Cosmic Neutron Showers
- generated constantly in the top atmosphere
- produce all sorts of high energetic particles, including
neutrons
- in total around 100-150 n/(m2s)
- in the air and in the soil neutrons are also constantly
created
Soil
Moisture Sensitivity
- depending on the amount of water (hydrogen)
- neutrons are either reflected (dry)
- or absorbed (wet)
- the above-ground neutron density scales by soil moisture,
air humidity and biomass
From high
energy and nuclear physics to environmental sciences
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Soil Moisture Map,
measured at the UFZ Site Schäfteral,
with the Cosmic Ray Rover
from dry regions more neutrons enter the detector than
from wet ones
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Measurement Range
- Neutron scatter off other nuclei in the atmosphere and the
soil and form a neutron gas above the ground
- they can easily travel several hundred meter in air
- the range of influence is several hundred m2 and
50 cm in depth
- measurement depth and footprint radius depend on the en
Detection
- fast neutrons are slowed down by a polyethylene casing
(moderator), then
- thermal neutrons are converted by 3Helium
gas or 10Boron layers and
- detected by a wire-based proportional counter
- several modules increase the detection efficiency
Suited
for time resolved field-scale soil moisture determination
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