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SurfaSens – small-scale, downward-looking sensor

SurfaSens [Patented technology] measures neutrons at the scale that is commensurate with the dimension of the instrument’s bottom plate. This sensor enables high-resolution (1 m to 10 m) mapping of cosmogenic neutrons, soil moisture, and other hydrogenous materials at or near the land surface. It is uniquely useful in measuring moisture of soils with stones or rock outcrops. It can be used to calibrate the standard, wide-area COSMOS sensor.

The sensor is also suitable for finding hydrogenous materials in soil or at its surface, measuring water content of bulk materials such as grain or ore, solid materials such as concrete, construction materials such as wood, agricultural materials such as crops or hay, etc.

SurfaSens prototype (© 2017 Lab C).

The SurfaSens’s response (calibration) function is shown below.

© 2017-2020 Lab C

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New Li-core detector

A new moderated sensor with Li-core thermal neutron detector (left side in the photo) has been constructed and is being tested against the standard He-core sensor (right side) at the Santa Rita Mesquite COSMOS site.

Li-core moderated sensor (left) collocated with the He-core COSMOS sensor at the Santa Rita Creosote COSMOS site (© 2017-2020 Lab C).

The side-by-side measurements conducted between December 2017 and March 2018 revealed that:

(1) The count rate of the new sensor is more than three times higher than that of the He-based system. Therefore, the uncertainty due to counting statistics is reduced by approximately a factor of 1.7. In the figure below it is manifested by smaller noise in the Li-core count data (top figure) and by lower coefficient of variation (bottom figure).

(2) The dynamic range of the Li-core sensor is almost identical to the standard He-core COSMOS sensor.

Side by side comparison of neutron count rates measured with the standard COSMOS He-core sensor (black) and the new Li-core sensor (red). (© 2018-2020 Lab C).

Application. The new Li-core moderated sensor is an excellent replacement for the He systems. The price of the Li-core sensor is comparable to that of the standard He-core sensor. Combined with other count-enhancing techniques, it yields an estimated nine-fold increase of the count rate, as compared with the standard COSMOS He-core sensor.

© 2017-2020 Lab C