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Photodiode-Based, Passive Ultraviolet DosimetersSimple, passive instruments have been developed for measuring the exposure of material specimens to vacuum ultraviolet (VUV) radiation from the Sun. Each instrument contains a silicon photodiode and a coulometer. The photocharge generated in the photodiode is stored in the coulometer. The accumulated electric charge measured by use of the coulometer is assumed to be proportional to the cumulative dose of VUV radiation expressed in such convenient units as equivalent Sun hours (ESH) [defined as the number of hours of exposure to sunlight at normal incidence]. Intended originally for use aboard spacecraft, these instruments could also be adapted to such terrestrial uses as monitoring the curing of ultraviolet-curable epoxies. Each instrument includes a photodiode and a coulometer assembly mounted on an interface plate (see figure). The photodiode assembly includes an aluminum housing that holds the photodiode, a poly(tetrafluoroehylene) cosine receptor, and a narrow-band optical filter. The cosine receptor ensures that the angular response of the instrument approximates the ideal angular response (proportional to the cosine of the angle of incidence). The filter is chosen to pass the ultraviolet wavelength of interest in a specific experiment. The photodiode is electrically connected to the coulometer. The factor of proportionality between the charge stored in the coulometer and ultraviolet dosage (in units of ESH) is established, prior to use, in calibration experiments that involve the use of lamps and current sources traceable to the National Institute of Standards and Technology.
Document ID
20110020542
Acquisition Source
Marshall Space Flight Center
Document Type
Other - NASA Tech Brief
External Source(s)
http://www.techbriefs.com/component/content/article/309
Authors
Vaughn, Jason A. (NASA Marshall Space Flight Center Huntsville, AL, United States)
Gray, Perry (Micro Craft, Inc. Huntsville, AL, United States)
Date Acquired
August 25, 2013
Publication Date
September 1, 2004
Publication Information
Publication: NASA Tech Briefs, September 2004
Subject Category
Man/System Technology And Life Support
Report/Patent Number
MFS-31316-1
Distribution Limits
Public
Copyright
Public Use Permitted.

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IDRelationTitle20110020517Collected WorksNASA Tech Briefs, September 2004
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