Davide Piccolo - INFN NapoliSIENA maggio 2004 Production and Quality control of RPCs for the CMS muon barrel system Davide Piccolo – INFN Napoli

Davide Piccolo - INFN NapoliSIENA maggio 2004 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

Davide Piccolo - INFN NapoliSIENA maggio 2004 RPCs as trigger detector Pattern of fired strips is compared to predefined patterns corresponding to specific P t

Davide Piccolo - INFN NapoliSIENA maggio 2004 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) Forward UP Forward Down Backward UP Backward Down

Davide Piccolo - INFN NapoliSIENA maggio 2004 Chamber production Several steps are involved in the chamber production. GT HT: Napoli Bari Pavia Sofia PanPla CERN ISR

Davide Piccolo - INFN NapoliSIENA maggio 2004 Chamber production Pavia PanPla Bakelite is produced at PanPla factory Bakelite production and QC PanPla factory

Davide Piccolo - INFN NapoliSIENA maggio 2004 Chamber production GT Bari Single gaps and Double gaps produced at General Tecnica factory General Tecnica Single gap Double gap

Davide Piccolo - INFN NapoliSIENA maggio 2004 Chamber production GT HT: Napoli Bari Sofia RB1 assembled in HT (napoli) RB2 assembled in GT RB3 assembled in Bari and Sofia RB4 assembled in GT Chamber assembly

Davide Piccolo - INFN NapoliSIENA maggio 2004 Chamber test (phase I) Bari Pavia Sofia RB1 tested in Pavia RB2/RB4 tested in Bari RB3 tested in Sofia Cosmic ray test

Davide Piccolo - INFN NapoliSIENA maggio 2004 Chamber test (phase II) 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 Bari Pavia Sofia CERN ISR

Davide Piccolo - INFN NapoliSIENA maggio 2004 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 ADC resolution: 12 bit python strength: 70 kg readout electrode diameter : 5 cm 9 measurement points humidity and temperature monitored

Davide Piccolo - INFN NapoliSIENA maggio 2004 Bakelite production (.. Continue)

Davide Piccolo - INFN NapoliSIENA maggio 2004 Bakelite resistivity distribution Resistivity is corrected for temperature dependency according to:  (T)/  (20) = e - (T-20)/7.8 bakelite resitivity accepted Accepted bakelite plates between 1 and  cm Resitivity precision

Davide Piccolo - INFN NapoliSIENA maggio 2004 Bakelite coupling in RPCs Bakelite plates with similar resistivity are coupled together Resistivity Difference Between gap electrodes Average Resistivity of gap electrodes

Davide Piccolo - INFN NapoliSIENA maggio 2004 Single gap production Single gaps are produced at General Tecnica Produced1655 Accepted1082 Rejected283 Under test265 Spare/on wait25 Total to install2040 Accepted1082 Accepted/To install53.04 % 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 Updated to may 15

Davide Piccolo - INFN NapoliSIENA maggio 2004 Quality control of single gaps SG assembled by GT Gas leakage test Overpressure test Control the gap “bubbles” in 30 s Reach an inside overpressure of 20 mbar: check if spacers or frame detach 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 Bring the SG at 9500V and measure the current: reject if I > 5  A

Davide Piccolo - INFN NapoliSIENA maggio 2004 Single gap QC results Rejections Pressure test and leak test % HV test9534 % Spacers already detached Rejected sg cut Overpressure (mbar)

Davide Piccolo - INFN NapoliSIENA maggio 2004 Double gap production Two single gaps are joined together with strips running in the middle. Produced501 Accepted458 Rejected15 Spare/On wait3 Total to install1020 Acceped458 Accepted/to install44.90 % DG production status Updated to may 15 Single gap down Single gap up strips

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

Davide Piccolo - INFN NapoliSIENA maggio 2004 Critical issues on double gaps Average current absorbed by a SG (in DG) before PET: kV Average current absorbed by a SG (in DG) after PET: kV 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;

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

Davide Piccolo - INFN NapoliSIENA maggio 2004 Chamber assembly QC Double gaps inventory DB update Check list filling Chambers assembled in several sites: RB1 in HT near Napoli RB2 in GT RB3 in Bari and now in Sofia RB4 in GT Cooling system testGas flow test electronic testKapton-FEB connectivity test QC during assembly assembly Status of production: Chamber type assembled Assembled/total RB15243 % RB % RB35445 % RB41412 % HV test: I vs HV I vs time Noise rate strip by strip QC after assembly

Davide Piccolo - INFN NapoliSIENA maggio 2004 QC results at HT Chamber accepted if: < 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

Davide Piccolo - INFN NapoliSIENA maggio 2004 Selection criteria on assembled chamber cut Number of gaps Average current rms current Gas mixture used in assembling sites: C 2 H 2 F 4 96 % Iso_C 4 H 10 4 % Gas mixture used in assembling sites: C 2 H 2 F 4 96 % Iso_C 4 H 10 4 %

Davide Piccolo - INFN NapoliSIENA maggio 2004 Problems during assembly

Davide Piccolo - INFN NapoliSIENA maggio 2004 Cosmics tests Final test with cosmic rays in Bari, Pavia, Sofia. BARI test site (10 slots) Gas mixture Pavia test site (5 slots) SF 6..…… 0.3 % I-C 4 H % C 2 H 2 F 4 … 96.2 %

Davide Piccolo - INFN NapoliSIENA maggio 2004 Test procedure gas 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 gas 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

Davide Piccolo - INFN NapoliSIENA maggio 2004 Some results

Davide Piccolo - INFN NapoliSIENA maggio 2004 Efficiency distribution: summary 50 % Efficiency HV Corrected For T and P Maximum Efficiency dg = 97 % sg = 95 % Double gaps Single gaps Double gaps Single gaps

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

Davide Piccolo - INFN NapoliSIENA maggio 2004 Dark current distribution Dark current at working voltage 9400 Volts Current of 2 gaps

Davide Piccolo - INFN NapoliSIENA maggio 2004 Noise rate distribution Average single rate at 9400 V. Most of these rates are due to a single noisy channel. Chamber accepted Double gaps Single gaps

Davide Piccolo - INFN NapoliSIENA maggio 2004 Cluster size distribution No cut on cluster size: Trigger algorithm uses cluster baricenter Mean cluster size vs HV Mean cluster size at 9400 V.

Davide Piccolo - INFN NapoliSIENA maggio 2004 Final test at CERN (ISR) Chambers from Bari, Pavia, Sofia  CERN Chambers at ISR116 Tested chambers at ISR59 Under observation1 Rejected5 Storage/test area I vs. V Noise rate Cluster size Current stability for ~30 days Chambers suspicious have been monitored for > 1 month Upgrade: cosmics test Test at ISR

Davide Piccolo - INFN NapoliSIENA maggio 2004 Test at Cern AA Dark 9400 V. Noise 9400 V. Hz/cm 2 Cluster 9400 V. Forw Back Middle -total up Down -total HV not corrected for T and P

Davide Piccolo - INFN NapoliSIENA maggio 2004 Dark current stability Suspicious chambers

Davide Piccolo - INFN NapoliSIENA maggio 2004 Conclusions Production and quality certification of CMS RPC chambers involve several steps 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