Miguel Cerqueira Bastos

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.

This article explores the current and future roles of power electronics converters in particle accelerators, highlighting key challenges and requirements. Specific examples of converter designs and their associated challenges for upcoming large-scale accelerator projects are also presented.

A new digitizer, the HPM7177, which is a fundamental component of the signal chain for high precision measurement of particle accelerator magnet currents, is presented. It was designed to meet the unprecedented performance requirements for new 14 kA and 18 kA power converters for the High Luminosity Large Hadron Collider project at CERN, particularly in terms of low-frequency noise and stability. To determine accurately the performance of the digitizer, which is on a similar level as state-of-the-art classical metrological equipment, we carried out a thorough characterization using the programmable Josephson voltage standard (PJVS) at PTB-Braunschweig. At its nominal full scale of 10 V, the digitizer has a white noise level of -1/2 , 1/ f noise floor ≈ 7 × 10 ^-8 V, and a 12-hour peak-to-peak stability better than 2 μV or 0.2 partspermillion(ppm). The static non-linearity from 0V to +10V is -7 level in 12 months. The digitizer operates at a fixed rate of 10 kSamples/s and can be synchronized externally. Besides qualifying HPM7177 for its application, the characterization reveals important aspects of its operation, as well as some performance limitations.