Taichiro Tamida

Determining parameter sets for low-frequency-oscillation-free operation of Hall thruster

We performed a theoretical and experimental study of low-frequency oscillation in a Hall thruster. The oscillation phenomenon depends on various external control parameters. However, we found that such dependence can be observed very clearly using certain expressions, which are combinations of external control parameters. Using these expressions, one can observe the oscillation strength and oscillation mode for a given set of external control parameters. We considered that low-frequency oscillation can be essentially suppressed by a method of determining parameter sets. The method of determining the parameter sets is very important for Hall thruster design and control; in particular, it makes it easy to manage electromagnetic compatibility with the other equipments in a satellite, using a power supply control.

Annular resonator with a Cassegrain configuration

An advanced annular resonator is studied both theoretically and experimentally. This resonator has a Cassegrain mirror configuration and is designed to extract circular and high-quality beams from annular gain media. We carried out beam propagation in this resonator, calculating the intensity distributions of the laser beam. We also proved the performance experimentally by applying the resonator to a CO2 laser. The operation of the new resonator is demonstrated successfully. The quality of the output beam is in good agreement with theoretical calculations of laser output power of 20 W.

Measurement and Modeling of Xe Vacuum Ultraviolet Emission and Radiative Transfer in a Plasma Display Panel Discharge

A detailed study of radiative transfer of vacuum ultraviolet emission in a plasma display panel is presented for the first time. Extensive experimental data obtained from a front panel in a test chamber are compared with a theoretical model. The model accounts for radiation trapping and opacity broadening of resonance lines, as well as the major collisional dynamics among ions, neutrals, and electrons in a xenon/neon discharge. The model was also used to predict the panel illumination efficiency, a parameter of prime importance for display designers. The results from the model yielded good agreement with experimental results over a wide range of pressures and cell geometries.

Transverse-flow radio-frequency-excited amplifier seeded by a cavity-dumped CO 2 laser for an extreme ultraviolet light source

A transverse-flow radio-frequency-exited CO2 laser amplifier was evaluated by a short-pulse seed laser. We constructed a prototype transverse-flow amplifier for the extreme UV laser-produced-plasma source. The electrical power for the discharge was enhanced to 100 kW at a 100% duty cycle. A Q-switched cavity-dumped CO2 seed laser emitting 13 ns pulses with a repetition rate of 100 kHz was amplified along a fivefold optical path in the amplifier gain medium. As a result, the amplifier output an average power of 3.07 kW with an 8.5 W laser input. The electrical-to-optical efficiency was 3.1%, which was far higher than that of axial-flow amplifiers at the same laser input power. The pulse showed a slight stretch from an input duration of 13 ns to an output of 15 ns.

Electrical Circuit Analysis of Coplanar Plasma Display Panels Using a Simple Discharge Model

We have developed a simple method of modeling the electrical characteristics of a plasma display panel discharge. We analyze the discharge phenomena of coplanar plasma display panels (PDPs), and the model is sufficiently simple to express the electrical characteristics of the phenomena. Being a combination of primitive electric elements, this model can be calculated using a general-purpose circuit simulator, which enables us to simulate the PDP electrical characteristics easily and promptly. This model can quantitatively predict the discharge current waveform, and its dependence on the power supply condition and electrode geometry within the range of practical conditions. We can state that this model is a very useful tool for the analysis and design of PDP apparatus.

Development of a Novel Power Processing Unit for Hall Thrusters

A newly developed power processing unit (PPU) offers the advantages of smaller size and lighter weight than conventional PPUs. The thrust performance of a magnetic layer type Hall thruster developed at Kyushu University with this new PPU was investigated; it showed a good performance as compared with conventional power supplies. The thrust to power ratio was improved to 58 mN/kW at discharge voltage of 150 V and anode xenon mass flow rate of 1.0 mg/s.

A new conditioners control for optimal power efficiency of Hall thruster

This paper presents controlling parameters of a Hall thruster with simple performance maps. As a result of performance experiments, the anthers have achieved the over 36% thrust efficiency of the Hall thruster. We propose the optimal control method for thrust efficiency within a stable operation zone on the performance maps.

Highly-efficient high-power pulsed CO2 laser characterized by transverse-flow laser amplifiers

In this paper, we provide a detailed review of development of a highly-efficient high-power nanosecond pulse CO2 laser using transverse-flow radio-frequency (RF)-exited laser amplifiers, which is for extreme ultraviolet (EUV) light source of a next generation of nano-lithography. High-density excited high-power transverse-flow CO2 lasers were designed and built for the application of laser produced plasma (LPP) EUV source. We carried out an amplification test of the transverse-flow CO2 laser seeded by a nanosecond pulse CO2 laser. A four-amplifier system generated an average output power of 21 kW with an electrical input power of 400 kW for discharges. The electrical-to-optical efficiency was 5.2%. The input pulse laser had an average power of 46 W, the repetition rate was 100 kHz, and the pulse duration was 15 ns. The transverse-flow CO2 laser has strong points in high gain and availability of the multi-fold optical path. A highly-efficient amplification was experimentally proved characterized by transverse-flow CO2 laser amplifiers even with low-power seed. A transverse-flow CO2 laser is a promising candidate for an amplifier in the LPP EUV light source.

Development of current by-pass circuit of series connection current drive device

This paper has proposed a self-turn-on type current by-pass circuit which is a new circuit method. The main circuit current can continuously flow in this circuit, even if several of the current drive devices connected in series are open due to breakdowns. The composition, operation, and the circuit design method of the proposed circuit have been described in detail. Moreover, the method of constructing a simulation model of the fuse, which is an element of the circuit, was described. Moreover, the proposed circuit was simulated using that fuse model, the circuit constant was set, and the circuit operation was confirmed. As a result, a circuit that operated without increasing the MOSFET loss was achieved. Moreover, the proposed circuit was constructed for trial purposes, and a current by-pass examination when the diode was opened was executed. As a result, it was proven to be able to pass a current of 60 A continuously even when the diode was open.

Development of Soft Actuator: Mechanism with Vibration Element Using Dielectric Elastomer to Generate Large Displacement

An electric active polymer (EAP) using a dielectric elastomer is superior in the points of view of generated stress and strain, response velocity, and energy efficiency. On the other hand, it is well known that a high polymer material has creep properties. There is no research about creep of a dielectric elastomer actuator (DEA) as far as we know. It is necessary to get a clear grasp of the creep properties of a DEA in order to design a DEA. The purpose of our research was to investigate the creep characteristics and propose a mechanism of a DEA that can generate a large displacement without creep deformation. At first, a sample element of a DEA was made and tested. As a result, it was found that creep deformation was generated and accumulated by the repeated actions. Secondly, an element structure of a DEA was proposed. The element had two driven areas on opposite sides and these two areas are actuated alternately. Therefore, the proposed element worked as a vibration element. The repeated fatigue tests of the proposed vibration element gave proof of the effectiveness against creep deformation. At last, a unit mechanism of a DEA was proposed. The proposed unit mechanism was a combination of the vibration element and a ratchet mechanism. Through a performance test of the proposed experimental unit mechanism, it was confirmed that the mechanism was able to be driven and the transport velocity was changed by changing the drive frequency of the vibration element.