a thyristor has a radiation - sensitive breakdown structure , a gate electrode that is placed at a distance from the latter in a lateral direction and an ignition stage structure having at least one ignition stage equipped with an n - doped auxiliary emitter , which forms a pn - junction together with the p - doped base , the thyristor being both electrically and radiation - ignited . in a method for contacting a thyristor that can be ignited by radiation with a gate electrode , a contact ram that is adapted to the geometry of the gate electrode is pressed against the thyristor . in a method for monitoring the ignition of a thyristor that is ignited by incident radiation , the electric voltage that is applied to the gate electrode or the electrically conductive electrode is monitored .