Direct measurements of classical and enhanced gradient-aligned cross-field ion flows in a helicon plasma source using laser-induced fluorescence

作者：Siddiqui M Umair; Thompson Derek S; McIlvain Julianne M; Short Zachary D; Scime Earl E

来源：Physics of Plasmas, 2015, 22(12): 122103.

DOI：10.1063/1.4936871

Direct laser induced fluorescence measurements are shown of cross-field ion flows normal to an absorbing boundary that is aligned parallel to the axial magnetic field in a helicon plasma. We show Langmuir and emissive probe measurements of local density and plasma potential in the same region, as well as floating probe spectra near the boundary. With these measurements, we investigate the influence of ion-neutral collisionality on radial ion transport by varying the ratio of the ion gyro-radius, rho i, to the ion-neutral collision length, k, over the range 0.34 <= rho(i)lambda(-1) <= 1.60. Classical drift-diffusion transport along density and potential gradients is sufficient to describe flow profiles for most cases. For two parameter regimes (rho(i)lambda(-1) = 0.65 and 0.44), low-frequency electrostatic fluctuations (f<10 kHz) and enhanced cross-field bulk ion flow to the boundary are observed.

• 出版日期2015-12