A Generalized Analytical Model for the Micro-dosimeter Response 2007-01-3112

An analytical prediction capability for space radiation in Low Earth Orbit (LEO), correlated with the Space Transportation System (STS) Shuttle Tissue Equivalent Proportional Counter (TEPC) measurements is presented. The model takes into consideration the energy loss straggling and chord length distribution of the detector, and is capable of predicting energy deposition fluctuations in a micro-volume by incoming ions through direct events. The charged particle transport calculations correlated with STS 56, 51, 110 and 114 flights are accomplished by using the most recent version (2005) of the Langley Research Center (LaRC) deterministic ionized particle transport code High charge (Z) and Energy TRaNsport (HZETRN) which has been extensively verified with laboratory beam measurements and available space flight data. The agreement between the TEPC model prediction (response function) and the TEPC measured differential and integral spectra in lineal energy (y) domain is promising, as the model correctly accounts for the increase in flux at low y where energetic ions are the primary contributor. Comparison of the Galactic Cosmic Rays (GCR) differential and integral flux in y domain between STS 56, 51, 110 and 114 TEPC measured data and current calculations indicate that there may exist an underestimation by the transport code simulations at low to mid range y values. This underestimation is argued to be partly related to the LEO geomagnetic transmission function which traditionally uses only vertical components of the GCR cutoffs, and also to the exclusion of the secondary pion and kaon particle production from the current version of HZETRN.