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Construction and Quality Control of Large-Scale GEM Detectors for CMS Prototype II

This report details the construction and quality assurance processes of six large-scale GEM detectors developed under the GEM collaboration for the CMS experiment. It outlines the assembly techniques for prototypes, including the installation of GND connectors and adjustment screws. Quality control measures on GEM foils involve applying high voltage and measuring leakage currents to ensure performance meets specifications. The report highlights improvements in mechanical assembly processes and the availability of tools for assessing gain uniformity across various sectors.

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Construction and Quality Control of Large-Scale GEM Detectors for CMS Prototype II

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  1. Construction and Quality control of large scale GEM detectors On behalf on the collaboration GEM for CMS

  2. Status Prototype II Prototype I New NS2 technicassembly 4 prototypes produced

  3. NS2 assemblytechnic Readout connector 10 to 15mm GND O-ring Free to slide GND Drift electrode External screws to adjust stretching GEM attaching structure (4 pieces defining gaps) Embedded nut O-ring Rui De Oliveira GEM workshop IV

  4. GEM stackready

  5. Inserting drift board

  6. Install pullingscrews • Install 50 pullingscrews

  7. Oring installation

  8. Closingwithreadoutboard • Colsingwith the readoutboard 50 screws.

  9. Producing 6 new NS2 Large scale detectors External frame Produced in severalpieces, thengluedtogether. GEM foils ready, waiting for the readout and drift boards. Assemblynextweek.

  10. GEM foils quality control • Sector to test from -50V to -500V by step of 50V. • High voltage applied on the top, bottom and first neighborssectorsconnected to ground. • Measuring the leakagecurrent

  11. Expectedleakagecurrent • Kaptonresisitvity ~1019ohm.m • Air resistivity ~1016ohm.m • R// = Rkaptonx Rair / (Rkapton+Rair) • R//(60µm)~1016 x 60.10-6= 6. 1011ohm • Iexpected~ 500/ R//(60µm)= 0.8 nA Leakagecurrent RKapton Rair HV (-500V)

  12. RESULTS HV (Volts) HV (Volts) GEM1 I (nA) I (nA) HV (Volts) HV (Volts) GEM2 I (nA) I (nA)

  13. Gain Uniformity Control Set up

  14. Eta Sector 4 Peak Position (ADC counts) 15 slices ->1 slice ~ 3cm X Position (mm)

  15. Eta Sector 5 Peak Position (ADC counts) X Position (mm)

  16. Eta Sector 6 Peak Position (ADC counts) X Position (mm)

  17. Eta Sector 7 Peak Position (ADC counts) X Position (mm)

  18. Eta Sector 8 Peak Position (ADC counts) X Position (mm)

  19. Slice N°1

  20. Slice N°2

  21. Uniformity Plot PeakPosition Variation (%)

  22. Uniformity TOP view

  23. Conclusion • Construction of 6 large scale production prototypes isgoing on • Improvements made on mechanicalassembly (NS2 technic and flat boards) • Powerfulltool to check gain uniformityisavailable

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