Masaru Todoriki

Surface sorption and surface diffusion of NpO2+ with poorly crystallized ferric oxide

The sorption of NpO 2 + onto synthetic poorly crystallized ferric oxide was studied by conducting batch experiments in the pH range from 4 to 8 as well as adsorption isotherm studies and constant boundary condition studies. The sorption process was characterized by two steps. The first step was a rapid reaction between the bulk solution and the external surfaces of the poorly crystallized ferric oxide. In this step, NpO +∼2 was sorbed on the external sites of the poorly crystallized ferric oxide by formation of an inner-sphere complex. The second step was a slow and rate-limiting reaction wherein the NpO +∼2 diffused through small pores in the poorly crystallized ferric oxide. By taking account of these two steps and the mass balance of NpO +∼2 in the poorly crystallized ferric oxide, we applied the diffusion model to our experimental results, and evaluated the surface diffusion coefficient of NpO 2 + at 2.0×10 -13 cm 2 s -1 .

Sorption Equilibrium and Kinetics of NpO+2 Uptake onto Illite

The equilibrium and kinetics of sorption of NpOJ onto illite were investigated at pH = 6 by using differential pulse anodic stripping voltammetry and spectroscopy, respectively. It was found that the sorption isotherm obtained was fitted better by a Langmuir-Freundlich type equation than by the Langmuir equation. The heterogeneity coefficient was 0.89 ± 0.05 and the half width at half maximum (HWHM) of the affinity spectrum was 0.19 log units, indicating that the surface of illite used has a low degree of heterogeneity. The kinetic spectra indicate that the sorption of NpOJ occurs only at the outer surface. The mean HWHM of the kinetic spectra was 0.18 log units. This also suggests that the sorption kinetics of NpOJ on the illite used is controlled by the same heterogeneity of the sorption sites. From the dependence of mean rate constants on temperature, a mean apparent activation enthalpy and a mean apparent activation entropy were evaluated at 37 ± 3 kJ/mol and — 69 ± 7 J/K · mol, respectively. This value of enthalpy suggests that sorption is not controlled by diffusion through the hydrodynamic film around the illite.

REGARD: A new GNSS‐based real‐time finite fault modeling system for GEONET

The short period seismometer-based magnitude saturation problem, especially for events with magnitude > 8, can be improved by a real-time Global Navigation Satellite System (GNSS) positioning technique, which has enabled rapid estimation of a finite fault model for a large earthquake without any saturation. A new real-time fault modeling system based on the GNSS Earth Observation Network (GEONET) is developed and is under experimental operation in Japan. In this paper, we present the newly developed system REGARD (the Real-time GEONET Analysis system for Rapid Deformation monitoring), which consists of real-time GNSS positioning, automatic detection of coseismic displacement by the event, and quasi real-time finite fault model inversion routines. The performance of the automatic event detection system is tested through experimental real-time operation based on GEONET data for two months. Furthermore, we also test the reliability of the finite fault model inversion routines using real raw GNSS data observed for past large earthquakes: the 2003 Tokachi-oki earthquake (moment magnitude (Mw) 8.3), the 2011 Tohoku earthquake (Mw 9.0), and the 2011 off Ibaraki earthquake (Mw 7.7). A simulated 1707 Hoei-type Nankai Trough earthquake (Mw 8.7) is also tested. The real-time experimental operation shows that real-time GNSS positioning is precise enough to detect all the tested earthquakes, and the inversion results demonstrate that the REGARD can reliably estimate the earthquake size and its extent within 3 min after the origin time. These results suggest that the REGARD system will complement the seismometer-based magnitude determination system.

Development and Assessment of Real-Time Fault Model Estimation Routines in the GEONET Real-Time Processing System

The recent development of Global Navigation Satellite Systems (GNSS) and communication infrastructure provides real-time displacement data, enabling the real-time estimation of coseismic fault models for large earthquakes and the potential improvement of tsunami warning systems. In this paper, we present two real-time coseismic fault model estimation procedures implemented in the GEONET real-time processing system: a single rectangular fault model and a slip distribution model on the subducting plate interface. We evaluate the fault modeling procedures for two past large interplate earthquakes: the 2003 Tokachi-oki earthquake and the 2011 Tohoku earthquake. Furthermore, we also evaluate a potential large interplate earthquake along the Nankai trough based on simulated GPS time series. We obtained reasonable coseismic simple rectangular fault models for the past two large earthquakes. In contrast, the simulated interplate event along the Nankai trough clearly indicates the great advantage of estimation of the coseismic slip distribution on the plate interface. These results clearly show that reliable estimation of the coseismic fault model and/or slip distribution on the subducting plate interface will be possible in Japan based on the real-time GNSS data. This result will contribute to a more reliable tsunami early warning system.

Numerical evaluation of nuclide analysis of I129, Sr90, and Cs137 using bremsstrahlung high energy x ray generated by ultrashort pulse laser

We analyzed numerically the feasibility of nuclide analysis of spent fuels using an ultraintense, ultrashort laser. The (γ,n) reaction yields for each nuclide such as I129, Sr90, and Cs137 were calculated using the bremsstrahlung spectrum and the nuclear reaction cross sections. The dependence of the (γ,n) reaction yield on the irradiation time was derived. We also calculated the dependence of the nuclide ratio on the bremsstrahlung photon temperature. In order to investigate the influence of electron temperature and target thickness on the bremsstrahlung photon spectrum, the calculations were performed using the Monte Carlo code GEANT4. When gold was used as bremsstrahlung converter target at a temperature of the incident electrons of 30MeV, the target thickness providing maximum nuclear reaction yield was found to be 5mm.We analyzed numerically the feasibility of nuclide analysis of spent fuels using an ultraintense, ultrashort laser. The (γ,n) reaction yields for each nuclide such as I129, Sr90, and Cs137 were calculated using the bremsstrahlung spectrum and the nuclear reaction cross sections. The dependence of the (γ,n) reaction yield on the irradiation time was derived. We also calculated the dependence of the nuclide ratio on the bremsstrahlung photon temperature. In order to investigate the influence of electron temperature and target thickness on the bremsstrahlung photon spectrum, the calculations were performed using the Monte Carlo code GEANT4. When gold was used as bremsstrahlung converter target at a temperature of the incident electrons of 30MeV, the target thickness providing maximum nuclear reaction yield was found to be 5mm.

Hard x-ray generation by low energy, tightly focused laser pulses

The interaction of λ2 laser pulses with plasma is studied to scale the high-field physics from high power laser systems to low-energy, high-repetition-rate lasers. For this purpose, 20mJ, 40fs Ti:sapphire laser pulses were focused in a spot of 2.2×2.3μm2 with a maximum intensity of I∼1019W∕cm2. Efficient generations of energetic electrons (∼1MeV) and hard x-rays with energies of over 100keV were obtained by irradiating the low-energy, tightly focused laser pulses on a massive Cu target.

Determination of the temperature of bremsstrahlung photon generated by ultraintense laser using various thickness attenuators

We evaluate the simplified method using the Lambert-Beer law to measure the temperature of bremsstrahlung photon generated by an ultraintense laser. Analytical values are compared to the results of the Monte Carlo calculation of GEANT4 and they agreed very well on the condition of the appropriate distance between the attenuator and the detector. We performed the experiment to measure the temperature of bremsstrahlung x-ray emitted from a metal target irradiated by a Ti:sapphire laser with 76 mJ, 72 fs, 2.2 × 10(18)  W∕cm(2). For a Cu target of 30  μm thick, the photon temperature was reasonably determined to be 0.18 MeV, which is in good agreement with previous studies.

Experimental investigation of new concentration measurements using nonlinear dynamics through laser-induced thermal lens oscillation

The laser-induced thermal lens oscillation that is generated in an organic solution by Ar-ion laser irradiation was studied as a nonlinear dynamic system. The different dynamic states depend on three control parameters: laser beam power (P), depth (d) from a surface to a laser beam position, and solvent concentration. The transitions of dynamic states including several complicated states, for example, periodic, double periodic, were investigated by varying the parameters (P, d) for 27%, 30%, and 33% of tri-n-butyl phosphate solution diluted with n-dodecane. It was found that these transitions were strongly dependent on the concentration of the TBP solution. Based on this result, we also propose an application to solvent concentration measurement with a difference of 3%.

High energy electron generation by the 15 mJ ultrashort pulse laser

We propose a small size high energy X-ray source utilizing ultrashort pulse lasers, and a new scheme for generating quasi-monoenergetic electrons. In this paper, we developed a compact laser electron generator and performed experiment that generated energetic electrons over 1 MeV electrons with only 15 mJ laser energy. The temperatures of emitted electrons were measured to be 0.2 MeV and 0.25 MeV without and with prepulse, respectively.

Diffusion in binary suspensions of charged colloids

The dependence of diffusion coefficient in the binary suspension system of charged spherical colloidal particles on the colloid diameter and surface potential was investigated experimentally. A ratio of the diffusion coefficient in the binary system to that in free water was less than unity. This means that the diffusion of a charged colloidal particle is slowed down through the friction induced on the colloidal particle by the electrostatic interaction in the binary system. The ratio was calculated by generalized Langevin equation, and it was found that the calculated ratio agreed well with the experimental ratio. Diffusion behavior of a charged colloidal particle through quartz powder was also studied in the binary suspension system. A decrease in the effective diffusion coefficient, in comparison with that in monodispersed system, was observed.