Time-dependent, x-ray spectral unfolds and brightness temperatures for intense Li+ ion beam-driven hohlraums

X-ray-producing hohlraums are being studied as indirect drives for inertial confinement fusion targets. In a 1994 target series on the PBFAII accelerator, cylindrical hohlraum targets were heated by an intense Li+ ion beam and viewed by an array of 13 time-resolved, filtered x-ray detectors (XRDs). The unfold operator (UFO) code and its suite of auxiliary functions were used extensively in obtaining time-resolved x-ray spectra and radiation temperatures from this diagnostic. The UFO was also used to obtain fitted response functions from calibration data, to simulate data from blackbody x-ray spectra of interest, to determine the suitability of various unfolding parameters (e.g., energy domain, energy partition, smoothing conditions, and basis functions), to interpolate the XRD signal traces, and to unfold experimental data. The simulation capabilities of the code were useful in understanding an anomalous feature in the unfolded spectra at low photon energies (less than or equal to 100 eV). Uncertainties in the differential and energy-integrated unfolded spectra were estimated from uncertainties in, the data. The time-history of the radiation temperature agreed well with independent calculations of the wall temperature in the hohlraum. (C) 1997 American Institute of Physics.