IPAC2016 - Classification: 03 Alternative Particle Sources and Acceleration Techniques / A22 Plasma Wakefield Acceleration

Paper	Title	Page
MOYBA01	Limits and Possibilities of Laser Wakefield Accelerators	16
	W. Leemans LBNL, Berkeley, California, USA
	This presentation provides an outlook into the future of laser-driven plasma wakefield accelerators. What has been achieved, what more is possible and what are the limits.
	Slides MOYBA01 [43.465 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOYBA01
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TUYB01	Stabilization of GeV Electron Beams by Coherent Control of LWFA Process
	H.T. Kim APRI-GIST, Gwangju, Republic of Korea
	Laser-driven compact particle accelerators have been one of the hottest research topics owing to the potential to overcome the limitations on conventional accelerators. Recently, advancement of laser technology has enabled the generation of PW pulses, which is opening the door to the new regime of laser-particle accelerations. In this talk, the author presents a new method to stabilize multi-GeV electron beams by manipulating the spectral phase of PW laser pulses, coherently controlling the laser wake-field acceleration process. They have demonstrated the stable generation of 2-GeV electron beams in a 1-cm gas cell of He using the PW Ti:Sapphire laser system.
	Slides TUYB01 [11.602 MB]
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TUOBB03	CERN AWAKE Facility Readiness for First Beam	1071
	C. Bracco, M. Bernardini, A.C. Butterworth, H. Damerau, S. Döbert, V. Fedosseev, E. Feldbaumer, E. Gschwendtner, W. Höfle, A. Pardons, E.N. Shaposhnikova, H. Vincke CERN, Geneva, Switzerland
	The AWAKE project at CERN was approved in August 2013 and since then a big effort was made to be able to probe the acceleration of electrons before the "2019-2020 Long Shutdown". The next steps in this challenging schedule will be a dry run of all the beam line systems, at the end of the HW commissioning in June 2016, and the first proton beam sent to the plasma cell one month later. The current status of the project is presented together with an outlook over the foreseen works for operation with electrons in 2018.
	Slides TUOBB03 [10.682 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUOBB03
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WEPMB049	Transverse Defocusing Study in LPWA Channel for Linear and Bubble Modes	2224
	S.M. Polozov, V.I. Rashchikov, Ya.V. Shashkov MEPhI, Moscow, Russia
	Laser plasma wakefield acceleration (LPWA) is one of most popular novel trends of acceleration. The LPWA has two serous disadvantages as very high energy spread and low part of electrons capturing into acceleration. The waveguide and klystron type beam pre-modulation schemes was proposed , * to growth capturing and to limit the energy spectrum of 2-3 % for 200-300 MeV beam. One interesting effect was detected due to numerical simulation of beam dynamics in plasma channel. Not captured electrons are escape to the channel border fast and this effect should be explained. It was shown that such effect is caused by effective potential function which forms very high defocusing transverse field after its trailing edge. The results of such explanation verified by numerical simulations are discussed in report for linear and bubble LPWA modes. * S.M. Polozov. NIM A, 729, p.517-521, 2013 ** S.M. Polozov. Problems of Atomic Science and Technology. Series: Nuclear Physics Investigations, 6 (88), p. 29- 34, 2013
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB049
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WEPMY003	Simulations of the Acceleration of Externally Injected Electrons in a Plasma Excited in the Linear Regime	2542
	N. Delerue, C. Bruni, S. Jenzer LAL, Orsay, France S. Kazamias, B. Lucas, G. Maynard Laboratoire de Physique des Gaz et des Plasmas, Universite Paris-Sud, Orsay, France M. Pittman CLUPS, Orsay, France
	We have investigated numerically the coupling between a 10 \si{MeV} electron bunch of high charge (§I{> 100}{pc}) with a laser generated accelerating plasma wave. Our results show that a high efficiency coupling can be achieved using a §I{50}{TW}, §I{100}{μ \meter} wide laser beam, yielding accelerating field above §I{1}{ GV/m}. We propose an experiment where these predictions could be tested.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY003
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WEPMY004	Development of an Injector and a Magnetic Transfer Line in the Framework of Cilex	2545
	A. Chancé CEA/DSM/IRFU, France T. Audet, B. Cros, P. Lee, G. Maynard Laboratoire de Physique des Gaz et des Plasmas, Universite Paris-Sud, Orsay, France M. Bougeard, S. Dobosz-Dufrénoy, A. Maitrallain CEA, Gif-sur-Yvette, France N. Delerue LAL, Orsay, France O. Delferrière, A. Mosnier, J. Schwindling CEA/IRFU, Gif-sur-Yvette, France P. Monot CEA/DSM, Gif-sur-Yvette, France A. Specka LLR, Palaiseau, France
	Funding: Investments for the Future program under reference ANR-10-EQPX-25, by the Triangle de la Physique under contract 2011-086TMULTIPLACCELE, 2012-032TELISA, and by the Labex PALM and P2IO. Laser plasma accelerators (LPAs) have proven their capability to produce accelerating gradients three orders of magnitude higher than RF cavity-based accelerators. The present challenges of LPAs are to achieve the beam quality and stability required by users and to show the feasibility of plasma staging for high-energy applications. As one of the experiments planned at the PetaWatt laser APOLLON facility, currently under construction in France, aims at testing the two-stage scheme, a dedicated plasma injector which will be used as the first stage has been developed and tested at the UHI100 facility at CEA Saclay. The electron source, as well as the beam characterization line, will be presented and the first results will be discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY004
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WEPMY005	Upgrades of the Experimental Setup for Electron Beam Self-modulation Studies at PITZ	2548
	M. Groß, J. Engel, G. Koss, O. Lishilin, G. Loisch, G. Pathak, S. Philipp, R. Schütze, F. Stephan DESY Zeuthen, Zeuthen, Germany R. Brinkmann, J. Osterhoff DESY, Hamburg, Germany F.J. Grüner CFEL, Hamburg, Germany F.J. Grüner University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany D. Richter HZB, Berlin, Germany C.B. Schroeder LBNL, Berkeley, California, USA
	The self-modulation instability is fundamental for the plasma wakefield acceleration experiment of the AWAKE collaboration at CERN where this effect is supposed to be used to generate proton bunches short enough for producing high acceleration fields. For ease of experimentation it was decided to set up a supporting experiment at the electron accelerator PITZ (Photo Injector Test facility at DESY, Zeuthen site), given that the underlying physics is the same. The goals are to demonstrate and investigate in detail the self-modulation of long electron beams. In 2015 a first set of experiments was conducted utilizing as key elements a novel cross-shaped lithium plasma cell and an ArF excimer laser for plasma generation. No self-modulation was observed yet because of various experimental shortcomings. The properties of the experimental setup were studied in detail and in this contribution we report about the upgrades which are projected to enable the observation of the self-modulation in the upcoming experimental run.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY005
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WEPMY006	A High Transformer Ratio Scheme for PITZ PWFA Experiments	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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WEPMY007	Plasma Density Profile Characterization for Resonant Plasma Wakefield Acceleration Experiment at SPARC_LAB	2554
	F. Filippi INFN-Roma1, Rome, Italy M.P. Anania, A. Biagioni, E. Chiadroni, M. Ferrario INFN/LNF, Frascati (Roma), Italy A. Cianchi INFN-Roma II, Roma, Italy F. Filippi, A. Giribono, A. Mostacci, L. Palumbo University of Rome La Sapienza, Rome, Italy F. Filippi, A. Giribono, A. Mostacci, L. Palumbo INFN-Roma, Roma, Italy A. Giribono University of Rome "La Sapienza", Rome, Italy A. Zigler The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem, Israel
	New generation of particle accelerators is based on the excitation of large amplitude plasma waves driven by either electron or laser beams, named as Plasma Wakefield Accelerator (PWFA) and Laser Wakefield Accelerator (LWFA), respectively. Future experiments scheduled at the SPARC_LAB test facility aim to demonstrate the acceleration of externally injected high brightness electron beams through both schemes. In particular, in the so-called resonant PWFA a train of more than two driver electron bunches generated with the laser comb technique resonantly excites wakefields into the plasma, the last bunch (witness) is injected at the proper accelerating phase gaining energy from the wake. The quality of the accelerated beam depends strongly on plasma density and its distribution along the acceleration length. The desired density can be achieved with a correct shaping of the capillary in which plasma is formed. The measurements of plasma density, as well as other plasma characteristics, can be performed with spectroscopic measurements of the plasma self emitted light. The measurement of density distribution for hydrogen filled capillaries is here reported.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY007
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WEPMY008	Towards Awake Applications: Electron Beam Acceleration in a Proton Driven Plasma Wake	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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WEPMY009	Transverse Tolerances of a Multi-Stage Plasma Wakefield Accelerator	2561
SUPSS034	use link to see paper's listing under its alternate paper code
	C.A. Lindstrøm, E. Adli, J. Pfingstner University of Oslo, Oslo, Norway E. Marín, D. Schulte CERN, Geneva, Switzerland
	Funding: This work is supported by the Research Council of Norway. Plasma wakefield acceleration (PWFA) provides GeV/m-scale accelerating fields, ideal for applications such as a future linear collider. However, strong focusing fields imply that a transversely offset beam with an energy spread will experience emittance growth from the energy dependent betatron oscillation. We develop an analytic model for estimating tolerances from this effect, as well as an effective simplified simulation tool in Elegant. Estimations for a proposed 1 TeV PWFA linear collider scheme indicate tight tolerances of order 40 nm and 1 μrad in position and angle respectively.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY009
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WEPMY010	Considerations for a Drive Beam Scheme for a Plasma Wakefield Linear Collider	2565
	J. Pfingstner, E. Adli, C.A. Lindstrøm University of Oslo, Oslo, Norway E. Marín, D. Schulte CERN, Geneva, Switzerland
	The potential for high average gradients makes plasma wakefield acceleration (PWFA) an attracting option for future linear colliders. For a beam-driven PWFA collider a sequence of cells has to be supplied with synchronised drive beam bunches. This paper is concerned with the generation, transport and distribution of these drive beam bunches in a so-called drive beam complex for a 3 TeV collider. Based on earlier concepts, several modifications are suggested. The new design includes a superconducting linac and an optimised bunch delay system with a tree structure. To verify the feasibility for the overall complex, a lattice design and tracking studies for the critical bending arc subsystem are presented. Also the feasibility of a compact bunch separation system is shown. The result of these efforts is a drive beam complex that is optimised for construction cost and power efficiency that favours unified lattice solutions.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY010
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WEPMY011	Compact Laser Plasma Accelerator at Peking University	2569
SUPSS033	use link to see paper's listing under its alternate paper code
	L.R.F. Li, J.E. Chen, S.C. Gao, Y.X. Geng, Q. Liao, J B. Liu, H.Y. Lu, X.Q. Yan, Y.Y. Zhao, Y.Y. Zhu PKU, Beijing, People's Republic of China Y.R. Shou Peking University, School of Physics, Beijing, People's Republic of China
	A brand new and solely accelerator based on the interaction physics of high intensity ultrafast laser and plasmas, named Compact LAser Plasma Accelerator (CLAPA), was recently built. The laser system can deliver 5J/25fs @ 800nm pulses with contrast of 10^-10. Experiments on electron acceleration is scheduled with the regime of laser wakefield acceleration. The charge and the energy spread of the accelerated electron beams will be concerned mainly. The experiments is planned with gas targets with single and dual stages. For the single stage acceleration, we will try density ramp injection and a loose focusing for a monoenergetic electron beam with more charge for some applications. With the PIC simulations and new injection methods, it is expected to generate GeV/tens pC electron beam with an energy spread of <1%. For the two stage cascaded acceleration, we will focus on the staged acceleration and control of the injection of the second stage, as well as the acceleration length of the second stage by manipulating the parameters of the gas target as well as the laser itself. The far future goal of the second plan is to develop a designable and applicable accelerators. * W.Lu, Phys. Rev.ST Accel. Beams 10.061301 （2007） J. Faure, Nature 431, 541 (2004) *J.S. Liu, Phys. Rev. Lett 107, 035001 (2011)
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY011
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WEPMY014	Feasibility Study of a Laser-Driven High Energy Electron Acceleration in a Long Up-Ramp Density	2576
	M. Kim, J. Kim, S.W. Lee, I.H. Nam, H. Suk GIST, Gwangju, Republic of Korea
	Laser-driven wakefield acceleration (LWFA) has received much attention as it can produce GeV-level high-energy electrons in cm-scale distance. However, the accelerated electron energies are still limited by several factors, especially by the dephasing problem that is caused by different velocities between the plasma wake wave and the accelerated electron beam. In order to increase the acceleration length restricted by the dephasing problem, we developed a gas-cell with density-tapering, which is realized by applying different gas pressures into two gas inlets in the gas cell. In this way, the gas density and gradient can be easily controlled in the gas cell. We used the density-tapered gas-cell for laser wakefield acceleration experiments in our laboratory with a 20 TW/40 fs Ti:sapphire laser system*. The results show that the electron energy can be significantly enhanced (about twice) with the tapered density gas-cell, compared with a uniform density conventional gas-cell. In this presentation, we show the experimental results and comparison with two-dimensional (2-D) particle-in-cell (PIC) simulation results. W. P. Leemans et al. Phy. Rev. Lett. 113, 245002 (2014). M. S. Kim et al. Appl. Phy. Lett. 102, 204103 (2013). * I. H. Nam et al. Curr. Appl. Phy. 15, 468 (2015).
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY014
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WEPMY015	Numerical Studies on Tunable Coherent Radiations with a Laser-Plasma Accelerator	2579
	J. Kim, M. Kim, I.H. Nam, H. Suk GIST, Gwangju, Republic of Korea M.S. Hur UNIST, Ulsan, Republic of Korea
	Generation of tunable coherent radiation is numerically investigated via the two-dimensional particle-in-cell (2D-PIC) code developed by UNIST* and SIMPLEX developed by Spring-8. The electron beams can be produced by the laser-driven wakefield acceleration technique. The electron beam energy can be easily adjusted between 450 MeV and 800 MeV with a tapered density plasma on the order of 1×10¹⁸ cm^-3 while the driving laser power is fixed, and the high-energy electron beams can be sent through the undulator arrays for the coherent light emission. The energy-controllable electron bunches can provide an opportunity to control the radiation wave-length with the fixed gap undulators. For the tapered density profile, a capillary cell with two gas inlets can be used. In this paper, we show some simulation and numerical research results regarding these issues, which reveal the possibility for a tunable light source in the soft X-ray regime. * M. S. Hur, H. Suk, Phys. Plasmas 18 033102 (2011).
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY015
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WEPMY016	Development of RF System for Measuring Plasma Density Modulation of Proton Beam-driven Plasma Wakefield	2582
SUPSS031	use link to see paper's listing under its alternate paper code
	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	2585
SUPSS035	use link to see paper's listing under its alternate paper code
	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	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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WEPMY020	Integration of a Terawatt Laser at the CERN SPS Beam for the AWAKE Experiment on Proton-Driven Plasma Wake Acceleration	2592
	V. Fedosseev, M. Battistin, E. Chevallay, N. Chritin, V. Clerc, T. Feniet, F. Friebel, F. Galleazzi, P. Gander, E. Gschwendtner, J. Hansen, C. Heßler, M. Martyanov, A. Masi, A. Pardons, F. Salveter, K.A. Szczurek CERN, Geneva, Switzerland M. Martyanov, J.T. Moody, P. Muggli MPI-P, München, Germany
	In the AWAKE experiment a high-power laser pulse ionizes rubidium atoms inside a 10 m long vapor cell thus creating a plasma for proton-driven wakefield acceleration of electrons. Propagating co-axial with the SPS proton beam the laser pulse seeds the self-modulation instability within the proton bunch on the front of plasma creation. The same laser will also generate UV-pulses for production of a witness electron beam using an RF-photoinjector. The experimental area formerly occupied by CNGS facility is being modified to accommodate the AWAKE experiment. A completely new laser laboratory was built, taking into account specific considerations related to underground work. The requirements for AWAKE laser installation have been fulfilled and vacuum beam lines for delivery of laser beams to the plasma cell and RF-photoinjector have been constructed. First results of laser beam hardware commissioning tests following the laser installation will be presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY020
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WEPMY021	Beam-Plasma Interaction Simulations for the AWAKE Experiment at CERN	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	2599
SUPSS032	use link to see paper's listing under its alternate paper code
	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	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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WEPMY024	A Spectrometer for Proton Driven Plasma Accelerated Electrons at AWAKE - Recent Developments	2605
	L.C. Deacon, S. Jolly, F. Keeble, M. Wing UCL, London, United Kingdom B. Biskup, A. Goldblatt, S. Mazzoni, A.V. Petrenko CERN, Geneva, Switzerland B. Biskup Czech Technical University, Prague 6, Czech Republic M. Wing DESY, Hamburg, Germany M. Wing University of Hamburg, Hamburg, Germany
	The AWAKE experiment is to be constructed at the CERN Neutrinos to Gran Sasso facility (CNGS). This will be the first experiment to demonstrate proton-driven plasma wakefield acceleration. The 400 GeV proton beam from the CERN SPS will excite a wakefield in a plasma cell several meters in length. To probe the plasma wakefield, electrons of 10–20 MeV will be injected into the wakefield following the head of the proton beam. Simulations indicate that electrons will be accelerated to GeV energies by the plasma wakefield. The AWAKE spectrometer is intended to measure both the peak energy and energy spread of these accelerated electrons. Results of beam tests of the scintillator screen output are presented, along with tests of the resolution of the proposed optical system. The results are used together with a BDSIM simulation of the spectrometer system to predict the spectrometer performance for a range of possible accelerated electron distributions.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY024
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WEPMY025	iMPACT, Undulator-Based Multi-Bunch Plasma Accelerator	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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WEPMY026	A Gas-filled Capillary Based Plasma Source for Wakefield Experiments	2613
	O. Mete Apsimon, K. Hanahoe, T.H. Pacey, G.X. Xia UMAN, Manchester, United Kingdom
	Funding: This work is supported by the University of Manchester Strategic Grant. A plasma medium can be formed when a gas is discharged via an applied high voltage within a capillary tube. A high voltage discharge based plasma source for plasma wake- field acceleration experiment is being developed. Design considered a glass capillary tube with various inner radii. Glass was preferred to sapphire or quartz options to ease the machining. Electrodes will be attached to the tube using a sealant resistant to high vacuum conditions and baking at high temperatures. Each electrode will be isolated from the neighbouring one using nuts or washers from a thermoplastic polymer insulator material to prevent unwanted sparking outside of the tube. In this paper, general design considerations and possible working points of this plasma source are presented for a range of plasma densities from 1×10²⁰ to 1×10²² m^−3. Consideration was also given to plasma density diagnostic techniques due to critical dependence of accelerating gradient on plasma density.
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WEPMY027	Feasibility Study of Plasma Wakefield Acceleration at the CLARA Front End Facility	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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FRXCB01	Two Beam Wakefield Acceleration at Argonne Wakefield Accelerator Facility	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

Title

Page

Limits and Possibilities of Laser Wakefield Accelerators

16

W. Leemans
LBNL, Berkeley, California, USA

This presentation provides an outlook into the future of laser-driven plasma wakefield accelerators. What has been achieved, what more is possible and what are the limits.

Slides MOYBA01 [43.465 MB]

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TUYB01

Stabilization of GeV Electron Beams by Coherent Control of LWFA Process

H.T. Kim
APRI-GIST, Gwangju, Republic of Korea

Laser-driven compact particle accelerators have been one of the hottest research topics owing to the potential to overcome the limitations on conventional accelerators. Recently, advancement of laser technology has enabled the generation of PW pulses, which is opening the door to the new regime of laser-particle accelerations. In this talk, the author presents a new method to stabilize multi-GeV electron beams by manipulating the spectral phase of PW laser pulses, coherently controlling the laser wake-field acceleration process. They have demonstrated the stable generation of 2-GeV electron beams in a 1-cm gas cell of He using the PW Ti:Sapphire laser system.

Slides TUYB01 [11.602 MB]

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TUOBB03

CERN AWAKE Facility Readiness for First Beam

1071

C. Bracco, M. Bernardini, A.C. Butterworth, H. Damerau, S. Döbert, V. Fedosseev, E. Feldbaumer, E. Gschwendtner, W. Höfle, A. Pardons, E.N. Shaposhnikova, H. Vincke
CERN, Geneva, Switzerland

The AWAKE project at CERN was approved in August 2013 and since then a big effort was made to be able to probe the acceleration of electrons before the "2019-2020 Long Shutdown". The next steps in this challenging schedule will be a dry run of all the beam line systems, at the end of the HW commissioning in June 2016, and the first proton beam sent to the plasma cell one month later. The current status of the project is presented together with an outlook over the foreseen works for operation with electrons in 2018.

Slides TUOBB03 [10.682 MB]

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WEPMB049

Transverse Defocusing Study in LPWA Channel for Linear and Bubble Modes

2224

S.M. Polozov, V.I. Rashchikov, Ya.V. Shashkov
MEPhI, Moscow, Russia

Laser plasma wakefield acceleration (LPWA) is one of most popular novel trends of acceleration. The LPWA has two serous disadvantages as very high energy spread and low part of electrons capturing into acceleration. The waveguide and klystron type beam pre-modulation schemes was proposed *, ** to growth capturing and to limit the energy spectrum of 2-3 % for 200-300 MeV beam. One interesting effect was detected due to numerical simulation of beam dynamics in plasma channel. Not captured electrons are escape to the channel border fast and this effect should be explained. It was shown that such effect is caused by effective potential function which forms very high defocusing transverse field after its trailing edge. The results of such explanation verified by numerical simulations are discussed in report for linear and bubble LPWA modes.
* S.M. Polozov. NIM A, 729, p.517-521, 2013
** S.M. Polozov. Problems of Atomic Science and Technology. Series: Nuclear Physics Investigations, 6 (88), p. 29- 34, 2013

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WEPMY003

Simulations of the Acceleration of Externally Injected Electrons in a Plasma Excited in the Linear Regime

2542

N. Delerue, C. Bruni, S. Jenzer
LAL, Orsay, France
S. Kazamias, B. Lucas, G. Maynard
Laboratoire de Physique des Gaz et des Plasmas, Universite Paris-Sud, Orsay, France
M. Pittman
CLUPS, Orsay, France

We have investigated numerically the coupling between a 10 \si{MeV} electron bunch of high charge (§I{> 100}{pc}) with a laser generated accelerating plasma wave. Our results show that a high efficiency coupling can be achieved using a §I{50}{TW}, §I{100}{μ \meter} wide laser beam, yielding accelerating field above §I{1}{ GV/m}. We propose an experiment where these predictions could be tested.

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WEPMY004

Development of an Injector and a Magnetic Transfer Line in the Framework of Cilex

2545

A. Chancé
CEA/DSM/IRFU, France
T. Audet, B. Cros, P. Lee, G. Maynard
Laboratoire de Physique des Gaz et des Plasmas, Universite Paris-Sud, Orsay, France
M. Bougeard, S. Dobosz-Dufrénoy, A. Maitrallain
CEA, Gif-sur-Yvette, France
N. Delerue
LAL, Orsay, France
O. Delferrière, A. Mosnier, J. Schwindling
CEA/IRFU, Gif-sur-Yvette, France
P. Monot
CEA/DSM, Gif-sur-Yvette, France
A. Specka
LLR, Palaiseau, France

Funding: Investments for the Future program under reference ANR-10-EQPX-25, by the Triangle de la Physique under contract 2011-086TMULTIPLACCELE, 2012-032TELISA, and by the Labex PALM and P2IO.
Laser plasma accelerators (LPAs) have proven their capability to produce accelerating gradients three orders of magnitude higher than RF cavity-based accelerators. The present challenges of LPAs are to achieve the beam quality and stability required by users and to show the feasibility of plasma staging for high-energy applications. As one of the experiments planned at the PetaWatt laser APOLLON facility, currently under construction in France, aims at testing the two-stage scheme, a dedicated plasma injector which will be used as the first stage has been developed and tested at the UHI100 facility at CEA Saclay. The electron source, as well as the beam characterization line, will be presented and the first results will be discussed.

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WEPMY005

Upgrades of the Experimental Setup for Electron Beam Self-modulation Studies at PITZ

2548

M. Groß, J. Engel, G. Koss, O. Lishilin, G. Loisch, G. Pathak, S. Philipp, R. Schütze, F. Stephan
DESY Zeuthen, Zeuthen, Germany
R. Brinkmann, J. Osterhoff
DESY, Hamburg, Germany
F.J. Grüner
CFEL, Hamburg, Germany
F.J. Grüner
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
D. Richter
HZB, Berlin, Germany
C.B. Schroeder
LBNL, Berkeley, California, USA

The self-modulation instability is fundamental for the plasma wakefield acceleration experiment of the AWAKE collaboration at CERN where this effect is supposed to be used to generate proton bunches short enough for producing high acceleration fields. For ease of experimentation it was decided to set up a supporting experiment at the electron accelerator PITZ (Photo Injector Test facility at DESY, Zeuthen site), given that the underlying physics is the same. The goals are to demonstrate and investigate in detail the self-modulation of long electron beams. In 2015 a first set of experiments was conducted utilizing as key elements a novel cross-shaped lithium plasma cell and an ArF excimer laser for plasma generation. No self-modulation was observed yet because of various experimental shortcomings. The properties of the experimental setup were studied in detail and in this contribution we report about the upgrades which are projected to enable the observation of the self-modulation in the upcoming experimental run.

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WEPMY006

A High Transformer Ratio Scheme for PITZ PWFA Experiments

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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WEPMY007

Plasma Density Profile Characterization for Resonant Plasma Wakefield Acceleration Experiment at SPARC_LAB

2554

F. Filippi
INFN-Roma1, Rome, Italy
M.P. Anania, A. Biagioni, E. Chiadroni, M. Ferrario
INFN/LNF, Frascati (Roma), Italy
A. Cianchi
INFN-Roma II, Roma, Italy
F. Filippi, A. Giribono, A. Mostacci, L. Palumbo
University of Rome La Sapienza, Rome, Italy
F. Filippi, A. Giribono, A. Mostacci, L. Palumbo
INFN-Roma, Roma, Italy
A. Giribono
University of Rome "La Sapienza", Rome, Italy
A. Zigler
The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem, Israel

New generation of particle accelerators is based on the excitation of large amplitude plasma waves driven by either electron or laser beams, named as Plasma Wakefield Accelerator (PWFA) and Laser Wakefield Accelerator (LWFA), respectively. Future experiments scheduled at the SPARC_LAB test facility aim to demonstrate the acceleration of externally injected high brightness electron beams through both schemes. In particular, in the so-called resonant PWFA a train of more than two driver electron bunches generated with the laser comb technique resonantly excites wakefields into the plasma, the last bunch (witness) is injected at the proper accelerating phase gaining energy from the wake. The quality of the accelerated beam depends strongly on plasma density and its distribution along the acceleration length. The desired density can be achieved with a correct shaping of the capillary in which plasma is formed. The measurements of plasma density, as well as other plasma characteristics, can be performed with spectroscopic measurements of the plasma self emitted light. The measurement of density distribution for hydrogen filled capillaries is here reported.

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WEPMY008

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

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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WEPMY009

Transverse Tolerances of a Multi-Stage Plasma Wakefield Accelerator

2561

SUPSS034

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C.A. Lindstrøm, E. Adli, J. Pfingstner
University of Oslo, Oslo, Norway
E. Marín, D. Schulte
CERN, Geneva, Switzerland

Funding: This work is supported by the Research Council of Norway.
Plasma wakefield acceleration (PWFA) provides GeV/m-scale accelerating fields, ideal for applications such as a future linear collider. However, strong focusing fields imply that a transversely offset beam with an energy spread will experience emittance growth from the energy dependent betatron oscillation. We develop an analytic model for estimating tolerances from this effect, as well as an effective simplified simulation tool in Elegant. Estimations for a proposed 1 TeV PWFA linear collider scheme indicate tight tolerances of order 40 nm and 1 μrad in position and angle respectively.

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WEPMY010

Considerations for a Drive Beam Scheme for a Plasma Wakefield Linear Collider

2565

J. Pfingstner, E. Adli, C.A. Lindstrøm
University of Oslo, Oslo, Norway
E. Marín, D. Schulte
CERN, Geneva, Switzerland

The potential for high average gradients makes plasma wakefield acceleration (PWFA) an attracting option for future linear colliders. For a beam-driven PWFA collider a sequence of cells has to be supplied with synchronised drive beam bunches. This paper is concerned with the generation, transport and distribution of these drive beam bunches in a so-called drive beam complex for a 3 TeV collider. Based on earlier concepts, several modifications are suggested. The new design includes a superconducting linac and an optimised bunch delay system with a tree structure. To verify the feasibility for the overall complex, a lattice design and tracking studies for the critical bending arc subsystem are presented. Also the feasibility of a compact bunch separation system is shown. The result of these efforts is a drive beam complex that is optimised for construction cost and power efficiency that favours unified lattice solutions.

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WEPMY011

Compact Laser Plasma Accelerator at Peking University

2569

SUPSS033

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L.R.F. Li, J.E. Chen, S.C. Gao, Y.X. Geng, Q. Liao, J B. Liu, H.Y. Lu, X.Q. Yan, Y.Y. Zhao, Y.Y. Zhu
PKU, Beijing, People's Republic of China
Y.R. Shou
Peking University, School of Physics, Beijing, People's Republic of China

A brand new and solely accelerator based on the interaction physics of high intensity ultrafast laser and plasmas, named Compact LAser Plasma Accelerator (CLAPA), was recently built. The laser system can deliver 5J/25fs @ 800nm pulses with contrast of 10^-10. Experiments on electron acceleration is scheduled with the regime of laser wakefield acceleration. The charge and the energy spread of the accelerated electron beams will be concerned mainly. The experiments is planned with gas targets with single and dual stages. For the single stage acceleration, we will try density ramp injection and a loose focusing for a monoenergetic electron beam with more charge for some applications. With the PIC simulations and new injection methods, it is expected to generate GeV/tens pC electron beam with an energy spread of <1%. For the two stage cascaded acceleration, we will focus on the staged acceleration and control of the injection of the second stage, as well as the acceleration length of the second stage by manipulating the parameters of the gas target as well as the laser itself. The far future goal of the second plan is to develop a designable and applicable accelerators.
* W.Lu, Phys. Rev.ST Accel. Beams 10.061301 （2007）
** J. Faure, Nature 431, 541 (2004)
***J.S. Liu, Phys. Rev. Lett 107, 035001 (2011)

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WEPMY014

Feasibility Study of a Laser-Driven High Energy Electron Acceleration in a Long Up-Ramp Density

2576

M. Kim, J. Kim, S.W. Lee, I.H. Nam, H. Suk
GIST, Gwangju, Republic of Korea

Laser-driven wakefield acceleration (LWFA) has received much attention as it can produce GeV-level high-energy electrons in cm-scale distance*. However, the accelerated electron energies are still limited by several factors, especially by the dephasing problem that is caused by different velocities between the plasma wake wave and the accelerated electron beam. In order to increase the acceleration length restricted by the dephasing problem**, we developed a gas-cell with density-tapering, which is realized by applying different gas pressures into two gas inlets in the gas cell. In this way, the gas density and gradient can be easily controlled in the gas cell. We used the density-tapered gas-cell for laser wakefield acceleration experiments in our laboratory with a 20 TW/40 fs Ti:sapphire laser system***. The results show that the electron energy can be significantly enhanced (about twice) with the tapered density gas-cell, compared with a uniform density conventional gas-cell. In this presentation, we show the experimental results and comparison with two-dimensional (2-D) particle-in-cell (PIC) simulation results.
* W. P. Leemans et al. Phy. Rev. Lett. 113, 245002 (2014).
** M. S. Kim et al. Appl. Phy. Lett. 102, 204103 (2013).
*** I. H. Nam et al. Curr. Appl. Phy. 15, 468 (2015).

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WEPMY015

Numerical Studies on Tunable Coherent Radiations with a Laser-Plasma Accelerator

2579

J. Kim, M. Kim, I.H. Nam, H. Suk
GIST, Gwangju, Republic of Korea
M.S. Hur
UNIST, Ulsan, Republic of Korea

Generation of tunable coherent radiation is numerically investigated via the two-dimensional particle-in-cell (2D-PIC) code developed by UNIST* and SIMPLEX developed by Spring-8. The electron beams can be produced by the laser-driven wakefield acceleration technique. The electron beam energy can be easily adjusted between 450 MeV and 800 MeV with a tapered density plasma on the order of 1×10¹⁸ cm^-3 while the driving laser power is fixed, and the high-energy electron beams can be sent through the undulator arrays for the coherent light emission. The energy-controllable electron bunches can provide an opportunity to control the radiation wave-length with the fixed gap undulators. For the tapered density profile, a capillary cell with two gas inlets can be used. In this paper, we show some simulation and numerical research results regarding these issues, which reveal the possibility for a tunable light source in the soft X-ray regime.
* M. S. Hur, H. Suk, Phys. Plasmas 18 033102 (2011).

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WEPMY016

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

2582

SUPSS031

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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

2585

SUPSS035

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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

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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WEPMY020

Integration of a Terawatt Laser at the CERN SPS Beam for the AWAKE Experiment on Proton-Driven Plasma Wake Acceleration

2592

V. Fedosseev, M. Battistin, E. Chevallay, N. Chritin, V. Clerc, T. Feniet, F. Friebel, F. Galleazzi, P. Gander, E. Gschwendtner, J. Hansen, C. Heßler, M. Martyanov, A. Masi, A. Pardons, F. Salveter, K.A. Szczurek
CERN, Geneva, Switzerland
M. Martyanov, J.T. Moody, P. Muggli
MPI-P, München, Germany

In the AWAKE experiment a high-power laser pulse ionizes rubidium atoms inside a 10 m long vapor cell thus creating a plasma for proton-driven wakefield acceleration of electrons. Propagating co-axial with the SPS proton beam the laser pulse seeds the self-modulation instability within the proton bunch on the front of plasma creation. The same laser will also generate UV-pulses for production of a witness electron beam using an RF-photoinjector. The experimental area formerly occupied by CNGS facility is being modified to accommodate the AWAKE experiment. A completely new laser laboratory was built, taking into account specific considerations related to underground work. The requirements for AWAKE laser installation have been fulfilled and vacuum beam lines for delivery of laser beams to the plasma cell and RF-photoinjector have been constructed. First results of laser beam hardware commissioning tests following the laser installation will be presented.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY020

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WEPMY021

Beam-Plasma Interaction Simulations for the AWAKE Experiment at CERN

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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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

2599

SUPSS032

use link to see paper's listing under its alternate paper code

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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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

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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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY023

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WEPMY024

A Spectrometer for Proton Driven Plasma Accelerated Electrons at AWAKE - Recent Developments

2605

L.C. Deacon, S. Jolly, F. Keeble, M. Wing
UCL, London, United Kingdom
B. Biskup, A. Goldblatt, S. Mazzoni, A.V. Petrenko
CERN, Geneva, Switzerland
B. Biskup
Czech Technical University, Prague 6, Czech Republic
M. Wing
DESY, Hamburg, Germany
M. Wing
University of Hamburg, Hamburg, Germany

The AWAKE experiment is to be constructed at the CERN Neutrinos to Gran Sasso facility (CNGS). This will be the first experiment to demonstrate proton-driven plasma wakefield acceleration. The 400 GeV proton beam from the CERN SPS will excite a wakefield in a plasma cell several meters in length. To probe the plasma wakefield, electrons of 10–20 MeV will be injected into the wakefield following the head of the proton beam. Simulations indicate that electrons will be accelerated to GeV energies by the plasma wakefield. The AWAKE spectrometer is intended to measure both the peak energy and energy spread of these accelerated electrons. Results of beam tests of the scintillator screen output are presented, along with tests of the resolution of the proposed optical system. The results are used together with a BDSIM simulation of the spectrometer system to predict the spectrometer performance for a range of possible accelerated electron distributions.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY024

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WEPMY025

iMPACT, Undulator-Based Multi-Bunch Plasma Accelerator

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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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY025

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WEPMY026

A Gas-filled Capillary Based Plasma Source for Wakefield Experiments

2613

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

Funding: This work is supported by the University of Manchester Strategic Grant.
A plasma medium can be formed when a gas is discharged via an applied high voltage within a capillary tube. A high voltage discharge based plasma source for plasma wake- field acceleration experiment is being developed. Design considered a glass capillary tube with various inner radii. Glass was preferred to sapphire or quartz options to ease the machining. Electrodes will be attached to the tube using a sealant resistant to high vacuum conditions and baking at high temperatures. Each electrode will be isolated from the neighbouring one using nuts or washers from a thermoplastic polymer insulator material to prevent unwanted sparking outside of the tube. In this paper, general design considerations and possible working points of this plasma source are presented for a range of plasma densities from 1×10²⁰ to 1×10²² m^−3. Consideration was also given to plasma density diagnostic techniques due to critical dependence of accelerating gradient on plasma density.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY026

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WEPMY027

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

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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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY027

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FRXCB01

Two Beam Wakefield Acceleration at Argonne Wakefield Accelerator Facility

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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