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We report a recent study undertaken at the Council for the Central Laboratory of the Research Councils (CCLRC) Rutherford Appleton Laboratory to evaluate the performance of a gas electron multiplier (GEM) coupled with a microstrip gas counter (MSGC) for X-ray spectroscopy. The parameters investigated during this study were effective gain, effective gain stability, and energy resolution at 8.05 keV using Cu-K X-rays. These parameters were studied as a function of drift field, induction field, and potential differences across the GEM holes and that across the MSGC anodes and cathodes. This study demonstrates that a single stage GEM can sustain effective gains up to 6000 whilst retaining adequate X-ray energy resolution. By utilizing the MSGC as well as the GEM amplification the gains easily exceed 100 000 and allow the MSGC operation at much lower voltages. This study also demonstrates that the introduction of the GEM preamplification to the MSGC enables the operation of the latter at much higher effective gains (30 000) before any degradation in the X-ray energy resolution [ABSTRACT FROM PUBLISHER]

The development and testing of a two-dimensional (2-D) prototype detector based on a microstrip gas chamber (MSGC) is reported using a gas mixture of 2.5 bar ³He and 2.5 bar CF4. The second coordinate is obtained by utilising a plane of wires as pick up electrodes. The detector is operated with the wire plane at such a potential so as not to induce any gain around the wires. This means that the high tolerances normally associated with wire planes in multi wire proportional counters are not mandatory. The detector comprises of 48 individually instrumented channels in both X (MSGC strips) and Y (orthogonal wire plane). A specially designed encoding module has been constructed which feeds digital addresses for each event to the ISIS Data Acquisition Electronics (DAE) system. An intrinsic detector resolution of ∼1 mm full-width at half-maximum has been measured for both dimensions (in experimental exposures on the ROTAX beamline at ISIS) which is degraded slightly by the digital resolution for the overall system. This readout method is shown to be very tolerant of a poor signal to noise ratio in the readout channels (unlike traditional analogue wire chamber readout systems) and permits the operation of the MSGC at low avalanche gains (∼10) which helps to maximize the rate and lifetime performance of the detector as well as permitting data capture rates in the megahertz range. The event timing resolution is comfortably submicrosecond and is, therefore, suitable for applications on spallation neutron sources. [ABSTRACT FROM AUTHOR]

The development and testing of a two-dimensional (2-D) prototype detector based on a microstrip gas chamber (MSGC) are reported. The second coordinate is obtained by utilising a plane of wires as pick up electrodes. The detector is operated with the wire plane at such a potential so as not to induce any gain around the wires. This means that the high tolerances normally associated with wire planes in multiwire proportional counters are not necessary, making the manufacture and repair of such a device relatively easier. The detector comprises of 48 individually instrumented channels in both X (MSGC strips) and Y (transverse wire plane). A specially designed encoding module has been constructed which feeds digital addresses for each event to the ISIS data acquisiton electronics (DAE) system. (ISIS is the spaliation neutron source at the Rutherford Appleton Laboratory.) An intrinsic detector resolution of ∼ 0.5 mm full-width at half-maximum (FWHM) has been measured for both dimensions which is degraded slightly by the digital resolution for the overall system. This readout method is shown to be very tolerant of a poor signal-to-noise ratio in the readout channels (unlike traditional analogue wire chamber readout systems) and permits the operation of the MSGC at moderate avalanche gains (∼ 1000) which helps to maximize the rate and lifetime performance of the detector as well as permitting data capture rates in the MHz range. [ABSTRACT FROM AUTHOR]

We introduce the microhole and strip plate (MHSP) detector as a micropattern detector for the detection of thermal and epithermal neutrons. Detection sensitivity is obtained by filling these detectors with ³He at high pressures. We propose the use of argon-xenon penning mixtures as the stopping gas as opposed to the usual carbon based stopping gases. These argon-xenon mixtures provide suitable gas gains for the high pressure/high resolution neutron detector applications. With these mixture it is possible to obtain a sealed detector with only rare-gas filling which is simple to purify and not subject to ageing. An MHSP gas detector filled with a 3-bar argon/50-mbar xenon/6-bar helium mixture can achieve gains above 2 ×103. This mixture allows neutron detection efficiencies of about 70% at 1 Å for a 2.5-cm thick absorption region and intrinsic position resolution (full-width at half-maximum) of about 1.8 mm. The sensitivity to γ-rays of the present mixture will be the same when compared to that of 2.6-bar CF4. [ABSTRACT FROM AUTHOR]