Radioactivation background in satellites’ orbits

Our paper titled “Modeling of proton-induced radioactivation background in hard X-ray telescopes: Geant4-based simulation and its demonstration by Hitomi’s measurement in a low Earth orbit” has been published in Nuclear Instruments and Methods A.

Hard X-ray observation must be conducted in a satellite’s orbit due to atmospheric absorption, and therefore suffers from significant backgrounds induced by cosmic rays and/or geomagnetically trapped charged particles. Hirokazu Odaka et al. have developed a new, effective, general-purpose framework of full Monte Carlo simulation of radioactivation background. We applied this framework to data measured with the Hard X-ray Imager onboard the Hitomi satellite, and obtained excellent agreement between the in-orbit background data and the simulation. The simulation technique newly developed in this work will be indispensable for designing future hard X-ray missions and for making their scientific plans. (This work was mainly done when H. Odaka was working at Stanford University.)