lamp tube has the same inner diameter along the pin cathode as in the discharge region z is measured from the cathode working surface to the point where the inner diameter of the material surrounding the pin cathode changes z u2267 0 is valid for all of the examples shown in fig1 3 in fig6 b z can also be negative z lt x is valid according to the invention whereas z x corresponds to the pin cathode lamp having ignition characteristics which need to be improved in the example according to fig1 the outer diameter and the inner diameter a of the quartz glass tube are smaller in the region of the cathode pin 1 in addition the wall thickness in the region of the cathode pin 1 is greater than in the main part left side in fig1 of the quartz tube such a configuration can be achieved easily by the connection joint 2 of two quartz tubes preferably the outer diameter of one tube corresponds approximately to the inner diameter of the other tube in addition the wall thickness of the tube with the smaller diameter is preferably greater the smaller diameter does not have to correspond to the total length x of the cathode pin 1 it can be shortened by the set parameter which is preferably small in comparison with x preferably the length of the lamp equals about 10 to 40 cm the preferred length of the pin cathode equals approximately about 1 to 3 cm and the.