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Digital Calorimetry using GEM technology Andy White for UTA group (A. Brandt, K. De, S. Habib, V. Kaushik, J. Li, M. Sosebee, Jae Yu) 6/28/2002. Goals. Develop digital hadron calorimetry for use with energy flow algorithms Develop flexible, robust design
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Digital Calorimetry using GEM technology Andy White for UTA group (A. Brandt, K. De, S. Habib, V. Kaushik, J. Li, M. Sosebee, Jae Yu) 6/28/2002
Goals • Developdigital 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)
Requirements for DHCAL • 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
(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
(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
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 104 have been developed and spark probabilities per incident less than 10-10. Fast operation -> Ar CO2 40 ns drift for 3mm gap. Relatively low HV (~ few x100V per GEM layer) (cf. 10-16kV for RPC!)
Double GEM schematic From S.Bachmann et al. CERN-EP/2000-151
Micrograph of GEM foil From CERN GDD Group
Detail of GEM foil hole From CERN GDD Group
GEM foils • 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 70m holes 140m pitch ~$300 • - Foils HV tested/verified at CERN.
GEM gains From CERN GDD group
GEM amplification vs. metal hole size from A. Sharma CERN OPEN-98-030
Initial design concept for gas amplification DHCAL using GEMs
Readout schematic Anode pad Ground thr thr AMP DISC AMP DISC REG REG Digital/serial output
Detail of GEM prototype chamber - pad contact
Single GEM gain/discharge probability A.Bressan et al NIM A424 (1998) 321
GEM aging study from A. Sharma CERN OPEN-98-030
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
UTA Simulation Status • 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 pain… • 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 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