Los Alamos National Laboratory Los Alamos United States
Los Alamos National Laboratory has developed an end-to-end model that quantifies the total ionizing dose that a shielded component on a space asset will accrue due to interactions with trapped beta-decay electrons produced after a high-altitude nuclear explosion. The model consists of three major components initial trapping, spatio-temporal evolution of the trapped population, and interaction of the evolving trapped population with a space asset to produce total ionizing dose. The initial trapping module calculates the fraction of betas produced by radioactive decay of nuclear fission products that will be trapped in the magnetic field surrounding Earth for at least one drift around Earth. Previously, the initial trapping Calculation assumed a centered dipole magnetic field model whereas we know that Earths magnetic field is offset from its geographic center and has higher-order non-dipole terms. Both the offset and the higher-order terms are captured in the International Geomagnetic Reference Field IGRF internal field model. In a centered dipole, the electrons that are trapped on a magnetic field line at one longitude will be trapped at all other longitudes as they drift around Earth due to azimuthal symmetry of the field, but the offset and higher-order terms of the IGRF field affects the drift of the trapped electrons and causes some that are trapped at one longitude to be lost at other longitudes. These electrons are called quasitrapped and are said to be in the drift loss cone since they will be lost during their first drift around Earth. In this paper we report on the effect of incorporating the drift of electrons around Earth using the IGRF field on the trapping fraction as compared to using a centered dipole.
Journal Article - Open Access
Journal of Radiation Effects: Research and Engineering, 35, 1, 01 Jan 0001, 01 Jan 0001, SEE AD1042393 JOURNAL OF RADIATION EFFECTS RESEARCH AND ENGINEERING VOL. 35, NO. 1, APRIL 2017. 33RD ANNUAL HARDENED ELECTRONICS AND RADIATION TECHNOLOGY (HEART) TECHNICAL INTERCHANGE MEETING MONTEREY, CA APRIL 4-8, 2016