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Measurement and calculation of the emissivity of a high-temperature black body

S Galal Yousef, P Sperfeld and J Metzdorf

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The emissivity of a high-temperature black body, used for the realization of the spectral irradiance scale at the Physikalisch-Technische Bundesanstalt (PTB), has been examined experimentally by direct reflection measurements. Measurements at two laser wavelengths show a significant dependence on temperature of the normal effective emissivity of the cavity. The emissivity is very close to the ideal value of unity at temperatures above 2000 K. Preliminary experiments on the reflectance and emissivity of graphite, the material from which the black-body cavity is made, were carried out at room temperature. Using the results of these measurements as input parameters for Monte Carlo calculations of the effective emissivity of the cavity, good agreement with the measurements is obtained.


PACS

07.60.Dq Photometers, radiometers, and colorimeters

02.50.Ng Distribution theory and Monte Carlo studies

07.60.Hv Refractometers and reflectometers

42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

42.60.Da Resonators, cavities, amplifiers, arrays, and rings

02.70.Uu Applications of Monte Carlo methods

Subjects

Computational physics

Condensed matter: electrical, magnetic and optical

Instrumentation and measurement

Optics, quantum optics and lasers

Dates

Issue 5 (October 2000)



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