The invention relates to a spark gap comprising a cathode (12) and an anode (11). According to the invention, said spark gap is divided into two partial spark gaps by means of a central piece (13), namely a high-pressure spark gap (14) and an effective spark gap (15) Said effective spark gap (15) can for example, be used to generate monochromatic x-rays (26). In order to guarantee a defined switching time, the high-pressure spark gap (14) which is initially switched to defined, is used. The switching initiates a potential so high on the centre piece that, when the high pressure spark gap (14) is switched, the effective spark gap (15) can also be switched in a defined manner without significant delays, to a visibly higher voltage.