Quantitative neutron imaging in soil physics and other fields

Data from neutron imaging experiments can also be used for the quantification of the content and material amount of the investigated samples. According to the exponential attenuation behavior of the transmitted radiation we can derive density values when the well-known cross-section data are taken into consideration. The determination of moisture in soil and other porous media under various conditions is an essential topic. However, the exponential law is only valid in first order for hydrogenous media because the multiple scattering at hydrogen nuclei is not correctly described. For the purpose of a more precise quantification of even high amounts of water we developed a correction tool which is based on Monte Carlo simulations of the neutron propagation process through the sample [1, 2]. This IDL based tool QNI can be made available for customers of our facilities on demand for the more precise quantification of their image data.
Horizontal slice of the neutron tomography data set of a sand package (10 cm x 10 cm) with different sub-cubes (1 cm x 1 cm). The left data set was obtained after reconstruction without scattering correction. The right data represent the correct moisture values which were obtained after application of the QNI correction tool.
Horizontal slice of the neutron tomography data set of a sand package (10 cm x 10 cm) with different sub-cubes (1 cm x 1 cm). The left data set was obtained after reconstruction without scattering correction. The right data represent the correct moisture values which were obtained after application of the QNI correction tool.
The scattering in the sample is not only relevant for hydrogen but also for structural materials like metals. We intend to extend QNI for other materials where the often complicated scattering cross-sections have to be taken into account correctly. The new QNI tool should be more flexible and has to be usable also for the range of cold neutrons.
Correction Methods for the Quantitative Evaluation of Thermal Neutron Tomography
R. Hassanein (2006)
Diss. ETH Zurich No. 16809
PhD Thesis ETH 16809

Investigation of water imbibition in porous stone by thermal neutron radiography.
Hassanein R., Meyer H.O., Carminati A., Estermann M., Lehmann E., Vontobel P., 2006
JOURNAL OF PHYSICS D: Appl. Phys 39, 4284-4291, 2006.
DOI: 10.1088/0022-3727/39/19/023