M.R. Torquati

A microstrip gas avalanche chamber with two-dimensional readout

A microstrip gas avalanche chamber with a 200 μm anode pitch has been built and successfully tested in our laboratory. A gas gain of 104 and an energy resolution of 18% (FWHM) at 6 keV have been measured using a gas mixture of argon-CO2 at atmospheric pressure. A preliminary measurement of the positional sensitivity indicates that a spatial resolution of 50 μm can be obtained.

A microstrip gas chamber with true two-dimensional and pixel readout

A true two-dimensional μstrip gas chamber has been constructed and successfully tested. This new detector has an effective substrate thickness of less than 2 μm. An ion implanted oxide layer of 1.8 μm thickness provides the necessary insulation between the front and back plane and permits collection on the back electrodes of a large fraction of the induced charge. The back electrode signal is used to measure the coordinate along the anode strips (X-Y readout) or to provide true space points (pixel readout). Very good imaging capabilities have been obtained in both cases. A flux of 107 particles/mm2 s has been measured without significant gain loss. No charging effect has been observed after three days continuously running at a flux of 104 particles/mm2 s, while a 15% gain loss, probably due to ageing effects, has been measured after collection on the strips of a charge corresponding to the more than six years of running at the design luminosity of LHC, at 50 cm from the beam axis.

Results from the first use of microstrip gas chambers in a high-energy physics experiment

Abstract The first use of microstrip gas chambers in a high-energy physics experiment is described. The forward magnetic spectrometer of NA12 (GAMS) experiment at CERN-SPS has been equipped with 8 planes of microstrip gas chambers for a total of 1100 low-noise analog channels. The detectors have been exposed for 100 days to a high flux proton beam. A 0.2% momentum resolution at 450 GeV/c, a rate capability higher than 5 × 105/s−1mm−2 and a 9 ns time resolution have been measured.

Production of G(1590) in 300 GeV central

Abstract Significant production of G(1590), a scalar glueball candidate, is observed in a study of η pairs produced in π−N central collisions at 300 GeV/ c .

\pi^-

Abstract The effective mass spectrum of π0 pairs produced in pp central collisions (pp → pfπ0π0ps) at 450 GeV/c, s = 29 GeV , below 1 GeV differs from that observed in peripheral charge exchange reactions. In particular, there is a large number of events between ππ-threshold and 1 GeV, that interfere with f0(980) destructively. The possible existence of a broad S-wave state is suggested.

N collisions

Abstract The operation of a microstrip gas chamber built on a silicon substrate is described. The insulation between the low-resistivity silicon and the anode-cathode structure is provided by a 2 μm thick thermal oxide layer. A gas gain of 10 4 has been measured at potential differences much lower than those usually needed with glass or quartz substrates. No surface charging or gain drift have been observed up to a measured flus of 5 × 10 5 particles/cm 2 s. A device with such a thin dielectric between strips and back plane, makes a true two-dimensional readout possible.

Study of the π0π0 system in pp central collisions at 450 GeV/c

Abstract We describe the operating principles of the microstrip gas chamber and the main results of measurements realized with several prototype devices in the detection of X-rays and charged particles. Detectors with 3, 5 and 10 μm anode widths and 125 or 200μm pitch have been successfully tested. A gas gain of 10 4 and an energy resolution of 12.2% fwhm at 6 KeV have been measured. A localization accuracy for minimum ionizing particles of 30 μm rms, a two track resolution of 250 μm and a high rate capability (above 2·10 7 cm −2 s −1 ) make the device a good candidate for tracking at high luminosity colliders.

A MICROSTRIP GAS CHAMBER ON A SILICON SUBSTRATE

Abstract A parallel plate counter with a resistive anode and a two-dimensional readout is presented. The anode is made of a thin germanium layer with a sheet resistivity ⩾ 1 M ω /square and the cathode is made of aluminized mylar 5 μm thick. The anode is transparent to the fast impulse due to the collection of the multiplication electrons. A chessboard of “pads” placed behind the anode plane is used to obtain the positional information. The detector and the readout system are physically and logically separated. An overall spatial resolution of 70 μm (rms) for both coordinates has been measured.

The microstrip gas chamber

The results of a test-beam study of the performance of the microstrip gas avalanche chamber (MISGAC) for the detection of minimum ionizing particles are reported. A detection efficiency of 95%, a position resolution of 30 mu m (RMS), and a two-track resolution of 250 mu m have been measured using a 9-GeV particle beam at the CERN PS. Xenon-DME (dimethyl-ether) and argon-DME mixtures have been used as gas filling for a detector having a total gas thickness of 5 mm. >

A novel type of parallel plate chamber with resistive germanium anode and a two-dimensional readout

Abstract The operation of a microstrip gas chamber with two stages of gas amplification is discussed. An average gas gain for ionizing tracks of ≈ 10 is obtained while drifting the ionization electrons in a uniform electric field of 6 kV/cm, while a further factor ≈ 5 × 10 3 is obtained from the avalanche process starting close to thin anodic microstrips. The operation of the microstrip gas chamber in this regime should improve both time and spatial resolution, especially for inclined tracks.