A FAST READOUT SYSTEM FOR 2D GAS-FILLED DETECTORS BASED ON THE DELAY-LINE METHOD

The new generation of high brilliance synchrotron radiation sources such as the ESRF requires detectors with improved counting rate capability and resolution. Gas filled detectors are of particular interest for small-angle scattering applications due to their low inherent background. A counting rate increase of delay-line based 2D detectors is possible through the reduction of the delay line and a modularisation of the detector. To this end a new readout system has been designed based on VME/VXI modules. The heart of the system is a Time-to-Digital Converter (TDC) with 50 ps resolution (at 200 MHz master clock frequency). Counting rates in excess of 1.8 MHz have been demonstrated with a 100 x 100 mm2 detector and 20 ns delay line. A further improvement of the TDC should allow counting rates up to 5 MHz.