Volume 96, Issue 3, 01 August 2004
Index of content:
- PLASMAS AND ELECTRICAL DISCHARGES (PACS 51-52)
Hydrogen emission by laser-induced shock wave plasma and its application to the quantitative analysis of zircalloy96(2004); http://dx.doi.org/10.1063/1.1763990View Description Hide Description
An experiment was carried out to demonstrate the detection of a hydrogen emission line, , in a plasma induced by a -switched (YAG,yttrium aluminium garnet) laser in a low pressure gas on various types of samples, such as zinc, a glass slide, and a zircalloy tube. Contribution by surface water could be suppressed by a laser cleaning treatment and the resulting calibration curve obtained for zircalloy tube samples doped with various concentrations of hydrogen (, , , and ) suggest potential applications to the quantitative analysis of hydrogen. A study of the dynamic process represented by the time profiles of the hydrogen emission, in comparison with those for zinc atomic emission, revealed a specific feature that is related to the small mass of hydrogen. This specific feature can be explained by the shock wave excitation mechanism in terms of new hypothetical process, namely, a mismatch between the movement of ablated hydrogen atoms and the formation of the shock wave.
96(2004); http://dx.doi.org/10.1063/1.1767620View Description Hide Description
In this study, we will investigate the electron transport in the downstream region of a planar and unbalanced (type II) magnetron discharge. The effects of the anodesheath boundary and diverging magnetic field on the electron kinetics such as the electron loss mechanism at plasma-sheath boundary and the electron distribution function will be examined through the probe measurements. The spatially resolved probe measurements reveal the existence of an electron drift from the cathode fall region to the downstream region. It is found that this drift is caused by the axial gradient of magnetic field (the magnetic mirror force) and then derives an electron current to the grounded substrate on which the potential of the sheath is very low; so the current balance between the cathode and anode currents is kept. The experimental results show that the electron transport in the downstream region is not governed by the classical diffusion (mobility and diffusion dominated) but is dominated by the modified diffusion including the electron drift caused by the magnetic mirror force. Additionally, the mechanism and the experimental evidence on the presence of a non-Maxwellian electron energy distribution function (in particular, bi-Maxwellian distribution) in magnetron discharge will be presented showing that the non-Maxwellian electron energy distribution function is due to the combined effects of the electron drift toward the substrate and the sheath boundary condition.