Method and arrangement for an X-ray source

An X-ray source comprising:

• an electron source for providing an electron beam, the electron source comprising a cathode, a Wehnelt, and an anode;
• an electron optic arrangement configured to deflect and focus the electron beam towards a target for generation of X-ray radiation;
• an arrangement for determining a quantity indicative of a width of the electron beam;
• and
• a controller operatively connected to the electron source, the electron optic arrangement, and the arrangement for determining the quantity indicative of the width of the electron beam, the controller configured to:
• compute a quantity dependent on a divergence of the electron beam at an entrance of the electron optic arrangement based on the quantity indicative of the width of the electron beam;
• and
• apply a bias voltage to the Wehnelt to compensate for aging of the cathode, such that the quantity dependent on the divergence of the electron beam at the entrance of the electron optic arrangement is adjusted towards a desired value, wherein the bias voltage is positive relative to a cathode voltage.