Shot-by-shot spectrum model for rod-pinch, pulsed radiography machines

Abstract

A simplified model of bremsstrahlung production is developed for determining the x-ray spectrum output of a rod-pinch radiography machine, on a shot-by-shot basis, using the measured voltage, V(t), and current, I(t). The motivation for this model is the need for an agile means of providing shot-by-shot spectrum prediction, from a laptop or desktop computer, for quantitative radiographic analysis. Simplifying assumptions are discussed, and the model is applied to the Cygnus rod-pinch machine. Output is compared to wedge transmission data for a series of radiographs from shots with identical target objects. Resulting model enables variation of parameters in real time, thus allowing for rapid optimization of the model across many shots. “Goodness of fit” is compared with output from LSP Particle-In-Cell code, as well as the Monte Carlo Neutron Propagation with Xrays (“MCNPX”) model codes, and is shown to provide an excellent predictive representation of the spectral output of the Cygnus machine. Improvements to the model, specifically for application to other geometries, are discussed.

High-energy X-ray spectrum reconstruction: solving the inverse problem from optimized multi-material transmission measurements

“…If the source flux is low, spectrometers are usually preferred to estimate the spectrum. If a very precise modeling of the source is available, a good knowledge of the X-ray spectrum can be obtained, provided that the model input parameters, such as voltage, are measured precisely enough during the pulse [3]. When none of the two previous conditions are met, transmission measurements are most frequently used to recover the X-ray spectrum, as a solution to an inverse problem [4][5][6][7].…”