Liquid argon as an active medium

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Liquid argon as an active medium
Better title What has been learned by ICARUS
collaboration from 20 years of drifting
electrons in LAr
Carl Bromberg Michigan State University
Fermilab (2004)
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Sources
See list of ICARUS talks and papers on FLARE web
site /www-off-axis/flare/documents.htm
Particularly

• Talk by F. Sergiampietri, at NuFact 01 (LANNDD)
• Talk by A. Para at Fermilab (Wine Cheese)
• Publications
• Design, construction and tests of the ICARUS
  T600 detector, NIM A527, 329 (2004)
• Study of electron recombination in liquid Argon
  with the ICARUS TPC NIM A523, 275 (2004)
• Measurement of the muon decay spectrum with the
  ICARUS T600 liquid Argon TPC, Euro Phys J C33,2
  (2004) 233

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Liquid Argon basics
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TPC operation

• Time Projection
• electrons drift toward transparent wire planes
  (minimum 1), and collection wire plane
• planes with wires at various angles for stereo
• Ambiguities
• track parallel to wire planes, all hits have same
  time, i.e., x.
• track dip resolved by space points vertices,
  delta rays or ionization bumps
• distance between space points changes in the two
  views

delta ray
vertex
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Signal characteristics
D tracks 16 mm
FWHM 4.5 mm
D

• Diffusion not a big factor in signal shape for d
  2 m
• Fit for x-position, resolution lt 1 mm (2.5 MHz
  clock), helps with ambiguity resolution.
• Even with significant overlap in time,
  distinguish 1 track from 2, by consistent
  ionization/pulse width over many wires.
• But tracks in drift direction have very distorted
  pulse shapes

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Energy Resolution
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FLARE is not ICARUS

• Typical ICARUS capacitance is 20 pF/m 200 pF
  cable 400 pF (max) induction wire
• Induction signals are smaller than collection
  signals by 30
• FLARE will have wires 4 times as long, noise will
  be 1.6 times larger, yielding S/N 8
• Does increasing wire spacing (to say 5 mm) help
  by lowering capacitance and increasing the
  signal?
• Cables for horizontal or stereo wires? Long
  cables mean more capacitance. Restrict to
  collection wires.
• Pixels anyone? K. McDonald.

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For what is needed?

• Energy resolution of 2 great for EM shower. For
  total energy, make corrections based on particle
  ID via ionization changes, range, p-gtm-gte decays,
  nuclear fragments n-stars
• Full reconstruction is probably not needed.
  Automated scanning perhaps possible in 2D
• In scanning simulations, stereo views were not
  that useful. Helped in large angle particle ID,
  but not often in electron ID.
• Automatic space point finding is a challenge
• Cosmic Rays (during 1.3 ms readout). Should do
  simulation. Get ICARUS raw data? Interest by
  others trying to do surface calorimetry and
  tracking.