Patent ID: 8692185

Claim:
A method comprising: disposing a logging tool within a borehole, wherein the borehole penetrates a formation; producing neutrons by a neutron source within the logging tool; detecting neutrons produced by the neutron source, the detecting by a neutron detector having a detection chamber that comprises Helium-3 at a pressure of ten atmospheres or below; creating an indication of a number of neutrons produced by the neutron source, the indication based on a measure of those detections by the neutron detector which represent neutrons that have not interacted with other elements before entering the neutron detector; obtaining data regarding gammas from a gamma detector responsive to the production of neutrons by the neutron source; determining a parameter associated with the formation based on the data regarding gammas and on the indications of the number of neutrons products; and adjusting the pressure of the Helium-3 of the neutron detector.