Transcript Slide 1

Beam Test of a Large-Area GEM Detector
Prototype for the Upgrade of the
CMS Muon Endcap System
Vallary Bhopatkar
M. Hohlmann, M. Phipps, J. Twigger, A. Zhang
Dept. of Physics and Space Sciences, Florida Institute of Technology
(for the CMS GEM Collaboration)
APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar
Outline
• Motivation
• Gas Electron Multiplier (GEM) Detectors
• Construction of GE1/1 Prototype III Large Area GEM Detector
• FNAL Test Beam Oct 2013: Setup and Measurements
• Detector performance in FNAL Test Beam
 Uniformity, Cluster Size, Efficiency
• Preliminary Tracking Results
 Correlation of GE 1/1 Detector with Trackers, Resolution
• Summary and Future Plans
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APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar
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Motivation
CMS Upgrade
View from the top of CMS down
Source: Worshop-Intro-Asharma-24-3-2014
 During the phase II
upgrade process of CMS
detector at CERN, we are
planning to install largearea GEM detectors in the
forward muon region.
 This installation will help
to restore redundancy for
tracking and triggering in
muon system.
 GEM detector can
sustain in high rate
environment, provides
precise tracking, which
improves muon
momentum resolution
and helps to maintain the
global muon trigger rate
 The combination of GEM+CSC can provide an accurate measurement of the muon bending angle
unaffected by multiple scattering, which can be used at the L1 trigger to reduce the soft muon rate.
 Florida Tech is planning to contribute to this upgrade project by producing and commissioning approximately
40 detectors. We constructed a first large-area GE1/1 GEM detector and studied its characteristics at a test
beam at Fermilab in Oct. 2013
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Gas Electron Multiplier Detector
 Micro Pattern Gas Detector (MPGD)
 GEM foil is a kapton foil coated with copper
on both sides that has an array of holes
(typically 140µm pitch)
 High voltage is applied across foils, which
creates avalanche of electrons through
holes
 Provides good efficiency and spatial
resolution
70µm
140µm
Source: http://gdd.web.cern.ch/GDD/
 Typical gas gain
of 104 with gas
mixture of Ar/CO2
Triple GEM configuration:
Most popular and reliable
Murtas, F.: “Development of a gaseous detector based
on Gas Electron Multiplier (GEM) Technology
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Source: http://www.flc.desy.de/tpc/basicsgem.php
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Construction of GE1/1 Prototype III Large-Area GEM
Detector at Florida Tech
Total assembly time 3 Hrs 40 mins with 2 people
Step I
GEM foils
assembly
with inner
frames
Stack of
GEM foils
with inner
frames
ready to
place on
drift
electrode
 Internal gap configuration of the
detector: 3/1/2/1mm
 GEM foils produced by single mask
etching technique at CERN
 Active area: approximately
99×(28-45)cm2
 “Largest GEM detector in existence"
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Stretched
GEM foils
with inner
and outer
frames
Step II
Stretching GEM
foils by providing
tension
Step III Finished GEM detector w/ APV frontend hybrids connected
Eta 8
7
6
5
4
3
2
1
1D readout board with 3,072 radial strips connected
through 24 Panasonic connectors to 24 APV hybrids
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FNAL Test Beam Oct 2013
Setup and Measurements
CMS GE1/1-III Detector
Trackers
Gas mixture used in all
detectors: Ar/CO2 70:30
Beam Energies:
1. Mixed hadrons: 32 GeV
2. Proton: 120 GeV
3 (10cm x 10cm) &
1 (50cm x 50cm) GEM
trackers with 2D readout
Trackers
area @ 4200V
DAQ with RD51 SRS
CMS detector tests:
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1. High voltage scan from
2900V to 3300V
2. Position Scan at 3250V
in 3 positions:
Upper row APV
Middle row APV
Lower row APV
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Basic Performance Characteristics of Detector
from FNAL Test Beam Data
Cluster Charge Distribution
Cluster Size at 3250V
Cluster Size vs. High Voltage
Cluster size
increases
with voltage
Cluster charge
distribution at 3250V
fitted with Landau
function
Charge Uniformity
 Average cluster size at
Detection Efficiency with
Different Cuts on Pedestal Widths
operating voltage is 2.4 strips
 At 3250V, most probable
values for all 3 APV position
are used to determine the
charge uniformity across the
detector:
At 3250V
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 Detection efficiency measured
with this detector is 97.8%
(with 5-sigma cut on pedestal
width).
Detection
Efficiency is
97.8%
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Preliminary Tracking Results
Reference Tracker and Correlations with CMS GE1/1 Detector
Correlation of GE1/1 detector hits
with hits in first tracker detector:
Beam Profile
120 GeV proton
Residuals of Tracker 1 in φ
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APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar
Tracker 4
Tracker 3
Exclusive
σ = 75µrad
Tracker 1
Inclusive
σ = 21µrad
Reference Detector resolution in φ
Tracker 2
32 GeV mixed-hadron
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Preliminary Tracking Results
Resolutions for CMS GEM Detector in Eta Sector 5
Inclusive Residual
σ = 92μrad in φ
Exclusive Residual
σ = 116μrad in φ
 This translates to residual widths of σ = 172 µm (inclusive) and σ = 217 µm (exclusive)
in the azimuthal direction (at the center of the eta sector 5) using R=1874 mm.
 Taking the geometric mean of exclusive and inclusive residual widths we find a
resolution of σ = 103 µrad (22% of strip pitch) which corresponds to σ = 193 µm in the
center of eta sector 5 when using the pulse-height sensitive analog readout
Resolution of the detector: σ = (103 ± 1) µrad (22% of strip pitch)
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Comparison of Resolution and
Detection Efficiency
Resolution
Best resolution is
obtained at the
efficiency plateau
(as expected)
Efficiency
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Summary
 The beam test at FNAL was successful as the performance of the
GE1/1 prototype large area detector meets the expectation.
 Detection efficiency of the detector is 97.8% in eta sector 5 and it is
consistent with all other sectors.
 Charge uniformity shows similar response for all three APV position.
 Spatial resolution improves with high voltage and gives the best value
when it reaches a plateau which corresponds to the efficiency plateau.
 Spatial resolution at 3250V of eta sector 5 is (103 ± 1) μrad which is
equivalent to 193 μm.
 Future work:
 Measure the spatial resolution of the other sectors of the GEM
detector.
 Measure eff. and res. with simulated binary-output electronics (as
planned for CMS upgrade).
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Thank You!
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Backup Slides
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Efficiency Measurement
• Studied the hit distribution, charge distribution and
cluster size for HV scan and Position scan
• Evaluates the efficiency from cluster multiplicity(CM)
Where, N1: No. of events with CM≥1 for given sector
N: Total no. of events
N2: sum of the no. of events with CM≥1 for other sectors
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Tracking
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