Keyword: wakefield
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MOPWA018 Loss Factor and Impedance Analysis of Warm Components of BERLinPro factory, impedance, simulation, operation 128
 
  • H.-W. Glock, M. Abo-Bakr, J. Kolbe, F. Pflocksch, A. Schälicke
    HZB, Berlin, Germany
  • H.-W. Glock, C. Potratz
    COMPAEC e.G., Rostock, Germany
  
  Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association
The ongoing component design for the HZB 50 MeV, 100mA ERL project BERLinPro is accompanied by loss factor and impedance computations. A list of accelerator components including bellows, collimators, tapers, shutter valves etc. is given, some of them with alternative shapes. Loss factors, calculated using CSTParticleStudio®, are presented together with important properties of the impedance spectrum. Scaling of the loss factors with respect to bunch length is calculated on base of the numerical simulations and is used to extrapolate down to a bunch length (1 standard deviation) of 0.6 mm, which is hard to reach directly in numerical simulations. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA018  
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MOPWA030 Simulations of Electron Cloud Long Range Wakefields electron, simulation, dipole, proton 165
 
  • F.B. Petrov, O. Boine-Frankenheim
    TEMF, TU Darmstadt, Darmstadt, Germany
  
  Funding: Work supported by the BMBF under Contract No. 05H12RD7
A typical approach to electron cloud simulations is to split the problem in two steps: buildup simulations and instability simulations. In the latter step the cloud distribution is usually refreshed after each full interaction with the bunch. This approach does not consider multibunch effects. We present studies of the long range electron cloud wakefields generated in electron clouds after interaction with relativistic proton bunch trains. Several pipe geometries - relevant to CERN accelerators - with and without external magnetic field are considered. Using simple examples we show that the long range wakefields depend significantly on the secondary emission curve as well as on the pipe geometry. Additivity of electron cloud wakefields is studied as well. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA030  
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MOPWA031 A New Approach for Resistive Wakefield Calculations in Time Domain impedance, simulation, cavity, controls 168
 
  • A.V. Tsakanian, H. De Gersem, E. Gjonaj, T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
  • M. Dohlus, I. Zagorodnov
    DESY, Hamburg, Germany
  
  We report on a new numerical technique for the computation of the wakefields excited by ultra-short bunches in the structures with walls of finite conductivity. The developed 3D numerical method is fully time domain. It is based on special Staggered Finite Volume Time Domain (SFVTD) method and has no numerical dispersion in all three axial directions simultaneously. This results in large saving in computational time as well as improved accuracy. The resistive boundary model applies Surface Impedance Boundary Condition (SIBC) evaluation in time domain and covers boundary effects like frequency dependent conductivity, surface roughness and metal oxidation. A good agreement between numerical simulation and perturbation theory is obtained. In addition the new method allows implementation of moving mesh approach that considerably reduces requirements on computational resources. The developed method is especially effective for short range resistive wakefield calculations excited by ultra-short bunches used in FEL based LINACs.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA031  
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MOPWA053 Emittance Preservation in SuperKEKB Injector emittance, simulation, linac, injection 239
 
  • S. Kazama, Y. Ogawa, M. Satoh, H. Sugimoto, M. Yoshida
    KEK, Ibaraki, Japan
  
  Injector linac at KEK is now under the way to produce high current and low emittance beams for SuperKEKB. The target luminosity for SuperKEKB is 40 times higher than that of KEKB. Short-range transverse wakefield and dispersive effects at the linac cause an emittance growth, and longitudinal wakefield effect enlarges an energy spread of the beams. In this presentation, we will report simulation studies of the emittance preservation issues and how to suppress the increase of the energy spread of the beams.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA053  
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MOPJE001 Effect on Beam Dynamics From Wakefields in Travelling Wave Structure Excited by Bunch Train simulation, electron, dipole, radiation 289
 
  • D. Wang, C.-X. Tang
    TUB, Beijing, People's Republic of China
  • W. Gai, C.-J. Jing, J.G. Power
    ANL, Argonne, Illinois, USA
  • J.Q. Qiu
    Euclid TechLabs, LLC, Solon, Ohio, USA
  
  Electron bunch train technology is used to excited coherent high power RF radiation in travelling wave (TW) structures. This article concentrates on the analytical expression of wakefields excited by bunch train in TW structures and the effects of wakefields on beam dynamics. We focus on the first monopole mode and the first dipole mode wakefields. The long range wake function has a linear decrease which agrees well with the ABCi simulations. Taking example of the 11.7 GHz wakefields structure at the Argonne Wakefield Accelerator (AWA) facility, with 1.3 GHz interval drive electron bunch train, we have done the beam dynamics simulation with a point to point (P2P) code. Results shows the effects of wakefields on the energy distribution and the transverse instability for each sub-bunch.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE001  
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MOPJE019 Categorization and Estimation of Possible Deformation in Emittance Exchange based Current Profile Shaping cavity, emittance, acceleration, collective-effects 317
 
  • G. Ha, M.-H. Cho, W. Namkung
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • W. Gai, G. Ha, K.-J. Kim, J.G. Power
    ANL, Argonne, Illinois, USA
  
  Funding: This work is partly supported by POSTECH BK21+ program and Argonne National Laboratory
Shaping the current profile is one of the important issues in collinear wakefield acceleration. In the emittance exchange based shaping technique, the shaped current profile seriously depends on the incoming beam and beam line parameters. To design the beam and beam line properly, it is important to estimate the deformation in the shaped current profile. There are several different deformation types whose level depend on deformation parameter. We categorize the possible deformation types and observe the deformation patterns of the current profile depending on its type and the deformation parameter. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE019  
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MOPJE059 Tests of Wakefield-Free Steering at ATF2 emittance, cavity, extraction, alignment 438
 
  • A. Latina, J. Pfingstner, D. Schulte
    CERN, Geneva, Switzerland
  • E. Adli
    University of Oslo, Oslo, Norway
  • N. Fuster-Martínez
    IFIC, Valencia, Spain
  • J. Snuverink
    JAI, Egham, Surrey, United Kingdom
  
  Charge-dependent effects on the orbit and on the beam size affect the performance of the Accelerator Test Facility (ATF2) in a non-negligible way. Until now small beam sizes have only been achieved running with a beam charge significantly smaller than the nominal value. These detrimental effects on the beam have been attributed to wakefields, in the cavity BPMs, in the multi-Optical Transition Radiation (OTR) systems as well as in other components of the beamline. The successful tests of a Wakefield-free Steering (WFS) algorithm at FACET have encouraged performing tests of the same correction scheme at ATF2. The performance of the algorithm has been simulated in detail, including several realistic imperfection scenarios, including charge-dependent BPMs resolution, and incoming injection error and position jitters, which are described in this paper. Tests of WFS have been performed at ATF2 during December 2014. The results are discussed here.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE059  
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MOPJE083 Implications of Manufacturing Errors on Higher Order Modes and on Beam Dynamics in the ESS Linac HOM, cavity, coupling, linac 514
 
  • A. Farricker, R.M. Jones
    UMAN, Manchester, United Kingdom
  • S. Molloy
    ESS, Lund, Sweden
  
  The European Spallation Source (ESS) in Lund, Sweden, will be a facility for fundamental physics studies of atomic structure using a spallation source of unparalleled brightness. To achieve this end, protons will be accelerated up to 2 GeV using a suite of cavities. Here we focus on the Medium Beta (β =0.67) elliptical superconducting cavities and we assess the influence of potential errors in fabrication to shift eigenmode frequencies onto an harmonic of the bunch frequency. If this occurs, and countermeasures are not adopted, the beam quality will be appreciably diluted *. We provide details on the geometrical parameters which are particularly sensitive to frequency errors from intensive finite element simulations of the electromagnetic fields. A circuit model is also employed to rapidly assess the shift in the eigenmodes from their anticipated design values due a variety of potential errors.
* Aaron Farricker et al, Physics Procedia, Proceedings of HOMSC14 (in press), 2014. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE083  
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MOPMA001 Comparison of Measurements and Simulations for Single Bunch Instabilities at Diamond impedance, radiation, simulation, synchrotron 521
 
  • M. Atay, R. Bartolini
    JAI, Oxford, United Kingdom
  • R. Bartolini, R.T. Fielder, I.P.S. Martin
    DLS, Oxfordshire, United Kingdom
  
  The single bunch dynamics in the Diamond storage ring has been analysed with a multiparticle tracking code and compared with the results of a wealth of diagnostics, including streak camera, Schottky diodes and FTIR spectra. The interplay of various wakefield sources has been studied and it has been found that the THz spectrum can be reproduced in many cases with simple impedance models, both below and above the bursting threshold.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA001  
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MOPMA047 Nonlinear Beam Dynamics Studies of the Next Generation Strong Focusing Cyclotrons as Compact High Brightness, Low Emittance Drivers cavity, cyclotron, focusing, proton 656
 
  • S. Assadi, P.M. McIntyre, A. Sattarov
    Texas A&M University, College Station, Texas, USA
  • N. Pogue
    PSI, Villigen, Villigen, Switzerland
  
  Funding: Work is partially supported by grants from the State of Texas (ASE) & the Michelle foundation.
The Strong Focusing Cyclotron development at Texas A&M University has evolved from stacks of cyclotrons to a single layer high brightness, low emittance to produce greater than 10 mA of proton beam to a desired target at 800 MeV. The latest design has a major geometric design optimization of strong focusing quadrupoles and a modified algorithm of high gradient cavities to address the small turn separation, and interaction of radially neighboring bunches and reduced the number of turns necessary to reach the desired final energy under control conditions. In this paper, we present the new design, physics of nonlinear synchrobetratron coupling, mνh+nνv=p causing beam blow-up in other form of cyclotrons and how we have resolved it. The cavity beam loading and space charge effects of multi turns at low energies to reduce losses are discussed. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA047  
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MOPMA056 Measurement and Modeling of Single Bunch Wake Field Effects in CESR emittance, simulation, impedance, storage-ring 681
 
  • J.R. Calvey, M.G. Billing, W. Hartung, J.D. Perrin, D. L. Rubin, D. Sagan, S. Wang
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: Work supported by NSF PHY-1416318 and NSF DMR 1332208. This research used the National Energy Research Scientific Computing Center, which is supported by DOE Contract No. DE-AC02-05CH11231.
Short-range wake fields have been incorporated into a Bmad-based particle tracking code in order to assess their contribution to current-dependent emittance growth, tune shift, and single bunch instabilities. The wakes are computed for CESR vacuum components using the T3P modeling software. Simulation results are compared with measurements of bunch length, vertical beam size, and coherent tune shift. Additionally, we use insertable scrapers to vary the transverse wake and measure the effect on the beam. We show that a vertical emittance increase at high current may be due to a transverse monopole wake, originating in the lump pump slots throughout CESR. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA056  
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MOPMA059 Lorentz boosted frame simulation of Laser wakefield acceleration using hybrid Yee-fft solver in quasi-3d geometry simulation, plasma, laser, acceleration 691
 
  • P. Yu, A.W. Davidson, V.K. Decyk, W.B. Mori, A. Tableman, F.S. Tsung
    UCLA, Los Angeles, California, USA
  • F. Fiuza, L.O. Silva, J. Vieira
    IPFN, Lisbon, Portugal
  • R.A. Fonseca
    ISCTE - IUL, Lisboa, Portugal
  • W. Lu, X.L. Xu
    TUB, Beijing, People's Republic of China
  
  We present results from a preliminary study on modeling Laser wakefield acceleration (LWFA) with OSIRIS in a Lorentz boosted frame using a quasi-3D algorithm. In the quasi-3D algorithm, the fields and currents are expanded into azimuthal harmonics and only a limited number of harmonics are kept. Field equations in (r,z) space are solved for a desired number of harmonics in φ. To suppress the numerical Cerenkov instability (NCI) that inevitably arises due to the relativistic plasma drift in the simulation, we use a hybrid Yee-FFT solver in which the field equations are solved in (kz, r) space, where \hat{z} is the drifting direction. Preliminary results show that high fidelity LWFA boosted frame simulations can be carried out with no evidence of the NCI. Good agreement is found when comparing LWFA boosted frame simulations in the full 3D geometry against those in the quasi-3D geometry. In addition, we discuss how the moving window can be combined with the hybrid Yee-FFT solver to further speed up the simulation. The results indicate that unprecedented speed ups for LWFA simulations can be achieved when combining the Lorentz boosted frame technique, the quasi-3D algorithm, and a moving window.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA059  
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MOPMN004 CSR Impedance for Non-Ultrarelativistic Beams impedance, radiation, space-charge, synchrotron 709
 
  • R. Li
    JLab, Newport News, Virginia, USA
  • C.-Y. Tsai
    Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
  
  Funding: This work is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
For the analysis of the coherent synchrotron radiation (CSR) induced microbunching gain in the low energy regime, such as when a high-brightness electron beam is transported through a low-energy merger in an energy-recovery linac (ERL) design, it is necessary to extend the CSR impedance expression in the ultrarelativistic limit to the non-ultrarelativistic regime. This paper presents our analysis of CSR impedance for general beam energies. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMN004  
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MOPHA038 Studies for a Wakefield-Optimized Near-Field EO Setup at the ANKA Storage Ring laser, simulation, operation, electron 869
 
  • P. Schönfeldt, A. Borysenko, N. Hiller, B. Kehrer, A.-S. Müller
    KIT, Karlsruhe, Germany
  
  Funding: This work is funded by the BMBF contract numbers 05K10VKC, and 05K13VKA.
ANKA, the synchrotron light source of the Karlsruhe Institute of Technology (KIT), is the first storage ring with a near-field single-shot electro-optical (EO) bunch profile monitor inside its vacuum chamber. Using the method of electro-optical spectral decoding (EOSD), the current setup made it possible to study longitudinal beam dynamics (e.g. microbunching) occurring during ANKA's low-alpha-operation with sub-ps resolution (granularity). However, the setup induces strong wake-fields spanning the distance between consecutive bunches which cause heat load to the in-vacuum setup for high beam currents. This heat load in turn leads to a laser misalignment thus preventing measurements during multi-bunch operation. Fortunately, the EOSD setup also allows us to directly study these wake-fields so simulation results can be compared to measurement data. This paper reviews possible changes of the setup's geometry with respect to a reduction of the wakefield effects. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPHA038  
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MOPTY004 Wakefield Monitor Experiments with X-Band Accelerating Structures linac, pick-up, hardware, dipole 947
 
  • R.L. Lillestøl, E. Adli, J. Pfingstner
    University of Oslo, Oslo, Norway
  • R. Corsini, S. Döbert, W. Farabolini, L. Malina, W. Wuensch
    CERN, Geneva, Switzerland
  
  The accelerating structures for CLIC must be aligned with a precision of a few um with respect to the beam trajectory in order to mitigate emittance growth due to transverse wake fields. We report on first results from wake field monitor tests in an X-band structure, with a probe beam at the CLIC Test Facility. The monitors are currently installed in the CLIC Two-Beam Module. In order to fully demonstrate the feasibility of using wakefield monitors for CLIC, the precision of the monitors must be verified using a probe beam while simultaneously filling the structure with high power rf used to drive the accelerating mode. We outline plans to perform such a demonstration in the CLIC Test Facility.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPTY004  
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TUBD3 Effects of Accelerating Structures on On-line DFS in the Main Linac of CLIC emittance, linac, dipole, simulation 1387
 
  • J. Pfingstner, E. Adli
    University of Oslo, Oslo, Norway
  • D. Schulte
    CERN, Geneva, Switzerland
  
  Long-term ground motion will create significant dispersion in the time-scale of hours in the main linac of CLIC. To preserve the emittance to an acceptable level, a dispersion correction with on-line dispersion-free steering (DFS) is inevitable. For this on-line technique, the dispersion has to be measured using beam energy variations of only about one per mil in order to not disturb the operation of the accelerator. For such small energy variations, the interaction of the particle beam and the accelerating structures creates large enough additional signals components in the measured dispersion to cause the dispersion correction to not work properly anymore. In this paper, the additional signals are described and their effect on the DFS algorithm is analysed. Finally, methods for the mitigation of the deteriorating signal components are presented and studied via simulations.  
slides icon Slides TUBD3 [1.697 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUBD3  
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TUPJE016 COHERENT SYNCHROTRON RADIATION FIELD AND THE ENERGY LOSS IN A WAVY BEAM electron, radiation, synchrotron, synchrotron-radiation 1650
 
  • D.R. Xu, H. Xu
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  The synchrotron radiation will be coherent when the wavelength of the radiation can be compared with the bunch length. There are two approaches to produce Coherent Synchrotron Radiation (CSR) on a storage ring. One is to compress the bunch length, the other one is to produce a wavy beam which has high spatial repetition along the longitudinal direction. The latter one can expand the radiation frequency range of a light source. However, CSR can bring nonlinear effect which brings in extra instability. The Lienard-Wiechert potentials in three-dimensional space may have very complicated forms. The most common way to investigate CSR is numerical method. This paper try to use a simple model to obtain energy loss of the electrons in theory.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPJE016  
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TUPJE077 Instability Thresholds for the Advanced Photon Source Multi- Bend Achromat Upgrade impedance, simulation, injection, collective-effects 1822
 
  • R.R. Lindberg
    ANL, Argonne, Illinois, USA
  • A. Blednykh
    BNL, Upton, Long Island, New York, 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 important operating mode for the multi-bend achromat (MBA) upgrade at the Advanced Photon Source (APS) calls for 200 mA average current divided evenly over 48 bunches. Ensuring that the desired 4.2 mA single bunch current can be stably stored requires a detailed understanding of the impedance in the MBA ring. We briefly discuss modeling sources of impedance using the electromagnetic codes GdfidL and ECHO, and how we then include both geometric and resistive wall wakefields using the tracking code elegant to predict collective instabilities. We first validate our procedures by comparing APS experimental measurements to tracking predictions using the APS storage ring impedance model. We then discuss the MBA impedance model, for which we find that a chromaticity of 5 units is sufficient to obtain the required 4.2 mA single bunch current. Finally, we mention certain design changes that may reduce the impedance and allow for a reduction in chromaticity. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPJE077  
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TUPJE078 Modeling of Impedance Effects for the APS-MBA Upgrade impedance, vacuum, photon, simulation 1825
 
  • R.R. Lindberg
    ANL, Argonne, Illinois, USA
  • A. Blednykh
    BNL, Upton, Long Island, New York, 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.
Understanding the sources of impedance is critical to accelerator design, and only becomes more important as vacuum chambers become smaller and closer to the electron beam. The multibend achromat upgrade at the Advanced Photon Source (APS) requires small, 22-mm diameter vacuum chambers and even smaller (6 mm) gaps for the insertion devices, so that both rf heating and wakefield-driven transverse instabilities become important concerns. We discuss modeling the primary sources of geometric impedance using the electromagnetic finite difference codes GdfidL and ECHO, and how these codes are influencing vacuum and accelerator component design. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPJE078  
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TUPMA042 THz Radiation Generation in a Multimode Wakefield Structure radiation, experiment, electron, linac 1929
 
  • S.P. Antipov, S.V. Baryshev, C.-J. Jing, A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • M.G. Fedurin
    BNL, Upton, Long Island, New York, USA
  • W. Gai, D. Wang, A. Zholents
    ANL, Argonne, Illinois, USA
  
  Funding: Work supported by the Department of Energy SBIR program under Contract #DE-SC0009571
A number of methods for producing sub-picosecond beam microbunching have been developed in recent years. A train of these bunches is capable of generating THz radiation via multiple mechanisms like transition, Cherenkov and undulator radiation. We utilize a bunch train with tunable spacing to selectively excite high order TM0n - like modes in a multimode structure. In this paper we present experimental results obtained at the Accelerator Test Facility of Brookhaven National Laboratory. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA042  
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TUPMA043 Experimental Test of Semiconductor Dechirper electron, FEL, experiment, emittance 1932
 
  • S.P. Antipov, S.V. Baryshev, C.-J. Jing, A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • S. Baturin
    LETI, Saint-Petersburg, Russia
  • M.G. Fedurin, K. Kusche, C. Swinson
    BNL, Upton, Long Island, New York, USA
  • W. Gai, S. Stoupin, A. Zholents
    ANL, Argonne, Illinois, USA
  
  Funding: Work supported by the Department of Energy SBIR program under Contract #DE-SC0006299
We report the observation of de-chirping of a linearly chirped (in energy) electron bunch by its passage through a 4 inch long rectangular waveguide loaded with two silicon bars 0.25 inch thick and 0.5 inch wide. Silicon being a semiconductor has a conductivity that allows it to drain the charge fast in case if some electrons get intercepted by the dechirper. At the same time the conductivity is low enough for the skin depth to be large (on the order of 1 cm) making the silicon loaded waveguide a slow wave structure supporting wakefields that dechirp the beam. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA043  
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TUPTY054 RF Design of the CLIC Structure Prototype Optimized for Manufacturing from Two Halves linac, multipole, simulation, collider 2147
 
  • H. Zha, A. Grudiev
    CERN, Geneva, Switzerland
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
  
  We present the RF design of a 12GHz Compact Linear Collider (CLIC) main linac accelerating structure prototype. The structure is made from two longitudinally symmetric halves. The main manufacturing process of each half is precision milling. The structure uses the same iris dimensions as the CLIC-G structure but the cell shape is optimized for milling. The geometry is optimized to reduce the surface electric and magnetic fields and the modified Poynting vector. This design can potentially reduce fabrication cost.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY054  
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TUPTY055 Optimization of the RF Design of the CLIC Main Linac Accelerating Structure linac, simulation, collider, cavity 2150
 
  • H. Zha, A. Grudiev
    CERN, Geneva, Switzerland
  
  We present a new optimized design of the accelerating structure for the main linac of CLIC (Compact Linear Collider). The new structure has lower surface magnetic fields and a significantly smaller transverse size compared to the baseline design described in the CLIC Concept Design Report (CDR). This new design should reach higher accelerating gradients and have a reduced manufacturing cost. The details of the RF design procedure and the obtained results are presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY055  
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TUPTY056 Beam-Based Measurements of Long Range Transverse Wakefields in CLIC Main Linac Accelerating Structure positron, electron, linac, experiment 2153
 
  • H. Zha, A. Grudiev, A. Latina, D. Schulte, A. Solodko, W. Wuensch
    CERN, Geneva, Switzerland
  • E. Adli
    University of Oslo, Oslo, Norway
  • G. De Michele
    EPFL, Lausanne, Switzerland
  • G. De Michele
    PSI, Villigen PSI, Switzerland
  • N. Lipkowitz, G. Yocky
    SLAC, Menlo Park, California, USA
  
  The baseline design of CLIC (Compact Linear Collider) uses X-band accelerating structures in the main linac. Every accelerating structure cell has four waveguides, terminated with individual RF loads, to damp the unwanted long-range transverse wakefields, in order to maintain beam stability in multi-bunch operation. In order to experimentally verify the calculated suppression of the wakefields, a prototype structure has been built and installed in FACET test facility at SLAC. The results of the measurements of the wakefields in the prototype structure by means of positron and electron bunches are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY056  
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WEAD1 Commissioning and Recent Experimental Results at the Argonne Wakefield Accelerator Facility (AWA) experiment, electron, acceleration, laser 2472
 
  • M.E. Conde, D.S. Doran, W. Gai, G. Ha, W. Liu, J.G. Power, J.H. Shao, D. Wang, C. Whiteford, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  • S.P. Antipov, C.-J. Jing, J.Q. Qiu
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • G. Ha
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • J.H. Shao, D. Wang
    TUB, Beijing, People's Republic of China
  
  Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-06CH11357.
The commissioning of the upgraded AWA facility has been recently completed. The L-band electron gun has been fully commissioned and has been successfully operated with its Cesium Telluride photocathode at a gradient of 80 MV/m. Single bunches of up to 100 nC, and bunch trains of up to 32 bunches have been generated. The six new pi-mode accelerating cavities bring the beam energy to 75 MeV. Initial measurements of the beam parameters have been performed. This intense beam has been used to drive high gradient wakefields in several structures. A second beamline provides electron bunches to probe the wakefields generated by the intense drive beam. One of the main goals of the facility is to generate short RF pulses with GW power levels, corresponding to accelerating gradients of hundreds of MV/m and energy gains on the order of 100 MeV per structure. 		 
slides icon Slides WEAD1 [2.091 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEAD1  
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WEPWA003 Simulations of Electron-Proton Beam Interaction before Plasma in the AWAKE Experiment proton, plasma, electron, quadrupole 2492
 
  • U. Dorda, R.W. Aßmann, J. Grebenyuk
    DESY, Hamburg, Germany
  • C. Bracco, A.V. Petrenko, J.S. Schmidt
    CERN, Geneva, Switzerland
  
  The on-axis injection of electron bunches in the proton-driven plasma wake at the AWAKE experiment at CERN implies co-propagation of a low-energy electron beam with the long high-energy proton beam in a common beam pipe over several meters upstream of the plasma chamber. The possible effects of the proton-induced wakefields on the electron bunch phase space in the common beam pipe region may have crucial implications for subsequent electron trapping and acceleration in plasma. We present the CST Studio simulations of the tentative common beam pipe setup and the two beam co-propagating in it. Simulated effects of the proton wakefields on electrons are analysed and compared to analytical predictions.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA003  
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WEPWA005 Simulations Study for Self-Modulation Experiment at PITZ plasma, electron, simulation, experiment 2496
 
  • G. Pathak, F.J. Grüner
    Uni HH, Hamburg, Germany
  • C. Benedetti, C.B. Schroeder
    LBNL, Berkeley, California, USA
  • M. Groß, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • A. Martinez de la Ossa, T.J. Mehrling, J. Osterhoff
    DESY, Hamburg, Germany
  
  Self-modulation (SM) of proton beams in plasma has recently gained interest in context with the ongoing PWFA experiment of the AWAKE collaboration at CERN. Instrumental for that experiment is the SM of a proton beam to generate bunchlets for resonant wave excitation and efficient acceleration. A fundamental understanding of the underlying physics is vital, and hence an independent experiment has been set up at the beamline of the Photo Injector Test Facility at DESY, Zeuthen Site (PITZ), to study the SM of electron beams in a plasma. This contribution presents simulation results on SM experiments at PITZ using the particle-in-cell code HiPACE. The simulation study is crucial to optimize the beam and plasma parameters for the experiment. Of particular interest is the energy modulation imprinted onto the beam by means of the generated wakefields in the plasma. With the support of simulations the observation of this information in the experiment can be used to deduce key properties of the accelerating electric fields such as their magnitude and their phase velocity, both of significant importance for the design of self-modulated plasma-based acceleration experiments.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA005  
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WEPWA006 Laser Propagation Effects During Photoionization of Meter Scale Rubidium Vapor Source laser, plasma, experiment, proton 2499
 
  • J.T. Moody, F. Batsch, A. Joulaei, P. Muggli, E. Öz
    MPI-P, München, Germany
  • N. Berti, J. Kasparian
    University of Geneva, GAP Biophotonics, Carouge, Switzerland
  
  The baseline AWAKE experiment requires a 10 meter long plasma source with a density of 1015 cm􀀀-3 and a density uniformity of 0.2%. To produce this plasma, a temperature stabilized rubidium vapor source is photoionized by a terawatt peak power laser pulse. In this paper we describe the laser pulse evolution within the plasma source including the dispersive, diffractive, and photoionization effects on the laser pulse. These calculations will be experimentally investigated in a meter long heat pipe oven using scaled laser parameters.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA006  
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WEPWA007 The AWAKE Proton-driven Plasma Wakefield Experiment at CERN plasma, electron, injection, experiment 2502
 
  • P. Muggli
    MPI-P, München, Germany
  
  Funding: For the AWAKE collaboration
The AWAKE experiment at CERN * aims at studying plasma wakefield generation and acceleration driven by proton bunches. The first experiments will focus on the self-modulation instability of the long (~12cm, rms) proton bunch in the plasma. This instability is used to transform the incoming bunch into a train of short bunches with a period approximately equal to the plasma wavelength, ~1.2mm at a nominal plasma electron density of 7·1014/cc. These experiments are planned for the end of 2016. Later, low energy (~15MeV) electrons will be externally injected to sample the wakefields and be accelerated beyond 1GeV. The main goals of the experiment will be summarized and the progress with the plasma source, beam diagnostics and injection method will be presented.
* AWAKE Collaboration, Plasma Phys. Control. Fusion 56 084013 (2014) 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA007  
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WEPWA034 High-charge-short-bunch Operation Possibility at Argonne Wakefield Accelerator Facility emittance, linac, dipole, simulation 2572
 
  • G. Ha, M.-H. Cho, W. Namkung
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • W. Gai, G. Ha, K.-J. Kim, J.G. Power
    ANL, Argonne, Illinois, USA
  
  Originally the drive beam line at Argonne Wakefield Accelerator (AWA) Facility was designed to generate the high charge bunch train. However, we recently installed the double dog-leg type emittance exchange beam line which have two identical dog-leg structures. With this beam line, it is possible to compress the bunch by introducing the chicane or using single dog-leg. Simulation studies have been carried out to confirm the minimum bunch length for each charge and the emittance growth by the coherent synchrotron radiation. We present GPT simulation results to show high-charge-short-bunch operation possibility at AWA facility.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA034  
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WEPWA038 Mode Transformation in Waveguide with Transversal Boundary Between Vacuum and Partially Dielectric Area vacuum, radiation, acceleration, electron 2581
 
  • A.A. Grigoreva, T.Yu. Alekhina, S.N. Galyamin, A.V. Tyukhtin
    Saint-Petersburg State University, Saint-Petersburg, Russia
  
  We consider the mode transformation in a circular waveguide with a transversal boundary between a vacuum part and a part with a cylindrical dielectric layer and a vacuum channel. It is assumed that an incident mode can be both propagating and evanescent. Analysis is carried out with the using the mode decomposition technique. Numerical algorithm for calculating the mode transformation at an arbitrary channel radius is also developed. Typical dependences for the reflection and transmission coefficients on the channel radius are presented and discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA038  
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WEPWA039 The AWAKE Electron Primary Beam Line electron, proton, plasma, dipole 2584
 
  • J.S. Schmidt, J. Bauche, B. Biskup, C. Bracco, E. Bravin, S. Döbert, M.A. Fraser, B. Goddard, E. Gschwendtner, L.K. Jensen, O.R. Jones, S. Mazzoni, M. Meddahi, A.V. Petrenko, F.M. Velotti, A.S. Vorozhtsov
    CERN, Geneva, Switzerland
  • U. Dorda
    DESY, Hamburg, Germany
  • L. Merminga, V.A. Verzilov
    TRIUMF, Vancouver, Canada
  • P. Muggli
    MPI, Muenchen, Germany
  
  The AWAKE project at CERN is planned to study proton driven plasma wakefield acceleration. The proton beam from the SPS will be used in order to drive wakefields in a 10 m long Rb plasma cell. In the first phase of this experiment, scheduled in 2016, the self-modulation of the proton beam in the plasma will be studied in detail, while in the second phase an external electron beam will be injected into the plasma wakefield to probe the acceleration process. The installation of AWAKE in the former CNGS experimental area and the required optics flexibility define the tight boundary conditions to be fulfilled by the electron beam line design. The transport of low energy (10-20 MeV) bunches of 1.25·109 electrons and the synchronous copropagation with much higher intensity proton bunches (3E11) determines several technological and operational challenges for the magnets and the beam diagnostics. The current status of the electron line layout and the associated equipments are presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA039  
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WEPWA047 Emittance Growth in a Plasma Wakefield Accelerator plasma, emittance, electron, scattering 2609
 
  • Ö. Mete, K. Hanahoe, G.X. Xia
    UMAN, Manchester, United Kingdom
  • M. Labiche
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  
  The interaction of the witness beam with the surrounding plasma particles and wakefields was studied. The implications of the elastic scattering process on beam emittance and, emittance evolution under the focusing and acceleration provided by plasma wakefields were discussed. Simulations results from GEANT4 are presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA047  
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WEPWA048 Design Studies and Commissioning Plans for PARS Experimental Program plasma, acceleration, electron, beam-loading 2612
 
  • Ö. Mete, K. Hanahoe, J. Wright, G.X. Xia
    UMAN, Manchester, United Kingdom
  • M. Dover, M. Wigram, J. Zhang
    University of Manchester, Manchester, United Kingdom
  • J.D.A. Smith
    Tech-X, Boulder, Colorado, USA
  
  Funding: Science and Technology Facilities Council and Cockcroft Institute Core Grant
PARS (Plasma Acceleration Research Station) is an electron beam driven plasma wakefield acceleration test stand proposed for VELA/CLARA facility in Daresbury Laboratory. In order to optimise various operational configurations, 2D numerical studies were performed by using VSIM for a range of parameters such as bunch length, radius, plasma density and positioning of the bunches with respect to each other for the two-beam acceleration scheme. In this paper, some of these numerical studies and considered measurement methods are presented. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA048  
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WEPWA060 Interaction of a Volumetric Metamaterial Structure with an Electron Beam electron, radiation, acceleration, coupling 2640
 
  • X.Y. Lu, M.A. Shapiro, R.J. Temkin
    MIT/PSFC, Cambridge, Massachusetts, USA
  
  Funding: The U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0010075 and the Air Force Office of Scientific Research under MURI Grant Number FA550-12-1-0489.
A volumetric metallic metamaterial structure with a cubic unit cell is introduced. The unit cells can naturally fill all of space without additional substrates or waveguides. The structure can support a negative longitudinal electric mode that can couple to an electron beam. The dispersion characteristics of the unit cell are modeled by the effective medium theory with spatial dispersion. The theory also predicts the correct resonant frequencies of the emitted radiation excited by an electron beam traversing the structure. In the wakefield simulations, a backward radiation pattern is observed. The proposed metamaterial can be applied to beam diagnostics and wakefield acceleration. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA060  
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WEPWA061 High-Gradient Testing of Metallic Photonic Band-gap (PBG) and Disc-Loaded Waveguide (DLWG) Structures at 17 GHz operation, flattop, coupling, diagnostics 2643
 
  • B.J. Munroe, M.A. Shapiro, R.J. Temkin, J.X. Zhang
    MIT/PSFC, Cambridge, Massachusetts, USA
  
  Funding: This work supported by the DOE, Office of High Energy Physics, Grant No. DE-SC0010075
Photonic Band-gap (PBG) structures continue to be a promising area of research for future accelerator structures. Previous experiments at 11 GHz have demonstrated that PBG structures can operate at high gradient and low breakdown probability, provided that pulsed heating is controlled. A metallic single-cell standing-wave PBG structure has been tested at 17 GHz at MIT to investigate how breakdown probability scales with frequency in these structures. A single-cell standing-wave disc-loaded waveguide (DLWG) was also tested at MIT as a reference structure. The PBG structure achieved greater than 90 MV/m gradient at 100 ns pulse length and a breakdown probability of 1.1 *10-1 /pulse/m. The DLWG structure achieved 90 MV/m gradient at 100 ns pulse length and a breakdown probability of 1.2 *10-1 /pulse/m, the same as the PBG structure within experimental error. These tests were conducted at the MIT structure test stand, and represent the first long-pulse breakdown testing of accelerator structures above X-Band. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA061  
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WEPWA071 A Compact X-Ray Source Based on a Low-Energy Beam-Driven Wakefield Accelerator electron, acceleration, laser, bunching 2667
 
  • F. Lemery, D. Mihalcea, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • K. Chouffani
    IAC, Pocatello, Idaho, USA
  • P. Piot
    Fermilab, Batavia, Illinois, USA
  
  Accelerator-based X-ray sources have led to many scientific breakthroughs. Yet, their limited availability in large national laboratory settings due to the required infrastructure is a major limitation to their disseminations to a larger user community. In this contribution we explore the use of a low-energy electron beam produced out of a photoinjector coupled to a dielectric structure to produce a higher energy (~10-20 MeV) beam via a beam-driven acceleration scheme. The accelerated beam can then be used to produce X-ray via inverse Compton scattering. This paper discusses the concept and presents start-to-end simulations of the proposed setup.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA071  
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WEPWA072 Feasibility of Continuously Focused TeV/m Channeling Acceleration with CNT-Channel acceleration, plasma, electron, simulation 2670
 
  • Y.-M. Shin
    Northern Illinois University, DeKalb, Illinois, USA
  • A.H. Lumpkin, V.D. Shiltsev, R.M. Thurman-Keup
    Fermilab, Batavia, Illinois, USA
  
  Funding: This work was supported by the DOE contract No. DEAC02-07CH11359 to the Fermi Research Alliance LLC.
Atomic channels in crystals are known to consist of 10 – 100 V/Å potential barriers capable of guiding and collimating a high energy beam and continuously focused acceleration with exceptionally high gradients (TeV/m)*,**,***. However, channels in natural crystals are only angstrom-size and physically vulnerable to high energy interactions. Carbon-based nano-crystals such as carbon-nanotubes (CNTs) and graphenes have a large degree of dimensional flexibility and thermo-mechanical strength, which could be suitable for channeling acceleration of MW beams. Nano-channels of the synthetic crystals can accept a few orders of magnitude larger phase-space volume of channeled particles with much higher thermal tolerance than natural crystals****. Our particle-in-cell simulations with 100 um long effective CNT model indicated that a beam-driven self-acceleration produces 1 – 2 % net energy gain in the quasi-linear regime (off-resonance beam-plasma coupling, np = 1000 nb) with ASTA 50 MeV injector beam parameters. This paper presents current status of CNT-channeling acceleration experiment planned at the Advanced Superconducting Test Accelerator (ASTA) in Fermilab.
* T. Tajima, PRL 59, 1440 (1987)
** P. Chen and R. Noble, slac-pub-4187
*** Y. M. Shin, APL 105, 114106 (2014)
**** Y.M. Shin, D. A. Still, and V. Shiltsev, Phys. Plasmas 20, 123106 (2013) 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA072  
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WEPJE001 Optimal Positron-Beam Excited Plasma Wakefields in Hollow and Ion-Wake Channels plasma, electron, positron, ion 2674
 
  • A. A. Sahai, T.C. Katsouleas
    Duke ECE, Durham, North Carolina, USA
  
  Funding: DE-SC-0010012, NSF-PHY-0936278
A positron-beam interacting with the plasma electrons drives radial suck-in, in contrast to an electron-beam driven blow-out in the over-dense regime, nb>n0. In a homogeneous plasma, the electrons are radially sucked-in from all the different radii. The electrons collapsing from different radii do not simultaneously compress on-axis driving weak fields. A hollow-channel allows electrons from its channel-radius to collapse simultaneously exciting coherent fields *. We analyze the optimal channel radius. Additionally, the low ion density in the hollow allows a larger region with focusing phase. We have shown the formation of an ion-wake channel behind a blow-out electron bubble-wake. Here we explore positron acceleration in the over-dense regime comparing an optimal hollow-plasma channel to the ion-wake channel **. The condition for optimal hollow-channel radius is also compared. We also address the effects of a non-ideal ion-wake channel on positron-beam excited fields.
* S Lee, T Katsouleas, Phys. Rev. E, vol 64, 045501(R) (2001)
** A A Sahai, T Katsouleas, Non-linear ion-wake excitation by ultra relativistic electron wakefields, in review (http://arxiv.org/pdf/1504.03735v1.pdf) 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPJE001  
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WEPJE006 Dielectric Wakefield Accelerator Experiments at ATF experiment, electron, dipole, controls 2681
 
  • D.Y. Shchegolkov, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
  • S.P. Antipov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • M.G. Fedurin
    BNL, Upton, Long Island, New York, USA
  
  Funding: This work is supported by the U.S. Department of Energy through the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory.
Dielectric wakefield acceleration (DWA) presents us with means to achieve the accelerating gradient high above the limits of conventional accelerators. In a typical DWA scheme a higher energy lower charge main bunch is accelerated in the wakefield produced by a preceding lower energy higher charge drive bunch inside of a hollow metal-encapsulated dielectric tube. To make use of as much energy of the drive bunch as possible, it is highly important that all parts of it decelerate uniformly. Close to uniform drive bunch deceleration can be achieved if its current is properly shaped.* At Accelerator Test Facility (ATF) at BNL we shaped the current of a chirped electron beam with an adjustable mask placed inside of the highly dispersive region in the magnetic dogleg. We passed the shaped beam current through a quartz tube and observed the beam particles’ energy modulation at the tube’s output with a spectrometer. By tuning the mask we were able to control the beam energy modulation and thus the wakefield profile in the tube.
* B. Jiang, C. Jing, P. Schoessow, J. Power, and W. Gai, PRSTAB 15, 011301 (2012).
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPJE006  
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WEPJE007 Simulation Studies of BBU Suppression Methods and Acceptable Tolerances in Dielectric Wakefield Accelerators quadrupole, lattice, simulation, dipole 2685
 
  • D.Y. Shchegolkov, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
  • A. Zholents
    ANL, Argonne, Illinois, USA
  
  Funding: This work is supported by the U.S. Department of Energy through the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory.
The advantage of dielectric wakefield accelerators (DWAs) is the ability to achieve accelerating gradients well above the limits of conventional accelerators. However DWAs will also produce high transverse wakefields if the beam propagates off-center, which grow even faster than the accelerating gradient when the width of the beam channel is decreased.* It is highly important to suppress single beam breakup (BBU) instability in order for the beam to propagate long enough so that a reasonable amount of energy (e.g., 80%) from the drive bunch is extracted. In addition bending of the dielectric channel has a similar effect to off-center steering of the beam with the required tolerances on the channel straightness typically in a few micron range. For both rectangular and circular dielectric lined waveguides we use a FODO lattice with a tapered strength for suppression of BBU. We impose initial energy chirp on the drive beam to make use of the BNS damping. We change rectangular waveguide orientation by 90 degrees with a small step to make use of the quadrupole wakefield focusing. These and other techniques and tolerance requirements are discussed and simulation results are presented in this presentation.
* C. Li, W. Gai, C. Jing, J.G. Power, C.X. Tang, and A. Zholents, High gradient limits due to single bunch beam breakup in a collinear dielectric wakefield accelerator, PRSTAB 17, 091302 (2014). 		 
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WEPJE008 Experimental Study of Wakefields in an X-band Photonic Band Gap Accelerating Structure HOM, higher-order-mode, coupling, electron 2689
 
  • E.I. Simakov, S. Arsenyev, C.E. Buechler, R.L. Edwards, W.P. Romero
    LANL, Los Alamos, New Mexico, USA
  • M.E. Conde, G. Ha, C.-J. Jing, J.G. Power, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
  
  Funding: This work is supported by U.S. Department of Energy (DOE) Office of Science Early Career Research Program.
We designed an experiment to conduct a detailed investigation of higher order mode spectrum in a room-temperature traveling-wave photonic band gap (PBG) accelerating structure at 11.7 GHz. 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. Since then, the importance of that device has been recognized by many research institutions. However, the full experimental characterization of the wakefield spectrum in a beam test has not been performed to date. The Argonne Wakefield Accelerator (AWA) test facility at the Argonne National Laboratory represents a perfect site where this evaluation could be conducted with a single high charge electron bunch and with a train of bunches. Here we describe fabrication and tuning of PBG cells, the final cold-test of the traveling-wave accelerating structure, and the results of the beam testing at AWA. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPJE008  
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WEPJE020 The Two Beam Acceleration Staging Experiment at Argonne Wakefield Accelerator Facility acceleration, experiment, timing, kicker 2714
 
  • C.-J. Jing, S.P. Antipov, A. Kanareykin, J.Q. Qiu
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • M.E. Conde, D.S. Doran, W. Gai, G. Ha, W. Liu, J.G. Power, J.H. Shao, D. Wang, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  • J. Shi
    TUB, Beijing, People's Republic of China
  
  Funding: DoE SBIR Program
Staging, defined as the accelerated bunch in a wakefield accelerator continues to gain energy from sequential drive bunches, is one of the most critical technologies, yet be demonstrated, required to achieve high energy. Using the Two Beam Acceleration (TBA) beamline at Argonne Wakefield Accelerator facility, we will perform a staging experiment using two X-band TBA units. The experiment is planned to conduct in steps. We report on the most recent progress. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPJE020  
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WEPMA029 Design of a Normal Conducting Cavity for Arrival Time Stabilization at FLASH cavity, coupling, simulation, HOM 2818
 
  • M. Fakhari, K. Flöttmann, S. Pfeiffer, H. Schlarb
    DESY, Hamburg, Germany
  • J. Roßbach
    Uni HH, Hamburg, Germany
  
  It has been shown, that beam-based feedback loops stabilize the bunch arrival time in the femtoseconds range. However, further minimizing the bunch arrival time jitter requires a faster actuator that is a normal conducting cavity with higher bandwidth compared to narrow-band superconducting cavities. We present the design of a 4-cell normal conducting cavity that is going to be used in a fast beam-based feedback at free-electron laser FLASH at Hamburg. The input power will be injected to the cavity via a loop coupler from the side of the first cell. The operating frequency of the designed cavity is about 3 GHz with an adjustable bandwidth. The long range longitudinal wakefield calculation results are reported to investigate the cavity performance for multi-beam operation up to 3 MHz bunch repetition rate. The results declare that the influence of the long range wakefield on the arrival time jitter is less than 1 fs.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA029  
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WEPMN017 High Power RF Radiation at W-band Based on Wakefields Excited by Intense Electron Beam electron, simulation, experiment, radiation 2960
 
  • D. Wang, C.-X. Tang
    TUB, Beijing, People's Republic of China
  • S.P. Antipov, C.-J. Jing, J.Q. Qiu
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • M.E. Conde, D.S. Doran, W. Gai, G. Ha, W. Liu, J.G. Power, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  
  We report the experiment design and preliminary results on high power RF generation at W-band based on coherent wakefields from the metallic periodic structure of 91 GHz PETS (power extraction and transfer structure), excited by intense electron beam at the Argonne Wakefield Accelerator (AWA) facility. The recently output RF power is 0.7 MW, with 67 MeV, 1.4 nC single electron beam going through the structure. The RF pulse length is 3.4 ns. We measure the energy loss of electron beam as reference to the RF generation, which agrees well with the simulation results. Next run is to increase the output RF power with higher charge and to excite coherent wakefields with electron bunch train. The output RF peak power is expected to be ~100 MW and the electrical field gradient can reach up to 400 MV/m, with RF pulse duration adjustable from few ns to 30 ns when excited with 5~10 nC charge in a single bunch and up to 32 sub bunches in total.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN017  
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WEPMN047 Suppression of Higher Order Modes in an Array of Cavities Using Waveguides HOM, damping, impedance, cavity 3033
 
  • Ya.V. Shashkov, N.P. Sobenin
    MEPhI, Moscow, Russia
  • M. Zobov
    INFN/LNF, Frascati (Roma), Italy
  
  Funding: Work is supported by Ministry of Education and Science grant 3.245.2014/r и and by the EU FP7 HiLumi LHC - Grant Agreement 284404
In the frameworks of the High Luminosity LHC upgrade program an application of additional harmonic cavities operating at multiplies of the main RF system frequency of 400 MHz is currently under discussion. A structure consisting of two 800 MHz single cell superconducting cavities with grooved beam pipes coupled by drift tubes has been suggested for implementation. However, it is desirable to increase the number of single cells installed in one cryomodule in order to decrease the number of transitions between “warm” and “cold” parts of the collider vacuum chamber. Unfortunately it can lead to the appearance of higher order modes (HOM) trapped between the cavities. In order to solve this problem the methods of HOM damping with rectangular waveguides connected to the drift tubes were investigated and compared. In this paper we describe the results obtained for arrays of 2, 4 and 8 cavities. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN047  
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WEPMN059 Design Study and Construction of a Transverse Beam Halo Collimation System for ATF2 simulation, collimation, dipole, background 3062
 
  • N. Fuster-Martínez, A. Faus-Golfe
    IFIC, Valencia, Spain
  • P. Bambade, S. Liu, S. Wallon
    LAL, Orsay, France
  • K. Kubo, T. Okugi, T. Tauchi, N. Terunuma
    KEK, Ibaraki, Japan
  • I. Podadera, F. Toral
    CIEMAT, Madrid, Spain
  
  Funding: Work supported by IDC-20121074, FPA2013-47883-C2-1-P and ANR-11-IDEX-0003-02
The feasibility and efficiency of a transverse beam halo collimation system for reducing the background in the ATF2 beamline has been studied in simulations. In this paper the design and construction of a retractable transverse beam halo collimator device is presented. The wakefield induced-impact of a realistic mechanical prototype has been studied with CST PS, as well as the wakefield beam dynamics impact by using the tracking code PLACET. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMN059  
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WEPHA057 High Gradient Testing of an X-band Crab Cavity at XBox2 cavity, klystron, electron, network 3242
 
  • B.J. Woolley, P.K. Ambattu, R. Apsimon, G. Burt, A.C. Dexter
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • A. Grudiev, I. Syratchev, R. Wegner, B.J. Woolley, W. Wuensch
    CERN, Geneva, Switzerland
  
  CERN’s Compact linear collider (CLIC) will require crab cavities to align the bunches to provide effective head-on collisions. An X-band quasi-TM11 deflecting cavity has been designed and manufactured for testing at CERN’s Xbox-2 high power standalone test stand. The cavity is currently under test and has reached an input power level in excess of 40MW, with a measured breakdown rate of better than 10-5 breakdowns per pulse. This paper also describes surface field quantities which are important in assessing the expected BDR when designing high gradient structures.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA057  
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WEPTY013 Cs2Te Photocathode Performance in the AWA High-charge High-gradient Drive Gun laser, cathode, gun, space-charge 3283
 
  • E.E. Wisniewski, S.P. Antipov, M.E. Conde, D.S. Doran, W. Gai, C.-J. Jing, W. Liu, J.G. Power, C. Whiteford
    ANL, Argonne, Illinois, USA
  • S.P. Antipov, C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
  
  Funding: U.S. Dept of Energy Office of Science under contract number DE-AC02-06CH11357
The unique high-charge L-band, 1.3 GHz, 1.5 cell gun for the new 75 MeV drive beam is in operation at the Argonne Wakefield Accelerator (AWA) facility (see M.E. Conde, this proceedings.) The high-field (> 80 MV/m) photoinjector has a large area, high QE Cesium telluride photocathode (diameter > 30 mm). The photocathode, a crucial component of the upgraded facility, is fabricated on-site. The photoinjector generates high-charge, short pulse, single bunches (Q > 100 nC) and long bunch-trains (Q > 600 nC) for wakefield experiments. The performance of the photocathode for the AWA drive gun is detailed. Quantum efficiency (QE) measurements indicate long, stable photocathode lifetime under demanding conditions. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY013  
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WEPTY018 Analysis of a Quasi-waveguide Multicell Resonator for SPX cavity, resonance, higher-order-mode, niobium 3299
 
  • M.H. Awida, I.V. Gonin, T.N. Khabiboulline, A. Lunin, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
  • A. Zholents
    ANL, Argonne, Ilinois, USA
  
  A compact deflecting cavity is needed for the Short Pulse X-rays (SPX) at the Advanced Photon Source (APS) of Argonne national laboratory. The deflecting cavity has to quite efficient providing a 2 MV kick voltage and satisfying stringent requirements on aperture size and total cavity length. Meanwhile, the cavity should allow operation up to 100 mT peak surface magnetic field before quenching. In this paper, we report on the latest analysis carried out on the cavity structure to investigate frequency sensitivity to pressure fluctuations, frequency sensitivity to tuning forces, modal frequency, and wakefield losses.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY018  
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