The Mi's Ii Drift Chamber System*

The MPS II detectors are narrow drift space chambers designed for high position resolution in a magnetic field and in a very high particle flux environment. Central to this implementation was the development of 3 multi-channel custom IC's and one multi-channel hybrid. The system is deadtimeless and requires no corrections on an anode-to-anode basis. Operational experience and relevance to ISABELLE detectors is discussed. as a facility instrumented with magnetostrictive spark chambers, PWC's, scintillator and Cerenkov hodoscopes and a variety of user-provided detectors including shower counters and transition radiation devices. However, since its initial operation, the greatest physics interest has fallen into the sub-nanobarn cross section region. Therefore, replacement of the spark chambers with detectors capable of efficient operation in rates a 100 times higher became essential. It was also desirable to improve the position resolution and absolute accuracy of the tracking detectors.