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The electropolishing process has shown promising results for improving the surface finish of small apertures in laser-stencils. We report on the results of the investigations of the parameters that control the electropolishing process using highly concentrated phosphoric acid. The effect of the phosphoric acid solution on the finish of the polished small apertures and the effect of the electropolishing time were investigated. An optimized process was established through inspection of the polished stencil apertures of the laser-stencil. The results demonstrated that the acid solution for the electrolyte as well as the electropolishing time had a significant effect on the small stencil's aperture quality and the solder paste's stencil-printing performance. In particular, a 95 wt.% phosphoric acid-based electrolyte showed encouraging results in terms of surface smoothness, improved solder-paste printing, and surface-mount-technology yields. The most effective electropolishing times were 5, 10, and 20 s for stencils thicknesses of 0.05, 0.08, and 0.10 mm, respectively.

Micrometer-sized Ag particles adsorb substantial oxygen above 200°C and a dispersion of these particles in alcohol can be successfully used as a die-attach material by sintering to form a soft porous bonding layer. The characteristics of a light-emitting diode (LED) using this Ag paste as a die-attach material were evaluated. The LED was assembled on an alumina ceramic package, which did not degrade upon sintering, with a sapphire-based InGaN LED die. The bonding strength was twice as high to the ceramic package as to a copper alloy lead frame. Thus, the Ag paste is suitable for use with LED ceramic packages as a bonding material. In addition, a significant reduction of the thermal resistance and improvement of the reliability are achieved by using the Ag sintered layer for die-attaching the ceramic LED package. To improve the bond reliability between sapphire and alumina, both of which are low-thermal-expansion materials, the thermal expansion of the Ag sintered layer was reduced by the addition of Kovar particles. The addition of Kovar particles, with or without Ag plating, to Ag particles exhibited a desirable effect. The present mounting method for LEDs was proved to be useful for die-bonding electronic components, providing an alternative technique to high-temperature high-lead soldering.

In this article, the mechanisms of these low-temperature curable inks are briefly reviewed. The dispersant removal by washing in alcohols for the nanoparticle ink and the decomposition behavior of the β-ketocarboxylate ink were clarified by thermal and microstructural analyses. The sintering and growth behaviors were also examined.

To develop an optimal surface mount reflow soldering process with Sn-Ag-Cu, the influences of atmosphere and cooling speed on soldering reliability have been examined by using Sn plated chip components and of Pd plated small outline packages (SOPs) on a printed circuit board (PCB). Typical three Sn-Ag-Cu alloy pastes, i.e., Sn-3.0wt%Ag-0.5wt%Cu, Sn-3.8wt%Ag-0.75wt%Cu, and Sn-4.0wt%Ag-0.9wt%Cu, were used for reflow soldering in air or N2 atmospheres. In the case of chip component joints, the solder compositions, cooling speed, and atmospheres during reflow treatment slightly affect the dendritic microstructure of the solder fillets. In contrast, these parameters rarely affect the solder wettability both on boards/components and shear strengths of the solder joints. In the case of the SOP joints, however, the atmospheres in reflow treatment and the fluxes strongly affect the appearances of solder fillet surfaces structure. Despite the types of solder fluxes, N2 process atmosphere obviously improved wettability of the solders on the lead-frames of the SOP. Moreover, the scatter in shear strengths becomes smaller and the wetting of solders on the lead-frames becomes stabler in N2 atmosphere than in air atmosphere.

A series of silver(I) β-ketocarboxylates were prepared by reaction of β-ketocarboxylic acids with silver nitrate in the presence of diethanolamine. The silver(I) β-ketocarboxylates decomposed over a narrow temperature range to form metallic silver, CO2, and the corresponding ketones. In addition, products derived from radical intermediates were detected by mass spectroscopic analysis for some silver(I) β-ketocarboxylates. Infrared and solid state (13)C-NMR spectra of silver(I) β-ketocarboxylates suggested the presence of two types of structures involving a carbonyl group in addition to the dimeric eight-membered ring structure as in the structure of silver(I) stearate. The silver(I) β-ketocarboxylate model compound used was HCOCH2COOAg and its structures were determined using density functional theory (DFT) and atoms-in-molecules (AIM) methods. Three types of coordinations around the Ag ion differing significantly in Ag-O bond strengths were found. Based on the calculated structures and experimental results, the relationships between the structures and decomposition temperatures are discussed in terms of the thermal decomposition process.

Despite the semi-routine use of color Doppler sonography for evaluating portal circulation abnormalities, there is a relative paucity of detailed color Doppler findings of portal systemic (P-S) shunt through the renal vein (P-SR shunt). We reviewed the color Doppler findings of 18 patients with P-SR shunt to determine its clinical significance and appropriate scanning techniques for diagnosing accurately P-SR shunt. The splenorenal shunt was imaged as a highly tortuous vessel at the splenic hilum, which then coursed backward behind the spleen. Splenic vein flow was reversed or very slow. The gastrorenal shunt originated from the splenic vein, coursed backward, and joined the left renal vein. Flow direction in the splenic vein was always hepatopetal. The P-S shunt through the right renal vein originated from duodenal or jejunal varices, coursed posterolaterally, and joined the right renal vein at the renal hilum. Familiarity with these color Doppler findings will help increase the diagnostic confidence of P-SR shunt by color Doppler sonography.

We have successfully used the Spindt field emitter array (FEA) in the pressure measurements in ultrahigh vacuum (UHV) and extremely high vacuum (XHV). For applying the FEA to pressure measurements, we have made evaluation tests, focusing on gas exposure and outgassing characteristics. The cold cathode hardly influenced the vacuum conditions, compared to a hot-filament cathode.

Electron cyclotron resonance discharge cleaning (ECR-DC) has been studied on JT-60U in which the first wall is completely covered by graphite tiles. The radio frequency (RF) waves at 2 GHz band, which are generated by the lower hybrid range of frequency (LHRF) system, are applied to the ECR-DC at the toroidal magnetic field of around 0.06 T. RF power up to ∼125 kW with a pulse length of ∼60 s has been repeatedly injected from the LH current drive launcher. An ECR-DC increases the particle recycling rate on the graphite first wall, and a remarkable desorption of water vapor (mass number of m/e=20) has been observed by the ECR in deuterium gas. Moreover, it is found that the ECR in D2 is effective to desorb tritium from the graphite first wall which are implanted during high power heating in deuterium discharges. This suggests that ECR-DC is one of effective tool to reduce a tritium inventory in a future tokamak fusion reactor.

A mock-up module of an antenna tip made of carbon fiber composite (CFC) was fabricated for the development of a heat-resistive front of the lower hybrid current drive (LHCD) antenna. The CFC surface was coated with a thin Ti layer and was plated with Cu. The mock-up module has three waveguides and is designed to simulate the front tip of the 8 GHz LHCD antenna. The module has an active water cooling channel and the length is 200 mm, the mouth dimension is 19.5×50 mm 2 . The mock-up module was tested with heat fluxes up to 20 MW m −2 due to electron beam irradiation. No damage of the waveguide mouth was observed up to the heat flux of 3.2 MW m −2 for 2 min, though a maximum temperature of 762°C was measured at the septum plate. The obtained heat load of 3.2 MW m −2 is about 10 times higher than the steady-state surface-averaged heat load of the first wall required in the ITER design.

Fusion performance of reversed shear discharges with an {ital L}-mode edge has been significantly improved in a thermonuclear dominant regime with up to 2.8 MA of plasma current in the JT-60U tokamak. The core plasma energy is efficiently confined due to the existence of persistent internal transport barriers formed for both ions and electrons at a large minor radius of r/a{approximately}0.7 near the boundary of the reversed shear region. In an assumed deuterium-tritium fuel, the peak fusion amplification factor defined for transient conditions involving the dW/dt term would be in excess of unity. {copyright} {ital 1997} {ital The American Physical Society}

Power capacitors are widely used for regulating voltage and improving the power factor of power systems, and the type in most frequent use today are capacitors made of oil-impregnated paper film, a growing number of which will soon have been in operation in the field for 20 years. This has prompted the authors to study techniques for diagnosing deterioration in oil-impregnated paper film capacitors. It was found that thermal stress causes deterioration of the insulating paper, which increases the amount of dissolved CO and CO/sub 2/ in the oil and lowers the partial discharge inception voltage, determining the useful lifetime of the capacitor. Based on this idea, techniques have been proposed for diagnosing deterioration, consisting of caution level and danger level, from actual stress in the field. Further, a trial calculation was made for the number of years and months it takes for a capacitor to reach this caution level, based on an investigation of capacitors in service for many years.

The outgassing properties of the lower hybrid current drive (LHCD) antenna during r.f. operation were studied on the JT-60U tokamak. The antenna is not equipped with a differential pumping system to evacuate the outgassing of the antenna. The pressure rise in the antenna during r.f. operation strongly depended on the r.f. power when r.f. conditioning was started. However, the outgassing rate was quickly reduced after several shots, and showed weak r.f. power dependence after sufficient r.f. conditioning. Finally, the outgassing rate of the LHCD antenna was in the range of approximately 10−6 Pa m3 s−1 m−2 after four weeks operation at the working temperature of 250 °C. Then a power density of up to 25 MW m−2 was successfully injected into the plasma without the differential pumping system at the antenna on JT-60U.

A new method of brazing aluminium to austenitic stainless steel involving squeeze casting has been established and has been named ‘cast brazing’. Without melt flow control, strengths exceeding 40 MN m−2 were achieved for the aluminium/stainless steel joint. The presence of a porous sintered layer on the bond face of the stainless steel increased the strength of the joint to ~70 MN m−2. By controlling the flow of aluminium braze during casting, the formation of an intermetallic reaction layer at the interface was effectively suppressed and the strength of the brazed interface was increased to a value exceeding the strength of the aluminium. On brazing aluminium to aluminium with a preliminary nickel coating on the surfaces to be joined, interfacial strengths exceeding 50 MN m−2 were attained. Before fracture, this type of joint exhibited an elongation of up to 10%.MST/1635

The luminescence from excited helium atoms is measured on a small tokamak Hamana-T. The exponential growth rate of the luminescence is maximized when the resultant effect of the toroidal and the error field drifts of electrons is compensated by the optimum value Bvo of external vertical magnetic field. The error vertical magnetic field Bve and the equivalent vertical magnetic field Bvd, which yields the same displacement as the toroidal drift and is proportional to toroidal magnetic field Bt, are experimentally determined by the values of Bvo obtained with different values of Bt and electric field E. The field Bvd is approximately proportional to E1/2.

A series of experiments was performed to study the erosion behavior of a structure by an impinging molten metal jet under severe accident conditions in nuclear reactors. In the first series of experiments a molten tin jet having a diameter of 10–30 mm and a temperature of 350–500°C was gravitationally accelerated and then perpendicularly impinged onto a tin plate at room temperature. In the second series of experiments a molten stainless steel jet having a diameter of 10–20 mm and a temperature of 1600–1700°C impinged onto a stainless steel plate. From the present experiments a new empirical correlation is obtained for assessing the erosion rate when a turbulent molten metal jet with a low Prandtl number (0.0095

From the results of the bending strength and Weibull modulus of the joints of silicon nitride ceramics brazed using aluminium-silicon and aluminium-magnesium alloy filler metals at a temperature of 1073 K for 0.9 ksec in a vacuum of 1.3 × 10−3 Pa, silicon, especially, present in a small amount in the filler metals, was found to be effective in improving the bond strength, while magnesium in the filler metals was harmful to the joining. This can result in the formation of a thick stable alumina layer on the surfaces of the filler metals containing magnesium during brazing which prevented contact of the filler metals with the silicon nitride ceramics.

Interfacial reaction and reliability of Si die attached joints with Zn-xSn (chi= 20, 30, 40 wt%) were investigated, and Pb-5wt%Sn, and Au-20wt% were compared as a typical high temperature solder alloy. The joining strength of Cu/solder/Cu joints was investigated using the as soldered joints and thermal cycled joints up to 2000 cycles. At the interface with Si die coated with Au/TiN thin layers, the TiN layer did not react with the solder and worked as a good protective layer. At the interface with Cu, for Zn-Sn solders, CuZn5 and Cu5Zn8 IMC layers was confirmed. Au-20Sn and Pb-5Sn solder forms zeta-Au5Sn and Cu3Sn IMC layers at the interface with Cu, respectively. For improving the joint reliability, TiN layer was proposed as a protective layer and was applied to the DBC substrates. For the die attached joints on DBC substrates coated with Au/TiN thin layers, no fatigue crack has been found until 1000 cycles of thermal cycling test. The joining strength of the Cu/solder/Cu joints with Zn-Sn solder was about 30~34 MPa, which was higher than that of Pb-5Sn solder (26.2 MPa). For the thermal cycled Cu/solder/Cu joints up to 2000cycles, Zn-Sn solder also shows the higher joining strength than that of Pb-5Sn solder.

On etudie la resistance mecanique et la rupture de joints ceramique/metal en atmosphere d'argon et dans l'eau. Les essais portent sur les interfaces Si 3 Ni 4 /brasage d'aluminium, Si 3 N 4 /Ni (eutectique liquide) et Al 2 O 3 /Nb. On examine la corrosion sous tension et les moyens de la prevenir

The JT-60 LHRF heating system was designed with broad frequency capability to inject a long-pulse-width high-power RF wave into a plasma. The system uses 24 high-power klystrons, each with an output power rating of 1 MW. Five operating frequencies are available within the range of 1.74 GHz to 2.23 GHz. The frequency can be changed at a rate of 150 MHz/0.3 s. This feature provides both plasma heating and plasma current drive. It also permits frequency correlation with the plasma density and current profile. This paper describes both the high-speed frequency tuning system for the JT-60 klystrons and the results of fast frequency change tests of the LHRF over the range of 1.74 GHz to 2 GHz when RF power was launched from the same launcher during a plasma shot.

Recent lower hybrid current drive (LHCD), and heating (LHH) experiments on JT-60 are reported. The current drive product of neRpIRF approximately 12.5*1019 m-2 MA was achieved at the LH power of approximately 4.5 MW, and the CD efficiency, the energy confinement, the global power balance and the heat load on divertor plates were investigated in high power LHCD plasmas. Nearly steady state H-mode discharges were found during LHCD with two different frequency injections. Sawtooth suppression in NB heated plasmas by LHCD have shown an improvement in confinement near the plasma center. Parametric instabilities in LH heating experiments were significantly reduced by increasing the plasma current, and the stored energy increased linearly with heating power of up to approximately 9 MW at ne approximately 7*1019 m-3 and Ip=2.75 MA. Parametric instabilities near the plasma edge in the ion heating regime were also reduced in peaked density plasmas produced by pellet injection and LH waves increased the central plasma pressure at ne(0) > 1.4*1020 m-3.

Pressureless-sintered silicon nitride was bonded using a nickel interlayer in the temperature range 1273–1573 K, such that a eutectic melt of silicon and nickel was formed at the interface. The silicon reacted with and diffused deeply into the nickel. No suicide was identified at the interface. Nickel also reacted with oxide additives in the silicon nitride, namely Y2O3 and A12O3, to form compounds at the interface. The additive elements mostly formed small particles of the YAG phase (3Y2O35Al2O3) in the reaction layer. When bonded between 1373 and 1473 K, the interfacial strength was more than 200 MPa as measured by a bending test. The heat and oxidation resistance of the bond above 873 K were better than could be achieved through bonding by active-metal brazing with an AgCu/Ti laminate foil.

In oil-filled equipment such as transformers, local overheating or discharges will precede a final shutdown. Along with such minor internal problems, decomposition of the insulating materials into gases, which are dissolved into the insulating oil, occurs. For preventive maintenance of transformers, dissolved gas analysis is currently made using a gas chromatograph, which takes time to analyze. Since hydrogen gas is always one of the decomposed gases, a portable oil-dissolved hydrogen gas detector was developed for quick field screening of oil-filled equipment for detailed inspection. The operation and performance of this detector are described, and comparison with existing methods is made. >

To develop an optimal soldering process of Sn-Ag-Cu soldered joints, the influences of atmosphere and cooling speed during reflow treatment on soldering reliability have been examined through the use of Sn plated chip components and of Pd plated small outline packages (SOPs) on a printed circuit board (PCB) soldered with Sn-3wt.%Ag-0.5wt.%Cu, Sn-3.8wt.%Ag-0.75wt.%Cu and Sn-4wt.%Ag-0.9wt.%Cu solder pastes under air or N2 atmospheres. In the case of chip component joints, the solder compositions, cooling speed and atmospheres during reflow treatment slightly affect the dendritic microstructure. Those parameters rarely affect the wetting behavior and mechanical properties. In the case of SOP joints, however, the atmospheres during reflow treatment and fluxes strongly affect the appearances of fillet surfaces structure. Despite the types of solder fluxes, N2 process atmosphere obviously improved wettability of solder on lead-frame of the SOP.

This paper investigates the test speed dependency of peel strength of model ACF joints in order to clarify the influential factors in determining adhesive strength of ACF joints. Three types of flexible substrates including polyimide, polyimide covered with Cu foil and polyimide with an interdigitated Cu circuit were bonded to a glass substrate using a typical ACF with an epoxy-based binder for fabricating the model joints. The interdigitated Cu electrode pattern on the flexible substrates is able to contribute to the improvement in the peel strength of the joints by acting as an anchoring pattern. The strong interfacial adhesion that is achieved with appropriate bonding conditions can enhance the effect of the anchoring pattern. The effect of the electrode pattern also plays an important role in suppressing the decrease in the peel strength during the exposure to severe environments such as 85°C /85%RH and 85°C.

Coating Ti-based implants with bioactive materials promotes joining between the prostheses and the bone as well as increasing long-term implant stability. In the present work, the interface between Ti-6Al-4V and bioactive silicate glass coatings, prepared using a simple enameling technique, is analyzed. High-resolution transmission electron microscopy of the glass/alloy interface shows the formation of a reaction layer ( approximately 150 nm thick) composed of Ti5Si3 nanoparticles with a size of approximately 20 nm. This nanostructured interface facilitates the formation of a stable joint between the glass coating and the alloy.

A multijunction-type launcher was installed on the JAERI (Japan Atomic Energy Research Institute) Tokamak-60 (JT-60). It is composed of 32 modules consisting of 96 secondary waveguides, in which E-plane junctions are used to divide each main waveguide into three secondary waveguides at its grill mouth. The waveguides are equipped with geometrical phase shifters yielding 70 degrees of phase shift in order to launch a peak parallel refractive index (N/sub /// peak) of 1-2.5 at 2 GHz. In the course of fabricating the multijunction launcher, the main technological problem was to fabricate multijunction modules with good RF properties (phase angle, power dividing ratio, etc.). A TIG (tungsten inert gas) welding method was adopted after a study of applicable fabrication methods. The phase shift and the power dividing ratio were verified to be 70 degrees +or-10 degrees and 1/3+or-1/15, respectively. The N/sub /// spectrum of the multijunction launcher calculated from measured values of phase shift was not so different from the design value. Using a test module, the authors also performed a high-power transmission test up to a power level of approximately 700 kW without breakdown. After installation of the multijunction launcher in the JT-60 tokamak, it was quickly conditioned up to a power level of 2.75 MW and maximum current drive efficiency eta /sub CD/ of 3.4*10/sup 19/ M/sup -2/A/W. Experimental results verify the adequacy of the launcher's method of fabrication and its satisfaction of requirements. >

Conirolling solidijication behavior becomes one of the keyfactors because the formation of solidifiction defects must be prevented in order to accomplish stable and reliable assembling. It is expected that the addition of some solidification nuclei for Sn-Ag-Cu solder can refne the solidification microshlciure and will suppress ' undercooling. In this study, the effects of the fourih elements, i.e., Ni and CO, on microsmciural feaiures of S~-~WP/&~~-O.~WP ?CU Ied-fiee solder and Cu joints were investigated. The interfcial phases of Sn-3Ag0.5CdCu joints are typical Cudn, scallops. Sn-3Ag0.5Cu (-O.lwtY&; X = Ni and Co)/Cu joints form very $ne Sn-Cu-Ni and Sn-Cu-CO scallops at interfce. The growth kinetics of total ternary compound layers was examined. The apparent activation energis of Sn-Cu-Ni and Sn-Cu-CO layers were 64 and 112 kJmol. respectively. The usefirl effects ofprwenting solidification defect and improving solder shlciure can be obtained by the addition ofNi, Co.

For oil-impregnated type capacitors, thermal and electrical accelerating deterioration tests were conducted to study their various characteristics until their dielectric breakdown occurred. A diagnosis method for the deterioration analysis of gases dissolved in oil was also studied. CO+CO/sub 2/ gas is shown to be an effective index for the thermal deterioration. Since C/sub 2/H/sub 2/ is generated only by the partial discharge, it is possible to estimate the occurrence of partial discharge. While capacitors are deteriorated by thermal stress, it is considered that the dielectric strength of the insulating oil decreases due to gases dissolved in oil. >

The main objective of the LHCD (lower hybrid current drive) on JT-60U (JAERI Tokamak-60 Upgrade) is to drive plasma current and to control plasma current profile with high efficiency. A new multijunction launcher is being prepared to further improve the efficiency. The launcher features 4*4 multijunction modules, each of which is composed by 12 sub-waveguides and an oversized waveguide The RF power in the module is divided into 12 at a junction point in the toroidal direction. This design makes the launcher structure very simple. The RF properties of a prototype module are studied by using dummy loads. It is shown that the phasing and power dividing rate are well explained by the scattering matrix method when the reflection coefficient of the subwaveguides is less than approximately 10%. This launcher is expected to improve current drive efficiency by 20-30% compared with the previous JT-60 LHCD multijunction launcher. >

Ag-epoxy isotropic conductive adhesives are expected to be one of the alternatives to solder. One of the fatal drawbacks is, however, the poor compatibility between Ag fillers and Sn plating on components at elevated temperature. In the present work, the Ag-Sn alloy fillers were examined for replacing Ag filler to prevent this degradation. Two types of joints of Cu/adhesive/Cu with or without Sn plating on Cu were exposed at 150/spl deg/C. The initial strength of both joints was about 40 MPa and those increased about 65 MPa after 100 h exposure. Beyond 100 h exposure, the strength of the Sn plated joint decreased gradually as increasing exposure time. However, even after 1000 h exposure, the joint maintained high strength of 45 MPa. Thus, the Ag-Sn alloy fillers can be good replacement fillers compared with Ag fillers. On the other hand, the joint without any plating decreased strength to 25 MPa after 1000 h exposure. The interface reaction has a key role for such degradation mechanisms.

This is the first report on the metal matrix composite reinforced with a new aluminium borate whisker

According to the expansion of the applications of ceramics as both electronics and structural materials, many methods have been established for joining ceramics to metals. For the electronics applications, Al2O3 ceramics have been used as insulator materials represented by the substrates for electronics packages for many years, on which metallic electrodes are patterned and joined with tight interfaces. In addition to them a variety of ceramics have been applied as various sensors connected with metallic electrodes. As structural materials, non-oxide ceramics such as Si3N4 have been successfully applied to vehicle engine components replacing the heavy metallic materials since the beginning of the 1980’s. Table 1 summarizes the typical Si3N4 parts established in the last 15 years in the commercial fields [1]. Although many methods have been already established for joining ceramics and metals, one has to notice the fact that no ceramic/metal joint structure is stable because of the big gaps both in chemical and in physical nature between two materials. There are always some sorts of latent defects in an interfacial region. They are, for example, a brittle reaction layer, voids, unjoined area, microcracks from thermal stress, and etc., which may not only exist just after fabrication but also will be formed in service. Therefore, in practical uses of ceramic/metal joints, one has to take the influence of all defect structures in a joint into account and should design some optimized joint structure that can compensate for these potentially exiting defects. The commercial products in vehicles and also in electronics are usually required to have a high reliability as 1 ppm fracture probability through their life times. This requirement is quite severe even for ceramics materials themselves and moreover for joint structures. Thus life time prediction and insurance test becomes very important. TABLE 1 Commercial Si3N4 products for vehicles in Japan [1]. Products Vehicle Manufactures Ceramic Manufactures Year Bonding or assembling methods Plug Isuzu Mitsubishi Mazuda Nissan Kyocera Kyocera Kyocera NTK 1981 1983 1985 1985 Fitting (Brazing without active metals) Intake burner Isuzu Kyocera 1983 - Hot plug Isuzu Toyota Mazuda Kyocera Toyota NGK 1983 1984 1986 - Shrunk-in-fitting Shrunk-in-fitting Rocker arm Mitsubishi Nissan NGK NGK, NTK 1984 1987 Shrunk-in-molding Active metal brazing Tappet - NTK 1993 Active metal brazing Turbo charger rotor Nissan Isuzu Toyota NTK, NGK Kyocera Kyocera 1985 1987 1989 Active metal brazing Active metal brazing + Shrunk-in-fitting

For simplification of Lower Hybrid Current Drive (LHCD) antenna system and reduction of power density in the antenna, three types of poloidal power divider which split the power in three, and 3 × 6 multi-junction module were developed. A good power dividing ratio of 33 ± 4 % was obtained for each of these dividers. In combination with two dividers connected to the 3 × 6 multi-junction module, a good high power handling capability was assessed: 420 kW-100 sec was transmitted without breakdown. Quasi stationary operation for r.f. injection time of 1000 sec at 300 kW was also demonstrated under water cooling. The outgassing rate at that time is in range of 10−7 Pa m3 s−1 m−2 with maximum temperature of 100°C, which requires no active vacuum pumping of the LHCD antenna.

A 10MW Lower Hybrid Current Drive system with two launchers on the JT-60U is described. This system is the upgrade of the 2GHz LHCD system of the JT-60, and two launchers have been newly fabricated for driving plasma current efficiently. A launcher of 24×4 multijunction grill has been installed and conditioned at the power level of ˜2.6MW. A good coupling is observed on this launcher even though the plasma is more than 0. 1m far from the launcher mouth due to plasma production at the launcher mouth by RF power. The other launcher is of 48×4 multijunction grill to excite very narrow and highly directive spectra. This launcher has been manufactured and will be operated at the beginning of 1993. A infrared camera for measuring the heat load on the launcher mouth, a fast scanning probe and a gas puffing system at the launcher mouth will be equipped for investigating an active coupling control on the launcher.

Pressureless-sintered silicon nitride was bonded using a nickel interlayer in the temperature range 1273–1573 K, such that a eutectic melt of silicon and nickel was formed at the interface. The silicon reacted with and diffused deeply into the nickel. No suicide was identified at the interface. Nickel also reacted with oxide additives in the silicon nitride, namely Y2O3 and A12O3, to form compounds at the interface. The additive elements mostly formed small particles of the YAG phase (3Y2O35Al2O3) in the reaction layer. When bonded between 1373 and 1473 K, the interfacial strength was more than 200 MPa as measured by a bending test. The heat and oxidation resistance of the bond above 873 K were better than could be achieved through bonding by active-metal brazing with an AgCu/Ti laminate foil.