Shimadzu Corporation

Toshiya Habu

Eizo Kawato

PROBLEM: To improve the stability of the process of the plasma ignition, by allowing a high current to pass through an induction coil without increasing the power-supply voltage in the process of the plasma ignition. SOLUTION: An impedance conversion circuitincluding an inductorand a capacitoris arranged between a full-bridge drive circuitfor switching DC voltage and an LC resonance circuitincluding an induction coilfor plasma generation. The capacitance of the capacitorcan be varied between two levels, with a switching driverserving as a switcher. When the plasma is to be ignited, the capacitance of the capacitoris set at the higher level to allow a high current to be supplied to the LC resonance circuitAfter the plasma is brought into a steady state of lighting, the capacitance of the capacitoris changed to the lower level at which an impedance matching is achieved so as to maximize the power efficiency.

Radio-frequency power unit

A high-frequency input voltage and a high-frequency input current to a series resonant circuit are detected by a voltage detection unit and a current detection unit, respectively, and plasma input power is detected by a plasma input power detection unit based on the detected high-frequency input voltage and high-frequency input current. By directly detecting the plasma input power in this manner, the plasma input power may be accurately controlled regardless of the state of a plasma-generating gas or an analysis sample. Also, use of a switching circuit including a semiconductor device allows an inexpensive configuration compared with a configuration where a vacuum tube or the like is used.

High-frequency power supply device

A transformer is formed into a substantially U shape. The length of the transformer may thus be secured, and also the length of pattern wiring between an input terminal and an output terminal of a secondary coil of the transformer and the control terminals of a semiconductor device may be reduced. Moreover, the primary coil and the secondary coil of the transformer are arranged in parallel. The coupling coefficient between the primary coil and the secondary coil is thereby increased. An LC resonant circuit, not including the induction coil, and a switching circuit and the transformer are accommodated inside a housing. A water-cooling radiator is provided inside the housing, and also air inside the housing is circulated by a cooling fan while being guided to the radiator.

A starter is provided for a self-oscillating radio frequency oscillation circuit for high-power applications used for plasma generation in an ICP emission spectrometer or for other purposes. A secondary winding of a starting transformer is arranged in an LC resonance circuit including an induction coil, capacitor and other elements. A starter, e.g. a Clapp oscillator circuit, is connected to a primary winding magnetically coupled with the secondary winding. A radio-frequency current is induced in the LC resonance circuit by energizing the starter for a certain period of time in a starting phase. As a result, electric current flows through the secondary windings in a full-bridge drive circuit which are magnetically coupled with primary windings, whereby voltage is developed between the gate and source of MOSFETs, causing these MOSFETs to begin an ON/OFF operation, whereby the self-oscillation is started.

Radio-frequency oscillation circuit

An emission spectrophotometer capable of inhibiting non-uniformity of spectral intensities of component elements is provided. The emission spectrophotometer generates pulse light emission by supplying an energy accumulated in an electricity accumulating and discharging unit to a gap between an electrode and a test material, and the emission spectrophotometer includes a detection unit, for detecting an energy charged to the electricity accumulating and discharging unit before the pulse light emission; and a detection unit, for detecting an energy remaining in the electricity accumulating and discharging unit after the pulse light emission. It is determined whether the detected light is emitted by fully using the energy accumulated in the electricity accumulating and discharging unit.

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Kyoto, Japan

Toshiya Habu