Transcript Document 7277424

Status of EXO-200
Carter Hall, University of Maryland
DUSEL town meeting
November 4, 2007
ITEP
ИТЭФ
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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
Copper liquid xenon vessel
HFE-7000 cryofluid
copper cryostat
lead shielding
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.
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EXO-200 is housed in a 100 class clean room
Refrigerators hold the
cryostat at liquid xenon
temperature
three of six
modular clean rooms
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2
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EXO clean rooms assembled at Stanford
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March 30, 2007: commissioning of cryogenics and fluid handling
Refrigeration
feedthrus
Liquid xenon
supply line
HFE feedthru
Liquid xenon
return line
Insulating
vacuum
pump-out
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
Underground site is the WIPP facility
in Carlsbad, NM
A salt mine for storage of radioactive waste....
and for low radioactivity experiments!
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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
Liquid xenon inside
HFE outside
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.
Low Background Liquid Xenon Vessel Under Construction
Each part made from ultra-pure copper
Finished part
Vessel made by e-beam welding
The EXO-200 detector: a dual TPC
cathode
crossed wire
planes and avalanche
photodiodes
charge drift direction
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field shaping rings
Central HV plane
(photo-etched
phosphor bronze)
flex cables on back
of APD plane (copper
on kapton, no glue)
acrylic
supports
LAAPD plane (copper) and x-y
wires (photo-etched phosphor
bronze)
teflon light reflectors
field shaping rings
(copper)
x-y crossed
wires, 60o
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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Liquid xenon data show an anti-correlation
between ionization and scintillation
1 kV/cm
~570 keV
Bi-207 source
Energy resolution: 3.0% @ 570 keV or 1.4 % @ Q()
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Factor of two better than most recent Xe experiment
TPC wire grids produced by photoetching
Charge collection with
photoetched wire grids
Wires connected in
gangs-of-three to reduce
channel count
Wire
-grid closeup
Wire-grid
closeup
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Scintillation detected by Avalanche Photodiodes
Gang-of-seven APDs
Triply redundant electrical
connections made by
photoetched “spider”
EXO-200 will have 259 APDs
in each half of the detector
Copper APD holder
Sensitivity of EXO-200
Case
Mass Eff.
(ton)
(%)
Run
Time
(yr)
EXO-200
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0.2
70
2
σE/E @ Radioactive
2.5MeV Background
(%)
(events)
1.6*
40
T1/20ν
Majorana mass
(yr,
90%CL)
(meV)
6.4*1025
QRPA1 NSM2
133
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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
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EXO-200 will also make the first observation of 2 in Xe-136.
1) Rodin, et. al., Nucl. Phys. A 793 (2007) 213-215
2) Caurier, et. al., arXiv:0709.2137v1
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