ANALYSIS OF K-ALPHA LINE EMISSION FROM ALUMINUM PLASMAS CREATED BY INTENSE PROTON-BEAMS

X-ray satellite line emission from targets irradiated by intense-light ion beams can be used to diagnose plasma conditions and beam properti es. We present results from our analysis of spectroscopic measurements of x-ray Kalpha satellites emitted from a target irradiated by an int ense-light ion beam. In this experiment, performed on the Particle Bea m Fusion Accelerator-II device at Sandia, an Al target was irradiated with a 4-6 MeV proton beam with a peak power density of 1-2 TW/cm2. Up to 15% of the beam electrical current was in the form of carbon conta minants. A time-integrated spectrum was obtained with a resolution of lambda/DETLAlambda > 1200. In our analysis, collisional radiative equi librium (CRE) calculations were performed to study the dependence of t he Al Kalpha emission spectrum on plasma and beam properties. Good agr eement is obtained between calculated satellite spectra and the emissi on features observed in the experimental spectrum. We find that excite d states with M-shell spectator electrons contribute significantly to Kalpha satellite emission spectra, exhibiting relatively broad lines a t wavelengths blueshifted with respect to those originating from groun d-state configurations. Because of opacity effects, it is likely that only radiation emitted from the outer skin of the target plasma was se en by the detector in the experiment. It is also shown that resonant s elf-absorption can skew the spectrum towards apparent higher ionizatio n stage. Our results suggest that emission spectroscopy of x-ray satel lite lines from thin tracer layers offers a potentially valuable techn ique for determining plasma conditions in intense-light-ion-beam exper iments.