Probing the diffusive behaviour of beam-halo dynamics in circular accelerators

Abstract

Circular particle accelerators at the energy frontier are based on superconducting magnets that are extremely sensitive to beam losses as these might induce quenches, i.e. transitions to the normal-conducting state. Furthermore, the energy stored in the circulating beam is so large that hardware integrity is put in serious danger, and machine protection becomes essential for reaching the nominal accelerator performance. In this challenging context, the beam halo becomes a potential source of performance limitations and its dynamics needs to be understood in detail to assess whether it could be an issue for the accelerator. In this paper, we discuss in detail a recent framework, based on a diffusive approach, to model beam-halo dynamics. The functional form of the optimal estimate of the perturbative series, as given by Nekhoroshev’s theorem, is used to provide the functional form of the action diffusion coefficient. The goal is to propose an effective model for the beam-halo dynamics and to devise an efficient experimental procedure to obtain an accurate measurement of the diffusion coefficient.

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

“…Finally, a selection of papers discussing future advances is given in [26][27][28][29]. The use of nonlinear beam dynamics to extend the domain of possible beam manipulations is discussed in [26,28], where resonances are used as a means to provide an alternative transition-crossing scheme [26]or to manipulate transverse emittances [28].…”

“…The use of nonlinear beam dynamics to extend the domain of possible beam manipulations is discussed in [26,28], where resonances are used as a means to provide an alternative transition-crossing scheme [26]or to manipulate transverse emittances [28]. The Vlasov description of collective effects in circular accelerators is described in detail in [27] and, last, a novel diffusive model to describe the beam halo dynamics is presented in [29] with the focus on the determination of effective techniques to reconstruct the functional form of the diffusion coefficient with the longer-term goal of estimating the beam lifetime.…”