02: Photon Sources and Electron Accelerators
Paper Title Page
MOZBA1 LCLS-II SC Linac: Challenges and Status 51
 
  • M.C. Ross
    SLAC, Menlo Park, California, USA
 
  Funding: ∗ This work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515
The Linac Coherent Light Source II (LCLS-II) project requires the assembly, test, and installation of 37 cry-omodules (CM) in order to deliver a 4 GeV CW electron beam to the FEL undulators for production of both hard and soft X-ray pulses at a repetition rate of up to 1 MHz. All of the cryomodules will operation in continuous wave mode, with 35 operating at 1.3 GHz for acceleration and 2 operating at 3.9 GHz to linearize the longitudinal beam profile. The assembly and testing of the 1.3 GHz cry-omodules is nearing completion and the 3.9 GHz cry-omodules work is entering to assembly and testing phase. Roughly 60% of the cryomodules have been shipped to SLAC for installation in the accelerator enclosure. The status and challenges of these efforts will be reported in this paper.
 
slides icon Slides MOZBA1 [80.533 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA1  
About • paper received ※ 02 September 2019       paper accepted ※ 12 September 2019       issue date ※ 08 October 2019  
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MOZBA2 Operational Experience with Superconducting Undulators at APS 57
 
  • K.C. Harkay, L.E. Boon, M. Borland, J.C. Dooling, L. Emery, V. Sajaev, Y.P. Sun
    ANL, Lemont, Illinois, USA
 
  Funding: Work supported by U. S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
APS has been developing superconducting undulators for over a decade. Presently, two planar and one helical device are in operation in the APS storage ring, and a number of devices will be installed in the APS Upgrade ring. All superconducting devices perform with very high reliability and have very minor effect on the storage ring operation. To achieve this, a number of storage ring modifications had to be done, such as introduction of the beam abort system to eliminate device quenches during beam dumps, and lattice and orbit modifications to allow for installation of the small horizontal aperture helical device with magnet coils in the plane of synchrotron radiation.
 
slides icon Slides MOZBA2 [3.424 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA2  
About • paper received ※ 02 September 2019       paper accepted ※ 19 November 2019       issue date ※ 08 October 2019  
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MOZBA3 Strongly Tapered Helical Undulator System for TESSA-266 63
TUPLH14   use link to see paper's listing under its alternate paper code  
 
  • 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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MOZBA4 Recent Developments in High Power High Brightness Double Bunch Self-Seeding at LCLS-II 67
TUPLH12   use link to see paper's listing under its alternate paper code  
 
  • A. Halavanau, F.-J. Decker, Y. Ding, C. Emma, Z. Huang, A.A. Lutman, G. Marcus, C. Pellegrini
    SLAC, Menlo Park, California, USA
 
  We discuss the power and spectral characteristics of an X-ray FEL, LCLS-II, operating in a double bunch self-seeding scheme (DBFEL). We show that it can reach very high power levels in the photon energy range of 4-8 keV. We discuss the system implementation on LCLS-II, including the design of a four-bounce crystal monochromator, and linac wakefields effects. Finally, we offer multiple applications of the DBFEL for high-field QED, AMO physics and single particle imaging.  
slides icon Slides MOZBA4 [3.175 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA4  
About • paper received ※ 02 September 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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MOZBA5 Optimized Linear and Second Order Chromaticity Setpoints for the Advanced Photon Source Upgrade 70
 
  • Y.P. Sun
    ANL, Lemont, Illinois, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The nominal single particle dynamics optimizations of the Advanced Photon Source upgrade (APS-U) lattice are performed with dense numerical simulations of local momentum acceptance and dynamic acceptance. These simulations are quite time consuming, which may take weeks for optimizing one setpoint of linear chromaticity. In this paper, an alternative optimization method is adopted to generate optimized linear and second order chromaticity setpoints for the Advanced Photon Source upgrade lattice. This method is efficient in computing time needed, which is capable to generate a grid of optimized chromaticity setpoints in a relatively short time. The performance of these lattice solutions are verified by simulations with reasonable errors. These lattice solutions with different linear (or second order) chromaticity may be useful for the future APS-U commissioning and operations.
 
slides icon Slides MOZBA5 [3.350 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA5  
About • paper received ※ 31 August 2019       paper accepted ※ 02 September 2019       issue date ※ 08 October 2019  
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MOZBA6 The Broad-Band Impedance Budget of the Accumulator Ring in the ALS-U Project 74
MOPLM26   use link to see paper's listing under its alternate paper code  
 
  • D. Wang, S. De Santis, D. Li, T.H. Luo, M. Venturini
    LBNL, Berkeley, California, USA
  • K.L.F. Bane
    SLAC, Menlo Park, California, USA
 
  Design work is underway for the upgrade of the Advanced Light Source (ALS-U) to a diffraction-limited soft x-rays radiation source. It consists of an accumulator and a storage ring. In both rings, coupling-impedance driven instabilities need careful evaluation to ensure meeting the machine high-performance goals. This paper presents the impedance budget of the accumulator ring both longitudinally and transversely. The budget includes the resistive wall impedance as well as the geometric impedance from the main vacuum components. Our calculations primarily rely on electromagnetic simulations with the CST code; when possible validation has been sought against analytical modeling, typically in the low-frequency limit, and good agreement generally found. Collective-instability current thresholds are also discussed.  
slides icon Slides MOZBA6 [8.926 MB]  
poster icon Poster MOZBA6 [3.542 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA6  
About • paper received ※ 27 August 2019       paper accepted ※ 06 September 2019       issue date ※ 08 October 2019  
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MOPLM01 Alternative Injection Schemes to the NSLS-II Using Nonlinear Injection Magnets 91
 
  • R.P. Fliller, III, G. Bassi, A. Blednykh, C. Hetzel, V.V. Smaluk, C.J. Spataro, P. Zuhoski
    BNL, Upton, New York, USA
 
  Funding: This manuscript has been authored by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy
The NSLS-II storage ring uses the standard four bump injection scheme to inject beam off axis. BESSY and MAX IV are now using a pulsed multipole magnet as an injection kicker. The injected beam sees a field off axis for injection while the stored beam experiences no field on the magnet axis. The principle advantage of using a pulsed multipole for injection is that the stored beam motion is greatly reduced since the field on axis is negligible. The number of pulsed magnets is reduced from five in the nominal scheme (septum and four bumps) to two or three thereby reducing the possible failure modes. This also eliminates the need to precisely match the pulse shapes of four dipole magnets to achieve minimal stored beam motion outside of the bump. In this paper we discuss two schemes of injecting into the NSLS-II using a pulsed multipole magnet. The first scheme uses a single pulsed multipole located in one cell downstream of the injection septum as the injection kicker. The second scheme uses two pulsed multipoles in the injection straight to perform the injection. We discuss both methods of injection and compare each method.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM01  
About • paper received ※ 27 August 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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MOPLM03 Correlations Between Beta Beating and APS-U Single Particle Dynamics Performance 95
 
  • Y.P. Sun
    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.
In the optimizations and evaluations process of the Advanced Photon Source upgrade (APS-U) lattice, it was observed that there are negative correlations between beta beating and APS-U single particle dynamics performance (such as dynamic acceptance and local momentum acceptance). These correlations are not always present due to different reasons. In this paper, a systematic simulation study is performed to understand the correlations between beta beating and APS-U single particle dynamics performance. Relatively high beta beatings are generated to reveal these effects.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM03  
About • paper received ※ 31 August 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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MOPLM04 First Attempts at Applying Machine Learning to ALS Storage Ring Stabilization 98
 
  • S.C. Leemann, Ph. Amstutz, W.E. Byrne, M.P. Ehrlichman, T. Hellert, A. Hexemer, S. Liu, M. Marcus, C.N. Melton, H. Nishimura, G. Penn, F. Sannibale, D.A. Shapiro, C. Sun, D. Ushizima, M. Venturini
    LBNL, Berkeley, USA
 
  Funding: This research is funded by the US Department of Energy (BES & ASCR Programs), and supported by the Director of the Office of Science of the US Department of Energy under Contract No. DEAC02-05CH11231.
The ALS storage ring operates multiple feedbacks and feed-forwards during user operations to ensure that various source properties such as beam position, beam angle, and beam size are maintained constant. Without these active corrections, strong perturbations of the electron beam would result from constantly varying ID gaps and phases. An important part of the ID gap/phase compensation requires recording feed-forward tables. While recording such tables takes a lot of time during dedicated machine shifts, the resulting compensation data is imperfect due to machine drift both during and after recording of the table. Since it is impractical to repeat recording feed-forward tables on a more frequent basis, we have decided to employ Machine Learning techniques to improve ID compensation in order to stabilize electron beam properties at the source points.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM04  
About • paper received ※ 26 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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MOPLM06 High Voltage Design of a 350 kV DC Photogun at BNL 102
 
  • W. Liu, O.H. Rahman, E. Wang
    BNL, Upton, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Brookhaven National Laboratory is constructing a 350 kV DC high voltage photogun to provide spin-polarized electron beam for the proposed eRHIC facility. The photogun employs a compact inverted-tapered-geometry ceramic insulator that extends into the vacuum chamber and mechanically holds the cathode electrode. By operating at high voltage, the photogun will provide lower beam emittance, thereby improving the beam transmission through the injector apertures, and prolong the operating lifetime of the photogun. However, high voltage increases the field emission, which can result in high voltage breakdown and even lead to irreparable damage of the ceramic insulator. This work describes the methods to minimize the electric field near the metal-vacuum-insulator interface, and to avoid high voltage breakdown and ceramic insulator damage. The triple point junction shields are designed. The simulated electric field, field emission and beam transportation will be presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM06  
About • paper received ※ 19 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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MOPLM07 Simulation of Beam Aborts for the Advanced Photon Source to Probe Material-Damage Limits for Future Storage Rings 106
 
  • M. Borland, J.C. Dooling, R.R. Lindberg, V. Sajaev, Y.P. Sun
    ANL, Lemont, Illinois, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Damage to tungsten beam dumps has been observed in the Advanced Photon Source (APS), a 7-GeV, third-generation storage ring light source. This issue is expected to be much more severe in the APS Upgrade, owing to doubling of the stored charge and much lower emittance. An experiment was conducted in the existing APS ring to test several possible dump materials and also assess the accuracy of predictions of beam-induced damage. Prior to the experiments, extensive beam abort simulations were performed with ELEGANT to predict thresholds for material damage, dependence on vertical beam size, and even the size of the trenches expected to be created by the beam. This paper presents the simulation methods, simple models for estimating damage, and results. A companion paper in this conference presents experimental results.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM07  
About • paper received ※ 27 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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MOPLM08 Controlling Transient Collective Instabilities During Swap-Out Injection 110
 
  • R.R. Lindberg
    ANL, Lemont, Illinois, USA
 
  Funding: Supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
Previous work has shown that collective instabilities at injection may reduce injection efficiency even for on-axis injection as planned for the APS-Upgrade*. Stability at injection is governed by a number of factors, including phase-space mismatch between injected and stored bunch, strength of the impedance, degree of nonlinearities, and feedback. We find that the large tune-shift with amplitude of the most recent APS-U lattice largely tames the transient instability via Landau damping, and show that using octupoles to increase the nonlinear tune shift can stabilize the transient instability at injection that plagued a previously unstable lattice.
* R.R. Lindberg, M. Borland, and A. Blednykh, Proc. of NA-PAC 2016, pp. 901
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM08  
About • paper received ※ 24 August 2019       paper accepted ※ 01 September 2019       issue date ※ 08 October 2019  
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MOPLM09 High-Power Design of a Cavity Combiner for a 352-MHz Solid State Amplifier System at the Advanced Photon Source 113
 
  • G.J. Waldschmidt, D.J. Bromberek, A. Goel, D. Horan, A. Nassiri
    ANL, Lemont, Illinois, USA
 
  A cavity combiner has been designed as part of a solid state amplifier system at the Advanced Photon Source with a power requirement of up to 200 kW for the full system. Peak field levels and thermal loading have been optimized to enhance the rf and mechanical perfor-mance of the cavity and to augment its reliability. The combiner consists of 16 rotatable input couplers, a re-duced-field output coupler, and static tuning. The power handling capability of the cavity will be evaluated during a back-feed test where an external klystron source will be used to transmit power through the cavity into loads on each of the input couplers.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM09  
About • paper received ※ 28 August 2019       paper accepted ※ 04 December 2019       issue date ※ 08 October 2019  
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MOPLM10 Simulation Study With Septum Field Map for the APS Upgrade 116
 
  • A. Xiao, M. Abliz, M. Borland
    ANL, Lemont, Illinois, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
One of the biggest challenges faced by the Advanced Photon Source Upgrade injection system design is the septum magnet. Not only does the required leakage field inside the stored beam chamber need to be smaller than for the present ring, the magnet has to be slightly tilted about the z-axis to provide a gentle vertical bend that brings the injected beam trajectory close to y=0 when it passes through the storage ring quadrupole magnets upstream of the straight section. This paper describes the coordinate system transformation necessary to properly model the magnet from field maps. The main field is checked by tracking the injected beam backwards, while leakage fields are included in dynamic aperture simulation and beam lifetime calculation. Simulation results show that the magnet design satisfies the physics requirement.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM10  
About • paper received ※ 28 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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MOPLM12 Progress on the Injection Transport Line Design for the APS Upgrade 120
 
  • A. Xiao, M. Borland
    ANL, Lemont, Illinois, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An on-axis vertical injection scheme was adopted for the Advanced Photon Source upgrade multi-bend achromat lattice. As the design of the injection scheme has become more detailed, the booster to storage ring transport line (BTS) has advanced, including effects such as the septum field map and stray fields of storage ring magnets. Various error effects are simulated for setting specifications and predicting expected performance. The beam diagnostic scheme, including emittance measurement, is incorporated into the beamline design.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM12  
About • paper received ※ 28 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 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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MOPLM14 Studies of Beam Dumps in Candidate Horizontal Collimator Materials for the Advanced Photon Source Upgrade Storage Ring 128
 
  • J.C. Dooling, W. Berg, M. Borland, G. Decker, L. Emery, K.C. Harkay, R.R. Lindberg, A.H. Lumpkin, G. Navrotski, V. Sajaev, Y.P. Sun, K.P. Wootton, A. Xiao
    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
We present the results of experiments intended to show the effects of beam dumps on candidate collimator materials for the Advanced Photon Source Upgrade (APS-U) storage ring (SR). Due to small transverse electron beam sizes, whole beam loss events are expected to yield dose levels in excess of 10 MGy in beam-facing components, pushing irradiated regions into a hydrodynamic regime. Whole beam aborts have characteristic time scales ranging from 100s of ps to 10s of microseconds which are either much shorter than or roughly equal to thermal diffusion times. Aluminum and titanium alloy test pieces are each exposed to a series of beam aborts of varying fill pattern and charge. Simulations suggest the high energy/power densities are likely to lead to phase transitions and damage in any material initially encountered by the beam. We describe measurements used to characterize the beam aborts and compare the results with those from the static particle-matter interaction code, MARS; we also plan to explore wakefield effects. Beam dynamics modeling, done with elegant is discussed in a companion paper at this conference. The goal of this work is to guide the design of APS-U SR collimators.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM14  
About • paper received ※ 27 August 2019       paper accepted ※ 04 September 2019       issue date ※ 08 October 2019  
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MOPLM15 Design of the ASU Photocathode Lab 132
SUPLH06   use link to see paper's listing under its alternate paper code  
 
  • C.J. Knill, S.S. Karkare
    Arizona State University, Tempe, USA
  • J.V. Conway, B.M. Dunham, K.W. Smolenski
    Xelera Research LLC, Ithaca, New York, USA
  • H.A. Padmore
    LBNL, Berkeley, California, USA
 
  Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams.
Recent investigations have shown that it is possible to obtain an order of magnitude smaller intrinsic emittance from photocathodes by precise atomic scale control of the surface, using an appropriate electronic band structure of single crystal cathodes and cryogenically cooling the cathode. Investigating the performance of such cathodes requires atomic scale surface diagnostic techniques connected in ultra-high vacuum (UHV) to the epitaxial thin film growth and surface preparation systems and photo-emission and photocathode diagnostic techniques. Here we report the capabilities and design of the laboratory being built at the Arizona State University for this purpose. The lab houses a 200 kV DC gun with a cryogenically cooled cathode along with a beam diagnostics and ultra fast electron diffraction beamline. The cathode of the gun can be transported in UHV to a suite of UHV growth chambers and surface and photoemission diagnostic techniques.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM15  
About • paper received ※ 26 August 2019       paper accepted ※ 04 September 2019       issue date ※ 08 October 2019  
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MOPLM16 Design of a 200 kV DC Cryocooled Photoemission Gun for Photocathode Investigations 136
SUPLH01   use link to see paper's listing under its alternate paper code  
 
  • G.S. Gevorkyan, S.S. Karkare
    Arizona State University, Tempe, USA
  • I.V. Bazarov, A. Galdi, J.M. Maxson
    Cornell University, Ithaca, New York, USA
  • L. Cultrera, W.H. Li
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: This work was supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams.
Intrinsic emittance of photocathodes limits the brightness of electrons beams produced from photoemission guns. Recent advancements have shown that an order of magnitude improvement in intrinsic emittance over the commonly used polycrystalline metal and semiconductor cathodes is possible via use of single crystalline ordered surfaces of metals, semiconductors and other exotic materials at cryogenic temperatures as cathodes. However, due to practical design considerations, it is not trivial to test such cathodes in existing electron guns. Here we present the design of a 200kV DC electron gun being developed at the Arizona State University for this purpose.
 
poster icon Poster MOPLM16 [1.549 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM16  
About • paper received ※ 27 August 2019       paper accepted ※ 12 September 2019       issue date ※ 08 October 2019  
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MOPLM17 Longitudinal Impedance Modeling of APS Particle Accumulator Ring with CST 140
 
  • C. Yao, J. Carvelli, K.C. Harkay, L.H. Morrison
    ANL, Lemont, Illinois, USA
  • D. Hui
    University of Arizona, Tucson, Arizona, USA
  • J.S. Wang
    Dassault Systems Simulia, Waltham, Massachusetts, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
The APS-U (APS upgrade) ring plans implement a "swap out" injection scheme, which requires a injected beam of 15.6 nC single-bunch beam. The Particle Accumulator Ring (PAR), originally designed for up to 6 nC charge, must be upgraded to provide 20 nC single bunch beam. Our studies have shown that bunch length of the PAR beam, typically 300 ps at lower charge, increases to 800 ps at high charge due to longitudinal instabilities, which causes low injection efficiency of the downstream Booster ring. We completed beam impedance of all the PAR vacuum components recently with CST wakefield solver. 3D CAD models are directly imported into CST and various techniques were explored to improve and verify the results. The results are also cross-checked with that from GdfidL and Echo simulation. We identified 23 bellow- and 24 non-bellow flanges that contribute to as much as 50% of the total loss factor. We are considering upgrade options to reduce over all beam loading and longitudinal impedance. Beam tracking simulation is in progress that including the longitudinal impedance results from the simulations. We report the results and methods of the CST impedance simulations.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM17  
About • paper received ※ 22 August 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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MOPLM18 Design of the 2-Stage Laser Transport for the Low Energy RHIC Electron Cooling (LEReC) DC Photogun 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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MOPLM20 Impedance Considerations for the APS Upgrade 147
 
  • R.R. Lindberg
    ANL, Lemont, Illinois, USA
  • A. Blednykh
    BNL, Upton, New York, USA
 
  Funding: Supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
The APS-Upgrade is targeting a 42 pm lattice that requires strong magnets and small vacuum chambers. Hence, impedance is of significant concern. We overview recent progress on identifying and modelling vacuum components that are important sources of impedance in the ring, including photon absorbers, BPMs, and flange joints. We also show how these impact collective dynamics in the APS-U lattice.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM20  
About • paper received ※ 27 August 2019       paper accepted ※ 01 September 2019       issue date ※ 08 October 2019  
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MOPLM21 Circuit Model Analysis for High Charge in the APS Particle Accumulator Ring 151
 
  • K.C. Harkay, J.R. Calvey, J.C. Dooling, L. Emery, R.R. Lindberg, K.P. Wootton, C. Yao
    ANL, Lemont, Illinois, USA
 
  Funding: Work supported by U. S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source (APS) particle accumulator ring (PAR) was designed to accumulate linac pulses into a single bunch with a fundamental rf system, and longitudinally compress the beam with a harmonic rf system prior to injection into the booster. For APS Upgrade, the injectors will need to supply full-current bunch replacement with high single-bunch charge for swap-out in the new storage ring. Significant bunch lengthening, energy spread, and synchrotron sidebands are observed in PAR at high charge. Lower-charge dynamics are dominated by potential well distortion, while higher-charge dynamics appear to be dominated by microwave instability. Before a numerical impedance model was available, a simple circuit model was developed by fitting the measured bunch distributions to the Haissinski equation. Energy scaling was then used to predict the beam energy sufficient to raise the instability threshold to 18-20 nC. With the beam in a linear or nearly linear regime, higher harmonic radio frequency (rf) gap voltage can be used to reduce the bunch length at high charge and better match the booster acceptance.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM21  
About • paper received ※ 27 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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MOPLM23 Senis Hall Probe Speed Dependence Issues 155
 
  • I. Vasserman
    ANL, Lemont, Illinois, USA
 
  An extensive test of a Senis 2-axis Hall probe was done at the Advanced Photon Source. Strong dependence of the measurement data on the speed of the sensor is observed. Discussion of the possible reason of such dependence is provided.
Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM23  
About • paper received ※ 21 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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MOPLM24 LCLS-II Injector Commissioning Beam Based Measurements 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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TUYBA1
Generation and Characterization of Attosecond Pulses From X-Ray Free-Electron Laser  
MOPLM25   use link to see paper's listing under its alternate paper code  
SUPLH04   use link to see paper's listing under its alternate paper code  
 
  • S. Li
    SLAC, Menlo Park, California, USA
 
  In this talk I will discuss the production and application of sub-femtosecond x-ray pulses recently generated at LCLS. I will focus on angular streaking as the measurement technique to resolve the extremely short x-ray pulses. This method exploits phase dependent energy modulation of a photoelectron ionized in the presence of a strong laser field with circular polarization. I will present experimental results of single shot images and preliminary analysis results. Specifically I will discuss two applications of this technique: streaking of the Auger electrons and measuring the shape resonance directly in the time domain.  
slides icon Slides TUYBA1 [9.757 MB]  
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TUYBA2
Ultrafast Relativistic Nanoprobes  
 
  • F. Ji
    LBNL, Berkeley, California, USA
 
  Taking advantage of the unprecedented average brightness of the APEX electron gun providing relativistic electron pulses at high repetition rates, we demonstrate for the first time the generation of ultrafast relativistic electron beams with picometer-scale emittance and their ability to probe nanoscale features on materials with complex microstructures. At the sample plane, the APEX beam is tightly focused by a custom in-vacuum lens system based on permanent magnet quadrupoles, and its evolution around the waist is tracked by a knife-edge technique, allowing accurate reconstruction of the beam shape and local density. We then use the focused beam to characterize a Ti-6 wt\% Al polycrystalline sample by correlating the diffraction and imaging modality, showcasing the capability to locate grain boundaries and map adjacent crystallographic domains with sub-micron precision. This work provides a new paradigm for ultrafast electron instrumentation.  
slides icon Slides TUYBA2 [14.270 MB]  
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TUYBA3 Benchmarking the LCLS-II Photoinjector 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 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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TUYBA5
New Methods of Synthesizing Ultra-Smooth and High Efficiency Alkali Antimonide Photocathodes for Future Light Sources  
 
  • M. Gaowei, J. Cen
    BNL, Upton, New York, USA
 
  High quantum yield, low emittance, long lifetime bi-alkali photocathode has been one of the most significant directions in the photocathode development in recent years. Among various studies effusion cell evaporation has been proven for high potential in achieving such requirements. In this paper we report the results of the study on both the 1 step and 2 step tenuary co-evaporation of cesium potassium antimonide (K-Cs-Sb) photocathodes from alkali effusion cells, with in situ and operando X-ray characterization techniques. We were able to achieve 1.2 nm of surface roughness from an 80 nm thick photocathode film, with high crystallinity and a quantum efficacy exceeds 30% at 360 nm wavelength and 5.8% at 530 nm wavelength.  
slides icon Slides TUYBA5 [5.209 MB]  
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TUYBA6
Attosecond Pulses and Advanced Techniques Planned for LCLS-II  
 
  • Z. Zhang, J.P. Duris, Z. Huang, J.P. MacArthur, A. Marinelli
    SLAC, Menlo Park, California, USA
 
  Attosecond X-ray free-electron laser (XFEL) pulses can be generated by the chirp-taper technique at the LCLS-II. The electron beam is modulated through the self-modulation process in a wiggler and the taper of the undulator is optimized to amplify the XFEL pulse along the beam. In this paper, we present start-to-end numerical simulations to demonstrate the generation of two kinds of attosecond XFEL pulses at the LCLS-II: (1) two attosecond XFEL pulses with variable time delay and energy separation, and (2) isolated attosecond pulses with TW peak power. The output of this method provides a powerful tool for users to study ultrafast science at the attosecond timescale.  
slides icon Slides TUYBA6 [3.586 MB]  
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TUPLH01 Status of the Superconducting Undulator Program at the Advanced Photon Source 490
 
  • M. Kasa, E.R. Anliker, J.D. Fuerst, E. Gluskin, Q.B. Hasse, Y. Ivanyushenkov, W.G. Jansma, I. Kesgin, Y. Shiroyanagi
    ANL, Lemont, Illinois, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
Since 2013 there has been at least one superconducting undulator (SCU) in operation at the Advanced Photon Source (APS), currently there are two planar SCUs and one helical SCU. The combined operational experience of SCUs at the APS is more than 11 years and counting. Through all these years, APS SCUs operated with the predicted or better than predicted radiation performance and with 99% availability. With this demonstrated reliability and experimentally confirmed spectral performance, the APS upgrade project is planning on leveraging the advantages of SCU technology. The present planar SCUs are comprised of ~1.1-m-long magnets, each operated within a 2-m-long cryostat, while the planar SCUs for the upgrade will have two ~1.8-m-long magnets operating within a 5-m-long cryostat. Progress is also being made in other areas of SCU development with work on an arbitrary polarizing SCU, referred to as SCAPE, and a planar SCU wound with Nb3Sn superconductor. A Nb3Sn SCU is being designed with two 1.3-m-long magnets within a 5-m-long cryostat, and installation is planned for 2021. Also under development are the alignment and magnetic measurement systems for use with the 5-m-long cryostat.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH01  
About • paper received ※ 26 August 2019       paper accepted ※ 02 September 2019       issue date ※ 08 October 2019  
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TUPLH03 Double-Bend Achromat Beamline for Injection Into a High-Power Superconducting Electron Linac 494
 
  • C.H. Boulware, T.L. Grimm, R. Hipple
    Niowave, Inc., Lansing, Michigan, USA
  • S.M. Lund
    FRIB, East Lansing, Michigan, USA
  • V.S. Morozov
    JLab, Newport News, Virginia, USA
 
  To take advantage of the high duty cycle operation of superconducting electron linacs, commercial systems use thermionic cathode electron guns that fill every RF bucket with an electron bunch. In continuous operation, the exit energy is limited when compared to pulsed systems. Bunch length and energy spread at the exit of the gun are incompatible with low losses in the superconducting cavity. A solenoid double-bend achromatic beamline is in operation at Niowave which allows energy and bunch length filtering of the beam leaving the gun before injection into the superconducting cavity. This system uses two solenoids and two dipoles to produce a round beam, using the edge angles of the dipoles to balance the focusing effects in the two transverse planes. The design allows beam filtering on the symmetry plane where the dispersion is maximum. Additionally, the bend angle moves the electron gun off the high-energy beam axis, allowing multiple-pass operation of the superconducting booster. This contribution will discuss the beam optics design of the double-bend achromat along with the design of the magnets and beam chambers and the operational experience with the system.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH03  
About • paper received ※ 28 August 2019       paper accepted ※ 02 September 2019       issue date ※ 08 October 2019  
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TUPLH04 Feasibility Study of Fast Polarization Switching Superconducting Undulator 497
 
  • I. Kesgin, Y. Ivanyushenkov, M. Kasa
    ANL, Lemont, Illinois, USA
 
  Funding: U.S. Department of Energy, Office of Science, under Contract No. DE-ACO2-O6CH11357.
Polarization switching x-ray probes coupled with high-flux provide a unique tool to unraveling the nature of electronic heterogeneity and drive discovery of novel phases of electronic matter. Superconducting Arbitrary Polarization Emitter (SCAPE) is a new concept for a universal undulator, which offers linear or circular polarization states in one device and is ideal for experiments that require polarization switching. Polarization switching relies on modulating the magnetic field in the undulator. This, however, inevitably incurs losses in superconductors, which need to be mitigated. In this study, feasibility of fast switching SCAPE has been investigated through fabricating and testing several short prototype magnets wound with different superconductors and new design concepts. The losses at different frequencies and field amplitudes are measured and details will be discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH04  
About • paper received ※ 27 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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TUPLH07 High-Gradient Short Pulse Accelerating Structures 500
 
  • S.V. Kuzikov, S.P. Antipov, E. Gomez
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
 
  High gradients are necessary for lots of applications of electron accelerators. As the maximum gradient is limited by effects of RF breakdown, we present a development of an electron accelerating structure operating with a short multi-megawatt RF pulse. The structure exploits an idea to decrease the breakdown probability due to RF pulse length reduction. This concept requires to distribute RF power so that all accelerating cells are fed independently each other. This implies waveguide net system which allows to delay and to distribute properly RF radiation along the structure keeping synchronism of particles and waves. We have designed an X-band pi-mode structure including the RF design, optimization, and engineering. The structure will be tested as an RF power extractor at the Argonne Wakefield Accelerator Facility for two-beam acceleration experiments. In this regime we anticipate to obtain 10 ns, gigawatt power level RF pulses generated by train consisted of eight 25-50 nC relativistic bunches.  
poster icon Poster TUPLH07 [0.999 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH07  
About • paper received ※ 27 August 2019       paper accepted ※ 31 August 2019       issue date ※ 08 October 2019  
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TUPLH08 X-Ray and Charged Particle Detection by Detuning of a Microwave Resonator 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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TUPLH09 Thermal Effects on Bragg Diffraction of XFEL Optics 506
SUPLH05   use link to see paper's listing under its alternate paper code  
 
  • Z. Qu, J. Wu, G. Zhou
    SLAC, Menlo Park, California, USA
  • Y. Ma, Z. Qu
    UC Merced, Merced, California, USA
  • B. Yang
    Western Digital, Milpitas, California, USA
 
  Funding: The US Department of Energy (DOE) (DE-AC02-76SF00515); The US DOE Office of Science Early Career Research Program grant (FWP-2013-SLAC-100164).
Crystal optical devices are widely used in X-ray free electron laser (XFEL) systems, monochromators, beam splitters, high-reflectance backscattering mirrors, lenses, phase plates, diffraction gratings, and spectrometers. The absorption of X-ray in these optical devices can cause increase of temperature and consequent thermal deformation, which can dynamic change in optic output. In self-seeding XFEL, the thermal deformation and strain in monochromator could cause significant seed quality degradation: central energy shift, band broadening and reduction in seed power. To quantitatively estimate the impact of thermomechanical effects on seed quality, we conduct thermomechanical simulations combined with diffraction to evaluate the seed quality with residual temperature field in a pump-probe manner. With our results, we show that a critical repetition rate could be determined, once the criteria for deviation of the seed quality are selected. This tool shows great potential for the design of XFEL optics for stable operation.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH09  
About • paper received ※ 28 August 2019       paper accepted ※ 13 September 2019       issue date ※ 08 October 2019  
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TUPLH10 Fabrication Progress of a Superconducting Helical Undulator with Superimposed Focusing Gradient for High Efficiency Tapered X-Ray FELs 509
 
  • S.M. Lynam, R.B. Agustsson, I.I. Gadjev, A.Yu. Smirnov
    RadiaBeam, Santa Monica, California, USA
  • F.H. O’Shea
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
 
  Funding: This work is supported by DOE grant no. DE-SC0017072, "Superconducting Helical Undulator with Superimposed Focusing Gradient for High Efficiency Tapered X-Ray FELs"
The Advanced Gradient Undulator (AGU) represents a potentially significant advancement in x-ray conversion efficiency for x-ray FELs. This increase in efficiency would have broad implications on the capabilities of x-ray light sources. To achieve this high conversion efficiency, the inner diameter of the undulator coil is a mere 7mm, even with the use of superconducting coils. To accommodate the beamline at the Advanced Photon Source this yields in a chamber with a wall thickness of 0.5mm fabricated from Aluminum. With a period of 2cm and a conductor position tolerance of <100 µm over a length of >80cm at 4.2K, the engineering and fabrication challenges for the undulator alone are substantial. We will discuss these fabrication challenges and present solutions to meet the tolerances required for desired performance, and provide an update on current progress of the construction of a section of the AGU insertion device.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH10  
About • paper received ※ 28 August 2019       paper accepted ※ 16 November 2020       issue date ※ 08 October 2019  
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TUPLH17 Design Study of Low-Level RF Control System for CW Superconducting Electron Linear Accelerator in KAERI 512
 
  • S.H. Lee, J.Y. Lee
    Korea Atomic Energy Research Institute (KAERI), Daejeon, Republic of Korea
  • P. Buaphad, I.G. Jeong, Y.J. Joo, H.R. Lee
    University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
  • M.-H. Chun, I.H. Yu
    PAL, Pohang, Republic of Korea
  • Y. Kim
    KAERI, Jeongeup-si, Republic of Korea
 
  Korea Atomic Energy Research Institute (KAERI) has been operating a 20 MeV superconducting RF linear accelerator (SRF LINAC) to conduct research on atom/nuclear reaction using neutron Time-Of-Flight (nTOF). It can accelerate electron beams up to 20 MeV with 1 kW continuous wave (CW) operation mode. Unfortunately, this machine has been aged over 15 years that brings about considerably difficulty in normal operation due to the performance degradation of sub-systems. To improve the operation condition of 20 MeV SRF LINAC, we has been carrying out an upgrade project with replacement and repair of old sub-systems from 2018. This paper describes a design study of Low-Level RF (LLRF) feedback system to raise the stability and acceleration efficiency of the electric field generated in the superconducting RF cavity structure in 20 MeV SRF LINAC.  
poster icon Poster TUPLH17 [0.644 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH17  
About • paper received ※ 30 August 2019       paper accepted ※ 04 September 2019       issue date ※ 08 October 2019  
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TUPLH18 NSLS-II Inject Linac RF Control Electronics Upgrade 516
 
  • H. Ma
    BNL, Upton, New York, USA
 
  Funding: US DOE
The electron LINAC injector of NSLS-II synchrotron light-source runs both Single-Bunch beam and long Multi-Bunch beam of up to 150 bunches. The key component for achieving this dual injector beam mode support capability is a high-speed rf modulator (or RFM) in the LINAC RF electronics front-end, which performs the necessary rf control and the beam loading compensation of different injection beams. The original LINAC rf electronics front-end successfully supported the machine commissioning and meets the basic needs of the machine operation. The upgrade being pursued is focused on improving the RFM control performance through replacing the current analog implementation in the RFM with a much more capable digital implementation, while still maintaining the necessary control bandwidth that is required for long and short Multi-Bunch beams. A variety of modern COTS rf transmission/reception DSP technology will be incorporated in the new design. The improvement in the reliability of network connection between the RFM’s and their host server is another focus in the upgrade, and the solution includes the adoption of the COTS TCP/IP and other communication protocol offload engines.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH18  
About • paper received ※ 27 August 2019       paper accepted ※ 15 September 2019       issue date ※ 08 October 2019  
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TUPLH19 Upgrade and Operation Experience of Solid-State Switching Klystron Modulator in NSLS-II Linac 519
 
  • H. Ma, J. Rose
    BNL, Upton, New York, USA
 
  Funding: US DOE
The NSLS-II synchrotron light-source at BNL uses three S-band, 45MW klystrons in its injector LINAC. At the core of the klystron station design is the novel solid-state switching modulators (or SSM). Compared to the conventional PFN klystron modulators, the main advantages of the SSM include the compact size requiring a smaller footprint in the LINAC, and a very flat top in the produced klystron HV pulses. The flatness of the HV pulses is very important for NSLS-II LINAC that runs multi-bunch beams to keep the beam energy dispersion within the tolerance. The principle of the SSM is fairly simple. It uses a large number of relatively low-voltage switched charging capacitor cells (or SU’s) in parallel. A specially designed, high step-up ratio, pulse transformer in the oil-tank with the same number of primary windings (as SU’s) combines the power from all the SU’s, and steps up to the required ~300kV klystron beam voltage. The operation experience at NSLS-II has proven the performance and reliability of the SSM’s. The BNL Model K2 SSM’s are currently being upgraded to Model K300 to run more powerful, and more cost-effective Canon’s E37302A klystrons.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH19  
About • paper received ※ 27 August 2019       paper accepted ※ 19 November 2019       issue date ※ 08 October 2019  
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TUPLH20 Commissioning of the CESR Upgrade for CHESS-U 522
 
  • J.P. Shanks, G.W. Codner, M.J. Forster, D.L. Rubin, S. Wang, L. Ying
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: Funding for the CHESS-U upgrade provided by New York State Capital Grant #AA737 / CFA #53676
The Cornell Electron Storage Ring (CESR) was upgraded in the second half of 2018 to become a dedicated synchrotron light source, CHESS-U. The upgrade is by far the largest modification to CESR in its 40-year history, replacing one-sixth of the storage ring with six new double-bend achromats, increasing beam energy from 5.3 GeV to 6.0 GeV, and switching from two counter-rotating beams to a single on-axis positron beam. The new achromats include combined-function dipoles, a first in CESR, and reduce the horizontal emittance by a factor of four. Eight compact narrow-gap undulators (4.6mm vacuum chamber aperture) and one high-energy 24-pole wiggler feed a total of six new and five existing x-ray end stations from a single positron beam. Commissioning of CHESS-U took place in the first half of 2019. We report on the methods and results of beam commissioning, including initial beam accumulation, optics correction, characterization, and commissioning of compact permanent-magnet insertion devices.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH20  
About • paper received ※ 26 August 2019       paper accepted ※ 02 September 2019       issue date ※ 08 October 2019  
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TUPLH24 Performance of CeC PoP Accelerator 526
 
  • I. Pinayev, Z. Altinbas, J.C. Brutus, A.J. Curcio, A. Di Lieto, T. Hayes, R.L. Hulsart, P. Inacker, Y.C. Jing, V. Litvinenko, J. Ma, G.J. Mahler, M. Mapes, K. Mernick, K. Mihara, T.A. Miller, M.G. Minty, G. Narayan, I. Petrushina, F. Severino, K. Shih, Z. Sorrell, J.E. Tuozzolo, E. Wang, G. Wang, A. Zaltsman
    BNL, Upton, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Coherent electron cooling experiment is aimed for demonstration of the proof-of-principle demonstration of reduction energy spread of a single hadron bunch circulating in RHIC. The electron beam should have the required parameters and its orbit and energy should be matched to the hadron beam. In this paper we present the achieved electron beam parameters including emittance, energy spread, and other critical indicators. The operational issues as well as future plans are also discussed.
 
poster icon Poster TUPLH24 [11.180 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH24  
About • paper received ※ 29 August 2019       paper accepted ※ 03 September 2019       issue date ※ 08 October 2019  
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WEPLE06 Linear and Second Order Map Tracking with Artificial Neural Network 895
 
  • Y.P. Sun
    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.
In particle accelerators, the tracking simulation is usually performed with symplectic integration, or linear/nonlinear transfer maps. In this paper, it is shown that the linear/nonlinear transfer maps may be represented by an artificial neural network. To solve this multivariate regression problem, both random datasets and structured datasets are explored to train the neural networks. The achieved accuracy will be discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLE06  
About • paper received ※ 30 August 2019       paper accepted ※ 04 September 2019       issue date ※ 08 October 2019  
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WEPLE07 Transfer Matrix Classification with Artificial Neural Network 898
 
  • Y.P. Sun
    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.
Standard neural network algorithms are developed for classification and regression applications. In this paper, the details of the neural network algorithms are presented, together with several applications. Artificial neural network is trained to classify multi-class transfer matrix of different types of particle accelerator components. It is shown that with a fully-connected feedforward neural network, it is possible to get high accuracy of 99% on training data, validation data and test data.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLE07  
About • paper received ※ 30 August 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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THYBA1 Status of the CBETA Cornell-BNL ERL Prototype 923
 
  • K.E. Deitrick, N. Banerjee, A.C. Bartnik, J.A. Crittenden, L. Cultrera, J. Dobbins, C.M. Gulliford, G.H. Hoffstaetter, W. Lou, P. Quigley, D. Sagan, K.W. Smolenski, D. Widger
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • J.S. Berg, S.J. Brooks, R.L. Hulsart, R.J. Michnoff, S. Peggs, D. Trbojevic
    BNL, Upton, New York, USA
 
  CBETA, the Cornell-BNL ERL Test Accelerator, is an SRF multi-turn ERL which has been commissioned in the one-turn configuration from March to July 2019. During this time, the project has demonstrated an energy acceptance of 1.5 in the FFA arc, high-transmission energy recovery performance, and increased the CBETA energy-recovered maximum average current.  
slides icon Slides THYBA1 [11.605 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THYBA1  
About • paper received ※ 28 August 2019       paper accepted ※ 06 September 2019       issue date ※ 08 October 2019  
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THYBA2
Multi-Pulse Scorpius Linear Induction Accelerator for Flash X-Ray Radiography  
 
  • N. Pogue, Y.-J. Chen
    LLNL, Livermore, California, USA
  • M.T. Crawford, D.J. Funk
    LANL, Los Alamos, New Mexico, USA
 
  The Scorpius electron linear induction accelerator is currently being developed for NNSA stockpile stewardship’s Enhanced Capabilities for Subcritical Experiments (ECSE) Program. The purpose is to provide multiple x-ray pulses for flash radiography of large hydrodynamic experiments driven by high explosive. The Scorpius accelerator is designed to produce four 90-ns, 2-kA, 20-MeV electron pulses with the inter-pulse separation varying from 100 ns to 900 ns. The exiting electron pulses will be focused onto a high-Z target to produce the needed radiographic x-ray sources. The ECSE Scorpius project is managed at Los Alamos National Laboratory with cooperation from Lawrence Livermore National Laboratory, Sandia National Laboratory and Nevada National Security Site. Currently, the project completion date is set for 2024. This presentation will cover Scorpius accelerator’s development status.  
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THYBA3 Use of Solid Xenon as a Beam Dump Material for 4th-Generation Storage Rings 927
 
  • M. Borland, H. Cease, J.C. Dooling
    ANL, Lemont, Illinois, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
Damage to tungsten beam dumps has been observed in the Advanced Photon Source due to the high charge (368 nC/store), high energy (7 GeV), and short loss time (about 15 microseconds). Owing to the higher charge (736 nC/store) and much lower emittance (42 pm vs 2.5 nm), this issue is expected to be much more severe in the APS Upgrade. This strongly suggests that such dumps are necessary in 4th-generation electron storage rings to prevent catastrophic damage to vacuum systems when, for example, rf systems trip. However, it also implies that the dump will be damaged by each strike and will thus need to be "refreshed," perhaps by moving the dump surface vertically to expose undamaged material. Xenon, a gas that solidifies at 161K, is an intriguing possibility for a beam dump material. Calculations suggest that as the beam spirals in toward a dump in a high-dispersion area the tails of the electron beam would vaporize sufficient xenon to rapidly diffuse the beam and render it harmless. The dump surface could be periodically reformed without breaking vacuum. Issues with the concept include the need to protect the frozen xenon from wakefield heating.
 
slides icon Slides THYBA3 [2.451 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THYBA3  
About • paper received ※ 27 August 2019       paper accepted ※ 04 September 2019       issue date ※ 08 October 2019  
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THYBA4 Status of the Magnetized Thermionic Electron Source at Jefferson Lab 931
 
  • F.E. Hannon, D.B. Bullard, C. Hernandez-Garcia, M.A. Mamun, M. Poelker, R. Suleiman
    JLab, Newport News, Virginia, USA
  • J.V. Conway, B.M. Dunham, R.G. Eichhorn, C.E. Mayes, K.W. Smolenski, N.W. Taylor
    Xelera Research LLC, Ithaca, New York, USA
  • C.M. Gulliford, V.O. Kostroun
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • M.S. Stefani
    ODU, Norfolk, Virginia, USA
 
  A 125kV DC gridded thermionic gun has been de-signed and constructed through a collaboration between Jefferson Lab and Xelera Research LLC. The gun has been recently installed at the Gun Test Stand diagnostic line at Jefferson Lab where transverse and longitudinal parameter space will be experimentally explored. The status and results characterizing the commissioning and trouble-shooting the thermionic gun are presented.  
slides icon Slides THYBA4 [13.653 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THYBA4  
About • paper received ※ 28 August 2019       paper accepted ※ 15 September 2019       issue date ※ 08 October 2019  
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THYBA5 Study of Fluctuations in Undulator Radiation in the IOTA Ring at Fermilab 934
SUPLH03   use link to see paper's listing under its alternate paper code  
TUPLH13   use link to see paper's listing under its alternate paper code  
 
  • I. Lobach
    University of Chicago, Chicago, Illinois, USA
  • A. Halavanau, Z. Huang, V. Yakimenko
    SLAC, Menlo Park, California, USA
  • K. Kim
    ANL, Lemont, Illinois, USA
  • V.A. Lebedev, S. Nagaitsev, A.L. Romanov, G. Stancari
    Fermilab, Batavia, Illinois, USA
  • A.Y. Murokh
    RadiaBeam, Marina del Rey, California, USA
  • T.V. Shaftan
    BNL, Upton, New York, USA
 
  We study turn-by-turn fluctuations in the number of emitted photons in an undulator, installed in the IOTA electron storage ring at Fermilab, with an InGaAs PIN photodiode and an integrating circuit. In this paper, we present a theoretical model for the experimental data from previous similar experiments and in our present experiment, we attempt to verify the model in an independent and a more systematic way. Moreover, in our experiment we consider the regime of very small fluctuation when the contribution from the photon shot noise is significant, whereas we believe it was negligible in the previous experiments. Accordingly, we present certain critical improvements in the experimental setup that let us measure such a small fluctuation.  
slides icon Slides THYBA5 [8.048 MB]  
poster icon Poster THYBA5 [3.079 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THYBA5  
About • paper received ※ 24 August 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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THYBA6 Active Pointing Stabilization Techniques Applied to the Low Energy RHIC Electron Cooling Laser Transport at BNL 938
MOPLM22   use link to see paper's listing under its alternate paper code  
SUPLH07   use link to see paper's listing under its alternate paper code  
 
  • 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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THAHC5
Some Challenges for High-Brightness Electron Linac Based Accelerators  
 
  • P. Craievich
    PSI, Villigen PSI, Switzerland
 
  Award session talk  
slides icon Slides THAHC5 [22.591 MB]  
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FRCHC2 Possibilities for Future Synchrotron Radiation Sources 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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