Microchannel Plate, High Resolution Imager, Chandra

This microchannel plate formed part of the High Resolution Camera (HRC) on the Chandra X-ray observatory. The HRC consists of two components: microchannel plates (upper square) feeding a signal to a cross-grid detector (lower square). A set of two 10 cm (4-inch) square microchannel plates sitting above the grid completes the detector system. The two components are separated to make them both visible for display. Normally they would be nearly in contact.

X-rays collected by a set of nested grazing incidence Wolter mirrors are focused onto the array of microchannel plates. This x-ray photon flux strikes the cluster of 69 million lead-oxide coated glass tubes (each are only 10 micrometers in diameter and just over a millimeter long). When an x-ray photon hits the side of one of these tubes, an electron is emitted. The resulting charge is then amplified by orders of magnitude by a cascade effect within the tube which is held at an electrical potential. The electron flux out the bottom of the microchannel plate impinges onto the cross grid detector. The location of charges on the grid is processed to build an image of the source of X-rays. The resolution of this system, a combination of the scale of the collecting aperture focal plane (the telescopic resolution), the sizes of the microchannel plates and the grid spacing of the wires, is on the order of a half second of arc, which is comparable to the best optical telescopes on Earth during periods of excellent seeing, or atmospheric stability. Images from the HRC on Chandra have provided data on high energy events in the universe such as the accretion of matter by supermassive black holes. This HRC was built at the Smithsonian Astrophysical Observatory.