The WP6B “Class 0” ultra-high precision current measurement devices, or DCCTs (direct current current transformers), are used for the accurate current measurement/regulation in the 14kA (D1: MBXF, D2: MBRD) and 18kA (Main Inner Triplet) power converters. Two prototype DCCTs, from the IT-4514 HL-LHC contract (PM Special Measurement Systems), have been fully tested at CERN and approval has been granted for the pre-series phase, another six units for the HL-LHC IT String in SM18.

All performance aspects of the detailed technical specification were verified. This included the very strict accuracy requirements, as well as EMC (electro-magnetic compatibility). The setup for EMC testing is shown in the image above. The unprecedented 12-hour stability requirements (±0.5 ppm) for HL-LHC could only have been achieved, and measured, by combining CERN’s “state of the art” measurement capabilities with industry’s manufacturing know-how. The chart below shows the spec-compliant 12h stability test, that could be repeated consistently, boding well for the next phase of the project: the integration of the DCCTs into the control system of the power converters.

12 Hour Stability Test Results (Graphics: Greg Hudson)

By Greg Hudson, on behalf of WP6B