S. Ando

Laser frequency locking with 46 GHz offset using an electro-optic modulator for magneto-optical trapping of francium atoms.

We demonstrate frequency offset locking between two laser sources using a waveguide-type electro-optic modulator (EOM) with 10th-order sidebands for magneto-optical trapping of Fr atoms. The frequency locking error signal was successfully obtained by performing delayed self-homodyne detection of the beat signal between the repumping frequency and the 10th-order sideband component of the trapping light. Sweeping the trapping-light and repumping-light frequencies with keeping its frequency difference of 46 GHz was confirmed over 1 GHz by monitoring the Doppler absorption profile of I₂. This technique enables us to search for a resonance frequency of magneto-optical trapping of Fr.

Are there nuclear structure effects on the isoscalar giant monopole resonance and nuclear incompressibility near A∼90?

Abstract “Background-free” spectra of inelastic α-particle scattering have been measured at a beam energy of 385 MeV in 90,92Zr and 92Mo at extremely forward angles, including 0°. The ISGMR strength distributions for the three nuclei coincide with each other, establishing clearly that nuclear incompressibility is not influenced by nuclear shell structure near A ∼ 90 as was claimed in recent measurements.

Transportation of a radioactive ion beam for precise laser-trapping experiments.

Francium is the heaviest species among the alkali elements. Due to its properties, francium is said to be of advantage in measurements of tiny observations, such as atomic parity violation and electric dipole moment. Before executing experiments with francium, it must be produced artificially because it is one of the most unstable elements. We produced francium with the nuclear fusion reaction of an oxygen beam and gold target, ionized the produced francium through a thermal ionization process, and extracted the ion with electrostatic fields. However, the thermal ionization process is known to ionize not only an objective atom but also other atomic species. Therefore, a Wien filter was installed to analyze the composition of the ion beam and purify the beam. This allowed us to improve the beam purity from ∼10(-6) to ∼10(-3).

Radioactive ion beam transportation for the fundamental symmetry study with laser-trapped atoms

The search for the violation of the fundamental symmetry in a radioactive atom is the promising candidate for precision tests of the standard model and its possible extensions. The subtle signal arising from the symmetry violation is enhanced in heavy atoms, such as a francium (Fr). To realize high precision measurements, a large amount of radioactive isotopes is required. The Fr is produced via a nuclear fusion reaction using a melted gold target with a (18)O primary beam at Cyclotron and Radioisotope Center, Tohoku University. The maximum extraction efficiency of the Fr ion was achieved at approximately 35%. The beam line consists of an electrostatic deflector, three electrostatic quadrupole triplets to the measurement area at 10 m away from the reaction point, and several beam diagnosis systems. We optimized parameters of the beam line.

Laser Cooled Francium Factory for the Electron Electric Dipole Moment Search

Cyclotron and Radioisotope Center, Tohoku University, Sendai, Miyagi 980-8578, Japan aGraduate school of Arts and Sciences, University of Tokyo, Meguro 153-8902, Tokyo, Japan bDepartment of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 102-0397, Japan cDepartment of Applied Physics, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan dResearch Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047, Japan eAdvanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1184, Japan fDepartment of Physics, Kyoto University, Kyoto, Kyoto 606-8502, Japan gIndian Institute of Technology Roorkee, Roorkee, Uttarakhand 247667, India hDepartment of Physics, Tohoku University, Sendai, Miyagi 980-8578, Japan iDepartment of Physics, Kyushu University, Fukuoka, Fukuoka 812-8581, Japan

Measurement of the 3-α decay from the Hoyle and the broad 10 MeV states in12C

The measurements of the 3-α decay from the Hoyle and the broad 10 MeV state in12C have been performed using an inverse kinematic method of the12C(12C,3α)12C reaction at E12C = 110 MeV. In the measurement of the Hoyle state, the upper limit of the direct decay was improved to be 0.2 %. This was inconsistent with the recent reported nonzero value of 0.9 %, but an order larger than the direct decay branch predicted in the 3-α model. The branching ratios of the sequtial decay for the broad 10 MeV state were also obtained. They were higher than those obtained in the RCNP experiment, since they contained the contributions of higer multipole components. Their contributions will be estimated.

Feasibility study to search for the rare γ-decay mode in 12C

Excited states in 12C nuclei play a very important role in the nucleosynthesis in the universe. 12C nuclei are synthesized by the triple α reaction. Normally this process proceeds via the 0+2 state (Hoyle state) at Ex = 7.65 MeV in 12C, however, at high temperature T > 109 the highly excited 3α resonant states such as the 3−1 state at Ex = 9.64 MeV and the 2+2 state at Ex = 9.84 MeV play a part of the triple α reaction. Unfortunately, the γ-decay probability of the 3p state has not been determined, therefore we planned to determine the 7- decay probability using the inverse kinematic reaction 1H(12C, 12Cp) without measuring γ-rays. The test experiment was carried out at the cyclotron facility in RCNP. The results of the test experiment are reported in the present paper.