IPAC2022 - Classification: MC3: Novel Particle Sources and Acceleration Techniques / T02: Electron Sources

Paper	Title	Page
MOPOTK027	Characterization of Various GaN Samples for Photoinjectors	500
	M.B. Andorf, I.V. Bazarov, S.J. Levenson, J.M. Maxson Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA J. Encomendero, D. Jena, V.V. Protasenko, H.G. Xing Cornell University, Ithaca, New York, USA
	Funding: DOE-HEP DESC0021002 DOE-NP DE-SC0021425 Photoemission properties (quantum efficiency, spectral response, and lifetime) of various GaN based photocathodes are summarized, including p-doped samples in its hexagonal phase, cubic GaN and a more exotic 2-D hole gas sample. The 2-D hole contains no dopant impurity but achieves high conductivity via polarization fields produced at the heterojunction of GaN and AlN. For efficient electron production, cesium is used to achieve Negative Electron Affinity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOTK027
About •	Received ※ 08 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 26 June 2022
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MOPOMS004	Optimizing Activation Recipe with Cs, Te, O for GaAs-Based Photocathodes	628
	J. Bae, M.B. Andorf, I.V. Bazarov, A. Galdi, J.M. Maxson Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA L. Cultrera BNL, Upton, New York, USA
	Funding: Department of Energy (DOE) DE-SC0021039. GaAs-based photocathodes are the most popular electron sources for producing highly spin-polarized electron beams in accelerator physics and condensed matter physics. Spin-polarized photoemission requires activation to achieve Negative Electron Affinity (NEA). Conventional NEA surfaces such as CS-O/NF3 are extremely vacuum sensitive, and this results in rapid QE degradation. In this work, we activated GaAs with various recipes using Cs, Te, and oxygen. We demonstrate NEA activation on GaAs surfaces. Among Cs-Te activated samples, the oxidized sample showed the highest QE and longest lifetime at 780 nm.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS004
About •	Received ※ 04 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 24 June 2022
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MOPOMS014	Commissioning of a High-Gradient X-Band RF Gun Powered by Short RF Pulses from a Wakefield Accelerator	652
SUSPMF040	use link to see paper's listing under its alternate paper code
	W.H. Tan, X. Lu, P. Piot Northern Illinois University, DeKalb, Illinois, USA S.P. Antipov, C.-J. Jing, E.W. Knight, S.V. Kuzikov Euclid TechLabs, Solon, Ohio, USA D.S. Doran, G. Ha, C.-J. Jing, W. Liu, X. Lu, P. Piot, P. Piot, J.G. Power, J. Shao, C. Whiteford, E.E. Wisniewski ANL, Lemont, Illinois, USA
	Funding: This work is supported by the U.S. DOE, under award No. DE-SC0018656 to NIU, DOE SBIR grant No DE-SC0018709 at Euclid Techlabs LLC, and contract No. DE-AC02-06CH11357 with ANL. A high-gradient X-band (11.7-GHz) photoinjector developed by Euclid Techlabs, was recently commissioned at the Argonne Wakefield Accelerator (AWA). The system comprises a 1+1/2-cell RF gun powered by short RF pulses generated as a train of high-charge bunches from the AWA accelerator passes through a slow-wave power extraction and transfer structure. The RF photoinjector was reliably operating with electric fields in excess of 300 MV/m on the photocathode surface free of breakdown and with an insignificant dark-current level. We report on the RF-gun setup, commissioning, and the associated beam generation via photoemission.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS014
About •	Received ※ 08 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 18 June 2022 — Issue date ※ 19 June 2022
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MOPOMS018	Tungsten Electron Emitter (TE²) with Direct Heated Cathode by Plasma Stream	667
	K.I. Thoma, M. Droba, T. Dönges, O. Meusel, H. Podlech, K. Schulte-Urlichs IAP, Frankfurt am Main, Germany K. Schulte-Urlichs, K.I. Thoma GSI, Darmstadt, Germany
	At Goethe-University, a novel concept of heating metallic cathodes is currently under investigation. In the scope of the ARIES collaboration WP16, an RF-modulated electron gun was developed and manufactured for application in electron lenses for space charge compensation. The goal of this project is to increase the intensity of primary beams, especially in low energy booster synchrotrons like the SIS18 and SIS100 at GSI/FAIR or the SPS at CERN. The gun was designed to produce electron currents of 10 A at extraction voltages of 30 kV. The tungsten electron emitter (TE²) and the grid electrode were designed and manufactured to be integrated in the extractor of the original volume type ion source. Significant effort was put into a robust and flexible design with highly reliable key components. The cathode is heated by a plasma stream generated in the plasma chamber of the source. Different heating options of the cathode are currently being studied. This contribution presents the working principles of the electron gun and first measurements results of cathode heating.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS018
About •	Received ※ 18 May 2022 — Revised ※ 12 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 26 June 2022
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MOPOMS019	The New SPARC_LAB RF Photo-Injector	671
	D. Alesini, M.P. Anania, M. Bellaveglia, A. Biagioni, F. Cardelli, G. Costa, M. Del Franco, G. Di Pirro, L. Faillace, M. Ferrario, G. Franzini, A. Gallo, A. Giribono, L. Piersanti, L. Sabbatini, A. Stella, A. Vannozzi INFN/LNF, Frascati, Italy A. Battisti, E. Chiadroni, G. Di Raddo, A. Liedl, V.L. Lollo, L. Pellegrino, R. Pompili, S. Romeo, V. Shpakov, C. Vaccarezza, F. Villa LNF-INFN, Frascati, Italy M. Carillo, E. Chiadroni Sapienza University of Rome, Rome, Italy A. Cianchi, M. Galletti Università di Roma II Tor Vergata, Roma, Italy
	A new RF photo-injector has been designed, realized and successfully installed at the SPARC_LAB facility (INFN-LNF, Frascati, Rome). It is based on a 1.6 cell RF gun fabricated with the new brazing free technology recently developed at the National Laboratories of Frascati. The electromagnetic design has been optimized to have a full compensation of the dipole and quadrupole field components introduced by the coupling hole with an improvement of the effective pumping speed with two added pumping ports. The gun is overcoupled (\beta=2) to reduce the filling time and to allow the operation with short RF pulses. The overall injector integrates a new solenoid with a remote control of the transverse position and a variable skew quadrupole for the compensation of residual quadrupole field components. It also allows an on axis laser injection system with the last mirror in air, and the possibility of a future integration of an X/C band cavity linearizer. In the paper we report the main characteristics of the electromagnetic and mechanical design and the low and high power test results that shows the extremely good perfomances of the new device.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS019
About •	Received ※ 07 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 26 June 2022
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MOPOMS020	Dark Current Studies for a High Gradient SW C-Band RF Gun	675
	F. Cardelli, D. Alesini, L. Faillace, A. Giribono, A. Vannozzi INFN/LNF, Frascati, Italy G. Di Raddo LNF-INFN, Frascati, Italy T.G. Lucas PSI, Villigen PSI, Switzerland
	It is now well-established that for the generation of very high brightness beams, required for fourth generation light sources, it is highly advantageous to use injectors based on Radiofrequency photo-guns with very high peak electric fields on the cathode (>120 MV/m). This very high surface electric field leads to the generation of undesirable electrons due to the field emission effect. The emitted electrons can be captured and propagate along the Linac forming a dark current beam, leading to background radiation that can damage the instrumentation and radioactivate components. Consequently, it is important that the emission of these electrons, and their subsequent transportation, is carefully evaluated. Recently, in the framework of the I-FAST project, a high gradient, standing wave, C-band (5712 MHz) RF photogun has been designed and will be realized soon. In this paper, the results of dark current studies and simulations are illustrated. The transport efficiency and the spectrum of the dark current have been evaluated by Particle-In-Cell simulations for different cathode peak field values considering also the effect of the focusing solenoid on the dark current beam.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS020
About •	Received ※ 08 June 2022 — Revised ※ 09 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 30 June 2022
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MOPOMS021	The New C Band Gun for the Next Generation RF Photo-Injectors	679
	D. Alesini, M. Ferrario, A. Giribono, A. Gizzi, L. Piersanti, A. Vannozzi INFN/LNF, Frascati, Italy F. Cardelli, G. Di Raddo, L. Faillace, S. Lauciani, A. Liedl, L. Pellegrino, C. Vaccarezza LNF-INFN, Frascati, Italy G. Castorina AVO-ADAM, Meyrin, Switzerland M. Croia ENEA Casaccia, Roma, Italy L. Ficcadenti INFN-Roma, Roma, Italy G. Pedrocchi SBAI, Roma, Italy
	Funding: European Union’s Horizon 2020 Research and Innovation programme under GA No 101004730 and INFN Commission V. RF photo-injectors are widely used in modern facilities, especially in FEL, as very low-emittance and high-brightness electron sources. Presently, the RF technology mostly used for RF guns is the S band (3 GHz) with typical cathode peak fields of 80-120 MV/m and repetition rates lower than 120 Hz. There are solid reasons to believe that the frequency step-up from S band to C band (6 GHz) can provide a strong improvement of the beam quality due to the potential higher achievable cathode field (>160 MV/m) and higher repetition rate (that can reach the kHz level). In the contest of the European I.FAST project, a new C band gun has been designed and will be realized and tested. It is a 2.5 cell standing wave cavity with a four port mode launcher, designed to operate with short RF pulses (<300 ns) and cathode peak field larger than 160 MV/m. In the paper we present the electromagnetic and thermo-mechanical design and the results of the prototyping activity and rf measurements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS021
About •	Received ※ 07 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 28 June 2022
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MOPOMS022	Studies of a Ka-Band High Power Klystron Amplifier at INFN-LNF	683
	M. Behtouei, L. Faillace, A. Mostacci, B. Spataro LNF-INFN, Frascati, Italy F. Bosco, M. Carillo, M. Migliorati, A. Mostacci, L. Palumbo Sapienza University of Rome, Rome, Italy F. Di Paolo, S. Fantauzzi, A. Leggieri, F. Marrese, L. Valletti Università degli Studi di Roma "Tor Vergata", Roma, Italy G. Torrisi INFN/LNS, Catania, Italy
	In the framework of the Compact Light XLS project, a Ka-band linearizer with electric field ranging from 100 to 150 MV/m is requested. In order to feed this structure, a proper Ka-band high power klystron amplifier with a high efficiency is needed. This paper reports a possible solution for a klystron amplifier operating on the TM₀₁₀ mode at 36 GHz, the third harmonic of the 12 GHz linac frequency, with an efficiency of 44% and 10.6 MW radiofrequency output power. We discuss also here the high-power DC gun with the related magnetic focusing system, the RF beam dynamics and finally the multiphysics analysis of a high- power microwave window for a Ka-band klystron providing 16MW of peak power.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS022
About •	Received ※ 18 May 2022 — Revised ※ 12 June 2022 — Accepted ※ 18 June 2022 — Issue date ※ 10 July 2022
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MOPOMS023	Start-to-End Beam-Dynamics Simulations of a Compact C-Band Electron Beam Source for High Spectral Brilliance Applications	687
	L. Faillace, M. Behtouei, B. Spataro, C. Vaccarezza LNF-INFN, Frascati, Italy R.B. Agustsson, I.I. Gadjev, S.V. Kutsaev, A.Y. Murokh RadiaBeam, Santa Monica, California, USA F. Bosco, M. Carillo, L. Giuliano, M. Migliorati, A. Mostacci, L. Palumbo Sapienza University of Rome, Rome, Italy D.L. Bruhwiler RadiaSoft LLC, Boulder, Colorado, USA O. Camacho, A. Fukasawa, N. Majernik, J.B. Rosenzweig, O. Williams UCLA, Los Angeles, USA A. Giribono INFN/LNF, Frascati, Italy S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: This work is partially supported by DARPA under the Contract No. HR001120C0072, by DOE Contract DE-SC0009914, DOE Contract DE-SC0020409, and by the National Science Foundation Grant No. PHY-1549132. Proposals for new linear accelerator-based facilities are flourishing world-wide with the aim of high spectral brilliance radiation sources. Most of these accelerators are based on electron beams, with a variety of applications in industry, research and medicine such as colliders, free-electron lasers, wake-field accelerators, coherent THz and inverse Compton scattering X/’ sources as well as high-resolution diagnostics tools in biomedical science. In order to obtain high-quality electron beams in a small footprint, we present the optimization design of a C-band linear accelerator machine. Driven by a novel compact C-band hybrid photoinjector, it will yield ultra-short electron bunches of few 100’s pC directly from injection with ultra-low emittance, fraction of mm-mrad, and a few hundred fs length simultaneously, therefore satisfying full 6D emittance compensation. The normal-conducting linacs are based on a novel high-efficiency design with gradients up to 50 MV/m. The beam maximum energy can be easily adjusted in the mid-GeV’s range. In this paper, we discuss the start-to-end beam-dynamics simulations in details.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS023
About •	Received ※ 07 June 2022 — Revised ※ 09 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 03 July 2022
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MOPOMS025	Photocathode Performance Characterisation of Ultra-Thin MgO Films on Polycrystalline Copper	691
SUSPMF039	use link to see paper's listing under its alternate paper code
	C. Benjamin, H.M. Churn, L.B. Jones, T.C.Q. Noakes STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G.R. Bell, C. Benjamin, T.J. Rehaag University of Warwick, Coventry, United Kingdom H.M. Churn, L.B. Jones, T.C.Q. Noakes Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: Department of Physics, The University of Warwick, Coventry, United Kingdom STFC ASTeC, Daresbury, Warrington, United Kingdom WA4 4AD The performance expected from the next generation of electron accelerators is driving research into photocathode technology as this fundamentally limits the achievable beam quality. The performance characteristics of a photocathode are most notably; normalised emittance, brightness and energy spread. Ultra–thin Oxide films on metal substrates have been shown to lower the work function (WF) of the surface, enhancing commonly utilised metal photocathodes, potentially improving lifetime and performance characteristics. We present the characterisation of two MgO/Cu photocathodes grown at Daresbury. The surface properties such as; surface roughness, elemental composition and WF, have been studied using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The photoemissive properties have been characterised with quantum efficiency (QE) measurements at 266 nm. Additionally, we measure the Transverse Energy Distribution Curves (TEDC) for these photocathodes under illumination at various wavelengths using ASTeC’s Transverse Energy Spread Spectrometer (TESS) and extract the Mean Transverse Energy (MTE)*. D.H. Dowell, et al, Nucl. Instr. and Meth A (2010), doi:10.1016/j.nima.2010.03.104 V. Chang, et al, Phys. Rev. B (2018), doi.org/10.1103/PhysRevB.97.155436 *Proc. FEL ’13, TUPPS033, 290-293
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS025
About •	Received ※ 19 May 2022 — Revised ※ 11 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 21 June 2022
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MOPOMS027	Synthesis of First Caesium Telluride Photocathode at ASTeC Using Sequential and Co-Deposition Method	695
	R. Valizadeh, A.N. Hannah STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom V.R. Dhanak The University of Liverpool, Liverpool, United Kingdom S. Lederer DESY, Hamburg, Germany
	Caesium Telluride (Cs₂Te) photocathodes, are the elec-tron source of choice, by many global accelerators such as European XFEL, FLASH and AWA. It offers high quantum efficiency and reasonable operational lifetime with lower vacuum requirements than multi-alkali photocathodes. In this paper, we report on the first synthesised CsxTe photocathodes at ASTeC, using both sequential and co-deposition of Te and Cs on Mo substrate. Te deposition is carried out using ion beam deposition whilst the Cs is deposited using a SAES getter alkali. The ion beam deposition of Te provides a high degree of control to give a dense, smooth layer with a reproducible film thickness. The chemical state with respect to film composition of the deposited CsxTe is determined with in-situ XPS anal-yses. The films exhibit a quantum efficiency between 7.5 to 9 % at 266 nm wavelength.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS027
About •	Received ※ 07 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 06 July 2022
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MOPOMS028	Stability and Lifetime Studies of Carbon Nanotubes for Electron Cooling in ELENA	699
	B. Galante, G. Tranquille CERN, Meyrin, Switzerland J. Resta-López, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom J. Resta-López, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom J. Resta-López ICMUV, Paterna, Spain
	Funding: Work supported by EU Horizon 2020 research and innovation programme under the Marie Sk’odowska-Curie grant agreement No 721559. Electron cooling is a fundamental process to guarantee beam quality in low energy antimatter facilities. In ELENA, the electron cooler reduces the emittance blow-up of the antiproton beam so that a focused and bright beam can be delivered to the experiments at the unprecedentedly low energy of 100 keV. To achieve a cold beam at this low energy, the electron gun must emit a monoenergetic and relatively intense electron beam. An optimization of the electron gun involving a cold cathode is studied to investigate the feasibility of using carbon nanotubes (CNTs) as cold electron field emitters. CNTs are considered among the most promising field emitting materials. However, stability data for emission over hundreds of hours, as well as lifetime and conditioning process studies to ensure optimal performance, are still incomplete or missing, especially if the aim is to use them in operation. This contribution reports experiments that characterize these properties and assess whether CNTs are suitable to be used as cold electron field emitters for many hundreds of hours.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS028
About •	Received ※ 20 May 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 22 June 2022
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MOPOMS029	HPC Modeling of a High-Gradient C-Band Linac for Hard X-Ray Free-Electron Lasers	703
	T.B. Bolin, S. Biedron UNM-ECE, Albuquerque, USA S. Sosa ODU, Norfolk, Virginia, USA
	The production of soft to hard x-rays (up to 25 keV) at XFEL (x-ray free-electron laser) facilities has enabled new developments in a broad range of disciplines. Great potential exists for new scientific discovery at higher energies (42+ keV) such as envisioned at MaRIE (Matter-Radiation Interactions in Extremes) at Los Alamos National Laboratory. These instruments can require a large amount of real estate, which quickly escalates costs: The driver of the FEL is typically an electron beam linear accelerator (LINAC) and the need for higher beam energies capable of generating these X-rays can dictate that the linac becomes longer. State of art accelerating technology is required to reduce the linac length by reducing the size of the cavities, providing for compact, high-frequency, high acceleration gradients. Here, we describe using the Argonne Leadership Computing Facility (ALCF) to facilitate our investigations into design concepts for future XFEL high-gradient LINAC’s in the C-band (~4-8 GHz). We investigate two different traveling wave (TW) geometries optimized for high-gradient operation as modeled at the ALCF using VSim software.* * https://www.txcorp.com
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS029
About •	Received ※ 03 July 2022 — Accepted ※ 04 July 2022 — Issue date ※ 08 July 2022
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MOPOMS033	Emittance Measurements of Nanoblade-Enhanced High Field Cathode	709
	G.E. Lawler, N. Majernik, J.I. Mann, N.E. Montanez, J.B. Rosenzweig UCLA, Los Angeles, California, USA V.S. Yu RadiaBeam, Santa Monica, California, USA
	Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132. High brightness cathodes are increasingly a focus for accelerator applications ranging from free electron lasers to ultrafast electron diffraction. There is further an increasing interest in fabrication and control of cathode surface to better control the emission characteristics and improve beam brightness. One method which we can consider is based on well-known silicon nanofabrication techniques which we use to create patterned cathode surfaces. The sharp edges produced lead to field emission increases and high brightness emission. We have demonstrated that a beam can be successfully extracted with a low emittance and we have reconstructed a portion of the energy spectrum. Due to the simplicity of extended geometries in nanofabrication our beam uniquely possesses a high aspect ratio in its transverse cross section. We can begin to consider modifications for emittance exchange beamlines and having shown the patterning principle is sound we can consider additional patterns such as hollow beams. Future work will continue to characterize the produced beam and the addition of fabrication steps to remove one of the blades in the double blade geometry in order to more accurately characterize the emission.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS033
About •	Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 10 July 2022
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MOPOMS034	Material Normal Energy Distribution for Field Emission Analyses From Monocrystalline Surfaces	713
	J.I. Mann, Y. Li, J.B. Rosenzweig UCLA, Los Angeles, California, USA T. Arias, J.K. Nangoi Cornell University, Ithaca, New York, USA
	Funding: National Science Foundation Grant No. PHY-1549132 Electron field emission is a complicated phenomenon which is sensitive not only to the particular material under illumination but also to the specific crystalline orientation of the surface. Summarizing the ability for a crystal to emit in a particular direction would be of great use when searching for good field emitters. In this paper we propose a material normal energy distribution which describes the ability of the bound electrons to tunnel under an intense electric field. This framework breaks a computationally expensive 3-D system down to a source distribution representation applicable for more efficient 1-D models. We use the Fowler-Nordheim framework to study the yield and MTE (mean transverse energy) from sources including gold, copper, and tungsten in both monocrystalline and polycrystalline forms. We find an increase in effective work function for field emission in the (111) direction for gold and copper associated with the Bragg plane intersections of the Fermi surface.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS034
About •	Received ※ 20 May 2022 — Revised ※ 12 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 06 July 2022
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MOPOMS036	Simulations of Laser Field Emission from Nanostructures with Image Charge Trapping and Band Structure Transitions	717
	B. Wang, G.E. Lawler, J.I. Mann, J.B. Rosenzweig UCLA, Los Angeles, California, USA T. Arias, J.K. Nangoi Cornell University, Ithaca, New York, USA S.S. Karkare Arizona State University, Tempe, USA
	Funding: National Science Foundation Grant No. PHY-1549132 Laser-induced field emission from nanostructures as a means to create high brightness electron beams has been a continually growing topic of study. Experiments using nanoblade emitters have achieved peak fields upwards of 40 GV/m, begging further investigation in this extreme regime. A recent paper has provided analytical reductions of the common semi-infinite Jellium system for pulsed incident lasers. We utilize these results as well as similar previous results to further understand the physics underlying electron rescattering-type emissions. We progress in numerically evaluating the analytical solution to attempt to more efficiently generate spectra for this system. Additionally, we use the full 1-D time-dependent Schrödinger equation with a Hartree potential and a dispersion-relation transition from material to vacuum to study the same system. We determine what importance the inclusion of the material band structure may have on emissions using this computationally challenging approach.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS036
About •	Received ※ 08 June 2022 — Revised ※ 21 June 2022 — Accepted ※ 27 June 2022 — Issue date ※ 01 July 2022
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MOPOMS052	6 MeV Novel Hybrid (Standing Wave - Traveling Wave) Photo-Cathode Electron Gun for a THz Superradiant FEL	760
	A. Nause, L. Feigin, A. Friedman, A. Weinberg Ariel University, Ariel, Israel A. Fukasawa, J.B. Rosenzweig UCLA, Los Angeles, California, USA B. Spataro LNF-INFN, Frascati, Italy
	A novel 6 MeV hybrid photo injector was designed and commissioned at Ariel University in Israel as an on-going collaboration with UCLA. This unique, new generation design provides a radically simpler approach to RF feeding of a gun/buncher system, leading to a much shorter beam via velocity bunching owed to an attached traveling wave section of the photo-injector. This design results in better performance in beam parameters, providing a high quality electron beam, with energy of 6 MeV, emittance of less than 3 ’m, and a 150 fs pulse duration at up to 1 nC per pulse. The Hybrid gun is driven by a SLAC XK5 Klystron as the high power RF source, and third harmonic of a fs level IR Laser amplifier (266 nm) to extract electrons from the Cathode. The unique e-gun will produce a bunched electron pulse to drive a THz FEL, which will operate at the super-radiance regime, and therefore requires extraordinary beam properties. It will also be used for MeV UED experiments in a separate line using a dogleg section. Here we describe the gun and presents experimental results from the gun and its sub-systems, including energy and charge measurements, compared with the design simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS052
About •	Received ※ 11 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 18 June 2022
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Paper

Title

Page

Characterization of Various GaN Samples for Photoinjectors

500

M.B. Andorf, I.V. Bazarov, S.J. Levenson, J.M. Maxson
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
J. Encomendero, D. Jena, V.V. Protasenko, H.G. Xing
Cornell University, Ithaca, New York, USA

Funding: DOE-HEP DESC0021002 DOE-NP DE-SC0021425
Photoemission properties (quantum efficiency, spectral response, and lifetime) of various GaN based photocathodes are summarized, including p-doped samples in its hexagonal phase, cubic GaN and a more exotic 2-D hole gas sample. The 2-D hole contains no dopant impurity but achieves high conductivity via polarization fields produced at the heterojunction of GaN and AlN. For efficient electron production, cesium is used to achieve Negative Electron Affinity.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOTK027

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Received ※ 08 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 26 June 2022

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MOPOMS004

Optimizing Activation Recipe with Cs, Te, O for GaAs-Based Photocathodes

628

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

Funding: Department of Energy (DOE) DE-SC0021039.
GaAs-based photocathodes are the most popular electron sources for producing highly spin-polarized electron beams in accelerator physics and condensed matter physics. Spin-polarized photoemission requires activation to achieve Negative Electron Affinity (NEA). Conventional NEA surfaces such as CS-O/NF3 are extremely vacuum sensitive, and this results in rapid QE degradation. In this work, we activated GaAs with various recipes using Cs, Te, and oxygen. We demonstrate NEA activation on GaAs surfaces. Among Cs-Te activated samples, the oxidized sample showed the highest QE and longest lifetime at 780 nm.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS004

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Received ※ 04 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 24 June 2022

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MOPOMS014

Commissioning of a High-Gradient X-Band RF Gun Powered by Short RF Pulses from a Wakefield Accelerator

652

SUSPMF040

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W.H. Tan, X. Lu, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
S.P. Antipov, C.-J. Jing, E.W. Knight, S.V. Kuzikov
Euclid TechLabs, Solon, Ohio, USA
D.S. Doran, G. Ha, C.-J. Jing, W. Liu, X. Lu, P. Piot, P. Piot, J.G. Power, J. Shao, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA

Funding: This work is supported by the U.S. DOE, under award No. DE-SC0018656 to NIU, DOE SBIR grant No DE-SC0018709 at Euclid Techlabs LLC, and contract No. DE-AC02-06CH11357 with ANL.
A high-gradient X-band (11.7-GHz) photoinjector developed by Euclid Techlabs, was recently commissioned at the Argonne Wakefield Accelerator (AWA). The system comprises a 1+1/2-cell RF gun powered by short RF pulses generated as a train of high-charge bunches from the AWA accelerator passes through a slow-wave power extraction and transfer structure. The RF photoinjector was reliably operating with electric fields in excess of 300 MV/m on the photocathode surface free of breakdown and with an insignificant dark-current level. We report on the RF-gun setup, commissioning, and the associated beam generation via photoemission.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS014

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Received ※ 08 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 18 June 2022 — Issue date ※ 19 June 2022

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MOPOMS018

Tungsten Electron Emitter (TE²) with Direct Heated Cathode by Plasma Stream

667

K.I. Thoma, M. Droba, T. Dönges, O. Meusel, H. Podlech, K. Schulte-Urlichs
IAP, Frankfurt am Main, Germany
K. Schulte-Urlichs, K.I. Thoma
GSI, Darmstadt, Germany

At Goethe-University, a novel concept of heating metallic cathodes is currently under investigation. In the scope of the ARIES collaboration WP16, an RF-modulated electron gun was developed and manufactured for application in electron lenses for space charge compensation. The goal of this project is to increase the intensity of primary beams, especially in low energy booster synchrotrons like the SIS18 and SIS100 at GSI/FAIR or the SPS at CERN. The gun was designed to produce electron currents of 10 A at extraction voltages of 30 kV. The tungsten electron emitter (TE²) and the grid electrode were designed and manufactured to be integrated in the extractor of the original volume type ion source. Significant effort was put into a robust and flexible design with highly reliable key components. The cathode is heated by a plasma stream generated in the plasma chamber of the source. Different heating options of the cathode are currently being studied. This contribution presents the working principles of the electron gun and first measurements results of cathode heating.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS018

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Received ※ 18 May 2022 — Revised ※ 12 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 26 June 2022

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MOPOMS019

The New SPARC_LAB RF Photo-Injector

671

D. Alesini, M.P. Anania, M. Bellaveglia, A. Biagioni, F. Cardelli, G. Costa, M. Del Franco, G. Di Pirro, L. Faillace, M. Ferrario, G. Franzini, A. Gallo, A. Giribono, L. Piersanti, L. Sabbatini, A. Stella, A. Vannozzi
INFN/LNF, Frascati, Italy
A. Battisti, E. Chiadroni, G. Di Raddo, A. Liedl, V.L. Lollo, L. Pellegrino, R. Pompili, S. Romeo, V. Shpakov, C. Vaccarezza, F. Villa
LNF-INFN, Frascati, Italy
M. Carillo, E. Chiadroni
Sapienza University of Rome, Rome, Italy
A. Cianchi, M. Galletti
Università di Roma II Tor Vergata, Roma, Italy

A new RF photo-injector has been designed, realized and successfully installed at the SPARC_LAB facility (INFN-LNF, Frascati, Rome). It is based on a 1.6 cell RF gun fabricated with the new brazing free technology recently developed at the National Laboratories of Frascati. The electromagnetic design has been optimized to have a full compensation of the dipole and quadrupole field components introduced by the coupling hole with an improvement of the effective pumping speed with two added pumping ports. The gun is overcoupled (\beta=2) to reduce the filling time and to allow the operation with short RF pulses. The overall injector integrates a new solenoid with a remote control of the transverse position and a variable skew quadrupole for the compensation of residual quadrupole field components. It also allows an on axis laser injection system with the last mirror in air, and the possibility of a future integration of an X/C band cavity linearizer. In the paper we report the main characteristics of the electromagnetic and mechanical design and the low and high power test results that shows the extremely good perfomances of the new device.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS019

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Received ※ 07 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 26 June 2022

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MOPOMS020

Dark Current Studies for a High Gradient SW C-Band RF Gun

675

F. Cardelli, D. Alesini, L. Faillace, A. Giribono, A. Vannozzi
INFN/LNF, Frascati, Italy
G. Di Raddo
LNF-INFN, Frascati, Italy
T.G. Lucas
PSI, Villigen PSI, Switzerland

It is now well-established that for the generation of very high brightness beams, required for fourth generation light sources, it is highly advantageous to use injectors based on Radiofrequency photo-guns with very high peak electric fields on the cathode (>120 MV/m). This very high surface electric field leads to the generation of undesirable electrons due to the field emission effect. The emitted electrons can be captured and propagate along the Linac forming a dark current beam, leading to background radiation that can damage the instrumentation and radioactivate components. Consequently, it is important that the emission of these electrons, and their subsequent transportation, is carefully evaluated. Recently, in the framework of the I-FAST project, a high gradient, standing wave, C-band (5712 MHz) RF photogun has been designed and will be realized soon. In this paper, the results of dark current studies and simulations are illustrated. The transport efficiency and the spectrum of the dark current have been evaluated by Particle-In-Cell simulations for different cathode peak field values considering also the effect of the focusing solenoid on the dark current beam.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS020

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Received ※ 08 June 2022 — Revised ※ 09 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 30 June 2022

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MOPOMS021

The New C Band Gun for the Next Generation RF Photo-Injectors

679

D. Alesini, M. Ferrario, A. Giribono, A. Gizzi, L. Piersanti, A. Vannozzi
INFN/LNF, Frascati, Italy
F. Cardelli, G. Di Raddo, L. Faillace, S. Lauciani, A. Liedl, L. Pellegrino, C. Vaccarezza
LNF-INFN, Frascati, Italy
G. Castorina
AVO-ADAM, Meyrin, Switzerland
M. Croia
ENEA Casaccia, Roma, Italy
L. Ficcadenti
INFN-Roma, Roma, Italy
G. Pedrocchi
SBAI, Roma, Italy

Funding: European Union’s Horizon 2020 Research and Innovation programme under GA No 101004730 and INFN Commission V.
RF photo-injectors are widely used in modern facilities, especially in FEL, as very low-emittance and high-brightness electron sources. Presently, the RF technology mostly used for RF guns is the S band (3 GHz) with typical cathode peak fields of 80-120 MV/m and repetition rates lower than 120 Hz. There are solid reasons to believe that the frequency step-up from S band to C band (6 GHz) can provide a strong improvement of the beam quality due to the potential higher achievable cathode field (>160 MV/m) and higher repetition rate (that can reach the kHz level). In the contest of the European I.FAST project, a new C band gun has been designed and will be realized and tested. It is a 2.5 cell standing wave cavity with a four port mode launcher, designed to operate with short RF pulses (<300 ns) and cathode peak field larger than 160 MV/m. In the paper we present the electromagnetic and thermo-mechanical design and the results of the prototyping activity and rf measurements.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS021

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Received ※ 07 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 28 June 2022

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MOPOMS022

Studies of a Ka-Band High Power Klystron Amplifier at INFN-LNF

683

M. Behtouei, L. Faillace, A. Mostacci, B. Spataro
LNF-INFN, Frascati, Italy
F. Bosco, M. Carillo, M. Migliorati, A. Mostacci, L. Palumbo
Sapienza University of Rome, Rome, Italy
F. Di Paolo, S. Fantauzzi, A. Leggieri, F. Marrese, L. Valletti
Università degli Studi di Roma "Tor Vergata", Roma, Italy
G. Torrisi
INFN/LNS, Catania, Italy

In the framework of the Compact Light XLS project, a Ka-band linearizer with electric field ranging from 100 to 150 MV/m is requested. In order to feed this structure, a proper Ka-band high power klystron amplifier with a high efficiency is needed. This paper reports a possible solution for a klystron amplifier operating on the TM₀₁₀ mode at 36 GHz, the third harmonic of the 12 GHz linac frequency, with an efficiency of 44% and 10.6 MW radiofrequency output power. We discuss also here the high-power DC gun with the related magnetic focusing system, the RF beam dynamics and finally the multiphysics analysis of a high- power microwave window for a Ka-band klystron providing 16MW of peak power.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS022

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Received ※ 18 May 2022 — Revised ※ 12 June 2022 — Accepted ※ 18 June 2022 — Issue date ※ 10 July 2022

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MOPOMS023

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

687

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

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

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

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

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MOPOMS025

Photocathode Performance Characterisation of Ultra-Thin MgO Films on Polycrystalline Copper

691

SUSPMF039

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C. Benjamin, H.M. Churn, L.B. Jones, T.C.Q. Noakes
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G.R. Bell, C. Benjamin, T.J. Rehaag
University of Warwick, Coventry, United Kingdom
H.M. Churn, L.B. Jones, T.C.Q. Noakes
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: Department of Physics, The University of Warwick, Coventry, United Kingdom STFC ASTeC, Daresbury, Warrington, United Kingdom WA4 4AD
The performance expected from the next generation of electron accelerators is driving research into photocathode technology as this fundamentally limits the achievable beam quality. The performance characteristics of a photocathode are most notably; normalised emittance, brightness and energy spread*. Ultra–thin Oxide films on metal substrates have been shown to lower the work function (WF) of the surface, enhancing commonly utilised metal photocathodes, potentially improving lifetime and performance characteristics**. We present the characterisation of two MgO/Cu photocathodes grown at Daresbury. The surface properties such as; surface roughness, elemental composition and WF, have been studied using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The photoemissive properties have been characterised with quantum efficiency (QE) measurements at 266 nm. Additionally, we measure the Transverse Energy Distribution Curves (TEDC) for these photocathodes under illumination at various wavelengths using ASTeC’s Transverse Energy Spread Spectrometer (TESS) and extract the Mean Transverse Energy (MTE)***.
*D.H. Dowell, et al, Nucl. Instr. and Meth A (2010), doi:10.1016/j.nima.2010.03.104
**V. Chang, et al, Phys. Rev. B (2018), doi.org/10.1103/PhysRevB.97.155436
***Proc. FEL ’13, TUPPS033, 290-293

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS025

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Received ※ 19 May 2022 — Revised ※ 11 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 21 June 2022

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MOPOMS027

Synthesis of First Caesium Telluride Photocathode at ASTeC Using Sequential and Co-Deposition Method

695

R. Valizadeh, A.N. Hannah
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
V.R. Dhanak
The University of Liverpool, Liverpool, United Kingdom
S. Lederer
DESY, Hamburg, Germany

Caesium Telluride (Cs₂Te) photocathodes, are the elec-tron source of choice, by many global accelerators such as European XFEL, FLASH and AWA. It offers high quantum efficiency and reasonable operational lifetime with lower vacuum requirements than multi-alkali photocathodes. In this paper, we report on the first synthesised CsxTe photocathodes at ASTeC, using both sequential and co-deposition of Te and Cs on Mo substrate. Te deposition is carried out using ion beam deposition whilst the Cs is deposited using a SAES getter alkali. The ion beam deposition of Te provides a high degree of control to give a dense, smooth layer with a reproducible film thickness. The chemical state with respect to film composition of the deposited CsxTe is determined with in-situ XPS anal-yses. The films exhibit a quantum efficiency between 7.5 to 9 % at 266 nm wavelength.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS027

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Received ※ 07 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 06 July 2022

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MOPOMS028

Stability and Lifetime Studies of Carbon Nanotubes for Electron Cooling in ELENA

699

B. Galante, G. Tranquille
CERN, Meyrin, Switzerland
J. Resta-López, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
J. Resta-López, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
J. Resta-López
ICMUV, Paterna, Spain

Funding: Work supported by EU Horizon 2020 research and innovation programme under the Marie Sk’odowska-Curie grant agreement No 721559.
Electron cooling is a fundamental process to guarantee beam quality in low energy antimatter facilities. In ELENA, the electron cooler reduces the emittance blow-up of the antiproton beam so that a focused and bright beam can be delivered to the experiments at the unprecedentedly low energy of 100 keV. To achieve a cold beam at this low energy, the electron gun must emit a monoenergetic and relatively intense electron beam. An optimization of the electron gun involving a cold cathode is studied to investigate the feasibility of using carbon nanotubes (CNTs) as cold electron field emitters. CNTs are considered among the most promising field emitting materials. However, stability data for emission over hundreds of hours, as well as lifetime and conditioning process studies to ensure optimal performance, are still incomplete or missing, especially if the aim is to use them in operation. This contribution reports experiments that characterize these properties and assess whether CNTs are suitable to be used as cold electron field emitters for many hundreds of hours.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS028

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Received ※ 20 May 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 22 June 2022

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MOPOMS029

HPC Modeling of a High-Gradient C-Band Linac for Hard X-Ray Free-Electron Lasers

703

T.B. Bolin, S. Biedron
UNM-ECE, Albuquerque, USA
S. Sosa
ODU, Norfolk, Virginia, USA

The production of soft to hard x-rays (up to 25 keV) at XFEL (x-ray free-electron laser) facilities has enabled new developments in a broad range of disciplines. Great potential exists for new scientific discovery at higher energies (42+ keV) such as envisioned at MaRIE (Matter-Radiation Interactions in Extremes) at Los Alamos National Laboratory. These instruments can require a large amount of real estate, which quickly escalates costs: The driver of the FEL is typically an electron beam linear accelerator (LINAC) and the need for higher beam energies capable of generating these X-rays can dictate that the linac becomes longer. State of art accelerating technology is required to reduce the linac length by reducing the size of the cavities, providing for compact, high-frequency, high acceleration gradients. Here, we describe using the Argonne Leadership Computing Facility (ALCF) to facilitate our investigations into design concepts for future XFEL high-gradient LINAC’s in the C-band (~4-8 GHz). We investigate two different traveling wave (TW) geometries optimized for high-gradient operation as modeled at the ALCF using VSim software.*
* https://www.txcorp.com

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS029

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Received ※ 03 July 2022 — Accepted ※ 04 July 2022 — Issue date ※ 08 July 2022

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MOPOMS033

Emittance Measurements of Nanoblade-Enhanced High Field Cathode

709

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

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

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

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

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MOPOMS034

Material Normal Energy Distribution for Field Emission Analyses From Monocrystalline Surfaces

713

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

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

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

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

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MOPOMS036

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

717

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

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

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

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

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MOPOMS052

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

760

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

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

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

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

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reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)