Resistance bridge based on the Cryogenic Current Comparator in a transportdewar

An optimized resistance bridge based on the Cryogenic Current Comparator (C CC) with SQUID readout has been developed. The bridge can be used for routi ne secondary resistance calibrations as well as for the traceability of 100 Omega to the quantum Hall resistance. The CCC-SQUID, shielding and wiring are mounted in a telescopic insert, fitted in a low-evaporation Omega rate, transportable liquid He dewar, with an autonomy of around 1 month. A diffe rence compensator method is used to balance the bridge. A new, more reliabl e and self-standing bridge electronics has been fabricated and tested. An u ncertainty in the comparison of resistors at least one order of magnitude b etter than room temperature CCs is expected.