CHEM 1225B

swipp [at] umd [dot] edu

William McDonough

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My research focuses on differentiating between various models of the Bulk Silicate Earth (BSE). The surface heat flow is 46 ± 3 TW, with contributions from primordial and radiogenic energy. The abundance of heat producing elements (HPE; uranium (U), thorium (Th), and potassium (K)) in the Earth varies by a factor of 3 among the diverse BSE models. The continental crust is estimated to contain 7 ± 1 TW of radiogenic energy, the mantle is estimated to have between 2-29 TW of radiogenic energy, and the core’s contribution is considered to be negligible. The factor of ten uncertainties for estimates of the radiogenic heat in the mantle reveal that the ratio of primordial vs. radioactive heat production in the mantle is a significant unknown. Radioactive heat drives mantle convection, plate tectonics, and the geodynamo.

Over the last decade particle physicists have detected and analyzed the Earth’s flux of geo-neutrinos, electron antineutrinos of terrestrial origin produced during β⁻ decay (n → p + e^- + v_e), providing directed evidence for the concentration and distribution of U and Th inside the Earth. The crustal geoneutrino signal represents a significant component of the total measured flux in continental-based detectors. I am developing models to accurately and precisely predict the concentration and distribution of U and Th in the crustal regions surrounding existing and future detectors. Such data can be used to define the relative mantle and crustal flux contributions and infer the absolute mantle contribution to the total geoneutrino signal. At present, the large uncertainties associated with our estimates of the crustal signal limit our ability to constrain the BSE composition.

There are two actively operating, anti-neutrino detectors (KamLAND [1kT] (Japan)) and Borexino [0.3 kT] (Italy)) online, one to come on-line in 2015 (SNO+ [1kT] (Canada)) and another scheduled to come on-line in 2020 (JUNO [20kT] (China)). Detailed geological models have been developed for the Italian and Canadian detectors. In collaboration with the Japanese and the Italians, I am working to improve upon the geological model for the Japanese detector. I am also beginning a similar effort for the next generation JUNO detector in China. This work primarily involves numerical modeling of the near-field (closest ~500 km) crust surrounding the detector. This data is used in combination with global models for the far-field crust and mantle to predict the signal before it is actually detected by JUNO. By increasing the accuracy of our estimates of the U and Th abundance in the crust, we can better constrain the amount of U and Th in the mantle, which in turn will place constraints on the BSE models. Our group is also involved in collaborative work on precision anti-neutrino flux measurements for the monitoring of nuclear reactors.

Baldoncini, M., Strati, V., Wipperfurth, S.A., Ricci, B., McDonough, W.F., Mantovani, F., and Fiorentini, G. (2016) Geoneutrinos and reactor antineutrinos at SNO+. Journal of Physics: Conference Series. 718 062003. DOI: 10.1088/1742-6596/718/6/062003

Li, V.A., Dorril, R., Duvall, M.J, Koblanski, J., Negrashov, S., Sakai, M., Wipperfurth, S.A., Engel, K., Jocher, G.R., Learned, J.G., Macchiarulo, L., Matsuno, S., McDonough, W.F., Mumm, H.P., Murillo, J., Nishimura, K., Rosen, M., Usman, S.M., Varner, G.S. (2016) Invited Article: miniTimeCube. AIP Review of Scientific Instruments. 87 021301. DOI: 10.1063/1.4942243

Šrámek, O., Roskovec, B., Wipperfurth, S.A., Xi, Y., and McDonough, W.F. (2016) Revealing the Earth's mantle from the tallest mountains using the Jinping Neutrino Experiment. Scientific Reports. 6 33034. DOI: 10.1038/srep33034

Strati, V., Wipperfurth, S.A., Baldoncini, M., Mantovani, F., and McDonough, W.F. (2017) Perceiving the crust in 3D: a model integrating geological, geochemical, and geophysical data. Geochemistry, Geophysyics, Geosystems. 18 DOI: 10.1002/2017GC007067

Wipperfurth, S.A., Guo, M., Sramek, O., and McDonough, W.F. (2018) Earth's chondritic Th/U: Negligible fractionation during accretion, core formation, and crust–mantle differentiation. Earth and Planetary Science Letters. 498 196-202. DOI: 10.1016/j.epsl.2018.06.029

Li, V.A., Koblanski, J., Dorrill, R., Duvall, M.J., Engel, K., Jocher, G.R., Learned, J.G., Matsuno, S., McDonough, W.F., Mumm, H.P., Negrashov, S., Nishimura, K., Rosen, M., Sakai, M., Usman, S.M., Varner, G.S., Wipperfurth, S.A.. (2018) Studies of MCP-PMTs in the miniTimeCube neutrino detector. AIP Advances. 8 095003. DOI: 10.1063/1.5043308

Strati, V., Wipperfurth, S. A., Baldoncini, M., McDonough, W. F., Gizzi, S., Mantovani, F. (2020) Geoneutrinos from the rock overburden at SNO+. Journal of Physics: Conference Series. 1342 DOI: 10.1088/1742-6596/1342/1/012020

Wipperfurth, S. A., Šrámek, O., McDonough, W. F. (2020) Reference Models for Lithospheric Geoneutrino Flux. Journal of Geophysical Research: Solid Earth. 125 e2019JB018433. DOI: 10.1029/2019JB018433

McDonough, W. F., Šrámek, O., Wipperfurth, S. A. (2020) Radiogenic power and geoneutrino luminosity of the Earth and other terrestrial bodies through time. Geochemistry, Geophysics, Geosystems. 21 (7) e2019GC008865. DOI: 10.1029/2019GC008865