HR: 0800h
AN: H31D-0443    [Abstracts]
TI: Thermal Neutron Radiography of Deuteriated Water in Soils
AU: * Tumlinson, L G
EM: lgtumlinson@ucdavis.edu
AF: University of California, Davis, Department of Land, Air, and Water Resources University of California, Davis, CA 95616
AU: Hopmans, J W
EM: jwhopmans@ucdavis.edu
AF: University of California, Davis, Department of Land, Air, and Water Resources University of California, Davis, CA 95616
AU: Wilding, M C
EM: mcwilding@ucdavis.edu
AF: University of California, Davis, Department of Geology University of California, Davis, Davis, CA 95616
AU: Silk, W K
EM: wksilk@ucdavis.edu
AF: University of California, Davis, Department of Land, Air, and Water Resources University of California, Davis, CA 95616
AU: Huerta, N J
EM: njhuerta@ucdavis.edu
AF: University of California, Davis, Department of Geology University of California, Davis, Davis, CA 95616
AU: Tabor, M M
EM: mmtabor@ucdavis.edu
AF: University of California, Davis, Department of Geology University of California, Davis, Davis, CA 95616
AB: As for x-rays, neutron radiography is a noninvasive imaging technique based on the attenuation of thermal neutrons by the object in question, described by BeerAŸA›A›ƒ_sAªA›ƒ_zA›s law. However, neutron imaging is complementary to x-rays, as it is especially well suited for materials containing hydrogen atoms and mostly other low atomic weight attenuating materials. Although neutron attenuation techniques are routinely used in engineering, relatively little is known about its application to soils. We will present results demonstrating the tremendous potential of using neutron attenuation techniques to measure spatial and temporal distribution of water in soils at the 50 micrometer spatial resolution. The neutron source is a Mark II Triga Reactor at McClellan Nuclear Radiation Center (MNRC) in Sacramento, CA. The reactor runs at 1.8 MW and emits a poly-energetic neutron beam, including the thermal range. Unfortunately beam hardening and backscattering are a major source of uncertainty. Recent laboratory experiments conducted at MNRC suggest that beam hardening is considerably reduced when using deuteriated water, because its cross-section for attenuation of thermal neutrons is much lower than for regular water.
DE: 1866 Soil moisture
DE: 1875 Unsaturated zone
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting