What is a Gamma Ray Spectrum Core Logger & How Does it Work?

Posted by Ivan Wortman on

We are focusing on the gamma ray spectrum core loggers, who uses them, and how they work. This post is valuable if you are looking to expand your knowledge with a general overview of the gamma ray spectrum core logger.

Let’s begin...

What is a Gamma Ray Spectrum Core Logger?

A gamma ray spectrum core logger is a form of radiation detector that measures and analyzes natural gamma radiation from potassium (K), thorium (Th), uranium (U). This radioactive material is called NORM an acronym for Naturally Occurring Radioactive Material.  The data collected by a gamma ray spectrum core logger can be used to quantitatively and qualitatively characterize the material makeup of the source used. The instrument normally utilizes a scintillation detector with a NaI:Ti crystal that is coupled to a photomultiplier tube and then a spectrum analyzer. There are older models of gamma ray core loggers that just capture the gross or total counts and do not provide any spectral analysis like the modern gamma ray spectrum core loggers.


Who Benefits from them?

The gamma ray spectrum core logger is commonly employed in the Exploration industry to characterize the rock or sediment that a company is core drilling. Since different rock structures emit different amounts of gamma rays (shales usually emit more than sandstone, limestone, etc.), the corporation can use data from the gamma ray spectrum core logger to make informed decisions while onsite in parallel with logging while drilling measurements or other analytical measurements.


How Do They Work?

When the gamma ray logger is in use, the energy emitted by K, Th, or U is captured by the instrument’s detector. After absorbing the energy, the scintillation crystal (commonly, a sodium iodide crystal) within the detector emits a pulse of light which is captured by the photomultiplier tube. The photomultiplier tube captures the pulses of light and outputs a proportional electronic current pulse. Each pulse is significant as it is proportional and representative to the kiloelectronvolts (KeV) value of the K, Th, and U. The instrument records both the number of pulses it receives and the intensity of each pulse via a spectrum analyzer.

The data is typically reported through a display and a data file within the instrument. This information allows operators to make informed decisions about the quantitative and qualitative makeup of the K, Th & U sources.  By using spectrum analysis of the NORM the user is provided much more information than is available from a simple gross counting device.


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