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
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 23-26 maggio 2004
RPCs as trigger detector
Pattern of fired strips
is compared to predefined
patterns corresponding to specific Pt
Davide Piccolo - INFN
Napoli
SIENA 23-26 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
Backward UP
Forward Down
Backward Down
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
Chamber production
CERN
Several steps are
Pavia
ISR
involved in the
chamber production.
PanPla
Sofia
Bari
GT
HT: Napoli
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
Chamber production
Bakelite is produced
at PanPla factory
Pavia
PanPla factory
Bakelite production
and QC
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
PanPla
Chamber production
Single gaps and
Double gaps produced
at General Tecnica
factory
General Tecnica
Bari
Single gap
GT
Double gap
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
Chamber production
RB1
RB2
RB3
RB4
assembled in
assembled in
assembled in
assembled in
HT (napoli)
GT
Bari and Sofia
GT
Sofia
Chamber assembly
Bari
GT
HT: Napoli
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
Chamber test (phase I)
RB1 tested in Pavia
RB2/RB4 tested in Bari
RB3 tested in Sofia
Pavia
Sofia
Cosmic ray test
Davide Piccolo - INFN
Napoli
Bari
SIENA 23-26 maggio 2004
Chamber test (phase II)
CERN
Pavia
ISR
Sofia
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
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
Bari
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
Davide Piccolo - INFN
Napoli
• humidity and temperature monitored
SIENA 23-26 maggio 2004
Bakelite production (.. Continue)
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
Bakelite resistivity distribution
Accepted bakelite plates
between 1 and 6 1010 •cm
bakelite
resitivity
accepted
Resistivity is corrected for temperature
dependency according to:
(T)/(20) = e -(T-20)/7.8
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
Resitivity
precision
Bakelite coupling in RPCs
Resistivity Difference
Between gap electrodes
Bakelite plates
with similar resistivity
are coupled together
Davide Piccolo - INFN
Napoli
Average Resistivity
of gap electrodes
SIENA 23-26 maggio 2004
Single gap production
Single gaps
are produced
at General
Tecnica
Updated to may 15
Produced
1655
Accepted
1082
Rejected
283
Under test
265
Spare/on wait
25
Davide Piccolo - INFN
Napoli
Critical issues:
•
Spacers gluing
•
Oiling
-
-
problem has been solved washing
and brushing bakelite surface
with dimethylketon
good quality, rpcs are opened one per
sample to check quality of the surfaces
Total to install
2040
Accepted
1082
Accepted/To install
53.04 %
SIENA 23-26 maggio 2004
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
Davide Piccolo - INFN
Napoli
Bring the SG at 9500V and measure
the current:
reject if I > 5 A
SIENA 23-26 maggio 2004
Single gap QC results
Rejections
Pressure test
and leak test
188
66 %
HV test
95
34 %
cut
Rejected sg
Spacers already detached
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
Overpressure (mbar)
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
Produced
501
Accepted
458
Rejected
15
Spare/On wait
3
Davide Piccolo - INFN
Napoli
Total to install
1020
Acceped
458
Accepted/to install
44.90 %
SIENA 23-26 maggio 2004
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 23-26 maggio 2004
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
Davide Piccolo - INFN
Napoli
Average current absorbed by
a SG (in DG) after PET:
0.83 µA @ 8 kV
SIENA 23-26 maggio 2004
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
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
Chamber assembly QC
Chambers assembled in several sites:
RB1 in HT near Napoli
RB2 in GT
RB3 in Bari and now in Sofia
RB4 in GT
Double gaps inventory
assembly
Cooling system test
Gas flow test
QC during assembly
electronic test
Kapton-FEB
connectivity test
Status of production:
Chamber
type
assembled
Assembled/total
RB1
52
43 %
RB2
45
37.5 %
RB3
54
45 %
RB4
14
12 %
Davide Piccolo - INFN
Napoli
Check list filling
QC after assembly
HV test:
I vs HV
I vs time
Noise rate strip by strip
DB update
SIENA 23-26 maggio 2004
QC results at HT
HV scan
4
Chamber accepted if:
9500 V
forw up
forw down
back up
back down
3,5
3
9200 V
9000 V
• <I(@9500V)> < 5 A per gap,
• I not increasing in one hour
• (I) < 1 A per gap.
8000 V
2,5
6000 V
5000 V
1,5
4000 V
3000 V
1
CHAMBER 173
2000 V
1000 V
4,5
0,5
4
3,5
321
311
301
291
281
271
261
251
241
231
221
211
201
191
181
171
161
151
141
131
121
111
91
101
81
71
61
51
41
31
21
1
0
11
time (10 sec)
ant sup
ant inf
post sup
post inf
3
For each HV point
measure average and
rms of current
I (uA)
2,5
2
Temp 22 degrees
1,5
1
0,5
HV (Volts)
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
316
307
298
289
280
271
262
253
244
235
226
217
208
199
190
181
172
163
154
145
136
127
118
109
91
100
82
73
64
55
46
37
28
19
1
0
10
I (uA)
7000 V
2
cut
Average
current
Davide Piccolo - INFN
Napoli
Gas mixture used in
assembling sites:
C2H2F4 96 %
Iso_C4H10 4 %
Number of gaps
Number of gaps
Selection criteria on assembled chamber
SIENA 23-26 maggio 2004
rms
current
cut
Problems during assembly
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
Cosmics tests
Final test with cosmic rays in Bari, Pavia, Sofia.
BARI test site
(10 slots)
Gas mixture
Davide Piccolo - INFN
Napoli
Pavia test site
(5 slots)
SF6 ..…… 0.3 %
I-C4H10 .. 3.5 %
C2H2F4 … 96.2 %
SIENA 23-26 maggio 2004
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
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
Some results
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
Efficiency distribution: summary
<>dg = 97 %
<>sg = 95 %
Double gaps
Single gaps
Maximum Efficiency
50 % Efficiency HV
Corrected
For T and P
Double gaps
Single gaps
Davide Piccolo - INFN
Napoli
SIENA 23-26 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)
Work in progress
Shift due to
geometry and
sample purity
Tracking
No tracking
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
Dark current distribution
Current of
2 gaps
Dark current
at working voltage
9400 Volts
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
Noise rate distribution
Average single
rate at 9400 V.
Double gaps
Single gaps
Davide Piccolo - INFN
Napoli
Most of these rates
are due to a single
noisy channel.
Chamber accepted
SIENA 23-26 maggio 2004
Cluster size distribution
Mean cluster
size at 9400 V.
No cut on cluster size:
Trigger algorithm uses
cluster baricenter
Mean cluster size vs HV
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
Final test at CERN (ISR)
Chambers from
Bari, Pavia, Sofia  CERN
Storage/test area
Test at ISR
Davide Piccolo - INFN
Napoli
Chambers at ISR
116
Tested chambers at ISR
59
Under observation
1
Rejected
5
• I vs. V
• Noise rate
• Cluster size
• Current stability for ~30 days
• Chambers suspicious have been
monitored for > 1 month
• Upgrade: cosmics test
SIENA 23-26 maggio 2004
Test at Cern
HV not corrected
for T and P
Dark current @ 9400 V.
•up
•Down
-total
A
Noise rate @ 9400 V.
•Forw
•Back
•Middle
-total
Hz/cm2
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
Cluster size @ 9400 V.
Dark current stability
Suspicious chambers
Davide Piccolo - INFN
Napoli
SIENA 23-26 maggio 2004
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 23-26 maggio 2004