中性束加热用离子源弧放电特性和性能优化研究

The magnetic multi-pole cusp configuration was widely used in neutral beam ion sources, for the reason that the magnetic multi-pole cusp field can shield most of the anode area in the discharge chamber, thus increases the confinement time of charged particles and then raises the plasma density.In the recent arc discharge and beam extraction experiment operated in the ion sources with 20 rows magnet multi-pole cusp field and that with 36 rows magnet multi-pole cusp field, the results shows: with the same discharge parameters, the difference of extraction beam current between the two kinds of ion sources is little, which is inconsistent with the anticipated result by the classical theories of bucket ion source. Thereby, further experimental and theoretical studies are required on the influence of surface magnet in the arc discharge chamber for neutral beam injection on arc discharge characters..This item firstly will go deep into theoretical studies about arc discharge plsama with magnetic cusp field confinement, numerically simulate the relationships among the discharge gas pressure, arc voltage, arc current, cusp magnetic field and the plasma parameters during the arc discharge in bucket ion source. Then with adjusting the magnetic field and axial dimension of the arc discharge chamber, we will carry on experimental studies of the influence of different magnetic fields, different axial dimensions to the plama temperature, density, arc discharge stability and the extracted beam intensity. Lastly, through comparing and combining the results by numerical simulating calculation and the experiments, we will perfect arc discharge theory of the bucket ion source with cusp magnetic field.

多磁极会切场位形在中性束加热用离子源上得到了广泛的应用，原因是，多极会切场可以屏蔽放电室大部分阳极面积，从而增加带电粒子的约束时间，提高等离子体密度。.在HL-2A装置中性束加热系统上近期开展了周边20列磁体和周边36列磁体会切场离子源弧放电和束流引出实验，实验结果表明，在相同的放电参数下两种源引出束流差异很小，与经典桶式源放电理论预期结果不一致。因此，需要从实验和理论上进一步深入研究中性束加热用离子源放电室表面磁体位形与弧放电特性的关系。.本项目将首先深入开展会切场磁约束弧放电等离子体的理论研究，数值模拟桶式离子源放电气压、弧压、弧流、会切磁场位形与等离子体参数的关系。然后调整放电室磁场位形和轴向尺寸，通过实验研究不同位形、不同轴向尺寸对等离子体温度、密度、放电稳定性和引出束流强度的影响。最后通过数值模拟计算与实验结果的比较和结合，完善会切场桶式离子源弧放电理论。