Developments of micromegas detector at CERN/Saclay Shuoxing Wu 08-03-2010.
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Transcript of Developments of micromegas detector at CERN/Saclay Shuoxing Wu 08-03-2010.
Developments of micromegas detector at CERN/Saclay
Shuoxing Wu
08-03-2010
Outline:• Introduction to Micromegas detector 1. properties 2. main problem with micromegas• November test beam 1. test beam set up 2. current-voltage monitoring 3. offline analysis 4. spark topology
Part 1 Introduction to micromegas
Working principle
1 ) Conversion stage:
Ionization of gas by the charged particle which produces electron-ion pairs.Electrons directed by E1 (0.1 to 1 kV / cm) to the micro-grid, and cross the mesh holes.
2 ) Amplification stage:
E2 (≈ 50 kV/cm) >> E1 avalanche, electrons mulitplication.
High voltage 2
cathode
Micro-grille
High voltage 1
Anode strip
Anode plane
Incident charged particle
Avalanche
e-
Conversion gap
Amplification gap
Gas
E1
E2
Widely used in particle physics experiments:
Prototype for ILC-TPC:
Compass:
Prototype for ILC-DHCAL:
CAST@CERN:
The Upgrade of ATLAS muon spectrometer LHC upgrade
LSLHC~ 10 LLHC bunch crossing time:
50ns (25 ns) Critical regions in ATLA
S Muon Spectrometer: EI layers:
CSC (27 m2) EIS/L1 (54 m2) EIS/L2 (68 m2)
EM >2: EMS/L1 (85 m2)
6
Micromegas for ATLAS Muon upgrade
• Combine triggering and tracking functions• Matches required performances:
– Spatial resolution ~ 100 m – Good double track resolution– Time resolution ~ few ns– Efficiency > 98%– Rate capability > 5 kHz/cm2
• Potential for going to large areas (1 m x 2 m) with industrial processes – Cost effective– Robustness
7
Spark in micromegas and resistive coating solution:
-8
-6
-4
-2
0
2
4
6
8
0 0. 1 0. 210. 310. 41 0. 510. 610. 720. 820. 92 1. 021. 12Ti me/ us
Volt
age
drop
/V
A point charge being deposited at t=0, r=0, the charge density at (r,t) is a solution of the 2D telegraph equation. Only one parameter, RC (time per unit surface), links spread in space with time. R~1 M/ and C~1pF per pad area matches µs signal duration:
e tr RC
ttr
RC4
2
2),(
Micro-grid
Resistive film (kapton) or ink(1k-500MΩ/ )
Insulator (75 µm) AnodesMicro-grille
Resistive strip(few hundreds of kΩ/ )
Anodes
Anodes
Resistive pad(few tens of kΩ/ )
Micro-grille
Vacrel
Part2 November test beam
10
Test beam set up:• Telescope:
3 X-Y detectors(10 x 10 cm2) manufactured at Saclay
• Aim: Test different resistive films detectors manufactured
by Rui De Oliveira at CERN and compare behaviour to non-
resistive detectors
• Electronics: GASSIPLEX
• DAQ: realised by Demokritos
• Gas: 95%Ar + 3% CF4 + 2% isobutane
120 Gev π+
Y
ResistiveN
on-Resistive
X Y X X
Beam
1 mm 0.25 mm 1 mm
Detectors in test
YTested detectors:Standard bulk detectors; Resistive coating detectors; Segmented mesh detector
SPS-H6
Summary of tested detectors:Type Name Properties:
Standard bulk: SLHC3 1mm pitch
SLHC2 2mm pitch
Resistive coating:
R3&R4 2mm,2MΩ/ ,kapton+insulator
R5 2mm,250MΩ/ ,resistive paste
R6 1mm,400KΩ/ , resistive strip
R7 0.5mm, tens of KΩ/ , resistive pad
Segmented mesh
S1 1mm pitch,8 segmentations
12
Readout and online monitoring:
Data acquistion based on Labview: Monitoring through raw data by C++/Root code:
Maximum strip ID:
Charge spectrum:
13
Spark counting device:
MM detector
C=50 pF
R1=5,6 kΩ R2=5,6 kΩ
C=470 pF
HVmesh
Pre-amplifer
C=50 pF Voltage-Current monitoring PC
for standard ones for resistive ones
Different sparking behaviors of standard and resistive detector:
Standard SLHC2 (2mm) (@10KHz): R6(1mm,400kΩ/ resistive strip) (@10KHz):
SLHC2: HV=400 V (Gain ~3000): current when sparking < 0.4 A voltage drop< 5%R6: HV=390 V (Gain ~3000): current when sparking < 0.08 A voltage drop<0.5%
350
360
370
380
390
400
410
420
430
440
1 542 1083162421652706324737884329487054115952Spark number
Mesh voltage/V
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1Mesh current/ua
250
270
290
310
330
350
370
390
410
430
1 77 153 229 305 381 457 533 609 685 761 837 913 989 10651141121712931369144515211597Spark number
V
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1 uAMesh Vol tageMesh Current
Sparking behavior of resistive detector R3:
Standard SLHC2 (2mm) (@10KHz): Resistive R3(2mm,2MΩ/ ) (@10KHz):
SLHC2: HV=400 V (Gain ~3000): current when sparking < 0.4 A voltage drop< 5%R3: HV=410 V (Gain ~3000): current when sparking < 0.2 A voltage drop<2%
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1 301 601 901 120115011801210124012701300133013601Spark number
Mesh current
340
360
380
400
420
440
460
Mesh voltage
250
270
290
310
330
350
370
390
410
430
1 77 153 229 305 381 457 533 609 685 761 837 913 989 10651141121712931369144515211597Spark number
V
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1 uAMesh Vol tageMesh Current
250
270
290
310
330
350
370
390
410
1 92 183 274 365 456 547 638 729 820 911 1002109311841275136614571548
V
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Spark number
uAS1 mesh vol tageS1 mesh current
Sparking behavior of S1:
Seven,eight sparking
six sparking
five sparking
four sparking
three sparking
two sparking
one sparking
S1:Standard bulk: SLHC2
16
250
270
290
310
330
350
370
390
410
430
1 77 153 229 305 381 457 533 609 685 761 837 913 989 10651141121712931369144515211597Spark number
V
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1 uAMesh Vol tageMesh Current
Charge vs. channel ID:
17
1mm
1mm 1mm
1mm
250m
250m
R3
R6
Pedestal shift in standard MM (telescope) due to sparks.
No pedestal shift in resistive detectors (R3&R6).
Spark rate vs mesh voltage and beam intensity:
R3(2mm, 2MΩ/ ):
18
0. 00E+00
5. 00E-07
1. 00E-06
1. 50E-06
2. 00E-06
2. 50E-06
3. 00E-06
3. 50E-06
4. 00E-06
4. 50E-06
0 10 20 30 40 50Beam I ntensi ty/ KHz*cm-2
Spark rate
Spark rate= #sparks/#incident hadron
19
Detector type Spark rate Spark current /A
Voltage drop
SLHC2 Standard bulk 7*E-5 0.4 5%
R3 2 M Ω/
resistive kapton9.6*E-6 0.2 2%
R6 400K Ω/
resistive strip6.4*E-6 0.08 0.5%
R5 250 M Ω/
resistive paste1.6*E-4 0.1 1.5%
R7 tens of K Ω/
resistive pad5.9*E-4 0.35 4.5%
Detector performance at same gas gain (~3000):
Process to analysis the data:
1. Covert raw data into root tree
1. Decoding
2. Pedestal calculation and subtraction
3. Event filtering
4. Clusterization
5. Track reconstruction
6. Efficiency and spatial resolution studies based on the track
Binary data format:
1.run header (run ID, time, type, …..)
2. event loop:
Loop over 8 detectors: .number of active strips Strip loop: Word 1: 31 30 … 2 1 0
Word 2: 31 30 … 2 1 0...
Word NAS[det]:
3. run footer (event number, run end time….)
31 30 … 2 1 0
….
31 30 29 … 12 11 … 0
Ovf Vld strip data strip ID
Conversion from raw data into root tree:
‘Detector’ class:NofStrips; stripID;stripCharge;
Channel-pin relation
Decoding matrix:
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 3132 30 28 26 24 22 20 18 16 14 12 10 8 6 4 233 35 37 39 41 43 45 47 49 51 53 55 57 59 61 6364 62 60 58 56 54 52 50 48 46 44 42 40 38 36 3465 67 69 71 73 75 77 79 81 83 85 87 89 91 93 9596 94 92 90 88 86 84 82 80 78 76 74 72 70 68 66
1. Decoding:
Before decoding: After decoding:
Check decoding:
2.Pedestal calculation and subtractionCharge-ID distribution: Strip out of event: Strip within event:
Case of ‘noisy’ strip: Charge-ID distribution: Channel noise level:
3. Filter event: Based on the cut on pedestal sigma, only strips with charge larger t
han the threshold are kept.
threshold
4. Clusterization:
Strips with charge above the threshold form a ‘Cluster’( 1 gap is allowed). The cluster center is the charge-weighted barycentre of the strips, the cluster charge is the sum of strips charge within the cluster, cluster size is the number of strips within the cluster.
Number of clusters in one event: Cluster size:
1mm
1mm
1mm
1mm
1mm
1mm 1mm
1mm0.25mm
0.25mm 0.25mm
0.25mm
R3
R6
R3
R6
5. Track fitting:
y=a*x+b, a and b are determined by minimizing the chi-square.
Track angle X: Track angle Y:
R6 (1mm, 400KΩ/ ) efficiency :
>98%
drop<3%
29
@beam intensity of 11kHz/cm2: @voltage of 400V:
Resolution:
beam
MM
MM under test
MMMM
1mm 0.25 mm 1mm
•Residuals of MM cluster position and extrapolated track from MM telescope: •Convolution of: - Intrinsic MM resolution - Track resolution (extrapolated) ~68m
R6(1mm pitch, 400kΩ/ ) R3(2mm pitch, 2mΩ/ )
δ=112mδmm= 90±0.8m
δ=199mδmm= 187±1.9m
30
Resolution vs mesh voltage:
31
R6(1mm, 400kΩ/ resistive strip): R3(2mm, 2MΩ/ resistive kapton):
Pillars:Track position( with hit in test detector): Track position( without hit in test
detector):
32
Combination:
Cluster size:
33
R3 : 2mm , 2 M Ω/ Resistive kapton +insulator
R6 : 1mm , 400 k Ω/ Resistive stripSLHC2: 2mm standard bulk
Number of missing strips in cluster:R6( 1mm, 400 KΩ/ ): R3( 2mm, 2 mΩ/ ):
34
Probability to have missing strips in cluster and number of missing strips:
0
0. 2
0. 4
0. 6
0. 8
1
1. 2
1. 4
1. 6
1. 8
2
0 2 4 6 8 10Cl uster si ze/ stri p
Si ze
R6
R3
00. 10. 20. 30. 40. 50. 60. 70. 80. 9
1
0 5 10 15 20Cl uster si ze/ mm
Probabi l i ty
R6R3
35
Sparks in R7(few tens of kΩ/ Resistive pads):
36
All the ‘sparks’ in R7: Three ‘spark’ type:
‘Spark’ amplitude distribution:
Sparks in R5(250 MΩ/ Resistive kapton):
37
All the ‘sparks’ in R5:
‘Spark’ amplitude distribution:
Four ‘spark’ type:
Sparks in SLHC2(standard bulk):
38
All the ‘sparks’ in SLHC2: One ‘spark’ type:
‘Sparks’ amplitude distribution:
Sparks in R3(2 MΩ/ resistive kapton):
39
All ‘sparks’ in R3:
‘sparks’ amplitude distribution:
One ‘spark’ type:
Sparks in R6(400 kΩ/ resistive strip):
40
All ‘sparks’ in R6:
‘sparks’ amplitude distribution:
One ‘spark’ type:
Spark amplitude vs voltage and beam intensity:
0
0. 2
0. 4
0. 6
0. 8
1
1. 2
1. 4
1. 6
1. 8
2
375 380 385 390 395 400 405 410 415
Vol tage/ V
Spar
k am
plit
ude
mean
/V
0. 5
0. 52
0. 54
0. 56
0. 58
0. 6
0. 62
385 390 395 400 405 410 415
Vol tage/ V
Spar
k am
plit
ude
mean
/V5. 15
5. 2
5. 25
5. 3
5. 35
5. 4
5. 45
5. 5
5. 55
5. 6
370 380 390 400 410
R5 voltage: R7 voltage:
0
0. 1
0. 2
0. 3
0. 4
0. 5
0. 6
0. 7
380 390 400 410 420 430 440 450
Vol tage/ V
Spar
k am
plit
ude
mean
/V
0
0. 1
0. 2
0. 3
0. 4
0. 5
0. 6
0. 7
0. 8
360 370 380 390 400 410 420 430
Vol tage/ V
Spar
k am
plit
ude
mean
/V
0
0. 1
0. 2
0. 3
0. 4
0. 5
0. 6
0. 7
0 5 10 15 20 25 30 35 40 45Beam I ntensi ty
Spar
k am
plit
ude
mean
/V
SLHC2 voltage:
R3 intensity:R6 voltage:R3 voltage:
41
Conclusion:
• Today’s micromegas detector is facing the spark problem, resistive coating is a successful way to solve it.
• High efficiency achieved with a resistive strip detector R6.
• Good spatial resolution.