| Paper | Title | Other Keywords | Page |
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| MOPRB067 | High-gradient Single Cycle Terahertz Accelerating Structures | GUI, gun, acceleration, electron | 731 |
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| Recently, gradients on the order of 1 GV/m level have been obtained in a form of single cycle (~1 ps) THz pulses produced by conversion of a high peak power laser radiation in nonlinear crystals (~1 mJ, 1 ps, up to 3% conversion efficiency). These pulses however are broadband (0.1-5 THz) and therefore a new accelerating structure type is required. For electron beam acceleration with such pulses we propose arrays of parabolic focusing micro-mirrors with common central. These novel structures could be produced by a femtosecond laser ablation system developed at Euclid Techlabs. This technology had already been tested for production of several millimeters long, multi-cell structure which has been testing with electron beam. We also propose using of structures where necessary GV/m E-fields are excited by a drive bunch travelling in the corrugated waveguide. The radiated by drive bunch sequence of short range delayed wakes are guided in this case by metallic disks and reflected back being focused exactly at time when the witness bunch arrives. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB067 | ||
| About • | paper received ※ 21 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| MOPRB085 | First Results from Commissioning of Low Energy RHIC Electron Cooler (LEReC) | electron, cavity, MMI, gun | 769 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The brand new non-magnetized bunched beam electron cooler (LEReC) [1] has been built to provide luminosity improvement for Beam Energy Scan II (BES-II) physics program at the Relativistic Heavy Ion Collider (RHIC) BES-II [2]. The LEReC accelerator includes a photocathode DC gun, a laser system, a photocathode delivery system, magnets, beam diagnostics, a SRF booster cavity, and a set of Normal Conducting RF cavities to provide sufficient flexibility to tune the beam in the longitudinal phase space. This high-current high-power accelerator was successfully commissioned in period of March -September 2018. Beam quality suitable for cooling has been demonstrated. In this paper we discuss beam commissioning results and experience learned during commissioning. [1] A. Fedotov et al., ’Status of bunched beam electron cooler LEReC’ in these proceedings. [2] C.Liu et al., ’Improving luminosity of Beam Energy Scan II at RHIC’ in these proceedings. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB085 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | ||
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| MOPRB110 | Simulation Study of the Emittance Measurements in Magnetized Electron Beam | solenoid, emittance, electron, gun | 822 |
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Funding: This work is supported by the Department of Energy, Laboratory Directed Research and Development funding, under contract DE-AC05-06OR23177 Electron cooling of the ion beam is key to obtaining the required high luminosity of proposed electron-ion colliders. For the Jefferson Lab Electron Ion Collider, the expected luminosity of 1034 〖 cm〗-2 s-1 will be achieved through so-called ’magnetized electron cooling’, where the cooling process occurs inside a solenoid field, which will be part of the collider ring and facilitated using a circulator ring and Energy Recovery Linac (ERL). As an initial step, we generated magnetized electron beam using a new compact DC high voltage photogun biased at -300 kV employing an alkali-antimonide photocathode. This contribution presents the characterization of the magnetized electron beam (emittance variations with the magnetic field strength for different laser spot sizes) and a comparison to GPT simulations. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB110 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | ||
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| MOPTS099 | The Development Programme of Cathodes and Electron Guns for the Hollow Electron Lenses of the High Luminosity LHC Project | electron, gun, luminosity, proton | 1102 |
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Funding: Research supported by the HL-LHC project The High Luminosity LHC project (HL-LHC) foresees the construction and installation of important new equipment to increase the performance of the LHC machine. The Hollow Electron Lens (HEL) is a promising system to control the beam halo. It improves the beam collimation system of the HL-LHC and mitigates possible equipment damage in case of failure scenarios from halo losses. The halo can store up to 30 MJ energy. The specifications for this new device are quite demanding. The source, an electron gun with an annular shaped cathode, has to deliver a current up to 5 A. This is five times higher than the current in the existing electron lenses in Fermi and Brookhaven national laboratories. This note describes the programme carried out to design and test high-perveance guns equipped with two types of high-performance scandate cathodes. The size of the final gun is now considerably smaller than the one of the first prototype, allowing a reduction of diameter and cost of the superconducting magnet system used to steer the electron beam. The tests carried out at FNAL, BVERI and BJUT demonstrated that the developed cathodes fulfil the specifications and can supply a 5 A fully Space Charge Limited (SCL) current. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS099 | ||
| About • | paper received ※ 17 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| TUPGW051 | Generation of Two Terahertz Radiation Pulses with Continuously Tunable Frequency and Time Delay | electron, radiation, laser, gun | 1518 |
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| We propose to generate two narrow band terahertz pulses radiated from two temporally modulated relativistic electron beams, which are generated in a photo-injector. The temporal profile of the drive laser is modulated by means of the paired chirped pulses beating technique, leading to the generation of two pre-bunched electron beams. Coherent transient radiation (CTR) is considered as the mechanism for terahertz radiation generation. The frequencies of the two terahertz pulses can be independently tuned by adjusting the paired beating frequencies, and the interval between the two terahertz pulses can be adjusted by the optical delay line. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW051 | ||
| About • | paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| TUPRB010 | FIRST DESIGN STUDIES OF A NC CW RF GUN FOR EUROPEAN XFEL | gun, cavity, simulation, FEL | 1698 |
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| After the successful commissioning of the European XFEL in pulsed mode, continuous wave (CW) mode operation of European X-ray Free-Electron Laser (XFEL) is under considerations for future upgrade. DESY is push-ing R&D on CW electron sources. A fully superconducting CW gun is under experimental development at DESY in Hamburg, and a normal conducting (NC) CW gun is under physics design at the Photo Injector Test facility at DESY in Zeuthen (PITZ) as a backup option. A 217 MHz NC CW gun is developed from the LBNL 187 MHz VHF gun, with enhancement on both cathode gradient and gun voltage to further improve beam brightness. This paper presents the cavity RF design, multipacting (MP) simula-tions and beam dynamics studies. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB010 | ||
| About • | paper received ※ 17 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | ||
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| TUPRB092 | Cherenkov Radiation in Periodic Wire Medium Formed by Transversely Modulated Electron Beams | radiation, electron, laser, experiment | 1878 |
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Funding: Work was supported by the U.S. Department of Energy Contract No. DE-AC02-76SF00515. We investigate the properties of Cherenkov, quasi-Cherenkov (parametric) and diffraction radiation generated in the periodic conducting wire medium by transversely modulated electron beams. Such beams were recently obtained at Argonne Wakefield Accelerator (AWA) facility using microlens array (MLA) laser shaping technique. We consider in details the case of one dimensional periodic tungsten wire structure and transverse electron beamlets separation of mm scale. We look at possible enhancements of the radiation field due to transverse periodicity of the electron beam. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB092 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019 | ||
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| TUPRB097 | Recent Progress on the Design of Normal Conducting APEX-II VHF CW Electron Gun | cavity, gun, electron, brightness | 1891 |
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Funding: Director of Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 We report recent progress on the design of a normal conducting CW electron gun, APEX-II (Advanced Photo-injector EXperiment-II) at Lawrence Berkeley National Laboratory. APEX-II is an upgrade of the successful APEX gun and the LCLS-II (Linac Coherent Light Source-II) injector, aiming at applications for Free electron laser (FEL) such as LCLS-II High Energy upgrade, UED (Ultrafast Electron Diffraction) and UEM (Ultrafast Electron Microscopy). The APEX-II adopted a two-cell cavity design with resonant frequency of 162.5 MHz. The APEX-II gun is targeting to achieve exceeding 30 MV/m of launch gradient at the cathode and output energy above 1.5 MeV with transverse emittance of 0.1 um at 100 pC. Advanced MOGA optimization technique has been used for both the RF cavity design and extensive beam dynamics studies using APEX-like and LCLS-II like injector layout. Detailed RF designs, beam dynamics studies, preliminary engineering design and FEA analysis will be presented, with cavity features that were demonstrated to be crucial in the operation of the APEX gun. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB097 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS004 | Development of a Penning Ion Source Test Stand for Production of Alpha Particles | ion-source, plasma, cyclotron, electron | 1932 |
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Medical cyclotron manufacturers are seeking less-costly and more compact ion sources than Electron Cyclotron Resonance Ion Sources (ECRIS) for alpha particle production, which are currently capable of generating beam currents up to 2 mA at energies of 30 keV for axial injection into these cyclotrons. Penning Ion Sources by comparison are relatively old technologies mostly used for cheap singly-charged ion production. However, these ion sources have been used in the past for high-current multiply-charged state ion production of heavy ions up to a few mA of current, and are much smaller, cheaper, and less complex than ECRISs. Therefore, we are developing a Penning Ion source test stand to produce high-current alpha-particles for medical cyclotrons. This requires designs and simulations of all the primary components of the ion source. This system will be used to fully characterize the output beam current and internal plasma properties as a function of varying gas pressure, ion source geometries, magnetic field strength, arc voltage/current, and material properties. The result will be a source optimized for maximum alpha particle beam currents, to be used as a prototype for a commercial Penning Ion Source.
* J. Bennet. A Review of PIG Sources for Multiply Charged Heavy Ions. IEEE Transactions on Nuclear Science, 1972. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS004 | ||
| About • | paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS011 | Vacuum Lifetime and Surface Charge Limit Investigations Concerning High Intensity Spin-polarized Photoinjectors | electron, vacuum, laser, experiment | 1954 |
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Funding: DFG excellence initiative PRISMA+, Bundesministerium für Bildung und Forschung "Verbundforschung FKZ 05K16UMA" The Small Thermalized Electron Source at Mainz (STEAM) is a dc photoemission source. It is designed to operate at up to 200kV bias voltage with an accelerating field of up to 5 MV/m at the cathode surface. In several experiments, the properties of GaAs operating under the conditions of spin-polarized photoemission were investigated. Its performance, quantum efficiency lifetime and surface charge limit observations for bulk-GaAs will be discussed. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS011 | ||
| About • | paper received ※ 29 April 2019 paper accepted ※ 28 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS012 | Emittance Reduction of RF Photoinjector Generated Electron Beams By Transverse Laser Beam Shaping | laser, emittance, simulation, experiment | 1958 |
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| Laser pulse shaping is one of the key elements to generate low emittance electron beams with RF photoinjectors. Ultimately high performance can be achieved with ellipsoidal laser pulses, but 3-dimensional shaping is challenging. High beam quality can also be reached by simple transverse pulse shaping, which has demonstrated improved beam emittance compared to a transversely uniform laser in the ‘pancake’ photoemission regime. In this contribution we present the truncation of a Gaussian laser at a radius of approximately one σ in the intermediate (electron bunch length directly after emission about the same as radius) photoemission regime with high acceleration gradients (up to 60 MV/m). This type of electron bunch is used e.g. at the European XFEL and FLASH free electron lasers at DESY, Hamburg site and is being investigated in detail at the Photoinjector Test facility at DESY in Zeuthen (PITZ). Here we present ray-tracing simulations and experimental data of a laser beamline upgrade enabling variable transverse truncation. Initial projected emittance measurements taken with help of this setup are shown, as well as supporting beam dynamics simulations. Additional simulations show the potential for substantial reduction of slice emittance at PITZ. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS012 | ||
| About • | paper received ※ 24 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS013 | Characterization of an Electron Gun Test Setup Based on Multipacting | cavity, electron, multipactoring, gun | 1961 |
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| A multipacting electron gun (MEG) is a micro-pulse electron source, based on secondary electron emission in a resonant microwave cavity structure, for the generation of low emittance electron bunches in continuous wave operation. Based on numerical simulations, an experimental test setup for low-energy electron beams at 3 GHz has been established. In this contribution we show a detailed description and characterization of the RF test stand, supported by first results on charge collection measurements of the output current with respect to important operational parameters like power transmission and modifiable mechanical dimensions in the assembly of the experiment. This is a milestone in the development of a MEG setup for higher energetic electron beams and subsequent investigation of essential beam characteristics like emittance and energy distribution for the optimization with regard to best possible beam quality and future fields of application. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS013 | ||
| About • | paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS014 | SINGLE SHOT CATHODE TRANSVERSE MOMENTUM IMAGING IN PHOTOINJECTORS | solenoid, emittance, electron, simulation | 1964 |
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| In state of the art photoinjector electron sources, cathode performance determines the lower limit of achievable beam emittance. Measuring the thermal emittance at the photocathodes in electron guns is of vital importance for improving the injectors. Traditional methods, like solenoid scan, pepper-pot, need multi-shots and are time-consuming, therefore suffer from machine stability. Here we propose a new method, named cathode transverse momentum imaging. By tuning the gun solenoid focusing, the electrons’ transverse momentum at the cathode is imaged to a downstream screen, which enables a single shot measurement. Several experiments have been done at the Photo Injector Test Facility at DESY in Zeuthen (PITZ) with a Cs2Te cathode. Measurements of cathode transverse momentum, the corresponding spectra, cathode transverse momentum map and its correlation with surface electric field are presented. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS014 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS024 | Design of a Full C-Band Injector for Ultra-High Brightness Electron Beam | gun, emittance, klystron, brightness | 1979 |
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| High gradient rf photo-injectors have been a key development to enable several applications of high quality electron beams. They allow the generation of beams with very high peak current and low transverse emittance, satisfying the tight demands for free-electron lasers, energy recovery linacs, Compton/Thomson sources and high-energy linear colliders. In the paper we present the design of a new full C-band RF photo-injector recently developed in the framework of the XLS-Compact Light design study and of the EuPRAXIA@SPARC_LAB proposal. It allows to reach extremely good beam performances in terms of beam emittance (at the level of few hundreds nm), energy spread and peak current. The photo-injector is based on a very high gradient (>200 MV/m) ultra-fast (RF pulses <200 ns) C-band RF gun, followed by two C band TW structures. Different types of couplers for the 1.6 cell RF gun have been considered and also a new compact low pulsed heating coupler working on the TM020 mode on the full cell has been proposed. In the paper we report the design criteria of the gun, the powering system, and the results of the beam dynamics simulations. We also discuss the case of 1 kHz repetition rate. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS024 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS026 | Negative Electron Affinity GaAs Cathode Activation With CsKTe Thin Film | electron, photon, vacuum, gun | 1986 |
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Funding: This work is partly supported by Japan-US Cooperative grant for scientific studies, Grant aid for scientific study by MEXT Japan (KAKENHI). Negative Electron Affinity (NEA) GaAs cathode is an unique device which can generate a highly polarized electron beam with circularly polarized light. The NEA surface is conventionally made by Cs and \rm O/NF3 adsorption on the cleaned p-doped GaAs crystal, but the robustness of the cathode is very limited, so that the electron emission is easily lost by residual gas adsorption, ion back-bombardment, etc. To improve the cathode robustness, NEA activation with a stable thin-film on GaAs surface according to Hetero junction hypothesis has been proposed by the author. An experiment of the NEA activation with CsKTe thin film was carried out at Hiroshima University and a significant electron emission with 1.43 eV photon was observed which strongly suggested NEA activation. The cathode showed 16 to 20 times improvement of lifetime comparing to GaAs activated with Cs and O. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS026 | ||
| About • | paper received ※ 26 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS047 | Improvement of 6D Brightness by a 1.4-cell Photocathode RF Gun for MeV Ultrafast Electron Diffraction | gun, emittance, electron, brightness | 2033 |
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| Recent research indicates that ultrafast electron diffraction and microscopy (UED/M) have unprecedented potential in probing ultrafast dynamic processes, especially in organic and biological materials. However, reaching the required brightness while maintaining high spatiotemporal resolution requires new design of electron source. In order to produce ultrashort electron beam with extreme high brightness, a 1.4-cell RF gun is being developed to reach higher acceleration gradient near the photocathode and thus suppress the space charge effect in the low energy region. Simulation of the 1.4-cell RF photocathode gun shows considerable improvement in bunch length, emittance and energy spread, which all lead to better temporal and spatial resolution comparing to traditional 1.6-cell RF photocathode gun. The results demonstrate the feasibility of sub-ps temporal resolution with normalized emittance less than 0.1 πmm·mrad while maintaining 1 pC electron pulse. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS047 | ||
| About • | paper received ※ 24 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS050 | Design and Analysis of the Cold Cathode Ion Source for 200 MeV Superconducting Cyclotron | ion-source, electron, proton, cyclotron | 2040 |
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| SC200 is a superconducting isochronous cyclotron which generates 200 MeV, 400 nA proton beam for particle therapy. The cold-cathode-type Penning ion gauge (PIG) ion source for the internal ion source of SC200 has been selected as an alternative and preliminary designed. In this paper, design of ion source and test bench are demonstrated. Currently, the properties of ion source have been simulated for a variety of electric field distributions and magnetic field strengths. The secondary electron emission in electromagnetic field has been simulated. It provides reference for the optimization design of arc chamber. In addition, the sample of cold-cathode-type ion source has been tested on the test bench and extracted beam intensity has been measured over 200 μA. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS050 | ||
| About • | paper received ※ 30 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS052 | Conceptual Design of a High-Performance Injector Based on Rf-Gated Gridded Thermionic Gun for Thz Fel | gun, electron, linac, bunching | 2046 |
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| Free-Electron Laser (FEL) has higher requirements on electron beam properties, for example, low transverse emittance, small energy spread, short bunch length and high peak current. Taking compactness and economy into account, we aim to design a high-performance linear accelerator based on a RF-gated gridded thermionic electron gun, which will be used as the injector of the oscillator-type THz FEL facility at Huazhong University of Science and Technology of China. The RF-gated grid will be modulated with the fundamental and 3rd harmonic microwave of the LINAC frequency, which will be very helpful to get high electron capture efficiency and short bunch length. Concerning velocity bunching effect in the LINAC, electron bunch with good symmetry of current profile and bunch length less than 10 ps can be obtained at the exit of the injector. In this paper, design and beam dynamics simulation for the high-performance injector are presented. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS052 | ||
| About • | paper received ※ 26 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS053 | Design of a 217 MHz VHF Gun at Tsinghua University | gun, electron, cavity, simulation | 2050 |
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| A 217 MHz VHF gun operating in CW mode is designing at Tsinghua University. The cathode gradient is designed to be 30 MV/m to accelerate the electron bunches up to 878 keV. The cavity profile is optimized in CST to minimize the input power, peak surface electric field, and peak wall power density. The multipacting analysis and the thermal analysis are also presented in this paper. Further gun shape optimization and mechanical design are ongoing. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS053 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS054 | 1st+2nd Harmonic Photocathode Bimodal Gun R&D | gun, emittance, electron, cavity | 2054 |
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Funding: U.S. Dept. of Energy A novel Bimodal Electron Gun is designed to apply microwaves at two harmonically-related frequency in a 0.6 cell RF gun to increase the RF breakdown threshold and enhance the beam quality. This stratagem is intended to allow the RF gun structure to support a high accelera-tion gradient as well as to manipulate the emittance evolution in the half cell. By selecting a proper ampli-tude ratio and phase relationship between the first and second harmonic RF field components in the gun cavity, the superposition of the harmonic field components can provide a flat-top like RF profile to omitting the RF emittance component in the gun, while increase the RF breakdown threshold. The recent status of the Bimodal Electron Gun R&D is presented, including the designs of the novel two frequency RF structure and the simulation of the beam dynamic. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS054 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS061 | The Pre-Injector and Photocathode Gun Design for the MAX IV SXL | gun, emittance, linac, laser | 2064 |
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| The design of the pre-injector, including the new gun, for the SXL project is being finalised for the desired modes of operation, 100 pC and 10 pC with short bunches. The photocathode gun is currently being manufactured and experiments in the MAX IV guntest facility are under preparation to verify the design. In this paper we present the design of the gun and the pre-injector and show some results from simulations using MOGA indicating an emittance below 0.3 mm mrad. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS061 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS066 | Re-optimisation of the ALICE Gun Upgrade Design for the 500-pC Bunch Charge Requirements of PERLE | gun, electron, operation, laser | 2071 |
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| The injector for PERLE, a planned ERL test facility, must be capable of delivering 500 pC bunches at a repetition rate of 40.1 MHz to provide a beam with 20 mA average current with a projected rms emittance of less than 6 mm mrad. This must be achieved at two different operational voltages 350 kV and 220 kV for unpolarised and polarised operation respectively. The PERLE injector will be based on an upgrade of a DC photocathode electron gun operated previously at ALICE ERL at Daresbury. The upgrade will add a load lock system for photocathode interchange. This paper presents the results of a re-optimisation of the electrode system as ALICE operated with a bunch charge of around 80 pC while PERLE needs a bunch charge of 500 pC. This re-optimisation was done using the many-objective genetic algorithm NSGAIII to minimise both the slice emittance and transverse beam size for both required operational voltages. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS066 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS069 | A Plasmonic Niobium Photocathode for SRF Gun Applications | gun, laser, cavity, photon | 2079 |
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| The typical quantum efficiency of niobium is of the order 10-4, whilst also requiring UV lasers for emission. This paper presents the results of a plasmonic niobium surface that operates with IR laser via multiphoton emission. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS069 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS070 | Systematic Benchmarking of a Planar (N)UNCD Field Emission Cathode | gun, experiment, electron, ECR | 2083 |
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| Planar nitrogen-incorporated ultrananocrystalline diamond, (N)UNCD, is a unique and attractive field emission source because of the capability to generate high charge beam, the simplicity of production without shaped emitters, and the ease of handling with moderate vacuum requirement. In the presented study using an L-band normal conducting single-cell rf gun, a (N)UNCD cathode has been conditioned to 42 MV/m with a well-controlled manner and reached a maximum charge of 15 nC and an average emission current of 6~mA during a 2.5 us emission period. The systematic study of emission properties during the rf conditioning process illustrates the tunability of (N)UNCD in a wide range of surface gradients. This research demonstrates the versatility of (N)UNCD cathode which could enable multiple designs of field emission rf injector for industrial and scientific applications. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS070 | ||
| About • | paper received ※ 20 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS071 | H+ and H− Ion Beam Injectors at LANSCE: Beam Production Status and Planned Injector Upgrades | ion-source, plasma, proton, LEBT | 2087 |
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| The Los Alamos Neutron Science Center operates with two 750 keV Cockcroft-Walton accelerators for simultaneous injection of H+ and H− ion beams into a 800 MeV linear accelerator. The proton ion beam is produced using a duoplasmatron source and the H− ion beam is formed with a cesiated, multi-cusp-field, surface converter ion source. An overview of ion injector status, recent low energy beam transport line optimizations and ion source performance improvements will be presented. To reduce long term operational risks and to improve existing LANSCE beam production for all facility users, new injector upgrades are underway: 1) replacing the H+ CW injector with a Radio-Frequency Quadruple accelerator and 2) increasing H− ion beam brightness and extending source lifetime using the novel SNS RF negative ion source. The status of upgrade projects will be discussed. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS071 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS073 | Analysis of Electron Beam Divergence in Diamond Field Emitter Array Cathodes | focusing, experiment, simulation, electron | 2090 |
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Funding: Los Alamos National Laboratory (LANL) Laboratory Directed Research and Development (LDRD) program (Contract DE-AC52-06NA25396) and Sandia National Laboratories (Contract DE-NA-0003525). At Los Alamos National Laboratory (LANL), we have recently established a capability to fabricate diamond array cathodes for electron beam sources. Our fabricated diamond field emitter arrays (DFEAs) are the arrays of micrometer-scale diamond pyramids with nanometer-scale sharp tips and produce high per-tip current (> 15 μA per-tip) in DC testing. For the beam divergence measurements, we designed and assembled a test stand consisting of a DFEA cathode, a mesh aperture of 0.375-inch for an anode, and AZO (ZnO:Al2O3) screen coated on a sapphire substrate for beam visualization. A negative voltage of about 40 kV is applied to the cathode, and the mesh and the screen are kept at ground. We measure a size of the electron beam on the AZO screen at different mesh to screen distances at a fixed cathode-mesh gap in order to calculate the beam divergence angles. We also perform the beam dynamics simulations with Computer Simulation Technology (CST) Studio and General Particle Tracer (GPT) using a single pyramidal shape with a nanowire tip model. In this presentation, the measured experimental results of the beam divergences will be compared to the beam dynamic simulations. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS073 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS076 | RF Design of APEX2 Cavities | gun, cavity, electron, brightness | 2094 |
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Funding: Director of Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 APEX2 is a proposed high repetition rate, high brightness electron source based on CW normal conducting RF cavities, aiming to further extend the brightness performance for FEL and UED/UEM beyond APEX. APEX2 consists of two cavities, one gun cavity for generating photo-electrons and one following cavity for beam energy boosting. In this paper, we present the RF design of the APEX2 cavities. The design has considered both beam dynamics requirements and engineering feasibility. A novel geometry optimization method with Genetic Algorithm has been implemented in the design procedure. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS076 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS079 | Overcoming Multipacting Barriers in SRF Photoinjectors | cavity, gun, electron, SRF | 2105 |
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| Superconducting RF (SRF) photoinjectors are considered to be a potential breakthrough in the area of high brightness electron sources. However, there is always the very important question of the compatibility of SRF cavities and high quantum efficiency (QE) photocathodes. A deposition of active elements from high QE photocathodes on the surface of a cavity makes it more vulnerable to multipacting (MP) and could affect the operation of an SRF gun. On the other side, MP can significantly reduce the lifetime of a photocathode. It is well known in the SRF community that a strong coupling, high forward power and sufficient cleanliness of cavity walls are the key components to overcome a low-level MP zone. In this paper we present a theoretical model of passing a MP barrier which could help estimate the desirable conditions for successful operation of an SRF gun. We demonstrate our results for the 113 MHz SRF photo-injector for Coherent electron Cooling (CeC) alongside with the experimental observations and 3D simulations of the MP discharge in the cavity. The results of the theoretical model and simulations show good agreement with the experimental results, and demonstrate that, if approached carefully, MP zones can be easily passed without any harm to the photocathode. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS079 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS080 | Beam Dynamics Studies of an APEX2-Based Photoinjector | solenoid, gun, emittance, focusing | 2109 |
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| APEX2 is a proposed normal conducting radio-frequency (RF) electron gun operating in the very high frequency (VHF) range in continuous wave (CW) mode, designed to drive applications that require both high beam brightness and high repetition rate, such as free electron lasers (such as LCLS-II-HE), ultra-fast electron diffraction, and microscopy. The gun consists of a two-cell RF cavity operating at 162.5 MHz with a cathode field of 34 MV/m, together with an embedded focusing solenoid. We study the beam dynamics in an APEX-II-based photoinjector (up to ~20 MeV), targeting a transverse 95% beam emittance of 0.1 um at 12.5 A peak current for the case of 100 pC charge for FEL applications. The high cathode field leads to enhanced beam brightness, while the increased gun exit energy of ~1.5 MeV reduces the effects of space charge, and possibly eliminates the need for an RF buncher. The embedded solenoid is designed to control the transverse beam size while minimizing emittance growth due to geometric aberrations. As a result, the transverse beam performance targets are achieved, and ongoing work will further optimize longitudinal beam quality for downstream FEL transport. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS080 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS083 | Simulations and Experimental Plans for a High-Repetition-Rate Field-Enhanced Conduction-Cooled Superconducting RF Electron Source | cavity, electron, SRF, simulation | 2113 |
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Funding: Work supported by DOE awards DE-SC0018367 with NIU and DE-AC02-07CH11359 with Fermilab. We present a novel RF design for a field enhanced electron source driven by field emission cathodes. The proposed electron source relies on the enhanced high electric field gradients at the cathode to simultaneously extract and accelerate electrons. The system will be tested in a conduction-cooled superconducting radio-frequency cavity recently demonstrated at Fermilab. In this paper, we present electromagnetic and thermal simulations of the setup that support the feasibility of the design. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS083 | ||
| About • | paper received ※ 18 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS084 | Performances of Silicon-Based Field-Emission Cathodes Coated with UltraNano Crystalline Diamond | electron, experiment, vacuum, simulation | 2117 |
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Funding: Work supported by NSF grant PHY-1535401 and DOE award DE-SC0018367 with NIU Field-emission electron sources have been considered as possible candidates for the production of bright or high-current electron bunches. In this paper, we report on the experimental characterization of silicon-based field-emitter arrays (FEA) in a DC high voltage gap. The silicon cathodes are produced via a simple self-assembling process. The measurement reported in this paper especially compares the field-emission properties of a nanostructured and planar diamond-coated Si-based cathode. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS084 | ||
| About • | paper received ※ 17 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS085 | Design Study of 3.6-cell C-band Photocathode Electron Gun | gun, emittance, simulation, FEL | 2121 |
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| A C-band photocathode injector composed of a 3.6-cell C-band photocathode RF gun and two 1.8-meter C-band accelerating structures is proposed. The injector is a low emittance electron source for Free Electron Lasers (FEL) and other compact light sources. The RF structure of the cavities is designed with 2D SUPERFISH simulation. The Beam dynamic study in ASTRA helps rectify the 2D RF simulation. To feed the cavities, a design of extra coaxial coupler with RF gun structure is presented. With compact focusing solenoids, for 0.25nC bunch charge, the final energy can reach 6.9 MeV energy and the 95% emittance can be as low as 0.23 mm mrad (95%). All the details of RF design and beam dynamics studies are presented in this paper. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS085 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS088 | A Normal Conducting RF Gun as an Electron Source for JLEIC Cooling | gun, emittance, electron, solenoid | 2127 |
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| The baseline design for a magnetized injector for the bunched-beam electron cooler ring, as part of the Jeffer-son Lab Electron Ion Collider (JLEIC) uses a DC photo-cathode electron gun as the source. A challenging aspect of this concept is transporting a 3.2nC electron bunch at low energy and preserving the angular momentum. An RF gun source has been investigated to gauge the potential advantages of high gradient on the photocathode and higher exit energy. The design is presented and compared with the baseline results. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS088 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS089 | Observations of the Femtosecond Laser-Induced Emission From the Diamond Field Emitter Tips | laser, electron, photon, experiment | 2130 |
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Funding: Los Alamos National Laboratory LDRD Program We present the results of experimental observation of emission from single diamond field emitter tips when triggered by an ultra-short laser pulse. Diamond field emitter array (DFEA) cathodes were originally proposed for applications that require large current densities. DFEAs represent periodic arrays of diamond pyramids with micron-size dimensions and tips with diameters of the order of tens of nanometers. DFEAs are known to produce significant currents in field emission regime under direct current (DC) fields and in radio-frequency (RF) guns. It has been proposed that single diamond tip emitters can be employed for production of small tightly focused electron beams for dielectric laser accelerators (DLAs) that accelerate particles using the energy of light produced by infrared lasers. To generate short electron bunches required by DLAs diamond pyramids may be triggered with a laser. We have recently observed emission produced by a single diamond pyramid when triggered by a laser at different wavelengths from 256 nm to 2020 nm. We have conducted studies with the goal to understand mechanism of the emission. We clearly observed the change in emission mechanism when the wavelength changed from 256 nm to 512 nm. We believe that while the emission at 256 nm is a clear photoemission, the emission at longer wavelengths is likely the field emission caused by intense electric fields of the laser. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS089 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS090 | Experimental Results of Dense Array Diamond Field Emitters in RF Gun | gun, experiment, solenoid, wakefield | 2134 |
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| We present experimental emission results from arrays of diamond field emitter tips operating in an RF gun at the Argonne Cathode Test-stand. Results from various arrays will be presented with different spacing between array elements. Very high charge densities were produced at various field gradients. The maximum field gradient for a particular geometry was discovered and break-down effects will be presented. Cathode lifetime was preliminarily studied. Further experiments are being planned and work on the cathode design optimization to produce higher quality beams will be discussed. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS090 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS091 | Physics of Electron Beam Generation and Dynamics From Diamond Field Emitter Arrays | electron, simulation, ECR, experiment | 2137 |
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Funding: Work supported by the LDRD program at Los Alamos National Laboratory Many applications such as compact accelerators and electron microscopy demand high brightness electron beams with small beam size and low emittance. Electric-field-assisted diamond emitters manufactured from semiconductor processes are strong candidates for cathodes in such sources. The micro-scale pyramid structure of the emitter has the desirable attribute of significant field enhancement at the sharp interfaces (apex and edges) to facilitate electron emission. We use the LSP particle-in-cell code to simulate the diamond emitter in a diode setup and obtain the beam size and divergence. An empirical fit of the fields around the apex is extracted for detail study. The trend of the beam divergence observed in the simulation is further corroborated using electron’s trajectory in the empirical field model. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS091 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS093 | Magnetized Gridded Thermionic Electron Source | electron, gun, emittance, simulation | 2140 |
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Funding: This manuscript has been authored by Jefferson Science Associates, LLC under Contract No. DE-AC05-06OR23177 with the U.S. Department of Energy. The study of magnetized electron beam has become a high priority for its use in ion beam cooling as part of Electron Ion Colliders and the potential of easily forming flat beams for various applications. The demand for high average current for effective ion beam cooling has caused consideration of using bunched magnetized electron beam produced by a gridded thermionic electron gun. This paper presents the design of a potential electron source for JCIEC first measurements characterizing the beam properties of a magnetized thermionic gun. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS093 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS101 | Bi-Alkali Antimonide Photocathodes for LEReC DC Gun | electron, gun, vacuum, laser | 2154 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Low Energy RHIC electron cooling (LEReC) is a bunched electron cooler at RHIC. The Bi-alkali photocathodes are chosen as electron source due to its long lifetime and high QE at visible wavelength. Because the DC gun needs to produce 24/7 beams over several months, cathode production system and multiple cathodes transferring systems are designed, commissioned and in operation. In this report, we will describe our photocathodes production and discuss the cathode’s performance from cathode growth system to the DC gun. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS101 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS102 | New Activation Techniques for Higher Charge Lifetime from GaAs Photocathodes | electron, gun, laser, site | 2157 |
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| GaAs is the choice of photocathode material for polarized electron sources. The well established method of activating GaAs for beam extraction is to use Cs and Oxygen to create a ’Negative Electron Affinity’(NEA) layer. However, this layer is highly sensitive to vacuum and gets damaged due to ion back bombardment in DC guns. In this work, we explore activation methods that used Tellurium in conjunction with the usual Cs and Oxygen. We report our method to activate GaAs and show charge lifetime results for our activation method. Our results show that the use of Te could potentially help with longer charge lifetimes from GaAs cathodes in DC guns. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS102 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS103 | The Progress of High Current High Bunch Charge Polarized Electron HVDC Gun | gun, electron, vacuum, high-voltage | 2160 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The high current and high bunch charge polarized electron source is essential for cost reduction of eRHIC. It aims to deliver electron beam with 10 mA average current and 5.3 nC bunch charge. We analyzed the mechanism of cathode degradation and proposed using a large strain superlattice GaAs photocathode in a high voltage DC gun to increase the charge lifetime above kilo Coulomb. The gun has been designed and fabricated and expected to start commissioning by the mid of this year. In this paper, we will present the modeling of ion back bombardment and cathode degrading. We proposed an anode offset scheme to increase cathode lifetime. Also, we will describe the details of gun design and the strategies to demonstrate high current high charge polarized electron beam from this source. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS103 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS104 | Spatio-Temporal Shaping of the Photocathode Laser Pulse for Low-Emittance Shaped Electron Bunches | laser, electron, emittance, simulation | 2163 |
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Funding: This work is supported by the U.S. DOE contract No. DE- SC0017750 with Euclid Techlabs LLC., No. DE-SC0018656 with NIU, and No. DE-AC02-06CH11357 with ANL. Photocathode laser shaping techniques to generate temporally shaped electron bunches are appealing owing to their simplicity. Such technique is being considered to form shaped electron bunches to enhance the transformer ratio in beam-driven accelerators. At low energy (i.e. during the emission process) the transverse and longitudinal space charge effects are coupled so that attaining a low beam transverse emittance require the laser to be spatiotemporal shaped. In this paper, we explore the generation of a linearly-ramped bunch with optimized transverse emittance by temporally and radially shaping the laser pulse to provide an adequate initial distribution. We discuss a possible implementation of the optical shaping technique and describe a planned experiment. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS104 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS105 | High Current High Charge Magnetized and Bunched Electron Beam from a DC Photogun for JLEIC Cooler | laser, electron, gun, emittance | 2167 |
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Funding: This project was supported by the U.S. DOE Basic Energy Sciences under contract No. DE-AC05-060R23177. Additional support comes from Laboratory Directed Research and Development program. A high current, high charge magnetized electron beamline that has been under development for fast and efficient cooling of ion beams for the proposed Jefferson Lab Electron Ion Collider (JLEIC). In this paper, we present the latest progress over the past year that include the generation of picosecond magnetized beam bunches at average currents up to 28 mA with exceptionally long photocathode lifetime, and the demonstrations of magnetized beam with high bunch charge up to 700 pC at 10s of kHz repetition rates. Detailed studies on a stable drive laser system, long lifetime photocathode, beam magnetization effect, beam diagnostics, and a comparison between experiment and simulations will also be reported. These accomplishes marked an important step towards the essential feasibility for the JLEIC cooler design using magnetized beams. (To be inserted) |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS105 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS111 | Study on Improving Durability of Cs-Te Photocathode for an RF-gun | gun, electron, vacuum, brightness | 2182 |
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| At Waseda University, we have been studying for high quality electron beam generation using 1.6 cell Cs-Te photocathode rf-gun. We use photocathode as the electron source, which can generate high- quality electron beam such as low emittance, and short bunch. The performance of photocathode is evaluated mainly in terms of quantum efficiency (Q.E.) and lifetime. Cs-Te photocathode used in the rf-gun is known for high Q.E. about 10% with UV light and relatively longer lifetime among semiconductor photocathodes. Since it is a hard environment for photocathode inside the gun, it is necessary to replace the photocathode every several months. In other words, in order to achieve long-term operation of rf-gun, it is necessary to find highly durable photocathode recipe. It has been reported that the Cs-Te photocathode by co-evaporation can produce a photocathode having a longer lifetime as compared with the sequential evaporation. Moreover, we have done studies to improve lifetime and durability of Cs-Te photocathode by coating the cathode surface with CsBr thin film. In this conference, we report the evaluation results of Cs-Te photocathode by co-evaporation, CsBr coating and future prospects. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS111 | ||
| About • | paper received ※ 12 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS113 | Microwave Thermionic Electron Gun for Synchrotron Light Sources | gun, electron, cavity, coupling | 2189 |
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Funding: This work was supported by the U.S. Department of Energy, Office of Basic Energy Science, under contracts DE-SC0015191 and DE- AC02-06CH11357. Thermionic RF guns are the source of electrons used in many practical applications, such as drivers for synchrotron light sources, preferred for their compactness and efficiency. RadiaBeam Technologies has developed a new thermionic RF gun for the Advanced Photon Source at Argonne National Laboratory, which would offer substantial improvements in reliable operations with a robust interface between the thermionic cathode and the cavity, as well as better RF performance, compared to existing models. This improvement became possible by incorporating new pi-mode electromagnetic design, robust cavity back plate design, and a cooling system that will allow stable operation for up to 1 A of beam current and 100 Hz rep rate at 1.5 μs RF pulse length, and 70 MV/m peak on-axis field in the cavity. In this paper, we discuss the electromagnetic and engineering design of the cavity and provide the test results of the new gun. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS113 | ||
| About • | paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS117 | Photocathode Activities at INFN LASA | operation, electron, laser, gun | 2203 |
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| We present the activity on alkali antimonide photocathodes at INFN LASA. The long term goal is to transfer to these photocathodes the know-how acquired in the successful development of cesium telluride photocathodes, nowadays used in many leading FEL facilities and accelerator complex. In this paper we present and discuss the results so far obtained on alkali antimonide films grown in our R&D system and the status of the new preparation system specifically designed for these sensitive materials. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS117 | ||
| About • | paper received ※ 16 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS118 | LASA Activities on Surface Treatment of Low-beta Elliptical Cavities | cavity, SRF, FEL, superconductivity | 2207 |
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| This paper describes the efforts made by LASA on the development of surface treatments for low-beta elliptical cavities, for the current series production of ESS and the foreseen series production of PIP-II. The traditional techniques of buffered chemical polishing and electropolishing are here discussed taking into account the industrial environment, the practical issues due to the size and geometry of such cavities and according to the required qualification values for quality factor and accelerating gradient. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS118 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| WEPMP044 | Mu2e Electrostatic Septa Volumetric Exchange of Fc-40 Dielectric in High Radiation Environments | radiation, GUI, septum, extraction | 2434 |
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Funding: * Operated by FRA, LLC under Contract No. DEAC02-07CH11359 and Grant Award No. LAB 18-1802 with the United States Department of Energy. Two electrostatic septa (ESS) are being designed for the slow extraction of 8 GeV proton beam for the Mu2e experiment at Fermilab. Special attention is given to the high voltage feedthrough (HVF), which energizes the cathode creating the bending field. The FC-40 dielectric fluid, surrounding the HV cable breaks down from radiation exposure, which reduces its insulating capabilities. The new HVF design focuses on effective replacement of the exposed fluid and eliminating the stagnant areas of low exchange rate. A preliminary test using a fully transparent prototype HVF and water was conducted to understand the volumetric exchange rate of the high radiation region. Here we discuss the results of these tests and further studies using the FC-40. ** malvare4@fnal.gov *** vnagasl@fnal.gov |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP044 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| WEPGW010 | Diagnostics and First Beam Measurements at FLUTE | electron, laser, diagnostics, experiment | 2484 |
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| FLUTE (Ferninfrarot Linac- Und Test-Experiment) is a compact versatile linear accelerator at the Karlsruhe Institute of Technology (KIT). It serves as a platform for a variety of accelerator studies as well as a source of strong ultra-short THz pulses for photon science. In the commissioning phase of the 7 MeV low energy section the electron bunches are used to test the different diagnostics systems installed in this section. An example is the split-ring-resonator-experiment. In this contribution we report on the commissioning status of the beam diagnostics and present first beam measurements at FLUTE. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW010 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| WEPGW051 | Designing of a Solenoid Lens for the Application to a Compact Electron Beam Testing Bench | solenoid, electron, gun, space-charge | 2591 |
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| To calculate beams transport is vital for designing vacuum pipe and arranging focusing elements for each electron beam line system. Space charge effects of a low-energy, high-intensity DC electron beam focused by a solenoid lens with bucking coil are investigated theoretically in this paper. A second-order equation is numerical solved for the beam envelope focused by a short solenoid lens. In addition, a conventional transfer matrix of solenoid is not applicable to low-energy, high-intensity electron beams because the strong space charge effects are ignored. By cutting a solenoid into several segments, we have derived a micro-transfer matrix which takes space charge fields into account, and a complete beam envelope for a transport system. A simulation is used to verify our theoretical calculation results, and corresponding discussions are given in detail. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW051 | ||
| About • | paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| WEPGW105 | Measuring Beam Parameters with Solenoid | solenoid, focusing, experiment, emittance | 2739 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. We have developed methods of measuring electron beam energy and trajectory including angle and position based on the analysis of beam steering by a solenoid. Beam energy measurement is performed in the straight beamline and is suitable for the beams with substantial energy spread. In this paper, we describe the experimental set-up and the obtained results. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW105 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| WEPGW108 | Transverse Uncorrelated Emittance Diagnostic for Magnetized Electron Beams | emittance, electron, diagnostics, simulation | 2745 |
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Funding: This manuscript has been authored by Jefferson Science Associates, LLC under Contract No. DE-AC05-06OR23177 with the U.S. Department of Energy. The study of magnetized electron beam has become a high priority for its use in ion beam cooling as part of Electron Ion Colliders and the potential of easily forming flat beams for various applications. In this paper, a new diagnostic is described with the purpose of studying transverse magnetized beam properties. The device is a modification to the classic pepper-pot, used in this novel context to measure the uncorrelated components of transverse emittance in addition to the typical effective emittance. The limitations of traditional methods are discussed, and simulated demonstrations of the new technique shown. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW108 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| WEPGW114 | Interferometric Measurement of Bunch Length of a 3Mev Picocoulomb Electron Beam | laser, electron, experiment, space-charge | 2766 |
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Funding: BNL LDRD We report the bunch length measurement of low-energy 3 MeV electron beams in picosecond regime with the charge from 1.0 to 14 pC. It is the first time that we demonstrate single-cycle nano-joule coherent terahertz (THz) radiation from 3MeV electron beam can be meas-ured via a far-infrared Michelson interferometer using a QOD. At this low energy range, when charge is about 1 pC, the signal from the conventional helium-cooled sili-con composite bolometer is too low. Compared to the bunch length measurement via the ultrafast-laser-pump and electron-beam-probe in the timescale 10-14 to 10-12 s which is determined by the phase-transition dynamics in solids, the advantages are: there are no needs of pump laser and probe sample, greatly simplifying the experi-ment; the timing jitter between laser and electron beams contributes no error to the bunch length measurement; furthermore, the method can be extended to sub-picosecond regime enabling bunch length measurement in a much broader timescale 10-14 to 10-11 s for low-energy electron beams. In the current experiment the bunch length is limited to 1 ps only because the setup of driving laser to cathode with a large 70° incident angle, effective-ly lengthening the laser pulse to ≥1 ps. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW114 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| WEPRB037 | Development of EP System at IHEP | cavity, controls, MMI, power-supply | 2890 |
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| Electropolishing (EP) is a necessary technology for high quality cavities including both high accelerating gradient and high quality factor cavities, which will be used for several future large projects such as CEPC, Shanghai hard X-ray FEL, ILC, and so on. An EP system was development at IHEP, CAS. In last years, we finished all the engineering design and fabrication including functional circulation loops design, system parameters choices, key equipment choice or design, components test and fabrication. According to the functions of various components, the whole system were divided into three main units: electrolyte mixing, acid solution and mechanical platform, and several key components such as rotation sleeves, DC power supply and so on. Since the system is designed for both R&D and mass production, several characteristics comparing with those in other labs in the world can be realized, including dozens of solution circulations, electrolyte mixing, new and old acid separation, cavity outside water cooling, cathode vertical assembly, and compatible for several types of cavities. We will report them in this paper. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB037 | ||
| About • | paper received ※ 21 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| WEPRB072 | Ultra-High Gradient Short RF Pulse Gun | gun, electron, emittance, brightness | 2987 |
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Funding: DOE SBIR DE-SC0018709 High brightness beams enable novel applications like x-ray free electron lasers and ultrafast electron microscopes. High brightness beams essentially consist of a large number of electrons in a small phase space volume, i.e. a high peak current. When such beams are generated from the cathode, there is a strong space charge force, which elongates the bunch and reduces its brightness. An optimal solution is to raise the accelerating voltage in the gun. However, the maximum gradient is limited by the effects of RF breakdown. The probability of RF breakdown is reduced as the RF pulse length decreases. We present a development of an electron photoinjector operating with short RF pulse, 10 ns scale. We have designed an X-band gun including the RF design, beam quality optimization, and engineering. The gun will be fed by 10 ns, 300 MW RF pulse generated at the Argonne Wakefield Accelerator Facility for two-beam acceleration experiments. We also manufactured an aluminum prototype and measured its microwave properties, most importantly, fill time. The proposed high brightness beam source can be used as the main beam in wakefield accelerators. It will find commercial applications in ultrafast electron diffraction and microscopy systems. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB072 | ||
| About • | paper received ※ 21 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019 | ||
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| WEPRB084 | Mechanical Design and Analysis of the Proposed APEX2 VHF CW Electron Gun | cavity, gun, vacuum, electron | 3014 |
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Funding: Work supported by the Office of Science, U.S. Department of Energy under DOE contract number DEAC02-05CH11231 Normal conducting radio-frequency (RF) guns resonating in the very high frequency (VHF) range (30-300 MHz) and operating in continuous wave (CW) mode have successfully achieved the targeted brightness and reliability necessary for upgrading the performance of current lower repetition rate accelerator-based instruments such as X-ray free electron lasers (FELs), and ultra-fast electron diffraction (UED) and microscopy (UEM). The APEX2 (Advanced Photo-injector Experiment 2) electron gun is a proposed upgrade for the current LCLS-II injector, which was based on the original APEX design. In contrast, APEX2 is designed as a two-cell cavity operating at 162.5 MHz with a launching field at the cathode equal to 34 MV/m, producing a beam energy of 1.5 to 2 MeV, more than double APEX. Operation of the gun in this condition will require upwards of 200 kW of RF power, thus proper thermal management is crucial to achieve target performance. This paper describes the current design, thermal performance and tuning methods. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB084 | ||
| About • | paper received ※ 13 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019 | ||
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| WEPRB094 | Measurements of the Electrical Axes of the CeC PoP RF Cavities | cavity, gun, SRF, electron | 3031 |
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| It is common knowledge that every mode in an SRF cavity has a so-called electrical axis, and only in an ideal cavity would this axis align exactly with the geometrical axis of the device. The misalignment of the electrical axis creates an additional undesirable transverse kick to the beam, which has to be corrected to achieve the designed beam parameters. In this paper we present the two methods which have been used in order to determine the electrical axes in the RF cavities of the Coherent electron Cooling (CeC) Proof of Principle (PoP) accelerator. The electron accelerator for the CeC PoP consists of the three main RF components: the 113 MHz SRF gun, the two normal-conducting 500 MHz bunching cavities, and the 704 MHz SRF 5-cell elliptical cavity. We discuss, in detail, the specifics of the measurement for each cavity and provide the corresponding results. In addition, we describe the influence of the field asymmetry in the 500 MHz bunchers on the beam dynamics, which was observed experimentally and confirmed by simulations. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB094 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | ||
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| WEPTS007 | Short Bunch Experiment at EXALT Facility | laser, experiment, electron, gun | 3100 |
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| Nowdays, different applications required short bunches, with low energy spread and low emittances. On EXALT facility, we perform an experiment with a short (few100 femtosecond) laser pulse on a photocathode in a 3 GHz RF gun. We perform the measurement of the single photon emission process with a copper cathode. We show that the longitudinal photoinjector model via transfer matrix is suitable for the reconstruction of the bunch duration even in short pulse mode with an increased accurracy charge below 20 pC. We clearly measure the parabolic profile in the energy spectrum resulting from blow out phenomena at the cathode due to strong space charge forces. Measurements are also compared with the Astra simulations. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS007 | ||
| About • | paper received ※ 21 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| WEPTS013 | The Cooling Effect of Beam Self-Fields on the Photocathode Surface in High Gradient RF Injectors | emittance, laser, electron, space-charge | 3112 |
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| The intrinsic slice emittance of the emitted electrons on the photocathode surface at each moment during the transient photoemission process depends on the transverse size of the slice and the mean kinetic energy of the electrons within the slice. The latter relies on the surface barrier potentials of the cathode material at a fixed wavelength of the incident light, and is thus significantly influenced by the presence of strong rf and beam self-fields at / close to the cathode surface. This is, in particular, the case in high brightness injectors for modern free electron lasers. In this article, the beam self-fields are determined in a self-consistent approach, based on which improved transverse and temporal emission distributions are obtained. The nonlinear correlations of the intrinsic surface slice emittance within the bunch are shown for multiple bunch charges. A peak to peak variation of the intrinsic surface emittance is estimated as 30\% for the highest charge-density case considered in this paper. An overall reduction of the average intrinsic emittance is computed as 10\% accordingly. The cooling effect on the cathode surface is enhanced as the local space-charge density rises. Furthermore, the impacts of the cooling effect on downstream beam qualities are demonstrated through particle tracking simulations based on the injector setup at the Photo Injector Test Facility at DESY in Zeuthen (PITZ). | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS013 | ||
| About • | paper received ※ 27 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| WEPTS048 | Electron Beam Dynamics Simulation for Electron Lenses | electron, gun, simulation, experiment | 3220 |
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| A test stand is under construction at CERN to study high perveance electron guns, electron beam dynamics, and electron beam diagnostics for electron lenses. It will be used to test electron guns for the Hollow Electron Lenses under consideration for beam halo control for High Luminosity LHC (CERN), and for the Space Charge Compensation at SIS18 (GSI) in the frame of the EU funded ARIES project. In order to prepare for this test stand, simulations will be presented and compared with experiments undertaken at the Fermilab (FNAL) electron lens test stand. These were conducted using a hollow electron gun, with the magnetic field configuration and beam current varied to study their effect. The impact of imperfections on the beam dynamics and overall quality of the electron beam will be discussed. A method for comparing experimental data with simulation is also presented to allow bench-marking of the computer models and simulation tools that will later be applied to the analysis of measurements performed at CERN. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS048 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| WEPTS069 | The Effects of Stochastic Space Charge in High Brightness Photolectron Beamlines for Ultrafast Electron Diffraction | space-charge, simulation, electron, emittance | 3283 |
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Funding: This work was supported by the U.S. National Science Foundation under award PHY-1549132, the Center for Bright Beams. As we move to ultra-high brightness photocathodes and ultra-cold beams, we may become more sensitive to stochastic, point-to point effects such as disorder induced heating and the Boersch effect, given the failure of Debye screening. In this study, we explore the effects of stochastic scattering. Modern beam dynamics codes often approximate point to point interactions with a potential created by smoothing the charge over space, removing sensitivity to stochastic effects. This approximation is often used in beamline optimization, because it is much faster. We study the limits of validity of this approximation. In particular, we will simulate effects of stochastic space charge on a high brightness photoemission beamline, an ultrafast electron diffraction beamline with a photocathode temperature of 5 meV with a final beam energy of 225 keV. Emittance dilution in the transverse plane and transverse beam size relative to smooth space charge simulations will be presented. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS069 | ||
| About • | paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| THPMP013 | Challenges Towards Industrialization of the ERL-FEL Light Source for EUV Lithography | FEL, cavity, SRF, undulator | 3478 |
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| EUV Lithography is going to HVM (high volume manufacturing) stage with 250-W-class laser-produced plasma sources and it is important to develop a new-type EUV light source to meet future demand for higher power. Energy-recovery linac based free-electron lasers (ERL-FELs) are possible candidates of a high-power EUV light source that can distribute 1 kW power to multiple scanners simultaneously. In Japan, an ERL-FEL based EUV light source has been designed using available technologies without much development to demonstrate generation of EUV power more than 10 kW and the EUV-FEL Light Source Study Group for Industrialization has been established since 2015 to realize industrialization of the light source and the related items. For industrialization, high availability is essential as well as high power and reduction of the light source size is also required. In this paper, we will report an overview of the designed ERL-FEL light source for EUV lithography and some activities for the industrialization and describe considerations and developments for obtaining high availability and size reduction of the light source. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP013 | ||
| About • | paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| THPMP016 | Design of the Condenser System and Imaging System for a UEM | electron, gun, experiment, cavity | 3485 |
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| The ultrafast electron microscope provides a useful tool for exploring fine structure and observing dynamic process at nanometer and picosecond scale, which has been extensively applied in chemistry and biological field. After emitting from the electron gun, electron beams are focused on the stage sample by the condenser system and then be projected by the imaging system on the screen. In the present study, a two-lens condenser system is simulated by Parmela and a three-lens imaging system is designed using thin-lens approximation. Besides, the shape factor of metallic spheres which have different radius for perturbation method is measured, which is conductive to measuring the Z/Q parameter and the electric field along the axis of the C-band 3MeV photocathode gun for the UEM. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP016 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| THPMP047 | Advanced Modeling and Optimization of Thermionic Energy Converters | interface, simulation, framework, diagnostics | 3552 |
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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 DE-SC0017162 Thermionic energy converters (TEC) are a class of thermoelectric devices, which promise improvements to the efficiency and cost of both small- and large-scale electricity generation. A TEC is comprised of a narrowly-separated thermionic emitter and an anode. Simple structures are often space-charge limited as operating temperatures produce currents exceeding the Child-Langmuir limit. We present results from 3D simulations of these devices using the particle-in-cell code Warp, developed at Lawrence Berkeley National Lab. We demonstrate improvements to the Warp code permitting high fidelity simulations of complex device geometries. These improvements include modeling of non-conformal geometries using mesh refinement and cut-cells with a dielectric solver, in addition to importing geometries directly from standard CAD output. In this paper we showcase some of these new features and demonstrate their use. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP047 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| THPMP052 | Recent Progress in R&D for Ionetix Ion-12SC Superconducting Cyclotron for Production of Medical Isotopes | cyclotron, ion-source, target, controls | 3568 |
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| The Ion-12SC is a sub-compact, 12.5 MeV proton su-perconducting isochronous cyclotron for commercial medical isotope production recently developed at Ionetix Corporation [1]. The machine features a patented cold steel and cryogen-free conduction cooling magnet, a low power internal cold-cathode PIG ion source, and an inter-nal liquid target [2]. It was initially designed to produce N-13 ammonia for dose on-demand cardiology applica-tions but can also be used to produce F-18, Ga-68 and other medical isotopes widely used in Positron Emission Tomography (PET). The 1st engineering prototype was completed and commissioned in September 2015, and four additional units have been completed since [3]. The first two units have been installed and operated at the University of Michigan and MIT. R&D efforts in physics and engineering have continued to improve machine performance, stability and reliability. These improve-ments include: 1) Water cooling added to the dummy dee to limit the operating temperature of the ion source to improve lifetime and performance, 2) Magnetic field maps, obtained with a Hall probe based mapper, were used to accurately measure the isochronism and provide information needed to compensate for any unwanted 1st harmonics and 3) Feedback based control methods ap-plied to regulate the beam intensity on target by adjusting the ion source cathode current. The C1 unit installed at the University of Michigan Medical School early this year treated ~100 patients/month with N-13 ammonia. The machines are now capable of routinely producing > 21 doses/day with > 99% availability. The Ionetix manu-facturing facility is capable of producing up to 30 ma-chines per year. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP052 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| THPGW043 | Conceptual design of a MeV Ultrafast Electron Diffraction Based on 1.4 Cell RF Gun | electron, gun, emittance, laser | 3679 |
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| Ultrafast Electron Diffraction (UED) is a powerful tool to investigate the dynamic structure with temporal scale of 100 femtoseconds and spatial scale of atomic length. To achieve high quality diffraction patterns, the transverse emittance and the longitudinal length of electron bunches should be reduced. MeV UED, using photocath-ode RF gun instead of traditional DC gun, is being developed to produce high quality electron bunches with lower emittance and shorter length. We are developing a MeV UED facility based on a 1.4 cell photocathode RF gun that can provide higher acceleration gradient at Huazhong University of Science and Technology. In this paper, the conceptual design of the MeV UED is pro-posed with typical parameters of the system, as well as the ASTRA simulation results of optimization. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW043 | ||
| About • | paper received ※ 11 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| THPGW054 | Generation and Delivery of an Ultraviolet Laser Beam for the RF-Photoinjector of the Awake Electron Beam | laser, electron, plasma, proton | 3709 |
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| In the AWAKE experiment, the electron beam is used to probe the proton-driven wakefield acceleration in a 10 m long rubidium vapor source. Electron bunches are produced using an RF-gun equipped with a Cs2Te photocathode illuminated by an ultraviolet (UV) laser pulse. To generate the UV laser beam a fraction of the infrared (IR) laser beam used for ionization of rubidium is extracted from the laser system, time-compressed to a picosecond scale and frequency tripled using nonlinear crystals. The transport line of the laser beam over the 20 m distance was built using rigid supports for mirrors and air-evacuated tube to prevent any possible beam pointing instabilities due to vibrations and air convection. Construction of the UV beam optical system enables appropriate beam shaping and control of its size and position on the cathode, as well as time delay with respect to the IR pulse, i.e. with respect to the plasma wakefield seeder. In this paper, we present the design of the UV beam line and results of its commissioning regarding IR/UV conversion, beam pointing stability, and means of beam control and monitoring. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW054 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019 | ||
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| THPRB050 | LLRF System Modelling and Controller Design in UED | LLRF, electron, cavity, controls | 3924 |
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| In the Ultrafast Electron Diffraction (UED) facility for investigating material structure, drifts of amplitude and phase in cavity have different effects on beam quality. So it is critical for pump-probe experiments in the UED to keep accurate synchronization between the laser and electron. To achieve the desired 50fs resolution, the Low Level Radio Frequency (LLRF) controller in S-band normal conducting cavity needs to satisfy the stability: ±0.01% (rms) for the amplitude and ±0.01° (rms) for the phase, respectively. Then we can study the performance of the RF control system by simulating the LLRF system. In the simulation program, feedback, feed-forward algorithms, and beam current variations can be simulated in a Matlab/Simulink environment. This paper shows that a model-based controller design can meet the necessary requirements of the field regulation and implement the algorithms. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB050 | ||
| About • | paper received ※ 20 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| THPRB105 | ESS Klystron Production Test Stand | klystron, high-voltage, controls, power-supply | 4074 |
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| Diversified Technologies, Inc. (DTI) has delivered a new long-pulse modulator klystron test stand to Communication and Power Industries (CPI) in Palo Alto, CA for full power testing of production VKP-8292A klystrons for the European Spallation Source (ESS). This test stand was built using hardware and designs from an earlier SBIR effort for the US Department of Energy, with modifications to support ESS requirements and klystron testing operation. Earlier versions of this design are in use at IPN Orsay and CEA Saclay in France to test RF components for ESS. This new klystron test stand allows testing of klystrons at the full ESS specifications: 100 kV, 50 A, 3.5 ms pulse, 14 Hz,. This design is based on a (patent pending) non-dissipative regulator that compensates for the capacitor droop voltage (~20%) during the pulse. This allows a much smaller capacitor than would nominally be required for the long ESS pulse, eliminating the need for larger, more expensive capacitor bank. This test stand will speed delivery of ESS klystrons, and similar, long pulse, high power klystrons at CPI. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB105 | ||
| About • | paper received ※ 19 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| THPTS064 | Sub-Picosecond X-Ray Streak Camera using High-Gradient RF Cavities | electron, photon, gun, simulation | 4256 |
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Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515. We are developing an ultrafast diagnostic system for X-ray beams from Synchrotron Light Sources and Free-Electron Lasers. In this system, the X-ray beam is focused on the photocathode of a high-gradient radio-frequency cavity that accelerates the photo-emitted electrons to a few MeV while preserving their time structure. The accelerated electron beam is streaked by radio-frequency deflectors and then imaged on a screen. This approach will allow orders of magnitude improvement in time resolution over traditional streak cameras and could potentially enable time-resolved diagnostics of sub-100 fs X-ray pulses. We present preliminary beam dynamics simulations of this system and discuss the implementation. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS064 | ||
| About • | paper received ※ 11 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| THPTS080 | Novel Technique Ion Assisted In-Situ Coating of Long, Small Diameter, Accelerator Beam Pipes with Compacted Thick Crystalline Copper Film | lattice, cryogenics, vacuum, plasma | 4301 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy Although great progress was made with in-situ copper coating, by magnetron sputtering, to address the high room temperature resistivity, literature indicates that conventionally deposited thick copper films do not retain the same RF conductivity at cryogenic temperatures, since straightforward deposition tends to result in films with columnar structure and other lattice defects, which cause significant conductivity degradation at cryogenic temperatures. We utilize energetic ions for ion assisted deposition (IAD) to reduce lattice imperfections, for coating. IAD that can in-situ coat long small diameter tubes with compacted crystalline structure thick copper films has been developed. Moreover, development of techniques and devices can resurrect IAD for other applications, which have been impractical and/or not viable economically. Comparison of conductivity at cryogenic temperatures between straight magnetron physical vapor deposition and IAD will be presented. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS080 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| THPTS090 | Injection Locked 1497 MHz Magnetron | klystron, status, operation, injection | 4322 |
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| Muons, In is building an amplitude modulated phase-locked magnetron to replace the klystrons in CEBAF. To do that requires changing the magnetic field at a rate that would induce eddy currents in the standard magnetron. We report on the status of the project to make a stainless steel anode with copper elements to minimize heating while the stainless steel reduces eddy current effects. The construction of the magnetron is two months from completion, while the test stand is ready for delivery of the magnetron | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS090 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| THPTS091 | Phase and Frequency Locked 350 MHz Magnetron | operation, injection, status, vacuum | 4325 |
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| The 120kW 350 MHz magnetron is being developed for a number of RF systems, chiefly among them, Niowave’s 10 MeV accelerator. Industri-al applications of the magnetron have also been explored. The CW magnetron can be operated in the pulse mode by a novel injection locking system. We report on the status of the program and progress to date | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS091 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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