IPAC2022 - List of Authors (Rosenzweig, J.B.)

Paper	Title	Page
MOPOPT063	Reconstruction of Beam Parameters from Betatron Radiation Using Maximum Likelihood Estimation and Machine Learning	407
	S. Zhang, G. Andonian, C.E. Hansel, P. Manwani, B. Naranjo, M.H. Oruganti, J.B. Rosenzweig, M. Yadav UCLA, Los Angeles, California, USA Ö. Apsimon, C.P. Welsch, M. Yadav The University of Liverpool, Liverpool, United Kingdom
	Funding: US Department of Energy, Division of High Energy Physics, Contract No. DE-SC0009914 STFC Liver-pool Centre for Doctoral Training on Data Intensive Science, grant agreement ST/P006752/1 Betatron radiation that arises during plasma wakefield acceleration can be measured by a UCLA-built Compton spectrometer, which records the energy and angular position of incoming photons. Because information about the properties of the beam is encoded in the betatron radiation, measurements of the radiation can be used to reconstruct beam parameters. One method of extracting information about beam parameters from measurements of radiation is maximum likelihood estimation (MLE), a statistical technique which is used to determine unknown parameters from a distribution of observed data. In addition, machine learning methods, which are increasingly being implemented for different fields of beam diagnostics, can also be applied. We assess the ability of both MLE and other machine learning methods to accurately extract beam parameters from measurements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOPT063
About •	Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 24 June 2022 — Issue date ※ 26 June 2022
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MOPOPT066	Gas Sheet Diagnostics Using Particle in Cell Code	410
	M. Yadav, P. Manwani, J.B. Rosenzweig UCLA, Los Angeles, California, USA G. Andonian RadiaBeam, Santa Monica, California, USA Ö. Apsimon, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom N.M. Cook, A. Diaw, C.C. Hall RadiaSoft LLC, Boulder, Colorado, USA N.P. Norvell UCSC, Santa Cruz, California, USA
	Funding: This work was supported by the STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) under grant agreement ST/P006752/1 and DE-SC0019717. When intense particle beam propagates in dense plasma or gas, ionization can yield valuable information on the drive beam properties. Impact ionization and tunnel ionization are the two ionization regimes that must be accounted for varying beam properties. Due to these ionization mechanisms, new plasma electrons are generated causing different instabilities, dependent on the dominant ionization process considered. In order to accomplish the ambitious experimental goals of sophisticated beam diagnostics using ionization imaging, careful studies on the different ionization regimes, and the cross-over periods, required. Here we will discuss the impact ionization using fully parallel PIC code OSIRIS. We focus on understanding the gas sheet ionization diagnostics for characterizing high intensity charged particle beams. We study the interaction of neutral gas with an electron beam and varying density. We will also investigate the principle of detecting photon emission, rather than direct primary ion imaging, from the ionization induced in the interaction between the gas jet and charged particle beams.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOPT066
About •	Received ※ 07 June 2022 — Revised ※ 19 June 2022 — Accepted ※ 21 June 2022 — Issue date ※ 26 June 2022
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MOPOMS023	Start-to-End Beam-Dynamics Simulations of a Compact C-Band Electron Beam Source for High Spectral Brilliance Applications	687
	L. Faillace, M. Behtouei, B. Spataro, C. Vaccarezza LNF-INFN, Frascati, Italy R.B. Agustsson, I.I. Gadjev, S.V. Kutsaev, A.Y. Murokh RadiaBeam, Marina del Rey, California, USA F. Bosco, M. Carillo, L. Giuliano, M. Migliorati, A. Mostacci, L. Palumbo Sapienza University of Rome, Rome, Italy D.L. Bruhwiler RadiaSoft LLC, Boulder, Colorado, USA O. Camacho, A. Fukasawa, N. Majernik, J.B. Rosenzweig, O. Williams UCLA, Los Angeles, California, USA A. Giribono INFN/LNF, Frascati, Italy S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: This work is partially supported by DARPA under the Contract No. HR001120C0072, by DOE Contract DE-SC0009914, DOE Contract DE-SC0020409, and by the National Science Foundation Grant No. PHY-1549132. Proposals for new linear accelerator-based facilities are flourishing world-wide with the aim of high spectral brilliance radiation sources. Most of these accelerators are based on electron beams, with a variety of applications in industry, research and medicine such as colliders, free-electron lasers, wake-field accelerators, coherent THz and inverse Compton scattering X/’ sources as well as high-resolution diagnostics tools in biomedical science. In order to obtain high-quality electron beams in a small footprint, we present the optimization design of a C-band linear accelerator machine. Driven by a novel compact C-band hybrid photoinjector, it will yield ultra-short electron bunches of few 100’s pC directly from injection with ultra-low emittance, fraction of mm-mrad, and a few hundred fs length simultaneously, therefore satisfying full 6D emittance compensation. The normal-conducting linacs are based on a novel high-efficiency design with gradients up to 50 MV/m. The beam maximum energy can be easily adjusted in the mid-GeV’s range. In this paper, we discuss the start-to-end beam-dynamics simulations in details.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS023
About •	Received ※ 07 June 2022 — Revised ※ 09 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 03 July 2022
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MOPOMS033	Emittance Measurements of Nanoblade-Enhanced High Field Cathode	709
	G.E. Lawler, N. Majernik, J.I. Mann, N.E. Montanez, J.B. Rosenzweig UCLA, Los Angeles, California, USA V.S. Yu RadiaBeam, Santa Monica, California, USA
	Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132. High brightness cathodes are increasingly a focus for accelerator applications ranging from free electron lasers to ultrafast electron diffraction. There is further an increasing interest in fabrication and control of cathode surface to better control the emission characteristics and improve beam brightness. One method which we can consider is based on well-known silicon nanofabrication techniques which we use to create patterned cathode surfaces. The sharp edges produced lead to field emission increases and high brightness emission. We have demonstrated that a beam can be successfully extracted with a low emittance and we have reconstructed a portion of the energy spectrum. Due to the simplicity of extended geometries in nanofabrication our beam uniquely possesses a high aspect ratio in its transverse cross section. We can begin to consider modifications for emittance exchange beamlines and having shown the patterning principle is sound we can consider additional patterns such as hollow beams. Future work will continue to characterize the produced beam and the addition of fabrication steps to remove one of the blades in the double blade geometry in order to more accurately characterize the emission.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS033
About •	Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 10 July 2022
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MOPOMS034	Material Normal Energy Distribution for Field Emission Analyses From Monocrystalline Surfaces	713
	J.I. Mann, Y. Li, J.B. Rosenzweig UCLA, Los Angeles, California, USA T. Arias, J.K. Nangoi Cornell University, Ithaca, New York, USA
	Funding: National Science Foundation Grant No. PHY-1549132 Electron field emission is a complicated phenomenon which is sensitive not only to the particular material under illumination but also to the specific crystalline orientation of the surface. Summarizing the ability for a crystal to emit in a particular direction would be of great use when searching for good field emitters. In this paper we propose a material normal energy distribution which describes the ability of the bound electrons to tunnel under an intense electric field. This framework breaks a computationally expensive 3-D system down to a source distribution representation applicable for more efficient 1-D models. We use the Fowler-Nordheim framework to study the yield and MTE (mean transverse energy) from sources including gold, copper, and tungsten in both monocrystalline and polycrystalline forms. We find an increase in effective work function for field emission in the (111) direction for gold and copper associated with the Bragg plane intersections of the Fermi surface.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS034
About •	Received ※ 20 May 2022 — Revised ※ 12 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 06 July 2022
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MOPOMS036	Simulations of Laser Field Emission from Nanostructures with Image Charge Trapping and Band Structure Transitions	717
	B. Wang, G.E. Lawler, J.I. Mann, J.B. Rosenzweig UCLA, Los Angeles, California, USA T. Arias, J.K. Nangoi Cornell University, Ithaca, New York, USA S.S. Karkare Arizona State University, Tempe, USA
	Funding: National Science Foundation Grant No. PHY-1549132 Laser-induced field emission from nanostructures as a means to create high brightness electron beams has been a continually growing topic of study. Experiments using nanoblade emitters have achieved peak fields upwards of 40 GV/m, begging further investigation in this extreme regime. A recent paper has provided analytical reductions of the common semi-infinite Jellium system for pulsed incident lasers. We utilize these results as well as similar previous results to further understand the physics underlying electron rescattering-type emissions. We progress in numerically evaluating the analytical solution to attempt to more efficiently generate spectra for this system. Additionally, we use the full 1-D time-dependent Schrödinger equation with a Hartree potential and a dispersion-relation transition from material to vacuum to study the same system. We determine what importance the inclusion of the material band structure may have on emissions using this computationally challenging approach.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS036
About •	Received ※ 08 June 2022 — Revised ※ 21 June 2022 — Accepted ※ 27 June 2022 — Issue date ※ 01 July 2022
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MOPOMS052	6 MeV Novel Hybrid (Standing Wave - Traveling Wave) Photo-Cathode Electron Gun for a THz Superradiant FEL	760
	A. Nause, L. Feigin, A. Friedman, A. Weinberg Ariel University, Ariel, Israel A. Fukasawa, J.B. Rosenzweig UCLA, Los Angeles, California, USA B. Spataro LNF-INFN, Frascati, Italy
	A novel 6 MeV hybrid photo injector was designed and commissioned at Ariel University in Israel as an on-going collaboration with UCLA. This unique, new generation design provides a radically simpler approach to RF feeding of a gun/buncher system, leading to a much shorter beam via velocity bunching owed to an attached traveling wave section of the photo-injector. This design results in better performance in beam parameters, providing a high quality electron beam, with energy of 6 MeV, emittance of less than 3 ’m, and a 150 fs pulse duration at up to 1 nC per pulse. The Hybrid gun is driven by a SLAC XK5 Klystron as the high power RF source, and third harmonic of a fs level IR Laser amplifier (266 nm) to extract electrons from the Cathode. The unique e-gun will produce a bunched electron pulse to drive a THz FEL, which will operate at the super-radiance regime, and therefore requires extraordinary beam properties. It will also be used for MeV UED experiments in a separate line using a dogleg section. Here we describe the gun and presents experimental results from the gun and its sub-systems, including energy and charge measurements, compared with the design simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS052
About •	Received ※ 11 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 18 June 2022
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TUPOPT034	Modelling of X-Ray Volume Excitation of the XLO Gain Medium Using Flash	1081
	P. Manwani, N. Majernik, B. Naranjo, J.B. Rosenzweig UCLA, Los Angeles, California, USA E.C. Galtier, A. Halavanau, C. Pellegrini SLAC, Menlo Park, California, USA
	Funding: This work was performed with the support of the US Department of Energy under Contract No. DE-AC02-76SF00515 and DESC0009914. Plasma dynamics and crater formation of laser excited volumes in solids is a complex process due to thermalization, shockwave formation, varying absorption mechanisms, and a wide range of relevant physics timescales. The properties and interaction of such laser-matter systems can be modeled using an equation of state and opacity based multi-temperature treatment of plasma using a radiation hydrodynamics code. Here, we use FLASH, an adaptive mesh radiation-hydrodynamics code, to simulate the plasma expansion following after the initial energy deposition and thermalization of the column, to benchmark the results of experiments undertaken at UCLA on optical laser ablation. These computational results help develop a quantitative understanding of the material excitation process and enable the optimization of the gain medium delivery system for the x-ray laser oscillator project . Halavanau, Aliaksei, et al. "Population Inversion X-Ray Laser Oscillator." Proceedings of the National Academy of Sciences, vol. 117, no. 27, 2020, pp. 15511-15516.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOPT034
About •	Received ※ 08 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 18 June 2022 — Issue date ※ 24 June 2022
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TUPOPT035	Introduction of Westwood Linear Accelerator Test Facility in University of California Los Angeles	1085
	Y. Sakai, G. Andonian, O. Camacho, A. Fukasawa, G.E. Lawler, N. Majernik, P. Manwani, B. Naranjo, J.B. Rosenzweig, O. Williams UCLA, Los Angeles, California, USA
	Funding: U.S. DOE: DE-SC0009914 U.S. DOD: DARPA GRIT Contract 20204571 U.S. DOE: DE-SC0020409 - Cryo RF An electron linear accelerator test facility located on UCLA’s southwest campus in Westwood, SAMURAI, is presently being constructed. A RF-based accelerator consists of a compact, 3 MeV S-band hybrid gun capable of velocity bunching to bunch lengths in the 100s fs range with 100s pC of charge. This beam is accelerated by an 1.5 m S-band linac with a peak output energy of 30 MeV which can be directed to either a secondary beamline or remain on the main beamline for final acceleration by a SLAC 3 m S-band linac to an energy of 80 MeV. Further acceleration by advanced boosters such as a cryo-cooled C-band structure or numerous optical or wakefield methods is under active investigation. In combination with a 3 TW Ti:Sapphire laser, initial proof of principle experiments will be conducted on topics including the ultra-compact x-ray free-electron laser, advanced dielectric wakefield acceleration, bi-harmonic nonlinear inverse Compton scattering, and various radiation detectors. Furthermore, development of a tertiary beamline based on an ultra low emittance, cryo-cooled gun will eventually enable two-beam experiments, expanding the facility’s unique experimental capabilities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOPT035
About •	Received ※ 08 June 2022 — Revised ※ 09 June 2022 — Accepted ※ 20 June 2022 — Issue date ※ 24 June 2022
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TUPOPT047	Progress Report on Population Inversion X-Ray Laser Oscillator at LCLS	1107
	A. Halavanau, R. Alonso-Mori, A. Aquila, U. Bergmann, F.-J. Decker, F. Fuller, M. Liang, A.A. Lutman, R.A. Margraf, R.H. Paul, C. Pellegrini SLAC, Menlo Park, California, USA R. Ash, N.B. Welke UW-Madison/PD, Madison, Wisconsin, USA A.I. Benediktovitch DESY, Hamburg, Germany S.C. Krusic JSI, Ljubljana, Slovenia N. Majernik, P. Manwani, J.B. Rosenzweig UCLA, Los Angeles, California, USA R. Robles Stanford University, Stanford, California, USA N. Rohringer Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
	We report the progress in the design and construction of a population inversion x-ray laser oscillator (XLO) using LCLS as an x-ray laser pump, being developed by a SLAC, CFEL, University of Hamburg (Germany), University of Wisconsin, Josef Stefan Institute (Slovenia) and UCLA collaboration. In this proceeding, we will present the latest XLO design and numerical simulations substantiated by our first experimental results. In our next experimental step XLO will be tested on the Coherent X-ray Imaging (CXI) end-station at LCLS as a two pass Regenerative Amplifier operating at the Copper K_α1 photon energy of 8048 eV. When built, XLO will generate fully coherent transform limited pulses with about 50 meV FWHM bandwidth. We expect the XLO will pave the way for new user experiments, e.g. in inelastic x-ray scattering, parametric down conversion, quantum science, x-ray interferometry, and external hard x-ray XFEL seeding.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOPT047
About •	Received ※ 12 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 24 June 2022
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WEPOST040	Comparing Methods of Recovering Gamma Energy Distributions from PEDRO Spectrometer Responses	1784
	M.H. Oruganti, B. Naranjo, J.B. Rosenzweig, M. Yadav UCLA, Los Angeles, California, USA
	To calculate the energy levels of the photons emitted from high-energy particle interactions, the new pair spectrometer (PEDRO) channels the photons through several Beryllium nuclear fields to produce electron-positron pairs through the nuclear field interaction. This project compared several methods of reconstruction and determined which best predicts original energy distributions based on simulated spectra. These methods included using Maximum Likelihood Estimation, Machine Learning, and directly analyzing a response matrix that modeled PEDRO’s response to any photon energy distribution. We report that performing the direct analysis, also known as QR decomposition, on a PEDRO-generated spectrum provides by far the most accurate calculation of the spectrum’s original energy distribution. These methods were tested against results from experimental cases, including Nonlinear Compton Scattering and Filamentation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST040
About •	Received ※ 15 June 2022 — Revised ※ 01 July 2022 — Accepted ※ 08 July 2022 — Issue date ※ 08 July 2022
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WEPOST041	Physical Aspects of Collinear Laser Injection at SLAC FACET-II E-310: Trojan Horse Experiment	1787
	M. Yadav, Ö. Apsimon, E. Kukstas, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom C.E. Hansel, P. Manwani, B. Naranjo, J.B. Rosenzweig UCLA, Los Angeles, California, USA B. Hidding USTRAT/SUPA, Glasgow, United Kingdom
	Funding: This work was performed with support of the US Department of Energy, Division of High Energy Physics, un-der Contract No. DE-SC0009914, and the STFC grant ST/P006752/1. The Facility for Advanced Accelerator Experimental Tests (FACET-II) is a test accelerator infrastructure at SLAC dedicated to the research and development of advanced accelerator technologies. We performed simulations of electron beam driven wakefields, with collinear lasers used for ionization injection of electrons. We numerically generated a witness beam using the OSIRIS code in an up ramp plasma as well as uniform plasma regimes. We report on challenges and details of the E-310 experiment which aims to demonstrate this plasma photocathode injection at FACET-II. We examine the phenomena beam hosing and drive beam depletion. Details of the witness beam generated are discussed. Computation of betatron-radiation X-ray spatial distribution and critical energy are done for FACET-II low emittance beams.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST041
About •	Received ※ 07 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 21 June 2022 — Issue date ※ 23 June 2022
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WEPOST042	Radiation Diagnostics for AWA and FACET-II Flat Beams in Plasma	1791
	M. Yadav, Ö. Apsimon, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom H.S. Ancelin, G. Andonian, P. Manwani, J.B. Rosenzweig UCLA, Los Angeles, California, USA
	Funding: This work was performed with support of the US Department of Energy, Division of High Energy Physics, under Contract No. DE-SC0009914, DE-SC0017648 - AWA and STFC grant ST/P006752/1 , In energy beam facilities like FACET and AWA, beams with highly asymmetric emittance are of interest because they are the preferred type of beam for linear colliders. That is ultimately the motivation: building a plasma based LC. In this case, the blowout region is no longer symmetric around an axis is not equal in the two transverse planes. Focusing is required to keep the particles within the tight apertures and characterizing these accelerators shows the benefits of employing ultra low beam emittances. Beams with high charge and high emittance ratios in excess of 100:1 are available at AWA. If the focusing will not be equal, then we will have different radiation signatures for the flat and symmetric beams in plasma. We use OSIRIS particle-in-cell codes to compare various scenarios including a weak blowout and a strong blowout. Further, we determine the radiation generated in the system by importing particle trajectories into a Liénard Weichert code. We discuss future steps towards full diagnostics of flat beams using radiation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST042
About •	Received ※ 07 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 20 June 2022 — Issue date ※ 05 July 2022
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WEPOST045	Simulating Enhanced Focusing Effects of Ion Motion in Adiabatic Plasmas	1798
	D.R. Chow, C.E. Hansel, P. Manwani, J.B. Rosenzweig, M. Yadav UCLA, Los Angeles, California, USA Ö. Apsimon, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom
	Funding: This work was performed with support of the US Department of Energy, Division of High Energy Physics, under Contract No. DE-SC0009914, and the STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) under grant agreement ST/P006752/1. The FACET-II facility offers the unique opportunity to study low emittance, GeV beams and their interactions with high density plasmas in plasma wakefield acceleration (PWFA) scenarios. One of the experiments relevant to PWFA research at FACET-II is the ion collapse experiment E-314, which aims to study how ion motion in a PWFA can produce dual-focused equilibrium. As nonlinear focusing effects due to nonuniform ion distributions have not been extensively studied; we explore the difficulties of inducing ion motion in an adiabatic plasma and examines the effect an ion column has on beam focusing. A case study is performed on a system containing a plasma lens and adiabatic PWFA. Ions in the lens section are assumed to be static, while simulations of an adiabatic matching section are modified to include the effects of ion column collapse and their nonlinear focusing fields. Using the parameters of the FACET-II beam, we find that a collapsed ion column amplifies the focusing power of a plasma without compromising emittance preservation. This led to a spot size orders of magnitude less than that of a simply matched beam.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST045
About •	Received ※ 07 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 23 June 2022 — Issue date ※ 25 June 2022
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WEPOST046	Beam Matching in an Elliptical Plasma Blowout Driven by Highly Asymmetric Flat Beams	1802
SUSPMF037	use link to see paper's listing under its alternate paper code
	P. Manwani, H.S. Ancelin, G. Andonian, N. Majernik, J.B. Rosenzweig, M. Yadav UCLA, Los Angeles, California, USA G. Andonian RadiaBeam, Marina del Rey, California, USA G. Ha, J.G. Power ANL, Lemont, Illinois, USA M. Yadav The University of Liverpool, Liverpool, United Kingdom M. Yadav Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: This work was performed with the support of the US Department of Energy under Contract No. DE-SC0017648 and DESC0009914. Particle beams with highly asymmetric emittance ratios, or flat beams, are employed at accelerator facilities such as the AWA and foreseen at FACET-II. Flat beams have been used to drive wakefields in dielectric structures and are an ideal candidate for high-gradient wakefields in plasmas. The high aspect ratio produces a blowout region that is elliptical in cross section and this asymmetry in the ion column structure creates asymmetric focusing in the two transverse planes. The ellipticity of the plasma blowout decreases as the normalized peak current increases, and gradually approaches an axisymmetric column. An appropriate matching condition for the beam envelope inside the elliptical blowout is introduced. Simulations are performed to investigate the ellipticity of the resultant wakefield based on the initial drive beam parameters, and are compared to analytical calculations. The parameter space for two cases at the AWA and FACET facilities, with requirements for plasma profile and achievable fields, is presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST046
About •	Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 29 June 2022
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WEPOST048	Excitation of Very High Gradient Plasma Wakefields From Nanometer Scale Beams	1806
	P. Manwani, H.S. Ancelin, G. Andonian, D.R. Chow, N. Majernik, J.B. Rosenzweig, M. Yadav UCLA, Los Angeles, California, USA G. Andonian RadiaBeam, Marina del Rey, California, USA R. Robles SLAC, Menlo Park, California, USA M. Yadav The University of Liverpool, Liverpool, United Kingdom M. Yadav Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: This work was performed with the support of the US Department of Energy under Contract No. DESC0009914. The plasma based terawatt attosecond project at SLAC, termed PAX, offers near mega-Ampere beams that could be used to demonstrate plasma wakefield acceleration at very high gradients (TV/m). The beam has a large aspect ratio which allows it to be used at high densities since the longitudinal beam size is lower than the plasma skin depth. This beam can be focused using a permanent magnitude quadrupole (PMQ) triplet to further reduce its transverse size. Since the beam is extremely short compared to the plasma skin depth, it behaves like a delta-function perturbation to the plasma. This reduces the expected focusing effect of the ion column and simulations show that only the tail of the beam is notably focused and decelerated. This scenario is investigated with attendant experimental considerations discussed. The creation of the witness beam by the deceleration of the tail of the beam is also discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST048
About •	Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 29 June 2022
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WEPOMS017	Space Charge Analysis for Low Energy Photoinjector	2272
SUSPMF075	use link to see paper's listing under its alternate paper code
	M. Carillo, F. Bosco, E. Chiadroni, L. Giuliano, M. Migliorati, A. Mostacci, L. Palumbo Sapienza University of Rome, Rome, Italy M. Behtouei, B. Spataro LNF-INFN, Frascati, Italy O. Camacho, A. Fukasawa, J.B. Rosenzweig UCLA, Los Angeles, California, USA L. Faillace INFN/LNF, Frascati, Italy L. Ficcadenti INFN-Roma, Roma, Italy
	Funding: This work is supported by DARPA under Contract HR001120C0072, by DOE Contract DE-SC0009914 & DE-SC0020409, by the National Science Foundation Grant N.PHY-1549132 and by INFN through the project ARYA. Beam dynamics studies are performed in the context of a C-Band hybrid photo-injector project developed by a collab- oration between UCLA/Sapienza/INFN-LNF/RadiaBeam. These studies aim to explain beam behaviour through the beam-slice evolution, using analytical and numerical approaches. An understanding of the emittance oscillations is obtained starting from the slice analysis, which allows correlation of the position of the emittance minima with the slope of the slices in the transverse phase space (TPS). At the end, a significant reduction in the normalized emittance is obtained by varying the transverse shape of the beam while assuming a longitudinal Gaussian distribution. Indeed, the emittance growth due to nonlinear space-charge fields has been found to occur immediately after moment of the beam emission from the cathode, giving insight into the optimum laser profile needed for minimizing the emittance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS017
About •	Received ※ 16 May 2022 — Revised ※ 12 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 01 July 2022
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WEPOMS045	Modeling and Mitigation of Long-Range Wakefields for Advanced Linear Colliders	2350
SUSPMF071	use link to see paper's listing under its alternate paper code
	F. Bosco, M. Carillo, L. Giuliano, M. Migliorati, A. Mostacci, L. Palumbo Sapienza University of Rome, Rome, Italy O. Camacho, A. Fukasawa, N. Majernik, J.B. Rosenzweig UCLA, Los Angeles, California, USA E. Chiadroni, B. Spataro, C. Vaccarezza LNF-INFN, Frascati, Italy L. Faillace, A. Giribono INFN/LNF, Frascati, Italy
	Funding: This work is supported by DARPA under Contract N.HR001120C0072, by DOE Contract DE-SC0009914 and DE-SC0020409, by the National Science Foundation Grant N.PHY-1549132 and by INFN. The luminosity requirements of TeV-class linear colliders demand use of intense charged beams at high repetition rates. Such features imply multi-bunch operation with long current trains accelerated over the km length scale. Consequently, particle beams are exposed to the mutual parasitic interaction due to the long-range wakefields excited by the leading bunches in the accelerating structures. Such perturbations to the motion induce transverse oscillations of the bunches, potentially leading to instabilities such as transverse beam break-up. Here we present a dedicated tracking code that studies the effects of long-range transverse wakefield interaction among different bunches in linear accelerators. Being described by means of an efficient matrix formalism, such effects can be included while preserving short computational times. As a reference case, we use our code to investigate the performance of a state-of-the-art linear collider currently under design and, in addition, we discuss possible mitigation techniques based on frequency detuning and damping.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS045
About •	Received ※ 20 May 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 10 July 2022
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THPOST045	Temperature Dependent Effects on RF Surface Resistivity	2540
	G.E. Lawler, A. Fukasawa, N. Majernik, J.B. Rosenzweig UCLA, Los Angeles, California, USA
	Funding: This work was supported by DOE Contract DE-SC0020409 A promising future for linear accelerators such as compact free electron lasers and electron positron colliders is higher gradient RF cavities enabled by cryogenic temperature operation. Breakdown rates have been shown empirically to be significantly reduced at low temperatures allowing for higher gradient. The surface physics associated with this observation is complicated and there many remain questions as to the exact phenomena responsible. One major figure of merit that can better inform the theory of breakdown is the RF surface resistivity which can be used to compute for example the RF pulse heating during operation. We then use techniques developed for previous Xband and Sband low power surface resistivity measurement by way of temperature dependent quality factor measurements to study Cband cavities. We first present a review of low temperature effects that may be responsible for the change in surface resistivity at low temperature. We then explain some of the initial measurements of these low power RF quality factor tests and compare them to a review some of the physical phenomena that could determine the low temperature surface effects.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOST045
About •	Received ※ 08 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 20 June 2022
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THPOST046	CrYogenic Brightness-Optimized Radiofrequency Gun (CYBORG)	2544
SUSPMF021	use link to see paper's listing under its alternate paper code
	G.E. Lawler, A. Fukasawa, N. Majernik, J.R. Parsons, J.B. Rosenzweig, Y. Sakai, A. Suraj UCLA, Los Angeles, California, USA
	Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE Contract DE-SC0020409 Producing higher brightness beams at the cathode is one of the main focuses for future electron beam applications. For photocathodes operating close to their emission threshold, the cathode lattice temperature begins to dominate the minimum achievable intrinsic emittance. At UCLA, we are designing a radiofrequency (RF) test bed for measuring the temperature dependence of the mean transverse energy (MTE) and quantum efficiency for a number of candidate cathode materials. We intend to quantify the attainable brightness improvements at the cathode from cryogenic operation and establish a proof-of-principle cryogenic RF gun for future studies of a 1.6-cell cryogenic photoinjector for the UCLA ultra compact XFEL concept (UC-XFEL). The test bed will use a C-band 0.5-cell RF gun designed to operate down to 45 K, producing an on-axis accelerating field of 120 MV/m. The cryogenic system uses conduction cooling and a load-lock system is being designed for transport and storage of air-sensitive high brightness cathodes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOST046
About •	Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 01 July 2022
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THPOTK027	Temperature Dependent Effects on Quality Factor in C-band RF Cavities	2826
	J.R. Parsons, A. Fukasawa, G.E. Lawler, N. Majernik, J.B. Rosenzweig UCLA, Los Angeles, California, USA
	Funding: This work was supported by DOE Contract DE-SC0020409 Cryogenic operation and associated skin effects are encouraging fields of study for increasing RF gradients of beams within cavities and decreasing the required size for linear accelerators such as free electron lasers. Notably, a cavity’s RF quality factor Q, the ratio of the outgoing RF signal power to the input power, is theoretically multiplied by over 4 when subjected to cryogenic temperatures. Precise measurements of this Q factor require defining a cryostat unit, which consists of a high vacuum chamber, a coldhead, and MLI shielding. We optimized the cryostat by running several cool down tests at high vacuum, incorporating different geometries of MLI shielding to achieve the lowest possible temperatures. We then performed a low power C-band test after installing a cylindrical copper RF cavity to measure the Q factor. Finally, we improved stability and amplification within the chamber by installing edge welded bellows to the coldhead to reduce vibrations. These measurements provide a basis for the development of cryogenic infrastructure to sustain a cryogenic temperature environment for future RF applications.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK027
About •	Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 27 June 2022
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THPOTK053	Foiled Again: Solid-State Sample Delivery for High Repetition Rate XFELs	2899
	N. Majernik, N. Inzunza, P. Manwani, J.B. Rosenzweig UCLA, Los Angeles, California, USA R.B. Agustsson, A. Moro RadiaBeam, Santa Monica, California, USA R. Ash, N.B. Welke UW-Madison/PD, Madison, Wisconsin, USA U. Bergmann, A. Halavanau, C. Pellegrini SLAC, Menlo Park, California, USA
	Funding: Department of Energy DE-SC0009914 and DE-AC02-76SF00515 XFELs today are capable of delivering high intensity pulse trains of x-rays with up-to MHz to sub-GHz frequency. These x-rays, when focused, can ablate a sample in a single shot, requiring the sample material to be replaced in time for the next shot. For some applications, especially serial crystallography, the sample may be renewed as a dilute solution in a high speed jet. Here, we describe the development and characterization of a system to deliver solid state sample material to an XFEL nanofocus. The first application of this system will be an x-ray laser oscillator operating at the copper Kα line with a ~30 ns cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK053
About •	Received ※ 06 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 02 July 2022
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Paper

Title

Page

Reconstruction of Beam Parameters from Betatron Radiation Using Maximum Likelihood Estimation and Machine Learning

407

S. Zhang, G. Andonian, C.E. Hansel, P. Manwani, B. Naranjo, M.H. Oruganti, J.B. Rosenzweig, M. Yadav
UCLA, Los Angeles, California, USA
Ö. Apsimon, C.P. Welsch, M. Yadav
The University of Liverpool, Liverpool, United Kingdom

Funding: US Department of Energy, Division of High Energy Physics, Contract No. DE-SC0009914 STFC Liver-pool Centre for Doctoral Training on Data Intensive Science, grant agreement ST/P006752/1
Betatron radiation that arises during plasma wakefield acceleration can be measured by a UCLA-built Compton spectrometer, which records the energy and angular position of incoming photons. Because information about the properties of the beam is encoded in the betatron radiation, measurements of the radiation can be used to reconstruct beam parameters. One method of extracting information about beam parameters from measurements of radiation is maximum likelihood estimation (MLE), a statistical technique which is used to determine unknown parameters from a distribution of observed data. In addition, machine learning methods, which are increasingly being implemented for different fields of beam diagnostics, can also be applied. We assess the ability of both MLE and other machine learning methods to accurately extract beam parameters from measurements.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOPT063

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Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 24 June 2022 — Issue date ※ 26 June 2022

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MOPOPT066

Gas Sheet Diagnostics Using Particle in Cell Code

410

M. Yadav, P. Manwani, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
G. Andonian
RadiaBeam, Santa Monica, California, USA
Ö. Apsimon, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
N.M. Cook, A. Diaw, C.C. Hall
RadiaSoft LLC, Boulder, Colorado, USA
N.P. Norvell
UCSC, Santa Cruz, California, USA

Funding: This work was supported by the STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) under grant agreement ST/P006752/1 and DE-SC0019717.
When intense particle beam propagates in dense plasma or gas, ionization can yield valuable information on the drive beam properties. Impact ionization and tunnel ionization are the two ionization regimes that must be accounted for varying beam properties. Due to these ionization mechanisms, new plasma electrons are generated causing different instabilities, dependent on the dominant ionization process considered. In order to accomplish the ambitious experimental goals of sophisticated beam diagnostics using ionization imaging, careful studies on the different ionization regimes, and the cross-over periods, required. Here we will discuss the impact ionization using fully parallel PIC code OSIRIS. We focus on understanding the gas sheet ionization diagnostics for characterizing high intensity charged particle beams. We study the interaction of neutral gas with an electron beam and varying density. We will also investigate the principle of detecting photon emission, rather than direct primary ion imaging, from the ionization induced in the interaction between the gas jet and charged particle beams.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOPT066

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Received ※ 07 June 2022 — Revised ※ 19 June 2022 — Accepted ※ 21 June 2022 — Issue date ※ 26 June 2022

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MOPOMS023

Start-to-End Beam-Dynamics Simulations of a Compact C-Band Electron Beam Source for High Spectral Brilliance Applications

687

L. Faillace, M. Behtouei, B. Spataro, C. Vaccarezza
LNF-INFN, Frascati, Italy
R.B. Agustsson, I.I. Gadjev, S.V. Kutsaev, A.Y. Murokh
RadiaBeam, Marina del Rey, California, USA
F. Bosco, M. Carillo, L. Giuliano, M. Migliorati, A. Mostacci, L. Palumbo
Sapienza University of Rome, Rome, Italy
D.L. Bruhwiler
RadiaSoft LLC, Boulder, Colorado, USA
O. Camacho, A. Fukasawa, N. Majernik, J.B. Rosenzweig, O. Williams
UCLA, Los Angeles, California, USA
A. Giribono
INFN/LNF, Frascati, Italy
S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This work is partially supported by DARPA under the Contract No. HR001120C0072, by DOE Contract DE-SC0009914, DOE Contract DE-SC0020409, and by the National Science Foundation Grant No. PHY-1549132.
Proposals for new linear accelerator-based facilities are flourishing world-wide with the aim of high spectral brilliance radiation sources. Most of these accelerators are based on electron beams, with a variety of applications in industry, research and medicine such as colliders, free-electron lasers, wake-field accelerators, coherent THz and inverse Compton scattering X/’ sources as well as high-resolution diagnostics tools in biomedical science. In order to obtain high-quality electron beams in a small footprint, we present the optimization design of a C-band linear accelerator machine. Driven by a novel compact C-band hybrid photoinjector, it will yield ultra-short electron bunches of few 100’s pC directly from injection with ultra-low emittance, fraction of mm-mrad, and a few hundred fs length simultaneously, therefore satisfying full 6D emittance compensation. The normal-conducting linacs are based on a novel high-efficiency design with gradients up to 50 MV/m. The beam maximum energy can be easily adjusted in the mid-GeV’s range. In this paper, we discuss the start-to-end beam-dynamics simulations in details.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS023

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Received ※ 07 June 2022 — Revised ※ 09 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 03 July 2022

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MOPOMS033

Emittance Measurements of Nanoblade-Enhanced High Field Cathode

709

G.E. Lawler, N. Majernik, J.I. Mann, N.E. Montanez, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
V.S. Yu
RadiaBeam, Santa Monica, California, USA

Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132.
High brightness cathodes are increasingly a focus for accelerator applications ranging from free electron lasers to ultrafast electron diffraction. There is further an increasing interest in fabrication and control of cathode surface to better control the emission characteristics and improve beam brightness. One method which we can consider is based on well-known silicon nanofabrication techniques which we use to create patterned cathode surfaces. The sharp edges produced lead to field emission increases and high brightness emission. We have demonstrated that a beam can be successfully extracted with a low emittance and we have reconstructed a portion of the energy spectrum. Due to the simplicity of extended geometries in nanofabrication our beam uniquely possesses a high aspect ratio in its transverse cross section. We can begin to consider modifications for emittance exchange beamlines and having shown the patterning principle is sound we can consider additional patterns such as hollow beams. Future work will continue to characterize the produced beam and the addition of fabrication steps to remove one of the blades in the double blade geometry in order to more accurately characterize the emission.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS033

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Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 10 July 2022

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MOPOMS034

Material Normal Energy Distribution for Field Emission Analyses From Monocrystalline Surfaces

713

J.I. Mann, Y. Li, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
T. Arias, J.K. Nangoi
Cornell University, Ithaca, New York, USA

Funding: National Science Foundation Grant No. PHY-1549132
Electron field emission is a complicated phenomenon which is sensitive not only to the particular material under illumination but also to the specific crystalline orientation of the surface. Summarizing the ability for a crystal to emit in a particular direction would be of great use when searching for good field emitters. In this paper we propose a material normal energy distribution which describes the ability of the bound electrons to tunnel under an intense electric field. This framework breaks a computationally expensive 3-D system down to a source distribution representation applicable for more efficient 1-D models. We use the Fowler-Nordheim framework to study the yield and MTE (mean transverse energy) from sources including gold, copper, and tungsten in both monocrystalline and polycrystalline forms. We find an increase in effective work function for field emission in the (111) direction for gold and copper associated with the Bragg plane intersections of the Fermi surface.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS034

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Received ※ 20 May 2022 — Revised ※ 12 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 06 July 2022

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MOPOMS036

Simulations of Laser Field Emission from Nanostructures with Image Charge Trapping and Band Structure Transitions

717

B. Wang, G.E. Lawler, J.I. Mann, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
T. Arias, J.K. Nangoi
Cornell University, Ithaca, New York, USA
S.S. Karkare
Arizona State University, Tempe, USA

Funding: National Science Foundation Grant No. PHY-1549132
Laser-induced field emission from nanostructures as a means to create high brightness electron beams has been a continually growing topic of study. Experiments using nanoblade emitters have achieved peak fields upwards of 40 GV/m, begging further investigation in this extreme regime. A recent paper has provided analytical reductions of the common semi-infinite Jellium system for pulsed incident lasers. We utilize these results as well as similar previous results to further understand the physics underlying electron rescattering-type emissions. We progress in numerically evaluating the analytical solution to attempt to more efficiently generate spectra for this system. Additionally, we use the full 1-D time-dependent Schrödinger equation with a Hartree potential and a dispersion-relation transition from material to vacuum to study the same system. We determine what importance the inclusion of the material band structure may have on emissions using this computationally challenging approach.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS036

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Received ※ 08 June 2022 — Revised ※ 21 June 2022 — Accepted ※ 27 June 2022 — Issue date ※ 01 July 2022

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MOPOMS052

6 MeV Novel Hybrid (Standing Wave - Traveling Wave) Photo-Cathode Electron Gun for a THz Superradiant FEL

760

A. Nause, L. Feigin, A. Friedman, A. Weinberg
Ariel University, Ariel, Israel
A. Fukasawa, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
B. Spataro
LNF-INFN, Frascati, Italy

A novel 6 MeV hybrid photo injector was designed and commissioned at Ariel University in Israel as an on-going collaboration with UCLA. This unique, new generation design provides a radically simpler approach to RF feeding of a gun/buncher system, leading to a much shorter beam via velocity bunching owed to an attached traveling wave section of the photo-injector. This design results in better performance in beam parameters, providing a high quality electron beam, with energy of 6 MeV, emittance of less than 3 ’m, and a 150 fs pulse duration at up to 1 nC per pulse. The Hybrid gun is driven by a SLAC XK5 Klystron as the high power RF source, and third harmonic of a fs level IR Laser amplifier (266 nm) to extract electrons from the Cathode. The unique e-gun will produce a bunched electron pulse to drive a THz FEL, which will operate at the super-radiance regime, and therefore requires extraordinary beam properties. It will also be used for MeV UED experiments in a separate line using a dogleg section. Here we describe the gun and presents experimental results from the gun and its sub-systems, including energy and charge measurements, compared with the design simulations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS052

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Received ※ 11 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 18 June 2022

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TUPOPT034

Modelling of X-Ray Volume Excitation of the XLO Gain Medium Using Flash

1081

P. Manwani, N. Majernik, B. Naranjo, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
E.C. Galtier, A. Halavanau, C. Pellegrini
SLAC, Menlo Park, California, USA

Funding: This work was performed with the support of the US Department of Energy under Contract No. DE-AC02-76SF00515 and DESC0009914.
Plasma dynamics and crater formation of laser excited volumes in solids is a complex process due to thermalization, shockwave formation, varying absorption mechanisms, and a wide range of relevant physics timescales. The properties and interaction of such laser-matter systems can be modeled using an equation of state and opacity based multi-temperature treatment of plasma using a radiation hydrodynamics code. Here, we use FLASH, an adaptive mesh radiation-hydrodynamics code, to simulate the plasma expansion following after the initial energy deposition and thermalization of the column, to benchmark the results of experiments undertaken at UCLA on optical laser ablation. These computational results help develop a quantitative understanding of the material excitation process and enable the optimization of the gain medium delivery system for the x-ray laser oscillator project *.
* Halavanau, Aliaksei, et al. "Population Inversion X-Ray Laser Oscillator." Proceedings of the National Academy of Sciences, vol. 117, no. 27, 2020, pp. 15511-15516.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOPT034

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Received ※ 08 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 18 June 2022 — Issue date ※ 24 June 2022

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TUPOPT035

Introduction of Westwood Linear Accelerator Test Facility in University of California Los Angeles

1085

Y. Sakai, G. Andonian, O. Camacho, A. Fukasawa, G.E. Lawler, N. Majernik, P. Manwani, B. Naranjo, J.B. Rosenzweig, O. Williams
UCLA, Los Angeles, California, USA

Funding: U.S. DOE: DE-SC0009914 U.S. DOD: DARPA GRIT Contract 20204571 U.S. DOE: DE-SC0020409 - Cryo RF
An electron linear accelerator test facility located on UCLA’s southwest campus in Westwood, SAMURAI, is presently being constructed. A RF-based accelerator consists of a compact, 3 MeV S-band hybrid gun capable of velocity bunching to bunch lengths in the 100s fs range with 100s pC of charge. This beam is accelerated by an 1.5 m S-band linac with a peak output energy of 30 MeV which can be directed to either a secondary beamline or remain on the main beamline for final acceleration by a SLAC 3 m S-band linac to an energy of 80 MeV. Further acceleration by advanced boosters such as a cryo-cooled C-band structure or numerous optical or wakefield methods is under active investigation. In combination with a 3 TW Ti:Sapphire laser, initial proof of principle experiments will be conducted on topics including the ultra-compact x-ray free-electron laser, advanced dielectric wakefield acceleration, bi-harmonic nonlinear inverse Compton scattering, and various radiation detectors. Furthermore, development of a tertiary beamline based on an ultra low emittance, cryo-cooled gun will eventually enable two-beam experiments, expanding the facility’s unique experimental capabilities.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOPT035

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Received ※ 08 June 2022 — Revised ※ 09 June 2022 — Accepted ※ 20 June 2022 — Issue date ※ 24 June 2022

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TUPOPT047

Progress Report on Population Inversion X-Ray Laser Oscillator at LCLS

1107

A. Halavanau, R. Alonso-Mori, A. Aquila, U. Bergmann, F.-J. Decker, F. Fuller, M. Liang, A.A. Lutman, R.A. Margraf, R.H. Paul, C. Pellegrini
SLAC, Menlo Park, California, USA
R. Ash, N.B. Welke
UW-Madison/PD, Madison, Wisconsin, USA
A.I. Benediktovitch
DESY, Hamburg, Germany
S.C. Krusic
JSI, Ljubljana, Slovenia
N. Majernik, P. Manwani, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
R. Robles
Stanford University, Stanford, California, USA
N. Rohringer
Max Planck Institute for the Physics of Complex Systems, Dresden, Germany

We report the progress in the design and construction of a population inversion x-ray laser oscillator (XLO) using LCLS as an x-ray laser pump, being developed by a SLAC, CFEL, University of Hamburg (Germany), University of Wisconsin, Josef Stefan Institute (Slovenia) and UCLA collaboration. In this proceeding, we will present the latest XLO design and numerical simulations substantiated by our first experimental results. In our next experimental step XLO will be tested on the Coherent X-ray Imaging (CXI) end-station at LCLS as a two pass Regenerative Amplifier operating at the Copper K_α1 photon energy of 8048 eV. When built, XLO will generate fully coherent transform limited pulses with about 50 meV FWHM bandwidth. We expect the XLO will pave the way for new user experiments, e.g. in inelastic x-ray scattering, parametric down conversion, quantum science, x-ray interferometry, and external hard x-ray XFEL seeding.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOPT047

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Received ※ 12 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 24 June 2022

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WEPOST040

Comparing Methods of Recovering Gamma Energy Distributions from PEDRO Spectrometer Responses

1784

M.H. Oruganti, B. Naranjo, J.B. Rosenzweig, M. Yadav
UCLA, Los Angeles, California, USA

To calculate the energy levels of the photons emitted from high-energy particle interactions, the new pair spectrometer (PEDRO) channels the photons through several Beryllium nuclear fields to produce electron-positron pairs through the nuclear field interaction. This project compared several methods of reconstruction and determined which best predicts original energy distributions based on simulated spectra. These methods included using Maximum Likelihood Estimation, Machine Learning, and directly analyzing a response matrix that modeled PEDRO’s response to any photon energy distribution. We report that performing the direct analysis, also known as QR decomposition, on a PEDRO-generated spectrum provides by far the most accurate calculation of the spectrum’s original energy distribution. These methods were tested against results from experimental cases, including Nonlinear Compton Scattering and Filamentation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST040

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Received ※ 15 June 2022 — Revised ※ 01 July 2022 — Accepted ※ 08 July 2022 — Issue date ※ 08 July 2022

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WEPOST041

Physical Aspects of Collinear Laser Injection at SLAC FACET-II E-310: Trojan Horse Experiment

1787

M. Yadav, Ö. Apsimon, E. Kukstas, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
C.E. Hansel, P. Manwani, B. Naranjo, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
B. Hidding
USTRAT/SUPA, Glasgow, United Kingdom

Funding: This work was performed with support of the US Department of Energy, Division of High Energy Physics, un-der Contract No. DE-SC0009914, and the STFC grant ST/P006752/1.
The Facility for Advanced Accelerator Experimental Tests (FACET-II) is a test accelerator infrastructure at SLAC dedicated to the research and development of advanced accelerator technologies. We performed simulations of electron beam driven wakefields, with collinear lasers used for ionization injection of electrons. We numerically generated a witness beam using the OSIRIS code in an up ramp plasma as well as uniform plasma regimes. We report on challenges and details of the E-310 experiment which aims to demonstrate this plasma photocathode injection at FACET-II. We examine the phenomena beam hosing and drive beam depletion. Details of the witness beam generated are discussed. Computation of betatron-radiation X-ray spatial distribution and critical energy are done for FACET-II low emittance beams.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST041

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Received ※ 07 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 21 June 2022 — Issue date ※ 23 June 2022

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WEPOST042

Radiation Diagnostics for AWA and FACET-II Flat Beams in Plasma

1791

M. Yadav, Ö. Apsimon, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
H.S. Ancelin, G. Andonian, P. Manwani, J.B. Rosenzweig
UCLA, Los Angeles, California, USA

Funding: This work was performed with support of the US Department of Energy, Division of High Energy Physics, under Contract No. DE-SC0009914, DE-SC0017648 - AWA and STFC grant ST/P006752/1 ,
In energy beam facilities like FACET and AWA, beams with highly asymmetric emittance are of interest because they are the preferred type of beam for linear colliders. That is ultimately the motivation: building a plasma based LC. In this case, the blowout region is no longer symmetric around an axis is not equal in the two transverse planes. Focusing is required to keep the particles within the tight apertures and characterizing these accelerators shows the benefits of employing ultra low beam emittances. Beams with high charge and high emittance ratios in excess of 100:1 are available at AWA. If the focusing will not be equal, then we will have different radiation signatures for the flat and symmetric beams in plasma. We use OSIRIS particle-in-cell codes to compare various scenarios including a weak blowout and a strong blowout. Further, we determine the radiation generated in the system by importing particle trajectories into a Liénard Weichert code. We discuss future steps towards full diagnostics of flat beams using radiation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST042

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Received ※ 07 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 20 June 2022 — Issue date ※ 05 July 2022

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WEPOST045

Simulating Enhanced Focusing Effects of Ion Motion in Adiabatic Plasmas

1798

D.R. Chow, C.E. Hansel, P. Manwani, J.B. Rosenzweig, M. Yadav
UCLA, Los Angeles, California, USA
Ö. Apsimon, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

Funding: This work was performed with support of the US Department of Energy, Division of High Energy Physics, under Contract No. DE-SC0009914, and the STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) under grant agreement ST/P006752/1.
The FACET-II facility offers the unique opportunity to study low emittance, GeV beams and their interactions with high density plasmas in plasma wakefield acceleration (PWFA) scenarios. One of the experiments relevant to PWFA research at FACET-II is the ion collapse experiment E-314, which aims to study how ion motion in a PWFA can produce dual-focused equilibrium. As nonlinear focusing effects due to nonuniform ion distributions have not been extensively studied; we explore the difficulties of inducing ion motion in an adiabatic plasma and examines the effect an ion column has on beam focusing. A case study is performed on a system containing a plasma lens and adiabatic PWFA. Ions in the lens section are assumed to be static, while simulations of an adiabatic matching section are modified to include the effects of ion column collapse and their nonlinear focusing fields. Using the parameters of the FACET-II beam, we find that a collapsed ion column amplifies the focusing power of a plasma without compromising emittance preservation. This led to a spot size orders of magnitude less than that of a simply matched beam.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST045

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Received ※ 07 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 23 June 2022 — Issue date ※ 25 June 2022

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WEPOST046

Beam Matching in an Elliptical Plasma Blowout Driven by Highly Asymmetric Flat Beams

1802

SUSPMF037

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P. Manwani, H.S. Ancelin, G. Andonian, N. Majernik, J.B. Rosenzweig, M. Yadav
UCLA, Los Angeles, California, USA
G. Andonian
RadiaBeam, Marina del Rey, California, USA
G. Ha, J.G. Power
ANL, Lemont, Illinois, USA
M. Yadav
The University of Liverpool, Liverpool, United Kingdom
M. Yadav
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work was performed with the support of the US Department of Energy under Contract No. DE-SC0017648 and DESC0009914.
Particle beams with highly asymmetric emittance ratios, or flat beams, are employed at accelerator facilities such as the AWA and foreseen at FACET-II. Flat beams have been used to drive wakefields in dielectric structures and are an ideal candidate for high-gradient wakefields in plasmas. The high aspect ratio produces a blowout region that is elliptical in cross section and this asymmetry in the ion column structure creates asymmetric focusing in the two transverse planes. The ellipticity of the plasma blowout decreases as the normalized peak current increases, and gradually approaches an axisymmetric column. An appropriate matching condition for the beam envelope inside the elliptical blowout is introduced. Simulations are performed to investigate the ellipticity of the resultant wakefield based on the initial drive beam parameters, and are compared to analytical calculations. The parameter space for two cases at the AWA and FACET facilities, with requirements for plasma profile and achievable fields, is presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST046

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Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 29 June 2022

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WEPOST048

Excitation of Very High Gradient Plasma Wakefields From Nanometer Scale Beams

1806

P. Manwani, H.S. Ancelin, G. Andonian, D.R. Chow, N. Majernik, J.B. Rosenzweig, M. Yadav
UCLA, Los Angeles, California, USA
G. Andonian
RadiaBeam, Marina del Rey, California, USA
R. Robles
SLAC, Menlo Park, California, USA
M. Yadav
The University of Liverpool, Liverpool, United Kingdom
M. Yadav
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work was performed with the support of the US Department of Energy under Contract No. DESC0009914.
The plasma based terawatt attosecond project at SLAC, termed PAX, offers near mega-Ampere beams that could be used to demonstrate plasma wakefield acceleration at very high gradients (TV/m). The beam has a large aspect ratio which allows it to be used at high densities since the longitudinal beam size is lower than the plasma skin depth. This beam can be focused using a permanent magnitude quadrupole (PMQ) triplet to further reduce its transverse size. Since the beam is extremely short compared to the plasma skin depth, it behaves like a delta-function perturbation to the plasma. This reduces the expected focusing effect of the ion column and simulations show that only the tail of the beam is notably focused and decelerated. This scenario is investigated with attendant experimental considerations discussed. The creation of the witness beam by the deceleration of the tail of the beam is also discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST048

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Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 29 June 2022

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WEPOMS017

Space Charge Analysis for Low Energy Photoinjector

2272

SUSPMF075

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M. Carillo, F. Bosco, E. Chiadroni, L. Giuliano, M. Migliorati, A. Mostacci, L. Palumbo
Sapienza University of Rome, Rome, Italy
M. Behtouei, B. Spataro
LNF-INFN, Frascati, Italy
O. Camacho, A. Fukasawa, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
L. Faillace
INFN/LNF, Frascati, Italy
L. Ficcadenti
INFN-Roma, Roma, Italy

Funding: This work is supported by DARPA under Contract HR001120C0072, by DOE Contract DE-SC0009914 & DE-SC0020409, by the National Science Foundation Grant N.PHY-1549132 and by INFN through the project ARYA.
Beam dynamics studies are performed in the context of a C-Band hybrid photo-injector project developed by a collab- oration between UCLA/Sapienza/INFN-LNF/RadiaBeam. These studies aim to explain beam behaviour through the beam-slice evolution, using analytical and numerical approaches. An understanding of the emittance oscillations is obtained starting from the slice analysis, which allows correlation of the position of the emittance minima with the slope of the slices in the transverse phase space (TPS). At the end, a significant reduction in the normalized emittance is obtained by varying the transverse shape of the beam while assuming a longitudinal Gaussian distribution. Indeed, the emittance growth due to nonlinear space-charge fields has been found to occur immediately after moment of the beam emission from the cathode, giving insight into the optimum laser profile needed for minimizing the emittance.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS017

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Received ※ 16 May 2022 — Revised ※ 12 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 01 July 2022

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WEPOMS045

Modeling and Mitigation of Long-Range Wakefields for Advanced Linear Colliders

2350

SUSPMF071

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F. Bosco, M. Carillo, L. Giuliano, M. Migliorati, A. Mostacci, L. Palumbo
Sapienza University of Rome, Rome, Italy
O. Camacho, A. Fukasawa, N. Majernik, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
E. Chiadroni, B. Spataro, C. Vaccarezza
LNF-INFN, Frascati, Italy
L. Faillace, A. Giribono
INFN/LNF, Frascati, Italy

Funding: This work is supported by DARPA under Contract N.HR001120C0072, by DOE Contract DE-SC0009914 and DE-SC0020409, by the National Science Foundation Grant N.PHY-1549132 and by INFN.
The luminosity requirements of TeV-class linear colliders demand use of intense charged beams at high repetition rates. Such features imply multi-bunch operation with long current trains accelerated over the km length scale. Consequently, particle beams are exposed to the mutual parasitic interaction due to the long-range wakefields excited by the leading bunches in the accelerating structures. Such perturbations to the motion induce transverse oscillations of the bunches, potentially leading to instabilities such as transverse beam break-up. Here we present a dedicated tracking code that studies the effects of long-range transverse wakefield interaction among different bunches in linear accelerators. Being described by means of an efficient matrix formalism, such effects can be included while preserving short computational times. As a reference case, we use our code to investigate the performance of a state-of-the-art linear collider currently under design and, in addition, we discuss possible mitigation techniques based on frequency detuning and damping.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS045

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Received ※ 20 May 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 10 July 2022

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THPOST045

Temperature Dependent Effects on RF Surface Resistivity

2540

G.E. Lawler, A. Fukasawa, N. Majernik, J.B. Rosenzweig
UCLA, Los Angeles, California, USA

Funding: This work was supported by DOE Contract DE-SC0020409
A promising future for linear accelerators such as compact free electron lasers and electron positron colliders is higher gradient RF cavities enabled by cryogenic temperature operation. Breakdown rates have been shown empirically to be significantly reduced at low temperatures allowing for higher gradient. The surface physics associated with this observation is complicated and there many remain questions as to the exact phenomena responsible. One major figure of merit that can better inform the theory of breakdown is the RF surface resistivity which can be used to compute for example the RF pulse heating during operation. We then use techniques developed for previous Xband and Sband low power surface resistivity measurement by way of temperature dependent quality factor measurements to study Cband cavities. We first present a review of low temperature effects that may be responsible for the change in surface resistivity at low temperature. We then explain some of the initial measurements of these low power RF quality factor tests and compare them to a review some of the physical phenomena that could determine the low temperature surface effects.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOST045

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Received ※ 08 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 20 June 2022

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THPOST046

CrYogenic Brightness-Optimized Radiofrequency Gun (CYBORG)

2544

SUSPMF021

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G.E. Lawler, A. Fukasawa, N. Majernik, J.R. Parsons, J.B. Rosenzweig, Y. Sakai, A. Suraj
UCLA, Los Angeles, California, USA

Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE Contract DE-SC0020409
Producing higher brightness beams at the cathode is one of the main focuses for future electron beam applications. For photocathodes operating close to their emission threshold, the cathode lattice temperature begins to dominate the minimum achievable intrinsic emittance. At UCLA, we are designing a radiofrequency (RF) test bed for measuring the temperature dependence of the mean transverse energy (MTE) and quantum efficiency for a number of candidate cathode materials. We intend to quantify the attainable brightness improvements at the cathode from cryogenic operation and establish a proof-of-principle cryogenic RF gun for future studies of a 1.6-cell cryogenic photoinjector for the UCLA ultra compact XFEL concept (UC-XFEL). The test bed will use a C-band 0.5-cell RF gun designed to operate down to 45 K, producing an on-axis accelerating field of 120 MV/m. The cryogenic system uses conduction cooling and a load-lock system is being designed for transport and storage of air-sensitive high brightness cathodes.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOST046

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Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 01 July 2022

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THPOTK027

Temperature Dependent Effects on Quality Factor in C-band RF Cavities

2826

J.R. Parsons, A. Fukasawa, G.E. Lawler, N. Majernik, J.B. Rosenzweig
UCLA, Los Angeles, California, USA

Funding: This work was supported by DOE Contract DE-SC0020409
Cryogenic operation and associated skin effects are encouraging fields of study for increasing RF gradients of beams within cavities and decreasing the required size for linear accelerators such as free electron lasers. Notably, a cavity’s RF quality factor Q, the ratio of the outgoing RF signal power to the input power, is theoretically multiplied by over 4 when subjected to cryogenic temperatures. Precise measurements of this Q factor require defining a cryostat unit, which consists of a high vacuum chamber, a coldhead, and MLI shielding. We optimized the cryostat by running several cool down tests at high vacuum, incorporating different geometries of MLI shielding to achieve the lowest possible temperatures. We then performed a low power C-band test after installing a cylindrical copper RF cavity to measure the Q factor. Finally, we improved stability and amplification within the chamber by installing edge welded bellows to the coldhead to reduce vibrations. These measurements provide a basis for the development of cryogenic infrastructure to sustain a cryogenic temperature environment for future RF applications.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK027

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Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 27 June 2022

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THPOTK053

Foiled Again: Solid-State Sample Delivery for High Repetition Rate XFELs

2899

N. Majernik, N. Inzunza, P. Manwani, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
R.B. Agustsson, A. Moro
RadiaBeam, Santa Monica, California, USA
R. Ash, N.B. Welke
UW-Madison/PD, Madison, Wisconsin, USA
U. Bergmann, A. Halavanau, C. Pellegrini
SLAC, Menlo Park, California, USA

Funding: Department of Energy DE-SC0009914 and DE-AC02-76SF00515
XFELs today are capable of delivering high intensity pulse trains of x-rays with up-to MHz to sub-GHz frequency. These x-rays, when focused, can ablate a sample in a single shot, requiring the sample material to be replaced in time for the next shot. For some applications, especially serial crystallography, the sample may be renewed as a dilute solution in a high speed jet. Here, we describe the development and characterization of a system to deliver solid state sample material to an XFEL nanofocus. The first application of this system will be an x-ray laser oscillator operating at the copper Kα line with a ~30 ns cavity.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK053

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Received ※ 06 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 02 July 2022

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