Conversion of laser radiation into X-rays in the subnanosecond region

Year: 1977

Authors: Bertotti B., Garifo L., Arecchi F.T., Greco A.

Autors Affiliation: Istituto di Fisica, Univ. of Pavia, Pavia, Italy;
CISE Segrate Milano, Italy;
Istituto Nazionale di Ottica, Largo E. Fermi 6, 50125 Firenze, Italy

Abstract: X-ray radiation from the plasma generated on a solid target by a subnanosecond laser pulse is investigated. The analysis is a semiquantitative one, based upon the energy equation with the relevant microscopic processes taken into account. For the simple case of a rectangular pulse, there are three different phases: a heating transient stage, a stationary regime in which all absorbed radiation is reradiated as soft X-rays and a cooling phase. The conditions to be fulfilled in order that the expansion be neglected are investigated in detail. These analytical estimates are compared with the results of a computer code. In a model where energy propagates from the laser absorption layer into the target by heat conduction, the conversion efficiency at moderate fluxes is drastically reduced by the expansion which sets on before the regime is reached. Moreover the emission is delayed. For lage power fluxes, following a recent suggestion by Brueckner, we consider also an energy transfer by fast (10-50 keV) electrons, which thermalize by collisions in a region larger than the layer directly heated by conduction. This reduces the time lag and yields a good power efficiency. Results are presented for absorbed laser fluxes in range 1013-1017W cm-2.

Journal/Review: JOURNAL OF PHYSICS D-APPLIED PHYSICS

Volume: 10      Pages from: 1557  to: 1573

KeyWords: X-ray radiation
DOI: 10.1088/0022-3727/10/12/005

Citations: 4
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