Digital HCAL using GEM

1
Digital HCAL using GEM

• J. Yu
• Univ. of Texas at Arlington
• , Aug. 26 30, 2002
• Jeju Island, Korea

• Introduction
• Digital Hadron Calorimeter Requirements
• GEM in the sensitive gap
• UTA GEM DHCAL Prototype Status
• Simulation Status
• Plans for Hardware, Simulation Algorithms
• Summary

(on behalf of the UTA team A. Brandt, K. De, S.
Habib, V. Kaushik, J. Li, M. Sosebee, A. White)
2
Introduction

• LC physics topics
• Distinguish W from Z in two jet final states ?
  Good jet mass resolution
• Higher Jet energy resolution
• Excellent jet angular resolution
• Energy flow algorithm is one of the solutions
• Replace charged track energy with momentum
  measured in the tracking system
• Requires efficient removal of associated energy
  cluster
• Higher calorimeter granularity
• Use calorimeter only for neutral particle
  energies
• Best known method for jet energy resolution
  improvement
• Large number of readout channel will drive up the
  cost for analogue style energy measurement ?
  Digital HCAL
• Tracking calorimeter with high gain sensitive gap

3
DHCAL General Requirements

• Thin and sensitive readout layer for compact
  design
• 1 or 2 level digital hit recording for EFA use
• On-board amplification, digitization and
  discrimination for readout, minimizing noise and
  cross-talk
• Flexible design for easy implementation of
  arbitrary cell size for upgrade
• Minimal intrusion for crackless design
• Ease of construction and maintenance
• Cost effective

4
DHCAL Gas Amplification Requirements

• Sufficiently large gain for good S/N ratio
• Minimize cross-talk between cells in readout
• Isolated readout path from active volume to avoid
  coherent noise
• Modularity, retaining continuity for gas and HV
  supplies and readout
• Digitized readout from each cell
• Allow pad design to avoid strip ambiguity
• Keep low HV for safety and reliability
• Simple readout electronics for cost savings and
  reliability

5
DHCAL Requirements for EFA

• Small cell size for good multiple track shower
  separation
• High efficiency for MiPs in a cell for effective
  shower particle counting
• Possibility for Multiple thresholds
• Dense and compact design for quick shower
  development to minimize confusion
• Large tracking radius with optimized magnetic
  field for sufficient separation between tracks
  for shower isolation

6
Goals for UTA DHCAL Development

• Develop digital hadron calorimetry for use with
  EFA
• Aim for cost effective high granularity
• Look for a good tracking device for the sensitive
  gap
• Develop GEM cell(s) and prototype
• Develop module/stack design for EFA optimization
• Simulate GEM behavior in calorimeter
• Implement GEM readout structure into simulation
• Develop EF and calorimeter tracking algorithms
• Cost effective, large scale GEM DHCAL

7
Why GEM?

• GEM developed by F. Sauli (CERN) for use as
  pre-amplification stage for MSGCs
• Allow flexible and geometrical design, using
  printed circuit readout ? Can be as fine a
  readout as GEM tracking chamber!!
• High gains, above 104,with spark probabilities
  per incident ? less than 10-10
• Fast response
• 40ns drift time for 3mm gap with ArCO2
• Relative low HV
• A few 100V per each GEM gap compared to 10-16kV
  for RPC
• Rather reasonable cost
• Foils are basically copper-clad kapton
• 400 for a specially prepared and framed
  10cmx10cm foil

8
Double GEM schematic
S.Bachmann et al. CERN-EP/2000-151
9
CERN-open-2000-344, A. Sharma
10
GEM Foils

• Most foils made at CERN
• A total of about 1000 foils made
• COMPASS experiment has large scale, 31cmx31cm,
  GEM
• Kapton etching most difficult step ? Work with
  Saulis group

A. Sharma CERN OPEN-98-030
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GEM gains
CERN GDD group
12
Triple GEM DHCAL Design
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Triple GEM test chamber
1cmx1cm pad design

• Sufficient space for foil manipulation
• Readout feed-through, retaining large space for
  ease of connection
• Clear cover to allow easy monitoring
• Readout pads connection at the bottom

J. Li, UTA
14
GEM prototype readout path

• Readout through a gas tight feed-through on the
  test chamber
• Double copper clad with 1cmx1cm pads readout
  through the holes on the other side
• Board being redesigned due to complication in the
  readout hole contact

15
UTA GEM Test Chamber HV layout
Drift gap
2.9kV

• Could be achieved with /- 1500V
• HV fed from one supply but individually adjusted

Transfer gap
Transfer gap
Induction gap
16
UTA GEM Prototype Status

• Constructed
• Test chamber box
• Readout circuit board (1cmx1cm pads) ? being
  redesigned
• HV layout design complete
• Two GEM foils arrived and two more on the way

17
Single GEM gain/discharge probability

• Simulation study in progress using multi-jet
  final states
• Understand average total charge deposit in a cell
  of various sizes
• Study fake signal from spiraling charged particle
  in the gap

A.Bressan et al, NIM A424, 321 (1998)
18
UTA Simulation Status

• Two masters students have been working on this
  project
• Mokka installed as the interface to Geant4
• Pandora-Pythia HEPEvt ASCII output working (Many
  thanks to Masako Iwasaka from U. of Tokyo!!!) ?
  Why ASCII output?
• Generated 1000 tt?6 jet events at ECMS500GeV
  and processed through Mokka for GEM discharge
  study
• In the process of analyzing the data using
  vanilla root macro ? Are there a reconstruction
  and analysis packages for Mokka?
• Output format needs improvement ? A file per
  event per detector component is not that helpful
  for sophisticated studies
• In the process of implementing Mokka geometry
  database
• To implement prototype GEM cell geometry

19
Plans

• Year 1Test and prototype development
• Hardware
• Develop a test chamber for operation
• Produce a single layer (Absorber TGEM)
• Investigate and learn production of large size
  GEM
• Simulation and algorithm development
• Establish MC environment with Geant4 (Mokka?)
• Implement prototype GEM design (single cell)
• Study design for performance optimization
• Study and develop EFA and tracking algorithms
  using MC
• Year 2 Cosmic ray run
• Hardware
• Build a multi-layer (gt5 layers) prototype
• Perform cosmic ray data taking and analyses
• Simulation and algorithms
• Simulate the single muon tracking with
  multi-layer geometry
• Develop EFA and tracking algorithms using cosmic
  way data

20
Plans cntd

• Year34 Testbeam
• Hardware
• Construct thicker prototype for beam exposure if
  the studies turn out feasible
• Would like to explore this possibility
• Simulation and EFA/TRKA development
• Implement testbeam geometry for realistic
  simulation of TB
• Develop Testbeam data reconstruction
• Study performances with various options of EM
  calorimeters and tracking detectors
• Need a system that can allow various plug-in
  detector modules without complicated geometry
  manipulation
• Need reconstruction and analysis packages that
  can work in a modular manner

21
Summary

• GEM based DHCAL looks feasible and interesting ?
  UTAs effort supported by both DoE ADR and local
  funds
• Start collaborating with CALICE collaboration for
  development
• Test chamber being constructed
• Obtained two GEM foils from Sauli and two more on
  the way, if not they already have arrived
• Detailed design work in progress
• HV layout, readout structure, gas supply, etc
• Simulation effort making slow and painful
  progress
• Mokka operational
• Pandora-pythia output in HEPEvt ASCII working
• Working on understanding discharge probability
• UTA local SLAC simulation team
• Working on GEM geometry implementation for design
  optimization
• Will collaborate with ANL/NIU/SLAC for simulation
  and EF algorithm development