Total Hemispherical Emittance of Irtran 2, 4, and 6 at Low Temperatures

E. R. Schleiger, L. A. Webb

Measurements of total hemispherical emittance of selected Irtran filters are reported for the temperature range 45°K to 312°K. Values obtained for 1-mm thick specimens are 0.38, 0.23, and 0.15 for Irtran 2, 4, and 6, respectively, at 312°K and 0.49 for Irtran 2 at 75°K and 0.35 and 0.43 for Irtran 4 and 6 at 45°K. All three specimens have emittance maxima of approximately 0.5 at intermediate temperatures. Thicker specimens have somewhat greater values. Total normal emissivity calculated from spectral normal emissivity data for Irtran 2 and 4 agree well with the experimental results. Specific heat measurements of the Irtran specimens for the same temperature range are also reported. © 1968 Optical Society of America.

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Materials
Curve 1
Temperature Range, K: 44.5-311 Composition (weight percent), Specifications, and Remarks: Irtran 6; polycrystal (1 mm thick).
Curve 2
Temperature Range, K: 75.2-311 Composition (weight percent), Specifications, and Remarks: Above specimen and conditions.
Curve 3
Temperature Range, K: 75.1-312 Composition (weight percent), Specifications, and Remarks: Irtran 6; polycrystal (2 mm thick).
Curve 4
Temperature Range, K: 75.2-311 Composition (weight percent), Specifications, and Remarks: Irtran 6; polycrystal (3 mm thick).
Curve 1
Temperature Range, K: 44.4-311 Composition (weight percent), Specifications, and Remarks: Irtran 4 (1 mm thick); polycrystal; [Authors' designation: Specimen 1].
Curve 2
Temperature Range, K: 44.4-312 Composition (weight percent), Specifications, and Remarks: Similar to above specimen and conditions except [Authors' designation: Specimen 2].
Curve 3
Temperature Range, K: 75.1-311 Composition (weight percent), Specifications, and Remarks: Irtran 4 (2 mm thick); polycrystal.
Curve 4
Temperature Range, K: 75.0-311 Composition (weight percent), Specifications, and Remarks: Irtran 4 (3 mm thick); polycrystal.
Curve 5
Temperature Range, K: 44.4-311 Composition (weight percent), Specifications, and Remarks: Irtran 4 (3 mm thick); polycrystal; [Authors' designation: Specimen 1].
Curve 6
Temperature Range, K: 44.4-312 Composition (weight percent), Specifications, and Remarks: Similar to above specimen and conditions except [Authors' designation: Specimen 2].
Curve 7
Temperature Range, K: 75.1-311 Composition (weight percent), Specifications, and Remarks: Irtran 4 (5 mm thick); polycrystal.
Curve 8
Temperature Range, K: 75.0-311 Composition (weight percent), Specifications, and Remarks: Irtran 4 (5 mm thick); polycrystal.
Curve 1
Temperature Range, K: 74.9-312 Composition (weight percent), Specifications, and Remarks: Irtran 2 (1 mm thick); polycrystal.
Curve 2
Temperature Range, K: 84.9-312 Composition (weight percent), Specifications, and Remarks: Irtran 2 (2 mm thick); polycrystal.
Curve 3
Temperature Range, K: 75.3-287 Composition (weight percent), Specifications, and Remarks: Irtran 2 (3 mm thick); polycrystal.