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 10(7) photons s(-1) with a maximum local count rate of similar to 10(6) photons mm(-2) s(-1). A spatial resolution of similar to 200 mu m, 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.

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 x 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 mu s. Also presented are recent beamline results.

The multiwire proportional counter (MWPC) is well established device for capturing x-ray images at synchrotron sources such as at the synchrotron radiation source (SRS) at Daresbury. The latest generation of synchrotrons can deliver much more intense x-ray fluxes than the SRS which itself produces xray fluxes well beyond the capabilities of current photon counting detectors, There is an imminent demand for 2-D photon counting detectors which can cope with rates >10(5) photons/mm(2)/sec locally and readout systems with an unbuffered throughput of >10(7) events per second. This must be achieved with a high dynamic range and a good efficiency. The detector development group at the SRS have developed the wire microgap detector to address these problems. A new readout system has been designed using a highly parallel approach. Each detector channel in the detector is separately instrumented, and the data is accumulated using fast, state-of-the-art electronics systems. A prototype of the system has been constructed and tested with the 2 dimensional wire microgap detector. We report the results of the use of a wire microgap linear detector on the SRS and the first results from the 2D wire microgap detector system.

Multiwire proportional counters (MWPCs) currently in use for synchrotron radiation diffraction offer unrivalled dynamic range and detection efficiency. Unfortunately they have, until recently, been somewhat limited in count rate performance and suffer from parallax problems with incoming photons at high angles of incidence. We report on the progress of a fast 2-D proportional counter detector for use on the beamlines at the Synchrotron Radiation source at Daresbury. It utilises a highly parallel data acquisition system in order to achieve photon counting rates in excess of 106 counts per second. This is coupled to a pressurised proportional counter to reduce the parallax errors. The detector will have a 200 mm by 200 mm active area and the system will yield a real spatial resolution of ∼ 200 μm (FWHM). A review of the system components is made, and a technique for further improving the performance is described.

Multiwire gas proportional counters (MWPCs) have been used over several years for small angle X-ray scattering experiments on synchrotron radiation sources. A common readout system uses a delay line and a Time to Digital Converter (TDC) to encode the position of the event. This type of system has count rate limitations imposed by the length of the delay line. The present detectors on the Daresbury Synchrotron Radiation Source (SRS) use 120 ns delay lines which limit the count rate performance to around 1 × 106 photons/s. The emergence of new TDCs which offer reset times around 30 ns offer the possibility of using detectors with shorter delay lines. We report here the results of a feasibility study in which a 28 ns, 200 mm delay line was designed and tested on a MWPC. The preamplifiers were modified to improve the noise and a resolution of 2.5 mm FWHM was acheived.

New high rate multiwire gas proportional counters for X-ray detection under development at Daresbury require low noise, fast preamplifiers to achieve minimum dead time. We present a design for a fast preamplifier with a rise time of 8 ns, noise better than 1300 electrons rms and a gain of 4.8 μV per electron. Results of a computer simulation run to predict the optimum differentiate constant needed to ensure a short dead time are also presented. The application of this preamplifier on a fast multiwire linear detector is discussed and results are presented.

Multiwire gas proportional detectors have been used for many years on synchrotron radiation experiments and offer unrivaled dynamic range and detection efficiency but have been somewhat limited in count rate performance. We report here recent test results from two new rapid data acquisition systems developed at Daresbury and in addition the results of comparative tests on a new design of gas detector, the Microgap, and a gas Microstrip detector. Both designs appear capable of high rate > 100 kHz/mm2 operation and combined with the new acquisition systems should begin to alleviate the count rate problems for some types of experiment.

Multiwire proportional counters are widely used in synchrotron radiation studies, for example in small angle diffraction experiments on biological systems. The active area and positional resolution of the detector can be conveniently matched to the dimensions of the synchrotron beam and to the optics of the beamline. Furthermore, the large dynamic range available from single photon counting systems is vital to exploit the true benefits of using synchrotron radiation for X-ray diffraction.

Multiwire detectors have certain characteristics that can be used to advantage, particularly in small-angle diffraction or scattering experiments on biological systems. The size of the active region of the detector and the total number of pixels can be conveniently matched to the dimensions of the synchrotron beam and to the optics of the beam line camera. Furthermore, the large dynamic range inherent in single-photon counting systems can be exploited to ensure the collection of high-quality data even when the scattering factor varies over several orders of magnitude.

Although multiwire detectors have been overtaken in some applications of x-ray imaging, they have certain characteristics which can be used to advantage in synchrotron radiation studies, for example in small angle diffraction or scattering experiments on biological systems.In particular,the size of the active region of the detector and the total number of pixels can be conveniently matched to the dimensions of the synchrotron beam and to the optics of the beam line camera.Furthermore,the large dynamic range inherent in single photon counting systems can be exploited to ensure the collection of high quality data even when the diffuse and coherent scattering factor varies over several orders of magnitude. Linear and two dimensional detectors are in regular use at the Daresbury Synchrotron Radiation Source all using the delay line readout method and a standardised data acquisition system which includes facilities for time resolved measurements. The source characteristics and the beam line optical instrumentation are described to show the properties which influence the design of imaging detectors and from this the parameters of the detectors currently in use are examined together with details of test measurements. Some examples of experimental results are given. The development of systems for one and two dimensional detectors to replace the delay line readout method and to operate at the very high count rates available from synchrotron sources is being actively pursued and will soon reach prototype stage.The design of these systems which use custom designed circuits and high speed digital correlation techniques will be outlined.