Author: Adelmann, A.
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MOB03
 On Uncertainty Quantification in Particle Accelerator Modelling  
 
  • A. Adelmann
    PSI, Villigen PSI, Switzerland
  
  Using a cyclotron based model problem, we demonstrate for the first time [1] the applicability and usefulness of a uncertainty quantification (UQ) approach in order to construct surrogate models for quantities such as emittance, energy spread but also the halo parameter, and construct a global sensitivity analysis together with error propagation and L2 error analysis. The model problem is selected in a way that it represents a template for general high intensity particle accelerator modelling tasks. The presented physics problem has to be seen as hypothetical, with the aim to demonstrate the usefulness and applicability of the presented UQ approach and not solving a particulate problem. The proposed UQ approach is based on sparse polynomial chaos expansions and relies on a small number of high fidelity particle accelerator simulations. Within this UQ framework, the identification of most important uncertainty sources is achieved by performing a global sensitivity analysis via computing the so-called Sobols' indices. [1] A. Adelman, arXiv:1509.08130v6, 2016  
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MOD03
 A Precise 3D Beam Dynamics Model of the PSI Injector II  
 
  • A.M. Kolano
    University of Huddersfield, Huddersfield, United Kingdom
  • A. Adelmann, C. Baumgarten
    PSI, Villigen PSI, Switzerland
  • R.J. Barlow
    IIAA, Huddersfield, United Kingdom
  
  A precise beam dynamics model of the PSI Injector II operating at 2.2 mA is presented, including 3D space charge, and the collimation system. A particle distribution with an intensity of 9.5 mA (DC) is injected into the central region, shaped by a sophisticated collimator system. This defines the initial condition for the subsequent formation of a round stationary bunch. The intensity limits are estimated based on this model, additionally supported by an idealised collimator model and measurements. The production configuration current scales to the power of four with the beam size setting the limit to approximately 3 mA. Further analysis of an upgraded configuration (adding two new cavities) suggests that intensities of 5 mA could be produced with an adjusted collimation scheme. The precise beam dynamics model is based on the OPAL (Object Oriented Parallel Accelerator Library) simulation code, a tool for charged-particle optics calculations in large accelerator structures and beam lines including 3D space charge.  
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WEA04
 Update on OPAL  
 
  • A. Adelmann, A. Gsell, V. Rizzoglio
    PSI, Villigen PSI, Switzerland
  • Y. Ineichen
    IBM Research - Zurich, Rueschlikon, Switzerland
  • C.J. Metzger-Kraus
    HZB, Berlin, Germany
  • X. Pang, S.J. Russell
    LANL, Los Alamos, New Mexico, USA
  • C.T. Rogers, S.L. Sheehy
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
  • S.L. Sheehy
    JAI, Oxford, United Kingdom
  • C. Wang, J.J. Yang
    CIAE, Beijing, People's Republic of China
  • D. Winklehner
    MIT, Cambridge, Massachusetts, USA
  
  OPAL (Object Oriented Parallel Accelerator Library) is a open source tool for charged-particle optics calculations in accelerator structures and beam lines including 3D space charge, short range wake-fields, 1D coherent synchrotron radiation and particle matter interaction. OPAL admits simulations of any scale, from the laptop to the largest HPC clusters. OPAL has a fast FFT based direct solver and an iterative solver with AMR, able to handle efficiently exact boundary conditions on complex geometries. We will discuss new capabilities such as Graphical Processing Units (GPUs) support, turning your workstation into a super computer, time dependent fields necessary for modelling FFAGs, synchrotrons and synchro-cyclotrons and the creation of matched distributions with linear space charge.  
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THP18 Suppression of RF Radiation Originating from the Flattop Cavity in the PSI Ring Cyclotron 348
 
  • M. Schneider, A. Adelmann, N. Pogue, L. Stingelin
    PSI, Villigen PSI, Switzerland
  
  In the PSI Ring cyclotron, protons are accelerated from 72 MeV to 590 MeV. In several upgrade programs, the beam current was increased from the initial design value of 100 μA up to 2.4 mA. The rf-system of this separated sector cyclotron consists of 4 copper cavities running at 50 MHz for the main acceleration. For the purpose of increasing the phase acceptance of the Ring, an aluminum flattop cavity is operated at a gap voltage of 555 kVp at the 3rd harmonic frequency. As a result of the progressively increased flattop voltage, this cavity was pushed toward its mechanical and electrical limits. As a consequence rf-power is leaking into the cyclotrons vacuum chamber, which in turn caused several problems. A visible effect was the formation of plasma in the vacuum chamber *. In the last shutdown, an attempt was made to reduce the radiated rf-power. On the vacuum sealing between the flattop cavity and sector magnet 6, a shim was installed which reduces the gap for the beam from 60mm to 25mm in height. Results of this intervention will be presented and compared with finite element model simulations **.
* N.J. Pogue et al.
NIM-A: Volume 821, 11 June 2016, pp. 87 - 92.
** N.J. Pogue et al.
NIM-A: Volume 828, 21 August 2016, pp. 156 - 162. 		 
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THC02
 Matched Distributions with Linear and Non-Linear Space Charge  
 
  • M. Frey, A. Adelmann
    PSI, Villigen PSI, Switzerland
  
  This paper covers the topic of finding matched, i.e. stationary, distributions for coasting beams that takes into account higher order moments of the charge distribution. We present a general approach based on Lie-Algebra and Truncated-Power-Series Algebra, where the non-linear space-charge maps up to k-th order are constructed. The physical input parameters are intensity, projected emittances, and the energy. Our general approach is firstly compared and benchmarked with the well-known linear theory applied to the PSI Injector-2, the Ring Cyclotron and the IsoDAR machine. Secondly we compared the non-linear approach to PIC calculations. Open questions such as constraining the higher order moments will be discussed as well as applications beyond cyclotrons.  
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