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We developed a prototype laser ionization gas cell with a beam extraction system. This device is for use of PArasitic Laser Ion-Source (PALIS), which will be implemented into RIKEN’s fragment separator, BigRIPS as a part of SLOWRI. Off-line resonant laser ionization for stable Co, Cu, Fe, Ni, Ti, Nb, Sn, In and Pd inside the gas cell, ion extraction and transport to the high-vacuum region via SPIG and QMS have been confirmed (Sonoda et al, Nucl Instrum Meth B 295:1, 2013).

We have measured the energy spectrum of pionic 121Sn atoms by missing-mass spectroscopy of the 122Sn(d, 3He) reaction near the π − emission threshold. The measurement serves as a pilot experiment for high precision systematic spectroscopy of deeply bound pionic atoms in a new pionic Atom Factory project (piAF) at the RI beam factory (RIBF) of RIKEN. The status of the analysis is reported.

We measured the polarization of the β-emitting 23Ne (I π =5/2+, T 1/2=37.24 s) and 25Al(I π =5/2+, T 1/2=7.18 s) produced through the one nucleon pickup reactions and 24mAl(I π =1+, T 1/2=131 ms, E ex=426keV) and 28P(I π =3+, T 1/2=270 ms) produced through charge-exchange reactions in the intermediate energy heavy ion collisions. We compared them with those from the projectile fragmentation process. The larger polarization seems to persistently be positive throughout the momentum distribution, and sharper momentum distributions suggest that nuclear friction mechanism is responsible for the polarization phenomena.

A next-generation slow radioactive nuclear ion beam facility (SLOWRI) which provides slow, high-purity and small emittance ion beams of all elements is being build as one of the principal facilities at the RIKEN RI-beam factory (RIBF). High energy radioactive ion beams from the projectile fragment separator BigRIPS are thermalized in a large gas catcher cell The thermalized ions in the gas cell are guided and extracted to a vacuum environment by a combination of de electric fields and inhomogeneous rf fields (rf carpet ion guide). From there the slow ion beam is delivered via a mass separator and a switchyard to various devices: such as an ion trap, a collinear fast beam apparatus, and a multi-reflection time of flight mass spectrometer. In the R&D works at the present RIKEN facility, an overall efficiency of 5% for a 100A MeV 8Li ion beam from the present projectile fragment separator RIPS was achieved and the dependence of the efficiency on the ion beam intensity was investigated. Recently our first spectroscopy experiment at the prototype SLOWI was performed on Be isotopes. Energetic ions of 10Be and 7Be from the RIPS were trapped and laser cooled in a linear rf trap and the specific mass shifts of these isotopes were measured for the first time.

Beams of spin-polarized radioactive nuclei are produced in the projectile fragmentation reaction induced by intermediate-energy heavy ion beams, and are used for the measurement of magnetic dipole and electric quadrupole moments of nuclei in the regions far from stability. In this paper, after remarking the mechanism of fragment polarization and the experimental techniques to make use of it, we discuss the recent results obtained for the electromagnetic moments of light neutron-rich nuclei at RIKEN. Analyses of the observed magnetic moments in terms of shell models show intriguing results which imply that some of the basic nuclear properties, such as the order in energy of the single-particle orbits, the pairing energy between the excess neutrons, and the effective gs-factor for a halo nucleon, tend to alter as the degree of neutron excess increases. Also, the measured electric quadrupole moments reveal remarkable quenching of the E2 effective charge in nuclei with large N/Z ratios.

We discuss a new method of producing spin-polarized radioactive nuclear probes which capitalizes characteristic features of projectile fragmentation reaction at intermediate energies. Experimental results are given for the behavior of polarization as a function of the fragment momentum, target mass number, and beam energy. As an application of this method, we also report on results ofg-factor measurements for several neutron-rich nuclei. A full account of theg-factor measurement will be presented elsewhere.

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.