NAPAC2019 - List of Keywords (electron)

Paper	Title	Other Keywords	Page
MOOHC2	The US Electron Ion Collider Accelerator Designs	collider, polarization, luminosity, proton	1
	A. Seryi, S.V. Benson, S.A. Bogacz, P.D. Brindza, M.W. Bruker, A. Camsonne, E. Daly, P. Degtiarenko, Y.S. Derbenev, M. Diefenthaler, J. Dolbeck, R. Ent, R. Fair, D. Fazenbaker, Y. Furletova, B.R. Gamage, D. Gaskell, R.L. Geng, P. Ghoshal, J.M. Grames, J. Guo, F.E. Hannon, L. Harwood, S. Henderson, H. Huang, A. Hutton, K. Jordan, D.H. Kashy, A.J. Kimber, G.A. Krafft, R. Lassiter, R. Li, F. Lin, M.A. Mamun, F. Marhauser, R. McKeown, T.J. Michalski, V.S. Morozov, P. Nadel-Turonski, E.A. Nissen, G.-T. Park, H. Park, M. Poelker, T. Powers, R. Rajput-Ghoshal, R.A. Rimmer, Y. Roblin, D. Romanov, P. Rossi, T. Satogata, M.F. Spata, R. Suleiman, A.V. Sy, C. Tennant, H. Wang, S. Wang, C. Weiss, M. Wiseman, W. Wittmer, R. Yoshida, H. Zhang, S. Zhang, Y. Zhang, Z.W. Zhao JLab, Newport News, Virginia, USA D.T. Abell, D.L. Bruhwiler, I.V. Pogorelov RadiaSoft LLC, Boulder, Colorado, USA E.C. Aschenauer, G. Bassi, J. Beebe-Wang, J.S. Berg, M. Blaskiewicz, A. Blednykh, J.M. Brennan, S.J. Brooks, K.A. Brown, K.A. Drees, A.V. Fedotov, W. Fischer, D.M. Gassner, W. Guo, Y. Hao, A. Hershcovitch, H. Huang, W.A. Jackson, J. Kewisch, A. Kiselev, V. Litvinenko, C. Liu, H. Lovelace III, Y. Luo, F. Méot, M.G. Minty, C. Montag, R.B. Palmer, B. Parker, S. Peggs, V. Ptitsyn, V.H. Ranjbar, G. Robert-Demolaize, T. Roser, S. Seletskiy, V.V. Smaluk, K.S. Smith, S. Tepikian, P. Thieberger, D. Trbojevic, N. Tsoupas, E. Wang, W.-T. Weng, F.J. Willeke, H. Witte, Q. Wu, W. Xu, A. Zaltsman, W. Zhang BNL, Upton, New York, USA D.P. Barber DESY, Hamburg, Germany I.V. Bazarov Cornell University, Ithaca, New York, USA G.I. Bell, J.R. Cary Tech-X, Boulder, Colorado, USA Y. Cai, Y.M. Nosochkov, A. Novokhatski, G. Stupakov, M.K. Sullivan, C.-Y. Tsai SLAC, Menlo Park, California, USA Z.A. Conway, M.P. Kelly, B. Mustapha, U. Wienands, A. Zholents ANL, Lemont, Illinois, USA S.U. De Silva, J.R. Delayen, H. Huang, C. Hyde, S. Sosa, B. Terzić ODU, Norfolk, Virginia, USA K.E. Deitrick, G.H. Hoffstaetter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA D. Douglas Douglas Consulting, York, Virginia, USA V.G. Dudnikov, R.P. Johnson Muons, Inc, Illinois, USA B. Erdelyi, P. Piot Northern Illinois University, DeKalb, Illinois, USA J.D. Fox Stanford University, Stanford, California, USA J. Gerity, T.L. Mann, P.M. McIntyre, N. Pogue, A. Sattarov Texas A&M University, College Station, USA E. Gianfelice-Wendt, S. Nagaitsev Fermilab, Batavia, Illinois, USA Y. Hao, P.N. Ostroumov, A.S. Plastun, R.C. York FRIB, East Lansing, Michigan, USA T. Mastoridis CalPoly, San Luis Obispo, California, USA J.D. Maxwell, R. Milner, M. Musgrave MIT, Cambridge, Massachusetts, USA J. Qiang, G.L. Sabbi LBNL, Berkeley, California, USA D. Teytelman Dimtel, Redwood City, California, USA R.C. York NSCL, East Lansing, Michigan, USA
	With the completion of the National Academies of Sciences Assessment of a US Electron-Ion Collider, the prospects for construction of such a facility have taken a step forward. This paper provides an overview of the two site-specific EIC designs: JLEIC (Jefferson Lab) and eRHIC (BNL) as well as brief overview of ongoing EIC R&D.
	Slides MOOHC2 [14.774 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOOHC2
About •	paper received ※ 29 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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MOYBA1	LHC Status and Plans	luminosity, operation, experiment, proton	8
	X. Buffat CERN, Geneva, Switzerland
	Performance and accelerator physics challenges from LHC Run 2 are reviewed, along with the ongoing preparation and plans for LHC Runs 3 and 4.
	Slides MOYBA1 [13.269 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBA1
About •	paper received ※ 26 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019
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MOYBA4	eRHIC Design Update	luminosity, hadron, interaction-region, proton	18
	C. Montag, G. Bassi, J. Beebe-Wang, J.S. Berg, M. Blaskiewicz, A. Blednykh, J.M. Brennan, S.J. Brooks, K.A. Brown, K.A. Drees, A.V. Fedotov, W. Fischer, D.M. Gassner, Y. Hao, A. Hershcovitch, C. Hetzel, D. Holmes, H. Huang, W.A. Jackson, J. Kewisch, Y. Li, C. Liu, H. Lovelace III, Y. Luo, F. Méot, M.G. Minty, R.B. Palmer, B. Parker, S. Peggs, V. Ptitsyn, V.H. Ranjbar, G. Robert-Demolaize, S. Seletskiy, V.V. Smaluk, K.S. Smith, S. Tepikian, P. Thieberger, D. Trbojevic, N. Tsoupas, S. Verdú-Andrés, W.-T. Weng, F.J. Willeke, H. Witte, Q. Wu, W. Xu, A. Zaltsman, W. Zhang BNL, Upton, New York, USA Y. Cai, Y.M. Nosochkov SLAC, Menlo Park, California, USA E. Gianfelice-Wendt Fermilab, Batavia, Illinois, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The future electron-ion collider (EIC) aims at an electron-proton luminosity of 10³³ to 10³⁴ cm^-2 sec^-1 and a center-of-mass energy range from 20 to 140 GeV. The eRHIC design has been continuously evolving over a couple of years and has reached a considerable level of maturity. The concept is generally conservative with very few risk items which are mitigated in various ways.
	Slides MOYBA4 [5.466 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBA4
About •	paper received ※ 24 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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MOYBA6	Accelerator Performance During the Beam Energy Scan II at RHIC in 2019	operation, luminosity, cavity, MMI	26
	C. Liu, I. Blacker, M. Blaskiewicz, K.A. Brown, D. Bruno, K.A. Drees, A.V. Fedotov, W. Fischer, C.J. Gardner, C.E. Giorgio, X. Gu, T. Hayes, H. Huang, R.L. Hulsart, D. Kayran, N.A. Kling, Y. Luo, D. Maffei, G.J. Marr, B. Martin, A. Marusic, K. Mernick, R.J. Michnoff, M.G. Minty, C. Montag, J. Morris, C. Naylor, S. Nemesure, I. Pinayev, S. Polizzo, V.H. Ranjbar, D. Raparia, G. Robert-Demolaize, T. Roser, J. Sandberg, V. Schoefer, F. Severino, T.C. Shrey, K.S. Smith, S. Tepikian, P. Thieberger, A. Zaltsman, K. Zeno, I.Y. Zhang, W. Zhang BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. RHIC provided Au-Au collisions at beam energies of 9.8, 7.3, 4.59 and 3.85 GeV/nucleon during the first year of the Beam Energy Scan II in 2019. The physics goals at the first two higher beam energies were achieved. At the two lower beam energies, bunched electron beam cooling has been demonstrated successfully. The accelerator performance was improved compared to when RHIC was operated at these energies in earlier years. This article will introduce the challenges to operate RHIC at low energies and the corresponding countermeasures, and review the improvement of accelerator performance during the operation in 2019.
	Slides MOYBA6 [6.579 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBA6
About •	paper received ※ 21 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019
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MOYBB2	Recent Advance in ECR Ion Sources	ECR, ion-source, plasma, operation	31
	G. Machicoane, N.K. Bultman, P. Morrison, M. Omelayenko, X. Rao FRIB, East Lansing, Michigan, USA D. Arbelaez, R.R. Hafalia, P. Pan, S. Prestemon LBNL, Berkeley, California, USA
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University. High continuous wave (cw) current of highly charged ion beams are required for several heavy ion accelerator facilities including the Facility for Rare Isotope Beams (FRIB). In most cases, Electron-Cyclotron-Resonance (ECR) ion sources remain the only ion source capable to meet the beam intensity requirement for these facilities. Performances of ECR ion source have increased by several order of magnitude since their inception in the 1970s mostly driven by increasing the resonance frequency with today current state of the art ECR ion source operating from 24 to 28 GHz. This paper provides an overview of recent advance in the design and operation of ECR ion source including plans to develop the next generation of ion source capable of operating above 40 GHz. A detailed account of the design and status of the new superconducting ECR ion source in construction for FRIB will also be reported.
	Slides MOYBB2 [9.483 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB2
About •	paper received ※ 02 September 2019 paper accepted ※ 16 November 2020 issue date ※ 08 October 2019
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MOYBB5	Characterization and Performance of Plasma Window for Gas Flow Restriction in Different Geometries	plasma, cathode, target, diagnostics	44
	A. Lajoie NSCL, East Lansing, Michigan, USA J. Gao, F. Marti FRIB, East Lansing, Michigan, USA
	Funding: This work is supported by NSF Award PHY-1565546. The plasma window is a DC cascaded arc whose function is to restrict gas flow from a high pressure region to a low pressure region without the use of any solid separation. As a result, the plasma window allows a greater pressure to be maintained than otherwise possible. This is a beneficial characteristic for gas charge strippers for ion accelerators, since the higher pressures enable the stripper to be shorter and allow the same amount of stripping interactions. The flow rate reduction is established by the increase in gas temperature from the power deposited into the plasma via the cathodes, resulting in a dramatically increased viscosity. The flow rate reduction, depends on the properties of the plasma, including the electron density and temperature, pressure, and electrical conductivity. Understanding these properties in multiple arc geometries - in this work having either 6 mm or 10 mm channel diameter - provides a means optimizing the plasma window for a given design. Determinations of the properties for different conditions are shown, and results are compared with a PLASIMO simulation, which has been shown to yield comparable properties to measurements in an argon arc*. A. Hershcovitch, Phys. Plasma 5, 2130 (1998). J. A. Nolen and F. Marti, Rev. Accel. Sci. Tech. 6, 221 (2013). *G. M. W. Kroesen et al., Plas. Chem. and Plas. Proc. 10, 531 (1990).
	Slides MOYBB5 [4.132 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB5
About •	paper received ※ 27 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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MOZBA3	Strongly Tapered Helical Undulator System for TESSA-266	undulator, experiment, laser, permanent-magnet	63
	T.J. Campese, R.B. Agustsson, I.I. Gadjev, A.Y. Murokh RadiaBeam, Santa Monica, California, USA W. Berg, A. Zholents ANL, Lemont, Illinois, USA P.E. Denham, P. Musumeci, Y. Park UCLA, Los Angeles, USA
	Funding: DOE SBIR Award No. DE-SC0017102 RadiaBeam, in collaboration with UCLA and Argonne National Laboratory (ANL), is developing a strongly tapered helical undulator system for the Tapering Enhanced Stimulated Superradiant Amplification experiment at 266 nm (TESSA-266). The experiment will be carried out at the APS LEA facility at ANL and aims at the demonstration of very high energy conversion efficiency in the UV. The undulator system was designed by UCLA, engineered by RadiaBeam, and is presently in fabrication at RadiaBeam. The design is based on a permanent magnet Halbach scheme and includes a short 30 cm long buncher section and four 1 m long undulator sections. The undulator period is fixed at 32 mm and the magnetic field amplitude can be tapered by tuning the gap along the interaction. Each magnet can be individually adjusted by 1.03 mm, offering up to 25% magnetic field tunability with a minimum gap of 5.58 mm. A custom designed 316L stainless steel beampipe runs through the center with a clear aperture of 4.5 mm. This paper discusses the design and engineering of the undulator system, fabrication status, and plans for magnetic measurements, and tuning.
	Slides MOZBA3 [8.942 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA3
About •	paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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MOZBA4	Recent Developments in High Power High Brightness Double Bunch Self-Seeding at LCLS-II	FEL, undulator, photon, simulation	67
	A. Halavanau, F.-J. Decker, Y. Ding, C. Emma, Z. Huang, A.A. Lutman, G. Marcus, C. Pellegrini SLAC, Menlo Park, California, USA
	We discuss the power and spectral characteristics of an X-ray FEL, LCLS-II, operating in a double bunch self-seeding scheme (DBFEL). We show that it can reach very high power levels in the photon energy range of 4-8 keV. We discuss the system implementation on LCLS-II, including the design of a four-bounce crystal monochromator, and linac wakefields effects. Finally, we offer multiple applications of the DBFEL for high-field QED, AMO physics and single particle imaging.
	Slides MOZBA4 [3.175 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA4
About •	paper received ※ 02 September 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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MOZBB5	Magnetized Electron Source for JLEIC Cooler	cathode, gun, solenoid, high-voltage	83
	R. Suleiman, P.A. Adderley, J.F. Benesch, D.B. Bullard, J.M. Grames, J. Guo, F.E. Hannon, J. Hansknecht, C. Hernandez-Garcia, R. Kazimi, G.A. Krafft, M.A. Mamun, M. Poelker, M.G. Tiefenback, Y.W. Wang, S. Zhang JLab, Newport News, Virginia, USA J.R. Delayen, G.A. Krafft, S.A.K. Wijethunga, J.T. Yoskowitz ODU, Norfolk, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and supported by Laboratory Directed Research and Development funding. Magnetized bunched-beam electron cooling is a critical part of the Jefferson Lab Electron Ion Collider (JLEIC). Strong cooling of ion beams will be accomplished inside a cooling solenoid where the ions co-propagate with an electron beam generated from a source immersed in magnetic field. This contribution describes the production and characterization of magnetized electron beam using a compact 300 kV DC high voltage photogun and bialkali-antimonide photocathodes. Beam magnetization was studied using a diagnostic beamline that includes viewer screens for measuring the shearing angle of the electron beamlet passing through a narrow upstream slit. Correlated beam emittance with magnetic field at the photocathode was measured for various laser spot sizes. Measurements of photocathode lifetime were carried out at different magnetized electron beam currents up to 28 mA and high bunch charge up to 0.7 nano-Coulomb was demonstrated.
	Slides MOZBB5 [9.236 MB]
	Poster MOZBB5 [1.564 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBB5
About •	paper received ※ 27 August 2019 paper accepted ※ 01 September 2019 issue date ※ 08 October 2019
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MOZBB6	Measuring the Mean Transverse Energy of Pump-Probe Photoemitted Electrons	cathode, photon, experiment, vacuum	87
	C.M. Pierce, I.V. Bazarov, L. Cultrera, J.M. Maxson Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams. Low effective mass semiconductor photocathodes have historically failed to exhibit the sub-thermal mean transverse energies (MTEs) expected of them based on their band structure. However, conservation of transverse momentum across the vacuum interface, and therefore a low MTE in these materials, has been observed in time resolved ARPES. To help bridge this gap, we measured the MTE of the pump probe photoemitted electrons seen in the ARPES experiment using methods typical of accelerator physics. We compare the results of these measurements with those of both communities and discuss them in the context of photoemission physics. Kanasaki, J., Tanimura, H., & Tanimura, K. (2014). Imaging Energy-, Momentum-, and Time-Resolved Distributions of Photoinjected Hot Electrons in GaAs. Physical Review Letters, 113(23), 237401.
	Slides MOZBB6 [7.348 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBB6
About •	paper received ※ 28 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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MOPLM06	High Voltage Design of a 350 kV DC Photogun at BNL	cathode, gun, high-voltage, vacuum	102
	W. Liu, O.H. Rahman, E. Wang BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Brookhaven National Laboratory is constructing a 350 kV DC high voltage photogun to provide spin-polarized electron beam for the proposed eRHIC facility. The photogun employs a compact inverted-tapered-geometry ceramic insulator that extends into the vacuum chamber and mechanically holds the cathode electrode. By operating at high voltage, the photogun will provide lower beam emittance, thereby improving the beam transmission through the injector apertures, and prolong the operating lifetime of the photogun. However, high voltage increases the field emission, which can result in high voltage breakdown and even lead to irreparable damage of the ceramic insulator. This work describes the methods to minimize the electric field near the metal-vacuum-insulator interface, and to avoid high voltage breakdown and ceramic insulator damage. The triple point junction shields are designed. The simulated electric field, field emission and beam transportation will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM06
About •	paper received ※ 19 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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MOPLM13	Investigations of the Electron Beam Energy Jitter Generated in the Photocathode RF Gun at the Advanced Photon Source Linac	gun, timing, laser, cathode	124
	J.C. Dooling, D. Hui, A.H. Lumpkin, T.L. Smith, Y. Sun, K.P. Wootton, A. Zholents ANL, Lemont, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02- 06CH11357. Characterizations continue of the electron beam properties of a recently installed S-band photocathode (PC) rf gun at the Advanced Photon Source Linac facility. In this case, we have utilized a low-energy spectrometer beam line located 1.3 m downstream of the gun cavity to measure the electron beam energy, energy spread, and energy jitter. The nominal energy was 6.5 MeV using a gun gradient of 110 MV/m, and the energy spread was ~17 keV when driven by a 2.5-ps rms duration UV laser pulse at the selected rf gun phase. An energy jitter of 25 keV was initially observed in the spectrometer focal plane images. This jitter was partly attributed to the presence of both the 2nd and 3rd harmonics of the 119 MHz synchronization signal provided to the phase locked loop of the drive laser oscillator. The addition of a 150-MHz low-pass filter in the 119-MHz line strongly attenuated the two harmonics and resulted in a reduced energy jitter of ~15 keV. Comparisons of the gun performance to ASTRA simulations will also be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM13
About •	paper received ※ 28 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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MOPLM15	Design of the ASU Photocathode Lab	cathode, gun, diagnostics, emittance	132
	C.J. Knill, S.S. Karkare Arizona State University, Tempe, USA J.V. Conway, B.M. Dunham, K.W. Smolenski Xelera Research LLC, Ithaca, New York, USA H.A. Padmore LBNL, Berkeley, California, USA
	Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams. Recent investigations have shown that it is possible to obtain an order of magnitude smaller intrinsic emittance from photocathodes by precise atomic scale control of the surface, using an appropriate electronic band structure of single crystal cathodes and cryogenically cooling the cathode. Investigating the performance of such cathodes requires atomic scale surface diagnostic techniques connected in ultra-high vacuum (UHV) to the epitaxial thin film growth and surface preparation systems and photo-emission and photocathode diagnostic techniques. Here we report the capabilities and design of the laboratory being built at the Arizona State University for this purpose. The lab houses a 200 kV DC gun with a cryogenically cooled cathode along with a beam diagnostics and ultra fast electron diffraction beamline. The cathode of the gun can be transported in UHV to a suite of UHV growth chambers and surface and photoemission diagnostic techniques.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM15
About •	paper received ※ 26 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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MOPLM16	Design of a 200 kV DC Cryocooled Photoemission Gun for Photocathode Investigations	cathode, gun, emittance, radiation	136
	G.S. Gevorkyan, S.S. Karkare Arizona State University, Tempe, USA I.V. Bazarov, A. Galdi, J.M. Maxson Cornell University, Ithaca, New York, USA L. Cultrera, W.H. Li Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: This work was supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams. Intrinsic emittance of photocathodes limits the brightness of electrons beams produced from photoemission guns. Recent advancements have shown that an order of magnitude improvement in intrinsic emittance over the commonly used polycrystalline metal and semiconductor cathodes is possible via use of single crystalline ordered surfaces of metals, semiconductors and other exotic materials at cryogenic temperatures as cathodes. However, due to practical design considerations, it is not trivial to test such cathodes in existing electron guns. Here we present the design of a 200kV DC electron gun being developed at the Arizona State University for this purpose.
	Poster MOPLM16 [1.549 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM16
About •	paper received ※ 27 August 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019
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MOPLM18	Design of the 2-Stage Laser Transport for the Low Energy RHIC Electron Cooling (LEReC) DC Photogun	laser, gun, cathode, alignment	144
	P. Inacker, S. Bellavia, A.J. Curcio, A.V. Fedotov, W. Fischer, D.M. Gassner, J.P. Jamilkowski, P.K. Kankiya, D. Kayran, D. Lehn, R. Meier, T.A. Miller, M.G. Minty, S.K. Nayak, L.K. Nguyen, L. Smart, C.J. Spataro, A. Sukhanov, J.E. Tuozzolo, Z. Zhao BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The electron beam for the recently constructed Low Energy RHIC electron Cooler (LEReC) at Brookhaven National Laboratory is generated by a high-power fiber laser illuminating a photocathode. The pointing stability of the low-energy electron beam, which is crucial to maintain within acceptable limits given the long beam transport, is highly dependent on the center-of-mass (CoM) stability of the laser spot on the photocathode. For reasons of accessibility during operations, the laser itself is located outside the accelerator tunnel, leading to the need to propagate the laser beam 34 m via three laser tables to the photocathode. The challenges to achieving the required CoM stability of 10 microns on the photocathode thus requires mitigation of vibrations along the transport and of weather- and season-related environmental effects, while preserving accessibility and diagnostic capabilities with proactive design. After successful commissioning of the full transport in 2018/19, we report on our solutions to these design challenges. LEReC Photocathode DC Gun Beam Test Results - D. Kayran Conference: C18-04-29, p.TUPMF025 Commissioning of Electron Accelerator LEReC for Bunch Beam Cooling - D.Kayran, NAPAC19
	Poster MOPLM18 [1.970 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM18
About •	paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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MOPLM24	LCLS-II Injector Commissioning Beam Based Measurements	gun, laser, cathode, MMI	157
	C.M. Zimmer, T.J. Maxwell, F. Zhou SLAC, Menlo Park, California, USA
	Funding: Department of Energy Injector commissioning is underway for the LCLS-II MHz repetition rate FEL, currently under construction at SLAC. Methodology of injector beam-based measurements and early results with low beam charge will be presented, along with the software tools written to automate these various measurements.
	Poster MOPLM24 [10.104 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM24
About •	paper received ※ 28 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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MOPLS08	Error Tolerance Characterization for the HUST MeV Ultrafast Electron Diffraction System	emittance, injection, laser, simulation	166
	Y. Song, K. Fan, C.-Y. Tsai HUST, Wuhan, People’s Republic of China
	Ultrafast electron diffraction (UED) is a powerful tool for probing atomic dynamics with a femtosecond resolution. Such a spatiotemporal resolution requires error tolerance for the UED system which includes the RF system, the laser system, the beamline elements, etc. To characterize the error tolerance of the required spatiotemporal resolution for the 1.4-cell MeV UED we are developing, we use ASTRA to simulate the UED model with errors including initial transverse beam centroid offset, RF amplitude jitter and injection phase jitter, etc. By performing simulations with different errors omitted, we can characterize the contribution of each error and thus set the tolerance for each error to obtain the required performance of UED experiment. In the end, we present the error tolerance for 10% emittance growth and 100 fs time of flight variation to maintain the required spatiotemporal resolution.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLS08
About •	paper received ※ 25 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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MOPLH02	Study of Photocathode Surface Damage due to Ion Back-Bombardment in High Current DC Gun	cathode, gun, simulation, laser	174
	J.P. Biswas Stony Brook University, Stony Brook, USA O.H. Rahman, E. Wang BNL, Upton, New York, USA
	Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704, with the U.S. DOE In high current DC gun, GaAs photocathode lifetime is limited by the ion back-bombardment. While gun operation ions are generated and accelerate back towards the cathode thus remove the activation layer’s material Cesium from the photocathode surface. We have developed an object-oriented code to simulate the ion generation due to dynamic gas pressure and ion trace in the electromagnetic field. The pressure profile varies from cathode position towards the transfer line behind the anode, which signifies the importance of dynamic simulation for ion back-bombardment study. In our surface damage study, we traced the energy and position of the ions on the photocathode surface and performed the Stopping and Range of Ions in Matter(SRIM) simulation to count the number of Cesium atoms removed from the surface due to single bunch impact. Cesium atom removal is directly related to the photocathode Quantum Efficiency(QE) decay. Our new dynamic simulation code can be used in any DC gun to study ion back-bombardment. We have used this new code to better understand the ion generation in prototype BNL 350 KV DC gun, and we have also estimated the normalized QE decay due to ion back-bombardment.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH02
About •	paper received ※ 27 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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MOPLH04	Design for HyRES Cathode Nanotip Electron Source	cavity, solenoid, gun, cathode	177
	R.M. Hessami, A.F. Amhaz, P. Musumeci UCLA, Los Angeles, USA
	A new ultrafast electron diffraction (UED) instrument is being developed by UCLA-Colorado University collaboration for the STROBE NSF Center with the goal of using electron and EUV photon beams to reveal the structural dynamics of materials in non-equilibrium states at fundamental atomic and temporal scales. This paper describes the design of the electron beamline of this instrument. In order to minimize the initial emittance, a nanotip photocathode, 25 nm in radius, will be used. This requires a redesign of the cathode and anode components of the electron gun to allow for the tip to be properly aligned. Solenoidal lenses are used to focus the beam transversely to a sub-micron spot at the sample and a radiofrequency (RF) cavity, driven by a continuous wave S-band RF source, longitudinally compresses the beam to below 100 fs, required for atomic resolution.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH04
About •	paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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MOPLH06	Study of the Mean Transverse Energy and the Emission Mechanism of (N)UNCD Photocathodes	cathode, photon, experiment, emittance	181
	G. Chen IIT, Chicago, Illinois, USA G. Adhikari, W.A. Schroeder UIC, Chicago, Illinois, USA S.P. Antipov, E. Gomez Euclid TechLabs, LLC, Solon, Ohio, USA S.V. Baryshev, T. Nikhar Michigan State University, East Lansing, Michigan, USA L.K. Spentzouris Illinois Institute of Technology, Chicago, Illinois, USA
	Funding: This project is supported by NSF grant No. NSF-1739150, NSF-1535676, and NSF grant No. PHYS-1535279. Nitrogen incorporated ultrananocrystalline diamond ((N)UNCD) is promising for photocathode applications due to its high quantum efficiency (QE). The mean transverse energy (MTE) which, along with QE, defines the brightness of the emitted electron beam must be thoroughly characterized and understood for (N)UNCD. Our previous work* further corroborated the important role of graphitic grain boundaries (GB’s). UNCD consists of diamond (sp3-hybrized) grains and graphitic (sp2-hybrized) GB’s: GB’s are behind the high emissivity of (N)UNCD and therefore play a crucial role in defining and controlling the MTE. In this work, the MTE of two different (N)UNCD samples having different ratios of sp3/sp2 were measured versus the primary photon energies. As a reference, MTE of highly oriented pyrolytic graphite (HOPG, canonical sp2-hybrized graphite) was also measured. * G. Chen et al., Appl. Phys. Lett. 114, 093103 (2019).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH06
About •	paper received ※ 27 August 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019
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MOPLH09	Photoluminescence Studies of Alkali-Antimonide Photocathodes	experiment, cathode, laser, photon	188
	P. Saha, O. Chubenko, S.S. Karkare Arizona State University, Tempe, USA H.A. Padmore LBNL, Berkeley, California, USA
	Alkali-antimonide photocathodes have a very high quantum efficiency and a low intrinsic emittance, making them excellent electron sources for Energy Recovery Linacs, X-ray Free Electron Lasers, Electron Cooling, and Ultrafast Electron Diffraction applications. Despite numerous studies of their photoemission spectra, there has been nearly no conclusive experimental investigation of their basic electronic and optical properties (e.g. band gap, electron affinity, optical constants, etc.), which determine the nature of photoemission. Therefore, the systematic study and deep understanding of fundamental characteristics of alkali-antimonide photocathodes are required in order to develop next-generation electron sources with improved crystal and electronic structures to fit specific application. Here we report on the development of an experimental setup to measure photoluminescence (PL) spectra from alkali-antimonide photocathodes, enabling estimation of a material band gap and defect state energies, and provide preliminary results for Cs3Sb films.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH09
About •	paper received ※ 27 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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MOPLH10	Field-Emission Electron Source Embedded in a Field-Enhanced Conduction-Cooled Superconducting RF Cavity	cavity, cathode, experiment, niobium	192
	D. Mihalcea, V. Korampally, A. McKeown, O. Mohsen, P. Piot, I. Salehinia Northern Illinois University, DeKalb, Illinois, USA R. Dhuley, M.G. Geelhoed, P. Piot, J.C.T. Thangaraj Fermilab, Batavia, Illinois, USA
	We present simulations and experimental progress toward the development of a high-current electron source with the potential to deliver high charge electron bunches at GHz-level repetition rates. To achieve these goals electrons are generated through field-emission and the cathode is immersed in a conduction-cooled superconducting 650-MHz RF cavity. The field-emitters consist of microscopic silicon pyramids and have a typical enhancement factor of about 500. To trigger field-emission, the peak field inside the RF cavity of about 6 MV/m is further enhanced by placing the field-emitters on the top of a superconducting Nb rod inserted in the RF cavity. So far, we cannot control the duration of the electron bunches which is of the order of RF period. Also, the present cryo-cooler power of about 2 W limits the beam current to microamp level.
	Poster MOPLH10 [1.063 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH10
About •	paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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MOPLH11	Nanostructured Photocathodes for Spin-Polarized Electron Beams	cathode, polarization, lattice, scattering	196
	E.J. Montgomery, C. Jing, S. Poddar Euclid Beamlabs LLC, Bolingbrook, USA A. Afanasev GWU, Washington, USA R. Kumar, G.J. Salamo University of Arkansas, Fayetteville, Arkansas, USA S. Zhang JLab, Newport News, Virginia, USA
	Funding: Work supported by US DOE Office of Science, Office of Nuclear Physics, SBIR grant DESC0019559. CNM work supported by US DOE Office of Science, Basic Energy Sciences, contract DE-AC02-06CH11357. We present progress on incorporation of nanopillar arrays into spin-polarized gallium arsenide photocathodes in pursuit of record high tolerance to ion back-bombardment. Our goal is to exceed the 400 Coulomb record for a high polarization milliampere-class electron source set at Jefferson Laboratory in 2017, while maintaining high quantum efficiency (QE) and spin polarization with a superlattice. Because the Mie effect is resonant, uniformity and careful control over nanostructure geometry is key. We report excellent uniformity and straight sidewall geometry with improved optical absorption using a painstakingly optimized inductively coupled plasma reactive ion etch. We also report the application of Kerker theory to spin-polarized photocathode nanopillar arrays, setting new requirements on nanostructure dimensions to avoid spoiling spin polarization. Finally, we also report initial steps toward re-establishing U.S. production of strained superlattice photocathodes towards integration with nanopillar arrays.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH11
About •	paper received ※ 03 September 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019
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MOPLH13	STARRE Lab: The Sub-THz Accelerator Research Laboratory	laser, experiment, GUI, operation	199
	J.F. Picard, S.C. Schaub, R.J. Temkin MIT/PSFC, Cambridge, Massachusetts, USA
	Funding: Department of Energy, Office of HEP, DE- SC0015566; Office of Fusion Energy Sciences, DE-FC02-93ER54186; National Institutes of Health, NIBIB, EB004866 and EB001965; This work presents the development of the STARRE Lab, a facility at MIT for testing breakdown in high gradient accelerator structures at 110 GHz. The system utilizes a Laser-Driven Semiconductor Switch (LDSS) to modulate the output of a megawatt gyrotron, which generates 3 μs pulses at up to 6 Hz. The LDSS employs silicon (Si) and gallium arsenide (GaAs) wafers to produce nanosecond-scale pulses at the megawatt level from the gyrotron output. Photoconductivity is induced in the wafers using a 532 nm Nd:YAG laser, which produces 6 ns, 230 mJ pulses. A single Si wafer produces 110 GHz RF pulses with 9 ns width, while under the same conditions, a single GaAs wafer produces 24 ns 110 GHz RF pulses. In dual-wafer operation, which uses two active wafers, pulses of variable length down to 3 ns duration can be created at power levels greater than 300 kW. The switch has been successfully tested at incident 110 GHz RF power levels up to 720 kW.* The facility has been used to successfully test an advanced 110 GHz accelerator structure built by SLAC to gradients in excess of 220 MV/m. *J.F. Picard et al., Appl. Phys. Lett. 114, 164102 (2019); doi: https://doi.org/10.1063/1.5093639
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH13
About •	paper received ※ 24 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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MOPLH14	Ultrafast Nonlinear Photoemission from Alkali Antimonide Photocathodes	photon, cathode, laser, gun	203
	W.H. Li, M.B. Andorf, I.V. Bazarov, L. Cultrera, C.J.R. Duncan, A. Galdi, J.M. Maxson, C.A. Pennington Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: This work was supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams. Alkali antimonides photocathodes are a popular choice of electron source for high average brightness beams, due to their high quantum efficiency (QE) and low mean transverse energy (MTE). This paper describes the first measurements of their nonlinear photoemission properties under sub-ps laser illumination. These measurements include wavelength-resolved power dependence, pulse length dependence, and temporal response. The transition between linear and nonlinear photoemission is observed through the wavelength-resolved scan, and implications of nonlinear photoemission are discussed.
	Poster MOPLH14 [0.543 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH14
About •	paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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MOPLH17	Enhanced Robustness of GaAs-Based Photocathodes Activation by Cs, Sb, and O2	cathode, polarization, vacuum, extraction	210
	J. Bae, L. Cultrera, A. Galdi, F. Ikponmwen Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA I.V. Bazarov, J.M. Maxson Cornell University, Ithaca, New York, USA
	Funding: This work is funded by Department of Energy: DE-SC0016203. Operational lifetime of GaAs photocathodes is the primary limit for applications as high current spin polarized electron sources in future nuclear physics facilities, such as Electron Ion Collider. Recently, ultrathin Cs₂Te on GaAs has shown a successful negative electron affinity (NEA) activation with an improved lifetime by a factor of 5 . In this work, we report activation of GaAs with Cs, Sb and oxygen. Four different methods of introducing oxygen during the growth was investigated. Cs-Sb-O activated GaAs has shown up to a factor of 40 and 13 improvement in charge extraction lifetime and dark lifetime, respectively. Bae, et al. (2018). Rugged spin-polarized electron sources based on negative electron affinity GaAs photocathode with robust Cs₂Te coating. Applied Physics Letters, 112(15), 154101.
	Poster MOPLH17 [0.926 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH17
About •	paper received ※ 28 August 2019 paper accepted ※ 01 September 2019 issue date ※ 08 October 2019
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MOPLH19	Beam Dynamics Simulations for a Conduction-Cooled Superconducting RF Electron Source	cathode, simulation, emittance, experiment	213
	O. Mohsen, V. Korampally, A. McKeown, D. Mihalcea, P. Piot, I. Salehinia Northern Illinois University, DeKalb, Illinois, USA R. Dhuley, M.G. Geelhoed, J.C.T. Thangaraj Fermilab, Batavia, Illinois, USA
	Funding: Work supported by DOE awards DE-SC0018367 with NIU and DE-AC02-07CH11359 The development of robust and portable high-average power electron sources is key to many societal applications. An approach toward such sources is the use of cryogen-free superconducting radiofrequency cavities. This paper presents beam-dynamics simulations for a proof-of-principle experiment on a cryogen-free SRF electron source being prototyped at Fermilab. The proposed design implement a geometry that enhances the electric field at the cathode surface to simultaneously extract and accelerate electrons. In this paper, we explore the beam dynamics considering both the case of field and photoemission mechanism.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH19
About •	paper received ※ 02 September 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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MOPLH22	Focusing Studies of an Electron Beam in Diamond Field Emitter Array Cathodes	cathode, experiment, focusing, laser	217
	R.L. Fleming, H.L. Andrews, D. Gorelov, C.-K. Huang, D. Kim, J.W. Lewellen, K.E. Nichols, V.N. Pavlenko, E.I. Simakov LANL, Los Alamos, New Mexico, USA
	Funding: Los Alamos National Laboratory LDRD Program We present the simulations and test results for focusing studies performed on diamond field emitter array cathodes. This design utilized a simple variable-focus solenoidal lens in conjunction with a scanning wire technique in order to measure the beam spot size. The spot size was measured by scanning a thin copper wire across the beam in 1 µm increments, with voltage being measured and averaged at each location in order to map the location and intensity of the beam. Scans were taken at different distances away from the magnetic center of the lens, and show good agreement with our simulations of the beam. Ultimately this has allowed us to focus the beam to a spot size of 5.72 µm with an average current of 15.78 µA.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH22
About •	paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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MOPLH24	Towards the Optimization Of Photocathode Properties Via Surface Science Techniques: A Study On Cs3Sb Thin Film Growth	cathode, vacuum, laser, emittance	224
	A. Galdi, J. Balajka, W.J.I. DeBenedetti, M. Hines Cornell University, Ithaca, New York, USA I.V. Bazarov, L. Cultrera, F. Ikponmwen, J.M. Maxson, S.A. McBride Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: National Science Foundation Grant No. PHY-1549132 A better understanding of the properties of photocathode materials can be achieved by integrating advanced growth and surface science techniques in their synthesis and analysis. This is a main research theme of the Center for Bright Beams, whose goal is increasing the brightness of linear electron accelerators. Alkali antimonides are efficient photocathode materials and have very low intrinsic emittance at cryogenic temperatures.* A limiting factors is the surface roughness and chemical inhomogeneity of the films.** We studied the influence of growth parameters on the morphology and composition of Cs3Sb thin films. The films are codeposited using pure element sources and transferred via UHV suitcase to a STM/XPS analysis chamber, to study in particular the influence of substrate temperature and material. This platform can be expanded to more analysis and growth systems thanks to a specially designed sample holder and suitcase. An example is a new cryogenic instrument for intrinsic emittance measurements. * L. Cultrera et al., Phys. Rev. ST ’ Acc. Beams 18 (2015) 113401 ** G. Gevorkian et al., Phys. Rev. Accel. Beams, 21 (2018) 093401
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH24
About •	paper received ※ 28 August 2019 paper accepted ※ 30 August 2019 issue date ※ 08 October 2019
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MOPLH25	Characterization of Femtosecond-Laser-Induced Electron Emission from Diamond Nano-Tips	laser, FEM, photon, polarization	228
	V.N. Pavlenko, H.L. Andrews, R.L. Fleming, D. Gorelov, D. Kim, E.I. Simakov LANL, Los Alamos, New Mexico, USA D.S. Black, K.J. Leedle Stanford University, Stanford, California, USA
	Funding: LANL Laboratory Directed Research and Development (LDRD). Nanocrystalline diamond is a promising material for electron emission applications, as it combines robustness of diamond and ability to easily conform to a pre-defined shape, even at nano-scale. However, its electron emission properties are yet to be fully understood. Recently, we started to investigate femtosecond-laser-induced strong-field photoemission from nanocrystalline diamond field emitters with very sharp (~10 nm apex) tips. Initial results show that the mechanism of electron emission at ~10¹⁰ W/cm² light intensities in the near UV to near IR range is more complex than in metals. We present our latest experimental results obtained at Stanford University, while LANL’s strong-field photoemission test stand is being commissioned. We show that strong-field photoemission occurs not only at the nano-tip’s apex, but also on flat diamond surfaces (e.g., pyramid sides), that is why extra care needs to be taken to differentiate between emission spots on the chip. Qualitatively, we discuss the models that explain the observed dependences of electron emission on the optical power, polarization of the light, etc.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH25
About •	paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019
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MOPLH26	Design of a Compact Wakefield Accelerator Based on a Corrugated Waveguide	GUI, wakefield, coupling, simulation	232
	A.E. Siy UW-Madison/PD, Madison, Wisconsin, USA G.J. Waldschmidt, A. Zholents ANL, Lemont, Illinois, USA
	A compact wakefield accelerator is being developed at the Argonne National Laboratory for a future multiuser x-ray free electron laser facility. A cylindrical structure with a 2 mm internal diameter and fine corrugations on the wall will be used to create Čerenkov radiation. A "drive" bunch producing radiation at 180 GHz will create accelerating gradients on the order of 100 MV/m for the "witness" bunch. The corrugated structure will be approximately half meter long with the entire accelerator spanning a few tens of meters. An ultra-compact transition region between each corrugated structure has been designed to accommodate an output coupler, a notch filter, an integrated offset monitor, bellows, pumping and water cooling ports. The output coupler will extract on the order of a kilowatt of power from the Čerenkov radiation unused by the witness bunch. The integrated offset monitor is a novel diagnostic which will measure the cumulative offset of the electron beam in the corrugated structure upstream of the monitor. The specific details of the rf design will be presented here.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH26
About •	paper received ※ 27 August 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019
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MOPLO01	A Beam Spreader System for LCLS-II	kicker, septum, undulator, FEL	236
	T.G. Beukers, J.W. Amann, Y.M. Nosochkov SLAC, Menlo Park, California, USA
	For the LCLS-II project, the SLAC National Accelerator Laboratory is installing a new superconducting RF linac capable of continuously delivering 4 GeV electron bunches spaced 1.1 microseconds apart. A spreader system is required to distribute the beam between a soft X-ray or hard X-ray undulator, and a beam dump. An additional beam diverter is required in the front end of the linac to divert 100 MeV electrons to a diagnostic line. Both the spreader and diagnostic diversion systems are designed to operate on a bunch by bunch basis via the combination of fast kickers and a Lambertson septum. This paper presents a summary of the optics, kicker, and septum design. Of specific interest is the unique challenge associated with building a high repetition, high stability, spreader capable of diverting a single bunch without disturbing neighboring bunches. Additional discussion includes the application of the spreader technology to the proposed DASEL/S30XL beamline. This beamline will acceptμbunches evenly spaced between the undulator bound bunches, thus requiring a kicker with the same repetition rate as LCLS-II but a pulse width extended to approximately 600 ns.
	Poster MOPLO01 [1.256 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO01
About •	paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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MOPLO04	Progress in Time-Resolved MeV Transmission Electron Microscopy at UCLA	quadrupole, cavity, alignment, detector	243
	P.E. Denham UCLA, Los Angeles, USA
	We describe here two new enhancements developed for the time-resolved microscope at the UCLA PEGASUS Lab based on the use of a radiofrequency photoinjector as an ultrafast electron source and permanent magnet quadrupoles as electron lenses. The first enhancement is a flexible optical column design including hybrid-style stronger focusing quadrupoles, yielding a 60% magnification increase, and a collimator to improve imaging contrast. This new optical system will have the ability to switch between real-space imaging and diffraction pattern imaging with variable magnification. The second enhancement is a high-frequency (X-band) cavity downstream from the (S-band) photoinjector to reduce the beam energy spread. These enhancements are crucial for improving contrast and image quality. In addition, a pulse-wire alignment method to fiducialize the quadrupole positions to better than 20-um precision is used to reduce the aberrations induced by misalignment and achieve spatial resolution at the 20 nm-level.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO04
About •	paper received ※ 28 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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MOPLO06	Black Gun Technologies for DC Photoinjectors	gun, vacuum, laser, scattering	247
	E.J. Montgomery, C. Jing, S. Poddar Euclid Beamlabs LLC, Bolingbrook, USA J.E. Butler Euclid TechLabs, LLC, Solon, Ohio, USA S. Zhang JLab, Newport News, Virginia, USA
	Funding: Work supported by the US DOE Office of Science, Office of Nuclear Physics, grant number DESC0019688. Work at Argonne CNM under Contract No. DE-AC02-06CH11357. Euclid Beamlabs is developing a new "Black Gun" concept in direct current (DC) photoinjectors. To reduce electron-stimulated desorption indirectly influenced by stray photoemission, we are testing advanced optical coatings and low-scattering optics compatible with the extreme high vacuum (XHV) environment of modern DC photoinjectors. Stray light in DC photoinjectors (in proportion to the photoemitted charge) causes off-nominal photoemission, initiating electron trajectories which intercept downstream surfaces. This causes electron-stimulated desorption of atoms, which ionize and may back-bombard the cathode, reducing its charge lifetime. Back-bombardment is key for high average current or high repetition rate. First, we report on progress developing optical skimmers based on Butler baffles to collimate both incoming and outgoing laser beams. Second, we describe candidate coatings for reduction of scattered light. Requirements for these coatings are that they be conducting, optically black at the drive laser wavelength, conformally applied to complex geometry, and XHV-compatible with negligible outgassing.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO06
About •	paper received ※ 04 September 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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MOPLO12	The RF BPM Pickup Electrodes Development for the APS-MBA Upgrade	pick-up, vacuum, simulation, storage-ring	256
	X. Sun, R.M. Lill ANL, Lemont, Illinois, USA
	Beam stability is critical for the Advanced Photon Source (APS) multi-bend achromat (MBA) lattice up-grade and will employ 560 radio frequency (RF) beam position monitors (BPMs). The RF BPMs will provide the primary measurement of the electron beam. Design goals for the BPM assembly include high sensitivity, low wakefield impedance, and ultra-mechanically stability. The design, electromagnetic simulation, manufacturing tolerance and prototype testing will be presented in this paper. *Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO12
About •	paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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MOPLO13	Field Quality Analysis of Interaction Region Quadrupoles for JLEIC	quadrupole, collider, interaction-region, operation	259
	G.L. Sabbi LBNL, Berkeley, California, USA B.R. Gamage, T.J. Michalski, V.S. Morozov, R. Rajput-Ghoshal, M. Wiseman JLab, Newport News, Virginia, USA Y.M. Nosochkov, M.K. Sullivan SLAC, Menlo Park, California, USA
	Funding: Work supported by the US Department of Energy Office of Science. The JLEIC physics goals of high luminosity and a full acceptance detector result in significant design challenges for the Interaction Region quadrupoles. Key requirements include large aperture, high field, compact transverse and longitudinal dimensions, and tight control of the field errors. In this paper, we present and discuss field quality estimates for the IR Quadrupoles of both electron and ion beamlines, obtained by integrating experience from pre-vious projects with realistic designs consistent with the specific requirements of the JLEIC collider.
	Poster MOPLO13 [0.847 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO13
About •	paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019
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MOPLO23	Investigation of Various Fabrication Methods to Produce a 180GHz Corrugated Waveguide Structure in 2mm Diameter 0.5m Long Copper Tube for the Compact Wakefield Accelerator for FEL Facility	GUI, laser, wakefield, FEL	286
	K.J. Suthar, D.S. Doran, W.G. Jansma, S.S. Sorsher, E. Trakhtenberg, G.J. Waldschmidt, A. Zholents ANL, Lemont, Illinois, USA A.E. Siy UW-Madison/PD, Madison, Wisconsin, USA
	Funding: This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility operated by the Argonne National Laboratory under Contract No. DEAC0206CH11357. Argonne National Laboratory is developing a 180 GHz wakefield structure that will house in a co-linear array of accelerators to produce free-electron laser-based X-rays. The proposed corrugated waveguide structure will be fabricated on the internal wall of 0.5m long and 2mm nominal diameter copper tube. The estimated dimensions of these parallel corrugations are 200 µm in pitch with 100 µm side length (height and width). The length scale of the structure and requirements of the magnetic field-driven dimensional tolerances have made the structure challenging to produce. We have employed several method such as optical lithography, electroforming, electron discharge machining, laser ablation, and stamping to produce the initial structure from a sheet form. The successive fabrication steps, such as bending, brazing, and welding, were performed to achieve the long tubular-structure. This paper discusses various fabrication techniques, characterization, and associated technical challenges in detail. [1] A. Zholents et al., Proc. 9-th Intern. Part. Acc. Conf., IPAC2018, Vancouver, BC, Canada, p. 1266, (2018)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO23
About •	paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019
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TUYBA4	Optimization of an SRF Gun Design for UEM Applications	SRF, gun, laser, cavity	305
	A. Liu, P.V. Avrakhov Euclid TechLabs, LLC, Solon, Ohio, USA C. Jing, R.A. Kostin Euclid Beamlabs LLC, Bolingbrook, USA
	Funding: DOE contract DE-SC0018621 Benefiting from the rapid progress on RF photocathode gun technologies in the past two decades, the development of MeV-range ultrafast electron diffraction/microscopy (UED and UEM) has been identified as an enabling instrumentation, which may lead to breakthroughs in fundamental science and applied technologies . Euclid is designing an SRF cavity as the UEM electron gun. As implementing a solenoid for emittance compensation in the gun is limited by the superconductivity performance and available space, the geometry of the first 0.3 cell of the cavity is optimized for transverse focusing and emittance reduction. : T. Chase, et al, "Ultrafast electron diffraction from non- equilibrium phonons in femtosecond laser heated Au films." Applied Physics Letters, 2016
	Slides TUYBA4 [7.583 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUYBA4
About •	paper received ※ 30 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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TUYBB2	Manipulating H⁻ Beams with Lasers	laser, proton, extraction, emittance	309
	A. Rakhman, A.V. Aleksandrov, S.M. Cousineau, T.V. Gorlov, Y. Liu, A.P. Shishlo ORNL, Oak Ridge, Tennessee, USA
	Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. In recent years lasers have been playing a vital role in many H− beam measurements and experiments. This talk will review current state of development of various applications using lasers for manipulating H− ion beams in accelerators. A wide range of applications will be reviewed such as beam diagnostics, laser-assisted charge-exchange injection, generation of arbitrary H⁰ pulse patterns and others. An overview of ongoing developments and prospects for other laser H− beam interactions will also be given.
	Slides TUYBB2 [16.483 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUYBB2
About •	paper received ※ 28 August 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019
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TUYBB5	Design and Analysis of a Halo-Measurement Diagnostics	diagnostics, radiation, optics, experiment	322
	C.J. Marshall, P. Piot Northern Illinois University, DeKalb, Illinois, USA S.V. Benson, J. Gubeli JLab, Newport News, Virginia, USA P. Piot, J. Ruan Fermilab, Batavia, Illinois, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear physics under contract DE-AC05-06OR23177 and DE-AC02-07CH11359. A large dynamical-range diagnostics (LDRD) design at Jefferson Lab will be used at the FAST-IOTA injector to measure the transverse distribution of halo associated with a high-charge electron beam. One important aspect of this work is to explore the halo distribution when the beam has significant angular momentum (i.e. is magnetized). The beam distribution is measured by recording radiation produced as the beam impinges a YAG:Ce screen. The optical radiation is split with a fraction directed to a charged-couple device (CCD) camera. The other part of the radiation is reflected by a digital micromirror device (DMD) that masks the core of the beam distribution. Combining the images recorded by the two cameras provides a measurement of the transverse distribution with over a large dynamical range. The design and analysis of the optical system will be discussed including optical simulation using SRW and the result of a mockup experiment to test the performances of the system will be presented.
	Slides TUYBB5 [3.013 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUYBB5
About •	paper received ※ 02 September 2019 paper accepted ※ 13 September 2019 issue date ※ 08 October 2019
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TUYBB6	Beam Dynamics in a High Gradient RF Streak Camera	cathode, experiment, photon, gun	326
	F. Toufexis, V.A. Dolgashev, A. Landa SLAC, Menlo Park, California, USA
	Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515. Traditionally, time-resolved experiments in storage ring synchrotron light sources and free-electron lasers are performed with short x-ray pulses with time duration smaller than the time resolution of the phenomenon under study. Typically, storage-ring synchrotron light sources produce x-ray pulses on the order of tens of picoseconds. Newer diffraction limited storage rings produce even longer pulses. We propose to use a high-gradient RF streak camera for time-resolved experiments in storage-ring synchrotron light sources with potential for sub-100 fs resolution. In this work we present a detailed analysis of the effects of the initial time and energy spread of the photo-emitted electrons on the time resolution, as well as a start-to-end beam dynamics simulation in an S-Band system. * F. Toufexis, et al, "Sub-Picosecond X-Ray Streak Camera using High-Gradient RF Cavities", in Proceedings of IPAC’19.
	Slides TUYBB6 [5.958 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUYBB6
About •	paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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TUZBA1	Commissioning of the Electron Accelerator LEReC for Bunched Beam Cooling	cavity, operation, cathode, gun	330
	D. Kayran, Z. Altinbas, D. Bruno, M.R. Costanzo, K.A. Drees, A.V. Fedotov, W. Fischer, M. Gaowei, D.M. Gassner, X. Gu, R.L. Hulsart, P. Inacker, J.P. Jamilkowski, Y.C. Jing, J. Kewisch, C.J. Liaw, C. Liu, J. Ma, K. Mernick, T.A. Miller, M.G. Minty, L.K. Nguyen, M.C. Paniccia, I. Pinayev, V. Ptitsyn, V. Schoefer, S. Seletskiy, F. Severino, T.C. Shrey, L. Smart, K.S. Smith, A. Sukhanov, P. Thieberger, J.E. Tuozzolo, E. Wang, G. Wang, W. Xu, A. Zaltsman, H. Zhao, Z. Zhao BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The brand-new state of the art electron accelerator, LEReC, was built and commissioned at BNL. LEReC accelerator includes a photocathode DC gun, a laser system, a photocathode delivery system, magnets, beam diagnostics, a SRF booster cavity, and a set of Normal Conducting RF cavities to provide sufficient flexibility to tune the beam in the longitudinal phase space. Electron beam quality suitable for cooling in the Relativistic Heavy Ion Collider (RHIC) was achieved [1], which lead to the first demonstration of bunched beam electron cooling of hadron beams [2]. This presentation will discuss commissioning results, achieved beam parameters and performance of the LEReC systems. [1] D.Kayran et al., First results from Commissioning of LEReC, in Proc of IPAC2019 [2] A.Fedotov et al., First electron cooling of hadron beams using a bunched electron beam, presented at NAPAC2019
	Slides TUZBA1 [18.343 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUZBA1
About •	paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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TUZBA2	Electron Ion Collider Machine Detector Interface	detector, hadron, quadrupole, collider	335
	B. Parker, E.C. Aschenauer, A. Kiselev, C. Montag, R.B. Palmer, V. Ptitsyn, F.J. Willeke, H. Witte BNL, Upton, New York, USA M. Diefenthaler, Y. Furletova, T.J. Michalski, V.S. Morozov, D. Romanov, A. Seryi, R. Yoshida JLab, Newport News, Virginia, USA C. Hyde ODU, Norfolk, Virginia, USA M.K. Sullivan SLAC, Menlo Park, California, USA
	This presentation summarizes the physics requirements as they translate into accelerator requirements at the machine-detector interface. Unique aspects of the Interaction Region and detector acceptance – unique to an Electron Ion Collider – are summarized. Designs of both site-specific concepts are outlined.
	Slides TUZBA2 [13.525 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUZBA2
About •	paper received ※ 29 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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TUZBA3	A High-Energy Design for JLEIC Ion Complex	booster, proton, collider, linac	341
	B. Mustapha, J.L. Martinez Marin ANL, Lemont, Illinois, USA Y.S. Derbenev, F. Lin, V.S. Morozov, Y. Zhang JLab, Newport News, Virginia, USA
	Funding: This work was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357 for ANL and by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357. A recent assessment of the scientific merit for a future Electron Ion Collider (EIC) in the US, by the National Academy of Sciences, found that such a facility would be unique in the world and would answer science questions that are compelling, fundamental, and timely. This assessment confirmed the recommendations of the 2015 Nuclear Science Advisory Committee for an EIC with highly polarized beams of electrons and ions, sufficiently high luminosity and variable center-of-mass (CM) energy. The baseline design of Jefferson Lab Electron-Ion Collider (JLEIC) has been updated to 100 GeV CM energy, corresponding to 200 GeV proton energy. We here present a high-energy design for the JLEIC ion complex. It consists of a 135 MeV injector linac, a 6-GeV non figure-8 pre-booster ring and a 40-GeV large ion booster, which could also serve as electron storage ring (e-ring). The energy choice in the accelerator chain is beneficial for a future upgrade to 140 GeV CM energy. The large booster is designed with the same shape and size of the original e-ring allowing for the option of building separate electron and ion rings by stacking them in the same tunnel along with the ion collider ring.
	Slides TUZBA3 [5.435 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUZBA3
About •	paper received ※ 03 September 2019 paper accepted ※ 25 November 2019 issue date ※ 08 October 2019
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TUZBA4	Interaction Region Magnets for Future Electron-Ion Collider at Jefferson Lab	quadrupole, solenoid, interaction-region, collider	345
	R. Rajput-Ghoshal, C. Hutton, F. Lin, T.J. Michalski, V.S. Morozov, M. Wiseman JLab, Newport News, Virginia, USA
	The Jefferson Lab Electron Ion Collider (JLEIC) is a proposed new machine for nuclear physics research. It uses the existing CEBAF accelerator as a full energy injector to deliver 3 to 12 GeV electrons into a new electron collider ring. An all new ion accelerator and collider complex will deliver up to 200 GeV protons. The machine has luminosity goals of 10³⁴ cm^-2 ses⁻¹. The whole detector region including forward detection covers about 80 meters of the JLEIC complex. The interaction region design has recently been optimized to accommodate 200 GeV proton energy using conventional NbTi superconducting magnet technology. This paper will describe the requirements and preliminary designs for both the ion and electron beam magnets in the most complex 32 m long interaction region (IR) around the interaction point (IP). The interaction region has over thirty-seven superconducting magnets operating at 4.5K; these include dipoles, quadrupoles, skew-quadrupoles, solenoids, horizontal and vertical correctors and higher order multipole magnets. The paper will also discuss the electromagnetic interaction between these magnets.
	Slides TUZBA4 [6.444 MB]
	Poster TUZBA4 [1.549 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUZBA4
About •	paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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TUZBB3	Precise Beam Velocity Matching for the Experimental Demonstration of Ion Cooling With a Bunched Electron Beam	factory, beam-cooling, acceleration, dipole	356
	S. Seletskiy, M. Blaskiewicz, K.A. Drees, A.V. Fedotov, W. Fischer, D.M. Gassner, R.L. Hulsart, D. Kayran, J. Kewisch, K. Mernick, R.J. Michnoff, T.A. Miller, G. Robert-Demolaize, V. Schoefer, H. Song, P. Thieberger, P. Wanderer BNL, Upton, New York, USA
	The first ever electron cooling based on the RF acceleration of electron bunches was experimentally demonstrated on April 5, 2019 at the Low Energy RHIC Electron Cooler (LEReC) at BNL. The critical step in obtaining successful cooling of the Au ion bunches in the RHIC cooling sections was the accurate matching of average longitudinal velocities of electron and ion beams corresponding to a relative error of less than 5·10^-4 in the e-beam momentum. Since the electron beam kinetic energy is just 1.6 MeV, measuring the absolute e-beam energy with sufficient accuracy and eventually achieving the electron-ion velocity matching was a nontrivial task. In this paper we describe our experience with measuring and setting the e-beam energy at LEReC.
	Slides TUZBB3 [1.340 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUZBB3
About •	paper received ※ 26 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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TUZBB4	Space Charge Study of the Jefferson Lab Magnetized Electron Beam	laser, cathode, space-charge, gun	360
	S.A.K. Wijethunga, J.R. Delayen, G.A. Krafft ODU, Norfolk, Virginia, USA J.F. Benesch, F.E. Hannon, C. Hernandez-Garcia, G.A. Krafft, M.A. Mamun, M. Poelker, R. Suleiman, S. Zhang JLab, Newport News, Virginia, USA
	Magnetized electron cooling could result in high luminosity at the proposed Jefferson Lab Electron-Ion Collider (JLEIC). In order to increase the cooling efficiency, a bunched electron beam with high bunch charge and high repetition rate is required. We generated magnetized electron beams with high bunch charge using a new compact DC high voltage photo-gun biased at -300 kV with alkali-antimonide photocathode and a commercial ultrafast laser. This contribution explores how magnetization affects space charge dominated beams as a function of magnetic field strength, gun high voltage, laser pulse width, and laser spot size.
	Slides TUZBB4 [12.582 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUZBB4
About •	paper received ※ 28 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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TUZBB5	Transverse Ion Beam Emittance Growth Due to Low Frequency Instabilities in Microwave Ion Source Plasma	plasma, emittance, experiment, HOM	363
	C. Mallick, M. Bandyopadhyay, R. Kumar Institute for Plasma Research, Bhat, Gandhinagar, India
	The ion source is accompanied by the generation of low frequency (LF) plasma instabilities (PI). Its signature is also visible in high current heavy ion beam required for any accelerator. These LFs affect the profile of the ion beam in transverse phase-space. These issues are investigated in detail by measuring the emittance of beam. Beam oscillations are extracted from the transverse emittance data by taking Fast Fourier Transform (FFT) of it. PI frequencies are identified in the measured electromagnetic emission from the plasma, in which these frequencies appeared as sidebands around pump frequency 2.45 GHz. The PI components i.e.,ion acoustic (IA) and ion cyclotron (IC) waves are also visible in the FFT spectra. Low and high frequency oscillations in the beam are 476 kHz and ~1.3 MHz respectively. These two groups of frequencies also exist within the PI induced IA (238 - 873 kHz) and IC (1.29 - 1.3 MHz) frequency ranges. The measured emittance (rms-normalized) in horizontal and vertical phase-space varies from 0.002-0.098 𝜋 mm mrad and 0.004-0.23 𝜋 mm mrad respectively. PI induced beam oscillation is the reason behind such broad transverse emittance growth. Reference ’S. Kumar et al.,Phys. Rev. Accel. Beams 21, 093402 (2018)’ ’R. D’Arcy et al., Nucl. Instrum. Methods Phys. Res. A 815 7(2016)’ ’L. Groening et al., Phys. Rev. Lett. 113, 264802 (2014)’
	Slides TUZBB5 [5.298 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUZBB5
About •	paper received ※ 26 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019
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TUZBB6	Nonlinear Tune-Shift Measurements in the Integrable Optics Test Accelerator	experiment, optics, lattice, betatron	368
	S. Szustkowski, S. Chattopadhyay Northern Illinois University, DeKalb, Illinois, USA S. Chattopadhyay, A.L. Romanov, A. Valishev Fermilab, Batavia, Illinois, USA N. Kuklev University of Chicago, Chicago, Illinois, USA
	Funding: US Department of Energy, Office of High Energy Physics, General Accelerator Research and Development (GARD) Program The first experimental run of Fermilab’s Integrable Optics Test Accelerator (IOTA) ring aimed at testing the concept of nonlinear integrable beam optics. In this report we present the preliminary results of the studies of a nonlinear focusing system with two invariants of motion realized with the special elliptic-potential magnet. The key measurement of this experiment was the horizontal and vertical betatron tune shift as a function of transverse amplitude. A vertical kicker strength was varied to change the betatron amplitude for several values of the nonlinear magnet strength. The turn-by-turn positions of the 100 MeV electron beam at twenty-one beam position monitors around the ring were captured and used for the analysis of phase-space trajectories.
	Slides TUZBB6 [12.888 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUZBB6
About •	paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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TUPLM07	First Experimental Observations of the Plasma-Cascade Instability in the CeC PoP Accelerator	plasma, experiment, lattice, solenoid	379
	I. Petrushina SUNY SB, Stony Brook, New York, USA Y.C. Jing, V. Litvinenko, J. Ma, I. Pinayev, G. Wang, Y.H. Wu BNL, Upton, New York, USA V. Litvinenko Stony Brook University, Stony Brook, USA K. Shih SBU, Stony Brook, New York, USA
	Preservation of the beam quality is important for attaining the desirable properties of the beam. Collective effects can produce an instability severely degrading beam emittance, momentum spread and creating filamentation of the beam. Microbunching instability for beams traveling along a curved trajectory, and space charge driven parametric transverse instabilities are well-known and in-depth studied. However, none of the above include a microbunching longitudinal instability driven by modulations of the transverse beam size. This phenomenon was observed for the first time during the commissioning of the CeC PoP experiment. Based on the dynamics of this instability we named it a Plasma-Cascade Instability (PCI). PCI can strongly intensify longitudinal micro-bunching originating from the beam’s shot noise, and even saturate it. Resulting random density and energy microstructures in the beam can become a serious problem for generating high quality electron beams. On the other hand, such instability can drive novel high-power sources of broadband radiation. In this paper we present our experimental observations of the PCI and the supporting results of the numerical simulations.
	Poster TUPLM07 [17.319 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM07
About •	paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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TUPLM11	Beam-Beam Damping of the Ion Instability	simulation, storage-ring, damping, feedback	391
	M. Blaskiewicz BNL, Upton, New York, USA
	Funding: Work Supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Beam-Beam damping of the Ion Instability The electron storage ring of the proposed electron ion collider at BNL has bunch charges as large as 50 nC and bunch spacings as small as 10 ns. For molecules like CO a dangerous buildup of positive ions is possible and a significant fraction of these ions can survive allowable clearing gaps. The instability is thus multi-turn and the weak damping required to stop the ion instabilty with an ideal clearing gap is ineffective here. The beam-beam force is highly nonlinear and a potent source of tune spread. Simulations employing several macro-particles per electron bunch and several ion macroparticles are used to estimate maximum gas densities for some common molecules. A simplified model is introduced and compared with simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM11
About •	paper received ※ 26 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019
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TUPLM13	Two-Energy Storage-Ring Electron Cooler for Relativistic Ion Beams	cavity, storage-ring, emittance, damping	399
	B. Dhital, J.R. Delayen, G.A. Krafft ODU, Norfolk, Virginia, USA J.R. Delayen, Y.S. Derbenev, D. Douglas, G.A. Krafft, F. Lin, V.S. Morozov, Y. Zhang JLab, Newport News, Virginia, USA
	An electron beam based cooling system for the ion beam is one of the commonly used approaches. The proposed two’energy storage-ring electron cooler consists of damping and cooling sections at markedly different energies connected by an energy recovering superconducting RF structure. The parameters in the cooling and damping sections are adjusted for optimum cooling of a stored ion beam and for optimum damping of the electron beam respectively. This paper briefly describes a two cavities model along with a third cavity model to accelerate and decelerate the electron beam in two energy storage ring. Based on our assumed value of equilibrium emittance shows that these models give a bunch length of the order of cm and energy spread of the order of 〖10〗^-5 in the cooling section which are required parameters for the better cooling. Numerical calculations along with elegant simulation are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM13
About •	paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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TUPLM15	Arbitrary Transverse Profile Shaping using Transverse Wigglers	wiggler, controls, emittance, focusing	403
	G. Ha, M.E. Conde, J.G. Power ANL, Lemont, Illinois, USA
	Funding: This work is supported by the U.S. Department of Energy, Offices of HEP and BES, under Contract No. DE-AC02-06CH11357. Argonne Wakefield Accelerator (AWA) group demonstrated arbitrary longitudinal shaping capability of thee emittance exchange (EEX) beamline in 2016. Several different transverse masks were used to shape the beam transversely, and the transmission through the mask was around 40%. The masking is one of the easiest ways to control the profile, but this low transmission would make significant drop of the beam quality due to a higher charge requirement in the gun, and it can make thermal issues for high repetition rate or high intensity beams. At the same time, it only controls the profile not a 2D phase space. We recently proposed a scheme to generate a tunable bunch train using a EEX beamline with a transverse wiggler. This wiggler provides a sinusoidal magnetic field which makes a sinusoidal modulation on the transverse phase space. If the beam passes series of transverse wigglers with different period and strength, one can make arbitrary correlation on the horizontal position and momentum. It opens up totally new way to control all longitudinal properties including arbitrary current profile shaping without charge loss. In this poster, we present the concept of the work and plan.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM15
About •	paper received ※ 02 September 2019 paper accepted ※ 13 September 2019 issue date ※ 08 October 2019
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TUPLM18	Improving Energy Resolution and Compensating Chromatic Aberration With a TM010 Microwave Cavity	cavity, gun, simulation, laser	411
	C.J.R. Duncan Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA P. Cueva, J.M. Maxson, D.A. Muller Cornell University, Ithaca, New York, USA
	Funding: National Science Foundation under Award OIA-1549132, the Center for Bright Beams The intrinsic energy spread of electron sources limits the achievable resolution of electron microscopes in both spectroscopic and spatially resolved measurements. We propose that the TM010 mode of a single radio frequency (RF) cavity be used to dramatically reduce this energy spread in a pulsed beam. We show with analytic approximations, confirmed in simulations, that the non-linear time-energy correlations that develop in an electron gun can be undone by the RF cavity running near-crest. We derive an expression that gives the required RF field strength as a function of accelerating voltage. We explore multiple applications, including EELS and SEM. By pulsing a photocathode with commercially available, high repetition-rate lasers, our scheme could yield competitive energy spread reduction at higher currents when compared with monochromated continuous-wave sources for electron microscopes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM18
About •	paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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TUPLM20	Generation of High-Charge Magnetized Electron Beams Consistent With JLEIC Electron Cooling Requirements	emittance, cathode, simulation, experiment	414
	A.T. Fetterman, P. Piot Northern Illinois University, DeKalb, Illinois, USA S.V. Benson, F.E. Hannon, S. Wang JLab, Newport News, Virginia, USA D.J. Crawford, D.R. Edstrom, P. Piot, J. Ruan Fermilab, Batavia, Illinois, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear physics under contract DE-AC05-06OR23177 and DE-AC02-07CH11359. The proposed Jefferson Lab Electron-Ion Collider (JLEIC), currently under design, relies on electron cooling in order to achieve the desired luminosity. This includes an electron beam with >55 Mev, 3.2 nC bunches that cools hadron beams with energies up to 100 GeV. To enhance the cooling, the electron beam must be magnetized with a specific eigen-emittance partition. This paper explores the use of the Fermilab Accelerator Science and Technology (FAST) facility to demonstrate the generation of an electron beam with parameters consistent with those required in the JLEIC high-energy cooler. We demonstrate via simulations the generation of the required electron-beam parameters and perform a preliminary experiment to validate FAST capabilities to produce such beams.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM20
About •	paper received ※ 07 September 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019
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TUPLM21	Optical Stochastic Cooling Program at Fermilab’s Integrable Optics Test Accelerator	experiment, radiation, lattice, optics	418
	J.D. Jarvis, S. Chattopadhyay, V.A. Lebedev, H. Piekarz, P. Piot, A.L. Romanov, J. Ruan Fermilab, Batavia, Illinois, USA S. Chattopadhyay, P. Piot Northern Illinois University, DeKalb, Illinois, USA
	Funding: Fermi National Accelerator Laboratory is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. Beam cooling enables an increase of peak and average luminosities and significantly expands the discovery potential of colliders. Optical Stochastic Cooling (OSC) is a high-bandwidth cooling technique that will advance the present state-of-the-art, stochastic-cooling rate by more than three orders of magnitude. A proof-of-principle demonstration with protons or heavy ions involves prohibitive costs, risks and technological challenges; however, exploration of OSC with electrons is a cost-effective alternative for studying the beam-cooling physics, optical systems and diagnostics. The ability to demonstrate OSC was a key requirement in the design of Fermilab’s Integrable Optics Test Accelerator (IOTA) ring. The IOTA program will explore the physics and technology of OSC in amplified and non-amplified configurations. We also plan to investigate the cooling and manipulation of a single electron stored in the ring. The OSC apparatus is currently being fabricated, and installation will begin in the fall of 2019. In this contribution, we will describe the IOTA OSC program, the upcoming passive-OSC experimental runs and ongoing preparations for an amplified-OSC experiment
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM21
About •	paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019
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TUPLM22	Off Axis Dependence of Current Dependent Coherent Tune Shifts in the UMER Ring	experiment, space-charge, dipole, storage-ring	422
	D.F. Sutter, B.L. Beaudoin, L. Dovlatyan UMD, College Park, Maryland, USA
	Funding: Work supported by U. S. Department of Energy grant number DESC00010301 The University of Maryland Electron Ring (UMER) was built to explore space charge effects in the extreme - beyond the space charge limit of most existing storage rings. At the nominal operating kinetic energy of 10 keV, the beam is also non relativistic. We have experimentally verified that the current dependent coherent tune shift obeys the Laslett formula over a wide current range for a cylindrical geometry and non penetrating magnetic fields when the beam is on axis; i.e. the average closed orbit displacement around the ring is essentially zero.* In the current experiment this measurement is extended to the change in current dependent coherent tune shift as the average closed orbit is moved off axis. It can be displaced over approximately ±10 mm of the vacuum pipe diameter of 50 mm without loss of beam. Because the 36 bending magnets in UMER are very short, we treat each of them as a local kick and then increment each by a calculated small amount to achieve the desired, global closed orbit displacement. Experimental results are compared to predictions by Zotter and others. * D. für Sutter, M.Cornacchia, et al, "Current dependent tune shifts in the University of Maryland electron ring", NAPAC 2013.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM22
About •	paper received ※ 29 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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TUPLM24	Electron Heating by Ions in Cooling Rings	radiation, proton, scattering, damping	426
	H. Zhao, M. Blaskiewicz BNL, Upton, New York, USA
	Hadron beam cooling at high energy is a critical technique for Electron-Ion Colliders (EIC). We consider using an electron storage ring for the EIC at BNL. For such a cooler, the electron beam quality plays an important role since it directly determines the cooling rate. Besides the effects of IBS, space charge and synchrotron damping, which are calculable with well known methods, the heating effect by ions also needs to be carefully considered in electron beam dynamics. In this paper, we present an analytical model to calculate the heating rate by ions and give some example calculations. In addition, this model was benchmarked by applying it on the IBS calculation. * Work supported by States Department of Energy
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM24
About •	paper received ※ 26 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019
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TUPLM25	Connecting Gas-Scattering Lifetime and Ion Instabilities	scattering, experiment, storage-ring, vacuum	430
	B. Podobedov, M. Blaskiewicz BNL, Upton, New York, USA
	Recently there is a renewed interest in fast ion instability (FII) which is of concern for future low-emittance electron storage rings, such as MBA light sources and colliders, i.e. eRHIC. While analytical theories and numerical codes exist to model the effect, due to various assumptions and limitations, accurate experimental verification is often desirable. Unfortunately, one of the most critical parameters for FII (as well as the classical "trapped-ion" instability), the residual ion concentration, is usually the most uncertain. Vacuum gauges and residual gas analyzers (RGAs) provide some useful data, but they are often not accurate enough, and, more importantly, they cannot directly probe the ion concentration along the beam orbit. In this paper we show how one could use gas-scattering lifetime measurements to infer the residual gas concentration suitable for ion instability experiment modelling.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM25
About •	paper received ※ 21 September 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019
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TUPLM33	Optimization of Beam Parameters for UEM with Photo-Emission S-Band RF Gun and Alpha Magnet	gun, emittance, laser, simulation	440
	H.R. Lee, P. Buaphad, I.G. Jeong, Y. Joo, Y. Kim University of Science and Technology of Korea (UST), Daejeon, Republic of Korea P. Buaphad, I.G. Jeong, Y. Joo, Y. Kim KAERI, Jeongeup-si, Republic of Korea B.L. Cho KRISS, Daejeon, Republic of Korea M.Y. Han, J.Y. Lee, S.H. Lee Korea Atomic Energy Research Institute (KAERI), Daejeon, Republic of Korea H. Suk GIST, Gwangju, Republic of Korea
	Ultrafast Electron Microscopy (UEM) is a powerful tool to observe ultrafast dynamical processes in sample materials at the atomic level. By collaborating with KRISS and GIST, the future accelerator R&D team at KAERI has been developing a UEM facility based on a photo-emission S-band (=2856 MHz) RF gun. Recently, we have added an alpha magnet in the beamline layout of the UEM to improve beam qualities such as emittance, divergence, energy spread, and bunch length. To achieve high spatial and time resolutions, we have been optimizing those beam parameters and other machine parameters by performing numerous ASTRA and ELEGANT code simulations. In this paper, we describe our ASTRA and ELEGANT code optimizations to obtain high-quality beam parameters for the UEM facility with a photo-emission S-band RF gun and an alpha magnet.
	Poster TUPLM33 [0.931 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM33
About •	paper received ※ 30 August 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019
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TUPLS10	Troubleshooting and Characterization of Gridded Thermionic Electron Gun	cathode, gun, controls, operation	474
	M.S. Stefani ODU, Norfolk, Virginia, USA F.E. Hannon JLab, Newport News, Virginia, USA
	Jefferson National Laboratory has, in collaboration with Xelera research group, designed and built a gridded thermionic election gun with the potential for magnetization; in an effort to support research towards electron sources that may be utilized for the electron cooling process in the Jefferson Laboratories Electron Ion collider design. Presented here is the process and result of troubleshooting the electron gun components and operation to ensure functionality of the design.
	Poster TUPLS10 [10.691 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLS10
About •	paper received ※ 27 August 2019 paper accepted ※ 13 September 2019 issue date ※ 08 October 2019
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TUPLS13	Evaluation of the Xilinx RFSoC for Accelerator Applications	controls, detector, interface, instrumentation	483
	J.E. Dusatko SLAC, Menlo Park, California, USA
	As electronic technology has evolved, accelerator system functions (e.g. beam instrumentation, RF cavity field control, etc.) are increasingly performed in the digital domain by sampling, digitizing, processing digitally, and converting back to the analog domain as needed. A typical system utilizes analog to digital (ADC) and digital to analog (DAC) converters with intervening digital logic in a field programmable gate array (FPGA) for digital processing. For applications (BPMs, LLRF, etc.) requiring very high bandwidths and sampling rates, the design of the electronics is challenging. Silicon technology has advanced to the state where the ADC and DAC can be implemented into the same device as the FPGA. Xilinx, Inc. has released a muti-GHz sample rate RF System on Chip (RFSoC) device. It presents many advantages for implementing accelerator and particle detector systems. Because direct conversion is possible, RF analog front/back end and overall system design is simplified. This paper presents the results of an evaluation study of the RFSoC device for accelerator and detector work, including test results. It then discusses possible applications and work done at SLAC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLS13
About •	paper received ※ 30 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019
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TUPLH03	Double-Bend Achromat Beamline for Injection Into a High-Power Superconducting Electron Linac	solenoid, gun, dipole, cavity	494
	C.H. Boulware, T.L. Grimm, R. Hipple Niowave, Inc., Lansing, Michigan, USA S.M. Lund FRIB, East Lansing, Michigan, USA V.S. Morozov JLab, Newport News, Virginia, USA
	To take advantage of the high duty cycle operation of superconducting electron linacs, commercial systems use thermionic cathode electron guns that fill every RF bucket with an electron bunch. In continuous operation, the exit energy is limited when compared to pulsed systems. Bunch length and energy spread at the exit of the gun are incompatible with low losses in the superconducting cavity. A solenoid double-bend achromatic beamline is in operation at Niowave which allows energy and bunch length filtering of the beam leaving the gun before injection into the superconducting cavity. This system uses two solenoids and two dipoles to produce a round beam, using the edge angles of the dipoles to balance the focusing effects in the two transverse planes. The design allows beam filtering on the symmetry plane where the dispersion is maximum. Additionally, the bend angle moves the electron gun off the high-energy beam axis, allowing multiple-pass operation of the superconducting booster. This contribution will discuss the beam optics design of the double-bend achromat along with the design of the magnets and beam chambers and the operational experience with the system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH03
About •	paper received ※ 28 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019
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TUPLH07	High-Gradient Short Pulse Accelerating Structures	experiment, wakefield, impedance, acceleration	500
	S.V. Kuzikov, S.P. Antipov, E. Gomez Euclid TechLabs, LLC, Solon, Ohio, USA A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia
	High gradients are necessary for lots of applications of electron accelerators. As the maximum gradient is limited by effects of RF breakdown, we present a development of an electron accelerating structure operating with a short multi-megawatt RF pulse. The structure exploits an idea to decrease the breakdown probability due to RF pulse length reduction. This concept requires to distribute RF power so that all accelerating cells are fed independently each other. This implies waveguide net system which allows to delay and to distribute properly RF radiation along the structure keeping synchronism of particles and waves. We have designed an X-band pi-mode structure including the RF design, optimization, and engineering. The structure will be tested as an RF power extractor at the Argonne Wakefield Accelerator Facility for two-beam acceleration experiments. In this regime we anticipate to obtain 10 ns, gigawatt power level RF pulses generated by train consisted of eight 25-50 nC relativistic bunches.
	Poster TUPLH07 [0.999 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH07
About •	paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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TUPLH08	X-Ray and Charged Particle Detection by Detuning of a Microwave Resonator	laser, resonance, coupling, experiment	503
	S.P. Antipov, P.V. Avrakhov, E. Dosov, E. Gomez, S.V. Kuzikov Euclid TechLabs, LLC, Solon, Ohio, USA S. Stoupin Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia
	Funding: DOE SBIR Charged particle detection is important for beam alignment, beam loss and background control. In case of halo detection, traditional wire scanner measurement utilizing carbon or tungsten wires is limited by the damage threshold of these materials. In this paper we present an electrodeless method to measure halo with a diamond scraper. This measurement utilizes a microwave resonator placed around the diamond scraper which is sensitive to charged particle-induced conductivity. Due to this transient induced conductivity in the dielectric, a microwave coupling to the resonator changes. Diamond in this case is chosen as a radiation hard material with excellent thermal properties. The absence of electrodes makes the device robust under the beam. The same measurement can be done for x-ray flux monitoring which is important for measurement feedback and calibration at modern x-ray light sources. In this case x-rays passing through the diamond sensing element enable a photo-induced conductivity and that in turn detunes the cavity placed around the diamond. Diamond being a low-Z material allows for in-line x-ray flux measurement without significant beam attenuation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH08
About •	paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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TUPLH24	Performance of CeC PoP Accelerator	FEL, gun, SRF, hadron	526
	I. Pinayev, Z. Altinbas, J.C. Brutus, A.J. Curcio, A. Di Lieto, T. Hayes, R.L. Hulsart, P. Inacker, Y.C. Jing, V. Litvinenko, J. Ma, G.J. Mahler, M. Mapes, K. Mernick, K. Mihara, T.A. Miller, M.G. Minty, G. Narayan, I. Petrushina, F. Severino, K. Shih, Z. Sorrell, J.E. Tuozzolo, E. Wang, G. Wang, A. Zaltsman BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Coherent electron cooling experiment is aimed for demonstration of the proof-of-principle demonstration of reduction energy spread of a single hadron bunch circulating in RHIC. The electron beam should have the required parameters and its orbit and energy should be matched to the hadron beam. In this paper we present the achieved electron beam parameters including emittance, energy spread, and other critical indicators. The operational issues as well as future plans are also discussed.
	Poster TUPLH24 [11.180 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH24
About •	paper received ※ 29 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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TUPLO01	Dual-Function Electron Ring-Ion Booster Design for JLEIC High-Energy Option	booster, collider, quadrupole, lattice	529

Paper

Title

Other Keywords

Page

MOOHC2

The US Electron Ion Collider Accelerator Designs

collider, polarization, luminosity, proton

1

A. Seryi, S.V. Benson, S.A. Bogacz, P.D. Brindza, M.W. Bruker, A. Camsonne, E. Daly, P. Degtiarenko, Y.S. Derbenev, M. Diefenthaler, J. Dolbeck, R. Ent, R. Fair, D. Fazenbaker, Y. Furletova, B.R. Gamage, D. Gaskell, R.L. Geng, P. Ghoshal, J.M. Grames, J. Guo, F.E. Hannon, L. Harwood, S. Henderson, H. Huang, A. Hutton, K. Jordan, D.H. Kashy, A.J. Kimber, G.A. Krafft, R. Lassiter, R. Li, F. Lin, M.A. Mamun, F. Marhauser, R. McKeown, T.J. Michalski, V.S. Morozov, P. Nadel-Turonski, E.A. Nissen, G.-T. Park, H. Park, M. Poelker, T. Powers, R. Rajput-Ghoshal, R.A. Rimmer, Y. Roblin, D. Romanov, P. Rossi, T. Satogata, M.F. Spata, R. Suleiman, A.V. Sy, C. Tennant, H. Wang, S. Wang, C. Weiss, M. Wiseman, W. Wittmer, R. Yoshida, H. Zhang, S. Zhang, Y. Zhang, Z.W. Zhao
JLab, Newport News, Virginia, USA
D.T. Abell, D.L. Bruhwiler, I.V. Pogorelov
RadiaSoft LLC, Boulder, Colorado, USA
E.C. Aschenauer, G. Bassi, J. Beebe-Wang, J.S. Berg, M. Blaskiewicz, A. Blednykh, J.M. Brennan, S.J. Brooks, K.A. Brown, K.A. Drees, A.V. Fedotov, W. Fischer, D.M. Gassner, W. Guo, Y. Hao, A. Hershcovitch, H. Huang, W.A. Jackson, J. Kewisch, A. Kiselev, V. Litvinenko, C. Liu, H. Lovelace III, Y. Luo, F. Méot, M.G. Minty, C. Montag, R.B. Palmer, B. Parker, S. Peggs, V. Ptitsyn, V.H. Ranjbar, G. Robert-Demolaize, T. Roser, S. Seletskiy, V.V. Smaluk, K.S. Smith, S. Tepikian, P. Thieberger, D. Trbojevic, N. Tsoupas, E. Wang, W.-T. Weng, F.J. Willeke, H. Witte, Q. Wu, W. Xu, A. Zaltsman, W. Zhang
BNL, Upton, New York, USA
D.P. Barber
DESY, Hamburg, Germany
I.V. Bazarov
Cornell University, Ithaca, New York, USA
G.I. Bell, J.R. Cary
Tech-X, Boulder, Colorado, USA
Y. Cai, Y.M. Nosochkov, A. Novokhatski, G. Stupakov, M.K. Sullivan, C.-Y. Tsai
SLAC, Menlo Park, California, USA
Z.A. Conway, M.P. Kelly, B. Mustapha, U. Wienands, A. Zholents
ANL, Lemont, Illinois, USA
S.U. De Silva, J.R. Delayen, H. Huang, C. Hyde, S. Sosa, B. Terzić
ODU, Norfolk, Virginia, USA
K.E. Deitrick, G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
D. Douglas
Douglas Consulting, York, Virginia, USA
V.G. Dudnikov, R.P. Johnson
Muons, Inc, Illinois, USA
B. Erdelyi, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
J.D. Fox
Stanford University, Stanford, California, USA
J. Gerity, T.L. Mann, P.M. McIntyre, N. Pogue, A. Sattarov
Texas A&M University, College Station, USA
E. Gianfelice-Wendt, S. Nagaitsev
Fermilab, Batavia, Illinois, USA
Y. Hao, P.N. Ostroumov, A.S. Plastun, R.C. York
FRIB, East Lansing, Michigan, USA
T. Mastoridis
CalPoly, San Luis Obispo, California, USA
J.D. Maxwell, R. Milner, M. Musgrave
MIT, Cambridge, Massachusetts, USA
J. Qiang, G.L. Sabbi
LBNL, Berkeley, California, USA
D. Teytelman
Dimtel, Redwood City, California, USA
R.C. York
NSCL, East Lansing, Michigan, USA

With the completion of the National Academies of Sciences Assessment of a US Electron-Ion Collider, the prospects for construction of such a facility have taken a step forward. This paper provides an overview of the two site-specific EIC designs: JLEIC (Jefferson Lab) and eRHIC (BNL) as well as brief overview of ongoing EIC R&D.

Slides MOOHC2 [14.774 MB]

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MOYBA1

LHC Status and Plans

luminosity, operation, experiment, proton

8

X. Buffat
CERN, Geneva, Switzerland

Performance and accelerator physics challenges from LHC Run 2 are reviewed, along with the ongoing preparation and plans for LHC Runs 3 and 4.

Slides MOYBA1 [13.269 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBA1

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paper received ※ 26 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

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MOYBA4

eRHIC Design Update

luminosity, hadron, interaction-region, proton

18

C. Montag, G. Bassi, J. Beebe-Wang, J.S. Berg, M. Blaskiewicz, A. Blednykh, J.M. Brennan, S.J. Brooks, K.A. Brown, K.A. Drees, A.V. Fedotov, W. Fischer, D.M. Gassner, Y. Hao, A. Hershcovitch, C. Hetzel, D. Holmes, H. Huang, W.A. Jackson, J. Kewisch, Y. Li, C. Liu, H. Lovelace III, Y. Luo, F. Méot, M.G. Minty, R.B. Palmer, B. Parker, S. Peggs, V. Ptitsyn, V.H. Ranjbar, G. Robert-Demolaize, S. Seletskiy, V.V. Smaluk, K.S. Smith, S. Tepikian, P. Thieberger, D. Trbojevic, N. Tsoupas, S. Verdú-Andrés, W.-T. Weng, F.J. Willeke, H. Witte, Q. Wu, W. Xu, A. Zaltsman, W. Zhang
BNL, Upton, New York, USA
Y. Cai, Y.M. Nosochkov
SLAC, Menlo Park, California, USA
E. Gianfelice-Wendt
Fermilab, Batavia, Illinois, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The future electron-ion collider (EIC) aims at an electron-proton luminosity of 10³³ to 10³⁴ cm^-2 sec^-1 and a center-of-mass energy range from 20 to 140 GeV. The eRHIC design has been continuously evolving over a couple of years and has reached a considerable level of maturity. The concept is generally conservative with very few risk items which are mitigated in various ways.

Slides MOYBA4 [5.466 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBA4

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paper received ※ 24 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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MOYBA6

Accelerator Performance During the Beam Energy Scan II at RHIC in 2019

operation, luminosity, cavity, MMI

26

C. Liu, I. Blacker, M. Blaskiewicz, K.A. Brown, D. Bruno, K.A. Drees, A.V. Fedotov, W. Fischer, C.J. Gardner, C.E. Giorgio, X. Gu, T. Hayes, H. Huang, R.L. Hulsart, D. Kayran, N.A. Kling, Y. Luo, D. Maffei, G.J. Marr, B. Martin, A. Marusic, K. Mernick, R.J. Michnoff, M.G. Minty, C. Montag, J. Morris, C. Naylor, S. Nemesure, I. Pinayev, S. Polizzo, V.H. Ranjbar, D. Raparia, G. Robert-Demolaize, T. Roser, J. Sandberg, V. Schoefer, F. Severino, T.C. Shrey, K.S. Smith, S. Tepikian, P. Thieberger, A. Zaltsman, K. Zeno, I.Y. Zhang, W. Zhang
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
RHIC provided Au-Au collisions at beam energies of 9.8, 7.3, 4.59 and 3.85 GeV/nucleon during the first year of the Beam Energy Scan II in 2019. The physics goals at the first two higher beam energies were achieved. At the two lower beam energies, bunched electron beam cooling has been demonstrated successfully. The accelerator performance was improved compared to when RHIC was operated at these energies in earlier years. This article will introduce the challenges to operate RHIC at low energies and the corresponding countermeasures, and review the improvement of accelerator performance during the operation in 2019.

Slides MOYBA6 [6.579 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBA6

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paper received ※ 21 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019

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MOYBB2

Recent Advance in ECR Ion Sources

ECR, ion-source, plasma, operation

31

G. Machicoane, N.K. Bultman, P. Morrison, M. Omelayenko, X. Rao
FRIB, East Lansing, Michigan, USA
D. Arbelaez, R.R. Hafalia, P. Pan, S. Prestemon
LBNL, Berkeley, California, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University.
High continuous wave (cw) current of highly charged ion beams are required for several heavy ion accelerator facilities including the Facility for Rare Isotope Beams (FRIB). In most cases, Electron-Cyclotron-Resonance (ECR) ion sources remain the only ion source capable to meet the beam intensity requirement for these facilities. Performances of ECR ion source have increased by several order of magnitude since their inception in the 1970s mostly driven by increasing the resonance frequency with today current state of the art ECR ion source operating from 24 to 28 GHz. This paper provides an overview of recent advance in the design and operation of ECR ion source including plans to develop the next generation of ion source capable of operating above 40 GHz. A detailed account of the design and status of the new superconducting ECR ion source in construction for FRIB will also be reported.

Slides MOYBB2 [9.483 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB2

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paper received ※ 02 September 2019 paper accepted ※ 16 November 2020 issue date ※ 08 October 2019

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MOYBB5

Characterization and Performance of Plasma Window for Gas Flow Restriction in Different Geometries

plasma, cathode, target, diagnostics

44

A. Lajoie
NSCL, East Lansing, Michigan, USA
J. Gao, F. Marti
FRIB, East Lansing, Michigan, USA

Funding: This work is supported by NSF Award PHY-1565546.
The plasma window is a DC cascaded arc whose function is to restrict gas flow from a high pressure region to a low pressure region without the use of any solid separation*. As a result, the plasma window allows a greater pressure to be maintained than otherwise possible. This is a beneficial characteristic for gas charge strippers for ion accelerators, since the higher pressures enable the stripper to be shorter and allow the same amount of stripping interactions**. The flow rate reduction is established by the increase in gas temperature from the power deposited into the plasma via the cathodes, resulting in a dramatically increased viscosity. The flow rate reduction, depends on the properties of the plasma, including the electron density and temperature, pressure, and electrical conductivity. Understanding these properties in multiple arc geometries - in this work having either 6 mm or 10 mm channel diameter - provides a means optimizing the plasma window for a given design. Determinations of the properties for different conditions are shown, and results are compared with a PLASIMO simulation, which has been shown to yield comparable properties to measurements in an argon arc***.
*A. Hershcovitch, Phys. Plasma 5, 2130 (1998).
**J. A. Nolen and F. Marti, Rev. Accel. Sci. Tech. 6, 221 (2013).
***G. M. W. Kroesen et al., Plas. Chem. and Plas. Proc. 10, 531 (1990).

Slides MOYBB5 [4.132 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB5

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paper received ※ 27 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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MOZBA3

Strongly Tapered Helical Undulator System for TESSA-266

undulator, experiment, laser, permanent-magnet

63

T.J. Campese, R.B. Agustsson, I.I. Gadjev, A.Y. Murokh
RadiaBeam, Santa Monica, California, USA
W. Berg, A. Zholents
ANL, Lemont, Illinois, USA
P.E. Denham, P. Musumeci, Y. Park
UCLA, Los Angeles, USA

Funding: DOE SBIR Award No. DE-SC0017102
RadiaBeam, in collaboration with UCLA and Argonne National Laboratory (ANL), is developing a strongly tapered helical undulator system for the Tapering Enhanced Stimulated Superradiant Amplification experiment at 266 nm (TESSA-266). The experiment will be carried out at the APS LEA facility at ANL and aims at the demonstration of very high energy conversion efficiency in the UV. The undulator system was designed by UCLA, engineered by RadiaBeam, and is presently in fabrication at RadiaBeam. The design is based on a permanent magnet Halbach scheme and includes a short 30 cm long buncher section and four 1 m long undulator sections. The undulator period is fixed at 32 mm and the magnetic field amplitude can be tapered by tuning the gap along the interaction. Each magnet can be individually adjusted by 1.03 mm, offering up to 25% magnetic field tunability with a minimum gap of 5.58 mm. A custom designed 316L stainless steel beampipe runs through the center with a clear aperture of 4.5 mm. This paper discusses the design and engineering of the undulator system, fabrication status, and plans for magnetic measurements, and tuning.

Slides MOZBA3 [8.942 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA3

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paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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MOZBA4

Recent Developments in High Power High Brightness Double Bunch Self-Seeding at LCLS-II

FEL, undulator, photon, simulation

67

A. Halavanau, F.-J. Decker, Y. Ding, C. Emma, Z. Huang, A.A. Lutman, G. Marcus, C. Pellegrini
SLAC, Menlo Park, California, USA

We discuss the power and spectral characteristics of an X-ray FEL, LCLS-II, operating in a double bunch self-seeding scheme (DBFEL). We show that it can reach very high power levels in the photon energy range of 4-8 keV. We discuss the system implementation on LCLS-II, including the design of a four-bounce crystal monochromator, and linac wakefields effects. Finally, we offer multiple applications of the DBFEL for high-field QED, AMO physics and single particle imaging.

Slides MOZBA4 [3.175 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA4

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paper received ※ 02 September 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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MOZBB5

Magnetized Electron Source for JLEIC Cooler

cathode, gun, solenoid, high-voltage

83

R. Suleiman, P.A. Adderley, J.F. Benesch, D.B. Bullard, J.M. Grames, J. Guo, F.E. Hannon, J. Hansknecht, C. Hernandez-Garcia, R. Kazimi, G.A. Krafft, M.A. Mamun, M. Poelker, M.G. Tiefenback, Y.W. Wang, S. Zhang
JLab, Newport News, Virginia, USA
J.R. Delayen, G.A. Krafft, S.A.K. Wijethunga, J.T. Yoskowitz
ODU, Norfolk, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and supported by Laboratory Directed Research and Development funding.
Magnetized bunched-beam electron cooling is a critical part of the Jefferson Lab Electron Ion Collider (JLEIC). Strong cooling of ion beams will be accomplished inside a cooling solenoid where the ions co-propagate with an electron beam generated from a source immersed in magnetic field. This contribution describes the production and characterization of magnetized electron beam using a compact 300 kV DC high voltage photogun and bialkali-antimonide photocathodes. Beam magnetization was studied using a diagnostic beamline that includes viewer screens for measuring the shearing angle of the electron beamlet passing through a narrow upstream slit. Correlated beam emittance with magnetic field at the photocathode was measured for various laser spot sizes. Measurements of photocathode lifetime were carried out at different magnetized electron beam currents up to 28 mA and high bunch charge up to 0.7 nano-Coulomb was demonstrated.

Slides MOZBB5 [9.236 MB]

Poster MOZBB5 [1.564 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBB5

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paper received ※ 27 August 2019 paper accepted ※ 01 September 2019 issue date ※ 08 October 2019

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MOZBB6

Measuring the Mean Transverse Energy of Pump-Probe Photoemitted Electrons

cathode, photon, experiment, vacuum

87

C.M. Pierce, I.V. Bazarov, L. Cultrera, J.M. Maxson
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams.
Low effective mass semiconductor photocathodes have historically failed to exhibit the sub-thermal mean transverse energies (MTEs) expected of them based on their band structure. However, conservation of transverse momentum across the vacuum interface, and therefore a low MTE in these materials, has been observed in time resolved ARPES*. To help bridge this gap, we measured the MTE of the pump probe photoemitted electrons seen in the ARPES experiment using methods typical of accelerator physics. We compare the results of these measurements with those of both communities and discuss them in the context of photoemission physics.
* Kanasaki, J., Tanimura, H., & Tanimura, K. (2014). Imaging Energy-, Momentum-, and Time-Resolved Distributions of Photoinjected Hot Electrons in GaAs. Physical Review Letters, 113(23), 237401.

Slides MOZBB6 [7.348 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBB6

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paper received ※ 28 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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MOPLM06

High Voltage Design of a 350 kV DC Photogun at BNL

cathode, gun, high-voltage, vacuum

102

W. Liu, O.H. Rahman, E. Wang
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Brookhaven National Laboratory is constructing a 350 kV DC high voltage photogun to provide spin-polarized electron beam for the proposed eRHIC facility. The photogun employs a compact inverted-tapered-geometry ceramic insulator that extends into the vacuum chamber and mechanically holds the cathode electrode. By operating at high voltage, the photogun will provide lower beam emittance, thereby improving the beam transmission through the injector apertures, and prolong the operating lifetime of the photogun. However, high voltage increases the field emission, which can result in high voltage breakdown and even lead to irreparable damage of the ceramic insulator. This work describes the methods to minimize the electric field near the metal-vacuum-insulator interface, and to avoid high voltage breakdown and ceramic insulator damage. The triple point junction shields are designed. The simulated electric field, field emission and beam transportation will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM06

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paper received ※ 19 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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MOPLM13

Investigations of the Electron Beam Energy Jitter Generated in the Photocathode RF Gun at the Advanced Photon Source Linac

gun, timing, laser, cathode

124

J.C. Dooling, D. Hui, A.H. Lumpkin, T.L. Smith, Y. Sun, K.P. Wootton, A. Zholents
ANL, Lemont, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02- 06CH11357.
Characterizations continue of the electron beam properties of a recently installed S-band photocathode (PC) rf gun at the Advanced Photon Source Linac facility. In this case, we have utilized a low-energy spectrometer beam line located 1.3 m downstream of the gun cavity to measure the electron beam energy, energy spread, and energy jitter. The nominal energy was 6.5 MeV using a gun gradient of 110 MV/m, and the energy spread was ~17 keV when driven by a 2.5-ps rms duration UV laser pulse at the selected rf gun phase. An energy jitter of 25 keV was initially observed in the spectrometer focal plane images. This jitter was partly attributed to the presence of both the 2nd and 3rd harmonics of the 119 MHz synchronization signal provided to the phase locked loop of the drive laser oscillator. The addition of a 150-MHz low-pass filter in the 119-MHz line strongly attenuated the two harmonics and resulted in a reduced energy jitter of ~15 keV. Comparisons of the gun performance to ASTRA simulations will also be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM13

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paper received ※ 28 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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MOPLM15

Design of the ASU Photocathode Lab

cathode, gun, diagnostics, emittance

132

C.J. Knill, S.S. Karkare
Arizona State University, Tempe, USA
J.V. Conway, B.M. Dunham, K.W. Smolenski
Xelera Research LLC, Ithaca, New York, USA
H.A. Padmore
LBNL, Berkeley, California, USA

Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams.
Recent investigations have shown that it is possible to obtain an order of magnitude smaller intrinsic emittance from photocathodes by precise atomic scale control of the surface, using an appropriate electronic band structure of single crystal cathodes and cryogenically cooling the cathode. Investigating the performance of such cathodes requires atomic scale surface diagnostic techniques connected in ultra-high vacuum (UHV) to the epitaxial thin film growth and surface preparation systems and photo-emission and photocathode diagnostic techniques. Here we report the capabilities and design of the laboratory being built at the Arizona State University for this purpose. The lab houses a 200 kV DC gun with a cryogenically cooled cathode along with a beam diagnostics and ultra fast electron diffraction beamline. The cathode of the gun can be transported in UHV to a suite of UHV growth chambers and surface and photoemission diagnostic techniques.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM15

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paper received ※ 26 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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MOPLM16

Design of a 200 kV DC Cryocooled Photoemission Gun for Photocathode Investigations

cathode, gun, emittance, radiation

136

G.S. Gevorkyan, S.S. Karkare
Arizona State University, Tempe, USA
I.V. Bazarov, A. Galdi, J.M. Maxson
Cornell University, Ithaca, New York, USA
L. Cultrera, W.H. Li
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work was supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams.
Intrinsic emittance of photocathodes limits the brightness of electrons beams produced from photoemission guns. Recent advancements have shown that an order of magnitude improvement in intrinsic emittance over the commonly used polycrystalline metal and semiconductor cathodes is possible via use of single crystalline ordered surfaces of metals, semiconductors and other exotic materials at cryogenic temperatures as cathodes. However, due to practical design considerations, it is not trivial to test such cathodes in existing electron guns. Here we present the design of a 200kV DC electron gun being developed at the Arizona State University for this purpose.

Poster MOPLM16 [1.549 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM16

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paper received ※ 27 August 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019

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MOPLM18

Design of the 2-Stage Laser Transport for the Low Energy RHIC Electron Cooling (LEReC) DC Photogun

laser, gun, cathode, alignment

144

P. Inacker, S. Bellavia, A.J. Curcio, A.V. Fedotov, W. Fischer, D.M. Gassner, J.P. Jamilkowski, P.K. Kankiya, D. Kayran, D. Lehn, R. Meier, T.A. Miller, M.G. Minty, S.K. Nayak, L.K. Nguyen, L. Smart, C.J. Spataro, A. Sukhanov, J.E. Tuozzolo, Z. Zhao
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The electron beam for the recently constructed Low Energy RHIC electron Cooler (LEReC) at Brookhaven National Laboratory is generated by a high-power fiber laser illuminating a photocathode. The pointing stability of the low-energy electron beam, which is crucial to maintain within acceptable limits given the long beam transport, is highly dependent on the center-of-mass (CoM) stability of the laser spot on the photocathode. For reasons of accessibility during operations, the laser itself is located outside the accelerator tunnel, leading to the need to propagate the laser beam 34 m via three laser tables to the photocathode. The challenges to achieving the required CoM stability of 10 microns on the photocathode thus requires mitigation of vibrations along the transport and of weather- and season-related environmental effects, while preserving accessibility and diagnostic capabilities with proactive design. After successful commissioning of the full transport in 2018/19, we report on our solutions to these design challenges.
LEReC Photocathode DC Gun Beam Test Results - D. Kayran Conference: C18-04-29, p.TUPMF025
Commissioning of Electron Accelerator LEReC for Bunch Beam Cooling - D.Kayran, NAPAC19

Poster MOPLM18 [1.970 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM18

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paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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MOPLM24

LCLS-II Injector Commissioning Beam Based Measurements

gun, laser, cathode, MMI

157

C.M. Zimmer, T.J. Maxwell, F. Zhou
SLAC, Menlo Park, California, USA

Funding: Department of Energy
Injector commissioning is underway for the LCLS-II MHz repetition rate FEL, currently under construction at SLAC. Methodology of injector beam-based measurements and early results with low beam charge will be presented, along with the software tools written to automate these various measurements.

Poster MOPLM24 [10.104 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM24

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paper received ※ 28 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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MOPLS08

Error Tolerance Characterization for the HUST MeV Ultrafast Electron Diffraction System

emittance, injection, laser, simulation

166

Y. Song, K. Fan, C.-Y. Tsai
HUST, Wuhan, People’s Republic of China

Ultrafast electron diffraction (UED) is a powerful tool for probing atomic dynamics with a femtosecond resolution. Such a spatiotemporal resolution requires error tolerance for the UED system which includes the RF system, the laser system, the beamline elements, etc. To characterize the error tolerance of the required spatiotemporal resolution for the 1.4-cell MeV UED we are developing, we use ASTRA to simulate the UED model with errors including initial transverse beam centroid offset, RF amplitude jitter and injection phase jitter, etc. By performing simulations with different errors omitted, we can characterize the contribution of each error and thus set the tolerance for each error to obtain the required performance of UED experiment. In the end, we present the error tolerance for 10% emittance growth and 100 fs time of flight variation to maintain the required spatiotemporal resolution.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLS08

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paper received ※ 25 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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MOPLH02

Study of Photocathode Surface Damage due to Ion Back-Bombardment in High Current DC Gun

cathode, gun, simulation, laser

174

J.P. Biswas
Stony Brook University, Stony Brook, USA
O.H. Rahman, E. Wang
BNL, Upton, New York, USA

Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704, with the U.S. DOE
In high current DC gun, GaAs photocathode lifetime is limited by the ion back-bombardment. While gun operation ions are generated and accelerate back towards the cathode thus remove the activation layer’s material Cesium from the photocathode surface. We have developed an object-oriented code to simulate the ion generation due to dynamic gas pressure and ion trace in the electromagnetic field. The pressure profile varies from cathode position towards the transfer line behind the anode, which signifies the importance of dynamic simulation for ion back-bombardment study. In our surface damage study, we traced the energy and position of the ions on the photocathode surface and performed the Stopping and Range of Ions in Matter(SRIM) simulation to count the number of Cesium atoms removed from the surface due to single bunch impact. Cesium atom removal is directly related to the photocathode Quantum Efficiency(QE) decay. Our new dynamic simulation code can be used in any DC gun to study ion back-bombardment. We have used this new code to better understand the ion generation in prototype BNL 350 KV DC gun, and we have also estimated the normalized QE decay due to ion back-bombardment.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH02

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paper received ※ 27 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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MOPLH04

Design for HyRES Cathode Nanotip Electron Source

cavity, solenoid, gun, cathode

177

R.M. Hessami, A.F. Amhaz, P. Musumeci
UCLA, Los Angeles, USA

A new ultrafast electron diffraction (UED) instrument is being developed by UCLA-Colorado University collaboration for the STROBE NSF Center with the goal of using electron and EUV photon beams to reveal the structural dynamics of materials in non-equilibrium states at fundamental atomic and temporal scales. This paper describes the design of the electron beamline of this instrument. In order to minimize the initial emittance, a nanotip photocathode, 25 nm in radius, will be used. This requires a redesign of the cathode and anode components of the electron gun to allow for the tip to be properly aligned. Solenoidal lenses are used to focus the beam transversely to a sub-micron spot at the sample and a radiofrequency (RF) cavity, driven by a continuous wave S-band RF source, longitudinally compresses the beam to below 100 fs, required for atomic resolution.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH04

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paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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MOPLH06

Study of the Mean Transverse Energy and the Emission Mechanism of (N)UNCD Photocathodes

cathode, photon, experiment, emittance

181

G. Chen
IIT, Chicago, Illinois, USA
G. Adhikari, W.A. Schroeder
UIC, Chicago, Illinois, USA
S.P. Antipov, E. Gomez
Euclid TechLabs, LLC, Solon, Ohio, USA
S.V. Baryshev, T. Nikhar
Michigan State University, East Lansing, Michigan, USA
L.K. Spentzouris
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: This project is supported by NSF grant No. NSF-1739150, NSF-1535676, and NSF grant No. PHYS-1535279.
Nitrogen incorporated ultrananocrystalline diamond ((N)UNCD) is promising for photocathode applications due to its high quantum efficiency (QE). The mean transverse energy (MTE) which, along with QE, defines the brightness of the emitted electron beam must be thoroughly characterized and understood for (N)UNCD. Our previous work* further corroborated the important role of graphitic grain boundaries (GB’s). UNCD consists of diamond (sp3-hybrized) grains and graphitic (sp2-hybrized) GB’s: GB’s are behind the high emissivity of (N)UNCD and therefore play a crucial role in defining and controlling the MTE. In this work, the MTE of two different (N)UNCD samples having different ratios of sp3/sp2 were measured versus the primary photon energies. As a reference, MTE of highly oriented pyrolytic graphite (HOPG, canonical sp2-hybrized graphite) was also measured.
* G. Chen et al., Appl. Phys. Lett. 114, 093103 (2019).

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH06

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paper received ※ 27 August 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019

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MOPLH09

Photoluminescence Studies of Alkali-Antimonide Photocathodes

experiment, cathode, laser, photon

188

P. Saha, O. Chubenko, S.S. Karkare
Arizona State University, Tempe, USA
H.A. Padmore
LBNL, Berkeley, California, USA

Alkali-antimonide photocathodes have a very high quantum efficiency and a low intrinsic emittance, making them excellent electron sources for Energy Recovery Linacs, X-ray Free Electron Lasers, Electron Cooling, and Ultrafast Electron Diffraction applications. Despite numerous studies of their photoemission spectra, there has been nearly no conclusive experimental investigation of their basic electronic and optical properties (e.g. band gap, electron affinity, optical constants, etc.), which determine the nature of photoemission. Therefore, the systematic study and deep understanding of fundamental characteristics of alkali-antimonide photocathodes are required in order to develop next-generation electron sources with improved crystal and electronic structures to fit specific application. Here we report on the development of an experimental setup to measure photoluminescence (PL) spectra from alkali-antimonide photocathodes, enabling estimation of a material band gap and defect state energies, and provide preliminary results for Cs3Sb films.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH09

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paper received ※ 27 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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MOPLH10

Field-Emission Electron Source Embedded in a Field-Enhanced Conduction-Cooled Superconducting RF Cavity

cavity, cathode, experiment, niobium

192

D. Mihalcea, V. Korampally, A. McKeown, O. Mohsen, P. Piot, I. Salehinia
Northern Illinois University, DeKalb, Illinois, USA
R. Dhuley, M.G. Geelhoed, P. Piot, J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA

We present simulations and experimental progress toward the development of a high-current electron source with the potential to deliver high charge electron bunches at GHz-level repetition rates. To achieve these goals electrons are generated through field-emission and the cathode is immersed in a conduction-cooled superconducting 650-MHz RF cavity. The field-emitters consist of microscopic silicon pyramids and have a typical enhancement factor of about 500. To trigger field-emission, the peak field inside the RF cavity of about 6 MV/m is further enhanced by placing the field-emitters on the top of a superconducting Nb rod inserted in the RF cavity. So far, we cannot control the duration of the electron bunches which is of the order of RF period. Also, the present cryo-cooler power of about 2 W limits the beam current to microamp level.

Poster MOPLH10 [1.063 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH10

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paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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MOPLH11

Nanostructured Photocathodes for Spin-Polarized Electron Beams

cathode, polarization, lattice, scattering

196

E.J. Montgomery, C. Jing, S. Poddar
Euclid Beamlabs LLC, Bolingbrook, USA
A. Afanasev
GWU, Washington, USA
R. Kumar, G.J. Salamo
University of Arkansas, Fayetteville, Arkansas, USA
S. Zhang
JLab, Newport News, Virginia, USA

Funding: Work supported by US DOE Office of Science, Office of Nuclear Physics, SBIR grant DESC0019559. CNM work supported by US DOE Office of Science, Basic Energy Sciences, contract DE-AC02-06CH11357.
We present progress on incorporation of nanopillar arrays into spin-polarized gallium arsenide photocathodes in pursuit of record high tolerance to ion back-bombardment. Our goal is to exceed the 400 Coulomb record for a high polarization milliampere-class electron source set at Jefferson Laboratory in 2017, while maintaining high quantum efficiency (QE) and spin polarization with a superlattice. Because the Mie effect is resonant, uniformity and careful control over nanostructure geometry is key. We report excellent uniformity and straight sidewall geometry with improved optical absorption using a painstakingly optimized inductively coupled plasma reactive ion etch. We also report the application of Kerker theory to spin-polarized photocathode nanopillar arrays, setting new requirements on nanostructure dimensions to avoid spoiling spin polarization. Finally, we also report initial steps toward re-establishing U.S. production of strained superlattice photocathodes towards integration with nanopillar arrays.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH11

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paper received ※ 03 September 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019

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MOPLH13

STARRE Lab: The Sub-THz Accelerator Research Laboratory

laser, experiment, GUI, operation

199

J.F. Picard, S.C. Schaub, R.J. Temkin
MIT/PSFC, Cambridge, Massachusetts, USA

Funding: Department of Energy, Office of HEP, DE- SC0015566; Office of Fusion Energy Sciences, DE-FC02-93ER54186; National Institutes of Health, NIBIB, EB004866 and EB001965;
This work presents the development of the STARRE Lab, a facility at MIT for testing breakdown in high gradient accelerator structures at 110 GHz. The system utilizes a Laser-Driven Semiconductor Switch (LDSS) to modulate the output of a megawatt gyrotron, which generates 3 μs pulses at up to 6 Hz. The LDSS employs silicon (Si) and gallium arsenide (GaAs) wafers to produce nanosecond-scale pulses at the megawatt level from the gyrotron output. Photoconductivity is induced in the wafers using a 532 nm Nd:YAG laser, which produces 6 ns, 230 mJ pulses. A single Si wafer produces 110 GHz RF pulses with 9 ns width, while under the same conditions, a single GaAs wafer produces 24 ns 110 GHz RF pulses. In dual-wafer operation, which uses two active wafers, pulses of variable length down to 3 ns duration can be created at power levels greater than 300 kW. The switch has been successfully tested at incident 110 GHz RF power levels up to 720 kW.* The facility has been used to successfully test an advanced 110 GHz accelerator structure built by SLAC to gradients in excess of 220 MV/m.
*J.F. Picard et al., Appl. Phys. Lett. 114, 164102 (2019); doi: https://doi.org/10.1063/1.5093639

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH13

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paper received ※ 24 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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MOPLH14

Ultrafast Nonlinear Photoemission from Alkali Antimonide Photocathodes

photon, cathode, laser, gun

203

W.H. Li, M.B. Andorf, I.V. Bazarov, L. Cultrera, C.J.R. Duncan, A. Galdi, J.M. Maxson, C.A. Pennington
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work was supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams.
Alkali antimonides photocathodes are a popular choice of electron source for high average brightness beams, due to their high quantum efficiency (QE) and low mean transverse energy (MTE). This paper describes the first measurements of their nonlinear photoemission properties under sub-ps laser illumination. These measurements include wavelength-resolved power dependence, pulse length dependence, and temporal response. The transition between linear and nonlinear photoemission is observed through the wavelength-resolved scan, and implications of nonlinear photoemission are discussed.

Poster MOPLH14 [0.543 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH14

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paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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MOPLH17

Enhanced Robustness of GaAs-Based Photocathodes Activation by Cs, Sb, and O2

cathode, polarization, vacuum, extraction

210

J. Bae, L. Cultrera, A. Galdi, F. Ikponmwen
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
I.V. Bazarov, J.M. Maxson
Cornell University, Ithaca, New York, USA

Funding: This work is funded by Department of Energy: DE-SC0016203.
Operational lifetime of GaAs photocathodes is the primary limit for applications as high current spin polarized electron sources in future nuclear physics facilities, such as Electron Ion Collider. Recently, ultrathin Cs₂Te on GaAs has shown a successful negative electron affinity (NEA) activation with an improved lifetime by a factor of 5 *. In this work, we report activation of GaAs with Cs, Sb and oxygen. Four different methods of introducing oxygen during the growth was investigated. Cs-Sb-O activated GaAs has shown up to a factor of 40 and 13 improvement in charge extraction lifetime and dark lifetime, respectively.
* Bae, et al. (2018). Rugged spin-polarized electron sources based on negative electron affinity GaAs photocathode with robust Cs₂Te coating. Applied Physics Letters, 112(15), 154101.

Poster MOPLH17 [0.926 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH17

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paper received ※ 28 August 2019 paper accepted ※ 01 September 2019 issue date ※ 08 October 2019

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MOPLH19

Beam Dynamics Simulations for a Conduction-Cooled Superconducting RF Electron Source

cathode, simulation, emittance, experiment

213

O. Mohsen, V. Korampally, A. McKeown, D. Mihalcea, P. Piot, I. Salehinia
Northern Illinois University, DeKalb, Illinois, USA
R. Dhuley, M.G. Geelhoed, J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA

Funding: Work supported by DOE awards DE-SC0018367 with NIU and DE-AC02-07CH11359
The development of robust and portable high-average power electron sources is key to many societal applications. An approach toward such sources is the use of cryogen-free superconducting radiofrequency cavities. This paper presents beam-dynamics simulations for a proof-of-principle experiment on a cryogen-free SRF electron source being prototyped at Fermilab. The proposed design implement a geometry that enhances the electric field at the cathode surface to simultaneously extract and accelerate electrons. In this paper, we explore the beam dynamics considering both the case of field and photoemission mechanism.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH19

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paper received ※ 02 September 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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MOPLH22

Focusing Studies of an Electron Beam in Diamond Field Emitter Array Cathodes

cathode, experiment, focusing, laser

217

R.L. Fleming, H.L. Andrews, D. Gorelov, C.-K. Huang, D. Kim, J.W. Lewellen, K.E. Nichols, V.N. Pavlenko, E.I. Simakov
LANL, Los Alamos, New Mexico, USA

Funding: Los Alamos National Laboratory LDRD Program
We present the simulations and test results for focusing studies performed on diamond field emitter array cathodes. This design utilized a simple variable-focus solenoidal lens in conjunction with a scanning wire technique in order to measure the beam spot size. The spot size was measured by scanning a thin copper wire across the beam in 1 µm increments, with voltage being measured and averaged at each location in order to map the location and intensity of the beam. Scans were taken at different distances away from the magnetic center of the lens, and show good agreement with our simulations of the beam. Ultimately this has allowed us to focus the beam to a spot size of 5.72 µm with an average current of 15.78 µA.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH22

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paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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MOPLH24

Towards the Optimization Of Photocathode Properties Via Surface Science Techniques: A Study On Cs3Sb Thin Film Growth

cathode, vacuum, laser, emittance

224

A. Galdi, J. Balajka, W.J.I. DeBenedetti, M. Hines
Cornell University, Ithaca, New York, USA
I.V. Bazarov, L. Cultrera, F. Ikponmwen, J.M. Maxson, S.A. McBride
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: National Science Foundation Grant No. PHY-1549132
A better understanding of the properties of photocathode materials can be achieved by integrating advanced growth and surface science techniques in their synthesis and analysis. This is a main research theme of the Center for Bright Beams, whose goal is increasing the brightness of linear electron accelerators. Alkali antimonides are efficient photocathode materials and have very low intrinsic emittance at cryogenic temperatures.* A limiting factors is the surface roughness and chemical inhomogeneity of the films.** We studied the influence of growth parameters on the morphology and composition of Cs3Sb thin films. The films are codeposited using pure element sources and transferred via UHV suitcase to a STM/XPS analysis chamber, to study in particular the influence of substrate temperature and material. This platform can be expanded to more analysis and growth systems thanks to a specially designed sample holder and suitcase. An example is a new cryogenic instrument for intrinsic emittance measurements.
* L. Cultrera et al., Phys. Rev. ST ’ Acc. Beams 18 (2015) 113401
** G. Gevorkian et al., Phys. Rev. Accel. Beams, 21 (2018) 093401

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH24

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paper received ※ 28 August 2019 paper accepted ※ 30 August 2019 issue date ※ 08 October 2019

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MOPLH25

Characterization of Femtosecond-Laser-Induced Electron Emission from Diamond Nano-Tips

laser, FEM, photon, polarization

228

V.N. Pavlenko, H.L. Andrews, R.L. Fleming, D. Gorelov, D. Kim, E.I. Simakov
LANL, Los Alamos, New Mexico, USA
D.S. Black, K.J. Leedle
Stanford University, Stanford, California, USA

Funding: LANL Laboratory Directed Research and Development (LDRD).
Nanocrystalline diamond is a promising material for electron emission applications, as it combines robustness of diamond and ability to easily conform to a pre-defined shape, even at nano-scale. However, its electron emission properties are yet to be fully understood. Recently, we started to investigate femtosecond-laser-induced strong-field photoemission from nanocrystalline diamond field emitters with very sharp (~10 nm apex) tips. Initial results show that the mechanism of electron emission at ~10¹⁰ W/cm² light intensities in the near UV to near IR range is more complex than in metals. We present our latest experimental results obtained at Stanford University, while LANL’s strong-field photoemission test stand is being commissioned. We show that strong-field photoemission occurs not only at the nano-tip’s apex, but also on flat diamond surfaces (e.g., pyramid sides), that is why extra care needs to be taken to differentiate between emission spots on the chip. Qualitatively, we discuss the models that explain the observed dependences of electron emission on the optical power, polarization of the light, etc.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH25

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paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019

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MOPLH26

Design of a Compact Wakefield Accelerator Based on a Corrugated Waveguide

GUI, wakefield, coupling, simulation

232

A.E. Siy
UW-Madison/PD, Madison, Wisconsin, USA
G.J. Waldschmidt, A. Zholents
ANL, Lemont, Illinois, USA

A compact wakefield accelerator is being developed at the Argonne National Laboratory for a future multiuser x-ray free electron laser facility. A cylindrical structure with a 2 mm internal diameter and fine corrugations on the wall will be used to create Čerenkov radiation. A "drive" bunch producing radiation at 180 GHz will create accelerating gradients on the order of 100 MV/m for the "witness" bunch. The corrugated structure will be approximately half meter long with the entire accelerator spanning a few tens of meters. An ultra-compact transition region between each corrugated structure has been designed to accommodate an output coupler, a notch filter, an integrated offset monitor, bellows, pumping and water cooling ports. The output coupler will extract on the order of a kilowatt of power from the Čerenkov radiation unused by the witness bunch. The integrated offset monitor is a novel diagnostic which will measure the cumulative offset of the electron beam in the corrugated structure upstream of the monitor. The specific details of the rf design will be presented here.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH26

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paper received ※ 27 August 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019

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MOPLO01

A Beam Spreader System for LCLS-II

kicker, septum, undulator, FEL

236

T.G. Beukers, J.W. Amann, Y.M. Nosochkov
SLAC, Menlo Park, California, USA

For the LCLS-II project, the SLAC National Accelerator Laboratory is installing a new superconducting RF linac capable of continuously delivering 4 GeV electron bunches spaced 1.1 microseconds apart. A spreader system is required to distribute the beam between a soft X-ray or hard X-ray undulator, and a beam dump. An additional beam diverter is required in the front end of the linac to divert 100 MeV electrons to a diagnostic line. Both the spreader and diagnostic diversion systems are designed to operate on a bunch by bunch basis via the combination of fast kickers and a Lambertson septum. This paper presents a summary of the optics, kicker, and septum design. Of specific interest is the unique challenge associated with building a high repetition, high stability, spreader capable of diverting a single bunch without disturbing neighboring bunches. Additional discussion includes the application of the spreader technology to the proposed DASEL/S30XL beamline. This beamline will acceptμbunches evenly spaced between the undulator bound bunches, thus requiring a kicker with the same repetition rate as LCLS-II but a pulse width extended to approximately 600 ns.

Poster MOPLO01 [1.256 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO01

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paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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MOPLO04

Progress in Time-Resolved MeV Transmission Electron Microscopy at UCLA

quadrupole, cavity, alignment, detector

243

P.E. Denham
UCLA, Los Angeles, USA

We describe here two new enhancements developed for the time-resolved microscope at the UCLA PEGASUS Lab based on the use of a radiofrequency photoinjector as an ultrafast electron source and permanent magnet quadrupoles as electron lenses. The first enhancement is a flexible optical column design including hybrid-style stronger focusing quadrupoles, yielding a 60% magnification increase, and a collimator to improve imaging contrast. This new optical system will have the ability to switch between real-space imaging and diffraction pattern imaging with variable magnification. The second enhancement is a high-frequency (X-band) cavity downstream from the (S-band) photoinjector to reduce the beam energy spread. These enhancements are crucial for improving contrast and image quality. In addition, a pulse-wire alignment method to fiducialize the quadrupole positions to better than 20-um precision is used to reduce the aberrations induced by misalignment and achieve spatial resolution at the 20 nm-level.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO04

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paper received ※ 28 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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MOPLO06

Black Gun Technologies for DC Photoinjectors

gun, vacuum, laser, scattering

247

E.J. Montgomery, C. Jing, S. Poddar
Euclid Beamlabs LLC, Bolingbrook, USA
J.E. Butler
Euclid TechLabs, LLC, Solon, Ohio, USA
S. Zhang
JLab, Newport News, Virginia, USA

Funding: Work supported by the US DOE Office of Science, Office of Nuclear Physics, grant number DESC0019688. Work at Argonne CNM under Contract No. DE-AC02-06CH11357.
Euclid Beamlabs is developing a new "Black Gun" concept in direct current (DC) photoinjectors. To reduce electron-stimulated desorption indirectly influenced by stray photoemission, we are testing advanced optical coatings and low-scattering optics compatible with the extreme high vacuum (XHV) environment of modern DC photoinjectors. Stray light in DC photoinjectors (in proportion to the photoemitted charge) causes off-nominal photoemission, initiating electron trajectories which intercept downstream surfaces. This causes electron-stimulated desorption of atoms, which ionize and may back-bombard the cathode, reducing its charge lifetime. Back-bombardment is key for high average current or high repetition rate. First, we report on progress developing optical skimmers based on Butler baffles to collimate both incoming and outgoing laser beams. Second, we describe candidate coatings for reduction of scattered light. Requirements for these coatings are that they be conducting, optically black at the drive laser wavelength, conformally applied to complex geometry, and XHV-compatible with negligible outgassing.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO06

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paper received ※ 04 September 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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MOPLO12

The RF BPM Pickup Electrodes Development for the APS-MBA Upgrade

pick-up, vacuum, simulation, storage-ring

256

X. Sun, R.M. Lill
ANL, Lemont, Illinois, USA

Beam stability is critical for the Advanced Photon Source (APS) multi-bend achromat (MBA) lattice up-grade and will employ 560 radio frequency (RF) beam position monitors (BPMs). The RF BPMs will provide the primary measurement of the electron beam. Design goals for the BPM assembly include high sensitivity, low wakefield impedance, and ultra-mechanically stability. The design, electromagnetic simulation, manufacturing tolerance and prototype testing will be presented in this paper.
*Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO12

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paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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MOPLO13

Field Quality Analysis of Interaction Region Quadrupoles for JLEIC

quadrupole, collider, interaction-region, operation

259

G.L. Sabbi
LBNL, Berkeley, California, USA
B.R. Gamage, T.J. Michalski, V.S. Morozov, R. Rajput-Ghoshal, M. Wiseman
JLab, Newport News, Virginia, USA
Y.M. Nosochkov, M.K. Sullivan
SLAC, Menlo Park, California, USA

Funding: Work supported by the US Department of Energy Office of Science.
The JLEIC physics goals of high luminosity and a full acceptance detector result in significant design challenges for the Interaction Region quadrupoles. Key requirements include large aperture, high field, compact transverse and longitudinal dimensions, and tight control of the field errors. In this paper, we present and discuss field quality estimates for the IR Quadrupoles of both electron and ion beamlines, obtained by integrating experience from pre-vious projects with realistic designs consistent with the specific requirements of the JLEIC collider.

Poster MOPLO13 [0.847 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO13

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paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019

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MOPLO23

Investigation of Various Fabrication Methods to Produce a 180GHz Corrugated Waveguide Structure in 2mm Diameter 0.5m Long Copper Tube for the Compact Wakefield Accelerator for FEL Facility

GUI, laser, wakefield, FEL

286

K.J. Suthar, D.S. Doran, W.G. Jansma, S.S. Sorsher, E. Trakhtenberg, G.J. Waldschmidt, A. Zholents
ANL, Lemont, Illinois, USA
A.E. Siy
UW-Madison/PD, Madison, Wisconsin, USA

Funding: This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility operated by the Argonne National Laboratory under Contract No. DEAC0206CH11357.
Argonne National Laboratory is developing a 180 GHz wakefield structure that will house in a co-linear array of accelerators to produce free-electron laser-based X-rays. The proposed corrugated waveguide structure will be fabricated on the internal wall of 0.5m long and 2mm nominal diameter copper tube. The estimated dimensions of these parallel corrugations are 200 µm in pitch with 100 µm side length (height and width). The length scale of the structure and requirements of the magnetic field-driven dimensional tolerances have made the structure challenging to produce. We have employed several method such as optical lithography, electroforming, electron discharge machining, laser ablation, and stamping to produce the initial structure from a sheet form. The successive fabrication steps, such as bending, brazing, and welding, were performed to achieve the long tubular-structure. This paper discusses various fabrication techniques, characterization, and associated technical challenges in detail.
[1] A. Zholents et al., Proc. 9-th Intern. Part. Acc. Conf., IPAC2018, Vancouver, BC, Canada, p. 1266, (2018)

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO23

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paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019

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TUYBA4

Optimization of an SRF Gun Design for UEM Applications

SRF, gun, laser, cavity

305

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

Funding: DOE contract DE-SC0018621
Benefiting from the rapid progress on RF photocathode gun technologies in the past two decades, the development of MeV-range ultrafast electron diffraction/microscopy (UED and UEM) has been identified as an enabling instrumentation, which may lead to breakthroughs in fundamental science and applied technologies *. Euclid is designing an SRF cavity as the UEM electron gun. As implementing a solenoid for emittance compensation in the gun is limited by the superconductivity performance and available space, the geometry of the first 0.3 cell of the cavity is optimized for transverse focusing and emittance reduction.
*: T. Chase, et al, "Ultrafast electron diffraction from non- equilibrium phonons in femtosecond laser heated Au films." Applied Physics Letters, 2016

Slides TUYBA4 [7.583 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUYBA4

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paper received ※ 30 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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TUYBB2

Manipulating H⁻ Beams with Lasers

laser, proton, extraction, emittance

309

A. Rakhman, A.V. Aleksandrov, S.M. Cousineau, T.V. Gorlov, Y. Liu, A.P. Shishlo
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
In recent years lasers have been playing a vital role in many H− beam measurements and experiments. This talk will review current state of development of various applications using lasers for manipulating H− ion beams in accelerators. A wide range of applications will be reviewed such as beam diagnostics, laser-assisted charge-exchange injection, generation of arbitrary H⁰ pulse patterns and others. An overview of ongoing developments and prospects for other laser H− beam interactions will also be given.

Slides TUYBB2 [16.483 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUYBB2

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paper received ※ 28 August 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019

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TUYBB5

Design and Analysis of a Halo-Measurement Diagnostics

diagnostics, radiation, optics, experiment

322

C.J. Marshall, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
S.V. Benson, J. Gubeli
JLab, Newport News, Virginia, USA
P. Piot, J. Ruan
Fermilab, Batavia, Illinois, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear physics under contract DE-AC05-06OR23177 and DE-AC02-07CH11359.
A large dynamical-range diagnostics (LDRD) design at Jefferson Lab will be used at the FAST-IOTA injector to measure the transverse distribution of halo associated with a high-charge electron beam. One important aspect of this work is to explore the halo distribution when the beam has significant angular momentum (i.e. is magnetized). The beam distribution is measured by recording radiation produced as the beam impinges a YAG:Ce screen. The optical radiation is split with a fraction directed to a charged-couple device (CCD) camera. The other part of the radiation is reflected by a digital micromirror device (DMD) that masks the core of the beam distribution. Combining the images recorded by the two cameras provides a measurement of the transverse distribution with over a large dynamical range. The design and analysis of the optical system will be discussed including optical simulation using SRW and the result of a mockup experiment to test the performances of the system will be presented.

Slides TUYBB5 [3.013 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUYBB5

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paper received ※ 02 September 2019 paper accepted ※ 13 September 2019 issue date ※ 08 October 2019

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TUYBB6

Beam Dynamics in a High Gradient RF Streak Camera

cathode, experiment, photon, gun

326

F. Toufexis, V.A. Dolgashev, A. Landa
SLAC, Menlo Park, California, USA

Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515.
Traditionally, time-resolved experiments in storage ring synchrotron light sources and free-electron lasers are performed with short x-ray pulses with time duration smaller than the time resolution of the phenomenon under study. Typically, storage-ring synchrotron light sources produce x-ray pulses on the order of tens of picoseconds. Newer diffraction limited storage rings produce even longer pulses. We propose to use a high-gradient RF streak camera for time-resolved experiments in storage-ring synchrotron light sources with potential for sub-100 fs resolution. In this work we present a detailed analysis of the effects of the initial time and energy spread of the photo-emitted electrons on the time resolution, as well as a start-to-end beam dynamics simulation in an S-Band system.
* F. Toufexis, et al, "Sub-Picosecond X-Ray Streak Camera using High-Gradient RF Cavities", in Proceedings of IPAC’19.

Slides TUYBB6 [5.958 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUYBB6

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paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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TUZBA1

Commissioning of the Electron Accelerator LEReC for Bunched Beam Cooling

cavity, operation, cathode, gun

330

D. Kayran, Z. Altinbas, D. Bruno, M.R. Costanzo, K.A. Drees, A.V. Fedotov, W. Fischer, M. Gaowei, D.M. Gassner, X. Gu, R.L. Hulsart, P. Inacker, J.P. Jamilkowski, Y.C. Jing, J. Kewisch, C.J. Liaw, C. Liu, J. Ma, K. Mernick, T.A. Miller, M.G. Minty, L.K. Nguyen, M.C. Paniccia, I. Pinayev, V. Ptitsyn, V. Schoefer, S. Seletskiy, F. Severino, T.C. Shrey, L. Smart, K.S. Smith, A. Sukhanov, P. Thieberger, J.E. Tuozzolo, E. Wang, G. Wang, W. Xu, A. Zaltsman, H. Zhao, Z. Zhao
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The brand-new state of the art electron accelerator, LEReC, was built and commissioned at BNL. LEReC accelerator includes a photocathode DC gun, a laser system, a photocathode delivery system, magnets, beam diagnostics, a SRF booster cavity, and a set of Normal Conducting RF cavities to provide sufficient flexibility to tune the beam in the longitudinal phase space. Electron beam quality suitable for cooling in the Relativistic Heavy Ion Collider (RHIC) was achieved [1], which lead to the first demonstration of bunched beam electron cooling of hadron beams [2]. This presentation will discuss commissioning results, achieved beam parameters and performance of the LEReC systems.
[1] D.Kayran et al., First results from Commissioning of LEReC, in Proc of IPAC2019
[2] A.Fedotov et al., First electron cooling of hadron beams using a bunched electron beam, presented at NAPAC2019

Slides TUZBA1 [18.343 MB]

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paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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TUZBA2

Electron Ion Collider Machine Detector Interface

detector, hadron, quadrupole, collider

335

B. Parker, E.C. Aschenauer, A. Kiselev, C. Montag, R.B. Palmer, V. Ptitsyn, F.J. Willeke, H. Witte
BNL, Upton, New York, USA
M. Diefenthaler, Y. Furletova, T.J. Michalski, V.S. Morozov, D. Romanov, A. Seryi, R. Yoshida
JLab, Newport News, Virginia, USA
C. Hyde
ODU, Norfolk, Virginia, USA
M.K. Sullivan
SLAC, Menlo Park, California, USA

This presentation summarizes the physics requirements as they translate into accelerator requirements at the machine-detector interface. Unique aspects of the Interaction Region and detector acceptance – unique to an Electron Ion Collider – are summarized. Designs of both site-specific concepts are outlined.

Slides TUZBA2 [13.525 MB]

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paper received ※ 29 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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TUZBA3

A High-Energy Design for JLEIC Ion Complex

booster, proton, collider, linac

341

B. Mustapha, J.L. Martinez Marin
ANL, Lemont, Illinois, USA
Y.S. Derbenev, F. Lin, V.S. Morozov, Y. Zhang
JLab, Newport News, Virginia, USA

Funding: This work was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357 for ANL and by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357.
A recent assessment of the scientific merit for a future Electron Ion Collider (EIC) in the US, by the National Academy of Sciences, found that such a facility would be unique in the world and would answer science questions that are compelling, fundamental, and timely. This assessment confirmed the recommendations of the 2015 Nuclear Science Advisory Committee for an EIC with highly polarized beams of electrons and ions, sufficiently high luminosity and variable center-of-mass (CM) energy. The baseline design of Jefferson Lab Electron-Ion Collider (JLEIC) has been updated to 100 GeV CM energy, corresponding to 200 GeV proton energy. We here present a high-energy design for the JLEIC ion complex. It consists of a 135 MeV injector linac, a 6-GeV non figure-8 pre-booster ring and a 40-GeV large ion booster, which could also serve as electron storage ring (e-ring). The energy choice in the accelerator chain is beneficial for a future upgrade to 140 GeV CM energy. The large booster is designed with the same shape and size of the original e-ring allowing for the option of building separate electron and ion rings by stacking them in the same tunnel along with the ion collider ring.

Slides TUZBA3 [5.435 MB]

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paper received ※ 03 September 2019 paper accepted ※ 25 November 2019 issue date ※ 08 October 2019

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TUZBA4

Interaction Region Magnets for Future Electron-Ion Collider at Jefferson Lab

quadrupole, solenoid, interaction-region, collider

345

R. Rajput-Ghoshal, C. Hutton, F. Lin, T.J. Michalski, V.S. Morozov, M. Wiseman
JLab, Newport News, Virginia, USA

The Jefferson Lab Electron Ion Collider (JLEIC) is a proposed new machine for nuclear physics research. It uses the existing CEBAF accelerator as a full energy injector to deliver 3 to 12 GeV electrons into a new electron collider ring. An all new ion accelerator and collider complex will deliver up to 200 GeV protons. The machine has luminosity goals of 10³⁴ cm^-2 ses⁻¹. The whole detector region including forward detection covers about 80 meters of the JLEIC complex. The interaction region design has recently been optimized to accommodate 200 GeV proton energy using conventional NbTi superconducting magnet technology. This paper will describe the requirements and preliminary designs for both the ion and electron beam magnets in the most complex 32 m long interaction region (IR) around the interaction point (IP). The interaction region has over thirty-seven superconducting magnets operating at 4.5K; these include dipoles, quadrupoles, skew-quadrupoles, solenoids, horizontal and vertical correctors and higher order multipole magnets. The paper will also discuss the electromagnetic interaction between these magnets.

Slides TUZBA4 [6.444 MB]

Poster TUZBA4 [1.549 MB]

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paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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TUZBB3

Precise Beam Velocity Matching for the Experimental Demonstration of Ion Cooling With a Bunched Electron Beam

factory, beam-cooling, acceleration, dipole

356

S. Seletskiy, M. Blaskiewicz, K.A. Drees, A.V. Fedotov, W. Fischer, D.M. Gassner, R.L. Hulsart, D. Kayran, J. Kewisch, K. Mernick, R.J. Michnoff, T.A. Miller, G. Robert-Demolaize, V. Schoefer, H. Song, P. Thieberger, P. Wanderer
BNL, Upton, New York, USA

The first ever electron cooling based on the RF acceleration of electron bunches was experimentally demonstrated on April 5, 2019 at the Low Energy RHIC Electron Cooler (LEReC) at BNL. The critical step in obtaining successful cooling of the Au ion bunches in the RHIC cooling sections was the accurate matching of average longitudinal velocities of electron and ion beams corresponding to a relative error of less than 5·10^-4 in the e-beam momentum. Since the electron beam kinetic energy is just 1.6 MeV, measuring the absolute e-beam energy with sufficient accuracy and eventually achieving the electron-ion velocity matching was a nontrivial task. In this paper we describe our experience with measuring and setting the e-beam energy at LEReC.

Slides TUZBB3 [1.340 MB]

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paper received ※ 26 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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TUZBB4

Space Charge Study of the Jefferson Lab Magnetized Electron Beam

laser, cathode, space-charge, gun

360

S.A.K. Wijethunga, J.R. Delayen, G.A. Krafft
ODU, Norfolk, Virginia, USA
J.F. Benesch, F.E. Hannon, C. Hernandez-Garcia, G.A. Krafft, M.A. Mamun, M. Poelker, R. Suleiman, S. Zhang
JLab, Newport News, Virginia, USA

Magnetized electron cooling could result in high luminosity at the proposed Jefferson Lab Electron-Ion Collider (JLEIC). In order to increase the cooling efficiency, a bunched electron beam with high bunch charge and high repetition rate is required. We generated magnetized electron beams with high bunch charge using a new compact DC high voltage photo-gun biased at -300 kV with alkali-antimonide photocathode and a commercial ultrafast laser. This contribution explores how magnetization affects space charge dominated beams as a function of magnetic field strength, gun high voltage, laser pulse width, and laser spot size.

Slides TUZBB4 [12.582 MB]

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paper received ※ 28 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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TUZBB5

Transverse Ion Beam Emittance Growth Due to Low Frequency Instabilities in Microwave Ion Source Plasma

plasma, emittance, experiment, HOM

363

C. Mallick, M. Bandyopadhyay, R. Kumar
Institute for Plasma Research, Bhat, Gandhinagar, India

The ion source is accompanied by the generation of low frequency (LF) plasma instabilities (PI). Its signature is also visible in high current heavy ion beam required for any accelerator. These LFs affect the profile of the ion beam in transverse phase-space. These issues are investigated in detail by measuring the emittance of beam. Beam oscillations are extracted from the transverse emittance data by taking Fast Fourier Transform (FFT) of it. PI frequencies are identified in the measured electromagnetic emission from the plasma, in which these frequencies appeared as sidebands around pump frequency 2.45 GHz. The PI components i.e.,ion acoustic (IA) and ion cyclotron (IC) waves are also visible in the FFT spectra. Low and high frequency oscillations in the beam are 476 kHz and ~1.3 MHz respectively. These two groups of frequencies also exist within the PI induced IA (238 - 873 kHz) and IC (1.29 - 1.3 MHz) frequency ranges. The measured emittance (rms-normalized) in horizontal and vertical phase-space varies from 0.002-0.098 𝜋 mm mrad and 0.004-0.23 𝜋 mm mrad respectively. PI induced beam oscillation is the reason behind such broad transverse emittance growth.
Reference
’S. Kumar et al.,Phys. Rev. Accel. Beams 21, 093402 (2018)’
’R. D’Arcy et al., Nucl. Instrum. Methods Phys. Res. A 815 7(2016)’
’L. Groening et al., Phys. Rev. Lett. 113, 264802 (2014)’

Slides TUZBB5 [5.298 MB]

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TUZBB6

Nonlinear Tune-Shift Measurements in the Integrable Optics Test Accelerator

experiment, optics, lattice, betatron

368

S. Szustkowski, S. Chattopadhyay
Northern Illinois University, DeKalb, Illinois, USA
S. Chattopadhyay, A.L. Romanov, A. Valishev
Fermilab, Batavia, Illinois, USA
N. Kuklev
University of Chicago, Chicago, Illinois, USA

Funding: US Department of Energy, Office of High Energy Physics, General Accelerator Research and Development (GARD) Program
The first experimental run of Fermilab’s Integrable Optics Test Accelerator (IOTA) ring aimed at testing the concept of nonlinear integrable beam optics. In this report we present the preliminary results of the studies of a nonlinear focusing system with two invariants of motion realized with the special elliptic-potential magnet. The key measurement of this experiment was the horizontal and vertical betatron tune shift as a function of transverse amplitude. A vertical kicker strength was varied to change the betatron amplitude for several values of the nonlinear magnet strength. The turn-by-turn positions of the 100 MeV electron beam at twenty-one beam position monitors around the ring were captured and used for the analysis of phase-space trajectories.

Slides TUZBB6 [12.888 MB]

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TUPLM07

First Experimental Observations of the Plasma-Cascade Instability in the CeC PoP Accelerator

plasma, experiment, lattice, solenoid

379

I. Petrushina
SUNY SB, Stony Brook, New York, USA
Y.C. Jing, V. Litvinenko, J. Ma, I. Pinayev, G. Wang, Y.H. Wu
BNL, Upton, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA
K. Shih
SBU, Stony Brook, New York, USA

Preservation of the beam quality is important for attaining the desirable properties of the beam. Collective effects can produce an instability severely degrading beam emittance, momentum spread and creating filamentation of the beam. Microbunching instability for beams traveling along a curved trajectory, and space charge driven parametric transverse instabilities are well-known and in-depth studied. However, none of the above include a microbunching longitudinal instability driven by modulations of the transverse beam size. This phenomenon was observed for the first time during the commissioning of the CeC PoP experiment. Based on the dynamics of this instability we named it a Plasma-Cascade Instability (PCI). PCI can strongly intensify longitudinal micro-bunching originating from the beam’s shot noise, and even saturate it. Resulting random density and energy microstructures in the beam can become a serious problem for generating high quality electron beams. On the other hand, such instability can drive novel high-power sources of broadband radiation. In this paper we present our experimental observations of the PCI and the supporting results of the numerical simulations.

Poster TUPLM07 [17.319 MB]

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TUPLM11

Beam-Beam Damping of the Ion Instability

simulation, storage-ring, damping, feedback

391

M. Blaskiewicz
BNL, Upton, New York, USA

Funding: Work Supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Beam-Beam damping of the Ion Instability The electron storage ring of the proposed electron ion collider at BNL has bunch charges as large as 50 nC and bunch spacings as small as 10 ns. For molecules like CO a dangerous buildup of positive ions is possible and a significant fraction of these ions can survive allowable clearing gaps. The instability is thus multi-turn and the weak damping required to stop the ion instabilty with an ideal clearing gap is ineffective here. The beam-beam force is highly nonlinear and a potent source of tune spread. Simulations employing several macro-particles per electron bunch and several ion macroparticles are used to estimate maximum gas densities for some common molecules. A simplified model is introduced and compared with simulations.

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paper received ※ 26 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

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TUPLM13

Two-Energy Storage-Ring Electron Cooler for Relativistic Ion Beams

cavity, storage-ring, emittance, damping

399

B. Dhital, J.R. Delayen, G.A. Krafft
ODU, Norfolk, Virginia, USA
J.R. Delayen, Y.S. Derbenev, D. Douglas, G.A. Krafft, F. Lin, V.S. Morozov, Y. Zhang
JLab, Newport News, Virginia, USA

An electron beam based cooling system for the ion beam is one of the commonly used approaches. The proposed two’energy storage-ring electron cooler consists of damping and cooling sections at markedly different energies connected by an energy recovering superconducting RF structure. The parameters in the cooling and damping sections are adjusted for optimum cooling of a stored ion beam and for optimum damping of the electron beam respectively. This paper briefly describes a two cavities model along with a third cavity model to accelerate and decelerate the electron beam in two energy storage ring. Based on our assumed value of equilibrium emittance shows that these models give a bunch length of the order of cm and energy spread of the order of 〖10〗^-5 in the cooling section which are required parameters for the better cooling. Numerical calculations along with elegant simulation are presented.

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paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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TUPLM15

Arbitrary Transverse Profile Shaping using Transverse Wigglers

wiggler, controls, emittance, focusing

403

G. Ha, M.E. Conde, J.G. Power
ANL, Lemont, Illinois, USA

Funding: This work is supported by the U.S. Department of Energy, Offices of HEP and BES, under Contract No. DE-AC02-06CH11357.
Argonne Wakefield Accelerator (AWA) group demonstrated arbitrary longitudinal shaping capability of thee emittance exchange (EEX) beamline in 2016. Several different transverse masks were used to shape the beam transversely, and the transmission through the mask was around 40%. The masking is one of the easiest ways to control the profile, but this low transmission would make significant drop of the beam quality due to a higher charge requirement in the gun, and it can make thermal issues for high repetition rate or high intensity beams. At the same time, it only controls the profile not a 2D phase space. We recently proposed a scheme to generate a tunable bunch train using a EEX beamline with a transverse wiggler. This wiggler provides a sinusoidal magnetic field which makes a sinusoidal modulation on the transverse phase space. If the beam passes series of transverse wigglers with different period and strength, one can make arbitrary correlation on the horizontal position and momentum. It opens up totally new way to control all longitudinal properties including arbitrary current profile shaping without charge loss. In this poster, we present the concept of the work and plan.

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paper received ※ 02 September 2019 paper accepted ※ 13 September 2019 issue date ※ 08 October 2019

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TUPLM18

Improving Energy Resolution and Compensating Chromatic Aberration With a TM010 Microwave Cavity

cavity, gun, simulation, laser

411

C.J.R. Duncan
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
P. Cueva, J.M. Maxson, D.A. Muller
Cornell University, Ithaca, New York, USA

Funding: National Science Foundation under Award OIA-1549132, the Center for Bright Beams
The intrinsic energy spread of electron sources limits the achievable resolution of electron microscopes in both spectroscopic and spatially resolved measurements. We propose that the TM010 mode of a single radio frequency (RF) cavity be used to dramatically reduce this energy spread in a pulsed beam. We show with analytic approximations, confirmed in simulations, that the non-linear time-energy correlations that develop in an electron gun can be undone by the RF cavity running near-crest. We derive an expression that gives the required RF field strength as a function of accelerating voltage. We explore multiple applications, including EELS and SEM. By pulsing a photocathode with commercially available, high repetition-rate lasers, our scheme could yield competitive energy spread reduction at higher currents when compared with monochromated continuous-wave sources for electron microscopes.

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paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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TUPLM20

Generation of High-Charge Magnetized Electron Beams Consistent With JLEIC Electron Cooling Requirements

emittance, cathode, simulation, experiment

414

A.T. Fetterman, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
S.V. Benson, F.E. Hannon, S. Wang
JLab, Newport News, Virginia, USA
D.J. Crawford, D.R. Edstrom, P. Piot, J. Ruan
Fermilab, Batavia, Illinois, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear physics under contract DE-AC05-06OR23177 and DE-AC02-07CH11359.
The proposed Jefferson Lab Electron-Ion Collider (JLEIC), currently under design, relies on electron cooling in order to achieve the desired luminosity. This includes an electron beam with >55 Mev, 3.2 nC bunches that cools hadron beams with energies up to 100 GeV. To enhance the cooling, the electron beam must be magnetized with a specific eigen-emittance partition. This paper explores the use of the Fermilab Accelerator Science and Technology (FAST) facility to demonstrate the generation of an electron beam with parameters consistent with those required in the JLEIC high-energy cooler. We demonstrate via simulations the generation of the required electron-beam parameters and perform a preliminary experiment to validate FAST capabilities to produce such beams.

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paper received ※ 07 September 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019

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TUPLM21

Optical Stochastic Cooling Program at Fermilab’s Integrable Optics Test Accelerator

experiment, radiation, lattice, optics

418

J.D. Jarvis, S. Chattopadhyay, V.A. Lebedev, H. Piekarz, P. Piot, A.L. Romanov, J. Ruan
Fermilab, Batavia, Illinois, USA
S. Chattopadhyay, P. Piot
Northern Illinois University, DeKalb, Illinois, USA

Funding: Fermi National Accelerator Laboratory is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Beam cooling enables an increase of peak and average luminosities and significantly expands the discovery potential of colliders. Optical Stochastic Cooling (OSC) is a high-bandwidth cooling technique that will advance the present state-of-the-art, stochastic-cooling rate by more than three orders of magnitude. A proof-of-principle demonstration with protons or heavy ions involves prohibitive costs, risks and technological challenges; however, exploration of OSC with electrons is a cost-effective alternative for studying the beam-cooling physics, optical systems and diagnostics. The ability to demonstrate OSC was a key requirement in the design of Fermilab’s Integrable Optics Test Accelerator (IOTA) ring. The IOTA program will explore the physics and technology of OSC in amplified and non-amplified configurations. We also plan to investigate the cooling and manipulation of a single electron stored in the ring. The OSC apparatus is currently being fabricated, and installation will begin in the fall of 2019. In this contribution, we will describe the IOTA OSC program, the upcoming passive-OSC experimental runs and ongoing preparations for an amplified-OSC experiment

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paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019

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TUPLM22

Off Axis Dependence of Current Dependent Coherent Tune Shifts in the UMER Ring

experiment, space-charge, dipole, storage-ring

422

D.F. Sutter, B.L. Beaudoin, L. Dovlatyan
UMD, College Park, Maryland, USA

Funding: Work supported by U. S. Department of Energy grant number DESC00010301
The University of Maryland Electron Ring (UMER) was built to explore space charge effects in the extreme - beyond the space charge limit of most existing storage rings. At the nominal operating kinetic energy of 10 keV, the beam is also non relativistic. We have experimentally verified that the current dependent coherent tune shift obeys the Laslett formula over a wide current range for a cylindrical geometry and non penetrating magnetic fields when the beam is on axis; i.e. the average closed orbit displacement around the ring is essentially zero.* In the current experiment this measurement is extended to the change in current dependent coherent tune shift as the average closed orbit is moved off axis. It can be displaced over approximately ±10 mm of the vacuum pipe diameter of 50 mm without loss of beam. Because the 36 bending magnets in UMER are very short, we treat each of them as a local kick and then increment each by a calculated small amount to achieve the desired, global closed orbit displacement. Experimental results are compared to predictions by Zotter and others.
* D. für Sutter, M.Cornacchia, et al, "Current dependent tune shifts in the University of Maryland electron ring", NAPAC 2013.

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paper received ※ 29 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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TUPLM24

Electron Heating by Ions in Cooling Rings

radiation, proton, scattering, damping

426

H. Zhao, M. Blaskiewicz
BNL, Upton, New York, USA

Hadron beam cooling at high energy is a critical technique for Electron-Ion Colliders (EIC). We consider using an electron storage ring for the EIC at BNL. For such a cooler, the electron beam quality plays an important role since it directly determines the cooling rate. Besides the effects of IBS, space charge and synchrotron damping, which are calculable with well known methods, the heating effect by ions also needs to be carefully considered in electron beam dynamics. In this paper, we present an analytical model to calculate the heating rate by ions and give some example calculations. In addition, this model was benchmarked by applying it on the IBS calculation.
* Work supported by States Department of Energy

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paper received ※ 26 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

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TUPLM25

Connecting Gas-Scattering Lifetime and Ion Instabilities

scattering, experiment, storage-ring, vacuum

430

B. Podobedov, M. Blaskiewicz
BNL, Upton, New York, USA

Recently there is a renewed interest in fast ion instability (FII) which is of concern for future low-emittance electron storage rings, such as MBA light sources and colliders, i.e. eRHIC. While analytical theories and numerical codes exist to model the effect, due to various assumptions and limitations, accurate experimental verification is often desirable. Unfortunately, one of the most critical parameters for FII (as well as the classical "trapped-ion" instability), the residual ion concentration, is usually the most uncertain. Vacuum gauges and residual gas analyzers (RGAs) provide some useful data, but they are often not accurate enough, and, more importantly, they cannot directly probe the ion concentration along the beam orbit. In this paper we show how one could use gas-scattering lifetime measurements to infer the residual gas concentration suitable for ion instability experiment modelling.

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paper received ※ 21 September 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019

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TUPLM33

Optimization of Beam Parameters for UEM with Photo-Emission S-Band RF Gun and Alpha Magnet

gun, emittance, laser, simulation

440

H.R. Lee, P. Buaphad, I.G. Jeong, Y. Joo, Y. Kim
University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
P. Buaphad, I.G. Jeong, Y. Joo, Y. Kim
KAERI, Jeongeup-si, Republic of Korea
B.L. Cho
KRISS, Daejeon, Republic of Korea
M.Y. Han, J.Y. Lee, S.H. Lee
Korea Atomic Energy Research Institute (KAERI), Daejeon, Republic of Korea
H. Suk
GIST, Gwangju, Republic of Korea

Ultrafast Electron Microscopy (UEM) is a powerful tool to observe ultrafast dynamical processes in sample materials at the atomic level. By collaborating with KRISS and GIST, the future accelerator R&D team at KAERI has been developing a UEM facility based on a photo-emission S-band (=2856 MHz) RF gun. Recently, we have added an alpha magnet in the beamline layout of the UEM to improve beam qualities such as emittance, divergence, energy spread, and bunch length. To achieve high spatial and time resolutions, we have been optimizing those beam parameters and other machine parameters by performing numerous ASTRA and ELEGANT code simulations. In this paper, we describe our ASTRA and ELEGANT code optimizations to obtain high-quality beam parameters for the UEM facility with a photo-emission S-band RF gun and an alpha magnet.

Poster TUPLM33 [0.931 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM33

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paper received ※ 30 August 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019

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TUPLS10

Troubleshooting and Characterization of Gridded Thermionic Electron Gun

cathode, gun, controls, operation

474

M.S. Stefani
ODU, Norfolk, Virginia, USA
F.E. Hannon
JLab, Newport News, Virginia, USA

Jefferson National Laboratory has, in collaboration with Xelera research group, designed and built a gridded thermionic election gun with the potential for magnetization; in an effort to support research towards electron sources that may be utilized for the electron cooling process in the Jefferson Laboratories Electron Ion collider design. Presented here is the process and result of troubleshooting the electron gun components and operation to ensure functionality of the design.

Poster TUPLS10 [10.691 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLS10

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paper received ※ 27 August 2019 paper accepted ※ 13 September 2019 issue date ※ 08 October 2019

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TUPLS13

Evaluation of the Xilinx RFSoC for Accelerator Applications

controls, detector, interface, instrumentation

483

J.E. Dusatko
SLAC, Menlo Park, California, USA

As electronic technology has evolved, accelerator system functions (e.g. beam instrumentation, RF cavity field control, etc.) are increasingly performed in the digital domain by sampling, digitizing, processing digitally, and converting back to the analog domain as needed. A typical system utilizes analog to digital (ADC) and digital to analog (DAC) converters with intervening digital logic in a field programmable gate array (FPGA) for digital processing. For applications (BPMs, LLRF, etc.) requiring very high bandwidths and sampling rates, the design of the electronics is challenging. Silicon technology has advanced to the state where the ADC and DAC can be implemented into the same device as the FPGA. Xilinx, Inc. has released a muti-GHz sample rate RF System on Chip (RFSoC) device. It presents many advantages for implementing accelerator and particle detector systems. Because direct conversion is possible, RF analog front/back end and overall system design is simplified. This paper presents the results of an evaluation study of the RFSoC device for accelerator and detector work, including test results. It then discusses possible applications and work done at SLAC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLS13

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paper received ※ 30 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

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TUPLH03

Double-Bend Achromat Beamline for Injection Into a High-Power Superconducting Electron Linac

solenoid, gun, dipole, cavity

494

C.H. Boulware, T.L. Grimm, R. Hipple
Niowave, Inc., Lansing, Michigan, USA
S.M. Lund
FRIB, East Lansing, Michigan, USA
V.S. Morozov
JLab, Newport News, Virginia, USA

To take advantage of the high duty cycle operation of superconducting electron linacs, commercial systems use thermionic cathode electron guns that fill every RF bucket with an electron bunch. In continuous operation, the exit energy is limited when compared to pulsed systems. Bunch length and energy spread at the exit of the gun are incompatible with low losses in the superconducting cavity. A solenoid double-bend achromatic beamline is in operation at Niowave which allows energy and bunch length filtering of the beam leaving the gun before injection into the superconducting cavity. This system uses two solenoids and two dipoles to produce a round beam, using the edge angles of the dipoles to balance the focusing effects in the two transverse planes. The design allows beam filtering on the symmetry plane where the dispersion is maximum. Additionally, the bend angle moves the electron gun off the high-energy beam axis, allowing multiple-pass operation of the superconducting booster. This contribution will discuss the beam optics design of the double-bend achromat along with the design of the magnets and beam chambers and the operational experience with the system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH03

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paper received ※ 28 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

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TUPLH07

High-Gradient Short Pulse Accelerating Structures

experiment, wakefield, impedance, acceleration

500

S.V. Kuzikov, S.P. Antipov, E. Gomez
Euclid TechLabs, LLC, Solon, Ohio, USA
A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia

High gradients are necessary for lots of applications of electron accelerators. As the maximum gradient is limited by effects of RF breakdown, we present a development of an electron accelerating structure operating with a short multi-megawatt RF pulse. The structure exploits an idea to decrease the breakdown probability due to RF pulse length reduction. This concept requires to distribute RF power so that all accelerating cells are fed independently each other. This implies waveguide net system which allows to delay and to distribute properly RF radiation along the structure keeping synchronism of particles and waves. We have designed an X-band pi-mode structure including the RF design, optimization, and engineering. The structure will be tested as an RF power extractor at the Argonne Wakefield Accelerator Facility for two-beam acceleration experiments. In this regime we anticipate to obtain 10 ns, gigawatt power level RF pulses generated by train consisted of eight 25-50 nC relativistic bunches.

Poster TUPLH07 [0.999 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH07

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paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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TUPLH08

X-Ray and Charged Particle Detection by Detuning of a Microwave Resonator

laser, resonance, coupling, experiment

503

S.P. Antipov, P.V. Avrakhov, E. Dosov, E. Gomez, S.V. Kuzikov
Euclid TechLabs, LLC, Solon, Ohio, USA
S. Stoupin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia

Funding: DOE SBIR
Charged particle detection is important for beam alignment, beam loss and background control. In case of halo detection, traditional wire scanner measurement utilizing carbon or tungsten wires is limited by the damage threshold of these materials. In this paper we present an electrodeless method to measure halo with a diamond scraper. This measurement utilizes a microwave resonator placed around the diamond scraper which is sensitive to charged particle-induced conductivity. Due to this transient induced conductivity in the dielectric, a microwave coupling to the resonator changes. Diamond in this case is chosen as a radiation hard material with excellent thermal properties. The absence of electrodes makes the device robust under the beam. The same measurement can be done for x-ray flux monitoring which is important for measurement feedback and calibration at modern x-ray light sources. In this case x-rays passing through the diamond sensing element enable a photo-induced conductivity and that in turn detunes the cavity placed around the diamond. Diamond being a low-Z material allows for in-line x-ray flux measurement without significant beam attenuation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH08

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paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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TUPLH24

Performance of CeC PoP Accelerator

FEL, gun, SRF, hadron

526

I. Pinayev, Z. Altinbas, J.C. Brutus, A.J. Curcio, A. Di Lieto, T. Hayes, R.L. Hulsart, P. Inacker, Y.C. Jing, V. Litvinenko, J. Ma, G.J. Mahler, M. Mapes, K. Mernick, K. Mihara, T.A. Miller, M.G. Minty, G. Narayan, I. Petrushina, F. Severino, K. Shih, Z. Sorrell, J.E. Tuozzolo, E. Wang, G. Wang, A. Zaltsman
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Coherent electron cooling experiment is aimed for demonstration of the proof-of-principle demonstration of reduction energy spread of a single hadron bunch circulating in RHIC. The electron beam should have the required parameters and its orbit and energy should be matched to the hadron beam. In this paper we present the achieved electron beam parameters including emittance, energy spread, and other critical indicators. The operational issues as well as future plans are also discussed.

Poster TUPLH24 [11.180 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH24

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paper received ※ 29 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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TUPLO01

Dual-Function Electron Ring-Ion Booster Design for JLEIC High-Energy Option

booster, collider, quadrupole, lattice

529

J.L. Martinez Marin, B. Mustapha
ANL, Lemont, Illinois, USA
L.K. Spentzouris
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: This work was supported by the U.S. DOE, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357 for ANL and by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
As part of the alternative design approach for the Jeffer-son Laboratory Electron-Ion Collider (JLEIC) ion com-plex, the electron storage ring (e-ring) is consolidated to also serve as a large booster for the ions. The goal of reaching 16 GeV/u or higher for all ions using only room-temperature magnets forces the re-design of the e-ring because of magnetic field and lattice limitations. The new design is challenging due to several imposed constraints: (1) use of room-temperature magnets, (2) avoiding transi-tion crossing, and (3) maintaining the size and shape of the original e-ring design as much as possible. A design study is presented for a 16 GeV/u large ion booster after analyzing different alternatives that use: (1) combined-function magnets, (2) large quadrupoles or (3) quadrupole doublets in the lattice design. This design boosts the injection energy to the collider ring from 8 GeV (proton-equivalent) in the original baseline design to 16 GeV/u for all ions which is beneficial for the high-energy option of JLEIC of 200 GeV or higher. A scheme for adapting the new large ion booster design to also serve as electron storage ring is presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLO01

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paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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TUPLO04

The Latest Code Development Progress of JSPEC

simulation, emittance, collider, operation

539

H. Zhang, S.V. Benson, Y. Roblin, Y. Zhang
JLab, Newport News, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
The JLab Simulation Package on Electron Cooling (JSPEC) is an open source software developed at Jefferson Lab for electron cooling and intrabeam scattering (IBS) simulations. IBS is an important factor that leads to the growth of the beam emittance and hence the reduction of the luminosity in a high density ion collider ring. Electron cooling is an effective measure to overcome the IBS effect. Although JSPEC is initiated to fulfill the simulation needs in JLab Electron Ion Collider project, it can be used as a general design tool for other accelerators. JSPEC provides various models of the ion beam and the electron beam and it calculates the expansion rate and simulates the evolution of the ion beam under the IBS and/or electron cooling effect. In this report, we will give a brief introduction of JSPEC and then present the latest code development progress of JSPEC, including new models, algorithms, and the user interface.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLO04

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paper received ※ 20 September 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019

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TUPLO06

Weak-Strong Beam-Beam Simulation for eRHIC

proton, cavity, simulation, luminosity

545

Y. Luo, G. Bassi, M. Blaskiewicz, W. Fischer, C. Montag, V. Ptitsyn, F.J. Willeke
BNL, Upton, New York, USA
Y. Hao, D. Xu
FRIB, East Lansing, Michigan, USA
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In the eRHIC, to compensate the geometric luminosity loss due to the crossing angle, crab cavities are to be installed on both sides of the interaction point. When the proton bunch length is comparable to the wavelength of its crab cavities, protons will not be perfectly tilted in the x-z plane. In the article, we employ weak-strong beam-beam interaction model to calculate the proton beam size growth rates and luminosity degradation rate with various machine and time parameters. The goal of these studies is to optimize the the beam-beam related machine and beam parameters of eRHIC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLO06

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paper received ※ 29 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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TUPLO07

Calculation of Action Diffusion With Crabbed Collision in eRHIC

proton, cavity, simulation, luminosity

549

Y. Luo, G. Bassi, M. Blaskiewicz, W. Fischer, C. Montag, V. Ptitsyn, F.J. Willeke
BNL, Upton, New York, USA
Y. Hao, D. Xu
FRIB, East Lansing, Michigan, USA
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In the eRHIC, to compensate the geometric luminosity loss due to the crossing angle, crab cavities are to be installed on both sides of the interaction point. When the proton bunch length is comparable to the wavelength of its crab cavities, protons will not be perfectly tilted in the x-z plane. In the article, we develop a simulation code to calculate the transverse action diffusion rate as function of the initial proton longitudinal action. The goal of this study is to identify the contributions from various protons to the overall emittance growth. Tune scan is also performed to locate optimum working points which yield less proton emittance growth.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLO07

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paper received ※ 29 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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TUPLO09

Electron-Ion Collider Performance Studies With Beam Synchronization via Gear-Change

luminosity, collider, simulation, beam-beam-effects

553

I. Neththikumara, G.A. Krafft, B. Terzić
ODU, Norfolk, Virginia, USA
G.A. Krafft, Y. Roblin
JLab, Newport News, Virginia, USA

Beam synchronization of the future electron-ion collider (EIC) is studied with introducing different bunch numbers in the two colliding beams. This allows non-pairwise collisions between the bunches of the two beams and is known as "gear-change", whereby one bunch of the first beam collides with all other bunches of the second beam, one at a time. Here we report on the study of how the beam dynamics of the Jefferson Lab Electron Ion collider concept is affected by the gear change. For this study, we use the new GPU-based code (GHOST). It features symplectic one-turn maps for particle tracking and Bassetti-Erskine approach for beam-beam interactions.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLO09

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paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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TUPLO15

Multipole Effects on Dynamic Aperture in JLEIC Ion Collider Ring

multipole, quadrupole, collider, detector

559

B.R. Gamage, F. Lin, T.J. Michalski, V.S. Morozov, R. Rajput-Ghoshal, M. Wiseman
JLab, Newport News, Virginia, USA
Y. Cai, Y.M. Nosochkov, M.K. Sullivan
SLAC, Menlo Park, California, USA
G.L. Sabbi
LBNL, Berkeley, California, USA

Funding: This material is based upon work supported by the U.S. DoE under Contracts No. DE-AC05-06OR23177, DE-AC02-76SF00515, and DEAC03-76SF00098.
In a collider, stronger focusing at the interaction point (IP) for low beta-star and high luminosity produces large beams at final focusing quadrupoles (FFQs). To achieve the high luminosity requirement in the Jefferson Lab Electron-Ion Collider (JLEIC), the interaction region (IR) beta functions peak at 4.2 km in downstream FFQs. These large beta functions and FFQ multipoles reduce the dynamic aperture (DA) of the ring. A study of the multipole effects on the DA was performed to determine limits on multipoles, and to include a multipole compensation scheme to increase the DA and beam lifetime.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLO15

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paper received ※ 28 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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TUPLE04

An Iris Diaphragm Beam Detector for Halo or Profile Measurements

detector, experiment, GUI, laser

566

A. Liu
Euclid TechLabs, LLC, Solon, Ohio, USA

Funding: DOE contract DE-SC0019538
Beam halo includes the part of beam that ends up outside of the phase space of the main beam core. It can arise from field emission in the gun and accelerating structures (dark current) and be emitted independently in time and space from the photoelectric emission at the cathode generated by the drive laser. In order to fully understand and characterize the beam halo, Euclid is developing an iris diaphragm detector that allows the beam core to pass without interception, while the halo is collimated. The detector can also work for beam profile measurements. This paper discusses about the recent studies on the iris detector.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLE04

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paper received ※ 27 August 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019

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TUPLE08

Commissioning Update on RF Station #5 of AWA

high-voltage, klystron, MMI, cavity

580

W. Liu, M.E. Conde, D.S. Doran, G. Ha, J.G. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA
C. Jing
Euclid Beamlabs LLC, Bolingbrook, USA

Funding: The US Department of Energy, Office of Science
The RF system of Argonne Wakefield Accelerator (AWA) facility has grown over the years from one RF power station into 4 RF power stations. The demand for RF power keeps growing as the capability of AWA continues to grow. Now the 5th RF station is needed to fulfill the RF power needs of AWA facility. Some details regarding the construction and commissioning of the 5th RF station of AWA facility are documented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLE08

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paper received ※ 29 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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TUPLE11

Proposed Enhanced Imaging Station in the 6-GeV Booster-to-Storage Ring Transport Line for APS Upgrade

radiation, booster, emittance, linac

583

A.H. Lumpkin
Fermilab, Batavia, Illinois, USA
W. Berg, J.C. Dooling, K.P. Wootton, C. Yao
ANL, Lemont, Illinois, USA

Funding: This manuscript has been authored by FRA, LLC under Contract No.DE-AC02-07CH11359 with the U.S.DoE, Office of HEP. Work supported by U.S.DoE, Office of Science, under Contract No.DE-AC02-06CH11357.
One of the challenges of the injector for the Advanced Photon Source Upgrade (APS-U) is the measurement and monitoring of the required high charge electron beam at 6 GeV between the Booster synchrotron and the storage ring in the transport line (BTS. In APS-U charges of up to 17 nC per micropulse are specified with a beam geometrical horizontal emittance of 60 nm rad. Vertical beam sizes at the imaging station of ~80 µm (σ) are expected so system resolutions of <30 µm are warranted. A phased approach to enhance the imaging station performance has been initiated. Recently, the 20-year-old Chromox screen oriented at 45 degrees to the beam was replaced by a 100-micron thick YAG:Ce screen which gave an improved screen resolution of <10 micron(σ. However, the optical magnification of the system still needs to be increased. In addition, the high areal charge densities are expected to exceed the scintillator mechanism’s saturation threshold so an optical transition radiation (OTR) screen will be added to the station for high-charge studies. A final phase would be the use of optical diffraction radiation (ODR) as a non-intercepting, beam-size monitor during top-up injections.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLE11

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paper received ※ 22 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

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TUPLE13

Analytical Thermal Analysis of Thin Diamond in High-Intensity High-Repetition-Rate Application

laser, FEL, operation, free-electron-laser

587

Y. Hong, B. Yang
University of Texas at Arlington, Arlington, USA
J. Wu, G. Zhou
SLAC, Menlo Park, California, USA

Thin diamond plates are used in monochromator for X-ray Free-Electron Laser self-seeding scheme. To function properly, they must endure high-intensity and high-repetition-rate laser pulses without crossing thresholds set by various adverse effects, such as thermal strain-induced diffraction distortion and graphitization. In this work, a theoretical model is developed, and an analytical solution is derived to elucidate potential thermal runaway under edge cooling condition. It is shown that the crystal edge cooling can effectively mitigate the issue to a certain extent. The analytical solution can be used as an efficient tool for XFEL operation parameter setup.

Poster TUPLE13 [0.939 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLE13

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paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019

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TUPLE16

RFA Measurement of E-Cloud Generation Process at Fermilab Main Injector

acceleration, simulation, ECR, proton

595

Y. Ji
IIT, Chicago, Illinois, USA
L.K. Spentzouris
Illinois Institute of Technology, Chicago, Illinois, USA
R.M. Zwaska
Fermilab, Batavia, Illinois, USA

Fermilab aims to provide greater beam power for the neutrino physics program. As the beam power increases, the unwanted production of secondary electrons in the beam pipe, known as ‘electron cloud’ or ‘E-cloud’ may become disruptive to high intensity operation. Instrumentation has been deployed in the Fermilab Main Injector (MI) to study E-cloud. One of these is a Retard Field Analyzer (RFA) that can be used to directly measure E-cloud generation at the location of the instrument. Studies of the dependence of E-cloud on beam intensity and bunch length have been carried out. The experimental results are compared to POSINST simulations. These simulations are guided by measurements from a Secondary Electron Yield (SEY) test stand installed in the MI to measure the SEY of materials such as the beam pipe stainless steel. The SEY has a strong influence on the E-cloud density. Results of these comprehensive studies comparing the RFA data with realistic MI simulations will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLE16

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paper received ※ 28 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019

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WEXBA2

Recent Results and Opportunities at the IOTA Facility

experiment, radiation, undulator, proton

599

A.L. Romanov, D.R. Broemmelsiek, K. Carlson, D.J. Crawford, N. Eddy, D.R. Edstrom, J.D. Jarvis, V.A. Lebedev, S. Nagaitsev, J. Ruan, J.K. Santucci, V.D. Shiltsev, G. Stancari, A. Valishev, A. Warner
Fermilab, Batavia, Illinois, USA
S. Chattopadhyay, S. Szustkowski
Northern Illinois University, DeKalb, Illinois, USA
Y.K. Kim, N. Kuklev, I. Lobach
University of Chicago, Chicago, Illinois, USA

The Integrable Optics Test Accelerator (IOTA) was recently commissioned as part of the Fermilab Accelerator Science and Technology (FAST) facility. The IOTA ring was briefly operated with electrons at 47 MeV followed by a 6-months run with 100 MeV electrons. The main goal of the first run was to study beam dynamics in the integrable lattices with elliptical nonlinear magnets and in the quasi-integrable case with profiled octupole channel. The flexibility of the IOTA ring allowed a wide range of complementary studies, such as experiments with a single electron; studies of fluctuations in undulator radiation and operation with low emittance beams. Over the next year the proton injector will be installed and two runs carried out. One run will be dedicated to the refinement of nonlinear experiments and another will be dedicated to the proof-of-principle demonstration of Optical Stochastic Cooling.

Slides WEXBA2 [12.702 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEXBA2

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paper received ※ 31 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEXBB1

Adaptive Machine Learning and Automatic Tuning of Intense Electron Bunches in Particle Accelerators

FEL, controls, feedback, target

609

A. Scheinker
LANL, Los Alamos, New Mexico, USA

Machine learning and in particular neural networks, have been around for a very long time. In recent years, thanks to growth in computing power, neural networks have reshaped many fields of research, including self driving cars, computers playing complex video games, image identification, and even particle accelerators. In this tutorial, I will first present an introduction to machine learning for beginners and will also touch on a few aspects of adaptive control theory. I will then introduce some problems in particle accelerators and present how they have been approached utilizing machine learning techniques as well as adaptive machine learning approaches, for automatically tuning extremely short and high intensity electron bunches in free electron lasers.

Slides WEXBB1 [58.913 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEXBB1

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paper received ※ 28 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019

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WEYBA5

Diamond Field Emitter Array Cathode Experimental Tests in RF Gun

cathode, gun, experiment, emittance

618

K.E. Nichols, H.L. Andrews, D. Kim, E.I. Simakov
LANL, Los Alamos, New Mexico, USA
S.P. Antipov
Euclid Beamlabs LLC, Bolingbrook, USA
G. Chen
IIT, Chicago, Illinois, USA
M.E. Conde, D.S. Doran, G. Ha, W. Liu, J.F. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA

Funding: LANL/LDRD
Diamond Field Emitter Array (DFEA) cathodes are arbitrarily shaped arrays of sharp (~50 nm tip size) nano-diamond pyramids with bases on the order of 3 to 25 microns and pitches 5 microns and greater. These cathodes have demonstrated very high bunch charge in tests at the L-band RF gun at the Argonne National Laboratory (ANL) Advanced Cathode Test Stand (ACTS). Intrinsically shaped electron beams have a variety of applications, but primarily to achieve high transformer ratios for Dielectric Wakefield Accelerators (DWA) when used in conjunction with Emittance Exchange (EEX) systems. Here we will present results from a number of recent cathode tests including bunch charge and YAG images. We have demonstrated shaped beam transport down the 2.54-meter beamline. In addition we will present emission simulations that demonstrate shielding effects for this geometry.

Slides WEYBA5 [13.017 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEYBA5

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paper received ※ 01 September 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019

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WEYBA6

A High-Precision Emission Computational Model for Ultracold Electron Sources

cathode, simulation, framework, multipole

622

A.J. Tencate, B. Erdelyi
Northern Illinois University, DeKalb, Illinois, USA

Funding: This work is supported by NSF award #1535401.
The high-intensity, high-brightness and precision frontiers for charged particle beams are an increasingly important focus for study. Ultimately for electron beam applications, including FELs and microscopy, the quality of the source is the limiting factor in the final quality of the beam. It is imperative to understand and develop a new generation of sub-Kelvin electron sources, and the current state of PIC codes are not precise enough to adequately treat this ultracold regime. Our novel computational framework is capable of modelling electron field emission from nanoscale structures on a substrate, with the precision to handle the ultracold regime. This is accomplished by integrating a newly developed Poisson integral solver capable of treating highly curved surfaces and an innovative collisional N-body integrator to propagate the emitted electron with prescribed accuracy. The electrons are generated from a distribution that accounts for quantum confinement and material properties and propagated to the cathode surface. We will discuss the novel techniques that we have developed and implemented, and show emission characteristics for several cathode designs.

Slides WEYBA6 [4.215 MB]

Poster WEYBA6 [5.758 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEYBA6

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paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEYBB1

ELENA Commissioning

proton, MMI, experiment, antiproton

626

D. Gamba, M.E. Angoletta, P. Belochitskii, L. Bojtár, F. Butin, C. Carli, B. Dupuy, Y. Dutheil, T. Eriksson, P. Freyermuth, C. Grech, M. Hori, J.R. Hunt, M. Jaussi, L.V. Jørgensen, B. Lefort, S. Pasinelli, L. Ponce, G. Tranquille
CERN, Meyrin, Switzerland
R. Gebel
FZJ, Jülich, Germany
C. Grech
University of Malta, Information and Communication Technology, Msida, Malta
M. Hori
MPQ, Garching, Munich, Germany

The Extra Low ENergy Antiproton storage ring (ELENA) is an upgrade project at the CERN AD (Antiproton Decelerator). ELENA will further decelerate the 5.3 MeV antiprotons coming from the AD down to 100 keV. ELENA features electron cooling for emittance control during deceleration thus preserving the beam intensity and allowing to extract bright bunches towards the experiments. The lower energy will allow for increasing the antiproton trapping efficiency up to two orders of magnitude, which is typically less than 1% with the present beam from AD. The ring was completed with the installation of the electron cooler at the beginning of 2018. Decelerated beams with characteristics close to the design values were obtained before the start of CERN Long Shutdown 2 (LS2). During LS2 electrostatic transfer lines from the ELENA ring to the experimental zones will be installed, replacing the magnetic transfer lines from the AD ring. The latest results of commissioning with H⁻ and antiprotons and the first observation of electron cooling in ELENA will be presented, together with an overview of the project and status and plans for LS2 and beyond.

Slides WEYBB1 [20.792 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEYBB1

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paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEYBB4

Progress of Liquid Lithium Stripper for FRIB

operation, vacuum, MMI, gun

636

T. Kanemura, J. Gao, R. Madendorp, F. Marti, Y. Momozaki
FRIB, East Lansing, Michigan, USA
M.J. LaVere
MSU, East Lansing, Michigan, USA
Y. Momozaki
ANL, Lemont, Illinois, USA

Funding: This work is supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
The Facility for Rare Isotope Beams (FRIB) at Michigan State University is building a heavy ion linear accelerator (linac) to produce rare isotopes by the fragmentation method. At energies between 16 and 20 MeV/u ions are further stripped by a charge stripper increasing the energy gain downstream in the linac. The main challenges in the stripper design are high power deposited by the ions in the stripping media and radiation damage to the media itself. To overcome these challenges, self-recovering stripper media are the most suitable solutions. The FRIB baseline choice is a high-velocity thin film of liquid lithium*. Because liquid lithium is highly reactive with air, we have implemented rigorous safety measures. Since May 2018, the lithium stripper system has been operated safely at an offline test site to accumulate operational experience. Recently, we successfully completed a 10-day long unattended continuous operation without any issue, which proved the reliability of the system. The next step is to characterize the lithium film stability with diagnostics. In 2020, we plan to bring the lithium stripper into the accelerator tunnel and commission it with ion beams.
*Jie Wei, et al., TU1A04, Proceedings of LINAC 2012, Tel-Aviv, Israel

Slides WEYBB4 [6.012 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEYBB4

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paper received ※ 03 September 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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WEPLM07

Low Level RF Test System for the Compact X-Ray Light Source at Arizona State University

controls, klystron, cavity, LLRF

680

H.S. Marks, W.S. Graves, M.R. Holl, L.E. Malin
Arizona State University, Tempe, USA

A compact femtosecond X-Ray Light Source (CXLS) for time-resolved scientific and medical studies is being constructed at Arizona State University. The CXLS X-rays will be generated by the inverse Compton scattering (ICS) collision of 200 mJ, 1 ps, IR laser pulses with 300 fs electron bunches with energy up to 35 MeV. The electron beam is accelerated via a photoinjector and three standing-wave 20-cell linac sections driven by two klystrons delivering up to 6 MW 1 µs pulses at 9.3 GHz with a pulse repetition rate of 1 kHz. For initial testing of the CXLS klystrons a hybrid digital-analog low-level RF (LLRF) driver has been developed which allows for inter-pulse phase and amplitude corrections based on feedback from waveguide-couplers. The micro-controller based system can also be programmed to adjust continuously in advance of predictable drifts.

Poster WEPLM07 [2.226 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM07

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paper received ※ 27 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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WEPLM13

Multipactor Electron Cloud Analysis in a 17 GHz Standing Wave Accelerator Cavity

multipactoring, cavity, simulation, experiment

687

H. Xu, M.A. Shapiro, R.J. Temkin
MIT/PSFC, Cambridge, Massachusetts, USA

Funding: US Department of Energy High Energy Physics
Theoretical predictions of single-surface one-point multipactor modes have been confirmed in experiments with a 17 GHz standing wave single cell disk-loaded waveguide accelerator structure operated in gradient range of 45-90 MV/m. A dc-biased probe placed outside of a slit in the side wall of the structure was used to measure the internal dark current electron energy distribution. The results indicated that the electrons had kinetic energy up to about 50 eV, in agreement with our CST particle-in-cell (PIC) simulations. Further theoretical calculations were performed to calculate the frequency detuning introduced by the multipactor electron cloud on the cell side wall for different electron cloud thicknesses and densities. We found that the detuning (Δf/f) due to the electron cloud was small, about two orders of magnitude smaller than the reciprocal of the cavity loaded quality factor. This detuning is sufficiently small that it does not cause significant power reflection. Similar calculations were carried out for high gradient operation of accelerator structures at frequencies of 2.856 GHz and 110.0 GHz, showing similar small detuning by multipactor discharges.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM13

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paper received ※ 19 August 2019 paper accepted ※ 16 November 2020 issue date ※ 08 October 2019

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WEPLM23

Updated Applications of Advanced Compact Accelerators

linac, radiation, laser, site

694

M. Uesaka
The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan

We are working for downsizing of RF accelerators from room-size to portable and table-top sizes and applying them to industril and social uses. We have developed portable 950 keV / 3.95 MeV X-band (9.3 GHz) electron linac based X-ray/neutron sources and successfully applied to on-site nondestructive inspection of industrial and social infrastructures such as chemical reaction chambers and bridges following the radiation safety law and regulation in Japan. By using the portable 950 keV / 3.95 MeV X-band electron linac based X-ray sources for on-site actual bridge inspection, we visualize inner reinforcement iron structure. The information of of the iron states is used for the structural analysis of the a bridge in order to evaluate its residual strength and sustainability. Table-topμelectron / ion beam sources using laser dielectric accelerating techniques are under development. The beam energy is ~ 1 MeV, the beam size is ~1 micron. We aim to apply them to 3D dynamic observation of radiation-induced DNA damage / repair for basic research of radiation therapy and low dose effect.

Poster WEPLM23 [0.778 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM23

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paper received ※ 30 August 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019

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WEPLM53

50 kW CW Multi-Beam Klystron

cavity, klystron, gun, cathode

717

S.V. Shchelkunov
Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
J.L. Hirshfield, V.E. Teryaev
Omega-P, Inc., New Haven, Connecticut, USA

Funding: Funded by the US Department of Energy; grant DE-SC-0018471.
Main components, which are the electron gun, cavity-chain, magnetic system, and partially- grounded depressed four-stage collector, of a novel klystron were conceptually designed. This klystron is to deliver 50 kW CW at 952.6 MHz and to serve as a microwave power source for ion acceleration at the Electron Ion Collider (EIC) being developed at Thomas Jefferson National Accelerator Facility. The efficiency is 80%, a number to which the power consumption by the solenoid and filament are already factored in. The tube is a combination of proven technologies put together: it uses multiple beams to have its perveance low to boost beam-power to RF-power efficiency. It uses a partially grounded depressed collector to recover energy thereby increasing the overall efficiency. A low operating voltage of 14kV makes the tube more user-friendly avoiding need for costly modulators and oil insulation. A sectioned solenoid is used to insure superb beam-matching to all components downstream of the electron gun, increasing the tube performances. Details of the components designs will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM53

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paper received ※ 14 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

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WEPLM57

200 kW, 350 - 700 MHz RF Sources using Multiple Beam Triodes

cavity, cathode, vacuum, klystron

724

R.L. Ives, T. Bui, D. Marsden, M.E. Read
CCR, San Mateo, California, USA
B. Henderson, L. Higgins, R. Ho
CPI, Palo Alto, California, USA

Funding: U.S. Department of Energy Grant No. DE-SC0018838
Calabazas Creek Research, Inc. and Communications & Power Industries, LLC are developing multiple beam triodes to produce more than 200 kW of RF power at extremely low cost and efficiencies exceeding 85%. RF power is achieved by installing the triode inside coaxial input and output cavities at the desired frequency. The multiple beam triodes developed in this program will provide RF power from 350 MHz to 700 MHz using the appropriate, tuned, resonant cavities. This program is using eight grid-cathode assemblies to achieve 200 kW with a target efficiency exceeding 80%. A 350 MHz RF source would be approximately 36 inches high, 18 inches in diameter and weigh approximately 150 pounds. This is significantly smaller than any other RF source at this frequency and power level. The gain is limited to approximately 14 dB, so a single beam triode-based source will serve as a driver. The combined cost and efficiency will still exceed the performance of other comparable RF sources, including solid state sources. Design issues, include grid cooling, uniformity of RF electric fields on the grids, and efficiency, will be discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM57

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paper received ※ 27 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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WEPLM60

Fast Sn-Ion Transport on Nb Surface for Generating NbxSn Thin Films and XPS Depth Profiling

interface, cavity, radio-frequency, SRF

727

Z. Sun, M. Liepe, J.T. Maniscalco, T.E. Oseroff, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
X. Deng
University of Virginia, Charlottesville, Virginia, USA
D. Zhang
Cornell University, Ithaca, New York, USA

Funding: U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams
In this work, we propose and demonstrate a fast and facile approach for NbxSn thin film deposition through the ion exchange reaction. By simply dipping a tin precursor on the Nb substrate surface, a ~600 nm thin film is generated due to the electronegativity differ-ence between Sn and Nb. Through X-ray photoelec-tron spectroscopy (XPS) depth profiling, the composi-tional information as a function of film thickness was obtained. Results showed a Sn layer on the film sur-face, Sn-rich and Nb-rich NbxSn layers as the majority of the film, and a ~60 nm Nb₃Sn layer at the film/substrate interface. Quantitative analysis con-firmed stoichiometric Nb/Sn ratio for the Nb₃Sn layer. This deposition method is demonstrated to be an alter-native choice for Nb₃Sn film growth.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM60

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paper received ※ 05 September 2019 paper accepted ※ 15 September 2019 issue date ※ 08 October 2019

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WEPLS02

Simulation of a Klystron Input Cavity using a Steady-State Full-Wave Solver

simulation, experiment, klystron, cavity

768

A.R. Gold, S.G. Tantawi
SLAC, Menlo Park, California, USA

The simulation of vacuum electronic radio-frequency (RF) power sources is generally done through semi-analytical modeling approaches. These techniques are computationally efficient as they make assumptions on the source topology, such as the requirement that the electron beam travel longitudinally and interact with cylindrical modes. To simulate more general interactions, transient particle-in-cell (PIC) codes are currently required. We present here simulation results of a 5045 klystron using a newly developed steady state code which does not make assumptions on the beam configuration or geometry of the structure and resonant modes. As we solve directly for the steady-state system dynamics, this approach is computationally efficient yet, as demonstrated through comparison with experimental results, provides similar accuracy.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLS02

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paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEPLS04

Simulations of Low Energy Au⁷⁸⁺ Losses in RHIC

lattice, MMI, optics, closed-orbit

775

G. Robert-Demolaize, K.A. Drees, Y. Luo
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The RHIC Run19 BES-II program features the commissioning of the Low Energy RHIC electron Cooling (LEReC) Project, which uses electron cooling techniques to compensate for intra-beam scattering and thus to improve the luminosity lifetime. During RHIC operations at 3.85 GeV (beam energy) with LEReC, one needs to ensure that the electron beam energy is properly matched for cooling purposes: if so, some of the circulating Au-79 ions can recombine with an electron, turning into Au-78 and circulating with a large momentum offset. Part of the LEReC commissioning steps is therefore to drive a maximized number of Au-78 ions towards a chosen location of the RHIC mechanical aperture to generate particle showers that can be detected by a Recombination Monitor outside the cryostat. This article introduces the baseline lattice design, then discusses the few scenarios considered for optimizing Au-78 losses at a given location. Each scenario is then simulated using new tracking tools for generating beam loss maps.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLS04

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paper received ※ 27 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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WEPLS09

Fast Two-Dimensional Calculation of Coherent Synchrotron Radiation in Relativistic Beams

radiation, synchrotron, wakefield, synchrotron-radiation

783

J. Tang, G. Stupakov
SLAC, Menlo Park, California, USA

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

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLS09

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paper received ※ 28 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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WEPLS12

A Semi-Analytical Approach to Six-Dimensional Path-Dependent Transport Matrices With Application to High-Brightness Charged-Particle Beam Transport

solenoid, simulation, emittance, cavity

792

C.-Y. Tsai
HUST, Wuhan, People’s Republic of China
K. Fan
Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People’s Republic of China

Funding: This work was supported by the Fundamental Research Funds for the Central Universities under Project No. 5003131049.
Efficient and accurate estimate of high-brightness electron beam dynamics is an important step to the overall performance evaluation in modern particle accelerators. Utilizing the moment description to study multi-particle beam dynamics, it is necessary to develop a path-dependent transport matrix, together with application of the drift-kick algorithm*. In this paper we will construct semi-analytical models for three typical beam transport elements, solenoid with fringe fields, transverse deflecting cavity, and a beam slit. To construct the semi-analytical models for these elements, we begin by formulating the simplified single-particle equations of motion, and apply typical numerical techniques to solve the corresponding six-by-six transport matrix as a function of the path coordinate. The developed semi-analytical models are demonstrated with three practical examples, where our numerical results are discussed, compared with and validated by particle tracking simulations. These path-dependent transport matrix models can be incorporated to the analysis based on beam matrix method for the application to high-brightness charged-particle beam transport.
* C.-Y. Tsai et al., Nuclear Inst. And Methods in Physics Research, A 937 (2019) 1-20

Poster WEPLS12 [3.099 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLS12

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paper received ※ 20 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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WEPLH10

Efficiency Estimation for Sequential Excitation Laser Stripping of H⁻ Beam

laser, experiment, cavity, proton

827

T.V. Gorlov, A.V. Aleksandrov, S.M. Cousineau, Y. Liu, A. Rakhman
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL is managed by UTBattelle, LLC, under contract DEAC0500OR22725 for the U.S. Department of Energy.
A new laser stripping scheme for charge exchange injection of H⁻ beam is considered. The sequential scheme for the planned demonstration experiment includes two step excitation that requires much smaller laser power compared to the traditional 1-step excitation. The new scheme can be applied to a wider range of H⁻ beam energies and provides more flexibility on the choice of laser frequency. In this paper we discuss the two-step excitation method and estimate laser stripping parameters and stripping efficiency for the SNS accelerator and its future H⁻ energy upgrade to 1.3 GeV.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH10

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paper received ※ 22 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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WEPLH16

Tolerances on Energy Deviation in Microbunched Electron Cooling

plasma, hadron, impedance, kicker

837

P. Baxevanis, G. Stupakov
SLAC, Menlo Park, California, USA

The performance of microbunched electron cooling (MBEC)* is highly dependent on the quality of the hadron and cooler electron beams. As a result, understanding the influence of beam imperfections is very important from the point of view of determining the tolerances of MBEC. In this work, we incorporate a non-zero average energy offset into our 1D formalism (**,***), which allows us to study the impact of effects such as correlated energy spread (chirp). In particular, we use our analytical theory to calculate the cooling rate loss due to the electron beam chirp and discuss ways to minimize the influence of this effect on MBEC.
* D. Ratner, Phys. Rev. Lett. 111, 084802 (2013).
** G. Stupakov, Phys. Rev. AB, 21, 114402 (2018).
*** G. Stupakov and P. Baxevanis, Phys. Rev. AB, 22, 034401 (2019).

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH16

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paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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WEPLH17

Diffusion and Nonlinear Plasma Effects in Microbunched Electron Cooling

hadron, plasma, emittance, kicker

841

P. Baxevanis, G. Stupakov
SLAC, Menlo Park, California, USA

The technique of michrobunched electron cooling (MBEC) is an attractive scheme for enhancing the brightness of hadron beams in future high-energy circular colliders (*). To achieve the required cooling times for a realistic machine configuration, it is necessary to boost the bunching of the cooler electron beam through amplification sections that utilize plasma oscillations. However, these plasma sections also amplify the intrinsic noise of the electron beam, leading to additional diffusion that can be very detrimental to the cooling. Moreover, they can exhibit nonlinear gain behavior, which reduces performance and limits the applicability of theory. In this paper, we study both of these important effects analytically with the aim of quantifying their influence and keeping them under control.
* D. Ratner, Phys. Rev. Lett. 111, 084802 (2013).

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH17

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paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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WEPLH20

Modeling of H⁻ Ion Source at LANSCE

ion-source, experiment, plasma, operation

848

N.A. Yampolsky, I. Draganić, L. Rybarcyk
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by the US Department of Energy under Contract Number DE-AC52-06NA25396
We report on the progress in modeling performance of the H⁻ ion source at LANSCE. The key aspect we address is the lifetime of the tungsten filament. The lifetime depends on multiple parameters of the ion source and can dramatically vary in different regimes of operation. We use the multiphysics approach to model the performance of the ion source. The detailed analysis has been made to recognize key physical processes, which affect the degradation of the filament. The analysis resulted in the analytical model, which includes relevant processes from the first principles. The numerical code based on this model has been developed and benchmarked. The results of the modeling show good agreement with experimental data. As a result, the developed model allows predicting the performance of the ion source in various regimes of operation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH20

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paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEPLO05

Developing Criteria for Laser Transverse Instability in LWFA Simulations

laser, plasma, simulation, wakefield

855

Y. Yan, L.D. Amorim, P. Iapozzuto, V. Litvinenko, N. Vafaei-Najafabadi
Stony Brook University, Stony Brook, USA
M. Babzien, M.G. Fedurin, Y.C. Jing, K. Kusche, M.A. Palmer, I. Pogorelsky, M.N. Polyanskiy
BNL, Upton, New York, USA
M. Downer, J.R. Welch, R. Zgadzaj
The University of Texas at Austin, Austin, Texas, USA
C. Joshi, W.B. Mori
UCLA, Los Angeles, California, USA
P. Kumar, V. Samulyak
SBU, Stony Brook, USA

Funding: We acknowledge resources of NERSC facility, operated under Contract No. DE-AC02-5CH11231, and of SEAWULF at Stony Brook University as well as funding from SBU-BNL Seed Grants.
Laser-driven plasma wakefield acceleration (LWFA) is considered as a potential technology for future colliders and light sources. To make the best use of a laser’s power, the laser is expected to maintain a stable propagation. A transverse instability is observed in our previous simulations when a long, intense CO₂ laser propagates inside a plasma*. This unstable motion is accompanied by strong transverse diffraction of the laser power and results in the disruption of the ion channel typically used for radiation generation**. We investigated the hosing-like instability using the Particle-in-Cell code OSIRIS*** by modeling the laser portion where this instability is seeded and then evolves. In this proceeding, a criteria will be described that allows for the characterization of the temporal and spatial evolution of this instability.
*J. Yan, et al. , AAC, IEEE, 2018.
** L. Nemos et al., PPCF, 58(3), 2016.
***R. A. Fonseca et al., Lecture Notes Computation Science (2331) 342, 2002.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO05

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paper received ※ 16 September 2019 paper accepted ※ 04 December 2019 issue date ※ 08 October 2019

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WEPLO06

Start-to-End Simulation of the Drive-Beam Longitudinal Dynamics for Beam-Driven Wakefield Acceleration

laser, simulation, wakefield, linac

858

W.H. Tan, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
P. Piot
Fermilab, Batavia, Illinois, USA
A. Zholents, A. Zholents
ANL, Lemont, Illinois, USA

Funding: This work is supported by the U.S. Department of Energy, Office of Science under contracts No. DE-AC02-06CH11357 (via a laboratory- directed R&D program at ANL) and No. DE-SC0018656 at NIU.
Collinear beam-driven wakefield acceleration (WFA) relies on shaped driver beam to provide higher accelerating gradient at a smaller cost and physical footprint. This acceleration scheme is currently envisioned to accelerate electron beams capable of driving free-electron laser *. Start-to-end simulation of drive-bunch beam dynamics is crucial for the evaluation of the design of accelerators built upon WFA. We report the start-to-end longitudinal beam dynamics simulations of an accelerator beamline capable of producing high charge drive beam. The generated wakefield when it passes through a corrugated waveguide results in a transformer ratio of 5. This paper especially discusses the challenges and criteria associated with the generation of temporally-shaped driver beam, including the beam formation in the photoinjector, and the influence of energy chirp control on beam transport stability.
A. Zholents et al., "A Conceptual Design of a Compact Wakefield Accelerator for a High Repetition Rate Multi User X-ray Free-Electron Laser Facility"

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO06

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paper received ※ 27 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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WEPLO11

Single Cycle THz Acceleration Structures

GUI, laser, focusing, acceleration

862

S.V. Kuzikov, A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia
S.P. Antipov, E. Gomez
Euclid TechLabs, LLC, Solon, Ohio, USA

Funding: This work was supported by the Russian Science Foundation under grant 19-42-04133 in the part of CST simulations for THz structures.
Recently, gradients on the order of 1 GV/m level have been obtained in a form of single cycle (~1 ps) THz pulses produced by conversion of a high peak power laser radiation in nonlinear crystals (~1 mJ, 1 ps, up to 3% conversion efficiency). These pulses however are broadband (0.1-5 THz) and therefore a new accelerating structure type is required. For electron beam acceleration with such pulses we propose arrays of parabolic focusing micro-mirrors with common central. These novel structures could be produced by a femtosecond laser ablation system developed at Euclid Techlabs. This technology had already been tested for production of several millimeters long, multi-cell structure which has been testing with electron beam. We also propose using of structures where necessary GV/m E-fields are excited by a drive bunch travelling in the corrugated waveguide. The radiated by drive bunch sequence of short range delayed wakes are guided in this case by metallic disks and reflected back being focused exactly at time when the witness bunch arrives.

Poster WEPLO11 [2.124 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO11

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paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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WEPLO17

Ultrashort Laser Pulse Shaping and Characterization for Tailored Electron Bunch Generation

laser, controls, FEM, diagnostics

871

T. Xu, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
M.E. Conde, G. Ha, J.G. Power
ANL, Lemont, Illinois, USA
P. Piot
Fermilab, Batavia, Illinois, USA

Temporally shaped laser pulses are desirable in various applications including emittance reduction and beam-driven acceleration. Pulse shaping techniques enable flexible controls over the longitudinal distribution of electron bunches emitted from the photocathode. While direct manipulation and measurement of an ultrashort pulse can be challenging in the time domain, both actions can be performed in the frequency domain. In this paper, we report the study and development of laser shaper and diagnostics at Argonne Wakefield Accelerator (AWA). Simulations of the shaping process for several sought-after shapes are presented along with the temporal diagnosis. Status of the experiment at the AWA facility is also discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO17

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paper received ※ 05 September 2019 paper accepted ※ 04 December 2019 issue date ※ 08 October 2019

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WEPLO19

Probing Multiperiod Plasma Response Regimes using Single Shot Wakefield Measurements

plasma, wakefield, emittance, cathode

878

R.J. Roussel, G. Andonian, W.J. Lynn, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
M.E. Conde, D.S. Doran, G. Ha, J.G. Power, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA
J. Seok
UNIST, Ulsan, Republic of Korea

Funding: DE-SC0017648
Systematic differences between the linear and nonlinear regimes of plasma wakefield acceleration from electron beams are manifested in the plasma response. Typically, the ratio of peak beam density to nominal plasma density determines operation in the linear or nonlinear regime. Previous reports have shown that a the cross-over into the nonlinear regime is associated with an increase in the wakefield amplitude, as well as sawtooth-like shape. In this paper, we present preliminary measurements of quasi-nonlinear wakefields driven by a linearly ramped beam, with a maximum charge close to the unperturbed plasma density. We also demonstrate nonlinear wakefield behavior in a probe bunch using a single shot, multi-period wakefield measurement and its dependency on plasma density.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO19

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paper received ※ 31 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEPLO20

High Gradient High Efficiency C-Band Accelerator Structure Research at LANL

simulation, operation, experiment, cavity

882

E.I. Simakov, A.W. Garmon, T.C. Germann, M.F. Kirshner, F.L. Krawczyk, J.W. Lewellen, D. Perez, G. Wang
LANL, Los Alamos, New Mexico, USA
A. Fukasawa, J.B. Rosenzweig
UCLA, Los Angeles, California, USA

Funding: Los Alamos National Laboratory LDRD Program
This poster will report on the status of the new high gradient C-band accelerator project at LANL. Modern applications such as X-ray sources require accelerators with optimized cost of construction and operation, naturally calling for high-gradient acceleration. Our goal is to use a multi-disciplinary approach that includes accelerator design, molecular dynamics simulations, and advanced manufacturing to develop high gradient, high efficiency RF structures for both compact and facility-size accelerator systems. We considered common operation frequencies for accelerators and identified C-band as the optimal frequency band for high gradient operations based on achievable gradients and means to control wakefields. We are putting together a high gradient C-band test facility that includes a 50 MW Toshiba klystron and cryo-coolers for operating copper NCRF accelerator cavities at long pulse duration. We plan to conduct high gradient testing of the optimized RF structures made of copper and novel copper alloys. LANL modeling capabilities will be used to systematically study the formation of breakdown precursors at high fields to develop basic theoretical understanding of the breakdown.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO20

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paper received ※ 27 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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WEPLE02

Integrated Accelerator Simulation with Electromagnetics and Beam Physics Codes

simulation, cavity, plasma, emittance

885

L. Ge, Z. Li, C.-K. Ng, L. Xiao
SLAC, Menlo Park, California, USA
D.A. Bizzozero, J. Qiang, J.-L. Vay
LBNL, Berkeley, California, USA
D.P. Grote
LLNL, Livermore, California, USA

Funding: Work supported by US Department of Energy under contracts AC02-76SF00515, DE-AC02-05CH11231 and DE-AC52-07NA27344. Used resources of the National Energy Research Scientific Computing Center.
This paper presents an integrated simulation capability for accelerators including electromagnetic field and beam dynamics effects. The integrated codes include the parallel finite-element code suite ACE3P for electromagnetic field calculation of beamline components, the parallel particle-in-cell (PIC) code IMPACT for beamline particle tracking with space-charge effects, and the parallel self-consistent PIC code Warp for beam and plasma simulations. The common data format OpenPMD has been adopted for efficient field and particle I/O data transfer between codes. One application is to employ ACE3P and IMPACT for studying beam qualities in accelerator beamlines. Another is to combine ACE3P and Warp for investigating plasma processing for operational performance of RF cavities. A module for mapping the CAD geometry used in ACE3P to Warp Cartesian grid representation has been developed. Furthermore, a workflow has been implemented that enables the execution of integrated simulation on HPC systems. Examples for simulation of the LCLS-II injector using ACE3P-IMPACT and plasma ignition in SRF cavities using ACE3P-Warp will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLE02

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paper received ※ 20 August 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019

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WEPLE05

Tracking With Space Harmonics in ELEGANT Code

cavity, electromagnetic-fields, simulation, photon

892

Y.P. Sun, C. Yao
ANL, Lemont, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The elegant code has the capability of simulating particle motion in accelerating or deflecting RF cavities, with a simplified (or ideal) model of the electromagnetic fields. To improve the accuracy of RF cavity simulations, the ability to track with space harmonics has been added to the elegant code. The sum of all the space harmonics will mimic the real electromagnetic fields in the RF cavity. These space harmonics will be derived from electromagnetic fields simulation of the RF cavity. This method should be general, which can be applied to any RF cavity structure, including accelerating and deflecting cavities.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLE05

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paper received ※ 31 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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WEPLE08

Parallel Tracking-Based Modeling of Gas Scattering and Loss Distributions in Electron Storage Rings

scattering, lattice, simulation, storage-ring

901

M. Borland
ANL, Lemont, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Estimation of gas scattering lifetimes in storage rings is typically done using a simple approach that can readily be performed by hand. A more sophisticated approach uses linear mapping of the angular dynamic acceptance around the ring and allows including variation of gas pressure and composition*. However, neither approach is appropriate for highly nonlinear lattices, in which the angular acceptance does not map according to the linear optics. Further, these approaches provide no detailed information about the location of losses. To address these limitations, a tracking-based approach was implemented in the program Pelegant**. We describe the implementation and performance of this method, as well as several applications to the Advanced Photon Source Upgrade.
* M. Borland, J. Carter, H. Cease, and B. Stillwell, Proc. IPAC 2015, 546.
** Y. Wang and M. Borland, AIP Conf. Proc. 877, 241 (2006).

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLE08

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paper received ※ 27 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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THXBA3

Adaptive Machine Learning and Feedback Control for Automatic Particle Accelerator Tuning

FEL, controls, target, laser

916

A. Scheinker
LANL, Los Alamos, New Mexico, USA

Free electron lasers (FEL) and plasma wakefield accelerators (PWA) are creating more and more complicated electron bunch configurations, including multi-color modes for FELs such as LCLS and LCLS-II and custom tailored bunch current profiles for PWAs such as FACET-II. These accelerators are also producing shorter and higher intensity bunches than before and require an ability to quickly switch between many different users with various specific phase space requirements. For some very exotic setups it can take hours of tuning to provide the beams that users require. In this work, we present results adaptive machine learning and model independent feedback techniques and their application in both the LCLS and European XFEL to 1) control electron bunch phase space to create desired current profiles and energy spreads by tuning FEL components automatically, 2) maximize the average pulse output energy of FELs by automatically tuning over 100 components simultaneously, 3) preliminary results on utilizing these techniques for non-invasive electron bunch longitudinal phase space diagnostics at PWAs.

Slides THXBA3 [8.110 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THXBA3

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paper received ※ 27 August 2019 paper accepted ※ 15 September 2019 issue date ※ 08 October 2019

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THXBA4

Update on BPM Signal Processing Circuitry Development at AWA

detector, controls, pick-up, electronics

919

W. Liu, M.E. Conde, D.S. Doran, G. Ha, J.G. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA
C. Jing
Euclid Beamlabs LLC, Bolingbrook, USA

Funding: The US Department of Energy, Office of Science
Beam position monitor (BPM) is widely used in accelerator facilities worldwide. It is a device which is capable of providing, non-destructively, accurate beam centroid and charge information of a passing charged beam. A typical BPM system contains customized hardware and specialized processing electronics. The cost is often too high for small facilities to afford them. As a small facility, Argonne Wakefield Accelerator (AWA) decided to develop a solution with high cost-efficiency to fit in its budget. Some details about the development are presented in this paper.

Slides THXBA4 [8.544 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THXBA4

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paper received ※ 29 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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THYBA1

Status of the CBETA Cornell-BNL ERL Prototype

cavity, MMI, radiation, beam-loading

923

K.E. Deitrick, N. Banerjee, A.C. Bartnik, J.A. Crittenden, L. Cultrera, J. Dobbins, C.M. Gulliford, G.H. Hoffstaetter, W. Lou, P. Quigley, D. Sagan, K.W. Smolenski, D. Widger
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
J.S. Berg, S.J. Brooks, R.L. Hulsart, R.J. Michnoff, S. Peggs, D. Trbojevic
BNL, Upton, New York, USA

CBETA, the Cornell-BNL ERL Test Accelerator, is an SRF multi-turn ERL which has been commissioned in the one-turn configuration from March to July 2019. During this time, the project has demonstrated an energy acceptance of 1.5 in the FFA arc, high-transmission energy recovery performance, and increased the CBETA energy-recovered maximum average current.

Slides THYBA1 [11.605 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THYBA1

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paper received ※ 28 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019

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THYBA3

Use of Solid Xenon as a Beam Dump Material for 4th-Generation Storage Rings

emittance, simulation, storage-ring, vacuum

927

M. Borland, H. Cease, J.C. Dooling
ANL, Lemont, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
Damage to tungsten beam dumps has been observed in the Advanced Photon Source due to the high charge (368 nC/store), high energy (7 GeV), and short loss time (about 15 microseconds). Owing to the higher charge (736 nC/store) and much lower emittance (42 pm vs 2.5 nm), this issue is expected to be much more severe in the APS Upgrade. This strongly suggests that such dumps are necessary in 4th-generation electron storage rings to prevent catastrophic damage to vacuum systems when, for example, rf systems trip. However, it also implies that the dump will be damaged by each strike and will thus need to be "refreshed," perhaps by moving the dump surface vertically to expose undamaged material. Xenon, a gas that solidifies at 161K, is an intriguing possibility for a beam dump material. Calculations suggest that as the beam spirals in toward a dump in a high-dispersion area the tails of the electron beam would vaporize sufficient xenon to rapidly diffuse the beam and render it harmless. The dump surface could be periodically reformed without breaking vacuum. Issues with the concept include the need to protect the frozen xenon from wakefield heating.

Slides THYBA3 [2.451 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THYBA3

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paper received ※ 27 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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THYBA4

Status of the Magnetized Thermionic Electron Source at Jefferson Lab

gun, cathode, emittance, diagnostics

931

F.E. Hannon, D.B. Bullard, C. Hernandez-Garcia, M.A. Mamun, M. Poelker, R. Suleiman
JLab, Newport News, Virginia, USA
J.V. Conway, B.M. Dunham, R.G. Eichhorn, C.E. Mayes, K.W. Smolenski, N.W. Taylor
Xelera Research LLC, Ithaca, New York, USA
C.M. Gulliford, V.O. Kostroun
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
M.S. Stefani
ODU, Norfolk, Virginia, USA

A 125kV DC gridded thermionic gun has been de-signed and constructed through a collaboration between Jefferson Lab and Xelera Research LLC. The gun has been recently installed at the Gun Test Stand diagnostic line at Jefferson Lab where transverse and longitudinal parameter space will be experimentally explored. The status and results characterizing the commissioning and trouble-shooting the thermionic gun are presented.

Slides THYBA4 [13.653 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THYBA4

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paper received ※ 28 August 2019 paper accepted ※ 15 September 2019 issue date ※ 08 October 2019

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THYBA5

Study of Fluctuations in Undulator Radiation in the IOTA Ring at Fermilab

experiment, radiation, undulator, wiggler

934

I. Lobach
University of Chicago, Chicago, Illinois, USA
A. Halavanau, Z. Huang, V. Yakimenko
SLAC, Menlo Park, California, USA
K. Kim
ANL, Lemont, Illinois, USA
V.A. Lebedev, S. Nagaitsev, A.L. Romanov, G. Stancari
Fermilab, Batavia, Illinois, USA
A.Y. Murokh
RadiaBeam, Marina del Rey, California, USA
T.V. Shaftan
BNL, Upton, New York, USA

We study turn-by-turn fluctuations in the number of emitted photons in an undulator, installed in the IOTA electron storage ring at Fermilab, with an InGaAs PIN photodiode and an integrating circuit. In this paper, we present a theoretical model for the experimental data from previous similar experiments and in our present experiment, we attempt to verify the model in an independent and a more systematic way. Moreover, in our experiment we consider the regime of very small fluctuation when the contribution from the photon shot noise is significant, whereas we believe it was negligible in the previous experiments. Accordingly, we present certain critical improvements in the experimental setup that let us measure such a small fluctuation.

Slides THYBA5 [8.048 MB]

Poster THYBA5 [3.079 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THYBA5

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paper received ※ 24 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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THYBA6

Active Pointing Stabilization Techniques Applied to the Low Energy RHIC Electron Cooling Laser Transport at BNL

laser, controls, operation, cathode

938

L.K. Nguyen, A.J. Curcio, W.J. Eisele, A.V. Fedotov, A. Fernando, W. Fischer, P. Inacker, J.P. Jamilkowski, D. Kayran, K. Kulmatycski, D. Lehn, T.A. Miller, M.G. Minty, A. Sukhanov
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The electron beam for the Low Energy RHIC electron Cooler (LEReC) at Brookhaven National Laboratory (BNL) is generated by a high-power fiber laser illuminating a photocathode. The pointing stability of the electron beam, which is crucial given its long transport, is highly dependent on the center-of-mass (CoM) stability of the laser spot on the photocathode. For reasons of accessibility during operations, the laser is located outside the accelerator tunnel, and the laser beam is propagated over a total distance of 34 m via three laser tables to the photocathode. The challenges to achieving the required CoM stability of 10 microns RMS on the photocathode include mitigation of the effects of vibrations along the transport and of weather- and season-related environmental effects, while preserving accessibility and diagnostic capabilities. Due to the insufficiency of infrastructure alone in overcoming these challenges, two active laser transport stabilization systems aimed at addressing specific types of position instability were installed during the 2018 Shutdown. After successful commissioning of the full transport in 2018/19, we report on our solutions to these design challenges.

Slides THYBA6 [3.426 MB]

Poster THYBA6 [1.299 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THYBA6

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paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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THYBB3

Compact 1 MeV Electron Accelerator

cavity, GUI, gun, vacuum

942

S.V. Kuzikov
IAP/RAS, Nizhny Novgorod, Russia
S.P. Antipov, P.V. Avrakhov
Euclid TechLabs, LLC, Solon, Ohio, USA

The cost of the accelerating structure in modern medical accelerators and industrial linacs is substantial. This comes to no surprise, as the accelerating waveguide is a set of diamond-turned copper resonators brazed together. Such a multistep manufacturing process is not only expensive, but also prone to manufacturing errors, which decrease the production yield. In the big picture, the cost of the accelerating waveguide precludes the use of accelerators as a replacement option for radioactive sources. Here we present a new cheap brazeless electron accelerating structure made out of two copper plates tightened together by means of an additional stainless steel plate. This additional plate, having sharp blades, is aimed to provide vacuum inside the whole system. The designed X-band 1 MeV structure consists of eight different length cells and accelerates field-emitted electrons from copper cathode. The structure is fed by 9 GHz magnetron which produces 240 kW, 1 µs pulses. The average gradient is as high as 10.6 MV/m, maximum surface fields do not exceed 50 MV/m.

Slides THYBB3 [19.559 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THYBB3

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paper received ※ 27 August 2019 paper accepted ※ 15 September 2019 issue date ※ 08 October 2019

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THZBA5

First Electron Cooling of Hadron Beams Using a Bunched Electron Beam

cavity, MMI, laser, gun

957

A.V. Fedotov, Z. Altinbas, M. Blaskiewicz, J.M. Brennan, D. Bruno, J.C. Brutus, M.R. Costanzo, K.A. Drees, W. Fischer, J.M. Fite, M. Gaowei, D.M. Gassner, X. Gu, J. Halinski, K. Hamdi, L.R. Hammons, T. Hayes, R.L. Hulsart, P. Inacker, J.P. Jamilkowski, Y.C. Jing, P.K. Kankiya, D. Kayran, J. Kewisch, D. Lehn, C.J. Liaw, C. Liu, J. Ma, G.J. Mahler, M. Mapes, A. Marusic, K. Mernick, C. Mi, R.J. Michnoff, T.A. Miller, M.G. Minty, S.K. Nayak, L.K. Nguyen, M.C. Paniccia, I. Pinayev, S. Polizzo, V. Ptitsyn, T. Rao, G. Robert-Demolaize, T. Roser, J. Sandberg, V. Schoefer, S. Seletskiy, F. Severino, T.C. Shrey, L. Smart, K.S. Smith, H. Song, A. Sukhanov, R. Than, P. Thieberger, S.M. Trabocchi, J.E. Tuozzolo, P. Wanderer, E. Wang, G. Wang, D. Weiss, B.P. Xiao, T. Xin, W. Xu, A. Zaltsman, H. Zhao, Z. Zhao
BNL, Upton, New York, USA

Funding: Work supported by the U.S. Department of Energy.
The Low Energy RHIC electron Cooler (LEReC) was recently constructed and commissioned at BNL. The LEReC is the first electron cooler based on the RF acceleration of electron bunches (previous electron coolers all used DC beams). Bunched electron beams are necessary for cooling hadron beams at high energies. The challenges of such an approach include generation of electron beams suitable for cooling, delivery of electron beams of the required quality to the cooling sections without degradation of beam emittances and energy spread, achieving required small angles between electrons and ions in the cooling sections, precise energy matching between the two beams, high-current operation of the electron accelerator, as well as several physics effects related to bunched beam cooling. Following successful commissioning of the electron accelerator in 2018, the focus of the LEReC project in 2019 was on establishing electron-ion interactions and demonstration of cooling process using electron energy of 1.6MeV (ion energy of 3.85GeV/n), which is the lowest energy of interest. Here we report on the first demonstration of Au ion cooling in RHIC using this new approach.

Slides THZBA5 [16.417 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THZBA5

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paper received ※ 16 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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THZBB3

Novel Emittance Measurement Combining Foil Focusing and Pepper-Pot Techniques

focusing, emittance, space-charge, experiment

961

K.A. Schultz, G.T. Ortiz, M.E. Schulze
LANL, Los Alamos, New Mexico, USA
C. Carlson, D. Guerrero
NSTec, Los Alamos, New Mexico, USA

Funding: Work supported by the US National Nuclear Security Agency and the US Department of Energy under contract DE-AC52-06NA25396.
In this paper, we describe a direct measurement of foil focusing of an intense, relativistic electron beam com-bined with the pepper-pot technique to perform emit-tance measurements. Foil focusing occurs when a thin, grounded, conducting foil shorts out the radial electric field of a transiting electron beam, causing its self-magnetic field to focus the beam. A 40-ns pulse was extracted from the main pulse of the 16-MeV, 1.65 kA beam from Axis-II of the Dual Axis Radiographic Hy-drodynamic Test Facility to perform the measurements. We show that not accounting for foil focusing signifi-cantly reduces the measured emittance.

Slides THZBB3 [5.382 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THZBB3

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paper received ※ 27 August 2019 paper accepted ※ 15 September 2019 issue date ※ 08 October 2019

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THZBB5

Present Status and Upgrades of the SNS Ion Beam Bunch Shape Monitors

controls, power-supply, high-voltage, operation

968

V. Tzoganis, A.V. Aleksandrov, R.W. Dickson
ORNL, Oak Ridge, Tennessee, USA

Six interceptive Feschenko-style longitudinal bunch profile monitors have been deployed in the normal conducting part of the SNS linac and HEBT. They have been operational for more than 10 years and although their performance has been satisfactory, reliability and parts obsolescence must be addressed. The upgrade plan focuses in mainly two areas, electronics architecture modernization and improvement of measurement resolution. In the first phase that is presented here the objective is to improve the control and readout electronics taking advantage of more recent technology. This will primarily address the obsolescence issues with older components, the frequent RF power failures, the non-trivial maintenance and troubleshooting and will lead to a simpler and more reliable system. This contribution describes in detail the implemented upgrades and presents the first experimental data.

Slides THZBB5 [4.926 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THZBB5

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paper received ※ 29 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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FRXBA3

Applications and Opportunities for the Emittance Exchange Beamline

emittance, controls, wiggler, wakefield

981

G. Ha, M.E. Conde, J.G. Power
ANL, Lemont, Illinois, USA
M. Chung, J. Seok
UNIST, Ulsan, Republic of Korea

Funding: This work is supported by the U.S. Department of Energy, Offices of HEP and BES, under Contract No. DE-AC02-06CH11357.
Emittance exchange (EEX) provides a powerful method of controlling the longitudinal phase space using the relatively simpler methods of transverse control. An EEX beamline was installed at the Argonne Wakefield Accelerator (AWA) facility in 2015. Several experiments important to the wakefield acceleration, such as a high transformer ratio from shaped bunches, have already been demonstrated. We are currently developing several applications of the EEX beamline including temporal profile shaping, THz radiation generation, time-energy correlation control, diagnostic uses of EEX etc. We will present the on-going EEX program for longitudinal phase space control taking place at the AWA facility, and discuss recently discovered new opportunities.

Slides FRXBA3 [6.814 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-FRXBA3

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paper received ※ 02 September 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

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FRXBA4

Maximizing 2-D Beam Brightness Using the Round to Flat Beam Transformation in the Ultralow Charge Regime

emittance, quadrupole, cathode, laser

986

F.W. Cropp V, P.E. Denham, J. Giner Navarro, E.T. Liu, P. Musumeci
UCLA, Los Angeles, USA
N. Burger, L. Phillips
PBPL, Los Angeles, USA
A.L. Edelen, C. Emma
SLAC, Menlo Park, California, USA

Funding: This work is supported by the United States National Science Foundation award PHY-1549132 (the Center for Bright Beams)
We seek to maximize the 2-D beam brightness in an RF photoinjector operating in an ultralow charge (<1 pC) regime by implementing the FBT. Particle tracking simulations suggest that in one dimension, normalized projected emittances smaller than 5 nm can be obtained at the UCLA Pegasus facility with up to 100 fC beam charge. A tunable magnetic field is put on the cathode. Three skew quadrupoles are used to block-diagonalize the beam matrix and recover the vastly different eigenemittances as the projected emittances. Emittance measurement routines, including grid-based, pepperpot-based and quad scan routines, have been developed for on-line calculation of the 4-D beam matrix and its eigenemittances. Preliminary measurements are in agreement with simulations and indicate emittance ratios larger than 10 depending on the laser spot size on the cathode. Fine tuning the quadrupole gradients for the FBT has a significant effect on the 2-D beam brightness. We have made concrete steps toward computer minimization and machine learning optimization of the quadrupole gradients in order to remove the canonical angular momentum from the beam and achieve the target normalized projected emittances.

Slides FRXBA4 [3.059 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-FRXBA4

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paper received ※ 28 August 2019 paper accepted ※ 05 December 2019 issue date ※ 08 October 2019

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FRXBA5

The Role of Laser Shaping in Microbunching Instability Suppression and Seeded X-Ray Free Electron Emission

laser, bunching, FEL, experiment

990

J. Tang, S. Carbajo, F.-J. Decker, Z. Huang, J. Krzywiński, R.A. Lemons, W. Liu, A.A. Lutman, G. Marcus, T.J. Maxwell, S.P. Moeller, D.F. Ratner, S. Vetter
SLAC, Menlo Park, California, USA

Microbunching instability (MBI) driven by collective effects in an accelerator is known to be detrimental for the performance of X-ray free electron lasers. At the Linac Coherent Light Source (LCLS), laser heater (LH) system was installed to suppress the microbunching instability by inducing a small amount of slice energy spread to the electron beam. The distribution of the induced energy spread greatly effects MBI suppression and can be controlled by shaping the transverse profile of the heater laser. In this paper, we present theoretical and experimental results on utilizing a Laguerre-Gaussian 01 Mode (LG01) laser at LCLS to obtain better suppression of the instability. We demonstrate experimentally that Gaussian-shaped energy distribution is induced by LG01 mode LH and final microbunching gain is better suppressed. We finally discuss the role of LH spatial shaping in soft X-ray self-seeded (SXRSS) FEL emission and demonstrate that this LH configuration is capable of generating high spectral brightness FEL pulses.

Slides FRXBA5 [3.162 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-FRXBA5

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paper received ※ 28 August 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019

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FRCHC2

Possibilities for Future Synchrotron Radiation Sources

laser, free-electron-laser, FEL, radiation

1000

M.-E. Couprie
SOLEIL, Gif-sur-Yvette, France

The landscape of present accelerator based light sources is drawn. The photon beam brightness increases opens new areas of user applications, both with the arrival of low emittance rings getting closer to diffraction limit and the advent of X-ray Free Electron Lasers, providing agility in terms of performance (two colors, attosecond pulse…). Finally, the path towards light sources using alternate accelerator schemes, such as plasma acceleration is discussed.

Slides FRCHC2 [76.897 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-FRCHC2

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paper received ※ 04 September 2019 paper accepted ※ 16 November 2020 issue date ※ 08 October 2019

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