Measurements of neutral helium density in helicon plasmas.
Measurements of neutral helium density in helicon plasmas.
复制标题
螺旋等离子体中中性氦密度的测量。
DOI：
10.1063/1.3466796
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
E. Scime
中科院分区：
文献类型：
--
作者：
S. Houshmandyar;S. Sears;S. C. Thakur;J. Carr;M. Galante;E. Scime
利用激光诱导荧光（LIF）技术测量了螺旋等离子体源中氦原子的密度。对于587.725 nm的泵浦波长（真空）和激光注入沿着磁场，LIF信号在多普勒频移的中心波长处表现出信号减小。信号的下降是由等离子体的有限光学深度引起的，并且下降的幅度与激发态中性原子的密度成正比。利用朗缪尔探针测量的等离子体密度和电子温度和碰撞辐射模型，绝对基态中性密度计算的光学深度测量。最佳等离子体性能，即，在13.0和13.5 MHz的天线频率和550-600 G的磁场强度下观察到系统轴上的最大中性损耗。
Laser-induced-fluorescence (LIF) is used to measure the density of helium atoms in a helicon plasma source. For a pump wavelength of 587.725 nm (vacuum) and laser injection along the magnetic field, the LIF signal exhibits a signal decrease at the Doppler shifted central wavelength. The drop in signal results from the finite optical depth of the plasma and the magnitude of the decrease is proportional to the density of excited state neutral atoms. Using Langmuir probe measurements of plasma density and electron temperature and a collisional-radiative model, the absolute ground state neutral density is calculated from the optical depth measurements. Optimal plasma performance, i.e., the largest neutral depletion on the axis of the system, is observed for antenna frequencies of 13.0 and 13.5 MHz and magnetic field strengths of 550-600 G.