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