Designs of Large Liquid Argon TPCs

— from MicroBooNE to LBNE LAr40

Bo Yu

Brookhaven National Laboratory

On behalf of MicroBooNE and the LBNE LAr Working Group

TIPP 2011, 8-14 June 2011

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Outline

LArTPC principle of operations MicroBooNE TPC design LBNE LAr40 TPC design Summary

Other presentations describing MicroBooNE and LBNE LAr40:• Membrane cryostat technology and prototyping program towards

kton scale Neutrino detectors, Rucinski• Front End Readout Electronics of the MicroBooNE Experiment,

Chen• Cold electronics development for the LBNE LArTPC, Thorn

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How Does a LArTPC Work

dE/dx of 1 MIP: 2.1MeV/cm

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Advantages of LAr TPCsNeutrino interactions recorded in the small LAr TPC at FNAL: ArgoNeut

•Full 3D event reconstruction sub-mm position resolution

•dE/dx for particle ID e/g separation >90%

•Low energy threshold particle energies →15 MeV

•Scalable to multi‐kiloton size

Optimized TPC geometry

Low noise electronics

Multiplexed readout

High LAr purity

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Stacked detectors for large cryostats

Key Technology in Building Large Scale LArTPC: Cold Electronics

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Having front-end electronics in the cryostat, close to the wire electrodes yields the best SNR

Highly multiplexed circuits with fewer digital output lines not only greatly reduce the number of cryostat penetrations, but also give the designers of both the TPC and the cryostat the freedom to choose the optimum configurations

A typical readout configuration with warm electronics: long cables connect the sense wires to the FEE, resulting in large electronics noise. To reduce the cable length, one has to implement cold feedthroughs below the liquid level, which increases the cryostat complexity.

Noise (ENC) vs Sense Wire and Signal Cable Length - in relation to MIP Signal for 3x3 and 5x5 mm Wire Spacing

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MicroBooNE Introduction

MicroBooNE is the first large LArTPC that will be exposed to a high intensity neutrino beam (BNB @ FNAL)

It has 3 goals:1. Resolving the source of the MiniBooNE low energy excess by

employing precision electron/photon differentiation offered by LArTPC’s;

2. Measuring exclusive cross sections on argon in the 1 GeV range by exploiting high resolution of event topology available from LArTPC’s;

3. Exploring technological innovations and methods to provide a basis for the design of the next generation of LArTPC detectors at larger scales.

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MicroBooNE TPC Key Design Parameters

Parameter Value

TPC active volume 2.33m (H) x 2.56m (W) x 10.37m (L), 86 ton

Sense wire planes 3 planes of wires (Y: vertical, U&V: ±60°from Y), 3mm between wires, 3mm between planes

Wire properties 150µm, SS304+2µmCu+Au flash, 9.8N tension

Field cage 2.54cm tube at 4cm pitch, four 1G resistors in parallel between tubes

Cathode bias -128 kV, 500V/cm drift field

In vessel electronics CMOS ASIC, 16ch chips, 8256 ch. totalENC: 660e@220 pF, 1µs peaking time.

Cryostat 12.2m(L) x 3.9m(OD), holds 170 ton LAr.

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A Partial Cross Section of the Cryostat

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Major Differences from ICARUS, other than the shape and size

Cryostat uses foam insulation to reduce cost. It will be purged with argon gas instead of vacuum

evacuation to demonstrate the feasibility of very large non-evacuable cryostat for LBNE.

All front end analog electronics for the wire readout are submerged in the LAr, directly connected to the sensing wires to reduce electronic noise (~600e vs. 1500e).

2.5 m maximum drift length (vs. 1.5m) It has a $20M cost cap

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A Wire Carrier Design Enables Direct Connection to the Front-End Electronics

Shown here is a stack of MicroBooNE wire carrier boards on the readout side of the frame. Copper posts on the bottom boards making electrical connection to the two boards above via through hole sockets. The ASIC motherboards are plugged onto these pins.

Wire ends are terminated by a machine onto brass rings

A wire carrier base boardThe cavities hold the terminated wire ends, while the pins define the wire locations and making electrical connections to the wires

32 wires placed onto the wire carrier board

A cover is riveted onto the board, locking down the wires.

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The Wire Frame

The top and bottom C-channel frames hold adjustable tensioning bars on which the wire carriers are attached.

Each tensioning bar can be adjusted along two guiding rods on the C-frame, and many tensioning screws (not shown) to ensure the tension and the position accuracy of all wires.

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In Vessel Front End Electronics

Preampmotherboards

CMOS preamp/shaper ASIC motherboards are installed on the mounting rails attached to the TPC wire frame. The input connectors are plugged into the mating pins on the wire carriers. Bias voltages to the wires are provided through the preamp motherboard.

The ASICs are fully submerged in the liquid argon.

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MicroBooNE TPC Inside the Cryostat

The TPC will be fully assembled outside of the cryostat, mounted onto a cart and inserted into the cryostat.

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LBNE LAr40 Introduction

LAr40 is one of the two technology options for the far detector of the Long Baseline Neutrino Experiment.

LBNE Primary Objectives:• Neutrino oscillation• Nucleon decay• Supernova,…

LAr40 has 33 kton fiducial LAr mass to achieve the sensitivity of “two 100-kt (fiducial) Water Cherenkov Module equivalents”

Currently sited at the 800’ level at the Homestake Mine at SD.

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LAr40 Conceptual Design at 800L

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LAr40 Key Design Parameters

Cryostat 2 x 49m(L) x 19m(H) x 24m(W), 50 kton total LAr mass

TPC cell active volume

7m (H) x 7.5m (W) x 2.5m (L), 180 ton active LAr mass

Number of TPC cells In each cryostat: 108 = 2(high) x3(across) x18(deep)

Anode Plane Assembly (APA)

7m x 2.5m active area, 5cm thick, with cold electronics mounted on one end.

Wire properties 150µm, CuBe, 4.9N tension

Wire planes 4 planes on either side of an APAGrid (vertical, non-readout), U & V wrapped in a helical pattern (±45º nominal), X (vertical)5mm nominal wire pitch

Cathode bias -187 kV, 500V/cm drift field, 3.7m drift

In vessel electronics CMOS ASICs, 2304 front-end ch. per APA, ~0.5 x106 ch. total. ~15mW per ch. Highly multiplexed and redundant digital output with zero suppression

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Anode Plane Assemblies (APA)

7mx2.5m, stainless steel construction, 250kg 4 planes of wires @ 5mm pitch2304 sense wires, 3312 wires totalElectronics on one end of the frame

The central part of a TPC cell is the anode plane assembly. It is a stainless steel framework, with 4 layers of wires on either side. The two induction wire planes (U & V) are ±45º, and wrap around the APA in a helical fashion. This enables all the wires to be readout at one narrow end of the APA, greatly simplifies the placement of the front-end electronics. In the cryostat, two APAs are stacked with minimal dead space at the joint.

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APA Cross Section Views

Cross section of the readout end of an APA Cross section of the non-readout short end of an APA

Cross section of a long end of an APA

A design to achieve modularity and minimum dead space between modules

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APA Close-up View A smaller scale model is shown

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Cathode Plane Assemblies (CPA)

7mx2.5m, stainless steel construction, ~100kg One stainless steel wire mesh plane-187kV bias voltage

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TPC Assembly in the Cryostat

APAs

CPAs

Field cage

108 APAs144 CPAs

Installed under 7 mounting rails hanging from the cryostat ceiling

This construction is chosen to simplify the TPC structure: gravity helps to keep the modules stable.

A very small roof hatch is needed in the cryostat for TPC installation

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Summary and Outlook The use of in vessel cold electronics is the key for the new

generation of LArTPCs.• MicroBooNE: superior signal to noise• LAr40: results in drastic reduction in the cable plant (source of

contaminants), enables highly modular and efficient TPC construction, and allows the cryostat to be optimized with minimal penetrations.

The modular design of the LAr40 TPC simplifies fabrication, transport, storage and installation of the detector, makes scaling straightforward.

MicroBooNE is currently preparing for the DOE CD2 review this summer. TPC Construction is scheduled to start in the fall.

LBNE is planning to make a “Technology Decision” near the end of this year, and the DOE CD1 early next year. If LArTPC is chosen to move forward, we’ll start to construct a 1kton scale TPC (LAr1) to demonstrate and validate the LAr40 design.

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Backup Slides

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Signals in LAr TPC

A 3mm MIP track should create 210keV/mm x 3mm /23.6eV/e = 4.3fC. 

After a 1/3 initial recombination loss: ~2.8fC

It is expected that the TPC design will maximize the drift path to equal or exceed the charge life time, thereby reducing the signal to 1/e≈0.368.

The expected signal for 3mm wire spacing is then ≈1fC=6250 electrons,

… and for 5mm, ≈104

electrons, for the collection signal. The induction signals are smaller

Induced Current Waveforms on 3 Sense Wire Planes:

Charge signal:

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LAr40 TPC Readout Scheme

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Intermediate Wire Support

Wire support structures are mounted along the 5 internal frame bracings.

Maximum unsupported wire length =1.6m

Dead space introduced ~ 1mm