Natural Spectral Gamma Ray


The QL40-SGR probe measures the total gamma counts in API as well as the full energy spectrum of the natural gamma radiations emitted naturally from within the formations.

A Full Spectrum Analysis (FSA)1 is performed on the recorded energy spectra. The FSA derives in real time the concentration of the three main radioisotopes 40K, 212 Th and 238U and thus provides insight into the mineral composition of the formations. The QL40 SGR is equipped with a scintillation  BGO (Bismuth Germanium Oxyde) crystal. The BGO crystal has a high scintillation efficiency, good energy resolution and is mechanically strong.

The QL40-SGR is supplied as an inline sub. It can be combined with other logging tools of the QL40 (Quick Link) product line or can be operated as a standalone tool. It is compatible with Matrix, Scout and ALTlogger acquisition systems.

QL Stack Possibilities

  • QL40SGR + QL40IP (Induced Polarization) + QL40HM453 (Magnetic Susceptibility): Mining, Exploration
  • QL40SGR + QL40OBI (Optical Televiewer): Exploration, Bedding Planes, and Fractures in Dry holes
  • QL40SGR + QL40ABI (Acoustic Televiewer): Exploration, Bedding Planes, and Fractures in Fluid-filled holes
  • QL40SGR + QL40ELOG (Resistivity) + QL40FTC (Fluid Res, Temp): Hydrogeologist’s  or Environmentalist’s Tool, Groundwater exploration and assessment
  • QL40SGR + QL40DEV (Deviation): Lithology, Borehole location
  • QL40SGR + QL40IND (Dual Induction): Clay Analysis through PVC Casing


NaI (Tl) crystal ( 1 x 4”) BGO crystal ( 1 x 4”)

Temperature – Pressure

0-70°C (32-158°F) 200 bar (2900 psi)

Diameter – Length

40 mm (1.6”) – 0.93 m (36”)


6 kg (13 lbs)


256 channels spectrum

spectrum stabilized (software)

Nuclides concentrations

Window gamma counts

Total gamma counts in CPS and/or API unit


Manufactured by Geotomographie GmbH

Technical Details

Generated wave types: SV
Signal frequencies: Up to 500 Hz (depending on geology and borehole distance)
Operational depth: Up to 100 m
Source length: 1015 mm
Source weight: 6 kg
Cable weight per metre: 377 g
Borehole diameter: 75-100 mm (or larger if spacers are used)
Clamping system: Infatable bladder
Depth indicator: Cable marking every 2 m
Connector: To impulse generator IPG800 or IPG5000
Storage: On drum
Switch box: Switch between two vertical shot directions

If you have a question OR REQUIRE A QUOTE, CONTACT us and one of our professional team members will assist you