arXiv subjects

Foteini Asvesta

Publications and source records attributed to Foteini Asvesta.

4 recordsLinked to original sources

arXiv2026

Interplay of space charge and intrabeam scattering in the LHC ion injector chain

The ion injectors of the CERN accelerator chain, in particular the Super Proton Synchrotron (SPS) and the Low Energy Ion Ring (LEIR), operate in a strong space charge (SC) and intrabeam scattering (IBS) regime, which can degrade beam quality. Optimizing the ion beam performance therefore requires studying the interplay of these two effects in tracking simulations by incorporating both SC and IBS effects interleaved with lattice nonlinearities. In this respect, the kinetic theory approach of treating IBS effects has been deployed. A modified stochastic IBS kick is introduced, with friction and diffusion coefficients derived in two forms: an efficient Nagaitsev formulation based on complete elliptic integrals of the second kind, and a complete Bjorken-Mtingwa formulation. This IBS kick is implemented in PyORBIT and extensively benchmarked against analytical models. Results of combined space charge and intrabeam scattering simulations for the SPS and LEIR are presented and compared with observations from beam measurements.

physics.acc-ph↗

arXiv2025

Space-Charge Effects During Half-Integer Resonance Crossing in the CERN PSB

The survival of charged particles in synchrotrons requires avoiding setting the beam on machine resonances, the most dangerous of which are the integer and half-integer. Nevertheless, operationally, the transverse tunes may change dynamically, crossing these resonances, and resulting in unwanted beam quality degradation and beam loss. For high intensity beams the process of resonance crossing is even more critical as space charge, in addition to the incoherent effects, may generate also coherent effects on the beam envelope dynamics. The interplay of the speed of resonance crossing, the space charge incoherent tune spread, and half-integer resonance width are fundamental for the beam behavior. In this paper we study the crossing of the half-integer resonance $2Q_y=9$ in the CERN Proton Synchrotron Booster~(PSB) for a range of parameters using a coasting beam. We take advantage of the newly commissioned PSB to investigate the beam response experimentally. The experimental findings are also discussed with the support of simulations.

physics.acc-ph↗

arXiv2024

Interplay of space charge, intrabeam scattering and synchrotron radiation in the Compact Linear Collider damping rings

Future ultra-low emittance rings for electron/positron colliders require extremely high beam brightness and can thus be limited by collective effects. In this paper, the interplay of effects such as synchrotron radiation, intra-beam scattering (IBS) and space charge in the vicinity of excited betatron resonances is assessed. In this respect, two algorithms were developed to simulate IBS and synchrotron radiation effects and integrated in the PyORBIT tracking code, to be combined with its widely used space charge module. The impact of these effects on the achievable beam parameters of the Compact Linear Collider (CLIC) Damping Rings was studied, showing that synchrotron radiation damping mitigates the adverse effects of IBS and space charge induced resonance crossing. The studies include also a full dynamic simulation of the CLIC damping ring cycle starting from the injection beam parameters. It is demonstrated that a careful working point choice is necessary, in order to accommodate the transition from a non-linear lattice induced detuning to a space-charge dominated one and thereby avoid excessive losses and emittance growth generated in the vicinity of strong resonances.

physics.acc-ph↗

arXiv2020

Identification and characterization of high order incoherent space charge driven structure resonances in the CERN Proton Synchrotron

Space charge is typically one of the performance limitations for the operation of high intensity and high brightness beams in circular accelerators. In the Proton Synchrotron (PS) at CERN, losses are observed for vertical tunes above $Q_y=6.25$, especially for beams with large space charge tune shift. The work presented here shows that this behaviour is associated to structure resonances excited by space charge due to the highly symmetric accelerator lattice of the PS, typical for first generation alternating gradient synchrotrons. Experimental studies demonstrate the dependency of the losses on the beam brightness and the harmonic of the resonance, and simulation studies reveal the incoherent nature of the resonance. Furthermore, the calculation of the Resonance Driving Terms (RDT) generated by the space charge potential shows that the operational working point of the PS is surrounded by multiple space charge driven incoherent resonances. Finally, measurements and simulations on both lattice driven and space charge driven resonances illustrate the different behaviour of the beam loss depending on the source of the resonance excitation and on the beam brightness.

physics.acc-ph↗