Mechanisms affecting performance of the BaBar resistive plate chambers and searches for remediation

F. Anulli, S. Bagnasco, R. Baldini, H. R. Band, R. Bionta, J. E. Brau, V. Brigljevic, A. Buzzo, A. Calcaterra, M. Carpinelli, T. Cartaro, N. Cavallo, G. Crosetti, R. De Sangro, G. De Nardo, A. Eichenbaum, F. Fabozzi, D. Falciai, F. Ferrarotto, F. FerroniG. Finocchiaro, F. Forti, R. Frey, C. Gatto, E. Grauges, M. Iwasaki, J. R. Johnson, D. J. Lange, Y. P. Lau, L. Lista, M. Lovetere, C. Lu, M. Macri, T. B. Moore, S. Morganti, N. Neri, H. Neal, A. Palano, E. Paoloni, P. Paolucci, S. Passaggio, F. Pastore, P. Patteri, I. Peruzzi, M. Piccolo, D. Piccolo, G. Piredda, E. Robutti, A. Roodman, A. Santroni, C. Sciacca, N. B. Sinev, D. Strom, A. Soha, S. Tosi, J. Va'vra, W. J. Wisniewski, D. M. Wright, Y. Xie, A. Zallo

Research output: Contribution to journalConference articlepeer-review

20 Scopus citations


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 (RPCs) operated in streamer mode. Since the start of operation the RPCs have suffered persistent efficiency deterioration and dark current increase problems. The "autopsy" of bad BaBar RPCs 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 2mm 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.

Original languageEnglish (US)
Pages (from-to)128-132
Number of pages5
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Issue number1-2
StatePublished - Aug 1 2003
Externally publishedYes
EventProceedings of the Sixth International Workshop on Resistive P (RPC 2001) - Coimbra, Portugal
Duration: Nov 26 2001Nov 27 2001

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Instrumentation


  • Linseed oil stalagmite
  • Oxygen treatment
  • Polymerization
  • RPC
  • Remediation


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