Status of EXO-200Carter Hall, University of Maryland

DUSEL town meetingNovember 4, 2007

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ИТЭФ

ITEP

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A liquid xenon TPC as a 0 detector

•Monolithic TPC design has optimal surface area to volume ratio•Full three dimensional event reconstruction•Fluid can be purified in situ •Noble gas isotope enrichment relatively easy and safe•No crystal growth•No long-lived xenon isotopes to activate

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The Centerpiece of EXO-200

200 kg of xenon enriched to 80% in 136Xe:the most isotope in possession by any 0 collaboration.

11 times larger than previous experiments.

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EXO-200: the first 200 kg 0 experiment

200 kg of Liquid Xenon to be contained in copper vessel, surrounded by 50 cm of ultra pure cryofluid inside a

copper cryostat and shielded by 25 cm of lead.

Copper liquid xenon vessel

HFE-7000 cryofluid copper cryostat lead shielding

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1

2

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EXO-200 is housed in a 100 class clean room

three of six modular clean rooms

EXO clean rooms assembled at Stanford

Refrigerators hold the cryostat at liquid xenon

temperature

March 30, 2007: commissioning of cryogenics and fluid handling

Refrigerationfeedthrus

HFE feedthru

Insulatingvacuum pump-out

Liquid xenonsupply line

Liquid xenonreturn line

24 hour shifts for two months. First cooldown of 4 tons of HFE-7000. First xenon liquefaction for EXO-200.

Dummy LXe vessel

Summer 2007: cleanrooms being seperated at Stanford

Summer 2007: moving the experiment underground

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Underground site is the WIPP facilityin Carlsbad, NM

A salt mine for storage of radioactive waste....and for low radioactivity experiments!

Fitting the cleanroom into the “waste hoist” – one ¼” to spare!

EXO-200 underground at WIPP – September 2007

Cleanrooms expected to be fully operational in mid November.Plan to re-commission cryogenics in February.

Thin (1.5 mm) copper liquid xenon vessel minimizes radioactivity, but it can’t withstand a large pressure differential.

Inner cryostat door

copper liquid xenon vessel

Xenon pressure and HFE pressure must be

controlled to maintain no more than a 5 psi

pressure difference across the xenon vessel.

Liquid xenon insideHFE outside

Low Background Liquid Xenon Vessel Under Construction

Each part made from ultra-pure copper

Finished part

Vessel made by e-beam welding

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charge drift direction

The EXO-200 detector: a dual TPCcathode

field shaping rings

crossed wireplanes and avalanche

photodiodes

teflon light reflectors

flex cables on back of APD plane (copper on kapton, no glue)

field shaping rings (copper)

acrylic supports

LAAPD plane (copper) and x-y wires (photo-etched phosphor bronze)

Central HV plane (photo-etched phosphor bronze)

~40

cm

x-y crossed wires, 60o

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Crossed wire planes and APD array measure event energy and position

y-position given by induction signal on shielding grid.x-position and energy given by charge collection grid.

APD array observes prompt scintillation to measure drift time.

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1 kV/cm

Liquid xenon data show an anti-correlation between ionization and scintillation

~570 keV~570 keVBi-207 source

Energy resolution: 3.0% @ 570 keV or 1.4 % @ Q(

Factor of two better than most recent Xe experiment

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TPC wire grids produced by photoetching

Charge collection with photoetched wire grids

Wire-grid closeupWireWire--grid grid closeupcloseupWire-grid closeupWireWire--grid grid closeupcloseup

Wires connected in gangs-of-three to reduce

channel count

Scintillation detected by Avalanche Photodiodes

Gang-of-seven APDs EXO-200 will have 259 APDsin each half of the detector

Copper APD holder

Triply redundant electrical connections made by photoetched “spider”

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EXO-200

Case

186133

Majorana mass

(meV)

QRPA1 NSM240

Radioactive

Background

(events)6.4*10251.6*2700.2

T1/20ν

(yr, 90%CL)

σE/E @

2.5MeV

(%)

Run Time

(yr)

Eff.

(%)

Mass

(ton)

Sensitivity of EXO-200

• Improves on previous 136Xe experiments by one order-of-magnitude,and competitive with the best 0 experiments in the world.

HM and IGEX (76Ge): ‹m› < 340 meV1

• EXO-200 will also make the first observation of 2 in Xe-136.

1) Rodin, et. al., Nucl. Phys. A 793 (2007) 213-2152) Caurier, et. al., arXiv:0709.2137v1