The Rare-RI Ring (R3) is a recently commissioned cyclotronlike storage ring mass spectrometer dedicated to mass measurements of exotic nuclei far from stability at Radioactive Isotope Beam Factory ...(RIBF) in RIKEN. The first application of mass measurement using the R3 mass spectrometer at RIBF is reported. Rare isotopes produced at RIBF—127Sn, 126In, 125Cd, 124Ag, 123Pd—were injected in R3. Masses of 126In, 125Cd, and 123Pd were measured whereby the mass uncertainty of 123Pd was improved. This is the first reported measurement with a new storage ring mass spectrometry technique realized at a heavy-ion cyclotron and employing individual injection of the preidentified rare nuclei. The latter is essential for the future mass measurements of the rarest isotopes produced at RIBF. The impact of the new 123Pd result on the solar r-process abundances in a neutron star merger event is investigated by performing reaction network calculations of 20 trajectories with varying electron fraction Ye. It is found that the neutron capture cross section on 123Pd increases by a factor of 2.2 and β-delayed neutron emission probability, P1n, of 123Rh increases by 14%. The neutron capture cross section on 122Pd decreases by a factor of 2.6 leading to pileup of material at A = 122, thus reproducing the trend of the solar r-process abundances. The trend of the two-neutron separation energies (S2n) was investigated for the Pd isotopic chain. The new mass measurement with improved uncertainty excludes large changes of the S2n value at N = 77. Finally, such large increase of the S2n values before N = 82 was proposed as an alternative to the quenching of the N = 82 shell gap to reproduce r-process abundances in the mass region of A = 112 – 124.
Development of a new in-ring beam monitor in the Rare-RI Ring Omika, S.; Yamaguchi, T.; Tadano, N. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
01/2020, Letnik:
463
Journal Article
Recenzirano
A beam monitor is developed at the Rare-RI Ring storage ring facility at the RI beam factory at RIKEN. Because the Rare-RI Ring stores only a single exotic ion according to the operation principle, ...conventional beam instruments cannot be employed. In the present study, we design a simple monitoring system to confirm particle storage. The system comprises a thin foil and scintillators with photon sensors. When an ion passes through the foil, secondary electrons, including δ-rays, are emitted and are detected by a set of scintillation detectors without any guiding field. A beam test using 78Ge with 175 MeV/nucleon successfully demonstrates the periodic revolution of the stored ions.
The question of whether charge-changing interactions can be used to probe point-proton radii of nuclei remains unanswered. Charge-changing cross sections, sigma sub(cc), were systematically ...investigated using stable and unstable nuclear beams of intermediate-energy. The ratios of the experimental sigma sub(cc) values to the calculated ones obtained from a phenomenological Glauber-type model analysis are found to be nearly constant in a broad range of Z/N for light neutron-rich nuclei. This enables the determination of density distributions, i.e., the radii of protons tightly bound in nuclei. To test the applicability of the present method to all nuclei in the nuclear chart, extensive measurements were performed for medium-mass nuclei ranging from Z = 18 to 32. The present study suggests the potential capability of a new experimental approach for exploring exotic nuclei.
An experiment addressing electron capture (EC) decay of hydrogen-like Pm60+142 ions has been conducted at the experimental storage ring (ESR) at GSI. The decay appears to be purely exponential and no ...modulations were observed. Decay times for about 9000 individual EC decays have been measured by applying the single-ion decay spectroscopy method. Both visually and automatically analysed data can be described by a single exponential decay with decay constants of 0.0126(7)s−1 for automatic analysis and 0.0141(7)s−1 for manual analysis. If a modulation superimposed on the exponential decay curve is assumed, the best fit gives a modulation amplitude of merely 0.019(15), which is compatible with zero and by 4.9 standard deviations smaller than in the original observation which had an amplitude of 0.23(4).
The periodic time modulations, found recently in the two-body orbital electron capture (EC) decay of both, hydrogen-like Pr-140(58+) and Pm-142(60+) ions, with periods near to 7 s and amplitudes of ...about 20%, were re-investigated for the case of Pm-142(60+) by using a 245 MHz resonator cavity with a much improved sensitivity and time resolution. We observed that the exponential EC decay is modulated with a period T = 7.11(11) s, in accordance with a modulation period T = 7.12(11) s as obtained from simultaneous observations with a capacitive pick-up, employed also in the previous experiments. The modulation amplitudes amount to a(R) = 0.107(24) and a(P) = 0.134(27) for the 245 MHz resonator and the capacitive pick-up, respectively. These new results corroborate for both detectors exactly our previous findings of modulation periods near to 7 s, though with distinctly smaller amplitudes. Also the three-body beta(+) decays have been analyzed. For a supposed modulation period near to 7 s we found an amplitude a = 0.027(27), compatible with a = 0 and in agreement with the preliminary result a = 0.030(30) of our previous experiment. These observations could point at weak interaction as origin of the observed 7 s-modulation of the EC decay. Furthermore, the data suggest that interference terms occur in the two-body EC decay, although the neutrinos are not directly observed. (C) 2013 Elsevier B.V. All rights reserved.
The long-lived 60Fe (with a half-life of 2.62 Myr) is a crucial diagnostic of active nucleosynthesis in the Milky Way galaxy and in supernovae near the solar system. The neutron-capture reaction ...59Fe(n,γ)60Fe on 59Fe (half-life = 44.5 days) is the key reaction for the production of 60Fe in massive stars. This reaction cross section has been previously constrained by the Coulomb dissociation experiment, which offered partial constraint on the E1 γ-ray strength function but a negligible constraint on the M1 and E2 components. In this work, for the first time, we use the surrogate ratio method to experimentally determine the 59Fe(n,γ)60Fe cross sections in which all the components are included. We derived a Maxwellian-averaged cross section of 27.5 ± 3.5 mb at kT = 30 keV and 13.4 ± 1.7 mb at kT = 90 keV, roughly 10%–20% higher than previous estimates. We analyzed the impact of our new reaction rates in nucleosynthesis models of massive stars and found that uncertainties in the production of 60Fe from the 59Fe(n,γ)60Fe rate are at most 25%. We conclude that stellar physics uncertainties now play a major role in the accurate evaluation of the stellar production of 60Fe.
Abstract
The long-lived
60
Fe (with a half-life of 2.62 Myr) is a crucial diagnostic of active nucleosynthesis in the Milky Way galaxy and in supernovae near the solar system. The neutron-capture ...reaction
59
Fe(n,
γ
)
60
Fe on
59
Fe (half-life = 44.5 days) is the key reaction for the production of
60
Fe in massive stars. This reaction cross section has been previously constrained by the Coulomb dissociation experiment, which offered partial constraint on the
E
1
γ
-ray strength function but a negligible constraint on the
M
1 and
E
2 components. In this work, for the first time, we use the surrogate ratio method to experimentally determine the
59
Fe(n,
γ
)
60
Fe cross sections in which all the components are included. We derived a Maxwellian-averaged cross section of 27.5 ± 3.5 mb at
kT
= 30 keV and 13.4 ± 1.7 mb at
kT
= 90 keV, roughly 10%–20% higher than previous estimates. We analyzed the impact of our new reaction rates in nucleosynthesis models of massive stars and found that uncertainties in the production of
60
Fe from the
59
Fe(n,
γ
)
60
Fe rate are at most 25%. We conclude that stellar physics uncertainties now play a major role in the accurate evaluation of the stellar production of
60
Fe.
20pAB-5 Present status of Rare-RI Ring Abe, Y.; Yamaguchi, Y.; Uesaka, T. ...
Meeting Abstracts of the Physical Society of Japan,
2016/03/19
Journal Article
The periodic time modulations, found recently in the two-body orbital electron capture (EC) decay of both, hydrogen-like 140Pr58+ and 142Pm60+ ions, with periods near to 7 s and amplitudes of about ...20%, were re-investigated for the case of 142Pm60+ by using a 245 MHz resonator cavity with a much improved sensitivity and time resolution. We observed that the exponential EC decay is modulated with a period T=7.11(11) s, in accordance with a modulation period T=7.12(11) s as obtained from simultaneous observations with a capacitive pick-up, employed also in the previous experiments. The modulation amplitudes amount to aR=0.107(24) and aP=0.134(27) for the 245 MHz resonator and the capacitive pick-up, respectively. These new results corroborate for both detectors exactly our previous findings of modulation periods near to 7 s, though with distinctly smaller amplitudes. Also the three-body β+ decays have been analyzed. For a supposed modulation period near to 7 s we found an amplitude a=0.027(27), compatible with a=0 and in agreement with the preliminary result a=0.030(30) of our previous experiment. These observations could point at weak interaction as origin of the observed 7 s-modulation of the EC decay. Furthermore, the data suggest that interference terms occur in the two-body EC decay, although the neutrinos are not directly observed.
PDF
