Keyword: electron
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MO1A02 Status of the European XFEL linac, undulator, klystron, operation 7
 
  • H. Weise
    DESY, Hamburg, Germany
  
  Funding: Work supported by the respective funding agencies of the contributing institutes; for details please see http:www.xfel.eu
The European XFEL under construction in Hamburg, Northern Germany, aims at producing X-rays in the range from 260 eV up to 24 keV out of three undulators that can be operated simultaneously with up to 27,000 pulses per second. The FEL is driven by a 17.5 GeV superconducting linac. Installation of this linac is now finished and commissioning is next. First lasing is expected for spring 2017. The paper summarizes the status of the project. First results of the injector commissioning are given. 		 
slides icon Slides MO1A02 [28.909 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MO1A02  
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MO2A03 Commissioning and Early Operation of the ARIEL e-Linac linac, gun, TRIUMF, solenoid 12
 
  • T. Planche, M. Alcorta, F. Ames, R.A. Baartman, C.B. Barquest, B. Humphries, D. Kaltchev, S.R. Koscielniak, R.E. Laxdal, Y. Ma, M. Marchetto, S. Saminathan, E. Thoeng
    TRIUMF, Vancouver, Canada
  • P. Jung
    UW/Physics, Waterloo, Ontario, Canada
  
  The ARIEL electron linac has been added to the TRIUMF facility as a new driver for the production of radioactive isotopes through photo-fission to complement the existing 500 MeV, H- TRIUMF cyclotron. The electron beam driver is specified as a 50 MeV, 10 mA cw superconducting electron linac at 1.3 GHz. The first 30 MeV stage of the e-linac consisting of two cryomodules is completed. The paper will describe the recent commissioning and early operation results.  
slides icon Slides MO2A03 [25.277 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MO2A03  
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MO2A04 Low Emittance and High Current Electron Linac Development at Tsinghua University gun, emittance, laser, experiment 17
 
  • C.-X. Tang, H.B. Chen, Z.J. Chi, Y.-C. Du, W.-H. Huang, J. Shi, Q.L. Tian, D. Wang, W. Wang, L.X. Yan, Z. Zhang, Z. Zhang, L.M. Zheng, Z. Zhou
    TUB, Beijing, People's Republic of China
  
  A 50MeV electron linac have been developed in Tsinghua University, which consists of a 1.6Cell photocathode rf gun, a 3-meter s-band SLAC type traveling wave (TW) accelerating structure an a s-band TW buncher. The photocathode rf gun is working at 120MV/m, 2856MHz, with very small dark current. The emittance of the electron beam is less than 1mm.mrad at 500pC, and 0.5mm.mrad at 200pC. The linac is designed for Tsinghua Thomson scattering X-ray source (TTX), and 2x107 photon/bunch at 50keV has been got and some application experiments with the x-ray have been carried out. The new photocathode rf gun and x-band high gradient accelerating structure development will also be introducted in this talk.  
slides icon Slides MO2A04 [11.413 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MO2A04  
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MO3A01 Status of SwissFEL linac, undulator, gun, laser 22
 
  • F. Löhl
    PSI, Villigen PSI, Switzerland
  
  SwissFEL is a hard x-ray free-electron laser facility that is currently constructed at PSI. This paper gives an overview of the facility, describes the main sub-systems of the accelerator, and summarizes the installation and commissioning status.  
slides icon Slides MO3A01 [315.102 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MO3A01  
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MO3A03 Spaceborne Electron Accelerators linac, cavity, gun, controls 32
 
  • J.W. Lewellen, C.E. Buechler, G.E. Dale, N.A. Moody, D.C. Nguyen
    LANL, Los Alamos, New Mexico, USA
  
  High-power electron beam generators in space will enable the studies of solar and space physics, specifically the interrogation of magnetic connection between the magnetosphere and ionosphere. This study plans to map the magnetic connection between the magnetosphere and ionosphere, using a satellite equipped with an electron beam accelerator that can create a spot in the ionosphere, observable by optical and radar detectors on the ground. To date, a number of spacecraft carrying low-power, <50-keV DC electron beam sources have been launched to study the upper ionosphere. The overall instrument weight will likely be dominated by the weight of the energy storage, the RF power amplifiers and the accelerator structure. We present the notional concept of a quasi-CW, C-band electron accelerator with 1-MeV beam energy, 10-mA beam current, and requiring 40 kW of prime power during operation. Our novel accelerator concept includes the following features: individually powered cavities driven by 6-GHz high-electron mobility transistors (HEMT), passively cooled accelerator structures with heat pipe technology, and active frequency control for operating over a range of temperatures.  
slides icon Slides MO3A03 [3.191 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MO3A03  
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MOOP04 Traveling Wave Linear Accelerator With RF Power Flow Outside of Accelerating Cavities impedance, coupling, linac, cavity 48
 
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
  
  Funding: Work supported by the U.S. DOE under Contract No. DE-AC02-76-SF00515.
An accelerating structure is a critical component of particle accelerators for medical, security, industrial and scientific applications. Standing-wave side-coupled accelerating structures are used where available RF power is at a premium, while average current and average RF power lost in the structure are high. These structures are expensive to manufacture and typically require a circulator to divert structure-reflected power away from RF source, klystron or magnetron. In this report a traveling wave accelerating structure is presented which combines high shunt impedance of the side-coupled standing wave structure with such advantages as simpler tuning and manufacturing. In addition, the structure is matched to the RF source so no circulator is needed. This paper presents the motivation for this structure and shows a practical example. 		 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOOP04  
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MOOP09 Dielectric and THz Acceleration (Data) Programme at the Cockcroft Institute acceleration, laser, wakefield, accelerating-gradient 62
 
  • S.P. Jamison, Y.M. Saveliev
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • R.B. Appleby, H.L. Owen, T.H. Pacey, T.H. Pacey, G.X. Xia
    UMAN, Manchester, United Kingdom
  • G. Burt, R. Letizia, C. Paoloni
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • A.W. Cross
    USTRAT/SUPA, Glasgow, United Kingdom
  • D.M. Graham
    The University of Manchester, The Photon Science Institute, Manchester, United Kingdom
  • C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  • C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  
  Funding: This work has been funded by STFC
Normal conducting RF systems are currently able to pro-vide gradients of around 100 MV/m, limited by break-down on the metallic structures. The breakdown rate is known to scale with pulse length and, in conventional RF systems, this is limited by the filling time of the RF struc-ture. Progressing to higher frequencies, from RF to THz and optical, can utilise higher gradient structures due to the fast filling times. Further increases in gradient may be possible by replacing metallic structures with dielectric structures. The DATA programme at the Cockcroft Insti-tute is investigating concepts for particle acceleration with laser driven THz sources and dielectric structures, beam driven dielectric and metallic structures, and optical and infrared laser acceleration using grating and photonic structures. A cornerstone of the programme is the VELA and CLARA electron accelerator test facility at Daresbury Laboratory which will be used for proof-of-principle experiments demonstrating particle acceleration. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOOP09  
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MOOP11 Operation of the CEBAF 100 MV Cryomodules cryomodule, cavity, operation, controls 65
 
  • C. Hovater, T.L. Allison, R. Bachimanchi, G.H. Biallas, E. Daly, M.A. Drury, A. Freyberger, R.L. Geng, G.E. Lahti, R.A. Legg, C.I. Mounts, R.M. Nelson, T. E. Plawski, T. Powers
    JLab, Newport News, Virginia, USA
  
  Funding: Authored by JSA, LLC under U.S. DOE Contract DE-AC05- 06OR23177.
The Continuous Electron Beam Accelerator Facility (CEBAF) 12 GeV upgrade reached its design energy in December of 2015. Since then CEBAF has been delivering 12 GeV beam to experimental Hall D and 11 GeV to experimental halls A and B in support of Nuclear physics. To meet this energy goal, ten new 100 MV cryomodules (80 cavities) and RF systems were installed in 2013. The superconducting RF cavities are designed to operate CW at a average accelerating gradient of 19.2 MV/m. To support the higher gradients and higher QL (3.2×107) operations, the RF system uses 13 kW klystrons and digital LLRF to power and control each cavity. This paper reports on the C100 operation and optimization improvements of the RF system and cryomodules. 		 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOOP11  
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MOOP12 Klynac Design Simulations and Experimental Setup cavity, linac, klystron, simulation 68
 
  • K.E. Nichols, B.E. Carlsten, A. Malyzhenkov
    LANL, Los Alamos, New Mexico, USA
  
  Funding: The authors gratefully acknowledge the support of the US Department of Energy through the LANL/LDRD Program for this work.
We present results of a proof-of-principle demonstration of the first ever klynac, a compact 1 MeV linear accelerator with integrated klystron source using one electron beam. This device is bi-resonant, utilizing one resonant circuit for the klystron input and gain cavities, and one for the klystron output and linac cavities. The purpose of a klynac-type device is to provide a compact and inexpensive alternative for a conventional 1 to 6 MeV accelerator. A conventional accelerator requires a separate RF source and linac and all the associated hardware needed for that architecture. The klynac configuration eliminates many of the components to reduce the weight of the entire system by 60%. We have built an 8-cavity, 2.84-GHz RF structure for a 1-MeV bi-resonant klynac. A 50-kV, 10-A electron gun provides the single beam needed. Numerical modeling was used to optimize the design. The separation between the klynac ouput cavity and the first accelerator cavity was adjusted to optimize the bunch capture and a pin-hole aperture between the two cavities reduces the beam current in the linac section to about 0.1 A. Standard high-shunt impedance linac cavities designs are used. We have fabricated the first test structure. The structure will be tested with beam in early Summer 2016. Results will be presented at LINAC 2016. 		 
slides icon Slides MOOP12 [1.136 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOOP12  
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MOPRC014 Beam Dynamics Simulations of a High Charge S-Band Photoinjector for Electron Beam Imaging Experiments gun, solenoid, booster, simulation 97
 
  • Y.R. Wang
    AAI/ANL, Argonne, Illinois, USA
  • S. Cao, Z.M. Zhang
    IMP/CAS, Lanzhou, People's Republic of China
  • W. Gai
    ANL, Argonne, Illinois, USA
  • J.Q. Qiu
    Euclid TechLabs, LLC, Solon, Ohio, USA
  
  A major challenge for high energy density physics is to measure properties of matter under extreme states of temperature and pressure that only occur in a time scale of 10 ns to 1 μs. Here we propose to use a single shot electron beam from an S-band photoinjector with enough energy to penetrate the material as a diagnostic capable of time resolution (< ns). In this paper, we report on the primary beam dynamics simulation of a S-band photocathode electron gun and accelerator that capable of producing up to 10 nC charge with high enough energy. Optimizations of the system parameters, including gun, focusing solenoid and acceleration field are performed using particle tracking code. The beam-line is designed to be installed in the Institute of Modern Physics(IMP) electron accelerator centre for high precision electron imaging experimental studies.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPRC014  
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MOPRC023 Semi-3D Beam-Tracking Code for Electron Injectors Using Bulk-to-Point Calculation Technique for Space Charge Fields emittance, space-charge, simulation, gun 120
 
  • A. Mizuno, H. Hanaki
    JASRI/SPring-8, Hyogo-ken, Japan
  
  A new semi-three-dimensional beam-tracking simulation code for electron injectors using bulk-to-point calculation technique for space charge fields is developed. The calculated space charge fields are not produced by a point charge but a doughnut which has the volume and whose cross-section is ellipsoid. Since the calculation noise which is usually caused by distributions of positions of point charge can be minimized, high accuracy calculation on emittance is realized with small number of electrons. Simultaneously, the calculation time becomes markedly shortened. In this paper, calculation examples for asymmetrical beams are demonstrated by the new code. The accuracy of emittance is also discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPRC023  
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MOPRC029 Experiment of Plasma Discharge on HWR Cavity for In-Situ Surface Cleaning Study cavity, plasma, experiment, operation 133
 
  • A.D. Wu, Y. He, T.C. Jiang, C.L. Li, Y.M. Li, W.M. Yue, S.H. Zhang, H.W. Zhao
    IMP/CAS, Lanzhou, People's Republic of China
  • L.M. Chen
    Institute of Physics, Chinese Academy of Sciences, Beijing, People's Republic of China
  • L. Yang
    IHEP, Beijing, People's Republic of China
  
  Hydrocarbons, which migrate from the vacuum bumps system, will absorb on the cavity surface after periods of operation. The contaminants can reduce the surface electron work function to enhance the field emission effect and restrict the cavity accelerating gradient. The room temperature in-situ plasma surface processing to clean the hydrocarbon contaminants can act as a convenient and efficient technology for the accelerator on line performance recovery. For better control of the discharge inside the cavity, the experiment works on a single HWR cavity aims to research the ignition between the swarm parameters (gas flow, pressure, forward power).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPRC029  
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MOPLR004 Development of an High Gradient, S-band, Accelerating Structure for the FERMI Linac linac, quadrupole, operation, wakefield 136
 
  • C. Serpico, I. Cudin
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • A. Grudiev
    CERN, Geneva, Switzerland
  
  The FERMI seeded free-electron laser (FEL), located at the Elettra laboratory in Trieste, is driven by a 200 meter long, S-band linac routinely operated at nearly 1.5 GeV and 10 Hz repetition rate [1]. The high energy part of the Linac is equipped with seven, 6 meter long Backward Traveling Wave (BTW) structures: those structures have small iris radius and a nose cone geometry which allows for high gradient operation [2]. Nonetheless a possible development of high-gradient, S-band accelerating struc-tures for the replacement of the actual BTW structures is under consideration. This paper investigates a possible solution for RF couplers that could be suitable for linac driven FEL where reduced wakefields effects, high oper-ating gradient and very high reliability are required.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR004  
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MOPLR009 X-Band Travelling Wave Accelerating Section R&D for HTF operation, coupling, cavity, vacuum 152
 
  • K. Jin
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  Hefei Light Source (HLS) was mainly composed of an 800 MeV electron storage ring and an 800MeV-1GeV constant-gradient accelerator in NSRL. The new Linac with Full Energy Injection and the Top-up Injection scheme has been developed successfully. And the other functioning as X Ray Free Electron Laser test facility has been considered. In the project, in order to compress the bunch length and to achieve the beam energy distribution linearization. A 15MeV, operation frequency 11.424GHz traveling wave accelerating section as harmonic compensation is being developed. In this paper, X Ray Free Electron Laser Hefei Test Facility (HTF) is introduce briefly. And the R&D of the x-band accelerating section with collinear load are presented in detail.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR009  
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MOPLR011 Design of a Dielectric-lined Waveguide for Terahertz-driven Linear Electron Acceleration acceleration, accelerating-gradient, impedance, experiment 158
 
  • A.L. Healy, G. Burt
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • M.J. Cliffe, D.M. Graham
    The University of Manchester, The Photon Science Institute, Manchester, United Kingdom
  • S.P. Jamison
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • R. Valizadeh
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  
  A dielectric-lined waveguide has been designed for use as an accelerating structure in terahertz-driven electron acceleration experiments at Daresbury. Experimental verification of acceleration will take place on Versatile Electron Linear Accelerator (VELA). The choice of a rectangular waveguide structure with sidewall dielectric layers enables tuning by varying the spacing between dielectric slabs to account for potential manufacturing errors. Schemes for coupling free-space single cycle THz pulses into the waveguide have been evaluated and optimised through CST simulation. Comparison of simulation with experimental measurements will also be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR011  
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MOPLR012 Compact Beam Position Monitor for Electron and Proton Machines proton, linac, software, synchrotron 161
 
  • M. Žnidarčič, M. Cargnelutti
    I-Tech, Solkan, Slovenia
  
  Monitoring and subsequent optimization of the linacs, transfer lines, energy recovery linacs and synchrotrons, requires specific instrumentation optimized for beam position and charge measurements. Libera Spark is the newly developed instrument intended for position and charge monitoring in electron and proton machines. The motivation, processing principles and first results at laboratories are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR012  
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MOPLR013 Investigations on Electron Beam Imperfections at PITZ laser, simulation, solenoid, gun 165
 
  • M. Krasilnikov, P. Boonpornprasert, J.D. Good, M. Groß, H. Huck, I.I. Isaev, D.K. Kalantaryan, O. Lishilin, G. Loisch, D. Melkumyan, A. Oppelt, G. Pathak, Y. Renier, T. Rublack, F. Stephan, G. Vashchenko, Q.T. Zhao
    DESY Zeuthen, Zeuthen, Germany
  • G. Asova
    INRNE, Sofia, Bulgaria
  • C. Hernandez-Garcia
    JLab, Newport News, Virginia, USA
  
  Since more than a decade, the photo injector test facility at DESY, Zeuthen site (PITZ), has developed and optimized high brightness electron sources for modern Free Electros Lasers like FLASH and the European XFEL. Despite a very high performance of the photo injector was experimentally demonstrated, several discrepancies between measurements and beam dynamics simulations have been revealed. Although the optimized measured values of the projected transverse emittance are close to those obtained from the beam dynamics simulations, the corresponding experimental machine parameters show certain systematic deviations from the simulated optimized setup. As a source for these deviations, electron beam imperfections were experimentally investigated. This includes studies on bunch charge production, electron beam imaging using the RF gun with its solenoid, and investigations on the transverse asymmetry of the electron beam generated in a rotationally symmetric gun cavity. Experimental studies were supplied with corresponding beam dynamics simulations. The paper reports on results of these studies.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR013  
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MOPLR024 Progress Towards Nb3Sn CEBAF Injector Cryomodule cavity, cryomodule, niobium, operation 193
 
  • G.V. Eremeev, K. Macha, U. Pudasaini, C.E. Reece, A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
  
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Operations at 4 K instead of 2 K have the potential to reduce the operational cost of an SRF linac by a factor of 3, if the cavity quality factor can be maintained. Cavities coated with Nb3Sn have been shown to achieve the accelerating gradients above 10 MV/m with a quality factor around 1010 at 4 K. Because such performance is already pertinent for CEBAF injector cryomodule, we are working to extend these results to CEBAF accelerator cavities envisioning coating of two CEBAF 5-cell cavities with Nb3Sn. They will be installed in an injector cryomodule and tested with beam. The progress on this path is reported in this contribution. 		 
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MOPLR051 Simulation of Gas and Plasma Charge Strippers plasma, target, ion, heavy-ion 248
 
  • O.S.H. Haas, O. Boine-Frankenheim
    TEMF, TU Darmstadt, Darmstadt, Germany
  
  Funding: This work is supported by the BMBF as part of project 05P15RDRBA.
Charge stripping of intense heavy ion beams is a major challenge in current and future linear heavy ion accelerators. Conventional stripping techniques are limited in their applicability, e.g. solid carbon foils suffer from short lifetimes at high intensities. One possible alternative is the use of a plasma as a stripping medium, which the presented work focuses on. The main goal of the studies is the prediction of the final charge state distribution of the ion beam. Rate equations were implemented numerically, taking into account different models for ionization, recombination and energy loss processes. First quantitative results are presented in form of an overview of the charge state distributions of different charge stripping media. For fixed projectile properties and target phase, it is observed that the mean charge state q0 decreases for increasing nuclear charge Z\text{T} of the target. Plasmas show significantly increased q0 for the same ZT. The width d of the charge state distributions is larger for higher Z\text{T}. The latter is caused by multiple loss of the projectile and decreases the maximum stripping efficiency by typically less than a factor of 2. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR051  
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MOP106002 X-Band Photonic Band Gap Accelerating Structures with Improved Wakefield Suppression wakefield, HOM, dipole, acceleration 307
 
  • E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
  
  Funding: This work is supported by U.S. Department of Energy (DOE) Office of High Energy Physics.
We present the design of a novel photonic band gap (PBG) accelerating structure with elliptical rods and improved wakefields suppression. It has been long recognized that PBG structures have great potential in reducing long-range wakefields in accelerators. The first ever demonstration of acceleration in room-temperature PBG structures was conducted at MIT in 2005. The experimental characterization of the wakefield spectrum in a beam test was performed at Argonne Wakefield Accelerator facility in 2015, and the superior wakefield suppression properties of the PBG structure were demonstrated. In 2013 the team from MIT and SLAC demonstrated that the X-band PBG structures with elliptical rods have reduced breakdown rate compared to PBG structures with round rods, presumably due to the reduced surface magnetic fields. However, the structure with elliptical rods designed by MIT confined the dipole higher order mode in addition to the accelerating mode and thus did not have superior wakefield suppression properties. We demonstrate that PBG resonators can be designed with 40% smaller peak surface magnetic fields while preserving and even improving their wakefield suppression properties as compared to the structure with round rods. The design of the new structure is presented. The structure will be fabricated, tuned, and tested for high gradients and for wakefield suppression. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOP106002  
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MOP106012 MESA - an ERL Project for Particle Physics Experiments target, experiment, operation, linac 313
 
  • F. Hug, K. Aulenbacher, R.G. Heine, B. Ledroit, D. Simon
    IKP, Mainz, Germany
  
  The Mainz Energy-recovering Superconducting Accelerator (MESA) will be constructed at the Institut für Kernphysik of the Johannes Gutenberg University of Mainz. The accelerator is a low energy continuous wave (CW) recirculating electron linac for particle physics experiments. MESA will be operated in two different modes serving mainly two experiments: the first is the external beam (EB) mode, where the beam is dumped after being used with the external fixed target experiment P2, whose goal is the measurement of the weak mixing angle with highest accuracy. The required beam current for P2 is 150 μA with polarized electrons at 155 MeV. In the second operation mode MESA will be run as an energy recovery linac (ERL). The experiment served in this mode is a (pseudo) internal fixed target experiment named MAGIX. It demands an unpolarized beam of 1 mA at 105 MeV. In a later construction stage of MESA the achievable beam current in ERL-mode shall be upgraded to 10 mA. Within this contribution an overview of the MESA project will be given highlighting the latest accelerator layout and the challenges of operation with high density internal gas targets.
Work supported by DFG through cluster of excellence PRISMA, CRC 1044 and RTG 2128 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOP106012  
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MOP106015 Commissioning Status of the Chopper System for the MAX IV Injector injection, linac, radiation, storage-ring 316
 
  • D. Olsson, J. Andersson, F. Curbis, L. Isaksson, L. Malmgren, E. Mansten, S. Thorin
    MAX IV Laboratory, Lund University, Lund, Sweden
  
  The MAX IV facility in Lund, Sweden consists of two storage rings for production of synchrotron radiation. The two rings are designed for 1.5 GeV and 3 GeV, respectively, where the former is under construction, and the latter is undergoing beam commissioning. Both rings will be operating with top-up injections delivered by a full-energy injector that consists of 39 traveling-wave S-band LINAC structures. In order to reduce losses of high-energy electrons along the injector and in the rings during injection, only electrons that are within an allowed time structure are accelerated. This time structure depends on several parameters such as the available RF voltage and the radiation losses in the ring that is about to be injected, but also on the momentum acceptance of the transport lines in the injector. The electrons that are outside the allowed time structure are dumped when they have energies below 3 MeV by a chopper system that is located between a thermionic RF gun and the first LINAC structure. Basically, the chopper system consists of two planar striplines and a variable aperture, and the first stripline is fed with a superposed RF signal and the second one with HV pulses. The performance of the chopper system during commissioning of the 3 GeV ring is presented in this article.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOP106015  
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MOP106016 High Power RF Requirements for Driving Discontinuous Bunch Trains in the MaRIE Linac linac, cavity, beam-loading, booster 320
 
  • J.T. Bradley III, D. Rees, A. Scheinker, R.L. Sheffield
    LANL, Los Alamos, New Mexico, USA
  
  Funding: Work supported by the US Department of Energy.
The MaRIE project will use a superconducting linac to provide 12 GeV electron bunches to drive an X-ray FEL and to do electron radiography. Dynamic experiments planned for MaRIE require that the linac produce a series of micropulses that can be irregularly spaced within the macropulse, and these patterns can change from macropulse to macropulse. Irregular pulse structures create a challenge to optimizing the design of the RF and cryogenic systems. General formulas for cavities with beam loading can overestimate the power required for our irregular beam macropulse. The differing beam energy variations allowed for the XFEL and eRad micropulses produce cavity voltage control requirements that also vary within the macropulse. The RF pulse driving the cavities can be tailored to meet the needs of that particular beam macropulse because the macropulse structure is known before the pulse starts. We will derive a toolkit that can be used to determine the required RF power waveforms for arbitrary macropulse structures. We will also examine how the irregular RF power waveforms can impact RF and cryogenic system cost tradeoffs. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOP106016  
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MOP106022 Generation of Coherent Undulator Radiation at ELPH, Tohoku University radiation, undulator, ion, focusing 330
 
  • S. Kashiwagi, T. Abe, H. Hama, F. Hinode, T. Muto, I. Nagasawa, K. Nanbu, H. Saito, Y. Saito, Y. Shibasaki, K. Takahashi
    Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
  
  A test accelerator as a coherent terahertz source (t-ACTS) has been under development at Tohoku University, in which an intense coherent terahertz (THz) radiation generated by an extremely short electron bunch. Velocity bunching scheme in a traveling accelerating structure is employed to generate femtosecond electron bunches. Spatial and temporal coherent radiation in THz region can be produced by the electron bunches with small transverse emittance. A long-period undulator, which has 25 periods with a period length of 10 cm and a peak magnetic field of 0.41 T, has been also developed and installed to provide intense coherent THz undulator radiation. By optimizing the bunch length, we found that it is possible to generate a coherent undulator radiation that contain only the fundamental wave from numerical studies. We are planning an experiment with 30 MeV beam to generate a coherent undulator radiation of 2.5THz. In the conference, we will report the preliminary experimental results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOP106022  
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TU1A01 Review on Trends in Normal Conducting Linacs for Protons, Ions and Electrons, With Emphasis on New Technologies and Applications linac, DTL, rfq, proton 336
 
  • F. Gerigk
    CERN, Geneva, Switzerland
  
  In recent years a lot of attention was given to developments in the field of superconducting cavities. While these cavities can save operating costs and shorten the length of linacs, there are many applications and circumstances where normal conducting cavities are superior. This talk reviews some of the normal conducting linacs, which have been either recently commissioned, or which are currently under construction or in the design phase. Focus will be given to the choice between normal and superconducting cavities and to emerging normal conducting technologies and their applications.  
slides icon Slides TU1A01 [16.553 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TU1A01  
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TU2A03 Resonance Control for Future Linear Accelerators cavity, controls, resonance, SRF 363
 
  • W. Schappert
    Fermilab, Batavia, Illinois, USA
  
  Many of the next generation of particle accelerators (LCLS II, PIP II) are designed for relatively low beam loading. Low beam loading requirement means the cavities can operate with narrow bandwidths, minimizing capital and base operational costs of the RF power system. With such narrow bandwidths, however, cavity detuning from microphonics or dynamic Lorentz Force Detuning becomes a significant factor, and in some cases can significantly increase both the acquisition cost and the operational cost of the machine. In addition to the efforts to passive environmental detuning reduction (microphonics) active resonance control for the SRF cavities for next generation linear machine will be required. State of the art in the field of the SRF Cavity active resonance control and the results from the recent efforts at FNAL will be presented in this talk.  
slides icon Slides TU2A03 [0.897 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TU2A03  
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TUOP01 Applying Transverse Gradient Undulators to Suppression of Microbunching Instability linac, laser, FEL, simulation 380
 
  • D. Huang, H.X. Deng, C. Feng, D. Gu, Q. Gu, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
  
  Funding: Major State Basic Research Development Program of China (2011CB808300). National Natural Science Foundation of China (NSFC), grant No. 11275253.
The microbunching instability developed during the beam compression process in the linear accelerator (LIN-AC) of a free-electron laser (FEL) facility has always been a problem that degrades the lasing performance, and even no FEL is able to be produced if the beam quality is destroyed too much by the instability. A common way to suppress the microbunching instability is to introduce extra uncorrelated energy spread by the laser heater that heats the beam through the interaction between the electron and laser beam, as what has been successfully implemented in the Linac Coherent Light Source and Fermi@Elettra. In this paper, a simple and effective scheme is proposed to suppress the microbunching instability by adding two transverse gradient undulators (TGU) before and after the magnetic bunch compressor. The additional uncorrelated energy spread and the density mixing from the transverse spread brought up by the first TGU results in significant suppression of the instability. Meanwhile, the extra slice energy spread and the transverse emittance can also be effectively recovered by the second TGU. The magnitude of the suppression can be easily controlled by varying the strength of the magnetic fields of the TGUs. Theoretical analysis and numerical simulations demonstrate the capability of the proposed technique in the LINAC of an x-ray free-electron laser facility. 		 
slides icon Slides TUOP01 [1.148 MB]  
poster icon Poster TUOP01 [0.447 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUOP01  
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TUOP02 CBETA: The Cornell/BNL 4-Turn ERL with FFAG Return Arcs for eRHIC Prototyping linac, cryomodule, gun, SRF 384
 
  • G.H. Hoffstaetter, J. Barley, A.C. Bartnik, I.V. Bazarov, J. Dobbins, B.M. Dunham, R.G. Eichhorn, R.E. Gallagher, C.M. Gulliford, Y. Li, M. Liepe, W. Lou, C.E. Mayes, J.R. Patterson, D.M. Sabol, E.N. Smith, K.W. Smolenski
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • I. Ben-Zvi, J.S. Berg, S.J. Brooks, G.J. Mahler, F. Méot, M.G. Minty, S. Peggs, V. Ptitsyn, T. Roser, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, H. Witte
    BNL, Upton, Long Island, New York, USA
  • D. Douglas
    JLab, Newport News, Virginia, USA
  
  Cornell University has prototyped technology essential for any high brightness electron ERL. This includes a DC gun and an SRF injector Linac with world-record current and normalized brightness in a bunch train, a high-current CW cryomodule, a high-power beam stop, and several diagnostics tools for high-current and high-brightness beams, e.g. slid measurements for 6-D phase-space densities, a fast wire scanner for beam profiles, and beam loos diagnostics. All these are now available to equip a one-cryomodule ERL, and laboratory space has been cleared out and is radiation shielded to install this ERL at Cornell. BNL has designed a multi-turn ERL for eRHIC, where beam is transported more than 20 times around the RHIC tunnel. The number of transport lines is minimized by using two non-scaling (NS) FFAG arcs. A collaboration between BNL and Cornell has been formed to investigate the new NS-FFAG optics and the multi-turn eRHIC ERL design by building a 4-turn, one-cryomodule ERL at Cornell. It has a NS-FFAG return loop built with permanent magnets and is meant to accelerate 40mA beam to 200MeV.  
slides icon Slides TUOP02 [7.848 MB]  
poster icon Poster TUOP02 [13.981 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUOP02  
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TUOP09 State of the Art Advanced Magnetron for Accelerator RF Power Source cathode, linac, cavity, radiation 405
 
  • H. Obata, K. Furumoto, H. Miyamoto
    New Japan Radio Co., Ltd., Fujimino Saitama, Japan
  
  X ray sources for linear accelerators continue to be a necessary requirement for industries such as medical, inspection, and nondestructive test equipment. Future requirements for such sources are; low cost, compact packaging and high performance of the RF source for electron acceleration. The magnetron has proven to be a perfect source over other RF sources for linear accelerator use. Because of its simple design, low cost per output, small size and proven performance it meets all required characteristics. New Japan Radio Co., Ltd. has improved and modified its linac magnetrons' performance and characteristics enabling easy matching to the linac modulator, long life and maximum output power. This paper will provide a detailed explanation on the improved magnetron design methodology and its effects on the performance of these magnetrons installed in linac systems. These technologies have been utilized successfully on a commercial level worldwide over the last few years. The technology has been deployed into linac systems operating in S and X band and soon C band, at various output power levels.  
slides icon Slides TUOP09 [1.127 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUOP09  
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TUOP11 Methods for Bunch Shape Monitor Phase Resolution Improvement linac, focusing, space-charge, quadrupole 408
 
  • A. Feschenko, S.A. Gavrilov
    RAS/INR, Moscow, Russia
  
  Bunch shape monitors, based on secondary electrons emission, are widely used for measurements of longitudinal bunch profiles during a linac commissioning and initial optimization of beam dynamics. A typical phase resolution of these devices is about 1°. However it becomes insufficient for new modern linacs, which require a better resolution. Some developed methods for a phase resolution improvement are discussed.  
slides icon Slides TUOP11 [21.248 MB]  
poster icon Poster TUOP11 [1.888 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUOP11  
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TUPRC003 Effect of Number of Macro Particles on Time Evolution of Phase Space Distribution emittance, simulation, linac, operation 414
 
  • T. Miyajima
    KEK, Ibaraki, Japan
  
  Funding: This work was supported by JSPS KAKENHI Grant Number 26600147.
In particle tracking simulation with space charge effect, the macro-particle model, which has same mass-to-charge ratio, is widely used, since it does not require any symmetry of beam shape. However, selection of proper number of macro-particles is important, because the accuracy depends on it. Emittance, which is calculated by phase-space distribution, is especially affected by the number of macro-particles. In order to study the relation between the number of macro-particles and the resolution in the phase space, we defined a transformation, which describes reduction process of macro-particle number, and analyzed static phase space distribution. As a next step, we studied the effect of the macro-particle number on the dynamics of the phase space distribution for 1D charged particle distribution in the rest frame. The numerical result shows that the number of macro-particles affected the phase space distribution around the head and the tail of the bunch.
* T. Miyajima, "Effect of number of macro particles in phase space distribution", in Proc. of IPAC2015, Richmond, VA, USA, pp.242-244 (2015). 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC003  
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TUPRC008 Electron Driven ILC Positron Source with a Low Gradient Capture Linac positron, linac, beam-loading, simulation 430
 
  • M. Kuriki
    HU/AdSM, Higashi-Hiroshima, Japan
  • T. Kakita
    Hiroshima University, Graduate School of Advanced Sciences of Matter, Higashi-Hiroshima, Japan
  • S. Kashiwagi
    Tohoku University, School of Science, Sendai, Japan
  • K. Negishi
    Iwate University, Morioka, Iwate, Japan
  • T. Okugi, T. Omori, M. Satoh, Y. Seimiya, J. Urakawa, K. Yokoya
    KEK, Ibaraki, Japan
  • T. Takahashi
    Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
  
  ILC (International Linear Collider) is e+ e− linear collider in the next high energy program promoted by ICFA. In ILC, an intense positron pulse in a multi-bunch format is generated with gamma ray from Undulator radiation. As a technical backup, the electron driven positron source has been studied. By employing a standing wave L-band accelerator for the capture linac, an enough amount of positron can be captured due to the large aperture, even with a limited accelerator gradient. However, the heavy beam loading up to 2 A perturbs the field gradient and profile along the longitudinal position. We present the capture performance of the ILC positron source including the heavy beam loading effect.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC008  
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TUPRC016 S-Band Booster Design and Emittance Preservation for the Awake e-Injector emittance, linac, plasma, booster 449
 
  • O. Mete Apsimon, R. Apsimon, G. Burt
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • S. Döbert
    CERN, Geneva, Switzerland
  • G.X. Xia
    UMAN, Manchester, United Kingdom
  
  AWAKE is a proton driven plasma wakefield acceleration experiment at CERN which uses the protons from the SPS. It aims to study the self modulation instability of a proton bunch and the acceleration of an externally injected electron beam in the plasma wakefields, during the so called Phase II until the technical stop of LHC and its injector chain (LS2) in 2019. The external electron beam of 0.1 to 1nC charge per bunch will be generated using an S-band photo injector with a high QE semiconducting cathode. A booster linac was designed to allow variable electron energy for the plasma experiments from 16 to 20 MeV. For an RF gun and booster system, emittance control can be highlighted as a challenging transmission task. Once the beam emittance is compensated at the gun exit and the beam is delivered to the booster with an optimum beam envelope, fringing fields and imperfections in the linac become critical for preserving the injection emittance. This paper summarises the rf design studies in order to preserve the initial beam emittance at the entrance of the linac and alternative mitigation schemes in case of emittance growth.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC016  
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TUPRC019 Beam Instabilities in Electron Cyclotron Resonance Ion Sources plasma, ion, cyclotron, ion-source 455
 
  • B.C. Isherwood
    MSU, East Lansing, Michigan, USA
  • G. Machicoane, G. Pozdeyev
    NSCL, East Lansing, Michigan, USA
  • G. Machicoane, G. Pozdeyev, Y. Yamazaki
    FRIB, East Lansing, Michigan, USA
  
  Funding: This research is funded by joint assistance from the NSF and D.O.E.
Accelerator facilities for radioactive beams and low energy nuclear physics such as FRIB require intense, stable ion beam currents in order to achieve required reaction rates for rare and undiscovered isotopes. Presently, the only way to produce intense Continuous Wave beams of highly-charged, medium to heavy-mass ions is with Electron Cyclotron Resonance Ion Sources (ECRIS). The complex nature of these devices causes temporal instabilities to occur, most notably: Slow and fast instabilities. Slow instabilities and drifts, occurring over hours, decay the beam current intensity due to variations in ambient and hardware conditions. These drifts require beam operators to constantly monitor and tune ECRIS plasma parameters in order to maintain experimental beam requirements. Fast instabilities, in the form of ms oscillations, occur at operational parameters needed for high-intensity, high-charge state beams. These oscillations cause sudden drops in beam current of the order of 30%. We present here initial results of recent measurements to investigate these instabilities. Results for slow instabilities indicate a linear decay of beam intensity following a sharp current drop due to a brief source conditioning period. Results for fast instabilities show a relationship between the frequency and amplitude of beam oscillations and the electric potential of the plasma chamber bias disk. 		 
poster icon Poster TUPRC019 [0.817 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC019  
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TUPRC020 The TRIUMF ARIEL RF Modulated Thermionic Electron Source cathode, emittance, TRIUMF, target 458
 
  • F. Ames, Y.-C. Chao, K. Fong, N. Khan, S.R. Koscielniak, A. Laxdal, L. Merminga, T. Planche, S. Saminathan, D.W. Storey
    TRIUMF, Vancouver, Canada
  • Y.-C. Chao, L. Merminga
    SLAC, Menlo Park, California, USA
  • C.K. Sinclair
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: ARIEL is funded by the Canada Foundation for Innovation, the Provinces AB, BC, MA, ON, QC, and TRIUMF. TRIUMF receives funding via a contribution agreement with the National Research Council of Canada
Within the ARIEL (Advanced Rare IsotopE Laboratory) at TRIUMF, a high power electron beam is used to produce radioactive ion beams via photo-fission. The electron beam is accelerated in a superconducting linac up to 50 MeV. The electron source provides electron bunches with charge up to 16 pC at a repetition frequency of 650 MHz leading to an average current of 10 mA . The kinetic energy of the electrons has been chosen to be 300 keV to allow direct injection into an accelerator cavity. The main components of the source are a gridded dispenser cathode (CPI 'Y845) in an SF6 filled vessel and an in-air HV power supply. The beam is bunched by applying DC and RF fields to the grid. Unique features of the gun are its cathode/anode geometry to reduce field emission, and transmission of RF modulation via a dielectric (ceramic) waveguide through the SF6. The latter obviates the need for an HV platform inside the vessel to carry the RF generator and results in a significantly smaller/simpler vessel. The source has been installed and first tests with accelerated beams have been performed. Measurements of the beam properties and results from the commissioning of the source will be presented. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC020  
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TUPRC022 UPS Study for CsK2Sb Photocathode cathode, laser, experiment, ion 465
 
  • M. Kuriki, T. Konomi, Y. Seimiya
    KEK, Ibaraki, Japan
  • L. Guo, M. Urano, A. Yokota
    HU/AdSM, Higashi-Hiroshima, Japan
  • K. Negishi
    Iwate University, Morioka, Iwate, Japan
  
  CsK2Sb photo-cathode is one of the ideal cathode for accelerators requiring the high brightness electron beam. It can be driven with a green laser which can be generated as SHG from solid state laser. The QE (Quantum Efficiency) of photo-electron emission is as high as more than 10% with 532nm light. The material is robust and the typical operational lifetime is more than several months. It is also vital against the high intensity beam extraction. The photo-cathode is generated as a thin film in-situ and the material property and optimized condition for the cathode formation is not understood well. In this article, we present UPS analysis of CsK2Sb cathode for deeper understanding.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC022  
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TUPRC032 An Analysis of Fast Sputtering Studies for Ion Confinement Time ion, plasma, ECRIS, ion-source 475
 
  • D.E. Neben, G. Machicoane, A.N. Pham, J.W. Stetson
    NSCL, East Lansing, Michigan, USA
  • G. Machicoane
    FRIB, East Lansing, USA
  • G. Parsey
    MSU, East Lansing, Michigan, USA
  • J.P. Verboncoeur
    Michigan State University, East Lansing, Michigan, USA
  
  Funding: This work was supported by Michigan State University and the National Science Foundation: NSF Award Number PHY-1415462
Existing heavy ion facilities such as the National Superconducting Cyclotron Laboratory at Michigan State University rely on Electron Cyclotron Resonance (ECR) ion sources as injectors of highly charged ion beams. Long ion confinement times are necessary to produce dense populations of highly charged ions because of steadily decreasing ionization cross sections with increasing charge state. To further understand ion extraction and confinement we are using a fast sputtering technique first developed at Argonne National Laboratory (ANL) [1] to introduce a small amount of uranium metal into the plasma at a well-defined time. We present an analytical solution to the coupled ion density rate equations for using a piecewise constant neutral density to interpret the fast sputtering method.
*R. Vondrasek et al., Rev. Sci. Instrum. 73, 548-551 (2002). 		 
poster icon Poster TUPRC032 [0.699 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC032  
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TUPLR005 Development of 6 MeV European S-band Side-Coupled Industrial Electron Linear Accelerator at RTX & KAERI linac, coupling, target, gun 478
 
  • P. Buaphad, S.C. Cha
    KAERI, Jeongeup-si, Republic of Korea
  • P. Buaphad
    University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
  • P. Buaphad
    RTX, Daejeon, Republic of Korea
  • Y. Kim
    ISU, Pocatello, Idaho, USA
  
  There are growing demands on low energy electron linear accelerator (linac) for industrial applications. Most of industrial electron linacs require a compact structure and limited undesirable neutron production to avoid huge lead shielding. Radiation Technology eXcellence (RTX) and Korea Atomic Energy Research Institute (KAERI) have developed a 6 MeV compact side-coupled linac by using 2998 MHz European S-band RF technology to meet those requirements. To design the linac structure, the 3D CST MICROWAVE STUDIO (CST-MWS) was used for various electromagnetic simulations, and ASTRA code was used for particle beam dynamics simulations. After various optimizations, the shunt impedance of 61 MΩ/m is obtained at 2998.38 MHz. With a peak RF power of 2.2 MW and a 47 cm-long structure, electron beam with a peak current of 150 mA can be accelerated from 25 keV to 6 MeV. For the industrial linac, the electron beam spotsize at an X-ray target, located 5 cm downstream of the linac structure exit should be smaller than 2 mm (FW). In addition, it can supply an X-ray dose rate of 8 Gy/min at 1 m after the X-ray target. In this paper, we describe the design concepts and optimization of the 2998 MHz side-coupled industrial linac structure.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPLR005  
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TUPLR013 Lifetime Study of CKk2Sb Robust Photo-Cathode for a High Brightness Electron Source cathode, laser, vacuum, brightness 500
 
  • M. Kuriki, Y. Seimiya
    KEK, Ibaraki, Japan
  • L. Guo, K. Moriya, M. Urano, A. Yokota
    HU/AdSM, Higashi-Hiroshima, Japan
  • K. Negishi
    Iwate University, Morioka, Iwate, Japan
  
  CsK2Sb photo-cathode is one of the ideal cathode for accelerators requiring the high brightness electron beam. It can be driven with a green laser which can be generated as SHG from solid state laser. The QE (Quantum Efficiency) of photo-electron emission is as high as more than 10% with 532nm light. In this article, the robustness of the cathode is studied. Two indexes of lifetime regarding to time and extracted charge density were evaluated experimentally. The result shows that the cathode is robust enough for a high brightness accelerator.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPLR013  
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TUPLR015 Design of a Gamma-Ray Source Based on Inverse Compton Scattering at the Fast Superconducting Linac laser, photon, cavity, brightness 503
 
  • D. Mihalcea
    Northern Illinois University, DeKalb, Illinois, USA
  • B.T. Jacobson, A.Y. Murokh
    RadiaBeam, Santa Monica, California, USA
  • P. Piot, J. Ruan
    Fermilab, Batavia, Illinois, USA
  
  Funding: This work is sponsored by the DNDO via contract with NIU.
A Watt-level average-power gamma-ray source is currently under development at the FermiLab Accelerator Science & Technology (FAST) facility. The source is based on the inverse Compton scattering of a high-brightness 300-MeV beam against a high-power laser beam circulating in an optical cavity. The back scattered gamma rays are expected to have photon energies up to 1.5 MeV. This paper discusses the optimization of the source, its performance and the main challenges ahead. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPLR015  
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TUPLR025 Optimal Nitrogen Doping Level to Reach High Q0 cavity, cryomodule, SRF, niobium 523
 
  • D. Gonnella, T. Gruber, J.J. Kaufman, P.N. Koufalis, M. Liepe, J.T. Maniscalco
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: NSF and US DOE
New continuous wave (CW) accelerators such as LCLS-II at SLAC require many SRF cavities operating in the medium field region at unprecedented high Q. In order to achieve this demanding goal, nitrogen-doping of the SRF cavities will be used. Nitrogen-doping has been shown to affect the BCS resistance both by a lowering of Rbcs at low fields and by the introduction of an anti-Q slope which enables the Q to continue increasing as the RF field is increased. The exact strength of this anti-Q slope is heavily dependent on the doping recipe and specifically the mean free path of the RF penetration layer of the doped cavities. In addition to its effect on Rbcs, the mean free path affects the amount of residual resistance obtained due to trapped magnetic flux. We have analyzed nine cavities prepared with different levels of nitrogen-doping to understand how BCS and residual resistance are affected by changes in the mean free path. Here we present a model based on these experimental results to predict the optimal doping level to reach the maximum Q at 16 MV/m based on the ambient magnetic field conditions. We find that if the cavities can be cooled with small amounts of trapped flux, moderate nitrogen-doping is better, while if they will have large amounts of trapped flux, lighter dopings should be used. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPLR025  
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TUPLR069 Simulation Study on the Beam Loss Mitigation in the 1st Arc Section of FRIB Driver Linac ion, simulation, linac, heavy-ion 613
 
  • T. Maruta
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • M. Ikegami, F. Marti
    FRIB, East Lansing, USA
  
  Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661.
The Facility of Rare Isotope Beams (FRIB) at Michigan State University is now under construction toward user operation in year 2020. Charge-state transition of accelerating ions occurs in the beam line due to interaction with the residual gas. Since this exchange changes charge to mass ratio of the ions, the ion orbit is distorted especially in an arc section with the ion potentially hitting the vacuum pipe. This will generate outgassing from the beamline pipe. Moreover, they become a seed of further charge-state exchanges. Therefore, a collimation of charge exchanged ions is necessary to prevent this feedback cycle. In this presentation, the results of a simulation study on charge exchange reaction in the 1st arc section of FRIB and optimization of collimator position are presented. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPLR069  
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TH2A02 Results From the Laserwire Emittance Scanner and Profile Monitor at CERN's Linac4 laser, detector, linac, emittance 715
 
  • T. Hofmann, U. Raich, F. Roncarolo
    CERN, Geneva, Switzerland
  • G.E. Boorman, A. Bosco, S.M. Gibson
    Royal Holloway, University of London, Surrey, United Kingdom
  • G.E. Boorman, A. Bosco, S.M. Gibson
    JAI, Egham, Surrey, United Kingdom
  
  A novel, non-invasive, H− laser-wire scanner has been tested during the beam commissioning of CERN's new Linac4. Emittance measurements were performed at beam energies of 3 and 12 MeV with this new device and were found to closely match the results of conventional slit-grid methods. In 2015, the configuration of this laser-wire scanner was substantially modified. In the new setup the electrons liberated by the photo-detachment process are deflected away from the main beam and focused onto a single crystal diamond detector that can be moved in order to follow the laser beam scan. The beam profiles measured with the new laser-wire setup at 50 MeV, 80 MeV and 107 MeV are in good agreement with the measurements of nearby SEM grids and wire-scanners. The design of the final laser-wire scanner for the full 160 MeV beam energy will also be presented. In Linac4 two independent laser-wire devices will be installed in the transfer line to the BOOSTER ring. Each device will be composed of two parts: one hosting the laser-wire and the electron detector and the second hosting the segmented diamond detector used to acquire the transverse profiles of the H0 beamlets.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TH2A02  
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TH3A01 Making Molecular Movie with MeV Electrons laser, experiment, alignment, detector 725
 
  • X. Shen, X.J. Wang
    SLAC, Menlo Park, California, USA
  
  SLAC launched the Ultrafast Electron Diffraction and Imaging (UED&UEM) initiative with the objective of developing the world leading ultrafast electron scattering instrumentation, complementary to the X-ray Free Electron Laser - Linac Coherent Light Source (LCLS). SLAC has developed a UED setup at the Accelerator Structure Test Area (ASTA), with the goal of providing MeV, 100-femtosecond-scale electron pulses to support an ultrafast science program [1]. The first UED ultrafast science experiment published in Nano Letters, where large amplitude wrinkles of monolayer MoS2 generated by the light pulse' more than 15 percent of the layer's thickness, was observed. This is the first time anyone has visualized these ultrafast atomic motions. Ultrafast MeV electrons also made it possible the direct measurement of phonon occupations as energy is transferred from electrons into the lattice in laser-heated gold (APL). The rotational wavepacket dynamics of laser-aligned nitrogen molecules were captured in gas-phase electron diffraction experiment using MeV electrons. We achieved an unprecedented combination of 100-fs (rms) temporal resolution and sub-Angstrom (0.76 Å) spatial resolution that makes it possible to resolve the position of the nuclei within the molecule(Nature Communications).
[1] S. Weathersby, et al., Rev. Sci. Instrum. 86, 073702 (2015). 		 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TH3A01  
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TH3A02 The Los Alamos Multi-Probe Facility for Matter-Radiation Interactions in Extremes linac, photon, laser, proton 729
 
  • R.W. Garnett
    LANL, Los Alamos, New Mexico, USA
  
  Funding: This work is supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396.
A next-generation signature facility based on multi-probe capabilities is being planned at Los Alamos. This new facility will enable the first in a new generation of game-changing scientific facilities for the materials community. The new Matter-Radiation Interactions in Extremes (MaRIE) facility will be used to discover and design the advanced materials needed to meet 21st-century national security and energy-security challenges to develop next-generation materials that will perform predictably in extreme environments. The MaRIE facility will include a new 12-GeV electron linac using a state-of-the-art electron photoinjector and superconducting accelerator technology to drive a 42-keV XFEL to generate x rays of unprecedented flux and quality, coupled with the existing proton-beam capabilities of the LANSCE proton linac, new experimental halls, and new materials fabrication/characterization facilities. A description of this new facility, its requirements, and planned uses and capabilities will be presented. Status of the project will also be presented. 		 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TH3A02  
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TH3A03 The VELA and CLARA Test Facilities at Daresbury Laboratory FEL, gun, cavity, laser 734
 
  • P.A. McIntosh, D. Angal-Kalinin, J.A. Clarke, L.S. Cowie, B.D. Fell, S.P. Jamison, B.L. Militsyn, Y.M. Saveliev, D.J. Scott, N. Thompson, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • A. Gleeson, T.J. Jones
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  
  The Versatile Electron Linear Accelerator (VELA) provides enabling infrastructures targeted at the development and testing of novel and compact accelerator technologies, specifically through partnership with academia and industry, aimed at addressing applications in medicine, health, security, energy and industrial processing. The facility is now fully commissioned and is taking advantage of the variable electron beam parameters to demonstrate new techniques/processes or otherwise develop new technologies for future commercial realization. Examples of which include; electron diffraction and new cargo scanning processes. The Compact Linear Accelerator for Research and Applications (CLARA) will be a novel FEL test facility, focused on the generation of ultra-short photon pulses with extreme levels of stability and synchronization. The principal aim is to experimentally demonstrate that sub-cooperation length pulse generation with FELs is viable, and to compare the various schemes being championed. The results will translate directly to existing and future X-ray FELs, enabling attosecond pulse generation. Both the VELA and CLARA facilities are co-located at Daresbury Laboratory and provide the UK with a unique platform for scientific and commercial R&D using ultra-short pulse, high precision electron and photon beams.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TH3A03  
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THOP04 Measurements of the Beam Break-Up Threshold Current at the Recirculating Electron Accelerator S-DALINAC linac, recirculation, HOM, optics 751
 
  • T. Kürzeder, M. Arnold, L.E. Jürgensen, J. Pforr, N. Pietralla
    TU Darmstadt, Darmstadt, Germany
  • F. Hug
    IKP, Mainz, Germany
  
  Funding: *Supported by the German Federal Ministry for Education and Research (BMBF) under Grant No. 05K13RDA.
Linear accelerators, in particular those with a recirculating design and superconducting cavities, have to deal with the problem of Beam Break-Up (BBU). This instability can limit the maximum beam current in such accelerators. Knowing the effectiveness of prevention strategies is of great interest especially for future accelerators like energy recovery linacs (ERL) which aim for high beam currents. One option is to optimize the cavities and higher order mode couplers of those machines. In addition one may adapt the beam line lattice for further suppressing BBU. The superconducting recirculating accelerator S-DALINAC at the Technische Universität Darmstadt provides electron beams in c.w. for nuclear physics experiments since 1991. As the SRF components were never optimized for higher order mode suppression the S-DALINAC suffers from BBU at relatively low beam currents of a few μA. While those currents are sufficient for most nuclear physics experiments we can investigate BBU with respect to the beam optics. We will report on first measurements of threshold currents at different beam energies of the S-DALINAC. The results of a first test to increase the BBU limit by using skew quadrupoles will be presented. 		 
slides icon Slides THOP04 [1.473 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP04  
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THOP10 Design and Commissioning of FRIB Multipacting-Free Fundamental Power Coupler cavity, cryomodule, controls, impedance 767
 
  • Z. Zheng, J.T. Popielarski, K. Saito, S. Stark, T. Xu, Y. Yamazaki
    FRIB, East Lansing, USA
  
  Funding: *Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
The original Fundamental Power Coupler (FPC) of Half-Wave Resonator (HWR) for the Facility of Rare Isotope Beams (FRIB) requires multipacting conditioning at operating RF power which is up to 5 kW Continue Wave (CW). Conditioning takes a lot of time and RF power, and its elimination is highly desirable. To significantly shorten the RF conditioning, we developed a multipacting-free coupler design. This paper reports the latest progress in the optimization and prototype tests of multipacting-free coupler. The choke structure is removed and coupler geometry is further modified to protect the coupler RF window from the electron bombardment. The comparison result of multipacting-free coupler with original coupler was performed on automatic conditioning system, which showed significantly time reducing for RF conditioning. 		 
slides icon Slides THOP10 [2.442 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP10  
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THOP11 Ultra-Short Bunch Electron Injector for Awake plasma, gun, wakefield, acceleration 770
 
  • S. Döbert
    CERN, Geneva, Switzerland
  
  The proton driven plasma wake field acceleration experiment AWAKE at CERN will start at the end of this year. In 2017 an S-band electron injector producing bunches of a few ps length will be added to probe the wake fields stimulated by a driving proton beam. In the future this electron injector will have to be upgraded to obtain electron bunches with a length of 100 - 200 fs in order to demonstrate injection into a single bucket of the plasma wave and therefore sustainable acceleration with low energy spread. Target bunch parameters for the study are a bunch charge of 100 pC, 100 fs bunch length, an emittance smaller than 2 mm mrad and a beam energy of 100 MeV. The status of a study to achieve these parameters using X-band accelerator hardware and velocity bunching will be presented.  
slides icon Slides THOP11 [2.733 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP11  
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THOP12 Electron Linac Upgrade for Thomx Project gun, linac, emittance, laser 773
 
  • L. Garolfi, C. Bruni, M. El Khaldi
    LAL, Orsay, France
  • N. Faure, A. Perez Delaume
    PMB-ALCEN, PEYNIER, France
  
  The injector Linac for Thomx * consists of an electron gun and S-band accelerating section. The RF gun is a 2.5 cells photo-injector able to provide electron bunches with 5 MeV energy. During the commissioning phase, a standard S-band accelerating section is able to achieve around 50 MeV corresponding to around 45 keV X-rays energy. Since the maximum targeted X-ray energy is 90 keV, the Linac design will provide a beam energy of 70 MeV. The Linac upgrade of the machine covers many different aspects. The purpose is to increase the compactness of the accelerator complex whereas the beam properties for ring injection are kept. A LAL Orsay-PMB ALCEN collaboration has been established. The program foresees the RF design, prototyping and power tests of a high-gradient compact S-band accelerating structure. To fulfill the technical specifications at the interaction point, the Linac must be carefully designed. Beam dynamics simulations have been performed for optimizing the emittance and the energy spread for the ring entrance. The best set of parameters together with the effect of the accelerating section to the beam dynamics at the end of the LINAC will be presented.
* A. Variola, et al, "The Thomx Project Status", Proceedings of IPAC2014, Dresden, Germany. 		 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP12  
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THPRC006 Development of 704.4 MHz Power Coupler Window for Myrrha Project simulation, linac, cavity, Windows 776
 
  • F. Geslin, P. Blache, M. Chabot, J. Lesrel
    IPN, Orsay, France
  • Ch.L. Lievin, S. Sierra
    TED, Velizy, France
  
  Myrrha is an accelerator driven system (ADS) hybrid research reactor designed for spent nuclear fuel burning. The linac controlling the reactor has to be highly reliable (low failure rate). In order to fulfill requirements of ADS projects like Myrrha, IPNO and Thales are involved in a power couplers research and development program. We develop a power coupler window, with MAX RF design, for 80 kW CW input power. During the study, we take account of fabrication and cost issues. We present in this paper the result of simulations needed to design this coupler window. The electromagnetic, thermal and thermo-mechanical simulations were performed with Ansys. The multipacting simulations were performed with Musicc3D, software developed by IPNO. The conditioning and test bench is also described as two prototypes have to be tested this autumn.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPRC006  
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THPRC007 Development of 352.2 Mhz Power Coupler Window for R&D Purposes cavity, klystron, simulation, vacuum 779
 
  • F. Geslin, M. Chabot, J. Lesrel, D. Reynet
    IPN, Orsay, France
  • Ch.L. Lievin, S. Sierra
    TED, Velizy, France
  
  IPNO and Thales are conducting power couplers research and development. This paper present a new window design that fulfills European Spallation Source (ESS) requirements (400 kW RF peak power). The results of electromagnetic, thermal, thermo-mechanical, multipacting simulations and the consequences of the new ceramic window of power coupler will be reported. The multipacting simulations were performed with Musicc3D, software developed by IPNO. The new design overcome ceramic's weakness in tension and allows stronger constraints in the power coupler window.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPRC007  
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THPRC030 Plasma Window as Charge Stripper Complement plasma, ion, vacuum, interface 836
 
  • A. Lajoie
    NSCL, East Lansing, Michigan, USA
  • A. Hershcovitch, P. Thieberger
    BNL, Upton, Long Island, New York, USA
  • F. Marti
    FRIB, East Lansing, USA
  
  Funding: NSF Cooperative Agreement, Award No. PHY-1102511
Modern ion accelerators, particularly heavy ion accelerators, almost universally make use of charge stripping. A challenge facing facilities, as the demand for higher intensity beams rises, is a stripping media that's highly resistant to degradation, such as a recirculating He gas stripper. A method of keeping the He gas localized in a segment along the beamline by means of a Plasma Window (PW) positioned on both sides of the gas stripper has been proposed and the initial design set forth by Ady Hershcovitch. With a cascaded plasma arc being the interface between high pressure stripper and low pressure beamline, the goal is to minimize gas flowrate from the stripper to the beamline in order to maintain sufficient isolation of the He gas. We present the initial results from the test stand developed at Michigan State University and the planned experimental program that will follow. 		 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPRC030  
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THPLR007 Dark Current Studies in ILC Main Linac linac, focusing, radiation, operation 855
 
  • A.I. Sukhanov, I.L. Rakhno, N. Solyak, I.S. Tropin
    Fermilab, Batavia, Illinois, USA
  
  Studies and optimization of design of the International Linear Collider (ILC) based on the TESLA-type 9-cell 1.3 GHz superconducting RF (SRF) cavities are currently underway. Dark current electron generated by field emission (FE) in SRF cavities can be captured and accelerated in the main ILC linac up to very high energy before they are removed by focusing and steering magnets. Dark current electrons, interacting with the materials surrounding SRF cavities, produce electromagnetic showers and contribute to the radiation in the main ILC tunnel. In this paper present preliminary results of the simulation study of dark current in the ILC linac.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR007  
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THPLR009 A Compact Muon Accelerator for Tomography and Active Interrogation linac, target, cavity, simulation 861
 
  • R.W. Garnett, S.S. Kurennoy, L. Rybarcyk
    LANL, Los Alamos, New Mexico, USA
  • K. Hasegawa
    JAEA, Ibaraki-ken, Japan
  • S. Portillo, E. Schamiloglu
    University of New Mexico, Albuquerque, USA
  • N. Saito
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  
  Funding: This work is supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396.
Muons have been demonstrated to be great probes for imaging large and dense objects due to their excellent penetrating ability. At present there are no muon accelerators. Development of a compact system that can produce an intense beam of accelerated muons would provide unique imaging options for stockpile stewardship while delivering minimal radiation dose, as well as various homeland-security and industrial applications. Our novel compact accelerator approach allows a single linac to be used to first accelerate an electron beam to 800 MeV to generate muons by interacting with a production target in a high-field solenoid magnet and then to collect and accelerate these low-energy muons to 1 GeV to be used for imaging or active interrogation. The key enabling technology is a high-gradient accelerator with large energy and angular acceptances. Our proposed solution for efficient acceleration of low-energy muons is a 0-mode linac coupled with conventional electron RF accelerating structures to provide a compact system that could deliver a controllable high-flux beam of muons with well-defined energy to allow precise radiographic inspections of complicated objects. The details of the conceptual design will be discussed. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR009  
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THPLR012 Beam-Loading Compensation of a Multi-Bunch Electron Beam by Using RF Amplitude Modulation in Laser Undulator Compact X-Ray Source (LUCX) gun, laser, beam-loading, cavity 867
 
  • M.K. Fukuda, S. Araki, Y. Honda, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  • K. Sakaue
    Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
  • M. Washio
    Waseda University, Tokyo, Japan
  
  Funding: This work was supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
We have been developing a compact X-ray source via laser Compton scattering(LCS) at Laser Undulator Compact X-ray source(LUCX) accelerator in KEK. In here, a multi-bunch electron beam is generated by a 3.6cell photo-cathode RF-gun and accelerated to 18-24MeV by a 12cell booster. And then 6-10 keV X-rays are generated by LCS between the beam and a laser pulse stored in a 4-mirror planar optical cavity. Our aim is to take a phase contrast image with Talbot interferometer within a few minutes at present. The target flux of X-ray is 1.7x107 photons/pulse with 10% bandwidth. For an electron beam, the target of the intensity is 500nC/pulse with 1000 bunches at 30 MeV. Presently, we have achieved the generation of 24MeV beam with total charge of 600nC in 1000bunches. The energy difference is within 1.3% peak to peak. The beam-loading is compensated by delta T method and amplitude modulation(AM) of the RF pulse*. However there is the energy difference at the RF-gun. It is assumed that this causes the reduction of the X-ray flux due to change of the focused beam size. To reduce the energy difference, AM is also applied to the RF pulse for the gun. We will show the results of the beam-loading compensation and the generation of X-rays.
* Y. Yokoyama et al. , Proceedings IPAC2011, TUPC059 (2011). 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR012  
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THPLR013 LEETCHI: The High Current Electron Source for the CLIC Drive Beam Injector cathode, gun, high-voltage, simulation 870
 
  • K. Pepitone, S. Döbert
    CERN, Geneva, Switzerland
  • B. Cadilhon, B. Cassany, J. Gardelle
    CEA, LE BARP cedex, France
  
  LEETCHI is a source which will produce 140 keV, 5 A, 140 μs electron beams at a repetition rate of 50 Hz. The shot to shot and flat top current stability of this drive beam injector for CLIC has to be better than 0.1% and a geometrical emittance of 14 mm mrad is expected. The development of a high voltage modulator, to achieve those requirements, is ongoing. A small test stand has been built which allows to diagnose and dump the beam produced by the thermionic cathode. The thermionic cathode is equipped with a grid which will allow us to control the current and eventually to have a feedback on the flattop shape. The beam dump, made of graphite, has been designed using two different codes, the Monte Carlo code GEANT4 to simulate the energy deposition and ANSYS used to simulate the thermal resistance of the graphite due to the long pulse duration. The geometry has been optimized with the ray tracing code EGUN and the 2D PIC-code MAGIC. All these simulations allowed us to optimize the geometry of the gun and to develop diagnostics which must survive to the heat deposition. Finally, the first electrical measurements of the beam will be presented.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR013  
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THPLR014 Laser-Driven Dielectric Nano-Beam Accelerator for Radiation Biology Researches acceleration, laser, simulation, ion 873
 
  • K. Koyama, M. Yoshida
    KEK, Ibaraki, Japan
  • Z. Chen, H. Okamoto
    The University of Tokyo, Tokyo, Japan
  • M. Uesaka
    The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan
  
  Funding: This work was partly supported by JSPS KAKENHI (B)(Grant-in-Aid for Scientific Research) Grant Number 15H03595.
Since a laser-driven dielectric accelerator (LDA) is most likely to deliver a nano-beam with a small scale device, a combination of the LDA and a biological cell observation device such as a fluorescence microscope seems to be a powerful tool for radiation biology researches. The LDA consists of single or a pair of binary-blazed transmission grating. In case of normal incidence, a grating constant must be the same with a laser wavelength to synchronize with the electron and an acceleration field. Although demonstration experiments have been published from SLAC and MPQ, there are many problems to be solved, especially in the non-relativistic energy region. A crucial problem is to make it clear whether electrons are accelerated with negligibly small wiggling or lateral shift. We are simulating at various conditions with the aid of CST-code. We also analyze an oblique incidence (OI) scheme for the efficient acceleration of slow electron. The OI-scheme enables to use the grating of larger grating constant. Adoption of the large grating constant makes it easy to fabricate the grating. Besides analytical works, we are making gratings and developing an Yb-doped fiber laser for the acceleration experiment. Gratings of two different materials, a glass silica and crystal silica, were fabricated by the e-beam lithography technique. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR014  
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THPLR021 Identification of Emitting Sources of Dark Currents From Gridded Thermionic Electron Gun and Measures to Suppress Dark Currents From Electron Gun in SPring-8 Linear Accelerator cathode, gun, acceleration, synchrotron 888
 
  • T. Magome, H. Hanaki, T. Kobayashi, S. Suzuki, T. Taniuchi
    JASRI/SPring-8, Hyogo-ken, Japan
  
  The dark current is emitted from a gridded thermionic electron gun although the grid-electrode potential against the cathode is negative enough to suppress the cathode emission current. This dark current in the SPring-8 linear accelerator caused satellite bunches unignorable for precise experiments in the downstream electron storage ring. The dark current has been investigated by means of our electron-gun test equipment applying a DC accelerator voltage to the electron gun. The investigations revealed that the dark current was generated from the wehnelt electrode, the gird electrode, and the cathode surface. The dark current from the wehnelt electrode was decreased under the measurement limit 2·10-15 A by replacing the wehnelt and the anode electrodes with new electro-polished ones. The dark current from the cathode surface was reduced by lowering the grid-electrode potential against the cathode down to -160 V. To reduce the dark current from the grid electrode, the surface of the grid electrode was significantly smoothed by electro-polishing.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR021  
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THPLR026 Radio Frequency Surface Plasma Source With Solenoidal Magnetic Field plasma, ion, solenoid, ion-source 902
 
  • V.G. Dudnikov, R.P. Johnson
    Muons, Inc, Illinois, USA
  • G. Dudnikova
    UMD, College Park, Maryland, USA
  • G. Dudnikova
    ICT SB RAS, Novosibirsk, Russia
  • B. Han, S. Murrey, C. Stinson
    ORNL RAD, Oak Ridge, Tennessee, USA
  • T.R. Pennisi, C. Piller, M. Santana, M.P. Stockli, R.F. Welton
    ORNL, Oak Ridge, Tennessee, USA
  
  Funding: The work was supported in part by US DOE Contract DE-AC05-00OR22725 and by STTR grant, DE-SC0011323.
Operation of Radio Frequency surfaces plasma sources (RF SPS) with a solenoidal magnetic field are described. RF SPS with solenoidal and saddle antennas are discussed. Dependencies of beam current and extraction current on RF power, gas flow, solenoidal magnetic field are presented. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR026  
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THPLR047 The Beam Energy Feedback System in Beijing Electron Positron Collider II Linear Accelerator injection, feedback, positron, controls 962
 
  • S.Z. Wang, Y.L. Chi, X. Huang
    IHEP, Beijing, People's Republic of China
  
  The beam energy feedback system in Beijing electron positron collider II (BEPCII) linear accelerator consists of three parts. They are the beam energy measurement In-put/Output Controller (BEM IOC), the Graphical User Interface (GUI) based on Qt platform and the phasing system. This article describes the implementation of this system and the online testing which has been passed on March 16th, 2016. By using this feedback system, the injection rate and the energy fluctuation of the injection beam has been improved a lot. Now this system is steady running in the control room of BEPCII linear accelerator.  
poster icon Poster THPLR047 [0.569 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR047  
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THPLR074 N-Doped Niobium Accelerating Cavities: Analyzing Model Applicability niobium, cavity, vacuum, embedded 1014
 
  • R.G. Eichhorn, N.A. Stilin
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • W. Weingarten
    CERN, Geneva, Switzerland
  
  So-called Nitrogen-doped cavities show a rather strange field dependent behavior of the surface resistance. We had come up with a rather straightforward two fluid model description of the Q-slope in the low and high field domains in an earlier publication based on one dataset of a cavity. In this contribution we report on successfully applying this model to other cavity performance data as well as cases were the model fails.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR074  
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FR1A02 Installation and On-Line Commissioning of EBIS at ATLAS ion, rfq, emittance, beam-transport 1022
 
  • P.N. Ostroumov, A. Barcikowski, J.A. Clark, C. Dickerson, M.R. Hendricks, Y. Luo, R.C. Pardo, C.E. Peters, M.A. Power, G. Savard, S.I. Sharamentov, R.C. Vondrasek, G.P. Zinkann
    ANL, Argonne, USA
  
  Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract DE-AC02-06CH11357.
An Electron Beam Ion Source Charge Breeder (EBIS-CB) has been developed at Argonne to breed radioactive beams from the CAlifornium Rare Ion Breeder Upgrade (CARIBU) facility at ATLAS. The CARIBU EBIS-CB has been successfully commissioned offline with an external singly-charged cesium ion source. The EBIS performance meets the breeding requirements to deliver CARIBU beams to ATLAS. EBIS can provide charge-to-mass ratios >=1/7 for all CARIBU beams with breeding times in the range of 6 ms to 30 ms. A record high breeding efficiency of up to 28% into a single charge state of Cs28+ has been demonstrated. Following the offline testing EBIS was moved to the front end of ATLAS where the alignment of EBIS was substantially improved and additional beam diagnostic tools both for electron and ion beams were installed. This paper will discuss EBIS improvements and present the results of on-line commissioning. 		 
slides icon Slides FR1A02 [7.717 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-FR1A02  
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FR1A04 Ion Effects in High Brightness Electron Linac Beams ion, linac, experiment, radiation 1032
 
  • S.J. Full, A.C. Bartnik, I.V. Bazarov, J. Dobbins, B.M. Dunham, G.H. Hoffstaetter, K. J. Smith
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Electron beams ionize rest gas particles which then accumulate around them, disturbing beam dynamics and causing background radiation. While this effect has been predicted in the past, linacs have hitherto not suffered from it because of their rather small beam current. The effect of ions increases with larger currents and smaller cross sections of the beam, and it has clearly been observed in Cornell's high-brightness ERL injector for the first time. This presentation will show experimental evidence for ions, demonstrate strategies for their elimination, and will compare the experimental data to theories of beam-ion interactions.  
slides icon Slides FR1A04 [5.995 MB]  
poster icon Poster FR1A04 [2.630 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-FR1A04  
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