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11 October 2004 Next generation microchannel plate detector technologies for UV astronomy
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Abstract
Objectives for the next generation of UV microchannel plate astronomical detectors include development of efficient photocathodes, including gallium nitride (GaN), and diamond, and optimization of silicon based MCPs. Goals include the development of GaN photocathodes in sealed tube and open detectors with >50% DQE in the UV (>110nm), with tunable cutoffs around 400nm. Activated diamond photocathodes with >40% DQE @ >110nm, cutoffs >200nm, and their application to Si MCPs are also of interest. GaN photocathodes have been developed with efficiencies >60% and cutoffs of ~380nm. Diamond photocathodes with ~40% efficiency at 40nm have been achieved, and Cs activation shows promise for high efficiencies (>20% at 180nm). Silicon based MCPs have qualities that make them preferable to glass MCPs (very low intrinsic background, low fixed pattern noise). Large 8cm Si MCPs have been fabricated with large open area ratio, good lifetest data has been obtained, and techniques for coating high temperature/robust photocathode layers have been explored. We also report on a novel MCP imaging readout scheme, the Cross Strip (XS). This anode uses charge division, and centroiding, of microchannel plate charge signals detected on two orthogonal layers of sense strips to encode event X-Y positions, time tags and signal amplitudes. The XS anode is fabricated as a multilayer ceramic/metal structure that can be implemented in a footprint that is not much larger than the active area, and may accommodate formats up to 10cm x 10cm. To date the XS scheme has been tested with a 32 mm x 32 mm prototype anode and customized electronics. This has demonstrated excellent resolution (<7μm FWHM, ~5k x 5k resolution elements (limited by the MCP pore size)) using low MCP gain (~4 x 105), with anode & electronics resolution of ~3μm FWHM.
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Oswald H. W. Siegmund, John V. Vallerga, Jason B. McPhate, and Anton S. Tremsin "Next generation microchannel plate detector technologies for UV astronomy", Proc. SPIE 5488, UV and Gamma-Ray Space Telescope Systems, (11 October 2004); https://doi.org/10.1117/12.562696
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