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Gas Gain Monitoring e attivita’ all’ISR Status, problemi, organizzazione

Gas Gain Monitoring e attivita’ all’ISR Status, problemi, organizzazione. Stefano Bianco Laboratori Nazionali di Frascati dell ’ INFN Status of ISR Closed Loop recirculation gas system Gas Analyses Gas Gain Monitoring System Tests and Integration Master Planning

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Gas Gain Monitoring e attivita’ all’ISR Status, problemi, organizzazione

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  1. Gas Gain Monitoring e attivita’ all’ISRStatus, problemi, organizzazione Stefano Bianco Laboratori Nazionali di Frascati dell’INFN Status of ISR Closed Loop recirculation gas system Gas Analyses Gas Gain Monitoring System Tests and Integration Master Planning https://twiki.cern.ch/twiki/bin/view/CMS/RpcGasGain Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008

  2. 1.STATUS OF ISR CLOSED LOOP(see Roberto Guida’s Talks in Twiki Page) • Stable operation with 10% fresh mix during 2007 • Up to 2 months filters lifetime with no currents increase • August 2007 Freon supplier changed, air contamination discovered and studied by Roberto • Manpower burden for purging new bottles • September 2007 new double gaps installed at ISR • November-December 2007 new GC-MS arrived, commissioned, operated. • January 2008 one-year Technical Student for ISR Closed Loop (S.Colafranceschi, Frascati) • January - February 2008 problem of air intake in Closed Loop, fixed • Now Closed Loop operational, restarted, currents are slowly increasing Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008

  3. 1.STATUS OF ISR CLOSED LOOP(see Roberto Guida’s Talks in Twiki Page) • Run with saturated filters till currents increase, then regenerate • Perform Gas analysis samplings between filters regenerations • System operates correctly between filters regenerations • Currents increase was always recovered by regenerating filters and/or switching to Open Mode • No permanent damage was ever found • We use ISR as a unique tool to understand and optimize the chemistry of filters Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008

  4. 2.Gas analysisCONCLUSIONS AND OUTLOOK on analyses • Presence of HF in system, and trace elements (metals, etc) • The system is very complex. Many different chemical compositions in the system components. The presence of F compounds in gas-mix damages some af them. • These results are preliminary. We need different operating procedures for studying the filters kinetic and customize best desorbtion process. • Although filters need to be chemically characterized, the set-up currently used is able to operate correctly the CMS-RPC detector. • SEM-EDS analyses are currently in progress on bakelite • We are setting up a new procedure for analyses on gas at ISR G.SAVIANO RPC07 MUMBAI Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008

  5. 2. GAS SAMPLING AND ANALYSIS • Gas sampling and analysis at the ISR Closed Loop performed by Roberto in the past (see RPC07 Mumbai, January 2008) • Observed production of HF and metallic trace elements • Ad-hoc sampling points setup by Roberto (before and after filters) • New sampling scheme (Saviano, Piga, Ferrini) • Gas is bubbled in LiOH solution for a better absorption of pollutants Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008

  6. Gas mix One-way valve tubing for additional filtering LiOH 2. GAS SAMPLING AND ANALYSIS • Using LiOH solution reaction formula 2LiOH + Me 2+ --> Me(OH)2 + 2Li+ • After sampling amount of LiOH solution will be analyzed by IC (Ionic Chromatograph) for F- and other anions and the remnant will be acidified with HNO3 and analyzed by ICP-AES (Inductive Coupled Plasma- Atomic Emission Spectrometry) for metallic cations • Ppm-sensitivity analyses (Univ. Roma) using IC and ICP-AES • Anions F-, S--, solfati, cloruri using IC at Univ. Rome • Metals at Ministry of industry • F- specific electrodes for HF accumulation measurements (INFN funded) • Tested in Frascati sampling procedure to avoid backdiffusion of LiOH into Closed Loop, no big change in pH of H2O control flask, analysis of H2O in progress (ICP-AES) • Now procuring sampling material (plastic flasks, tubing, etc) Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008

  7. H2O H2O LiOH 2. TEST IN FRASCATI • Tested in Frascati sampling procedure to avoid backdiffusion of LiOH into Closed Loop. • Li concentration, mg/l: • flask 2 = 0.28 +- 0.06 mg/l • flask 4 = 0.22 +- 0.06 mg/l • NO BACKWARDS DIFFUSION OF Li OBSERVED One-way valve 4 Gas mix 3 2 1 empty Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008

  8. 3.Gas Gain Monitoring System tests • System operational at ISR, working on integration with DCS • Tests on sensitivity of charge and avalanche/streamer ratios for working point changes • Good sensitivity in avalanche-to-streamer transition regions • Run with (0% SF6) --> (0.3% SF6) taken at ISR last week, analysing results Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008

  9. Preliminary studiesCosmic Rays charge distribution HV=9.4kV; HVeff=9.9kV; Gate=100ns; T=22°C ; RH=50%; 26 Oct2007 counts Pedestal Avalanche Avalanche threshold CMS RPC preliminary ADC ch L.BENUSSI RPC07 MUMBAI HV= 10.2 kV; HVeff=10.7 kV; Gate=100ns; T=22°C; RH=50%; 26 Oct2007 counts Pedestal Avalanche + Streamer CMS RPC preliminary Avalanche threshold Streamer ADC ch pC Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008 pC

  10. Preliminary studiesSensitivity of charge distribution to HV (2/3)‏ Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008 100 pC L.BENUSSI RPC07 MUMBAI CMS RPC preliminary Avalanche + streamer A very rough estimate of sensitivity to working point changes in avalanche – streamer transition Working in the avalanche + streamer region provides a sensitivity of 1.25 pC/10 V avalanche Inefficiency region

  11. Preliminary studiesSensitivity of charge distribution to HV (3/3)‏ Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008 CMS RPC preliminary Transition region pedestal to avalanche and avalanche to streamer are sensitive to working point changes L.BENUSSI RPC07 MUMBAI avalanche Avalanche + streamer Blue curve avalanche yield black curve streamer yield Inefficiency region

  12. Integration with DCS • Yesterday CAEN SY1527 at ISR was read by PVSS/DCS (S.Colafranceschi, thanks to G.Polese helpdesk) CURRENTS MONITOR PLOT HERE Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008

  13. Master Planning V1 • 25/2 Closed Loop running with saturated filters • 3/3 Currents start increasing • stop CL • regenerate filters, take samples of used filters • restart CL • Switch gaps to individual CAEN HV SY1527 • 10/3 Giardoni, Pierluigi @ ISR • Transport material (PC, gas sensor box, RAID backup, opt fiber) • check air-tightness of 3 gas gain monitoring gaps, connect 3 gas gain monitoring gaps to closed loop • Connect 5 large DG to HV • 24/3 Currents start increasing Giardoni, Ponzio, Ferrini @ISR • stop CL • take samples of exausted filters, install new filters, • install sampling flasks, install F- specific electrodes • restart CL, start gas sampling • 30/3 Benussi, Pierluigi @ ISR • 6/4 Benussi, Passamonti @ISR • 13/4 Benussi, Russo @ ISR • 15/4 Currents start increasing • Stop CL • Take samples of used filters, regenerate filters, resume sampling 20/4 Benussi, Ponzio @ ISR • 27/4 Bianco, Russo @ISR • May • Start Gas and filters sampling with individual purifiers • May-June • Install gaps at SGX5 Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008

  14. Issues • Installation of gas gain monitoring at SGX5 • Gas Gain monitoring very useful at ISR now. Two-stage installation proposed: • Stage 0 • Installing gaps with no integration racks, minimal operation • Need basements, power, network • MAY - JUNE • Stage 1 • Gas integration rack • Negotiate cost with F.Hahn • Time schedule ? • Integration with DCS • HV and current monitoring OK • Gain monitoring parameters to DCS • Event Header 5words • 8gaps * 10words/gap • 1run=10k events = 1000s = 20min • TOT ~ 100words/run • PROPOSAL: RUN LOCALLY DAQ, write DST to file, access file via PVSS/DCS, load DCS Database. •  ADDITIONAL REQUESTS • Missioni estere, consumi Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008

  15. CONCLUSIONS • Closed Loop @ ISR showed how 10% fresh mix operation is possible for several weeks between filters regenerations • Results on filters bakelite and gas show presence of HF and trace elements (metals mainly) • System is complex (bakelite, gas, filters) and it is being characterized by new gas analyses • Closed Loop for CMS RPC can be used at SX5 • Full understanding of filter, gas, materials chemistry in progress at ISR (six months-one year) • DRAFTS • Gas filters bakelite analysis (90%) • CFD simulation of flux in small gaps (80%) • Gas Gain Monitoring gaps (10%) • High-statistics bakelite analysis Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008

  16. CMS-ATLAS-OPERA collaboration Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008

  17. SPARE Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008

  18. Gas Gain Monitor (conceptual design) USC5 UXC5 VENT RPC TRIG1 RPC TRIG2 Slow Ctrl GC, p/T/RH/Ph MONITOR VENT RPC PAD MON1 RPC PAD MON2 RPC PAD MON3 VENT RPC PAD MON4 RPC PAD MON5 CMS RPC PAD MON6 PURIFIERS REFERENCE half wheel lines VENT RPC PAD REF1 C2H2F4/SF6 /i-C4H10 /H2O RPC PAD REF2 VENT RPC TRIG3 RPC TRIG4 SGX Bldg Stefano Bianco (Frascati) - CMS RPC Italia Feb 2008

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