Beam-based aperture measurements with movable collimator jaws as performance booster of the CERN Large Hadron Collider

Abstract

The beam aperture of a particle accelerator defines the clearance available for the circulating beams and is a parameter of paramount importance for the accelerator performance. At the CERN Large Hadron Collider (LHC), the knowledge and control of the available aperture is crucial because the nominal proton beams carry an energy of 362 MJ stored in a superconducting environment. Even a tiny fraction of beam losses could quench the superconducting magnets or cause severe material damage. Furthermore, in a circular collider, the performance in terms of peak luminosity depends to a large extent on the aperture of the inner triplet quadrupoles, which are used to focus the beams at the interaction points. In the LHC, this aperture represents the smallest aperture at top-energy with squeezed beams and determines the maximum potential reach of the peak luminosity. Beam-based aperture measurements in these conditions are difficult and challenging. In this paper, we present different methods that have been developed over the years for precise beam-based aperture measurements in the LHC, highlighting applications and results that contributed to boost the operational LHC performance in Run 1 (2010–2013) and Run 2 (2015–2018)

Future Circular Hadron Collider FCC-hh: Overview and Status

“…In the case of the LHC, the attainable luminosity has surpassed the nominal one thanks to several elements. Higher-brightness beams delivered by the injectors boosted the luminosity, while in the LHC ring the excellent optics control, which includes measurement and correction, together with an optimal use of the available beam aperture, thanks also to the use of tighter collimators settings [2], provided the final touch. It is worth stressing that in the LHC, β * = 30 cm, corresponding to the nominal FCC-hh value, has already been achieved and surpassed.…”

Focus point on high-energy accelerators: advances, challenges, and applications

“…Contributions to this issue represent and attempt to cover a broad domain of topics in beam physics, with a loose classification into three categories of advances, challenges, and applications. References [13][14][15][16][17][18][19][20][21] provide a global overview of the applications of advanced beam dynamics concepts to existing or future machines. The nonlinear beam dynamics combined with the use of electron lenses has been considered in the framework of the High-Luminosity LHC Project and discussed in [21].…”

“…The nonlinear beam dynamics combined with the use of electron lenses has been considered in the framework of the High-Luminosity LHC Project and discussed in [21]. Various techniques devised to measure the available beam aperture in the LHC, which contributed to the astonishing performance reached during Run 2, are presented in [20]. A combined-function optics has been proposed as an alternative to the standard separate approach paradigm for high-energy colliders [19] with the goal of increasing the dipole filling factor.…”