Detection of antihydrogen with a Si- mu -strip and CsI-crystal detector at cryogenic temperature

ATHENA, one of 3 experiments at the new low energy antiproton facility at CERN (AD), is designed for testing fundamental physic principles (CPT, Gravitation) to a high degree of precision by comparing cold antihydrogen to hydrogen. To monitor the production of the antihydrogen atoms and their spectroscopic response, a new detector dedicated for the endproducts of antihydrogen annihilations was developed. To meet the requirements of low temperature operation (77 K) in a high magnetic field, compact size, low power consumption and high granularity, a combination of two layers of each 16 double sided Si- mu -strip modules (16 cm long) was chosen, surrounded by 192 pure-CsI crystals (each approximately= 4 cm/sup 3/), which are read by UV sensitive photo diodes. The frontend electronics (working point 77 K), realised in VLSI CMOS technique, features a self triggering capability of independent sub modules.