T. Hayamizu

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.

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).

Development of a Magneto-Optical Trap System of Francium Atoms for the Electron Electric-Dipole-Moment Search

The finite value of an electron electric dipole moment (eEDM) provides the direct evidence for the violation of time reversal symmetry. Fr atoms, whose enhancement factor is 895, trapped by laser cooling and trapping techniques are one of the strongest candidates for measuring the eEDM. We are constructing a beamline for measuring the eEDM using laser- cooled Fr atoms at the Cyclotron and Radioisotope Center. We have developed laser light sources including the frequency stabilization system and a magneto-optical trap system for Fr atoms. As the Fr production requires the cyclotron operation, we also use Rb atoms whose chemical properties are similar to those of the Fr atoms. Thus, the Rb beam is utilized for optimizing the operation parameters of the entire apparatus. We have also developed the laser light sources for Rb atoms and observed the beat signal for frequency stabilization of the source using the frequency offset locking method.

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

Parity-Nonconserving Interaction-Induced Light Shifts in the \( \mathbf{{7S}}_{\mathbf{1/2}} \)–\( \mathbf{6 D}_{\mathbf{3/2}} \) Transition of the Ultracold \( ^{\mathbf{210}}{\mathbf{Fr}} \) Atoms to Probe New Physics Beyond the Standard Model

We present an experimental technique to measure light shifts due to the nuclear spin independent (NSI) parity-nonconserving (PNC) interaction in the \( 7{S}_{1/2} \)–\( 6{D}_{3/2} \) transition in ultracold \( {}^{210}\mathrm{Fr} \) atoms. The approach we propose is similar to the one by Fortson (Phys Rev Lett 70:2383, 10) to measure the PNC-induced light shift which arises from the interference of parity nonconserving electric dipole transition and electric quadrupole transition amplitudes. Its major advantage is that it can treat more than \( {10}^4 \) ultracold \( {}^{210}\mathrm{Fr} \) atoms to enhance the shot noise limit. A relativistic coupled-cluster method has been employed to calculate the electric dipole transition amplitudes arising from the PNC interaction. Based on these calculations, we have evaluated the PNC-induced light shifts for transitions between the hyperfine levels of the \( 7{S}_{1/2} \) and \( 6{D}_{3/2} \) states and suitable transitions are identified for carrying out PNC measurements. It is possible in principle to probe new physics beyond the standard model with our proposed experimental scheme.

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.

Search for electron EDM with laser cooled radioactive atom

The permanent electric dipole moment (EDM) of the elementary particle has the sensitivity to the CP violation in the theories beyond the standard model (SM). The search for the EDM constitutes the stringent test to discriminate between the SM and beyond it. We plan to perform the electron EDM search by using the laser cooled francium (Fr) atom which has the largest enhancement factor of the electron EDM in the alkali atoms. In this paper, the present status of the laser cooled Fr factory that is being constructed at Cyclotron and Radioisotope Center (CYRIC), Tohoku University are reported.

SEARCH FOR THE α CONDENSED STATE IN 16O

In order to search for the α condensed state in 16O, we have performed the decay particle measurement via the reaction. Although the decay branching ratio of the α + 12C channel was predicted to be small, the branching ratio between the α + 12C and channels was obtained to be 7:3 by using the result of a simple simulation.