Paper  Title  Other Keywords  Page 

MOPA17  Symplectic Particle Tracking in a Thick Nonlinear McMillan Lens for the Fermilab Integrable Optics Test Accelerator (IOTA)  electron, solenoid, optics, simulation  83 


Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DEAC0207CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. The McMillan system is a novel method to increase the tune spread of a beam without decreasing its dynamic aperture due to the system’s integrability. While the ideal system is based on an infinitely thin kick, the physical design requires a thick electron lens, including a solenoid. Particle transport through the lens is difficult to simulate due to the nature of the force on the circulating beam. This paper demonstrates accurate simulation of a thick McMillan lens in a solenoid using symplectic integrators derived from Yoshida’s method. 

Poster MOPA17 [2.290 MB]  
DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022MOPA17  
About •  Received ※ 03 August 2022 — Revised ※ 04 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 09 October 2022  
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MOPA69  Adjoint Optimization Applied to Flat to Round Transformers  solenoid, quadrupole, spacecharge, electron  199 


Funding: This work was supported by DOEHEP Awards No. DESC0010301 and DESC0022009 We present the numerical optimization, using adjoint techniques, of FlattoRound (FTR) transformers operating in the strong selffield limit. FTRs transform an unmagnetized beam that has a high aspect ratio, elliptical spatial cross section, to a round beam in a solenoidal magnetic field. In its simplest form the flat to round conversion is accomplished with a triplet of quadrupoles, and a solenoid. FTR transformers have multiple applications in beam physics research, including manipulating electron beams to cool copropagating hadron beams. Parameters that can be varied to optimize the FTR conversion are the positions and strengths of the four magnet elements, including the orientations and axial profiles of the quadrupoles and the axial profile and strength of the solenoid’s magnetic field. The adjoint method we employ [1] allows for optimization of the lattice with a minimum computational effort including selffields. The present model is based on a moment description of the beam. However, the generalization to a particle description will be presented. The optimized designs presented here will be tested in experiments under construction at the University of Maryland. [1] Optimization of Flat to Round Transformers with selffields using adjoint techniques, L. Dovlatyan, B. Beaudoin, S. Bernal, I. Haber, D. Sutter and TMA, PhysRevAccelBeams.25.044002 (2022). 

DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022MOPA69  
About •  Received ※ 03 August 2022 — Revised ※ 25 September 2022 — Accepted ※ 05 December 2022 — Issue date ※ 05 December 2022  
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MOPA81  Study of Nonlinear Dynamics in the 4D Hénon Map Using the Square Matrix Method and Iterative Methods  resonance, dynamicaperture, lineardynamics, sextupole  232 


Funding: Accelerator Stewardship program under award number DESC0019403 US Department of Energy, Office of Science, High Energy Physics under award number DESC0018362 and Michigan State University The Hénon Map represents a linear lattice with a single sextupole kick. This map has been extensively studied due to its chaotic behavior. The case for the two dimensional phase space has recently been revisited using ideas from KAM theory to create an iterative process that transforms nonlinear perturbed trajectories into rigid rotations*. The convergence of this method relates to the resonance structure and can be used as an indicator of the dynamic aperture. The studies of this method have been extended to the four dimensional phase space case which introduces coupling between the transverse coordinates. *Hao, Y., Anderson, K., & Yu, L. H. (2021, August). Revisit of Nonlinear Dynamics in Hénon Map Using Square Matrix Method. https://doi.org/10.18429/JACoWIPAC2021THPAB016 

Poster MOPA81 [3.103 MB]  
DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022MOPA81  
About •  Received ※ 19 July 2022 — Revised ※ 04 August 2022 — Accepted ※ 15 August 2022 — Issue date ※ 26 August 2022  
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TUYD5  Epitaxial AlkaliAntimonide Photocathodes on Latticematched Substrates  cathode, ECR, electron, laser  289 


Alkaliantimonides photocathodes, characterized by high quantum efficiency (QE) and low mean transverse energy (MTE) in the visible range of spectrum, are excellent candidates for electron sources to drive Xray Free Electron Lasers (XFEL) and Ultrafast Electron Diffraction (UED). A key figure of merit for these applications is the electron beam brightness, which is inversely proportional to MTE. MTE can be limited by nanoscale surface roughness. Recently, we have demonstrated physically and chemically smooth Cs_{3}Sb cathodes on Strontium Titanate (STO) substrates grown via codeposition technique. Such flat cathodes could result from a more ordered growth. In this paper, we present RHEED data of codeposited Cs_{3}Sb cathodes on STO. Efforts to achieve epitaxial growth of Cs_{3}Sb on STO are then demonstrated via RHEED. We find that films grown epitaxially on substrates like STO and SiC (previously used to achieve single crystalline Cs_{3}Sb) exhibit QE higher than the polycrystalline Cs_{3}Sb cathodes, by an order of magnitude below photoemission threshold. Given the larger QE, lower laser fluence could be used to extract high charge densities, thereby leading to enhanced beam brightness.  
Slides TUYD5 [2.088 MB]  
DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022TUYD5  
About •  Received ※ 01 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 07 September 2022  
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TUZE3  Optimizing the Discovery of Underlying Nonlinear Beam Dynamics  simulation, MMI, lineardynamics, experiment  335 


Funding: Work supported by US DOEHEP grants: DESC0010301 and DESC0022009 One of the DOEHEP Grand Challenges identified by Nagaitsev et al. relates to the use of virtual particle accelerators for beam prediction and optimization. Useful virtual accelerators rely on efficient and effective methodologies grounded in theory, simulation, and experiment. This paper uses an algorithm called Sparse Identification of Nonlinear Dynamical systems (SINDy), which has not previously been applied to beam physics. We believe the SINDy methodology promises to simplify the optimization of accelerator design and commissioning, particularly where space charge is important. We show how SINDy can be used to discover and identify the underlying differential equation system governing the beam moment evolution. We compare discovered differential equations to theoretical predictions and results from the PIC code WARP modeling. We then integrate the discovered differential system forward in time and compare the results to data analyzed in prior work using a Machine Learning paradigm called Reservoir Computing. Finally, we propose extending our methodology, SINDy for Virtual Accelerators (SINDyVA), to the broader community’s computational and real experiments. 

Slides TUZE3 [3.141 MB]  
DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022TUZE3  
About •  Received ※ 08 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 22 August 2022  
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TUPA14  Fast FirstOrder Spin Propagation for Spin Matching and Polarization Optimization with Bmad  polarization, quadrupole, solenoid, electron  369 


Accurate spin tracking is essential for the simulation and propagation of polarized beams, in which a majority of the particles’ spin point in the same direction. Bmad, an opensourced library for the simulation of charged particle dynamics, traditionally tracks spin via integrating through each element of a lattice. While exceptionally accurate, this method has the drawback of being slow; at best, the runtime is proportional to the length of the element. By solving the spin transport equation for simple magnet elements, Bmad can reduce this algorithm to constant runtime while maintaining high accuracy. This method, known as "Sprint," enables quicker spin matching and prototyping of lattice designs via Bmad.  
DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022TUPA14  
About •  Received ※ 30 July 2022 — Revised ※ 09 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 24 August 2022  
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TUPA16  SingularityFree Exact Dipole Bend Transport Equations  dipole, simulation, GUI, framework  375 


Funding: Department of Energy Exact transport equations for a pure dipole bend (a bend with a dipole field and nothing else) have been derived and formulated to avoid singularities when evaluated. The transport equations include finite edge angles and no assumption is made in terms of the bending field being matched to the curvature of the coordinate system. 

DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022TUPA16  
About •  Received ※ 05 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 16 September 2022  
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TUPA17  BeamBased Alignment of Sextupole Families in the EIC  sextupole, kicker, alignment, closedorbit  378 


To steer the closed orbit in a storage ring through the center of its quadrupoles, it is important to accurately know the quadrupole centers relative to nearby beam position monitors. Usually this is achieved by beambased alignment (BBA). Assuming the quadrupole strength can be changed individually, one finds the BPM reading where changing a quadrupole’s strength does not alter the closed orbit. Since most quadrupoles are powered in series, they can only be varied independently if costly power supplies are added. For the EIC electron storage ring (ESR), we investigate whether sextupole BBA can be used instead. Individually powered sextupole BBA techniques already exist, but most sextupoles are powered in families and cannot be individually changed. We therefore developed a method where a localized bump changes the beam excursion in a single sextupole of a family, turning off all families that also have sextupoles in the bump. The bump amplitude at which the sextupole does not cause a closed orbit kick determines the sextupole’s alignment. This study was made to investigate the precision to which this method can be utilized.  
DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022TUPA17  
About •  Received ※ 04 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 29 August 2022  
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TUPA19  Avoiding Combinatorial Explosion in Simulation of Multiple Magnet Errors in SwapOut Safety Tracking for the Advanced Photon Source Upgrade  photon, simulation, injection, storagering  386 


Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DEAC0206CH11357. The Advanced Photon Source (APS) is upgrading the storage ring to a hybrid sevenbendachromat design with reverse bends, providing a natural emittance of 41 pm at 6 GeV. The small dynamic acceptance entails operation in onaxis swapout mode. Careful consideration is required of the safety implications of injection with shutters open. Tracking studies require simulation of multiple simultaneous magnet errors, some combinations of which may introduce potentially dangerous conditions. A naive grid scan of possible errors, while potentially very complete, would be prohibitively timeconsuming. We describe a different approach using biased sampling of particle distributions from successive scans. We also describe other aspects of the simulations, such as use of 3D field maps and a highly detailed aperture model. 

DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022TUPA19  
About •  Received ※ 01 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 10 September 2022  
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TUPA26  Fringe Field Maps for Cartesian Dipoles with Longitudinal and/or Transverse Gradients  dipole, quadrupole, photon, focusing  401 


Funding: This work was supported by U.S. Dept. of Energy Office of Sciences under Contract No. DEAC0206CH11357. Fringe fields effects in dipoles can give rise to important linear and nonlinear contributions. This paper describes how to extend the classic results of Brown [1] and the more recent calculations of Hwang and Lee [2] to Cartesian dipoles with transverse and/or longitudinal gradients. We do this by 1) introducing a more general definition of the fringe field that can be applied to longitudinal gradient dipoles, 2) allowing for quadrupole and/or sextupole content in the magnet body, and 3) showing how to employ the resulting fringe field maps as a symplectic transformation of the coordinates. We compare our calculation results with tracking for longitudinal and transverse gradient dipoles planned for the APSU. [1] K.L. Brown, Report SLAC75, 1982. [2] K. Hwang and S.Y. Lee, Phys. Rev. Accel. Beams, vol. 18, p. 122401 2015. 

Poster TUPA26 [2.090 MB]  
DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022TUPA26  
About •  Received ※ 26 July 2022 — Revised ※ 11 August 2022 — Accepted ※ 12 August 2022 — Issue date ※ 21 August 2022  
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TUPA36  The Advanced Photon Source Linac Extension Area Beamline  electron, gun, linac, photon  430 


Funding: This research used resources of the Advanced Photon Source, operated for the U.S. Department of Energy Office of Science by Argonne National Laboratory under Contract No. DEAC0206CH11357. The Linac Extension Area at the Advanced Photon Source is a flexible beamline area for testing accelerator components and techniques. Driven by the Advanced Photon Source electron linac equipped with a photocathode RF electron gun, the Linac Extension Area houses a 12 m long beamline. The beamline is furnished with YAG screens, BPMs and a magnetic spectrometer to assist with characterization of beam emittance and energy spread. A 1.4 m long insertion in the middle of the beamline is provided for the installation of a device under test. The beamline is expected to be available soon for testing accelerator components and techniques using round and flat electron beams over an energy range 150450 MeV. In the present work, we describe this beamline and summarise the main beam parameters. 

Poster TUPA36 [0.892 MB]  
DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022TUPA36  
About •  Received ※ 02 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 19 September 2022  
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TUPA48  Effect of Lattice Misalignments on Beam Dynamics in LANSCE Linear Accelerator  alignment, emittance, linac, simulation  455 


Funding: Work supported by US DOE under contract 89233218CNA000001 Accelerator channel misalignments can significantly affect beam parameters in long linear accelerators. Measurements of misalignments of the LANSCE linac lattice elements was performed by the Mechanical Design Engineering Group of the Los Alamos Accelerator Operations and Technology Division. In order to determine effect of misalignment on beam parameters in LANSCE linac, the starttoend simulations of LANSCE accelerator were performed using Beampath and CST codes including measured displacements of quadrupoles and accelerating tanks. Simulations were done for both H^{+} and H^{−} beams with various beam flavors. Effect of misalignments was compared with those due to beam space charge and distortion of RF field along the channel. Paper presents results of simulation and comparison with experimental data of beam emittance growth along the machine. 

Poster TUPA48 [1.547 MB]  
DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022TUPA48  
About •  Received ※ 23 July 2022 — Revised ※ 28 July 2022 — Accepted ※ 04 August 2022 — Issue date ※ 14 August 2022  
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WEXD2  Storage Ring Tracking Using Generalized Gradient Representations of Full Magnetic Field Maps  dipole, emittance, quadrupole, sextupole  542 


Funding: This work was supported by U.S. Dept. of Energy Office of Sciences under Contract No. DEAC0206CH11357. We have developed a set of tools to simulate particle dynamics in the full magnetic field using the generalized gradients representation. Generalized gradients provide accurate and analytic representations of the magnetic field that allow for symplectic tracking [1]. We describe the tools that convert magnetic field data into generalized gradients representations suitable for tracking in Elegant, and discuss recent results based upon tracking with the full field representations for all magnets in the APSU storage ring. [1] A. Dragt. Lie Methods for Nonlinear Dynamics with Applications to Accelerator Physics. University of Maryland (2019). 

Slides WEXD2 [3.841 MB]  
DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022WEXD2  
About •  Received ※ 16 July 2022 — Accepted ※ 29 July 2022 — Issue date ※ 04 August 2022  
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WEXD3  Map Tracking Including the Effect of Stochastic Radiation  radiation, emittance, damping, photon  548 


Funding: Department of Energy Using transfer maps to simulate charged particle motion in accelerators is advantageous since it is much faster than tracking stepbystep. One challenge to using transfer maps is to properly include radiation effects. The effect of radiation can be divided into deterministic and stochastic parts. While computation of the deterministic effect has been previously reported, handling of the stochastic part has not. In this paper, an algorithm for including the stochastic effect is presented including taking into account the finite opening angle of the emitted photons. A comparison demonstrates the utility of this approach. Generating maps which include radiation has been implemented in the PTC software library which is interfaced to the Bmad toolkit. 

DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022WEXD3  
About •  Received ※ 06 August 2022 — Revised ※ 16 August 2022 — Accepted ※ 21 August 2022 — Issue date ※ 24 August 2022  
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WEPA68  Record Quantum Efficiency from Superlattice Photocathode for Spin Polarized Electron Beam Production  electron, cathode, polarization, distributed  784 


Funding: The work is supported by Brookhaven Science Associates, LLC under Contract DESC0012704 with the U.S. DOE. SNL is managed and operated by NTESS under DOE NNSA contract DENA0003525. Electron sources producing highly spinpolarized electron beams are currently possible only with photocathodes based on GaAs and other IIIV semiconductors. GaAs/GaAsP superlattice (SL) photocathodes with a distributed Bragg reflector (DBR) represent the state of the art for the production of spinpolarized electrons. We present results on a SLDBR GaAs/GaAsP structure designed to leverage strain compensation to achieve simultaneously high QE and spin polarization. These photocathode structures were grown using molecular beam epitaxy and achieved quantum efficiencies exceeding 15% and electron spin polarization of about 75% when illuminated with near bandgap photon energies. 

Poster WEPA68 [4.506 MB]  
DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022WEPA68  
About •  Received ※ 20 July 2022 — Revised ※ 02 August 2022 — Accepted ※ 07 August 2022 — Issue date ※ 10 August 2022  
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WEPA74  Characterization of Fully Coupled Linear Optics with TurnbyTurn Data  optics, coupling, resonance, quadrupole  805 


Funding: This research used resources of the NSLSII, a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DESC0012704. In the future diffractionlimited light source rings, fully coupled linear optics to generate round beams is preferable. While machine tune approaching to linear difference resonances, small random errors, such as quadrupole rolls, can result in fully coupled optics. Consequently, some uncertainty exists in such optics due to random errors distributions. Given beam position monitors turnbyturn readings, the harmonic analysis method was used to characterize the coupled Ripken Twiss parameters. 

Poster WEPA74 [0.889 MB]  
DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022WEPA74  
About •  Received ※ 25 July 2022 — Revised ※ 30 July 2022 — Accepted ※ 08 August 2022 — Issue date ※ 19 August 2022  
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WEPA77  A New PCB Rotating Coil at NSLSII  quadrupole, dipole, emittance, permanentmagnet  816 


Several R&D projects are underway at NSLSII towards an upgrade of its storage ring with a new lattice that will use high field magnets with small bores of 1622 mm. A large fraction of the high field magnets are expected to be of permanent magnet technology that will require precise magnetic measurements and field harmonics corrections. A new magnetic measurement bench has been built based on a printed circuit board (PCB) coil of 12 mm diameter and 270 mm active length. This PCB coil has the capability of measuring field quality to a level of 10 ppm of the main field up to the 15th harmonic with a sensitivity between 0.01 m2 and 0.02 m2 at the reference radius of 5 mm. This paper will describe the main features of the rotating coil bench and discuss the measurement results of a permanentmagnet Halbach quadrupole of 12.7 mm bore diameter.  
DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022WEPA77  
About •  Received ※ 28 July 2022 — Revised ※ 06 August 2022 — Accepted ※ 12 August 2022 — Issue date ※ 29 August 2022  
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WEPA80  Progress on Convergence Map Based on Square Matrix for Nonlinear Lattice Optimization  dynamicaperture, resonance, storagering, lineardynamics  823 


Funding: DOE. We report progress on applying the square matrix method to obtain in high speed a "convergence map", which is similar but different from a frequency map. We give an example of applying the method to optimize a nonlinear lattice for the NSLSII upgrade. The convergence map is obtained by solving the nonlinear dynamical equation by iteration of the perturbation method and studying the convergence. The map provides information about the stability border of the dynamical aperture. We compare the map with the frequency map from tracking. The result in our example of nonlinear optimization of the NSLSII lattice shows the new method may be applied in nonlinear lattice optimization, taking advantage of the high speed (about 30~300 times faster) to explore x, y, and the offmomentum phase space. 

Poster WEPA80 [5.392 MB]  
DOI •  reference for this paper ※ doi:10.18429/JACoWNAPAC2022WEPA80  
About •  Received ※ 19 July 2022 — Revised ※ 26 July 2022 — Accepted ※ 08 August 2022 — Issue date ※ 10 August 2022  
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