Laser Plasma Particle Velocities
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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Experiments were performed on laser produced plasma from aluminum target discs in a vacuum chamber at pressures a few times 10 to the -6 power torr. Plasma analysis was achieved using a floating double electrostatic probe of tungsten wires biased at -15 volts DC. In analyzing 376 oscilloscope trace pictures of the probe signal, four velocity signals occurred with regularity. The plasma velocities detected by the probe were determined to be 3.7 X 10 to the 7th power cmsec, 1.5 X 10 to the 7th power cmsec, 5.6 X 10 to the 6th power cmsec the bulk of the plasma, and 4.0 X 10 to the 6th power cmsec. A fifth, very fast signal at 1.0 X 10 to the 8th power cmsec was also detected but it was not consistently present. Investigation of the velocity distributions as a function of time showed them not to be Boltzmann distributions, but exponential power distributions.
- Plasma Physics and Magnetohydrodynamics