A physics model of lutetium oxyorthosilicate detectors: theory and experimental validation

Abstract

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 highfidelity model of the Lu 2 SiO 5 :Ce 3+ (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.