THE MICRO-GAP CHAMBER

The micro-gap chamber (MGC), a new type of position sensitive proportional gas counter, is introduced. The device is built using microelectronics technology. In this detector the separation between the electrodes collecting the avalanche charge (the anode-cathode gap) is only a few microns. The time it takes to collect the positive ions is therefore very short (almost-equal-to 10 ns). The speed of the device now equals that of solid state detectors but it is more than three orders of magnitude higher than in standard proportional counters and one order of magnitude higher than in the recently introduced microstrip gas chamber (MSGC). As a result, the rate capability is extremely high (> 9 X 10(6) c/mm2 s). The amplifying electric field around the thin anode microstrip extends over a small volume but is very intense (270 kV/mm). It provides a gas gain of 2.5 x 10(3) at 400 V with 14% (FWHM) energy resolution at 5.4 keV. The anode pitch is 100 mum and the readout is intrinsically two-dimensional. Because there is practically no insulating material in view, charging was not observed even at the highest rate. This device seems very well suited for instrumentation of the tracking system at the new hadron colliders (LHC/SSC) as well as in many other fields of research.