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DPF 2002, May 26th
Williamsburg, VA
Triple GEM Tracking Detectors for COMPASS
Klaus Dehmelt
DPF 2002 – K. Dehmelt – May, 26th
A COCOmmon MMuon and PProton AApparatus for SStructure and SSpectroscopy COMPASS
Measurement of Gluon polarization G/G due to cross-section differences (asymmetry) of open charm production(among other things)
ECAL1+2
-Wall 1+2
RICH
SM1+2
HCAL
TrackingPolarized
target
DC
MicroMegas
DPF 2002 – K. Dehmelt – May, 26th
A COCOmmon MMuon and PProton AApparatus for SStructure and SSpectroscopy COMPASS
Fixed Target Experiment
at SPS-CERN
ECAL1+2
-Wall 1+2
RICH
SM1+2
HCAL
TrackingPolarized
target
DC
MicroMegas
DPF 2002 – K. Dehmelt – May, 26th
ECAL1+2
-Wall 1+2
RICH
SM1+2
HCAL
TrackingPolarized
target
DC
MicroMegas
A COCOmmon MMuon and PProton AApparatus for SStructure and SSpectroscopy COMPASS
DPF 2002 – K. Dehmelt – May, 26th
Cover area up to ~20 cm around beam 7 stations with 14 detectors in 2001 10 stations with 20 detectors in 2002 Each station equipped with two Triple-GEM-detectors, rotated by 45º with respect to each other
Small Area Tracking (SAT) GEM (Gas Electron Multiplier)
DPF 2002 – K. Dehmelt – May, 26th
GEM - Basics
GEM structure: photolithography – etching(A. Gandi, R. de Oliveira)
DPF 2002 – K. Dehmelt – May, 26th
Applied potential difference U ~ 500V between electrodes
GEM - Basics
DPF 2002 – K. Dehmelt – May, 26th
COMPASS - GEMs
GEM: COMPASS design
Ar/CO2
(70/30)
DPF 2002 – K. Dehmelt – May, 26th
GEM: COMPASS design
COMPASS - GEMs
2-Dim Readout structure
DPF 2002 – K. Dehmelt – May, 26th
COMPASS - GEMs
GEM: COMPASS design
DPF 2002 – K. Dehmelt – May, 26th
Single cluster @ U0=4050 V
G ~ 8000
Triple-GEM properties
COMPASS - GEMs
DPF 2002 – K. Dehmelt – May, 26th
COMPASS - GEMs
Triple-GEM properties
DPF 2002 – K. Dehmelt – May, 26th
COMPASS - GEMs
Triple-GEM properties
Charge correlation ~ 1
Narrow correlation ~ 0.1
Resolve hit ambiguities
DPF 2002 – K. Dehmelt – May, 26th
COMPASS - GEMs
Triple-GEM properties
Absolute efficiency >98% @ G ~ 8000
DPF 2002 – K. Dehmelt – May, 26th
Triple-GEM properties
COMPASS - GEMs
Spatial resolution
< 50m
DPF 2002 – K. Dehmelt – May, 26th
Hit map: Positions of maximum clusters for each event (2.1 x 108
per spill)
COMPASS – GEMs Performance
DPF 2002 – K. Dehmelt – May, 26th
Hit map: Correlation
between two different
detectors, 0.5 m apart in beam
direction
(2.1 x 108 per spill)
COMPASS – GEMs Performance
DPF 2002 – K. Dehmelt – May, 26th
Summary
GEM detectors meet requirements for tracking devices in modern HEP experiments:
High rate capability
High spatial resolution
Large active area
Low material budget
No aging observed for COMPASS Triple GEM
GEM detectors will contribute to success of COMPASS
DPF 2002 – K. Dehmelt – May, 26th
The Group
B. Ketzer, M.C. Altunbas, K. Dehmelt,J. Ehlers, J. Friedrich, B. Grube,S. Kappler, I. Konorov, S. Paul,
A. Placci, L. Ropelewski, and F. Sauli