CERN Accelerating science

Thesis
Report number	CERN-THESIS-2024-224
Title	Numerical Models and Interplay of Intrabeam Scattering with Incoherent Effects for High Brightness Circular Accelerators
Related title	Αριθμητικά μοντέλα και αλληλεπίδραση των ενδοδεσμικών σκεδάσεων με μη συνεκτικά φαινόμενα για κυκλικούς επιταχυντές υψηλής φωτεινότητας
Author(s)	Zampetakis, Michail (CERN)
Publication	175.
Thesis note	PhD : University of Crete : 2024
Thesis supervisor(s)	Bartosik, Hannes ; Papaphilippou, Ioannis ; Tsironis, Georgios
Note	Presented 16 Oct 2024
Subject category	Accelerators and Storage Rings
Accelerator/Facility, Experiment	CERN LEIR CERN SPS CLIC
Abstract	Future and existing circular accelerators require high beam brightness, which can be limited by collective effects such as space charge (SC) and intrabeam scattering (IBS). These effects can degrade beam quality, even in scenarios where strong damping due to synchrotron radiation (SR) is present. To optimize beam performance in such rings, it is essential to study the interplay of SC, IBS, and SR effects in macroparticle tracking simulations, while also accounting for lattice nonlinearities. To this end, numerical models for simulating IBS in rings operating both below and above transition, along with a simple model for SR damping, have been implemented in the PyORBIT tracking code, and combined with its widely used SC module. These models, have been extensively benchmarked against analytical predictions, demonstrating excellent agreement. This thesis investigates the interplay of relevant effects in two distinct types of machines: the Compact Linear Collider (CLIC) damping rings (DRs), which utilize electrons, and CERN's ion injectors, specifically the Super Proton Synchrotron (SPS) and the Low Energy Ion Ring (LEIR), which operate with lead (Pb) ions. In the context of the CLIC DRs, this thesis evaluates the interplay of SC, IBS, and SR near excited betatron resonances. The impact of these effects on the achievable beam parameters of the CLIC DRs is analyzed, revealing that SR damping helps mitigating the adverse effects of IBS and SC-induced resonance crossing. This research includes a comprehensive dynamic simulation of the CLIC damping ring cycle, beginning with the injection beam parameters. The findings demonstrate that a careful selection of the working point is essential to manage the transition from transverse detuning caused by lattice nonlinearities to space-charge-dominated detuning, thereby avoiding excessive losses and emittance growth near strong resonances. Experimental beam observations in LEIR and the SPS could not be fully explained by simulations of either SC or IBS alone. To address this, combined SC and IBS simulations were conducted for LEIR near a vertical resonance excited in a controlled way, showing good agreement with actual machine measurements. Likewise, for the first time, beam observations in the SPS were successfully explained using combined SC and IBS simulations.

Email contact: michail.zampetakis@cern.ch