B. Lisowski

A preliminary study of GaAs solid-state detectors for high-energy physics

Abstract The first phase of a study of GaAs as a base material for solid-state detectors has been completed. The main motivation behind this study is the greater radiation resistance of integrated circuits made of GaAs (compared with Si). Many diodes, of different sizes and shapes but built with the same technique, have been tested electrically and as detectors, using α sources and minimum-ionizing particles. The tests show that these devices work with a full detection effeciency, although there is evidence for trapping of a fraction of the charge produced by the particle inside the semiconductor.

MEASUREMENT OF THE STANDARD MODEL PARAMETERS FROM A STUDY OF W AND Z BOSONS

Abstract A study has been made of the decays W → ev and Z → e + e − , using the UA2 detector at the CERN pp Collider. The data correspond to an integrated luminosity of 142 nb −1 at a centre-of-mass collision energy √ s =546 GeV, and 768 nb −1 at √ s =630 GeV. Measurements of the standard model parameters from samples of 251 W decay and 39 Z decay candidates are compared with expectations of the standard electroweak model.

GaAs solid state detectors for particle physics

Abstract We report on progress with Schottky diode and p-i-n diode GaAs detectors for minimum ionising particles. The radiation hardness and potential speed of simple diodes is shown to be more than competitive with silicon detector. A discussion is given of the present understanding of the charge transport mechanism in the detectors since it influences their charge collection efficiency. Early results from microstrip detectors are also described.

The ZEUS vertex detector: Design and prototype test

Abstract A gas vertex detector, operated with dimethylether (DME) at atmospheric pressure, is presently being built for the ZEUS experiment at HERA. Its main design features, together with the performances of a prototype measured at various operating voltages, particle rates and geometrical conditions on a CERN Proton Synchrotron test beam, are presented. A spatial resolution down to 35 μm and an average wire efficiency of 96% have been achieved, for a 3 mm gas gap relative to each sense wire.

Charge transport properties of undoped SI LEC GaAs solid-state detectors

Abstract The GaAs detectors for minimum ionizing particles fabricated with commercial undoped SI GaAs show good quality as minimum ionizing particle detectors. A discussion is given of the present understanding of the charge transport mechanism in the detectors since it influences their charge collection efficiency.

Gallium arsenide microstrip detectors for charged particles

Microstrip detectors have been constructed from gallium arsenide (GaAs) wafers made from undoped LEC (liquid-encapsulated Czochralski) semi-insulating substrate material. Tests were performed using minimum ionising particles to ascertain their properties as charged particle detectors. The results show that the devices work wellm, with good signal-to-noise ratio (typically 7). The effects of gamma ray and neutron irradiation have been studied and shown to be small up to levels exceeding 20 Mrad and 1014 n/cm2, respectively.

Gallium arsenide charged particle detectors; trapping effects

The progress on the development of gallium arsenide particle detectors is reviewed. The limitation to the performance is the presence of traps. Studies of the trap properties using α particle DLTS measurements and C-V measurements are described.

First results from GaAs double-sided detectors

Abstract Preliminary results are presented on the performance of double-sided microstrip detectors using Schottky contacts on both sides of a semi-insulating (SI) GaAs substrate wafer, after exposure to 1014 neutrons cm−2 at the ISIS facility. A qualitative explanation of the device behaviour is given.

GaAs solid state detectors for physics at the LHC

The authors report on progress with Schottky diode and p-i-n diode GaAs detectors for minimum ionizing particles. The radiation hardness and potential speed of simple diodes are shown to be more than competitive with silicon detectors. A discussion is given of the present understanding of the charge transport mechanism in the detectors as it influences their charge collection efficiency. Early results from microstrip detectors which are relevant for high radiation regions of Large Hadron Collider (LHC) detectors near the beam pipe and in the forward region are also described. The authors have established the ability of GaAs Schottky diode detectors to tolerate radiation loads at the level expected in more than one year of running at a radial distance of only a few cm from the intersection point of the proposed LHC collider at nominal luminosity. The diode output signal of only a few nanoseconds is very satisfactory for the new colliders.<<ETX>>

GaAs Detectors for Physics at the LHC

Over the last two years the Glasgow and CERN-based LAA groups have successfully constructed GaAs detectors for minimum ionising particles with radiation hardness and potential speed which is more than competitive with silicon detectors. The timely development of this new technology, in particular for high radiation regions of LHC detectors near the beam pipe and in the forward region, now requires the investment of more resources and more intensive effort, including industrial collaboration in detector fabrication. In addition, there is an urgent need for the development of appropriate read-out electronics with radiation tolerance and speed characteristics to match the detectors, and with the lowest possible power consumption, needed for the large number of channels required in a vertex detector, for example. The present report describes the results obtained using GaAs Schottky diode detectors which we have constructed, and the initial steps which we have taken towards the design of a GaAs preamplifier to match the detectors.