Status of the High Energy Booster of the lepton option of the future circular collider

Abstract

In the context of the FCC IS European study, which investigates the feasibility of a 100 km circular 𝑒 + 𝑒 − collider for the future high-energy physics research, we present the design status of the High Energy Booster (HEB) ring. In order to perform precision measurements of the Z, W and H bosons, as well as of the top quark, unprecedented luminosities are required. To reach this goal and to fill the collider, it is mandatory to continuously top-up inject some beam with emittances comparable to those in the collider, so as to maintain an intensity difference between colliding electron and positron bunches below a few %. The main challenges of the HEB design are achieving the collider equilibrium emittances with a fast cycle, and determining the minimum booster injection energy allowing for stable operation. We present the status of the optics design of the HEB, taking into account the above challenges, and the impact of magnetic field imperfections on the dynamic aperture at injection.

Optics design and correction challenges for the high energy booster of FCC-ee

“…The effects of magnetic multipole errors on lattice momentum acceptance and a first analytical estimation of emittance growth in the presence of intra-beam scattering have been previously reported [2]. This paper is a status report on the aforementioned developments for the HEB design.…”

“…The correction strategy described in ref. [4] was employed to evaluate the tolerances for misalignment and field errors on the elements. To do so, we conducted several tests by gradually introducing different error types, each on 100 seeds.…”

“…Finally, the machine impedance model has to be built. For the IBS, an updated analytical study made with MadX with respect to the one published in [2] is represented in figure 7 (left). It shows an important contribution of the IBS after energy ramp to the energy spread making it higher than the collider threshold.…”