ICAP2018 - Table of Session: TUPAF (Tuesday Parallel Fiesta Key)

Paper	Title	Page
TUPAF01	Upgrade of MAD-X for HL-LHC Project and FCC Studies	165
	L. Deniau, H. Burkhardt, R. De Maria, M. Giovannozzi, J.M. Jowett, A. Latina, T. Persson, F. Schmidt, I.S. Shreyber, P.K. Skowroński CERN, Geneva, Switzerland T.G. Gläßle HIT, Heidelberg, Germany
	The design efforts for the High Luminosity upgrade of the Large Hadron Collider (HL-LHC) and for the FCC-ee project required significant extensions of the MAD-X code widely used for designing and simulating particle accelerators. The modelling of synchrotron radiation effects has recently been reviewed, improved and tested on the lattices of ESRF, LEP and CLIC Final Focus System. The results were cross checked with the codes AT, PLACET, Geant4, and MAD8. The implementation of space charge has been drastically restructured in a modular design. The linear coupling calculation has been completely reviewed and improved, from the theory to the implementation in MAD-X code to ensure its correctness in the presence of strong coupling as in the HL-LHC studies. The slicing module has been generalised to allow for thick slices of bending magnets, quadrupoles and solenoids. The SBEND element has been extended to support difference between bending angle and integrated dipole strength. Patches have been added to the list of supported elements. MAD-X PTC has also been extended to track resonance driving terms along layouts, and to support AC dipoles to simulate beams during optics measurements.
	Slides TUPAF01 [5.986 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF01
About •	paper received ※ 17 October 2018 paper accepted ※ 24 October 2018 issue date ※ 26 January 2019
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TUPAF02	SixTrack Project: Status, Runtime Environment, and New Developments	172
	R. De Maria, J. Andersson, L. Field, M. Giovannozzi, P.D. Hermes, N. Hoimyr, G. Iadarola, S. Kostoglou, E.H. Maclean, E. McIntosh, A. Mereghetti, J. Molson, V.K.B. Olsen, D. Pellegrini, T. Persson, M. Schwinzerl, K.N. Sjobak CERN, Geneva, Switzerland E.H. Maclean University of Malta, Information and Communication Technology, Msida, Malta S. Singh Indian Institute of Technology Madras, Chennai, India K.N. Sjobak University of Oslo, Oslo, Norway I. Zacharov EPFL, Lausanne, Switzerland
	Funding: Research supported by the HL-LHC project and Google Summer of Code 2018. SixTrack is a single-particle tracking code for high-energy circular accelerators routinely used at CERN for the Large Hadron Collider (LHC), its luminosity upgrade (HL-LHC), the Future Circular Collider (FCC), and the Super Proton Synchrotron (SPS) simulations. The code is based on a 6D symplectic tracking engine, which is optimised for long-term tracking simulations and delivers fully reproducible results on several platforms. It also includes multiple scattering engines for beam-matter interaction studies, as well as facilities to run integrated simulations with FLUKA and GEANT4. These features differentiate SixTrack from general-purpose, optics-design software like MAD-X. The code recently underwent a major restructuring to merge advanced features into a single branch, such as multiple ion species, interface with external codes, and high-performance input/output (XRootD, HDF5). This restructuring also removed a large number of build flags, instead enabling/disabling the functionality at run-time. In the process, the code was moved from Fortran 77 to Fortran 2018 standard, also allowing and achieving a better modularization. Physics models (beam-beam effects, RF-multipoles, current carrying wires, solenoid, and electron lenses) and methods (symplecticity check) have also been reviewed and refined to offer more accurate results. The SixDesk runtime environment allows the user to manage the large batches of simulations required for accurate predictions of the dynamic aperture. SixDesk supports CERN LSF and HTCondor batch systems, as well as the BOINC infrastructure in the framework of the LHC@Home volunteering computing project. SixTrackLib is a new library aimed at providing a portable and flexible tracking engine for single- and multi-particle problems using the models and formalism of SixTrack. The tracking routines are implemented in a parametrized C code that is specialised to run vectorized in CPUs and GPUs, by using SIMD intrinsics, OpenCL 1.2, and CUDA tech
	Slides TUPAF02 [0.938 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF02
About •	paper received ※ 18 October 2018 paper accepted ※ 24 October 2018 issue date ※ 26 January 2019
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TUPAF03	Update on the Status of Linac Part of the PyORBIT Code
	A.P. Shishlo ORNL, Oak Ridge, Tennessee, USA
	Funding: This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC0500OR22725 with the U.S. Department of Energy. The structure and capabilities of the linac beam dynamics part of the PyORBIT code are presented. The PyORBIT is an open source code, a descendant of the original ORBIT code that was developed at the Spallation Neutron Source (SNS) for design, commissioning, and studies of the ring. The linac part was started 8 years ago to utilize PyORBIT classes and infrastructure for the SNS linac simulations. The PyORBIT linac model has its own lattice description that is necessary to include lattice elements significantly different from the PyORBIT ring elements. The most important among them are accelerating RF structures. The five different RF gap models recently implemented in PyORBIT are discussed. Some benchmarks of the PyORBIT with Parmila, the XAL Online Model, and TraceWin code are presented.
	Slides TUPAF03 [3.244 MB]
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TUPAF04	Zgoubi: Recent Developments and Future Plans
	D.T. Abell RadiaSoft LLC, Boulder, Colorado, USA I.B. Beekman ParaTools, Inc., Eugene, Oregon, USA F. Méot BNL, Upton, Long Island, New York, USA D.W.I. Rouson Sourcery Institute, Oakland, California, USA
	Funding: This work was supported in part by the US Department of Energy, Office of Science, Office of Nuclear Physics under Award No. DE-SC0017181. 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
	Slides TUPAF04 [3.011 MB]
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TUPAF05	Advances in Accelerator Modeling with Parallel Multi-Physics Code Suite ACE3P
	L. Xiao, L. Ge, Z. Li, C.-K. Ng SLAC, Menlo Park, California, USA
	ACE3P is a comprehensive set of parallel finite-element codes for multi-physics modeling of accelerator structures including integrated electromagnetic, thermal and mechanical effects. Recent advances of ACE3P have been focused on the development of multi-physics modeling capabilities, implementation of advanced numerical algorithms, and improvement of code performance on state-of-the-art high-performance computing (HPC) platforms for large-scale accelerator applications. A nonlinear eigensolver using the CORK algorithm [1] has been implemented in the eigensolver module Omega3P to enable accurate determination of damping factors of resonant modes above the beampipe cutoff frequency. It has enabled the first-ever direct calculation of trapped modes in the TESLA TTF cryomodules, providing reliable damping factors that were validated against measurements. A newly developed mechanical eigensolver in the multi-physics module TEM3P has allowed the determination of mechanical modes in Fermilab PIP-II high beta 650 MHz cryomodule, demonstrating mode coupling between the 6 cavities in the cryomodule. To exploit multi-core computer architectures on supercomputers, a hybrid MPI+OpenMP parallel programing has been developed in the particle tracking module Track3P to speed up dark current simulation in multiple cavities for the LCLS-II linac. Highlights of these developments and their impacts on accelerator modeling using HPC will be presented. [1] R. Van Beeuman, Invited talk, this conference.
	Slides TUPAF05 [1.355 MB]
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TUPAF06	Simulations of Longitudinal Beam Stabilisation in the CERN SPS With BLonD	179
	J. Repond, K. Iliakis, M. Schwarz, E.N. Shaposhnikova CERN, Meyrin, Switzerland
	The Super Proton Synchrotron (SPS) at CERN, the Large Hadron Collider (LHC) injector, will be pushed to its limits for the production of the High Luminosity LHC proton beam while beam quality and stability in the longitudinal plane are influenced by many effects. Particle simulation codes are an essential tool to study the beam instabilities. BLonD, developed at CERN, is a 2D particle-tracking simulation code, modelling the longitudinal phase space motion of single and multi-bunch beams in multi-harmonic RF systems. Computation of collective effects due to the machine impedance and space charge is done on a multi-turn basis. Various beam and cavity control loops of the RF system are implemented (phase, frequency and synchro-loops, and one-turn delay feedback) as well as RF phase noise injection used for controlled emittance blow-up. The longitudinal beam stability simulations during long SPS acceleration cycle (~ 20 s) include a variety of effects (beam loading, particle losses, controlled blow-up, double RF system operation, low-level RF control, injected bunch distribution, etc.). Simulations for the large number of bunches in the nominal LHC batch (288) use the longitudinal SPS impedance model containing broad and narrow-band resonances between 50 MHz and 4 GHz. This paper presents a study of beam stabilisation in the double harmonic RF system of the SPS system with results substantiated, where possible, by beam measurements.
	Slides TUPAF06 [1.518 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF06
About •	paper received ※ 18 October 2018 paper accepted ※ 24 October 2018 issue date ※ 26 January 2019
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TUPAF07	Recent Developments of the Open Source Code OPAL
	A. Adelmann PSI, Villigen PSI, Switzerland
	After a general introduction of OPAL, I will introduce a set of new features available with version 2.0 released in July 2018. All new features will be presented together with examples of ongoing research projects. In the OPAL-t flavour, elements can now be placed in 3D, without restriction. Overlapping fringe fields are handled, and off-momentum beams as occurring in tolerance studies can be tracked. Furthermore, survey plots of placed elements are a valuable diagnostic when dealing with complex designs. A new element, a flexibly configurable collimator, will be presented. In the OPAL-cyc flavour, a robust way of generating matched distributions with linear space charge is introduced. A new method for describing fixed field accelerators (FFAs) in a very general way will be shown. A new element TRIMCOIL can be used to correct for field-errors in cyclotrons and FFAs. The OPAL language (a derivative of the MAD language) was extended to allow the specification of multi objective optimisation problems, which are then solved with a built in NGSA-II genetic algorithm. A new feature SAMPLER allows you to setup and run random or sequential parameter studies and seamless utilisation of a vast number of computing cores. Finally, a set of Python tools (pyOPALTools) was created for post processing. The manual is now available on the OPAL-wiki as well as in pdf format.
	Slides TUPAF07 [2.778 MB]
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TUPAF08	A Full Field-Map Modeling of Cornell-BNL CBETA 4-Pass Energy Recovery Linac	186
	F. Méot, S.J. Brooks, D. Trbojevic, N. Tsoupas BNL, Upton, Long Island, New York, USA J.A. Crittenden Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy 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.
	Slides TUPAF08 [2.568 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF08
About •	paper received ※ 23 October 2018 paper accepted ※ 07 December 2018 issue date ※ 26 January 2019
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TUPAF09	Multi Pass Energy Recovery Linac Design With a Single Fixed Field Magnet Return Line	191
	D. Trbojevic, J.S. Berg, S.J. Brooks, F. Méot, N. Tsoupas BNL, Upton, Long Island, New York, USA W. Lou Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	We present a new approach of the Energy Recovery Linac Design for the future projects: PERLE (Powerful Energy Recovery Linac for Experiments), LHeC/FCCeH and eR- HIC. The concept uses superconducting linacs and a single xed eld beam line with multiple energy passes of electron beams. This represents an update to the existing CBETA (Cornell University Brookhaven National Laboratory ERL Test Accelerator) where the superconducting linac uses a single xed eld magnet beam line with four energy passes during acceleration and four passes during the energy recov- ery. To match the single xed eld beam line to the linac the CBETA uses the spreaders and combiners on both sides of the linac, while the new concept eliminates them. The arc cells from the single xed eld beam line are connected to the linac with adiabatic transition arcs wher cells increase in length. The orbits of di erent energies merge into a sin- gle orbit through the interleaved linac within the straight sections as in the CBETA project. The betatron functions from the arcs are matched to the linac. The time of ight of di erent electron energies is corrected for the central orbits by additional correction magnet controlled induced beam oscillations.
	Slides TUPAF09 [3.935 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF09
About •	paper received ※ 22 October 2018 paper accepted ※ 27 January 2019 issue date ※ 26 January 2019
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TUPAF10	Experience With CBETA Online Modeling Tools	196
	C.M. Gulliford, A.C. Bartnik, J. Dobbins, D. Sagan Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA J.S. Berg BNL, Upton, Long Island, New York, USA A. Nunez-delPrado UCF, Orlando, USA
	Funding: NYSERDA, the New York StateEnergy Research and Development Agency The Cornell-Brookhaven CBETA machine is a four pass Energy Recovery Linac (ERL) with a Non-scaling Fixed-Field Alternating gradient (NS-FFA) arc. For online modeling of single particle dynamics in CBETA, a customized version of the Tao program, which is based upon the Bmad toolkit, has been developed. This online program, called CBETA-V, is interfaced to CBETA’s EPICS control system. This paper describes the online modeling system and initial experience during machine running.
	Slides TUPAF10 [4.227 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF10
About •	paper received ※ 17 October 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019
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TUPAF11	Advanced Design and Simulation of Fixed-Field Accelerators
	C. Johnstone Fermilab, Batavia, Illinois, USA M. Berz, K. Makino MSU, East Lansing, Michigan, USA P. Snopok Illinois Institute of Technology, Chicago, Illlinois, USA
	Funding: Work supported by Fermi Research Alliance, LLC under contract no. DE-AC02-07CH11359 The development of new types of accelerators that allow wide choices of parameters, promote complicated fields, and often need to efficiently handle very large emittance beams requires the availability of new simulation environments to design and accurately predict operation. This is particularly true of Fixed-field accelerators, FFAs, which apply arbitrary-order fields - both alternating gradient, strong focusing - but also weak-focusing cyclotrons. This is especially applicable at medium-to-high energy combined with high intensity (mA currents). Synchrotron and cyclotron codes are generally inadequate to simulate accurately the performance of these strong-focusing fixed-field accelerators, particularly the new breed of non-scaling machines which have difficult, high-order fringe-field and edge-angle effects. One well-supported code, COSY INFINITY (COSY) is particularly suitable for accurate, high-order descriptions of accelerators. New tools have been developed in COSY INFINITY to address and accurately represent complex fixed-field machines in both a sector and spiral sector footprint. A description, application, and comparison of these tools with fields from magnet lattice design is presented.
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TUPAF12	Longitudinal Beam Dynamics With a Higher-Harmonic Cavity for Bunch Lengthening	202
	G. Bassi, J. Tagger BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy We discuss the longitudinal beam dynamics in storage rings in the presence of a higher-harmonic cavity (HHC) system for bunch lengthening. We first review the general conditions for HHC operations, either in active or passive mode, assuming the stability of the system. For uniform filling patterns, a distinction is made between operations with a normal-conducting HHC, where optimal conditions for bunch lengthening can be satisfied, and operations with super-conducting HHC, where optimal conditions can be met only approximately. The option to operate the NSLS-II storage ring with a passive, super-conducting third harmonic cavity (3HC) system is discussed next. The stability and performance of the system in the presence of a gap in the uniform filling, which corresponds to the present mode of operation of the NSLS-II storage ring, is investigated with self-consistent Vlasov-Fokker-Planck simulations performed with the code SPACE. G. Bassi, A. Blednykh and V. Smaluk, Phys Rev. Accel. Beams 19, 024401 (2016).
	Slides TUPAF12 [17.562 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF12
About •	paper received ※ 20 October 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019
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TUPAF13	Calculation of the AGS Optics Based on 3D Fields Derived From Experimentally Measured Fields on Median Plane	209
	N. Tsoupas, J.S. Berg, S.J. Brooks, F. Méot, V. Ptitsyn, D. Trbojevic BNL, Upton, Long Island, New York, USA
	Funding: Work supported by the US Department of Energy 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/
	Slides TUPAF13 [1.772 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF13
About •	paper received ※ 20 October 2018 paper accepted ※ 07 December 2018 issue date ※ 26 January 2019
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TUPAF14	Analytical Calculations for Thomson Backscattering Based Light Sources	215
	P.I. Volz, A. Meseck HZB, Berlin, Germany
	There is a rising interest in Thomson-backscattering based light sources, as scattering intense laser radiation on MeV electrons produces high energy photons that would require GeV or even TeV electron beams when using conventional undulators or dipoles. Particularly, medium energy high brightness beams delivered by LINACs or Energy Recovery LINACs, such as BERLinPro being built at Helmholtz-Zentrum Berlin, seem suitable for these sources. In order to study the merit of Thomson-backscattering-based light sources, we are developing an analytical code to simulate the characteristics of the Thomson scattered radiation. The code calculates the distribution of scattered radiation depending on the incident angle and polarization of the laser radiation. Also the impact of the incident laser profile and the full 6D bunch profile, including microbunching, are incorporated. The Status of the code and first results will be presented.
	Slides TUPAF14 [3.289 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF14
About •	paper received ※ 21 October 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019
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TUPAF15	A Holistic Approach to Simulating Beam Losses in the Large Hadron Collider Using BDSIM	221
	S.D. Walker, A. Abramov, S.T. Boogert, H. Garcia Morales, S.M. Gibson, L.J. Nevay, H. Pikhartova, W. Shields JAI, Egham, Surrey, United Kingdom
	To fully understand the beam losses, subsequent radiation, energy deposition, backgrounds and activation in particle accelerators, a holistic approach combining a 3-D model, physics processes and accelerator tracking is required. Beam Delivery Simulation (BDSIM) is a program developed to simulate the passage of particles, both primary and secondary, in particle accelerators and calculate the energy deposited by these particles via material interactions using the Geant4 physics library. A Geant4 accelerator model is built from an existing optical description of a lattice by procedurally placing a set of predefined accelerator components. These generic components can be refined to an arbitrary degree of detail with the use of user-defined geometries, detectors, field maps, and more. A detailed model of the Large Hadron Collider has been created in BDSIM, validated with existing tracking codes and applied to study beam loss patterns.
	Slides TUPAF15 [2.065 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF15
About •	paper received ※ 31 October 2018 paper accepted ※ 08 December 2018 issue date ※ 26 January 2019
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TUPAF16	Analysis of the Beam Loss Mechanism During the Energy Ramp-Up at the SAGA-LS	227
	Y. Iwasaki SAGA, Tosu, Japan
	The accelerator of the SAGA Light Source consists of 255 MeV injector linac　and 1.4 GeV storage ring. The accumulated electron beam current of the　storage ring is about 300 mA. The energy of　the electrons are raised up to 1.4 GeV in 4 minutes in the storage ring. At the moment of the　beam acceleration (the beam energy is lower than 300 MeV), the electron　beam is lost like the step function. The lost beam current is normally　about 5 mA to 30 mA. The beam loss at the energy ramp-up is not observed, when the beam current is lower than 200 mA. To understand the beam loss mechanism, which depend on the beam current, we developed high-speed logging system of 100 kHz for monitoring the beam current and the magnets power supplies using National Instruments PXI. We investigated the relationship between the beam loss and the betatron tune shifts. The tune shifts during the beam acceleration were analyzed from the measured data of the output current of the magnets power supplies by using beam tracking code of TRACY2. By adopting the new high-speed logging system, the time structure of the beam loss process was clearly observed. We will present the high-speed logging system developed for monitoring the beam current and the power supplies at this meeting. The results of the investigation to find the relationship of the beam loss and the tune shifts will be also shown.
	Slides TUPAF16 [1.286 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF16
About •	paper received ※ 19 October 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019
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TUPAF19	pyaopt Optimization Suite and its Applications to an SRF Cavity Design for UEMs	229
	A. Liu, P.V. Avrakhov, R.A. Kostin Euclid TechLabs, LLC, Solon, Ohio, USA C.-J. Jing Euclid Beamlabs LLC, Bolingbrook, USA
	Funding: DOE SBIR In order to achieve sharp, high resolution real-time imaging, electrons in a MeV UEM (ultrafast electron microscope) beamline need to minimize instabilities. The Superconducting RF (SRF) photocathode gun is a promising candidate to produce highly stable electrons for UEM/UED applications. It operates in an ultrahigh Q, CW mode, and dissipates a few watts of RF power, which make it possible to achieve a 10s ppm level of beam stability by using modern RF control techniques. In order to find the best performance of the gun design, an optimization procedure is required. pyaopt is a Python-based optimization suite that supports multi-objective optimizations using advanced algorithms. In this paper, the novel SRF photogun design and its optimizations through pyaopt and Astra’s beam simulations will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF19
About •	paper received ※ 22 October 2018 paper accepted ※ 15 December 2018 issue date ※ 26 January 2019
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TUPAF20	Mean-Field Density Evolution of Bunched Particles With Non-Zero Initial Velocity	233
	B.S. Zerbe, P.M. Duxbury MSU, East Lansing, Michigan, USA
	Funding: NSF Grant 1625181 NSF Grant RC108666 MSU Col. Nat. Sci., Provost Off., Col. Comm. Art and Sci. Reed (2006) presented a 1D mean-field model of initially cold pancake-beam expansion demonstrating that the evolution of the entire spatial distribution can be solved for all time where the 1D assumption holds. This model is relevant to ultra-fast electron microscopy as it describes the evolution of the distribution within the photoelectron gun, and this model is similar to Anderson’s sheet beam density time dependence (Anderson 1987) except that Reed’s theory applies to freely expanding beams instead of beams within a focussing channel. Our recent work (Zerbe 2018) generalized Reed’s analysis to cylindrical and spherical geometries demonstrating the presence of a shock that is seen in the Coulomb explosion literature under these geometries and further discussed the absence of a shock in the 1D model. This work is relevant as it offers a mechanistic explanation of the ring-like density shock that arises in non-equilibrium pancake-beams within the photoelectron gun; moreover, this shock is coincident with a region of high-temperature electrons providing an explanation for why experimentally aperturing the electron bunch results in a greater than 10-fold improvement in beam emittance(Williams 2017), possibly even resulting in bunch emittance below the intrinsic emittance of the cathode. However, this theory has been developed for cold-bunches, i.e. bunches of electrons with 0 initial momentum. Here, we briefly review this new theory and extend the cylindrical- and spherical- symmetric distribution to ensembles that have non-zero initial momentum distributions that are symmetric but otherwise unrestricted demonstrating how initial velocity distributions couple to the shocks seen in the less general formulation. Further, we derive and demonstrate how the laminar condition may be propagated through beam foci.
	Slides TUPAF20 [1.396 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF20
About •	paper received ※ 19 October 2018 paper accepted ※ 15 December 2018 issue date ※ 26 January 2019
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TUPAF22	FEL Simulation Using the Lie Method	240
	K. Hwang, J. Qiang LBNL, Berkeley, California, USA
	Funding: U.S. Department of Energy under Contract No. DE-AC02-05CH11231 Advances in numerical methods for free-electron-laser~(FEL) simulation under wiggler period averaging~(WPA) are presented. First, WPA is generalized using perturbation Lie map method. The conventional WPA is identified as the leading order contribution. Next, a widely used shot-noise modeling method is improved along with a particle migration scheme across the numerical mesh. The artificial shot noise arising from particle migration is suppressed. The improved model also allows using arbitrary mesh size, slippage resolution, and integration step size. These advances will improve modeling of longitudinal beam profile evolution for fast FEL simulation.
	Slides TUPAF22 [2.245 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF22
About •	paper received ※ 17 October 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019
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TUPAF23	Start-to-End Simulations of THz SASE FEL Proof-of-Principle Experiment at PITZ	246
	M. Krasilnikov, P. Boonpornprasert, F. Stephan DESY Zeuthen, Zeuthen, Germany H.-D. Nuhn SLAC, Menlo Park, California, USA E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	The Photo Injector Test facility at DESY in Zeuthen (PITZ) develops high brightness electron sources for modern linac-based Free Electron Lasers (FELs). The PITZ accelerator has been proposed as a prototype for a tunable, high power THz source for pump and probe experiments at the European XFEL. A Self-Amplified Spontaneous Emission (SASE) FEL is considered to generate the THz pulses. High radiation power can be achieved by utilizing high charge (4 nC) shaped electron bunches from the PITZ photo injector. THz pulse energy of up to several mJ is expected from preliminary simulations for 100 um radiation wavelength. For the proof-of-principle experiments a re-usage of LCLS-I undulators at the end of the PITZ beamline is under studies. One of the challenges for this setup is transport and matching of the space charge dominated electron beam through the narrow vacuum chamber. Start-to-end simulations for the entire experimental setup - from the photocathode to the SASE THz generation in the undulator section - have been performed by combination of several codes: ASTRA, SC and GENESIS-1.3. The space charge effect and its impact onto the output THz radiation have been studied. The results of these simulations will be presented and discussed.
	Slides TUPAF23 [2.534 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF23
About •	paper received ※ 18 October 2018 paper accepted ※ 24 October 2018 issue date ※ 26 January 2019
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TUPAF24	Numerical Simulations for Generating Fully Coherent Soft X-Ray Free Electron Lasers With Ultra-Short Wavelength
	K.S. Zhou SINAP, Shanghai, People’s Republic of China
	Funding: Shanghai Institute of Applied Physics, Chinese Academy of Sciences For the fully coherent, ultra-short and high power soft x-rays are becoming key instruments in different research fields, such as biology, chemistry or physics. However it’s not easy to generate this kind of advantaged light source by conventional lasers, especially for the soft x-rays with ultra-short wavelength. The external seeded free electron laser (FEL) is considered as one feasible method. Here, we give an example to generate fully coherent soft x-rays with the wavelength 1nm by the two-stage cascaded FELs. The EEHG scheme is used in the first-stage while the HGHG scheme is used in the second-stage.
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Paper

Title

Page

Upgrade of MAD-X for HL-LHC Project and FCC Studies

165

L. Deniau, H. Burkhardt, R. De Maria, M. Giovannozzi, J.M. Jowett, A. Latina, T. Persson, F. Schmidt, I.S. Shreyber, P.K. Skowroński
CERN, Geneva, Switzerland
T.G. Gläßle
HIT, Heidelberg, Germany

The design efforts for the High Luminosity upgrade of the Large Hadron Collider (HL-LHC) and for the FCC-ee project required significant extensions of the MAD-X code widely used for designing and simulating particle accelerators. The modelling of synchrotron radiation effects has recently been reviewed, improved and tested on the lattices of ESRF, LEP and CLIC Final Focus System. The results were cross checked with the codes AT, PLACET, Geant4, and MAD8. The implementation of space charge has been drastically restructured in a modular design. The linear coupling calculation has been completely reviewed and improved, from the theory to the implementation in MAD-X code to ensure its correctness in the presence of strong coupling as in the HL-LHC studies. The slicing module has been generalised to allow for thick slices of bending magnets, quadrupoles and solenoids. The SBEND element has been extended to support difference between bending angle and integrated dipole strength. Patches have been added to the list of supported elements. MAD-X PTC has also been extended to track resonance driving terms along layouts, and to support AC dipoles to simulate beams during optics measurements.

Slides TUPAF01 [5.986 MB]

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TUPAF02

SixTrack Project: Status, Runtime Environment, and New Developments

172

R. De Maria, J. Andersson, L. Field, M. Giovannozzi, P.D. Hermes, N. Hoimyr, G. Iadarola, S. Kostoglou, E.H. Maclean, E. McIntosh, A. Mereghetti, J. Molson, V.K.B. Olsen, D. Pellegrini, T. Persson, M. Schwinzerl, K.N. Sjobak
CERN, Geneva, Switzerland
E.H. Maclean
University of Malta, Information and Communication Technology, Msida, Malta
S. Singh
Indian Institute of Technology Madras, Chennai, India
K.N. Sjobak
University of Oslo, Oslo, Norway
I. Zacharov
EPFL, Lausanne, Switzerland

Funding: Research supported by the HL-LHC project and Google Summer of Code 2018.
SixTrack is a single-particle tracking code for high-energy circular accelerators routinely used at CERN for the Large Hadron Collider (LHC), its luminosity upgrade (HL-LHC), the Future Circular Collider (FCC), and the Super Proton Synchrotron (SPS) simulations. The code is based on a 6D symplectic tracking engine, which is optimised for long-term tracking simulations and delivers fully reproducible results on several platforms. It also includes multiple scattering engines for beam-matter interaction studies, as well as facilities to run integrated simulations with FLUKA and GEANT4. These features differentiate SixTrack from general-purpose, optics-design software like MAD-X. The code recently underwent a major restructuring to merge advanced features into a single branch, such as multiple ion species, interface with external codes, and high-performance input/output (XRootD, HDF5). This restructuring also removed a large number of build flags, instead enabling/disabling the functionality at run-time. In the process, the code was moved from Fortran 77 to Fortran 2018 standard, also allowing and achieving a better modularization. Physics models (beam-beam effects, RF-multipoles, current carrying wires, solenoid, and electron lenses) and methods (symplecticity check) have also been reviewed and refined to offer more accurate results. The SixDesk runtime environment allows the user to manage the large batches of simulations required for accurate predictions of the dynamic aperture. SixDesk supports CERN LSF and HTCondor batch systems, as well as the BOINC infrastructure in the framework of the LHC@Home volunteering computing project. SixTrackLib is a new library aimed at providing a portable and flexible tracking engine for single- and multi-particle problems using the models and formalism of SixTrack. The tracking routines are implemented in a parametrized C code that is specialised to run vectorized in CPUs and GPUs, by using SIMD intrinsics, OpenCL 1.2, and CUDA tech

Slides TUPAF02 [0.938 MB]

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TUPAF03

Update on the Status of Linac Part of the PyORBIT Code

A.P. Shishlo
ORNL, Oak Ridge, Tennessee, USA

Funding: This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC0500OR22725 with the U.S. Department of Energy.
The structure and capabilities of the linac beam dynamics part of the PyORBIT code are presented. The PyORBIT is an open source code, a descendant of the original ORBIT code that was developed at the Spallation Neutron Source (SNS) for design, commissioning, and studies of the ring. The linac part was started 8 years ago to utilize PyORBIT classes and infrastructure for the SNS linac simulations. The PyORBIT linac model has its own lattice description that is necessary to include lattice elements significantly different from the PyORBIT ring elements. The most important among them are accelerating RF structures. The five different RF gap models recently implemented in PyORBIT are discussed. Some benchmarks of the PyORBIT with Parmila, the XAL Online Model, and TraceWin code are presented.

Slides TUPAF03 [3.244 MB]

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TUPAF04

Zgoubi: Recent Developments and Future Plans

D.T. Abell
RadiaSoft LLC, Boulder, Colorado, USA
I.B. Beekman
ParaTools, Inc., Eugene, Oregon, USA
F. Méot
BNL, Upton, Long Island, New York, USA
D.W.I. Rouson
Sourcery Institute, Oakland, California, USA

Funding: This work was supported in part by the US Department of Energy, Office of Science, Office of Nuclear Physics under Award No. DE-SC0017181.
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

Slides TUPAF04 [3.011 MB]

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TUPAF05

Advances in Accelerator Modeling with Parallel Multi-Physics Code Suite ACE3P

L. Xiao, L. Ge, Z. Li, C.-K. Ng
SLAC, Menlo Park, California, USA

ACE3P is a comprehensive set of parallel finite-element codes for multi-physics modeling of accelerator structures including integrated electromagnetic, thermal and mechanical effects. Recent advances of ACE3P have been focused on the development of multi-physics modeling capabilities, implementation of advanced numerical algorithms, and improvement of code performance on state-of-the-art high-performance computing (HPC) platforms for large-scale accelerator applications. A nonlinear eigensolver using the CORK algorithm [1] has been implemented in the eigensolver module Omega3P to enable accurate determination of damping factors of resonant modes above the beampipe cutoff frequency. It has enabled the first-ever direct calculation of trapped modes in the TESLA TTF cryomodules, providing reliable damping factors that were validated against measurements. A newly developed mechanical eigensolver in the multi-physics module TEM3P has allowed the determination of mechanical modes in Fermilab PIP-II high beta 650 MHz cryomodule, demonstrating mode coupling between the 6 cavities in the cryomodule. To exploit multi-core computer architectures on supercomputers, a hybrid MPI+OpenMP parallel programing has been developed in the particle tracking module Track3P to speed up dark current simulation in multiple cavities for the LCLS-II linac. Highlights of these developments and their impacts on accelerator modeling using HPC will be presented.
[1] R. Van Beeuman, Invited talk, this conference.

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TUPAF06

Simulations of Longitudinal Beam Stabilisation in the CERN SPS With BLonD

179

J. Repond, K. Iliakis, M. Schwarz, E.N. Shaposhnikova
CERN, Meyrin, Switzerland

The Super Proton Synchrotron (SPS) at CERN, the Large Hadron Collider (LHC) injector, will be pushed to its limits for the production of the High Luminosity LHC proton beam while beam quality and stability in the longitudinal plane are influenced by many effects. Particle simulation codes are an essential tool to study the beam instabilities. BLonD, developed at CERN, is a 2D particle-tracking simulation code, modelling the longitudinal phase space motion of single and multi-bunch beams in multi-harmonic RF systems. Computation of collective effects due to the machine impedance and space charge is done on a multi-turn basis. Various beam and cavity control loops of the RF system are implemented (phase, frequency and synchro-loops, and one-turn delay feedback) as well as RF phase noise injection used for controlled emittance blow-up. The longitudinal beam stability simulations during long SPS acceleration cycle (~ 20 s) include a variety of effects (beam loading, particle losses, controlled blow-up, double RF system operation, low-level RF control, injected bunch distribution, etc.). Simulations for the large number of bunches in the nominal LHC batch (288) use the longitudinal SPS impedance model containing broad and narrow-band resonances between 50 MHz and 4 GHz. This paper presents a study of beam stabilisation in the double harmonic RF system of the SPS system with results substantiated, where possible, by beam measurements.

Slides TUPAF06 [1.518 MB]

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TUPAF07

Recent Developments of the Open Source Code OPAL

A. Adelmann
PSI, Villigen PSI, Switzerland

After a general introduction of OPAL, I will introduce a set of new features available with version 2.0 released in July 2018. All new features will be presented together with examples of ongoing research projects. In the OPAL-t flavour, elements can now be placed in 3D, without restriction. Overlapping fringe fields are handled, and off-momentum beams as occurring in tolerance studies can be tracked. Furthermore, survey plots of placed elements are a valuable diagnostic when dealing with complex designs. A new element, a flexibly configurable collimator, will be presented. In the OPAL-cyc flavour, a robust way of generating matched distributions with linear space charge is introduced. A new method for describing fixed field accelerators (FFAs) in a very general way will be shown. A new element TRIMCOIL can be used to correct for field-errors in cyclotrons and FFAs. The OPAL language (a derivative of the MAD language) was extended to allow the specification of multi objective optimisation problems, which are then solved with a built in NGSA-II genetic algorithm. A new feature SAMPLER allows you to setup and run random or sequential parameter studies and seamless utilisation of a vast number of computing cores. Finally, a set of Python tools (pyOPALTools) was created for post processing. The manual is now available on the OPAL-wiki as well as in pdf format.

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TUPAF08

A Full Field-Map Modeling of Cornell-BNL CBETA 4-Pass Energy Recovery Linac

186

F. Méot, S.J. Brooks, D. Trbojevic, N. Tsoupas
BNL, Upton, Long Island, New York, USA
J.A. Crittenden
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
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.

Slides TUPAF08 [2.568 MB]

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paper received ※ 23 October 2018 paper accepted ※ 07 December 2018 issue date ※ 26 January 2019

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TUPAF09

Multi Pass Energy Recovery Linac Design With a Single Fixed Field Magnet Return Line

191

D. Trbojevic, J.S. Berg, S.J. Brooks, F. Méot, N. Tsoupas
BNL, Upton, Long Island, New York, USA
W. Lou
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

We present a new approach of the Energy Recovery Linac Design for the future projects: PERLE (Powerful Energy Recovery Linac for Experiments), LHeC/FCCeH and eR- HIC. The concept uses superconducting linacs and a single xed eld beam line with multiple energy passes of electron beams. This represents an update to the existing CBETA (Cornell University Brookhaven National Laboratory ERL Test Accelerator) where the superconducting linac uses a single xed eld magnet beam line with four energy passes during acceleration and four passes during the energy recov- ery. To match the single xed eld beam line to the linac the CBETA uses the spreaders and combiners on both sides of the linac, while the new concept eliminates them. The arc cells from the single xed eld beam line are connected to the linac with adiabatic transition arcs wher cells increase in length. The orbits of di erent energies merge into a sin- gle orbit through the interleaved linac within the straight sections as in the CBETA project. The betatron functions from the arcs are matched to the linac. The time of ight of di erent electron energies is corrected for the central orbits by additional correction magnet controlled induced beam oscillations.

Slides TUPAF09 [3.935 MB]

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paper received ※ 22 October 2018 paper accepted ※ 27 January 2019 issue date ※ 26 January 2019

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TUPAF10

Experience With CBETA Online Modeling Tools

196

C.M. Gulliford, A.C. Bartnik, J. Dobbins, D. Sagan
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
J.S. Berg
BNL, Upton, Long Island, New York, USA
A. Nunez-delPrado
UCF, Orlando, USA

Funding: NYSERDA, the New York StateEnergy Research and Development Agency
The Cornell-Brookhaven CBETA machine is a four pass Energy Recovery Linac (ERL) with a Non-scaling Fixed-Field Alternating gradient (NS-FFA) arc. For online modeling of single particle dynamics in CBETA, a customized version of the Tao program, which is based upon the Bmad toolkit, has been developed. This online program, called CBETA-V, is interfaced to CBETA’s EPICS control system. This paper describes the online modeling system and initial experience during machine running.

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TUPAF11

Advanced Design and Simulation of Fixed-Field Accelerators

C. Johnstone
Fermilab, Batavia, Illinois, USA
M. Berz, K. Makino
MSU, East Lansing, Michigan, USA
P. Snopok
Illinois Institute of Technology, Chicago, Illlinois, USA

Funding: Work supported by Fermi Research Alliance, LLC under contract no. DE-AC02-07CH11359
The development of new types of accelerators that allow wide choices of parameters, promote complicated fields, and often need to efficiently handle very large emittance beams requires the availability of new simulation environments to design and accurately predict operation. This is particularly true of Fixed-field accelerators, FFAs, which apply arbitrary-order fields - both alternating gradient, strong focusing - but also weak-focusing cyclotrons. This is especially applicable at medium-to-high energy combined with high intensity (mA currents). Synchrotron and cyclotron codes are generally inadequate to simulate accurately the performance of these strong-focusing fixed-field accelerators, particularly the new breed of non-scaling machines which have difficult, high-order fringe-field and edge-angle effects. One well-supported code, COSY INFINITY (COSY) is particularly suitable for accurate, high-order descriptions of accelerators. New tools have been developed in COSY INFINITY to address and accurately represent complex fixed-field machines in both a sector and spiral sector footprint. A description, application, and comparison of these tools with fields from magnet lattice design is presented.

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TUPAF12

Longitudinal Beam Dynamics With a Higher-Harmonic Cavity for Bunch Lengthening

202

G. Bassi, J. Tagger
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
We discuss the longitudinal beam dynamics in storage rings in the presence of a higher-harmonic cavity (HHC) system for bunch lengthening. We first review the general conditions for HHC operations, either in active or passive mode, assuming the stability of the system. For uniform filling patterns, a distinction is made between operations with a normal-conducting HHC, where optimal conditions for bunch lengthening can be satisfied, and operations with super-conducting HHC, where optimal conditions can be met only approximately. The option to operate the NSLS-II storage ring with a passive, super-conducting third harmonic cavity (3HC) system is discussed next. The stability and performance of the system in the presence of a gap in the uniform filling, which corresponds to the present mode of operation of the NSLS-II storage ring, is investigated with self-consistent Vlasov-Fokker-Planck simulations performed with the code SPACE*.
* G. Bassi, A. Blednykh and V. Smaluk, Phys Rev. Accel. Beams 19, 024401 (2016).

Slides TUPAF12 [17.562 MB]

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TUPAF13

Calculation of the AGS Optics Based on 3D Fields Derived From Experimentally Measured Fields on Median Plane

209

N. Tsoupas, J.S. Berg, S.J. Brooks, F. Méot, V. Ptitsyn, D. Trbojevic
BNL, Upton, Long Island, New York, USA

Funding: Work supported by the US Department of Energy
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/

Slides TUPAF13 [1.772 MB]

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paper received ※ 20 October 2018 paper accepted ※ 07 December 2018 issue date ※ 26 January 2019

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TUPAF14

Analytical Calculations for Thomson Backscattering Based Light Sources

215

P.I. Volz, A. Meseck
HZB, Berlin, Germany

There is a rising interest in Thomson-backscattering based light sources, as scattering intense laser radiation on MeV electrons produces high energy photons that would require GeV or even TeV electron beams when using conventional undulators or dipoles. Particularly, medium energy high brightness beams delivered by LINACs or Energy Recovery LINACs, such as BERLinPro being built at Helmholtz-Zentrum Berlin, seem suitable for these sources. In order to study the merit of Thomson-backscattering-based light sources, we are developing an analytical code to simulate the characteristics of the Thomson scattered radiation. The code calculates the distribution of scattered radiation depending on the incident angle and polarization of the laser radiation. Also the impact of the incident laser profile and the full 6D bunch profile, including microbunching, are incorporated. The Status of the code and first results will be presented.

Slides TUPAF14 [3.289 MB]

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paper received ※ 21 October 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019

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TUPAF15

A Holistic Approach to Simulating Beam Losses in the Large Hadron Collider Using BDSIM

221

S.D. Walker, A. Abramov, S.T. Boogert, H. Garcia Morales, S.M. Gibson, L.J. Nevay, H. Pikhartova, W. Shields
JAI, Egham, Surrey, United Kingdom

To fully understand the beam losses, subsequent radiation, energy deposition, backgrounds and activation in particle accelerators, a holistic approach combining a 3-D model, physics processes and accelerator tracking is required. Beam Delivery Simulation (BDSIM) is a program developed to simulate the passage of particles, both primary and secondary, in particle accelerators and calculate the energy deposited by these particles via material interactions using the Geant4 physics library. A Geant4 accelerator model is built from an existing optical description of a lattice by procedurally placing a set of predefined accelerator components. These generic components can be refined to an arbitrary degree of detail with the use of user-defined geometries, detectors, field maps, and more. A detailed model of the Large Hadron Collider has been created in BDSIM, validated with existing tracking codes and applied to study beam loss patterns.

Slides TUPAF15 [2.065 MB]

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paper received ※ 31 October 2018 paper accepted ※ 08 December 2018 issue date ※ 26 January 2019

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TUPAF16

Analysis of the Beam Loss Mechanism During the Energy Ramp-Up at the SAGA-LS

227

Y. Iwasaki
SAGA, Tosu, Japan

The accelerator of the SAGA Light Source consists of 255 MeV injector linac　and 1.4 GeV storage ring. The accumulated electron beam current of the　storage ring is about 300 mA. The energy of　the electrons are raised up to 1.4 GeV in 4 minutes in the storage ring. At the moment of the　beam acceleration (the beam energy is lower than 300 MeV), the electron　beam is lost like the step function. The lost beam current is normally　about 5 mA to 30 mA. The beam loss at the energy ramp-up is not observed, when the beam current is lower than 200 mA. To understand the beam loss mechanism, which depend on the beam current, we developed high-speed logging system of 100 kHz for monitoring the beam current and the magnets power supplies using National Instruments PXI. We investigated the relationship between the beam loss and the betatron tune shifts. The tune shifts during the beam acceleration were analyzed from the measured data of the output current of the magnets power supplies by using beam tracking code of TRACY2. By adopting the new high-speed logging system, the time structure of the beam loss process was clearly observed. We will present the high-speed logging system developed for monitoring the beam current and the power supplies at this meeting. The results of the investigation to find the relationship of the beam loss and the tune shifts will be also shown.

Slides TUPAF16 [1.286 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF16

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paper received ※ 19 October 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019

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TUPAF19

pyaopt Optimization Suite and its Applications to an SRF Cavity Design for UEMs

229

A. Liu, P.V. Avrakhov, R.A. Kostin
Euclid TechLabs, LLC, Solon, Ohio, USA
C.-J. Jing
Euclid Beamlabs LLC, Bolingbrook, USA

Funding: DOE SBIR
In order to achieve sharp, high resolution real-time imaging, electrons in a MeV UEM (ultrafast electron microscope) beamline need to minimize instabilities. The Superconducting RF (SRF) photocathode gun is a promising candidate to produce highly stable electrons for UEM/UED applications. It operates in an ultrahigh Q, CW mode, and dissipates a few watts of RF power, which make it possible to achieve a 10s ppm level of beam stability by using modern RF control techniques. In order to find the best performance of the gun design, an optimization procedure is required. pyaopt is a Python-based optimization suite that supports multi-objective optimizations using advanced algorithms. In this paper, the novel SRF photogun design and its optimizations through pyaopt and Astra’s beam simulations will be discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF19

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paper received ※ 22 October 2018 paper accepted ※ 15 December 2018 issue date ※ 26 January 2019

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TUPAF20

Mean-Field Density Evolution of Bunched Particles With Non-Zero Initial Velocity

233

B.S. Zerbe, P.M. Duxbury
MSU, East Lansing, Michigan, USA

Funding: NSF Grant 1625181 NSF Grant RC108666 MSU Col. Nat. Sci., Provost Off., Col. Comm. Art and Sci.
Reed (2006) presented a 1D mean-field model of initially cold pancake-beam expansion demonstrating that the evolution of the entire spatial distribution can be solved for all time where the 1D assumption holds. This model is relevant to ultra-fast electron microscopy as it describes the evolution of the distribution within the photoelectron gun, and this model is similar to Anderson’s sheet beam density time dependence (Anderson 1987) except that Reed’s theory applies to freely expanding beams instead of beams within a focussing channel. Our recent work (Zerbe 2018) generalized Reed’s analysis to cylindrical and spherical geometries demonstrating the presence of a shock that is seen in the Coulomb explosion literature under these geometries and further discussed the absence of a shock in the 1D model. This work is relevant as it offers a mechanistic explanation of the ring-like density shock that arises in non-equilibrium pancake-beams within the photoelectron gun; moreover, this shock is coincident with a region of high-temperature electrons providing an explanation for why experimentally aperturing the electron bunch results in a greater than 10-fold improvement in beam emittance(Williams 2017), possibly even resulting in bunch emittance below the intrinsic emittance of the cathode. However, this theory has been developed for cold-bunches, i.e. bunches of electrons with 0 initial momentum. Here, we briefly review this new theory and extend the cylindrical- and spherical- symmetric distribution to ensembles that have non-zero initial momentum distributions that are symmetric but otherwise unrestricted demonstrating how initial velocity distributions couple to the shocks seen in the less general formulation. Further, we derive and demonstrate how the laminar condition may be propagated through beam foci.

Slides TUPAF20 [1.396 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF20

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paper received ※ 19 October 2018 paper accepted ※ 15 December 2018 issue date ※ 26 January 2019

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TUPAF22

FEL Simulation Using the Lie Method

240

K. Hwang, J. Qiang
LBNL, Berkeley, California, USA

Funding: U.S. Department of Energy under Contract No. DE-AC02-05CH11231
Advances in numerical methods for free-electron-laser~(FEL) simulation under wiggler period averaging~(WPA) are presented. First, WPA is generalized using perturbation Lie map method. The conventional WPA is identified as the leading order contribution. Next, a widely used shot-noise modeling method is improved along with a particle migration scheme across the numerical mesh. The artificial shot noise arising from particle migration is suppressed. The improved model also allows using arbitrary mesh size, slippage resolution, and integration step size. These advances will improve modeling of longitudinal beam profile evolution for fast FEL simulation.

Slides TUPAF22 [2.245 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF22

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paper received ※ 17 October 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019

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TUPAF23

Start-to-End Simulations of THz SASE FEL Proof-of-Principle Experiment at PITZ

246

M. Krasilnikov, P. Boonpornprasert, F. Stephan
DESY Zeuthen, Zeuthen, Germany
H.-D. Nuhn
SLAC, Menlo Park, California, USA
E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany

The Photo Injector Test facility at DESY in Zeuthen (PITZ) develops high brightness electron sources for modern linac-based Free Electron Lasers (FELs). The PITZ accelerator has been proposed as a prototype for a tunable, high power THz source for pump and probe experiments at the European XFEL. A Self-Amplified Spontaneous Emission (SASE) FEL is considered to generate the THz pulses. High radiation power can be achieved by utilizing high charge (4 nC) shaped electron bunches from the PITZ photo injector. THz pulse energy of up to several mJ is expected from preliminary simulations for 100 um radiation wavelength. For the proof-of-principle experiments a re-usage of LCLS-I undulators at the end of the PITZ beamline is under studies. One of the challenges for this setup is transport and matching of the space charge dominated electron beam through the narrow vacuum chamber. Start-to-end simulations for the entire experimental setup - from the photocathode to the SASE THz generation in the undulator section - have been performed by combination of several codes: ASTRA, SC and GENESIS-1.3. The space charge effect and its impact onto the output THz radiation have been studied. The results of these simulations will be presented and discussed.

Slides TUPAF23 [2.534 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF23

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paper received ※ 18 October 2018 paper accepted ※ 24 October 2018 issue date ※ 26 January 2019

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TUPAF24

Numerical Simulations for Generating Fully Coherent Soft X-Ray Free Electron Lasers With Ultra-Short Wavelength

K.S. Zhou
SINAP, Shanghai, People’s Republic of China

Funding: Shanghai Institute of Applied Physics, Chinese Academy of Sciences
For the fully coherent, ultra-short and high power soft x-rays are becoming key instruments in different research fields, such as biology, chemistry or physics. However it’s not easy to generate this kind of advantaged light source by conventional lasers, especially for the soft x-rays with ultra-short wavelength. The external seeded free electron laser (FEL) is considered as one feasible method. Here, we give an example to generate fully coherent soft x-rays with the wavelength 1nm by the two-stage cascaded FELs. The EEHG scheme is used in the first-stage while the HGHG scheme is used in the second-stage.

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