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Gamma Spectroscopy Probe

The natural-gamma spectroscopy probe analyses the energy spectrum of gamma radiation from naturally occurring or man-made radioactive isotopes. The probe includes a large volume detector contained in a dewar flask for thermal stability. The Full Spectrum Analysis (FSA) technique used to compute the contributions of individual isotopes makes optimum use of all acquired data. It is also used for gain stabilisation by mapping spectral shifts between successive depth intervals. The software includes compensation for borehole size, mud weight and probe position. The tool is compatible with standard RG oilfield probes and surface equipment.

Principle of Measurement:

Gamma photons produced by radioactive decay of unstable isotopes create light emissions in the gamma scintillation detector. The amplitude of the pulses depends on the photon energy. An analyser within the probe separates the pulses into separate channels according to their amplitudes. Count-rates from groups of channels are converted in real-time by the surface software to concentrations of the originating elements using preset algorithms.


  • Large-volume scintillation detector for high sensitivity
  • Dewar flask for thermal stability
  • Full spectrum dynamic drift compensation


  • Uranium (ppm)
  • Thorium (ppm)
  • Potassium %)
  • Gross gamma
  • Full spectrum (static measurement)


Minerals / Water / Engineering / Oil and Gas

  • Lithology determination
  • Mineral detection
  • Sedimentology
  • Improved shale-content computation
  • Correlation
  • Contamination studies


Diameter: 63mm (2.5”)
Weight: 32kg (71lb)
Length: 2.29m (90”)
Temperature: 0-125degC
Max. pressure: 86MPa (12,500psi)
Detector: Na(Tl) scintillator
Detector Size: 51mm x 300mm
Energy range: 100keV to 3MeV
Number of channels: 300

Operating Conditions

Borehole type: open/cased, water/air-filled

Sales Information

I016424 Natural-gamma spectroscopy probe
I015464 Natural-gamma test blanket

Download Gamma Spectroscopy Probe sheet


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Robertson Geologging Ltd., 2017

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