Page 50 - bukuneutron

round by the soil causes neutrons to collide with hydro-
gen atoms in water and soil. Their energy is then lost
and conserved to a low-energy or thermal neutrons are
created. Some thermal neutrons are reflected back
and counted by the neutron detector. These raw counts
are transmitted to the gauge that contains a micropro-
cessor which has been programmed to give a value of
volumetric soil moisture content. Because hydrogen
atom is the primary source of moisture in the soil, neu-
tron moisture meters indirectly measure soil moisture
content.

An advantage of these meters is a volume of soil
can be measured and as is varies depending on the
tube depth and the strength of neutron source. Mea-
surements at various depths and sites can be done
quickly. One disadvantage of this technique is when
measurements is conducted at shallow depths where
some neutrons can escape from the soil surface into
the air instead of being detected. The main disad-
vantage of this method is not due to technical aspect,
where operator, storage, licensing and inspection re-
quirements because uses of the radioactive source.

2.6.1 Application in Hydrology.

Neutron moisture gauges are used in hydrology to mea-
sure the absolute and changes of moisture content in
the surrounding areas of water reservoir. Direct mea-

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