分类： 核科学技术 >> 核探测技术与核电子学 提交时间： 2024-03-07
Jieyu Zhu
Haibo Yang
Yangzhou Su
Fenhua Lu
Yan Yang
Xiwen Liu
Ping Wei
Shucai Wan
Haoqing Xie
Xianqin Li
Cong Dai
Huijun Hu
Hongbang Liu
Shuwen Tang
Chengxin Zhao
摘要： The High Energy Cosmic-Radiation Detection (HERD) facility is planned to launch in 2027 and scheduled to be installed on the China Space Station. It serves as a dark matter particle detector, a cosmic ray instrument, and an observatory for high-energy gamma rays. A transition radiation detector placed on one of its lateral sides serves dual purpose, (i) calibrating HERD’s electromagnetic calorimeter in the TeV energy range, and (ii) serving as an independent detector for high-energy gamma rays. In this paper, the prototype readout electronics design of the transition radiation detector is demonstrated, which aims to accurately measure the charge of the anodes using the SAMPA application specific integrated circuit chip. The electronic performance of the prototype system is evaluated in terms of noise, linearity, and resolution. Through the presented design, each electronic channel can achieve a dynamic range of 0-100 fC, the RMS noise level not exceeding 0.15 fC, and the integral nonlinearity was less than 0.2%. To further verify the readout electronic performance, a joint test with the detector was carried out, and the results show that the prototype system can satisfy the requirements of the detector’s scientific goals.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Francesco Pecora
Yan Yang
Alexandros Chasapis
Sergio Servidio
Manuel Cuesta
Sohom Roy
Rohit Chhiber
Riddhi Bandyopadhyay
D. J. Gershman
B. L. Giles
J. L. Burch
William H. Matthaeus
摘要： In turbulence, nonlinear terms drive energy transfer from large-scale eddies into small scales through the so-called energy cascade. Turbulence often relaxes toward states that minimize energy; typically these states are considered globally. However, turbulence can also relax toward local quasi-equilibrium states, creating patches or cells where the magnitude of nonlinearity is reduced and energy cascade is impaired. We show, for the first time, compelling observational evidence that this ``cellularization'' of turbulence can occur due to local relaxation in a strongly turbulent natural environment such as the Earth's magnetosheath.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Exploration of plasma dynamics in space, including turbulence, is entering a new era of multi-satellite constellation measurements that will determine fundamental properties with unprecedented precision. Familiar but imprecise approximations will need to be abandoned and replaced with more advanced approaches. We present a preparatory study of the evaluation of second- and third-order statistics, using simultaneous measurements at many points. Here, for specificity, the orbital configuration of the NASA Helioswarm mission is employed in conjunction with three-dimensional magnetohydrodynamics numerical simulations of turbulence. The Helioswarm 9-spacecraft constellation flies virtually through the turbulence to compare results with the exact numerical statistics. We demonstrate novel increment-based techniques for the computation of (1) the multidimensional spectra and (2) the turbulent energy flux. This latter increment-space estimate of the cascade rate, based on the third-order Yaglom-Politano-Pouquet theory, uses numerous increment-space tetrahedra. Our investigation reveals that Helioswarm will provide crucial information on the nature of astrophysical turbulence.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Numerical test of isotropic turbulence compressibility reduction with helicity in a cyclic box is performed. The ratios of compressibility-relevant-mode spectra over those of kinetic energy present power laws at large wavenumbers in the dissipation range, indicating a common difference of $11/15$ in the exponents of the algebraic prefactor of the nonhelical power spectra over those of helical ones. Our results being not derived from the shapes of the spectra themselves, the implied information about the helicity effect on the complex singularities of the discretized dynamical system can still be of reasonable value for insights of the Navier-Stokes equation, although the high-order finite difference scheme used for computation may not be as accurate in dissipation range as the state-of-the-art of incompressible turbulence with pseudo-spectral method. Possible applications in controlling flows, for the purposes of, say, decreasing turbulence noise, are also discussed according to the spectral fluctuations.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Numerical test of isotropic turbulence compressibility reduction with helicity in a cyclic box is performed. The ratios of compressibility-relevant-mode spectra over those of kinetic energy present power laws at large wavenumbers in the dissipation range, indicating a common difference of $11/15$ in the exponents of the algebraic prefactor of the nonhelical power spectra over those of helical ones. Our results being not derived from the shapes of the spectra themselves, the implied information about the helicity effect on the complex singularities of the discretized dynamical system can still be of reasonable value for insights of the Navier-Stokes equation, although the high-order finite difference scheme used for computation may not be as accurate in dissipation range as the state-of-the-art of incompressible turbulence with pseudo-spectral method. Possible applications in controlling flows, for the purposes of, say, decreasing turbulence noise, are also discussed according to the spectral fluctuations.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yan Yang
William H. Matthaeus
Sohom Roy
Vadim Roytershteyn
Tulasi Parashar
Riddhi Bandyopadhyay
Minping Wan
摘要： The dissipative mechanism in weakly collisional plasma is a topic that pervades decades of studies without a consensus solution. We compare several energy dissipation estimates based on energy transfer processes in plasma turbulence and provide justification for the pressure-strain interaction as a direct estimate of the energy dissipation rate. The global and scale-by-scale energy balances are examined in 2.5D and 3D kinetic simulations. We show that the global internal energy increase and the temperature enhancement of each species are directly tracked by the pressure-strain interaction. The incompressive part of the pressure-strain interaction dominates over its compressive part in all simulations considered. The scale-by-scale energy balance is quantified by scale filtered Vlasov-Maxwell equations, a kinetic plasma approach, and the lag dependent von K\'arm\'an-Howarth equation, an approach based on fluid models. We find that the energy balance is exactly satisfied across all scales, but the lack of a well-defined inertial range influences the distribution of the energy budget among different terms in the inertial range. Therefore, the widespread use of the Yaglom relation to estimating dissipation rate is questionable in some cases, especially when the scale separation in the system is not clearly defined. In contrast, the pressure-strain interaction balances exactly the dissipation rate at kinetic scales regardless of the scale separation.
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