TIME-RESOLVED X-RAY MEASUREMENTS ON MUSCLE USING A FAST MULTIWIRE LINEAR DETECTOR

The development of linear detectors, with parallel readout and thus capable of operating at very high speeds, was undertaken in order to make efficient use of the very high X-ray fluxes available from synchrotron cameras for time-resolved scattering studies on muscle. For example, one may expect typical counting rates in the equatorial pattern of 2-10 MHz, well beyond the capability of detectors based on delay-line readout. We describe the use of the multiwire linear detector for measuring the intensity changes in the equatorial and meridional pattern and for measuring the spacing changes in the 143 angstrom meridional reflection with a time resolution of a few milliseconds at the SRS, Daresbury. These experiments are designed to study the dynamics of acto-myosin cross-bridge behaviour under different mechanical conditions which are imposed by controlled length-changing devices. The spacing changes can be measured to a precision of +/- 25-mu-m, despite the relatively coarse sampling of 1 mm in the wire plane, by measuring the centroid of the 143 angstrom reflection.