Satoshi Sugimoto

Digital composition of images with increased depth of focus considering depth information

Two digital image processing methods, capable of composing microscope images with increased depth of focus and of mapping 3-D distribution on the altitude or depth of the thick object, are presented: one uses pseudocolor display of focal-series images, and the other considers the local variance of each of the focal-series images. Experimental results demonstrate the usefulness of both methods. The high-speed digital image processing system developed by the authors plays an important role in both methods.

Rethermalization of a field‐reversed configuration plasma in translation experiments

A translation experiment of field‐reversed configuration (FRC) plasma is performed on the FIX machine [Shiokawa and Goto, Phys. Fluids B 5, 534 (1993)]. The translated FRC bounces between magnetic mirror fields at both ends of a confinement region. The plasma loses some of its axial kinetic energy when it is reflected by the magnetic mirror field, and eventually settles down in the confinement region. In this reflection process, the plasma temperature rises significantly. Such plasma rethermalization has been observed in OCT‐L1 experiments [Ito et al., Phys. Fluids 30, 168 (1987)], but rarely in FRX‐C/T experiments [Rej et al., Phys. Fluids 29, 852 (1986)]. It is found that the rethermalization depends on the relation between the plasma temperature and the translation velocity. The rethermalization occurs only in the case where the translation velocity exceeds the sound velocity. This result implies the rethermalization is caused by a shock wave induced within the FRC when the plasma is reflected by the m...

Experiments on additional heating of FRC plasmas

Experiments on additional heating by neutral beam injection and application of a low frequency wave to a plasma with an extremely high averaged beta value of about 90% - a field reversed configuration (FRC) plasma - are carried out using the FRC Injection Experiment (FIX) apparatus. These experiments are made possible by translating the FRC plasma produced in a formation region of a theta pinch to a confinement region in order to secure better accessibility to heating facilities and to control plasma density. By determining the appropriate injection geometry and the mirror ratio of the confinement region, it became possible to inject a neutral beam with an energy of 14 keV and a current of 23 A into the FRC in a solenoidal confining field of only 0.04-0.05 T. Plasma confinement is improved in this experiment. Ion heating is observed to result from the application of a low frequency (80 kHz, about 1/4 of the ion gyrofrequency) compressional wave. A shear wave, probably mode converted from the compressional wave, is observed to propagate axially.

Fragment ions of dimethylsilane produced by hot tungsten wires

Fragment ions produced from dimethylsilane with a hot tungsten wire (i.e., catalyzer) in catalytic chemical vapor deposition (Cat-CVD, which is also known as hot wire CVD) processes are identified with a use of a low-energy mass analyzed ion beam system. The mass analysis shows that dominant fragment ions from dimethylsilane are H1+, H2+, CH3+, Si+, SiH3+, SiCH4+, SiC2H+, and SiC2H7+. The energy distributions of these ions are also measured. It is found that the spreads of the energy distributions are narrow and no energetic ions are produced, suggesting that the produced ions are unlikely to cause any significant damage to the deposited films in actual dimethylsilane Cat-CVD processes. The ion production rates are found to be strongly dependent on the catalyzer temperature.

Surface Modification of Poly(methyl methacrylate) by Hydrogen-Plasma Exposure and Its Sputtering Characteristics by Ultraviolet Light Irradiation

Surface modification of poly(methyl methacrylate) (PMMA) films by hydrogen-plasma exposure has been studied in the light of sputtering resistance of polymer-based materials in plasma etching processes. Surface measurements of PMMA were performed with X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and spectroscopic ellipsometry. It has been found that oxygen atoms are preferentially removed from the surface when a PMMA film is subjected to hydrogen-plasma exposure, with the depth of modification being about 40 nm in the case we examined. Hydrogen-plasma exposure is also found to reduce the sputtering yields of PMMA by ultraviolet light irradiation, as in the case of Ar+ ion irradiation [S. Yoshimura et al.: J. Vac. Soc. Jpn. 56 (2013) 129]. The results suggest that PMMA films become hardened and more sputtering resistant due to the formation of a thick (i.e., 40 nm in the case of this study) amorphous carbon layer by hydrogen-plasma exposure. Hydrogen-plasma exposure is thus an effective technique to increase etching resistance of polymer films.

Sputtering yields and surface modification of poly(methyl methacrylate) (PMMA) by low-energy Ar+/

Sputtering yields and surface modification of poly(methyl methacrylate) (PMMA) by mono-energetic ion beams and/or vacuum ultraviolet (VUV) light are studied with the use of a low-energy mass-selected ion beam system. Sputtering yields of PMMA by Ar+ or ion beams are obtained as functions of ion incident energy below 500?eV. It is found that surface modification of PMMA due to ion incidence is limited to the region near the film surface, whereas that due to Ar+ ion incidence is seen in a relatively deeper region of the film, where PMMA is partially carbonized and diamond-like carbon (DLC) is formed. Under the conditions of incident energies and fluxes of ion and VUV light used in the experiments, the sputtering yield of PMMA by simultaneous incidence of VUV light and ions is found to be nearly equal to the sum of the yields by separate incidences of VUV light and ions. Some of the etching characteristics observed in this study (such as DLC formation by ion sputtering) may be shared by a wide range of organic polymers that have main chain structures similar to those of PMMA.

{\rm CF}_3^+

A spectroscopic plasma tomography measurement system has been developed and operated on a field‐reversed configuration (FRC) plasma machine with the use of five photocollector arrays. Each photocollector array that is located azimuthally around the plasma column consists of ten optical fibers and a pinhole. Two‐dimensional (2D) and time‐resolved visible emission profiles can be reconstructed numerically from the fifty‐channel projection data. The use of five multichannel visible monochromators makes it possible to obtain a result that has explicit physical meanings. A computer simulation has been performed to demonstrate the potential to reconstruct the 2D profile without the assumptions about plasma rotation or symmetry. The first experimental result for visible bremsstrahlung emission profiles of the FRC plasma is presented.

ion bombardment with vacuum ultraviolet (VUV) photon irradiation

Low frequency f = ⅕ − ⅓fci, (fci: ion gyro frequency in the external field Bw) waves are excited with an antenna which is compatible with a reactor in a plasma with field reversed configuration (FRC). Near and outside the separatrix rs of the FRC plasma, though the applied wave is mainly in compressional mode, azimuthal and radial components are observed in the magnetic field disturbance of the excited wave, which propagate with the dispersion relation consistent with the shear Alfven wave. These disturbances penetrate deep into the FRC plasma across the surface where the wave frequency exceeds local ion gyro frequency and propagate along magnetic lines of force with sound velocity, which behaviour is consistent with the shear Alfven wave with finite temperature correction. Axial magnetic disturbance propagates axially and radially from the antenna across the plasma column.

Spectroscopic plasma tomography with multiple photocollector arrays

Abstract We have developed a bipolar pulsed dc glow plasma discharge system using an inverter power supply. A target of the developed system is a low-cost surface modification operated in a low background pressure region (10 1 –10 3 Pa) obtained with rotary pumps. In this pressure region, breakdown voltages for most gases have minimum values without the help of magnetic fields like a magnetron. Accordingly, we can use simple discharge electrodes such as parallel plates that would be extended for large area processing. These electrodes are driven by the bipolar voltage pulses including dc bias components which would drive both positive ions and electrons. A composition of the developed discharge system is shown. Voltage and current waveforms and emission light signals are measured to demonstrate a discharge operation. Initial applications of the developed system using a bipolar pulse processing technique are proposed.

Excitation and propagation of low frequency wave in a FRC plasma

A new concept for plasma heating using axial magnetic compression of a field reversed configuration (FRC) plasma is proposed. In this concept, the FRC plasma is compressed only axially, keeping the magnetic flux between the separatrix and the confining chamber (flux conserver) wall unchanged, while allowing the plasma to expand radially. A simple model based on an empirical scaling law of FRC confinement and on the assumption that the compression is done adiabatically predicts that, in addition to heating the plasma, improved confinement will also be accomplished with this concept. This compression is done by energizing segmented mirror coils successively in such a way as to decrease the length of the confinement region between the coils. The apparatus for this axial compression was developed and an experiment was carried out. In this experiment the plasma was compressed by about 30% and the plasma lifetime of about 500 μs was increased by about 50 μs.