Starting aid device for electrodless high luminous intensity discharge lamp

PURPOSE: To provide a starting aid device for an electrodless high luminous intensity discharge lamp which does not depend on metal parts such as a metal electrode, a metal probe and the like. CONSTITUTION: A RF stabilizer 18 applies RF power to a HID lamp through a combined exitation coil 16. An electrodless lamp 10 contains a light transmitting arc tube 14 with a wall portion of dielectric material arranged with an interval and the first gas filling is in the arc tube 14. The excitation coil 26 is excited by RF current and arc discharge 20 in a shape or a doughnut is generated in the first gas filling in the case of dielectric breakdown of the first gas filling. A starting container 24 has an edge wall composed by one of the arc tube wall portions 52. Insulation resistance of the second gas filling in the starting container is lower than that of the first gas filling. In order to start an arc dischage in a shape of a doughnut dielectric breakdown of the gas filling in the starting container and discharge are caused and by changing potential of the edge wall a way to cause dielectric breakdown of the first gas filling is provided.