High Energy Gamma-rays and Modern Electronics

As requirements for satellite on-board processing throughput continue to increase, users of radiation tolerant electronics are driven to ever decreasing feature sizes. As device feature sizes drop below the current radiation hardened capabilities of 130 nm one should include more of the high-energy space environment in the analysis of the potential effects. The effects due to particle showers produced by very high-energy celestial gamma-rays and charged particles have been neglected to date because of their low numbers, but small feature size large area devices may have susceptibilities. Above an energy of 30 MeV, the primary photon interaction with matter is pair production. These particles in turn interact producing an electromagnetic shower. The result of such an interaction is that many charged particles will pass through the system at one time. The integrated flux is approximately 10 photons/cm²/day with each photon producing two or more charged daughter particles. Since the incident particles are photons they are not affected by the Earth´s magnetic field and the integrated rate will be approximately the same for any orbit. An interaction anywhere on the space vehicle, primary structure, subsystem enclosures, or actual electronic parts will produce a shower that can affect any components downstream of it. There is a definite need to study this problem. The NASA gamma-ray large area space telescope, to be launched in the spring of 2008, will be the most sophisticated Gamma- ray telescope ever flown. GLAST is a pair conversion telescope which measures the direction and energy of the daughter products of the incident photon using a silicon strip tracker and CsI calorimeter. It will provide detailed information on both celestial and Earth albedo Gamma-rays as well as providing additional detail on the charged particle environment in low Earth orbit through its on-board and ground segment charged particle rejection capabilities.