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Microchannel plates (MCPs) are solid state electron multipliers consisting of millions (10E5 - 10E7 channels/cm2) of microscopic (typically 10 - 25 microns) continuous dynode electron multipliers all fused together in a solid array. Fabricated from an alkali doped, reduced lead silicate glass, microchannel plates are known as excellent high gain, low noise, two dimensional detectors of charged particles and electromagnetic radiation. The microchannel plate manufacturing process begins with a series of glass fiber draws in which an acid soluble core glass is combined with an alkali soluble clad tube and drawn to form a mono fiber. Mono fibers (typically 2,000 to 4,000) are then assembled into a hexagonal preform called a multi wrap. The preform is again drawn to form a multifiber producing an overall feature size reduction of typically 2000:1. The multi fibers then become the basic building blocks. Hundreds of multi fibers are next arranged to form the active area of the MCP. High temperature vacuum fusion is then used to fuse the multi fibers together with the solid glass border (if used) to form a billet or boule. Standard semiconductor slicing, lapping and polishing techniques are used to prepare the wafers for chemical processing. Chemical processing consists of etching open the microchannels, adjusting the open area ratio (OAR) and preparing the silica rich emissive layer. A hydrogen firing is used to reduce the lead glass making it electrically conductive. Finally a thin (typically 2,000 to 3,000 angstroms) film of metalization is vacuum deposited on both sides of the microchannel plate to electrically connect each of the channels in parallel, therefore ensuring the same potential is applied to each channel. Microchannel plates operate on the principle of secondary electron emission. In operation primary events enter the input side of the MCP and collide with the channel wall. If the primary event has sufficient energy, secondary electrons will result. The resultant secondary electrons will be accelerated down the channel by the electric field produced when a high voltage is applied between the electrode faces. Additional collisions with the channel walls produce still further secondary electrons.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. |
