Redesigned Core Gamma Spectrometer –A Difference That Counts

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Hamish Adam, David Freeman, Daniel Meer, Core Laboratories

Abstract

Historically core gamma spectrometry measurements have suffered from two main limitations: 1) low rock activity and 2) significant background interference. These two problems are related to the 1) low rock activity and 2) significant background interference. These two problems are related to the ‘geometry problem’ inherent in laboratory measurements of rock radioactivity and to low signal to ‘geometry problem’ inherent in laboratory measurements of rock radioactivity and to low signal to noise ratios. This paper describes a redesigned core gamma system which substantially overcomes noise ratios. This paper describes a redesigned core gamma system which substantially overcomes the geometry problem and improves resolution by: 1) increasing the dimensions of the Nal detector the geometry problem and improves resolution by: 1) increasing the dimensions of the Nal detector crystal, making it analogous to those used in downhole G.R. tools; 2) incorporating a shield design crystal, making it analogous to those used in downhole G.R. tools; 2) incorporating a shield design that reduces background noise by 50 percent overall; 3) including a multi-channel analyzer designed that reduces background noise by 50 percent overall; 3) including a multi-channel analyzer designed for optimal measurement of uranium, thorium, and potassium in low activity rocks and 4) using a for optimal measurement of uranium, thorium, and potassium in low activity rocks and 4) using a calibration system which automatically accounts for varying core mass. These design improvements calibration system which automatically accounts for varying core mass. These design improvements give results superior to other laboratory systems. The new system is fully automated with an IBM-PC give results superior to other laboratory systems. The new system is fully automated with an IBM-PC operator interface.