(On Behalf of CMS Muon Group) Quality Control and Production Status of Large-area GEM Detectors for the CMS Muon Endcap Upgrade Mehdi Rahmani Dept. of Aerospace, Physics and Space Sciences, Florida Institute of Technology (On Behalf of CMS Muon Group)

Outline Introduction Detector Construction & Quality Control (QC) What is a GEM Detector? Why GEM Detectors for CMS? Detector Construction & Quality Control (QC) Construction of GE1/1 Prototypes for Large-Area GEM Detector Layout - Cleanroom QC2: GEM Foil Testing QC3: Gas Leak Test QC4: High Voltage Test QC5: Gain Measurements Gain Calibration Response Uniformity Effective Gain Analysis Across the sites Outlook

What is a GEM Detector? Kapton foil coated with copper on both sides that has an array of microscopic holes Inserted between a drift and a charge collection electrode HHV creates high E-field in GEM holes Ionizing collisions with the gas molecules filling the structure creating an avalanche of electron-ion pairs

What is a GEM Detector? Kapton foil coated with copper on both sides that has an array of microscopic holes Inserted between a drift and a charge collection electrode HV creates high E-field in GEM holes Ionizing collisions with the gas molecules filling the structure creating an avalanche of electron-ion pairs 300- 500 V

Why GEM Detectors for CMS High-Luminosity LHC CMS group will install large-area GEM detectors in the forward muon region Help to restore redundancy for tracking and triggering in muon system The combination of GEM+CSC Provides accurate measurement of the muon bending angle unaffected by multiple Scattering Can be used in the L1 muon trigger to reduce the soft muon rate

Why GEM Detectors for CMS High-Luminosity LHC CMS group will install large-area GEM detectors in the forward muon region Help to restore redundancy for tracking and triggering in muon system The combination of GEM+CSC Provides accurate measurement of the muon bending angle unaffected by multiple scattering Reduces L1 muon trigger rate due to soft muons View from the top of CMS down

Construction Steps a. Mounting inner frames b. Assembling three GEM foils c. GEM stack on the drift d. Stretching foils with tension e. Stretched foils in frames f. Mounting readout board

Example Assembly & QC Site Layout (FIT) Cleanroom Flow of work DAQ rack (SRS, HV) Detector storage Outside hospital GEM stack assembly QC4 Material receiving General work benches Inside hospital QC2 (slow)* QC2 (fast) Chamber assembly & QC3 workflow dashboard QC5 X-ray box

QC Step 2 : GEM Foil acceptance Fast test Applying 550 V to the GEM foils and measuring the leakage current between top and bottom electrodes The GEM foil is accepted if its impedance is above 10 GΩ, with relative humidity lower than 40% and the number of sparks per minutes is lower than 2/3 during the last three minute

QC Step 3: Gas Leak Test After pressurizing the chamber to 25mbar, the pressure drop should not exceed 6 mbar per hour. Data Taken By Student

QC Step 4: High Voltage Test Aims to determine the V vs. I curve for HV divider Identify possible malfunctions and defects in the HV circuit Look for any spurious pulses Detector under CO2 Ionizing particles can not ionize the CO2 as much We expect no signals. FIT0008 Data Taken By Student

QC Step 4: High Voltage Test Aims to determine the V vs. I curve for the HV divider Identify possible malfunctions and defects in the HV circuit Look for any spurious pulses Detector under CO2 Ionizing particles can not ionize the CO2 as much We expect no signals FIT0008 Data Taken By Student

QC Step 5a: Effective Gain FIT0009 Measure the gain vs. current in HV divider (prop. to applied voltage) using X-ray source The gas gain is measured via the anode current produced in the chamber during this irradiation Data Taken By Student Typical effective gain curve obtained during the GE1/1 quality control. Idivider is the pressure and temperature corrected current flowing through the HV resistive divider that provides potential to the detector electrodes

QC Step 5b: Gain Uniformity FIT0003 The response uniformity is performed at a gas gain of ≈ 600 using Ar/CO2 (70:30) Given the large area of the CMS GEM chambers, the uniformity of the detector response across the surface should be assured. A basic quantity to verify that is the pulse height across the detector. Work in progress

Site model & Achievements DISTRIBUTED PRODUCTION MODEL PRODUCTION SUMMARY Chambers for the first endcap (36 Super Chambers) are ready & qualified. Installation of the first endcap expected by July 2019. Production for the second endcap is ongoing. Total chamber assembly progress India USA (FIT) CERN Central site Italy PAK Total chamber validation progress. Belgium/Germany LHCP5 09/04/2019

Gain Comparison Analysis Work in progress

Outlook GE1/1 Installation for the first endcap is foreseen to take place in July 2019. Second endcap is going to be equipped with the GE1/1 detectors in early 2020. After second long shut down GE2/1 will be installed. Will begin operating GE1/1 in LHC Run 3 starting in 2021.

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