# Presentation: 708695

## Liquid argon as an active medium

- Carl Bromberg
- Michigan State University
- & Fermilab (2004)

_***Better title***_
**What has been learned by ICARUS collaboration from ~20 years of drifting electrons in LAr**

- Carl Bromberg, FNAL LAr Exp. Workshop Nov. 4-6, 2004

- November 4, 2004

## Sources

- 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

**See list of ICARUS talks and papers on**
**FLARE web site**
**/www-off-axis/flare/documents.htm**

**Particularly:**

- Carl Bromberg, FNAL LAr Exp. Workshop Nov. 4-6, 2004

- November 4, 2004

## Liquid Argon basics

| Wion (1 MeV e–) | 23.6 eV |
| --- | --- |
| Radiation Length | 19.55 g/cm2 (14.0 cm) |
| Density | 1.395 g/cm3 (1 bar) |
| Boiling Point | 87.2 K (1 bar)
89.3 K (1.25 bar) |
| Nucl. Int. Length | 117 g/cm3 |
| Diffusion Coef. | 4.8 cm2/s  |
| Recombination factor | 0.64 (decreases ions/cm) |
| dE/dx (min) | 2.1 MeV/cm |
| e– in 3mm sample |  |

- Carl Bromberg, FNAL LAr Exp. Workshop Nov. 4-6, 2004

- November 4, 2004

**Notes:**
Boiling occurs only at the top of a uniform temperature column of liquid

- Carl Bromberg, FNAL LAr Exp. Workshop Nov. 4-6, 2004

- November 4, 2004

## 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

- Carl Bromberg, FNAL LAr Exp. Workshop Nov. 4-6, 2004

- November 4, 2004

## Signal characteristics

- Diffusion not a big factor in signal shape for d ~ 2 m
- Fit for x-position, resolution < 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

- FWHM ~ 4.5 mm

-  tracks = 16 mm

- 

- Carl Bromberg, FNAL LAr Exp. Workshop Nov. 4-6, 2004

- November 4, 2004

## Energy Resolution

- Carl Bromberg, FNAL LAr Exp. Workshop Nov. 4-6, 2004

- November 4, 2004

## 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.

- Carl Bromberg, FNAL LAr Exp. Workshop Nov. 4-6, 2004

- November 4, 2004

## 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, ->->e 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.

- Carl Bromberg, FNAL LAr Exp. Workshop Nov. 4-6, 2004

- November 4, 2004