Charge states of the metal ions generated from vacuum gaps between silver or zinc needle-cathode and a stainless steel rod-anode by a 13μs duration impulse arc were measured using a time-of-flight (TOF) method. Ag⁺, Ag⁺⁺ and Ag⁺⁺⁺ ions were generated from the silver cathode gap and Zn⁺ and Zn⁺⁺ ions were generated from the zinc cathode gap.
TOF measurements were made at variable delay times from the arc ignition and the ions were only detected for the ion-accelerations by a critical time. The difference of time between the arc extinction and the critical time was considered to be the upper limit of the ion-traveling-time between the cathode and the ion acceleration electrode.
The distance from the cathode to the ion acceleration electrode was 25mm and the velocities and kinetic energies of silver and zinc ions were calculated assuming collsionless equi-velocity ion-expansion from the cathode spot. The velocities and kinetic energies of copper and lead ions were also calculated from the experimental results of our previous paper. It was found that the lower limits of the kinetic energy of silver and copper ions were 10 eV and 20-30 eV, respectively. On the other hand, the kinetic energies of the low-melting-temperature-metal ions were very low and the most probable kinetic energies of zinc and lead ions released from the cathode spot with an extinction of the arc were less than 2 eV.

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The MIM samples of heterofilm composed of arachidic acid LB film (C₂₀, nonpolar) and 2-pentadecyle-7, 7', 8, 8' -tetracyanoquinodimethane LB film (C₁₅•TCNQ, polar)
Al/C₂₀(6L)/C₁₅TCNQ(2L)/C₂₀(6L)/Al are prepared, and the voltage generated in the MIM samples is analyzed. Here, (6L) and (2L) indicate LB films of six and two monolayers. It is shown that the generation of voltage is due to diffusion of carriers in LB heterofilm as same in polyimide LB film of MIM strcutures. Furthermore, generated voltage depends on polarization of C₁₅•TCNQ LB film, while the voltage generated in polyimide LB film in the MIM structures depends on the difference of work functions between Al and Au. The calculated values of generated voltage in LB heterofilms roughly coincide with the values of measurements.

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Measurements of the spectroscopic characteristics of argon plasma produced by multistage pseudospark discharges are described. Absorptions are observed when a cw argon ion (ArII) probe laser, whose wavelengths are 488.0, 476.5, and 514.5nm, passes through the pseudospark argon plasma. The number densities of the upper laser levels for 488.0, 476.5, 514.5, 351.1, and 363.8nm are (2.9±0.3)×10¹⁵/cm³, (2.4±0.2)×10¹⁵/cm³, (2.4±0.2)×10¹⁵/cm³, (4.1±0.4)×10¹⁴/cm³, (4.0±0.4)×10¹⁴/cm³, respectively at 0.8 Torr of Ar, and at a discharge current density of 3.4 kA/cm². The calculated population inversion density of 488.0nm is-1.4×10¹¹/cm³ (no inversion) under the same operational conditions. This is due to the electron collisional mixing of laser levels and the radiation trap between the lower laser level and the ground ionization level. When the pseudospark argon plasmas are placed in the injection-seeded optical resonators, amplifications of 514.5nm and 476.5nm laser lines are observed.

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The spatial distributions of metastable densities and line intensities were measured in He hollow cathode discharge at 3-12 Torr. At higher pressure (12Torr), the emission distributions are essentially equal to that of plane cathode glow discharge, and the light is emitted by the cause of excitation and collisional radiative recombination. While at lower pressure (3Torr), the emission intensities on the axis increase remarkably and the light is emitted only by the cause of excitation.
The metastable atom densities were measured by absorbtion method, and the distribution of He(2¹S) has a dip on the axis always larger than that of He(2³S).
Using the spatial distributions of line intensity and metastable densities, the excitation rate of singlet and triplet system are estimated. The excitation rate of triplet system is about two times larger than that of singlet system, on the contrary to the case of plane cathode glow discharge where the excitation rate of singlet system is larger.

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In order to minimize the effects of eddy currents induced in a cryostat, a magnetic shielding scheme has been employed for MRI field gradient coil system. In this scheme, the leakage magnetic field of a primary coil can be cancelled with the field of a secondary coil excited inversely to the primary one.
This paper presents a coil shape optimization method for magnetic-shielding-type transverse field gradient coils with eddy shapes which realize compactness of the coil system. In this method, optimum coil shapes are determined as paths of eddy currents induced in two thin conductive plates which represent a primary and secodary coil, respectively. To get the eddy currents, which produce target fields within a specific region, the distribution of the magnetic flux density impressed on the primary plate is optimized. At that time, the plate for the secondary coil is assumed to have zero resistivity and magnetic coupling between the two coils is considered. The general formulation of this method based on the FEM by current vector potential method (T-method) is shown. The validity of this method is demonstrated by shape optimizing of an X field gradient coil of an MRI system. The simulation results for the shielding ability of the coils is also shown when combined with cryostat conductive members.

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We are developing a new type of superconductor for the application of high-field pulsed superconducting magnets, which we call Fiber-Reinforced-Superconductor (FRS). A filament of FRS consists of a reinforcement fiber with high elastic modulus and a superconducting layer around it. The strain can be reduced against electromagnetic force because of high-elastic modulus fibers. If Nb₃Sn target is utilized, the preparation process of FRSs is shorten and there is possibility to produce Nb₃Sn layer which leads to high current density because of its uniform stoichiometric Nb₃Sn layer.
This paper presents first a preparation technique of single phase target of Nb₃Sn to produce superconducting layers on reinforcement fibers of FRSs. Mixture of niobium and tin powder was reacted in a furnace filled with argon gas to be Nb₃Sn, and then it was broken and cast into a stoichiometric target with a diameter of 77mm. The critical temperature of the target itself was 17.5K. The thin film deposited with the target showed no superconductivity without post annealing but it had critical temperature from 14.5K to 12.5K after heat treatment. We have secondly prepared a new target containing rich tin and the film deposited with it had superconductivity without post annealing.

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The development of surface corona on dielectric plates under negative impulse voltages has been observed with the dust figure technique in atmospheric air. The dielectric plate was inserted perpendicularly to the axis of a rod-to-plane electrode system and the thickness of the plate and the radius of the rod tip were changed to investigate the corona discharge mechanism at the respective corona onset voltages. Experiments show that the first negative corona along the plate surface with a thicker rod than 0.5 cm diameter forms a distribution of the negative space charge in ring shape and the diameter of the ring increases with the rod radius and the plate thickness.
The origin of the ring formation and characteristics on the ring pattern are discussed on the basis of a numerical analysis on electron avalanche developed along the line of electric force around the rod electrode.

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In the deposition chamber of a double-tubed coaxial-line type microwave plasma chemical vapor deposition system, internal plasma parameters are measured with varying the area of the substrate table to which DC bias voltage is applied in an Ar/SiH₄ plasma. It is clarified that the dependence of plasma space potential on DC bias voltage varies with varying the area of the substrate table only within a range of positive DC bias voltage. Namely, it is clarifled that sheath voltage varies with varying the area of the substrate table within the range of positive DC bias voltage. In addition, we fabricate hydrogenated amorphous silicon films with varying the area of the substrate table within the range of positive DC bias voltage and measure the deposition rate and the hydrogen concentration of films. We find that the dependence of the properties of films on DC bias voltage varies with varying the area of the substrate table. We find that the dependence of the properties of films on sheath voltage doesn't vary with varying the area of the substrate table. Therefore, it is clarified that one has to investigate the influence of positive DC bias voltage on the properties of films on the basis of sheath voltage insted of DC bias voltage.

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