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UTA GEM updates J.Li, A.White, J.Yu 5/9/02

UTA GEM updates J.Li, A.White, J.Yu 5/9/02. Preparations for prototype construction. Test GEM “chamber” designed at UTA - allows varying layer configurations - straightforward gas, HV etc. Main issue is acquisition of GEM foils - contact with GEM inventor, F.Sauli, CERN .

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UTA GEM updates J.Li, A.White, J.Yu 5/9/02

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  1. UTA GEM updates J.Li, A.White, J.Yu 5/9/02

  2. Preparations for prototype construction • Test GEM “chamber” designed at UTA - allows varying layer configurations - straightforward gas, HV etc. • Main issue is acquisition of GEM foils - contact with GEM inventor, F.Sauli, CERN 

  3. GEM test chamber J.Li, UTA

  4. Most foilsmade in CERN printed circuit workshop • Approximately 1,000 foils made • Big project for COMPASS expt. 31x31 cm2 foils • Most difficult step is kapton etching – Sauli has offered to reveal “trade secrets” in context of formal collaboration. • Fastest route – buy a few foils from Sauli: • 10x10 cm2 foils 70m holes 140m pitch ~$300 • - Foils HV tested/verified at CERN.

  5. Sauli - procure a fully assembled, dismountable detector for us…but prefer our design • Also… Edik Tsyganov at UT Southwestern Med. has working multi-gem detector • Ultimately we want to able to make our own foils. • Some interesting GEM details:

  6. CERN GDD Group – electron-micrograph of GEM foil

  7. CERN GDD Group – electron-micrograph of GEM foil hole

  8. GEM Issues • Gain uniformity ( ~15%) – should not be a big issue for digital mode operation • Discharges: single/double GEM’s: - single GEMS – OK for G  1500 - double GEM’s: “double detectors obtained cascading a Gas Electron Multiplier (GEM) as preamplification, and a second GEM, a MSGC or other devices as second amplifier permit to reach gains above 10000 before discharge under very high rates and exposure to heavily ionizing tracks.” GDD group Web site

  9. Single GEM gain/discharge probability A.Bressan et al NIM A424 (1998) 321

  10. -> We need to determine particle flux vs. particle type (MIP, neutral, heavily ionizing) from detailed simulation. -> Variations of hole sizes, shapes affect the discharge probability and hence operating region.

  11. CONCLUSIONS • Learning more about GEM’s • Source(s) of GEM foils identified • Test Chamber designed • Need studies of particle fluxes in calorimeter • Need $$$ !

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