adam bernstein lawrence livermore national laboratory rare event detection group 1 prepared by llnl...
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Adam BernsteinLawrence Livermore National Laboratory
Rare Event Detection Group
1
Prepared by LLNL under Contract DE-AC52-07NA27344
LLNL-PRES-653915
WATCHMAN: a WATer CHerenkov Monitor for ANtineutrinos
Simulation courtesy Jocher/Usman/Learned NGA and U of Hawaii
Reactors emit huge numbers of antineutrinos
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• 6 antineutrinos per fission
• 1021 fissions per second in a 3,000-MWt reactor
• About 1022 antineutrinos per second from a typical PWR - unattenuated and in all directions
• The catch: mean free path in water is ~300 light years
A look back: Small, deployable near field antineutrino detectors for reactor safeguards
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Determine reactor on/off statuswithin 5 hours with 99.9% C.L.
Measure thermal power to 3% in one week
Detect switch of 70 kg Pu-U with known power and initial fuel content
Rate-based (analysis improves with spectral measurement)• Simple detector design• 25 m from core, outside containment
8’useful for IAEA reactor safeguards• Shipper-receiver differences• Research reactor power• Safeguards by Design and Integrated Safeguards
Long-range reactor monitoring is possible right now– but only for high power reactors with hard-to-scale technology
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1000 tonnes scintillator
1000 m depth
Per month:- 16 reactor antineutrinos- 1 background event
From 130 GWt of reactors
~3% of signal from South Korean reactors @ 400 km standoff
The KamLAND detector
Standoff reactor monitoring is an NNSA Strategic Goal
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Current 3 year scoping project Consider Use Cases Select a Site Create a Preliminary Design, Budget and Schedule Measure of Shallow Depth Backgrounds
2014-15 Decision point to deploy WATCHMAN, a kiloton scale antineutrino detector, ~10 km from a US reactor
Proposed joint funding with Office of Science, High Energy Physics (DOE-SC-HEP)
Ultimate standoff depends on backgrounds from reactors and natural sources
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Global reactor antineutrino fluxessimulation courtesy Jocher/Learned NGA/UH
• Gadolinium-doped (light) wateris the most viable option for scaling to the largest sizes
• Strong synergy with fundamental physics research – Many groups/countries are already investing in this technology
• SuperKamiokande is today’s largest comparable detector - 50,000 tons of H2O
Science & Global Security, 18:127–192, 2010Background 99% confidence level scenarios Detector target mass Standoff in km
Low background Discover 10 MWt reactor in 1 year 1 MT 200
High reactor backgrounds Discover 15 MWt in 6 months 5 MT 100
Possible to extend beyond these limits if antineutrino direction can be recovered
Some current technologies for discovering unknown reactors
• Satellite imaging– Very effective at seeing plumes/heat signature– Non-specific signature– Susceptible to weather, and burial/heat removal countermeasures– Continuous power measurement not practical – Broad area search not practical – Cueing required from other sources of information
• Radionuclide detection– Specific to fissile material production– Cross-border detection possible– Depends on accidental release of activity from reactor– Localization and quantification difficult
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Possible advantages of remote reactor monitoring with antineutrinos
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• For monitoring State/agency– Antineutrinos are highly penetrating and difficult to shield– Continuous long term monitoring is possible– Difficult to mask without another reactor– Some directional information with sufficient statistics (or multiple detectors)
• For the State being monitored– Does not interfere with reactor operations or other activities– Provides limited and specific information about reactor – operational status
and/or thermal power– Willingness to deploy detector indicates likely adherence to any agreement
that restricts undeclared reactors
• For host and monitoring States– Science opportunities facilitate bilateral or multilateral engagements
• Background: Declared reactors near detector can ‘outshine’ small undeclared reactors
• Limited information: (see advantages) – Crude power estimate and operational status only in the far field
• Cost/Complexity: Current technology requires existing underground space (100-1000 meters deep) in the geographical region of interest
Disadvantages and complications
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Why is this work of potential interest ?
• Similar to other joint global nonproliferation and science efforts – CTBT’s International Data Center regularly shares seismic
data with the science community (Intl. Science Ctr.) – infrasound and hydroacoustic also shared
– The SESAME synchroton project in Jordan – “"SESAME…will serve as a beacon, demonstrating how shared scientific initiatives can help light the way towards peace” 45 Nobel Laureates
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• Exclude or discover small undeclared reactors with high confidence in a wide geographical region
• Small reactor 10 MWt standard: 4 kg Pu/year • Alternative technologies
– Radionuclide sensing - depends on accidental release from fuel rods in reactor, ambiguity about location
– Satellite surveillance - requires cueing information
Current Water Cherenkov detectors are large, but can’t identify antineutrinos
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• 20 years of use in neutrino detection
• IMB, Kamiokande, Super-Kamiokande, SNO -1000 – 50,000 tons
• Above the Cerenkov threshold (v>c/n), the number of emitted photons is proportional to the incident neutrino energy.
= q acos(1/n) = 42o
Ekin > 0.26 MeV
~40 m
The SuperKamiokande 50,000 ton water detector
e+ p = e+ + n
For Water Cherenkov antineutrino sensitivity we need Gadolinium doping to efficiently detect neutrons in water
Inverse Beta Decay in Theory
World’s firstGd-H2O detector @ LLNL0.25 ton
Neutron captures in Super-K - 4.3 MeV Evis
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Neutron captures in LLNLGd-H2O detector
n
ep
~ 8 MeV
511 keV
511 keV e+
Gd
t ~ 30 ms
Inverse Beta Decay in A Detector
Neutron sourcebackground
The WATCHMAN collaboration
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UC Davis
UC Berkeley
UC Irvine
U of Hawaii
Hawaii Pacific
A. Bernstein, N. Bowden, S. Dazeley, D. Dobie
P. Marleau, J. Brennan, M. Gerling, K. Hulin, J. Steele, D. Reyna
K. Van Bibber, G. Orebi Gann, C. Roecker, T. Shokair R. Svoboda, M. Askins, M. Bergevin
Students getting WATCHMAN-related Ph.D. s
J. Learned, J. Maricic
S. Dye
M. Vagins, M. Smy
S.D. Rountree, B. Vogelaar, C. Mariani, Patrick Jaffke
World Leaders in the Development and Use of Large Water Cherenkov Detectors
2 National Laboratories6 Universities25 collaborators 15 physicists5 engineers 2 Post-docs3 Ph.Ds
Compared with other large water detector R&D
Detector EGADS WATCHMAN Hyper-K
Status Ongoing 2016 start 2021 or beyond
Mass (ton) 200 1,000 500,000
Type Gd-WCD Gd-WCD Pure H2O or Gd-WCD
Purpose Measure background, material compatibility, energy thresholdToo small to see reactor antineutrinos
Remotely detect reactor antineutrinos – beam and reactor physics potential
Neutrino oscillations, proton decay, supernovae… WATCHMAN would demonstrate Gd option for HyperK or other future bigdetectors
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WATCHMAN Program Plan
4 year Construction and Operation Phase (2016-2019)• Demonstrate sensitivity to reactor ON/OFF transition at ~10 km standoff, with
at most 30 days of ON and OFF data, with at least 99% confidence, with a kiloton scale detector.
• Demonstrate innovative, scalable, cost-effective Gd-H2O Cherenkov technology, pioneered and patented by LLNL staff and WATCHMAN collaborators
• Provide a data-sharing and joint funding model for the scientific community
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3.5 year Scoping Phase (2012-2015)• Consider Use Cases• Find a Site • Create a Preliminary Design, Budget and Schedule• Measure of Shallow Depth Backgrounds
Two Possible Use Cases - Large Detectors
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Ensure no reactors are operating at 10-200 km standoff
Ensure only declared reactors are operating at a known site
•Simplest scenario– Searches for excess antineutrino signal
above background
•Low background levels
•Best suited to excluding new reactors in areas without existing reactors
•Countermeasures are costly– Build a declared reactor near the
detector– Physically attack the detector
•More complex– Requires knowledge of signal from
declared reactors
•Higher backgrounds due to other reactors
•Adjusting power of declared reactors is a potential countermeasure
Not yet claiming significance for any particular Treaty or Agreement
Preferred and Alternate sites identified
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Preferred Alternate Reactor Location PERRY Reactor
Perry OhioAdvanced Test Reactor,
Idaho Falls, Idaho
Thermal Power (MWt) 3875 120
Detector Location Morton Salt/IMB mine (!) Painesville, Ohio
New excavationIdaho National Laboratory
Standoff 13 km - the only reactor in the US at a suitable distance from a deep mine
1 km
Overburden (mwe) 1430 ~360
Approval status Morton Salt has approved installation
INL has approved excavation studies
Physics potential Greater physics potential due to greater depth
Antineutrino signal and background
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n (100-200 MeV)
n
n
m
m
9Lib
Signal in 1 kiloton of water
ne
p
~ 8 MeV
511 keV
511 keVe+
Gd
t ~ 30 msprompt e+ signal + n capture on Gd
• Exactly two Cerenkov flashes• within ~100 microseconds • Within a cubic meter voxel
Backgrounds:1. Real antineutrinos 2. Random event pair coincidences3. Muon induced high energy
neutrons4. Long-lived radionuclide decays
Very different from most backgrounds
Full Signal and Background Monte Carloat the PERRY reactor site
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Depth Dependent per day
• Fast Punch-through Neutrons ~1
• Radionuclides not well known ~1-10
Depth-Independent• PMT and Rock Gamma/Neutrons ~1
Other Reactors <1
Geo-antineutrinos negligible ___________________________________________Total Background ~10
Perry Reactor Signal 8-12
Preliminary Design Task
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• Stainless tank assembled in place
• ~3.5 kTon total mass ~1 kTon fiducial region
• ~4800 Target PMTS looking “in”
• 480 Veto PMTs on same frame looking “out”
• Custom recirculation system for Gd-doped water
Drift layout at Morton Salt Mine Close-up of Veto PMT Wall
450
feet
78 feet
Background Measurements at the Kimballton Underground Research Facility
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• Drive in access down to 1500 foot depth
• First-ever continuousmeasurement as a function of depth
• Most important at shallow depths (300 feet, alternative site)
• Final measurement will be at the 1400 foot depth of preferred site
Multiplicity and Recoil Spectrometerfor fast neutron energy spectrum
Small version of WATCHMAN(WATCHBOY) to measure muogenic radionuclide backgrounds
Entering KURF
Physics Synergy
WATCHMAN will provide:
• The U.S.’s only and one of the world’s largest supernova detectors
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Requires nearbyneutrino beam
Requires upgrade to scint.
Science funding agency co-investment is critical to the project’s success‘Positive dual-use’ aspect strengthens the case for long-range monitoring
WATCHMAN may also measure:
• the ordering of the neutrino masses – a major question for 21rst century physics
• a proposed 4th neutrino flavor ( ?)
• non-standard neutrino interactions
• A test facility for future large neutrino detectors (advanced PMTs, water-based scintillator…)
Georg Raffelt, MPI Physics, Munich ISOUPS, Asilomar, 24–27 May 2013
Underground Detectors for Supernova Neutrinos
Super-K (104)KamLAND (400)
WATCHMAN (400 events)
In brackets eventsfor a “fiducial SN”at distance 10 kpc
LVD (400)Borexino (100)
IceCube (106)
Baksan (100)
SNO+ (400)
Daya Bay (100)
~50% chance of Type-II SN occurring before LBNE comes on line.WATCHMAN would be the only detector in the U.S. to see it.Also the only detector in the world with real-time pointingcapability to the supernova source in the sky
• The ISODAR antineutrino source– 60 MEV H2+ cyclotron - strong interest from industry for
isotope production/medical applications– Be neutron production target– 7Li enriched lithium target
Isotope Decay at Rest (ISODAR) neutrino source at 16meters could extend WATCHMAN physics
1. Sterile neutrino searcharXiv:1205.4419v2
ISODAR (green) improves significantlyon previous constraints from LSND (red) and TEXONO (blue)
2. Non-standard interactions/Weinberg angle arXiv:1307.5081v1
ISODAR (solid) has outstanding sensitivity to sterile neutrinos (not affected by the reactor)
• Issues under study:• Accelerator deployment feasiblity
and mine acceptance
• Oil or water-based scintillator may be needed
• 2014 WATCHMAN decision will precede accelerator availabilty
and modifications seenin anomalous rate
Sensitivity of WATCHMAN to sterile neutrino oscillations using the ISODAR beam - examples
Predicted
Expectedmeasurement
Oscillation patterns for a sterile neutrinoISODAR 6 MeV antineutrino source16 meter standoff from detector center
Pure water, 1% scintillator andpure scintillator options
Plots courtesy of Mike Shaevitz, Columbia U.
Conclusions
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• Remote reactor monitoring may fill an important niche – Continued work on use cases, gap analysis, treaty relevance
• WATCHMAN is a natural next step in demonstrating this potential nonproliferation capability
• WATCHMAN also has strong physics potential
• Science community interest in WATCHMAN is strong – 2013 community report mentioned WATCHMAN– April 2014 APS front-page article– Major focus in May 2014 community workshop at LBL– R&D support in 2015 from science funding agencies
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