Vol.31,

In the core of a molten salt fast reactor (MSFR), heavy metal fuel and fission products can be dissolved in a molten fluoride salt to form a eutectic mixture that acts as both fuel and coolant. Fission energy is released from the fuel salt and transferred to the second loop by fuel salt circulation. Therefore, the MSFR is characterized by strong interaction between the neutronics and the thermal hydraulics. Moreover, recirculation flow occurs, and nuclear heat is accumulated near the fertile blanket, which significantly affects both the flow and the temperature field in the core. In this work, to further optimize the conceptual geometric design of the MSFR, three geometries of the core and fertile blanket are proposed, and the thermal-hydraulic characteristics, including the three-dimensional flow and temperature fields of the fuel and fertile salts, are simulated and analyzed using a coupling scheme between the open source codes OpenMC and OpenFOAM. The numerical results indicate that a flatter core temperature distribution can be obtained and the hot spot and flow stagnation zones that appear in the upper and lower parts of the core center near the reflector can be eliminated by curving both the top and bottom walls of the core. Moreover, eight cooling loops with a total flow rate of 0.0555 m³∙s⁻¹ ensure an acceptable temperature distribution in the fertile blanket.

883

In the design of filter shaping circuits for nuclear pulse signals, inverting filter shaping circuits perform better than non-inverting filter shaping circuits. Because these circuits facilitate changing the phase of a pulse signal, they are widely used in processing nuclear pulse signals. In this study, the transfer functions of four types of inverting filter shaping circuits, namely, the common inverting filter shaping, improved inverting filter shaping, multiple feedback low-pass filter shaping, and third-order multiple feedback low-pass filter shaping, in the Laplacian domain, are derived. We establish the numerical recursive function models and digitalize the four circuits, obtain the transfer functions in the Z domain, and analyze the filter performance and amplitude-frequency response characteristics in the frequency domain. Based on the actual nuclear pulse signal of the Si-PIN detector, we realize four types of inverting digital shaping. The results show that under the same shaping parameters, the common inverting digital shaping has better amplitude extraction characteristics, the third-order multiple feedback low-pass digital shaping has better noise suppression performance, and the multiple feedback digital shaping takes into account both pulse amplitude extraction and noise suppression performance.

816

Abstract With the advancements in nuclear energy, methods that can accurately obtain the spatial information of radioactive sources have become essential for nuclear energy safety. Coded aperture imaging technology is widely used because it provides two-dimensional distribution information of radioactive sources. The coded array is a major component of a coded aperture gamma camera, and it affects the key performance parameters of the camera. Currently, commonly used coded arrays such as uniformly redundant arrays (URA) and modified uniformly redundant arrays (MURA) have prime numbers of rows or columns and may lead to wastage of detector pixels. A 16 × 16 coded array was designed on the basis of an existing 16 × 16 multi-pixel position-sensitive cadmium zinc telluride (CZT) detector. The digital signal-to-noise (SNR) ratio of the point spread function (PSF) at the center of the array is 25.67. Furthermore, Monte Carlo camera models and experimental devices based on rank-13 MURA and rank-16 URA have been constructed. With the same angular resolution, the field size of view under rank-16 URA is 1.53 times that of under rank-13 MURA. Simulations (Am-241, Co-57, Ir-192, Cs-137) and experiments (Co-57) are conducted to compare the imaging performance between rank-16 URA and rank-13 MURA. The contrast-to-noise ratio of the reconstructed image of the rank-16 array is great and only slightly lower than that of rank-13 MURA. However, as the photon energy increases, the gap becomes almost negligible.

866

The charge read out of a liquid xenon (LXe) detector via proportional scintillation in the liquid phase was first realized by the Waseda group 40 years ago, but the technical challenges involved were overwhelming. Although the tests were successful, this method was finally discarded, and eventually nearly forgotten. Currently, this approach is not considered for large LXe dark matter detectors. Instead, the dual phase technology was selected despite many limitations and challenges. In two independent studies, two groups from Columbia University and Shanghai Jiao Tong University reevaluated proportional scintillation in the liquid phase. Both studies established the merits for very large LXe detectors, but the Columbia group also encountered apparent limitations, namely, the shadowing of the light by the anode wires, and a dependence of the pulse shape on the drift path of the electrons in the anode region. The differences between the two studies, however, are not intrinsic to the technique, but a direct consequence of the chosen geometry. Taking the geometrical differences into account, the results match without ambiguity. They also agree with the original results from the Waseda group.

559

The neutron flux monitor (NFM) system is an important diagnostic subsystem introduced by large nuclear fusion devices such as international thermonuclear experimental reactor (ITER), Japan torus-60, tokamak fusion test reactor, and HL-2A. Neutron fluxes can provide real-time parameters for nuclear fusion, including neutron source intensity and fusion power. Corresponding to different nuclear reaction periods, neutron fluxes span over seven decades, thereby requiring electronic devices to operate in counting and Campbelling modes simultaneously. Therefore, it is crucial to design a real-time NFM system to encompass such a wide dynamic range. In this study, a high-precision NFM system with a wide measurement range of neutron flux is implemented using real-time multipoint linear calibration. It can automatically switch between counting and Campbelling modes with variations in the neutron flux. We established a testing platform to verify the feasibility of the NFM system, which can output the simulated neutron signal using an arbitrary waveform generator. Meanwhile, the accurate calibration interval of the Campbelling mode is defined well. Based on the abovementioned design, the system satisfies the requirements, offering a dynamic range of 10⁸ cps, temporal resolution of 1 ms, and maximal relative error of 4% measured at the signal–noise ratio of 15.8 dB. Additionally, the NFM system is verified in a field experiment involving HL-2A, and the measured neutron flux is consistent with the results.

951

166.6-MHz quarter-wave β=1 superconducting cavities have been adopted for the High Energy Photon Source, a 6-GeV diffraction-limited synchrotron light source currently under construction. A large helium jacket was required to accommodate the enlarged cavity beam pipe for the heavy damping of higher order modes; the original electric-probe pickup thus becomes inevitably long with unfavorable mechanical properties. Relocated to an existing high-pressure-rinsing port, a magnetic-loop pickup was designed, characterized by low radio-frequency and cryogenic losses and being multipacting free and insensitive to manufacturing and assembly tolerances. The consequent removal of the original pickup port from the cavity largely simplified the helium jacket fabrication and may also reduce cavity contamination. This paper presents a comprehensive design of a low-loss magnetic-coupling pickup for quarter-wave β=1 superconducting cavities. The design can also be applied to other non-elliptical structures.

499

Optical vortices have the main features of helical wavefronts and spiral phase structures, and carry orbital angular momentum (OAM). This special structure of visible light has been produced and studied for various applications. These notable characteristics of photons were also tested in the extreme-ultraviolet and X-ray regimes. In this article, we simulate the use of a simple afterburner configuration by directly adding helical undulators after the SASE undulators with the Shanghai Soft X-ray FEL to generate high intensity X-ray vortices with wavelengths ∼1 nm. Compared to other methods, this approach is easier to implement, cost-effective, and more efficient.

794

In the present investigations, the fusion cross-sections for the formation of ²⁰⁰Pb compound nucleus (CN) using ¹⁶O + ¹⁸⁴W, ³⁰Si + ¹⁷⁰Er, and ⁴⁰Ar + ¹⁶⁰Gd nuclear reactions at energies above the Coulomb barrier were calculated to understand the effect of entrance channel mass asymmetry (α) on the fusion reactions; the Skyrme energy density formalism (SEDF) was used for this calculation. The SEDF uses the Hartree–Fock–Bogolyubov (HFB) computational program with Skyrme forces such as SkM*, SLy4, and SLy5 to obtain the nucleus-nucleus potential parameters for the above reactions. Using the SEDF model with SkM*, SLy4, and SLy5 interaction forces, the theoretical fusion cross-sections were determined to be above the barrier energy and compared with the available experimental fusion cross-sections. The results show a close agreement between the theoretical and experimental values for all selected systems at energies well above the barrier. However, near the barrier energies, the theoretical values were observed to be higher than the experimental values.

922

We give a brief overview of recent theoretical and experimental results on the chiral magnetic effect and spin polarization effect in heavy-ion collisions. We present updated experimental results for the chiral magnetic effect and related phenomena. The time evolution of the magnetic fields in different models is discussed. The newly developed quantum kinetic theory for massive fermions is reviewed. We present theoretical and experimental results for the polarization of Λ hyperons and the ρ₀₀ value of vector mesons.

1195

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