Neutron moisture gauge
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A neutron moisture meter is a moisture meter utilizing neutron scattering. The meters are most frequently used to measure the water content in soil or rock. The technique is non-destructive, and is sensitive to moisture in the bulk of the target material, not just at the surface.
Water, due to its hydrogen content, is an effective neutron moderator, slowing high-energy neutrons. With a source of high-energy neutrons and a detector sensitive to low-energy neutrons (thermal neutrons), the detection rate will be governed by the water content of the soil between the source and the detector. The neutron source typically contains a small amount of a radionuclide. Sources may emit neutrons during spontaneous fission, as with californium; alternatively, an alpha emitter may be mixed with a light element for a nuclear reaction yielding excess neutrons, as with americium in a beryllium matrix.
References
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- {{cite web| url = http://ucmanagedrought.ucdavis.edu/PDF/DROUGHT_WEB_NEUTRON_PRB.pdf|title =DROUGHT_WEB_NEUTRON_PRB}}
- {{cite web | url =http://www.iaea.org/programmes/nafa/d1/public/d1_pbl_2_1.pdf | title =BIBLIOGRAPHY – NEUTRON PROBE | url-status =dead | archiveurl =https://web.archive.org/web/20110628234609/http://www.iaea.org/programmes/nafa/d1/public/d1_pbl_2_1.pdf | archivedate =2011-06-28 }}