A. Ozawa

Experiment on the Synthesis of Element 113 in the Reaction 209Bi(70Zn,n)278113

The convincing candidate event of the isotope of the 113th element, 278 113, and its daughter nuclei, 274 111 and 270 Mt, were observed, for the first time, in the 209 Bi + 70 Zn reaction at a beam energy of 349.0 MeV with a total dose of 1.7 ×10 19 . Alpha decay energies and decay times of the candidates, 278 113, 274 111, and 270 Mt, were (11.68 ±0.04 MeV, 0.344 ms), (11.15 ±0.07 MeV, 9.26 ms), and (10.03 ±0.07 MeV, 7.16 ms), respectively. The production cross section of the isotope was deduced to be 55 +150 -45 fb (10 -39 cm 2 ).

Nuclear size and related topics

Abstract Experimental studies on nuclear sizes and related topics are reviewed. The recent development of radioactive nuclear beams has enabled us to study the nuclear sizes of unstable nuclei. The nuclear sizes for unstable nuclei, which are deduced by the interaction cross sections and reaction cross sections, are mainly reviewed. From a theoretical view point, a Glauber-model analysis is important to deduce nuclear sizes. Other related topics, such as halo and skin from a nuclear size point of view are also discussed.

Measurements of interaction cross sections for light neutron-rich nuclei at relativistic energies and determination of effective matter radii

Abstract We measured the interaction cross sections ( σ I ) of 10,11B, 12–20C, 14–23N, 16–24O and 18–26F on carbon targets at energies of around 950 A MeV. We then deduced the effective matter radii of the nuclei by a Glauber-model analysis. Based on the assumption of a core plus a valence neutron structure, we applied a Glauber-model analysis for a few-body system adapted for nuclei with an odd neutron number. We also deduced the effective nucleus-matter densities as well as some spectroscopic information for selected nuclei. Evidence for a one-neutron halo structure was found for 22N, 23O and 24F, as well as 19C.

Observation of Second Decay Chain from 278113

RIKEN (The Institute of Physical and Chemical Research), Wako, Saitama 351-0198 Department of Physics, Saitama University, Saitama 338-8570 Center for Instrumental Analysis, Niigata University, Niigata 950-2181 Center for Nuclear Study, University of Tokyo, Wako, Saitama 351-0198 Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 Department of Chemistry, Niigata University, Niigata 950-2181 University of Tsukuba, Tsukuba, Ibaraki 305-8571 Department of Physics, Tohoku University, Sendai 980-8578 Department of Physics, Yamagata University, Yamagata 990-8560

Identification of 45 New Neutron-Rich Isotopes Produced by In-Flight Fission of a 238U Beam at 345 MeV/nucleon

A search for new isotopes using in-flight fission of a 345 MeV/nucleon 238 U beam has been carried out at the RI Beam Factory at the RIKEN Nishina Center. Fission fragments were analyzed and identi...

Delay-line PPAC for high-energy light ions

Abstract We have developed a delay-line parallel-plate avalanche counter (PPAC) with high detection efficiency for high-energy light ions. A large signal-to-noise ratio was achieved by a newly designed pre-amplifier and the usage of C 3 F 8 gas at a pressure of 30 Torr . The counter has been tested with beams of 90 A MeV 7 Li at RIKEN, 340 A MeV 12 C at GSI, and 254 A MeV 8 B at GSI. We achieved high detection efficiencies (>95%) for all of these ions. Furthermore, we achieved reasonable position and timing resolutions.

Direct nano-printing on Al substrate using a SiC mold

Nanostructures in Al were generated by printing with hard SiC molds. This nano-printing technology replaces the lithography and the etching or deposition processes to produce patterns directly in metal. Dots, short lines, and long lines were formed in the SiC molds by electron beam lithography and reactive ion etching. High aspect ratio features as small as 40 nm with depth up to 840 nm were patterned in the SiC molds. By pressing the SiC mold onto the Al substrate at room temperature, nanostructures in the SiC mold were reproduced accurately and uniformly in Al. Large arrays of nanostructures down to 40 nm were printed in Al with similar results for dots, short lines, and long lines. Using atomic force microscopy to analyze the cross sections of the SiC molds and printed Al nanostructures, depth dependence on feature size was observed. This nano-printing technology simplifies the processes for generating nanostructures with high throughput and high uniformity.

MEASUREMENT OF THE COULOMB DISSOCIATION OF 8B AT 254 MEV/NUCLEON AND THE 8B SOLAR NEUTRINO FLUX

We have measured the Coulomb dissociation of 8B into 7Be and proton at 254 MeV/nucleon using a large-acceptance focusing spectrometer. The astrophysical S17 factor for the 7Be(p,gamma)8B reaction at E{c.m.} = 0.25-2.78 MeV is deduced yielding S17(0)=20.6 \pm 1.2 (exp.) \pm 1.0 (theo.) eV-b. This result agrees with the presently adopted zero-energy S17 factor obtained in direct-reaction measurements and with the results of other Coulomb-dissociation studies performed at 46.5 and 51.2 MeV/nucleon.

New Result in the Production and Decay of an Isotope, 278113, of the 113th Element

An isotope of the 113th element, i.e., 278 113, was produced in a nuclear reaction with a 70 Zn beam on a 209 Bi target. We observed six consecutive α-decays following the implantation of a heavy particle in nearly the same position in the semiconductor detector under an extremely low background condition. The fifth and sixth decays are fully consistent with the sequential decays of 262 Db and 258 Lr in both decay energies and decay times. This indicates that the present decay chain consisted of 278 113, 274 Rg ( Z =111), 270 Mt ( Z =109), 266 Bh ( Z =107), 262 Db ( Z =105), and 258 Lr ( Z =103) with firm connections. This result, together with previously reported results from 2004 and 2007, conclusively leads to the unambiguous production and identification of the isotope 278 113 of the 113th element.

Power scaling of a high-repetition-rate enhancement cavity

A passive optical resonator is used to enhance the power of a pulsed 78 MHz repetition rate Yb laser providing 200 fs pulses. We find limitations relating to the achievable time-averaged and peak power, which we distinguish by varying the duration of the input pulses. An intracavity average power of 18 kW is generated with close to Fourier-limited pulses of 10 W average power. Beyond this power level, intensity-related effects lead to resonator instabilities, which can be removed by chirping the seed laser pulses. By extending the pulse duration in this way to 2 ps, we could obtain 72 kW of intracavity circulating power with 50 W of input power.