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Spataru, A., Kripkó-Koncz, G., Dickel, T., Hornung, C., Plass, W. R., Constantin, P., et al. (2025). Broadband mass measurements with the FRS Ion Catcher facility at GSI and theory developments investigating the shape-phase transition near N=90. Phys. Rev. C, 111(5), 054307–13pp.
Abstract: Simultaneous, broadband, high-precision direct mass measurements of thermalized exotic nuclides are reported. The FRS Ion Catcher and, in particular, its high-resolution multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) was used to measure neutron-rich nuclides in the element range from barium to europium, produced by the spontaneous fission of 252Cf. Results include the measurement of 64 masses, including 13 masses with no previous direct determination; for four nuclides, a measurement with improved uncertainty is reported. Relative mass uncertainties below 1 x 10-7are routinely achieved. This work shows the first use of a multiple-reflection time-of-flight mass spectrometer to map a larger region of the nuclear chart covering 51 masses measured simultaneously in a single setting. The broadband capability is a design feature of the MR-TOF-MS of the FRS Ion Catcher which enables the large-scale mapping of the mass surface. The obtained data are compared to existing literature values and predictions of mass models and are used to study the shape-phase transition at N = 90. A theoretical study, employing a Hartree-Fock-BCS approach with adjustable pairing strengths, is implemented to examine the evolution of the two-neutron separation energies along this region of the chart of nuclei.
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Stuhl, L., Krasznahorkay, A., Csatlos, M., Algora, A., Gulyas, J., Kalinka, G., et al. (2014). A neutron spectrometer for studying giant resonances with (p,n) reactions in inverse kinematics. Nucl. Instrum. Methods Phys. Res. A, 736, 1–9.
Abstract: A neutron spectrometer, the European Low-Energy Neutron Spectrometer (ELENS), has been constructed to study exotic nuclei in inverse-kinematics experiments. The spectrometer, which consists of plastic scintillator bars, can be operated in the neutron energy range of 100 keV-10 MeV. The neutron energy is determined using the time-of-flight technique, while the position of the neutron detection is deduced from the time-difference information from photomultipliers attached to both ends of each bar. A novel wrapping method has been developed for the plastic scintillators. The array has a larger than 25% detection efficiency for neutrons of approximately 500 keV in kinetic energy and an angular resolution of less than 1 degrees. Details of the design, construction and experimental tests of the spectrometer will be presented.
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