关键词：
PIC simulation;pair generation and cascading;laser polarization
摘要：
Two-dimensional particle-in-cell simulations have been performed to study electron-positron pair production and cascade development in single ultra-relativistic laser interaction with solid targets. The spatiotemporal distributions of particles produced via QED processes are illustrated and their dependence on laser polarizations is investigated. The evolution of particle generation displays clear QED cascade characters. Studies show that although a circularly polarized laser delays the QED process due to the effective ion acceleration, it can reduce the target heating and confine high-energy charged particles, which leads to deeper QED cascade order and denser pair plasma production than linearly polarized lasers. These findings may benefit the understanding of the coming experimental studies of ultra-relativistic laser target interaction in the QED dominated regime.
摘要：
The through-diffusion method was employed to investigate the effect of the salt concentration on the diffusion behaviour of Re(VII) and Se(IV) in compacted bentonite. The accessible porosity, epsilon(acc) of Re(VII) increased from 025 to 0.38 with an increase of the ionic strength from 0.1 to 1.0 mol/L. The dependency of the accessible porosity epsilon(acc) on the salt concentration could be described approximately by a first-order decay exponential function. The interlayer porosity of GMZ bentonite was 21% of the total porosity at a bulk dry density of 1600 kg/m3 at 12 degrees C. The De values of Re(VII) and Se(IV) increased from 2.6 x 10(-11) to 6.1 x 10(-11) m(2)/s and from 1.6 x 10(-11) to 4.7 x 10(-11) m(2)/s in GMZ bentonite with an increase of the ionic strength from 0.1 to 1.0 mol/L, respectively. In the case of Se(IV), the adsorption showed a different ionic strength dependency in GMZ bentonite and montmorillonite. The ionic strength has no significant effect on the adsorption (K-d = 1.8 x 10(-4) m(3)/kg) on GMZ bentonite, indicating the formation of inner-sphere surface complexes. In the case of synthetic montmorillonite, the Kd values increased with increasing ionic strength. This can be explained by the fact that the electric potential of surface sites becomes less negative with increasing ionic strength resulting in an increase in the adsorption of Se(IV) at a pH above the point of zero salt effect (PZSE). The D-e values of both Re(VII) and Se(IV) increased with increasing salt concentration. Both anions are totally excluded from the interlayer space and partially from the diffuse double layer. Ionic strength alters the effective diffusion coefficient of anions by controlling the thickness of the diffuse double layer. Anion diffusion data from the literature (effective and apparent diffusion coefficients) were satisfactorily evaluated by Archie's relation. (C) 2017 Elsevier B.V. All rights reserved.
作者机构：
[谢金森; 陈珍平; 于涛; 谢芹; Zeng, Wenjie; 刘紫静; 何丽华] School of Nuclear Science and Technology, University of South China, Hengyang;Hunan;421001, China;Virtual Simulation Experimental Teaching Center on Nuclear Energy and Technology of University of South China, Hengyang;[谢金森; 陈珍平; 于涛; 谢芹; Zeng, Wenjie; 刘紫静; 何丽华] Hunan
通讯机构：
School of Nuclear Science and Technology, University of South China, Hengyang, Hunan, China
作者机构：
[陈云; 赵立宏] School of Electric Engineering, University of South China, Hengyang;Hunan;421001, China;[于涛; 何丽华; 刘紫静; 谢金森] School of Nuclear Science and Technology, University of South China Hengyang, Hunan;[陈云; 赵立宏] Hunan
通讯机构：
School of Nuclear Science and Technology, University of South China Hengyang, Hunan, China
会议名称：
14th Topical Seminar on Innovative Particle and Radiation Detectors
会议时间：
OCT 03-06, 2016
会议地点：
Siena, ITALY
会议主办单位：
[Shen, C.;Wang, Y.;Han, D.;Zou, Z.;Li, Y.] Tsinghua Univ, Dept Engn Phys, Key Lab Particle & Radiat Imaging, Beijing 100084, Peoples R China.^[Shen, C.;Xiao, D.] Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.^[Zheng, X.] Univ Virginia, 382 McCormick Rd, Charlottesville, VA 22904 USA.^[Chen, J.] Thomas Jefferson Natl Accelerator Facil, Newport News, VA 23606 USA.
关键词：
Calorimeter methods;Detector modelling and simulations I (interaction of radiation with matter, interaction of photons with matter, interaction of hadrons with matter, etc);Particle identification methods;Scintillators, scintillation and light emission processes (solid, gas and liquid scintillators)
作者机构：
[谭凯旋; 李春光; 谭婉玉] School of Nuclear Resources Engineering, University of South China, Hengyang, 421001, China;[夏良树] School of Nuclear Science and Technology, University of South China, Hengyang, 421001, China;[刘振中] School of Environmental Protection and Safety Engineering, University of South China, Hengyang, 421001, China
通讯机构：
School of Nuclear Resources Engineering, University of South China, Hengyang, China
作者机构：
[李小华; 赵阶成] School of Nuclear Science and Technology, University of South China, Hengyang, 421001, China;[李小华] Cooperative Innovation Center for Nuclear Fuel Cycle Technology &, Equipment, University of South China, Hengyang, 421001, China;[赵阶成; 陈晓亮; 喻宏; 陈效先] China Institute of Atomic Energy, Beijing, 102413, China
通讯机构：
School of Nuclear Science and Technology, University of South China, Hengyang, China
