Abstract
We report on a systematic study of double-gap and four-gap phenolic resistive plate chambers (RPCs) for the Phase-2 upgrade of the CMS muon system at high η. In the present study, we constructed real-sized double-gap and four-gap RPCs with gap thicknesses of 1.6 and 0.8 mm, respectively, with 2-mm-thick phenolic high-pressure-laminated (HPL) plates. We examined the prototype RPCs with cosmic rays and with 100-GeV muons provided by the SPS H4 beam line at CERN. To examine the rate capability of the prototype RPCs both at Korea University and at the CERN GIF++ facility, the chambers were irradiated with 137Cs sources providing maximum gamma rates of about 1.5 kHz cm−2. For the 1.6-mm-thick double-gap RPCs, we found the relatively high threshold on the produced detector charge was conducive to effectively suppressing the rapid increase of strip cluster sizes of muon hits with high voltage, especially when measuring the narrow-pitch strips. The gamma-induced currents drawn in the four-gap RPC were about one-fourth of those drawn in the double-gap RPC. The rate capabilities of both RPC types, proven through the present testing using gamma-ray sources, far exceeded the maximum rate expected in the new high-η endcap RPCs planned for future phase-II runs of the Large Hadron Collider (LHC).
Highlights
In the mid-section of efficiency plateau, the gamma-induced currents drawn in the four-gap resistive plate chambers (RPCs) were about one fourth of those drawn in the double-gap RPCs
In the present research, we examined two different phenolic RPC types with cosmic rays at Korea University and 100 GeV muons provided by the SPS H4 beam line at CERN
We examined the rate capabilities of the prototype RPCs with gamma-ray hits of maximum 1.5 kHz cm-2 provided by the 137Cs gamma sources at Korea University and the GIF++ irradiation facility at CERN
Summary
For the cosmic-muon test at Korea University, we used two different FEE types for the digitization of the signals: charge-sensitive FEEs for the operation of the current CMS RPCs; and voltage-sensitive FEEs developed for the present study of RPCs. For the beam test at the GIF++, we used only CMS RPC FEEs for the digitization.
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