Compact, inexpensive coaxial terminations and wiring for low temperature RF applications

We have examined a promising family of radio frequency coaxial connectors (the SSMCX range) suitable for use at low temperatures. We describe the measured characteristics of these connectors in typical arrangements using lossy Cooner stainless steel inner and outer (braided) coaxial cable and other specialty low temperature coaxial cables including Beryllium Copper (BeCu) outer and inner conductors, Copper Nickel (CuNi) outer and Niobium–Titanium (NbTi) superconducting inner conductors, and Nb outer/NbTi inner conductor (homemade) cables. Of these, the BeCu coaxial cable proves to rank among the smallest losses consistently from 300 K down to 4 K. We also characterize Copper, BeCu, and CuNi clad NbTi braided twisted pair “looms”, demonstrating that CuNi–NbTi is the most practical choice due to minimal heat leak.

► Electrical properties of BeCu coax make it invaluable for most low-temp RF setups.
► NbTi/Nb coax useful below Tc, having lowest losses measured at liquid He temp.
► Due to small heat leak, CuNi clad NbTi is most effective twisted pair loom choice.
► SSMCX family of coax connectors prove to be a viable option for low-temp standard.