LIPAc RF system commissioning: busting one EMC problem at a time

Addressing electromagnetic compatibility (EMC) issues at the design stage is important. However, for a prototype like the Linear IFMIF Prototype Accelerator (LIPAc) and its RadioFrequency (RF) system providing over 2 MW of RF power, problems during the commissioning have to be expected. Random interlocks and probability of occurrence increasing with the number RF modules, the power level or the duty cycle are often evidences of EMC problems, sometimes known as RF noise. Those conditions are difficult to reproduce by the manufacturers and if no margins are considered, they need to be addressed by a dedicated team onsite*. Two solved EMC problems will illustrate the basics of the mitigation strategy: locate and stop the RF noise at the source or protect the victims from the RF noise. The first approach is applied on the air cooling: the noise from an inverter, driving a motor over tens of meters of cables, affected multiple systems sharing the same cable tray and had to be fixed at its source. The second way is applied on the tetrodes high voltage input monitor, affected by RF leaking probably from the tetrode: a source difficult to stop that called for a protection of the victim.