FLUKA investigations of the applicability of pure propane gas for TEPC-based microdosimetry of space radiation in low Earth orbit.

Tissue-equivalent proportional counter (TEPC) filled with tissue-equivalent propane (TEP) gas is the standard choice for microdosimetric studies. However, pure propane (PP) gas serves as an effective alternative for long-duration space missions due to its superior compositional stability. This study addresses the applicability of PP gas for the microdosimetry of space radiation using the FLUKA Monte Carlo code. Towards this goal, microdosimetric distributions and total energy deposited in the TEPC cavity filled with PP and TEP gases are calculated at 1μm site size, for GCR ions, trapped protons (TPs) and albedo neutrons present in the lower Earth orbit (LEO). The density scaling factor () is calculated using the calculated energy deposited in the gas cavities. The study reveals that the calculated value offor GCR ions and TPs is about 0.93 and that for albedo neutron is 0.88.is about 0.93 for the combined radiation environment at LEO. Whenis applied on the density of PP, the resultant microdosimetric distributions and mean quality factors are comparable to those for TEP.