Spectroscopic investigations of hard x-ray emission from 120 ps laser-produced plasmas at intensities near 10(sup 17) W cm(sup (minus)2)

摘要

Spectroscopic investigations of the x-ray emission of plasmas heated by 120 ps, frequency doubled pulses from the JANUS Nd: glass laser are presented. High Z K-shell spectra emitted from slab targets heated to near 10(sup 17) W cm(sup (minus)2) intensity are investigated. High resolution ((gamma)/(Delta)(gamma)>5000) x-ray spectra of multicharged ions of H-like Ti, Co, Ni, Cu, and also H-like Sc in the spectral range 1.5--3.0 (angstrom) are obtained in single laser shots using a spherically bent Mica crystal spectrograph with a 186 mm radius of curvature. The spectra- have one dimensional spatial resolution of about 25(mu)m and indicate that the size of the emission zone of the resonance, transitions is <25(mu)m. Simultaneous x-ray images of the plasma from a charge-coupled device pinhole camera confirmed that the plasma x-ray emission is from a similar sized source. Survey spectra (gamma)/(Delta)(gamma)=500--1000) taken with a flat LiF (200) crystal spectrometer with a charge-coupled device detector complement the high resolution data. Two dimensional LASNEX modeling of the laser target conditions indicate that the high K-shell charge states are produced in the hot dense region of the plasma with electron temperature >2 keV and density(approximately)10(sup 22) cm(sup (minus)3). These experiments demonstrate that with modest laser energy, plasmas heated by high-intensity 120 ps lasers provide a very bright source of hard (approximately)8 keV x-ray emission.