Emission of a low-power laser-induced vacuum discharge plasma in the EUV and SXR spectral ranges

Abstract

Abstract. X-ray spectral characteristics of a vacuum discharge plasma with the storage energy lower than 30 J initiated on an Al or a Fe cathode by a 10 12 W/cm 2 neodymium laser were studied in the 30 -300 Å wavelength range. It is shown that both the spectral composition and intensity of radiation of a micropinch plasma produced in the cathode jet of the discharge are determined by parameters of the discharge and laser pulse. These parameters were optimized to achieve a regime in which a considerable part of radiation energy was concentrated in the long-wavelength band of the quasi-continuum (230 -270 Å and 160 -200 Å for Al and Fe, respectively), which makes this discharge a source of narrowband X-ray radiation.It is known that local regions of a hot micron-scale plasma produced in a high-current vacuum discharge plasma due pinching (micropinches) are sources of intense electromagnetic radiation in a broad spectral range. The emission spectra of micropinches in the hard X-ray range at wavelengths λ < 2 Å were studied in many works (see, for example, [1-3]). Soft X-ray (SXR) sources in the wavelength range above 20 Å attract considerable recent interest due to their possible scientific and technological applications including nanolithography, investigations of the inner structure of biological objects, astrophysical studies, etc. [4][5][6][7]. At present, as sources of such pulsed radiation, laser plasmas are mainly used. An important parameter for applications of radiation sources is the SXR conversion efficiency from a storage electric energy. From this point of view, it is interesting to use micropinch radiation sources. It was shown earlier that in vacuum discharge plasma with the storage energy about 10 J initiated on a cathode by a low-power laser pulse, micropinches emitting SXRs in the wavelength region > 40 Å are formed. The plasma pinching process stability and micropinch parameters were controlled by the laser pulse parameters [8,9]. These results suggest the possibility of making a local source of intense SXR with a comparatively low energy deposition based on the laserinduced vacuum discharge.