The decay of the primordial isotopes 238U, 235U, 232Th, and 40K has contributed to the terrestrial heat budget throughout the Earth's history. Hence, the individual abundance of those isotopes are ...key parameters in reconstructing contemporary Earth models. The geoneutrinos produced by the radioactive decays of uranium and thorium have been observed with the Kamioka Liquid‐Scintillator Antineutrino Detector (KamLAND). Those measurements have been improved with more than 18‐year observation time, and improvement in detector background levels mainly with an 8‐year nearly reactor‐free period, which now permit spectroscopy with geoneutrinos. Our results yield the first constraint on both uranium and thorium heat contributions. The KamLAND result is consistent with geochemical estimations based on elemental abundances of chondritic meteorites and mantle peridotites. The High‐Q model is disfavored at 99.76% C.L. and a fully radiogenic model is excluded at 5.2σ assuming a homogeneous heat producing element distribution in the mantle.
Plain Language Summary
The energy to drive the Earth's engine comes from two different sources: primordial and radiogenic. Primordial energy comes from the added heat by collisions of accreting material and less so by the energy accompanying the sinking of metal to form the core. The radioactive decays of heat producing elements (i.e., potassium, thorium, and uranium) also generate energy and some of these decaying elements produce antineutrinos (geoneutrinos). Geoneutrino measurements provide the Earth's fuel gauge for its radiogenic power supply and insights into the planet's cooling history. The measurement accuracy of the KamLAND experiment has been improved by an 18‐year long‐term observation and a reduction of the significant background generated by commercial reactors. Consequently, modern geoneutrino measurements have entered an era of distinct spectroscopic contributions coming from uranium and thorium. The KamLAND result is consistent with compositional models for the bulk silicate Earth (the crust plus the mantle) predicting low to medium radiogenic heat (10–20 TW (1012 W)) and disfavor high concentration models (30 TW). This constraint sets the best limit on the permissible radiogenic energy budget in the Earth. Geoneutrino observations now begin to make significant contributions to the understanding of fundamental driving forces powering the Earth dynamic behavior.
Key Points
Geoneutrino measurement with low reactor neutrino backgrounds improves the distinct spectroscopic contributions of U and Th
Radiogenic power in the Earth estimated from this geoneutrino measurement is consistent with a range of models and disfavors the higher power model
Identifying the Earth's mantle contribution to the total geoneutrino flux strongly depends on an accurate estimation of the crustal contribution
We report on the materials preparation and device fabrication for screen printed Bi2Te3/Bi0.5Sb1.5Te3 annular thermoelectric generators (TEGs) for use in ultra-low-power sensor applications. At a 20K ...temperature gradient, test couples - n- & p-type 1 cm2 squares connected electrically in series with printed Ag traces - demonstrated an average power of 0.068nW at 26nA and 2.6mV. The material preparation leverages mechanical alloying for both the n- and p-type materials in order to reduce electrical resistivity and increase device power output. Screen printed thermoelectric elements were found to have substantial challenges with mechanical failure due to cracking and delamination. This work specifically describes these challenges and corresponding mitigation strategies for screen printing the TEG slurries.
Cosmic-ray muons produce various radioisotopes when passing through material. These spallation products can be backgrounds for rare event searches such as in solar neutrino, double-β decay, and dark ...matter search experiments. The KamLAND-Zen experiment searches for neutrinoless double-β decay in 745 kg of xenon dissolved in liquid scintillator. The experiment includes dead-time-free electronics with a high efficiency for detecting muon-induced neutrons. The production yields of different radioisotopes are measured with a combination of delayed coincidence techniques, newly developed muon reconstruction, and xenon spallation identification methods. The observed xenon spallation products are consistent with results from the FLUKA and GEANT4 simulation codes.
We report a measurement of the strange axial coupling constant $g_A^s$ using atmospheric neutrino data at KamLAND. This constant is a component of the axial form factor of the neutral-current ...quasielastic (NCQE) interaction. The value of $g_A^s$ significantly changes the ratio of proton and neutron NCQE cross sections. KamLAND is suitable for measuring NCQE interactions as it can detect nucleon recoils with low-energy thresholds and measure neutron multiplicity with high efficiency. KamLAND data, including the information on neutron multiplicity associated with the NCQE interactions, makes it possible to measure $g_A^s$ with a suppressed dependence on the axial mass MA, which has not yet been determined. For a comprehensive prediction of the neutron emission associated with neutrino interactions, we establish a simulation of particle emission via nuclear deexcitation of 12C, a process not considered in existing neutrino Monte Carlo event generators. Energy spectrum fitting for each neutron multiplicity gives $g_A^s$ =-0.14$_{-0.26}^{+0.25}$, which is the most stringent limit obtained using NCQE interactions without MA constraints. The two-body current contribution considered in this analysis relies on a theoretically effective model and electron scattering experiments and requires future verification by direct measurements and future model improvement.
In this work, we report the results of a search for MeV-scale astrophysical neutrinos in KamLAND presented as an excess in the number of coincident neutrino interactions associated with the publicly ...available high-energy neutrino datasets from the IceCube Neutrino Observatory. We find no statistically significant excess in the number of observed low-energy electron antineutrinos in KamLAND, given a coincidence time window of ±500 s, ±1,000 s, ±3,600 s, and ±10,000 s around each of the IceCube neutrinos. We use this observation to present limits from 1.8 MeV to 100 MeV on the electron antineutrino fluence, assuming a mono-energetic flux. We then compare the results to several astrophysical measurements performed by IceCube and place a limit at the 90% confidence level on the electron antineutrino isotropic thermal luminosity from the TXS 0506+056 blazar.
Unsteady MHD free convective flow of a chemically reacting incompressible fluid over a vertical porous plate under the combined effects of thermal radiation, Dufour, Soret and constant suction is ...examined. The governing non-linear equations are solved semi analytically using the methods of similarity transformation and perturbation series expansions. Expressions for the velocity, temperature, concentration and Nusselt number for the flow are obtained and presented graphically. The analysis shows that Dufour number increases the temperature and velocity; Soret number increases the concentration and velocity; suction parameter decreases the temperature, concentration and velocity, but increases the Nusselt number; chemical reaction rate decreases the temperature but increases the concentration, velocity and Nusselt number; magnetic field force increases the velocity; Grashof numbers increase the velocity when their values are increasingly varied.
A system is developed to magnetically measure biological antigen-antibody reactions
with a superconducting quantum interference device (SQUID) magnetometer. In this system,
antibodies are labeled ...with magnetic nanoparticles of γ-Fe
2
O
3
, and the
antigen-antibody reactions are measured by detecting the magnetic field from the magnetic
nanoparticles. A setup of the system is described, and the sensitivity of the system is
studied in terms of detectable weight of nanoparticles. Magnetic particles as small as 600 pg
can be detected at present. An experiment is also conducted to measure antigen-antibody
reaction with the present system. It is shown that the sensitivity of the present system is
better than that of the conventional optical method. A one order of magnitude improvement
of sensitivity will be realized by the sophistication of the present system.
A prototype virtual reality simulator for mechanical operations in a sodium-cooled fast reactor is described. Developing simulation capabilities for fuel-handling operations and component inspection ...are of particular emphasis. Building on the first prototype, the objective is to provide multimodal (visual and haptic) sensing functionality, improve component models, and implement select scenarios for demonstration. RoboticsLab, a robotics software development framework, enables the necessary integration and development for mechanical operations simulation, supporting the capabilities for the construction of the virtual reality environment, fast robot prototyping, dynamics simulation, and customized sensing. Special emphasis was given to the simulation of the fuel-handling system and under-sodium viewing operation, which is one of the bottlenecks in the sodium-cooled fast reactor technology roadmap. By providing computer-based visualization, the virtual reality simulator can facilitate better reactor operation training and more comprehensive understanding and development of new concepts in integral mechanical operations.
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