The Space Telescope (ST), which carries two UV sensitive digicons, will ?ass several times per day througn a low altitude radiation belt called the South Atlantic Anomaly (CAA). This is expected to create interference in what is otherwise anticipated to be a noise-free device. Two essential components of the digicon, the semiconductor diode array and the UV transmitting window, have been shown by us to generate noise when subjected to medium energy proton radiation, a primary component of the belt. These trapped protons, having energies ranging from 2 to 400 HeV and fluences at the digicon up to 4000 P+/sec-cn2, will pass through both the window and the diode array depositing energy in each. To evaluate the effect of these protons, we irradiated engineering test models of digicon tubes to be flown on the ST with low-flux (104 10 P+/sec-cmz) monoenergetic proton beams at the University of Maryland Cyclotron. It was shown that electron-hole pairs produced by the protons passing through the diodes or the surrounding bulk causes a background count rate exceeding previous estimates by a factor of between 5 and 10. It was also shown that these counts can occur simultaneously in the output circuits of several adjacent diodes. Pulse height spectra of these proton induced counts indicate most of the bulk related counts overlap the single photoelectron peak.

Date Published: 9 November 1981
PDF: 12 pages
Proc. SPIE 0279, Ultraviolet and Vacuum Ultraviolet Systems, (9 November 1981); doi: 10.1117/12.965719

Published in SPIE Proceedings Vol. 0279:
Ultraviolet and Vacuum Ultraviolet Systems
William R. Hunter, Editor(s)