RF TRANSMISSION-LINE FOR CRYOGENIC APPLICATIONS

We have fabricated a miniature coaxial transmission line with characte ristics suitable for cryogenic applications. The materials were chosen for reduced thermal conduction and improved high-frequency signal tra nsmission, and for mechanical properties allowing easy connector assem bly and forming into complicated cryogenic structures. Comparing with the best commercial line, made with stainless steel outer conductor of twice larger diameter, the heat conduction integral of our line at 10 0 K temperature is slightly lower, while the signal attenuation is red uced by an factor of 1.34. Defining the figure of merit as a product o f the signal attenuation per unit length and the heat conduction integ ral, our line is superior to all commercial cryogenic lines above 80 K by a factor varying from 1 to more than 20, and allows much easier so ldering and bending. Further improvements of the line are also briefly discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.