3. Calibration files

The calibration of a specific Medusa detector is embedded in a "Medusa Calibration File" (MCF). Calibration files with extension MCF contain:

· Standard spectra;

· Information on the gain stabilization of the detector system;

· information on the supplier and owner of the tool;

· Date of the calibration.

The most important information inside the detector file is the information about the standard spectra. In the full spectrum analysis implemented in Gamman, the standard spectra are used to fit the measured spectrum. A standard spectrum is nuclide, detector and geometry specific; and it is defined as "a detector's response to a source of unit activity in a given geometry". An example is shown in the figure below.

Example of a set of standard spectra. In yellow: ¹³⁷Cs; red: ⁴⁰K; green: ²³⁸U; blue: ²³²Th. System: 4x4x16 CsI in a borehole geometry.

Calibration files are unique for a detector-acquisition system used in a certain geometry. This means that for each geometry, a separate calibration file is needed. The reason for this is that both the shape and the intensity of the standard spectra differ with the geometry of the source being measured.

The name of the MCF file is made up of the ID of the detector (serial number, or type id, etc), crystal volume and type, date of calibration, present radionuclides and then a single character determining the geometry and the extension MCF. For example; MS1000.0001_3x9CsI_01-01-2020_KUTh.a2320.mcf is a calibration file (including the radionuclides 40-K, 238-U and 232-Th) for a 3x9 inch CsI detector named MS1000.0001, calibrated at January 1st 2020 for use in an airborne/flatbed application (".a").
Calibration files are stored in the Gamman program directory, and cannot be moved to another location on your computer.

Note The Gamman installation comes with a single Gamman calibration file. This calibration file (SCB095.MCF) contains a set of calibration spectra for a 4x4x16 inch cesium iodide detector and was added for instructive purposes only.

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