The Oberon R infrared calibration source uses a sodium heat pipe to ensure an exceptionally low temperature gradient along the furnace core. This blackbody source is ideal for the realization of aluminum, silver or copper ITS-90 Fixed Point Cells.

It may be used as a Black Body source over the range of 450°C to 1100°C.

The furnace heater is of the non-inductive birdcage design insulated by twin bore alumina tubes. The heat pipe is designed so that the inner wall is not subject to thermal expansion stressed from the outer wall before the heat pipe reaches conduction temperature. The working fluid is permanently and safely sealed within the plasma-arc welded enclosure.