Digital HCAL using GEM

1
Digital HCAL using GEM

• J. Yu
• Univ. of Texas at Arlington
• Nov. 7 - 9, 2002
• NICADD/NIU

• 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)
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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

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DHCAL General Requirements

• Thin and sensitive readout layer for compact
  design
• One or two 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 (3
  orders of magnitude smaller signal in gas
  compared to scintillation counter)
• 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

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DHCAL Requirements for EFA

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

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Goals for UTA DHCAL Development

• Develop digital hadron calorimetry for use with
  EFA
• Aim for cost effectiveness and 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

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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

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CERN-open-2000-344, A. Sharma
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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
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Double GEM DHCAL Design
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Double GEM test chamber

• 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

2cmx2cm pad design
J. Li, UTA
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UTA GEM Test Chamber HV layout
Drift gap
HV fed from one supply but individually adjusted
? Good to prevent HV damage on the foils
2.1kV
Transfer gap
Induction gap
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UTA GEM Prototype Status

• Readout circuit board (2cmx2cm pads) constructed
• HV Connection implemented
• Two GEM foils in the UTA Nano fabrication
  facility cleanroom
• Preamp in hand and characterization completed

Amplification factor of 300 for GEM size signal
(LeCroy HQV800 )
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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)
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UTA Simulation Status

• Two masters students have been working on this
  project
• Mokka Geometry database downloaded and installed
  at UTA
• Preliminary mixture GEM geometry implemented
• Completed single pion studies using default
  geometry
• Reproduced expected response
• Energy resolution seems to be reasonable also
• Root macro based and JAS based analysis packages
  developed
• Proceed with more detailed GEM geometry
  implementation

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Single Pion Studies w/ Default TESLA Geometry

• 1000 single pion events using Mokka particle gun
  command.
• Incident energy range 5 200GeV
• kinematics information on primary particles in
  the files
• Developed an analysis program to read total
  energies deposited per pion for each incident
  energy.
• Mean Energy vs Incident pion energies
• Energy conversion from the slope of the straight
  line
• Conversion factor is 3.54 and agrees with the
  computed sampling fraction

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TESLA TDR Geometry

• Ecal Electromagnetic Calorimeter Material
  W/G10/Si/G10 plates (in yellow)
• 1mm W absorber plates
• 0.5 mm thick Si, embeded 2 G10 plates of 0.8 mm
  each

• Hcal Hadronic Calorimeter
• Material
• 18 mm of Fe
• 6.5 mm of Polystyrene scintillator (in green)

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TESLA TDR detector live energy deposit for single
pions
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TESLA TDR Elive vs Ep

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TESLA TDR CAL Single Pion Resolution
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GEM Simulation Status

• Mokka Geometry database downloaded and installed
  at UTA
• New Geometry driver written ? Mixture GEM
  geometry implemented ?Need to use ArCO2 only
• Single pion study begun for discharge probability
• Initial study shows that the number of electron,
  ion pair with gain of 104 will be on the order of
  107 for single 200GeV pions
• Getting pretty close to the 108 from other
  studies ? Might get worse for jets from W pairs,
  due to fluctuation
• Need more studies to compute the discharge
  probability.
• Cell energy deposit being investigated to
  determine optimal threshold based on cell energy
  ? Proceed to energy resolution studies
• Determine optimal gain using live energy deposit
  vs incident energy

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GEM Prototype Geometry
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GEM Geometry Implementation Mechanics in Mokka

• TDR / Hcal02 Model chosen for modification
• Fe-GEM sub-detector instead of the existing
  Fe-Scintillator
• New driver for the HCal02 sub-detector module
• Local database connectivity for HCal02 ? Database
  downloaded and implemented at UTA

Courtesy Paulo deFrietas
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Single pion study with GEM
15GeV
5GeV
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Cell Energy Deposit in GEM HCal
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GEM Sampling Weight
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Summary

• Hardware prototype making significant progress
• GEM foils delivered and are in the clean room for
  safe keeping
• Preamp and Discriminator in hands ? Preamp
  characterized
• HV System implemented
• Readout Pad implemented
• Almost ready to put GEM foils in the prototype
  box
• GEM foil mass production being looked into by
  3MSimulation effort made a marked progress
• Simulation effort made a marked progress
• Single pion study of Mokka default TESLA TDR
  geometry complete
• Analysis tools in place
• The resolution seems to be reasonable
• Preliminary GEM Mixture geometry implemented
• First results seems to be a bit confusing
• Initial estimate of eIon pair seems to be at
  about 107 for 200GeV pions
• Local Geometry database implemented
• Optimal threshold for digitization and gain will
  come soon
• Will soon move onto realistic events, WW, ZZ, or
  tt ? jets