1. Status of MWPC production and quality control
Requirements on MWPC parameters
wire pitch and tension
gas tightness, dark current, gain uniformity
Status of MWPC production in each site
chambers assembled and production rate
problems during production
results of tests on gain uniformity
Other tests on chambers
tests at GIF
Material procurement
tests on panels and panel production rate
Logistics
plans to equip and to install chambers
test with cosmic rays
C. Forti – LHCC Comprehensive Review – CERN - 1 February 2005
The measure of the gas leakage, is obtained by correcting the DP(t) behavior by using the data of the reference chamber.

2. Quality controls: requirements on MWPC
Panel planarity  gas gap uniformity: 95% panel area in ± 90 mm
(5% in ± 180 mm) PANELS REJECTED~7%
Distance wire plane - cathode plane: PANELS REJECTED: negligible
 height of HV bars with respect to the cathode plane: mm ± 100 mm
Wire pitch: 95% in 2 mm ± 50 mm (5% in 2 mm ± 100 mm)
Wire tension: 50 ÷ 90 g WIRES CHANGED < 1‰
Tests on assembled chambers (results shown later for each site)
Small dark current (< kV
Gas tightness: DP < 2 mbar/hr
Gain uniformity: G0/1.7 < G < G0*1.7 (in 100% of each double-gap area)
(equivalent to the plateau width ± 80 V) with respect to the average gain G0.
The measure of the gas leakage, is obtained by correcting the DP(t) behavior by using the data of the reference chamber.

3. Measurement of the gain uniformity
Uniformity of the gap gain is measured with a radioactive source. The current drawn by each gap is monitored while the lead case containing the source is moved by means of a mechanical arm.
These measurements allow to check the gain uniformity within each gap and to compare different chambers among them.
The method used is similar in INFN and PNPI sites.
At CERN, where chambers are smaller, a fixed source is used.
Example of a result of the scan with radioactive source
Current (nA)
X position in the gap
Y position in the gap
The measure of the gas leakage, is obtained by correcting the DP(t) behavior by using the data of the reference chamber.

4. Classification criteria on gain average and uniformity
The HV plateau width is determined by the minimum efficiency and by the maximum average number of pad-hit.
From test-beams, these requirements define a ~170 V wide region
Each double-gap is classified in A,B,C classes according to:
< I(2-gap) >/1.4 < I(i) < < I(2-gap) >*1.4 (equivalent to ± 50 V range)
B. < I(2-gap) >/1.7 < I(i) < < I(2-gap) >*1.7 (equivalent to ± 80 V range)
C. Requirement B not satisfied  DV > 80 V
For each double-gap, we provide the class:
A = 100% of double-gap area in DV<50 V
B = 100% of double-gap area in DV<80 V
C = not satisfying criteria A and B
Chamber class:
AA,AB,BA=GOOD
BB=SPARE
BC,CB,CC=RESERVE

5. Status of production in LNF
M3R3: needed=48 (+4 spare). We have built 58 chambers
2 not usable: 1 leaks gas; 1 has probably a broken wire;
Test with source: 52 chambers very good (class A); 4 are good (class B)
M5R3: needed=48 (+4 spare). We have closed chamber 28 (Jan-28).
21 chambers have been tested and ALL satisfy the criteria:
gas leaks < 2mbar/hr; dark current< kV;
good gain uniformity: gain fluctuates not more than 40%
LNF will complete:
(52) M5R3 in April 2005
(52) M5R4 before the end
of the year
M5R3: High production rate chambers/week
Still to build:
(52) M1R3
(40) M1R4
~ 9 months

6. LNF-M3R3 gain uniformity
No equalization is applied
< I > = 456 (nA)
4 SPARE CHAMBERS (14, 39, 44, 58)
52 GOOD CHAMBERS

7. LNF-M5R3 gain uniformity
No equalization is applied
All 21 chambers are GOOD

8. Status of production in Ferrara
M2R3: needed=48 (+4 spare) 32 chambers closed (25-Jan-05)
Gas leakage: 29 chambers tested: all OK
HV training: 24 with dark current < kV / 3 with wire
pads drawing current
Test with 90Sr source (by hand) : 27 chambers tested  no evident problems
Test with 90Sr source (in Rome-2) : 5 chambers tested  all GOOD
Production rate increasing ch/week
Will complete: 52 M2R3 at end of ~ 2 ch/week
Comments:

9. Test of Ferrara chambers @ Roma-2: method
Source: 90Sr (8 mCi)  electrons of ~2.5 MeV Collimated ~2 mm diameter
Since the electrons are attenuated, the chamber has to be measured also
upside-down  the measurement takes 2 days.
AB CD

10. Ferrara-M2R3 gain uniformity
The 5 tested chambers are classified as GOOD

11. Status of production in Firenze
M5R4: needed=192 (+8 spare) = 148 (Firenze) + 52 (LNF)
21 chambers closed (26-Jan-05)
Gas leakage: 18 chambers tested / 3 leaking
HV training and test with source: 6 chambers tested / 2 rejected
The 4 accepted chambers have : dark current < kV
and GOOD gain uniformity
Will complete:(148) M5R4 in June ~ 2 ch/week
Production rate > 2 chambers/week
Then (70) M1R4 in ~ 7 months
In late with tests of chambers as we aimed to reach asap the maximum production speed. Now equipping a more powerful and efficient test facility (many HV channels, automatic source test, etc) and we are going to test quickly all chambers.

12. Firenze-M5R4 gain uniformity
The 4 tested chambers are classified as GOOD
Current factor
Source is 90Sr
5 mCi
3 current measurements for each wire pad
Correction factors for e- attenuation going from top to bottom gap.

13. Status of production in PNPI
M3R4: needed=192 (+8 spare).
Assembled 91 chambers (26-Jan)
Gas leak test: 46 tested OK; 45 not tested
HV test: 86 tested
Test with source: 76 tested  75 GOOD
Production rate 3-4 chambers/week
Still to build:
(~100) M3R4
(150) M2R4

14. Test with radioactive source in PNPI
76 chambers tested: 75 GOOD / 1 RESERVE
The measure of the gas leakage, is obtained by correcting the DP(t) behavior by using the data of the reference chamber.

15. Status of production at CERN
M3R1: needed=12 (+2 spare). Total chambers built=16.
All tested for gas leaks  OK
All trained for HV: dark current < 10 HV=2.9 kV
Gas gain uniformity: 14 chambers tested: All good (class A)
M3R2: needed=24 (+2 spare).
Closed chamber 21 on JAN-20.
20 tested for leaks (2 will be re-visited);
12 HV trained:no dark current;
no chamber tested for gain uniformity
CERN will complete:
(26) M3R2 in end-Jan 2005
Average rate increased after summer 2004
1  2 chambers/week
Main problems encountered ?
Man-power situation ?
Still to build:
40 M2R1/2
28 M4/5R1
26 M1R2

16. Test of CERN chambers with radioactive source: method
241Am source
All anodes connected together  ADC Amplitude spectrum
Cathode connected to the delay line  TDC  Pad location
So we developed a dedicated test station based on the following observation:
When we put an Americium source on our chamber we observe a peak in the amplitude distribution of the output signal.
This peak is produced by the 8 keV X-ray emitted when the copper (that we have in the cathode panel) is excited by the 60 keV gamma rays coming from the source.
These X-rays can induce photoelectric effect on the Ar in the gas and produced electrons of a few keV which have a range of less than 1 mm in the gas, so they are stopped. Of course, our chambers are not optimized for energy resolution so, the peak is very broad and on the top of it, you have the Compton spectrum coming from the 60 keV gamma rays always going through the chamber.
G0 is about 105
Delay line output
ADC spectrum
Time (ns)

17. Test of CERN chambers with radioactive source
12 chambers tested
All GOOD
So we developed a dedicated test station based on the following observation:
When we put an Americium source on our chamber we observe a peak in the amplitude distribution of the output signal.
This peak is produced by the 8 keV X-ray emitted when the copper (that we have in the cathode panel) is excited by the 60 keV gamma rays coming from the source.
These X-rays can induce photoelectric effect on the Ar in the gas and produced electrons of a few keV which have a range of less than 1 mm in the gas, so they are stopped. Of course, our chambers are not optimized for energy resolution so, the peak is very broad and on the top of it, you have the Compton spectrum coming from the 60 keV gamma rays always going through the chamber.
G0 is about 105

18. Tests at GIF of a LNF chamber
GIF: 137Cs and ~100 GeV muon beam
One M3R3 chamber (LNF) tested in July’04 (Public Note LHCb-MUON )
The effect of dead-time due to electronics can be
studied also for hottest region M1R2. This is not
true for the space-charge effect.
Reults for the LNF chamber:
e > 98% and time r.m.s. < 4 ns in the worst background conditions: HV>2.6 kV

19. Tests at GIF: 137Cs and ~100 GeV muon beam
One M3R3 chamber (LNF) tested in July’04 (Public Note LHCb-MUON )
The effect of dead-time due to electronics can be
studied also for hottest region M1R2. This is not
true for the space-charge effect.
Reults for the LNF four-gap chamber:
e > 98% and time r.m.s. < 4 ns in the worst background conditions: HV>2.6 kV

20. Material Procurement
Construction material – All the material has been ordered with some spare (10%)
Delivered material
PNPI – M3R4 – Panels 70% - HV bars 100% - FR4 frames 100%
PNPI – M2R4 – Panels 20% - HV bars 100% - FR4 frames 100%
PNPI – M4R4 – Panels 0% - HV bars 90% - FR4 frames 0%
CERN – Panels 60%
INFN – M3R3 completed – M2R3 ~ completed – M5R4 Panels 20%
HV bars ~ 40% FR4 frames 100% Other elements 100%
M1 panels 0%
Faraday cage – Final FEE board dimensions – M3R3 FC is ready – All the others need the preparation of drawings (M3R4-M2R3-M5R4+....)
Honeycomb panels - We got samples of M1R3/R4 regions, cut at the right
dimension and a quotation. Early 2005 we should go for the purchase and the production.

21. Panel production rate
A rate of 250/month is mandatory to match the chamber production schedule.
To monitor the production yield a data base on each INFN site is operational.
This tool helps also to have a more efficient chamber production.
The yield appears quite good: approximately 90% .
Panels needed according to official plan

22. Check of panel planarity and thickness
PANEL PLANARITY is checked (by hand) in each production site on ALL panels, before gluing the HV bars  7% OF PANELS REJECTED
PANEL THICKNESS is measured at the company over a production sample
 Requirement T=9.0 ± 0.2 mm  NO PANEL REJECTED
Automatic system by Roma2 nearly ready
Laser
Beam
Panel d1 d2
Thi
90 mm D
planarity < 90 mm (95% of panel area) < 180 mm (5% of panel area)

23. Preliminary plans to equip and to install chambers
Once the chamber have been tested with radioactive source, FEE electronics, LV and Faraday Cage must be assembled on chamber (and tested).
Part of this work will be done at the production sites (at LNF, for whole INFN, at PNPI and at CERN).
Probably, for PNPI chambers, electronics will be assembled at CERN.
The first chambers will be equipped as soon as the CARDIAC boards will be available.
Shipping of INFN chambers to CERN: in special trolleys with shock absorbers stocked in a container (see photo).
Shipping of PNPI chambers: in wooden boxes (CSC-CMS like)
Storage at CERN : about 200 m2 available (not so much)
Gas flux – last test with HV – Installation on the detector
We have yet to deploy a detailed plan for this part of the installation:
check the time and the personnel needed;
logistics at CERN and the infrastructure needed (gas, HV, etc...)
set up the procedures and the team for the installation on the detector (integration among various labs)

24. Trolleys and container for chamber storage and tranportation
Container with 6 trolleys of 18 chambers each = 108 chambers.

25. Test with cosmic rays (LNF)
The use of a cosmic ray stand allows to measure:
efficiency
time resolution
average hit-multiplicity
electronics noise
The system allows to house and test up to six chambers simultaneously (600 channels).
The trigger is given by three large scintillators (one above and two below the chambers) read out on both sides.The trigger rate is of about 15 Hz and its time resolution is about 2.8 ns.
time spectrum
We tested only few chambers, because we do not have still the final FEE. We plan to test all (or part of the) chambers, after the final FEE and the Faraday cage will be mounted on them.This is still
under discussion.
The measure of the gas leakage, is obtained by correcting the DP(t) behavior by using the data of the reference chamber.

26. Conclusions

27. Spare transparencies follow

28. MWPC cross-section In stations M2-M5 the detectors are four-gap MWPCs
2 chamber layers are connected into one front-end.
4 layers are combined into one station.

29. Master plan june 2004

30. Closing dates of M5R3 LNF chambers

31. Closing dates of M5R4 Firenze chambers

32. Closing dates of Ferrara chambers

33. Closing dates of M3R1 and M3R2 CERN chambers

34. Closing dates of PNPI-M3R4 chambers

35. Sensitivity of the performance on chamber imperfections
The drift velocity is saturated I.e. it has a very weak dependence on the electric field. Therefore we mainly worry about gas gain variations that can move the working point within the plateau.
If G0 is the nominal gas gain, we want the gas gain in 95% of the area of a single gap to be within G0/1.25 and G0*1.25 I. e between 0.8G0 and 1.25G0.
The remaining 5% of the area should have a gain within a factor 1.5 I.e.
between 0.67G0 and 1.5G0
A gain change of a factor 1.25(1.50) corresponds to Voltage change of 34(62)V on top of the 2750V corresponding to 1.25(2.25)%.
The gas gain changes by a factor 1.25(1.5) if the wire surface field changes by 1.25(2.25)%.
 What chamber imperfections are allowed in order to keep the wire surface field within 1.25(2.25)% ?

36. Quality controls: MWPC specifications
(From W. Riegler simulations, EDR – CERN – April 2003)
The drift velocity is saturated I.e. it has a very weak dependence on the electric field. Therefore we mainly worry about gas gain variations that can move the working point within the plateau.
If G0 is the nominal gas gain, requiring :
G0/1.25 < G < G0*1.25 (in 95% of the gap area)
G0/1.50 < G < G0*1.50 (in 5% of the gap area)
translates into specifications of
gap (panel planarity): 95% in ±90 mm 5% in ±180 mm
pitch: 95% in ±50 mm 5% in ±100 mm
wire y-offset: 95% in ±100 mm 5% in ±200 mm
wire plane y-offset: % in ±100 mm 5% in ±200 mm

37. Panel planarity  Gap uniformity  Gain uniformity
From simulations (W. Riegler): G0/1.25 < G < G0*1.25 
Gap = 5 mm ± 90 mm (95% of detector area) ± 180 mm (5% of detector area)
Since the gap is provided by the 5mm spacers placed between the panels,
along their frames, the gap uniformity is related to the uniformity of the panel
thickness and to its planarity.
The absolute value of the panel thickness is crucial only when a panel is
wired on both sides (CERN and PNPI), because the distances between the
wire planes and the panel surfaces depend on thickness.
The requirement is T=9.0 ± 0.2 mm
Panel thickness is measured at the company over a production sample and
fluctuates by ~ ± 20 mm
The maximum fluctuation of the spacer thickness is ± 10 mm.
Here also we checked a production sample.
The measure of the gas leakage, is obtained by correcting the DP(t) behavior by using the data of the reference chamber.

38. Panel measurement table Status report (R. Messi/E.Santovetti)d1 d2 D
Laser Beam
Panel
Thi = D-d1-d2
Thi
Measurement scheme
The system appear to be extremely solid and precise
The measurement of each point is repeatable at the level of ~ 10 m
RMS ~ 3 m
Max-min ~ 12 m

39. Wire pitch measurement
The wire position is precisely determined by the pitch of the wiring machine combs.The requirement on the wire pitch (WP) is:
WP = 2 mm ± 50 µm (95% of pitches) ± 100 µm (5% of pitches)
The WP is measured with an automatic device, based on two cameras scanning the panel. An accuracy of about 20 µm is obtained.
2 mm ± 50 µm  211 ± 5 pixels.
Sample image from scanning device
Fraction of wires with wrong pitch < 1 per mil
The measure of the gas leakage, is obtained by correcting the DP(t) behavior by using the data of the reference chamber.

40. Wire tension measurement (I)
The wire mechanical tension must be in the range 50÷90 g in order to provide a good electrostatic stability. The tension is found by measuring the wire resonance frequency. Different methods are used.
LNF: oscillations of the wire to be tested are induced by applying a periodic
HV (about 900 V) with a frequency of 300 ÷ 400 Hz, between the wire and a
non-oscillating sense wire parallel and close (~1 mm) to it. As a consequence,
the capacitance C between the two wires oscillates. The maximum variation
of C occurs at the resonance of the wire.
Resolution is ~1 g and a M3R3 panel (660 wires) is measured in < 1 hour.
The measure of the gas leakage, is obtained by correcting the DP(t) behavior by using the data of the reference chamber.

41. Wire Tension Measurement (II)
Laser
Photodiode
wire
Mechanical excitation
Panel
This method has been developed together with Firenze and Roma II
Laser
Mechanical
Excitation
Photodiode
The signal is sent to a PC soundcard, a FFT is applied.
The resonance frequency is searched between 310 and 600 Hz (for M2R3 panels).
The measurement takes about 2 sec/wire ( 2 panels ~1200 wires in 40 min )

42. Gas leakage test (I)
In order to minimize the gas refill rate, the maximum leakage allowed for each chamber is 2 mbar/h.
To verify the gas tightness of a chamber, we inflate it with nitrogen up to an overpressure DP of 5 mbar.
Then, we record DP as a function of time, during about one hour.
The measurement is sensitive to variations of the external temperature. In order to correct this effect, a second chamber is used as a reference.
The measure of the gas leakage, is obtained by correcting the DP(t) behavior by using the data of the reference chamber.

43. Gas leakage test (II)
The measure of the gas leakage, is obtained by correcting the DP(t) behavior by using the data of the reference chamber.
If a chamber leaks, usually we can recover it by putting glue all around
the chamber, between each pair of panels.
For example, in LNF, over 84 chambers produced (58 M3R3+26M5R3), only one was not recovered.
The measure of the gas leakage, is obtained by correcting the DP(t) behavior by using the data of the reference chamber.

44. HV training and Dark current
Procedure for conditioning of the chambers:
Start with HV+ and go to HV at which the current reaches nA and does
not show the tendency to fast decrease (Normally this kV)
2) Switch to HV- and start from HV=0 to increase first quite fast (200 V/min)
up to 1.5 kV.
3) Increase HV slowly till the current jumps to some value which SHOULD NEVER
EXCEED 3-4 mA.
4) Stop and wait till current drops to nA. Normally this takes small time.
Then make the next step (~100 V) and so on.
The training stops at HV= 2.15 kV.
The procedure with the inverse polarity takes not more than one hour.
After that they go to the normal polarity. In most cases HV=2.95 kV can be reached
after such training. If not, a second round with the inverse polarity can be performed.
Anyhow, the whole procedure allows to reach 2.95 kV in one day.
LNF : all chambers with dark current < 2.85 kV
PNPI : all chambers < 2.95kV [Ar(40)/CO2(50)/CF4(10)]

45. Gain average and uniformity
The goal: to have all detector area within the HV plateau defined by the minimum efficiency and by the maximum cluster size
M1: the chamber is a double-gap; the efficiency must be e > 99%
The double-gap average n. of hits must be < 1.2
M2-M5: the chamber is a 4-gap; the efficiency of each double-gap must be e > 95%. The 4-gap average n. of hits must be < 1.2
From testbeam of LNF chambers, these requirements define the following 170 V wide regions:
M1: 2720 ± 85 V
M2-M5: 2620 ± 85 V

46. Test with radioactive source in PNPI: method
The measurements are performed using a 9 mCi source with a rectangular collimator. The size of the collimator slit is 10x1 cm2.
In regular measurements the slit is adjusted to be parallel to the wire direction.The source is moved along the central part of the chamber.
The chambers are operated at HV=2.7 kV with the gas mixture Ar(40)/CO2(50)/CF4(10).
The ionization current is measured with the gamma source positioned at each pad of the chamber. The dark current is subtracted.
The measure of the gas leakage, is obtained by correcting the DP(t) behavior by using the data of the reference chamber.

47. Last update: December 17, 2004, 3:21 pm
Chamber production Overview
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Shows chambers.
Last update: December 17, 2004, 3:21 pm
M5R3 Chamber 14
LNF results:
58 chambers M3R3: 1 leaks; 1 broken GIF (?); 39 AA; 13 AB/BA; 4 BB
21 chambers M5R3: all AA

48. Plateau width (M2-M5)
From testbeams: plateau width=170 V for bigaps; 150 V for 4-gaps
Lower plateau limits: 95% for bigap (2.53 kV) / 99% quadrigap (2.55 kV)
Upper limit: cluster size in quadrigap < 1.2  HV <2.7 kV
(calculated from oct’03 results on the bigaps)
GIF july ’04: 4-GAP
2.62 ± kV
99%
Testbeam oct. ’03: BIGAP

49. Plateau width (M1) Work point ~ 2.72 kV Plateau width ~ 170 V
FROM OCT’03 (BIGAP): Upper limit: cluster size =1.2; in bigap HV~2.82 kV
FROM GIF: Lower plateau limit: e=99% in double-monogap  HV=2.65 kV
Work point ~ 2.72 kV Plateau width ~ 170 V
Testbeam oct. ’03 : BIGAP
GIF july ’04: DOUBLE-MONOGAP