RF power transfer efficiency of inductively coupled low pressure H2 and D2 discharges
RF power transfer efficiency of inductively coupled low pressure H2 and D2 discharges
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DOI：
10.1088/1361-6595/aa8685
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发表时间：
2017-08
影响因子：
3.8
通讯作者：
D. Rauner;S. Briefi;U. Fantz
中科院分区：
文献类型：
--
作者：
D. Rauner;S. Briefi;U. Fantz
在 0.25 至 10 Pa 之间的低压区域内研究了感应加热氢和氘等离子体的 RF 功率传输效率和相关功率吸收机制。放电是通过应用 1 MHz 频率的螺旋线圈在圆柱形容器中产生的，并提供高达 800 W 的 RF 功率。功率传输效率 η 通过减法进行量化，该方法依赖于在有放电和无放电情况下对通过等离子体线圈的传输 RF 功率和 RF 电流的测量操作。通过光学发射光谱和电探针测量，获得了关键的等离子体参数。对于 H2 和 D2，功率传输效率的相对行为具有很好的可比性，功率传输效率随着传递的 RF 功率的增加而增加，并描述了压力在 1 到 3 Pa 之间的最大值，其中超过 90% 的所提供功率被等离子体吸收。观察到的 η 对操作参数的相对依赖性可以通过分析方法得到很好的解释，该分析方法通过基于测量的等离子体参数评估射频等离子体电导率来考虑等离子体的功率吸收。在目前的参数下，当压力 p ≤ 1 Pa 时，必须考虑电子的非碰撞随机加热，而碰撞加热在较高压力下占主导地位。研究发现分子解离对光分子放电的功率传输效率有显着影响。 H2 和 D2 的直接比较表明，氘具有较高的原子密度，由于当前电子温度范围内的电离率增加，因此系统地提高了功率传输效率。
The RF power transfer efficiency and the relevant power absorption mechanisms of inductively heated hydrogen and deuterium plasmas are investigated in the low-pressure region between 0.25 and 10 Pa. The discharges are generated in a cylindrical vessel via a helical coil applying a frequency of 1 MHz and delivered RF powers up to 800 W. The power transfer efficiency η is quantified by a subtractive method that relies on the measurement of the delivered RF power and of the RF current through the plasma coil both with and without discharge operation. By means of optical emission spectroscopy and electrical probe measurements, the key plasma parameters are obtained. For both H2 and D2, the relative behavior of the power transfer efficiency is well comparable, which increases with increasing delivered RF power and describes a maximum at pressures between 1 and 3 Pa where more than 90 % of the provided power are absorbed by the plasma. The observed relative dependencies of η on the operational parameters are found to be well explained by an analytical approach that considers the power absorption by the plasma via evaluating the RF plasma conductivity based on the measured plasma parameters. At the parameters present, non-collisional stochastic heating of electrons has to be considered for pressures p ≤ 1 Pa , while collisional heating dominates at higher pressure. Molecular dissociation is found to have a significant influence on the power transfer efficiency of light molecular discharges. The direct comparison of H2 and D2 identifies the higher atomic density in deuterium to cause a systematically increased power transfer efficiency due to an increased ionization rate in the present electron temperature region.