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HK: Fachverband Physik der Hadronen und Kerne
HK 39: Structure and Dynamics of Nuclei VIII
HK 39.5: Talk
Thursday, March 19, 2026, 17:15–17:30, AM 00.011
First Limits on Double Alpha Decay of Ra-224 — •Makar Simonov1 and Heinrich Wilsenach2 for the Double Alpha at FRS Ion Catcher collaboration — 1Justus-Liebig-Universität Gießen, Gießen, Germany — 2The Hebrew University of Jerusalem, Jerusalem, Israel
The simultaneous emission of two alpha particles was proposed as an exotic way for heavy nuclei to decay about 45 years ago, and the initial conservative estimate for the branching ratio was less than 10−20. Recent microscopic calculations have yielded an experimentally accessible estimate of 10−8 for radium isotopes with mass numbers A = 220, 222, 224, and an experiment to search for double alpha decay of Ra-224 was conducted at the FRS Ion Catcher, GSI, Germany.
Over four months of data taking, a 34 kBq radioactive source of Th-228 was used to produce Ra-224 ions. These ions, filtered from other Th-228 descendants by a radio-frequency quadrupole and electrostatically focused, were delivered to a thin carbon implantation foil. Two double-sided silicon strip detectors were used to record alpha and beta particles. The number of registered alpha decays of Ra-224 was approximately 109, which should be sufficient to verify the theoretical estimate.
This report will provide final assessments of the time and energy resolution of the detector system. The main focus is the evaluation of the random-coincidence background to set a limit on the branching ratio of the double alpha decay of Ra-224.
Keywords: Double alpha decay; Rare decay; Decay spectroscopy; Three-body decay; Silicon strip detector