| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | April 29, 2011 |
| Latest Amendment Date: | April 29, 2011 |
| Award Number: | 1068097 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Robin Reichlin
EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | June 1, 2011 |
| End Date: | May 31, 2015 (Estimated) |
| Total Intended Award Amount: | $35,142.00 |
| Total Awarded Amount to Date: | $35,142.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
1 ALOHA TOWER DR HONOLULU HI US 96813-4800 (808)544-0893 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
1 ALOHA TOWER DR HONOLULU HI US 96813-4800 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | STUDIES OF THE EARTHS DEEP INT |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
The investigators will identify the abundance and distribution of thorium (Th) and uranium (U) in the continental crust and underlying mantle beneath a 1000-km wide area in southern Canada - northern central US where there will be an underground laboratory constructed to measure the flux of geoneutrinos from inside the Earth. Geoneutrinos are electron antineutrinos produced inside the Earth during beta-decays of naturally occurring radioactive elements. These particles are messengers of the abundances and distribution of radioactive elements within our planet, and provide direct information that constrains all geochemical and geophysical models of the planet. Geoneutrino detection was successfully performed by two sub-kiloton, liquid scintillator detectors. The SNO+ detector (Sudbury, Ontario, Canada), a kiloton detector, will be the first liquid scintillation neutrino detector with ample fiducial volume and low enough reactor background to allow detection of sufficient geoneutrino counts in approximately 3 years to constrain the Th and U content of the Earth to within ~±25% (1 sigma) or better. All of these detectors are also capable of detecting the electron antineutrino emissions of power nuclear reactors.
By constraining the Earth's nuclear power to uncertainties of about 12% for the regional continental crust the investigators will be able to assess critically the Th and U content of the mantle. Their goals are to test interpretive compositional Earth models against real time neutrino data. The integration of these two independent data sets will provide transformative insights into how the Earth works and constrain the energy source driving Plate Tectonics. In turn, these data will provide unique bulk compositional information about the crust and mantle.
The team will unite scientists from earth sciences and physics with shared goals in antineutrino detection research and its applications. Undergraduate and graduate students will be involved in this research. Results will be communicated to the general public, K-12 educators and members of the US intelligence community. The detection of antineutrinos for nuclear nonproliferation purposes is of significant interest to US national security agencies.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
This project outcomes report describes the efforts of Hawaii Pacific University to complete "Collaborative Research: Estimating the mantle contribution to the geo-neutrino flux at the Sudbury Neutrino Observatory." Hawaii Pacific University provided particle physics expertise to this multidisciplinary project. Other collaborating institutions represented the geosciences. Although particle physics and geology seem distinct disciplines, demarcation between efforts of institutions engaged in collaborative research are often fuzzy. Any mis-attribution of efforts herein is unintended.
A major goal of measuring geo-neutrinos is an estimate of the amounts of thorium and uranium in Earth's mantle. Thorium and uranium are the main heat-producing elements in the Earth. Their amounts in the crust are relatively well known compared with their amounts in the mantle. Estimating the amounts of thorium and uranium in the mantle provides critical constraints on the thermal history and the origin of the Earth. Presently, geo-neutrino detection techniques limit measurements to rate and energy spectrum. Until developments provide access to direction information, separation of crust and mantle signals remains dependent on model inputs.
Motivated by the scheduled deployment of the SNO+ detector, which is capable of detecting geo-neutrinos, a main element of this collaborative research was to estimate the crust geo-neutrino flux at Sudbury. Once established, the mantle flux can be found by subtracting the estimated crust flux from the total flux measured by SNO+. Hawaii Pacific University successfully contributed to this effort through the publication of a review article on geo-neutrinos [1], which details calculations of the geo-neutrino flux.
There remains uncertainty in the amounts of thorium and uranium in the mantle even if the mantle flux is known precisely. Uncertainty arises from incomplete knowledge of the distribution of thorium and uranium in the mantle. Distributions with radial symmetry exhibit no surface variation, making them impossible to decipher without direction information. Different amounts with different distributions can produce the same flux. Distributions of thorium and uranium associated with seismically resolved deep mantle structures, such as the large low seismic velocity provinces, could potentially be determined with sufficient exposure and multiple observations [2]. Hawaii Pacific University successfully contributed to this effort.
Estimation of the mantle contribution to the geo-neutrino flux at the Sudbury Neutrino Observatory remains entirely determined by models until SNO+ begins operation. Once collection of geo-neutrino data commences, it will take several years to accumulate the statistical precision warranting a revisit of the estimated crust flux [3]. After sufficient exposure a careful evaluation of the Huronian Supergroup near SNO+ would improve the observationally informed estimate of the mantle contribution to the geo-neutrino flux at the Sudbury Neutrino Observatory.
1. S.T. Dye, "Geoneutrinos and the Radioactive Power of the Earth," Rev. Geophys. 50 (2012) RG3007.
2. O. Sramek, W.F. McDonough, E.S. Kite, V. Lekic, S.T. Dye, S. Zhong, "Geophysical and geochemical constraints on geoneutrino fluxes from Earth's mantle," Earth Planet. Sci. Lett. 361 (2013) 356-366.
3. Y. Huang et al., "Regional study of the Archean to Proterozoic crust at the Sudbury Neutrino Observatory (SNO+), Ontario: Predicting the geoneutrino flux," Geochem. Geophys. Geosyst. 10.1002/2014GC005397 (2014) 3925-3944.
Last Modified: 06/03/2015
Modified by: Stephen T Dye
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