Keyword: cathode
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MOYE6 Spin-Polarized Electron Photoemission and Detection Studies electron, experiment, simulation, polarization 26
 
  • A.C. Rodriguez Alicea, R. Palai
    University of Puerto Rico, Rio Piedras Campus, San Juan, Puerto Rico
  • O. Chubenko, S.S. Karkare
    Arizona State University, Tempe, USA
  • L. Cultrera
    BNL, Upton, New York, USA
  
  Funding: Brookhaven National Laboratory and the Department of Energy of United States under contract No. DE-SC0012704 Also, the Center for Bright Beams, NSF award PHY-1549132.
The experimental investigation of new photocathode ma- terials is time-consuming, expensive, and difficult to accom- plish. Computational modelling offers fast and inexpensive ways to explore new materials, and operating conditions, that could potentially enhance the efficiency of polarized electron beam photocathodes. We report on Monte-Carlo simulation of electron spin polarization (ESP) and quantum efficiency (QE) of bulk GaAs at 2, 77, and 300 K using the data obtained from Density Functional Theory (DFT) cal- culations at the corresponding temperatures. The simulated results of ESP and QE were compared with reported exper- imental measurements, and showed good agreement at 77 and 300 K. 		 
slides icon Slides MOYE6 [6.235 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOYE6  
About • Received ※ 03 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 04 September 2022
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MOPA22 Study on Electropolishing Conditions for 650 MHz Niobium SRF Cavity cavity, SRF, niobium, power-supply 97
 
  • V. Chouhan, D.J. Bice, F. Furuta, M. Martinello, M.K. Ng, H. Park, T.J. Ring, G. Wu
    Fermilab, Batavia, Illinois, USA
  • B.M. Guilfoyle, M.P. Kelly, T. Reid
    ANL, Lemont, Illinois, USA
  
  The PIP II linear accelerator includes different types of niobium SRF cavities including 650 MHz elliptical low (0.61) and high (0.92) beta cavities. The elliptical cavity surface is processed with the electropolishing method. The elliptical cavities especially the low-beta 650 MHz cavities showed a rough equator surface after the EP was performed with the standard EP conditions. This work was focused to study the effect of different EP parameters, including cathode surface area, temperature and voltage, and optimize them to improve the cavity surface.  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA22  
About • Received ※ 02 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 03 September 2022
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MOPA50 Integrated Photonics Structure Cathodes for Longitudinally Shaped Bunch Trains wakefield, emittance, simulation, laser 160
 
  • S.J. Coleman, D.T. Abell, C.C. Hall
    RadiaSoft LLC, Boulder, Colorado, USA
  • R. Kapadia
    University of Southern California, Los Angeles, California, USA
  • S.S. Karkare
    Arizona State University, Tempe, USA
  • S.Y. Kim, P. Piot, J.F. Power
    ANL, Lemont, Illinois, USA
  
  Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DOE DE-SC0021681
Compact, high-gradient structure wakefield accelerators can operate at improved efficiency using shaped electron beams, such as a high transformer ratio beam shape, to drive the wakes. These shapes have generally come from a photocathode gun followed by a transverse mask to imprint a desired shape on the transverse distribution, and then an emittance exchanger (EEX) to convert that transverse shape into a longitudinal distribution. This process discards some large fraction of the beam, limiting wall-plug efficiency as well as leaving a solid object in the path of the beam. In this paper, we present a proposed method of using integrated photonics structures to control the emission pattern on the cathode surface. This transverse pattern is then converted into a longitudinal pattern at the end of an EEX. This removes the need for the mask, preserving the total charge produced at the cathode surface. We present simulations of an experimental set-up to demonstrate this concept at the Argonne Wakefield Accelerator. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA50  
About • Received ※ 03 August 2022 — Revised ※ 05 August 2022 — Accepted ※ 26 August 2022 — Issue date ※ 03 October 2022
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MOPA78 Temporally-Shaped Ultraviolet Pulses for Tailored Bunch Generation at Argonne Wakefield Accelerator electron, laser, controls, wakefield 222
 
  • T. Xu, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • S. Carbajo
    UCLA, Los Angeles, California, USA
  • S. Carbajo, R.A. Lemons
    SLAC, Menlo Park, California, USA
  • P. Piot
    ANL, Lemont, Illinois, USA
  
  Photocathode laser shaping is an appealing technique to generate tailored electron bunches due to its versatility and simplicity. Most photocathodes require photon energies exceeding the nominal photon energy produced by the lasing medium. A common setup consists of an infrared (IR) laser system with nonlinear frequency conversion to the ultraviolet (UV). In this work, we present the numerical modeling of a temporal shaping technique capable of producing electron bunches with linearly-ramped current profiles for application to collinear wakefield accelerators. Specifically, we show that controlling higher-order dispersion terms associated with the IR pulse provides some control over the UV temporal shape. Beam dynamics simulation of an electron-bunch shaping experiment at the Argonne Wakefield Accelerator is presented.  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA78  
About • Received ※ 01 August 2022 — Revised ※ 06 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 31 August 2022
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MOPA79 Studying the Emission Characteristics of Field Emission Cathodes with Various Geometries emittance, experiment, ECR, simulation 226
 
  • M.R. Howard, S.M. Lidia
    FRIB, East Lansing, Michigan, USA
  • J.E. Coleman
    LANL, Los Alamos, New Mexico, USA
  
  Funding: Work supported by the NNSA of US DOE under contract 89233218CNA000001 and partially supported by the US DOE under Cooperative Agreement award number DE-SC0018362 and Michigan State University.
The cathode test stand (CTS) at LANL is designed to hold off voltages of up to 500kV and can supply pulse durations up to 2.6 μs. Using this test stand, we are able to test both field emission and photocathodes with different geometries and materials at various pulse lengths and PFN voltages. Currently, the test stand is used to evaluate field emission using a velvet cathode over various pulse lengths. The CTS employs various diagnostic tools, including E-dots, B-dots, and a scintillator coupled with a pepperpot mask in order to measure the extracted voltage, current, beam distribution, and transverse emittance. Xenos [1] has been used to create and simulate diode geometries that permits study to optimize various beam parameters. These geometries include changing the size and recess of the cathode as well as implementing a Pierce geometry. Here, we will discuss comparisons for various simulated cathodes and how changes in geometry impact given beam parameters.
[1] See https://www.fieldp.com/xenos.html for information about the Xenos software. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA79  
About • Received ※ 02 August 2022 — Revised ※ 10 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 30 August 2022
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MOPA85 Design of a 185.7 MHz Superconducting RF Photoinjector Quarter-Wave Resonator for the LCLS-II-HE Low Emittance Injector cavity, SRF, gun, electron 245
 
  • S.H. Kim, W. Hartung, T. Konomi, S.J. Miller, M.S. Patil, J.T. Popielarski, K. Saito, T. Xu, T. Xu
    FRIB, East Lansing, Michigan, USA
  • C. Adolphsen, L. Ge, F. Ji, J.W. Lewellen, L. Xiao
    SLAC, Menlo Park, California, USA
  • M.P. Kelly, T.B. Petersen, P. Piot
    ANL, Lemont, Illinois, USA
  • P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  
  Funding: Work supported by the U.S. Department of Energy Contract DE-AC02-76SF00515.
A 185.7 MHz superconducting quarter-wave resonator (QWR) was designed for the low emittance injector of the Linac Coherent Light Source high energy upgrade (LCLS-II-HE). The cavity was designed to minimize the risk of cathode efficiency degradation due to multipacting or field emission and to operate with a high RF electric field at the cathode for low electron-beam emittance. Cavity design features include: (1) shaping of the cavity wall to reduce the strength of the low-field coaxial multipacting barrier; (2) four ports for electropolishing and high-pressure water rinsing; and (3) a fundamental power coupler (FPC) port located away from the accelerating gap. The design is oriented toward minimizing the risk of particulate contamination and avoid harmful dipole components in the RF field. The ANL 162 MHz FPC design for PIP-II is being adapted for the gun cavity. We will present the RF design of the cavity integrated with the FPC. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA85  
About • Received ※ 03 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 30 August 2022
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MOPA87 Design of the Cathode Stalk for the LCLS-II-HE Low Emittance Injector cavity, gun, SRF, ISOL 253
 
  • T. Konomi, W. Hartung, S.H. Kim, S.J. Miller, D.G. Morris, J.T. Popielarski, K. Saito, A. Taylor, T. Xu
    FRIB, East Lansing, Michigan, USA
  • C. Adolphsen, J.W. Lewellen
    SLAC, Menlo Park, California, USA
  • S. Gatzmaga, P. Murcek, R. Xiang
    HZDR, Dresden, Germany
  • M.P. Kelly, T.B. Petersen
    ANL, Lemont, Illinois, USA
  
  Superconducting radio-frequency (SRF) electron guns are attractive for delivery of beams at a high bunch repetition rate with a high accelerating field. An SRF gun is the most suitable injector for the high-energy upgrade of the Linac Coherent Light Source (LCLS-II-HE), which will produce high-energy X-rays at high repetition rate. An SRF gun is being developed for LCLS-II-HE as a collaborative effort by FRIB, HZDR, ANL, and SLAC. The cavity operating frequency is 185.7 MHz, and the target accelerating field at the photocathode is 30 MV/m. The photocathode is replaceable. The cathode is held by a fixture (’cathode stalk’) that is designed for thermal isolation and particle-free cathode exchange. The stalk must allow for precise alignment of the cathode position, cryogenic or room-temperature cathode operating temperature, and DC bias to inhibit multipacting. We are planning a test of the stalk to confirm that the design meets the requirements for RF power dissipation and biasing. In this presentation, we will describe the cathode stalk design and RF/DC stalk test plan.  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA87  
About • Received ※ 04 August 2022 — Revised ※ 11 August 2022 — Accepted ※ 18 August 2022 — Issue date ※ 11 September 2022
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TUXD6 Dual Radiofrequency Cavity Based Monochromatization for High Resolution Electron Energy Loss Spectroscopy cavity, electron, simulation, space-charge 278
 
  • A.V. Kulkarni, P.E. Denham, A. Kogar, P. Musumeci
    UCLA, Los Angeles, USA
  
  Reducing the energy spread of electron beams can enable breakthrough advances in electron energy loss spectroscopic investigations of solid state samples where characteristic excitations typically have energy scales on the order of meV. In conventional electron sources the energy spread is limited by the emission process and typically on the order of a fraction of an eV. State-of-the-art energy resolution can only be achieved after significant losses in the monochromatization process. Here we propose to take advantage of photoemission from ultrashort laser pulses (~40 fs) so that after a longitudinal phase space manipulation that trades pulse duration for energy spread, the energy spread can be reduced by more than one order of magnitude. The scheme uses two RF cavities to accomplish this goal and can be implemented on a relatively short (~ 1m) beamline. Analytical predictions and results of 3D self consistent beam dynamics simulations are presented to support the findings.  
slides icon Slides TUXD6 [1.461 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUXD6  
About • Received ※ 03 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 18 August 2022
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TUYD3 The Quest for the Perfect Cathode gun, electron, emittance, photon 281
 
  • J.W. Lewellen, J. Smedley, T. Vecchione
    SLAC, Menlo Park, California, USA
  • D. Filippetto
    LBNL, Berkeley, California, USA
  • S.S. Karkare
    Arizona State University, Tempe, USA
  • J.M. Maxson
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • P. Musumeci
    UCLA, Los Angeles, California, USA
  
  Funding: U.S. Department of Energy.
The next generation of free electron lasers will be the first to see the performance of the laser strongly dependent on the materials properties of the photocathode. A new injector proposed for the LCLS-II HE is an example of this revolution, with the goal of increasing the photon energy achievable by LCLS-II to over 20 keV. We must now ask, what is the optimal cathode, temperature, and laser combination to enable this injector? There are many competing requirements. The cathode must be robust enough to operate in a superconducting injector, and must not cause contamination of the injector. It must achieve sufficient charge at high repetition rate, while minimizing the emittance. The wavelength chosen must minimize mean transverse energy while maintaining tolerable levels of multi-photon emission. The cathode must be capable of operating at high (~30 MV/m) gradient, which puts limits on both surface roughness and field emission. This presentation will discuss the trade space for such a cathode/laser combination, and detail a new collaborative program among a variety of institutions to investigate it. 		 
slides icon Slides TUYD3 [1.632 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUYD3  
About • Received ※ 02 August 2022 — Revised ※ 04 August 2022 — Accepted ※ 14 August 2022 — Issue date ※ 26 September 2022
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TUYD4 Towards High Brightness from Plasmon-Enhanced Photoemitters electron, laser, interface, emittance 285
 
  • C.M. Pierce, I.V. Bazarov, J.M. Maxson
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • D.B. Durham, D. Filippetto, F. Riminucci
    LBNL, Berkeley, USA
  • A.H. Kachwala, S.S. Karkare
    Arizona State University, Tempe, USA
  • A. Minor
    UC Berkeley, Berkeley, California, USA
  
  Funding: This work is supported by DOE BES Contract No. DE-AC02-05CH11231. C.P. acknowledges NSF Award PHY-1549132 (CBB) and the US DOE SCGSR program. DD was supported by NSF Grant No. DMR-1548924 (STROBE).
Plasmonic cathodes, whose nanoscale features may locally enhance optical energy from the driving laser trapped at the vacuum interface, have emerged as a promising technology for improving the brightness of metal cathodes. A six orders of magnitude improvement [1] in the non-linear yield of metals has been experimentally demonstrated through this type of nanopatterning. Further, nanoscale lens structures may focus light below its free-space wavelength offering multiphoton photoemission from a region near 10 times smaller [2] than that achievable in typical photoinjectors. In this proceeding, we report on our efforts to characterize the brightness of two plasmonic cathode concepts: a spiral lens and a nanogroove array. We demonstrate an ability to engineer and fabricate nanoscale patterned cathodes by comparing their optical properties with those computed with a finite difference time domain (FDTD) code. The emittance and nonlinear yield of the cathodes are measured under ultrafast laser irradiation. Finally, prospects of this technology for the control and acceleration of charged particle beams are discussed.
[1] Polyakov, A., et al. (2013). Physical Review Letters, 110(7), 076802.
[2] Durham, D. B., et al. (2019). Physical Review Applied, 12(5), 054057.
 		 
slides icon Slides TUYD4 [7.160 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUYD4  
About • Received ※ 05 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 13 September 2022
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TUYD5 Epitaxial Alkali-Antimonide Photocathodes on Lattice-matched Substrates ECR, electron, laser, lattice 289
 
  • P. Saha, S.S. Karkare
    Arizona State University, Tempe, USA
  • E. Echeverria, A. Galdi, J.M. Maxson, C.A. Pennington
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • E.J. Montgomery, S. Poddar
    Euclid Beamlabs, Bolingbrook, USA
  
  Alkali-antimonides photocathodes, characterized by high quantum efficiency (QE) and low mean transverse energy (MTE) in the visible range of spectrum, are excellent candidates for electron sources to drive X-ray Free Electron Lasers (XFEL) and Ultrafast Electron Diffraction (UED). A key figure of merit for these applications is the electron beam brightness, which is inversely proportional to MTE. MTE can be limited by nanoscale surface roughness. Recently, we have demonstrated physically and chemically smooth Cs3Sb cathodes on Strontium Titanate (STO) substrates grown via co-deposition technique. Such flat cathodes could result from a more ordered growth. In this paper, we present RHEED data of co-deposited Cs3Sb cathodes on STO. Efforts to achieve epitaxial growth of Cs3Sb on STO are then demonstrated via RHEED. We find that films grown epitaxially on substrates like STO and SiC (previously used to achieve single crystalline Cs3Sb) exhibit QE higher than the polycrystalline Cs3Sb cathodes, by an order of magnitude below photoemission threshold. Given the larger QE, lower laser fluence could be used to extract high charge densities, thereby leading to enhanced beam brightness.  
slides icon Slides TUYD5 [2.088 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUYD5  
About • Received ※ 01 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 07 September 2022
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TUYD6 Design of a 200 kV DC Cryocooled Photoemission Gun for Photocathode Investigations gun, electron, MMI, cryogenics 292
 
  • G.S. Gevorkyan, T.J. Hanks, A.H. Kachwala, S.S. Karkare, C.J. Knill, C.A. Sarabia Cardenas
    Arizona State University, Tempe, USA
  
  Funding: This work was supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams, and the DOE under Grant No. DE-SC0021092.
We present the first results of the commissioning of the 200 kV DC electron gun with a cryogenically cooled cathode at Arizona State University. The gun is specifically designed for studying a wide variety of novel cathode materials including single crystalline and epitaxially grown materials at 30 K temperatures to obtain the lowest possible intrinsic emittance of UED and XFEL applications [1]. We will present the measurements of the cryogenic performance of the gun and the first high voltage commissioning results.
[1] G. S. Gevorkyan et. al., Proc. of NAPAC19 MOPLM16 (2019) 		 
slides icon Slides TUYD6 [12.632 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUYD6  
About • Received ※ 03 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 29 September 2022
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TUZD5 Experience and Challenges with Electron Cooling of Colliding Ion Beams in RHIC electron, operation, collider, emittance 325
 
  • A.V. Fedotov, X. Gu, D. Kayran, J. Kewisch, S. Seletskiy
    BNL, Upton, New York, USA
  
  Funding: Work supported by the U.S. Department of Energy.
Electron cooling of ion beams employing rf-accelerated electron bunches was successfully used for the RHIC physics program in 2020 and 2021 and was essential in achieving the required luminosity goals. This presentation will summarize experience and challenges with electron cooling of colliding ion beams in RHIC. We also outline ongoing studies using rf-based electron cooler LEReC. 		 
slides icon Slides TUZD5 [1.373 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUZD5  
About • Received ※ 02 August 2022 — Accepted ※ 04 August 2022 — Issue date ※ 14 September 2022  
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TUPA04 Sheet Electron Probe for Beam Tomography electron, proton, diagnostics, simulation 354
 
  • V.G. Dudnikov, M.A. Cummings, G. Dudnikova
    Muons, Inc, Illinois, USA
  
  Funding: Supported by DOE SBIR grant # DE-SC0021581.
We propose a new approach to electron beam tomography: we will generate a pulsed sheet of electrons. As the ion beam bunches pass through the sheet, they cause distortions in the distribution of sheet electrons arriving at a luminescent screen with a CCD device on the other side of the beam; these sheet electrons are interpreted to give a continuous measurement of the beam profile. The apparatus to generate the sheet beam is a strip cathode, which, compared to the scanning electron beam probe, is smaller, has simpler design and less expensive manufacturing, has better magnetic shielding, has higher sensitivity and higher resolution, has better accuracy of measurement, and has better time resolution. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA04  
About • Received ※ 22 July 2022 — Revised ※ 02 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 10 August 2022
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TUPA05 An H− Injector for the ESS Storage Ring ion-source, rfq, plasma, operation 357
 
  • V.G. Dudnikov, M.A. Cummings, M. Popovic
    Muons, Inc, Illinois, USA
  
  H− charge exchange (stripping) injection into the European Spallation neutron Source (ESS) Storage Ring requires a 90 mA H− ion source that delivers 2.9 ms pulses at 14 Hz repetition rate (duty factor ~4%) that can be extended to 28 Hz (df 8%). This can be achieved with a magnetron surface plasma H− source (SPS) with active cathode and anode cooling. The Brookhaven National Laboratory (BNL) magnetron SPS can produce an H− beam current of 100 mA with about 2 kW discharge power and can operate up to 0.7 % duty factor (average power 14 W) without active cooling. We describe how active cathode and anode cooling can be applied to the BNL source to increase the average discharge power up to 140 W (df 8%) to satisfy the needs of the ESS. We also describe the use of a short electrostatic LEBT as is used at the Oak Ridge National Laboratory Spallation Neutron Source to improve the beam delivery to the RFQ.  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA05  
About • Received ※ 02 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 04 September 2022
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TUPA41 Applications of Machine Learning in Photo-Cathode Injectors laser, electron, controls, network 441
 
  • A. Aslam
    UNM-ECE, Albuquerque, USA
  • M. Babzien
    BNL, Upton, New York, USA
  • S. Biedron
    Element Aero, Chicago, USA
  
  To configure a photoinjector to reproduce a given electron bunch with the desired characteristics, it is necessary to adjust the operating parameters with high precision. More or less, the fine tunability of the laser parameters are of extreme importance as we try to model further applications of the photoinjector. The laser pulse incident on the photocathode critically affects the electron bunch 3D phase space. Parameters such as the laser pulse transverse shape, total energy, and temporal profile must be controlled independently, any laser pulse variation over both short and long-time scales also requires correction. The ability to produce arbitrary laser intensity distributions enables better control of electron bunch transverse and longitudinal emittance by affecting the space-charge forces throughout the bunch. In an accelerator employing a photoinjector, electron optics in the beamline downstream are used to transport, manipulate, and characterize the electron bunch. The adjustment of the electron optics to achieve a desired electron bunch at the interaction point is a much better understood problem than laser adjustment, so this research emphasizes laser shaping.  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA41  
About • Received ※ 30 July 2022 — Revised ※ 12 August 2022 — Accepted ※ 13 August 2022 — Issue date ※ 07 September 2022
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TUPA55 Progress Toward Improving Accelerator Performance and Automating Operations with Advanced Analysis Software diagnostics, operation, software, electron 465
 
  • J.E. Koglin, J.E. Coleman, M. McKerns, D. Ronquillo, A. Scheinker
    LANL, Los Alamos, New Mexico, USA
  
  Funding: Research presented in this conference paper was supported by the Laboratory Directed Research and Development program of Los Alamos National Laboratory under project numbers XXG2, XX8R and XXB6.
The penetrating radiography provided by the Dual Axis Radiographic Hydrodynamic Test (DARHT) facility is a key capability in executing a core mission of the Los Alamos National Laboratory (LANL). A new suite of software is being developed in the Python programming language to support operations of the of two DARHT linear induction accelerators (LIAs). Historical data, built as hdf5 data structures for over a decade of operations, are being used to develop automated failure and anomaly detection software and train machine learning models to assist in beam tuning. Adaptive machine learning (AML) that incorporate physics-based models are being designed to use non-invasive diagnostic measurements to address the challenge of time variation in accelerator performance and target density evolution. AML methods are also being developed for experiments that use invasive diagnostics to understand the accelerator behavior at key locations, the results of which will be fed back into the accelerator models. The status and future outlook for these developments will be reported, including how Jupyter notebooks are being used to rapidly deploy these advances as highly-interactive web applications. 		 
poster icon Poster TUPA55 [1.919 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA55  
About • Received ※ 15 July 2022 — Revised ※ 08 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 12 August 2022
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPA80 Cyborg Beamline Development Updates gun, cavity, cryogenics, simulation 512
 
  • G.E. Lawler, A. Fukasawa, N. Majernik, J.R. Parsons, J.B. Rosenzweig, Y. Sakai
    UCLA, Los Angeles, California, USA
  • F. Bosco
    Sapienza University of Rome, Rome, Italy
  • Z. Li, S.G. Tantawi
    SLAC, Menlo Park, California, USA
  • B. Spataro
    LNF-INFN, Frascati, Italy
  
  Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE Contract DE-SC0020409.
Xray free electron laser (XFEL) facilities in their current form are large, costly to maintain, and inaccessible due to their minimal supply and high demand. It is then advantageous to consider miniaturizing XFELs through a variety of means. We hope to increase beam brightness from the photoinjector via high gradient operation (>120 MV/m) and cryogenic temperature operation at the cathode (<77K). To this end we have designed and fabricated our new CrYogenic Brightness-Optimized Radiofrequency Gun (CYBGORG). The photogun is 0.5 cell so much less complicated than our eventual 1.6 cell photoinjector. It will serve as a prototype and test bed for cathode studies in a new cryogenic and very high gradient regime. We present here the fabricated structure, progress towards commissioning, and beamline simulations. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA80  
About • Received ※ 02 August 2022 — Accepted ※ 06 August 2022 — Issue date ※ 09 October 2022  
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEYE6 Thermionic Sources for Electron Cooling at IOTA electron, vacuum, proton, space-charge 588
 
  • M.K. Bossard, Y.K. Kim
    University of Chicago, Chicago, Illinois, USA
  • N. Banerjee, J.A. Brandt
    Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
  • B.L. Cathey, S. Nagaitsev, G. Stancari
    Fermilab, Batavia, Illinois, USA
  • M.A. Krieg
    Saint Olaf College, Northfield, MN, USA
  
  We are planning a new electron cooling experiment at the Integrable Optics Test Accelerator (IOTA) at Fermilab for cooling ~2.5 MeV protons in the presence of intense space-charge. Here we present the simulations and design of a thermionic electron source for cooling at IOTA. We particularly discuss parameters of the thermionic source electrodes, as well as the simulation results. We also present a new electron source test-stand at the University of Chicago, which will be used to test the new thermionic electron source, as well as other electron sources. In addition, we discuss results from analyzing the test stand operations with a currently existing electron source. Furthermore, we present future steps for the test stand as well as production and commissioning of the thermionic source at IOTA.  
slides icon Slides WEYE6 [3.182 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEYE6  
About • Received ※ 02 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 28 August 2022
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WEPA01 Beam Dynamics Optimization of a Low Emittance Photoinjector Without Buncher Cavities emittance, cavity, electron, gun 615
 
  • J. Qiang
    LBNL, Berkeley, California, USA
  • F. Ji, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
  
  The photoinjector plays an important role in generating high brightness low emittance electron beam for x-ray free electron laser applications. In this paper, we report on beam dynamics optimization study of a low emittance photoinjector based on a proposed superconducting gun without including any buncher cavities. Multi-objective optimization with self-consistent beam dynamics simulations was employed to attain the optimal Pareto front.  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA01  
About • Received ※ 02 August 2022 — Revised ※ 05 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 11 September 2022
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WEPA02 Beam Dynamics Studies on a Low Emittance Injector for LCLS-II-HE emittance, gun, solenoid, cavity 619
 
  • F. Ji, C. Adolphsen, R. Coy, L. Ge, C.E. Mayes, T.O. Raubenheimer, L. Xiao
    SLAC, Menlo Park, California, USA
  • J. Qiang
    LBNL, Berkeley, California, USA
  
  The SLAC High Energy upgrade of LCLS-II (LCLS-II-HE) will double the beam energy to 8 GeV, increasing the XFEL photon energy reach to about 13 keV. The energy reach can be extended to 20 keV if the beam emittance can be halved, which requires a higher gradient electron gun with a lower intrinsic emittance photocathode. To this end, the Low Emittance Injector (LEI) will be built that will run parallel to the existing LCLS-II Injector. The LEI design will be based on a state-of-the-art SRF gun with a 30 MV/m cathode gradient. The main goal is to produce transverse beam emittances of 0.1 mm-mrad for 100 pC bunch charges. This paper describes the beam dynamics studies on the design of the LEI including the simulations and multi-objective genetic algorithm (MOGA) optimizations. Performance with different injector layouts, cathode gradients, bunch charges and cathode mean transverse energies (MTEs) will be presented.  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA02  
About • Received ※ 02 August 2022 — Revised ※ 11 August 2022 — Accepted ※ 12 August 2022 — Issue date ※ 17 August 2022
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WEPA03 Status of the SLAC/MSU SRF Gun Development Project gun, cavity, SRF, cryomodule 623
 
  • J.W. Lewellen, C. Adolphsen, R. Coy, L. Ge, F. Ji, M.J. Murphy, L. Xiao
    SLAC, Menlo Park, California, USA
  • A. Arnold, S. Gatzmaga, P. Murcek, R. Xiang
    HZDR, Dresden, Germany
  • Y. Choi, C. Compton, X.-J. Du, D.B. Greene, W. Hartung, S.H. Kim, T. Konomi, S.J. Miller, D.G. Morris, M.S. Patil, J.T. Popielarski, L. Popielarski, K. Saito, T. Xu
    FRIB, East Lansing, Michigan, USA
  • M.P. Kelly, T.B. Petersen
    ANL, Lemont, Illinois, USA
  
  Funding: US Department of Energy.
The LCLS-II-HE project at SLAC is intended to increase the photon energy reach of the LCLS-II FEL to at least 20 keV. In addition to upgrading the undulator system, and increasing the electron beam energy to 8 GeV, the project will also construct a low-emittance injector (LEI) in a new tunnel. To achieve the LEI emittance goals, a low-MTE photocathode will be required, as will on-cathode electric fields up to 50% higher than those achievable in the current LCLS-II photoinjector. The beam source for the LEI will be based around a superconducting quarterwave cavity resonant at 185.7 MHz. A prototype gun is currently being designed and fabricated at the Facility for Rare Isotope Beams (FRIB) at Michigan State University. This paper presents the performance goals for the new gun design, an overview of the prototype development effort, current status, and future plans including fabrication of a "production" gun for the LEI. 		 
poster icon Poster WEPA03 [4.510 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA03  
About • Received ※ 21 July 2022 — Revised ※ 28 July 2022 — Accepted ※ 08 August 2022 — Issue date ※ 11 August 2022
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPA10 Determination of LCLS-II Gun-2 Prototype Dimensions gun, cavity, simulation, vacuum 637
 
  • L. Xiao, C. Adolphsen, E.N. Jongewaard, X. Liu, F. Zhou
    SLAC, Menlo Park, California, USA
  
  The LCLS-II spare gun (Gun-2) design is largely based on the existing LCLS-II gun (Gun-1), in which there is significant captured dark current (DC) that originates on the high field copper surface near the cathode plug gap opening. To help suppress DC, the Gun-2 cathode and anode noses and the cathode plug opening are elliptically shaped to minimize the peak surface field for a given cathode gradient. Stainless steel (SS) cathode and anode inserts are used in Gun-2 to further reduce dark current. The RF simulations were performed using a model that includes all the 3D features. The thermal and structural analyses were done to investigate the effects of the air pressure and RF heating. The multi-physics simulation results provided the information needed to compute the overall frequency change from the basic 2D model to the nominal frequency during operation. The Gun-2 cathode-to-anode gap distance will be made 1 mm longer than the nominal gap with the expectation that less than 1 mm will be machined off to meet the target frequency. In this paper, the Gun-2 frequency correction calculations are presented, and the cathode-to-anode gap determination is discussed.  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA10  
About • Received ※ 30 July 2022 — Revised ※ 03 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 10 August 2022
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPA13 New Results at JLab Describing Operating Lifetime of GaAs Photo-guns gun, electron, laser, experiment 644
 
  • M.W. Bruker, J.M. Grames, C. Hernandez-Garcia, M. Poelker, S. Zhang
    JLab, Newport News, Virginia, USA
  • V.M. Lizárraga-Rubio, C.A. Valerio-Lizárraga
    ECFM-UAS, Culiacan, Sinaloa, Mexico
  • J.T. Yoskowitz
    ODU, Norfolk, Virginia, USA
  
  Funding: This work is supported by U.S. Department of Energy under DE-AC05-06OR23177 and by Consejo Nacional de Ciencia y Tecnología and the Universidad Autonoma de Sinaloa under PRO_A1_022.
Polarized electrons from GaAs photocathodes have been key to some of the highest-impact results of the Jefferson Lab science program over the past 30 years. During this time, various studies have given insight into improving the operational lifetime of these photocathodes in DC high-voltage photo-guns while using lasers with spatial Gaussian profiles of typically 0.5 mm to 1 mm FWHM, cathode voltages of 100 kV to 130 kV, and a wide range of beam currents up to multiple mA. In this contribution, we show recent experimental data from a 100 kV to 180 kV setup and describe our progress at predicting the lifetime based on the calculable dynamics of ionized gas molecules inside the gun. These new experimental studies at Jefferson Lab are specifically aimed at exploring the ion damage of higher-voltage guns being built for injectors. 		 
poster icon Poster WEPA13 [1.644 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA13  
About • Received ※ 02 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 01 October 2022
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WEPA16 A 500 kV Inverted Geometry Feedthrough for a High Voltage DC Electron Gun gun, high-voltage, electron, power-supply 651
 
  • C. Hernandez-Garcia, D.B. Bullard, J.M. Grames, G.G. Palacios Serrano, M. Poelker
    JLab, Newport News, Virginia, USA
  
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177 and Office of Science Funding Opportunity LAB 20-2310 award PAMS-254442.
The Continuous Electron Beam Accelerator Facility injector at Jefferson Lab (JLab) utilizes an inverted-geometry ceramic insulator photogun operating at 130 kV direct current to generate spin-polarized electron beams for high-energy nuclear physics experiments. A second photogun delivers 180 keV beam for commissioning a SRF booster in a testbed accelerator, and a larger version delivers 300 keV magnetized beam in a test stand beam line. This contribution reports on the development of an unprecedented inverted-insulator with cable connector for reliably applying 500 kV DC to a future polarized beam photogun, to be designed for operating at 350 kV without field emission. Such a photogun design could then be used for generating a polarized electron beam to drive a spin-polarized positron source as a demonstrator for high energy nuclear physics at JLab. There are no commercial cable connectors that fit the large inverted insulators required for that voltage range. Our proposed concept is based on a modified epoxy receptacle with intervening SF6 layer and a test electrode in a vacuum vessel. 		 
poster icon Poster WEPA16 [6.217 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA16  
About • Received ※ 03 August 2022 — Revised ※ 05 August 2022 — Accepted ※ 07 August 2022 — Issue date ※ 09 October 2022
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WEPA17 Improved Electrostatic Design of the Jefferson Lab 300 kV DC Photogun and the Minimization of Beam Deflection gun, electron, high-voltage, laser 655
 
  • M.A. Mamun, D.B. Bullard, J.M. Grames, C. Hernandez-Garcia, G.A. Krafft, M. Poelker, R. Suleiman
    JLab, Newport News, Virginia, USA
  • J.R. Delayen, G.A. Krafft, G.G. Palacios Serrano, S.A.K. Wijethunga
    ODU, Norfolk, Virginia, USA
  
  Funding: This work is supported by the Department of Energy, under contract DE-AC05-06OR23177, JSA initiatives fund program, and the Laboratory Directed Research and Development program.
An electron beam with high bunch charge and high repetition rate is required for electron cooling of the ion beam to achieve the high luminosity required for the proposed electron-ion colliders. An improved design of the 300 kV DC high voltage photogun at Jefferson Lab was incorporated toward overcoming the beam loss and space charge current limitation experienced in the original design. To reach the bunch charge goal of ~ few nC within 75 ps bunches, the existing DC high voltage photogun electrodes and anode-cathode gap were modified to increase the longitudinal electric field (Ez) at the photocathode. The anode-cathode gap was reduced to increase the Ez at the photocathode, and the anode aperture was spatially shifted with respect to the beamline longitudinal axis to minimize the beam deflection introduced by the geometric asymmetry of the inverted insulator photogun. The electrostatic design and beam dynamics simulations were performed to determine the required modification. Beam-based measurement from the modified gun confirmed the reduction of the beam deflection, which is presented in this contribution. 		 
poster icon Poster WEPA17 [2.973 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA17  
About • Received ※ 23 July 2022 — Revised ※ 28 July 2022 — Accepted ※ 05 August 2022 — Issue date ※ 11 August 2022
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WEPA56 Encapsulation of Photocathodes Using High Power Pulsed RF Sputtering of hBN simulation, electron, vacuum, ion-effects 760
 
  • A. Liu, J.R. Callahan, S. Poddar
    Euclid TechLabs, Solon, Ohio, USA
  • J.P. Biswas, M. Gaowei
    BNL, Upton, New York, USA
  
  Funding: This work is supported by the US DOE SBIR program under contract number DE-SC0021511 and DE-SC0020573.
Photocathodes of various materials are used in photoinjectors for generating photoelectron beams. Of particular interest are the alkali antimonides because of their ultra-high quantum efficiency (QE) and relatively low requirements for growth, and metallic materials such as Cu and Mg which have lower QE but are easier to maintain and have longer lifetime. The biggest challenge of using the alkali antimonide photocathode is that it has an extremely stringent requirement on vacuum and is destroyed rapidly by residual air in the system, while exposure of Mg and Cu in air also impacts the photocathode performance because of the oxidation. The photocathode can be protected against harmful gas molecules by using one or two monolayers of a 2D material such as graphene or hexagonal boron nitride (hBN). Furthermore, hBN monolayers even have the potential to improve the QE of the photocathode when working as the encapsulation thin-film. In this paper, we will discuss the feasibility of coating a photocathode with hBN by high power pulsed RF sputtering by using metallic photocathodes as examples, and compare the performance with encapsulated photocathodes with transferred hBN thin-films. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA56  
About • Received ※ 31 July 2022 — Revised ※ 04 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 10 August 2022
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPA65 On-Chip Photonics Integrated Photocathodes GUI, electron, photon, coupling 773
 
  • A.H. Kachwala, O. Chubenko, S.S. Karkare
    Arizona State University, Tempe, USA
  • R. Ahsan
    USC, Los Angeles, California, USA
  • H.U. Chae, R. Kapadia
    University of Southern California, Los Angeles, California, USA
  
  Funding: This work is supported by the NSF Center for Bright Beams under award PHY-1549132, and by the Department of Energy, Office of Science under awards DE-SC0021092, and DE-SC0021213.
Photonics integrated photocathodes can result in advanced electron sources for various accelerator applications. In such photocathodes, light can be directed using waveguides and other photonic components on the substrate underneath a photoemissive film to generate electron emission from specific locations at sub-micron scales and at specific times at 100-femtosecond scales along with triggering novel photoemission mechanisms resulting in brighter electron beams and enabling unprecedented spatio-temporal shaping of the emitted electrons. In this work we have demonstrated photoemission confined in the transverse direction using a nanofabricated Si3N4 waveguide underneath a 40-nm thick cesiated GaAs photoemissive film, thus demonstrating a proof of principle feasibility of such photonics integrated photocathodes. This work paves the way to integrate the advances in the field of photonics and nanofabrication with photocathodes to develop better electron sources. 		 
poster icon Poster WEPA65 [0.642 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA65  
About • Received ※ 26 July 2022 — Revised ※ 06 August 2022 — Accepted ※ 07 August 2022 — Issue date ※ 10 August 2022
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WEPA66 Near-Threshold Photoemission from Graphene Coated Cu Single Crystals electron, experiment, cryogenics, brightness 776
 
  • C.J. Knill, S.S. Karkare
    Arizona State University, Tempe, USA
  • H. Ago, K. Kawahara
    Global Innovation Center, Kyushu University, Kasuga, Fukuoka, Japan
  • E. Batista, N.A. Moody, G.X. Wang, H. Yamaguchi, P. Yang
    LANL, Los Alamos, New Mexico, USA
  
  Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams, and by the Department of Energy under Grant DE-SC0021092.
The brightness of electron beams emitted from photocathodes plays a key role in the performance of x-ray free electron lasers (XFELs) and ultrafast electron diffraction (UED) experiments. In order to achieve the maximum beam brightness, the electrons need to be emitted from photocathodes with the smallest possible mean transverse energy (MTE). Recent studies have looked at the effect that a graphene coating has on the quantum efficiency (QE) of the cathode [1]. However, there have not yet been any investigations into the effect that a graphene coating has on the MTE. Here we report on MTE and QE measurements of a graphene coated Cu(110) single crystal cathode at room and cryogenic temperatures. At room temperature, a minimum MTE of 25 meV was measured at 295 nm. This MTE remained stable at 25 meV over several days. At 77 K, the minimum MTE of 9 meV was measured at 290 nm. We perform density functional theory (DFT) calculations to look at the effects of a graphene coating on a Cu(111) surface state. These calculations show that the graphene coating reduces the radius of the surface state, allowing for emission from a lower transverse energy state in comparison to bare Cu(111).
[1] F. Liu et al, Appl. Phys. Lett. 110, 041607 (2017); https://doi.org/10.1063/1.4974738 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA66  
About • Received ※ 28 July 2022 — Revised ※ 19 July 2022 — Accepted ※ 07 August 2022 — Issue date ※ 10 August 2022
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WEPA68 Record Quantum Efficiency from Superlattice Photocathode for Spin Polarized Electron Beam Production electron, polarization, lattice, distributed 784
 
  • J.P. Biswas, L. Cultrera, K. Kisslinger, W. Liu, J. Skarita, E. Wang
    BNL, Upton, New York, USA
  • S.D. Hawkins, J.F. Klem, S.R. Lee
    Sandia National Laboratories, Albuquerque, New Mexico, USA
  
  Funding: The work is supported by Brookhaven Science Associates, LLC under Contract DESC0012704 with the U.S. DOE. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
Electron sources producing highly spin-polarized electron beams are currently possible only with photocathodes based on GaAs and other III-V semiconductors. GaAs/GaAsP superlattice (SL) photocathodes with a distributed Bragg reflector (DBR) represent the state of the art for the production of spin-polarized electrons. We present results on a SL-DBR GaAs/GaAsP structure designed to leverage strain compensation to achieve simultaneously high QE and spin polarization. These photocathode structures were grown using molecular beam epitaxy and achieved quantum efficiencies exceeding 15% and electron spin polarization of about 75% when illuminated with near bandgap photon energies. 		 
poster icon Poster WEPA68 [4.506 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA68  
About • Received ※ 20 July 2022 — Revised ※ 02 August 2022 — Accepted ※ 07 August 2022 — Issue date ※ 10 August 2022
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THYD3 Update on the Status of C-Band Research and Facilities at LANL cavity, electron, klystron, operation 855
 
  • E.I. Simakov, A.M. Alexander, D.V. Gorelov, T.W. Hall, M.E. Middendorf, D. Rai, T. Tajima, M.R.A. Zuboraj
    LANL, Los Alamos, New Mexico, USA
  
  Funding: Los Alamos National Laboratory LDRD Program
We will report on the status of two C-band test facilities at Los Alamos National Laboratory (LANL): C-band Engineering Research Facility in New Mexico (CERF-NM), and Cathodes and Rf Interactions in Extremes (CARIE). Modern applications such as X-ray sources require accelerators with optimized cost of construction and operation, naturally calling for high-gradient acceleration. At LANL we commissioned a high gradient test stand powered by a 50 MW, 5.712 GHz Canon klystron. CERF-NM is the first high gradient C-band test facility in the United States. It was fully commissioned in 2021. In the last year, multiple C-band high gradient cavities and components were tested at CERF-NM. Currently we work to implement several updates to the test stand including the ability to remotedly operate at high gradient for the round-the-clock high gradient conditioning. Adding capability to operate at cryogenic temperatures is considered. The construction of CARIE will begin in October of 2022. CARIE will house a cryo-cooled copper RF photoinjector with a high quantum-efficiency cathode and a high gradient accelerator section. 		 
slides icon Slides THYD3 [3.331 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYD3  
About • Received ※ 31 July 2022 — Revised ※ 08 August 2022 — Accepted ※ 12 August 2022 — Issue date ※ 04 October 2022
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THYD5 Development of Nanopatterned Strong Field Emission Cathodes electron, laser, brightness, simulation 863
 
  • G.E. Lawler, N. Majernik, J.I. Mann, N. Montanez, J.B. Rosenzweig
    UCLA, Los Angeles, California, USA
  
  Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE HEP Grant DE-SC0009914.
Increasing brightness at the cathode is highly desirable for a diverse suite of applications in the electron accelerator community. These applications range from free electron lasers to ultrafast electron diffraction. Many options for higher brightness cathodes are under investigation notably semiconductor cathodes. We consider here the possibility for an alternative paradigm whereby the cathode surface is controlled to reduce the effective area of illumination and emission. We fabricated nanoblade metallic coated cathodes using common nanofabrication techniques. We have demonstrated that a beam can be successfully extracted with a low emittance and we have reconstructed a portion of the energy spectrum. As a result of our particular geometry, our beam possesses a notably high aspect ratio in its transverse plane. We can now begin to consider modifications for the production of intentionally patterned beams such as higher aspect ratios and hollow beams. 		 
slides icon Slides THYD5 [4.652 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYD5  
About • Received ※ 02 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 05 October 2022  
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)