Patent ID: 7728498
Filing Date: 2010-06-01
Classification: H01J

Abstract:
1. A hollow-cathode apparatus comprising: a first refractory-metal hollow tube having first and second open ends, wherein said first open end comprises a means of introducing an ionizable gas to the interior of said first tube; a plurality of concentric, refractory-metal thermal radiation shields surrounding said first tube; wherein all shields of said plurality are approximately flush with said first and second ends of said first tube; and wherein said radiation shields are adjacent to each other and support said first tube without intervening support structure between said first tube and the innermost of said plurality of radiation shields or between any adjacent pair of said plurality of radiation shields; a second refractory-metal hollow tube having first and second open ends, having a length equal to or greater than said first tube, and having an inside diameter approximately equal to the outside diameter of the said plurality of radiation shields; wherein said second tube surrounds said plurality of radiation shields without any intervening structure between the outside of said radiation shields and the inside of said second tube; wherein said first end of said second tube comprises a means of introducing an ionizable gas to the interior of said second tube and thence to the interior of said first tube; and wherein said second end of said second tube is approximately flush with said second end of said first tube; and a means for compressing said plurality of radiation shields between said first tube and said second tube thereby supporting said plurality of radiation shields by said second tube and supporting said first tube by said plurality of radiation shields and thereby further preventing leakage of said ionizable gas around said first tube.