Development of 170 GHz/500 kW gyrotron

A development of 170GHz/500kW level gyrotron was carried out as R&D work of ITER. The oscillation mode is TE_31,8. In a short pulse experiment, the maximum power of 750kW was achieved at 85kV/40A. The efficiency was 22%. In the depressed collector operation, 500kW/36%/50ms was obtained. The maximum efficiency of 40% was obtained at P_RF=470kW whereas the power decrease by the electron trapping was observed. Pulse extension was done up to 10s at P_RF=170kW with the depressed collector operation. The power was limited by the temperature increase of the output window.     

Light scattering studies on crystallization in polyethylene terephthalate

The light scattering from the spherulites of polyethylene terephthalate grown near the glass transition temperature has been investigated. The Hv scattering profiles can be reproduced by the sum of the ideal spherulite scattering with the distribution of spherulite radius and the isotropic scattering from randomly oriented crystallites. The ratio of optical anisotropies in the isotropic scattering to the ideal spherulite scattering is obtained by the method established to eliminate the effects of the number density of spherulites and the coefficient depending on the experimental conditions. It is found that the anisotropy ratio is almost independent of the crystallization time and of temperature above 106 °C, while it is larger at a crystallization temperature of 103 °C. The spherulitic structure is discussed in terms of the anisotropy ratio.     

Continuous formation of slurry ice by cooling water–oil emulsion in a tube

Water-silicone oil emulsion with an additive, (C₂H₅O)₃SiC₃H₆NH₂, was examined as a heat storage material. A spiral tube used as a heat exchanger was immersed in a low temperature bath and the emulsion was circulated in the tube to make ice continuously. Ice was separated from the ice–liquid suspension in an outlet tank. The amount of formed ice, the temperatures of the inlet and the outlet of the heat exchanger, and the temperatures in the tube wall were measured and the overall heat transfer coefficient and the heat flux through the tube were calculated. Experiments were carried out, varying the flow rate, the temperature of cooling brine, and the thickness of tube wall. The condition under which slurry ice was formed continuously without adhesion of ice to the cooling wall was clarified. Though decrease in the thermal resistance of the tube increased the rate of ice formation or raised the brine temperature, it narrowed the range of the flow rate and of the brine temperature in which slurry ice was formed continuously.     

BESS: a source structure that fully suppresses the floating bodyeffects in SOI CMOSFETs

The most serious problem preventing the widespread use of SOI CMOSFETs-the floating body effects-are almost fully suppressed by a new source structure. In an nMOSFET, this new structure can be represented by an equivalent circuit of a bipolar embedded source structure (BESS) just beneath the n⁺ source junction. In the source region, or p type (or n^--type) recombination centers are embedded in a low-impurity-diffusion region (the base) and acts as a collector of the excess body carriers. The low-impurity-source region lowers the diffusion potential barrier for holes at the source junction. The solid-phase epitaxial regrowth mechanism of the Si⁺ implanted amorphous SOI layer was studied and applied to fabricate a prototype of this device capable of symmetric source-drain operations with the same source-drain breakdown voltage as that of a bulk device     

Design optimization of tall tubular lead/acid cells based on an analysis of the reaction distribution

In order to estimate the discharge performance of tall lead/acid cells (with tubular positives), changes in current and potential distributions with discharge progress were calculated with a computer on the basis of plate resistance and the current—potential—time relationship between small facing parts of positive and negative plates. The taller the cell, the larger the voltage drop along the plates. Thus, the discharge time became shorter despite a large amount of available active mass remaining in the bottom part of the plates.Various current-collector designs were evaluated, e.g., one with varying resistance at each height; a side conductor placed along the plates and connected to them at the top, centre and bottom, etc. Results revealed an optimum collector design with which the maximum discharge capacity could be obtained. Furthermore, it was shown that the side conductor markedly improved the discharge performance because the active mass near the connecting parts was appreciably used.     

Development of a fast neutron radiography converter using wavelength-shifting fibers

A fluorescent converter for fast neutron radiography (FNR) comprising a scintillator and hydrogen-rich resin has been developed and applied to electronic imaging. The rate of the reaction between fast neutrons and the converter is increased by thickening the converter, but its opaqueness attenuates emitted light photons before they reach its surface. To improve the luminosity of a fluorescent converter for FNR, a novel type of converter was designed in which wavelength-shifting fibers were adopted to transport radiated light to the observation end face. The performance of the converter was compared with that of a polypropylene-based fluorescent converter in an experiment conducted at the fast-neutron-source reactor YAYOI in the University of Tokyo.     

Effects of cononsolvency on gelation of poly(vinyl alcohol) in mixed solvents of dimethyl sulfoxide and water

We studied the rates of gelation and phase separation of poly(vinyl alcohol) (PVA) solutions in mixtures of dimethyl sulfoxide (DMSO) and water at 25 °C and found that both the rates show a maximum at a volume fraction of DMSO φ_DMSO=0.60 while gelation was not observed either in pure DMSO or pure water, suggesting that water-DMSO is a cononsolvent system for PVA. On the basis of the data by Cowie [Can J Chem 36 (1961) 2240] we concluded that the 1:2 stable complex between one DMSO molecule and two water molecules is the main cause of this cononsolvency.     

Inhibition of natural killer cell cytotoxicity by cell growth-related molecules

Certain MHC class I molecules on target cells are known to inhibit the cytotoxic action of NK cells. By using monoclonal antibody (mAb) Cho-1, we have found inhibitory non-MHC class I cell surface molecules that are noncovalently-associated with 200 kDa and 40 kDa antigens. Poly I-C-induced rat NK cells were not cytotoxic to rat fetus-derived fibroblast WFB cell line. In contrast, NK cells were cytotoxic to H-ras oncogene-induced transformants of WFB, W14 and W31. FACS analysis indicated that mAb Cho-1 reacts with WFB, but not with W14 and W31 cells. Thus, this antigen may disappear concomitantly with cell growth and transformation. Cho-1 antigens were also expressed on other NK-resistant lines, such as mouse BALB3T3 fibroblast, EL-4 lymphoma and human fibroblast HEPM. However, they were not expressed on NK-sensitive mouse YAC-1 and H-ras transformant (Brash) of BALB3T3 cells. Furthermore, treatment of target cells with IFN-gamma clearly induced the cell surface expression of Cho-1 antigens, and conferred a resistance to NK cytolysis on target cells. These data strongly suggest that Cho-1 antigen expression may correlate with target cell susceptibility to NK cells. Indeed, treatment of NK-resistant WFB as well as HEPM cells with F(ab')2 fragments of mAb Cho-1 resulted in the acquisition of susceptibility to NK cytolysis. Cho-1 antigens may be novel molecules that regulate the NK resistance of cells.     

Interaction of soliton with sinusoidal wave packet

The interaction of a soliton of the Nonlinear Schrodinger Equation (NSE) with a weak sinusoidal wave packet is treated analytically. The second-order soliton solution containing the original soliton and a perturbing soliton is expanded to first order in the amplitude of the perturbating soliton. From this expansion, one obtains the associate function of Gordon (1992) and a continuous change of position and phase of the perturbed soliton. One finds that the soliton experiences a second-order change of velocity under the influence of the perturbation. This result is then used to derive the displacement due to a wave packet of general shape, which is also confirmed by computer simulation