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Updated: Jan 17, 2026

Molecular Beam Mass Spectrometry With Tunable Vacuum Ultraviolet VUV Synchrotron Radiation
Published on: October 30, 2012
Measurement of the 147Pm beta decay spectrum with a 4π Si(Li) beta spectrometer
Gaël Craveiro1, Sylvain Leblond1, Xavier Mougeot1
1Université Paris-Saclay, CEA, List, Laboratoire National Henri Becquerel (LNE-LNHB), 91120, Palaiseau, France.
Abstract:
This work presents major upgrades of a custom beta spectrometer, based on a quasi-4π configuration of two large-volume Si(Li) detectors, supporting beta spectra measurements up to 3 MeV. The electronics was modernized and a FASTER digital acquisition system was implemented for independent channel processing. Characterization using a 207Bi source confirmed good linearity and agreement with Geant4 simulations, though energy resolution remains limited by electronic noise. The first forbidden non-unique spectrum of 147Pm decay was measured and, after a neat coincidence analysis, was corrected for the remaining distortion using Tikhonov unfolding. Discrepancies below 80 keV were identified to unoptimized source preparation, later confirmed by autoradiography. These upgrades enhance the apparatus precision, with future efforts aimed at better resolution, lower thresholds and optimized source preparation. Eventually, a new Q-value of 225.84 (49) keV was determined from the analysis of the Kurie plot.
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