Geological X-ray fluorescence logging probe

A geological probe is described featuring a radiation source and a semiconductor radiation detector cooled with melting solid coolant. Low operating temperature of the semiconductor detector must be maintained for high resolution. A coolant is used whose triple point temperature is lower than the required detector temperature. Prior to start-up, the coolant is transformed into the solid phase using liquid nitrogen. During measurement it remains at triple point temperature until its whole volume melts. The probe consists of an inner cylindrical vessel of conducting material placed below the detector, which contains the melting solid coolant and is heat-conductively connected to the detector. The outer cylindrical vessel surrounds the inner vessel and the detector and also forms the outer probe jacket. A sealed expansion vessel is connected to the outer vessel bottom. The main support structure of the inner vessel consists of a thin-walled tube of stainless steel filled with a nonconducting foamy material. The design reduces the probe outer diameter while maintaining the required cooling effect. (Pu)