Broadband Shot Noise Measurement System at Low Temperature for Noise Thermometry Using a Tunnel Junction

We report our development of a broadband shot noise measurement experiment at Korea Research Institute of Standards and Science for noise thermometry. A precision RF measurement setup in the frequency range near 1 GHz has been installed in a He-3 refrigerator. For noise thermometry, we fabricated an Al-AlO
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-Al tunnel junction by the double-angle shadow evaporation technique as a source of noise. Temperature measurement was performed from 0.3 K to room temperature. The influence of each RF component was analyzed and tested to stabilize the measurement system. We compare two different diode detectors for RF power measurement. We describe the thermal anchoring scheme and the influence of tunnel junction imperfections.