Radioactive Ion Beams as Microscopic Probes into Matter

Abstract

During the last decade there has been a remarkable progress in technologies concerning beams of radioactive ions, and based on this, nuclear physics has enjoyed an expanding interest in the newly accessible regions of nuclide. The opportunities are now getting practicable to other fields where even improved production yields and/or ease-of-use of the beams are essential. In particular, the upcoming facility at RIKEN called RIBF is intended to magnify these opportunities with increased available intensities and varieties. After an introduction of principles and methods in the experimental techniques, we describe the characteristics of radioactive ion beams presently available at RIKEN as well as of those to be available at RIBF in a few years, and discuss material science studies to be enabled by the incorporation of radioactive beams. In particular, we focus our discussion on spin-oriented radioactive ion beams. β-rays or other radiations emitted in decays of spin polarized radioactive nuclei show asymmetric or anisotropic angular distributions, and provide unique tool to detect the spin precession and relaxation in material where they are implanted. A method of p olarization taking advantage of the projectile fragmentation kinematics has been developed to produce polarized radioactive beams at RIKEN. Furthermore, a new method to obtain highly polarized slow radioactive ions at RIBF is being developed. We report on the present status, and discuss possible applications to condensed matter studies.