title: Electronic and optical moi? Interference with microchannel plates: artifacts and benefits.
abstract: The spatial resolution of position-sensitive detectors that use stacks of microchannel plates (MCP's) with high-resolution anodes can be better than 20-microm FWHM [Proc. SPIE 3114, 283-294 (1997)]. At this level of accuracy, channel misalignments of the MCP's in the stack can cause observable moiré interference patterns. We show that the flat-field detector response can have moiré beat pattern modulations of as great as approximately 27% with periods from as small as a few channel diameters to as great as the size of a MCP multifiber. These modulations, however, may be essentially eliminated by rotation of the MCP's or by a mismatch of the channel sizes. We also discuss how the modulation phenomena can be a useful tool for mapping the metric nonlinearities of MCP detector readout systems. Employing the optical moiré effect, we demonstrate a simple, but effective, technique for evaluation of geometrical deformations simultaneously over a large MCP area. For a typical MCP, with a 60-channel-wide multifiber, we can obtain accuracies of 1.2 mrad for multifiber rotations and twists and 35/(L/p) mrad for channel-long axis distortions (where L/p is MCP thickness to interchannel distance ratio). This technique may be used for the development of MCP x-ray optics, which impose tight limitations on geometrical distortions, which in turn are not otherwise easily measurable with high accuracy.
authors.affiliation: Experimental Astrophysics Group, Space Sciences Laboratory, University of California at Berkeley, Berkeley, California 94720, USA.
authors.forename: A S
authors.initials: AS
authors.lastname: Tremsin
authors.forename: O H
authors.initials: OH
authors.lastname: Siegmund
authors.forename: M A
authors.initials: MA
authors.lastname: Gummin
authors.forename: P N
authors.initials: PN
authors.lastname: Jelinsky
authors.forename: J M
authors.initials: JM
authors.lastname: Stock