Paper  Title  Page 

WEPLS02  Simulation of a Klystron Input Cavity using a SteadyState FullWave Solver  1 
SUPLM12  use link to see paper's listing under its alternate paper code  


The simulation of vacuum electronic radiofrequency (RF) power sources is generally done through semianalytical modeling approaches. These techniques are computationally efficient as they make assumptions on the source topology, such as the requirement that the electron beam travel longitudinally and interact with cylindrical modes. To simulate more general interactions, transient particleincell (PIC) codes are currently required. We present here simulation results of a 5045 klystron using a newly developed steady state code which does not make assumptions on the beam configuration or geometry of the structure and resonant modes. As we solve directly for the steadystate system dynamics, this approach is computationally efficient yet, as demonstrated through comparison with experimental results, provides similar accuracy.  
WEPLS03  Analytical Expression for a NTurn Trajectory in the Presence of Quadrupole Magnetic Errors  1 
SUPLM20  use link to see paper's listing under its alternate paper code  


The action and phase jump method is a technique, based on the use of turnbyturn experimental data in a circular accelerator, to find and measure local sources of magnetic errors through abrupt changes in the values of action and phase. At this moment, this method uses at least one pair of adjacent BPMs (Beam Position Monitors) to estimate the action and phase at one particular position in the accelerator. In this work, we propose a theoretical expression to describe the trajectory of a charged particle for an arbitrary number of turns when a magnetic error is present in the accelerator. This expression might help to estimate action and phase at one particular position of the accelerator using only one BPM in contrast to the current method that needs at least two BPMs.  
WEPLS04  Simulations of Low Energy Au^{78+} Losses in RHIC  1 


Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DEAC0298CH10886 with the U.S. Department of Energy. The RHIC Run19 BESII program features the commissioning of the Low Energy RHIC electron Cooling (LEReC) Project, which uses electron cooling techniques to compensate for intrabeam scattering and thus to improve the luminosity lifetime. During RHIC operations at 3.85 GeV (beam energy) with LEReC, one needs to ensure that the electron beam energy is properly matched for cooling purposes: if so, some of the circulating Au79 ions can recombine with an electron, turning into Au78 and circulating with a large momentum offset. Part of the LEReC commissioning steps is therefore to drive a maximized number of Au78 ions towards a chosen location of the RHIC mechanical aperture to generate particle showers that can be detected by a Recombination Monitor outside the cryostat. This article introduces the baseline lattice design, then discusses the few scenarios considered for optimizing Au78 losses at a given location. Each scenario is then simulated using new tracking tools for generating beam loss maps. 

WEPLS05  Simulation Analysis of the LCLSII Injector using ACE3P and IMPACT  1 


Funding: This work is supported by the Director of the Office of Science of the US Department of Energy under contracts DEAC0205CH11231 and DEAC0276SF00515. The LCLSII beam injector system consists of a 186 MHz normalconducting RF gun, a twocell 1.3 GHz normalconducting buncher cavity, two transverse focusing solenoids, and eight 1.3 GHz 9cell Teslalike superconducting booster cavities. With a coordinated effort between LBNL and SLAC, we have developed a simulation workflow combining the electromagnetic field solvers from ACE3P with the beam dynamics modeling code IMPACT. This workflow will be used to improve performance and minimize beam emittance for given accelerator structures through iterative optimization. In our current study, we use this workflow to compare beam quality parameters between using 2D axisymmetric field profiles and fully 3D nonaxisymmetric fields caused by geometrical asymmetries (e.g. RF coupler ports). 

WEPLS06 
Betatron Frequencies and the Poincare Rotation Number  


Symplectic maps are routinely used to describe singleparticle dynamics in circular accelerators. In the case of a linear accelerator map, the rotation number (the betatron frequency) can be easily calculated from the map itself. In the case of a nonlinear map, the rotation number is normally obtained numerically, by iterating the map for given initial conditions, or through a normal form analysis, a type of a perturbation theory for maps. Integrable maps, a subclass of symplectic maps, allow for an analytic evaluation of their rotation numbers. In this presentation we will present an analytic expression to determine the rotation number for integrable symplectic maps of the plane and present several examples, relevant to circular accelerators.  
WEPLS07 
An Emerging Framework for Particle Accelerator Simulation, Collaboration and Education  


Funding: Work supported by US Department of Energy under Award Nos. DESC0011340, DESC0015212, DESC0017181 and DESC0019682. Accelerator designers work with command line interfaces (CLI) – scripting language, code editor, postprocessing and visualization tools, lattice files, etc. Sirepo* brings new capabilities without interrupting CLI workflows – lattice files are imported to and exported from the GUI. This enables designers to work easily with students, new hires, or an expert collaborator who doesn’t know the code. Sirepo codes include elegant, Synergia, Zgoubi and JSPEC. Recent initiatives will enable access to control systems for algorithmic tuning, to data analytics tools and to machine learning algorithms. Lattice and other configuration data is stored via JSON, encapsulating what is needed for each code. This declarative approach enables a similar GUI for each code and provides an optimal path for input file conversion, benchmarking and code coupling. Sirepo is an emerging framework that could, with community support, solve problems regarding the large number of available codes. Developers can use Sirepo** to create a GUI for their own code. * Sirepo Scientific Gateway, https://sirepo.com ** Sirepo cloud computing framework, https://github.com/radiasoft/sirepo 

WEPLS08 
Computing Wake Functions in Plasma Accelerators  


Funding: This work was supported by the United States Department of Energy, Office of Science, Office of High Energy Physics under contract no. DESC0018718. Plasma accelerators driven to the blowout regime with an intense laser or electron beam are a possible candidate for a TeV lepton collider. The small scale of the nonlinear plasma wave, responsible for the large accelerating fields, also makes the dipole wake fields quite large, and the witness bunch is susceptible to beam breakup instability. Computing the wake functions for these plasma waves is useful to understand the growth rate and how to mitigate the instability, but the variable bubble radius and witness bunch loading of the plasma wave makes this distinct from computing wake functions in a beam pipe. We present a process for extracting wake functions in the blowout regime from data generated using the FBPIC pseudospectral cylindrical electromagnetic particleincell code. We demonstrate this technique for computing the m=0 wake in an axisymmetric blowout plasma wakefield accelerator using FACETIIlike parameters for the drive and witness bunch. We compare these numerical results to analytical predictions, and show how the wakes scale with the bubble radius. 

WEPLS09  Fast TwoDimensional Calculation of Coherent Synchrotron Radiation in Relativistic Beams  1 
SUPLM08  use link to see paper's listing under its alternate paper code  


Coherent Synchrotron Radiation(CSR) in a relavistic beam during compression can lead to longitudinal modulation of the bunch with wavelength smaller than bunch length and is regarded as one of the main sources of emittance growth in the bunch compressor. Current simulations containing CSR wake fields often utilize onedimensional model assuming a line beam. Despite its good computation efficiency, 1D CSR model can be inaccurate in many cases because it ignores the socalled ’compression effect’. On the other hand, the existing 3D codes are often slow and have high demands on computational resources. In this paper we propose a new method for calculation of the threedimensional CSR wakefields in relativistic beams with integrals of retarded potentials. It generalizes the 1D model and includes the transient effects at the entrance and the exit from the magnet. Within given magnetic lattice and initial beam distributions, the formalism reduces to 2D or 3D integration along the trajectory and therefore allows fast numerical calculations using 2D or 3D matrices.  
WEPLS10  Modeling of SpaceCharge Effects in the ORISS MRTOF Device for Applications to FRIB  1 
SUPLM16  use link to see paper's listing under its alternate paper code  


The Oak Ridge Isotope/Isomer Spectrometer and Separator (ORISS) is an electrostatic multiply reflecting timeofflight (MRTOF) mass separator constructed by the University Radioactive Ion Beam Consortium (UNIRIB) and Louisiana State University. The device was never fully commissioned, and was eventually shipped to Michigan State University for use at the Facility for Rare Isotopes and Beams (FRIB). The separation process is sensitive to spacecharge effects due to the reflection of ions at both ends of the trap, as well as nonlinearities in the optics. In this study we apply the timebased particleincell code Warp to model the effects of intense spacecharge during the separation process. We find that the optics can be tuned for isochronous operation and focusing in the presence of intense spacecharge to enable separation of bunches with high particle counts. This suggests the device may be effectively utilized at FRIB as a separator, spectrograph and spectrometer.  
WEPLS11  Simulation of Transparent Spin Experiment in RHIC  1 


Funding: Work supported by the U.S. DOE under Contracts No. DEAC0506OR23177 and DEAC0298CH10886. The transparent spin mode has been proposed as a new technique for preservation and control of the spin polarization of ion beams in a synchrotron. The ion rings of the proposed Jefferson Lab ElectronIon Collider (JLEIC) adopted this technique in their figure8 design. The transparent spin mode can also be setup in a racetrack with two identical Siberian snakes. There is a proposal to test the predicted features of the spin transparent mode in Relativistic Heavy Ion Collider (RHIC), which already has all of the necessary hardware capabilities. We have earlier analytically estimated the setup parameters and developed a preliminary experimental plan. In this paper we describe simulation setup and benchmarking for the proposed experiment using a Zgoubi model of RHIC. 

WEPLS12  A SemiAnalytical Approach to SixDimensional PathDependent Transport Matrices With Application to HighBrightness ChargedParticle Beam Transport  1 


Funding: This work was supported by the Fundamental Research Funds for the Central Universities under Project No. 5003131049. Efficient and accurate estimate of highbrightness electron beam dynamics is an important step to the overall performance evaluation in modern particle accelerators. Utilizing the moment description to study multiparticle beam dynamics, it is necessary to develop a pathdependent transport matrix, together with application of the driftkick algorithm*. In this paper we will construct semianalytical models for three typical beam transport elements, solenoid with fringe fields, transverse deflecting cavity, and a beam slit. To construct the semianalytical models for these elements, we begin by formulating the simplified singleparticle equations of motion, and apply typical numerical techniques to solve the corresponding sixbysix transport matrix as a function of the path coordinate. The developed semianalytical models are demonstrated with three practical examples, where our numerical results are discussed, compared with and validated by particle tracking simulations. These pathdependent transport matrix models can be incorporated to the analysis based on beam matrix method for the application to highbrightness chargedparticle beam transport. * C.Y. Tsai et al., Nuclear Inst. And Methods in Physics Research, A 937 (2019) 120 

Poster WEPLS12 [7.643 MB]  
WEPLS14  A C++ TPSA/DA Library With Python Wrapper  1 


Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DEAC0506OR23177. Truncated power series algebra (TPSA) or differential algebra (DA) is often used by accelerator physicists to generate a transfer map of a dynamic system. The map then can be used in dynamic analysis of the system or in particle tracking study. TPSA/DA can also be used in some fast algorithms, eg. the fast multipole method, for collective effect simulation. This paper reports a new TPSA/DA library written in C++. This library is developed based on Dr. Lingyun Yang’s TPSA code, which has been used in MADX and PTC. Compared with the original code, the updated version has the following changes: (1) The memory management has been revised to improve the efficiency; (2) A new data type of DA vector is defined and supported by most frequently used operators; (3) Support of inverse trigonometric functions and hyperbolic functions for the DA vector has been added; (4) function composition is revised for better efficiency; (5) a python wrapper is provided. The code is hosted at github and available to the public. 

WEPLS15 
Density Evolution Equations, Emergent Density Peaks, and Laminar Flow  


Funding: This work was supported through the NSF grants 1803719 and RC108666 We recently derived meanfield density evolution equations for the expansion of initially cold arbitrary distributions of charged particles under planar, cylindrical, and spherical symmetries within both the nonrelativistic and relativistic regime. We also recently derived the extension of the nonrelativistic theory to situations where the velocity is a function of the spatial parameter. From these theories, we showed two mechanisms that result in emergent peaks in the density, and we showed conditions on nonuniform distributions that are necessary for retaining laminar behavior of the bunch – behavior that is associated with lower emittance growth. We review the cylindrical aspect of these theories and highlight some of the relevant outcomes for the accelerator community. 
