The fundamental photon and charged particle interaction data and the radiation transport methods, pioneered and developed at NIST to calculate the penetration of electrons and photons in matter, are used in most of the major Monte Carlo simulation codes today.
The Dosimetry Group applies these data and codes to fundamental and applied problems in radiation dosimetry. Monte Carlo simulation is increasingly applied to problems in radiation metrology, protection, therapy and processing as an accurate tool for design, optimization and insight often inaccessible to measurement. Our programs continue to develop and use interaction data and Monte Carlo calculations for the understanding and refinement of our measurement standards, and for the many applications of ionizing radiation with which we are involved. The applications of Monte Carlo simulations may encompass the whole problem from source to detector. Examples include the development of a computational model of the NIST’s Clinac 2100C medical accelerator. This source model was used for an international intercomparison of absorbed dose to water standards as well as for the computation of wall corrections for an ionization chamber developed for direct realization of air kerma in high energy photon fields used in non-intrusive cargo inspection systems. Other examples include the development of source models for our new Cs-137 range and for our x-ray sources that generate beam qualities used in digital mammography.