Tadanori Minamisono

Electromagnetic dissociation and soft giant dipole resonance of the neutron-dripline nucleus 11Li

Abstract The electromagnetic dissociation (EMD) cross sections of light neutron-dripline projectile 11Li have been inferred from the target dependence of the interaction cross section, σ1, and the two-neutron-removal cross section, σ−2n, at an incident energy of 0.8 GeV/nucleon. The EMD cross sections of 11Li projectiles on a lead target were found to be quite large; σ I EMD ( 11 Li + Pb )=1.72 ±0.65 b and σ −2 n EMD ( 11 Li + Pb )=0.89 ±0.10 b , which are approximately 80 times larger than those of 12C projectiles after scaling the cross section by Zproj2. The large EMD cross section is related to the possible existence of a soft mode of the giant dipole resonance at low excitation energy in the extremely neutron-rich nuclei.

Quadrupole Effects in NMR Spectra on Short-Lived β-Radioactive Nuclei, 12B and 12N

Quadrupole effects in NMR on 12 B( T 1/2 =20 ms) and 12 N( T 1/2 =11 ms) have been investigated by using the polarized nuclei produced and implanted through nuclear reactions and the resultant asymmetric β decay. The implantation media were polycrystalline bcc metals (Nb, Mo, Ta and W), TiB 2 and ZrB 2 . To increase the observable effects in NMR, a frequency-modu-lated r.f. field was employed. The spectra in bcc metals show the characteristics of quadrupole interaction for nuclear spin \(I{=}1\hslash\), and the determined coupling constants depend largely on the periodic groups of the related elements. The spectra in the bcc metals together with those in the fcc metals (Al, Cu, Pt and Au) indicate that the major implanted sites are interstitial. From the results on TiB 2 and ZrB 2 and the known values on 11 B, the ratio of quadrupole moments is determined as | Q ( 12 B)/ Q ( 11 B)|=0.42±0.04, and the moment of 12 B is deduced to be | Q ( 12 B)|=0.017 1 ±0.001 6 b.

Magnetic Moments of Short-Lived β-Radioactive Nuclei, 12B and 12N

The magnetic moments of 12 B( T 1/2 =20 ms) and 12 N( T 1/2 =11 ms) have been determined by an NMR method using the recoil polarization and the asymmetric β decay. The nuclear polarization was preserved by using a holding static magnetic field and a recoil stopper of metal foil. Several kinds of metal foils were employed. Relative shifts of the order of 10 -3 between the centers of NMR by different metals and the resonance widths comparable to the dipolar broadening were observed. The results obtained for the magnetic moments are µ( 12 B, 1 + )=+(1.003±0.001) nm and µ( 12 N, 1 + )=+(0.4571±0.0005) nm.

Laser-Induced Etching of Mn-Zn Ferrite an Its Application

Single-crystalline ferrite was masklessly etched by focused Ar+ laser irradiation in CCl4 gas and in H3PO4 solution. Etching rates up to 68 µm/s in CCl4 and 340 µm/s in H3PO4 have been achieved by laser processes. Bending of the etched narrow groove was observed in CCl4 gas due to the enhanced reflection caused by the polarization of the laser beam when focused by a microscope objective lens. A vertical slab structure with a high aspect ratio of up to 40 has been obtained by the light-guiding effect of the laser beam in wet-chemical etching. RBS analysis of the processed surface revealed that laser-induced damage was much lower than that induced by mechanical polishing.

Beta decay and hyperfine interactions

Experimental searches for the second-class currents and the soft pion effects in the nuclear weak axial currents are discussed. Also discussed are the hyperfine interactions of light interstitial impurities in ferromagnetic Fe and Ni, as well as in fcc and bcc non-magnetic metals. For these spinβ-ray correlation experiments, it is emphasized that the technical developments and improvements of the nuclear spin control by NMR and the production of polarization in the short-lived nuclear states are vital necessities.

Maskless Submicrometer Pattern Formation of Cr Films by Focused Sb Ion Implantation

Maskless submicrometer patterning of Cr films was done by implanting focused Sb+ ion and by plasma etching using CCl4 gas. Dose and depth dependence of the etching rate and Sb profiles were measured to investigate the concentration dependence of Sb. The present patterning characteristics are compared with conventional patterning characteristics using Au masks. It was found that a sharp threshold dose exists to form an etch resistant layer and this enables formation of few hundred nanometer thick, submicrometer patterns with vertical side walls. It was also found that the resistivity of patterned Cr films increase only 10%.

Residual Local Strain in Gallium Arsenide Induced by Laser Pyrolytic Etching in CCl4 Atmosphere

Residual local strain in GaAs induced by laser pyrolytic etching in a CCl4 gas atmosphere has, for the first time, been observed by microprobe Raman scattering and ion channeling measurements. It was found that local strain of 8.6×10-3, corresponding to tensile stress of 6.4 kbar, remained in the groove etched by laser pyrolysis at a CCl4 pressure of 32 Torr with a laser power of 0.5 W, while such strain was not induced for a laser power at and below 0.4 W.

Proton Irradiation Experiment for X-ray Charge-Coupled Devices of the Monitor of All-Sky X-ray Image Mission Onboard the International Space Station: II. Degradation of Dark Current and Identification of Electron Trap Level

We have investigated the radiation damage effects on a charge-coupled device (CCD) to be used for the Japanese X-ray mission, the monitor of all-sky X-ray image (MAXI), onboard the international space station (ISS). A temperature dependence of the dark current as a function of incremental dose is studied. We found that the protons having energy of >292 keV seriously increased the dark current of the devices. In order to improve the radiation tolerance of the devices, we have developed various device architectures to minimize the radiation damage in orbit. Among them, nitride oxide enables us to reduce the dark current significantly and therefore we adopted nitride oxide for the flight devices. We also compared the dark current of a device in operation and that out of operation during the proton irradiation. The dark current of the device in operation became twofold that out of operation, and we thus determined that devices would be turned off during the passage of the radiation belt. The temperature dependence of the dark current enables us to determine the electron trap level that generates the dark current. We fitted dark current as a function of temperature by the thoretical models and found that the dark current increase after proton irradiations is caused by, at least, two kinds of electron trap levels. The shallow trap level (Ec-Et 210 K. On the other hand, another trap level is located roughly at the center of the silicon bandgap which might be associated with divacancies or P–V traps. We finally investigated the spatial distribution of the low-energy protons in the orbit of the ISS. Their density has a peak around l ~20° and b ~-55° independent of the altitude. The peak value is roughly two orders of magnitude higher than that at the South Atlantic Anomaly.

Quadrupole moment of the doubly-closed-shell-plus-one-nucleon nucleus 41Sc and its core deformation

The nuclear quadrupole moment of 41Sc(Iπ = 7−2, T12 = 0.596 s) has been measured to be |Q(41Sc; 7−2)| = 16.6 ± 0.8 fm2, by use of a modified β-NMR technique. Combining the value with its mirror quadrupole moment Q(41Ca; 7−2), it is shown that the valence proton in 41Sc carries more than 90% of the moment, and that of the remaining core carries about 10%. This is consistent with the picture that the core of 41Sc, 40Ca, is deformed by about e = −(0.44 ± 0.22)%.

Polarization of 12B in deep-inelastic heavy-ion reaction 100Mo(14N, 12B)

Abstract Spin polarization of 12 B was measured for 100 Mo( 14 N, 12 B) at E i ( 14 N ) ≅ 200 MeV as a function of Q value down to Q ⋍ −150 MeV , and was found anti-parallel to k f × k i in the deep-inelastic region. The data together with those at lower incident energies show a systematic trend in Q -value dependence of the polarization.