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Proceedings Paper

Subnanosecond intensifier gating using heavy and mesh cathode underlays
Author(s): Stan W. Thomas; Alex R. Shimkunas; Phillip E. Mauger
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Paper Abstract

Irising time of microchannel plaie intensifiers with quartz cathode windows has been reduced to less than 100 ps. This is achieved by application of a metal underlay to reduce cathode substrata resistance. The first approach uses a 50%-transmissive Uniform nickel heavy underlay, while the second approach uses a 96%-transmissive nickel mesh. For the heavy underlay, approximately 5 nm of nickel is evaporated over the cathode side of the quartz window. For the mesh underlay, approximately 750 nm of nickel is sputtered onto the window and coated with photoresist, which is exposed through a mask of 100-micron-square spaces defined by 3.5-micron-wide lines. The photoresist is developed and washed off, exposing the nickel covering the square areas. At this point, photoresist still covers the nickel over the 3.5-micron-wide wires, protecting them when the exposed nickel covering the squares is etched away. Removal of the remaining photoresist leaves only the nickel wires, which have been reduced to 2 microns in width due to sideways etching during removal of the squares. As a prototype effort, Lawrence Livermore National Laboratory (LLNL) purchased two 1 8-mm heavy underlay tubes from Hamamatsu Photonics and formed a mesh underlay on faceplates which Hamamatsu used for construction of two additional tubes. Measurements of irising time were made on these four tubes. Irising is characterized by a bright ring, seen first at the edge as it propagates toward the center. The time lag is caused by the distributed time constant of the substrata resistance and the cathode-to-MCP capacitance. Since the capacitance is fixed by restraints of tube geometry, our goal was to reduce the distributed resistance sufficiently to achieve sub-nanosecond irising times. Testing showed no irising on one tube of each type of underlay. With these encouraging results, LLNL and Nanostructures refined the mesh application technology, and LLNL procured eight mesh tubes from ITT using meshes formed by Nanostructures. An additional 8 tubes with a 50% transmissive heavy underlay were procured from Hamamatsu. Testing of these tubes also showed no detectable irising, which leads us to conclude that tubes can be made with irising clearly faster than the time resolution of our measurement system, which we estimate to be less than 50Ps.

Paper Details

Date Published: 1 April 1991
PDF: 9 pages
Proc. SPIE 1358, 19th Intl Congress on High-Speed Photography and Photonics, (1 April 1991); doi: 10.1117/12.24084
Show Author Affiliations
Stan W. Thomas, Lawrence Livermore National Lab. (United States)
Alex R. Shimkunas, Nanostructures, Inc. (United States)
Phillip E. Mauger, Nanostructures, Inc. (United States)

Published in SPIE Proceedings Vol. 1358:
19th Intl Congress on High-Speed Photography and Photonics
Peter W. W. Fuller, Editor(s)

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