BNL, Upton, Long Island, New York, USA
Electron polarization in a storage ring is subject to two very long term effects: Sokolov-Ternov polarization and depolarization by diffusion. This leads to an equilibrium state over a very long time scale, and, simulation-wise, is highly CPU-time and -memory consuming. Simulations aimed at determining optimal ring storage energy in an electron-ion collider in this context, are always based on tracking bunches with thousands of particles, and in addition for short time scales in comparison, due to HPC limitations. Based on considerations of ergodicity of electron bunch dynamics in the presence of synchrotron radiation, and on the very slow depolarization aimed at in a collider, tracking a single particle instead is investigated, here. This saves a factor of more than 2 orders of magnitudes in the parameter CPU-time*Memory-allocation, it allows much longer tracking and thus improved accuracy on the evaluation of polarization and time constants. The concept is illustrated with polarization lifetime and equilibrium polarization simulations at the eRHIC electron-ion collider.
TUPAF04
RadiaSoft LLC, Boulder, Colorado, USA
ParaTools, Inc., Eugene, Oregon, USA
BNL, Upton, Long Island, New York, USA
Sourcery Institute, Oakland, California, USA
The particle tracking code Zgoubi [*] has been used for a broad array of accelerator design studies, including FFAGs and EICs [**]. Zgoubi is currently being used to evaluate proposed designs for both JLEIC and eRHIC [***], and to prepare for commissioning the CBETA BNL-Cornell FFAG return loop ERL [****]. Moreover, Zgoubi is now the subject of a Phase II SBIR aimed at improving its speed, flexibility, and ease-of-use. In this paper, we describe our on-going work on several fronts: (i) parallelizing Zgoubi using new features of Fortran 2018, including coarrays [*****]; (ii) implementing a new particle update algorithm that requires significantly less memory and arithmetic; and (iii) developing symplectic tracking for field maps. In addition, we describe plans for a web-based graphical interface to Zgoubi.
*F Meot, FERMILAB-TM-2010
**F Lemuet, NIM-A, 547:638; F Lin, IPAC17:WEPIK114
***A Kondratenko, IPAC18:MOPML007; F Meot, IPAC18:MOPMF013
****G Hoffstaetter, IPAC18:TUYGBE2
*****J Reid, WG5 N2145
BNL, Upton, Long Island, New York, USA
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
The Cornell-BNL Electron Test Accelerator (CBETA) is a four-pass, 150 MeV energy recovery linac (ERL), now in construction at Cornell. A single fixed-field alternating gradient (FFAG) beam line recirculates the four energies, 42, 78, 114 and 150 MeV. The return loop is comprised of 107 quadrupole-doublet cells, built using Halbach permanent magnet technology. Spreader and combiner sections (4 independent beam lines each) connect the 36 MeV linac to the FFAG loop. We present here a start-to-end simulation of the 4-pass ERL, entirely, and exclusively, based on the use of magnetic field maps to model the magnets and correctors. There are paramount reasons for that and this is discussed, detailed outcomes are presented, together with comparisons with regular beam transport (mapping based) techniques.
BNL, Upton, Long Island, New York, USA
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
BNL, Upton, Long Island, New York, USA
Closed orbit calculations of the AGS synchrotron were performed and the beam parameters at the extraction point of the AGS [1] were calculated using the RAYTRACE computer code [2] which was modified to generate 3D fields from the experimentally measured field maps on the median plane of the AGS combined function magnets. The algorithm which generates 3D fields from field maps on a plane is described in reference [3] which discusses the details of the mathematical foundation of this approach. In this presentation we will discuss results from studies [1,4] that are based on the 3D fields generated from the known field components on a rectangular grid of a plane. A brief overview of the algorithm used will be given, and two methods of calculating the required field derivatives on the plane will be presented. The calculated 3D fields of a modified Halbach magnet [5] of inner radius of 4.4 cm will be calculated using the two different methods of calculating the field derivatives on the plane and the calculated fields will be compared against the ’ideal’ fields as calculated by the OPERA computer code [6]. [1] N. Tsoupas et. al. ’Closed orbit calculations at AGS and Extraction Beam Parameters at H13 AD/RHIC/RD-75 Oct. 1994 [2] S.B. Kowalski and H.A. Enge ’The Ion-Optical Program Raytrace’ NIM A258 (1987) 407 [3] K. Makino, M. Berz, C. Johnstone, Int. Journal of Modern Physics A 26 (2011) 1807-1821 [4] N. Tsoupas et. al. ’Effects of Dipole Magnet Inhomogeneity on the Beam Ellipsoid’ NIM A258 (1987) 421-425 [5] ’The CBETA project: arXiv.org > physics > arXiv:1706.04245’’ [6] Vector Fields Inc. https://operafea.com/