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

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 (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

(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 10 4 have been developed and spark probabilities per incident  less than Fast operation -> Ar CO 2 40 ns drift for 3mm gap. Relatively low HV (~ few x100V per GEM layer) (cf kV for RPC!)

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

From CERN-open , A. Sharma

Micrograph of GEM foil From CERN GDD Group

Detail of GEM foil hole From CERN GDD Group

- 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

From CERN GDD group GEM gains

GEM amplification vs. metal hole size from A. Sharma CERN OPEN

Initial design concept for gas amplification DHCAL using GEMs

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

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

GEM aging study from A. Sharma CERN OPEN

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

-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

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