Temperature dependent polarization of the thermal radiation emitted by thin, hot tungsten wires

Abstract

We report measurements of the temperature $T$ dependence of the linear polarization $⟨P⟩$ of the thermal radiation emitted by thin, incandescent tungsten wires. We investigated an interval ranging from a little above room temperature up to melting, $T_m\approx 3700$K. These are the first measurements in such wide a range. We found that $⟨P⟩$ decreases with increasing $T.$ We obtained a satisfactory agreement with the theoretical predictions based on the Kirchhoff's law by using a Drude-type formula for the optical properties of tungsten. The validity of such formula is assessed in literature for $T\le 2400$K and for wavelengths in the range from visible up to $\lambda \approx 2.6\mu$m. We have extended the range of validity of this formula for $T$ up to $T_m$ and for $\lambda$ up to $\approx 12\mu$m.

arXiv comment35 pages, 28 figures, to be submitted to Phys. Rev. B