Super hard x-rays from two-plasmon decay in laser produced plasmas

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1982

OSTI ID:6897797

McAdoo, J H

X-ray Bremsstrahlung photons with energies in the vicinity of 100 keV are routinely observed in short pulse high intensity infra-red laser fusion experiments. The purpose of this work is to identify the source mechanism for these x-rays. The x-rays are generated by illuminating glass microballoons with light intensities of 10/sup 15/ to 10/sup 16/ W/cm/sup 2/ using a Nd laser. A pair of Nal(Tl) scintillator detectors with lead absorber filters are used to measure the average photon energy and spectral intensity of the super hard spectrum. This spectrum was assumed to decay exponentially with photon energy. Laser prepulse were used to control the density gradient scale length presented to the main beam. Unexpectedly the prepulses had no effect on the super hard x-ray spectrum. Happenstance changes in laser intensity resulted in variations in the x-ray energy output and also variations in spectrum's exponential decay constant. A strong correlation between the fraction of incident laser energy which was radiated and the decay constant was observed. The relation was found to be consistent with the temperature of the super fast electron distribution scaling with laser intensity as T approx. 1/sup 1/3/. This is charactristic of absorption mechanisms which produce high phase velocity electon plasma waves such as Raman scattering or Two-Plasmon Decay.

• OSTI ID: 6897797
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700208* -- Fusion Power Plant Technology-- Inertial Confinement Technology
ELECTROMAGNETIC RADIATION
ELECTRON PLASMA WAVES
INFRARED RADIATION
IONIZING RADIATIONS
LASER TARGETS
LASER-PRODUCED PLASMA
LASERS
PLASMA
PLASMA WAVES
PLASMONS
QUASI PARTICLES
RADIATIONS
TARGETS
X RADIATION