J. Lamas Valverde

A New type of resistive plate chamber: The Multigap RPC

Abstract This Letter describes the multigap resistive plate chamber (RPC). The goal is to obtain a much improved time resolution, keeping the advantages of the wide gap RPC in comparison with the conventional narrow gap RPC (smaller dynamic range and thus lower charge per avalanche which gives higher rate capability and lower power dissipation in the gas gap).

The non-spark mode and high rate operation of resistive parallel plate chambers

Abstract The good time and position resolution of the resistive plate chamber (RPC) make it an attractive candidate for muon trigger systems at future colliders. However, this device has severe rate problems that make it unusable above 1 Hz/cm 2 in its present form. We have investigated various materials and have also discovered a new mode of operation that allowed us to operate the RPC at 150 Hz/cm 2 . We discuss further improvements that may extend operation to even higher rates. We also discuss spark formation and explain the cause for the abnormally late spark signals.

Investigation of resistive parallel plate chambers

Abstract The resistive parallel plate chamber (RPC) has been developed during the last ten years. We have investigated two versions of these chambers, one with cellulose and the other with phenolic plates. We present a comparison between these two for various gas mixtures and the dependence on particle flux.

The wide gap resistive plate chamber

Abstract The resistive plate chamber (RPC) has good time and position resolution; these factors (coupled to its simple construction) make it an attractive candidate for muon trigger systems at future colliders. However, operated in spark mode, the RPC has severe rate problems that make it unusable above 10 Hz/cm 2 . We have previously published our results concerning the operation of the RPC in spark and in avalanche mode; we have shown that the rate limit can be increased to 150 Hz/cm 2 if the RPC is operated in avalanche mode. Here, we discuss the performance of chambers with 6 and 8 mm gas gaps (compared to the more usual 2 mm gap). We outline the reasons for this choice, and also discuss anode versus cathode strip readout. We have measured the efficiency versus flux, and also show that an enhanced rate limit can be obtained if only a small region of the chamber is exposed to the beam (spot illumination). Finally we have tested the performance of chambers constructed with other materials for the resistive plate and compare it to chambers constructed with our preferred plastic, melamine laminate.

Resistive plate chambers with secondary electron emitters and microstrip readout

Abstract We describe our attempt to develop Resistive Plate Chambers (RPCs). One study involves the use of secondary electron emitters that consist of porous photosensitive materials (CsI, diethylferocenil-mercury, SbCs and others) deposited on a cathode; this enhances efficiency, thus allowing the use of light, non-flammable gas mixtures. The other study concerns the operation of an RPC with a narrow strip readout - the “microstrip RPC”.

Pure avalanche mode operation of a 2-mm gap resistive plate chamber

Abstract It is necessary to operate the resistive plate chamber (RPC) in avalanche mode to obtain high efficiency at elevated particle fluxes. We examine this mode of operation with a 2 mm gap RPC using gas mixtures containing C 2 F 4 H 2 and C 2 F 5 H. In order to explain the data we propose that the avalanche growth is strongly limited by space charge effects.

Further studies of avalanche mode operation of resistive parallel plate chambers

Abstract We have investigated the high rate operation of the resistive plate chamber and have discovered that melamine-phenolic laminates are good candidates for a plate material. We have previously shown that avalanche mode (rather than spark mode) gives a substantial improvement in the rate capability. There are two new encouraging results; the timing spectra are not affected by the rate; and particles at non normal incidence have a higher detection efficiency; these substantially increase the rate capability of this device. However there are two results that show that further RD and the fall off of the efficiency with increasing high voltage. Our goal is to produce a cheap large area detector that has good spatial and time resolution and has a rate capability suitable for the muon system at a future collider. We believe that these results show that this detector is already promising and should satisfy these requirements with further R&D.

A comparison of the wide gap and narrow gap resistive plate chamber

Abstract In this paper we study the performance of a wide gap RPC and compare it with that of a narrow gap RPC, both operated in avalanche mode. We have studied the total charge produced in the avalanche. We have measured the dependence of the performance with rate. In addition we have considered the effect of the tolerance of gas gap and calculated the power dissipated in these two types of RPC. We find that the narrow gap RPC has better timing ability; however the wide gap has superior rate capability, lower power dissipation in the gas volume and can be constructed with less stringent mechanical tolerances.

High rate resistive plate chambers

Abstract In this paper we consider some factors that could improve the high rate performance of the RPC; we consider the role of freon in the operation of RPCs; we present results with an asymmetric RPC with one glass and one melamine resistive plate.

Avalanche fluctuations within the multigap resistive plate chamber

Abstract The multigap resistive plate chamber (MRPC) was originally designed to have improved time resolution (compared to the wide gap RPC), but also to keep the good high rate behaviour and ease of construction associated with the wide gap RPC. However in addition we observed a very long efficiency plateau, even at high rates. Here we consider fluctuations in avalanche growth, and show that the inherent “averaging” of these fluctuations can account for the enhanced performance of the multigap RPC.