Patent ID: 8253315

Claim:
A method for regulating a crossover point of an electron beam, the method comprising: arranging an electrode arrangement in a housing, the electrode system comprising an anode electrode system, a cathode electrode system and a near-cathode electrode assembly spaced apart from the cathode electrode by a cavity; generating an electron beam using the cathode electrode system and positioning the anode electrode system relative to the cathode electrode system such that the generated electron beam passes through an opening in the anode electrode system; providing the anode electrode system with a first anode portion extending radially outward from the opening and a second substantially cylindrical anode portion extending axially outward from the first anode portion in a direction toward the cathode electrode system, the second substantially cylindrical anode portion being radially outward of the first anode portion; providing the near-cathode assembly with a first portion adjacent to the cathode electrode system and a second substantially cylindrical portion extending axially outward from the first portion in a direction toward the anode electrode system, the second substantially cylindrical portion being radially outward of the first portion; and regulating a position of a crossover point on a longitudinal axis of the electrode arrangement by varying dimensions of the second substantially cylindrical portion of the anode electrode system and the second substantially cylindrical portion of the near-cathode electrode assembly.