Imaging detectors for 20-100 keV x-ray backlighters in high-energy-density experimental science petawatt experiments

Abstract

We are developing a petawatt laser for use as a high-energy backlighter source in the 20-100 keV range on the National Ignition Facility (NIF). High-energy x-ray backlighters will be essential for radiographing high-energy-density experimental science (HEDES) targets, especially to probe implosions and high areal density planar samples. For these high energy backlighter imaging experiments, we are developing two types of detectors: a columnar grown CsI scintillator coupled to a 2 K × 2 K charge-coupled device camera, and a CdTe crystal with special application specific integrated circuit readout electronics in a 508×512 format array. We characterized these sensors using Cd 109 and Am 241 radioactive isotopes. In addition, we employed them to measure the Sm Kα source size generated by the short pulse laser, JanUSP, at Lawrence Livermore National Laboratory. The CsI camera performed well, allowing a measurement of the Sm Ka source size. Calibration of this camera has shown that it has low noise and good resolution. The new CdTe camera performed well, however the noise level was too high for single photon counting. Some modifications to the camera will also be necessary in order to meet the needs of future hard x-ray experiments. Both cameras showed considerable promise as diagnostic tools for future high-energy x-ray backlighters for NIF HEDES experiments. This article will present the results of our characterizations of these detectors, and initial results from the JanUSP experiments. © 2004 American Institute of Physics.