Beam Longitudinal Dynamics Simulation Suite BLonD

The beam longitudinal dynamics code BLonD has been developed at CERN since 2014 and has become a central tool for longitudinal beam dynamics simulations. In this paper, we present this modular simulation suite and the various physics models that can be included and combined by the user. We detail the reference frame, the equations of motion, the BLonD-specific options for radio-frequency parameters such as phase noise, fixed-field acceleration, and feedback models for the CERN accelerators, as well as the modeling of collective effects and synchrotron radiation. We also present various methods of generating multi-bunch distributions matched to a given impedance model. BLonD is furthermore a well-tested and optimized simulation suite, which is demonstrated through examples, too

Modelling Control Loops for SPS-LHC Beam Transfer Studies

For HL-LHC æraen kan overføring av partikkelstråler fra SPS føre til tap av partikler og begrensninger i elektrisk effekt i radiofrekvens systemene til LHC. Presise numeriske modeller av kontrollsystemene i både SPS og LHC i simulatoren BLonD er essensielle for å gi estimater for både tap av partikler og begrensinger i elektrisk effekt. Denne masteroppgaven presenterer modeller av både SPS og LHC «cavity controllers», viser hvordan disse ble validert og sammenliknet med målinger. Disse kontrollsystemene regulerer spenningen i de akselererende strukturene i akseleratorene, både i amplitude og i fase under forhold med høy effekt grunnet partikkelstrålen. Ved bruk av SPS «cavity controller» modellen kan man skape realistiske høyintensitets stråler, som vil bli viktig for fremtidige studier av stråleoverføring mellom SPS og LHC. Det ble funnet at SPS modellen er i god enighet med eksperimentell data av partikkelstråler. Videre ble det vist at LHC «cavity loop» modellen kunne gjenskape målte overføringsfunksjoner til tilfredsstillende nøyaktighet

Advances on LHC RF Power Limitation Studies at Injection

The average power consumption of the main RF system during beam injection in the High-Luminosity Large Hadron Collider is expected to be close to the maximum available klystron power. Power transients due to the mismatch of the beam and the action of control loops will exceed the available power. This paper presents the most recent estimations of the injection voltage and steady-state power needed for HL-LHC intensities, taking also beam stability into account. It summarises measurement and simulation efforts ongoing to better understand power transients and beam losses, and describes the operational margin to be taken into account for different equipment

Refining the LHC Longitudinal Impedance Model

Modelling the longitudinal impedance for the Large Hadron Collider (LHC) has been a long-standing effort, especially in view of its High-Luminosity (HL) upgrade. The resulting impedance model is an essential input for beam dynamics studies. Increased beam intensities in the HL-LHC era will pose new challenges like RF power limitations, beam losses at injection and coupled-bunch instabilities throughout the acceleration cycle. Starting from the existing longitudinal impedance model, effort has been made to identify the main contributing devices and improve their modelling. Loss of Landau damping (LLD) simulations are performed to investigate the dependence of the stability threshold on the completeness of the impedance model and its broad-band cut-off frequency. Plans to perform beam measurements to estimate the cut-off frequency, by investigating the LLD threshold in operation, are also discussed