Fixed target beams are extracted in five turns from the Proton Synchrotron (PS) at CERN to fill almost half the circumference of the Super Proton Synchrotron (SPS) with each transfer. To avoid beam loss during the risetime of the extraction kickers a longitudinal gap is generated with an RF barrier-bucket scheme. However, the synchronization of the gap with the PS extraction and SPS injection kickers requires the RF system to operate without any beam feedback during the transverse splitting process at the flat-top. Low RF voltage is moreover required during the process to keep a small momentum spread. Both conditions are unfavorable for longitudinal stability and a campaign of beam measurements has been performed to explore potential intensity limitations. Up to 3.3e+13 protons have been accelerated and remained longitudinally stable at high energy. Longitudinal coupled-bunch instabilities occurring at the intermediate plateau below transition energy are moreover cured by a dipole-mode feedback system initially developed for LHC-type beams. The contribution summarizes the results of the beam tests, probing the limits of the fixed-target proton beam production.

A new design of fast wire scanner was installed in the CERN injector complex as part of the upgrades linked to the High-Luminosity LHC Project. Initial operations with these beams were good, but during the planned intensity ramp-up one early 2023, all four SPS scanners failed at the same time. An urgent program was put in place to understand and address this failure with experts from across the accelerator fields. Many measurements and simulations were performed and solutions implemented. This paper gives an overview of the issues seen, understanding and mitigations put in place to allow the instrument to perform at the maximum planned operational intensities.

Within the LHC Injectors Upgrade (LIU) project, the LHC injectors received major upgrades that resulted in an unprecedented brightness performance. In the framework of the Physics Beyond Colliders (PBC) study, the full potential of the upgraded injectors is being explored for the improvement of the Fixed Target (FT) beams as well. This contribution details the recent studies on the beam transmission and beam quality along the injectors of the SPS Fixed Target PROton (SFTPRO) beams that reach the North Area (NA) experiments. In particular, the possibilities for tailoring the transverse emittances out of the PSB and the impact on the beam transmission in the SPS are shown. Furthermore, the impact of the transverse damper excitation on the efficiency of the Multi-Turn-Extraction in the PS are discussed. Finally, the main factors that limit the intensity reach of the injectors are also discussed.

During the last long shutdown of the accelerators at CERN (LS2), the main radio frequency system of the Proton Synchrotron Booster (PSB) was upgraded. A wideband system with Finemet magnetic alloy cavities driven by solid-state amplifiers replaced several different ferrite-loaded cavities. In measurements post-LS2, the longitudinal beam stability did not match predictions, which triggered a survey of the PSB impedance model. This started with the Finemet RF system, which are expected to be the dominant impedance contribution. Single stretched wire measurements were carried out with a 6-cell Finemet test cavity with different amplifier configurations. Measurement results and electromagnetic simulations are presented in this paper and compared to the previous impedance model. The electromagnetic characterization presented in this contribution will complement the beam-based impedance and low-level RF measurements as an input for the simulations of beam stability.

The 40 MHz and 80 MHz Radio Frequency (RF) systems in the CERN Proton Synchrotron (PS) are required to perform non-adiabatic bunch shortening before beam ejection. This manipulation allows to fit the bunches into the short RF buckets of the 200 MHz Super Proton Synchrotron (SPS). Although the impedance of the cavities is strongly reduced by feedback, the detailed understanding of the beam-cavity interaction is essential to evaluate their impact on the beam. This contribution focuses on the impedance characterization of the 80 MHz RF systems to describe how the RF amplification chain behaves as a function of beam current changes. Complementary measurement techniques, both beam and RF-based, were adopted. The results of the different measurements show good agreement. The aim is to study and predict possible beam quality degradation at beam intensities required by the High Luminosity LHC (HL-LHC), as well as to propose future consolidation to the high-frequency RF systems in the PS.