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Theoretical and experimental results are presented for the conductance peaks at the cyclotron harmonics in a plasma-filled cylindrical capacitor. A theory is developed and is shown to predict peak height variation with density, harmonic number, and sheath thickness that is in agreement with experimental observation. A harmonic conductance peak is found to rise initially as density increases, only to fall to a minimum height as the upper hybrid frequency passes through that harmonic. Possible applications of this work to plasma diagnostics and further research are mentioned.

The fraction of the energy reflected by spherical glass shell targets irradiated with 1.06-μm laser pulses is measured for average intensities up to 4×1015 W/cm2. The on-target energies ranged up to 230 J with laser pulse half-widths of from 0.03 to 1.0 nsec. The glass shells ranged in diameter from 57 to 553 μm. Using the KMS Fusion two-channel disk laser system, the shells were illuminated at 1.06 μm from opposite sides at near-normal incidence. Two illumination systems were investigated. In the first, the target was illuminated with a pair of f/0.6 lenses providing approximately 80° per side (full cone angle) of near-normal incidence. In the second, the f/0.6 lenses were used in conjunction with an ellipsoidal mirror system which provides 144° per side (full cone angle) of normal illumination to with 18°. The fraction of the energy reflected from the targets was found to vary as a power of the average intensity on target over the range 4×1013 to 4×1015 W/cm2. Within this range no sudden onset of enhanced energy absorption or reflection by the targets was observed. Measurements were also made of the 1.06-μm radiation scattered from the target at 45° and 90° to the laser axis. The scattering was roughly isotropic. The light reflected from the targets was found to be approximately 20% depolarized.

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