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Particle Physics Design Group Studies

Big Liquid Argon Neutrino DetectorSubgroup

Particle Physics Design Group Studies: The BLAND Subgroup

BLAND

The BLAND Group

• Patrick Owen – Resolution and Efficiency

• Laurie Hudson– General design and Charge readout

• Stewart Hawkley– Triggering and Event reconstruction

• Cheryl Shepherd and James Mugliston– Magnetics and Cryogenics

• Oliver Cartz and Jeanette Avon– Calibration and Background

• Dee Campbell-Jackson– Avalanche Photodiodes and Purification


Introduction• General Setup and Material Choice• Collection Plate• Magnetisation• Photomultipliers• Electronics• Calibration • Background and Location• Purification• Triggering• Simulations• Sensitivity & Resolution• Cost• Summary


General Setup


-Tank has cylindrical geometry

- Gaseous argon at the top for bi-phase LEM that will used in charge readout.

- Non-magnetic tank and dome.

- Anti-coincidence shield

- This will all be contained within a cryostat. (Liquid Nitrogen)

- Magnet & a return yoke to provide a uniform B field.

Near Detector

• Exactly the same (except size)

• Cylindrical shape

• 6m diameter, 5m height

• Identical in functionality -

• Used for measuring cross sections and initial energy spectrum


Material Choice


• $0.6 kg-1 ≈ $10 million (for 1 detector)

• High density (1.4 gcm-3) and stability.

• εr = 1.6

• μ = 475 cm2V-1s-1

• High scintillation yield; 40,000 γ per MeV

• Background rejection of NC and junk CC interactions

Collection Plate


• Far detector - magnetises ~ 17 kTonnes of liquid argon• Solenoid produces a uniform field of 0.55 T • Correction currents with a return yoke• Total coil ~ 5.5 kTonnes• Iron yoke ~ 16.1 kTonnes• Magnet Cooling system• Feasible power consumption of 19.2MW

Magnet


BLAND magnet demonstration


Simulation result


Photomultipliers• Avalanche photodiodes (APD)– Small size– Low dead time

• Low temperatures• High B-field• Gain 106

Electronics


• Current collected is of order pC.• Install pre-amps inside cryostat to reduce capacitance.• Extended lifetime of electronics• High signal: noise ratio• 4 bytes per digitisation, 2.5MHz.• Bandwidth distributed around PC farm.

Pre-amplifier ADC

Collection Plate

Cryostat

Calibration

• Why calibrate?• Initial– Signal Level-> Energy– Test beam– Cosmic ray muons (anti-coincidence shield)– Electronics

• Ongoing calibration– Constantly changing variables– Correction factors– Cosmic ray muons


Before

After

Background

• Projected direction• Known energy range• Location• Expected background:– 10-8 s-1 neutrinos– 1s-1 cosmic ray muons at 1km underground


Location

• Underground• Low background radiation• Few nuclear power plants• High available energy• Existing underground facilities



• Average data rate ~45MB/s.• Trigger above background pedestal.• Scintillation light detected by PMTs used to trigger for 'interesting'

events.• Effectively segments detector, only reading out locally active regions.• An anti-coincidence shield is used to reject background.

Triggering

Purification of LAr


• Electron drift ~ 25m• Minimisation of

recombination• Purity of <0.1ppb

– Monitor contact materials– Hermetic system– Continual purification

• 100Watts

Purity Testing


Schematics Signals

Simulations



Charged current muon production

Charged current electron production

Incident neutrinos

Sensitivity


The QECC cross section (red line) is found to be 7.5x10-43 m2 and 6x10-43 m2 for the far detector and middle detector respectively (Half these values for antineutrinos).

http://www.fnal.gov/directorate/DirReviews/Neutrino_Wrkshp_files/Fleming.pdf



Sensitivity


1310)42.01.2(tnW QECCFar

1310)34.07.1(MiddleW

The average active thickness for the detector, t = 2d/π =14.1m

The number density under the average pressure, n = 2.0x1028

d =22m

Again these values are halved for antineutrinos

Energy Resolution• A 1GeV electron will ionise 1.45x107 atoms• The contribution from quantum fluctuations is

• Another contribution is from the time resolution which is a systematic error.

• Noise and avalanche variation is expected to be negligible.• Other effects such as electronics and dead zones.• These values are best estimates.

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Momentum Resolution• Spatial resolution arises from diffusion and channel size• Total spatial resolution is 6.7mm• Momentum resolution:

• Radiation length calculated to be 5.6km – multiple scattering contribution is negligible.

• Heavily dependent on path length, L – not constant.

4

720

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Average fractional momentum resolution is 1% and 3% for the middle and far detectors respectively (worse than energy resolution).

Momentum Resolution

0 5 10 15 20 250.0001

0.001

0.01

0.1

1Fractional Momentum Resolution vs Path Length

Middle DetectorFar Detector

Path Length (m)

Fractional Momentum Resolu-tion

Cost


Equipment Number Cost ($)

Liquid Argon 2x17KT + small 25 mil

Magnet & Yoke 2 24 mil

PMs (1/m2 ) ~4000 120 k

Liquid Nitrogen 2x104 m3 2 mil

LEM Channels + E-field 12x106 12 mil

Underground factor n/a 2

PC Farm 1 10 mil

Contingency n/a 80 mil

Engineers & Scientists 200 48 mil (over 6 years)

Total 264 mil + running costs

Summary…• Liquid Argon Time Projection Chamber• LEM readout• Uniform 0.55T B-field• Triggering using APDs• Calibration using test beams• Underground• Data Rate 45MB/sec• Purity < 0.1ppb• Great energy resolution, good momentum

resolution• Cost ~ $264 mil + running costs


References

• Neutrino Scattering in Liquid Argon TPC Detectors, Fleming.

• Radiation Detection and Measurement; 2nd ed, Knoll.

• Measurement of the muon decay spectrum with the ICARUS liquid Argon TPC, ICARUS Collaboration.

• Detectors for particle radiation, Kleinknecht.

• Calorimetry, Wigmans.


Questions?
