2011 HV scan SF6 flow-meter accident 2011 Results 2010-2011 comparison RPC HV efficiency scan Pigi...

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Transcript of 2011 HV scan SF6 flow-meter accident 2011 Results 2010-2011 comparison RPC HV efficiency scan Pigi...

  • Slide 1
  • 2011 HV scan SF6 flow-meter accident 2011 Results 2010-2011 comparison RPC HV efficiency scan Pigi Paolucci on behalf of RPC collaboration
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  • RPC Why an HV scan ? 11/04/11 Pigi - RPC project - XEB 12 April 2 2010 pressure P = 20 mbar 2010 efficiency =10% In 2010 we had not enough statistic to make a full efficiency scan RPC system worked with 2 common HV working point 9.35 & 9.55 kV RPC performance depends on P and T We decided to do an HV scan per year: To define a WP per chamber in order to improve the performance and avoid to stress the detector. Choose a WP in the plateau region in order to avoid instability with pressure RPC monitor stream is vital. Very high statistic in 1 hour at present L
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  • HV scan first 8 points RPC project - CMS GM 4 May 2011 3 18-19 March: HV scan (8 points HV corrected with pressure ) 27 March: full analysis completed About 60% of the rolls have a very good efficiency sigmoid fit more points needed ! An overall efficiency decrease of 3% seen in the only run comparable with 2011 WP !!! Pigi on behalf of RPC group plateau curves repository barrel endcap
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  • HV scan preliminary results 11/04/11 4 Pigi - RPC project - XEB 12 April Defined plateau region Knee 95% Working = knee + 150 V HV scan fit (HV) = max /(1 + e Slope (HV-HV50%) ) Working Point defined as Knee + 150 V taking into account the P of 2010 We can reduce to 100 in case of rate problem and even less when we will correct the Effective HV with the pressure variations.
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  • HV scan 11 points RPC project - CMS GM 4 May 2011 5 15 April: 3 more points taken scan completed (3.3 pb -1 BAD) 95% of the rolls have now a very good efficiency sigmoid fit Pigi on behalf of RPC group barrel endcap
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  • HV scan Chi2 distribution RPC project - CMS GM 4 May 2011 6 Pigi on behalf of RPC group
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  • HV scan all curves shifted RPC project - CMS GM 4 May 2011 7 it is now clear that was not an overall efficiency decrease but that all curves were shifted forward about 120 10 V (respect 2010) ?? We double checked HV, pressure, temperature, timing, Trigger, selection checked Everything seems to be ok what about the GAS ? Pigi on behalf of RPC group Artificial shift of 110 Volts 2010
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  • HV scan curve shifted RPC project - CMS GM 4 May 2011 8 Pigi on behalf of RPC group HV scan 2010 Fit HV Scan 2011
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  • HV scan SF6 shift measurement RPC project - CMS GM 4 May 2011 9 16 April: Gas expert called SF6 mass flow-meter replaced after few hours 18 April: System came back at nominal gas mixture SF6 mass flow-control analyzed by Gas Group: not working properly - 30% more !!! 0.39% not 0.30% (flow-meter monitoring was stable and at 0.3%) Only way to detect the failure was an external measurement with chromatograph 24 April: mini-scan in 2 sectors (39 rolls) to calibrate the shift due to the SF6 Pigi on behalf of RPC group HV (0.39% SF6 0.30% SF6) at 50% eff HV 50% shifted of 100 Volts RMS is 19 Volts 100 Volts renormalization will be applied to all the curves
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  • HV scan working points RPC project - CMS GM 4 May 2011 10 30 April: Rolls WP merged in chamber and then in HV channel (1 HV ch. 4 bi-gap rolls) 2011 final HV working point table is ready (average of 4 rolls WP) System should be now more stable.vs. pressure About 65% were working closer to the knee in the 2010 Pigi on behalf of RPC group Nominal voltage 2010 Nominal voltage 2010 P 2011 P
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  • HV scan final results I RPC project - CMS GM 4 May 2011 11 2172 (99%) fits are good (51 recovered deleting 1-2 bad points) Only 23 OFF rolls are without plateau Pigi on behalf of RPC group All Barrel HV scan 2011 HV value at 50% eff Barrel RMS 64 Volts Endcap RMS 84 Volts
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  • Pigi on behalf of RPC group RPC project - CMS GM 4 May 2011 12
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  • Pigi on behalf of RPC group RPC project - CMS GM 4 May 2011 13 Cluster size noise Public results on WEB page
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  • HV scan final results I RPC project - CMS GM 4 May 2011 14 Also low efficiency rolls have a very nice plateau Pigi on behalf of RPC group barrel 1 Front End board broken
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  • HV scan final results II RPC project - CMS GM 4 May 2011 15 Pigi on behalf of RPC group 2010 2011 Average Effective voltage over 1 month kV P T cut > 0 GeV Effective voltage in 1 hour 9.35 & 9.55 kV P T cut > 7 GeV Systematic error of about 1%
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  • ClusterSizeBarrel 2010 2011 Average Effective voltage over 1 month kV P T cut > 0 GeV Effective voltage in 1 hour 9.35 & 9.55 kV P T cut > 7 GeV Pigi on behalf of RPC group 16 RPC project - CMS GM 4 May 2011
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  • Cluster size distribution at WP Pigi on behalf of RPC group RPC project - CMS GM 4 May 2011 17 Cluster size distribution at the 2011 HV channel WP Measurement will be re-done in 1 day after the TS = 1.6 RMS 0.23
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  • HV scan gas monitoring improvements RPC project - CMS GM 4 May 2011 18 Central gas group is helping a lot in understanding the SF6 flow-meter failure and in improving the monitoring of this crucial component Thanks SF6 flow-meter is today monitored by the gas group with a gas chromatograph until the automatic procedure will be ready (June) RPC Gas system review 3 May (today): Gas Gain Monitor could be used to monitor the gas mixture (under study) Gas monitor parameters alarm/warning have been reviewed Instructions for the RPC shifter will be updated Pigi on behalf of RPC group
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  • Conclusions Pigi on behalf of RPC group RPC project - CMS GM 4 May 2011 19 Barrel Gaps have been produced from 2003 and after 8 years Stability and uniformity of 2172 bi-gap rolls is now evident: All the efficiency curve fits are good 23 (1%) rolls are OFF Average efficiency 95% - stable in time (2010-2011) Efficiency RMS = 5% HV 50% distribution has RMS = 64 Volts and 84 Volts (very uniform set) HV working point table is now ready. It will be uploaded after TS Expected at WP are 95-96 % and more stable.vs. P & T SF6 is a critical component for RPC detector 30% more corresponds to 110 Volts Gas chromatograph automatic measurement needed to control the gas mixture Online HV correction with pressure is needed to reduce the operating voltage and keep safe the detector (under-study) Final results WEB page