CRYOGENIC RADIOMETER AND COMPARISON WITH THE INM CRYOGENIC RADIOMETER

An Oxford Instruments Radiox cryogenic radiometer was recently install ed at the Bureau International des Poids et Mesures (BIPM). The first measurements were aimed at characterizing the performance of the syste m. The Radiox was then compared with the cryogenic radiometer of the F rench Institut National de Metrologie (INM), a CRT LaseRad, at the BIP M by successive measurements of the power in a laser beam at two wavel engths: 647 nm and 476 nm. The radiometers differed in these measureme nts by 1,9 parts in 10(4), the uncertainties in each being smaller tha n 1 part in 10(4).