Patent ID: 8581481

Claim:
A thermionic emission assembly, comprising: a Wehnelt cap having a cap beam aperture and an interior region within which a cathode is supported by multiple filament posts, the interior region defined by a side wall that encompasses the cathode and extends between a mounting side and a top side of the Wehnelt cap, the top side including the cap beam aperture, and the cathode, in response to applied electrical energy, reaching a sufficiently high temperature to emit a beam of electrons propagating through the cap beam aperture; an anode having an anode beam aperture positioned in spatial alignment with the cap beam aperture to receive the electrons propagating through the cap beam aperture, the anode having a base portion that includes the anode beam aperture and a spacer member that extends from the base portion of the anode and encompasses the Wehnelt cap, and the anode accelerating the electrons and directing them through the anode beam aperture for incidence on a target specimen; and a ceramic base operatively connected to the mounting side of the Wehnelt cap and the spacer member of the anode to form an integrated structure of which the multiple filament posts, Wehnelt cap, and anode are component parts, and the ceramic base positioned to form a combined electrical and thermal interface separating the filament posts, Wehnelt cap, and anode, the interface thermally isolating the Wehnelt cap from the anode to allow the Wehnelt cap to rapidly reach thermal equilibrium.