P. Camarri

STREAMER SUPPRESSION WITH SF6 IN RPCS OPERATED IN AVALANCHE MODE

We show that the addition of small amounts of sulphur hexafluoride, SF 6 , to the present ATLAS baseline gas mixture C 2 H 2 F 4 /C 4 H 10 has a very strong e⁄ect in suppressing the avalanche-to-streamer transition. An RPC of 50]50 cm2 area, 2 mm gas gap was operated in pure avalanche, streamer-free mode in a voltage range of about 1 kV. The results of the test suggest that the observed fast signal could be interpreted as the sum of contributions of a number of primary saturated avalanches. ( 1998 Elsevier Science B.V. All rights reserved.

RPC front-end electronics for the ATLAS LVL1 trigger detector

A front-end circuit for RPC detectors realized with an eight-channel full custom chip in GaAs technology is described. This chip exhibits a 150 lV minimum threshold, 3 dB noise figure, 160 MHz bandwidth and 50 mW/channel power consumption. ( 1998 Published by Elsevier Science B.V. All rights reserved.

Performance of RPCs and diamond detectors using a new very fast low noise preamplifier

The new high energy high luminosity experiments require an improvement in both the counting rate and the space resolution for the detectors. This improvement can be achieved by reducing the charge per count, however this implies a need for a better signal to noise ratio in the signal processing. In this article we will show the performances of diamond detectors and RPCs using a new preamplifier with low noise (500–1000 electrons RMS), fast shaping (about 10 ns) and large input capacitance.

Ageing test of the ATLAS RPCs at X5-GIF

Abstract An ageing test of three ATLAS production RPC stations is in course at X5-GIF, the CERN irradiation facility. The chamber efficiencies are monitored using cosmic rays triggered by a scintillator hodoscope. Higher statistics measurements are made when the X5 muon beam is available. We report here the measurements of the efficiency versus operating voltage at different source intensities, up to a maximum counting rate of about 700xa0Hz/cm2. We describe the performance of the chambers during the test up to an overall ageing of 4 ATLAS equivalent years corresponding to an integrated charge of 0.12xa0C/cm2, including a safety factor of 5.

Performance of a large-size RPC equipped with the final ATLAS front-end electronics at X5-GIF irradiation facility

We present results on e

An RPC γ irradiation test

ciency and time resolution of a large-resistive plate chamber prototype, equipped with the nal ATLAS front-end electronics, at the Gamma Irradiation Facility installed on the X5 beam of the CERN. ( 2000 Elsevier Science B.V. All rights reserved.

RPC operation at high temperature

Abstract LHC muon trigger detectors are supposed to work for 10 yr under an intense flux of radiation. Therefore, in the framework of ATLAS, the performance of full and reduced size RPC prototypes, heavily irradiated with γ sources, were measured for variable incident fluxes. We introduce here a detector description in terms of the “global” parameters based on experimental data such as current, total counting rate and γ fluxes. In this test the ATLAS final front-end electronics was used for the first time.

SF6 quenched gas mixtures for streamer mode operation of RPCs at very low voltages

Abstract The resistive electrodes of RPCs utilised in several current experiments (ATLAS, CMS, ALICE, BABAR and ARGO) are made of phenolic/melaminic polymers, with room temperature resistivities ranging from 10 10 Ω cm , for high rate operation in avalanche mode, to 5×10 11 Ω cm , for streamer mode operation at low rate. The resistivity has however a strong temperature dependence, decreasing exponentially with increasing temperature. We have tested several RPCs with different electrode resistivities in avalanche as well as in streamer mode operation. The behaviours of the operating current and of the counting rate have been studied at different temperatures. Long-term operation has also been studied at T=45°C and 35°C, respectively, for high and low resistivity electrodes RPCs.

Saturated logistic avalanche model

In the present paper we describe a search for gases that allow to reduce the energy of the electrical discharge produced in Resistive Plate Chambers (RPCs) operated in streamer mode, by reducing both the operating voltage and the released charge. This can be achieved, with current gas mixtures of argon, tetrafluoroethane (TFE) and isobutane, by reducing the total amount of quenching components (TFE+isobutane) down to 10–15% and compensating for the lower gas quenching power with the addition of small amounts of SF6: We show here that SF6; even for concentrations as low as 1% or less, has a strong effect in reducing the delivered charge in low quenched gases and allows to achieve a proper working mode of the RPC even at voltages as low as 4–5kV over a 2 mm gas gap. r 2002 Elsevier Science B.V. All rights reserved. PACS: 29.40.Cs

New results on ATLAS RPC's aging at CERN's GIF

The search for an adequate avalanche RPC working model evidenced that the simple exponential growth can describe the electron multiplication phenomena in the gas with acceptable accuracy until the external electric field is not perturbed by the growing avalanche. We present here a model in which the saturated growth induced by the space charge effects is explained in a natural way by a constant coefficient non-linear differential equation, the Logistic equation, which was originally introduced to describe the evolution of a biological population in a limited resources environment. The RPCs, due to the uniform and intense field, proved to be an ideal device to test experimentally the presented model.