Searching for Double Beta Decay with EXO200

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Searching for Double Beta Decay with
EXO-200 Carter Hall (SLAC)
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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

but

• Energy resolution modest compared to 76Ge 130Te
• Experimental technique less mature

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Xenon can be continuously purified of chemical
and radioactive contaminants
Two gamma lines from 207Bi
Fluids often have extraordinarily
low radioactivity, and noble gases are
particularly simple to purify.
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SLAC Xenon Purity Monitor
To measure the electron lifetime

• 106 photoelectric electrons produced by laser
• initial charge measured at photocathode
• electrons drift through 11 cm of LXe
• final charge measured by anode

laser
Purpose develop procedures for achieving and
maintaining high LXe purity, and test proposed
detector materials for outgassing and poisoning
properties.
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SLAC Xenon Purity Monitor
SAES purifier
Cooling loop from Polycold refrigerator
Xenon supply
purity monitor cryostat filled with HFE
recirculation pump
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Outgassing tests with detector materials
Outgassing poisons the LXe, but stops after
several weeks. Re-circulation recovers the
purity.
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Liquid xenon calorimetry
Measure the event energy by collecting the
ionization on the anode and/or observing the
scintillation.
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Liquid xenon data show an anti-correlation
between ionization and scintillation
1 kV/cm
Bi-207 source
570 keV
Energy resolution 3.0 _at_ 570 keV or 1.4 _at_
Q(bb)
Factor of two better than most recent Xe bb0n
experiment
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The crown jewels of EXO
200 kg of xenon enriched to 80 in 136Xe the
most isotope in possession by any ??0?
collaboration.
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EXO-200 the first 200 kg bb0n experiment
Copper liquid xenon vessel
lead shielding
HFE-7000 cryofluid
copper cryostat
200 kg of Liquid Xenon to be contained in low
background 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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Copper LXe vessel design is nearly finalized...
fabrication will begin soon
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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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EXO-200 dual TPC
charge drift direction
cathode
crossed wire planes and avalanche photodiodes
field shaping rings
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Hexagonal Wire Grids and APD array
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Cabling of APD array
Cable routing is tricky... Space must be
minimized to conserved enriched xenon
paper mock-up of cabling scheme
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TPC wire grids produced by photoetching
Charge collection with photoetched wire grids
Wires connected in gangs-of-three to reduce
channel count
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Scintillation detected by Avalanche Photodiodes
Gang-of-seven APDs
EXO-200 will have 518 APDs
Triply redundant electrical connections made by
photoetched spider
Sensitive area is 16 mm in diameter
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Assembly of EXO-200 lead shield in the EXO
cleanrooms at Stanford began last month
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Installation of EXO-200 cryostat at Stanford
May 25-28 2006
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EXO-200 xenon handling and cryogenics
refrigerators
Xenon purification system
xenon gas compressors
Crane for assembling lead arches
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EXO-200 Electronics designed and built at SLAC
Front-end board
Trigger module
One vessel contains a fully functional ionization
AND scintillation detector
One vessel contains a fully functional ionization
AND scintillation detector
Signal cables enter via 2 more teflon pipes in
the 90 plane (not shown)
Signal cables enter via 2 more teflon pipes in
the 90 plane (not shown)
Other configurations still under study
Other configurations still under study
Cryostat being fabricatedat SDMS (Grenoble)
Cryostat being fabricatedat SDMS (Grenoble)
EXO RD data show an anti-correlation between
ionization and scintillation
EXO RD data show an anti-correlation between
ionization and scintillation
EXO-200 xenon handling system
EXO-200 xenon handling system
Lead Shielding and Crane
Lead Shielding and Crane
Anti-correlated ionization and scintillation
improves the energy resolution in LXe
Anti-correlated ionization and scintillation
improves the energy resolution in LXe
Extensive operational experience gained with SLAC
xenon purity monitor
EXO-200 Electronics designed and built at SLAC
EXO-200 will be housed in a class-100 clean room
Extensive operational experience gained with SLAC
xenon purity monitor
EXO-200 Electronics designed and built at SLAC
EXO-200 will be housed in a class-100 clean room
Refrigeration Layout
Refrigeration Layout
A xenon vessel made from teflon could be free
from natural radioactivity
A xenon vessel made from teflon could be free
from natural radioactivity
SLAC Xenon Purity Monitor
SLAC Xenon Purity Monitor
Liquid xenon calorimetry
Liquid xenon calorimetry
The crown jewels of EXO
Re-purification cures poisoning by air
Purification system under construction in SLD
cleanroom
The crown jewels of EXO
Re-purification cures poisoning by air
Purification system under construction in SLD
cleanroom
SLAC Xenon Purity Monitor
SLAC Xenon Purity Monitor
Crossed wire planes and APD array measure event
energy and position
Crossed wire planes and APD array measure event
energy and position
Recirculation pump
Recirculation pump
Physics data taking will take place underground
at the WIPP facility in Carlsbad, NM
Physics data taking will take place underground
at the WIPP facility in Carlsbad, NM
Three heat exchangers integrated with cryostat
Three heat exchangers integrated with cryostat
TPC vessel cooled with HFE-7000 heat transfer
fluid
TPC vessel cooled with HFE-7000 heat transfer
fluid
EXO-200
EXO-200
Circular welds
Circular welds
xenon bottle farm
xenon bottle farm
EXO-200 will be ready very soon
EXO-200 will be ready very soon
1 kV/cm
1 kV/cm
Xe in
Xe in
triple redundant PolyCold refrigerators located
in Module 3
triple redundant PolyCold refrigerators located
in Module 3
Crane
Crane
vacuum insulated refrigerant lines
vacuum insulated refrigerant lines
teflon liquid xenon vessel
teflon liquid xenon vessel
Xenon supply
Xenon supply
Cooling loop from Polycold refrigerator
Cooling loop from Polycold refrigerator
three of six modular clean rooms
three of six modular clean rooms
APD plane below wire grids
APD plane below wire grids
Dual compressors in assembly
Dual compressors in assembly
refrigerant line layout
refrigerant line layout
SAES Zr purifier
SAES Zr purifier
To measure the electron lifetime
To measure the electron lifetime
Bellows pump
Bellows pump
xenon condenser
xenon condenser
ITEP
ITEP
Ionization alone ?(E)/E 3.8 _at_ 570 keV or
1.8 _at_ Q??
Compilation of Xe resolution results

• Largest double beta decay detector ever (factor
  of 5)
• Largest amount of separated isotope (factor of
  10) in hand
• Tie for the largest Xe detector ever
• But we are - ultra-clean
• - enriched xenon
• First liquid bath cooled/shielded LXe detector
• First massive use of APDs for scintillation
  readout
• First teflon detector vessel
• Expect first observation of ??2? decay in 136Xe
• Expect ??0??sensitivity equal to best experiments
  in the world

Ionization alone ?(E)/E 3.8 _at_ 570 keV or
1.8 _at_ Q??
Compilation of Xe resolution results

• Largest double beta decay detector ever (factor
  of 5)
• Largest amount of separated isotope (factor of
  10) in hand
• Tie for the largest Xe detector ever
• But we are - ultra-clean
• - enriched xenon
• First liquid bath cooled/shielded LXe detector
• First massive use of APDs for scintillation
  readout
• First teflon detector vessel
• Expect first observation of ??2? decay in 136Xe
• Expect ??0??sensitivity equal to best experiments
  in the world

underground at WIPP
underground at WIPP
Small RD teflon vessel
Small RD teflon vessel
APDs grids
APDs grids
570 keV
570 keV
HFE-7000
HFE-7000
motor
motor

• 106 photoelectric electrons produced by laser
• initial charge measured at photocathode
• electrons drift through 11 cm of LXe
• final charge measured by anode

• 106 photoelectric electrons produced by laser
• initial charge measured at photocathode
• electrons drift through 11 cm of LXe
• final charge measured by anode

SAES Zr purifier
SAES Zr purifier
valves and instrumentation manifold
electronics rack
valves and instrumentation manifold
electronics rack
LXe fill line
LXe fill line
refrigeration loop (heat exchanger)
refrigeration loop (heat exchanger)
PolyCold refrigerator
PolyCold refrigerator
????
????
Ionization Scintillation ?(E)/E 3.0 _at_ 570
keV or 1.4 _at_ Q?? (twice as good as
most recent xenon ??0? experiment)
Ionization Scintillation ?(E)/E 3.0 _at_ 570
keV or 1.4 _at_ Q?? (twice as good as
most recent xenon ??0? experiment)
motor control
motor control
LXe output line
LXe output line
ballast bottles
ballast bottles
RGA
RGA
Cradle bricks
Cradle bricks
purity monitor cryostat filled with HFE
purity monitor cryostat filled with HFE
lead shielding
lead shielding
HFE-7000 cryofluid
HFE-7000 cryofluid
laser
laser
Edrift1.5 kV/cm
Edrift1.5 kV/cm
copper cryostat
copper cryostat
TPC vessel
TPC vessel
First observation of ionization and scintillation
signals in a all plastic construction
LXe detector
First observation of ionization and scintillation
signals in a all plastic construction
LXe detector
purity monitor vessel
purity monitor vessel
Cathode
Cathode
turbo pump
turbo pump
EXO-200 will collect 3-4 times as much
scintillation... possibly giving further
improvement.
EXO-200 will collect 3-4 times as much
scintillation... possibly giving further
improvement.
Each refrigerator can deliver 1500 W of cooling,
but heat leak only 100 W. Fridge power will be
dialed down to match heat leak by on-off
cycling. Triple redundancy protects xenon
investment, and reduces initial cooldown time to
2 days.
Each refrigerator can deliver 1500 W of cooling,
but heat leak only 100 W. Fridge power will be
dialed down to match heat leak by on-off
cycling. Triple redundancy protects xenon
investment, and reduces initial cooldown time to
2 days.
Liquid Xenon to be contained in low background
vessel, surrounded by 50 cm of ultra pure
cryofluid inside a copper cryostat and shielded
by 25 cm of lead.
Liquid Xenon to be contained in low background
vessel, surrounded by 50 cm of ultra pure
cryofluid inside a copper cryostat and shielded
by 25 cm of lead.
EXO-200 will be assembled and commissioned at
Stanford, then the six clean rooms will be
shipped to WIPP. Operations expected in 1-2 years.
EXO-200 will be assembled and commissioned at
Stanford, then the six clean rooms will be
shipped to WIPP. Operations expected in 1-2 years.
Endwall bricks
Endwall bricks
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.
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.
this work
this work
200 kg of xenon enriched to 80 in 136Xe the
most isotope in possession by any ??0?
collaboration.
200 kg of xenon enriched to 80 in 136Xe the
most isotope in possession by any ??0?
collaboration.
purification system assembed in SLD cleanroom
purification system assembed in SLD cleanroom
We re-purifier LXe continuously while
simultaneously monitoring electron lifetime.
re-circ. pump
We re-purifier LXe continuously while
simultaneously monitoring electron lifetime.
re-circ. pump
cryostat located in Module 1
teflon weld to make the seal
cryostat located in Module 1
teflon weld to make the seal
Rear Wall Bricks
Rear Wall Bricks
Measure the event energy by collecting the
ionization on the anode and/or observing the
scintillation.
Measure the event energy by collecting the
ionization on the anode and/or observing the
scintillation.
Crane in construction Lead shielding final
activity measurements before production
Crane in construction Lead shielding final
activity measurements before production
After machining/welding plates are returned to
shielded storage
Purpose develop procedures for achieving and
maintaining high LXe purity, and test proposed
detector materials for outgassing and poisoning
properties.
After machining/welding plates are returned to
shielded storage
Purpose develop procedures for achieving and
maintaining high LXe purity, and test proposed
detector materials for outgassing and poisoning
properties.
inner and outer cryostat
inner and outer cryostat
Conclusion common impurities (O2, H2O, CO2)
efficiently removed by purifier, recirculation.
Conclusion common impurities (O2, H2O, CO2)
efficiently removed by purifier, recirculation.
Xe out HV feed
Xe out HV feed
Front-end board
Trigger module
EXO clean rooms assembled at Stanford
Front-end board
Trigger module
EXO clean rooms assembled at Stanford
Phys. Rev. B 68 054201
Phys. Rev. B 68 054201
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EXO-200 will move in November 2006 to WIPP in
Carlsbad, NM for physics data taking.
EXO-200 clean rooms at Stanford
EXO-200 cavern underground at WIPP
The EXO cavern underground at WIPP
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Sensitivity of EXO-200
Improves on previous 136Xe experiments by one
order-of-magnitude, and competitive with the best
??0? experiments in the world. EXO-200 will also
make the first observation of bb2n in Xe-136.
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• SLAC is contributing to nearly all aspects of
  EXO-200
• Mechanical design of detector and LXe vessel
• Electronics and DAQ
• Cryogenics, refrigeration, and HFE handling
• Xenon handling and purification
• Slow controls and monitoring
• APD testing and UV reflectance measurements
• Outgassing tests with the xenon purity monitor
• Detector simulation and event reconstruction
  software
• Computer networking and data handling
• Installation at Stanford and WIPP
• High voltage feedthrus
• Cleanroom UPS

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ITEP
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