Keyword: framework
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THA01 Precise Modelling and Large Scale Multiobjective Optimisation of Cyclotrons simulation, cyclotron 284
  • J. Snuverink, A. Adelmann, C. Baumgarten, M. Frey
    PSI, Villigen PSI, Switzerland
  The usage of numerical models to study the evolution of particle beams is an essential step in the design process of particle accelerators. However, uncertainties of input quantities such as beam energy and magnetic field lead to simulation results that do not fully agree with measurements. Hence the machine will behave differently compared to the simulations. In case of cyclotrons such discrepancies affect the overall turn pattern or alter the number of turns. Inaccuracies at the PSI Ring cyclotron that may harm the isochronicity are compensated by 18 trim coils. Trim coils are often absent in simulations or their implementation is simplistic. A realistic trim coil model within the simulation framework OPAL is presented. It was used to match the turn pattern of the PSI Ring. Due to the high-dimensional search space consisting of 48 simulation input parameters and 182 objectives (i.e. turns) simulation and measurement cannot be matched in a straightforward manner. Instead, an evolutionary multi-objective optimisation with more than 8000 simulations per iteration together with a local search approach was applied that reduced the maximum error to 4.5 mm over all 182 turns.  
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About • paper received ※ 25 September 2019       paper accepted ※ 27 September 2019       issue date ※ 20 June 2020  
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