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

Davide Piccolo - INFN Napoli

SIENA 23-26 maggio 2004

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 bothin barrel and endcap system 5 Wheels

12 sectors per wheel6 RPC station per sector8/7 chamber per sector

RPCs



RPCs as trigger detector

Pattern of fired stripsis compared to predefinedpatterns corresponding to specific Pt



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



Chamber productionSeveral steps areinvolved in thechamber production.

GTHT: Napoli

Bari

Pavia

Sofia

PanPlaCERNISR



Chamber production

PaviaPanPlaBakelite is

producedat PanPla factory

Bakelite production and QC

PanPla factory



Chamber production

GT

Bari

Single gaps and Double gaps producedat General Tecnica factory

General TecnicaSingle gap

Double gap



Chamber production

GTHT: Napoli

Bari

Sofia

RB1 assembled in HT (napoli)RB2 assembled in GTRB3 assembled in Bari and SofiaRB4 assembled in GT

Chamber assembly



Chamber test (phase I)

Bari

Pavia

Sofia

RB1 tested in PaviaRB2/RB4 tested in BariRB3 tested in Sofia

Cosmic ray test



Chamber test (phase II)

Chamber tested arrive at CERN.A final test is donebefore install chambers.Big effort has been doneto increase Quality Controlbefore final installation

Bari

Pavia

Sofia

CERNISR



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



Bakelite production (.. Continue)



Bakelite resistivity distribution

Resistivity is corrected for temperaturedependency according to:(T)/(20) = e -(T-20)/7.8

bakeliteresitivity

accepted

Accepted bakelite platesbetween 1 and 6 1010 •cm

Resitivityprecision



Bakelite coupling in RPCs

Bakelite plateswith similar resistivityare coupled together

Resistivity Difference Between gap electrodes

Average Resistivityof gap electrodes



Single gap production

Single gaps are produced at General Tecnica

Produced 1655

Accepted 1082

Rejected 283

Under test 265

Spare/on wait

25

Total to install 2040

Accepted 1082

Accepted/To install

53.04 %

Critical issues:• Spacers gluing

- problem has been solved washingand brushing bakelite surfacewith dimethylketon

• Oiling- good quality, rpcs are opened one per

sample to check quality of the surfacesUpdated to may 15



Quality control of single gaps

SG assembled by GTSG assembled by GT Gas leakage testGas leakage test

Overpressure testOverpressure test

Control the gap “bubbles” in 30 sControl 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

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



Single gap QC resultsRejection

s

Pressure test and leak test

188 66 %

HV test 95 34 %

Spacers already detached

Rejected sg

cut

Overpressure (mbar)



Double gap productionTwo single gaps are joined together with strips runningin the middle.

Produced 501

Accepted 458

Rejected 15

Spare/On wait 3

Total to install 1020

Acceped 458

Accepted/to install

44.90 %

DG production status

Updated to may 15

Single gap down

Single gap up

strips



Double gaps Quality control

DG assembled by GTDG assembled by GT Gas leakage testGas leakage test

Control the gap “bubbles” in 30 sControl 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 step2 SG validated by previews step

SG couplingSG coupling



Critical issues on double gaps

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

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;



Chamber production

2 Double gaps (3 for RB2-3) arecoupled in a mechanicalframework

Chamber isdressed withfront end boards,cables, gas tubesand cooling pipes

Preloaded bars mantain RPCsin the mechanicalframework



Chamber assembly QCDouble gaps inventory

DB update

Check list filling

Chambers assembled in several sites:RB1 in HT near NapoliRB2 in GT RB3 in Bari and now in SofiaRB4 in GT

Cooling system test Gas flow test

electronic test Kapton-FEB connectivity test

QC during assembly

assembly

Status of production:

Chamber type

assembled

Assembled/total

RB1 52 43 %

RB2 45 37.5 %

RB3 54 45 %

RB4 14 12 %

HV test:I vs HVI vs time

Noise rate strip by strip

QC after assembly



QC results at HTHV scan

0

0,5

1

1,5

2

2,5

3

3,5

4

1

11 21 31 41 51 61 71 81 91

101

111

121

131

141

151

161

171

181

191

201

211

221

231

241

251

261

271

281

291

301

311

321

time (10 sec)

I (uA

)

forw up

forw down

back up

back down

1000 V

2000 V

4000 V

3000 V

9500 V

9200 V

9000 V

8000 V

7000 V

6000 V

5000 V

CHAMBER 173

0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

1

10 19 28 37 46 55 64 73 82 91

100

109

118

127

136

145

154

163

172

181

190

199

208

217

226

235

244

253

262

271

280

289

298

307

316

HV (Volts)

I (uA

)

ant sup

ant inf

post sup

post inf

Temp 22 degrees

Chamber accepted if:

• <I(@9500V)> < 5 A per gap,• I not increasing in one hour• (I) < 1 A per gap.

For each HV pointmeasure average andrms of current



Selection criteria on assembled chamber

cut

cut

Nu

mb

er

of

gap

s

Nu

mb

er

of

gap

s

Average current

rms current

Gas mixture used inassembling sites:C2H2F4 96 %Iso_C4H10 4 %

Gas mixture used inassembling sites:C2H2F4 96 %Iso_C4H10 4 %



Problems during assembly



Cosmics testsFinal test with cosmic rays in Bari, Pavia, Sofia.

BARI test site(10 slots)

Gas mixture

Pavia test site(5 slots)

SF6 ..…… 0.3 %I-C4H10 .. 3.5 %C2H2F4 … 96.2 %



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

• 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



Some results



Efficiency distribution: summary

50 % Efficiency HV

CorrectedFor T and P

Maximum Efficiency

<>dg = 97 %<>sg = 95 %

Double gaps

Single gaps

Double gaps

Single gaps



Test performances with tracking

RPCs under test can be used to reconstruct the cosmic track.(Bari test station)

Select tracks with at least 4layers (do not require layer under test)

Shift due to geometry and sample purity

Tracking

No tracking

Work in progress



Dark current distribution

Dark currentat working voltage9400 Volts

Current of 2 gaps



Noise rate distribution

Average singlerate at 9400 V.

Most of these rates are due to a singlenoisy channel. Chamber accepted

Double gaps

Single gaps



Cluster size distributionNo cut on cluster size:Trigger algorithm usescluster baricenter

Mean cluster size vs HV

Mean clustersize at 9400 V.



Final test at CERN (ISR)Chambers from Bari, Pavia, Sofia CERN

Chambers at ISR 116

Tested chambers at ISR

59

Under observation 1

Rejected 5

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



Test at Cern

A

Dark current @ 9400 V.

Noise rate @ 9400 V.

Hz/cm2

Cluster size @ 9400 V.•Forw •Back•Middle-total

•up•Down-total

HV not corrected for T and P



Dark current stability

Suspicious chambers



ConclusionsProduction and quality certification of CMS RPC chambersinvolve 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

Documents

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