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Proceedings Paper

Low cost enhancements of photomultiplier sensitivity
Author(s): S. W. Harmer; Peter Townsend
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Paper Abstract

Photomultiplier tubes are widely used detectors of low level light signals; however their performance is often limited, especially at long wavelengths. Input signals are reduced both by surface reflection and by transmission through the photocathode layer. Earlier methods of overcoming these weaknesses are summarized. New predictive modelling of the reflectivity and absorption reveals dependencies that are a function of angle of incidence, cathode thickness and polarization. Improvements on normal usage using extremely simple and low cost techniques are effective. These are demonstrated using retrofits that can improve the overall sensitivity of many types of photomultiplier. Examples include a simple external conical torch reflector, which has raised the efficiency of an S20 multialkali photocathode by between 20 to 10% across the blue to red spectral range. A second example, of a semi-cylindrical glass coupler, improved the absorption efficiency by exploiting 60 degree, rather than normal incidence of the light. Enhancements are up to 500% at longer wavelengths. Such gains are particularly valuable as this is the region of lowest quantum efficiency for the standard operation of the tubes.

Paper Details

Date Published: 17 January 2011
PDF: 5 pages
Proc. SPIE 7747, 16th International School on Quantum Electronics: Laser Physics and Applications, 77470A (17 January 2011); doi: 10.1117/12.881090
Show Author Affiliations
S. W. Harmer, Manchester Metropolitan Univ. (United Kingdom)
Peter Townsend, Univ. of Sussex (United Kingdom)

Published in SPIE Proceedings Vol. 7747:
16th International School on Quantum Electronics: Laser Physics and Applications
Tanja Dreischuh; Dimitar Slavov, Editor(s)

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