Evaluation of Thermal Leakage in WR-5 Waveguide Calorimeter

In this study, an accurate calorimeter was developed for measuring radio-frequency power in the WR-5 waveguide band (140–220 GHz). To demonstrate a high-precision calorimetric measurement, the influence of heat leakage in an adiabatic waveguide (AW) of the calorimeter was investigated. Thermal responses by heat generation due to loss of the AW were independently measured using a gold foil shield. The index $\rho$ that represents the ratio of heat leakage to the total generated heat in the AW was estimated by analyzing the thermal response and scattering parameters of the AW. As a result, the index $\rho$ was found to be 0.50 ± 0.05 in the frequency range of 140–220 GHz.