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The diagnostic system of JT-60U (JT-60upgrade) is composed of about 50 individual diagnostic devices. Recently, the detailed radial profile measurements of plasma parameters have been improved, so that the internal structure of plasmas could be explored. The understanding of plasma confinement has been enhanced by density and temperature fluctuation measurements using a mm-wave reflectometer and electron cyclotron emission measurements, respectively. In addition, real-time control experiments of electron density, neutron yield, radiated power, and electron temperature gradient have been carried out successfully by corresponding diagnostic devices. These measurements and the real-time control contribute to improving plasma performance. Diagnostic devices for next generation fusion devices such as a CO2laser interferometer/polarimeter and a CO2laser collective Thomson scattering system have been developed.

Abstract: With an RF-trap connected to an Isotope Separator On-Line (ISOL), we aim to study nuclear magnetic properties of nuclei far from stability through the hyperfine interaction by a laser-microwave double-resonance method. As a first step, the hyperfine splitting of the ground state of87Sr+ was measured, and the magnetic dipole hyperfine constant was precisely determined to beA=−1,000,470.8(2.4) kHz.

Abstract: Radiation-detected optical pumping in solids has been developed to investigate the structure of unstable nuclei. Appreciable nuclear polarization of implanted or doped unstable-nuclei in a host crystal is achieved with the optical pumping in solids. The nuclear polarization achieved is enhanced/reduced by applying a radio-frequency magnetic field together with the optical pumping, radiation-detected magnetic resonance being thus observed to get information on electromagnetic properties of unstable nuclei. Two schemes have been successfully developed for the optical pumping of unstable nuclei in solids. One is to directly pump the atoms by the excitation from the ground state to a broad absorption band in visible and UV regions which shows a large magnetic circular dichroism. This scheme is applicable to many rare-earth atoms in alkaline-earth fluoride host. The other scheme is to pump the electrons in the conduction band of direct-type semiconductor and thus indirectly polarize the nuclei in the host material via a hyperfine interaction between the nuclei and the polarized conduction electrons. This scheme can be especially applied to the III to VI families of atoms in direct-type semiconductors. Principle of the methods, on-line experimental system, and a few examples of the results obtained so far are presented and discussed.

The ground state hyperfine splitting of87Sr+ was measured with a precision of 1×10-8. The experiments were performed with an RF ion trap connected to an ISOL (isotope separator on-line), where all the possible transitions between Zeeman sublevels were observed by a laser-microwave double resonance method. The magnetic dipole hyperfine constant was determined to beA=-1 000 473.673 (11) kHz.

Isomeric yield ratios of 30 fission products in 24 MeV proton-induced fission of238U were measured by the use of the ion-guide isotope separator on-line. The obtained isomeric yield ratios were converted to the angular momenta of primary fission fragments based on the statistical model. The deduced angular momenta were examined from various aspects. It is found that in general the angular momentum continuously increases with the fragment mass number including the region of symmetric mass division. However, there are some exceptions. For Sn isotopes the deduced angular momenta are quite small due to the spherical shape of the nuclear shell configuration. It is also concluded from the consideration of the charge distribution that the angular momentum of fission product scatters considerably within the narrow range of mass division. The dependence of the angular momentum on the available energy of fragments at scission point indicates that the individual fragment possesses a characteristic deformation at scission and/or the deduced angular momentum is seriously affected by the particle excitation after scission.

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