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The production of gas gaps, the core components of the Forward RPCs in the CMS experiment, has reached a mature stage of the production stream. A total of 360 gas gaps, equivalent to 120 RPCs, has been manufactured, tested for quality control, and delivered to CERN in Switzerland and to Pakistan, where the complete Forward RPCs are being assembled. In this paper, the layout of the gas gaps, the production procedures, facilities, and the selection process of the qualified gas gaps are presented.

We present the detailed analysis of the time and charge signals of a prototype double gap resistive plate chamber for the endcap region of the compact muon solenoid detector at CERN LHC. We demonstrate that the operating high-voltage plateau can be extended at least up to 400 V with the present design. The simple avalanche multiplication model can reproduce the experimental charge spectra reasonably well at the beginning of the high-voltage plateau region. The effective Townsend coefficient is estimated in the avalanche mode operation.

The Compact Muon Solenoid (CMS) forward resistivity plate chambers (RPCs) at the high eta region must be operated in presence of a radiation-induced rate as high as 1 kHz / cm 2 . It is still unknown if the RPCs coated with linseed oil can be operated under such a high-radiation environment over the lifetime of CMS. Non-oiled RPCs may be one of the options since phenolic or melamine-coated bakelite is chemically stabler than linseed oil. We have constructed oiled and non-oiled RPCs at the high eta region of CMS using phenolic bakelite and tested them in the Gamma Irradiation Facility at CERN. While both RPCs show the same characteristics in the efficiency and the strip multiplicity, the non-oiled RPC generates an intrinsic noise rate of 50 Hz / cm 2 , compared to only 5 Hz / cm 2 for the oiled RPC, both at 10.0 kV which is about 100 V above the 95 % knee of the efficiency curve.

Strip clusters of muons and background hits induced by gamma rays and spurious pulses are analyzed for the Forward Region Resistive Plate Chamber of the CMS/LHC. In order to perform the analysis, a real size RE2/1 prototype RPC manufactured with the final baseline design of the Forward Region RPCs was tested at the Gamma Irradiation Facility of CERN. Strip cluster sizes for muons and strip cluster rates for gamma rays are sensitive to the threshold setting while the efficiency to muons is relatively insensitive.

We present the first beam test results of a real size prototype RPC for the endcap region of the CMS, one of large detectors at CERN LHC. The chamber was built with relatively low resistivity bakelite made in Korea and was operated successfully at the Gamma Irradiation Facility at CERN under the highest photon flux available, which corresponds to an effective cluster rate up to about 800 Hz / cm 2 . The cross-talk effects between strips and sectors have been studied extensively. The high voltage plateau, which satisfies the CMS requirements for efficiency and the number of strips fired per cluster, extends to at least 300 V . The time resolution has been measured to be better than 1.3 ns in this HV plateau region. These results demonstrate that the current design of the device can be used as a muon trigger detector for the CMS forward region.

The KEK to Kamioka long-baseline neutrino experiment (K2K) has begun its investigation of neutrino oscillations suggested by atmospheric neutrino observations. Twenty-eight neutrino events have been detected in coincidence with the expected arrival time of the beam in the 22.5 kt fiducial volume of Super--Kamiokande, the far detector at 250 km distance. The expectation is 37.8+3.5-3.8, derived using measurements of neutrino interactions in a near detector and extrapolation using a beam simulation validated by a measurement of pion kinematics after production and focusing. The background is of order 10^-3 events., Comment: 6 pages, 3 embedded figures, LaTeX with RevTeX style, submitted to PRL. This version is As Submitted

This paper presents the results from cosmic ray tests performed in the framework of R&D effort on the forward Resistive Plate Chamber (RPC) for CMS. A double gapRPC of dimensions 50 � 50 cm 2 with 2 mm gas gaps was tested. We report data on the use of tetrafluorethane-based gas mixture, with additions of water vapour and SF6. Efficiency, time resolution and cross-talk behaviour of the detector were investigated. # 2001 Elsevier Science B.V. All rights reserved. PACS: 29.40.Cs

We present the results from cosmic ray tests on the forward Resistive Plate Chamber (RPC) for the CMS. Double-gap prototype RPC were built and tested in the Korea Detector Laboratory (KODEL). We found that addition of SF 6 and water vapor to the tetrafluorethane-based gas mixture was required for the long-term stable operation of RPC. Efficiency, time resolution as well as cross-talk behavior of the detector were investigated. In addition, we present the temperature and humidity dependence of bulk resistivity of Korean bakelite in detail.

In this report, first beam test results for a real size RE2-2 prototype RPC for the forward region of the CERN CMS are presented. The beam test for the prototype RPC was performed at the Gamma Irradiation Facility (GIF) in CERN with a particle rate ranging up to ∼700 Hz / cm 2 . These test results demonstrate that a real size RE2-2 RPC can be built with relatively low resistivity of bakelite (∼1010 Ω cm). The current design of the RPC can be an option for the CMS forward region with its good efficiency and time characteristics under high radiation environment.

This paper presents data obtained in a systematic study on the bulk resistivity of Korean bakelite as a function of temperature in the range 20–30°C and relative humidity in the range 35–65%. Strong dependence of resistivity on both temperature and humidity was observed. Measurements were carried out in the framework of R&D work on Resistive Plate Chambers (RPCs) which will be used in the CMS detector.

The first six Resistive Plate Chambers (RPCs) of RE1/1 in the forward region of the Compact Muon Solenoid (CMS) detector were constructed and are being tested. These RPCs cover the pseudo-rapidity region from 1.6 to 2.1 and will serve as the base detector for the CMS RPC muon trigger. We report that these six RPCs are being tested with the CMS RPC quality certification procedures and that a full measurement of a chamber efficiency of 95 ± 4 % has been achieved at an operating voltage of 9.4 kV. This performance demonstrates that the RPC is qualified to be tested at the closest distance to the beam pipe as the muon trigger detector at the full LHC design luminosity.

The production for the endcap RPCs in the CMS experiment has entered a mature stage of the production stream. In this paper, the production facilities and the selection procedures of the qualified RPC gaps are presented. The mass production and the quality control tests for the endcap RPCs have reached the maximum productivity. The yield to produce the qualified gaps is now above 80 % of the qualified bakelite sheets provided by Italy. We also report an intensive aging study for the endcap RPCs performed by using a 200 mCi 137 Cs gamma-ray source. A few diagnostic methods to observe aging phenomena are discussed. The test result is equivalent to approximately 12 years of Compact Muon Solenoid (CMS) RPC operation.