Reflection of Background Ions by an Expanding Laser-Produced Plasma.
MARYLAND UNIV COLLEGE PARK INST FOR FLUID DYNAMICS AND APPLIED MATHEMATICS
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A mass-spectroscopic study of a precursor feature, which propagates ahead of a laser-produced plasma expanding into a partially ionized background, has confirmed that the feature comprises fast ions of the background gas species. The maximum velocity of the precursor ions is found to be VMAX about 2 muM V sub LE, where muM is the ratio of reduced mass to background ion mass and V sub LE is the leading edge velocity of the laser-produced plasma the precursor ions therefore appear to result from two-body collisions. A theoretical model which includes screened-nuclear cross-sections and friction due to multiple small-angle collisions indicates that hard-knock ion-ion collisions are insufficient to explain the large precursor ion flux which is experimentally observed. The experimental results are in satisfactory agreement with a model which invokes ion-neutral rearrangement collisions for generation of the precursor ions. Author
- Plasma Physics and Magnetohydrodynamics