Patent ID: 7439495

Claim:
A nuclear imaging probe for measuring the density of a subsurface formation in a limited zone surrounding a well-bore hole, the probe comprises: a pad having a face arranged so as to be positioned in contact with a well-bore wall, a radioactive source arranged within the pad for transmitting incident photons towards the well-bore wall, at least one sensor arranged within the pad spaced away from the radioactive source and isolated from the radioactive source by a shield arranged into the pad for receiving photons scattered by the limited zone, wherein the radioactive source comprises a pumping arrangement comprising a container, a piston, a piston actuator and at least one emission chamber, the container being filled with a radioactive gas, a pumping tube coupling the container to the at least one emission chamber, the piston actuator activating the piston for pumping the radioactive gas from the container into the at least one emission chamber when measurements are performed.