| 摘要 |
A miniature x-ray unit includes a first electrical node, a second electrical node and an insulating material. The first and second nodes are separated by a vacuum gap. The first node includes a base portion and a projecting portion, wherein the projecting portion and the second node are surrounded by an x-ray transmissive window through which x-rays exit the unit. The insulating material coaxially surrounds the base portion of the first node such that the insulating material is recessed from the vacuum gap, and the insulator does not extend into the vacuum gap. Recessing the insulating material from the vacuum gap decreases the likelihood that the insulator will electrically break down due to the accumulation of electrical charge, and/or the accumulation of other materials on the surface of the insulator. In a preferred embodiment, the first node is an anode and the second node is a cathode. Alternatively, the first node may be the cathode and the second node may be the anode. The cathode is preferably a cold gated field emitter array (FEA) which provides a electron current having a magnitude that is sufficient to satisfy the time constraints on x-ray dose delivery.
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