Preliminary measurements of x-ray and neutron emission from laser-produced plasmas.
Two Nd-glass laser systems have been assembled for producing high-temperature plasmas. The smaller laser, which gives subnanosecond pulses of about 5 J, has been used primarily for x-ray studies. The spectrum above 2 keV is being explored using Bragg reflection from a cylindrically curved graphite crystal. Line radiation appears to be present in the spectra measured for laser-produced plasmas of lead and gold. Plasma temperatures implied by x-ray transmission measurements are found to vary with absorber thickness. Temperatures of a few tens of keV, inferred from thick-absorber measurements of low-Z plasmas, suggest the operation of anomalous heating mechanisms. A second glass laser system, involving face-pumped disks 14 cm in diameter, is also in use for plasma-heating experiments and has led to the production of D-D neutrons. This system has been used to produce pulses of several tens of joules in a few nanoseconds for recent experiments. A calibrated plastic scintillator with two photomultipliers is used f r neutron detection. Targets of CD(2) have produced total yields of more than 10(4) neutrons. Effective neutron production appears to require laser pulses longer than 2 nsec and to be accompanied by a large reflected pulse.
Mead
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Kidder
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Swain
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Ranier
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Petruzzi
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