Current Status of The EXO-200 Experiment

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Current Status of The EXO-200 Experiment
136Xe 136Ba 2e- ( 2?e)
Kevin OSullivan Stanford University
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Why use xenon?
Energy resolution is poorer than the crystalline
devices (factor 10), but
Xenon isotopic enrichment is easier. 200kg of Xe
has already been enriched to 80 in
136Xe Xenon is reusable. Can be
repurified recycled into new detector Monolithi
c detector. LXe is self shielding, surface
contamination minimized. Minimal cosmogenic
activation. No long lived radioactive isotopes
of Xe. admits a novel coincidence technique.
Background reduction by Ba daughter tagging.
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Ba Ion Identification

• Ba system well studied (Neuhauser, Hohenstatt,
  Toshek, Dehmelt 1980)
• Very specific signature shelving
• Single ions can be detected from a photon rate
  of 107/s

6P1/2
650nm
493nm
Metastable 47s
5D3/2

• Important additional
• constraint
• Drastic background
• reduction

GR 5.28 MHz GB 15.2 MHz
6S1/2
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Paths to a Ton Scale Experiment

• EXO-200
• Low-background Xe TPC with 200kg of 80 enriched
  136Xe
• No Ba Tagging

• Liquid Phase Barium Tagging
• Ion transfer from LXe to ion trap
• Ba tagging in Situ
• Ba tagging in SXe

• Gas Phase RD
• 100kg prototype detectors
• Ion manipulation in gas

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EXO-200
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Improving the Energy Resolution
Ionization and Scintillation results using 207Bi
Ionization alone s(E)/E 3.8 _at_ 570 keV or
1.8 _at_ Qßß Ionization Scintillation s(E)/E
3.0 _at_ 570 keV or 1.4 _at_ Qßß E.Conti et al.
Phys. Rev. B (68) 054201 EXO-200 will collect
3-4 times as much scintillation
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acrylic supports
LAAPD plane (copper) and x-y wires (photo-etched
phosphor bronze)
Central HV plane (photo-etched phosphor bronze)
teflon light reflectors
field shaping rings (copper)
flex cables on back of APD plane (copper on
kapton)
x-y crossed wires, 60o
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EXO-200 Copper Chamber
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The EXO-200 detector
class 100 clean room
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Materials qualification database
Neutron Activation Analysis (NAA) - Alabama
(MIT reactor) ICP-MS and GD-MS - INMS (Ottawa),
commercial outfits Radon emanation - Laurentian
(Sudbury) Gamma counting - Neuchâtel, Alabama
Alpha counting - Alabama, Carleton, SLAC,
Stanford Monte Carlo
330 entries
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Xenon Handling System
xenon condenser
xenon purity monitor and heater
EXO-200 goal 0.1 ppb O2 equivalent t 4 ms
(electrons)
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muon flux at WIPP ( 1700 m.w.e.) 4.7710-3 m-2
s-1 (3.1010-3 m-2 s-1sr-1, 15 m-2
h-1) E.-I.Esch et al., Nucl. Instr. Meth. A
538(2005)516
EXO-200
?
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EXO-200 Majorana mass sensitivity

• Assumptions
• 200kg of Xe enriched to 80 in 136
• s(E)/E 1.4 obtained in EXO RD, Conti et al.,
  Phys Rev B 68 (2003) 054201
• Low but finite radioactive background 20
  events/year in the 2s interval centered around
  the 2457.9(0.4) keV endpoint 1
• 5) Negligible background from 2nbb
  (T1/2gt11022yr) 2

• 1) M. Redshaw, J., McDaniel, E. Wingfield and
  E.G. Myers (Florida State Precision Penning
  Trap), to be submitted to Phys. Rev C.
• 2) R. Bernabei et al., Phys. Lett. B 546, 23
  (2002)
• 3) Rodin, et. al., Nucl. Phys. A 793 (2007)
  213-215
• 4) Caurier, Phys. Rev. Lett. 100, 052503 (2008)

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Future Plans

• All EXO-200 infrastructure is underground
  undergoing final testing
• The LXe TPC is built
• Electronics testing underway
• The TPC is scheduled to be installed in the
  cryostat before the end of 2009
• Running will start next year with natural Xenon
  with an eventual switch to enriched Xenon
• Ba Tagging and gas phase RD ongoing

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Enriched Xenon Observatoryfor double beta decay
K.Barry, E.Niner, A.Piepke Physics Dept, U. of
Alabama, Tuscaloosa Al P.Vogel Physics Dept
Caltech, Pasadena Ca M.Dixit, K.Graham, C.Green,
C.Hagemann, C.Hargrove, E.Rollin, D.Sinclair,
V.Strickland Carleton University, Ottawa,
Canada C. Benitez-Medina, S.Cook, W.Fairbank Jr.,
K.Hall, B.Mong Colorado State U., Fort Collins
Co M.Moe Physics Dept UC Irvine, Irvine
Ca D.Akimov, I.Alexandrov, A.Burenkov, M.Danilov,
A.Dolgolenko, A,Karelin, A.Kovalenko,
A.Kuchenkov, V.Stekhanov, O.Zeldovich ITEP
Moscow, Russia B.Aharmim, K.Donato, J.Farine,
D.Hallman, U.Wichoski Laurentian U., Sudbury,
Canada H.Breuer, C.Hall, L.Kaufman, D.Leonard, S.
Slutsky, Y-R. Yen U. of Maryland, College Park
Md K.Kumar, A.Pocar U. of Massachusetts, Amherst
Ma M.Auger, G.Giroux, R.Gornea, F.Juget,
G.Lutter, J-L.Vuilleumier, J-M.Vuilleumier Laborat
ory for High Energy Physics, Bern,
Switzerland N.Ackerman, M.Breidenbach, R.Conley,
W.Craddock, S. Herrin, J.Hodgson, D.McKay,
A.Odian, C.Prescott, P.Rowson, K.Skarpaas,
K.Wamba, J.Wodin, L.Yang, S.Zalog SLAC, Menlo
Park CA L.Bartoszek, R.DeVoe, M.Dolinski,
P.Fierlinger, B.Flatt, G.Gratta, M.Green,
F.LePort, M.Montero-Diez, R.Neilson,
A.Reimer-Müller, A.Rivas, K.OSullivan, K.Twelker
Stanford University, Stanford, Ca
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Back up Slides
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Xenon Enrichment
Natural Xe
Total of 200kg of Xe enriched to 80 in 136Xe
Enriched Xe
EXO Stockpile
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Ba Tagging
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Ba Tagging Schematic for EXO
Ba grabber
Quadrupole linear ion trap
CCD
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Single Ba ion trapping
RF quadrupole potential in each segment Multiply
by 16, and add a buffer gas to cool down the ions
injected at one end of the trap into a DC minimum
Ba oven
e-gun
Fluorescence imaging
...
longitudinal trapping
short longitudinal trapping segment
radial trapping
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Detection of Single Ions in Buffer Gas
3 ions
2 ions
1 ion
Single ion cloud (5 s integration)
0 ions
2 ions
1 ion
0 ions
10-3 Torr He P(493) 75 µW P(650) 300 µW
3 ions
Electrodes glowing from scattered laser light
M. Green, et al. Phys. Rev. A 76 023404 (2007)
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Capacitive cryo-tip
2 mm
Cryo-tip (ground)
1 mm
Picture of sensor
Electrostatic field lines
Capacitive sensor (-HV)
from LXe
Ion mobility µ 0.3 cm2/kVs
v µ x 1kV/cm 0.3 cm/s
K. Wamba et al., NIM A 555 (2005) 205
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Full EXO Sensitivity

• Assumptions
• 80 enrichment in 136
• Intrinsic low background Ba tagging eliminate
  all radioactive background
• Energy res only used to separate the 0? from 2?
  modes
• Select 0? events in a 2s interval centered
  around the 2457.9(0.4) keV endpoint1
• 4) Use for 2?ßß T1/2gt11022yr2

1) M. Redshaw, J., McDaniel, E. Wingfield and
E.G. Myers (Florida State Precision Penning
Trap), to be submitted to Phys. Rev C. 2) R.
Bernabei et al., Phys. Lett. B 546, 23 (2002) 3)
Rodin, et. al., Nucl. Phys. A 793 (2007)
213-215 4) Caurier, Phys. Rev. Lett. 100,
052503 (2008)