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

3. RPCs as trigger detector
LAYOUT
Pattern of fired strips
is compared to predefined
patterns corresponding to specific Pt
Davide Piccolo - INFN Napoli
SIENA maggio 2004

4. RPC chamber layout Forward UP Backward UP Forward Down Backward Down
RB chambers (2 double gaps per chamber)
RB chambers (2 double gaps per chamber)
RB2 60 chambers (2 double gaps per chamber) +
60 chambers (3 double gaps per chamber)
RB chambers (2 double gaps per chamber)
Forward UP
Backward UP
Forward Down
Backward Down
Davide Piccolo - INFN Napoli
SIENA maggio 2004

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

6. Chamber production Backelite is produced At PanPla factory
Pavia
PanPla factory
Backelite production and QC
Davide Piccolo - INFN Napoli
SIENA maggio 2004

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

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

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

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

11. Bachelite production and QC
Bachelite 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
Davide Piccolo - INFN Napoli
SIENA maggio 2004

12. Bachelite production (.. Continue)
Davide Piccolo - INFN Napoli
SIENA maggio 2004

13. Bachelite resistivity distribution
Accepted bachelite plates
Between 1 and •cm
bachelite
resitivity
accepted
Resitivity
precision
Resistivity is corrected for temperature
dependency according to:
(T)/(20) = e (T-20)/7.8
Davide Piccolo - INFN Napoli
SIENA maggio 2004

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

15. Single gap production Critical issues:
Spacers gluing
problem has been solved washing
and brushing bachelite 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
Produced
1655
Accepted
1082
Rejected
283
Under test
265
Spare/on wait 25
Total to install
2040
Accepted
1082
Accepted/To install
53.04 %
Davide Piccolo - INFN Napoli
SIENA 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
Davide Piccolo - INFN Napoli
SIENA maggio 2004

17. Pressure test and leak test
Single gap QC results
Rejections
Pressure test and leak test
188
66 %
HV test 95
34 %
Rejected sg
cut
Overpressure (mbar)
Spacers already detached
Davide Piccolo - INFN Napoli
SIENA maggio 2004

18. Double gap production Two single gaps are joined
together with strips running
in the middle.
Foto doppia gap
DG production status
Produced
501
Accepted
458
Rejected 15
Spare/On wait 3
Total to install
1020
Acceped
458
Accepted/to install
44.90 %
Davide Piccolo - INFN Napoli
SIENA 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
Davide Piccolo - INFN Napoli
SIENA 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: kV
Average current absorbed by a SG (in DG) after PET: kV
Davide Piccolo - INFN Napoli
SIENA maggio 2004

21. Chamber production Preloaded bars mantain RPCs in the mechanical
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
Davide Piccolo - INFN Napoli
SIENA maggio 2004

22. Chamber assembly QC Status of production:
Double gaps inventory
Chambers assembled in several sites:
RB1 in HT near Napoli
RB2 in Bari and now in GT
RB3 in Sofia
RB4 in GT
Cooling system test
Gas flow test
LV system test
Kapton-FEB
connectivity test
QC during assembly
assembly
Status of production:
Chamber type
assembled
Assembled to install
RB1 52
43 %
RB2 45
37.5 %
RB3 54
45 %
RB4 14
12 %
Check list filling
HV test:
I vs HV
I vs time
Noise rate strip by strip
QC after assembly
Davide Piccolo - INFN Napoli
SIENA maggio 2004
DB update

23. QC results at HT For each HV point Measure average and Rms of current
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 Napoli
SIENA maggio 2004

24. Selection criteria on assembled chamber
Gas mixture used in
assembling sites:
C2H2F %
Iso_C4H10 4 %
Number of gaps
cut
Average
current
rms
current
Number of gaps
cut
Davide Piccolo - INFN Napoli
SIENA maggio 2004

25. Problems during assembly
Davide Piccolo - INFN Napoli
SIENA 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-C4H %
C2H2F4 … 96.2 %
Gas mixture
Davide Piccolo - INFN Napoli
SIENA maggio 2004

27. Test procedure gas flow @ 4 volumes/day per 24 hours
HV conditioning scan (1 KV/30 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
measure of stability: dark current vs time
Davide Piccolo - INFN Napoli
SIENA maggio 2004

28. Typical results
Davide Piccolo - INFN Napoli
SIENA maggio 2004

29. Efficiency distribution: summary
HV at maximum
efficiency
<> = 97 %
Corrected
For T and P
50 % Efficiency HV
Double gap
results
Davide Piccolo - INFN Napoli
SIENA 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
Davide Piccolo - INFN Napoli
SIENA maggio 2004

31. Dark current distribution
Current of
2 gaps
cut
Dark current
at working voltage
9400 Volts
Davide Piccolo - INFN Napoli
SIENA maggio 2004

32. Noise rate distribution
cut
Average single
rate at 9400 V.
Most of these rates
are due to a single
noisy channel.
Chamber accepted
Davide Piccolo - INFN Napoli
SIENA maggio 2004

33. Cluster size distribution
No cut on cluster size:
Trigger algorithm uses
cluster baricenter
Mean cluster size vs HV
Davide Piccolo - INFN Napoli
SIENA maggio 2004

34. Final test at CERN (ISR)
Chambers from
Bari, Pavia, Sofia  CERN
Chambers at ISR
116
Tested chambers 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
Test at ISR
Davide Piccolo - INFN Napoli
SIENA maggio 2004

35. Test at Cern up Down -total Forw Back Middle -total
Dark 9400 V. up
Down
-total mA
Forw
Back
Middle
-total
Cluster 9400 V.
Noise 9400 V.
Hz/cm2
Davide Piccolo - INFN Napoli
SIENA maggio 2004

36. Dark current stability
Suspicious chambers
Davide Piccolo - INFN Napoli
SIENA 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
Davide Piccolo - INFN Napoli
SIENA maggio 2004