WEB —  FFA Concepts, Beam Dynamics and Simulations   (25-Sep-19   10:10—12:00)
Chair: Y. Mori, KEK, Ibaraki, Japan
Paper Title Page
WEB01 Status of FFAs (Modelling and Existing/planned Machines) 266
  • J.-B. Lagrange, D.J. Kelliher, S. Machida, C.R. Prior, C.T. Rogers
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  Since their rebirth two decades ago, great progress has been made in Fixed Field alternating gradient Accelerator (FFA) design, with different optical concepts and technological developments. Several machines have been built, and others are planned. The talk will review the recent progress around the world.  
slides icon Slides WEB01 [7.965 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-Cyclotrons2019-WEB01  
About • paper received ※ 15 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
slides icon Slides WEB02 [3.099 MB]  
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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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Beam dynamics and preliminary design of the RFQ Direct Injection Project  
  • D. Winklehner
    MIT, Cambridge, Massachusetts, USA
  Injecting beam into a compact cyclotron from an external ion source usually requires a low energy beam transport line (LEBT) with several beam shaping elements (magnets and a buncher), the transfer through the cyclotron axial bore hole, and finally, bending the beam into the median plane using a spiral inflector. In the RFQ Direct Injection Project we are combining LEBT, buncher, and axial transfer within one element, the RFQ (Radio Frequency Quadrupole), which is inserted axially into the cyclotron yoke. This is a very compact solution that offers an excellent bunching efficiency. To accommodate the small diameter that is available in the axial bore hole together with a low RF frequency of 32.8 MHz, a split-coaxial RFQ type was chosen. Longitudinal and transverse de-bunching are mitigated by an internal re-bunching cell, and an external electrostatic quadrupole, respectively. The preliminary design phase of this project has been concluded and the RFQ is currently under construction at Bevatech GmbH in Germany. Here, we present the beam dynamics simulations, showing the feasibility of the system, and the preliminary design of the RFQ and test cyclotron with central region.  
slides icon Slides WEB05 [6.177 MB]  
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