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 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

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

Micrograph of GEM foil From CERN GDD Group

Detail of GEM foil hole From CERN GDD Group

GEM foils Most foils made 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.

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 Digital/serial output Anode pad Ground AMP DISC AMP thr thr AMP DISC AMP DISC REG REG Digital/serial output

GEM test chamber ( J.Li, UTA )

Detail of GEM prototype chamber - pad contact

GEM prototype – readout path

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

from A. Sharma CERN OPEN-98-030 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