The ''RAPID'' high rate large area X-ray detector system

The multiwire proportional counter (MWPC) is a well-established device for capturing X-ray images from synchrotron sources and is particularly well suited to dynamic experiments. Its advantages include, almost zero noise, high dynamic range limited only by the electronic memory depth, large area and time resolutions of microseconds. It does however have some limitations, notably in global and local count rate performance. The RAPID two-dimensional detector system delivers a more than twentyfold increase in throughput over present systems. It comprises a ''wire microgap'' detector, which has much higher count rate performance than coventional MWPCs and a sophisticated multi-channel data acquisition system. The system has a global count rate capability of greater than 2 x 107 photons s-1 with a maximum local count rate of ∝106 photons mm-2 s-1. A spatial resolution of ∝200 μm, over an active area of 12.8 x 12.8 cm, has been achieved which compares well with exiting read-out systems. Each electrode of the detector is instrumented with a preamplifier and ADC and the position of the event is determined independently in X and Y by centroiding the induced charge distribution. The X and Y coordinates are correlated using a unique time stamp. This paper described the design and performance of the detector and read-out system and presents some recent beamline results. (orig.)