Calculation of the induced radioactivity background in OSSE

A considerable background response is produced in OSSE detectors by internal radioactivity induced by cosmic rays and trapped protons. It cannot be eliminated by anticoincidence methods because of its delayed nature, and is subtracted using offset pointing data. A computational scheme for simulating the background has been developed in the last few years at DRA Farnborough, and is now being updated. Use of a radiation transport code to predict spallation rates of individual product nuclides in OSSE (where before only the total rate was calculated, individual rates being inferred from semi‐empirical cross‐sections) has produced results of low statistical error for a large number of nuclides. A library of response functions for the most significant of these and their descendents (a total of 117 nuclides) has been generated and used with previously developed codes to yield total predicted background due to cosmic ray and trapped proton induced radioctivity.This calculated spectrum is considerably closer to t...