Transcript Document
Beam Test of a Large-area GEM Detector Prototype for the Upgrade of the CMS Muon Endcap System
V. Bhopatkar, M. Hohlmann, M. Phipps, J. Twigger, A. Zhang
Dept. of Physics and Space Sciences, Florida Institute of Technology, Melbourne, FL 32901, USA
(
for the CMS GEM Collaboration) Abstract Motivation
Gas Electron Multiplier (GEM) technology is being considered for the forward muon upgrade of the CMS experiment in Phase 2 of the CERN LHC. The first such implementation is planned for the GE1/1 system in the 1.5
<|η|<2.2 region of the muon endcap. With precise tracking and fast trigger information, this system can significantly improve the CMS muon trigger as shown previously in simulations. We assembled a 1m full-size prototype of a GE1/1 triple-GEM detector with 3,072 radial readout strips at Florida Tech and tested it in hadron beams at Fermilab in October 2013. Strip cluster parameters, detection efficiency, and spatial resolution for charged particles are studied with position and high voltage scans and at different inclination angles. Strip cluster sizes increase with high voltage. We find a plateau detection efficiency of (97.8
± 0.2)%. All eight eta sectors of the prototype detector show similar high efficiencies. Results of response uniformity and spatial resolution studies using four GEM-based reference tracking detectors are presented. Preliminary results show a spatial resolution of 97 µrad or 21% of strip pitch.
During the phase II upgrade process, we are planning to install large-area GEM detectors in muon region.
the forward GEM technology will improve overall muon trigger efficiency by providing fast triggering precise tracking information.
and Florida Tech is planning to contribute to this upgrade project by producing approximately 40 detectors. We constructed a first large-area GEM detector and studied its characteristics at a test beam at Fermilab in Oct. 2013
Construction of GE1/1 Prototype III Large-Area GEM Detector (at Florida Tech)
Step III: Finished GEM detector w/ APV frontend hybrids connected
Internal gap configuration of the detector: 3/1/2/1mm
Drift electrode 3mm 1mm 2mm 1mm GEM 1 GEM 2 GEM 3 Anode (readout)
GEM foils produced by single mask etching technique at CERN Active area: approximately 99 ×(28-45)cm 2
Step I: GEM foils assembly with inner frames Step II: Stretching GEM foils by providing tension Stretched GEM foils with inner and outer frames
Length 1m
1D readout board with
3,072 radial strips
connected through 24 Panasonic connectors to 24 APV hybrids
FNAL Test Beam Oct 2013 - Setup and Measurements
Gas mixture used in all detectors: Ar/CO 2 70:30
CMS GE1/1-III Detector Trackers
Beam Energies: 32 GeV mixed hadrons;120 GeV p 4 GEM trackers @ 4200V DAQ with RD51 SRS
Performance Characteristics from FNAL Test Beam Data
Cluster Charge Distribution Cluster charge distribution fitted with Landau function at 3250V Cluster Size at 3250V Cluster Size vs. High Voltage Cluster size increases with voltage
Trackers
CMS detector tests: 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
Reference Tracker and Correlations with CMS GE1/1 Detector
At 3250V, most probable values for all 3 APV position are used to determine the charge uniformity across the detector:
Charge Uniformity
Detection efficiency measured with this detector is 97.8% (with 5-sigma cut on pedestal width).
Beam profiles Tracking is done in three steps
:
At 3250V
Average cluster size at operating voltage is 2.3 strips
32 GeV mixed-hadron 120 GeV proton Residuals of Tracker 1
Step I - Alignment
: By iterating the shift parameters in X and Y, we center all detector residuals on zero and then with respect to the first reference tracker, we rotate the remaining three trackers until the residual widths are minimized.
Preliminary Tracking Results for CMS GE1/1-III
Exclusive Residual in Eta 5 Sector Detection Efficiency with Different Cuts on Pedestal Widths Detection Efficiency is 97.8% Inclusive Residual in Eta 5 Sector Inclusive σ = 21µrad Exclusive σ = 75µrad
Step II - Conversion from (x,y) to (r, φ) coordinate system:
Since we are dealing with radial readout strips in the GE1/1, it is more appropriate to use (r, φ) coordinates for tracking.
σ= 109 µrad in φ σ= 87 µrad in φ Reference detector resolutions in φ
Step III - Calculate final residuals (inclusive and exclusive) Correlation of GE1/1 detector hits with hits in first tracking detector:
This translates to residual widths of σ = 201 µm (exclusive) and σ = 160 µm (inclusive) in the azimuthal direction (at the center of the eta sector 5) using R=1850 mm.
Taking the geometric mean of exclusive and inclusive residual widths we find a resolution of
σ = 97µrad (21% of strip pitch)
which corresponds to σ = 179 µm in the center of eta sector 5 when using the pulse-height sensitive analog readout.