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A quality monitor and monitoring technique employing optically stimulated electron emissionA light source directs ultraviolet light onto a test surface and a detector detects a current of photoelectrons generated by the light. The detector includes a collector which is positively biased with respect to the test surface. Quality is indicated based on the photoelectron current. The collector is then negatively biased to replace charges removed by the measurement of a nonconducting substrate to permit subsequent measurements. Also, the intensity of the ultraviolet light at a particular wavelength is monitored and the voltage of the light source varied to maintain the light a constant desired intensity. The light source is also cooled via a gas circulation system. If the test surface is an insulator, the surface is bombarded with ultraviolet light in the presence of an electron field to remove the majority of negative charges from the surface. The test surface is then exposed to an ion field until it possesses no net charge. The technique described above is then performed to assess quality.
Document ID
19950018884
Acquisition Source
Legacy CDMS
Document Type
Other - Patent
Authors
Yost, William T. (NASA Langley Research Center Hampton, VA, United States)
Welch, Christopher S. (College of William and Mary Gloucester Point, VA., United States)
Joe, Edmond J. (AS&M, Inc. Hampton, VA., United States)
Hefner, Bill Bryan, Jr. (AS&M, Inc. Hampton, VA., United States)
Date Acquired
August 16, 2013
Publication Date
February 28, 1995
Subject Category
Quality Assurance And Reliability
Accession Number
95N25304
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
Patent
US-PATENT-5,393,980|NASA-CASE-LAR-15063-1-CU
Patent Application
US-PATENT-APPL-SN-060617

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