Patent ID: 7382862

Claim:
An x-ray source device, comprising: a) an evacuated dielectric tube having an outer diameter and a constant inner diameter; b) an anode, disposed at an end of the tube, including a material configured to produce x-rays in response to impact of electrons; and c) a cathode, disposed at an opposite end of the tube opposing the anode, including a cathode element configured to produce electrons accelerated towards the anode in response to an electric field between the anode and the cathode; d) an interface formed between the cathode and the end of the tube, the interface being disposed between the cathode and the anode; e) the interface at the outer diameter of the tube being closer to the anode than the interface at the inner diameter of the tube; and f) an annular flange, extending from the cathode toward the anode within the tube, having a smaller diameter than an inner diameter of the evacuated tube to form an annular space between the flange and the evacuated tube, and extending closer to the anode than the interface between the cathode and the tube.