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Investigation of image nonlinearities in a photon counting image tube
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Paper Abstract

The image linearity of a charge division position readout anode, for instance, a Wedge and Strip Anode (WSA), is controlled by several factors. In addition to the drift field uniformity and pattern geometry requirements, linearity can be affected by the surface characteristics of the anode itself. We have undertaken experiments to establish the mechanisms which lead to non-linear response and suggest ways to avoid it. We present measured image non linearity of image intensifier tubes using two different types of charge division position readout anode; the Wedge and Strip anode (WSA) and the Spiral Anode (SPAN) devices. Both intensifier tubes were manufactured by DEP bv., Holland and utilize S20 or Caesium Telluride semi- transparent photocathodes on Magnesium Fluoride, Fused Silica or Calcium fluoride windows, proximity focused to a microchannel plate (MCP) stack. All detector variants built thus far use a stack of three MCPs in a Z configuration. We have undertaken experiments using a de- mountable detector of similar design but without window or photocathode. The role of secondary electrons produced on the anode in charge redistribution was investigated by using an intermediate conductive grid of high open area between the MCP and anode. The grid was used to define the electric field in a region just above the anode in order to either suppress the range of the anode secondary electrons, or prevent them from returning to the anode by collecting them on the grid. We present some preliminary results from these experiments and suggest modifications to the intensifier design to maximize the detector performance.

Paper Details

Date Published: 13 September 1994
PDF: 8 pages
Proc. SPIE 2209, Space Optics 1994: Earth Observation and Astronomy, (13 September 1994); doi: 10.1117/12.185295
Show Author Affiliations
Jonathan S. Lapington, Univ. College London (United Kingdom)

Published in SPIE Proceedings Vol. 2209:
Space Optics 1994: Earth Observation and Astronomy
Guy Cerutti-Maori; Philippe Roussel, Editor(s)

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