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Production and Quality control of RPCs for the CMS muon barrel system

Production and Quality control of RPCs for the CMS muon barrel system. Davide Piccolo – INFN Napoli. RPCs in the CMS experiment. RPCs are used as muon trigger both in barrel and endcap system. 5 Wheels 12 sectors per wheel 6 RPC station per sector 8/7 chamber per sector. RPCs.

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Production and Quality control of RPCs for the CMS muon barrel system

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  1. Production and Quality control of RPCs for the CMS muon barrel system Davide Piccolo – INFN Napoli SIENA 23-26 maggio 2004

  2. RPCs in the CMS experiment RPCs are used as muon trigger both in barrel and endcap system 5 Wheels 12 sectors per wheel 6 RPC station per sector 8/7 chamber per sector RPCs SIENA 23-26 maggio 2004

  3. RPCs as trigger detector Pattern of fired strips is compared to predefined patterns corresponding to specific Pt SIENA 23-26 maggio 2004

  4. RPC chamber layout RB4 120 chambers (2 double gaps per chamber) RB3 120 chambers (2 double gaps per chamber) RB2 60 chambers (2 double gaps per chamber) + 60 chambers (3 double gaps per chamber) RB1 120 chambers (2 double gaps per chamber) Backward UP Forward UP Forward Down Backward Down SIENA 23-26 maggio 2004

  5. Chamber production CERN ISR Several steps are involved in the chamber production. PanPla Pavia Sofia Bari GT HT: Napoli SIENA 23-26 maggio 2004

  6. Chamber production Bakelite is produced at PanPla factory PanPla Pavia PanPla factory Bakelite production and QC SIENA 23-26 maggio 2004

  7. Chamber production Single gaps and Double gaps produced at General Tecnica factory General Tecnica Bari Single gap GT Double gap SIENA 23-26 maggio 2004

  8. Chamber production RB1 assembled in HT (napoli) RB2 assembled in GT RB3 assembled in Bari and Sofia RB4 assembled in GT Sofia Chamber assembly Bari GT HT: Napoli SIENA 23-26 maggio 2004

  9. Chamber test (phase I) RB1 tested in Pavia RB2/RB4 tested in Bari RB3 tested in Sofia Pavia Sofia Cosmic ray test Bari SIENA 23-26 maggio 2004

  10. Chamber test (phase II) CERN ISR Pavia Sofia Bari Chamber tested arrive at CERN. A final test is done before install chambers. Big effort has been done to increase Quality Control before final installation SIENA 23-26 maggio 2004

  11. Bakelite production and QC Bakelite sheets are produced at PanPla factory. Production and QC are under the control of the Pavia group • ADC resolution: 12 bit • python strength: 70 kg • readout electrode diameter : 5 cm • 9 measurement points • humidity and temperature monitored SIENA 23-26 maggio 2004

  12. Bakelite production (.. Continue) SIENA 23-26 maggio 2004

  13. Resistivity is corrected for temperature dependency according to: (T)/(20) = e -(T-20)/7.8 Bakelite resistivity distribution Accepted bakelite plates between 1 and 6 1010•cm bakelite resitivity accepted Resitivity precision SIENA 23-26 maggio 2004

  14. Bakelite coupling in RPCs Resistivity Difference Between gap electrodes Bakelite plates with similar resistivity are coupled together Average Resistivity of gap electrodes SIENA 23-26 maggio 2004

  15. Single gap production • Critical issues: • Spacers gluing • problem has been solved washing • and brushing bakelite surface • with dimethylketon • Oiling • - good quality, rpcs are opened one per • sample to check quality of the surfaces Single gaps are produced at General Tecnica Updated to may 15 SIENA 23-26 maggio 2004

  16. Quality control of single gaps SG assembled by GT Gas leakage test Control the gap “bubbles” in 30 s Overpressure test Reach an inside overpressure of 20 mbar: check if spacers or frame detach GT connects the HV wire ... The SG type (Right/Left) is assigned Bring the SG at 9500V and measure the current: reject if I > 5 A SIENA 23-26 maggio 2004

  17. cut Rejected sg Single gap QC results Overpressure (mbar) Spacers already detached SIENA 23-26 maggio 2004

  18. Double gap production Single gap up Two single gaps are joined together with strips running in the middle. strips Single gap down Updated to may 15 DG production status SIENA 23-26 maggio 2004

  19. Double gaps Quality control 2 SG validated by previews step SG coupling Gas leakage test DG assembled by GT Control the gap “bubbles” in 30 s Bring the DG at 9500V and measure the current: reject if I > 5 A per single gap SIENA 23-26 maggio 2004

  20. Critical issues on double gaps Discharges: in some DG, a discharge between the gap edge and the copper ground plane has been found (mostly on the side were solderings with the termination resistors are made). This was evident at a later stage, when DG had already been included in Chambers. An additional “C” made of PET has been added; Average current absorbed by a SG (in DG) before PET: 2.32 µA @ 8 kV Average current absorbed by a SG (in DG) after PET: 0.83 µA @ 8 kV SIENA 23-26 maggio 2004

  21. Chamber production 2 Double gaps (3 for RB2-3) are coupled in a mechanical framework Preloaded bars mantain RPCs in the mechanical framework Chamber is dressed with front end boards, cables, gas tubes and cooling pipes SIENA 23-26 maggio 2004

  22. assembly Cooling system test Gas flow test QC during assembly electronic test Kapton-FEB connectivity test QC after assembly HV test: I vs HV I vs time Noise rate strip by strip Chamber assembly QC Double gaps inventory Chambers assembled in several sites: RB1 in HT near Napoli RB2 in GT RB3 in Bari and now in Sofia RB4 in GT Status of production: Check list filling DB update SIENA 23-26 maggio 2004

  23. QC results at HT • Chamber accepted if: • <I(@9500V)> < 5 A per gap, • I not increasing in one hour • (I) < 1 A per gap. For each HV point measure average and rms of current SIENA 23-26 maggio 2004

  24. Selection criteria on assembled chamber Gas mixture used in assembling sites: C2H2F496 % Iso_C4H104 % Number of gaps cut Average current rms current Number of gaps cut SIENA 23-26 maggio 2004

  25. Problems during assembly SIENA 23-26 maggio 2004

  26. Cosmics tests Final test with cosmic rays in Bari, Pavia, Sofia. Pavia test site (5 slots) BARI test site (10 slots) SF6 ..…… 0.3 % I-C4H10 .. 3.5 % C2H2F4 … 96.2 % Gas mixture SIENA 23-26 maggio 2004

  27. Test procedure • gas flow @ 4 volumes/day per 4 days with gas • mixture humidified at 50 % • HV conditioning scan (1 kV/15 min) • dark current vs HV measurement • Take data with cosmic rays (gap Up, Down, both) • Efficiency vs HV • single rate vs HV • cluster multiplicity vs HV • monitor of T, P, H • measure of stability: dark current vs time SIENA 23-26 maggio 2004

  28. Some results SIENA 23-26 maggio 2004

  29. Double gaps Double gaps Single gaps Single gaps Efficiency distribution: summary <>dg = 97 % <>sg = 95 % Maximum Efficiency Corrected For T and P 50 % Efficiency HV SIENA 23-26 maggio 2004

  30. Test performances with tracking RPCs under test can be used to reconstruct the cosmic track. (Bari test station) Shift due to geometry and sample purity Select tracks with at least 4 layers (do not require layer under test) Work in progress Tracking No tracking SIENA 23-26 maggio 2004

  31. Dark current distribution Current of 2 gaps Dark current at working voltage 9400 Volts SIENA 23-26 maggio 2004

  32. Double gaps Single gaps Noise rate distribution Average single rate at 9400 V. Most of these rates are due to a single noisy channel. Chamber accepted SIENA 23-26 maggio 2004

  33. Cluster size distribution No cut on cluster size: Trigger algorithm uses cluster baricenter Mean cluster size at 9400 V. Mean cluster size vs HV SIENA 23-26 maggio 2004

  34. Final test at CERN (ISR) Chambers from Bari, Pavia, Sofia  CERN • I vs. V • Noise rate • Cluster size • Current stability for ~30 days • Chambers suspicious have been monitored for > 1 month • Upgrade: cosmics test Storage/test area Test at ISR SIENA 23-26 maggio 2004

  35. Test at Cern HV not corrected for T and P Dark current @ 9400 V. • up • Down • -total mA • Forw • Back • Middle • -total Cluster size @ 9400 V. Noise rate @ 9400 V. Hz/cm2 SIENA 23-26 maggio 2004

  36. Dark current stability Suspicious chambers SIENA 23-26 maggio 2004

  37. Conclusions • Production and quality certification of CMS RPC chambers • involve several steps. • 1655 single gaps have been produced (total 2040) • 165 chambers have been assembled (total 480) • 116 are at moment at ISR • 59 are ready to be installed SIENA 23-26 maggio 2004

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