# Presentation: 879752

## Liquid Argon as an Imaging Detector – an effort at Fermilab

- All Experimenters Meeting – February 27, 2006
-                     Presented by Petros Rapidis
- ( for Doug Jensen, Hans Jostlein, John Krider,  David Finley, Alberto Marchionni, Stephen Pordes, Terry Tope, Richard Schmitt, Walter Jaskierny, and Cary Kendziora and his wonderful crew at PAB; not to mention our friends from Michigan, Princeton, Tufts , Yale, York, and UCLA)
- Why and Whence ?
- Liquid Argon elsewhere
- Ultimate objective and the R&D plan at FNAL towards that objective
- Test setups at PAB and at the Village
- Recent work at PAB and our first success at obtaining highly pure Liquid Argon
- Other work (purging big tanks, long wire chamber studies)

- All Experimenters Mtg.

- Feb 27, 2006

*Historical aside  on the use of LAr as an imaging detector :*
- Carlo Rubbia (1977), H. Chen at Irvine (1978), BNL (1979)
- ICARUS experiment at Gran Sasso (LAr purification 1993)
- Talks by Adam Para  18 months ago, and by Rubbia in October 2005

- All Experimenters Mtg.

- Feb 27, 2006

- All Experimenters Mtg.

- Feb 27, 2006

## The Large Liquid Argon TPC: Sketch

- H
- V

- S
-  i
- g
- n
- a
-  l

- A large size, low rate, fully active, high efficiency, fine spatial resolution, imaging detector of relatively low cost. (5mm wire spacing, 3 meter drift)
- _Perfect_ for neutrino work (esp. off axis), but also for other uses (proton decay, super nova neutrino detection, and double beta decay)
- In contrast to low resolution, low efficiency, high rate detectors being considered.
- But note that it is not a fully proven technology, if it is to be based on an LNG tank design.

- All Experimenters Mtg.

- Feb 27, 2006

**The promise :**

**The outstanding issues : **a) Purity (without evacuating)
-                                             b) Huge wire chambers (20+ meters) in LAr

- All Experimenters Mtg.

- Feb 27, 2006

## NuMI Liquid Argon TPC Overview 

- From the submission to NUSAG – waiting with baited breath ...

- All Experimenters Mtg.

- Feb 27, 2006

**Setup at PAB**
- A test station to study (a) the contamination of LAr by various materials and (b) the efficacy of various ‘filters’ for the removal of oxygen (and other electronegative species)

- Mostly recycled equipment

- All Experimenters Mtg.

- Feb 27, 2006

## First use of new ‘filtering’ material based on reduced Cu and Cu oxides. (a significant ‘local’ contribution)

- All Experimenters Mtg.

- Feb 27, 2006

## Qanode/Qcathode = e-tdrift/

- photo-cathode

- ground grid

- anode grid

- anode

- -HV cathode

- RD = 50 M

- + HV  anode

- anode signal

- cathode signal

- light pulser

- quartz
-  fiber

- field rings

- ~ 20 cm

- R = 110 M

- liquid argon

- photodiode

- quartz fiber

- photodiode signal

- Schematic of Liquid Argon Purity Monitor (PrM)

- Qanode/Qcathode = e-tdrift/

- RD

- RD

- RD

- RD

- RD

- RD

- RD

- RD

- RD

- RD

- RD

- RD

- RD

- RD

- RD

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- All Experimenters Mtg.

- Feb 27, 2006

## tdrift= 150 s, Qanode/Qcathode= ~1 

- anode signal

-   cathode signal

- photodiode

- tdrift= 150 s, Qanode/Qcathode= ~1

- All Experimenters Mtg.

- Feb 27, 2006

## a 2.8 millisecond drift,   Qanode/Qcathode ~ 0.4 (*)

- a 2.8 millisecond drift,   Qanode/Qcathode ~ 0.4 (*)
-  (*) peaks need some correction for cathode signal rise-time

- anode signal

- cathode signal

- All Experimenters Mtg.

- Feb 27, 2006

## a plot of long drift times from another run a week later with fresh argon.

- An alternative way to calculate lifetimes would be to use just the anode signals at different drift times, making appropriate compensation for the different transmission efficiencies as the drift field changes at fixed cathode fields.

- Lifetime is in excess of ~5 msec -  for a single pass thru the filter!

- All Experimenters Mtg.

- Feb 27, 2006

## Test of purging a volume from atmosphere:

- insert Argon gas at bottom of tank over large area at low velocity;
- the Argon introduced being heavier than air will act as a piston and drive the air out of the tank at the top;
- fewer volume changes than simple mixing model will achieve a given reduction in air concentration.

- tank volume = 157 cf
- tank cross section = 19 sf
- flow rate ~ 73.2 cf/h climb rate ~ 3.8 f/h

- All Experimenters Mtg.

- Feb 27, 2006

## to 100 ppm (reduction of 2,000) takes 6 hrs = 2.6 volume changes

- (cf simple mixing, which predicts ln(2000) = 7.6 volume changes)

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- Feb 27, 2006

- Long wire tests (ultimately in a LN**2 **vessel)
- A first setup in air of 20 meter long wires to study noise (microphonics) and have a first stab at electronics.

- A long (>5 meter) drift test

- Other work

- All Experimenters Mtg.

- Feb 27, 2006

## Thank you and good bye

**Thank you and good bye**

- All Experimenters Mtg.

- Feb 27, 2006