The Application Of Multiwire Proportional Counters To Experiments Utilising Synchrotron Radiation

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.