Abstract
Future hadron colliders aim at producing larger integrated luminosities by burning-off an increased fraction of the bunch particles. This burn-off removes particles unevenly in the bunch distribution generating an emittance growth. Analytical equations are derived describing the bunch distribution suffering luminosity burn-off and cooling from synchrotron radiation damping, far from the equilibrium emittance, and possibly including transverse collision offsets. This effect is evaluated for HL-LHC [G. Apollinari et al., Report No. CERN-2017-007-M, 2017], HE-LHC [A. Abada et al., Eur. Phys. J. Spec. Top. 228, 1109 (2019)], and FCC-hh [A. Abada et al., Eur. Phys. J. Spec. Top. 228, 755 (2019).] and included into a step-by-step simulation of the physics fill, together with intrabeam scattering, to evaluate impact on performance.
Highlights
Understanding the evolution of luminosity during physics fills is of paramount importance in any particle collider in order to optimize its performance
The emittance growth from burn-off is important for future hadron colliders where it is expected to burn-off up to 80% of the beam, for the hadron-hadron Future Circular Collider (FCC-hh) [11] case
Performance reduction due to emittance growth resulting from particle burn-off is estimated for High Luminosity Large Hadron Collider (HL-LHC), High Energy LHC (HE-LHC), and FCC-hh using the LEVELLING code [14] already used for HL-LHC [15] and HE-LHC [16]
Summary
Understanding the evolution of luminosity during physics fills is of paramount importance in any particle collider in order to optimize its performance. The effect of emittance growth from luminosity burn-off was already studied in [6,7] for ion collisions in LHC and RHIC with an approximate analytical model and numerical simulations assuming Gaussian distributions throughout the fill. In this paper we derive analytical equations describing the non-Gaussian bunch density distribution in the two transverse dimensions after luminosity burn-off, including synchrotron radiation damping (far from equilibrium emittance) and possible offset collisions. Intrabeam scattering contributes to emittance growth and cannot be neglected in future colliders It will be added here as a perturbation after considering synchrotron radiation damping and emittance growth from luminosity burn-off. The derivations here do not apply for lepton colliders operating close to the equilibrium emittance
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