Radioactive cesium released into the atmosphere caused by the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011 has contaminated the surrounding area. We confirmed the applicability of in-situ methods to evaluate the depth distribution of 137Cs by employing the ratio of Compton-scattering and photo-peak components (rC) obtained from measured gamma-ray spectra. In the present study, we applied the in-situ method to farmlands in Fukushima Prefecture whose sites were disturbed by decontamination and plowing operations. rC and the net count of the 662-keV photo-peak, npeak, were obtained from gamma-ray spectra measured using a portable CsI detector. Reasonable rC was obtained by removing the contribution of naturally occurring radioactive materials through a simple and versatile procedure. The depth distribution of 137Cs measured using the conventional sampling method was reproduced using the Fermi distribution function. The concentration of 137Cs on the ground surface, N(0), and the depth at which the concentration becomes half of N(0), d1/2, can be described by simple functions of npeak and rC, respectively. We also confirmed that the Monte Carlo simulation is useful to reproduce the present results, taking into account the contribution of 134Cs and the detection system properly.

Longitudinal ( P L ) and transverse ( P T ) momentum distributions of 11 B and 11 C produced from a 12 C beam with C, Al, Nb, Tb, and Au targets observed at E = 100 MeV/nucleon are investigated. The observed P T distribution systematically changes according to the target and this change in behavior can be consistently explained by the orbital deflection effect, which is determined by the competitive contributions of attractive nuclear and repulsive Coulomb potentials acting between the projectile and target. The comprehensive examination of the observed P L and P T distributions resolves the fragmentation reaction into two reaction channels. One is the pure abrasion channel, which is characterized by small momentum transfer and an isotropic Gaussian function. The second is the two-step reaction channel, which is characterized by large momentum transfer and an anisotropic Gaussian function. The anisotropy of the second channel is consistently explained by the momentum of a picked-up nucleon.

A tractor-based robot with the capability of real-time assessing and visualizing the radioactive material density and fertility distribution of farmlands has been developed to accelerate the recovery process of the farmlands suffered by the accident of the Fukushima Daiichi Nuclear Power Plant (FDNPP). In a field test at a decontaminated farmland near FDNPP, within-field heterogeneities of soil contamination and fertility are clarified almost in real-time. Results obtained by this robot are consistent with the map by the conventional soil sampling or the history of decontamination activities.

The spin-lattice relaxation times T1 of an unstable nucleus 19O (T1/2 = 26.9 s, I = 5/2) implanted into Y2O3 stabilized ZrO2 (YSZ), which is a solid oxide fuel cell material, were measured at T = 278 − 333 K by means of the β-NMR technique, using a highly spin polarized 19O beam produced via the heavy ion reaction. The motional correlation times τc for oxygen motion derived from the T1 data are on the same straight line on the Arrhenius plot as those derived from the previous 17O-NMR data at above the room temperature. This indicates that 19O ions implanted into YSZ from outside seem to exhibit the same behavior as oxygen ions in the host YSZ material.

We have developed a new and compact β-nuclear magnetic resonance (NMR) system using beta-radioactive nuclei. By using a Halbach array permanent magnet to create a static magnetic field, and a scintillating fiber as a detector, we succeeded in significantly reducing the size and weight of the entire system. The performance of the new spectrometer was tested and evaluated by observing an NMR spectrum of 19O (T1/2 = 26.9 s, I = 5/2) in TiO2.

Nuclear magnetic resonance (NMR) spectrum of the short-lived nucleus 17 N ( I = 1/2, T 1/2 = 4.17 s ) in liquid water was measured by means of the β -NMR technique to clarify the chemical species formed by nitrogen ions injected into water. We have improved the spectral resolution to 5ppm in the full width at half maximum which is about 1/40 times compared to the previous study. The shape of the obtained spectrum indicated that it may consist of multiple resonance lines rather than a single line. Some possibilities regarding the chemical states of nitrogen in water are discussed based on the present result.

A series of experimental studies on ion-beam-induced swelling of silicon carbide (SiC), a promising ultra-hard materials, have shown that the swelling height varies with irradiation parameters, such as ion type, fluence, and beam energy. In order to confirm the feasibility of the swelling effect as a fabrication process for 3D micronanostructures, the effect of beam energy on swelling of the SIC substrate and a two-step irradiation method were investigated by using Ar beams in charge states of 1+, 4+, and 7+. The swelling height increases linearly with the fluence of the Ar beam up to n approximate to 5 x 10(15)/cm(2). In addition, the swelling height obtained by using Ar7+ ions is enhanced by about fivefold as compared with that for Ar1+. Multi-step swelling structures were fabricated through a two-step irradiation. A different irradiation pattern was used in each step, and the additivity of swelling height was confirmed. To understand the swelling behavior, the effect of irradiation is characterized by SRIM-2013 and the Rutherford bacicscattering-channeling technique.

The β-ray detected nuclear magnetic resonance (β-NMR) of a short lived-nucleus 17N (I = 1/2, T1/2 = 4.173 s) in liquid H2O and CH3NO2 has been performed. A π-pulse method was applied to obtain sharp NMR lines, from which the ratio of the Larmor frequencies of 17N in CH3NO2 and 1H was determined to be ν[17N in CH3NO2]/ν[1H2O] = 0.1265751 ± 0.0000019. Two resonance lines were observed for 17N in H2O with the relative frequency shifts of –(2.33 ± 0.37) × 10−4 and (2.91 ± 0.27) × 10−4 referenced to 17N in CH3NO2.

The nuclear shell structure, which originates in the nearly independent motion of nucleons in an average potential, provides an important guide for our understanding of nuclear structure and the underlying nuclear forces. Its most remarkable fingerprint is the existence of the so-called `magic numbers' of protons and neutrons associated with extra stability. Although the introduction of a phenomenological spin-orbit (SO) coupling force in 1949 helped explain the nuclear magic numbers, its origins are still open questions. Here, we present experimental evidence for the smallest SO-originated magic number (subshell closure) at the proton number 6 in 13-20C obtained from systematic analysis of point-proton distribution radii, electromagnetic transition rates and atomic masses of light nuclei. Performing ab initio calculations on 14,15C, we show that the observed proton distribution radii and subshell closure can be explained by the state-of-the-art nuclear theory with chiral nucleon-nucleon and three-nucleon forces, which are rooted in the quantum chromodynamics.

Longitudinal momentum (${P}_{\mathrm{L}}$) distributions of projectilelike fragments produced at $E=290\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}/\mathrm{nucleon}$ are investigated. ${P}_{\mathrm{L}}$ distributions of fragments produced by Ar and Kr beams with a wide variety of targets (C, Al, Nb, Tb, and Au) were measured using the fragment separator at HIMAC. ${P}_{\mathrm{L}}$ distributions observed for fragments with a wide range of mass losses $\mathrm{\ensuremath{\Delta}}A$ (1--30 for Ar beam and 1--64 for Kr beam), show a slightly, but definitely asymmetric nature. The peak shift and width were obtained from the observed ${P}_{\mathrm{L}}$ distributions. No significant target dependence was found in either the peak shift or width. For the practical application, the variation in momentum peak shift with fragment mass (${A}_{\mathrm{F}}$) was represented by a parabolic function. The width on the high-${P}_{\mathrm{L}}$ side (${\ensuremath{\sigma}}_{\mathrm{High}}$) is well reproduced by the Goldhaber formula, which is obtained from the contribution of the Fermi momentum. The behavior of the reduced width, ${\ensuremath{\sigma}}_{0}$, obtained from ${\ensuremath{\sigma}}_{\mathrm{High}}$ via the Goldhaber formulation, is consistent with the mass-dependent Fermi momentum of a nucleon. The width on the low-${P}_{\mathrm{L}}$ side (${\ensuremath{\sigma}}_{\mathrm{Low}}$) is markedly larger than ${\ensuremath{\sigma}}_{\mathrm{High}}$ and exhibits a clear ${A}_{\mathrm{F}}$ dependence.

Author(s) Ozawa, A., Matsuta, K., Nagatomo, T., Mihara, M. , Yamada, K., Yamaguchi, T., Momota, S., Izumika wa, T., Sumikama, T., Nakashima, Y., Fujiwara, H ., Kumashiro, S., Matsumiya, R., Ota, M., Shinoj ima, D., Tanaka, H., Yasuno, T., Nakajima, S., S uzuki, T., Yoshida, K., Muranaka, K., Maemura, T ., Chiba, A., Utsuno, Y., Fukuda, M., Tanaka, K. , Tanihata, I., Nojiri, Y., Minamisono, T., Alon so, J.R., Krebs, G.F., Symons, T.J.M.

In a series of previous experiments, a swelling structure, which was fabricated by ion-beam induced expansion effect, was observed on crystal materials and the height changes depending on irradiation condition. In case of SiC crystal, which is one of hopeful ultra-hard materials, the expansion rate is relatively large 10-20%. This result indicates the possibility of the expansion effect as a fabrication process for three-dimensional structures on SiC surface. In the present research, fabrication of swelling structure on 6H-SiC substrate, whose lateral size is in micro-meter scale, has been tried by irradiating Ar beams through a stencil mask.

Very neutron-rich $Z\ensuremath{\sim}60$ isotopes produced by in-flight fission of a 345 MeV/nucleon $^{238}\mathrm{U}$ beam at the RI Beam Factory, RIKEN Nishina Center, have been studied by delayed $\ensuremath{\gamma}$-ray spectroscopy. New isomers were discovered in the neutron-rich $N=100$ isotones $^{162}\mathrm{Sm}, ^{163}\mathrm{Eu}$, and $^{164}\mathrm{Gd}$. Half-lives, $\ensuremath{\gamma}$-ray energies, and relative intensities of these isomers were obtained. Level schemes were proposed for these nuclei and the first ${2}^{+}$ and ${4}^{+}$ states were assigned for the even-even nuclei. The first ${2}^{+}$ and ${4}^{+}$ state energies decrease as the proton numbers get smaller. The energies and the half-lives of the new isomers are very similar to those of ${4}^{\ensuremath{-}}$ isomers known in less neutron-rich $N=100$ isotones $^{168}\mathrm{Er}$ and $^{170}\mathrm{Yb}$. A deformed Hartree-Fock with angular momentum projection model suggests ${K}^{\ensuremath{\pi}}={4}^{\ensuremath{-}}$ two-quasiparticle states with $\ensuremath{\nu}7/2[633]\ensuremath{\bigotimes}\ensuremath{\nu}1/2[521]$ configurations with similar excitation energy. The results suggest that neutron-rich $N=100$ nuclei are well deformed and the deformation gets larger as $Z$ decreases to 62. The onset of $K$ isomers with the same configuration at almost the same energy in $N=100$ isotones indicates that the neutron single-particle structures of neutron-rich isotones down to $Z=62$ do not change significantly from those of the $Z=70$ stable nuclei. Systematics of the excitation energies of new isomers can be explained without the predicted $N=100$ shell gap.

A search for new isotopes in the neutron-rich rare-earth region has been carried out using a 345 MeV/nucleon 238U beam at the RIKEN Nishina Center RI Beam Factory. Fragments produced were analyzed and identified using the BigRIPS in-flight separator. We observed a total of 29 new neutron-rich isotopes: 153Ba, 154,155,156La, 156,157,158Ce, 156,157,158,159,160,161Pr, 162,163Nd, 164,165Pm, 166,167Sm, 169Eu, 171Gd, 173,174Tb, 175,176Dy, 177,178Ho, and 179,180Er.