Characterization of a multi-keV x-ray source produced by nanosecond laser irradiation of a solid target: The influence of laser focus spot and target thickness

Abstract

The influence of focus spot and target thickness on multi-keV x-ray sources generated by 2ns duration laser heated solid targets are investigated on the Shenguang II laser facility. In the case of thick-foil targets, the experimental data and theoretical analysis show that the emission volume of the x-ray sources is sensitive to the laser focus spot and proportional to the 3 power of the focus spot size. The steady x-ray flux is proportional to the 5∕3 power of the focus spot size of the given laser beam in our experimental condition. In the case of thin-foil targets, experimental data show that there is an optimal foil thickness corresponding to the given laser parameters. With the given laser beam, the optimal thin-foil thickness is proportional to the −2∕3 power of the focus spot size, and the optimal x-ray energy of thin foil is independent of focus spot size.

Angular distribution and conversion of multi-keV L-shell X-ray sources produced from nanosecond laser irradiated thick-foil targets

“…Most of the articles concerning this issue concentrate on the influence of the laser intensity (Mattews et al, 1983;Workman et al, 2003;Workman & Kyrala, 2001a, 2001bRiley et al, 2002b;Dunn et al, 1995;Kodama et al, 1986), the atomic number (Kauffman, 1991;Mattews et al, 1983;Workman & Kyrala, 2001a, 2001bDunn et al, 1995;Ruggles et al, 2003;Yaakobi et al, 1981;Kodama et al, 1986), and the initial density of the target (Back et al, 2001(Back et al, , 2003Fiedorowicz, 2005;Fournier et al, 2004Fournier et al, , 2006Kodama et al, 1987;Teubner et al, 1991;Pelletier et al, 1997;Girard et al, 2005Girard et al, , 2004Primout, 2005). We also found that by using a long pulse laser, the laser focus spot size and the thickness of the thinfoil target (the thickness is comparable to the burn through length, which is the initial target thickness that the laser beam can transmit through the entire plasma region with little absorption at the end of the laser pulse) can change the conversion of multi-keV K-shell X-ray emission significantly (Hu et al, 2007(Hu et al, , 2008. We also found that by using a long pulse laser, the laser focus spot size and the thickness of the thinfoil target (the thickness is comparable to the burn through length, which is the initial target thickness that the laser beam can transmit through the entire plasma region with little absorption at the end of the laser pulse) can change the conversion of multi-keV K-shell X-ray emission significantly (Hu et al, 2007(Hu et al, , 2008.…”

“…The detailed characteristics of multi-keV X-ray emission are important to optimize X-ray sources or design experiments. Some papers pay attention to the influence of the laser focus spot size (Mattews et al, 1983;Workman et al, 2003;Workman & Kyrala, 2001a, 2001bRiley et al, 2002b), the laser wavelength (Kauffman, 1991;Hu et al, 2008;Mattews et al, 1983;Yaakobi et al, 1981;Kodama et al, 1986), the laser incidence angle (Mattews et al, 1983), or the laser pulse duration (Mattews et al, 1983;Workman & Kyrala, 2001a, 2001bRiley et al, 2002b;Dunn et al, 1995;Phillion & Hailey, 1986;Kodama et al, 1987;Teubner et al, 1991;Pelletier et al, 1997;Girard et al, 2004;Eidmann & Schwanda, 1991;Limpouch et al, 2002;Von Der Linde et al, 2001), etc. Some papers pay attention to the influence of the laser focus spot size (Mattews et al, 1983;Workman et al, 2003;Workman & Kyrala, 2001a, 2001bRiley et al, 2002b), the laser wavelength (Kauffman, 1991;Hu et al, 2008;Mattews et al, 1983;Yaakobi et al, 1981;Kodama et al, 1986), the laser incidence angle (Mattews et al, 1983), or the laser pulse duration (Mattews et al, 1983;Workman & Kyrala, 2001a…”

“…X-ray angular distributions have been explored mainly in the region of extreme ultraviolet (EUV) and sub-keV X-ray emission (Higashiguchi et al, 2006;Kodama et al, 1986;Celliers et al, 1996;Mead et al, 1981Mead et al, , 1983. In this article, we measured the angular distribution of multi-keV Kand L-shell X-ray emission (4.75 keV for Ti K-shell, 3-3.8 keV for Ag, 2.8-3.5 keV for Pd, and 2-2.8 keV for Mo L-shell) produced by 2 ns-duration 527 nm laser irradiated thick-foil target (the thickness is much larger than the burn through length) (Hu et al, 2008). Additional experiments are needed to study the angular distribution of multi-keV X-ray emission sources produced with the widely used target materials in nowadays experiments of HEDP and ICF.…”

Diagnostic development in precise opacity measurement of radiatively heated Al plasma on Shenguang II laser facility

“…10 The large size of the backlighter with 120 m ͑full width at half maximum͒ in diameter slightly lower than the spectral resolution, but can satisfy the requirement for enough backlighting intensity. 20 The pulse width of the x-ray backlighter is about 200 ps. It can provide short enough pulse for time-resolving measurement.…”

“…18 Recently the additional ͑ninth͒ laser beam, which can also deliver 70-150 ps short pulse besides the nanosecond long pulse, was established on the Shenguang II laser facility. [19][20][21] The ninth laser beam could be used to generate shorter backlighter compared with the previous experiments. 7,[14][15][16][17] The shorter backlighter could provide better temporal resolution.…”