Excimer lamp light source device

An excimer lamp lighting method in an excimer lamp light source device comprising:

• an excimer lamp (Y) that has a pair of external electrodes (Ye1, Ye2) configured to induce an electric discharge in a discharge space (Yg) of a lamp bulb (Yt) and to cause a discharge current to flow in a tube axis direction of the lamp bulb (Yt), that does not have an internal electrode, and that generates UV light in the discharge space (Yg) by the discharge, the lamp bulb (Yt) enclosing the discharge space (Yg) filled with a discharge gas configured to generate xenon excimer molecules, having a shape in which both ends of a tubular body are hermetically sealed, and having an easily dischargeable substance layer (Yo) that facilitates a discharge formed on at least a part of a surface that is in contact with the discharge space (Yg);
• and
• an inverter (Ui) having a transformer (Tf) equipped with a secondary winding (Ls) to which the external electrodes (Ye1, Ye2) are connected in order to apply a high-voltage alternating current to the excimer lamp (Y), wherein
• the inverter (Ui) supplies power lower than power that causes a narrowly-defined contracted discharge to the excimer lamp (Y) to light the excimer lamp (Y) in a discharge state that is not the narrowly-defined contracted discharge,
• the narrowly-defined contracted discharge being a discharge that mainly has a form consisting of one linear discharge path extending from a vicinity of an inner surface portion of the lamp bulb (Yt) facing a portion of the lamp bulb (Yt) in which one of the external electrodes (Ye1, Ye2) is close to or in contact with, to a vicinity of the inner surface portion of the lamp bulb (Yt) facing a portion of the lamp bulb (Yt) in which another of the external electrodes (Ye1, Ye2) is close to or in contact with.