Evaluation of the Improved 10 mA and 10 V Reference and Transfer Standard for the High DC Current Test and Calibration Infrastructure at CERN

An improved variant of the 10mA and 10V dc reference and transfer standard developed for use at CERN is presented. The device achieves very low noise levels at sub-Hz frequencies, which enhances the capability for performance testing of direct-current current transformers (DCCTs) for the High Luminosity Large Hadron Collider project, where good short- and mid-term stability is essential. To characterize the standard, the 10V and 10mA outputs of a single unit were tested simultaneously against two Programmable Josephson Voltage Standards at PTB-Braunschweig. The measurements show negligible low-frequency noise contribution from the internal voltage-to-current conversion, while demonstrating Allan deviation better than 0.01 μA/A on a time scale up to one day, reaching down to few nA/A for shorter measurement times. The operation of multiple paralleled units is also presented as a viable way to further decrease both current and voltage noise.