The Super Proton Synchrotron at CERN serves the fixed-target experiments of the North Area, providing protons and ions via slow extraction, and employs the crystal shadowing technique to significantly minimize losses. Over the past three operational years, the use of a crystal, positioned upstream of the electrostatic septum to shadow its blade, has allowed to achieve a 25% reduction in losses. Additionally, a novel non-local shadowing technique, utilizing a different crystal location, has successfully halved these losses. While using a single crystal in this location resulted in a temporary 50% reduction in slow extraction losses at nominal intensity, this effect was not sustainable beyond a few hours. This limitation is primarily attributed to the magnetic non-reproducibility and hysteresis inherent to the SPS main dipoles and quadrupoles. In this paper, we introduce the application of the Rank-Weighted Gaussian Process Ensemble to the setup of shadowing. We demonstrate its superior efficiency and effectiveness in comparison to traditional Bayesian optimization and other numerical methods, particularly in managing the complex dynamics of local and non-local shadowing.

The Physics Beyond Colliders is a CERN exploratory study aimed to fully exploit the scientific potential of its accelerator complex. In this initiative, the Gamma Factory experiment aims to produce in the Large Hadron Collider (GF@LHC) high-intensity photon beams in the energy domain up to 400 MeV. The production scheme is based on the collisions of a laser with ultra-relativistic atomic beam of Partially Stripped Ions (PSI) circulating in a storage ring. The collision results in a resonant excitation of the atoms, followed by the spontaneous emission of high-energy photons. A Proof of Principle (PoP) experiment is being planned to study the GF scheme generating X-rays, in the range of keV, from lithium-like lead PSI stored at the CERN Super Proton Synchrotron (SPS). GF-PoP has undergone a series of exhaustive radiation effect studies in view of Radiation to Electronics (R2E) risks. With the use of FLUKA Monte Carlo code, the radiation environment in the laser room and its premises has been estimated during proton and PSI runs. Recorded data from beam instruments has been used to appropriately scale the computed results and to verify the compliance with general R2E limits.

During the Long Shutdown 2, the two internal dumps were replaced and successfully integrated into the CERN Proton Synchrotron operation to withstand the intense and bright beams for the High-Luminosity LHC. They function as safety devices, designed to swiftly intersect the beam’s trajectory and effectively stop the beam over multiple turns. A significant challenge arises from their limited energy absorption capacity. Previous studies indicate that at the maximum PS beam energy of 26 GeV, only about 7% of the energy is absorbed by the dumps upon their insertion. This study, employing a combination of the FLUKA and SixTrack simulation code chain, evaluates the absorbed dose in downstream elements in view of the projected increase of beam intensities, according to the LHC injector upgrade parameters, and explores the feasibility and potential benefits of implementing shielding as a mitigation measure.

The successful injection of proton beams into the Large Hadron Collider (LHC) depends on an efficient scraping mechanism in the Super Proton Synchrotron (SPS). The beams accelerated in the SPS contain a significant non-Gaussian tail population. If not removed, this transverse tail population can cause high losses in the transfer lines and in the LHC injection elements. Subsequently, the Beam Loss Monitor (BLM) system may trigger a beam dump reducing the machine availability. As beam intensities increase to meet the parameters set by the LHC Injector Upgrade (LIU), the efficiency of the scraping operation becomes increasingly crucial. To fully cope with higher beam intensities in the framework of the High-Luminosity LHC (HL-LHC) project, an upgrade of the scraper system, consisting of two movable graphite blades, is being developed and scheduled for installation in January 2025. This article presents the results of a comprehensive simulation study that employs the FLUKA code coupled with SixTrack to assess energy deposition in the scrapers.

In 2023, the LHC started its Run 3 operation with 208Pb82+ beams at 6.8 ZTeV, with a substantially higher number of bunches compared to past runs. Several new hardware systems were used operationally for the first time with high-intensity beams, including bent crystal collimators in the betatron cleaning insertion. Crystal-assisted collimation reduces the leakage of secondary ion fragments to the downstream dispersion suppressors, therefore decreasing the risk of quenching superconducting magnets. Nevertheless, one of the limitations encountered during the 2023 run were events with fast beam losses impacting the collimation system, which triggered multiple premature beam aborts on Beam Loss Monitors (BLMs). In this contribution, we present energy deposition simulations for these events, performed with the FLUKA tool, aiming to quantify the quench margin for the fast loss regime (~30 ms). To assess the predictive ability of the model, benchmarks against 2023 measurements are presented. The studies provide an important input for fine-tuning BLM thresholds in future heavy-ion runs, therefore increasing the tolerance to beam losses and hence the LHC availability.

Testing of space-bound microelectronics plays a crucial role in ensuring the reliability of electronics exposed to the challenging radiation environment of outer space. This contribution describes the beam optics studies carried out for the run held in November 2023 in the context of the CERN High-Energy Accelerators for Radiation Testing and Shielding (HEARTS) experiment. It also delves into an investigation of the initial conditions at the start of the transfer line from the CERN Proton Synchrotron (PS) to the CERN High Energy Accelerator Mixed-field (CHARM) facility. Comprehensive optics measurement and simulation campaigns were carried out for this purpose and are presented here. Using a validated optics model of the transfer line, the impact of air scattering on the beam size was quantified with MAD-X and FLUKA, providing valuable insights into the current performance and limitations for Single Event Effects (SEE) testing at CHARM.

Bent crystals are a mature technology used in several applications at CERN, such as the crystal-assisted collimation system for LHC ion operation and reduction of losses during the slow extraction from the SPS by shadowing the electrostatic septum. In the future, it is planned to measure electric and magnetic dipole moments of short-lived particles with a double-crystal experiment in the LHC. To consolidate their strategic use, CERN has been equipped to produce in-house bent crystals. Each crystal is required to be fully validated before its installation by different techniques, such as metrology, X-ray diffractometry and characterization with beams. The latter can measure the bending angle, the torsion, and the channeling efficiency, which is related to crystal imperfections. In this contribution, we present the performance with beams of the first prototype bent crystals manufactured at CERN and tested during a measurement campaign in the North Area.

An important upgrade programme is planned for the collimation system of Large Hadron Collider (LHC) for lead–ion beams that will already reach their high-luminosity target intensity upgrade in the LHC Run 3 (2022-2025). While certain effects like e-cloud, beam-beam, impedance, inject and dump protection are relaxed with ion beams, halo collimation becomes a challenge, as the conventional multi-stage collimation system is about two orders of magnitude less efficient than for proton beams. Ion fragments scattered out of the collimators in the betatron cleaning insertion risk to quench cold dipole magnets downstream and may represent performance limitations. Planar channeling in bent crystals has been proven effective for high energy heavy ions and is now considered as baseline solution for collimation at High-Luminosity LHC (HL-LHC). In this paper, simulation and measurement results, demonstrating the observation of channeling of heavy-ion beams and improvement of collimation cleaning in the multi-TeV energy regime, and the efficiency of the collimation scheme foreseen for HL-LHC are presented.