Paper  Title  Page 

TUPAG17  Beamline Map Computation for Paraxial Optics  297 


Funding: Department of Energy office of Basic energy sciences, DESC0018571 Modeling of radiation transport is an important topic tightly coupled to many charged particle dynamics simulations for synchrotron light sources and FEL facilities. The radiation is determined by the electron beam and magnetic field source, and then passes through beamlines with focusing elements, apertures and monochromators, in which one may typically apply the paraxial approximation of small angular deviations from the optical axis. The radiation is then used in a wide range of spectroscopic experiments, or else may be recirculated back to the electron beam source, in the case of an FEL oscillator. The Wigner function representation of electromagnetic wavefronts has been described in the literature and allows a phase space description of the radiation, similar to that used in charged particle dynamics. It can encompass both fully and partially coherent cases, as well as polarization. Here, we describe the calculation of a beamline map that can be applied to the radiation Wigner function, reducing the computation time. We discuss the use of ray tracing and wave optics codes for the map computation and benchmarking. We construct a four crystal 1:1 imaging beamline that could be used for recirculation in an XFEL oscillator, and benchmark the map based results with SRW wavefront simulations. 

Slides TUPAG17 [2.289 MB]  
DOI •  reference for this paper ※ https://doi.org/10.18429/JACoWICAP2018TUPAG17  
About •  paper received ※ 19 October 2018 paper accepted ※ 18 December 2018 issue date ※ 26 January 2019  
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WEPAF03 
Magnetized Electron Cooling Simulations for JLEIC  


Funding: This work is supported by the U.S. DOE Office of Science, Office of Nuclear Physics, under Award Number DESC0015212. Relativistic magnetized electron cooling in untested parameter regimes is essential to achieve the ion luminosity requirements of proposed electronion collider (EIC) designs. Therefore, accurate calculations of magnetized dynamic friction are required, with the ability to include all relevant physics that might increase the cooling time, including space charge forces, field errors and complicated phase space distributions of imperfectly magnetized electron beams. We present simulations relevant to the JLEIC design, using the BETACOOL and JSPEC codes. We also present recent work on Warp simulations of the electron beam through the solenoid field. Space charge neutralization is provided by impact ionization of a background hydrogen gas. For optimal cooling it is essential that space charge be sufficiently neutralized. We also present recent work on a new analytic treatment of momentum transfer from a single magnetized electron to a drifting ion, and its use for calculations of dynamic friction. 

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WEPLG03  Theoretical and Computational Modeling of a Plasma Wakefield BBU Instability  341 


Funding: This work was supported in part by the Department of Energy, Office of Science, Office of High Energy Physics, under contract number DESC0018718. Plasma wakefield accelerators achieve accelerating gradients on the order of the wavebreaking limit, m c^{2} k_{p}/e, so that higher accelerating gradients correspond to shorter plasma wavelengths. Smallscale accelerating structures, such as plasma and dielectric wakefields, are susceptible to the beam breakup instability (BBU), which can be understood from the PanofskyWenzel theorem: if the fundamental accelerating mode scales as b^{1} for a structure radius b, then the dipole mode must scale as b^{3}, meaning that high accelerating gradients necessarily come with strong dipole wake fields. Because of this relationship, any plasmaacceleratorbased future collider will require detailed study of the tradeoffs between extracting the maximum energy from the driver and mitigating the beam breakup instability. Recent theoretical work* predicts the tradeoff between the witness bunch stability and the amount of energy that can be extracted from the drive bunch, a socalled efficiencyinstability relation . We will discuss the beam breakup instability and the efficiencyinstability relation and the theoretical assumptions made in reaching this conclusion. We will also present preliminary particleincell simulations of a beamdriven plasma wakefield accelerator used to test the domain of validity for the assumptions made in this model. * V. Lebedev, A. Burov, and S. Nagaitsev, "Efficiency versus instability in plasma accelerators", Phys. Rev. Acc. Beams 20, 121301 (2017). 

Slides WEPLG03 [2.234 MB]  
DOI •  reference for this paper ※ https://doi.org/10.18429/JACoWICAP2018WEPLG03  
About •  paper received ※ 01 November 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019  
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