A FEASIBILITY STUDY ON A MULTIWIRE GAS PROPORTIONAL COUNTER USING A 28 NS DELAY-LINE

Multiwire gas proportional counters (MWPCs) have been used over severa l years for small angle X-ray scattering experiments on synchrotron ra diation sources. A common readout system uses a delay line and a Time to Digital Converter (TDC) to encode the position of the event. This t ype of system has count rate limitations imposed by the length of the delay line. The present detectors on the Daresbury Synchrotron Radiati on Source (SRS) use 120 ns delay lines which limit the count rate perf ormance to around 1 x 10(6) photons/s. The emergence of new TDCs which offer reset times around 30 ns offer the possibility of using detecto rs with shorter delay lines. We report here the results of a feasibili ty study in which a 28 ns, 200 mm delay line was designed and tested o n a MWPC. The preamplifiers were modified to improve the noise and a r esolution of 2.5 mm FWHM was achieved.