Search

A 200-m high-temperature superconducting (HTS) dc power cable was constructed in 2009 and since then, we have performed six cooling cycle tests to evaluate its performance. Current feeding test is one of the most important issues for this evaluation. This cable has a three-layer coaxial structure. The inner two layers are used as positive (+) polarity, and only one layer in the outmost is used as negative (−) polarity for dc electric energy power, respectively. In the summer of 2014, we started the sixth cooling cycle test on the 200-m cable. After cooling down to liquid nitrogen temperature, we applied a dc transport current to the 200-m cable. In this paper, we will present the current feeding test in the 200-m cable together with the critical current measurements. The critical currents of HTS tapes are enhanced in the assembled cable compared with the manufacturer's specifications. No degradation occurred after the cooling cycles.

In the 200 m high temperature superconducting cable test facility, BSCCO tapes with the critical current of 160 A in self field are used for the two superconducting conductors corresponding to each polarity of DC power transmission. In order to improve the cable property by tape configuration, we have investigated the critical current of a BSCCO tape with different structures. Previous study shows that the critical current of BSCCO tape decreases by 15% for the 3-layer stack structure. However, the stack structures are needed to obtain high current capacity of a cable. Therefore we study the performance of BSCCO tape in the stacked tapes conductor. The insulated tapes are arranged in a tape-above-tape structure and different currents are applied to each tape. The critical current of the target sample is measured by the four probe method by immersing the samples into liquid nitrogen bath. The experiments show that the improvement and degradation of the critical current of BSCCO tape in the stacked conductor are observed under different current feeding mode due to the magnetic field interactions between the tapes. The critical current of BSCCO in the stacked conductor is enhanced by 50% to more than 230 A under the opposite-direction current feeding mode.

A second cooling test of CASER2, the 200 m class superconducting direct current power transmission system at Chubu University, was performed from August to October 2010. During this time, the system was cooled down and the liquid nitrogen which cooled the superconducting power cable was circulated in the cryogenic pipe of CASER2. The heat leak of the cryogenic pipe was measured and the values of about 300 W was obtained. This result will be used further improvements of CASER2.

We designed and constructed the experimental device of 200-meter superconducting DC cable system in the beginning of 2010 and did the first experiment until March, 2010, and the second experiment has been done from August to October 2010. This experimental device is called CASER-2, and the main aim of the experiment is to demonstrate high performance of DC superconducting cable system for comparing the copper cable system. Thermal contraction and expansion during the thermal cycle are discussed in the paper because if the thermal stress of the HTS tape conductor is high, the critical current of the HTS tape is reduced. Therefore, it is the first priority to keep the system in high performance and safety. We also mentioned several experiments and ideas in the paper, such as the low heat leaks of the terminal cryostat and the cryogenic pipe, and the low circulation power, energy storage function of the cable system. In this paper, we present the experimental results of the CASER-2, and discuss and estimate the performance of the system and several ideas. These discussions include the specification of the future long cable system, and show the subjects to solve for the future system.

In the present experiments three straight high temperature superconducting BSCCO tapes were set parallel to each other on a board and the currents were fed to the tapes. The critical currents of the tape which was set between two tapes were measured with respect to the gap between the tapes. We observed that the critical current increases with decreasing the gap. The calculation of the magnetic flux lines around the tape by finite element method demonstrates the effect on self magnetic field by the adjacent tapes. We could provide some hints on how to arrange the tapes in the power cable for DC power transmission.

The 200-meter DC cable test facility was constructed in Chubu University. The cryogenic pipe is composed of two pipes, and the material of the inner pipe is stainless steel (SS304). The outer pipe is the straight pipe, and made from the iron steel because of high strength, low cost and not low temperature. If the cable structure is co-axial, the magnetic field is not generated outside the cable, and the ferromagnetism of the iron steel is not affected to the electric circuit. However, if the single core cable is used, the ferromagnetic effect of the outer pipe should be considered. Therefore, we measured the inductances of the cable after the construction of the experimental device. The measured inductance of the co-axial cable is matched with the analytical value, and it is very small. But the measured inductance of the single core cable configuration, it is 0. 4 mH. This is a large value, and therefore we can save the inductor in the power converter. Moreover, the energy storage can be available in the grid power line if large current operation is used.

For superconducting direct current applications, heat leak reduction at the terminal is a key issue for high performance systems and especially for small ones such as the distribution in internet data centers. We propose a double Peltier current lead (PCL), where the suitable combination of two Peltier modules can enhance the performance of PCL. Using the model parameters of actual thermoelectric materials, we estimated the heat leak on PCL using a thermal balance equation. At the double PCL, the large temperature difference on the current lead can be split to two thermoelectric materials and then the performance of PCL can be enhanced. As each of the thermoelectric materials has better working temperature range, an optimized combination of shape factors can be used for the high performance current lead at the terminals for superconducting application systems.

We constructed a test stand of 20 m-class DC superconducting power transmission cable in Chubu University, in 2006. The cable consisted of thirty-nine Bi-2223 HTS tapes in two layers; nineteen tapes were used in the first layer and twenty tapes were used in the second layer. One of the features of the cable is that each HTS tape in the first layer is electrically isolated. Therefore, we can apply the current to the individual HTS tapes in the first layer. We measured critical current of the one HTS tape in the first layer when current was applied to the other HTS tapes, and compared the result with the magnetic field calculation due to the applied current. The critical current increased by 2 ~ 4% when the current was applied to all other eighteen HTS tapes in the same layer. From the magnetic field calculation, we concluded that the self magnetic field of the measured HTS tape was eliminated at the tape edge by the applied magnetic field from the neighbor HTS tapes, and then the critical current increased.

A liquid nitrogen (LN2) is usually used to keep the high-temperature superconducting (HTS) cable low temperature. A pump is utilized to circulate LN2 inside the cryopipes. In order to minimize heat leakage, a thermal siphon circulation scheme can be realized instead. Here, we discuss the effectiveness of thermal siphon with counter-flow circulation loop composed of cryogen flow channel and inner cable channel. The main feature of the system is the existence of essential parasitic heat exchange between upwards and downwards flows. Feasibility of the proposed scheme for cable up to 500 m in length has been investigated numerically. Calculated profiles of temperature and pressure show small differences of T and p in the inner and the outer flows at the same elevation, which allows not worrying about mechanical stability of the cable. In the case under consideration the thermal insulating properties of a conventional electrical insulating material (polypropylene laminated paper, PPLP) appear to be sufficient. Two interesting effects were disclosed due to analysis of subcooling of LN2. In case of highly inclined siphon subcooling causes significant increase of temperature maximum that can breakup of superconductivity. In case of slightly inclined siphon high heat flux from outer flow to inner flow causes condensation of nitrogen gas in outer channel. It leads to circulation loss. Results of numerical analyses indicate that counter-flow thermosiphon cooling system is a promising way to increase performance of short-length power transmission (PT) lines, but conventional subcooling technique should be applied carefully.

A test stand of a DC superconducting power transmission cable was finished to construct in October 2006 in Chubu University, Japan, and three cooling cycles were carried out to measure the properties of the cable. Critical current of HTS tapes in the cable was measured at every cooling cycle and shows the similar temperature dependence; conclusively, the HTS tapes suffered no damage after cooling and heating process between the each cycle. Peltier current leads were partly installed in the test stand, and it was measured that the temperatures of the feedthrough near to the liquid nitrogen were decreased in spite of a current feeding.

Due to the recent developments of the electric power devices and the HTS power cables, DC superconducting power transmission system is considered to be practical. As one of the R & D issues of the DC superconducting power transmission system, we measured the radiation heat of the thermally-isolated stainless steel pipes with different surfaces. As the result, one sheet of aluminum foil pasted on the inner pipe surface reduced the heat radiation to 1.98 m/W between LN2 and the room temperature of 300 K.

Distributions of the velocity, the temperature and the pressure of a liquid nitrogen (LN2) flow are analyzed at hydraulic cross-sections on two types of superconducting power transmission lines (SC PT). One is on a DC-SC PT, the other is on a three phase AC-SC PT. Inflow heat from the pipe wall and the cables to LN2 are evaluated, however the heat flux from the DC cable is zero. The channels are straight, and hydraulic cross-sections are 3.77 times 10-3 m2 and 4.27 times 10-3 m2 on the DC and AC-SC PT lines, respectively. The increased temperature and the pressure drops on the DC-SC PT lines are lower than those of the AC-SC PT. The fluid velocity dependence on the distance between two cooling stations and on the pump power are estimated. When cooling stations are installed every 10 km, the flow velocity of the DC and AC system are 0.10 and 0.25 m/s, respectively. The pump power of the DC system is dramatically lower compared with the AC system. Therefore, minimizing the SC PT by using DC systems is much more practical.

Peltier current leads (PCL) were applied to a cryogen-free superconducting magnet (CFM) of 5 T/90 A. We measured the temperature profiles on the current lead of the CFM. Compared with the conventional copper current lead, the PCL reduced the temperature and the temperature gradient on the first stage of the cryocooler of the CFM at zero current. The current operation of the CFM improved the reductions due to the heat pump of the Peltier element. These results are the direct proof of the heat leakage reduction by the PCL

Peltier current lead is a promising method to reduce heat leakage from current lead. This paper reports development of Peltier current lead (PCL) with switching facilities to adopt the PCL to polarity-reversible superconducting magnet. In the present work, two types of the PCL were discussed. We mainly investigated the PCL with switching element installed in the copper part. Numerical analysis revealed that it is preferable to reduce heat leakage at the low temperature end of Peltier element. With switch resistance of /spl sim/100 /spl mu//spl Omega/, which enabled switch induced increment of the heat leakage to be suppressed by less than 10%. A transistor switching module with appropriate resistance were manufactured. We demonstrated that a temperature gradient at the end of the lead, corresponding to the heat leakage, could be reduced compared to a conventional current lead (CCL) even when the module was installed with the PCL.

We have studied the thermoelectric characteristics of Si/GeAu superlattice thin films at temperatures ranging from 290 K to 75 K and compared them to those of the SiGeAu alloy thin film. In the annealed Si/GeAu superlattice, the electrical resistivity was lower than that of the unannealed Si/GeAu superlattice at all temperatures. The annealed Si/GeAu superlattice showed a high thermoelectric power of 105 µV/K at 290 K. At temperatures less than 200 K, however, the polarity of the thermoelectric power of the unannealed Si/GeAu superlattice switched from positive to negative and a large negative thermoelectric power of -4.6 mV/K was attained at 80 K. On the other hand, the characteristics of all samples showed no magnetic field effect at all temperatures. To explain the causes of the extremely small variations in the characteristics by the magnetic field effects, we calculated the transport coefficients for the SiGeAu alloy using the two-band parabolic model, and compared them to those of experimentally measured values. When a large amount of acceptor concentration from Au doping and the very low carrier mobility were assumed, similar transport coefficients to the measured ones resulted.

A compact electrostatic quadrupole lens system has been developed, and experiments have been conducted to study transport and focusing of intense He + beams with β=v/c =0.0029 and generalized perveance (Theory and Design of Charged Particle Beams, Wiley, New York, 1994) K=0.0013. Such beams are transported without any loss of beam particles and focused at a distance of about 0.6 m from the source with emittance growth less than a factor of about 1.8. This compact ESQ system has merits to satisfy a critical demand for developing intense He 0 beams for alpha-particle diagnostics in fusion-relevant machines.

The Large Helical Device-Neutral Beam Injector (LHD-NBI) system uses 40 A×180 keV (10 s) negative hydrogen ion sources. Three studies of the H− ion source are reported, i.e., conditioned status, co-accelerated electron beam component, and weight loss of tungsten filaments. Total injection numbers through experimental cycles sum up to ∼8000 shots with four ion sources on two beam lines. Injection power reached a maximum of 5.2 MW. The maximum energy achieved was 171 keV. A pulse length up to 80 s was reached with 0.5 MW. Electron fraction in the accelerated H− beam was evaluated by measuring the heat load on the electron beam dump. Total fraction of the power in the electron beam component deposited on the dump was evaluated to be 1.5%–6% with up to ∼1 Pa of H2. Stripped electrons which were produced inside acceleration gap comprised the majority compared to electrons extracted from source plasma. The weight loss of tungsten filament was 0.01–0.103 mgr/shot/filament. The total loss was ∼0.5% after ∼6500 sh...

The Large Helical Device (LHD) is the only machine that relies upon negative ion-based neutral beam injection system (NBI) as the principal heating power source. Since the first injection in 1998, NBI has been used to heat over 3000 shots for 2 years. Performance has progressed step by step to reach an injection power of 4.5 MW, with beam energy up to 165 keV, and pulse lengths up to 80 s at 0.5 MW. System operating level has reached ∼30% of the design power and ∼65% of the H− design current. This tangential high-energy NBI system based on negative ions has proved to be as efficient a heating system in a helical device as in a tokamak. The ratio of injection neutral beam power to high voltage drain power (injection power efficiency) was typically about 0.3. This is a low efficiency compared to the design one. For long pulse injection beam blocking (such as observed on PLT) was encountered, but it did not limit the operation. In order to achieve the design output of 15 MW, a great R&D effort is underway on the negative ion test stand to improve the performance of 40 A 180 keV negative hydrogen ion source.

A compact cesium deposition system was used for direct deposition of cesium atoms and ions onto the inner surface of the 1/3 scale hydrogen negative ion source for the large helical device-neutral beam injection (LHD-NBI), system. A small, well defined amount of cesium deposition in the range of 3–200 mg was tested. Negative ion extraction and acceleration were carried out both in the pure hydrogen operation mode and in the cesium mode. Single Cs deposition of 3–30 mg to the plasma chamber has produced temporary 2–5 times increases of H− yield, but the yield was decreased within several discharge pulses to the previous steady-state value. Two consecutive 30 mg depositions done within a 3–5 h/60 shot interval, produced a similar temporary increase of H− beam, but reached a large H− yield steady-state value. Deposition of larger 0.1–0.2 g Cs portions with a 20–120 h/150–270 shot interval improved the H− yield for a long (2–5 days) period of operation. Directed depositions of Cs to the various walls of the p...

Time-resolved measurements of the negative ion density and of other plasma parameters in a pure hydrogen Tandem source have been effected using the laser photodetachment technique. The study was made for hydrogen filling pressures in the range 7–11 mTorr and an arc current of 120 A. We found a strong time variation in negative ion density was present during the discharge pulse (0.5 s). The maximum negative ion density was observed at the beginning of the pulse, at the lowest filling pressure studied, followed by a rapid decrease. An improvement of the current distribution during the pulse was obtained by increasing the filling pressure. The electron density is highest at 7 mTorr and stays almost constant during the pulse. The increase in filling pressure leads to electron density values lower by a factor of 4 which are constant during the discharge pulse. The highest relative negative ion density during the pulse is obtained at 9 mTorr. The time variation of the negative ion density does not follow that o...

A novel emittance meter is developed using the pepper‐pot method. Kapton foils are used to detect intensity distributions of small beamlets at the ‘‘image’’ plane of the pepperpot. Emittance of H− beams for the neutral beam injector of the large helical device has been measured. The normalized emittance (95%) of a 6 mA H− beam with an emission current density of about 10 mA/cm2 is ∼0.59 mm mrad. The present system is simple, and it eliminates many complexities of the existing schemes.

The increase of H− current is observed, when the tantalum filaments are used instead of the tungsten filaments. In terms of the production rate of vibrational populations of hydrogen molecules with tungsten and tantalum filaments, we measured the Werner and Lyman emission bands (90–170 nm) the vacuum ultraviolet region to obtain the spectra of molecular hydrogen in an ion source, and observed a significant difference of spectrum between the two cases. From the pressure dependence, it is found that the production rate of vibrationally excited hydrogen molecules is well correlated with the H− density measured by photodetachment in hydrogen plasmas.

The gas mixture effect upon the negative ion temperature in negative ion sources has been studied by the laser photodetachment technique. The ion source is operated at hydrogen pressure from 0.05 to 2.0 Pa. Then argon gas is added up to 100% of the hydrogen pressure. Maximum enhancement of the negative ion density is observed at around a 20%–40% argon to hydrogen mixture in the low hydrogen pressure region. The recovery time for the electron current signal after photodetachment becomes longer when more argon is added to hydrogen plasmas, indicating a lower negative ion temperature.

A cesiated hydrogen hollow cathode (CHC) was tested for plasma injection in the multicusp negative ion source (MS). The CHC arc with hydrogen feed and cesium seeding through the CHC volume was explored. One cathode unit (40 mm length, 19 mm in diameter, emission opening area 1–3 mm2) with no special cooling provided the MS discharge operation with direct current up to 30 A, and up to 60 A in the long-pulse mode. High efficiency of negative ion production in the MS discharge, driven by a CHC plasma injection was recorded.

Using the photodetachment technique we investigated the hydrogen negative ion density in the extraction region of a magnetically filtered multicusp ion source when argon is added to hydrogen. We found that the negative-ion density goes up at most by a factor of 1.5 when argon is added to low base hydrogen pressure (0.05 or 0.1 Pa), but goes down when argon is added to higher initial hydrogen pressure (0.5 or 1 Pa). Adding argon did not enhance the Werner and Lyman bands in the vacuum ultraviolet, which indicates that argon addition does not increase the production rate of vibrationally excited H2 molecules. The increase of the negative-ion density by adding argon into a low-pressure hydrogen discharge is probably due to the increase of the low-energy electron density.

For compensation of the magnetically deflected beamlets, a new type of grid system has been applied to a large negative ion source of a negative-ion-based neutral beam injector in the Large Helical Device (LHD) fusion experimental machine. Corresponding to deviation of the negative ion beamlet trajectory due to the electron suppression magnetic field at the extraction grid, the exit aperture of the extraction grid is displaced to cancel the beamlet deflection by electrostatic lens effect. As a result, the beamlet deflection was suppressed less than 2 mrad in a wide range of energy of 110–180 keV, and the port-through efficiency of the injected beam was improved to 90%–95% from 70%–75% in the case of the previous compensation by the grounded grid aperture displacement. The injected beam power was increased to 3.5 MW with an energy of 165 keV using one injector. To improve beam uniformity of the large area beam, individual arc currents through filaments are controlled for uniform plasma production, with ind...

A direct current superconducting power transmission (DC‐SCPT) test facility with 20‐meter power cable has been developed in Chubu University. Heat leakage through current leads dominates in case of short‐distance DC‐SCPT. To solve this problem, we have developed special Peltier current lead (PCL) with bismuth telluride (BiTe) alloy is used as a Peltier material, and have studied a gas‐cooled PCL as a novel type current lead for higher reduction of the heat leakage. In order to achieve high efficiency, highest thermoelectric figure of merit material is important to be used especially at low temperature conditions. In our work we measured the thermoelectric properties of BiTe samples, and optimized geometry of PCL by the numerical calculations. It was fount that the heat leakages through PCL and gas‐cooled PCL are reduced to 55% and to 36% of the conventional copper current lead (CCL) at the self‐cooling condition, correspondingly. PCL can reduce the total electric power consumption of the whole system. We also discuss the heat exchange ratio for the gas‐cooled PCL, and extend this approach for further reduction of the heat leakage.

The pepper-pot method and two slit-and-collector type techniques are tested for their applicability to measure the emittance of low energy ion beams. The exposure of Kapton foil, used here as the detector in the pepper-pot method, has been found to show a nonlinear behavior of the image contrast with the local power density of He+ beam for energy less than 10 keV. Therefore, the emittance measurement with the pepper-pot method must be made with the calibration of the contrast of the Kapton film in advance. The measured values of emittance, obtained by the different diagnostic schemes, are similar. From the view point of the negative ion beam measurement, the pepper-pot type system using Kapton film and the multislit-and-Faraday-cup system are proved to be promising.

A filament-type helium ion source has been developed for the purpose of alpha particle diagnostics and as a test beam for electrostatic quadrupole transport experiments. We have obtained preliminary results of He+ beam current, ∼60 mA/cm2. The normalized brightness of this beam is ∼1010 A/(m rad)2. The normalized emittance (90%) measured by multislit faraday cup emittance meter is ∼0.6 mm mrad below 100 V, 10 A arc discharge. The effects of plasma parameters in the source on the beam emittance and on the beam perveance are discussed.

Multilayer insulator (MLI) is a strong tool for use as a radiation heat shield, though the use of MLI has disadvantages in construction and evacuation for a long superconducting power cable. We have proposed the “MLI-free” radiation heat shielding for DC superconducting power cable and have measured the radiation heat transfer for thermally-isolated double-pipes with different surfaces. Here, Zn coating, MLI, and Al-foil sheet were tested. Consequently, from the radiation heat of 9.7 W/m for bare stainless-steel pipe, Zn-coated stainless-steel surface reduced to 2.6 W/m, whereas the use of MLI reduced to 0.2 W/m. It is expected that the simultaneous use of Zn coating and MLI can reduce the number of total MLI sheets to reduce the evacuation time.

In Chubu University, bellows pipes are applied to absorb the heat shrink as a part of straight pipes for superconducting power transmission lines (SC PT). In conventional SC PT systems, SC cables are put in corrugated pipe. Pressure drop of the liquid nitrogen flow in bellows and corrugated pipes are analyzed by a fluid-analysis software. Pressure drop per unit length in the bellows and corrugated pipes is respectively 2.6 and 3.7 times that in the straight pipes. Pressure drop in the bellows is smaller than that in the corrugated pipes. Therefore, bellows are preferable for the DC-SC PT.

Cooling is important to keep the temperatures of the highly integrated silicon electronic devices and power devices e.g. power MOSFET, IGBT. Yamaguchi et al. have proposed a new scheme to cool down the devices by its own current named ldquoself-cooling devicerdquo, in which the cooling process uses Peltier effect. In the proposed scheme, we should use the materials that have high thermal conductivity, high Seebeck coefficient and low electrical resistivity. These requirements are different from the conventional Peltier materialspsila. SiC is one of the candidate materials, and we measured the electrical resistivity, the Seebeck coefficient and the thermal conductivity of single-crystalline 4H-SiC in the temperature of 300 K - 400 K. We also evaluated the performance of the proposed cooling for the present power MOSFET by using the experimental data, and discuss the direction of the future study.

H− ion density in the extraction region of a volume-production-type ion source is measured, using the photodetachment method, and directly compared to H− ion beam extracted from the ion source in order to understand the effective production of H− ions. It is observed that there is qualitative similarity between H− density and extracted H− beam current, as expected. Characteristics of H− ion production under two values of magnetic strength are compared to study the effect of the filter field. It was found that the weaker magnetic field of 750 G cm is not sufficient for the filter field since high energy electrons can come into the extraction region across the magnetic field.

We have fabricated silicon structure in silicate glass prepared with metallic aluminum in the starting material, using femtosecond laser irradiation and subsequent annealing. Small Si-rich structures such as oxygen-deficiency (O-deficiency) defects or Si clusters transform into nano-sized Si particles by the focusing irradiation of the laser. Then the Si-rich structures grow into micro-size particles due to the thermite reaction promoted by heat treatment. We determine the effect of focused laser pulse on the Si deposition process by using a time-resolved transient lens method with a sub-picosecond laser pulse. Localized high-temperature, high-pressure, and the generation of shock waves appear to be very important in forming the Si-rich structures that ultimately grow into Si particles. The diffusion of oxygen by shock waves and the existence of Al-rich structures help form Si-rich structures as Si-O bonds continuously break under high temperature. The focusing irradiation of femtosecond lasers is very useful for fabricating Si structures inside glass.

We have installed Peltier current leads (PCLs) in a commercial, cryogen free magnet to reduce heat flow to the GM cooler. Experimental results show that the first stage temperatures of the GM cooler are lower with the application of the PCLs than with conventional current leads (CCLs). At each operating current, from 0 to 75 A, the temperature gradient across the copper portion of the PCL is lower than that across the CCL. Heat flow into the cryogen‐free magnet has been reduced from 16 to 30% by the application of the PCLs. Heat loss reduction was achieved by the installation of PCLs.

NGC 7742 is well known for its prominent blue nuclear ring around an EO-like core, and so appears as a Hoag-type galaxy, an elliptical galaxy with an outer ring (Schweizer et al. 1987). The galaxy is classified as Sa(r!) in the Revised Shapley-Ames Catalog (Sandage and Tammann 1987) with an exclamation mark to emphasize the prominence of the ring. Its photographs are published in Laustsen et al. (1987), Wray (1988), and Sandage & Bedke (1994).The ring has a diameter of 19″ = 1.6 kpc at a distance of 17.1 Mpc (Buta & Crocker 1993), and so should be a nuclear ring of the galaxy. Nuclear rings and pseudorings are often detected in strongly barred (SB) galaxies, and interpreted to be linked to the inner Lindblad resonance (Buta & Crocker 1993). These nuclear features are, however, also found in some weakly-barred (SAB) and non-barred (SA) galaxies. NGC 7742 is a galaxy of the highest circular symmetry in its core, ring, and main body, and so the best object for a detailed study of formation mechanisms of nuclear rings in non-barred galaxies.

We examined the magnetic field effects on thermoelectric properties, aiming to enhance the thermoelectric power generation. Here, we propose the "Nernst-Seebeck" element, which uses the hybrid electric field of the Seebeck effect and the Nernst effect in the magnetic field. The thermoelectric properties of the polycrystalline bismuth (Bi) in the magnetic field are measured at 200 K and 290 K, proving the enhancement of the effective thermoelectric power due to the Nernst+Seebeck hybrid effect. Using the measured thermoelectric properties, the maximum output power and the conversion efficiency of the Nernst-Seebeck element are calculated for the different widths of the electrodes. An enhancement of 10 /spl sim/ 12 % in the conversion efficiency is attained in the square geometry, compared with that of the standard Seebeck element.

We have been studied thermoelectric characteristics of Si/(Au-doped Ge) superlattice thin films at temperatures from room temperature (RT) to low temperatures less than 100 K and compared these to those of Si and (Au+Ge) alloy thin film. In the Si/(Ge+Au) superlattice after heating process the electric resistivity decreased at all temperature. This annealed Si/(Ge+Au) superlattice showed the high thermoelectric power of 105 /spl mu/V/K at 290 K, compared with the unannealed Si/(Ge+Au) or the alloy film. At temperatures less than 200 K, however, the thermoelectric power of the unannealed Si/(Ge+Au) switched polarities from positive to negative and reached -4.6 mV/K at 80 K. This large negative thermoelectric power at low temperature was not observed in the annealed Si/(Ge+Au) or the alloy film. On the other hand, magnetic field characteristics of all samples showed no effect at 100 K, 200 K or 290 K. This was explained using the two-band parabolic model calculation, assuming that a large amount of Au-doping caused a very low carrier mobility.

1. The distribution characteristics of clarithromycin to the lung were investigated in vivo and in isolated lung perfusion experiments. The in-vivo integration plot analysis showed that the pulmonary uptake and extracellular distribution in the lung were significantly higher for clarithromycin than for erythromycin. 2. In the rat lung single-pass perfusion study, the pulmonary extraction ratio (E(ss)) of clarithromycin at steady-state was significantly higher than that of erythromycin, and the E(ss) of clarithromycin tended to decrease as the inflow concentration increased, suggesting the involvement of carrier-mediated transport in the pulmonary disposition of clarithromycin. 3. The outflow patterns of clarithromycin or erythromycin at various inflow concentrations were simultaneously analysed based on a pharmacokinetic model, which consists of the non-specific binding site, the specific binding site and the subsequent uptake process. The parameters obtained suggested that clarithromycin would have the higher affinity and higher capacity for the specific binding site, and the higher equilibrium constant for the non-specific binding site than erythromycin. 4. The simulation study using those parameters demonstrated that clarithromycin could be bound to the specific binding site and subsequently taken up more extensively than erythromycin. 5. A multiple-indicator dilution study also indicated that clarithromycin was more readily associated and extracted with the lung than with erythromycin. In the inhibition study, it was suggested that the pulmonary uptake of clarithromycin could be ascribed not only to the non-specific binding depending on its lipophilic nature, but also in part to some specialized mechanisms such as organic cation transporters.

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

We constructed the 200 m class superconducting DC power transmission test facility (CASER-2) in 2010, and have carried out the cooling down and operation test. The 5th cooling down and operation test was carried out from August to November 2012. Long term current feeding was tested for a month with various currents and temperatures in the 5th test. From the long term current feeding test, the LN2 circulation was clearly affected by the operation of the cryogenic system and the atmosphere, not only by the operation DC current. It was also confirmed that the Peltier current leads worked effectively for the reduction of heat leak at the cable terminal.

A test stand with a multicusp type He/sup +/ ion source and an electrostatic transport system was built for the study of beam characteristics at relatively low energy, E

We constructed a facility of a 200-m HTS power transmission test cable (CASER-II) in 2010. Generally, an HTS cable contracts about 0.3% when it is cooled from room temperature to liquid nitrogen (LN2) temperature. The contraction of the 200-m HTS cable corresponds to 0.6 m. In order to realize the HTS power transmission system, it is an essential issue to absorb the mechanical stress of the HTS cable during the cycles of cooling-down and heating-up. The CASER-II uses smooth pipes as the cryogenic pipe for the cable line to reduce the pressure drop of the liquid nitrogen flow, whereas the other HTS cables use corrugated pipes to absorb the mechanical stress. The CASER-II employed (1) the movable terminals at the cable end, and (2) the extendable bellows inserted in the cryogenic pipe, to absorb the contraction of 0.6 m in cooling cycles. Even at the 4th cooling-down test, no damage was observed in the CASER-II. Use of the smooth cryogenic pipe enabled low pressure drop with low LN2 flow rate, and negative pressure drop appeared at less than 5 L/sec of the LN2 flow rate. This negative pressure drop was caused by the LN2 flow assisted by siphon effect due to the difference of LN2 density along the cryogenic pipe line with elevation of 2.6 m.

Heat leak from the current lead is the major source of power loss for superconducting (SC) magnets, motors and generators, and short distance SC power transmission lines. Therefore, reducing the heat leak from the current lead can improve the economy of the SC system and allow the use of SC systems commercially. The Peltier current lead was proposed and developed at Chubu University to reduce the electrical power consumption of the refrigerator. The heat leakage of the Peltier current lead saves almost 40%, but the power requirement of the refrigerator is still high. In order to realize greater power savings, the multistage current lead (MCL) and the gas-cooled MCL are proposed. The heat leakage reduction of the gas-cooled MCL depends on the characteristics of the cryogen and its pressure and the realization of high cost of performance and a high-temperature refrigerator. Here, we show the calculation results of the high-pressure effect of cryogen and discuss the performance of nitrogen trifluoride as cryogen.

The acceleration characteristics of H− beam have been investigated using a single beam let accelerated up to 100 keV. The H− beam is extracted from a large negative ion source operated with Cs seeding and is accelerated by a single‐stage accelerating system. The currents and the spatial profiles of the H− beams are measured calorimetrically. The beam divergent angles are obtained by means of Gaussian fitting to the measured plots. A minimum divergent angle of 5 mrad is achieved with an H− current densities of 32 mA/cm2 and the beam energy of 94 keV. A ratio of acceleration current to H− current increases suddenly at the region where the H− current begins to saturate due to a space charge limitation. This is considered to be caused by emission of secondary electrons at an extraction electrode by collisions of the divergent H− beams. The dependence of the divergent angle on the acceleration voltage is measured, and an optimum ratio the electric fields for H− extraction and for the acceleration is determined...

High current hydrogen negative ion source development has been intensively carried out for neutral beam injector for Large Helical Device (LHD), in which ion source capable of delivering a negative ion beam of 45 A at a beam energy of 125 keV is required. A multicups ion source of 1/3 scale of the prototype source in NBI for LHD and a large rf ion source has been studied for negative ion production, beam extraction and acceleration. A total H− current of 16 A is obtained at the 1/3 scale source with Cs seeding operation. The H− ion current is proportional to the input arc power. A 13.6 A of H− ion beam is accelerated to 125 keV at the two stage acceleration. A divergent angle of 9 mrad is obtained at multi beam. Preliminary experimental results of r.f. ion source are described.

A new 200 m high Tc superconducting DC cable test facility was successfully constructed in 2010. This cable is composed of two superconducting layers of the DI-BSCCO® tapes spirally and closely surrounding a copper former. The number of the tapes in each layer is different due to their different radii. We have investigated the effect of the way of the tape winding on the critical current (Ic) of the tapes in order to optimize the cable configuration for the DC transmission. This paper presents the measurements of Ic of DI-BSCCO® in a hybrid multi-stacking configuration composed of YBCO and BSCCO tapes by controlling the transport current in each tape independently. The Ic measurements were performed with the standard four-probe method at the liquid nitrogen temperature. The magnetic field distribution around the tapes was calculated by the finite element method to demonstrate the effects of the self field from the adjacent tapes. The enhancement and degradation of Ics in the hybrid multi-stacking tapes were observed in contrast to that of single tape. Through the experiments, we started to investigate optimized tape configuration of the DC power cable to enhance the superconducting characteristics.

We constructed a test stand of a 20 m DC superconducting power transmission cable in Chubu University in 2006. The cable uses thirty-nine Bi-2223 tapes. Four cycles of a cooling and current-feeding test have been carried out after the construction of the test stand. The cable suffered rapid temperature decrease of 20 K/hour at the daytime during the cooling process by cold nitrogen gas and liquid to the liquid nitrogen temperature. Nineteen HTS tapes in the cable are electrically isolated from each other, and the superconducting characteristics of these HTS tapes can be measured separately. At every cooling cycle, critical current of these isolated HTS tapes were measured. Consequently, no reduction of the critical current characteristics was observed through the 4 cooling cycles. We considered that this endurance of the cable against the cooling cycle is due to unfixed cable end structure of the cable, and that the cable was free from the mechanical stress in spite of the 6 cm shrinkage of the cable length under the low temperature.

Kapton foils can be used as a simple ion beam monitor. These foils act as a self-developing medium and quantitative information about the distribution of the striking beam can be obtained easily. The “burn” pattern on the film due to irradiation by the ion beam is analyzed to determine the beam distribution, here the beam power density distribution. Given the beam voltage this information can be translated to the ion current density distribution. The linearity of response of the Kapton foil with beam current density is shown. The threshold for response of the Kapton foil seems quite good; a clear response is observed with a foil of thickness=50 μm for H− beam current density of about 35 μA/cm2 at 88 kV.