High-Resolution Micromegas Based Pion and MuonTelescope
Jona Bortfeldt,O. Biebel, R. Hertenberger, A. Ruschke, N. Tyler, A. Zibell
LS SchaileLudwig-Maximilians-Universitat Munich, Germany
9th RD51 Collaboration MeetingFebruary 21st 2012
Introduction
Motivation
� tracking telescope for test beams: high resolution, high efficiency,good double hit resolution, high rate capablity
� development & comissioning of muon tracking detectors
⇒ four 9× 10 cm2 Micromegas with 360 strips (non-resistive)
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 2 / 23
Introduction
Calibration Experiments
� H6: 120 GeV - 300 GeV π−
� H8: . 160 GeV µ−
� rates between 1/cm2s and 4.2 × 103/cm2s
� two Ar:CO2 gas mixtures 93:7 and 85:15
� perpendicular tracks and tracks under non-zero angles
� multiple amplification and drift voltages
� statistics: ∼ 6M pion and ∼ 14M muon tracks
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 3 / 23
Setup
Setup
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 4 / 23
Setup
Micromegas Setup & Functional Principle
-500V
-1000Vcathode
mesh
anode strips
position / timing timing
pillars 128μm
6mmAr:CO2
250μm 150μm
0.8kV/cm
39kV/cm
� ionization in 6 mm drift region
� gas amplification in 128 µm amplification region
� 90× 100 mm2, 360 copper strips (150 µm width and 250 µm pitch)
� gas: Ar:CO2 93:7, 85:15 @ NTP
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 5 / 23
Setup
Testbeam Setup
3 41 2
360mm
1200
mm
x yz
beamtrigger hodoscope trigger hodoscope
active active layerlayer
four Micromegasfour Micromegas � 4 Micromegas with 360strips each, all strips parallel
� trigger: 2×3 scintillators
→ 3rd coordinate
� readout by Gassiplexfrontends, 1500 channels intotal
� gas-flux ∼ 1 ln/h @1013 mbar stabilizedpressure
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 6 / 23
Setup
Testbeam Setup
3 41 2
360mm
1200
mm
x yz
beamtrigger hodoscope trigger hodoscope
active active layerlayer
four Micromegasfour Micromegas
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 6 / 23
Setup
Gassiplex Readout Electronics
frontend boards:
� 4× 16 analog channels, charge sensitive, multiplexing Gassiplex chips
� A/D conversion
RIO2: PowerPC for VME
� readout control
� software threshold comparison
� ∼ 400 Hz readout frequency
� multi-event buffering (4000 events per SPS spill)
� data transfer
DAQ computer:
� ssh interface to RIO2
� data storage
� slow control (HV, flux, pressure, temperature)
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 7 / 23
Setup
Gassiplex Readout Electronics
frontend boards:
� 4× 16 analog channels, charge sensitive, multiplexing Gassiplex chips
� A/D conversion
RIO2: PowerPC for VME
� readout control
� software threshold comparison
� ∼ 400 Hz readout frequency
� multi-event buffering (4000 events per SPS spill)
� data transfer
DAQ computer:
� ssh interface to RIO2
� data storage
� slow control (HV, flux, pressure, temperature)
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 7 / 23
Setup
Gassiplex Readout Electronics
frontend boards:
� 4× 16 analog channels, charge sensitive, multiplexing Gassiplex chips
� A/D conversion
RIO2: PowerPC for VME
� readout control
� software threshold comparison
� ∼ 400 Hz readout frequency
� multi-event buffering (4000 events per SPS spill)
� data transfer
DAQ computer:
� ssh interface to RIO2
� data storage
� slow control (HV, flux, pressure, temperature)
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 7 / 23
Setup
Trigger Latency
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 8 / 23
Setup
Efficiency & Drift Field
Ar:CO2 85:15
[kV/cm]driftE0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2
hit
eff
icie
ncy
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
hit efficiency for pions, Ar:CO2 85:15, Micom 1
= 42.2kV/cmampE
= 41.4kV/cmampE
= 40.6kV/cmampE
= 39.1kV/cmampE
Ar:CO2 93:7
[kV/cm]driftE0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2
hit
eff
icie
ncy
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
hit efficiency for muons, Ar:CO2 93:7, Micom 1
= 39.1kV/cmampE
= 38.3kV/cmampE
= 37.5kV/cmampE
= 36.7kV/cmampE
ε1 = #hit1234#hit234
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 9 / 23
Optimization
Optimization
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 10 / 23
Optimization
Optimization
� optimize readout electronics w.r.t. speed, pulse height, stability
� optimize efficiency
� investigate stability (sparking) in high-rate hadron and muon beams
� determine and investigate spatial resolution
� investigate gas properties (drift velocity, diffusion ↔ spatialresolution)
� optimize reconstruction algorithms
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 11 / 23
Optimization
Pulse Height & Drift Field
[kV/cm]driftE0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2
pu
lse
hei
gh
t [a
dc
chan
nel
s]
0
10
20
30
40
50
60
70
80
90
100
pulse height for pions, Ar:CO2 85:15, Micom 1
= 42.2kV/cmampE
= 41.4kV/cmampE
= 40.6kV/cmampE
= 39.1kV/cmampE
[kV/cm]driftE0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2
pu
lse
hei
gh
t [a
dc
chan
nel
s]0
10
20
30
40
50
60
70
80
90
100
pulse height for muons, Ar:CO2 93:7, Micom 1
= 39.1kV/cmampE
= 38.3kV/cmampE
= 37.5kV/cmampE
= 36.7kV/cmampE
� separation of e− & Ar+ high ↔ Ed high
� electric opacity of mesh low ↔ Ed low
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 12 / 23
Optimization
Sparks & Spark Counting
� discharges between mesh (-HV) and anode strips (ground), inducedby large ionisation clusters (> 1000e−)
� non destructive, dead time < 20ms
� detect the mesh recharge
� pions: spark probability ∼ 10−5 per particle, similar for all detectors
10M5.6k10M
10k
2nF
470pF
mesh
anode
low pass filter
spark counting
HV-supplyC~1nF
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 13 / 23
Optimization
Sparking in Pion- and Muonbeamspions:
� particle flux 4.2× 103/cm2s
� sparking dominated by incidentparticles→ similar for all detectors
� sparking probability ∼ 10−5/particle
� ∼ 2 sparks per SPS spill→< 0.4% deadtime→ negligible
muons:� particle flux > 4/cm2s� sparking dominated by small detector defects, factor 6 difference
between detectors� spark rates 1/30min to 1/5min →< 0.04% deadtime→ completely negligible
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 14 / 23
Optimization
Sparking in Pion- and Muonbeamspions:
� particle flux 4.2× 103/cm2s
� sparking dominated by incidentparticles→ similar for all detectors
� sparking probability ∼ 10−5/particle
� ∼ 2 sparks per SPS spill→< 0.4% deadtime→ negligible
muons:� particle flux > 4/cm2s� sparking dominated by small detector defects, factor 6 difference
between detectors� spark rates 1/30min to 1/5min →< 0.04% deadtime→ completely negligible
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 14 / 23
Optimization
Spatial Resolution & Drift Field
[kV/cm]driftE0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2
m]
µsp
atia
l res
olu
tio
n [
20
30
40
50
60
70
80
spatial resolution with pions, Ar:CO2 85:15
=42.2kV/cmampE
=41.4kV/cmampE
=40.6kV/cmampE
=39.1kV/cmampE
[kV/cm]driftE0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2
m]
µsp
atia
l res
olu
tio
n [
20
30
40
50
60
70
80
spatial resolution with muons, Ar:CO2 93:7
=39.1kV/cmampE
=38.3kV/cmampE
=37.5kV/cmampE
=36.7kV/cmampE
� decrease not only due to rising pulse height
� resolution ↔ number of electrons, entering the amplification gap
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 15 / 23
Analysis
Analysis
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 16 / 23
Analysis
Analysis Program
� calibration (every few hours)� update offsets for all channels from non-hit strips
� event loop� build charge clusters in all detectors, charge mean� extract data from the hodoscope� build first track by using the leading cluster in all detectors,
y -info from hodoscope� fit track (90% of all tracks)� in case of multiple clusters: use chain algorithm for matching clusters
in all detectors to the track (10%)� calculate residuals
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 17 / 23
Analysis
Single Detector Spatial Resolution I – Track Extrapolation
σtrack
σSR
σSR,ref
track reference
resid
xz
the method:
� extrapolate track from n − 1detectors into the nth
� determine residual betweenmeasured hit and trackprediction
� σ2resid = σ2track,n + σ2SRdetails:
� fit line x(z) = az + b to n − 1detectors ↔ minimizeχ2 =
∑n−1i=1
xi−azi−bσSR,i
→ a and b
� σtrack(z)2 =⟨
(x(z)− 〈x(z)〉)2⟩
= σtrack(z , σSR,i )2
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 18 / 23
Analysis
Single Detector Spatial Resolution II – 3 Layer Method
δ
r1
r3
r2
MM 1
MM 2
MM 3
MM 4
1
2
3d13
d12
� interpolate track prediction by twodetectors into 3rd and comparewith measured hit in that detector
� δ = r3 − r2d13d12− r1
(1− d13
d12
)→
(∆δ)2 = (∆r3)2 +(d13d12
∆r2)2
+[(1− d13
d12
)∆r1
]2� 4 ∆ri & 4 different
triplett-equations→ solvable system
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 19 / 23
Analysis
Single Detector Spatial Resolution III – NIMA 538, 372
� determine σin and σex, i.e. the residual for the detector included inthe fit and excluded respectively
� Carnegie et al.: spatial resolution σSR =√σin × σex
�
√55× 25µm = 37µm
resoutfit0mm0Entries 28990
Mean -0.008882
RMS 0.08524
/ ndf 2χ 255.6 / 62
Constant 6.2±735.4
Mean 0.000369±-0.009497
Sigma 0.00034±0.05456
-0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.40
100
200
300
400
500
600
700
800
resoutfit0mm0Entries 28990
Mean -0.008882
RMS 0.08524
/ ndf 2χ 255.6 / 62
Constant 6.2±735.4
Mean 0.000369±-0.009497
Sigma 0.00034±0.05456
residual, micom not in fit, t0, mm0
mµ=55exσ
Δx [mm]
resinfit0mm0Entries 28990
Mean 0.0009425
RMS 0.06027
/ ndf 2χ 330.6 / 31
Constant 13.4±1576
Mean 0.000165±-0.003273
Sigma 0.00015±0.02513
-0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.40
200
400
600
800
1000
1200
1400
1600
resinfit0mm0Entries 28990
Mean 0.0009425
RMS 0.06027
/ ndf 2χ 330.6 / 31
Constant 13.4±1576
Mean 0.000165±-0.003273
Sigma 0.00015±0.02513
residual, all micoms in fit, t0, mm0
mµ=25
Δx [mm]
inσ
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 20 / 23
Analysis
Comparison of the Three Methods
[kV/cm]driftE0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2
m]
µsp
atia
l res
olu
tio
n [
25
30
35
40
45
50
55
60
65
=42.2kV/cmamp
spatial resolution pions, 85:15, E
track extrapolation
3-Layer-Method
NIMA 538, 372
totcha0Entries 1428320
Mean 116.8
RMS 80.23
pulse height [adc channels]0 100 200 300 400 500
0
2000
4000
6000
8000
10000totcha0
Entries 1428320
Mean 116.8
RMS 80.23
pulse height for 160GeV muons
� method I and II equivalent
� method III tends to decrease the difference of spatial resolution fordifferent detectors (σSR,ref = 44± 2µm)
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 21 / 23
Analysis
Tracking Accuracy of the Telescope
distance [mm]-1000 -500 0 500 1000
un
cert
ain
ty [
mm
]
0
0.02
0.04
0.06
0.08
0.1
track uncertainty for 500mm length
distance [mm]-1000 -500 0 500 1000
un
cert
ain
ty [
mm
]
0
0.02
0.04
0.06
0.08
0.1
track uncertainty for 1000mm length
mµdetector resolution 35
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 22 / 23
Summary
Summary & Outlook
� stable operation in pure hadron and muon beam over weeks,pspark,π . 10−5
� optimization w.r.t. gas gain, drift field, trigger latency, readoutconfiguration
� single detector spatial resolution σopt ∼ 35µm⇒ overall tracking resolution σ ∼ 20µm
� track merging with additional DAQ systems possible (analog triggertag)
to do:
� upgrade to 2× 4 detectors
� upgrade to RIO3 VME controller →∼ 10 kHz trigger rate
� merge readout system with MT-Online (spring test beam)
� merge readout system with SRS and 50× 50 cm2 floating stripMicromegas (summer test beam)
Jona Bortfeldt (LMU Munich) Micromegas Telescope 21/02/2012 23 / 23