Keyword: laser
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MOZBA3 Strongly Tapered Helical Undulator System for TESSA-266 undulator, electron, experiment, permanent-magnet 63
 
  • T.J. Campese, R.B. Agustsson, I.I. Gadjev, A.Y. Murokh
    RadiaBeam, Santa Monica, California, USA
  • W. Berg, A. Zholents
    ANL, Lemont, Illinois, USA
  • P.E. Denham, P. Musumeci, Y. Park
    UCLA, Los Angeles, USA
  
  Funding: DOE SBIR Award No. DE-SC0017102
RadiaBeam, in collaboration with UCLA and Argonne National Laboratory (ANL), is developing a strongly tapered helical undulator system for the Tapering Enhanced Stimulated Superradiant Amplification experiment at 266 nm (TESSA-266). The experiment will be carried out at the APS LEA facility at ANL and aims at the demonstration of very high energy conversion efficiency in the UV. The undulator system was designed by UCLA, engineered by RadiaBeam, and is presently in fabrication at RadiaBeam. The design is based on a permanent magnet Halbach scheme and includes a short 30 cm long buncher section and four 1 m long undulator sections. The undulator period is fixed at 32 mm and the magnetic field amplitude can be tapered by tuning the gap along the interaction. Each magnet can be individually adjusted by 1.03 mm, offering up to 25% magnetic field tunability with a minimum gap of 5.58 mm. A custom designed 316L stainless steel beampipe runs through the center with a clear aperture of 4.5 mm. This paper discusses the design and engineering of the undulator system, fabrication status, and plans for magnetic measurements, and tuning. 		 
slides icon Slides MOZBA3 [8.942 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA3  
About • paper received ※ 27 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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MOPLM13 Investigations of the Electron Beam Energy Jitter Generated in the Photocathode RF Gun at the Advanced Photon Source Linac gun, timing, electron, cathode 124
 
  • J.C. Dooling, D. Hui, A.H. Lumpkin, T.L. Smith, Y. Sun, K.P. Wootton, A. Zholents
    ANL, Lemont, Illinois, USA
  
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02- 06CH11357.
Characterizations continue of the electron beam properties of a recently installed S-band photocathode (PC) rf gun at the Advanced Photon Source Linac facility. In this case, we have utilized a low-energy spectrometer beam line located 1.3 m downstream of the gun cavity to measure the electron beam energy, energy spread, and energy jitter. The nominal energy was 6.5 MeV using a gun gradient of 110 MV/m, and the energy spread was ~17 keV when driven by a 2.5-ps rms duration UV laser pulse at the selected rf gun phase. An energy jitter of 25 keV was initially observed in the spectrometer focal plane images. This jitter was partly attributed to the presence of both the 2nd and 3rd harmonics of the 119 MHz synchronization signal provided to the phase locked loop of the drive laser oscillator. The addition of a 150-MHz low-pass filter in the 119-MHz line strongly attenuated the two harmonics and resulted in a reduced energy jitter of ~15 keV. Comparisons of the gun performance to ASTRA simulations will also be presented. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM13  
About • paper received ※ 28 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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MOPLM18 Design of the 2-Stage Laser Transport for the Low Energy RHIC Electron Cooling (LEReC) DC Photogun gun, electron, cathode, alignment 144
 
  • P. Inacker, S. Bellavia, A.J. Curcio, A.V. Fedotov, W. Fischer, D.M. Gassner, J.P. Jamilkowski, P.K. Kankiya, D. Kayran, D. Lehn, R. Meier, T.A. Miller, M.G. Minty, S.K. Nayak, L.K. Nguyen, L. Smart, C.J. Spataro, A. Sukhanov, J.E. Tuozzolo, Z. Zhao
    BNL, Upton, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The electron beam for the recently constructed Low Energy RHIC electron Cooler (LEReC) at Brookhaven National Laboratory is generated by a high-power fiber laser illuminating a photocathode. The pointing stability of the low-energy electron beam, which is crucial to maintain within acceptable limits given the long beam transport, is highly dependent on the center-of-mass (CoM) stability of the laser spot on the photocathode. For reasons of accessibility during operations, the laser itself is located outside the accelerator tunnel, leading to the need to propagate the laser beam 34 m via three laser tables to the photocathode. The challenges to achieving the required CoM stability of 10 microns on the photocathode thus requires mitigation of vibrations along the transport and of weather- and season-related environmental effects, while preserving accessibility and diagnostic capabilities with proactive design. After successful commissioning of the full transport in 2018/19, we report on our solutions to these design challenges.
LEReC Photocathode DC Gun Beam Test Results - D. Kayran Conference: C18-04-29, p.TUPMF025
Commissioning of Electron Accelerator LEReC for Bunch Beam Cooling - D.Kayran, NAPAC19 		 
poster icon Poster MOPLM18 [1.970 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM18  
About • paper received ※ 27 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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MOPLM24 LCLS-II Injector Commissioning Beam Based Measurements electron, gun, cathode, MMI 157
 
  • C.M. Zimmer, T.J. Maxwell, F. Zhou
    SLAC, Menlo Park, California, USA
  
  Funding: Department of Energy
Injector commissioning is underway for the LCLS-II MHz repetition rate FEL, currently under construction at SLAC. Methodology of injector beam-based measurements and early results with low beam charge will be presented, along with the software tools written to automate these various measurements. 		 
poster icon Poster MOPLM24 [10.104 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM24  
About • paper received ※ 28 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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MOPLS01 Spectroscopic Correlations to Resistive Switching of Ion Beam Irradiated Films radiation, ECR, experiment, scattering 160
 
  • K.N. Rathod, N.A. Shah, P.S. Solanki
    Saurashtra University, Rajkot, Gujarat, India
  • K. Asokan
    IUAC, New Delhi, India
  • K.H. Chae, J.P. Singh
    Korea Institute of Science and Technology, Advanced Analysis Center, Seoul, Republic of Korea
  
  Researchers concentrated on resistive random access memories (RRAMs) due to excellent scalability, high integration density, quick switching, etc*,**. Intrinsic physical phenomenon of RRAMs is resistive switching. In this work, ion beam irradiation was used as a tool to modify resistive switching of pulsed laser deposited (PLD) Y0.95Ca0.05MnO3/Si films. Ion irradiation induced optimal resistive switching with spectroscopic correlations has been attributed to oxygen vacancy gradient. Resistive switching ratio is estimated to be increased for the film irradiated with fluence 1×1011 ions/cm2 due to irradiation induced strain and oxygen vacancies verified by X’ray diffraction (XRD), Raman, atomic force microscopy (AFM), Rutherford backscattering spectrometry (RBS) and near-edge X-ray absorption fine structure (NEXAFS) measurements. Strain relaxation and oxygen vacancy annihilation have been realized for higher fluence (1×1012 and 1×1013 ions/cm2) owing to local annealing effect. Present study suggests that the films understudy can be considered as emerging candidates for RRAMs.
* X.J. Zhu et al., Front. Mater. Sci. 6 (2012) 183, 206.
** D.S. Jeong et al., Rep. Prog. Phys. 75 (2012) 076502:1,31.
 		 
poster icon Poster MOPLS01 [0.745 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLS01  
About • paper received ※ 26 August 2019       paper accepted ※ 16 November 2020       issue date ※ 08 October 2019  
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MOPLS08 Error Tolerance Characterization for the HUST MeV Ultrafast Electron Diffraction System emittance, electron, injection, simulation 166
 
  • Y. Song, K. Fan, C.-Y. Tsai
    HUST, Wuhan, People’s Republic of China
  
  Ultrafast electron diffraction (UED) is a powerful tool for probing atomic dynamics with a femtosecond resolution. Such a spatiotemporal resolution requires error tolerance for the UED system which includes the RF system, the laser system, the beamline elements, etc. To characterize the error tolerance of the required spatiotemporal resolution for the 1.4-cell MeV UED we are developing, we use ASTRA to simulate the UED model with errors including initial transverse beam centroid offset, RF amplitude jitter and injection phase jitter, etc. By performing simulations with different errors omitted, we can characterize the contribution of each error and thus set the tolerance for each error to obtain the required performance of UED experiment. In the end, we present the error tolerance for 10% emittance growth and 100 fs time of flight variation to maintain the required spatiotemporal resolution.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLS08  
About • paper received ※ 25 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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MOPLH02 Study of Photocathode Surface Damage due to Ion Back-Bombardment in High Current DC Gun cathode, gun, simulation, electron 174
 
  • J.P. Biswas
    Stony Brook University, Stony Brook, USA
  • O.H. Rahman, E. Wang
    BNL, Upton, New York, USA
  
  Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704, with the U.S. DOE
In high current DC gun, GaAs photocathode lifetime is limited by the ion back-bombardment. While gun operation ions are generated and accelerate back towards the cathode thus remove the activation layer’s material Cesium from the photocathode surface. We have developed an object-oriented code to simulate the ion generation due to dynamic gas pressure and ion trace in the electromagnetic field. The pressure profile varies from cathode position towards the transfer line behind the anode, which signifies the importance of dynamic simulation for ion back-bombardment study. In our surface damage study, we traced the energy and position of the ions on the photocathode surface and performed the Stopping and Range of Ions in Matter(SRIM) simulation to count the number of Cesium atoms removed from the surface due to single bunch impact. Cesium atom removal is directly related to the photocathode Quantum Efficiency(QE) decay. Our new dynamic simulation code can be used in any DC gun to study ion back-bombardment. We have used this new code to better understand the ion generation in prototype BNL 350 KV DC gun, and we have also estimated the normalized QE decay due to ion back-bombardment. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH02  
About • paper received ※ 27 August 2019       paper accepted ※ 03 September 2019       issue date ※ 08 October 2019  
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MOPLH09 Photoluminescence Studies of Alkali-Antimonide Photocathodes electron, experiment, cathode, photon 188
 
  • P. Saha, O. Chubenko, S.S. Karkare
    Arizona State University, Tempe, USA
  • H.A. Padmore
    LBNL, Berkeley, California, USA
  
  Alkali-antimonide photocathodes have a very high quantum efficiency and a low intrinsic emittance, making them excellent electron sources for Energy Recovery Linacs, X-ray Free Electron Lasers, Electron Cooling, and Ultrafast Electron Diffraction applications. Despite numerous studies of their photoemission spectra, there has been nearly no conclusive experimental investigation of their basic electronic and optical properties (e.g. band gap, electron affinity, optical constants, etc.), which determine the nature of photoemission. Therefore, the systematic study and deep understanding of fundamental characteristics of alkali-antimonide photocathodes are required in order to develop next-generation electron sources with improved crystal and electronic structures to fit specific application. Here we report on the development of an experimental setup to measure photoluminescence (PL) spectra from alkali-antimonide photocathodes, enabling estimation of a material band gap and defect state energies, and provide preliminary results for Cs3Sb films.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH09  
About • paper received ※ 27 August 2019       paper accepted ※ 04 September 2019       issue date ※ 08 October 2019  
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MOPLH13 STARRE Lab: The Sub-THz Accelerator Research Laboratory electron, experiment, GUI, operation 199
 
  • J.F. Picard, S.C. Schaub, R.J. Temkin
    MIT/PSFC, Cambridge, Massachusetts, USA
  
  Funding: Department of Energy, Office of HEP, DE- SC0015566; Office of Fusion Energy Sciences, DE-FC02-93ER54186; National Institutes of Health, NIBIB, EB004866 and EB001965;
This work presents the development of the STARRE Lab, a facility at MIT for testing breakdown in high gradient accelerator structures at 110 GHz. The system utilizes a Laser-Driven Semiconductor Switch (LDSS) to modulate the output of a megawatt gyrotron, which generates 3 μs pulses at up to 6 Hz. The LDSS employs silicon (Si) and gallium arsenide (GaAs) wafers to produce nanosecond-scale pulses at the megawatt level from the gyrotron output. Photoconductivity is induced in the wafers using a 532 nm Nd:YAG laser, which produces 6 ns, 230 mJ pulses. A single Si wafer produces 110 GHz RF pulses with 9 ns width, while under the same conditions, a single GaAs wafer produces 24 ns 110 GHz RF pulses. In dual-wafer operation, which uses two active wafers, pulses of variable length down to 3 ns duration can be created at power levels greater than 300 kW. The switch has been successfully tested at incident 110 GHz RF power levels up to 720 kW.* The facility has been used to successfully test an advanced 110 GHz accelerator structure built by SLAC to gradients in excess of 220 MV/m.
*J.F. Picard et al., Appl. Phys. Lett. 114, 164102 (2019); doi: https://doi.org/10.1063/1.5093639
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH13  
About • paper received ※ 24 August 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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MOPLH14 Ultrafast Nonlinear Photoemission from Alkali Antimonide Photocathodes photon, electron, cathode, gun 203
 
  • W.H. Li, M.B. Andorf, I.V. Bazarov, L. Cultrera, C.J.R. Duncan, A. Galdi, J.M. Maxson, C.A. Pennington
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: This work was supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams.
Alkali antimonides photocathodes are a popular choice of electron source for high average brightness beams, due to their high quantum efficiency (QE) and low mean transverse energy (MTE). This paper describes the first measurements of their nonlinear photoemission properties under sub-ps laser illumination. These measurements include wavelength-resolved power dependence, pulse length dependence, and temporal response. The transition between linear and nonlinear photoemission is observed through the wavelength-resolved scan, and implications of nonlinear photoemission are discussed. 		 
poster icon Poster MOPLH14 [0.543 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH14  
About • paper received ※ 27 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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MOPLH16 Femtosecond Laser Microfabrication for Advanced Accelerator Applications controls, FEM, polarization, cathode 207
 
  • S.P. Antipov, E. Dosov, E. Gomez, S.V. Kuzikov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
  
  Funding: DOE SBIR
Femtosecond laser microfabrication allows for precise dimension control and reduced thermal stress of the machined materials. It can be applied to a wide range of materials from copper to diamond. Combined with secondary operations like polishing laser microfabrication can be utilized in various state of the art components required for AAC community. In this paper we will review several applications of laser microfabrication for Advanced Accelerator research and development. These will include wakefield structures (corrugated metal and dielectric loaded), plasma capillaries, x-ray refractive optics, high power laser optical components: mirrors, phase plates. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH16  
About • paper received ※ 28 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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MOPLH22 Focusing Studies of an Electron Beam in Diamond Field Emitter Array Cathodes cathode, electron, experiment, focusing 217
 
  • R.L. Fleming, H.L. Andrews, D. Gorelov, C.-K. Huang, D. Kim, J.W. Lewellen, K.E. Nichols, V.N. Pavlenko, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
  
  Funding: Los Alamos National Laboratory LDRD Program
We present the simulations and test results for focusing studies performed on diamond field emitter array cathodes. This design utilized a simple variable-focus solenoidal lens in conjunction with a scanning wire technique in order to measure the beam spot size. The spot size was measured by scanning a thin copper wire across the beam in 1 µm increments, with voltage being measured and averaged at each location in order to map the location and intensity of the beam. Scans were taken at different distances away from the magnetic center of the lens, and show good agreement with our simulations of the beam. Ultimately this has allowed us to focus the beam to a spot size of 5.72 µm with an average current of 15.78 µA. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH22  
About • paper received ※ 27 August 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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MOPLH24 Towards the Optimization Of Photocathode Properties Via Surface Science Techniques: A Study On Cs3Sb Thin Film Growth cathode, electron, vacuum, emittance 224
 
  • A. Galdi, J. Balajka, W.J.I. DeBenedetti, M. Hines
    Cornell University, Ithaca, New York, USA
  • I.V. Bazarov, L. Cultrera, F. Ikponmwen, J.M. Maxson, S.A. McBride
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: National Science Foundation Grant No. PHY-1549132
A better understanding of the properties of photocathode materials can be achieved by integrating advanced growth and surface science techniques in their synthesis and analysis. This is a main research theme of the Center for Bright Beams, whose goal is increasing the brightness of linear electron accelerators. Alkali antimonides are efficient photocathode materials and have very low intrinsic emittance at cryogenic temperatures.* A limiting factors is the surface roughness and chemical inhomogeneity of the films.** We studied the influence of growth parameters on the morphology and composition of Cs3Sb thin films. The films are codeposited using pure element sources and transferred via UHV suitcase to a STM/XPS analysis chamber, to study in particular the influence of substrate temperature and material. This platform can be expanded to more analysis and growth systems thanks to a specially designed sample holder and suitcase. An example is a new cryogenic instrument for intrinsic emittance measurements.
* L. Cultrera et al., Phys. Rev. ST ’ Acc. Beams 18 (2015) 113401
** G. Gevorkian et al., Phys. Rev. Accel. Beams, 21 (2018) 093401 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH24  
About • paper received ※ 28 August 2019       paper accepted ※ 30 August 2019       issue date ※ 08 October 2019  
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MOPLH25 Characterization of Femtosecond-Laser-Induced Electron Emission from Diamond Nano-Tips electron, FEM, photon, polarization 228
 
  • V.N. Pavlenko, H.L. Andrews, R.L. Fleming, D. Gorelov, D. Kim, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
  • D.S. Black, K.J. Leedle
    Stanford University, Stanford, California, USA
  
  Funding: LANL Laboratory Directed Research and Development (LDRD).
Nanocrystalline diamond is a promising material for electron emission applications, as it combines robustness of diamond and ability to easily conform to a pre-defined shape, even at nano-scale. However, its electron emission properties are yet to be fully understood. Recently, we started to investigate femtosecond-laser-induced strong-field photoemission from nanocrystalline diamond field emitters with very sharp (~10 nm apex) tips. Initial results show that the mechanism of electron emission at ~1010 W/cm2 light intensities in the near UV to near IR range is more complex than in metals. We present our latest experimental results obtained at Stanford University, while LANL’s strong-field photoemission test stand is being commissioned. We show that strong-field photoemission occurs not only at the nano-tip’s apex, but also on flat diamond surfaces (e.g., pyramid sides), that is why extra care needs to be taken to differentiate between emission spots on the chip. Qualitatively, we discuss the models that explain the observed dependences of electron emission on the optical power, polarization of the light, etc. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH25  
About • paper received ※ 27 August 2019       paper accepted ※ 06 September 2019       issue date ※ 08 October 2019  
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MOPLO06 Black Gun Technologies for DC Photoinjectors gun, vacuum, electron, scattering 247
 
  • E.J. Montgomery, C. Jing, S. Poddar
    Euclid Beamlabs LLC, Bolingbrook, USA
  • J.E. Butler
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • S. Zhang
    JLab, Newport News, Virginia, USA
  
  Funding: Work supported by the US DOE Office of Science, Office of Nuclear Physics, grant number DESC0019688. Work at Argonne CNM under Contract No. DE-AC02-06CH11357.
Euclid Beamlabs is developing a new "Black Gun" concept in direct current (DC) photoinjectors. To reduce electron-stimulated desorption indirectly influenced by stray photoemission, we are testing advanced optical coatings and low-scattering optics compatible with the extreme high vacuum (XHV) environment of modern DC photoinjectors. Stray light in DC photoinjectors (in proportion to the photoemitted charge) causes off-nominal photoemission, initiating electron trajectories which intercept downstream surfaces. This causes electron-stimulated desorption of atoms, which ionize and may back-bombard the cathode, reducing its charge lifetime. Back-bombardment is key for high average current or high repetition rate. First, we report on progress developing optical skimmers based on Butler baffles to collimate both incoming and outgoing laser beams. Second, we describe candidate coatings for reduction of scattered light. Requirements for these coatings are that they be conducting, optically black at the drive laser wavelength, conformally applied to complex geometry, and XHV-compatible with negligible outgassing. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO06  
About • paper received ※ 04 September 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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MOPLO07 MEMS Based Multibeam Ion Linacs acceleration, extraction, quadrupole, ion-source 249
 
  • T. Schenkel, G. Giesbrecht, Q. Ji, A. Persaud, P.A. Seidl
    LBNL, Berkeley, California, USA
  • K. Afridi, A. Lal, D. Ni, S. Sinha
    Cornell University, Ithaca, New York, USA
  
  Funding: Work at LBNL was conducted under the auspices of the US DOE (DE-AC0205CH11231) and supported by ArpaE. Device fab at the Cornell Nano Fab facility was supported by NSF (Grant 384 No.ECCS-1542081).
We report on the development of multi-beam RF linear ion accelerators that are formed from stacks o low cost wafers. Wafers are prepared using MEMS techniques. We have demonstrated acceleration of ions in a 3x3 beamlet array with ion currents in the 0.1 mA range and acceleration at the 10 keV in lattice of RF (13 MHz) acceleration units and electrostatic quadrupoles. We will describe the status and plans for scaling to 10x10 beams, ion currents >1 mA and ion energies >100 keV in a compact, low cost setup for applications in materials processing.
[1] P. A. Seidl, et al., Rev. Sci. Instr. 89, 053302 (2018); doi: 10.1063/1.5023415 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO07  
About • paper received ※ 27 August 2019       paper accepted ※ 16 November 2020       issue date ※ 08 October 2019  
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MOPLO23 Investigation of Various Fabrication Methods to Produce a 180GHz Corrugated Waveguide Structure in 2mm Diameter ­0.5m ­Long Copper Tube for the Compact Wakefield Accelerator for FEL Facility GUI, electron, wakefield, FEL 286
 
  • K.J. Suthar, D.S. Doran, W.G. Jansma, S.S. Sorsher, E. Trakhtenberg, G.J. Waldschmidt, A. Zholents
    ANL, Lemont, Illinois, USA
  • A.E. Siy
    UW-Madison/PD, Madison, Wisconsin, USA
  
  Funding: This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility operated by the Argonne National Laboratory under Contract No. DE­AC02­06CH11357.
Argonne National Laboratory is developing a 180 GHz wakefield structure that will house in a co-linear array of accelerators to produce free-electron laser-based X-rays. The proposed corrugated waveguide structure will be fabricated on the internal wall of 0.5m long and 2mm nominal diameter copper tube. The estimated dimensions of these parallel corrugations are 200 µm in pitch with 100 µm side length (height and width). The length scale of the structure and requirements of the magnetic field-driven dimensional tolerances have made the structure challenging to produce. We have employed several method such as optical lithography, electroforming, electron discharge machining, laser ablation, and stamping to produce the initial structure from a sheet form. The successive fabrication steps, such as bending, brazing, and welding, were performed to achieve the long tubular-structure. This paper discusses various fabrication techniques, characterization, and associated technical challenges in detail.
[1] A. Zholents et al., Proc. 9-th Intern. Part. Acc. Conf., IPAC2018, Vancouver, BC, Canada, p. 1266, (2018)
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO23  
About • paper received ※ 27 August 2019       paper accepted ※ 06 September 2019       issue date ※ 08 October 2019  
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TUYBA3 Benchmarking the LCLS-II Photoinjector simulation, gun, solenoid, emittance 301
 
  • N.R. Neveu, T.J. Maxwell, C.E. Mayes
    SLAC, Menlo Park, California, USA
  
  Funding: DOE Contract No. DE-AC02-76SF00515
Commissioning of the LCLS-II photoinjector started in late 2018. Efforts to accurately model the gun and laser profiles is ongoing. Simulations of the photoinjector and solenoid are performed in ASTRA, IMPACT-T and OPAL-T. This work includes efforts to use the laser profile at the virtual cathode as the initial transverse beam distribution, and effects of 2D and 3D field maps. Beam size results are compared to experimental measurements taken at the YAG screen located after the gun. 		 
slides icon Slides TUYBA3 [1.320 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUYBA3  
About • paper received ※ 29 August 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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TUYBA4 Optimization of an SRF Gun Design for UEM Applications SRF, gun, cavity, electron 305
 
  • A. Liu, P.V. Avrakhov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • C. Jing, R.A. Kostin
    Euclid Beamlabs LLC, Bolingbrook, USA
  
  Funding: DOE contract DE-SC0018621
Benefiting from the rapid progress on RF photocathode gun technologies in the past two decades, the development of MeV-range ultrafast electron diffraction/microscopy (UED and UEM) has been identified as an enabling instrumentation, which may lead to breakthroughs in fundamental science and applied technologies *. Euclid is designing an SRF cavity as the UEM electron gun. As implementing a solenoid for emittance compensation in the gun is limited by the superconductivity performance and available space, the geometry of the first 0.3 cell of the cavity is optimized for transverse focusing and emittance reduction.
*: T. Chase, et al, "Ultrafast electron diffraction from non- equilibrium phonons in femtosecond laser heated Au films." Applied Physics Letters, 2016 		 
slides icon Slides TUYBA4 [7.583 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUYBA4  
About • paper received ※ 30 August 2019       paper accepted ※ 04 September 2019       issue date ※ 08 October 2019  
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TUYBB2 Manipulating H− Beams with Lasers proton, electron, extraction, emittance 309
 
  • A. Rakhman, A.V. Aleksandrov, S.M. Cousineau, T.V. Gorlov, Y. Liu, A.P. Shishlo
    ORNL, Oak Ridge, Tennessee, USA
  
  Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
In recent years lasers have been playing a vital role in many H− beam measurements and experiments. This talk will review current state of development of various applications using lasers for manipulating H− ion beams in accelerators. A wide range of applications will be reviewed such as beam diagnostics, laser-assisted charge-exchange injection, generation of arbitrary H0 pulse patterns and others. An overview of ongoing developments and prospects for other laser H− beam interactions will also be given. 		 
slides icon Slides TUYBB2 [16.483 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUYBB2  
About • paper received ※ 28 August 2019       paper accepted ※ 12 September 2019       issue date ※ 08 October 2019  
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TUZBB4 Space Charge Study of the Jefferson Lab Magnetized Electron Beam electron, cathode, space-charge, gun 360
 
  • S.A.K. Wijethunga, J.R. Delayen, G.A. Krafft
    ODU, Norfolk, Virginia, USA
  • J.F. Benesch, F.E. Hannon, C. Hernandez-Garcia, G.A. Krafft, M.A. Mamun, M. Poelker, R. Suleiman, S. Zhang
    JLab, Newport News, Virginia, USA
  
  Magnetized electron cooling could result in high luminosity at the proposed Jefferson Lab Electron-Ion Collider (JLEIC). In order to increase the cooling efficiency, a bunched electron beam with high bunch charge and high repetition rate is required. We generated magnetized electron beams with high bunch charge using a new compact DC high voltage photo-gun biased at -300 kV with alkali-antimonide photocathode and a commercial ultrafast laser. This contribution explores how magnetization affects space charge dominated beams as a function of magnetic field strength, gun high voltage, laser pulse width, and laser spot size.  
slides icon Slides TUZBB4 [12.582 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUZBB4  
About • paper received ※ 28 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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TUPLM18 Improving Energy Resolution and Compensating Chromatic Aberration With a TM010 Microwave Cavity cavity, electron, gun, simulation 411
 
  • C.J.R. Duncan
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • P. Cueva, J.M. Maxson, D.A. Muller
    Cornell University, Ithaca, New York, USA
  
  Funding: National Science Foundation under Award OIA-1549132, the Center for Bright Beams
The intrinsic energy spread of electron sources limits the achievable resolution of electron microscopes in both spectroscopic and spatially resolved measurements. We propose that the TM010 mode of a single radio frequency (RF) cavity be used to dramatically reduce this energy spread in a pulsed beam. We show with analytic approximations, confirmed in simulations, that the non-linear time-energy correlations that develop in an electron gun can be undone by the RF cavity running near-crest. We derive an expression that gives the required RF field strength as a function of accelerating voltage. We explore multiple applications, including EELS and SEM. By pulsing a photocathode with commercially available, high repetition-rate lasers, our scheme could yield competitive energy spread reduction at higher currents when compared with monochromated continuous-wave sources for electron microscopes. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM18  
About • paper received ※ 27 August 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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TUPLM26 Progress Toward a Laser Amplifier for Optical Stochastic Cooling radiation, undulator, experiment, synchrotron-radiation 434
 
  • A.J. Dick, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • M.B. Andorf
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Optical Stochastic Cooling (OSC) is a method of beam cooling using optical frequencies which compresses the phase space of the beam by correcting the deviation of each particle’s momentum. A particle bunch passing through an undulator produces radiation which is amplified and provides the corrective energy kick. In this project, we are testing a method of amplifying synchrotron radiation (SR) for the eventual use in OSC. The SR is amplified by passing through a highly-doped Chromium:Zinc Selenide (Cr:ZnSe) crystal which is pumped by a Thulium fiber laser. The SR will be produced by one of the bending magnets of the Advanced Photon Source. The first step is to detect and measure the power of SR using a photo-diode. The gain is then determined by measuring the radiation amplified after the single-pass through the crystal. This serves as a preliminary step to investigate the performance of the amplification of beam-induced radiation fields. The planned experiment is an important step towards achieving active OSC in a proof-of-principle demonstration in IOTA.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM26  
About • paper received ※ 02 September 2019       paper accepted ※ 13 September 2019       issue date ※ 08 October 2019  
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TUPLM33 Optimization of Beam Parameters for UEM with Photo-Emission S-Band RF Gun and Alpha Magnet electron, gun, emittance, simulation 440
 
  • H.R. Lee, P. Buaphad, I.G. Jeong, Y. Joo, Y. Kim
    University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
  • P. Buaphad, I.G. Jeong, Y. Joo, Y. Kim
    KAERI, Jeongeup-si, Republic of Korea
  • B.L. Cho
    KRISS, Daejeon, Republic of Korea
  • M.Y. Han, J.Y. Lee, S.H. Lee
    Korea Atomic Energy Research Institute (KAERI), Daejeon, Republic of Korea
  • H. Suk
    GIST, Gwangju, Republic of Korea
  
  Ultrafast Electron Microscopy (UEM) is a powerful tool to observe ultrafast dynamical processes in sample materials at the atomic level. By collaborating with KRISS and GIST, the future accelerator R&D team at KAERI has been developing a UEM facility based on a photo-emission S-band (=2856 MHz) RF gun. Recently, we have added an alpha magnet in the beamline layout of the UEM to improve beam qualities such as emittance, divergence, energy spread, and bunch length. To achieve high spatial and time resolutions, we have been optimizing those beam parameters and other machine parameters by performing numerous ASTRA and ELEGANT code simulations. In this paper, we describe our ASTRA and ELEGANT code optimizations to obtain high-quality beam parameters for the UEM facility with a photo-emission S-band RF gun and an alpha magnet.  
poster icon Poster TUPLM33 [0.931 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM33  
About • paper received ※ 30 August 2019       paper accepted ※ 19 November 2019       issue date ※ 08 October 2019  
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TUPLH08 X-Ray and Charged Particle Detection by Detuning of a Microwave Resonator electron, resonance, coupling, experiment 503
 
  • S.P. Antipov, P.V. Avrakhov, E. Dosov, E. Gomez, S.V. Kuzikov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • S. Stoupin
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
  
  Funding: DOE SBIR
Charged particle detection is important for beam alignment, beam loss and background control. In case of halo detection, traditional wire scanner measurement utilizing carbon or tungsten wires is limited by the damage threshold of these materials. In this paper we present an electrodeless method to measure halo with a diamond scraper. This measurement utilizes a microwave resonator placed around the diamond scraper which is sensitive to charged particle-induced conductivity. Due to this transient induced conductivity in the dielectric, a microwave coupling to the resonator changes. Diamond in this case is chosen as a radiation hard material with excellent thermal properties. The absence of electrodes makes the device robust under the beam. The same measurement can be done for x-ray flux monitoring which is important for measurement feedback and calibration at modern x-ray light sources. In this case x-rays passing through the diamond sensing element enable a photo-induced conductivity and that in turn detunes the cavity placed around the diamond. Diamond being a low-Z material allows for in-line x-ray flux measurement without significant beam attenuation. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH08  
About • paper received ※ 28 August 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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TUPLE04 An Iris Diaphragm Beam Detector for Halo or Profile Measurements detector, experiment, electron, GUI 566
 
  • A. Liu
    Euclid TechLabs, LLC, Solon, Ohio, USA
  
  Funding: DOE contract DE-SC0019538
Beam halo includes the part of beam that ends up outside of the phase space of the main beam core. It can arise from field emission in the gun and accelerating structures (dark current) and be emitted independently in time and space from the photoelectric emission at the cathode generated by the drive laser. In order to fully understand and characterize the beam halo, Euclid is developing an iris diaphragm detector that allows the beam core to pass without interception, while the halo is collimated. The detector can also work for beam profile measurements. This paper discusses about the recent studies on the iris detector. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLE04  
About • paper received ※ 27 August 2019       paper accepted ※ 19 November 2019       issue date ※ 08 October 2019  
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TUPLE13 Analytical Thermal Analysis of Thin Diamond in High-Intensity High-Repetition-Rate Application FEL, electron, operation, free-electron-laser 587
 
  • Y. Hong, B. Yang
    University of Texas at Arlington, Arlington, USA
  • J. Wu, G. Zhou
    SLAC, Menlo Park, California, USA
  
  Thin diamond plates are used in monochromator for X-ray Free-Electron Laser self-seeding scheme. To function properly, they must endure high-intensity and high-repetition-rate laser pulses without crossing thresholds set by various adverse effects, such as thermal strain-induced diffraction distortion and graphitization. In this work, a theoretical model is developed, and an analytical solution is derived to elucidate potential thermal runaway under edge cooling condition. It is shown that the crystal edge cooling can effectively mitigate the issue to a certain extent. The analytical solution can be used as an efficient tool for XFEL operation parameter setup.  
poster icon Poster TUPLE13 [0.939 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLE13  
About • paper received ※ 27 August 2019       paper accepted ※ 06 September 2019       issue date ※ 08 October 2019  
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WEYBB5 A Crab-Crossing Scheme for Laser-Ion Beam Applications experiment, linac, cavity, injection 639
 
  • A.V. Aleksandrov, S.M. Cousineau, T.V. Gorlov, Y. Liu, A. Rakhman, A.P. Shishlo
    ORNL, Oak Ridge, Tennessee, USA
  
  Lasers have recently been used in many applications to H− beams, including laser charge exchange, laser wire scanners, and laser temporal pulse patterning. The H− beam in these applications has wide variation ofμpulse length width dependence on focusing of the RF cavities, energy spread of the beam, and space charge forces. Achieving the required laser pulse length for complete overlap with the H− can be challenging in some scenarios when available laser power constrained. The scheme proposed here utilizes a crab-crossing concept between the laser and the ion beam to achieve overlap of a short laser pulse with an arbitrarily long H− beam pulse. An experiment to test the hypothesis in the context of H− charge exchange is described.  
slides icon Slides WEYBB5 [5.201 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEYBB5  
About • paper received ※ 30 August 2019       paper accepted ※ 02 September 2019       issue date ※ 08 October 2019  
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WEPLM23 Updated Applications of Advanced Compact Accelerators linac, electron, radiation, site 694
 
  • M. Uesaka
    The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan
  
  We are working for downsizing of RF accelerators from room-size to portable and table-top sizes and applying them to industril and social uses. We have developed portable 950 keV / 3.95 MeV X-band (9.3 GHz) electron linac based X-ray/neutron sources and successfully applied to on-site nondestructive inspection of industrial and social infrastructures such as chemical reaction chambers and bridges following the radiation safety law and regulation in Japan. By using the portable 950 keV / 3.95 MeV X-band electron linac based X-ray sources for on-site actual bridge inspection, we visualize inner reinforcement iron structure. The information of of the iron states is used for the structural analysis of the a bridge in order to evaluate its residual strength and sustainability. Table-topμelectron / ion beam sources using laser dielectric accelerating techniques are under development. The beam energy is ~ 1 MeV, the beam size is ~1 micron. We aim to apply them to 3D dynamic observation of radiation-induced DNA damage / repair for basic research of radiation therapy and low dose effect.  
poster icon Poster WEPLM23 [0.778 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM23  
About • paper received ※ 30 August 2019       paper accepted ※ 19 November 2019       issue date ※ 08 October 2019  
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WEPLH10 Efficiency Estimation for Sequential Excitation Laser Stripping of H− Beam experiment, electron, cavity, proton 827
 
  • T.V. Gorlov, A.V. Aleksandrov, S.M. Cousineau, Y. Liu, A. Rakhman
    ORNL, Oak Ridge, Tennessee, USA
  
  Funding: ORNL is managed by UTBattelle, LLC, under contract DEAC0500OR22725 for the U.S. Department of Energy.
A new laser stripping scheme for charge exchange injection of H− beam is considered. The sequential scheme for the planned demonstration experiment includes two step excitation that requires much smaller laser power compared to the traditional 1-step excitation. The new scheme can be applied to a wider range of H− beam energies and provides more flexibility on the choice of laser frequency. In this paper we discuss the two-step excitation method and estimate laser stripping parameters and stripping efficiency for the SNS accelerator and its future H− energy upgrade to 1.3 GeV. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH10  
About • paper received ※ 22 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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WEPLH11 RHIC Quench Protection Diode Radiation Damage radiation, kicker, experiment, detector 831
 
  • K.A. Drees, O. Biletskyi, D. Bruno, A. Di Lieto, J. Escallier, G. Heppner, C. Mi, T. Samms, J. Sandberg
    BNL, Upton, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Each of RHIC’s superconducting magnets is protected by a silicon quench protection diode (QPD). In total, RHIC has over 800 diodes installed inside the cryostat close to the vacuum pipe~[RHICconfig]. After years of operation with high energy heavy ion beams we experienced a first permanently damaged QPD in the middle of our FY2016 Au Au run and a second damaged diode in the following year. In 2016 the run had to be interrupted by 19 days to replace the diode, in 2017 RHIC could still operate with a reduced ramping speed of the superconducting magnets. Both diodes were replaced and examined "cold" as well as "warm". This paper reports on what we have learned so far about the conditions leading up to the damage as well as the damage itself. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH11  
About • paper received ※ 23 August 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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WEPLO05 Developing Criteria for Laser Transverse Instability in LWFA Simulations plasma, simulation, wakefield, electron 855
 
  • Y. Yan, L.D. Amorim, P. Iapozzuto, V. Litvinenko, N. Vafaei-Najafabadi
    Stony Brook University, Stony Brook, USA
  • M. Babzien, M.G. Fedurin, Y.C. Jing, K. Kusche, M.A. Palmer, I. Pogorelsky, M.N. Polyanskiy
    BNL, Upton, New York, USA
  • M. Downer, J.R. Welch, R. Zgadzaj
    The University of Texas at Austin, Austin, Texas, USA
  • C. Joshi, W.B. Mori
    UCLA, Los Angeles, California, USA
  • P. Kumar, V. Samulyak
    SBU, Stony Brook, USA
  
  Funding: We acknowledge resources of NERSC facility, operated under Contract No. DE-AC02-5CH11231, and of SEAWULF at Stony Brook University as well as funding from SBU-BNL Seed Grants.
Laser-driven plasma wakefield acceleration (LWFA) is considered as a potential technology for future colliders and light sources. To make the best use of a laser’s power, the laser is expected to maintain a stable propagation. A transverse instability is observed in our previous simulations when a long, intense CO2 laser propagates inside a plasma*. This unstable motion is accompanied by strong transverse diffraction of the laser power and results in the disruption of the ion channel typically used for radiation generation**. We investigated the hosing-like instability using the Particle-in-Cell code OSIRIS*** by modeling the laser portion where this instability is seeded and then evolves. In this proceeding, a criteria will be described that allows for the characterization of the temporal and spatial evolution of this instability.
*J. Yan, et al. , AAC, IEEE, 2018.
** L. Nemos et al., PPCF, 58(3), 2016.
***R. A. Fonseca et al., Lecture Notes Computation Science (2331) 342, 2002. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO05  
About • paper received ※ 16 September 2019       paper accepted ※ 04 December 2019       issue date ※ 08 October 2019  
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WEPLO06 Start-to-End Simulation of the Drive-Beam Longitudinal Dynamics for Beam-Driven Wakefield Acceleration simulation, electron, wakefield, linac 858
 
  • W.H. Tan, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • P. Piot
    Fermilab, Batavia, Illinois, USA
  • A. Zholents, A. Zholents
    ANL, Lemont, Illinois, USA
  
  Funding: This work is supported by the U.S. Department of Energy, Office of Science under contracts No. DE-AC02-06CH11357 (via a laboratory- directed R&D program at ANL) and No. DE-SC0018656 at NIU.
Collinear beam-driven wakefield acceleration (WFA) relies on shaped driver beam to provide higher accelerating gradient at a smaller cost and physical footprint. This acceleration scheme is currently envisioned to accelerate electron beams capable of driving free-electron laser *. Start-to-end simulation of drive-bunch beam dynamics is crucial for the evaluation of the design of accelerators built upon WFA. We report the start-to-end longitudinal beam dynamics simulations of an accelerator beamline capable of producing high charge drive beam. The generated wakefield when it passes through a corrugated waveguide results in a transformer ratio of 5. This paper especially discusses the challenges and criteria associated with the generation of temporally-shaped driver beam, including the beam formation in the photoinjector, and the influence of energy chirp control on beam transport stability.
A. Zholents et al., "A Conceptual Design of a Compact Wakefield Accelerator for a High Repetition Rate Multi User X-ray Free-Electron Laser Facility" 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO06  
About • paper received ※ 27 August 2019       paper accepted ※ 03 September 2019       issue date ※ 08 October 2019  
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WEPLO11 Single Cycle THz Acceleration Structures GUI, electron, focusing, acceleration 862
 
  • S.V. Kuzikov, A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
  • S.P. Antipov, E. Gomez
    Euclid TechLabs, LLC, Solon, Ohio, USA
  
  Funding: This work was supported by the Russian Science Foundation under grant 19-42-04133 in the part of CST simulations for THz structures.
Recently, gradients on the order of 1 GV/m level have been obtained in a form of single cycle (~1 ps) THz pulses produced by conversion of a high peak power laser radiation in nonlinear crystals (~1 mJ, 1 ps, up to 3% conversion efficiency). These pulses however are broadband (0.1-5 THz) and therefore a new accelerating structure type is required. For electron beam acceleration with such pulses we propose arrays of parabolic focusing micro-mirrors with common central. These novel structures could be produced by a femtosecond laser ablation system developed at Euclid Techlabs. This technology had already been tested for production of several millimeters long, multi-cell structure which has been testing with electron beam. We also propose using of structures where necessary GV/m E-fields are excited by a drive bunch travelling in the corrugated waveguide. The radiated by drive bunch sequence of short range delayed wakes are guided in this case by metallic disks and reflected back being focused exactly at time when the witness bunch arrives. 		 
poster icon Poster WEPLO11 [2.124 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO11  
About • paper received ※ 27 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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WEPLO16 Energy Spread Measurements for 400 MeV LINAC Beam at Fermilab Booster using a LASER Notcher System booster, linac, injection, experiment 868
 
  • C.M. Bhat, D.E. Johnson
    Fermilab, Batavia, Illinois, USA
  
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
To mitigate 8 GeV beam losses at extraction in the Fermilab Booster synchrotron, a LASER notcher system for multi-turn injection that produces notches at 720 keV is used. These notches synchronize with the revolution period of the beam [ref. HB2018, page 416] at injection in the Booster. Recently, a dedicated notching pattern that keeps a single 201 MHz LINAC bunch untouched in the middle of a notch is developed to measure the beam energy spread by studying the time evolution of this bunch in the Booster. A complementary to this method, recently, it has been realized that one can also measure energy spread of the LINAC beam by injecting <2 Booster turn beam and studying the time evolution of the multiple 201 MHz LINAC bunches. In this paper we present the general principle of the method and results from our measurements. 		 
poster icon Poster WEPLO16 [0.193 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO16  
About • paper received ※ 28 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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WEPLO17 Ultrashort Laser Pulse Shaping and Characterization for Tailored Electron Bunch Generation electron, controls, FEM, diagnostics 871
 
  • T. Xu, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • M.E. Conde, G. Ha, J.G. Power
    ANL, Lemont, Illinois, USA
  • P. Piot
    Fermilab, Batavia, Illinois, USA
  
  Temporally shaped laser pulses are desirable in various applications including emittance reduction and beam-driven acceleration. Pulse shaping techniques enable flexible controls over the longitudinal distribution of electron bunches emitted from the photocathode. While direct manipulation and measurement of an ultrashort pulse can be challenging in the time domain, both actions can be performed in the frequency domain. In this paper, we report the study and development of laser shaper and diagnostics at Argonne Wakefield Accelerator (AWA). Simulations of the shaping process for several sought-after shapes are presented along with the temporal diagnosis. Status of the experiment at the AWA facility is also discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO17  
About • paper received ※ 05 September 2019       paper accepted ※ 04 December 2019       issue date ※ 08 October 2019  
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WEPLO18 Numerical Study of Coherent Radiation from Induced Plasma Dipole Oscillation by Detuned Laser Pulses plasma, radiation, dipole, simulation 874
 
  • P.C. Castillo, S.D. Rodriguez, D.A. Wan
    SUNY Farmingdale State College, State University of New York, Farmingdale, New York, USA
  • B. Gross
    City College of The City University of New York, New York, USA
  • M.S. Hur, S. Kylychbekov, H.S. Song
    UNIST, Ulsan, Republic of Korea
  • D.G. Lee
    SBU, Stony Brook, New York, USA
  • K. Yu
    BNL, Upton, New York, USA
  
  The study of intense laser-plasma interactions is a growing field of both theoretical and applied research. This research focuses on simulating the cross/self-interactions between high-intense short laser pulses and an initial target for preliminary ionization. Unlike our previous studies of laser-matter interaction over preformed plasma, we will explore the injection of laser pulses to induce background plasma driven by the self-guided laser wakefield mechanism, which is used to perturb the plasma for induced dipole oscillations followed by radiation. Inducing a cylindrical spatial plasma column within the laser beam radius regime, it is expected that a stable spatially localized plasma channel will result and the emitted radiation from the plasma dipole oscillation (PDO) will not be affected by surrounding absorption, resulting in effective radiation. We will depict the injection of laser pulses accounting for parameters such as field intensity, profile and phase difference defining the coordinated pulses to assess the potential of enhancing the efficiency and spectral properties of the transverse emitted radiation due to the counter-propagating pulses interaction in plasma.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO18  
About • paper received ※ 27 August 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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THXBA3 Adaptive Machine Learning and Feedback Control for Automatic Particle Accelerator Tuning FEL, electron, controls, target 916
 
  • A. Scheinker
    LANL, Los Alamos, New Mexico, USA
  
  Free electron lasers (FEL) and plasma wakefield accelerators (PWA) are creating more and more complicated electron bunch configurations, including multi-color modes for FELs such as LCLS and LCLS-II and custom tailored bunch current profiles for PWAs such as FACET-II. These accelerators are also producing shorter and higher intensity bunches than before and require an ability to quickly switch between many different users with various specific phase space requirements. For some very exotic setups it can take hours of tuning to provide the beams that users require. In this work, we present results adaptive machine learning and model independent feedback techniques and their application in both the LCLS and European XFEL to 1) control electron bunch phase space to create desired current profiles and energy spreads by tuning FEL components automatically, 2) maximize the average pulse output energy of FELs by automatically tuning over 100 components simultaneously, 3) preliminary results on utilizing these techniques for non-invasive electron bunch longitudinal phase space diagnostics at PWAs.  
slides icon Slides THXBA3 [8.110 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THXBA3  
About • paper received ※ 27 August 2019       paper accepted ※ 15 September 2019       issue date ※ 08 October 2019  
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THYBA6 Active Pointing Stabilization Techniques Applied to the Low Energy RHIC Electron Cooling Laser Transport at BNL electron, controls, operation, cathode 938
 
  • L.K. Nguyen, A.J. Curcio, W.J. Eisele, A.V. Fedotov, A. Fernando, W. Fischer, P. Inacker, J.P. Jamilkowski, D. Kayran, K. Kulmatycski, D. Lehn, T.A. Miller, M.G. Minty, A. Sukhanov
    BNL, Upton, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The electron beam for the Low Energy RHIC electron Cooler (LEReC) at Brookhaven National Laboratory (BNL) is generated by a high-power fiber laser illuminating a photocathode. The pointing stability of the electron beam, which is crucial given its long transport, is highly dependent on the center-of-mass (CoM) stability of the laser spot on the photocathode. For reasons of accessibility during operations, the laser is located outside the accelerator tunnel, and the laser beam is propagated over a total distance of 34 m via three laser tables to the photocathode. The challenges to achieving the required CoM stability of 10 microns RMS on the photocathode include mitigation of the effects of vibrations along the transport and of weather- and season-related environmental effects, while preserving accessibility and diagnostic capabilities. Due to the insufficiency of infrastructure alone in overcoming these challenges, two active laser transport stabilization systems aimed at addressing specific types of position instability were installed during the 2018 Shutdown. After successful commissioning of the full transport in 2018/19, we report on our solutions to these design challenges. 		 
slides icon Slides THYBA6 [3.426 MB]  
poster icon Poster THYBA6 [1.299 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THYBA6  
About • paper received ※ 27 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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THZBA5 First Electron Cooling of Hadron Beams Using a Bunched Electron Beam electron, cavity, MMI, gun 957
 
  • A.V. Fedotov, Z. Altinbas, M. Blaskiewicz, J.M. Brennan, D. Bruno, J.C. Brutus, M.R. Costanzo, K.A. Drees, W. Fischer, J.M. Fite, M. Gaowei, D.M. Gassner, X. Gu, J. Halinski, K. Hamdi, L.R. Hammons, T. Hayes, R.L. Hulsart, P. Inacker, J.P. Jamilkowski, Y.C. Jing, P.K. Kankiya, D. Kayran, J. Kewisch, D. Lehn, C.J. Liaw, C. Liu, J. Ma, G.J. Mahler, M. Mapes, A. Marusic, K. Mernick, C. Mi, R.J. Michnoff, T.A. Miller, M.G. Minty, S.K. Nayak, L.K. Nguyen, M.C. Paniccia, I. Pinayev, S. Polizzo, V. Ptitsyn, T. Rao, G. Robert-Demolaize, T. Roser, J. Sandberg, V. Schoefer, S. Seletskiy, F. Severino, T.C. Shrey, L. Smart, K.S. Smith, H. Song, A. Sukhanov, R. Than, P. Thieberger, S.M. Trabocchi, J.E. Tuozzolo, P. Wanderer, E. Wang, G. Wang, D. Weiss, B.P. Xiao, T. Xin, W. Xu, A. Zaltsman, H. Zhao, Z. Zhao
    BNL, Upton, New York, USA
  
  Funding: Work supported by the U.S. Department of Energy.
The Low Energy RHIC electron Cooler (LEReC) was recently constructed and commissioned at BNL. The LEReC is the first electron cooler based on the RF acceleration of electron bunches (previous electron coolers all used DC beams). Bunched electron beams are necessary for cooling hadron beams at high energies. The challenges of such an approach include generation of electron beams suitable for cooling, delivery of electron beams of the required quality to the cooling sections without degradation of beam emittances and energy spread, achieving required small angles between electrons and ions in the cooling sections, precise energy matching between the two beams, high-current operation of the electron accelerator, as well as several physics effects related to bunched beam cooling. Following successful commissioning of the electron accelerator in 2018, the focus of the LEReC project in 2019 was on establishing electron-ion interactions and demonstration of cooling process using electron energy of 1.6MeV (ion energy of 3.85GeV/n), which is the lowest energy of interest. Here we report on the first demonstration of Au ion cooling in RHIC using this new approach. 		 
slides icon Slides THZBA5 [16.417 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THZBA5  
About • paper received ※ 16 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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FRXBA4 Maximizing 2-D Beam Brightness Using the Round to Flat Beam Transformation in the Ultralow Charge Regime emittance, quadrupole, cathode, electron 986
 
  • F.W. Cropp V, P.E. Denham, J. Giner Navarro, E.T. Liu, P. Musumeci
    UCLA, Los Angeles, USA
  • N. Burger, L. Phillips
    PBPL, Los Angeles, USA
  • A.L. Edelen, C. Emma
    SLAC, Menlo Park, California, USA
  
  Funding: This work is supported by the United States National Science Foundation award PHY-1549132 (the Center for Bright Beams)
We seek to maximize the 2-D beam brightness in an RF photoinjector operating in an ultralow charge (<1 pC) regime by implementing the FBT. Particle tracking simulations suggest that in one dimension, normalized projected emittances smaller than 5 nm can be obtained at the UCLA Pegasus facility with up to 100 fC beam charge. A tunable magnetic field is put on the cathode. Three skew quadrupoles are used to block-diagonalize the beam matrix and recover the vastly different eigenemittances as the projected emittances. Emittance measurement routines, including grid-based, pepperpot-based and quad scan routines, have been developed for on-line calculation of the 4-D beam matrix and its eigenemittances. Preliminary measurements are in agreement with simulations and indicate emittance ratios larger than 10 depending on the laser spot size on the cathode. Fine tuning the quadrupole gradients for the FBT has a significant effect on the 2-D beam brightness. We have made concrete steps toward computer minimization and machine learning optimization of the quadrupole gradients in order to remove the canonical angular momentum from the beam and achieve the target normalized projected emittances. 		 
slides icon Slides FRXBA4 [3.059 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-FRXBA4  
About • paper received ※ 28 August 2019       paper accepted ※ 05 December 2019       issue date ※ 08 October 2019  
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FRXBA5 The Role of Laser Shaping in Microbunching Instability Suppression and Seeded X-Ray Free Electron Emission bunching, FEL, electron, experiment 990
 
  • J. Tang, S. Carbajo, F.-J. Decker, Z. Huang, J. Krzywiński, R.A. Lemons, W. Liu, A.A. Lutman, G. Marcus, T.J. Maxwell, S.P. Moeller, D.F. Ratner, S. Vetter
    SLAC, Menlo Park, California, USA
  
  Microbunching instability (MBI) driven by collective effects in an accelerator is known to be detrimental for the performance of X-ray free electron lasers. At the Linac Coherent Light Source (LCLS), laser heater (LH) system was installed to suppress the microbunching instability by inducing a small amount of slice energy spread to the electron beam. The distribution of the induced energy spread greatly effects MBI suppression and can be controlled by shaping the transverse profile of the heater laser. In this paper, we present theoretical and experimental results on utilizing a Laguerre-Gaussian 01 Mode (LG01) laser at LCLS to obtain better suppression of the instability. We demonstrate experimentally that Gaussian-shaped energy distribution is induced by LG01 mode LH and final microbunching gain is better suppressed. We finally discuss the role of LH spatial shaping in soft X-ray self-seeded (SXRSS) FEL emission and demonstrate that this LH configuration is capable of generating high spectral brightness FEL pulses.  
slides icon Slides FRXBA5 [3.162 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-FRXBA5  
About • paper received ※ 28 August 2019       paper accepted ※ 12 September 2019       issue date ※ 08 October 2019  
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FRCHC2 Possibilities for Future Synchrotron Radiation Sources electron, free-electron-laser, FEL, radiation 1000
 
  • M.-E. Couprie
    SOLEIL, Gif-sur-Yvette, France
  
  The landscape of present accelerator based light sources is drawn. The photon beam brightness increases opens new areas of user applications, both with the arrival of low emittance rings getting closer to diffraction limit and the advent of X-ray Free Electron Lasers, providing agility in terms of performance (two colors, attosecond pulse…). Finally, the path towards light sources using alternate accelerator schemes, such as plasma acceleration is discussed.  
slides icon Slides FRCHC2 [76.897 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-FRCHC2  
About • paper received ※ 04 September 2019       paper accepted ※ 16 November 2020       issue date ※ 08 October 2019  
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