Patent ID: 7800051

Claim:
A gamma monitoring apparatus for measuring water equivalent of a snowpack over a selected ground area, comprising: a detector unit installable at a given height above the selected ground area, the detector unit having a collimator defining a field of view to be directed on the selected ground area, a scintillator coupled to a photomultiplier tube for detecting gamma rays emitted by naturally radioactive elements present in soil under the snowpack and absorbed by the snowpack in the field of view defined by the collimator, and a temperature sensor, the photomultiplier tube having an output for producing a signal having pulses indicative of the gamma rays; a circuit arrangement having: a measuring processor unit that measures the pulses in the signal; a registering processor unit that registers the pulses exceeding threshold energy levels in a number of energy windows as gamma counts; a computing processor unit that periodically computes the water equivalent of the snowpack as functions of the gamma counts in the energy windows and the height of the detector unit with respect to ground level; a compensating circuit that numerically corrects effects on the gamma counts resulting from a variation of temperature inside the detector unit measured by the temperature sensor; a memory unit that stores data representing the computed water equivalent; a transmission circuit that transmits the data; and a power supply that provides power to the circuit arrangement and the detector unit; and a thermal insulation insulating at least the scintillator of the detector unit.