IPAC2016 - List of Keywords (wakefield)

Paper	Title	Other Keywords	Page
MOPMB033	The Influence of Strip-line BPMs' Measuring Results Made by Edge of the Ultra-relativistic Electron Beam	simulation, electron, positron, linac	161
	S.Z. Wang, N. Gan, X. Huang IHEP, Beijing, People's Republic of China
	This paper describes the impact on the measuring results of the stripline beam position monitor (BPM) produced by the edge of the ultra-relativistic electron beam when we take the transverse size of the beam into account. Simulations have been made by using the Wakefield Solver of CST Particle Studio. And the result of this influence at different ratio of beam horizontal width σ and the BPM inner diameter a has been obtained. This kind of influence has been observed in the stripline BPMs in the transfer line of Beijing Positron Electron Colliders upgraded version II (BEPCII). The research is useful when we design the inner diameter of the stripline BPMs for ultra-relativistic electron beam, meanwhile it provides reference to distinguish the invalid ones from the measuring results obtained by the stripline BPMs in the ultra-relativistic situation.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB033
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MOPMB037	Beam Position Monitor Design for Dielectric Wakefield Accelerator In THz Range	dipole, simulation, polarization, controls	171
	Q. Gao, H.B. Chen, J. Shi TUB, Beijing, People's Republic of China W. Gai ANL, Argonne, Illinois, USA C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA
	Dielectric based collinear wakefield accelerator have been broadly selected for the THz accelerator due to its simplicity. In order to move the THz accelerators from the current exploratory research into the practical phase, certain common accelerator components are indispensable. Beam Position Monitor (BPM) is one of them. However, most of conventional BPM techniques are hardly scaled down to THz regime. Here we propose a BPM design which uses the dominant dipole mode excited in the dielectric wakefield accelerators to extract information of the beam position.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB037
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MOPMW015	Wakefields Studies of High Gradient X-band Accelerating Structure at SINAP	impedance, simulation, cavity, FEL	429
	X.X. Huang, W. Fang, Q. Gu, M. Zhang, Z.T. Zhao SINAP, Shanghai, People's Republic of China
	Shanghai compact hard x-ray free electron laser (CHXFEL)* is now proposed accompanied with a high-gradient accelerating structure, which is the trend of large scale and compact facility. This structure operated at X-band (11424 MHz) holds the promise to achieve high gradient up to 80 MV/m. However, due to its particular property, a more serious wakefields** will be generated, leading to worse beam instability effects. In this paper, the computation of this case will be carried out with simulation. Moreover, analysis and optimization will be adopted to suppress beam instability. * C. Feng, Z. T. Zhao, Chinese Sci Bull, 2010, 55, 221-227. ** K. Bane, SLAC, NLC-Note 9, Feb. 1995.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW015
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MOPMY026	Development of an X-Band Linearizer System for PAL-XFEL	klystron, LLRF, electron, acceleration	554
	H. Heo, J. Hu, H.-S. Kang, K.H. Kim, S.H. Kim, H.-S. Lee, B.G. Oh, S.S. Park, Y.J. Park, Y.J. Suh PAL, Pohang, Kyungbuk, Republic of Korea
	We developed an X-band RF system for the linear bunch compression in the PAL-XFEL. We installed a SLAC X-band accelerating structure on a precise mover stage and applied RF power by using a SLAC XL-4 11.424 GHz klystron driven by an inverter charging type modulator. We are developing a solid state amplifier controlled by an X-band LLRF system instead of using a TWTA as a driving RF source for the klystron. We present and discuss the recent test results of the system.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY026
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MOPOR002	Impedance Simulations and Measurements for ThomX Storage Ring	impedance, simulation, interface, storage-ring	586
	A.R. Gamelin, C. Bruni, V. Chaumat, D. Le Guidec, P. Lepercq, R. Marie LAL, Orsay, France
	Funding: Work is supported by ANR-10-EQPX-51, by grants from Région Ile-de-France, IN2P3 and Pheniics Doctoral School ThomX is a compact Compton Backscattering Source (CBS) which is being built at LAL, Orsay, France. ThomX ring has a short circumference of 18 m and a design energy of 50 MeV. Due to the low energy of the beam and in order to avoid beam degradation it is important to evaluate the ring components impedance. A CST Particle Studio impedance simulation of the different components of the ring (BPM, bellows, optical chamber, etc.) is under way. It will be followed by a bench measurement of the longitudinal and transverse impedance using the coaxial wire method. This paper will detail the preliminary results of the ThomX storage ring impedance simulations and the measurement principle we will use.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR002
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MOPOR005	Longitudinal Wakefields in the Undulator Section of SXFEL User Facility	undulator, FEL, vacuum, electron	595
	M. Song, H.X. Deng, C. Feng, D. Huang, B. Liu, D. Wang SINAP, Shanghai, People's Republic of China
	Shanghai soft x-ray free electron laser (SXFEL) user facility based on multi-stage seeded-FEL and self-amplified spontaneous emission (SASE) is recently proposed, which is aiming at generating 4-2nm fully-coherent, high-brightness FEL pulse. In this paper, the wakefields arise from the resistive wall and surface roughness in the vacuum chamber is obtained by theoretical models. And the computations of geometric wakefields are carried out using ABCI. According to the tracked beam profile, the overall wakefields in the undulator section of SXFEL user facility are presented. K. Bane, G. Stupakov, SLAC-PUB-15951, May 2014. ** ABCI website: http://abci.kek.jp/abci.htm
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR005
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MOPOW004	Electron Trajectory Caustic Formation Resulting in Current Horns present in Bunch Compression	electron, FEL, linac, simulation	708
	T.K. Charles, D.M. Paganin Monash University, Faculty of Science, Clayton, Victoria, Australia M.J. Boland, R.T. Dowd SLSA, Clayton, Australia
	Current horns are ubiquitous in Free Electron Laser (FEL) bunch compression. In this paper, we analyse the formation of these current spikes and identify the cause as caustic formation in the electron trajectories. We also present a possible solution to avoid or mitigate the current horns from developing through using optical linearization.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW004
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MOPOW044	Commissioning of the RadiaBeam / SLAC Dechirper	electron, photon, controls, alignment	809
	M.W. Guetg, K.L.F. Bane, A. Brachmann, A.S. Fisher, Z. Huang, R.H. Iverson, P. Krejcik, A.A. Lutman, T.J. Maxwell, A. Novokhatski, G. Stupakov, J. Zemella, Z. Zhang SLAC, Menlo Park, California, USA M.A. Harrison, M. Ruelas RadiaBeam Systems, Santa Monica, California, USA J. Zemella DESY, Hamburg, Germany Z. Zhang TUB, Beijing, People's Republic of China
	We present results on the commissioning of the two-module RadiaBeam / SLAC dechirper system at LCLS. This is the first installation and measurement of a corrugated dechirper at high energy (4.4 - 13.3 GeV), short pulses (< 200 fs) and while observing its effect on an operational FEL. Both the transverse and longitudinal wakefields allow more flexible electron beam tailoring. We verify that, for a single module at a given gap, the strength of the longitudinal wake on axis and the dipole near the axis agree well with the theoretical values. Using direct longitudinal phase space mapping and X-ray FEL spectrum measurements we demonstrate the energy chirp control capabilities.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW044
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MOPOW046	RadiaBeam/SLAC Dechirper as a Passive Deflector	electron, lattice, focusing, diagnostics	817
	A. Novokhatski, A. Brachmann, M. Dal Forno, V.A. Dolgashev, A.S. Fisher, M.W. Guetg, Z. Huang, R.H. Iverson, P. Krejcik, A.A. Lutman, T.J. Maxwell SLAC, Menlo Park, California, USA J. Zemella DESY, Hamburg, Germany
	Funding: This work was supported by Department of Energy Contract No. DE-AC02-76SF00515. We discuss the possibility of using the RadiBeam/SLAC dechirper recently installed at LCLS for measuring the bunch length of very short bunches, less than 1 fs perhaps as short as 100 atto second. When a bunch travels close to one of the jaws the particles of the bunch get a transverse kick depends upon the position of a particle in a bunch. The tail particles get more kick. The transverse force also gets a nonlinear dependence on the transverse position. The stretched bunch can be measured at the YAG screen that is 100 m downstream the dechirper. The most important aspect of this measurement is that that no synchronization is needed. The Green's function for the transverse kick was evaluated based on the precise wake field calculations of the dechirper corrugated structure. Using this function we can restore the longitudinal shape of the bunch. This may also help to see if a bunch has any micro-bunch structure. A. Noovokhatski "Wakefield potentials of corrugated structures",Phys. Rev. ST Accel. Beams 18, 104402 (2015)
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW046
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TUOAB01	Optimization of the Dechirper for Electron Bunches of Arbitrary Longitudinal Shapes	electron, simulation, controls, dipole	1054
	J.M. Seok, M. Chung UNIST, Ulsan, Republic of Korea J.H. Han, J.H. Hong, H.-S. Kang PAL, Pohang, Kyungbuk, Republic of Korea
	Dechirper is a passive device composed of a vacuum chamber of two corrugated, metallic plates with an adjustable gap. By introducing a small offset in the dechirper with respect to the reference axis, one might generate transverse wakefields and use the dechirper as a deflector. Understanding the interactions between electron beams of various longitudinal shapes with the wakefields generated by the dechirper is important to assess the feasibility of the dechirper for use as a deflector. Recently, using a set of alpha-BBO crystals, shaping of laser pulses and electron bunches on the order of ps is tested at the Injector Test Facility (ITF) of Pohang Accelerator Laboratory (PAL). Furthermore, we have investigated propagation of electron bunches of arbitrary longitudinal shapes through the dechirper. In the numerical simulations, we observed that the arbitrary electron beams were successful deflected except for lethal beam shape problems. Hence, in this work, we study optimization of the dechirper for electron bunches of arbitrary longitudinal shapes, using analytical theory and numerical simulations with the ASTRA and ELEGANT codes.
	Slides TUOAB01 [1.631 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUOAB01
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TUOBB01	Demonstration of Current Profile Shaping using Double Dog-Leg Emittance Exchange Beam Line at Argonne Wakefield Accelerator	emittance, quadrupole, dipole, experiment	1065
	G. Ha, M.-H. Cho, W. Namkung POSTECH, Pohang, Kyungbuk, Republic of Korea M.E. Conde, D.S. Doran, W. Gai, G. Ha, K.-J. Kim, W. Liu, J.G. Power, Y.-E. Sun, C. Whiteford, E.E. Wisniewski, A. Zholents ANL, Argonne, Illinois, USA C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA P. Piot Fermilab, Batavia, Illinois, USA
	Emittance exchange (EEX) based longitudinal current profile shaping is the one of the promising current profile shaping technique. This method can generate high quality arbitrary current profiles under the ideal conditions. The double dog-leg EEX beam line was recently installed at the Argonne Wakefield Accelerator (AWA) to explore the shaping capability and confirm the quality of this method. To demonstrate the arbitrary current profile generation, several different transverse masks are applied to generate different final current profiles. The phase space slopes and the charge of incoming beam are varied to observe and suppress the aberrations on the ideal profile. We present current profile shaping results, aberrations on the shaped profile, and its suppression.
	Slides TUOBB01 [5.032 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUOBB01
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TUPMY025	Proton-Driven Electron Acceleration in Hollow Plasma	plasma, electron, proton, acceleration	1601
	Y. M. Li, K. Hanahoe, O. Mete Apsimon, T.H. Pacey, G.X. Xia UMAN, Manchester, United Kingdom
	Funding: President's Doctoral Scholar Award from The University of Manchester. Proton driven plasma wakefield acceleration has been proposed to accelerate electrons to TeV-scale in a single hundreds of meters plasma section. However, it is difficult to conserve beam quality due to the positively charged driven scheme. In this paper, we demonstrate via simulation that hollow plasma is favourable to maintain the long and stable acceleration and simultaneously be able to achieve low normalized emittance and energy spread of the witness electrons. Moreover, it has much higher beam loading tolerance compared to the uniform case. This will potentially facilitates the acceleration of a large number of particles with high beam quality. * Caldwell A et al.Nature Physics, 2009, 5(5): 363-367 K. Lotov, Phys. Rev. ST Accel. Beams, 2010, 13(4): 041301. * W. Kimura et al., Phys. Rev. ST Accel. Beams, 2011, 14(4): 041301.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMY025
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TUPMY028	Ultra-high Gradient Acceleration in Nano-crystal Channels	electron, plasma, laser, acceleration	1607
	Y.-M. Shin Northern Illinois University, DeKalb, Illinois, USA D.M. Farinella, P. Taborek, T. Tajima UCI, Irvine, California, USA A.H. Lumpkin, V.D. Shiltsev, R.M. Thurman-Keup Fermilab, Batavia, Illinois, USA X. Zhang Shanghai Institute of Optics and Fine Mechanics, Shanghai, People's Republic of China
	Funding: This work was supported by the DOE contract No.DEAC02-07CH11359 to the Fermi Research Alliance LLC. We also thank the FAST Department team for the helpful discussions and technical support. Crystals behave like a non-equilibrium medium (e.g. plasma), but at a relatively low temperature, if heated by a high-power driving source. The warm dense matter contains many more ions (n0 ~ 10¹⁹ - 10²³ cm^-3) available for plasma acceleration than gaseous plasmas, and can possibly support electric fields of up to 30 TV/m of plasma oscillation,,,. Atomic lattice spaces in solid crystals are known to consist of 10 - 100 V/Å potential barriers capable of guiding and collimating high energy particles with continuously focused acceleration. Nanostructured crystals (e.g. carbon nanotube) with dimensional flexibilities can accept a few orders of magnitude larger phase-space volume of channeled particles than natural crystals. Our PIC simulation results*, **** obtained from two plasma acceleration codes, VORPAL and EPOCH, indicate that in the linear regime the beam-driven and laser-driven electrons channeled in a 100 micro-meter long effective nanotube gain 10 MeV (G = 1 - 10 TeV/m). Experimental tests, including slit-mask beam modulation and pump-probe electron diffraction, are designed in Fermilab and NIU to identify a wakefield effect in a photo-excited crystal. * Phys. Rev.Lett. 43, 267(1979) Phys. Plasmas 15, 103105(2008) * Nature Photonics 9, 274(2015) ** Phys. J. 223, 1037(2014) * Appl. Phys. Lett. 105, 114106(2014) **** Phys. Plasmas 20, 123106(2013)
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMY028
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TUPMY036	Drive Generation and Propagation Studies for the Two Beam Acceleration Experiment at the Argonne Wakefield Accelerator	kicker, laser, simulation, power-supply	1629
	N.R. Neveu, M.E. Conde, D.S. Doran, W. Gai, G. Ha, C.-J. Jing, W. Liu, J.G. Power, D. Wang, C. Whiteford, E.E. Wisniewski ANL, Argonne, Illinois, USA S.P. Antipov, C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA G. Ha POSTECH, Pohang, Kyungbuk, Republic of Korea N.R. Neveu IIT, Chicago, Illinois, USA D. Wang TUB, Beijing, People's Republic of China
	Funding: Work supported by by the U.S. Department of Energy under contract No. DE-AC02-06CH11357. Simplified staging in a two beam accelerator (TBA) has been accomplished at the Argonne Wakefield Accelerator (AWA) facility. This layout consists of a drive beamline and witness beamline operating synchronously. The drive photoinjector linac produces a 70 MeV drive bunch train of eight electron bunches (charge per bunch between 5-40 nC) that pass through decelerating structures in each TBA stage. The witness linac produces an 8 MeV witness bunch that passes through the accelerating structures in each TBA stage. Recent effort has been focused on improving the uniformity of the UV laser pulses that generate the bunch trains. Current work at the AWA is focused on the transition from simplified staging to full staging. A kicker will be designed and installed to direct bunch trains to one TBA stage only. Preliminary calculations and simulation results are presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMY036
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TUPOR013	Analysis of Multi-bunch Instabilities at the Diamond Storage Ring	impedance, damping, storage-ring, simulation	1685
	R. Bartolini, R.T. Fielder, G. Rehm DLS, Oxfordshire, United Kingdom V.V. Smaluk BNL, Upton, Long Island, New York, USA
	We present recent results of analytical, numerical and experimental analysis of multi-bunch instabilities at the Diamond storage ring. The works compares the impedance estimates from numerical modelling with the analysis of the growth rates of the excited multi-bunch modes in different machine configurations. The contribution of a number of wakefield sources has been identified with very high precision thanks to high quality data provided by the existing Transverse multi-bunch feedback diagnostics
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR013
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TUPOW017	Twin Bunches at the FACET-II	simulation, electron, acceleration, controls	1778
	Z. Zhang TUB, Beijing, People's Republic of China M.J. Hogan, Z. Huang, A. Marinelli SLAC, Menlo Park, California, USA
	Twin electron bunches, generated, accelerated and compressed in the same acceleration bucket, have attracted a lot of interest in the free-electron lasers and wakefield acceleration. The recent successful experiment at the LCLS used twin bunches to generate two-color two x-ray pulses with tunable time delay and energy separation. In this note, we apply the twin bunches to the plasma wakefield acceleration. Numerical simulations show that based on the beamline of the FACET-II, we can generate high-intensity two electron bunches with time delay from ∼ 100 fs to picoseconds, which will benefit the control of high-gradient witness bunch acceleration in a plasma.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW017
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TUPOW030	A CW Normal Conducting RF Cavity for Fast Chirp Control in the LCLS-II	linac, cavity, controls, FEL	1817
	M.H. Nasr, P. Emma, S.G. Tantawi SLAC, Menlo Park, California, USA
	The LCLS-II is a high repetition-rate Free-Electron Laser (FEL) facility under construction at SLAC. A new 4-GeV continuous wave (CW) superconducting (SC) L-band linac is being built to provide an electron bunch rate of up to 1 MHz, with bunches rapidly switched between two FEL undulators. It is desirable to provide peak current (i.e., pulse length) control in each FEL independently by varying the RF phase (chirp) prior to the first bunch compressor. However, the high-Q, SCRF, with its 1-ms fill-time, cannot be changed within one bunch spacing (1 us). So to provide a small chirp adjustment from bunch to bunch, we propose a short CW copper RF accelerating cavity, located just after the injector, with < 250-ns fill-time designed to adjust the beam chirp at zero-crossing phase. We examined RF cavity designs spanning RF frequencies from L-band to X-band. We considered both SW and TW structures. We found an optimal solution with 2 cm iris diameter, SW RF cavity, operating at C-band with input power of only 10 kW. If one can afford to operate with smaller diameter, from a wakefield point of view, then similar structure at X-band may require only 500 W with 5 mm iris diameter.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW030
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TUPOW033	Status of the BERLinPro Main Linac Module	linac, cavity, HOM, simulation	1823
	H.-W. Glock, A. Frahm, J. Knobloch, A. Neumann HZB, Berlin, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of the Helmholtz Association Beam operation of the BERLinPro energy recovery linac project, whose construction is under way, will initially start using the photoinjector and booster modules. In a second step the recirculation beam line and the main linac module will be added. Here the current design status of the main linac module is described. Results of wake field simulations are compared for different set ups. We also report on the manufacturing aspects including the design of the waveguide groups needed for HOM damping and the choice of flange-gasket-pairings appropriate for rectangular waveguides. Also mechanical considerations are included.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW033
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WEPMR037	Wakefield Analysis of the 56 MHz SRF Cavity	cavity, impedance, HOM, SRF	2354
	Q. Wu, Y. Hao BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The 56 MHz SRF cavity is a superconducting quarter-wave resonator installed in the common section of RHIC. Both beams share the cavity in an interwoven pattern over the entire store. The wake field excited in the cavity is the superposition of the two opposing bunches. This paper will discuss the wake field excited by both beams, and the higher order mode power as a result of the excited field.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR037
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WEPMY006	A High Transformer Ratio Scheme for PITZ PWFA Experiments	plasma, laser, acceleration, simulation	2551
	G. Loisch, M. Groß, H. Huck, A. Oppelt, Y. Renier, F. Stephan DESY Zeuthen, Zeuthen, Germany A. Aschikhin, A. Martinez de la Ossa, J. Osterhoff DESY, Hamburg, Germany M. Hochberg, M. Sack KIT, Karlsruhe, Germany
	In the field of plasma wakefield acceleration (PWFA) significant progress has been made throughout the recent years. However, an important issue in building plasma based accelerators that provide particle bunches suitable for user applications will be a high transformer ratio, i.e. the ratio between maximum accelerating field in the witness and maximum decelerating fields in the driver bunch. The transformer ratio for symmetrical bunches in an overdense plasma is naturally limited to 2. Theory and simulations show that this can be exceeded using asymmetrical bunches. Experimentally this was proven in RF-structures, but not in PWFA. To study transformer ratios above this limit in the linear regime of a plasma wake, an experimental scheme tailored to the unique capabilities of the Photoinjector Test Facility Zeuthen PITZ, a 20-MeV electron accelerator at DESY, is being investigated. This includes analytical plasma wakefield calculations, numerical simulations of beam transport and plasma wakefields, as well as preparatory studies on the photocathode laser system and the plasma sources. K. L. F. Bane, P. B. Wilson and T. Weiland, AIP Conference Proceedings 127, p. 875, 1984 ** C. Jing et al., Physical Review Letters 98, 144801, 2007
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY006
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WEPMY008	Towards Awake Applications: Electron Beam Acceleration in a Proton Driven Plasma Wake	plasma, electron, proton, acceleration	2557
	E. Adli University of Oslo, Oslo, Norway
	The first phases of the AWAKE experiment will study the wake structure and the potential for electron acceleration in a self-modulated proton driver. In AWAKE Run 2, expected to start after the LHC Long Shut Down 2, electron beam acceleration will be studied. Using a single proton driver and a long acceleration stage, an electron bunch will be accelerated to high energies. Demonstrating beam quality preservation and scalable plasma sources will be a significant step towards using proton driven plasma for applications. We report on the plans and preparations for AWAKE Run 2.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY008
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WEPMY016	Development of RF System for Measuring Plasma Density Modulation of Proton Beam-driven Plasma Wakefield	plasma, simulation, proton, focusing	2582
	S.Y. Kim, M. Chung UNIST, Ulsan, Republic of Korea
	Proton beam-driven plasma wakefield acceleration technique using the proton beam of Super Proton Syn-chrotron (SPS) at CERN has been actively researched these days. Plasma density modulation due to the proton beam will generate high-gradient's electric field within the modulated plasma. The key role is Self-Modulation Instability (SMI) of the long proton beam. To understand SMI phenomena, we have studied RF system such as heterodyne system for measuring modulated plasma den-sity caused by the SMI. In this work, we design the details of the RF system and optical system of focusing millimetre-sized electromagnetic wave using CODE V and plasma-electromagnetic wave interactions using simulation tools.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY016
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WEPMY017	Numerical Studies of Self Modulation Instability in the Beam-driven Plasma Wakefield Experiments	plasma, proton, electron, simulation	2585
	K. Moon, M. Chung UNIST, Ulsan, Republic of Korea
	Proton beam-driven plasma wakefield acceleration was recently proposed as a way to bring electrons to TeV energy range in a single plasma section. When the ultra-relativistic long proton beam propagates into the plasmas, this bunch splits into many small bunches. This phenomenon is known as a Self-Modulation Instability (SMI), and its characteristics depend on the ratio of bunch length and plasma wavelength. In this study, we first introduce a Particle-In-Cell (PIC) code WARP, focusing on the basis of parallel version structure. Through numerical simulations using the WARP, we investigate the characteristics of the SMI and propose possible experimental setup at the Injector Test Facility (ITF) of Pohang Accelerator Laboratory (PAL). Also, we present dependencies of the witness beam quality on both the driver beam and plasma parameters.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY017
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WEPMY019	AWAKE, the Advanced Proton Driven Plasma Wakefield Acceleration Experiment	plasma, laser, electron, experiment	2588
	P. Muggli MPI, Muenchen, Germany C. Bracco CERN, Geneva, Switzerland
	The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) aims at studying plasma wakefield generation and electron acceleration driven by proton bunches. It is a proof-of-principle R&D experiment at CERN and the world's first proton driven plasma wakefield acceleration experiment. The AWAKE experiment is currently being installed in the former CNGS facility and will use the 400 GeV/c proton beam bunches from the SPS to drive the wakefields in the plasma. The first experiments will focus on the self-modulation instability of the long (rms ~12 cm) proton bunch in the plasma. These experiments are planned for the end of 2016. Later, in 2017/2018, low energy (~15 MeV) electrons will be externally injected to sample the wakefields and be accelerated with GeV/m gradients. The main goals of the experiment will be summarized. A summary of the AWAKE design and construction status will be presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY019
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WEPMY021	Beam-Plasma Interaction Simulations for the AWAKE Experiment at CERN	plasma, proton, experiment, electron	2596
	A.V. Petrenko, E. Gschwendtner, G. Plyushchev, M. Turner CERN, Geneva, Switzerland K.V. Lotov BINP SB RAS, Novosibirsk, Russia K.V. Lotov, A. Sosedkin NSU, Novosibirsk, Russia G. Plyushchev EPFL, Lausanne, Switzerland M. Turner TUG/ITP, Graz, Austria
	The AWAKE experiment at CERN will be the first proof-of-principle demonstration of the proton-driven plasma wakefield acceleration using the 400 GeV proton beam extracted from the SPS accelerator. The plasma wakefield will be driven by a sequence of sub-millimeter long micro-bunches produced as a result of the self-modulation instability (SMI) of the 12 cm long SPS proton bunch in the 10 m long rubidium plasma with a density corresponding to the plasma wavelength of around 1 mm. A 16 MeV electron beam will be injected into the developing SMI and used to probe the plasma wakefields. The proton beam self-modulation in a wide range of plasma densities and gradients have been studied in detail via numerical simulations. A new configuration of the AWAKE experiment with a small plasma density step is proposed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY021
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WEPMY022	Homogeneous Focusing of Train of Short Relativistic Electron Bunches by Plasma Wakefield	focusing, plasma, electron, simulation	2599
	V.I. Maslov, I.N. Onishchenko NSC/KIPT, Kharkov, Ukraine I.P. Levchuk (Yarovaya) KhNU, Kharkov, Ukraine
	The focusing of bunches by wakefield, excited in plasma by resonant sequence of relativistic electron bunches (repetition frequency of the bunches coincides with the plasma frequency), is inhomogeneous. In this paper we investigate wakefield plasma lens, in which all bunches of sequence are focused identically and uniformly, for short relativistic electron bunches. For this it is necessary that the charge of 1-st bunch is smaller in determined times than the charges of the other bunches, the interval between back front of 1-st bunch and 1-st front of 2-nd bunch equals determined value, the interval between back front of N-th bunch and 1-st front of (N+1)-th bunch for all other bunches is multiple to excited wavelength. It is shown that only 1-st bunch is in finite Ez≠0. Other bunches are in zero longitudinal electrical wakefield. Hence the 1-st bunch interchange by energy with wakefield. The subsequent bunches don't interchange by energy with wakefield and the amplitude of wakefield doesn't change along sequence. Radial wake force Fr in regions, occupied by bunches, is approximately constant along bunches.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY022
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WEPMY023	Self-focusing and Wakefield-focusing of Relativistic Electron Bunches in Plasma	focusing, plasma, electron, space-charge	2602
	V.I. Maslov, I.P. Levchuk (Yarovaya), I.N. Onishchenko NSC/KIPT, Kharkov, Ukraine
	It was shown that at the wakefield excitation by electron bunch, the length of which is equal to half of the wavelength, the ratio of wakefield focusing to self-focusing is large at the end of the bunch, the shape of which is such that it falls from the current maximum value in the head of the bunch to zero at the end of the bunch. However, the ratio of wakefield focusing to self-focusing tends to zero at the end of the bunch, if the current increases along the bunch from zero in the head of the bunch to a maximum value at the end of the bunch. In the case of homogeneous bunch with sharp edges, the length of which is several plasma wavelength, the self-focusing force Fs is constant along the bunch, and wakefield force of focusing changes from -Fs to Fs. In the case of homogeneous bunch with precursor of half current and length, equal to half of wavelength, focusing of bunch is determined by the homogeneous self-focusing force and wakefield focusing force equals zero. Cases of rectangular and Gaussian bunches, the length of which is equal to half of wavelength, also were considered.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY023
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WEPMY025	iMPACT, Undulator-Based Multi-Bunch Plasma Accelerator	plasma, undulator, electron, simulation	2609
	O. Mete Apsimon, K. Hanahoe, G.X. Xia UMAN, Manchester, United Kingdom G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom B. Hidding USTRAT/SUPA, Glasgow, United Kingdom J.D.A. Smith Tech-X, Boulder, Colorado, USA
	Funding: This work is supported by the Cockcroft Institute Core Grant and STFC. The accelerating gradient measured in laser or electron driven wakefield accelerators can be in the range of 10-100GV/m, which is 2-3 orders of magnitude larger than can be achieved by conventional RF-based particle accelerators. However, the beam quality preservation is still an important problem to be tackled to ensure the practicality of this technology. In this global picture, the main goals of this study are planning and coordinating a physics program, the so-called iMPACT, that addresses issues such as emittance growth mechanisms in the transverse and longitudinal planes through scattering from the plasma particles, minimisation of the energy spread and maximising the energy gain while benchmarking the milestones. In this paper, a summary and planning of the project is introduced and initial multi-bunch simulations were presented.
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WEPMY027	Feasibility Study of Plasma Wakefield Acceleration at the CLARA Front End Facility	plasma, experiment, simulation, accelerating-gradient	2617
	K. Hanahoe, R.B. Appleby, Y. M. Li, T.H. Pacey, G.X. Xia UMAN, Manchester, United Kingdom B. Hidding USTRAT/SUPA, Glasgow, United Kingdom B. Kyle University of Manchester, Manchester, United Kingdom O. Mete Apsimon Cockcroft Institute, Lancaster University, Lancaster, United Kingdom J.D.A. Smith Tech-X, Boulder, Colorado, USA
	Funding: Cockcroft Institute Core Grant and STFC Plasma wakefield acceleration has been proposed at the CLARA Front End (FE) facility at Daresbury Laboratory. The initial phase of the experiment will acceleration of the tail of a single electron bunch, and the follow-up experiment will study preserving a high quality beam based on a two-bunch acceleration scenario. In this paper, a concept for the initial experiment is outlined and detailed simulation results are presented.
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WEPOR016	Pre-alignment of Accelerating Structures for Compact Acceleration and High Gradient using In-situ Radiofrequency Methods	alignment, dipole, linac, electromagnetic-fields	2696
	N. Galindo Munoz, N. Catalán Lasheras, A. Grudiev CERN, Geneva, Switzerland V.E. Boria DCOM-iTEAM-UPV, Valencia, Spain A. Faus-Golfe IFIC, Valencia, Spain
	Funding: PACMAN is founded under the European Union's 7th Framework Program Marie Curie Actions, grant PITN-GA-2013-606839 To achieve a high accelerating gradient of 100 MV/m, the CLIC project under study at CERN uses a 23 cm long tapered normal-conducting travelling wave Accelerating Structure (AS) operating at 12 GHz. Minimisation of the long-range wakefields (WF) is assured by damping of the HOM through four radial waveguides in each cell without distorting the accelerating mode. As an extension of them, there are four bent waveguides called WF monitors (WFM) in the middle cell with two RF pick-ups. To obtain a small beam emittance in the collision point, micro-metric pre-alignment of the AS is required. We work to find the electrical centre of the AS through the use of the asymmetry in the RF scattering parameters created by an off-centre conductive wire, stretched along the axis. The accuracy required is of 7 μm with a resolution of 3.5 μm for the WFM signals including the acquisition electronics. Our simulations have shown that a resolution of 1 μm is possible using a calibrated VNA. Measurement results and improvements of the final accuracy will be presented and discussed.
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WEPOY025	High Power RF Generation From a W-Band Corrugated Structure Excited by a Train of Electron Bunches	electron, experiment, simulation, acceleration	3040
	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, G. Ha, W. Liu, J.G. Power, E.E. Wisniewski ANL, Argonne, Illinois, USA V.A. Dolgashev SLAC, Menlo Park, California, USA
	We report on the generation of multi-megawatt peak RF power at 91textGHz, using an ultrarelativistic electron bunch train to excite electromagnetic fields in a high-impedance metallic corrugated structure. This device can be used as a power source for high gradient acceleration of electrons. To achieve precise control of the wakefield phase, a long range wakefield interferometry method was developed in which the RF energy due to the interference of the wakefields from two bunches was measured as a function of the bunch separation.
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WEPOY026	Simulation and Measurement of the Beam Breakup Instability in a W-band Corrugated Structure	dipole, electron, simulation, radiation	3044
	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
	The corrugated wakefield structure has wide application in electron beam energy manipulation and high frequency RF radiation generation. The transverse wakefield which cause beam breakup (BBU) instability is excited when the drive beam is not perfectly centered through the structure. Here we report on the numerical and experimental investigation of the BBU effect in a W-band corrugated structure, for both cases of short range wakefield and long range wakefield. In the numerical part we develop a point to point (P2P) code that allows rapid and efficiency simulations of the beam dynamics effect by wakefield, which is based on the the particle-wake function coupled dynamics equation of motion. And the experimental measurements of BBU effect are found to be in good agreement with the simulations.
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THPPA01	Demonstration of the Hollow Channel Plasma Wakefield Accelerator	plasma, positron, laser, acceleration	3202
	S.J. Gessner, J.M. Allen, C.I. Clarke, J.-P. Delahaye, J.T. Frederico, S.Z. Green, C. Hast, M.J. Hogan, N. Lipkowitz, M.D. Litos, B.D. O'Shea, D.R. Walz, V. Yakimenko, G. Yocky SLAC, Menlo Park, California, USA E. Adli, C.A. Lindstrøm University of Oslo, Oslo, Norway W. An, C.E. Clayton, C. Joshi, K.A. Marsh, W.B. Mori, N. Vafaei-Najafabadi UCLA, Los Angeles, California, USA S. Corde, A. Doche LOA, Palaiseau, France W. Lu TUB, Beijing, People's Republic of China
	Funding: Work supported by DOE contract DE-AC02-76SF00515. Over the past decade, there has been enormous progress in the field of beam and laser-driven plasma acceleration of electron beams. However, in order for plasma wakefield acceleration to be useful for a high-energy e⁺e^- collider, we need a technique for accelerating positrons in plasma as well. This is a unique challenge, because the plasma responds differently to electron and positron beams, with plasma electrons being pulled through the positron beam and creating a non-linear focusing force. Here, we demonstrate a technique called hollow channel acceleration that symmetrizes the wakefield response to beams of either charge. Using a transversely shaped laser pulse, we create an annular plasma with a fixed radius of 200 μm. We observe the acceleration of a positron bunch with energies up to 33.4 MeV in a 25 cm long channel, indicating an effective gradient greater than 100 MeV/m. This is the first demonstration of a technique that way be used for staged acceleration of positron beams in plasma.
	Slides THPPA01 [5.647 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPPA01
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THPOR030	Commissioning and First Performance Studies of a Single Vertical Beam Halo Collimation System at ATF2	background, photon, collimation, simulation	3844
	N. Fuster-Martínez, A. Faus-Golfe IFIC, Valencia, Spain P. Bambade, A. Faus-Golfe, S. Wallon, R.J. Yang LAL, Orsay, France K. Kubo, T. Okugi, T. Tauchi, N. Terunuma KEK, Ibaraki, Japan I. Podadera, F. Toral CIEMAT, Madrid, Spain T. Tauchi, N. Terunuma Sokendai, Ibaraki, Japan
	A single vertical beam halo collimation system has been installed in the ATF2 beamline to reduce the background that could limit the precision of the diagnostics located in the post-IP beamline. On this paper the commissioning and first performance studies of a single vertical beam halo collimation system are reported. Furthermore realistic efficiency studies have been done using the simulation code BDSIM and compared with the first experimental tests.
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FRXCB01	Two Beam Wakefield Acceleration at Argonne Wakefield Accelerator Facility	acceleration, experiment, electron, laser	4258
	W. Gai ANL, Argonne, Illinois, USA
	Structure based wakefield acceleration provides a viable approach capable of accelerating a sufficient electrons and positrons in a substantially high graident needed to meet the luminosity, efficiency, and cost requirements of a future linear collider. The short pulse Two Beam wakefield Acceleration (TBA) studied at the Argonne Wakefield Accelerator Facility is aimed to pave the way toward the next linear collider. Here we present the latest results including the 100MeV/m of the single stage TBA and the staged TBA in which a 0.5nC bunch gained equal amount of energy in two stages (~2.4 MeV per stage, corresponding to an average acceleration gradient ~70 MeV/m). The technique is scalable to a staged-acceleration at 200-300MeV/m by using a GeV-scale drive beam. Such a development will considerably reduce both cost and footprint of a future high-energy physics collider as well as future X-Ray light source.
	Slides FRXCB01 [11.937 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-FRXCB01
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Paper

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MOPMB033

The Influence of Strip-line BPMs' Measuring Results Made by Edge of the Ultra-relativistic Electron Beam

simulation, electron, positron, linac

161

S.Z. Wang, N. Gan, X. Huang
IHEP, Beijing, People's Republic of China

This paper describes the impact on the measuring results of the stripline beam position monitor (BPM) produced by the edge of the ultra-relativistic electron beam when we take the transverse size of the beam into account. Simulations have been made by using the Wakefield Solver of CST Particle Studio. And the result of this influence at different ratio of beam horizontal width σ and the BPM inner diameter a has been obtained. This kind of influence has been observed in the stripline BPMs in the transfer line of Beijing Positron Electron Colliders upgraded version II (BEPCII). The research is useful when we design the inner diameter of the stripline BPMs for ultra-relativistic electron beam, meanwhile it provides reference to distinguish the invalid ones from the measuring results obtained by the stripline BPMs in the ultra-relativistic situation.

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MOPMB037

Beam Position Monitor Design for Dielectric Wakefield Accelerator In THz Range

dipole, simulation, polarization, controls

171

Q. Gao, H.B. Chen, J. Shi
TUB, Beijing, People's Republic of China
W. Gai
ANL, Argonne, Illinois, USA
C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA

Dielectric based collinear wakefield accelerator have been broadly selected for the THz accelerator due to its simplicity. In order to move the THz accelerators from the current exploratory research into the practical phase, certain common accelerator components are indispensable. Beam Position Monitor (BPM) is one of them. However, most of conventional BPM techniques are hardly scaled down to THz regime. Here we propose a BPM design which uses the dominant dipole mode excited in the dielectric wakefield accelerators to extract information of the beam position.

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MOPMW015

Wakefields Studies of High Gradient X-band Accelerating Structure at SINAP

impedance, simulation, cavity, FEL

429

X.X. Huang, W. Fang, Q. Gu, M. Zhang, Z.T. Zhao
SINAP, Shanghai, People's Republic of China

Shanghai compact hard x-ray free electron laser (CHXFEL)* is now proposed accompanied with a high-gradient accelerating structure, which is the trend of large scale and compact facility. This structure operated at X-band (11424 MHz) holds the promise to achieve high gradient up to 80 MV/m. However, due to its particular property, a more serious wakefields** will be generated, leading to worse beam instability effects. In this paper, the computation of this case will be carried out with simulation. Moreover, analysis and optimization will be adopted to suppress beam instability.
* C. Feng, Z. T. Zhao, Chinese Sci Bull, 2010, 55, 221-227.
** K. Bane, SLAC, NLC-Note 9, Feb. 1995.

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MOPMY026

Development of an X-Band Linearizer System for PAL-XFEL

klystron, LLRF, electron, acceleration

554

H. Heo, J. Hu, H.-S. Kang, K.H. Kim, S.H. Kim, H.-S. Lee, B.G. Oh, S.S. Park, Y.J. Park, Y.J. Suh
PAL, Pohang, Kyungbuk, Republic of Korea

We developed an X-band RF system for the linear bunch compression in the PAL-XFEL. We installed a SLAC X-band accelerating structure on a precise mover stage and applied RF power by using a SLAC XL-4 11.424 GHz klystron driven by an inverter charging type modulator. We are developing a solid state amplifier controlled by an X-band LLRF system instead of using a TWTA as a driving RF source for the klystron. We present and discuss the recent test results of the system.

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MOPOR002

Impedance Simulations and Measurements for ThomX Storage Ring

impedance, simulation, interface, storage-ring

586

A.R. Gamelin, C. Bruni, V. Chaumat, D. Le Guidec, P. Lepercq, R. Marie
LAL, Orsay, France

Funding: Work is supported by ANR-10-EQPX-51, by grants from Région Ile-de-France, IN2P3 and Pheniics Doctoral School
ThomX is a compact Compton Backscattering Source (CBS) which is being built at LAL, Orsay, France. ThomX ring has a short circumference of 18 m and a design energy of 50 MeV. Due to the low energy of the beam and in order to avoid beam degradation it is important to evaluate the ring components impedance. A CST Particle Studio impedance simulation of the different components of the ring (BPM, bellows, optical chamber, etc.) is under way. It will be followed by a bench measurement of the longitudinal and transverse impedance using the coaxial wire method. This paper will detail the preliminary results of the ThomX storage ring impedance simulations and the measurement principle we will use.

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MOPOR005

Longitudinal Wakefields in the Undulator Section of SXFEL User Facility

undulator, FEL, vacuum, electron

595

M. Song, H.X. Deng, C. Feng, D. Huang, B. Liu, D. Wang
SINAP, Shanghai, People's Republic of China

Shanghai soft x-ray free electron laser (SXFEL) user facility based on multi-stage seeded-FEL and self-amplified spontaneous emission (SASE) is recently proposed, which is aiming at generating 4-2nm fully-coherent, high-brightness FEL pulse. In this paper, the wakefields arise from the resistive wall and surface roughness in the vacuum chamber is obtained by theoretical models*. And the computations of geometric wakefields are carried out using ABCI**. According to the tracked beam profile, the overall wakefields in the undulator section of SXFEL user facility are presented.
* K. Bane, G. Stupakov, SLAC-PUB-15951, May 2014.
** ABCI website: http://abci.kek.jp/abci.htm

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MOPOW004

Electron Trajectory Caustic Formation Resulting in Current Horns present in Bunch Compression

electron, FEL, linac, simulation

708

T.K. Charles, D.M. Paganin
Monash University, Faculty of Science, Clayton, Victoria, Australia
M.J. Boland, R.T. Dowd
SLSA, Clayton, Australia

Current horns are ubiquitous in Free Electron Laser (FEL) bunch compression. In this paper, we analyse the formation of these current spikes and identify the cause as caustic formation in the electron trajectories. We also present a possible solution to avoid or mitigate the current horns from developing through using optical linearization.

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MOPOW044

Commissioning of the RadiaBeam / SLAC Dechirper

electron, photon, controls, alignment

809

M.W. Guetg, K.L.F. Bane, A. Brachmann, A.S. Fisher, Z. Huang, R.H. Iverson, P. Krejcik, A.A. Lutman, T.J. Maxwell, A. Novokhatski, G. Stupakov, J. Zemella, Z. Zhang
SLAC, Menlo Park, California, USA
M.A. Harrison, M. Ruelas
RadiaBeam Systems, Santa Monica, California, USA
J. Zemella
DESY, Hamburg, Germany
Z. Zhang
TUB, Beijing, People's Republic of China

We present results on the commissioning of the two-module RadiaBeam / SLAC dechirper system at LCLS. This is the first installation and measurement of a corrugated dechirper at high energy (4.4 - 13.3 GeV), short pulses (< 200 fs) and while observing its effect on an operational FEL. Both the transverse and longitudinal wakefields allow more flexible electron beam tailoring. We verify that, for a single module at a given gap, the strength of the longitudinal wake on axis and the dipole near the axis agree well with the theoretical values. Using direct longitudinal phase space mapping and X-ray FEL spectrum measurements we demonstrate the energy chirp control capabilities.

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MOPOW046

RadiaBeam/SLAC Dechirper as a Passive Deflector

electron, lattice, focusing, diagnostics

817

A. Novokhatski, A. Brachmann, M. Dal Forno, V.A. Dolgashev, A.S. Fisher, M.W. Guetg, Z. Huang, R.H. Iverson, P. Krejcik, A.A. Lutman, T.J. Maxwell
SLAC, Menlo Park, California, USA
J. Zemella
DESY, Hamburg, Germany

Funding: This work was supported by Department of Energy Contract No. DE-AC02-76SF00515.
We discuss the possibility of using the RadiBeam/SLAC dechirper recently installed at LCLS for measuring the bunch length of very short bunches, less than 1 fs perhaps as short as 100 atto second. When a bunch travels close to one of the jaws the particles of the bunch get a transverse kick depends upon the position of a particle in a bunch. The tail particles get more kick. The transverse force also gets a nonlinear dependence on the transverse position. The stretched bunch can be measured at the YAG screen that is 100 m downstream the dechirper. The most important aspect of this measurement is that that no synchronization is needed. The Green's function for the transverse kick was evaluated based on the precise wake field calculations of the dechirper corrugated structure*. Using this function we can restore the longitudinal shape of the bunch. This may also help to see if a bunch has any micro-bunch structure.
* A. Noovokhatski "Wakefield potentials of corrugated structures",Phys. Rev. ST Accel. Beams 18, 104402 (2015)

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TUOAB01

Optimization of the Dechirper for Electron Bunches of Arbitrary Longitudinal Shapes

electron, simulation, controls, dipole

1054

J.M. Seok, M. Chung
UNIST, Ulsan, Republic of Korea
J.H. Han, J.H. Hong, H.-S. Kang
PAL, Pohang, Kyungbuk, Republic of Korea

Dechirper is a passive device composed of a vacuum chamber of two corrugated, metallic plates with an adjustable gap. By introducing a small offset in the dechirper with respect to the reference axis, one might generate transverse wakefields and use the dechirper as a deflector. Understanding the interactions between electron beams of various longitudinal shapes with the wakefields generated by the dechirper is important to assess the feasibility of the dechirper for use as a deflector. Recently, using a set of alpha-BBO crystals, shaping of laser pulses and electron bunches on the order of ps is tested at the Injector Test Facility (ITF) of Pohang Accelerator Laboratory (PAL). Furthermore, we have investigated propagation of electron bunches of arbitrary longitudinal shapes through the dechirper. In the numerical simulations, we observed that the arbitrary electron beams were successful deflected except for lethal beam shape problems. Hence, in this work, we study optimization of the dechirper for electron bunches of arbitrary longitudinal shapes, using analytical theory and numerical simulations with the ASTRA and ELEGANT codes.

Slides TUOAB01 [1.631 MB]

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TUOBB01

Demonstration of Current Profile Shaping using Double Dog-Leg Emittance Exchange Beam Line at Argonne Wakefield Accelerator

emittance, quadrupole, dipole, experiment

1065

G. Ha, M.-H. Cho, W. Namkung
POSTECH, Pohang, Kyungbuk, Republic of Korea
M.E. Conde, D.S. Doran, W. Gai, G. Ha, K.-J. Kim, W. Liu, J.G. Power, Y.-E. Sun, C. Whiteford, E.E. Wisniewski, A. Zholents
ANL, Argonne, Illinois, USA
C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA
P. Piot
Fermilab, Batavia, Illinois, USA

Emittance exchange (EEX) based longitudinal current profile shaping is the one of the promising current profile shaping technique. This method can generate high quality arbitrary current profiles under the ideal conditions. The double dog-leg EEX beam line was recently installed at the Argonne Wakefield Accelerator (AWA) to explore the shaping capability and confirm the quality of this method. To demonstrate the arbitrary current profile generation, several different transverse masks are applied to generate different final current profiles. The phase space slopes and the charge of incoming beam are varied to observe and suppress the aberrations on the ideal profile. We present current profile shaping results, aberrations on the shaped profile, and its suppression.

Slides TUOBB01 [5.032 MB]

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TUPMY025

Proton-Driven Electron Acceleration in Hollow Plasma

plasma, electron, proton, acceleration

1601

Y. M. Li, K. Hanahoe, O. Mete Apsimon, T.H. Pacey, G.X. Xia
UMAN, Manchester, United Kingdom

Funding: President's Doctoral Scholar Award from The University of Manchester.
Proton driven plasma wakefield acceleration has been proposed to accelerate electrons to TeV-scale in a single hundreds of meters plasma section. However, it is difficult to conserve beam quality due to the positively charged driven scheme. In this paper, we demonstrate via simulation that hollow plasma is favourable to maintain the long and stable acceleration and simultaneously be able to achieve low normalized emittance and energy spread of the witness electrons. Moreover, it has much higher beam loading tolerance compared to the uniform case. This will potentially facilitates the acceleration of a large number of particles with high beam quality.
* Caldwell A et al.Nature Physics, 2009, 5(5): 363-367
** K. Lotov, Phys. Rev. ST Accel. Beams, 2010, 13(4): 041301.
*** W. Kimura et al., Phys. Rev. ST Accel. Beams, 2011, 14(4): 041301.

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TUPMY028

Ultra-high Gradient Acceleration in Nano-crystal Channels

electron, plasma, laser, acceleration

1607

Y.-M. Shin
Northern Illinois University, DeKalb, Illinois, USA
D.M. Farinella, P. Taborek, T. Tajima
UCI, Irvine, California, USA
A.H. Lumpkin, V.D. Shiltsev, R.M. Thurman-Keup
Fermilab, Batavia, Illinois, USA
X. Zhang
Shanghai Institute of Optics and Fine Mechanics, Shanghai, People's Republic of China

Funding: This work was supported by the DOE contract No.DEAC02-07CH11359 to the Fermi Research Alliance LLC. We also thank the FAST Department team for the helpful discussions and technical support.
Crystals behave like a non-equilibrium medium (e.g. plasma), but at a relatively low temperature, if heated by a high-power driving source. The warm dense matter contains many more ions (n0 ~ 10¹⁹ - 10²³ cm^-3) available for plasma acceleration than gaseous plasmas, and can possibly support electric fields of up to 30 TV/m of plasma oscillation*,**,***,****. Atomic lattice spaces in solid crystals are known to consist of 10 - 100 V/Å potential barriers capable of guiding and collimating high energy particles with continuously focused acceleration. Nanostructured crystals (e.g. carbon nanotube) with dimensional flexibilities can accept a few orders of magnitude larger phase-space volume of channeled particles than natural crystals. Our PIC simulation results*****, ****** obtained from two plasma acceleration codes, VORPAL and EPOCH, indicate that in the linear regime the beam-driven and laser-driven electrons channeled in a 100 micro-meter long effective nanotube gain 10 MeV (G = 1 - 10 TeV/m). Experimental tests, including slit-mask beam modulation and pump-probe electron diffraction, are designed in Fermilab and NIU to identify a wakefield effect in a photo-excited crystal.
* Phys. Rev.Lett. 43, 267(1979)
** Phys. Plasmas 15, 103105(2008)
*** Nature Photonics 9, 274(2015)
**** Phys. J. 223, 1037(2014)
***** Appl. Phys. Lett. 105, 114106(2014)
****** Phys. Plasmas 20, 123106(2013)

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TUPMY036

Drive Generation and Propagation Studies for the Two Beam Acceleration Experiment at the Argonne Wakefield Accelerator

kicker, laser, simulation, power-supply

1629

N.R. Neveu, M.E. Conde, D.S. Doran, W. Gai, G. Ha, C.-J. Jing, W. Liu, J.G. Power, D. Wang, C. Whiteford, E.E. Wisniewski
ANL, Argonne, Illinois, USA
S.P. Antipov, C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA
G. Ha
POSTECH, Pohang, Kyungbuk, Republic of Korea
N.R. Neveu
IIT, Chicago, Illinois, USA
D. Wang
TUB, Beijing, People's Republic of China

Funding: Work supported by by the U.S. Department of Energy under contract No. DE-AC02-06CH11357.
Simplified staging in a two beam accelerator (TBA) has been accomplished at the Argonne Wakefield Accelerator (AWA) facility. This layout consists of a drive beamline and witness beamline operating synchronously. The drive photoinjector linac produces a 70 MeV drive bunch train of eight electron bunches (charge per bunch between 5-40 nC) that pass through decelerating structures in each TBA stage. The witness linac produces an 8 MeV witness bunch that passes through the accelerating structures in each TBA stage. Recent effort has been focused on improving the uniformity of the UV laser pulses that generate the bunch trains. Current work at the AWA is focused on the transition from simplified staging to full staging. A kicker will be designed and installed to direct bunch trains to one TBA stage only. Preliminary calculations and simulation results are presented.

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TUPOR013

Analysis of Multi-bunch Instabilities at the Diamond Storage Ring

impedance, damping, storage-ring, simulation

1685

R. Bartolini, R.T. Fielder, G. Rehm
DLS, Oxfordshire, United Kingdom
V.V. Smaluk
BNL, Upton, Long Island, New York, USA

We present recent results of analytical, numerical and experimental analysis of multi-bunch instabilities at the Diamond storage ring. The works compares the impedance estimates from numerical modelling with the analysis of the growth rates of the excited multi-bunch modes in different machine configurations. The contribution of a number of wakefield sources has been identified with very high precision thanks to high quality data provided by the existing Transverse multi-bunch feedback diagnostics

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TUPOW017

Twin Bunches at the FACET-II

simulation, electron, acceleration, controls

1778

Z. Zhang
TUB, Beijing, People's Republic of China
M.J. Hogan, Z. Huang, A. Marinelli
SLAC, Menlo Park, California, USA

Twin electron bunches, generated, accelerated and compressed in the same acceleration bucket, have attracted a lot of interest in the free-electron lasers and wakefield acceleration. The recent successful experiment at the LCLS used twin bunches to generate two-color two x-ray pulses with tunable time delay and energy separation. In this note, we apply the twin bunches to the plasma wakefield acceleration. Numerical simulations show that based on the beamline of the FACET-II, we can generate high-intensity two electron bunches with time delay from ∼ 100 fs to picoseconds, which will benefit the control of high-gradient witness bunch acceleration in a plasma.

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TUPOW030

A CW Normal Conducting RF Cavity for Fast Chirp Control in the LCLS-II

linac, cavity, controls, FEL

1817

M.H. Nasr, P. Emma, S.G. Tantawi
SLAC, Menlo Park, California, USA

The LCLS-II is a high repetition-rate Free-Electron Laser (FEL) facility under construction at SLAC. A new 4-GeV continuous wave (CW) superconducting (SC) L-band linac is being built to provide an electron bunch rate of up to 1 MHz, with bunches rapidly switched between two FEL undulators. It is desirable to provide peak current (i.e., pulse length) control in each FEL independently by varying the RF phase (chirp) prior to the first bunch compressor. However, the high-Q, SCRF, with its 1-ms fill-time, cannot be changed within one bunch spacing (1 us). So to provide a small chirp adjustment from bunch to bunch, we propose a short CW copper RF accelerating cavity, located just after the injector, with < 250-ns fill-time designed to adjust the beam chirp at zero-crossing phase. We examined RF cavity designs spanning RF frequencies from L-band to X-band. We considered both SW and TW structures. We found an optimal solution with 2 cm iris diameter, SW RF cavity, operating at C-band with input power of only 10 kW. If one can afford to operate with smaller diameter, from a wakefield point of view, then similar structure at X-band may require only 500 W with 5 mm iris diameter.

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TUPOW033

Status of the BERLinPro Main Linac Module

linac, cavity, HOM, simulation

1823

H.-W. Glock, A. Frahm, J. Knobloch, A. Neumann
HZB, Berlin, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of the Helmholtz Association
Beam operation of the BERLinPro energy recovery linac project, whose construction is under way, will initially start using the photoinjector and booster modules. In a second step the recirculation beam line and the main linac module will be added. Here the current design status of the main linac module is described. Results of wake field simulations are compared for different set ups. We also report on the manufacturing aspects including the design of the waveguide groups needed for HOM damping and the choice of flange-gasket-pairings appropriate for rectangular waveguides. Also mechanical considerations are included.

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WEPMR037

Wakefield Analysis of the 56 MHz SRF Cavity

cavity, impedance, HOM, SRF

2354

Q. Wu, Y. Hao
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The 56 MHz SRF cavity is a superconducting quarter-wave resonator installed in the common section of RHIC. Both beams share the cavity in an interwoven pattern over the entire store. The wake field excited in the cavity is the superposition of the two opposing bunches. This paper will discuss the wake field excited by both beams, and the higher order mode power as a result of the excited field.

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WEPMY006

A High Transformer Ratio Scheme for PITZ PWFA Experiments

plasma, laser, acceleration, simulation

2551

G. Loisch, M. Groß, H. Huck, A. Oppelt, Y. Renier, F. Stephan
DESY Zeuthen, Zeuthen, Germany
A. Aschikhin, A. Martinez de la Ossa, J. Osterhoff
DESY, Hamburg, Germany
M. Hochberg, M. Sack
KIT, Karlsruhe, Germany

In the field of plasma wakefield acceleration (PWFA) significant progress has been made throughout the recent years. However, an important issue in building plasma based accelerators that provide particle bunches suitable for user applications will be a high transformer ratio, i.e. the ratio between maximum accelerating field in the witness and maximum decelerating fields in the driver bunch. The transformer ratio for symmetrical bunches in an overdense plasma is naturally limited to 2*. Theory and simulations show that this can be exceeded using asymmetrical bunches. Experimentally this was proven in RF-structures**, but not in PWFA. To study transformer ratios above this limit in the linear regime of a plasma wake, an experimental scheme tailored to the unique capabilities of the Photoinjector Test Facility Zeuthen PITZ, a 20-MeV electron accelerator at DESY, is being investigated. This includes analytical plasma wakefield calculations, numerical simulations of beam transport and plasma wakefields, as well as preparatory studies on the photocathode laser system and the plasma sources.
* K. L. F. Bane, P. B. Wilson and T. Weiland, AIP Conference Proceedings 127, p. 875, 1984
** C. Jing et al., Physical Review Letters 98, 144801, 2007

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WEPMY008

Towards Awake Applications: Electron Beam Acceleration in a Proton Driven Plasma Wake

plasma, electron, proton, acceleration

2557

E. Adli
University of Oslo, Oslo, Norway

The first phases of the AWAKE experiment will study the wake structure and the potential for electron acceleration in a self-modulated proton driver. In AWAKE Run 2, expected to start after the LHC Long Shut Down 2, electron beam acceleration will be studied. Using a single proton driver and a long acceleration stage, an electron bunch will be accelerated to high energies. Demonstrating beam quality preservation and scalable plasma sources will be a significant step towards using proton driven plasma for applications. We report on the plans and preparations for AWAKE Run 2.

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WEPMY016

Development of RF System for Measuring Plasma Density Modulation of Proton Beam-driven Plasma Wakefield

plasma, simulation, proton, focusing

2582

S.Y. Kim, M. Chung
UNIST, Ulsan, Republic of Korea

Proton beam-driven plasma wakefield acceleration technique using the proton beam of Super Proton Syn-chrotron (SPS) at CERN has been actively researched these days. Plasma density modulation due to the proton beam will generate high-gradient's electric field within the modulated plasma. The key role is Self-Modulation Instability (SMI) of the long proton beam. To understand SMI phenomena, we have studied RF system such as heterodyne system for measuring modulated plasma den-sity caused by the SMI. In this work, we design the details of the RF system and optical system of focusing millimetre-sized electromagnetic wave using CODE V and plasma-electromagnetic wave interactions using simulation tools.

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WEPMY017

Numerical Studies of Self Modulation Instability in the Beam-driven Plasma Wakefield Experiments

plasma, proton, electron, simulation

2585

K. Moon, M. Chung
UNIST, Ulsan, Republic of Korea

Proton beam-driven plasma wakefield acceleration was recently proposed as a way to bring electrons to TeV energy range in a single plasma section. When the ultra-relativistic long proton beam propagates into the plasmas, this bunch splits into many small bunches. This phenomenon is known as a Self-Modulation Instability (SMI), and its characteristics depend on the ratio of bunch length and plasma wavelength. In this study, we first introduce a Particle-In-Cell (PIC) code WARP, focusing on the basis of parallel version structure. Through numerical simulations using the WARP, we investigate the characteristics of the SMI and propose possible experimental setup at the Injector Test Facility (ITF) of Pohang Accelerator Laboratory (PAL). Also, we present dependencies of the witness beam quality on both the driver beam and plasma parameters.

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WEPMY019

AWAKE, the Advanced Proton Driven Plasma Wakefield Acceleration Experiment

plasma, laser, electron, experiment

2588

P. Muggli
MPI, Muenchen, Germany
C. Bracco
CERN, Geneva, Switzerland

The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) aims at studying plasma wakefield generation and electron acceleration driven by proton bunches. It is a proof-of-principle R&D experiment at CERN and the world's first proton driven plasma wakefield acceleration experiment. The AWAKE experiment is currently being installed in the former CNGS facility and will use the 400 GeV/c proton beam bunches from the SPS to drive the wakefields in the plasma. The first experiments will focus on the self-modulation instability of the long (rms ~12 cm) proton bunch in the plasma. These experiments are planned for the end of 2016. Later, in 2017/2018, low energy (~15 MeV) electrons will be externally injected to sample the wakefields and be accelerated with GeV/m gradients. The main goals of the experiment will be summarized. A summary of the AWAKE design and construction status will be presented.

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WEPMY021

Beam-Plasma Interaction Simulations for the AWAKE Experiment at CERN

plasma, proton, experiment, electron

2596

A.V. Petrenko, E. Gschwendtner, G. Plyushchev, M. Turner
CERN, Geneva, Switzerland
K.V. Lotov
BINP SB RAS, Novosibirsk, Russia
K.V. Lotov, A. Sosedkin
NSU, Novosibirsk, Russia
G. Plyushchev
EPFL, Lausanne, Switzerland
M. Turner
TUG/ITP, Graz, Austria

The AWAKE experiment at CERN will be the first proof-of-principle demonstration of the proton-driven plasma wakefield acceleration using the 400 GeV proton beam extracted from the SPS accelerator. The plasma wakefield will be driven by a sequence of sub-millimeter long micro-bunches produced as a result of the self-modulation instability (SMI) of the 12 cm long SPS proton bunch in the 10 m long rubidium plasma with a density corresponding to the plasma wavelength of around 1 mm. A 16 MeV electron beam will be injected into the developing SMI and used to probe the plasma wakefields. The proton beam self-modulation in a wide range of plasma densities and gradients have been studied in detail via numerical simulations. A new configuration of the AWAKE experiment with a small plasma density step is proposed.

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WEPMY022

Homogeneous Focusing of Train of Short Relativistic Electron Bunches by Plasma Wakefield

focusing, plasma, electron, simulation

2599

V.I. Maslov, I.N. Onishchenko
NSC/KIPT, Kharkov, Ukraine
I.P. Levchuk (Yarovaya)
KhNU, Kharkov, Ukraine

The focusing of bunches by wakefield, excited in plasma by resonant sequence of relativistic electron bunches (repetition frequency of the bunches coincides with the plasma frequency), is inhomogeneous. In this paper we investigate wakefield plasma lens, in which all bunches of sequence are focused identically and uniformly, for short relativistic electron bunches. For this it is necessary that the charge of 1-st bunch is smaller in determined times than the charges of the other bunches, the interval between back front of 1-st bunch and 1-st front of 2-nd bunch equals determined value, the interval between back front of N-th bunch and 1-st front of (N+1)-th bunch for all other bunches is multiple to excited wavelength. It is shown that only 1-st bunch is in finite Ez≠0. Other bunches are in zero longitudinal electrical wakefield. Hence the 1-st bunch interchange by energy with wakefield. The subsequent bunches don't interchange by energy with wakefield and the amplitude of wakefield doesn't change along sequence. Radial wake force Fr in regions, occupied by bunches, is approximately constant along bunches.

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WEPMY023

Self-focusing and Wakefield-focusing of Relativistic Electron Bunches in Plasma

focusing, plasma, electron, space-charge

2602

V.I. Maslov, I.P. Levchuk (Yarovaya), I.N. Onishchenko
NSC/KIPT, Kharkov, Ukraine

It was shown that at the wakefield excitation by electron bunch, the length of which is equal to half of the wavelength, the ratio of wakefield focusing to self-focusing is large at the end of the bunch, the shape of which is such that it falls from the current maximum value in the head of the bunch to zero at the end of the bunch. However, the ratio of wakefield focusing to self-focusing tends to zero at the end of the bunch, if the current increases along the bunch from zero in the head of the bunch to a maximum value at the end of the bunch. In the case of homogeneous bunch with sharp edges, the length of which is several plasma wavelength, the self-focusing force Fs is constant along the bunch, and wakefield force of focusing changes from -Fs to Fs. In the case of homogeneous bunch with precursor of half current and length, equal to half of wavelength, focusing of bunch is determined by the homogeneous self-focusing force and wakefield focusing force equals zero. Cases of rectangular and Gaussian bunches, the length of which is equal to half of wavelength, also were considered.

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WEPMY025

iMPACT, Undulator-Based Multi-Bunch Plasma Accelerator

plasma, undulator, electron, simulation

2609

O. Mete Apsimon, K. Hanahoe, G.X. Xia
UMAN, Manchester, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
B. Hidding
USTRAT/SUPA, Glasgow, United Kingdom
J.D.A. Smith
Tech-X, Boulder, Colorado, USA

Funding: This work is supported by the Cockcroft Institute Core Grant and STFC.
The accelerating gradient measured in laser or electron driven wakefield accelerators can be in the range of 10-100GV/m, which is 2-3 orders of magnitude larger than can be achieved by conventional RF-based particle accelerators. However, the beam quality preservation is still an important problem to be tackled to ensure the practicality of this technology. In this global picture, the main goals of this study are planning and coordinating a physics program, the so-called iMPACT, that addresses issues such as emittance growth mechanisms in the transverse and longitudinal planes through scattering from the plasma particles, minimisation of the energy spread and maximising the energy gain while benchmarking the milestones. In this paper, a summary and planning of the project is introduced and initial multi-bunch simulations were presented.

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WEPMY027

Feasibility Study of Plasma Wakefield Acceleration at the CLARA Front End Facility

plasma, experiment, simulation, accelerating-gradient

2617

K. Hanahoe, R.B. Appleby, Y. M. Li, T.H. Pacey, G.X. Xia
UMAN, Manchester, United Kingdom
B. Hidding
USTRAT/SUPA, Glasgow, United Kingdom
B. Kyle
University of Manchester, Manchester, United Kingdom
O. Mete Apsimon
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
J.D.A. Smith
Tech-X, Boulder, Colorado, USA

Funding: Cockcroft Institute Core Grant and STFC
Plasma wakefield acceleration has been proposed at the CLARA Front End (FE) facility at Daresbury Laboratory. The initial phase of the experiment will acceleration of the tail of a single electron bunch, and the follow-up experiment will study preserving a high quality beam based on a two-bunch acceleration scenario. In this paper, a concept for the initial experiment is outlined and detailed simulation results are presented.

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WEPOR016

Pre-alignment of Accelerating Structures for Compact Acceleration and High Gradient using In-situ Radiofrequency Methods

alignment, dipole, linac, electromagnetic-fields

2696

N. Galindo Munoz, N. Catalán Lasheras, A. Grudiev
CERN, Geneva, Switzerland
V.E. Boria
DCOM-iTEAM-UPV, Valencia, Spain
A. Faus-Golfe
IFIC, Valencia, Spain

Funding: PACMAN is founded under the European Union's 7th Framework Program Marie Curie Actions, grant PITN-GA-2013-606839
To achieve a high accelerating gradient of 100 MV/m, the CLIC project under study at CERN uses a 23 cm long tapered normal-conducting travelling wave Accelerating Structure (AS) operating at 12 GHz. Minimisation of the long-range wakefields (WF) is assured by damping of the HOM through four radial waveguides in each cell without distorting the accelerating mode. As an extension of them, there are four bent waveguides called WF monitors (WFM) in the middle cell with two RF pick-ups. To obtain a small beam emittance in the collision point, micro-metric pre-alignment of the AS is required. We work to find the electrical centre of the AS through the use of the asymmetry in the RF scattering parameters created by an off-centre conductive wire, stretched along the axis. The accuracy required is of 7 μm with a resolution of 3.5 μm for the WFM signals including the acquisition electronics. Our simulations have shown that a resolution of 1 μm is possible using a calibrated VNA. Measurement results and improvements of the final accuracy will be presented and discussed.

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WEPOY025

High Power RF Generation From a W-Band Corrugated Structure Excited by a Train of Electron Bunches

electron, experiment, simulation, acceleration

3040

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, G. Ha, W. Liu, J.G. Power, E.E. Wisniewski
ANL, Argonne, Illinois, USA
V.A. Dolgashev
SLAC, Menlo Park, California, USA

We report on the generation of multi-megawatt peak RF power at 91textGHz, using an ultrarelativistic electron bunch train to excite electromagnetic fields in a high-impedance metallic corrugated structure. This device can be used as a power source for high gradient acceleration of electrons. To achieve precise control of the wakefield phase, a long range wakefield interferometry method was developed in which the RF energy due to the interference of the wakefields from two bunches was measured as a function of the bunch separation.

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WEPOY026

Simulation and Measurement of the Beam Breakup Instability in a W-band Corrugated Structure

dipole, electron, simulation, radiation

3044

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

The corrugated wakefield structure has wide application in electron beam energy manipulation and high frequency RF radiation generation. The transverse wakefield which cause beam breakup (BBU) instability is excited when the drive beam is not perfectly centered through the structure. Here we report on the numerical and experimental investigation of the BBU effect in a W-band corrugated structure, for both cases of short range wakefield and long range wakefield. In the numerical part we develop a point to point (P2P) code that allows rapid and efficiency simulations of the beam dynamics effect by wakefield, which is based on the the particle-wake function coupled dynamics equation of motion. And the experimental measurements of BBU effect are found to be in good agreement with the simulations.

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THPPA01

Demonstration of the Hollow Channel Plasma Wakefield Accelerator

plasma, positron, laser, acceleration

3202

S.J. Gessner, J.M. Allen, C.I. Clarke, J.-P. Delahaye, J.T. Frederico, S.Z. Green, C. Hast, M.J. Hogan, N. Lipkowitz, M.D. Litos, B.D. O'Shea, D.R. Walz, V. Yakimenko, G. Yocky
SLAC, Menlo Park, California, USA
E. Adli, C.A. Lindstrøm
University of Oslo, Oslo, Norway
W. An, C.E. Clayton, C. Joshi, K.A. Marsh, W.B. Mori, N. Vafaei-Najafabadi
UCLA, Los Angeles, California, USA
S. Corde, A. Doche
LOA, Palaiseau, France
W. Lu
TUB, Beijing, People's Republic of China

Funding: Work supported by DOE contract DE-AC02-76SF00515.
Over the past decade, there has been enormous progress in the field of beam and laser-driven plasma acceleration of electron beams. However, in order for plasma wakefield acceleration to be useful for a high-energy e⁺e^- collider, we need a technique for accelerating positrons in plasma as well. This is a unique challenge, because the plasma responds differently to electron and positron beams, with plasma electrons being pulled through the positron beam and creating a non-linear focusing force. Here, we demonstrate a technique called hollow channel acceleration that symmetrizes the wakefield response to beams of either charge. Using a transversely shaped laser pulse, we create an annular plasma with a fixed radius of 200 μm. We observe the acceleration of a positron bunch with energies up to 33.4 MeV in a 25 cm long channel, indicating an effective gradient greater than 100 MeV/m. This is the first demonstration of a technique that way be used for staged acceleration of positron beams in plasma.

Slides THPPA01 [5.647 MB]

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPPA01

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THPOR030

Commissioning and First Performance Studies of a Single Vertical Beam Halo Collimation System at ATF2

background, photon, collimation, simulation

3844

N. Fuster-Martínez, A. Faus-Golfe
IFIC, Valencia, Spain
P. Bambade, A. Faus-Golfe, S. Wallon, R.J. Yang
LAL, Orsay, France
K. Kubo, T. Okugi, T. Tauchi, N. Terunuma
KEK, Ibaraki, Japan
I. Podadera, F. Toral
CIEMAT, Madrid, Spain
T. Tauchi, N. Terunuma
Sokendai, Ibaraki, Japan

A single vertical beam halo collimation system has been installed in the ATF2 beamline to reduce the background that could limit the precision of the diagnostics located in the post-IP beamline. On this paper the commissioning and first performance studies of a single vertical beam halo collimation system are reported. Furthermore realistic efficiency studies have been done using the simulation code BDSIM and compared with the first experimental tests.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR030

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FRXCB01

Two Beam Wakefield Acceleration at Argonne Wakefield Accelerator Facility

acceleration, experiment, electron, laser

4258

W. Gai
ANL, Argonne, Illinois, USA

Structure based wakefield acceleration provides a viable approach capable of accelerating a sufficient electrons and positrons in a substantially high graident needed to meet the luminosity, efficiency, and cost requirements of a future linear collider. The short pulse Two Beam wakefield Acceleration (TBA) studied at the Argonne Wakefield Accelerator Facility is aimed to pave the way toward the next linear collider. Here we present the latest results including the 100MeV/m of the single stage TBA and the staged TBA in which a 0.5nC bunch gained equal amount of energy in two stages (~2.4 MeV per stage, corresponding to an average acceleration gradient ~70 MeV/m). The technique is scalable to a staged-acceleration at 200-300MeV/m by using a GeV-scale drive beam. Such a development will considerably reduce both cost and footprint of a future high-energy physics collider as well as future X-Ray light source.

Slides FRXCB01 [11.937 MB]

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-FRXCB01

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