Downhole tools that include a radiation detector and processes for using same

A process for determining at least one property of a formation having a wellbore drilled therein, comprising:

• lowering a downhole tool into the wellbore, wherein the downhole tool comprises a tool housing comprising a radiation detector disposed therein, wherein the radiation detector comprises a scintillator material optically coupled to a photodetector, and wherein the scintillator material comprises a cerium-activated gadolinium pyrosilicate;
• absorbing natural gamma-rays incoming from the formation with the scintillator material;
• emitting light from the scintillator material in response to the absorbed natural gamma-rays;
• detecting at least a portion of the light emitted from the scintillator material with the photodetector;
• and
• determining the at least one property of the formation based at least in part on the light detected by the photodetector.

A process for determining at least one property of a formation having a wellbore drilled therein, comprising:

• lowering a downhole tool into the wellbore, wherein the downhole tool comprises a tool housing comprising a radiation detector comprising a radiation source, a scintillator material, and a photodetector disposed therein, wherein:
• the scintillator material is optically coupled to the photodetector,
• the scintillator material comprises a cerium-activated gadolinium pyrosilicate, and
• the radiation source comprises at least one of a neutron source, a gamma-ray source, and an x-ray source;
• emitting outgoing radiation from the radiation source into the formation;
• absorbing incoming radiation resulting from interactions between the outgoing radiation and the formation with the scintillator material;
• emitting light from the scintillator material in response to the absorbed radiation;
• detecting at least a portion of the light emitted from the scintillator material with the photodetector;
• and
• determining the at least one property of the formation based at least in part on the light detected by the photodetector.