B. Liberti

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.

An RPC γ irradiation test

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.

RPC operation at high temperature

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

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.

New RPC gas mixtures for large area apparatuses

The working gas choise has always been a crucial topic for RPC. The optimization of the gas mixture, for different purposes, allowed the RPC detector to be successful in many experiments of today physics [1,2]. Both running and future experiments however could profit from new gases with low environmental impact, low cost and good behavior with respect to ageing and RPC performances. We present here the first results in the search for this new gas.

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

In order to ensure that the resistive plate chambers used in the ATLAS experiment will not show, during their operation, any abnormal aging effect which could degrade their performances, an aging test is being performed at X5-GIF, CERNs gamma irradiation facility. In this paper, the latest results are presented, together with an example of successful damage recovery technique.

Test beam results and integration of the ATLAS level-1 muon barrel trigger

The ATLAS level-1 muon trigger will be crucial for the online selection of events with high transverse momentum muons and for its correct association to the bunch-crossing corresponding to the detected events. This system uses dedicated coarse granularity and fast detectors capable of providing measurements in two orthogonal projections. The resistive plate chambers (RPCs) are used in the barrel region (|/spl eta/| < 1). The associated trigger electronics is based on a custom chip, the coincidence matrix, that performs space coincidences within programmable roads and time gates. The system is highly redundant and communicates with the ATLAS level-1 trigger processor with the MUCTPI interface. The trigger electronics provides also the readout of the RPCs. Preliminary results achieved with a full trigger tower with production detectors in the H8 test beam at CERN will be shown, in particular preliminary results on the integration of the barrel muon trigger electronics with the MUCTPI interface and with the ATLAS DAQ system will be discussed.

The RPC LVL1 trigger system of the muon spectrometer of the ATLAS experiment at LHC

The Atlas Trigger System has been designed to reduce the LHC interaction rate of about 1 GHz to the foreseen storage rate of about 100 Hz. Three trigger levels are applied in order to fulfill such a requirement. A detailed simulation of the ATLAS experiment including the hardware components and the logic of the Level-1 Muon trigger in the barrel of the muon spectrometer has been performed. This simulation has been used not only to evaluate the performances of the system but also to optimize the trigger logic design. In the barrel of the muon spectrometer the trigger will be given by means of resistive plate chambers (RPCs) working in avalanche mode. Before being mounted on the experiment, accurate quality tests with cosmic rays are carried out on each RPC chamber using the test station facility of the INFN and University laboratory of Napoli. All working parameters are measured and the uniformity of the efficiency on the whole RPC surface is required. A summary of the Napoli cosmic rays tests, together with a brief description of the Atlas Trigger, in particular of the Level-1 Muon Trigger in the barrel, and the results of the trigger simulation will be given.

The RPC space resolution with the charge centroid method

RPC detectors were originally developed to exploit the very good intrinsic time resolution of the plane geometry and have been used as muon trigger in most of their high energy physics applications, disregarding the detector space resolution. Due to the high luminosity of future colliders, new experiments will be very demanding in terms of momentum selection of the muon spectrometer. For this reason, trigger detectors will be required to have a sub-millimeter space resolution as well as a sub-nanosecond time resolution. RPCs are good candidates for these applications, as it can be shown that they have excellent intrinsic space resolution, while the actual results depend mostly on the front-end electronics performance. Here we present a beam test carried out on a small size RPC. The results are consistent with a space resolution of ~ 130 μm.

Response uniformity of a large size RPC

The response uniformity of a 90]290 cm2 RPC prototype working in avalanche mode has been tested using cosmic rays. The high statistics needed for the test has also been used for accurate e