@inproceedings{HartmannTaubertFischer1999,
  author    = {Hartmann, J{\"u}rgen and Taubert, Dieter Richard and Fischer, Joachim},
  title     = {Characterization of the double-heatpipe blackbody LABB for use at temperatures below 500 C},
  booktitle = {Proceedings of TEMPMEKO (99)},
  editor    = {Dubbeldam, J.F. and de Groot, M.J.},
  publisher = {IMEKO},
  address   = {Delft},
  pages     = {511 -- 516},
  year      = {1999},
  abstract  = {The large area double-heatpipe blackbody (LABB) used for comparing thermodynamic temperatures with the International Temperature Scale of 1990 (ITS-90) at temperatures higher than 600 C is based on two sodium heat pipes. The lowest temperature at which the sodium heat pipes work properly is strongly correlated to the onset of sodium evaporation. This is expected for temperatures well above 500 C. Planning to use the LABB for extending the comparison of thermodynamic temperatures with the ITS-90 to temperatures as low as possible, we measured the isothermal behaviour of the blackbody cavity starting at heatpipe temperatures of 400 C. The temperature of the cylindrical part of the cavity was measured with a standard platinum resistance thermometer (SPRT) sensing the bottom of the cavity and up to three quarter of the cylindrical part of the cavity. The obtained temperature profiles are well explained assuming the occurrence of two superimposing effects: a real nonisothermal behaviour of the LABB for temperatures below 500 C and a cooling of the SPRT caused by radiation loss through the aperture of the cavity. Applying a Monte-Carlo simulation we calculated the emissivity of the LABB at different heatpipe temperatures below 600 C using the obtained non-isothermal temperature distribution at the cylindrical walls. It was found that even at temperatures as low as 415 C the accuracy of the LABB is sufficient for comparison of thermodynamic temperatures and the ITS-90.},
  language  = {en}
}