Russell Randall and E. C. Hopkinson
Dresser Atlas, Dresser Industries, Inc.
Houston, Texas
ABSTRACT
Recent improvements to the Neutron Lifetime Log service are discussed. The progress in signal processing includes the average time technique of 2-computation and the self-consistent method of adjusting the starting of the single fixed-width gate. The application to a background subtracting system of the S-measurement is outlined.
The average time technique is a means of obtaining the decay rate from a pulsed neutron capture instrument. The time after each neutron burst is measured for each detector pulse within a gate of fixed width. The arithmetic mean of all these pulse-times is uniquely related to the decay rate as seen by the detector. The resulting improvement of these techniques is indicated by a more repeatable X-value.
A background subtraction technique is consistent with the single gate system. The ability to background subtract (or correct) the average time generated S-value gives a wider range of applicability to the technique.
The delay after the neutron burst to the single gate can be automatically adjusted without changing the measured average time. A self-consistent method of positioning this average time gate is possible and results in reduced statistical error.
The theoretical motivation and construction of the modifications are developed. Discussion of their application with the single gate system and field examples are reviewed.