Real-Time control system upgrade of the CERN Linac4 pre-chopper

The CERN Linac4 pre-chopper, installed right after the H- ion source in the Low Energy Beam Transport (LEBT) section, plays a crucial role in providing the 45 keV H- beam to the first accelerating structure, the Radio Frequency Quadrupole (RFQ). By applying a pulsed electric field of -20 kV, the pre-chopper deflects the beam when not required and sharps its head and tail in order to remove the long rise time of the source and avoid transmission losses. The existing pre-chopper controller was implemented in 2015 using National Instruments (NI) LabVIEW and PXIe hardware, relying on their proprietary Real-Time (RT) operating system (Phar Lap) and a secondary Linux Front-End Computer (FEC) for the integration in the CERN control system. Phar Lap is EOL since 2025 and will be discontinued during the upcoming Long Shutdown 3 (LS3). This paper presents an upgrade of the control system, aimed at replacing the LabVIEW-RT control layer with standard CERN solutions, leveraging the new Debian-based Linux RT OS, Front-End Computer Operating System (FECOS), and consolidating all functionalities into a single computer. The goal was achieved using the CERN Front-End Software Architecture (FESA) 3 framework and C++ libraries to interface with the NI hardware via NI Linux drivers deployed on FECOS. A new PyQt-based graphical user interface will be developed to ease system monitoring and operation. Installation of the upgraded system is expected for LS3, using a custom PXIe crate and CPU from CERN instead of NI solutions.