Abstract: A starting assist control circuit for an electrodeless light source in which a UV source for assisting in starting an electrodeless lamp is coupled in series with the DC supply for a microwave power source for the lamp so that a reduced DC voltage is supplied to the microwave power source at lamp starting. An electronic circuit is provided which continuously decreases the DC current through the UV source and increases the DC voltage for the microwave power source in relation to the amount of light generated by the electrodeless lamp. More specifically, the emitter and collector of a transistor are coupled across the UV source to provide a shunt path and the potential of the base of the transistor is controlled by a photosensitive resistor which senses the amount of light from the lamp. As the lamp generates increased light, the transistor becomes more conductive, thereby continuously decreasing current to the UV source and increasing voltage to the microwave power source.

Abstract: A starting assist control circuit for an electrodeless light source in which a UV source for assisting in starting an electrodeless lamp is coupled in series with the dc supply for a microwave power source for the lamp so that a reduced dc voltage is supplied to the microwave power source at lamp starting. At staring, a capacitive impedance element is coupled across the inner and outer conductors of the fixture to provide an additional starting assist by creating a condition of resonance in the fixture. A heat responsive bimetallic switch element associated with both the capacitor and the UV source automatically shorts out the UV source and decouples the capacitor after the lamp has started thereby permitting full dc power to the microwave power source during the operating condition of the lamp.

Abstract: A tunable microwave cavity permits adjustment of the penetration of a power coupling probe into the main cavity by adjusting a grounded element of the cavity. A pair of conductive tubes are in telescoping relationship and have mutually engaging threads so that a rotation of one tube causes one tube to pass over the other. A first one of the tubes is mounted to the main cavity and around an aperture in the cavity wall. A power coupling connector is mounted with the second tube, and a rotating electrical contactor is disposed between the outer conductor of the connector and the second tube so that the connector does not rotate with the second tube. A power coupling probe affixed to the end of the inner conductor of the connector assumes various penetration depths within the main cavity in response to a rotation of the second tube. The cavity may be used in a light source including a high frequency power source and an electrodeless lamp disposed in the main cavity.

Abstract: In a light source excited with power at a high frequency, an electrodeless lamp is located in a termination fixture comprising an inner and outer conductor, the lamp being located at the end of the inner conductor. An internal tuning element is located within the fixture for creating a resonant condition when the lamp is to be started to create a maximum electric field for initiating breakdown and excitation of the fill material within the lamp. The tuner may comprise a variable capacitance coupled in parallel across the conductors at the power input end of the fixture or a variable inductance connected across the conductors at the lamp end of the fixture.

Abstract: In a light source in which an electrodeless lamp is excited by high frequency power coupled into a lamp termination fixture having an inner and outer conductor, the fixture has a dynamically variable characteristic impedance, thereby facilitating dynamic matching of the variable impedance of the lamp during the lamp-off to lamp-run conditions to the output impedance of the power source. This feature is possible because the position of the inner conductor with respect to the outer conductor is controlled as a function of the heat generated within the fixture. The inner conductor is made of a conductive material having a non-uniform coefficient of thermal expansion. When the fixture is cold, the lamp and the lamp-coupled end of the inner conductor are substantially concentric to the outer conductor thereby creating a high characteristic impedance to match the high starting lamp impedance to the source impedance.