Comparison of the B field dependency of plasma parameters of a weakly magnetized inductive and Helicon hydrogen discharge
Comparison of the B field dependency of plasma parameters of a weakly magnetized inductive and Helicon hydrogen discharge
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DOI：
10.1088/0963-0252/25/3/035015
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发表时间：
2016-04
影响因子：
3.8
通讯作者：
S. Briefi;P. Gutmann;D. Rauner;U. Fantz
中科院分区：
文献类型：
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作者：
S. Briefi;P. Gutmann;D. Rauner;U. Fantz
利用光学发射光谱技术研究了弱磁化感应耦合氢气放电(工作压力为1Pa)的放电特性。研究了电子密度Ne、温度Te和原子与分子氢密度比Nh/NH2在不同磁场强度(高达12mT)下的行为。将沿着圆柱形放电容器中心轴的视线进行的OES测量结果与名古屋III型螺旋管天线取代电感耦合等离子体天线的情况进行了比较。在电感耦合等离子体情况下，由于径向电子扩散受阻，圆柱形放电容器轴线上的电子温度和密度随着磁场的增加而降低。这导致了从均匀的径向发射轮廓逐渐过渡到在放电中心具有最小发射的中空轮廓。在原子与分子氢的密度比方面，在低B场下可以得到高达0.32的值，而在高磁场下则表现出下降的趋势。对于螺旋管的情况，得到的Ne和Te的值几乎不受外部磁场的影响。此外，在低B场强下已经观察到了中空的径向发射分布。在螺旋管装置中，NH/NH_2有增加的趋势，在12mT时最大值约为0.2。
The discharge properties of a weakly magnetized inductively coupled hydrogen discharge (operating pressure 1 Pa) are evaluated by using optical emission spectroscopy. The behaviour of the electron density ne, temperature Te and the density ratio of atomic to molecular hydrogen nH/nH2 with varying magnetic field strength (up to 12 mT) is investigated. The results obtained from the OES measurements performed with a line of sight directed along the central axis of the cylindrical discharge vessel are compared to the case when the ICP antenna is replaced by a Nagoya-type-III Helicon antenna. In the ICP case, the electron temperature and density at the axis of the cylindrical discharge vessel decrease with increasing magnetic field due to the hindered radial electron diffusion. This results in a gradual transition from a homogeneous radial emission profile to a hollow profile with minimal emission in the discharge centre. Concerning the density ratio of atomic to molecular hydrogen, one obtains very high values of up to 0.32 at low B field and a decreasing behaviour with higher magnetic fields. For the Helicon case, the obtained values of ne and Te are virtually unaffected by the external magnetic field. Furthermore, a hollow radial emission profile is observed already at low B field strengths. In the Helicon setup one obtains an increasing trend for nH/nH2 with a maximum of about 0.2 at 12 mT.