Energy distribution mapping of beta radioactive sources

We have developed a novel procedure in extracting the energy distribution of radioactive beta emitters that has a direct application in detector energy calibration. The method employs a highly non-uniform magnetic field from a permanent dipole magnet and an array of 12 0.1×0.1×31cm3 scintillating fibers. By scanning the radioactive source across the entire entrance face of the magnet and recording the exit position of the electrons on the dispersive plane, we generated a full 2D map of the energy-position correlation functions. By combining the ADC spectra and a Geant4 simulation of the experimental setup, we were able to reconstruct the entire energy spectrum of a 25μCi90Sr/90Y point source used within a 1.4% accuracy.