Spectral emissivity of tungsten: analytic expressions for the 340-nm to 2. 6-. mu. m spectral region
To correct emission spectra a standard radiance source is often used to determine the spectral responsivity of the detection system. In the near-UV, visible, and near-IR spectral regions the most common radiance standard is a tungsten strip lamp calibrated by a standards laboratory. For day-to-day experiments where slightly less accuracy is acceptable, a less expensive uncalibrated lamp is useful. In this case, the radiant temperature T/sub r/ of the lamp is measured with an optical pyrometer, generally at a single wavelength such as 650 nm, and the source spectral radiance L(lambda) is calculated from L(lambda) = tau(lambda)epsilon(lambda,T)L/sub B/(lambda,T). The transmittance of the source is tau(lambda), the spectral emissivity is epsilon(lambda,T), and L/sub B/(lambda,T) is the spectral distribution of blackbody radiation, Planck's radiation law. To obtain the true temperature T, Wien's approximation is employed. To conveniently calibrate a system, especially one which utilizes a microcomputer, it is advantageous to have analytic expressions for the spectral emissivity of tungsten. Although Larrabee has published such expressions, they are limited to the 450-800-nm spectral region. To obtain analytic expressions from 340 nm to 2.6 ..mu..m they have used the measurements of DeVos. Although DeVos's results differ by 2% from those of Larrabee, this difference is assumed to be acceptable.
- Research Organization:
- Argonne National Lab., IL
- DOE Contract Number:
- W-31-109-ENG-38
- OSTI ID:
- 5461821
- Journal Information:
- Appl. Opt.; (United States), Vol. 23:7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
RADIATION SOURCES
CALIBRATION
EMISSION SPECTRA
EMISSIVITY
ENERGY DEPENDENCE
INFRARED RADIATION
TEMPERATURE DEPENDENCE
TUNGSTEN
ULTRAVIOLET RADIATION
ELECTROMAGNETIC RADIATION
ELEMENTS
METALS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
SPECTRA
SURFACE PROPERTIES
TRANSITION ELEMENTS
655002* - Medical Physics- Radiation Source Calibration & Standardization