K. Matsuta

Density distribution of 8B studied via reaction cross sections

Abstract Reaction cross sections ( σ R ) for 8 B on Be, C and Al targets were measured at energies of 40 A and 60 A MeV. The density distribution of 8 B was studied through a χ 2 -fitting procedure on the σ R including the high-energy data using the optical limit of Glauber theory with assumptions on the enhancement of the σ R at low energies. The result shows a long tail in the density distribution. Large one-proton removal cross sections were also observed to support the existence of a long proton tail consistent with its binding energy.

Lattice locations of 8Li in Cu

The dipolar broadening of the NMR on short-lived β-emitter 8Li implanted in single crystal Cu has been observed as a function of crystal orientation at several temperatures. From the orientation angle dependence of the line width, it was found that the main component of the 8Li occupies substitutional site, while about 30% of 8Li occupies octahedral interstitial site at temperatures below 300 K.

Nuclear electromagnetic moments. β-NMR and its applications

Abstract Studies of magnetic moments and electric quadrupole moments for light unstable nuclei, which have been opened up by the recent development of spin-polarized radioactive nuclear beams and the β -ray detected nuclear magnetic resonance technique, are reviewed. The results lead to several intriguing findings concerning structures and interactions in unstable nuclei far from the stability line, such as a proton-halo structure in proton-rich nuclei, displacement of the single particle levels and quenching of the neutron effective charge in neutron-rich nuclei, and an anomalously large spin expectation value in a T=3/2 mirror pair. Applications of the present techniques to the study of hyperfine interactions of radioactive atoms introduced in solids are also discussed.

CREATION OF SPIN POLARIZATION IN UNSTABLE NUCLEI AND CORRELATION-TYPE EXPERIMENTS

Abstract Kinematical selection works efficiently to polarize reaction products in both low energy direct reactions and heavy ion reactions at a wide range of energy. This polarization technique has been applied to β-ray correlation-type experiments. In such studies, the asymmetry parameter for the 23 Mg β decay was measured to be A = −(0.606 ± 0.007). The alignment correlation coefficients for 12 B and 12 N β decays were determined to be α − = 0.0107 ± 0.0053%/MeV and α + = − (0.2841 ± 0.0072)%/MeV.

Behavior of Boron Implanted in Semiconductor Si

Using β-NMR with 12B nuclei the temperature dependence of the lattice locations of boron implanted in Si is studied. At low temperature almost 100% of the implanted B is in either substitutional site or nonsubstitutional site. Above 260 K, the nonsubstitutional B rapidly becomes undetectable and disappears at a temperature higher than 325 K due to the fast spin-lattice relaxation. Above 450 K, the fraction of substitutional B increases to 100%. These experimental results are consistently explained by the thermal atomic jump and the dissociation of the defect associated with the nonsubstitutional B.

Hyperfine interactions of short-lived β-emitter 8Li in ferromagnetic Ni

Hyperfine interactions of 8Li impurity nucleus imbedded in ferromagnetic Ni metal were studied using the β-NMR technique. Two kinds of hyperfine fields B82 were found, corresponding to two different final sites of Li atoms in the Ni lattice. The nuclear spin-lattice relaxation times T1 of 8Li in Ni were also determined for each field. Temperature dependencies of B82 and T1 were observed to deduce these values at T=0 K that can be compared with those calculated recently by Akai et al.

A plan for on-line production and acceleration of radioactive isotope beams by use of electron cyclotron resonance ion source NANOGAN

For the precise low background experiments on β decay and material sciences, we are planning to build a new ISOL-type facility to accelerate various β-radioactive nuclei utilizing the existing 5 MV Van de Graaff accelerator and an RFQ linac. Present status of the designing work is reported. In the present work, optical elements of the 41-m-long beam transport line to connect Van de Graaff accelerator and an RFQ linac were designed. Using two dipole magnets, two electric quadrupole doublets and six electric quadrupole triplets, low energy radioactive nuclear beams can be transported with sufficient efficiency.

Hyperfine Interactions of 8Li in Ferromagnetic Single Crystal Fe

The hyperfine interactions of 8Li implanted in single crystal Fe have been studied using the β-NMR technique. One kind of hyperfine field Bhf was found. Since no dipolar field was observed, 8Li nuclei are suggested to sit in substitutional sites. The Bhf and the spin-lattice relaxation time T1 were observed as functions of temperature. The experimental Bhf and T1 were compared with the theoretical predictions from the first principles KKR-band-structure calculations. While predicted Bhf for the substitutional site is consistent with the experiment, predicted T1 cannot reproduce the experiment well.

Sign of the quadrupole moment of proton drip-line nucleus 8B

The sign of the quadrupole coupling constant eqQ of 8B in ZrB2 is determined to be positive through the β-delayed α-ray anisotropy measurement combined with the spin manipulation technique by use of the β-NMR. According to the theoretical calculation of the electric field gradient in ZrB2, the sign of the quadrupole moment of 8B is deduced to be positive.

INTERDISCIPLINARY REGIONS OF NUCLEAR PHYSICS STUDIED BY USE OF SPIN-POLARIZED SHORT-LIVED NUCLEI

Abstract The creation of nuclear spin polarization is the first step for correlation-type experiments in which correlations between the polarization and out going radiations is detected. Of particular interest is to extract clear non-nucleonic degrees of freedom and to test the conservation laws in weak nuclear currents.