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In this paper, we describe new developments in gas mixtures which have occurred during the last three to four years. In particular, we discuss new results on the measurement and modeling of electron drift parameters, the modeling of drift chamber resolution, measurements of primary ionization and the choice of gas for applications such as tracking, single electron detection, X-ray detection and visual imaging. In addition, new results are presented on photon feedback, breakdown and wire aging.

The front-end electronics of the Cerenkov Ring Imaging Detector (CRID) used in the Stanford Large Detector (SLD) spectrometer at the Stanford Linear Accelerator Center (SLAC) Linear Collider is described. The Plessey process provides a straightforward and low-cost path toward system miniaturization. System tests show good noise performance, calibration precision, system linearity, and signal shape uniformity over the full dynamic range.<>

The authors present recent progress on the construction and testing of the first drift boxes and single-electron detectors as they come from the production line. These detectors will be used for particle identification using the ring imaging technique in the SLD (Standard Linear Collider Large Detector) experiment. Various experimental results are presented, including single-electron pulse height measurements as a function of gas gain, detector gating capability, uniformity of response across the wire plane, charge division performance of a single-electron signal, average pulse shape and its comparison with predicted shape, and crosstalk.<>

A full size prototype cell of a multiwire detector similar in design to the JADE[2] drift cell geometry was tested in a beam of pions and electrons at SLAC. The motivation was to explore the possibility of identifying particles through a measurement of energy loss in the HRS experiment[1]. The purpose of the test was to investigate the extent of which the measurement of the energy loss is degraded as one makes the transition from a small chamber to a full size detector. We also measured the reduction in gas gain due to saturation effects as a function of the track angles relative to the chamber wires and as a function of the total gain in the chamber.

This paper reviews the progress of photon detectors with gaseous amplification.

Wire-chamber gaseous electron multipliers coupled to CsI photocathodes, provide interesting means for UV-photon imaging over a very large area. We report on the measurement of the CsI resistivity, important for the understanding of rate-dependent effects in CsI-based detectors. Photon counting at high rates is also closely connected to long-term photocathode stability. We present results on ageing of CsI photocathodes under high photon flux, with one atmosphere CH4and under a detector gain of 105, for several substrate materials. We compare the ageing results with that of CsI photocathodes coated with thin NaF protective films.

We report on operational experience with and experimental performance of the SLD barrel Cherenkov Ring Imaging Detector from the 1992 and 1993 physics runs. The liquid (C/sub 6/F/sub 14/) and gas (C/sub 5/F/sub 12/) radiator recirculation systems have performed well, and the drift gas supply system has operated successfully with TMAE for three years. Cherenkov rings have been observed from both the liquid and gas radiators. The number and angular resolution of Cherenkov photons have been measured, and found to be close to design specifications.<>

The construction of the Cherenkov Ring Imaging Detector (CRID) for the SLD (Stanford Linear Collider Large Detector) experiment at the SLAC (Stanford Linear Accelerator Center) Linear Collider and the testing of its components is reported. Results are included from testing the drift boxes, liquid radiator trays, and mirrors for the barrel CRID. The development of the support systems essential for the operation of the CRID, namely, gas and liquid recirculation systems and monitoring, are discussed.<>

Recently several RICH prototypes successfully tested a gaseous TEA photocathode. However, its wire ageing behavior is unknown. In principle, TEA is a more strongly bonded molecule than TMAE, and, as a result, one would expect better wire ageing behavior. This paper explores this question.