Detector-specific separation of spectral components from repetitive measurements in environmental radiation monitoring

Identifier:  imarina:9470881

Handle: https://hdl.handle.net/20.500.11797/imarina9470881

Authors:  Reichardt, Ignasi; Cerezo, Agustin; Prieto, Elena; Salvado, Marcal

Abstract:
Gamma-ray spectrometers for environmental radiation monitoring on field routinely record short-duration spectra. Under normal conditions, these spectra are the sum of a constant background plus photo-peaks from natural emitters, and their resulting bremsstrahlung and Compton scattering radiation. For each monitor, the constant background is specific to the monitor components and the composition of the soil and of the surroundings. On the other hand, the spectrum of the natural gamma-ray emitters also depends on the aspects above, but may also have variable intensity owing to aerosol scavenging in case of rain. We present a case of a large network of detectors where it is unpractical to perform dedicated simulations or measurements of calibration sources. To overcome this difficulty, we propose a method to remotely and systematically extract fundamental spectra. For each spectrum we measure the activity concentration of natural emitters. Then, for each channel, the activity concentration of each natural emitter constitute the coefficients of an equation, where the unknowns are the fundamental spectra of the natural emitters and of the constant background. After repeated measurements, we can construct an over-determined system of equations that is solvable as a non-negative least-squares problem. As a result of the least-squares minimization we obtain the separate spectra of the constant background and of the most relevant natural gamma-ray emitters. This method allows to produce highly specific fundamental spectra for each monitor. This improves the characterization of each monitor and allows to accurately reconstruct subsequently measured spectra using the Full Spectrum Analysis.