Thermal and Electrical Performance Study of Cold-Finger ³He Cryostat in Precision Measurement of Quantum Hall Resistance and Single-Electron Current

The performance of our newly constructed cold-finger cryostat is investigated for quantum Hall resistance (QHR) and single-electron pump (SEP) devices. The cryostat features a vacuum-sealed sample chamber (SC) attached to a 0.3 K plate inside the inner vacuum can. The SC is designed to accommodate both the SEP and the QHR devices with a shielding partition between them. The measured QHR in the chamber approaches the nominal value for filling factor 2 within 20 parts in 109. The white-noise level of the SEP module, as obtained from the Allan deviation data, is 4.5 fA/ $\sqrt {\mathrm{ Hz}}$ . We also investigated the thermometry of the SC either under vacuum or filled with 3He gas. We calculated the thermal conductivity of the different heat conduction channels in the sample holder and found the dominant channel to be through the chip carriers not signal lines.