Digital Calorimetry
using
GEM technologyAndy 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 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
- 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 70m holes 140m 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-98-030
Initial design concept for gas amplification DHCAL using
GEMs
Readout schematic
AMP DISC AMP DISC
REG REG
Digital/serial output
thr 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-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
- 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
