Measurements of reflection and transmission in a laser-produced plasma
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Author
Butler, Thomas Harold
Date
1974-12Advisor
Cooper, A.W.
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Show full item recordAbstract
A high energy laser with a pulse width of 30 nsecs (FWHM)
irradiated an aluminum target at an angle 30° from the target's
normal. The power density at the target's surface was varied
between 10 8 and 10 10 W/cm2
. Measurements were made of the
reflective and transmissive characteristics of the ablated
surface particles, and from the measured data, an absorption
coefficient was inferred. At intensities greater than 10 9 W/cm2
the transmitted beam showed a cutoff approximately 25 nsecs
after the start of the laser pulse, indicative of the formation
of an overdense plasma. All reflection measurements showed
that the scattering was primarily specular. At intensities
between 10 8 and 10 9W/cm2
, the reflected beam exhibited a
narrow pulse attributable to thermal damage at the target
surface. At intensities of 10 9W/cm2 or greater, the reflected
beam also indicated a sharp decrease in amplitude attributed
to absorption in the newly- formed plasma. The value of the
absorption coefficient was calculated to be 0.545.
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