ND weekly meeting 8th August 2018

James Sinclair, LHEP

ArgonCube Update

1Braque’s Violin and Candle Stick, Paris 1910

ArgonCube

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Cut-away illustration of an ArgonCube module, and an array of modules in a common cryostat (N.B. Modules will be sealed.)

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The 4x5 geometry optimised for the DUNE ND. In the FNAL low-density cryostat with beam window.

Instrumented modules sharing common cryostat (initially filled from and cooled by).

Service volumes housing cryocoolers and recirculation pumps (move cold LAr through heat exchanger at base of modules)

Module Requirements

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Cut-away illustration of an ArgonCube module

Transparent to tracks: LAr– Radiation length = 14.0 cm– Hadronic interaction length 83.7 cm

G10 structure– Radiation length = 19.4 cm– Hadronic interaction length 53.1 cm.

Minimise all material in surrounding active volume.

Light readout:Compact (thin), dielectric, and large area coverage

Charge readout:Compact, mechanically robust, and unambiguous

Module Component

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Pump and filter no longer required “on-module”. Clean LAr supplied by external lines – less dead material.Clean LAr circulated through heat exchange, extracted above cathode and readout electronics.

Charge readout: 2 x 3 m2 pixel planes, 3 mm pixel pitch, 6.6x105 pixels per module. Signals digitized by LArPix ASICs mounted on rear of pixel PCB. Cooled by LAr flow.

Light readout:ArCLight (arXiv:1711.11409), dielectric tiles supporting and lining the inside of the field-shell.

Field-shell… most of what I’ll be talking about today

3.0

m

0.1

m0.

4 m

1.0 m

Why a Field-Shell?

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Why move from a field cage to a field-shell?

Physics:Minimize dead material and maximize active volume.

Reliability:Reduce component count and therefore points of failure.

Limit power release in the case of breakdown.

Suitable Material

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Provide continuous linear potential distribution along the drift direction.

Uniform resistance O 10 GΩ/□ at desired voltage and temperature; -50 kV and 87 K.

Field-shell can be produced with resistive sheet in the form O 100 μm foil, or as a O 10 μm laminate on a G10 substrate (module walls). 50 μm sample of Carbon loaded Kapton had resistance of 16 GΩ/□ at 77 K (at 0 V).

Resistive Kapton test sample in Bern, April 2018

Field-Shell Test TPC

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15 cm drift length. 7 x 7 cm2 cathode & anode. E-field range 0 kV/cm → 1.5 kV/cm. Kapton charge readout and pre-amps

Perforated Kapton field shell

PAI support structure

Kapton cathode

Electrostatic shielding

Trigger: Muon telescope (foil wrapped scintillator tiles instrumented with SiPMs)

15 c

m

7 cm

A Note on Charge Readout

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This is to test the field-shell not the readout.

Leftovers from early prototypes…

2-plane wire readout printed on 50 μm Kapton.

64 channel: 32 induction, 32 collection.

Combination of BNL LARASIC4* and LARASIC7.

...No pixels – no nice 3D event displays, sorry.

7 cm

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Results So Far

Cosmic muon crossing resistive shell TPC at 1.0kV/cm, July 2018

Triggering on only crossing muons produces a data set of clean tracks.

Straight tracks observed across a range of E-fields.

Field uniformity will be studied further by comparing with the expected distribution of tracks for the telescope geometry.

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Expected Track Distribution

Assuming a cosine distribution, the expected distribution of crossing tracks triggering the muon telescope is:

(from above) (from side)

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Expected Track Distribution

Efficiency of muon telescope as function of position still needs to be determined, this will alter the expected distribution. (more efficient closer to SiPMs)

Measurement under way.

ArCLight tile photon detetection effeincy

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Electrical Properties of the Field-Shell

From voltage and current measured at the high voltage power supply.

Non linear I-V relation ship observed.

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Electrical Properties of the Field-Shell

Almost 1 W dissipated into the LAr.

Unlike a field cage this is not localized to resistors, but spread across the 0.04 m2 area of the field-shell.

No boiling was observed.

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Electrical Properties of the Field-Shell

Variation of resistance with voltage could explain the difference between the CERN measurement of the Kapton cathode.

The resistance remains in a usable range O 10 GΩ/□.

It should be determined if this is area dependent – larger samples needed.

Limited by resolution of power supply

Field-Shell Summary

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A field-shell formed of resistive Kapton foil looks like a viable option for field shaping in ArgonCube, and future LArTPCs.

The field uniformity is still to be determined, and the electrical properties as a function of area. These measurement will require a larger sample.

In order to secure larger quantities, issues with the supplier need to be addressed.