Generation of energetic protons from thin foil targets irradiated by a high-intensity ultrashort laser pulse

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• 作者：Badziak ; J. ; Woryna ; E. ; Parys ; P. ; Platonov ; K.Yu. ; Jablonski ; S. ; Ryc ; L. ; Vankov ; A.B. ; Wolowski ; J.
• 关键词：52.38.Kd ; 52.50.Jm ; Proton beam ; Laser ; Plasma
• 刊名：Nuclear Instruments and Methods in Physics Research Section A ; Accelerators ; Spectrometers ; Detectors and Associated Equipment
• 出版年：2003
• 期刊代码：41_01689002
• 类别：ph
• 出版时间：February 11, 2003
• 卷：498
• 期：1-3
• 页码：503-516
• 文件大小：395 K

摘要

The results of investigations of fast proton generation from thin foil targets irradiated by 1-ps laser pulses of intensities up to 1.5×10¹⁷W/cm² are reported. The characteristics of forward-emitted proton beams produced from both single- and double-layer targets have been determined by the time-of-flight method for various thicknesses, atomic numbers (Z) and structure of the target. It is found that using a double-layer target, containing high-Z front layer and low-Z hydrogen-rich back layer, allows to obtain significantly higher energies and a current of protons as well as shorter proton pulse duration than in the case of a commonly used single-layer target. Both the maximum and the mean proton energies as well as the proton current are correlated with the yield of hard X-rays emitted from the target and they increase with the increase in the Z number of the front layer. For maximizing the energies and/or the current of protons and for minimizing the proton pulse duration both total target thickness and high-Z layer thickness must be carefully selected regarding particularly the hot electron range in the target and a possible overheating of the back target surface by the electron heat wave generated by the prepulse and the leading edge of a laser pulse. If the target thickness is smaller than the characteristic path length of the heat wave, the proton energies can be a decreasing function of laser energy. The angular divergence of a proton beam emitted from a properly prepared double-layer target are rather low (≤30°) which results in the high proton current density in a far expansion zone (border=0 SRC=/images/glyphs/BQ1.GIF>0.4mA/cm² at 1m from Au/polystyrene target) in spite of relatively low energy (<0.5J) and intensity of a laser pulse.