PERFORMANCE OF 2MM RADIUS STRAW TUBE DRIFT CELLS

The performance of a 128 channel test module made with straw tubes of 2mm radius has been studied in a test beam and with cosmic rays. Diffe rent gases were used and for each one the time-to-distance relation an d the hit efficiency was measured. Comparisons are made between result s when two different electronics readouts were used. The information w as recorded with 106M Hz FADC units and also with TDCs (50ps resolutio n). The best resolution, of 135 mum, was obtained using 50% Ethane, 50 % Argon and reading out the information with the TDCs, at an operating HV of 1750V.