X-ray spectroscopy of hot solid density plasmas produced by subpicosecond high contrast laser pulses at 10{sup 18}--10{sup 19} W/cm{sup 2}
- Institut National de la Recherche Scientifique, Energie et Materiaux, 1650 Montee Saint Julie, Varennes, Quebec J3X 1S2 (Canada)
- Commissariat a l`Energie Atomique, Limeil Center, Villeneuve, St. Georges (France)
- Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan 48109 (United States)
Analysis is presented of K-shell spectra obtained from solid density plasmas produced by a high contrast (10{sup 10}:1) subpicosecond laser pulse (0.5 {mu}m) at 10{sup 18}--10{sup 19} W/cm{sup 2}. Stark broadening measurements of He-like and Li-like lines are used to infer the mean electron density at which emission takes place. The measurements indicate that there is an optimum condition to produce x-ray emission at solid density for a given isoelectronic sequence, and that the window of optimum conditions to obtain simultaneously the shortest and the brightest x-ray pulse at a given wavelength is relatively narrow. Lower intensity produces a short x-ray pulse but low brightness. The x-ray yield (and also the energy fraction in hot electrons) increases with the laser intensity, but above some laser intensity (10{sup 18} W/cm{sup 2} for Al) the plasma is overdriven: during the expansion, the plasma is still hot enough to emit, so that emission occurs at lower density and lasts much longer. Energy transport measurements indicate that approximately 6% of the laser energy is coupled to the target at 10{sup 18} W/cm{sup 2} (1% in thermal electrons with {ital T}{sub {ital e}}{approx}0.6 keV and 5% in suprathermal electrons with {ital T}{sub {ital h}}{approx}25 keV). At {ital I}{lambda}{sup 2}=10{sup 18} W {mu}m{sup 2}/cm{sup 2} (no prepulse) around 10{sup 10} photons are emitted per laser shot, in 2{pi} srd in cold K{sub {alpha}} radiation (2--9 A, depending on the target material) and up to 2{times}10{sup 11} photons are obtained in 2{pi} srd with the unresolved transition array (UTA) emission from the Ta target. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
- OSTI ID:
- 165186
- Journal Information:
- Physics of Plasmas, Vol. 2, Issue 5; Other Information: PBD: May 1995
- Country of Publication:
- United States
- Language:
- English
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