for a Higgs factory. Its accelerator system is composed of 100-km long storage rings and an injector. The design goal of the positron source is to obtain positron beams with a bunch charge of 3 nC. The flux concentrator (FC) is one of the cores of the positron source. This paper reports the design, development, and measurements of an FC prototype system. The prototype includes an FC and an all-solid-state high-current pulse modulator. Preliminary tests show that the peak current on the FC can reach 15.5 kA, and the peak magnetic field can reach 6.2 T. The test results are consistent with the theoretical simulation. The FC system fulfills the requirements of the CEPC positron source as well as provides a reference for the development of similar devices both domestically and abroad.

353

Energetic particle radiation diagnoses mainly detect the particles (such as neutrons, gamma rays, hard X-rays, and escaping electrons) that are radiated in the discharge process of the experimental advanced superconducting tokamak device to characterize the operating state of the plasma in real time. The upgrading of these diagnoses requires new instruments based on national (here, "national" means developed and produced by a Chinese company) core chips and open-source software with advanced digitization, a high sampling rate, and a high time resolution. The new spectroscopy system designed in this study adopts the national field-programmable gate array (FPGA) and an analog to digital converter as the core chip, and it is developed using Qt on Linux. The communication between the FPGA and embedded controller occurs via a high-speed peripheral component interconnect eXtension for instrument express protocol with a direct memory access mode. On this basis, the time resolution of the system is improved from 2 ms to 1 ms, the maximum channel address is increased to 4096, and the sampling rate is increased from 10 Msps to 80 Msps. Calibration experiments of the spectroscopy system with ¹⁵²Eu and ¹³⁷Cs sources demonstrate that the best energy resolution is 0.27% and the measurement error is less than ±0.5 keV.

639

The neutral particle analyzer (NPA) is one of the crucial diagnostic devices in a Tokamak facility. The stripping unit is one of the main parts of the NPA. A windowless gas stripping room with two differential pipes has been constructed in a parallel electric and magnetic fields (E//B) NPA. The pressure distributions in the stripping chamber are simulated by ANSYS Fluent together with MolFlow+. Based on the pressure distributions obtained from the simulation, the stripping efficiency of the E//B NPA is studied using GEANT4. Hadron reaction physics is modified to track the charge state of each particle in a cross-section based method in GEANT4. The transmission rates (R) and stripping efficiencies f₊₁ are examined for particle energies ranging from 20 to 200 keV with the input pressure (P₀), ranging from 20 to 400 Pa. According to the combined global efficiency, R × f₊₁, P₀ = 240 Pa is obtained as the optimum pressure for the maximum global efficiency in the incident energy range investigated.

353

Effects of finite-range tensor force on β decay of magic and semimagic nuclei of ³⁴Si, ^68,78Ni, and ¹³²Sn have been investigated using the self-consistent Hartree-Fock plus random phase approximation model. The tensor force shifts the low-lying Gamow-Teller states downward and systematically improves the calculations of Q and log ft values. Consequently, it systematically reduces the deviations between the theoretical and experimental data and significantly improves the calculation of β-decay half-lives. This effect is similar to that of zero-range tensor force.

347

The supersonic gas-jet target is an important experimental target for laser wakefield acceleration (LWFA), which has great potential for driving novel radiation sources such as betatron radiation and Compton scattering gamma rays. According to different electron acceleration requirements, it is necessary to provide specific supersonic gas jets with different density profiles to generate electron beams with high quality and high repetition rates. In this study, the interference images and density profiles of different gas-jet targets were obtained through a modified Nomarski interference diagnosis system. The relationships between the gas density and back pressure, nozzle structure, and other key parameters were studied. Targets with different characteristics are conducive to meeting the various requirements of LWFA.

409

Membrane fouling is always the biggest problem in the practice of membrane separation technologies, which strongly impacts their applicability, separation efficiency, cost effectiveness, and service lifespan. Herein, a simple but effective 3D modification approach was designed for permanently functionalizing polymeric membranes by directly crosslinking polyvinyl alcohol (PVA) under gamma-ray irradiation at room temperature without any additives. After the modification, a PVA layer was constructed on the membrane surface and the pore inner surface of polyvinylidene fluoride (PVDF) membranes. This endowed them with good hydrophilicity, low adsorption of protein model foulants, and easy recoverability properties. In addition, the pore size and distribution were customized by controlling the PVA concentration, which enhanced the rejection ability of the resultant membranes and converted them from microfiltration to ultrafiltration. The crosslinked PVA layer was equipped with the resultant membranes with good resistance to chemical cleaning by acidic, alkaline, and oxidative reagents, which could greatly prolong the membrane service lifetime. Furthermore, this approach was demonstrated as a universal method to modify PVDF membranes with other hydrophilic macromolecular modifiers, including polyethylene glycol, sodium alginate, and polyvinyl pyrrolidone. This modification of the membranes effectively endowed them with good hydrophilicity and antifouling properties, as expected.

359

In recent years, a new generation of storage ring-based light sources, known as diffraction- limited storage rings (DLSRs), whose emittance approaches the diffraction limit for the range of X-ray wavelengths of interest to the scientific community, has garnered significant attention worldwide. Researchers have begun to design and build DLSRs. Among various DLSR proposals, the hybrid multibend achromat (H-MBA) lattice enables sextupole strengths to be maintained at a reasonable level when minimizing the emittance; hence, it has been adopted in many DLSR designs. Based on the H-7BA lattice, the design of the Advanced Photon Source Upgrade Project (APS-U) can effectively reduce emittance by replacing six quadrupoles with anti-bends. Herein, we discuss the feasibility of designing an APS-U-type H-MBA lattice for the Southern Advanced Photon Source, a mid-energy DLSR light source with ultralow emittance that has been proposed to be built adjacent to the China Spallation Neutron Source. Both linear and nonlinear dynamics are optimized to obtain a detailed design of this type of lattice. The emittance is minimized, while a sufficiently large dynamic aperture (DA) and momentum acceptance (MA) are maintained. A design comprising 36 APS-U type H-7BAs, with an energy of 3 GeV and a circumference of 972 m, is achieved. The horizontal natural emittance is 20 pm∙rad, with a horizontal DA of 5.8 mm, a vertical DA of 4.5 mm, and an MA of 4%, as well as a long longitudinal damping time of 120 ms. Subsequently, a few modifications are performed based on the APS-U-type lattice to reduce the longitudinal damping time from 120 to 44 ms while maintaining other performance parameters at the same level.

361

Real-time feedback control of vertical growth rate, called gamma control, has been successfully applied to experimental advanced superconducting tokamak (EAST). In this paper, a new gamma control method is proposed to regulate the vertical growth rate, which is an estimator of plasma vertical instability. Thus, the gamma controller can be utilized to keep the tokamak plasma away from its unstable boundary. In this work, the main development process includes three steps: 1) real-time implementation of model-based vertical growth rate calculation, taking advantage of GPU parallel computing capability, 2) design of plasma shape response for dynamic shape control using a slight modification to the plasma boundary; and 3) development of a gamma control algorithm integrated into an EAST plasma control system (PCS). The gamma control was experimentally verified in the EAST 2019 experiment campaign. It is shown that the time evolution of the real-time vertical growth rate agrees with the target value, indicating that the real-time vertical growth rate can be regulated by gamma control.

491

Background:The accelerator-driven subcritical transmutation system (ADS) is an advanced technology for the harmless disposal of nuclear waste. A theoretical analysis of the ingredients and content of nuclear waste, particularly long-lived waste in a pressurized water reactor (PWR), will provide important information for future spent fuel disposal.Purpose:The present study is an attempt to investigate the yields of isotopes in the neutron-induced fission process and estimate the content of long-lived ingredients of nuclear waste in a PWR.Method:We combined an approximation of the mass distribution of five Gaussians with the most probable charge model (Z_p model) to obtain the isotope yields in the ²³⁵U(n,f) and ²³⁹Pu(n,f) processes. The potential energy surface based on the concept of a di-nuclear system model was applied to an approximation using five Gaussian functions. A mathematical formula for the neutron spectrum in a PWR was established, and sets of differential equations were solved to calculate the content of long-lived nuclides in a PWR.Results:The calculated isotopic fission yields were in good agreement with the experimental data. Except for ²³⁸U, the contents of ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu, ²⁴²Pu, ²³⁷Np, ²³⁵U, and ²³⁶U are predominant in the PWR after reaching a discharge burnup. In addition, some isotope pairs of heavy nuclei reach a similar value after stabilization, which can be explained by the decay chain and effective fission cross-sections. For fission fragments, we simulated the content evolution of some long-lived nuclides ⁹⁰Sr, ¹⁰⁷Pd,¹³⁵Cs, and their isobars ⁹⁰Rb, ¹⁰⁷Rh, and ¹³⁵Xe during a fuel cycle in a PWR. The variations in the inventories of uranium and plutonium were in good agreement with the data in Daya Bay.Conclusion:A new method is proposed for the prediction of the isotopic fission yield. The inventory of long-lived nuclides was analyzed and predicted after reaching a discharge burnup.

370

During a loss of vacuum accident (LOVA), the air ingress into a vacuum vessel (VV) may lead to radioactive dust resuspension, migration, and even explosion, thereby posing a great threat to the safe operation of future fusion reactors; thus, it is crucial to understand the flow characteristics and radioactive dust transport behavior induced by LOVA. However, only a few studies have identified the characteristics of the highly under-expanded jet flow at a scale of milliseconds during LOVA. Particularly, the occurrence and behavior of a Mach disk is yet to be captured in existing studies. In this study, we used a more advanced model with a finer mesh and adaptive mesh strategies to capture the Mach disk in a VV during LOVA. In detail, a computational fluid dynamics–discrete phase model one-way coupled multiphase approach was established using the computational ﬂuid dynamics code ANSYS FLUENT and applied to the analysis during the first seconds of LOVA. The results showed that air ingress into the VV behaved like a highly free under-expanded jet at the initial stage and Mach disk was formed at ~6 ms. Moreover, the flow field dramatically changed at the position of the Mach disk. The jet core before the Mach disk had a maximum velocity of ~8 Mach with the corresponding lowest static pressure (~100 Pa) and temperature (few tens of K). The friction velocities in the lower part of the VV, which is an area of concern due to dust deposition, was generally larger than 15 m/s near the inlet region. Lastly, the crude prediction of the particle trajectories demonstrated the spiral trajectories of the dust following the air motion. Therefore, this study provided a basis for further safety analysis and accident prevention related to dust transport and explosion in future fusion reactors.

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