Masahiro Miyamoto

Generation of 50-kHz large area induction thermal plasma for high rate, uniform processing

Numerical and experimental approaches were made to produce a large area induction thermal plasma as a basic technology for high rate, uniform processing of materials. A high-power 50-kHz magnetic field was applied to a small dc plasma as a source of charged particles and a transient expansion of it was initiated in the radial direction. The time necessary to reach a new steady state plasma with a larger diameter of 100 mm was found to be around 20 and 2 ms, and the minimum sustaining power for the plasma to be 65 and 25 kW under the plasma pressure of 100 and 10 kPa, respectively. Experiments were performed to produce a 100-mm diameter plasma under a soft vacuum condition of 10 kPa. At a plate power level of 60 kW, the 50-kHz magnetic field was coupled with a small source plasma and expanded it successfully to a wide plasma of 100 mm in diameter. The temperature of the induction plasma was uniformly distributed and estimated as around 10000 K by spectroscopic analysis.

Pulse excitation method for measurement of high frequency magnetic properties of large cores (abstract)

It is very important to obtain saturated magnetic properties from reverse saturation (full B‐H curve) of ferromagnetic cores to design magnetic switches which are used in high power pulse generators. The magnetic switch is excited in the high frequency range (∼MHz). But, it is extremely difficult to measure full B‐H curve of large toroidal cores of which diameter is some hundreds of mm, using the conventional ac excitation method at high frequency. The main reason is poor output ability of power source for core excitation. Therefore we have developed pulse excitation method to get high frequency magnetic properties. The measurement circuit has two sections. One is excitation part composed by charge transfer circuit. The others is reset part for adjustment initial point on direct B‐H curve. The sample core is excited by sinusoidal voltage pulse expressed as 1−cos(2π ft). Excitation frequency f is decided by the constants of the elements of the charge transfer circuit. The change of magnetic flux density ΔB...