A neutron activation detector comprises a first enclosure, a plurality of electrical leads, and an activation medium disposed within the enclosure. The activation medium consists substantially of a material that is activated by fast neutrons, and is arranged within the enclosure so that activation of the material by fast neutrons results in a current between the plurality of electrical leads.

A neutron activation detector comprises a first enclosure, a plurality of electrical leads, and an activation medium disposed within the enclosure. The activation medium consists substantially of a material that is activated by fast neutrons, and is arranged within the enclosure so that activation of the material by fast neutrons results in a current between the plurality of electrical leads.

A local area cosmogenic neutron sensor is used for detecting moisture within a measurement surface. A neutron detector is positioned on a stand structure holding the detector above a measurement surface. A moderator material and neutron shield are positioned around at least a portion of the neutron detector. The neutron shield substantially covers lateral sides and an entirety of a top of the neutron detector and is not positioned on a bottom side of the neutron detector. A second neutron shield is positioned below the neutron detector and in a path of neutron travel between the measurement surface and the neutron detector to substantially block neutrons from reaching the neutron detector.

A local area cosmogenic neutron sensor is used for detecting moisture within a measurement surface. A neutron detector is positioned on a stand structure holding the detector above a measurement surface. A moderator material and neutron shield are positioned around at least a portion of the neutron detector. The neutron shield substantially covers lateral sides and an entirety of a top of the neutron detector and is not positioned on a bottom side of the neutron detector. A second neutron shield is positioned below the neutron detector and in a path of neutron travel between the measurement surface and the neutron detector to substantially block neutrons from reaching the neutron detector.