Abstract: An x-ray tube includes an anode, a cathode, and an electrode disposed in an evacuated envelope. The electrode is positioned such that the electrode is remote from an area in immediate proximity to the envelope. An electric field defined by electrode is of sufficient strength such that arcing preferentially occurs between the electrode and the anode as opposed to occurring between the cathode and anode. The electrode is further situated such that metal sputtered from the electrode substantially falls in a define region on the anode and serves as an active getter for pumping gas from the envelope. The electrode is composed of an active metal which, upon being passively heated by the anode, also acts as a getter material to aid in pumping gas from the envelope.

Abstract: An X-ray tube comprising an evacuated envelope having therein a plurality of anode target materials suitably disposed for bombardment by respective electron beams, either simultaneously or alternatively, each of the electron beams being independently variable with respect to one another.