The Daresbury fast multi-wire linear X-ray detector system

Abstract

Multiwire proportional counters (MWPCs) have been used regularly on the Synchrotron Radiation Source (SRS) at Daresbury. They are photon counting, can cover large areas, and have fast readout times which makes them attractive to study dynamic processes such as muscle contraction. However, their operation at high rates has been a major limitation, due to two factors, space charge in the detector reducing the local count rate capability, and slow readout electronics which reduces the global count rate. The Daresbury biological X-ray detector group have developed a new type of detector called the wire microgap which significantly improves the local count rate capability of the detector. Coupled to this is a complex 1D electronic readout system which uses an amplifier and discriminator per wire and can handle charge spreading across two wires. The result is a 1D detector system 200 × 15 mm active area which can accept a global count rate of 200 MHz. This paper describes the design and performance of the detector and readout system and presents some results illustrating the fast framing capability of the detector which demonstrate a single shot timing sequence with a resolution of 50 μs. Also presented are recent beamline results.