1. Digital Calorimetry using GEM technology Andy White for UTA group (A. Brandt, K. De, S. Habib, V. Kaushik, J. Li, M. Sosebee, Jae Yu) U.C. Santa Cruz 6/28/2002

2. Goals  Develop digital hadron calorimetry for use with energy flow algorithms  Develop flexible, robust design  Design GEM cell(s) and prototype  Develop module/stack design  Simulate GEM behavior  Develop simulation software and energy flow and cal tracking algorithm(s)

3. Requirements for DHCAL (A) General -Thin sensitive/readout layer for compact calorimeter design -Simple 1- or 2-level “hit” recording for energy flow algorithm use -On-board amplification/digitization/discrimination for digital readout – noise/cross-talk minimization -Flexible design for easy implementation of arbitrary “cell” size -Minimal intrusions for “crackless” design -Ease of construction/cost minimization

4. (B) Gas Amplification Specific - Sufficient gain for good S/N - Minimized cross-talk between “cells” - Readout path isolated from active volume - Modular design with easy module-to-module continuity for supplies, readout path - Digital readout from each cell - Pad design (to avoid x-y strip complications) - Keep HV low for safe/reliable use - Keep electronics simple = cheap/reliable

5. (c) Energy flow requirements - small cell size for good two/multiple track separation - high efficiency for MIPs in a cell - option for multiple thresholds - non-alignment of dead areas for efficient track following

6. GEM (Gas Electron Multiplier) Approach GEM developed by F. Sauli (CERN) for use as pre- amplification stage for MSGC’s. GEM also can be used with printed circuit readout – allows very flexible approach to geometrical design. GEM’s with gains above 10 4 have been developed and spark probabilities per incident  less than 10 -10. Fast operation -> Ar CO 2 40 ns drift for 3mm gap. Relatively low HV (~ few x100V per GEM layer) (cf. 10-16kV for RPC!)

7. Double GEM schematic From S.Bachmann et al. CERN-EP/2000-151

8. From CERN-open-2000-344, A. Sharma

9. Micrograph of GEM foil From CERN GDD Group

10. Detail of GEM foil hole From CERN GDD Group

11. - Most foils made in CERN printed circuit workshop - Approximately 1,000 foils made - Big project for COMPASS expt. 31x31 cm 2 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 cm 2 foils 70  m holes 140  m pitch ~$300 - Foils HV tested/verified at CERN. GEM foils

12. From CERN GDD group GEM gains

13. GEM amplification vs. metal hole size from A. Sharma CERN OPEN-98-030

14. Initial design concept for gas amplification DHCAL using GEMs

15. Readout schematic AMPDISCAMPDISC REG Digital/serial output thr Anode pad Ground

16. GEM test chamber ( J.Li, UTA )

17. Detail of GEM prototype chamber - pad contact

18. GEM prototype – readout path

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

20. GEM aging study from A. Sharma CERN OPEN-98-030

21. UTA Simulation Plans - Working with NIU/SLAC to develop GEANT4 based simulation - Investigating GEANT4 – CAD linkage for easier implementation of geometry - Use for detailed cell/module design - Simulate performance of GEM cells for single particles and hadronic showers -Develop Energy flow and cal tracking algorithms using GEM based had-cal

22. -Two graduate students working on this -Currently Gismo installed but having linking problem due to xml library setup -Mokka installed for the use of GEANT4 -Having growing pains… -Will generate events using existing geometries in Gismo and Mokka to get familiar with the tools and analysis -Implement prototype GEM cell geometry -By hand initially, moving slowly into CAD -At the lower end of learning curve UTA Simulation Status

23. UTA R+D Plans - Now supported by DOE ADR ! - Develop GEM calorimeter cell design - Understand GEM issues (discharges,…) - Develop module design/readout -Build/operate GEM test chamber(s) (with local support) - Simulate performance using GEANT4 and other MC tools  Having growing pain -Develop EF and cal tracking algorithms