To collect radiometric data (natural radioistope concentrations of U, Th, and K) we use Pico Envirotec GRS-10 and AGRS intelligent spectrometers. Spectrometer detectors are always mounted inside the helicopter (cargo box or cargo floor) to allow low-level flight patterns without the compromise of slung geophysical sensors. The spectrometer is self-calibrating and outputs the full 256 (512) channel radiometric spectrum for processing using PC-based Praga-3 software.
For routine surveys we use two 4.2 litre NaI(Tl) crystals (total of 8.4 liters) shielded against cosmic radiation with RayShield® gamma-attenuating material to provide a very high signal/noise ratio without having to resort to complex and heavy upward-looking detectors. For specialty surveys requiring high definition radiometric data we use additional crystal volume (up to 16.8 liters downward plus 4.2 liters upward).
Flying low level, terrain-following, flights by helicopter provides high downward-looking sensitivity and a high signal/noise ratio which reduces complex mathematical data reduction procedures. Low-level survey flights have the added bonus of enhancing identification of subtle radioactive sources, such as potassium alteration zones in porphyry environments, thorium enrichments associated with rare earth (REE) mineralization, and veins and boulders mineralized with uranium, which may not be detectable by surveys flown at higher altitudes.
For detailed ground radiometric surveys such as rare earth element (REE) exploration, uranium target follow-up, and potassium alteration mapping, we use a Pico GRS-2 spectrometer which is fully integrated with GPS navigation and a digital data logger. Detector volume is 0.35 liters with full 256 channel resolution. The GRS-2 system can be backpack mounted, or carried by ATV or other vehicle at speeds up to about 40 km/h. This system is available for rent, or we can provide an operator.