We present the latest development for the FCC-ee interaction region. It represents a major challenge for the FCC-ee collider, which has to achieve extremely high luminosity over a wide range of centre-of-mass energies. The FCC-ee will host two or four high-precision experiments. The machine parameters have to be well controlled and the design of the machine-detector-interface has to be carefully optimized. In particular, the complex final focus hosted in the detector region has to be carefully designed, and the impact of beam losses and of any type of radiation generated in the interaction region, including beamstrahlung, have to be simulated in detail. We discuss mitigation measures and the expected impact of beam losses and radiation on the detector background. We also report the progress of the mechanical model of the interaction region layout, including the engineering design of the central beampipe, and other MDI components.

The proposed FCC-ee machine is a high-energy, high-intensity and high-precision lepton collider which will require to reduce as much as possible the differential motions of its two beams at the interaction points. In this prospect, the vibration impacts of the quadrupoles in the region close to the interaction point are investigated. Considering the z-pole optics design and its dedicated optics simulation under MAD-X, the present paper describes the integration of the dynamics aspects (vibrations mitigation) to render the modelling more realistic towards operation. This simulation is based on the "particle tracking" mode. In this prospect, dynamic characteristics of the designed mechanical assembly are estimated according to an analysis in finite element models. Required transfer functions and realistic temporal sequences along the assembly are thus created and they can be implemented as inputs to the optical simulations to verify that this assembly allows the expected beam parameters. The obtained results on a dedicated cantilever mock-up are presented and the last optics simulations are discussed.

SuperKEKB is an asymmetrical lepton collider with a circumference of 3 016 meters, which collides 7 GeV electrons with 4 GeV positrons. To optimize the luminosity, which recently reached a world record of 4.71 10^34 cm-2 s-1, all the undesirable effects on beam parameters must be analyzed in detail, especially close to the interaction point where the Belle II detector is operated. The presented study investigates the influence of mechanical vibration on the luminosity. For this purpose, four seismic sensors (Guralp 6T) were installed and collect data 24 hours a day, two on the ground and another two located on the supports of the two cantilevered cryostats, inside which the last focusing magnets on both sides of the interaction point (the most critical for vibrations) are mounted. The luminosity is measured thanks to the LumiBelle2 fast luminosity monitor, which is based on diamond detectors installed in both beam lines. Vibration-induced disturbances in the luminosity frequency spectrum are investigated for several types of perturbations, in particular the ones resulting from ground motion amplified by the dynamical behavior of the cryostat, as well as also from external vibrations sources.