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Present and future
of Geo-neutrinos
Bill McDonough
Geology, U Maryland
Plate Tectonics,
Convection,
Geodynamo
Does heat from radioactive decay
drive the Earth’s engine?
Nature & amount of Earth’s thermal power
radiogenic heating vs secular cooling
- abundance of heat producing elements (K, Th, U) in
estimates of BSE from 9TW to 36TW
the Earth
- clues to planet formation processes
constrains chondritic Earth models
- amount of radiogenic power to drive mantle
convection & plate tectonics
estimates of mantle 1.3TW to 28TW
- is the mantle compositionally layered? or has large
layers, LLSVP, superplume piles
structures?
the future is…
Geoneutrino studies
Summary of geoneutrino results
SILICATE EARTH MODELS
TW scales relative to U
Cosmochemical: uses meteorites – 10 TW
10, 20, 30 TW ≈ 10, 20, 30 ppb
Geochemical: uses terrestrial rocks –20 TW
Geodynamical: parameterized convection – 30 TW
Constructing a 3-D
reference model Earth
assigning chemical
and physical states
to Earth voxels
1o x 1o x “z” tile
mapping of elements
Huang et al (2013) G-cubed arXiv:1301.0365
Uranium Abundance in Middle Continental Crust layer
UMCC
(mg/g)
Average middle Cont. Crust U abundance is 0.97 0.58
0.36 mg/g
Rudnick and Gao (2003) 1.3 mg/g
Predicted Global geoneutrino flux
based on our new Reference Model
Geoneutrino detection rate
Huang et al (2013) G-cubed
arXiv:1301.0365 10.1002/ggge.20129
--TNU: Terrestrial Neutrino Unit
-- 1 TNU = one geoneutrino event
per 1032 free protons per year
Near Field: six closest 2° × 2° crustal voxels
Far Field = bulk crust – near field crust
What’s hidden in the mantle?
Seismically slow “red” regions in the deep mantle
Can we image it
with geonus?
Ritsema et al (Science, 1999)
Testing Earth Models
Mantle geoneutrino flux (238U & 232Th)
Šrámek et al (2013) EPSL 10.1016/j.epsl.2012.11.001; arXiv:1207.0853
50
40
30
Total flux
(TNU)
20
Intercept = ~8 TNU
present uncertainty is
large (±6 TNU),
comparable to other
recent reports
SNO+
Borexino
KamLAND
m=
1.0
Slope = 1.0
The Mantle beneath
the global array of
detectors sees a
uniform mantle flux
(~10% variation)
Oceanic
detector
10
b = 8.4 (TNU)
Mantle
contribution
0
0
10
20
30
40
Crustal contribution to flux (TNU)
Predicted geoneutrino flux
Total flux at surface
dominated by
Continental crust
Yu Huang et al (2013) G-cubed arXiv:1301.0365
10.1002/ggge.20129
Mantle flux at the
Earth’s surface
dominated by
deep mantle structures
Šrámek et al (2013) EPSL 10.1016/j.epsl.2012.11.001; arXiv:1207.0853
Hanohano
An experiment with joint
interests in Physics,
Geology, and Security
Size: scalable from 1 to 50 kT
10-yr cost est: $250M @ 10 kT
- multiple deployments
- deep water cosmic shield
- control-able L/E detection
A Deep Ocean
Deployment Sketch
e Electron
Anti-Neutrino
Observatory
Descent/ascent 39 min
2 Candidate
Off-shore Sites
for Physics
San Onofre, California- ~6 GWth
Maanshan, Taiwan- ~5 GWth
Need study of backgrounds versus depth
16 June 2008
John Learned at LBL
14
Addressing Technology
Issues
• Scintillating oil studies in lab
20m x 35m
fiducial vol.
– P=450 atm, T=0°C
– Testing PC, PXE, LAB and
dodecane
– No problems so far, LAB
favorite… optimization needed
1 m oil
• Implosion studies
2m pure water
– Design with energy absorption
– Computer modeling & at sea
– No stoppers
• Power and comm, no problems
• Optical detector, prototypes OK
• Need second round design
Implosion signals from empty sphere and a sphere with 30%
volume filled with foam
1
0.8
Pressure (norm)
0.6
0.4
0.2
0
0.0025
-0.2
0.0035
0.0045
0.0055
0.0065
0.0075
0.0085
0.0095
-0.4
-0.6
30% Foam filled (4105m)
Empty (4280m)
-0.8
-1
Time (seconds)
16 June 2008
John Learned at LBL
15
Ocean Deployments
Sketch of prototype detector ~ 1m
for deployment off Honolulu
by Kilo Moana
Kilo Moana:
U Hawaii operated UNOLS vessel, based at HNL
UNOLS:
University-National
Oceanographic Laboratory
System