The thermocoax cable as the microwave frequency filter for single electron circuits

Abstract

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 Td to the rf filter having a temperature Tf 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 Ω source anchored at Tf (below 25 K), making its effect comparable with the effect of the thermal fluctuations in the device for Td≊40 mK. The calculated attenuation is in reasonable agreement with the data measured at frequencies up to 18 GHz.