Recent research activities on atomic time and frequency standards are introduced. Especially two topics are selected and explained in detail. One topic is “accurate optical frequency standards" which may be a primary standard of “one second" in the next generation. Another is “chip-scale atomic clocks" which may be useful for industries, communications and various scenes in our daily life.

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A high-pressure microwave discharges in compact-size quartz discharge chambers were investigated in order to apply to high intensity discharge lamps. It could be ignited by low-power microwave using a launcher which is the annular slot antenna opened on the top plane of a coaxial waveguide. It was found that the discharge could be sustained by the microwave power of 10 ˜ 30 W even at the atmospheric pressure of argon gas and that the microwave leakage from the discharge chamber was much lower than the warning level when the slot was opened in the most appropriated position. When the additives such as NaI and ScI₃ were mixed into argon in the discharge chamber, the light intensity emitted from the discharge significantly increased and the lamp efficiency estimated from the measured illumination amounted to 38.8lm/W. This value remained small because the ratio of discharge chamber volume to microwave power is much smaller than that of the conventional lamps.

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An effect of electrode shape on ozone generation in dielectric barrier discharge reactor is described in this article. Three different shape electrodes were employed as ground electrodes. A plane electrode is 6 cm in width, and 20 cm in length. A trench electrode has large number of knife-edge rails. A multipoint electrode has large number of four-sided pyramid projections on the plane. A high voltage plane electrode is covered with 0.5 mm thickness alumina layer worked as dielectric barrier. The experimental results show that the breakdown for the multipoint electrode occurs at 7.0 kVpp. This value is lower than 8.4 kVpp that is the breakdown voltage of the plane electrode. The ozone yield increases from 80 g/kWh to 130 g/kWh by changing the electrode shape from the plane to the multipoint. The ozone generation efficiency decreased with increase of the ozone concentration.

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While silent discharge ozonizer feeding high-grade pure oxygen is operated for many hours, the ozone concentration decreases remarkably with time. In the extreme case, the ozone concentration comes down to almost zero. Therefore, we call this “ozone zero phenomenon". The phenomenon was first discovered in about 1990 and various examinations were performed by many researchers. However, the explicit clarification has not yet been found. In order to clarify the mechanism of this phenomenon, the authors developed an ozone production system which consists of two ozonizers connected with cascade in the same direction with the flowing gas. With feeding the pure oxygen, ozone produced by the primary ozonizer was provided into the secondary ozonizer that causes the ozone zero phenomenon and both ozonizers were driven sequentially to observe the each response of the ozone concentration. Moreover, the same investigations were conducted by adding NOx and Ar from an external gas inlet attached between the primary and secondary ozonizers. It is found that the ozone zero phenomenon disappears and ozone concentration is recovered by adding NOx without electrical discharge. Therefore, the phenomenon is considered by decompositions of ozone produced at wall surface.

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Dependence in pulse duration of heavy ion beam is investigated for effective pellet implosion in an inertial confinement fusion. Not only the spatial nonuniformity of the beam illumination, but also the errors of the beam pulse duration cause changes of implosion dynamics. The allowable regime of beam pulse duration is given by the implosion calculation using numerical simulation techniques. The regime of the beam pulse duration for the effective fusion output becomes narrow with decreasing the input beam energy. The voltage accuracy requirement at the beam velocity modulator is also estimated for the final beam bunching. The voltage error tolerance is estimated as a few percent.

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Color variable pulsed Hg-Ne discharge lamp was invented and reported by Itatani's group in 1973. The color of Hg-Ne discharge was controlled by changing electron temperature by changing pulse frequency. Maya's group reported about color variable mercury fluorescent lamps using burst pulse and different type of phosphors. Kroesen's group proposed Hg-Ne color variable lamp using depletion effect. All these lamps use electrodes inside a tube. The authors propose a new type of color variable discharge lamp using inductively coupled plasma (ICP), electrodeless discharge. Color variable lamp using ICP is demonstrated. Just after starting discharge of Hg-Ne, the luminescent color of the lamp is red because of Ne emission. After that, the color changes gradually toward blue resulting from increase in mercury vapor pressure. When the color change stoppes and it is in the steady state with blue color, the color can be changed toward red by increasing input power. This is due to Ne emission resulting from increase in current density.

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Diamond-like Carbon (DLC) films show high hardness, high electric resistivity, and the self-lubricant characteristic, and many applications and synthesis methods were reported. Pulse plasma Chemical vapor deposition (CVD) method is one of the synthesis methods suitable for DLC films on complicated form work, such as molding and extruding die. Ordinary, microsecond order pulse is used in this method. This paper describes the development of the synthesis method using nanosecond order pulse plasma CVD to DLC films. To realize this process, a static induction (SI) thyristor with an Inductive Energy Storage (IES) circuit was used. Compared with microsecond, nanosecond order pulse plasma CVD method shows the characteristics of the high electron temperature and the exponential relationship between pulse frequency and growth rate. The characteristics of the thus-obtained DLC films show two broad peaks of the disordered band at 1360 cm^-1 and the graphitic band at 1580 cm^-1 by Raman spectroscopy and hardness of 16.0 GPa and elastic modulus of 170 GPa.

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This paper presents a generalized equivalent multipole-moment method for calculating three-dimensional Laplacian fields in multi-spherical system. The Greengard & Rokhlin's M2M, M2L, and L2L formulae enable the multipole-moment method to calculate the fields in general arrangement of multi-spheres, which involve exclusive and multi-layered spherical arrangement. We applied this method to electric field calculation in biological structures induced by ELF magnetic fields. The induced electric fields in a three eccentric and exclusive spheres system, which models human head with two eyeballs, are calculated under the application of homogeneous and magnetic-dipole fields. The validity of this method is successfully confirmed by comparing the calculated fields with those by the fast-multipole surface-charge-simulation method.

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A simple measurement method, which determines inductance from the capacitance standards, is presented. This method is cost effective because no special instrument other than a commercially available LCR meter is used. The measurement principle is the compensation method using the LC series circuit. At the frequency near its resonating condition, the reactance of the inductor is offset by that of the capacitor. The reactance of the capacitor was precisely calibrated beforehand, and the LCR meter measures the reactance value of the residual difference much smaller than the total reactance of the inductor itself. This means that the accuracy of LCR meter affects the measurement uncertainty of inductance less than the uncertainty of direct deflection measurement of inductance. Two 10 mH standard inductors and a 100 mH standard inductor were measured at 1592 Hz (angular frequency of ω = 10⁴ rad/s). The relative combined standard uncertainties of measurement were estimated to be 9.2 parts per million (ppm), 9.8 ppm and 12.0 ppm, respectively. These values are small enough for the industrial use.

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The topology optimization, which determines the optimal topology by distributing the magnetic material in the design domain, is attractive for designers of magnetic devices because an initial conceptual design can be obtained. As there occurs some gray scale elements (medium value of material density) in the optimal topology obtained by density method, it is not clear whether the region of gray scale can be treated as magnetic material or not.
In this paper, a novel topology optimization technique, which judges the existence of the magnetic material in a finite element taking account of nonlinearity of magnetic property, is proposed. The sensitivity analysis is efficiently utilized. An optimal topology of actual magnetic circuit can be obtained by using this method. The effectiveness of the proposed method is illustrated by applying it to the topology optimization of a C-core actuator. The effect of nonlinearity on the obtained optimal shape is also discussed.

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The effect of both Mn and Co addition on the electrical degradation of ZnO varistors were investigated based on voltage-current (V-I) characteristics, capacitance-voltage (C-V) characteristics, isothermal capacitance spectroscopy (ICTS), and X-ray diffraction (XRD). The optimum Co content to prevent the electrical degradation is approximately 0.5mol% for Bi-Mn(0.5)-Co-added ZnO varistors. Correlation of the improvement of the electrical degradation with the structure changes of ZnO varistor by Mn and Co addition was investigated by XRD. It is found that the crystal structure of α-Bi₂O₃ in the grain boundary changed to Bi_7.65Zn_0.35O_11.38 for Bi-Mn-Co(0.5mol%) added samples. It is suggested that these structure changes of varistors with Mn and Co addition contribute to the improvement of the electrical degradation characteristics of Bi-Mn-Co-added ZnO varistors.

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The reaction coefficients of radicals on the growing surface of hydrogenated amorphous silicon nitride (a-SiN:H) were studied by applying Monte Carlo simulation. These a-SiN:H films were deposited on trench-patterned silicon wafers using two kinds of gas mixture, SiH₄-NH₃ and SiH₄-N₂, and then measured for their film thickness profiles and composition on the trench wall. The derived total loss probability (β) of radicals was estimated from comparison between the experimental results and the simulation. On the basis of these results, the main radicals during depositions will be discussed.

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