196-198Irのガスセル内レーザー共鳴イオン化分光

筑波大学 (University of Tsukuba)201

196-198Irのガスセル内レーザー共鳴イオン化分光

この博士論文は内容の要約のみの公開（または一部非公開）になっています筑波大学 (University of Tsukuba)201

Design report of the KISS-II facility for exploring the origin of uranium

One of the critical longstanding issues in nuclear physics is the origin of the heavy elements such as platinum and uranium. The r-process hypothesis is generally supported as the process through which heavy elements are formed via explosive rapid neutron capture. Many of the nuclei involved in heavy-element synthesis are unidentified, short-lived, neutron-rich nuclei, and experimental data on their masses, half-lives, excited states, decay modes, and reaction rates with neutron etc., are incredibly scarce. The ultimate goal is to understand the origin of uranium. The nuclei along the pathway to uranium in the r-process are in "Terra Incognita". In principle, as many of these nuclides have more neutrons than 238U, this region is inaccessible via the in-flight fragmentation reactions and in-flight fission reactions used at the present major facilities worldwide. Therefore, the multi-nucleon transfer (MNT) reaction, which has been studied at the KEK Isotope Separation System (KISS), is attracting attention. However, in contrast to in-flight fission and fragmentation, the nuclei produced by the MNT reaction have characteristic kinematics with broad angular distribution and relatively low energies which makes them non-amenable to in-flight separation techniques. KISS-II would be the first facility to effectively connect production, separation, and analysis of nuclides along the r-process path leading to uranium. This will be accomplished by the use of a large solenoid to collect MNT products while rejecting the intense primary beam, a large helium gas catcher to thermalize the MNT products, and an MRTOF mass spectrograph to perform mass analysis and isobaric purification of subsequent spectroscopic studies. The facility will finally allow us to explore the neutron-rich nuclides in this Terra Incognita.Comment: Editors: Yutaka Watanabe and Yoshikazu Hirayam

Experimental studies of neutron-rich nuclei around

Nuclear parameters such as lifetimes and masses of the waiting point nuclei of r-process nucleosynthesis are significant to investigate its astrophysical environment. However, the difficulty in the production of extremely neutron-rich nuclei at the 126 neutron closed shell makes their experimentalstudies unfeasible. Therefore, the theoretical nuclear models play crucial roles in the simulation of the r-process nucleosynthesis. The systematic nuclear spectroscopy of the neutron-rich nuclei around the 126 neutron closed shell provides significant inputs to those theoretical models to improve their predictability for the waiting point nuclei. We are developing KEK Isotope Separation System (KISS) to perform the systematic nuclear spectroscopy of those neutron-rich nuclei. The nuclei of interest are produced by multi-nucleon transfer reactions between 136Xe and 198Pt. The experimental study demonstrated its promising potential to produce them. We have successfully performed the β­γ spectroscopy and the laser ionization spectroscopy at KISS using the nuclear production by the multi-nucleon transfer reactions

Experimental studies of neutron-rich nuclei around N = 126 at KEK isotope separation system

Nuclear parameters such as lifetimes and masses of the waiting point nuclei of r-process nucleosynthesis are significant to investigate its astrophysical environment. However, the difficulty in the production of extremely neutron-rich nuclei at the 126 neutron closed shell makes their experimentalstudies unfeasible. Therefore, the theoretical nuclear models play crucial roles in the simulation of the r-process nucleosynthesis. The systematic nuclear spectroscopy of the neutron-rich nuclei around the 126 neutron closed shell provides significant inputs to those theoretical models to improve their predictability for the waiting point nuclei. We are developing KEK Isotope Separation System (KISS) to perform the systematic nuclear spectroscopy of those neutron-rich nuclei. The nuclei of interest are produced by multi-nucleon transfer reactions between 136Xe and 198Pt. The experimental study demonstrated its promising potential to produce them. We have successfully performed the β­γ spectroscopy and the laser ionization spectroscopy at KISS using the nuclear production by the multi-nucleon transfer reactions

Off-line test of the KISS gas cell

The KEK Isotope Separation System (KISS) has been constructed at RIKEN to study the β-decay properties of neutron-rich isotopes with neutron numbers around N = 126 for application to astrophysics. A key component of KISS is a gas cell filled with argon gas at a pressure of 50 kPa to stop and collect the unstable nuclei, where the isotopes of interest will be selectively ionized using laser resonance ionization. We have performed off-line tests to study the basic properties of the gas cell and of KISS using nickel and iron filaments placed in the gas cell.status: publishe

Measurements of total reaction cross sections for 17Ne using a solid hydrogen target

We measured the energy dependence of the total reaction cross sections (σR) for the proton-drip-line nucleus, 17Ne, using a solid hydrogen target. We compared the experimental data with theoretical calculations using the Glauber model. We found that the theoretical cross sections overestimate the experimental ones in the low-energy region (∼100A MeV), whereas they significantly underestimate the experimental data in the intermediate-energy region (∼300-500A MeV). These trends are the same as those for σR for carbon–proton collisions, which were measured previously. We discuss several possibilities for resolving this discrepancy. This work demonstrates the necessity of additional careful investigations of the energy dependence of σR for various nuclei on proton targets in order to determine nuclear size properties precisely