[en] We have investigated the possibility of using a parallel plate avalanche chamber as endcap detector for the time projection chamber instead of a multiwire proportional chamber. Such a solution has several advantages. The positive ion feedback in the drift volume and the ExB distortions are considerably reduced; moreover, space charge effects in the detector are smaller allowing higher rates and probably higher gains without deterioration of the energy resolution. Detection of the fast electron signal component allows to obtain two-track separation in the drift direction of 1.5-2 mm; the localization in the two other directions can be realized with accuracies better than 100 μm and with typical two-track separations between 1 and 2 mm. The detector is realized exclusively with grids and thick wires, thus eliminating breakdown problems. (orig.)

[en] A small, 10 x 10 cm², parallel plate avalanche counter has been tested paying special attention to those features which can be important in the Time Projection Chamber. The structure of the test chamber is shown. It has a conversion and drift volume, 11 mm thick, delimited by two stainless steel cross wire grids, of 100 μm wire diameter and 500 μmm pitch, identified by HV1 and HV2. The anode is made of thick wires, 100 μm in diameter spaced every 500 μm. The amplification gap is 4 mm thick. Below the anode, 1 mm apart, we have paced an identical wire plane, HV4, with wires perpendicular to the anode wires. Both electrodes are equipped with electronics and read out. All measurements were performed with a mixture of argon and methane (83% - 17%), a typical gas for Time Projection Chambers. A multiplication factor up to 10⁵ was attained

[en] The principle of operation of the Time Projection Chamber is described. The dependence of the resolution on the diffusion, on the track-to-sense wire crossing angle and on the ExB effect near the anode wire are discussed in terms of recent experience from operating time projection chambers. Possible improvements in the space resolution obtained by changing the cathode plane segmentation are presented

[en] In the course of development of the multistep avalanche chamber the authors have realized several multiple electrode parallel-plate devices exhibiting stable gains well in excess of 10⁵ which are thus capable of detecting minimum ionizing particles. This paper presents the design and discusses the performance of a two-step parallel-plate avalanche chamber. A region of moderate electric field --the drift region where charges are released by ionizing radiation--is followed by two layers of comparable and very high field where charge multiplication occurs. Owing to the choice of the electrodes--either cross-wire meshes or parallel thick-wire grids at small pitch--the electric field is uniform over most of the gaps, and charge multiplication proceeds through a parallel-plate avalanche mode. In order to obtain a fast signal and a reduced avalanche spread in their prototypes, the authors have adopted rather narrow typical gaps of 4 mm for the first amplification region and 1 mm for the second. To avoid edge sparking, they have used either a gap increase at the edges or the insertion of thin mylar foil around the frame's edges. The last electrode in the structure, made with a printed-circuit board, is the only one equipped with electronics and is conveniently operated at ground potential. At regular intervals, four rows of pads are used to determine the coordinates of tracks in selected positions. Argon (90%) and methane (10%) comprise the gas filling

[en] We have investigated the possibility of using a parallel plate avalanche chamber as endcap detector for the time projection chamber instead of a multiwire proportional chamber. Such a solution has several advantages. The positive ions feedback in the drift volume and the E vectorxB vector distortions are considerably reduced; moreover, space charge effects in the detector are smaller allowing higher rates and probably higher gains without deterioration of the energy resolution. Detection of the fast electron signal component allows to obtain two-track separation in the drift direction of 1.5-2 mm; the localization in the two other directions can be realized with accuracies better than 100 μm and with typical two-track separations between one and two mm. The detector is realized exclusively with grids and thick wires, thus eliminating breakdown problems. (orig.)

[en] We describe a soft X-ray detector having a 20x20 cm² active area and constituted by a conversion and drift space followed by a parallel-plate avalanche chamber. Bidimensional localization of the detected charge is performed on the last electrode recording the pulse-height profiles of the fast electron-induced signals on a two-sided thin printed circuit with orthogonal sets of conducting strips at 500 μm pitch. Localization accuracies of around 120 μm rms are obtained in both directions for 8 keV X-rays. It has been observed that, whilst the induced charge on the side of the board internal to the chamber (the anode) is negative (as one would expect), the charge seen by the pickup electrode on the back face of the readout board is positive, much as it would appear on the cathode of a multiwire proportional chamber. Because of its very good two-cluster resolution, one can envisage the use of this device in transition radiation detectors. (orig.)

[en] This report is organized in two sections. The first contains an elementary introduction to the theory of electron transport in gases under the action of electric and magnetic fields, and gives indications on the use of two programs to compute drift and diffusion properties of electrons in gas mixtures. The second section contains an extensive collection of experimental and computed data on electron drift velocity and diffusion, as a function of electric field; an index allows one to find the data referring to any given gas mixture. (orig.)

[en] A small time projection chamber with a parallel-plate avalanche chamber as an end-cap detector was tested in a magnetic field of up to 10 kG. An increase of sparking rate at a given gain with increasing magnetic field was observed. (orig.)

[en] We have built and tested several 80 cm long multiwire drift tubes, each with 128 independent drifts cells consisting of individual anodes centered in a hexagonal cell, 1 mm in radius, defined by six cathode wires. A thin hexagonal carbon-fibre envelope supports the wire tension and provides gas tightness. Charge tracks are measured recording drift times on all anodes, on an average ten times on each module; the longitudinal coordinate can be measured from current division at the two ends of each wire. Several modules can be packed to build a compact, fast vertex detector suitable for collider experiments. (orig.)

[en] In this paper we report on the development of a silicon microstrip detector with integrated coupling capacitors and polysilicon biasing resistors. These new detectors show the same performance as standard detectors made at our laboratory with regard to leakage current and spatial resolution. Leakage currents as low as 200 pA/strip at 120 volts and a spatial resolution as good as 3.5 μm has been achieved. (author)