In 2023, about 2 months of the LHC operation were devoted to the Heavy Ions physics, after more than 5 years since the last ion run. In this paper, the results of the 2023 Ion optics commissioning are reported. Local corrections in Interaction Point (IP) 1 and 5 were reused from the regular proton commissioning, but the optics measurement showed the need for new local corrections in IP2. We observed that an energy trim of the level of 10e-4 helped to reduce the optics errors at top energy. The dedicated measurements during the energy ramp revealed a larger than expected beta-beat, which is consistent with an energy mismatch. Furthermore, global corrections were performed to reach a β-beating of about 5% for the collision optics.

The LHC machine configuration was changed in 2023 compared to previous years, requiring a new set of optics configurations to be measured and corrected. A telescopic optics was deployed in energy the ramp for the first time, which gave rise to a beta-beating of up to 25%. This was corrected using a global correction approach which reduced the beta-beat down to 10%. A change in the phase advance at injection was also applied to mitigate the negative effect of the main octupoles used to stabilize the beam. These measurements and corrections, coupled with the results from the 2024 commissioning, will be presented in this paper

During 2023, examination of the action dependence of sextupolar resonance driving terms (RDT) in the LHC at injection, as measured with an AC-dipole, demonstrated that a robust measurement of the RDTs could still be achieved even with very small amplitude kicks, typically used for linear optics studies. Consequently, analysis of optics measurements from 2022 and 2023 during the LHC energy ramp allowed a first measurement of the sextupole resonance evolution. A large asymmetry was observed between the two LHC beams, with the clockwise circulating beam (LHCB1) significantly worse than the counter-clockwise circulating beam (LHCB2), and a clear increase in the RDT strength during the ramp was observed. Results are presented and compared to MAD-X simulations, in this report.

In 2023, about 2 months of the LHC operation were devoted to the Heavy Ions physics, after more than 5 years since the last ion run. In this paper, the results of the 2023 Ion optics commissioning are reported. Local corrections in Interaction Point (IP) 1 and 5 were reused from the regular proton commissioning, but the optics measurement showed the need for new local corrections in IP2. We observed that an energy trim of the level of 10e-4 helped to reduce the optics errors at top energy. The dedicated measurements during the energy ramp revealed a larger than expected beta-beat, which is consistent with an energy mismatch. Furthermore, global corrections were performed to reach a β-beating of about 5% for the collision optics.

The Karlsruhe Research Accelerator (KARA) is a synchrotron light source user and test facility, operating at an electron beam energy ranging from 0.5 to 2.5 GeV. Performing optics measurements and comparing with the machine model promises an improved understanding of the lattice and the underlying beam dynamics. Horizontal and vertical turn-by-turn Beam Position Monitor data are acquired and used for performing optics measurements in this storage ring. The results of these studies are presented in this paper.

The Karlsruhe research accelerator KARA offers a setup to measure the beam energy with resonant spin depolarization. The depolarization is excited by the stripline kickers of the bunch-by-bunch feedback system and the resonant frequency is measured via change in Touschek lifetime. Energy measurements with resonant spin depolarization are implemented as a standard routine in the control system and are used regularly to measure both the beam energy and the momentum compaction factor for different energies and optics regimes. Long-time experience with the setup, short polarization time, and variation options of beam energy in combination with much available beam time qualify KARA as a test facility for systematic studies. Such studies are of particular interest for future colliders designed for precision studies like FCC-ee, as resonant spin depolarization is known for its high accuracy. This contribution presents the resonant spin depolarization setup at KARA and selected results of recent measurement campaigns.

With a circumference of approximately 91 km, the Future Circular electron-positron Collider, FCC-ee, aims for unprecedented luminosities at beam energies from 45.6 to 182.5 GeV. A major challenge is reaching its design performance in the presence of magnet misalignments and field errors. The FCC-ee optics tuning working group studies all related aspects, and applies state-of-the-art techniques for beam-based alignment, commissioning simulations, beam threading, optics measurements and corrections, which are probed at numerous world-leading accelerator physics facilities. Advanced optics correction simulations include interaction-point tuning, magnetic tolerances are studied, and a new optics is under scrutiny. The current status of tuning simulations for different FCC-ee lattices is presented.

In autumn 2023, the FCC Feasibility Study underwent a crucial “mid-term review”. We describe some accelerator performance risks for the proposed future circular electron- positron collider, FCC-ee, identified for, and during, the mid-term review. For the collider rings, these are the collective effects when running on the Z resonance – especially resistive wall, beam-beam, and electron cloud –, the beam lifetime, dynamic aperture, alignment tolerances, and beam-based alignment. For the booster, the primary concern is the vacuum system, with regard to impedance and effects of the residual gas. For the injector, the layout and the linac repetition rate are primary considerations. We discuss the various issues and report the planned mitigations.

The FCC-ee collider physics program requires a precise determination of the center-of-mass energy. The average energies of the two colliding beams can be measured by resonant depolarization (RDP) of polarized electron and positron bunches. The depolarization is achieved by an electromagnetic device, e.g., a strip line, excited at a sweeping frequency. Once the excitation frequency is equal to the spin precession frequency, which is directly proportional to the beam energy, the polarization is lost or reduced. At KARA the resonant frequency is routinely measured via the change of the Touschek lifetime. We report on an RDP beam measurement campaign at the Karlsruhe Research Accelerator (KARA), exploring how this technique could be applied at the FCC-ee. In particular, we examine the sensitivity of the inferred value of beam energy to various parameters, such as the depolarize scan speed, the scan direction, and the beam operation energy.