The response of a spherical tissue-equivalent proportional counter to iron particles from 200-1000 MeV/nucleon

Abstract

The radiation environment aboard the space shuttle and the International Space Station includes high-Z and high-energy (HZE) particles that are part of the galactic cosmic radiation (GCR) spectrum. The 56Fe ion is considered to be one of the most biologically important parts of the GCR spectrum. Tissue-equivalent proportional counters (TEPC) are used as active dosimeters on manned space flights. These TEPC's are further used to determine average quality factor for each space mission. A TEPC simulating a 1-μm diameter sphere of tissue was exposed as part of a particle spectrometer to 56Fe at energies from 200-1000 MeV/nucleon. The response of TEPC in terms of mean lineal energy ӯF, and dose mean lineal energy, ӯD, as well as energy deposited at different impact parameters through detector was determined for six different incident energies of 56Fe in this energy range. Calculations determined that charged particle equilibrium was achieved for each of the six experiments. Energy depositions at different impact parameters were calculated using the spatially restricted LET model, a radial dose distribution model. Energy deposition at one impact parameter (0-mm) was calculated with a track structure model code called BTC4. Results from these three model calculations were compared to experimental data.