Root distribution and soil water content using thermal neutron radiography

Thermal neutron radiography imaging is utilized for providing data of root location and volumetric water content in soil-root systems. Images with this nondestructive method are acquired in short times of 10 to 20 seconds, allowing for detection of water locations and dynamics when taking a time-series of images. The advantage of using thermal neutron imaging for this application over other beam methods (e.g. x-ray imaging), is the extremely-high attenuation coefficient due to the high thermal neutron cross-section with hydrogen, as compared to other elements in the soil-root system (mainly SiO2) that have insignificant attenuation coefficients for neutrons. The amount of water (hydrogen) in the roots is considerably higher than that in the surrounding soil, allowing for good separation between roots and soil in the image. The separation in the image is seen in the grey levels of the image, which display the difference in the number of neutrons that arrive to each pixel in the detector screen. The contrast in the image improves as these differences get larger.