Beam Test of a Largearea GEM Detector Prototype

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 GE 1/1 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 1 m full -size prototype of a GE 1/1 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. Ø During the phase II upgrade process, we are planning to install large-area GEM detectors in the forward muon region. Ø GEM technology will improve overall muon trigger efficiency by providing fast triggering and precise tracking information. Ø 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 GE 1/1 Prototype III Large-Area GEM Detector (at Florida Tech) GEM 1 GEM 2 GEM 3 2 mm 1 mm Stretched GEM foils with inner and outer frames Step II: Stretching GEM foils by providing tension Anode (readout) Ø GEM foils produced by single mask etching technique at CERN Strip Pitch 1. 05 mm 3 mm Length 1 m Ø 1 D readout board with 3, 072 radial strips connected through 24 Panasonic connectors to 24 APV hybrids Ø Active area: approximately 99×(28 -45)cm 2 FNAL Test Beam Oct 2013 - Setup and Measurements Performance Characteristics from FNAL Test Beam Data Ø Gas mixture used in all detectors: Ar/CO 2 70: 30 CMS GE 1/1 -III Detector Trackers Ø DAQ with RD 51 SRS Trackers Cluster Charge Distribution Ø CMS detector tests: 1. High voltage scan from 2900 V to 3300 V 2. Position Scan at 3250 V in 3 positions: Cluster size increases with voltage Cluster charge distribution fitted with Landau function at 3250 V Ø At 3250 V, most probable values for all 3 APV position are used to determine the charge uniformity across the detector: Charge Uniformity Up per row APV Mid Reference Tracker and Correlations with CMS GE 1/1 Detector dle row APV Tracking is done in three steps: Beam profiles 120 Ge. V proton Residuals of Tracker 1 Inclusive σ = 21µrad Lo Ø Step I wer - Alignment: row APV 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. Ø Step II - Conversion from (x, y) to (r, φ) coordinate system: Since we are dealing with radial readout strips in the GE 1/1, it is more appropriate to use (r, φ) coordinates for tracking. Exclusive σ = 75µrad Ø Step III - Calculate final residuals (inclusive and exclusive) Correlation of GE 1/1 detector hits with hits in first tracking detector: Tracker 4 Tracker 3 Tracker 2 Tracker 1 Reference detector resolutions in φ Cluster Size vs. High Voltage Cluster Size at 3250 V Ø Beam Energies: 32 Ge. V mixed hadrons; 120 Ge. V p Ø 4 GEM trackers @ 4200 V 32 Ge. V mixed-hadron Strip Pitch 0. 67 mm Drift electrode 1 mm Step III: Finished GEM detector w/ APV frontend hybrids connected Step I: GEM foils assembly with inner frames Internal gap configuration of the detector: 3/1/2/1 mm Detection Efficiency with Different Cuts on Pedestal Widths Ø Detection efficiency measured with this detector is 97. 8% (with 5 -sigma cut on pedestal width). Detection Efficiency is 97. 8% Ø Average cluster size at operating voltage is 2. 3 strips At 3250 V Preliminary Tracking Results for CMS GE 1/1 -III Exclusive Residual in Eta 5 Sector σ= 109 µrad in φ y r a in m i l e Pr Inclusive Residual in Eta 5 Sector σ= 87 µrad in φ y r a in m i l e Pr Ø 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. Ø 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. Ø Conclusion: The performance of this GE 1/1 prototype in a beam meets expectations. CMS Upgrade week, Karlsruhe (Germany) - April 2014