In a particle accelerator, radiofrequency (RF) systems are among the crucial components that make beam production possible. While magnets guide the particles around the ring, RF systems provide the beam with its longitudinal structure: they accelerate it, keep it captured in bunches, shape it, split it, rotate it and ensure synchronisation for transfer to the next machine.

On 21 May, an eight-hour stop in the Proton Synchrotron (PS) allowed the SY-RF and SY-EPC teams to take an important step in the renovation of one of the PS’s most central systems: the 10 MHz RF cavities. Eleven such cavities are installed around the PS ring: ten are used for operation, while one is kept as a hot-swappable spare. These ferrite-based cavities are tuneable between 2.8 MHz and 10 MHz and are used across the PS beam portfolio.

Renovating the PS’s RF systems is an essential step towards Long Shutdown 3 (LS3) and the HiLumi LHC era. As part of the existing hardware dates back to the early 1970s, several systems now require upgrades to maintain long-term availability, improve maintainability and ensure the flexibility required for Run 4. The upgrade programme includes new individual tuning power converters, new anode voltage power converters, solid-state driver amplifiers, gap relay consolidation, new digital low-level RF beam control and a review of RF settings management.

On 21 May, a prototype of the new tuning power converters was installed. Currently, tuning is split into coarse and fine tuning: coarse tuning converters provide the main current and are shared among several cavities, while fine tuning converters compensate for cavity-to-cavity differences. This architecture has served the machine well but imposes constraints, since a failure of one coarse converter affects all the cavities in the same group.

The new scheme changes this logic fundamentally. In the future system, each 10 MHz cavity will have its own tuning converter, allowing independent control. This represents a major gain in availability, as a failure would affect only one cavity. It also improves operational flexibility in distributing RF voltage.

Meanwhile, on 22 May, following the end of the proton run, commissioning for the LHC heavy-ion run started. A few days of intensive work were required to update and validate machine settings and ensure safe operation with ions. Physics data taking started on 26 May, when the LHC was filled with 119 bunches of fully stripped lead ions (Pb82⁺) per beam, which were then accelerated and brought into collision. The number of bunches was subsequently increased, reaching 1240 bunches per ring on 29 May. During this ramp-up phase, all four LHC experiments performed Van der Meer scans to calibrate their luminosity measurements.

This is the final period of data taking before the start of LS3, scheduled for 14 June for the LHC experiments. The LHC will continue to run for two more weeks for high-intensity tests, machine developments and quench tests, before shutting down on 29 June.