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Title: Mechanisms Affecting Performance of the BaBar Resistive Plate Chambers and Searches for Remediation

Abstract

The BaBar experiment at PEPII relies on the Instrumentation of the Flux Return (IFR) for both muon identification and KL detection. The active detector is composed of Resistive Plate Chambers (RPC's) operated in streamer mode. Since the start of operation the RPC's have suffered persistent efficiency deterioration and dark current increase problems. The ''autopsy'' of bad BaBar RPC's revealed that in many cases uncured Linseed oil droplets had formed on the inner surface of the Bakelite plates, leading to current paths from oil ''stalagmites'' bridging the 2 mm gap. In this paper a possible model of this ''stalagmite'' formation and its effect on the dark current and efficiency of RPC chambers is presented. Laboratory test results strongly support this model. Based upon this model we are searching for solutions to eliminate the unfavorable effect of the oil stalagmites. The lab tests show that the stalagmite resistivity increases dramatically if exposed to the air, an observation that points to a possible way to remedy the damage and increase the efficiency. We have seen that flowing an oxygen gas mixture into the chamber helps to polymerize the uncured linseed oil. Consequently the resistivity of the bridged oil stalagmites increases, as does thatmore » of the oil coating on the frame edges and spacers, significantly reducing the RPC dark currents and low-efficiency regions. We have tested this idea on two chambers removed from BaBar because of their low efficiency and high dark current. These test results are reported in the paper, and two other remediation methods also mentioned. We continue to study this problem, and try to find new treatments with permanent improvement.« less

Authors:
Publication Date:
Research Org.:
Stanford Linear Accelerator Center, Menlo Park, CA (US)
Sponsoring Org.:
USDOE Office of Science (US)
OSTI Identifier:
815623
Report Number(s):
SLAC-PUB-10174
TRN: US0304737
DOE Contract Number:  
AC03-76SF00515
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 19 Sep 2003
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; AIR; AUTOPSY; BAKELITE; COATINGS; DETECTION; EFFICIENCY; LINSEED OIL; MIXTURES; MUONS; OXYGEN; PERFORMANCE; PLATES; SPACERS

Citation Formats

Lu, Changguo. Mechanisms Affecting Performance of the BaBar Resistive Plate Chambers and Searches for Remediation. United States: N. p., 2003. Web. doi:10.2172/815623.
Lu, Changguo. Mechanisms Affecting Performance of the BaBar Resistive Plate Chambers and Searches for Remediation. United States. doi:10.2172/815623.
Lu, Changguo. Fri . "Mechanisms Affecting Performance of the BaBar Resistive Plate Chambers and Searches for Remediation". United States. doi:10.2172/815623. https://www.osti.gov/servlets/purl/815623.
@article{osti_815623,
title = {Mechanisms Affecting Performance of the BaBar Resistive Plate Chambers and Searches for Remediation},
author = {Lu, Changguo},
abstractNote = {The BaBar experiment at PEPII relies on the Instrumentation of the Flux Return (IFR) for both muon identification and KL detection. The active detector is composed of Resistive Plate Chambers (RPC's) operated in streamer mode. Since the start of operation the RPC's have suffered persistent efficiency deterioration and dark current increase problems. The ''autopsy'' of bad BaBar RPC's revealed that in many cases uncured Linseed oil droplets had formed on the inner surface of the Bakelite plates, leading to current paths from oil ''stalagmites'' bridging the 2 mm gap. In this paper a possible model of this ''stalagmite'' formation and its effect on the dark current and efficiency of RPC chambers is presented. Laboratory test results strongly support this model. Based upon this model we are searching for solutions to eliminate the unfavorable effect of the oil stalagmites. The lab tests show that the stalagmite resistivity increases dramatically if exposed to the air, an observation that points to a possible way to remedy the damage and increase the efficiency. We have seen that flowing an oxygen gas mixture into the chamber helps to polymerize the uncured linseed oil. Consequently the resistivity of the bridged oil stalagmites increases, as does that of the oil coating on the frame edges and spacers, significantly reducing the RPC dark currents and low-efficiency regions. We have tested this idea on two chambers removed from BaBar because of their low efficiency and high dark current. These test results are reported in the paper, and two other remediation methods also mentioned. We continue to study this problem, and try to find new treatments with permanent improvement.},
doi = {10.2172/815623},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Sep 19 00:00:00 EDT 2003},
month = {Fri Sep 19 00:00:00 EDT 2003}
}

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