Spectrum

The Spectrum page displays the collected spectra in real-time, along with the radionuclide concentrations that result from the onboard spectral processing. The plotted lines and data present in this view are explained in this section. Both the raw and the stabilized spectrum can be shown in the plot. The raw spectrum represents the actually measured spectrum and is plotted on an x-axis that represents channels. The onboard microprocessor stabilizes (converts to an energy scale) and analyzes (extracts radionuclide concentrations) this spectrum resulting in a energy spectrum and radionuclide concentrations.

Stabilization

When the detector is switched on the detector first needs to collect 10k counts in the analysis windows before it can calculate the energy stabilized spectrum. During this time no radionuclide concentrations will be visible and only the raw spectrum is shown.

Gamma Spectrum

The live spectrum is shown to check the spectral shape, energy stabilisation and the derived radionuclide concentrations (⁴⁰K, ²³⁸U, ²³²Th and optionally ¹³⁷Cs). When this page is opened the incoming as well as the accumulated spectra are shown in the figure. The accumulated spectrum (blue dots) is fitted using the calibration curves (the coloured lines, extracted from the calibration file) yielding (a) the blue "fitted spectrum" and (b) the concentrations of K, U, Th and Cs listed in the Spectrum block. The principles of the fitting procedure can for instance be found in the Gamman Software manual. Check the method of translating the measured spectrum to an energy scale and the method of extracting the nuclide concentrations by using standard spectra.

Line	Description	Stored in your project?
Grey dots	Spectrum collected by the spectrometer stabilised to an energy scale	Yes
Blue dots	This is the accumulated spectrum by summing the grey dots	no

Red line*	The standard spectrum for ⁴⁰K multiplied with the concentration shown in the Spectrum block	Individually for each measured spectrum
Green line*	The standard spectrum for ²³⁸U multiplied with the concentration shown in the Spectrum block	Individually for each measured spectrum
Blue line*	The standard spectrum for ²³²Th multiplied with the concentration shown in the Spectrum block	Individually for each measured spectrum
Yellow line*	The standard spectrum for ¹³⁷Cs multiplied with the concentration shown in the Spectrum block	Individually for each measured spectrum
Blue surface	The sum of the ⁴⁰K, ²³⁸U, ²³²Th and ¹³⁷Cs lines.	No

* The calibration spectra for these nuclides are extracted from the active Medusa Calibration File (MCF) that is present on the device. Calibration spectra are unique for each detector and cannot be interchanged between sensors.

The spectrum boxes contain an information icon (

) in the top bar. By clicking on the information icon the sensor infobox is opened. Through this window, it is possible to inspect the incoming data, which is displayed in the Medusa defined JSON sensor format, described on the JSON documentation page.

Spectrum block

Parameter	Description	Units
Counts per second	Count rate from the last measured spectrum (grey dots)	counts per second
Plot every	An input value that accumulates spectra before plotting	seconds
Measurement	The time the detector actually measured during the last recording. In brackets is the dead time (in percentage) of the measurement	seconds
Stabilization	A parameter that describes the stabilization shift	-
Accumulated live time:	The live time of the stacked spectrum (blue dots)	seconds
Potassium (K)	The concentration ⁴⁰K found (red line)	Becquerel/kilogram or %
Uranium (U)	The concentration ²³⁸U found (green line)	Becquerel/kilogram or ppm
Thorium (Th)	The concentration ²³²Th found (blue line)	Becquerel/kilogram or ppm
Cesium (Cs)	The concentration ¹³⁷Cs found (blue line)	Becquerel/kilogram