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Computer Simulation of Secondary Electron Emission From Plasma Facing Materials in Controlled Fusion Devices

受控聚变装置中等离子体表面材料二次电子发射的计算机模拟

基本信息

批准号：
06680481
负责人：
OHYA Kaoru
金额：
$ 1.28万
依托单位：
The University of Tokushima
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06680481/
关键词：
Secondary electron emission Plasma surface interaction Nuclear fusion Computer simulation

项目摘要

Particle-induced secondary electron emission from plasma-facing materials (PFM) in magnetic cofinement thermonuclear fusion devices is a plasma-surface interaction process of considerable importance for impurity production due to sputtering of the PFM.In this study, We have developed a Monte Carlo simulation (MCS) model of secondary electron emission from PFMs, which calculates the energy and angular distributions of emitted secondary electrons as well as the secondary electron yield.The MCS model is applied to bowl-and ripple-structures for the study of surface roughness effects on the energy and angular distributions of secondary electrons, as well as the secondary electron yield of the PFM under electron bombardment. With increasing roughness, the secondary electron yield becomes greater than that for a flat surface, whereas for large roughness the yield is smaller ; the former is due to the low-energy component in the energy distribution, and the latter results in a decrease the number of electrons emitted with oblique angles.The MCS model is also combined with an electron transport model in a sheath which is found at the interface between the surface and an edge plasma. In addition to acceleration of an electric field normal to the surface, there are gyromotion of emitted electrons in the sheath subjected to an oblique magnetic field. Some of the secondary electrons return to the surface within their first gyromotion, resulting in a considerably low effective secondary electron yield. The lowering of the yield is accompanied with a low-energy shift of the energy distribution.

磁约束热核聚变装置中面向等离子体材料（PFM）的粒子诱导二次电子发射是一种等离子体-表面相互作用过程，对于由于 PFM 溅射而产生的杂质非常重要。在这项研究中，我们开发了 PFM 二次电子发射的蒙特卡罗模拟（MCS）模型，该模型计算发射二次电子的能量和角分布： MCS模型应用于碗结构和波纹结构，研究表面粗糙度对二次电子能量和角度分布的影响，以及电子轰击下PFM的二次电子产额。随着粗糙度的增加，二次电子产额变得大于平坦表面的二次电子产额，而对于大粗糙度，二次电子产额较小；前者是由于能量分布中的低能成分，后者导致以倾斜角度发射的电子数量减少。MCS模型还与在表面和边缘等离子体之间的界面处发现的鞘层中的电子传输模型相结合。除了垂直于表面的电场的加速之外，在受到倾斜磁场作用的鞘层中还存在发射电子的回转运动。一些二次电子在第一次旋转运动中返回表面，导致有效二次电子产率相当低。产率的降低伴随着能量分布的低能量转变。