THE THERMOCOAX CABLE AS THE MICROWAVE FREQUENCY FILTER FOR SINGLE-ELECTRON CIRCUITS

We have analyzed the possibility of using the resistive coaxial cable, Thermocoax(R) Philips as a microwave cryofilter for single electron experiments performed in a top-loading system dilution refrigerator. The biasing and signal lines made of this cable are assumed to link a single electron device kept at the lowest temperature T-d to the rf filter having a temperature T-f of several kelvin. The attenuation in a wide frequency range has been calculated and it turned out that a 40-cm-long piece of this cable with an outer diameter of 0.5 mm could drastically reduce the effect of noise from the 50 Ohm source anchored at T-f (below 25 K), making its effect comparable with the effect of the thermal fluctuations in the device for T-d approximate to 40 mK. The calculated attenuation is in reasonable agreement with the data measured at frequencies up to 18 GHz. (C) 1995 American Institute of Physics.