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Mehdi Rahmani Dept. of Physics and Space Sciences, Florida Institute of Technology

Quality Control of the Large-area GEM detectors at Production Sites for the CMS Muon Endcap Upgrade. Mehdi Rahmani Dept. of Physics and Space Sciences, Florida Institute of Technology (On Behalf of CMS Muon Group). APS April Meeting 2017, Washington, DC. 1. Outline. Introduction

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Mehdi Rahmani Dept. of Physics and Space Sciences, Florida Institute of Technology

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  1. Quality Control of the Large-area GEM detectors at Production Sites for the CMS Muon Endcap Upgrade Mehdi Rahmani Dept. of Physics and Space Sciences, Florida Institute of Technology (On Behalf of CMS Muon Group) APS April Meeting 2017, Washington, DC 1

  2. Outline • Introduction • 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 • Summary & Conclusion 2

  3. Introduction • What is a GEM detector? • GEM foil is a Kapton foil coated with copper on both sides that has an array of microscopic holes (typically 140µm pitch). • These foils are inserted between a drift and a charge collection electrode. • By application of the right potentials on the foils, a high electric field will be developed in the GEM holes. • Electrons released in the upper region drift towards the holes and acquire sufficient energy in the holes to cause ionizing collisions with the gas molecules filling the structure creating an avalanche of electron-ion pairs. - 300- 500 V + 3

  4. Introduction • Why GEM Detectors for CMS? • During the phase II upgrade of the CMS detector at CERN for the High-Luminosity LHC, CMS group will install large-area GEM detectors in the forward muon region • This installation will help to restore redundancy for tracking and triggering in muon system. • GEM detector can operate in a high-rate environment, provides precise tracking, which improves muon momentum resolution. • The combination of GEM+CSC )Cathode Strip Chambers( can provide an accurate measurement of the muon bending angle unaffected by multiple scattering, which can be used in the L1 muon trigger to reduce the soft muon rate. • A QC procedure has to be developed to ensure a successful production run. 160 1-meter long GEM detectors will be produced. They are scheduled to be installed in the CMS endcap in 2019. 4

  5. Slice Test Slice test: • Install 50°coverage on one endcap of CMS built 10 detectors for installation. • The detectors are installed at 3 o'clock and 6 o'clock positions. 5

  6. Construction c. GEM stack on the drift a. Mounting inner frames b. Assembling three GEM foils e. Stretched foils in frames d. Stretching foils with tension f. Mounting readout board 6

  7. Example Assembly & QC Site Layout (FIT) • Because of the small holes (70 μm hole diameter) in the GEM foils, we can’t expose them to unfiltered air because otherwise dust might get into the holes and cause electrical shorts in the foil. • For example, at Florida Tech we have a class 1000 clean room. CO2 7

  8. QC Step 2 : GEM Foil Acceptance QC2_Long_FIT_Foil2_V Long test Monitoring the leakage current and any possible sparks: • HV  (600V(. • Period 30 minutes - 1hour • The foils  Plexiglass box filled with pure nitrogen. The GEM foils are accepted if the mean current is below 5 n amps. ________________________________________________________ Fast test Applying voltage 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 spark per minutes is lower than 2/3 during the last three minutes. Data Taken By Student 8

  9. QC Step 3: Gas Leak Test 1. Calibration of leak-check system • After pressurizing the chamber to 25mbar, the pressure drop should not exceed 1 mbar per hour. FIT_QC3_V 2. Leak measurement of detector Preliminary Setup GE1/1 Quality Control : instructions Michele Bianco, Brian Dorney, Jeremie A. Merlin CERNOn behalf of the CMS GEM Collaboration September 28, 2016 Data Taken By Student 9

  10. QC Step 4: High Voltage Test • Detector under CO2 High voltage can not ionize the CO2 so we expect to see no signals. If we any signals we consider them as spurious signal. • The QC4 test aims to determine the V vs. I curve and rate of a GE1/1 detector and identify possible malfunctions, defects in the HV circuit, and spurious signals. Preliminary Setup GE1/1 Quality Control : instructions Michele Bianco, Brian Dorney, Jeremie A. Merlin CERNOn behalf of the CMS GEM Collaboration September 28, 2016 Data Taken By Student 10

  11. QC Step 5a: Effective Gain • In order to confirm the high-rate capability of the GE1/1, we measure the gain vs. Incident rate using X-ray source. The gas gain is measured via the anode current produced in the chamber during this irradiation QC5_FIT_V Data Taken By Student 11

  12. QC Step 5b: Gain Uniformity • The camber response analysis routine produces an x-y color map of pulse height information. • The response uniformity is performed at a gas gain of ≈ 600 using Ar/CO2 (70:30) in all sites. • 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 gain of the detector. • Mass produced chambers are accepted if their response is within 15% of the average and efficiency is more than 97%. 12

  13. Summary and Conclusion • In order to cope with the harsh environment expected at the high-luminosity LHC, the CMS forward muon system requires an upgrade. • Following an extensive R&D program, CMS has identified triple-foil gas electron multiplier (GEM) detectors as a solution. • These detector will be constructed and quality controlled at CERN and at five external sites. • A stringent quality control procedure has been developed to ensure a successful production run. A total of 160 1-meter long GEM detectors will be produced. They are scheduled to be installed in the CMS endcap in 2019. • At Florida Tech we implemented all the Quality Control systems and successfully took a GE1/1-V GEM prototype through all QC steps. • As a conclusion, the quality controls procedures are being implemented and all sites are on schedule for 2019 installation. 13

  14. Pre-mass-production Steps • All Sites must take an old generation GE1/1 chamber through all QC steps and produce all deliverables compatible with CERN instructions. • Stage 1-QC3 to QC5 effective gain-Deliverables reviewed by collaboration • Stage 2- QC2 (fast) to QC5 effective gain + QC5 gain uniformity- Deliverables reviewed by collaboration + clean room status review-visit checkout on sites- Shipment of GE1/1 kit • Stage 3- Repeat QC2 to QC5, including assembly- Deliverables reviewed by collaboration- Final validation by collaboration Backup Slide 14

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