High-energy x-ray and neutron modeling and digital imaging for nondestructive testing applications

摘要

Adapting amorphous silicon imagers to the rigors of nondestructive evaluation has required the creation of new tools and techniques for successful detection of flaws in dense objects. At Los Alamos National Laboratory, extensive use of digital imagers and a desire to replace film with digital systems has led to additional research into modeling and simulation with an ultimate goal of improved techniques for using these imagers. The imagers have been used with varying success at x-ray energies ranging from 70 keV to 20 MeV, as well as with a variety of neutron energies at the Los Alamos Neutron Science Center (LANSCE). To simulate these diverse situations, a new version of the Monte Carlo Neutron/Photon (MCNP) simulation package, developed at Los Alamos, is employed (MCNP-X). The rapid simulation of various setups allows the rapid development of techniques without extensive and costly experimentation or test blocks. The simulations cover digital radiography as well as computed tomography. The results of these simulations leads to several techniques for digital radiography and computed tomography unique to amorphous silicon imagers, and provides additional information concerning the transition from film to digital imaging. Specifically, techniques have been developed to use the order of magnitude speed advantage of amorphous silicon detectors to provide density resolution in ways not possible with film. Also, the viability of amorphous silicon detectors at extremely high energies (1-20 MeV) is simulated and tested experimentally.