Filter stack spectrometer measurements of high energy x-ray sources for radiography

Abstract

Analyzing the spectra of MeV x-rays verifies the consistency of radiographic systems and provides a standardized way to compare outputs from different sources, such as traditional accelerator-based systems and newer laser-based systems. A stack of alternating image plates and filters, known as a Filter Stack Spectrometer (FSS), has been fielded at three x-ray sources: the Dual Axis Radiographic Hydrodynamic Test (DARHT) facility, the X5000 commercial x-ray cabinet, and the Texas Petawatt laser. On the radiographic sources tested, varying salient parameters such as electron energy and target material changes the output MeV x-ray spectra. This diagnostic, configured with a spectral range of 50 keV–35 MeV, is evaluated via a novel inversion routine insensitive to assumed spectral shape. This insensitivity to spectral shape is essential for measuring spectra of sources that are difficult to predict with radiation transport models, such as multi-pulse accelerators and laser-driven sources. Radiation transport calculations representative of the DARHT experiment, which is straightforward to model, show good agreement between simulated and measured spectra. Future improvements to the FSS, such as replacing time-integrated image plates with scintillators, are also discussed.