15 October 1997 Quantum efficiency and spatial resolution of microsphere plates stacked with microchannel plates
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Abstract
The principles and a detailed study of the basic operation of a relatively new type of electron multipliers -- microsphere plates (MSPs) has been reported recently. In this paper we extend these studied by presenting measurements of bare MSP quantum efficiency at incoming radiation wavelength range of 250 - 1450 angstrom. MSP efficiency appeared to be by an order of magnitude lower than that of bare microchannel plates (MCPs), having maximum of about 1% at 350 - 900 angstroms. We also extend the previous investigation of angular dependence of MSP gain and detection efficiency to an angular range of 90 plus or minus 40 degrees, when no gain depression was observed, while detection efficiency varied only by approximately 7%. The spatial charge cloud distribution of microsphere plates was measured with the help of a phosphor screen, showing that the dependence is quasi-symmetrical although featuring granular formations caused by the intrinsic structure of the plate. We also present a detailed study of combined MCP/MSP stack operation, suggested earlier by L. B. C. Worth et al. The gain of the stack was measured to be relatively high (108) with pulse height distribution FWHM values as low as approximately 62% and dark noise count rates less than 0.1 counts cm-2s-1, limited by the front MCP. The spatial resolution reached the best value of about 80 micrometers with a 250 micrometer gap between the plates and an accelerating bias in the gap of 50 V. The counting rate capabilities of this hybrid stack are much better (no gain drop was observed at count rates of 3.3 (DOT) 105 counts cm-2s-1) than those of purely MSP detector (103 counts cm-2s-1).
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Anton S. Tremsin, Anton S. Tremsin, Sharon R. Jelinsky, Sharon R. Jelinsky, Oswald H. W. Siegmund, Oswald H. W. Siegmund, } "Quantum efficiency and spatial resolution of microsphere plates stacked with microchannel plates", Proc. SPIE 3114, EUV, X-Ray, and Gamma-Ray Instrumentation for Astronomy VIII, (15 October 1997); doi: 10.1117/12.283774; https://doi.org/10.1117/12.283774
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