Description
Since the discovery of nuclear fission in 1938, its properties have been extensively investigated with various techniques, mostly relying on fission product kinematics and gamma spectroscopy. We propose to utilize present and upcoming ion catching, trapping and detecting facilities across Europe to develop novel methods for fission research, which are independent of and complementary to legacy methods.
Direct unambiguous identification of fission products by accurate measurements of their mass will enable systematic investigations of entire isotopic distributions of fission products. The technique is not limited to certain decay half-lives, nor does it depend on additional nuclear information such as unique delayed-gamma energies. Thus, in addition to increasing the reliability of existing data, it will be possible to replace evaluations and extrapolations by experimental measurements for various fission mechanisms, at controlled excitation energies.
We plan to measure isotopic fission yields and isomer yield ratios for spontaneous fission (GSI), charged-particle- (JYFL) and neutron-induced (JYFL, SARAF-II) fission, and gamma-induced fission at precise gamma energies that could map fission barriers (ELI-NP). The overarching concept is to induce fission in a thin target inside a gas-filled stopping cell, where the fission products are thermalized and stopped. They are then extracted and identified by accurate mass measurements via a Penning Trap or a multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS), reaching fission product half-lives as low as a few ms. Other detectors, in addition or instead of a mass spectrometer, will be used for investigations of known fission isomers and the discovery of new ones (GSI, JYFL), and of beta-delayed fission properties.
Nuclear fission is probably the most complex nuclear decay mode, so theories that attempt to describe it touch upon almost all facets of nuclear structure and reactions. Therefore, new fission data from complementary methods are called for to support these efforts. Better understanding of fission has also paramount societal impact, as it is the basis for safe operation of present nuclear reactors and the design of efficient and economically achievable future ones. In particular, the isotopic and isomeric content of nuclear waste determines its radiation content and thus contributes to its safe and efficient management.
A pan-European approach for next-generation fission research is called for, as it will enable synergy between experts in various experiments methods and facilities, joint research and solutions of inherent methodical challenges, and the comparison of fission properties in various mechanisms and excitation energies. This will help to obtain a better universal understanding of this exciting nuclear process.