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2 Performance Considerations
2.8 Low energy electrons
We have performed [2-10] a study using the AMS Monte-Carlo (version 207) in order to investigate whether low energy electrons trapped by the AMS magnetic field would degrade the performance of the ATC. The mean expected rate of low energy electrons above the Cerenkov threshold is 13 kHz, while the maximum expected rate will be 20 kHz. However, most of the electrons will give a signal of one to three photoelectrons which can be rejected by requiring in the event reconstruction analysis the presence of an associated track matching the ATC hit pattern. Furthermore, most of the low energy events are affecting the module in the +x side of the ATC lower layer because this side is not covered by the shuttle structure material. Therefore, it is proposed that the wall thickness of this module is increased to approximately 2 mm of carbon fiber in order to eliminate this background.
Issue: Draft - Revision: 04 - Last Modified: 20 April 1997