high-resolution micromegas based pion and muon telescope · sr,ref = 44 2 m) jona bortfeldt (lmu...

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


Setup

Setup


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


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


Setup

Testbeam Setup

3 41 2

360mm

1200

mm

x yz

beamtrigger hodoscope trigger hodoscope

active active layerlayer

four Micromegasfour Micromegas


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)


Setup

Trigger Latency


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


Optimization

Optimization


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


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


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


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


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


Analysis

Analysis


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


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


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


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


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)


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


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)


high-resolution micromegas based pion and muon telescope · sr,ref = 44 2 m) jona bortfeldt (lmu...

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