QL40 SGR2G CeBr3

The QL40-SGR2G is the new generation of slimhole Spectral gamma Tool. The new system consists of a completely redesigned and ruggedised mechanical assembly, electronics and gamma module. It implements also the latest ALT telemetry developments to enhance tool performances on long single and multi-conductor wirelines.

The QL40-SGR2G is equipped with a scintillation crystal. When exposed to gamma rays, the crystal emits light as a function of the gamma ray energies. The pulses of light are amplified by a photomultiplier tube and converted into electrical pulses which are distributed into discrete energy channels.

Gamma ray analysis is performed in two steps. First spectrum stabilization will be performed: each multichannel spectrum in the data set will be converted to a spectrum having all count peaks at the corresponding energy position. This Process implies a close comparison with the reference spectra obtained during the calibration process of the spectral gamma tool at the Medusa calibration facility. In a second step the stabilized spectrum will be convoluted into concentrations of naturally occurring radionuclides (40K, 238U, 212Th) or other manmade nuclides like 137Cs or 60Co. Corrections taking borehole diameter, rock density, casing type and thickness, tool position and borehole fluid  conditions into account can be applied.

QL Stack Possibilities

  • QL40SGR + QL40IP (Induced Polarization) + QL40HM (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 + QL40BMR (Borehole Magnetic Resonance): Advanced Coal Mining
  • QL40SGR + QL40IND (Dual Induction): Clay Analysis through PVC Casing


Scintillation crystal : CeBr3 (Cerium Bromide)

Temperature – Pressure

0-70°C (32-158°F)
200 bar (2900 psi)

Diameter – Length

40 mm (1.6”) – 1.01 m (39.4”)


6 kg (13 lbs)


Variable baudrate telemetry according to cable length/type & surface system

2048 channels gamma ray energy spectrum

Full spectrum analysis and stabilized spectrum

Total gamma counts [API]

Concentration of radioisotopes [Bq/kg or ppm]

Concentration error of radioisotopes [Bq/kg or ppm


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

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