Proportional Chamber Data Acquisition Providing Maximum Spatial Resolution at High Rates

Abstract

A proportional chamber readout system designed to provide maximum spatial resolution in two-dimensional images acquired at high data rates has been designed and constructed. This system has been tested on a spherical drift chamber area detector, described in another report at this conference, and it has yielded an image resolution of 0.4 mm FWHM at a count rate of 100,000 events per second in a finely collimated pencil beam. The ultimate resolution believed to be possible with the readout is about 0.2 mm FWHM, and the incident rate at which degredation of resolution occurs is expected to be in excess of 500,000 events per second. The readout is based on acquiring analog signal levels in time intervals comparable to the current pulses on anode wires, then processing these signals with high speed analog circuits and digitizing the result. The present system uses 80 parallel channels on each coordinate of a 50 cm square image area, has a total acquisition time of as little as 70 ns, and provides a throughput rate of up to 200,000 events per second.