Dynamic hohlrawn temperature diagnosis from absorption line spectroscopy

Abstract

Summary form only given. A dynamic hohlraum is produced by imploding an array or arrays of high atomic number wires onto a cylindrical hydrocarbon foam. The radiation field produced by this source is one of the closest laboratory realizations of a blackbody in the soft X-ray region of the spectrum. Dynamic hohlraums can be employed for fundamental radiation transport studies as well as for inertial confinement fusion experiments using indirect drive. The nature of the radiation field produced by this source depends critically on the conditions reached within the hohlraum: the electron temperature, density, and their gradients. A series of experiments has been carried out on the Z machine at Sandia National Laboratories in which thin tracer layers, bearing Al, Mg, or both, have been embedded in the foam. The K shell lines of these elements have been seen in both time-integrated and time-resolved spectra, usually as absorption features. Calculations using detailed configuration atomic physics and radiation transport with up to 4000 frequency groups have been used to diagnose the conditions for several shots. Best fits to both time-resolved and time-integrated spectra have been obtained by comparing the measured line intensities to those calculated for a wide range of assumed conditions. The results constitute an independent determination of the hohlraum temperature which can be compared to temperatures inferred from the absolute intensity of the continuum, and also from the slope of the continuum.