[en] A two stage position-sensitive gas proportional counter has been constructed by tightly coupling a Gas Electron Multiplier (GEM) with a Micro-Groove Detector (MGD). The GEM was used as the first amplifying stage and was optimised to transmit close to 100% of the primary charge even at very high drift fields (10 kV/cm). Very narrow GEM-MGD separations (0-600 μm) were used so that the active volume of the detector is still very thin (3-3.6 mm) and the required drift field could be maintained using an acceptable drift voltage (around 4000 V). Very high combined gains (up to 3x10⁵) were obtained with this system. The detector was found to be spark-free in the presence of HIPs (alpha particles) up to gains in excess of 20 000

[en] A 10x10 cm² MicroGap Chamber with a small stereo angle read-out has been developed for the inner tracking system of CMS. The anode strips are 9 microm wide with a pitch of 200 microm. The sampling pitch of the back cathode is 400 microm at a stereo angle of 50 mrad. Both coordinates are read-out from the same side of the detector substrate. Measurements of gain stability, fraction of induced charge on the back electrode, uniformity of response along the strip and rate capability have been performed in laboratory, using X-ray sources. Detection efficiency, spatial resolution, charge and space correlation have been measured with minimum ionizing particle beams at CERN. Due to the good space and time resolution, high rate capability, 2-D capability and considerable flexibility, this device seems very well suited for the instrumentation of tracking systems. It fulfills almost all the stringent requirements of the next generation of experiments which are being designed for the new high-energy, high luminosity accelerators (LHC and HERA)

[en] We have observed very high gains (up to 7000) from GEMs with 'standard' parameters (kapton thickness 50 μm, pitch 120 μm, copper hole diameter 65 μm, kapton hole diameter 30 μm). This was achieved using GEMs coupled to a simple array of copper read-out strips. From the measurements of the current on all the electrodes, we conclude that the high observed gains are fully attributable to electron multiplication in the holes of the mesh, and not to electronics related effects as had been previously suggested. Furthermore, we report that this large gain may only be fully exploited when the field in the second GEM gap is high. The effect on the gain of coupling a GEM to another charge amplifying device was investigated using a GEM-PMGC combination. (author)

[en] MicroStrip Gas Chambers (MSGC's) have been proposed for equipping the outer region of the tracker of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC). The MSGC's have undergone extensive development and tests during the last few years and their performance is well established. An important issue that has to be addressed to date is whether MSGC's can maintain their characteristics after a long exposure to an intense flux of particles, similar to LHC. We report results from the most recent beam test addressing this topic

[en] 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 (∼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 extremly high (>9x10⁶ 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 2.5x10³ at 400 V with 14% (FWHM) energy resolution at 5.4 keV. The anode pitch is 100 μm 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. (orig.)

[en] A new approach to the construction of the Micro Gap Chamber is presented. A 10x10 cm² MGC has been built using a 8 μm thick polyimide layer as anode-cathode insulator. Studies on gas gain, uniformity of response along the strip and charging-up have been carried out in laboratory by using X-ray sources. Very large proportional gains, up to similar 210⁴, have been reached working with gas mixtures based on Ne-DME. The simplified technology for the detector fabrication opens the possibility to produce very large area MGCs. (orig.)

[en] We report a systematic study of MSGCs built on thin-film Pestov-glass. The glass film prepared by sputtering was found to be electronically conductive. The MSGCs with conductive coatings show high stability in leakage current (less than 1% over 3 hr) and fast response (in seconds) to local charging induced by a high flux of X-rays. The spatial uniformity along the strip is quite good. A gas gain of 5000 is obtained in the Ne(50%)-DME(50%) mixture. The rate capability is over 10⁶ Hz/mm². (orig.)

[en] The design, construction and test of a thin (200 μm overall substrate thickness), large area (10 cm x 10 cm) microstrip gas chamber (MSGC) with both strip and pad readout is described. The device is built on a 6 in. silicon wafer. The characteristics of this detector make it suitable as a building block of a tracking system at LHC/SSC. (orig.)

[en] A very large area microstrip gas chamber (250x100 mm²), thought to be the building block of the CMS barrel tracker, has been built and undergone extensive tests with X-ray sources and particle beams. Rate capability, uniformity of response along the strip and charging-up effect for different gas gain and bias schemes have been measured in laboratory. A systematic study on the long-term stability of its performance (ageing) at high rates has been carried out both with standard and ''clean'' mechanical assemblies. Stability measurements under high voltage were performed. Studies of spatial resolution and efficiency for minimum ionizing particles were carried out with different gas gap, gas mixture, angle of incidence and avalanche gain. (orig.)

[en] Results from a beam test of the micro-gap chamber with minimum ionizing particles are reported. The dependence of the spatial resolution on the incidence angle of the beam with respect to the detector plane has been studied. Laboratory tests on new amplification structures, designed to increase gain and stability and to reduce the detector capacitance, are also shown. A maximum gas gain of 6000 and a specific capacitance of 0.5 pF/cm have been obtained. An optimised layout of the MGC's structure to avoid edge effects is discussed. ((orig.))