Detector physics is an important element in the simulation of X-ray radiography. In conjunction with the radiographic chain model (RCM) developed at Los Alamos National Laboratory (LANL), we have built a high-fidelity model of the Lu2SiO5:Ce3+ (LSO) detector system for use with the Cygnus rod-pinch X-ray source. In the RCM, the two-dimensional (2D) fully electromagnetic and relativistic particle-in-cell (PIC) code MERLIN is used to model the Cygnus electron diode. The electron distributions from PIC calculations are used in the Monte Carlo N-Particle (MCNP) code to model the generation of the X-rays via the bremsstrahlung process and subsequent transport through dense objects to detectors. Radiographs are calculated in conjunction with empirically measured scintillation efficiencies for light yields. To model detector blur, MCNP calculates the point-spread functions (PSF) of X-ray scattering in the LSO. Two length scales in the PSFs can account for correlated short-range (< 0.4 mm) and long-range (uncorrelated) blur. By employing a detector model methodology, we can examine detector parameters such as the detector quantum efficiency (DQE), blur, and photon statistics. The calculations are validated in juxtaposition with experimental radiographic data on step wedges, rolled edges, and static objects. In this paper, we focus on characterizing the detector performance.
It is well known that the attenuation length of radiation in any dense material increases with radiation energy. We propose a novel method of measuring x-ray and gamma spectra based on this principle. The multispectral x-ray and gamma spectrometer concept employs a scintillating material and optical camera system coupled via optical fibers. The optical fibers are placed sequentially at increasing depth with respect to the radiation path along the length of the scintillating material. Light generated by the interaction of radiation with the scintillating material is transported to the camera for recording and subsequent analysis. The proposed system will be used to determine the spectrum of incident radiation by deconvolving the radiation spectrum from the optical intensity (as a function of depth) of the recorded signals.