| CPC H01J 37/32623 (2013.01) [H01J 37/32642 (2013.01); H01J 37/32715 (2013.01); H01L 21/681 (2013.01); H01J 37/32633 (2013.01)] | 10 Claims |

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1. An apparatus comprising:
an annular member arranged along a first plane;
N first members extending from an outer diameter of the annular member perpendicularly to the first plane, where N is an integer greater than two, wherein a first portion of each of the N first members extends above the first plane, and wherein a second portion of each of the N first members extends below the first plane; and
N second members extending radially outward from the second portions of the N first members along a second plane that is parallel to the first plane, wherein each of the N second members lies between a different pair of the N first members.
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