The low-noise read-out electronics of the 187Re experiment

The low-noise read-out electronics for the rhenium experiment is presented. We have built three source followers with two matched J-FET in cascode configuration. These are cooled at about 150 K in a thermally shielded box in the inner vacuum chamber of the dilution cryostat. The output is forwarded to a noise-matched amplifier at room temperature. In the operating conditions, the overall voltage noise density ranges between 0.8 and 1.1 nV/Hz−1/2 at 1 kHz. The 1/f noise contributes with an excess noise lower than 3 nV/ Hz−1/2 at 1 Hz.