03 Theory, Models and Simulations
Paper Title Page
MOP034 Beam Stripping Interactions Implemented in Cyclotrons with OPAL Simulation Code 109
  • P. Calvo, C. Oliver
    CIEMAT, Madrid, Spain
  • A. Adelmann, M. Frey, A. Gsell, J. Snuverink
    PSI, Villigen PSI, Switzerland
  Beam transmission optimization and losses characterization, where beam stripping interactions are a key issue, play an important role in the design and operation of compact cyclotrons. A beam stripping model has been implemented in the three-dimensional object-oriented parallel code OPAL-cycl, a flavor of the OPAL framework. The model includes Monte Carlo methods for interaction with residual gas and dissociation by electromagnetic stripping. The model has been verified with theoretical models and it has been applied to the AMIT cyclotron according to design conditions.  
poster icon Poster MOP034 [0.880 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-Cyclotrons2019-MOP034  
About • paper received ※ 12 September 2019       paper accepted ※ 26 September 2019       issue date ※ 20 June 2020  
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MOP035 Extraction Beam Orbit of a 250 MeV Superconducting Cyclotron 113
  • H.J. Zhang, K. Fan, Y. Yan
    Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People’s Republic of China
  • Y.-N. Rao
    TRIUMF, Vancouver, Canada
  • L.G. Zhang
    HUST, Wuhan, People’s Republic of China
  Funding: The work is supported by the National Nature Science Foundation of China (11775087).
A superconducting cyclotron based on proton therapy facility is being developed at Huazhong university of science and technology (HUST). Due to the compact size of the main magnet, the beam orbits at the extraction region are distributed densely, which creates difficulties for beam extraction leading to severe beam loss. In order to deal with these challenges, the orbit precession method has been employed in the extraction system design. In this paper, we introduce a method of employing a first harmonic field near the nur=1 resonance where the beam energy is about 248 MeV to adjust the amplitude of beam orbit oscillation. The optimum amplitude and phase of the first harmonic field are designed to obtain a large turn separation in the extraction region. Three different ways of generating the first harmonic field are compared for optimization.
poster icon Poster MOP035 [0.777 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-Cyclotrons2019-MOP035  
About • paper received ※ 15 September 2019       paper accepted ※ 24 September 2019       issue date ※ 20 June 2020  
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MOP036 The Magnetic Field Design of Cyclotron at IMP 116
  • Q.G. Yao, B. Wang, B.M. Wu, W. Wu, L. Yang
    IMP/CAS, Lanzhou, People’s Republic of China
  A cyclotron magnet is studied at Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS), and the whole system include one main magnet and other magnetic gradient correctors, which is used to accelerate the Kr26+ beam. The structure of superconducting coils and room-temperature iron core are adopted for the main magnet. This paper describes the magnetic field design of the cyclotron, and several shimming methods are used to meet the isochronous magnetic field of Kr26+ beam, including pole face shimming method and side shimming method. The final optimization results show that the error between simulation and theory value is small. In addition, the magnet structure is also described.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-Cyclotrons2019-MOP036  
About • paper received ※ 17 September 2019       paper accepted ※ 26 September 2019       issue date ※ 20 June 2020  
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Surrogate Models for Particle Accelerators  
  • A. Adelmann
    PSI, Villigen PSI, Switzerland
  Precise accelerator simulations are powerful tools in the design and optimization of exiting and new charged particle accelerators. We all know from experience, the computational burden of precise simulations often limits their use in practice. This becomes a real hurdle when requiring real time computation. I will demonstrate two techniques, based on Polynomial Chaos Expansion [1] and Deep Neural Networks [2] that hints a path forward, towards precise real time computing. The examples will be based on linear accelerators and cyclotrons.
[1] A. Adelmann, "On Nonintrusive Uncertainty Quantification and Surrogate Model Construction in Particle Accelerator Modeling", SIAM/ASA J. Uncertainty Quantification, 7(2), 383-416 (2019) https://epubs.siam.org/doi/abs/10.1137/16M1061928
[2] A. Edelen, A. Adelmann, N. Neveu, Y. Huber, M. Frey, "Machine Learning to Enable Orders of Magnitude Speedup in Mult-Objective Optimization of Particle Accelerator Systems", https://arxiv.org/abs/1903.07759
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WEB03 Factors Influencing the Vortex Effect in High-Intensity Cyclotrons 270
  • C. Baumgarten
    PSI, Villigen PSI, Switzerland
  We discuss factors that have potential influence on the space charge induced vortex motion of particles within high intensity bunches (curling of bunches, Gordon 1969) in isochronous cyclotrons. The influence of the phase slip due to deviations from strict isochronism determines if the bunches of a specific turn are above, below or at "transition", and hence whether stable vortex motion of the bunches is possible at all. Secondly there are possible longitudinal and transverse effects of rf acceleration, the former depending on the bunch phase ("bunching" or "debunching"), the latter depending on the gradient of the accelerating voltage. High accelerating voltages in the first turns call the applicability of adiabatic approximations and analytic methods into question. The influence of the rf acceleration is expected to be significant only at low beam energy, i.e. should have small or even negligible effect beyond the central region of compact machines.  
slides icon Slides WEB03 [1.145 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-Cyclotrons2019-WEB03  
About • paper received ※ 16 September 2019       paper accepted ※ 26 September 2019       issue date ※ 20 June 2020  
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WEB04 BDSIM Simulation of the Complete Radionuclide Production Beam Line from Beam Splitter to Target Station at the PSI Cyclotron Facility 275
  • H. Zhang, R. Eichler, J. Grillenberger, W. Hirzel, S. Joray, D.C. Kiselev, J.M. Schippers, J. Snuverink, R. Sobbia, A. Sommerhalder, Z. Talip, N.P. van der Meulen
    PSI, Villigen PSI, Switzerland
  • L.J. Nevay
    Royal Holloway, University of London, Surrey, United Kingdom
  • L.J. Nevay
    JAI, Egham, Surrey, United Kingdom
  The beam line for radionuclide production on the PSI Cyclotron Facility starts with an electrostatic beam splitter, which peels protons of a few tens of microampere from a beam around two milliampere. The peeled beam is then guided onto a target station for routine production of a variety of radionuclides [1]. Beam Delivery Simulation (BDSIM), a Geant4 based simulation tool, enables the simulation of not only beam transportation through optics elements like dipoles and quadrupoles, but also particle passage through components like collimator and degrader [2-3]. Furthermore, BDSIM facilitates user built elements with accompanying electromagnetic field, which is essential for the modeling of the first element of the beam line, the electrostatic beam splitter. With a model including all elements from beam splitter to target, BDSIM simulation delivers a better specification of the beam along the complete line, for example, beam profile, beam transmission, energy spectrum, as well as power deposit, which is of importance not only for present operation but also for further development.
[1] M. Olivo and H. W. Reist, Proc. EPAC’88, Rome, Italy, June 1988, pp. 1300-1302.
[2] www.pp.rhul.ac.uk/bdsim
[3] S. Agostinelli, et al, Nucl. Instr. Meth. Phys. Res. A(3) 250-303.
slides icon Slides WEB04 [4.761 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-Cyclotrons2019-WEB04  
About • paper received ※ 13 September 2019       paper accepted ※ 26 September 2019       issue date ※ 20 June 2020  
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THA01 Precise Modelling and Large Scale Multiobjective Optimisation of Cyclotrons 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.  
slides icon Slides THA01 [6.834 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-Cyclotrons2019-THA01  
About • paper received ※ 25 September 2019       paper accepted ※ 27 September 2019       issue date ※ 20 June 2020  
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Recent Developments of the Open Source Code OPAL  
  • A. Adelmann
    PSI, Villigen PSI, Switzerland
  After a general introduction of OPAL, I will introduce a set of new features available with version 2.0 [1]. All new features will be presented together with examples of ongoing research projects. In the OPAL-cyc flavour, a robust way of generating matched distributions with linear space charge is introduced. A new method for describing fixed field accelerators (FFAs) in a very general way will be shown. A new element TRIMCOIL can be used to correct for field-errors in cyclotrons and FFAs [2]. The OPAL was extended to allow the specification of multi objective optimisation problems, which are then solved with a built in NGSA-II genetic algorithm. A new feature SAMPLER allows you to setup and run random or sequential parameter studies and seamless utilisation of a vast number of computing cores. Future plans such as the new AMR-Solver for preceise neighbouring bunch simulations will presented.
[1] A. Adelmann et al., "OPAL a Versatile Tool for Charged Particle Accelerator Simulations", arXiv:1905.06654
[2] Matthias Frey et al., "Matching of turn pattern measurements for cyclotrons using multiobjective optimization", Phys. Rev. Accel. Beams 22, 064602, 2019
slides icon Slides THA02 [15.093 MB]  
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FRB03 3D Radio Frequency Simulation of the INFN-LNS Superconducting Cyclotron 361
  • G. Torrisi, L. Allegra, L. Calabretta, A.C. Caruso, G. Costa, G. Gallo, A. Longhitano, L. Neri, D. Rifuggiato
    INFN/LNS, Catania, Italy
  An upgrade plan of the Superconducting Cyclotron operating at INFN-LNS is ongoing. In this paper, a 3D numerical model of the Cyclotron radio frequency cavity is presented. Simulations include the coaxial sliding shorts, liner vacuum chamber, coupler, trimming capacitor and the Dees structures. CST microwave studio software has been used for numerical computation. RF simulations are mandatory also in order to analyze the field in the beam region and evaluate the impact of different Dees geometry and eventual field asymmetries. Moreover, 3D COMSOL Multiphysics simulations have been carried out in order to couple the electromagnetic field solution to a custom beam-dynamics code developed in Matlab as a future plan. Time evolution of accelerated beam and electromagnetic field make also possible to verify the magnetic field synchronization. Experimental validation of the developed model will be also presented.  
slides icon Slides FRB03 [19.931 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-Cyclotrons2019-FRB03  
About • paper received ※ 15 September 2019       paper accepted ※ 25 September 2019       issue date ※ 20 June 2020  
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