Tomihiro Kamiya

Characteristics of single particles sampled in Japan during the Asian dust}storm period

Abstract To investigate the characteristics of Asian dust storm particles as single particles in Japan, we measured morphology, composition and concentration of single particles using Scanning Electron Microscope (SEM) coupled with an energy dispersive X-ray microanalyzer (EDX), particle induced X-ray emission (PIXE) and micro-PIXE. Particles were sampled in Kyoto, Japan from the middle of April to the end of July 1999. Mass concentration in Asian dust–storm events was roughly 3–5 times higher than that of the highest concentration measured in non-Asian dust storm seasons. Single particles were generally sharp-edged and irregular in shape and contained mostly crustal elements such as Si, Fe, Ca and Al. Particles which have more than 40% Si content comprised nearly 50% of coarse single particles in Asian dust storm events. Main concentration range of Al in single Asian dust storm particles was 10–20%, and those of Ca and Fe were below 10%. Even though S and Cl in soils of the desert and loess areas in northwest of China were not detected, significant concentration of S and Cl in coarse fraction in Asian dust storm event were detected in single particles. Especially, the maximum concentration of S in Asian dust storm event was about 5 times higher than that in non-Asian dust storm days. Every single particle in coarse fraction existed as the mixing state of soil components and S. Good agreement between the results of SEM–EDX analysis and that of micro-PIXE analysis was obtained in this study.

Single-event current transients induced by high energy ion microbeams

Focused high-energy ion microbeams were applied to the study of the basic mechanisms of single-event upset. Waveforms of the current transients induced by He-, C-, O- and Fe-ion strikes on silicon diodes were measured by applying extremely low beam currents of an order of 10 fA and a wide-bandwidth digitizing sampling technique. Total collected charges are evaluated from the transient currents as a function of LET (linear energy transfer), bias voltage, and doping level, and are compared with theoretical values calculated using conventional single-event models. It is found that irradiation effects on the total collected charges can be explained by the introduction of displacement atoms calculated using Coulomb potential and the Kinchin-Pease model. >

JAERI Takasaki in-air micro-PIXE system for various applications

Abstract In JAERI Takasaki, an in-air micro-PIXE system has been developed. This system enables multi-elemental mapping of samples in atmospheric environment with spatial resolution of 1 μm. Various research programs, such as biomedical research, dental study, environmental science and geology, have been started in recent years. Several related techniques for these applications were developed. A FTP server has been operated for the remote collaborators to share experimental data over the internet. We have developed image processing methods for elemental concentration analysis and a new beam monitoring technique in thick target irradiation.

Elemental analysis of cellular samples by in-air micro-PIXE

Abstract We developed a micro-PIXE system for the analysis of frozen cellular samples at atmospheric pressure under helium gas cooling. We analyzed bovine aortic endothelial (BAE) cells previously cultured in a medium containing bromodeoxyuridine (BrdU). It is known that these cells take BrdU into their nuclei at the S phase of their metabolic cycle. We examined the Br uptake for incubation times of 6, 12 and 24 h, respectively. The Br maps showed an accumulation in the nuclei and the Br concentration was found strongly dependent on the incubation time. We have demonstrated that in-air micro-PIXE analysis is a relevant technique for examining the molecular uptake in cells.

Development of an automated single cell irradiation system combined with a high-energy heavy ion microbeam system

Abstract An automated single cell recognition and irradiation system has been developed at a high-energy heavy ion microbeam. The system has been installed on a vertical beam line of the JAERI Takasaki AVF-cyclotron accelerator to irradiate individual biological cells in an air environment with energies of more than 10 MeV/u by single ions. The system consists of high-precision stages, optical microscopes with CCD camera, a computer network and software packages to obtain positional data from a cluster of individual samples randomly placed on a holder before irradiation and to irradiate them with individual ions according to the obtained data. This paper will describe the new systems, and show results from irradiation experiments for CR-39.

The Electrical Characteristics of Metal-Oxide-Semiconductor Field Effect Transistors Fabricated on Cubic Silicon Carbide

The n-channel metal-oxide-semiconductor field effect transistors (MOSFETs) were fabricated on cubic silicon carbide (3C-SiC) epitaxial layers grown on 3C-SiC substrates. The gate oxide of the MOSFETs was formed using pyrogenic oxidation at 1100 ?C. The 3C-SiC MOSFETs showed enhancement type behaviors after annealing at 200 ?C for 30 min in argon atmosphere. The maximum value of the effective channel mobility of the 3C-SiC MOSFETs was 260 cm2/V?s. The leakage current of gate oxide was of a few tens of nA/cm2 at an electric field range below 8.5 MV/cm, and breakdown began around 8.5 MV/cm.

Direct visualization and quantification of the anticancer agent, cis‐diamminedichloro‐platinum(II), in human lung cancer cells using in‐air microparticle‐induced X‐ray emission analysis

The authors designed an elemental analysis system using an ion microbeam combined with a microparticle‐induced X‐ray emission (micro‐PIXE) method for the analysis of biomedical samples in air with a spatial resolution of 1 µm (in‐air micro‐PIXE system). This system was used to develop an imaging and quantification method for intracellular cis‐diamminedichloro‐platinum(II) (CDDP) in a human lung cancer cell line. A human lung adenocarcinoma cell line, A549, was cultured and nuclear labeling was carried out by incubating the cells with BrdU. The cells were then exposed to CDDP at concentrations ranging from 1 µmol to 1 mmol, for 30 min to 24 h. After drug treatment, samples were washed and frozen with liquid nitrogen, and freeze‐dried for 24 h. Standard samples were made using agar containing several concentrations of CDDP. Experiments using standard samples showed a linear correlation between CDDP concentration and platinum signal strength. No clear platinum signal was detected after exposure to CDDP for 24 h at doses between 1 and 100 µmol. However, significant platinum signals were observed at 1 mmol. When nucleus and cytoplasm visualization was sufficiently clear to efficiently use in‐air micro‐PIXE, the platinum image quality was considered satisfactory. The detected signals of CDDP were stronger in the nucleus than in the cytoplasm. A time‐course study showed increased CDDP uptake in cells after longer drug exposure periods. The present study demonstrates the application of element analysis using in‐air micro‐PIXE to biomedical samples. The use of this system enables the high‐resolution visualization of intracellular CDDP distribution and measurement of intracellular CDDP concentrations. (Cancer Sci 2008; 99: 901–904)

N-channel MOSFETs fabricated on homoepitaxy-grown 3C-SiC films

We present results of the enhancement mode, n-channel 3C-silicon carbide (SiC) MOSFETs fabricated on homoepitaxy 3C-SiC films. The fabricated devices exhibit excellent gate-controlled linear and saturation regimes of operation. The average effective channel mobility is found to be 229 cm/sup 2//Vs. The breakdown field of the gate oxide is observed at be 11 MV/cm and the subthreshold swing is determined to be 280 mV/decade.

Development of a Micro-PIXE Camera

We developed a system of μ-PIXE analysis at the division of Takasaki ion accelerator for advanced radiation application (TIARA) in Japan Atomic Energy Research Institute (JAERI), which consists of a microbeam apparatus, a multi-parameter data acquisition system and a personal computer. Elemental analysis in the region of 500 μm × 500 μm can be performed with a spatial resolution of < 0.3 μm and multi-elemental distributions are presented as images on a computer display even during measurement. We call this system a micro-PIXE camera.

Fabrication of three-dimensional structures of resist by proton beam writing

The fabrication of three-dimensional (3D) structures was demonstrated by proton beam writing (PBW) using a MeV light-ion microbeam system at Japan Atomic Energy Agency. The fabrication of the 3D structures was performed using PBW in a thick SU-8 layer with a thickness of up to 50μm, which is a typical negative resist. The authors exposed the negative resist on a silicon substrate to focused MeV proton beams within 1μm in diameter, using two different beam energies to obtain two different depths in the resist aiming at fabrication of 3D structures. The two different beam energies were obtained using a 75μm Kapton film as a beam energy degrader to generate 1.6MeV proton beam from 3.0MeV, or using the accelerator voltage control in order to produce beam energy of 1.2MeV. The 3D lines and space structures with the same shape were fabricated using the two different methods. An Arc de Triomphe shape was also manufactured to demonstrate the superior and unique features of the PBW as a versatile tool for deep mic...