Figure 1

(a) Room temperature attenuation caused by conductor and dielectric losses in UT086SS-SS cable for the six modes with the lowest attenuation. All TM modes have higher attenuation. Blue squares show the data from Ref. [34] for the TEM mode. (b) Estimate of the noise photon occupation number at the mixing chamber stage and for a single coaxial cable without filtering computed as a sum of contributions caused by each of the modes: for attenuators (assuming a constant attenuation over the entire frequency range) and two different lengths of coaxial line – two lower lines, without attenuators – two higher lines. Here an ideal thermalization of coaxial line and attenuators is assumed. Shaded area denotes the average number of noise photons (\(\partial \overline{n}/\partial t = \int \mathcal{N}\,d\nu \)) exiting the coaxial line per second at the mixing chamber in the 82 to 110 GHz frequency range. See Appendix 1 and 2 for the details of calculation