In a high-energy lepton collider such as the Future Circular Collider (FCC-ee) at CERN, several phenomena create a challenging radiation environment for accelerator components and equipment including cables and electronics. This paper examines synchrotron radiation (SR), dominating at the highest beam energies (ttbar) for two different optics schemes. Recent developments in the design of photon stoppers and dedicated radiation shielding are presented, highlighting progress towards a more realistic configuration while maintaining acceptable annual ionizing dose levels. The study covers the contribution of the collider ring and the impact on the attached alcoves, housing radiation sensitive equipment. The absorbed power in accelerator components and the surrounding tunnel environment is evaluated for various operation modes to ensure compliance with the thermal load limits of the ventilation system. Furthermore, radiation and particle fluence levels dominated by photo-neutron production are quantified for the electronics bunkers located below the beamline. These results are used to assess the feasibility of employing radiation-tolerant, commercial-off-the-shelf electronics in these areas.

The betatron and momentum collimation system of the the Future Circular Collider (FCC-ee) is essential to isolate losses away from the experiments and other machine elements, thus reducing the radiation background in the experiments, and avoiding damage to the machine in case of accidental beam losses. The primary and secondary collimators of the collimation hierarchy, employed to scatter halo particles from the beam and remove them, respectively, will be accommodated in one of the technical insertions of the collider ring (Point F). In this paper, FLUKA simulations are presented for the collimation straight section, addressing both normal operation and accidental scenarios. The power deposition is determined for all elements in the section following beam impacts on the collimator jaws, including other collimators as well as dipole and quadrupole magnets. In particular, the fraction of the stored beam which can be safely absorbed by the collimators is estimated. Finally, the paper discusses the radiation levels in the Point F tunnel resulting from beam losses on the collimation system, and the resulting radiation hardness requirements for machine equipment and infrastructure.

Liquid lead is under investigation at CERN as a candidate material for a multi MW-Class production target for a future Muon Collider. A free-surface curtain was initially proposed to decouple structural walls from beam-driven shock waves resulting from the high instantaneous energy deposition on the target material. However, later studies revealed that the large vertical extent required for this configuration limits the particle production efficiency, which motivated the development of a jet concept proposed in this work. Because the target operates within a 20 T solenoidal magnetic field, magnetohydrodynamic (MHD) effects are expected to influence the liquid-metal flow. Estimates indicate operation at low magnetic Reynolds numbers, where electromagnetic induction is weak. Nevertheless, the strong applied magnetic field leads to significant Lorentz forces that can affect flow stability and hydraulic performance. Both configurations are analysed using coupled multiphase computational fluid dynamics-magnetohydrodynamics (CFD-MHD) simulations in the quasi-static approximation to investigate current distribution, magneto-hydrodynamic damping, and free-surface deformation. The comparison highlights the main physical trade-offs between the two concepts and defines the framework for ongoing design optimisation.

The Search for Hidden Particles (SHiP) is a new high-intensity fixed-target experiment to be located within the Experimental Cavern North 3 (ECN3) at CERN’s North Area, utilising a 400 GeV proton beam from the SPS. The construction of a Beam Dump Facility (BDF) target complex is required for the successful operation of SHiP. It comprises an underground target station within the Tunnel Target Cave 8 (TCC8) cavern, adjacent to ECN3, which will house a 1.5 m-long, 0.25 m-diameter tungsten target, and an above ground service building that includes the target cooling systems and waste package infrastructure. The required infrastructure to investigate target failures, including the cutting of spent targets and other CERN legacy waste in view of their packaging for disposal, has been studied. This contribution presents the current design status of the target complex, including radiation protection, remote handling, utilities and cooling/ventilation systems, installation and operation procedures, maintenance and decommissioning plans, and sustainability aspects.

At CERN’s Future Circular Collider (FCC-ee), the beamstrahlung photon beams produced at each interaction point carry several hundred kilowatts of power, requiring a reliable and thermally efficient absorber. Building upon an initial slope-based liquid-lead concept, this work investigates two improved configurations: 1) a double-slope geometry, designed to mitigate photon backscattering observed in earlier designs; and 2) an inclined slope section with an accumulation pool at the back, intended to maximize photon absorption, reduce system size, and ensure thermal and flow stability. Both concepts operate under an inert argon atmosphere and target an effective absorption thickness of 10–20 cm, with a liquid-lead mass flow rate of approximately 300 kg/s. Monte Carlo simulations are employed to compute photon energy deposition, while multiphase computational fluid dynamics (CFD) analyses characterize the coupled thermal and hydrodynamic behavior. The results compare the performance of the two configurations and identify key parameters for further optimization of the FCC-ee liquid-lead photon dump system.

In the Future Circular Collider (FCC-ee) at CERN, lead shielding will be required on the collider arc dipoles around synchrotron radiation (SR) absorber locations to reduce radiation levels in the tunnel and protect sensitive components. The shielding assemblies will be mounted around the yokes, where scattered SR photons are expected to deposit 10-15 MW of power in total (across all absorber locations combined over the entire collider) at the tt-bar operating point. Between the yokes and the shielding, a water-cooling system will be integrated to cool both the shielding and the magnet. Recent design studies have focused on refining the geometry and cooling layout to simplify manufacturing, control costs and maintain shielding performance. A shielding prototype is planned to inform design choices and further improvements. This contribution presents the design evolution, plans for a prototype, and cooling system optimisations.

In the Large Hadron Collider (LHC), two beam dumps (TDEs) ensure the safe and reliable disposal of the extracted beams. During Run 4, the stored beam energy will increase from 490 MJ achieved so far during Run 3 to a maximum of 710 MJ. A new design, capable of withstanding the increase in dump energy, is therefore presented for the High Luminosity LHC (HL-LHC) TDEs. This contribution includes an analysis of the beam energy actually dumped during Run 3, and presents energy deposition studies on the new design of the HL-LHC TDE. The energy absorption breakdown between the main components of the new TDE is presented, as well as the leakage to the surrounding shielding and cavern. Transverse and longitudinal peak energy densities are also shown, for standard dump events and considering failure scenarios in the beam dilution system.

The High Luminosity (HL) upgrade of the Large Hadron Collider (LHC) requires the installation of two new beam dumps capable of safely absorbing energies of up to 710 MJ per beam. The beam dump consists of an 8.4 m long, 700 mm diameter, thin-walled cylinder containing a shrink-fitted internal core made of carbon-based materials. This contribution reports on the critical R&D activities supporting the detailed design of both the dump vessel and the carbon-based core. The vessel is constructed from Ti-6Al-4V (Grade 5) segments joined circumferentially by electron-beam welding. Extensive fatigue testing has been performed to validate the structural integrity of these welds under the severe vibrational loads induced by beam impact, complemented by fracture-toughness and fatigue-crack-growth characterisation. For the absorbing materials, the HiRadMat-65 experiment evaluated several candidate core materials under HL-LHC nominal and accident beam-dilution scenarios, with no observable damage, thereby confirming their suitability for HL operation. Together, these results represent key steps toward the final engineering design of the HL-LHC beam dumps. Research supported by the HL-LHC project.