M. Koizumi

Deep-sea record of impact apparently unrelated to mass extinction in the Late Triassic

The 34-million-year (My) interval of the Late Triassic is marked by the formation of several large impact structures on Earth. Late Triassic impact events have been considered a factor in biotic extinction events in the Late Triassic (e.g., end-Triassic extinction event), but this scenario remains controversial because of a lack of stratigraphic records of ejecta deposits. Here, we report evidence for an impact event (platinum group elements anomaly with nickel-rich magnetite and microspherules) from the middle Norian (Upper Triassic) deep-sea sediment in Japan. This includes anomalously high abundances of iridium, up to 41.5 parts per billion (ppb), in the ejecta deposit, which suggests that the iridium-enriched ejecta layers of the Late Triassic may be found on a global scale. The ejecta deposit is constrained by microfossils that suggest correlation with the 215.5-Mya, 100-km-wide Manicouagan impact crater in Canada. Our analysis of radiolarians shows no evidence of a mass extinction event across the impact event horizon, and no contemporaneous faunal turnover is seen in other marine planktons. However, such an event has been reported among marine faunas and terrestrial tetrapods and floras in North America. We, therefore, suggest that the Manicouagan impact triggered the extinction of terrestrial and marine organisms near the impact site but not within the pelagic marine realm.

Neutron-capture cross-sections of 244Cm and 246Cm measured with an array of large germanium detectors in the ANNRI at J-PARC/MLF

The neutron neutron-capture cross cross-sections of 244Cm and 246Cm were measured by the time-of-flight method in the energy range of 1–300 300 eV with an array of large germanium detectors in the Accurate Neutron-Nucleus Reaction measurement InstrumentANNRI at Material and Life Science Experimental Facility (MLF) of the Japan Proton Accelerator Research ComplexJ-PARC/MLF. The 244Cm resonances at around 7.7 and 16.8 8 eV and the 246Cm resonances at around 4.3 and 15.3 3 eV were observed in the capture reactions for the first time. The uncertainties of the obtained cross cross-sections are 5.8% at the top of the first resonance of 244Cm and 6.6% at that of 246Cm. The rResonance analyses were performed for low-energy ones using the code SAMMY. The prompt γ-ray spectra of 244Cm and 246Cm were also obtained. Eight and five new prompt γ-ray emissions were observed in the 244Cm(n, γ) and 246Cm(n, γ) reactions, respectively.

New high‐pressure hot stage for optical microscopy

A new high‐pressure optical hot‐stage system combined with polarizing optical microscope has been constructed for in situ observation of optical texture of liquid crystals as well as polymers during the mode of either temperature or pressure scanning. It operated well in a temperature region between room temperature and 250 °C under hydrostatic pressures up to 300 MPa. The texture of a pressure‐induced crystal polymorph of a dimesogenic liquid crystal was successfully observed.

Cross-section measurement of 237Np (n, 𝛄) from 10 meV to 1 keV at Japan Proton Accelerator Research Complex

The cross-section of the 237Np reaction has been measured in the energy range from 10 meV to 1 keV using the ANNRI-NaI(Tl) spectrometer at the Japan Proton Accelerator Research Complex (J-PARC). The cross-section was obtained relative to that of the 10B reaction. The absolute value of the cross-section was deduced by normalizing the relative cross-section to the evaluated value of JENDL-4.0 at the first resonance. The thermal cross-section was obtained to be ( ) b. The Maxwellian-averaged cross-section for meV was derived as ( ) b by referring the cross-section below 10 meV from JENDL-4.0. These results lead to the Westcotts g-factor of .

Superdeformation in asymmetric N>Z nucleus 40Ar

Abstract A rotational band with five γ -ray transitions ranging from 2 + to 12 + states was identified in 40 Ar. This band is linked through γ transitions from the excited 2 + , 4 + and 6 + levels to the low-lying states; this determines the excitation energy and the spin–parity of the band. The deduced transition quadrupole moment of 1.45 − 0.31 + 0.49 ± 0.15 eb indicates that the band has a superdeformed shape. The nature of the band is revealed by cranked Hartree–Fock–Bogoliubov calculations and a multiparticle–multihole configuration is assigned to the band.

A stopped-flow apparatus with a push–pull coupler for the study of fast reactions in solution under high pressure

A new high-pressure stopped-flow apparatus equipped with a push–pull coupler has been developed which enables one to monitor fast reactions in various organic solvents as well as in strongly acidic media under pressure up to 200 MPa. Sample solutions come into contact only with chemically inert materials: Daiflon, quartz, and a Teflon-coated O-ring. The reactant-syringe and receiver-syringe pistons are driven at the same time with the aid of a push–pull coupler and an actuator. The dead time of this apparatus is ∼2 ms.

Improvement of a high speed and high density data acquisition system for multiple gamma-ray detection

To accelerate the data acquisition system (DAQ), which was reported in NSS 2004 [1], the authors improved the Main ADC Modules in the DAQ. The new Main ADC Module has 8 input channels. Each channel consists of analog circuits for pulse shaping, a high-speed ADC (14bit 125MSPS), and a high- power Digital Signal Processor (DSP: 8000MIPS). Shaped input signals are digitized with the ADC and analyzed by the DSP to calculate the energy data. For fast data transfer, the energy data from every four channels are bundled and stored into a large Dual Port Memory (DPM: 2MByte). The bundled data are read out to a PC through VME-BUS. By combining high-speed ADCs, high-power DSPs and large DPMs, high speed and high density DAQ was constructed.

Prolate and Oblate Shape Coexistence in 188Pt

A standard in-beam γ-spectroscopy experiment for 188Pt is performed via the 176 Yb(18O, 6n) reaction at beam energies of 88 and 95MeV, and the level scheme for 188Pt is established. Prolate and oblate shape coexistence has been demonstrated to occur in 188Pt by applying the projected shell model. The rotation alignment of i13/2 neutrons drives the yrast sequence changing suddenly from prolate to oblate shape at angular momentum 10h, indicating likely a new type of shape phase transition along the yrast line in 188Pt.

QEC Measurement of 124,125,127-130La

For neutron-deficient 124,125,127-130 La, Q EC measurement has been performed by determining β + -ray maximum energies. The radioactive sources were prepared by on-line mass-separation following the fusion-evaporation reactions 92, nat Mo( 36 Ar, 3 p x n ). The β + -rays were measured with an HPGe detector in β-γ coincidence mode in which γ-rays were detected with another HPGe detector for specifying an excited state in daughter nucleus. By unfolding the β + -ray spectra using experimental response functions, the Q EC -values of 124, 125, 127, 130 La were newly obtained, and those of 128, 129 La were improved in their accuracy. The Q EC -values obtained and the resulting atomic masses are compared with theoretical predictions. The results of half-life calculation and two-neutron separation energies using the experimental Q EC -values are also discussed.

Development of a 4π germanium spectrometer for nuclear data measurements at J-PARC

A 4π germanium spectrometer was developed for measurements of neutron capture cross sections of minor ac-tinides and long-lived-fission products. It was installed on the Beam Line No. 04 of the MLF in the J-PARC. We measured its full-energy peak efficiency and gamma-energy resolution at 1.3-MeV with a 60Co standard source (10kBq). As an example of a result of TOF measurements with the spectrometer, preliminary TOF and energy spectra of 108Pd are shown in this paper.