Characterisation of dry cold load for ALMA front-end verification

Several techniques for measuring the radiometric temperature (brightness) of a refrigerated dry calibration load for ALMA front-end verification are presented. The brightness of the load including the effects of the cryostat window is estimated using different techniques and compared at frequencies up to 1 THz. Measured results are compared with those obtained by a conventional calibration technique using a cooled receiver. The brightness estimated by the aforementioned methods show good agreement at lower ALMA bands (below 400 GHz) with increased deviation at higher frequencies.