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X-ray focusing with 11-μm square-pore microchannel plates

Focused x-ray images are reported for 21 X 21mm2 microchannel plate (MCP) optics having an eleven micron square-channel geometry. These are the smallest channel size square-pore MCPs yet evaluated. Because the limiting focal spot size in such optics is twice the channel width, their construction represents a significant advance towards focusing elements capable of very high intensification. The MCPs were fabricated with channel length- to-diameter ratios of 40 to 1 and 75 to 1; with an open area fraction of 85%. X-ray images were first obtained at 0.28keV and 1.74keV using a planar MCP geometry with a zero degree bias angle. These images indicate that subtle deviations from an ideal square channel geometry (i.e. vertex 'radiusing') can strongly influence the focal spot structure. Finally, one of the MCPs was spherically 'slumped' to a 1m radius and remeasured in x-rays, demonstrating for the first time the operation of a slumped square-channel MCP.