Laser prepulse dependency of proton-energy distributions in ultraintense laser-foil interactions with an online time-of-flight technique
- Advanced Photon Research Center, Japan Atomic Energy Agency (JAEA), Kyoto 619-0215 (Japan)
Fast protons are observed by a newly developed online time-of-flight spectrometer, which provides shot-to-shot proton-energy distributions immediately after the irradiation of a laser pulse having an intensity of {approx}10{sup 18} W/cm{sup 2} onto a 5-{mu}m-thick copper foil. The maximum proton energy is found to increase when the intensity of a fs prepulse arriving 9 ns before the main pulse increases from 10{sup 14} to 10{sup 15} W/cm{sup 2}. Interferometric measurement indicates that the preformed-plasma expansion at the front surface is smaller than 15 {mu}m, which corresponds to the spatial resolution of the diagnostics. This sharp gradient of the plasma has the beneficial effect of increasing the absorption efficiency of the main-pulse energy, resulting in the increase in the proton energy. This is supported by the result that the x-ray intensity from the laser plasma clearly increases with the prepulse intensity.
- OSTI ID:
- 20974943
- Journal Information:
- Physics of Plasmas, Vol. 14, Issue 4; Other Information: DOI: 10.1063/1.2721066; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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