A new determination of the emissivity of tungsten ribbon

J. C. DE Vos

A new determination of the spectral emissivity of tungsten has been performed in order to supply more reliable data for the use of the tungsten striplamp as a standard source of radiation. A great part of the data, used up to now for this purpose, has been obtained by extrapolation or by combination of the results of measurements carried out by different observers and relevant to tungsten of diverging origin and manufacture. The values of the emissivity of tungsten which are adopted by the principal standard laboratories show considerable differences. The present measurements have been carried out on straight-rolled tungsten strip, as used in striplamps, of well-defined composition, texture and surface condition. The emissivity was determined by comparing the spectral radiant intensity of the wall with that of a hole in a tubular blackbody to which the tungsten ribbon was shaped. The manufacture of the blackbody was based on a calculation given in a previous paper (Physica 20 (1954) 669. The accuracy achieved in the present measurements is shown to be much better than that in the earlier measurements. The results are given (Fig. 6) as a function of wavelength in the region 0.23-2.7 μ, for temperatures ranging from 1600°K to 2800°K. © 1954.

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Materials
Curve 1
Temperature, K: 1600 Wavelength Range, μm: 0.25-2.60 Geometry θ': ~0° Reported Error, %: 0.1 Composition (weight percent), Specifications and Remarks: 0. 014-0. 015 Fe, 0. 004-0. 008 Si, 0. 001-0. 003 Mn, 0. 0003-0. 0006 Mg, W balance; heated at 2400 K, treated in hydrogen, annealed at 2400 K for 100 hrs; measured in vacuum (5 x 10-6 mm Hg); data extracted from smooth curve.
Curve 2
Temperature, K: 1800 Wavelength Range, μm: 0.25-2.60 Geometry θ': ~0° Reported Error, %: 0.1 Composition (weight percent), Specifications and Remarks: Above specimen and conditions.
Curve 3
Temperature, K: 2000 Wavelength Range, μm: 0.25-2.60 Geometry θ': ~0° Reported Error, %: 0.1 Composition (weight percent), Specifications and Remarks: Above specimen and conditions.
Curve 4
Temperature, K: 2200 Wavelength Range, μm: 0.25-2.60 Geometry θ': ~0° Reported Error, %: 0.1 Composition (weight percent), Specifications and Remarks: Above specimen and conditions.
Curve 5
Temperature, K: 2400 Wavelength Range, μm: 0.25-2.60 Geometry θ': ~0° Reported Error, %: 0.1 Composition (weight percent), Specifications and Remarks: Above specimen and conditions.
Curve 6
Temperature, K: 2600 Wavelength Range, μm: 0.25-2.60 Geometry θ': ~0° Reported Error, %: 0.1 Composition (weight percent), Specifications and Remarks: Above specimen and conditions.
Curve 7
Temperature, K: 2800 Wavelength Range, μm: 0.25-2.60 Geometry θ': ~0° Reported Error, %: 0.1 Composition (weight percent), Specifications and Remarks: Above specimen and conditions.