Cable noise investigations for high-accuracy measurements of small direct currents

Single-electron experiments may provide possible realizations of the future SI ampere if they are performed at high accuracy corresponding to 0.1 ppm uncertainty or better. However, excess noise in the cabling between the room temperature equipment and the cryogenic quantum current source, typically mounted inside a refrigerator setup, limits the achievable accuracy. We present amplifier tools for precise noise investigations and first results of measurements on different cable specimens as starting point for a systematic study on the topic.