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arXiv 2023年

作者： Liu, Chang Du, Bao Song, Peng Institute of Applied Physics and Computational Mathematics Beijing China HEDPS Center for Applied Physics and Technology College of Engineering Peking University Beijing China

The plasma heating by the α particle transport is a main self-heating source in inertial confinement fusion (ICF) that determines the capsule implosion performance. Due to the high energy of α particle and the high temperature in the ICF capsule hot spot, significant non-equilibrium effect exists and the continuum mechanics breaks down. For the numerical simulation of implosion and charged particle transport, the Boltzmann equation needs to be solved to capture the kinetic effects. However, the 7-dimensional Boltzmann equation, the highly frequent Coulomb collision, and the multi-folded integral stopping power formulation greatly limits the computational efficiency and challenges the computational power. To overcome the high computational cost of high-frequent coulomb collisions, we propose a hybrid collision model according to which the collisions are categorized into low frequent large-angle collisions and high frequent small-angle grazing collisions. The large-angle collision process is precisely solved based on the Coulomb cross-section. For the highly frequent small-angle grazing, a statistic model is constructed with second-order accuracy in time. The hybrid collision model reduces the computational cost of scattering calculation by two magnitudes. For the multi-folded integral stopping power formulation, a neural network is used to improve computational efficiency. Based on the proposed algorithm, we develop one-dimensional to three-dimensional module code to directly solve the the α particle transport Boltzmann equation. The α transport module code is integrated into the multi-physics LARED-S program. The MC version ICF software is verified by a simulation study of the N191110 experiment. Copyright © 2023, The Authors. All rights reserved.

关键词： Monte Carlo methods

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Special Issues in Honor of Professor Zhong-Ci Shi(Part Ⅲ)

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Annals of applied mathematics 2023年第4期 383-384页

作者： Weinan E Song Jiang Tao Tang Pingwen Zhang Peking University Institute of Applied Physics and Computational Mathematics BNU-HKBU United International College Wuhan University & Peking University

Professor Zhong-Ci Shi, a professor of Chinese Academy of Sciences(CAS) and worldrenowned computational mathematician, passed away on 13 February, 2023. Annals of applied mathematics will devote a few special issues t...

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Detailed and Reduced Chemical Kinetic Model of Ch4/O2 Combustion Based on High-Precision First Principles Molecular Dynamics Simulation

SSRN

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SSRN 2023年

作者： Zhang, Teng Shou, Liefeng Chen, Lang Wang, Hongliang Long, Yao Wang, Zhongqi Chen, Jun Beijing Institute of Technology Beijing100081 China Northwest Institute of Nuclear Technology Xi'An710024 China Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing100088 China HEDPS Center for Applied Physics and Technology College of Engineering Peking University Beijing100871 China

CH4/O2 combustion reaction kinetics have been attracting many research interests, because of its potential application in engineering field. In this work, the combustion reaction of CH4/O2 at high temperature is simulated based on the first-principles molecular dynamics method first time. Two new intermediates, HCOOH and O3, and their effect to the formation of CO2 and OH radical are revealed. Our elementary reaction analysis also discovered that radical, OH, HO2 and others, play a key role in combustion process. They act as high active oxidant and promote final products formation. Combining elementary reaction with simplifying technique, a novel 30-step reduced chemical kinetic model is constructed. It is also successful verified by comparing simulation value with experimental ignition delay time, laminar flame speed, adiabatic flame temperature and CJ detonation velocity of CH4 combustion. This work is an implementation of the scheme of "first-principle model construction + model simplification + engineering verification". It also indicated the feasibility of this scheme to establish reduced chemical kinetic model of fuel/oxidant or energetic materials in future. © 2023, The Authors. All rights reserved.

关键词： Reaction kinetics

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Magnetic ground state of monolayer CeI2: Occupation matrix control and DFT+U calculations

arXiv

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arXiv 2024年

作者： Hou, Yue-Fei Li, Shujing Yang, Xinlong Jiang, Wei Wang, Qiuhao Zheng, Fawei Fu, Zhen-Guo Zhang, Ping Institute of Applied Physics and Computational Mathematics Beijing100088 China Graduate School China Academy of Engineering Physics Beijing100088 China College of Mathematics and Physics Beijing University of Chemical Technology Beijing100029 China School of physics Beijing institute of technology Beijing100081 China National Key Laboratory of Computational Physics Beijing100088 China School of Physics and Physical Engineering Qufu Normal University Qufu273165 China

The magnetic ground state is crucial for the applications of the two-dimension magnets as it decides fundamental magnetic properties of the material, such as magnetic order, magnetic transition temperature, and low-energy excitation of the spin waves. However, the simulations for magnetism of local-electron systems are challenging due to the existence of metastable states. In this study, occupation matrix control (OMC) and density functional theory plus Hubbard U calculations are applied to investigate the magnetic ground state of monolayer CeI2. Following the predicted ferromagnetic (FM) order, the FM ground state and the FM metastable states are identified and found to have different values of the magnetic parameters. Based on the calculated magnetic parameters of the FM ground state, the Curie temperature is estimated to be 128 K for monolayer CeI2. When spin-orbit coupling (SOC) is considered, the FM ground state is further confirmed to contain both off-plane and in-plane components of magnetization. SOC is shown to be essential for reasonably describing not only magnetic anisotropy but also local electronic orbital state of monolayer CeI2 © 2024, CC BY.

关键词： Magnetic anisotropy

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A low-profile EIA-like rasorber with ultra-wideband transmission band

A low-profile EIA-like rasorber with ultra-wideband transmis...

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2023 IEEE MTT-S International Microwave Workshop Series on Advanced Materials and Processes for RF and THz Applications, IMWS-AMP 2023

作者： Weiwei, Wu Shixian, Li Yizhong, Fang Jiaqi, Liu Naichang, Yuan School of Electronic Science National University of Defense Technology Hunan Changsha410003 China Beijing Institute of Space Long March Vehicle State Key Laboratory of Experimental Physics and Computational Mathematics Beijing100076 China

ISBN: (纸本)9798350308761

In this article, based on the theory of electromagnetic induced transparency (EIT) and electromagnetic induced absorption (EIA), a novel frequency selective rasorber (FSR) is proposed. This dual-polarized structure has an ultra-wideband transmission band in-between two absorption bands. When the bright mode resonant circuit (BMRC) is excited by incoming electromagnetic (EM) waves operating in the absorption bands, the EM energy is transferred to the dark mode resonant circuit (DMRC) by EM induction and coupling. The lumped resistors (LRs) of the DMRC absorb the coupled EM energy. The incoming EM waves at other frequencies will pass this proposed EIA-like FSR with low insertion loss (IL). Its transmission band is from 14.6 GHz to 18.2 GHz. Its absolute bandwidth is 3.6 GHz and the relative bandwidth is 22%. The absorption bands occur from 13.2 GHz to 14 GHz and from 18.7 GHz to 19.4 GHz. The RCS reduction range is from the minimum value of 2.63 dB at 10 GHz to the maximum value of 23.28 dB at 19.3 GHz. The unit cell has a dimension of 10 X 10 X 3 mm, which means its total thickness is only 3 mm. This proposed EIA-like FSR can be a good candidate both in radar stealth radome and EM compatibility domains. © 2023 IEEE.

关键词： electromagnetic bright and dark modes electromagnetic induced absorption electromagnetic induced transparency metamaterial

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Validation of Classical Transport Cross Section for Ion-Ion Interactions Under Repulsive Yukawa Potential

arXiv

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arXiv 2024年

作者： Hu, Tian-Xing Wu, Dong Lin, C.L. Sheng, Z.M. He, B. Zhang, J. Key Laboratory for Laser Plasmas School of Physics and Astronomy Collaborative Innovation Center of IFSA Shanghai Jiao Tong University Shanghai200240 China National Key Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing100088 China Institute for Fusion Theory and Simulation Department of Physics Zhejiang University Hangzhou310027 China Institute of Physics Chinese Academy of Sciences Beijing100190 China

Value of cross section is a fundamental parameter to depict the transport of charged particles in matters. Due to masses of orders of magnitude higher than electrons and convenience of realistic calculation, the cross section of elastic nuclei-nuclei collision is usually treated via classical mechanics. The famous Bohr criterion was firstly proposed to judge whether the treatment via classical mechanics is reliable or not. Later, Lindhard generalized the results of Coulomb to screening potentials. Considering the increasing importance of detailed ion-ion interactions under modern simulation codes in inertial confinement fusion (ICF) researches, the validation of classical transport cross section for ion-ion interactions in a big range of parameter space is certainly required. In this work, the transport cross sections via classical mechanics under repulsive Yukawa potential are compared with those via quantum mechanics. Differences of differential cross sections are found with respect to scattering angles and velocities. Our results generally indicate that the classical picture fails at the cases of both low and high velocities, which represent a significant extension of the famous Bohr criterion and its generalized variations. Furthermore, the precise validation zones of classical picture is also analysed in this work. This work is of significant importance for benchmarking the modern ion-kinetic simulation codes in ICF researches, concerning the stopping power of α particles in DT fuels, ion-ion friction and viscous effects in the formation of kinetic shocks. © 2024, CC BY.

关键词： Ions

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Theoretical Study on the Hydrogen Capture and Damage Mechanisms of Puo2 Nanograin Boundary

SSRN

引用

SSRN 2022年

作者： Zhang, Le Wang, Li-Fang Sun, Bo Liu, Haifeng Li, Gan Yu, Hui-Long Zhang, Qili Song, Haifeng Institute of Applied Physics and Computational Mathematics Beijing100094 China Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing100088 China Science and Technology on Surface Physics and Chemistry Laboratory Mianyang621908 China Insititute of Materials China Academy of Engineering Physics Jiangyou621907 China

The hydriding corrosion is harmful to the long-term storage of plutonium (Pu). Since the defect-free PuO 2 overlayer has been proved to resistance hydrogen attack, Pu hydriding is mainly related to such penetrating defects as the grain boundaries (GBs) of PuO 2 . We perform comprehensive DFT+ U -D3 calculation and tensile-test simulation to investigate the incorporation and dissolution behaviors of H in PuO 2 GB, and the induced hydrogen damage. The exothermic incorporation and dissolution of H confirm the capture effect of PuO 2 GB, which are contrary to endothermic behaviors of H in PuO 2 bulk. The predicted saturation solubility of H demonstrates that GB is the active site that promote H dissolution, which is one of the important factors to Pu hydriding. The dissolved H can further weaken the Pu-O bonds in GB and facilitate the intergranular fracture of PuO 2 overlayer. Our study provides key mechanistic insights towards interpreting of Pu hydriding corrosion, which is critical for predictive modeling of the induction time. © 2022, The Authors. All rights reserved.

关键词： Hydrogen

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Large-scale kinetic simulations of colliding plasmas within a hohlraum of indirect-drive inertial confinement fusion

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Physical Review E 2024年第3期109卷 035207-035207页

作者： Tianyi Liang Dong Wu Xiaochuan Ning Lianqiang Shan Zongqiang Yuan Hongbo Cai Zhengmao Sheng Xiantu He Institute for Fusion Theory and Simulation School of Physics Zhejiang University Hangzhou 310058 China Key Laboratory for Laser Plasmas and School of Physics and Astronomy and Collaborative Innovation Center of IFSA Shanghai Jiao Tong University Shanghai 200240 China National Key Laboratory of Plasma Physics Research Center of Laser Fusion CAEP Mianyang 621900 China Institute of Applied Physics and Computational Mathematics Beijing 100094 China

The National Ignition Facility has recently achieved successful burning plasma and ignition using the inertial confinement fusion (ICF) approach. However, there are still many fundamental physics phenomena that are not well understood, including the kinetic processes in the hohlraum. Shan et al. [Phys. Rev. Lett. 120, 195001 (2018)] utilized the energy spectra of neutrons to investigate the kinetic colliding plasma in a hohlraum of indirect drive ICF. However, due to the typical large spatial-temporal scales, this experiment could not be well simulated by using available codes at that time. Utilizing our advanced high-order implicit PIC code, LAPINS, we were able to successfully reproduce the experiment on a large scale of both spatial and temporal dimensions, in which the original computational scale was increased by approximately seven to eight orders of magnitude. Not only is the validity of the explanation of the experiment confirmed by our simulations, i.e., the abnormally large width of neutron spectra comes from beam-target nuclear fusions, but also a different physical insight into the source of energetic deuterium ions is provided. The acceleration of deuterium ions can be categorized into two components: one is propelled by a sheath electric field created by the charge separation at the onset, while the other is a result of the reflection of the potential of the shock wave. The robustness of the acceleration mechanism is analyzed with varying initial conditions, e.g., temperatures, drifting velocity, and ion components. This paper might serve as a reference for benchmark simulations of upcoming simulation codes and may be relevant for future research on mixtures and entropy increments at plasma interfaces.

关键词： Inertial confinement fusion Laser inertial confinement Particle-in-cell methods

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The Compressible Navier-Stokes Equations on the Multi-Connected Domains

arXiv

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arXiv 2024年

作者： Fan, Xinyu Jiang, Song Li, Jing Institute of Applied Physics and Computational Mathematics Beijing100088 China Department of Mathematics Nanchang University Nanchang330031 China Institute of Applied Mathematics AMSS Hua Loo-Keng Key Laboratory of Mathematics Chinese Academy of Sciences Beijing100190 China

This paper investigates the isentropic compressible Navier-Stokes equations on k-connected domains Ω under Navier-slip boundary conditions. We study the multi-solvability of the stationary systems on Ω, which is closely related with the Cauchy-Riemann systems and critical points of harmonic functions on Ω. Then based on the structure of Green's functions, the commutator estimates are obtained on the circular domains and extended to Ω with the help of conformal mappings. Moreover, we will utilize these assertions to discuss the global well-posedness and large time behaviours of the non-stationary systems on Ω with large initial values containing vacuum. Copyright © 2024, The Authors. All rights reserved.

关键词： Conformal mapping

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Isotope-Shift Measurement of Bosonic Yb^(+)Ions

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Chinese physics Letters 2023年第9期40卷 43-47页

作者：乐虹伶邵虎陈正方鹏程曾孟彦张宝林黄垚李冀光陈群峰管桦高克林 State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Innovation Academy of Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430071China University of the Chinese Academy of Sciences Beijing 100049China Key Laboratory of Atomic Frequency Standards Innovation Academy of Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430071China Institute of Applied Physics and Computational Mathematics Beijing 100088China Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences University of Science and Technology of ChinaHefei 230026China CAS Center for Excellence in Quantum Information and Quantum Physics University of Science and Technology of ChinaHefei 230026China Wuhan Institute of Quantum Technology Wuhan 430206China

We present a method that the atomic transition frequency measurement relies on the accurate wavemeter,optical frequency comb and stable Fabry–Pérot cavity to precise determination of stable even isotope shift on single Yb+ion(A=168,170,172,174,176).The 6s^(2)S_(1/2)←→6p^(2)P_(1/2)and 5d^(2)D_(3/2)←→6s^(3)[3/2]_(1/2)resonance dipole transition frequencies are preliminarily measured by using a wavemeter which is calibrated by the 729 nm clock laser of ^(40)Ca^(+).Meanwhile,those frequencies are double checked by using optical frequency comb for correction of ***,by changing frequency locking points at an ultralow expansion cavity more slightly and monitoring the corresponding atomic fluorescence changing with 17%,we finally improve the resonant frequency uncertainty to±6 MHz,which is one order of improvement in precision higher than previously published measurements on the same transitions.A King-plot analysis with sensitivity to coupling between electrons and neutrons is carried out to determine the field and mass shift *** measurement combined with existing or future isotope shift measurements can be used to determine basic properties of atomic nuclei,and to test new forces beyond the Standard Model.

关键词： checked correction resonant

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