Design study of a multibeam type IH-RFQ linac to accelerate high intensity and low energy heavy ion beams

A multibeam Radio Frequency Quadrupole (RFQ) linac with an Interdigital H-mode (IH) structure has been developed for high intensity heavy-ion beam acceleration. The defocusing force of space charge effect is proportional to the beam current and to the inverse square of the beam velocity. Therefore, multibeam acceleration is an attractive scheme to suppress this in the low energy region. The electromagnetic field distribution and the beam dynamics were studied for a prototype. We discuss the configuration of the multibeam IH-RFQ linac and the results of these simulations.     

Scavenging of Siliceous Grain-Boundary Phase of 8-mol%-Ytterbia-Stabilized Zirconia without Additive

The grain-boundary conductivity (ς_gb) of 8-mol%-ytterbia-stabilized zirconia increased markedly with heat treatment between 1000° and 1300°C with a slow heating rate (0.1°C/min) before sintering. The extent of the ς_gb improvement was the same or larger than that via Al₂O₃ addition. The heat treatment did not affect the grain-interior conduction when sintered at 1600°C, while Al₂O₃-derived scavenging significantly did, given the larger increment of total conductivity in the heat-treated sample. The formation of a silicon-containing phase in a discrete form was suggested as a possible route of scavenging the resistive phase from the correlation between average grain size and ς_gb.     

Mechanical characteristics of line post type polymer insulation arm for 154 kV

This paper describes the mechanical characteristics of a 154 kV line post type polymer insulation arm that functions both as the steel arm and as the porcelain insulator of the currently used steel transmission towers. The 154 kV line post‐type polymer insulation arm consists of polymer composite insulators, called units, that include two horizontal units with an open angle, to respond to a longitudinal load of 40 kN, and a suspension unit to respond to a vertical load. Its installation length is about 2.3 m. Samples of the insulation arm were installed at different places on an electric wire to form a truss structure and a frame structure, in order to examine their mechanical characteristics. For the truss structure, neither remarkable bending stress nor torsional stress was observed in the FRP core. The mechanical force design of the insulation arm can be evaluated in reference to the axial force of the FRP core only. The buckling coefficient, for evaluating the axial force of the insulation arm with the truss structure, was experimentally identified. Moreover, we were able to show that a static load test, for evaluating the mechanical force performance of the insulation arm against a longitudinal load, is more severe than an impact load test at the same longitudinal load. ©1998 Scripta Technica, Electr Eng Jpn, 126(2): 23–30, 1999     

A multiprocessor system architecture suited for power system transient calculation

In the field of power system calculation, much research has been devoted to using parallel computers to increase computation speed. However, unlike examples in other application areas, such as circuit simulation or computational fluid dynamics, the performance gain is small. Also, the performance gain begins to saturate after a small number of processors are utilized. This is due to the essential features of power system calculation: mainly, (1) the size of the problem is usually much smaller than in other application fields and (2) the sparsity of the problem is high. These two features amplify the effect of interprocessor communication overhead. In this study, the authors sought the most suitable parallel architecture for power system calculation, restricting the number of processors to about 16. The architectural features of interest are the memory architecture and the interprocessor connection method. The candidates chosen are: (1) distributed memory architecture connected by an interprocessor communication network, (2) distributed memory architecture connected by a bus, (3) shared memory architecture connected by a bus, and (4) composite distributed/shared memory architecture connected by a bus. We evaluate each architecture in terms of the data for transient stability analysis from a single PE execution, with consideration of memory operations, necessary interprocessor communication, and computations. The results show that although little increase in speed is gained by using a distributed shared memory architecture connected by an interconnection network, it is possible to attain a speedup by a factor of 6.5 by using 16 PEs on a composite distributed/shared memory architecture connected by a bus. © 1999 Scripta Technica, Electr Eng Jpn, 128(1): 26–36, 1999     

Preparation of an acrylics‐grafted polyester and its aqueous dispersion

An investigation was undertaken to develop a new class of water‐borne polyesters having excellent dispersibility without using emulsifiers. Grafting reactions of hydrophilic acrylics to polyesters and the relationships between reaction conditions and the dispersion diameters are discussed. Aqueous dispersions of particles having small diameters were obtained by use of an unsaturated polyester. Particle diameters were related to the grafting efficiency that could be enhanced by copolymerization of reactive monomers with the unsaturated bonds of polyesters. The relationships between particle diameters and the kind of acrylic monomers were described by the copolymerization reactivity ratio of the unsaturated polyester and acrylic monomers. Also, the influences of the solvency of the reaction medium and the influence of concentration of unsaturated bonds of the polyesters in the reaction medium were discussed to explain the low reactivity between the unsaturated bonds and acrylic monomers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1817–1825, 1999     

Corona discharge from a grounded needle electrode inserted into a charged droplet cloud

The discharge occurring in a space-charge cloud was investigated by using a cloud of charged droplets. To produce a charged cloud with a definite space charge density and to cause a reproducible discharge, droplets ejected from an airless nozzle were induction charged and transported by air flow. The transportation of charged droplets by air flow was found to be quite effective in increasing the charge on the droplets and the charge density. Corona discharge was observed at a grounded needle electrode inserted into a charged droplet cloud with a charge density not exceeding 13 μC/m³. In negatively charged droplets, positive streamer coronas occurred. As the charge density of the cloud increased, the time interval of streamer pulses decreased and the discharge shifted to a glow corona. In positively charged droplets, the height and frequency of negative corona pulses increased with the charge density and the velocity of the charged droplet cloud. © 1998 Scripta Technica. Electr Eng Jpn, 122(4): 1–7, 1998     

Generation of a large area thermal induction plasma by applying a 50 kHz magnetic field

Inductively coupled radio frequency plasmas are gradually becoming an important source of high-temperature and high-reactivity plasmas for processing new functional materials or for removal of unwanted substances. Spatially wider plasmas are required for higher rate, more uniform processing in the future. Although low MHz frequencies have been usually used for induction plasmas, an attempt to expand the high temperature plasma fields was made by superimposing lower frequency 50-kHz magnetic fields on the DC plasma discharge to obtain a small source plasma. Because the penetration depth in such a low frequency field is as long as a few hundred mm, a larger radius plasma can be expected. As a first step, we have investigated the operating conditions under which a stable low frequency plasma is generated, based on theoretical calculations that include the time dependent rate equations for heat transfer and fluid flow in conjunction with the Maxwell electro-magnetic equations. Results showed that the minimum necessary power for expanding a small DC plasma to a wider plasma 100 mm in diameter by applying a 50-kHz magnetic field, is about 130 kW at 0. 1-MPa pressure. This power level is recognized to be within the available range in existing high-power oscillator systems. Measurements were carried out of the time variation of the spectral emission from the plasma immediately after superimposing the 50-kHz magnetic field upon a small area plasma generated with DC power of 1.5 kW at a pressure of 0.01 MPa in Ar gas. At a low power level of about 60 kW, the small plasma starts to expand in the radial direction, and finally, converges to a new wider plasma with 100 mm diameter. FFT analysis of the oscillograph showed that during the transient state, a period fluctuation in light emission occurs at a few tens of Hz reflecting the thermal time constant of a few tens of ms, besides the power frequency of 41.7 kHz. The plasma temperature was estimated by using the spectroscopic line intensities from neutral Ar atoms, as between 8,000 and 11,000 K. A uniformly distributed temperature field was successfully produced by applying the 50-kHz magnetic field, as expected. © 1998 Scripta Technica, Electr Eng Jpn, 123 (4): 48–57, 1998     

Development of X-ray dark-field imaging towards clinical application

Review of X-ray dark-field imaging under development is presented. Its goal is its application to clini-cal diagnosis of organs that have been invisible by the ordinary techniques. In order to clinically visualize tissues in detail one needs high contrast and high spatial resolution say～50μm. This X-ray optics comprises a Bragg asymmet-ric monochro-collimator and a Bragg case or a Laue case filter with capability of analyzing angle in a parallel posi-tion. Their diffraction index is 4,4,0 and the X-ray energy 35 keV (λ=0.0354 nm). The filter has 0.6 mm thickness in the Bragg case or 1.075 mm or 2.15 mm thickness in the Laue case. Under this condition only the refracted X-rays from object can transmit through the filter while the beam that may receive absorption and/or phase change will not.Soft tissues at human joints thus taken show high contrast images so that the DFI is promising for clinical diagnosis.Preliminary X-ray absorption images of another clinical candidates of ear bones are also shown.     

Effects of Substitution on Cytotoxicity of Diphenyl Ditelluride in Cultured Vascular Endothelial Cells

Among organic–inorganic hybrid molecules consisting of organic structure(s) and metal(s), only few studies are available on the cytotoxicity of nucleophilic molecules. In the present study, we investigated the cytotoxicity of a nucleophilic organotellurium compound, diphenyl ditelluride (DPDTe), using a cell culture system. DPDTe exhibited strong cytotoxicity against vascular endothelial cells and fibroblasts along with high intracellular accumulation but showed no cytotoxicity and had less accumulation in vascular smooth muscle cells and renal epithelial cells. The cytotoxicity of DPDTe decreased when intramolecular tellurium atoms were replaced with selenium or sulfur atoms. Electronic state analysis revealed that the electron density between tellurium atoms in DPDTe was much lower than those between selenium atoms of diphenyl diselenide and sulfur atoms of diphenyl disulfide. Moreover, diphenyl telluride did not accumulate and exhibit cytotoxicity. The cytotoxicity of DPDTe was also affected by substitution. p-Dimethoxy-DPDTe showed higher cytotoxicity, but p-dichloro-DPDTe and p-methyl-DPDTe showed lower cytotoxicity than that of DPDTe. The subcellular distribution of the compounds revealed that the compounds with stronger cytotoxicity showed higher accumulation rates in the mitochondria. Our findings suggest that the electronic state of tellurium atoms in DPDTe play an important role in accumulation and distribution of DPDTe in cultured cells. The present study supports the hypothesis that nucleophilic organometallic compounds, as well as electrophilic organometallic compounds, exhibit cytotoxicity by particular mechanisms.     

Mechanism of Methylene Blue Bleaching by Lipoxygenase

A lipid peroxidation reaction and methylene blue bleaching reaction are thought to proceed in the presence of methylene blue with linoleic acid as the substrate from the time lipoxygenase is added until methylene blue bleaching concludes. For 15 s after adding the lipoxygenase, neither the lipid peroxidation reaction nor the bleaching reaction occurred, but they both proceeded after that time period. The results suggested that hydroperoxide is first formed by the lipid peroxidation reaction, after which methylene blue specifically picks the hydrogen from the hydroperoxide 13-OOH isomers, and then the methylene blue is reduced.