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2 Performance Considerations

2.1 Introduction

The aim of the Aerogel Threshold Counter (ATC) is to identify antiprotons over the (100-200 times) bigger electron background. In order to obtain the required separation, the performance of the detector has to be optimized by:

  1. selecting the index of refraction of aerogel (the lowest the index the highest momentum range)

  2. minimizing the acceptance losses (by optimizing the geometrical coverage of ATC w.r.t. the AMS shuttle flight setup)

  3. maximizing the electron rejection factor. Due to the high electron background a minimum rejection factor of 2000 has to be maintained. This factor depends on the number of photoelectrons collected per incident electron track.

In this chapter we are presenting the results of experimental tests performed at LAPP-Annecy [2-5] as well as the results of calculations concerning the acceptance and rejection power of various ATC designs.

Issue: Draft - Revision: 04 - Last Modified: 20 April 1997