Patent ID: 8084930

Claim:
An apparatus for focusing electron beams, said apparatus comprising: a housing comprising a first interior portion and a second interior portion; an electrode system disposed in said first interior portion, said electrode system comprising a cathode assembly and at least one anode assembly; and an insulator arranged between said first interior portion and said second interior portion, said at least one anode assembly being arranged between said cathode assembly and said insulator, said cathode assembly generating an electron beam that passes through an opening in each of said at least one anode assembly and then through an opening in said insulator into said second interior portion of said housing, said electrode system further comprising a near cathode assembly arranged alongside said cathode assembly, said cathode assembly comprising a front surface and a side surface and said near cathode assembly comprising a front surface and a side surface, said side surface of said near cathode assembly being spaced apart from said side surface of said cathode assembly by a cavity, said cathode assembly and said near cathode assembly having substantially the same electrical potential, said cathode assembly further comprising a cathode having a front surface with a flat form and said near-cathode assembly comprises a flat part that is at the same level as said flat front surface of said cathode, a curvilinear part contiguous with said flat part and situated radially outward from said flat part, and a cylindrical part contiguous with said curvilinear part and situated radially outward from said curvilinear part, said near-cathode assembly being spaced apart from said cathode assembly by the cavity.