IPAC2015 - Classification: 3: Alternative Particle Sources and Acceleration Techniques / A22

Paper	Title	Page
MOAC1	Awake: the Proof-of-principle R&D Experiment at CERN	34
	P. Muggli MPI, Muenchen, Germany M. Bernardini, T. Bohl, C. Bracco, A.C. Butterworth, S. Cipiccia, H. Damerau, S. Döbert, V. Fedosseev, E. Feldbaumer, E. Gschwendtner, W. Höfle, A. Pardons, A.V. Petrenko, J.S. Schmidt, M. Turner, H. Vincke CERN, Geneva, Switzerland
	The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) is a proof-of-principle R&D experiment at CERN. It is the world’s first proton driven plasma wakefield acceleration experiment, using a high-energy proton bunch to drive a plasma wakefield for electron beam acceleration. The AWAKE experiment will be installed in the former CNGS facility and uses the 400 GeV proton beam bunches from the SPS, which will be sent to a plasma source. An electron beam will be injected into the plasma cell to probe the accelerating wakefield. Challenging modifications in the area and new installations are required for AWAKE. First proton beam to the experiment is expected late 2016. The accelerating electron physics will start late 2017. This paper gives an overview of the project from a physics and engineering point of view, it describes the main activities, the milestones, the organizational set-up for the project management and coordination.
	Slides MOAC1 [21.632 MB]
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MOAC2	Laser-Plasma Acceleration in Hamburg
	A.R. Maier CFEL, Hamburg, Germany
	Plasma-based accelerators promise ultra-compact sources of highly relativistic electron beams, especially suited for driving novel x-ray light sources. The stability and reproducability of laser-plasma generated beams is, however, still not comparable to conventional machines. Within the LAOLA Collaboration, the University of Hamburg and DESY work closely together to combine university research with the expertise of a large and well-established accelerator facility. We will discuss the experimental programm and plasma-related activities in Hamburg, with a special focus on the recently commissioned 200 TW laser ANGUS. It drives two beamlines, REGAE and LUX, to study external injection of electrons from a conventional gun into a plasma stage, as well as plasma-driven undulator radiation. We present our progress in integrating the laser into the accelerator infrastructure at DESY, progress towards stable laser operation, as well as the commissioning of the LUX and REAGE beamlines. As an outlook, we will discuss the experimental strategies in Hamburg towards a first proof-of-principle FEL experiment using plasma-driven electron beams available today. on behalf of the LAOLA collaboration
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MOAC3	Coherent Phase Space Matching for Staging Plasma and Traditional Accelerator Using Longitudinally Tailored Plasma Structure
	X.L. Xu TUB, Beijing, People's Republic of China
	For the further development of plasma based accelerators, phase space matching between plasma acceleration stages and between plasma stages and traditional accelerator components becomes a very critical issue for high quality high energy acceleration and its applications in light sources and colliders. Without proper matching, catastrophic emittance growth in the presence of definite energy spread may occur when the beam propagating through different stages and components due to the drastic differences of transverse focusing strength. In this paper we propose to use longitudinally tailored plasma structures as phase space matching components to properly guide the beam through stages. Theoretical analysis and full 3-dimensional particle-in-cell simulations are utilized to show clearly how these structures may work in four different scenarios. Very good agreements between theory and simulations are obtained.
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TUYC1	Multi-GeV Electron and Positron Plasma Wakefield Acceleration Results at FACET
	S.J. Gessner, E. Adli, J.M. Allen, C.I. Clarke, J.-P. Delahaye, J.T. Frederico, S.Z. Green, M.J. Hogan, N. Lipkowitz, M.D. Litos, M.P. Schmeltz, D.R. Walz, V. Yakimenko, G. Yocky SLAC, Menlo Park, California, USA E. Adli 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 M. Downer, R. Zgadzaj The University of Texas at Austin, Austin, Texas, USA W. Lu TUB, Beijing, People's Republic of China P. Muggli MPI, Muenchen, Germany
	Funding: This work performed [in part] under DOE Contract DE-AC02-76SF00515. The FACET accelerator test facility at SLAC hosts a new generation of Plasma Wakefield Acceleration (PWFA) experiments. "Two-bunch" experiments have demonstrated high-gradient, highly efficient energy transfer in a plasma wakefield. I will discuss results of follow-up experiments that use a 1.3 meter long plasma to accelerate witness bunch electrons to even higher energies. In a first, we observed multi-GeV acceleration of positrons in a plasma. This is a critical step in demonstrating the applicability of PWFA for High-Energy Physics applications.
	Slides TUYC1 [8.619 MB]
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WEPWA001	Electron Beam Transfer Line for Demonstration of Laser Plasma Based Free Electron Laser Amplification	2489
	A. Loulergue, M.-E. Couprie, M. Khojoyan, M. Labat, W. Wang SOLEIL, Gif-sur-Yvette, France C. Evain PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
	One direction towards compact Free Electron Lasers is to replace the conventional linac by a laser plasma driven beam, provided proper electron beam manipulation to handle the value of the energy spread and of the divergence is done. Applying seeding techniques enables also to reduce the required undulator length. The rapidly developing LWFA are already able to generate synchrotron radiation. With an electron divergence of typically 1 mrad and an energy spread of the order of 1 %, an adequate beam manipulation through the transport to the undulator is needed for FEL amplification. A test experiment for the demonstration of FEL amplification with a LWFA is under preparation in the frame of the COXINEL ERC contract. A specific design of electron beam transfer line following different steps with strong focusing variable strength permanent magnet quadrupoles, an energy de-mixing chicane with conventional dipoles and second set of quadrupoles for further dedicated focusing in the undulator has been investigated. Beam transfer simulations and expected FEL power in the XUV will be presented.
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WEPWA003	Simulations of Electron-Proton Beam Interaction before Plasma in the AWAKE Experiment	2492
	U. Dorda, R.W. Aßmann, J. Grebenyuk DESY, Hamburg, Germany C. Bracco, A.V. Petrenko, J.S. Schmidt CERN, Geneva, Switzerland
	The on-axis injection of electron bunches in the proton-driven plasma wake at the AWAKE experiment at CERN implies co-propagation of a low-energy electron beam with the long high-energy proton beam in a common beam pipe over several meters upstream of the plasma chamber. The possible effects of the proton-induced wakefields on the electron bunch phase space in the common beam pipe region may have crucial implications for subsequent electron trapping and acceleration in plasma. We present the CST Studio simulations of the tentative common beam pipe setup and the two beam co-propagating in it. Simulated effects of the proton wakefields on electrons are analysed and compared to analytical predictions.
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WEPWA006	Laser Propagation Effects During Photoionization of Meter Scale Rubidium Vapor Source	2499
	J.T. Moody, F. Batsch, A. Joulaei, P. Muggli, E. Öz MPI-P, München, Germany N. Berti, J. Kasparian University of Geneva, GAP Biophotonics, Carouge, Switzerland
	The baseline AWAKE experiment requires a 10 meter long plasma source with a density of 10¹⁵ cm􀀀^-3 and a density uniformity of 0.2%. To produce this plasma, a temperature stabilized rubidium vapor source is photoionized by a terawatt peak power laser pulse. In this paper we describe the laser pulse evolution within the plasma source including the dispersive, diffractive, and photoionization effects on the laser pulse. These calculations will be experimentally investigated in a meter long heat pipe oven using scaled laser parameters.
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WEPWA007	The AWAKE Proton-driven Plasma Wakefield Experiment at CERN	2502
	P. Muggli MPI-P, München, Germany
	Funding: For the AWAKE collaboration The AWAKE experiment at CERN * aims at studying plasma wakefield generation and acceleration driven by proton bunches. The first experiments will focus on the self-modulation instability of the long (~12cm, rms) proton bunch in the plasma. This instability is used to transform the incoming bunch into a train of short bunches with a period approximately equal to the plasma wavelength, ~1.2mm at a nominal plasma electron density of 7·10¹⁴/cc. These experiments are planned for the end of 2016. Later, low energy (~15MeV) electrons will be externally injected to sample the wakefields and be accelerated beyond 1GeV. The main goals of the experiment will be summarized and the progress with the plasma source, beam diagnostics and injection method will be presented. * AWAKE Collaboration, Plasma Phys. Control. Fusion 56 084013 (2014)
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WEPWA008	Measuring the Self-modulation Instability of Electron and Positron Bunches in Plasmas	2506
	P. Muggli, O. Reimann MPI-P, München, Germany E. Adli, V.K.B. Olsen University of Oslo, Oslo, Norway J. Allen, S.J. Gessner, S.Z. Green, M.J. Hogan, M.D. Litos, B.D. O'Shea, V. Yakimenko SLAC, Menlo Park, California, USA L.D. Amorim IST, Lisboa, Portugal G. Andonian, C. Joshi, K.A. Marsh, W.B. Mori, N. Vafaei-Najafabadi, O. Williams UCLA, Los Angeles, California, USA N.C. Lopes, L.O. Silva, J. Vieira Instituto Superior Tecnico, Lisbon, Portugal
	The self-modulation instability (SMI) * can be used to transform a long, charged particle bunch into a train of periodically spaced shorter bunches. The SMI occurs in a plasma when the plasma wake period is much shorter than the bunch length. The train of short bunches can then resonantly drive wakefields to much larger amplitude that the long bunch can. The SMI will be used in the AWAKE experiment at CERN, where the wakefields will be driven by a high-energy (400GeV) proton bunch. However, most of the SMI physics can be tested with the electron and positron bunches available at SLAC-FACET. * In this case, the bunch is ~10 plasma wavelengths long, but can drive wakefields in the GV/m range. FACET has a meter-long plasma **** and is well equipped in terms of diagnostic for SMI detection: optical transition radiation for transverse bunch profile measurements, coherent transition radiation interferometry for radial modulation period measurements and energy spectrometer for energy loss and gain measurement of the drive bunch particles. The latest experimental results will be presented. * N. Kumar et al., PRL 104, 255003 (2010) AWAKE Collaboration, PPCF 56 084013 (2014) * J. Vieira et al., PoP 19, 063105 (2012) **** S.Z. Green et al., PPCF 56, 084011 (2014)
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WEPWA026	Loading of a Plasma-Wakefield Accelerator Section Driven by a Self-Modulated Proton Bunch	2551
	V.K.B. Olsen, E. Adli University of Oslo, Oslo, Norway L.D. Amorim IST, Lisboa, Portugal P. Muggli MPI, Muenchen, Germany J. Vieira Instituto Superior Tecnico, Lisbon, Portugal
	We investigate beam loading of a plasma wake driven by a self-modulated proton beam using particle-in-cell simulations for phase III of the AWAKE project. We address the case of injection after the proton beam has already experienced self-modulation in a previous plasma. Optimal parameters for the injected electron bunch in terms of initial beam energy and beam charge density are investigated and evaluated in terms of witness bunch energy and energy spread. An approximate modulated proton beam is emulated in order to reduce computation time in these simulations.
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WEPWA033	Characterization of Laser-plasma Accelerated Electron Beam for a Compact Storage Ring	2569
	S. H. Park, Y. Cha, Y.U. Jeong, J.S. Jo, H.N. Kim, K.N. Kim, K. Lee, W.J. Ryu, J.S. Shinn, N. Vinokurov KAERI, Daejon, Republic of Korea N. Vinokurov BINP SB RAS, Novosibirsk, Russia
	A compact radiation source can be utilized by an electron beam from a Laser-plasma acceleration combined with localized shielding in a small laboratory. The stability of synchrotron radiation in wavelength and power depends on the shot-to-shot jitters of the energy and charge of an electron beam, which is strongly influenced by the plasma density of target and the jitters of a laser beam. With the 30 TW fs laser in KAERI, the optimization for generating the electron beam have done using the different shape of gas nozzle. We also present the pointing stability and the energy spread of the laser-accelerated electron beams.
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WEPWA034	High-charge-short-bunch Operation Possibility at Argonne Wakefield Accelerator Facility	2572
	G. Ha, M.-H. Cho, W. Namkung POSTECH, Pohang, Kyungbuk, Republic of Korea W. Gai, G. Ha, K.-J. Kim, J.G. Power ANL, Argonne, Illinois, USA
	Originally the drive beam line at Argonne Wakefield Accelerator (AWA) Facility was designed to generate the high charge bunch train. However, we recently installed the double dog-leg type emittance exchange beam line which have two identical dog-leg structures. With this beam line, it is possible to compress the bunch by introducing the chicane or using single dog-leg. Simulation studies have been carried out to confirm the minimum bunch length for each charge and the emittance growth by the coherent synchrotron radiation. We present GPT simulation results to show high-charge-short-bunch operation possibility at AWA facility.
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WEPWA039	The AWAKE Electron Primary Beam Line	2584
	J.S. Schmidt, J. Bauche, B. Biskup, C. Bracco, E. Bravin, S. Döbert, M.A. Fraser, B. Goddard, E. Gschwendtner, L.K. Jensen, O.R. Jones, S. Mazzoni, M. Meddahi, A.V. Petrenko, F.M. Velotti, A.S. Vorozhtsov CERN, Geneva, Switzerland U. Dorda DESY, Hamburg, Germany L. Merminga, V.A. Verzilov TRIUMF, Vancouver, Canada P. Muggli MPI, Muenchen, Germany
	The AWAKE project at CERN is planned to study proton driven plasma wakefield acceleration. The proton beam from the SPS will be used in order to drive wakefields in a 10 m long Rb plasma cell. In the first phase of this experiment, scheduled in 2016, the self-modulation of the proton beam in the plasma will be studied in detail, while in the second phase an external electron beam will be injected into the plasma wakefield to probe the acceleration process. The installation of AWAKE in the former CNGS experimental area and the required optics flexibility define the tight boundary conditions to be fulfilled by the electron beam line design. The transport of low energy (10-20 MeV) bunches of 1.25·10⁹ electrons and the synchronous copropagation with much higher intensity proton bunches (3E11) determines several technological and operational challenges for the magnets and the beam diagnostics. The current status of the electron line layout and the associated equipments are presented in this paper.
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WEPWA045	Development of a Spectrometer for Proton Driven Plasma Wakefield Accelerated Electrons at AWAKE	2601
	L.C. Deacon, S. Jolly, F. Keeble, M. Wing UCL, London, United Kingdom B. Biskup Czech Technical University, Prague 6, Czech Republic B. Biskup, E. Bravin, A.V. Petrenko CERN, Geneva, Switzerland 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 metres in length. To observe 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. Improvements to the baseline design are presented, with an alternative dipole magnet and quadrupole focussing, with the resulting energy resolution calculated for various scenarios. The signal to background ratio due to the interaction of the SPS protons with upstream beam line components is calculated, and CCD camera location, shielding and light transport are considered.
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WEPWA047	Emittance Growth in a Plasma Wakefield Accelerator	2609
	Ö. Mete, K. Hanahoe, G.X. Xia UMAN, Manchester, United Kingdom M. Labiche STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	The interaction of the witness beam with the surrounding plasma particles and wakefields was studied. The implications of the elastic scattering process on beam emittance and, emittance evolution under the focusing and acceleration provided by plasma wakefields were discussed. Simulations results from GEANT4 are presented in this paper.
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WEPWA048	Design Studies and Commissioning Plans for PARS Experimental Program	2612
	Ö. Mete, K. Hanahoe, J. Wright, G.X. Xia UMAN, Manchester, United Kingdom M. Dover, M. Wigram, J. Zhang University of Manchester, Manchester, United Kingdom J.D.A. Smith Tech-X, Boulder, Colorado, USA
	Funding: Science and Technology Facilities Council and Cockcroft Institute Core Grant PARS (Plasma Acceleration Research Station) is an electron beam driven plasma wakefield acceleration test stand proposed for VELA/CLARA facility in Daresbury Laboratory. In order to optimise various operational configurations, 2D numerical studies were performed by using VSIM for a range of parameters such as bunch length, radius, plasma density and positioning of the bunches with respect to each other for the two-beam acceleration scheme. In this paper, some of these numerical studies and considered measurement methods are presented.
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WEPWA068	Simulation of Laser Pulse Driven Terahertz Generation in Inhomogeneous Plasmas	2661
	C.M. Miao, T.M. Antonsen UMD, College Park, Maryland, USA J. Palastro Icarus Research, Inc., Bethesda, Maryland, USA
	Intense, short laser pulses propagating through inhomogeneous plasma can ponderomotively drive THz radiation. Here we consider a transition radiation mechanism (TRM) for THz generation as a laser pulse crosses a plasma boundary. Full format PIC simulations and theoretical analysis are conducted demonstrating that TRM results in low frequency, broad band, coherent THz radiation. The effect of a density ramp is also considered and shown to enhance the radiated energy.
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WEPJE001	Optimal Positron-Beam Excited Plasma Wakefields in Hollow and Ion-Wake Channels	2674
	A. A. Sahai, T.C. Katsouleas Duke ECE, Durham, North Carolina, USA
	Funding: DE-SC-0010012, NSF-PHY-0936278 A positron-beam interacting with the plasma electrons drives radial suck-in, in contrast to an electron-beam driven blow-out in the over-dense regime, n_b>n₀. In a homogeneous plasma, the electrons are radially sucked-in from all the different radii. The electrons collapsing from different radii do not simultaneously compress on-axis driving weak fields. A hollow-channel allows electrons from its channel-radius to collapse simultaneously exciting coherent fields . We analyze the optimal channel radius. Additionally, the low ion density in the hollow allows a larger region with focusing phase. We have shown the formation of an ion-wake channel behind a blow-out electron bubble-wake. Here we explore positron acceleration in the over-dense regime comparing an optimal hollow-plasma channel to the ion-wake channel . The condition for optimal hollow-channel radius is also compared. We also address the effects of a non-ideal ion-wake channel on positron-beam excited fields. S Lee, T Katsouleas, Phys. Rev. E, vol 64, 045501(R) (2001) ** A A Sahai, T Katsouleas, Non-linear ion-wake excitation by ultra relativistic electron wakefields, in review (http://arxiv.org/pdf/1504.03735v1.pdf)
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Paper

Title

Page

Awake: the Proof-of-principle R&D Experiment at CERN

34

P. Muggli
MPI, Muenchen, Germany
M. Bernardini, T. Bohl, C. Bracco, A.C. Butterworth, S. Cipiccia, H. Damerau, S. Döbert, V. Fedosseev, E. Feldbaumer, E. Gschwendtner, W. Höfle, A. Pardons, A.V. Petrenko, J.S. Schmidt, M. Turner, H. Vincke
CERN, Geneva, Switzerland

The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) is a proof-of-principle R&D experiment at CERN. It is the world’s first proton driven plasma wakefield acceleration experiment, using a high-energy proton bunch to drive a plasma wakefield for electron beam acceleration. The AWAKE experiment will be installed in the former CNGS facility and uses the 400 GeV proton beam bunches from the SPS, which will be sent to a plasma source. An electron beam will be injected into the plasma cell to probe the accelerating wakefield. Challenging modifications in the area and new installations are required for AWAKE. First proton beam to the experiment is expected late 2016. The accelerating electron physics will start late 2017. This paper gives an overview of the project from a physics and engineering point of view, it describes the main activities, the milestones, the organizational set-up for the project management and coordination.

Slides MOAC1 [21.632 MB]

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MOAC2

Laser-Plasma Acceleration in Hamburg

A.R. Maier
CFEL, Hamburg, Germany

Plasma-based accelerators promise ultra-compact sources of highly relativistic electron beams, especially suited for driving novel x-ray light sources. The stability and reproducability of laser-plasma generated beams is, however, still not comparable to conventional machines. Within the LAOLA Collaboration, the University of Hamburg and DESY work closely together to combine university research with the expertise of a large and well-established accelerator facility. We will discuss the experimental programm and plasma-related activities in Hamburg, with a special focus on the recently commissioned 200 TW laser ANGUS. It drives two beamlines, REGAE and LUX, to study external injection of electrons from a conventional gun into a plasma stage, as well as plasma-driven undulator radiation. We present our progress in integrating the laser into the accelerator infrastructure at DESY, progress towards stable laser operation, as well as the commissioning of the LUX and REAGE beamlines. As an outlook, we will discuss the experimental strategies in Hamburg towards a first proof-of-principle FEL experiment using plasma-driven electron beams available today.
on behalf of the LAOLA collaboration

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MOAC3

Coherent Phase Space Matching for Staging Plasma and Traditional Accelerator Using Longitudinally Tailored Plasma Structure

X.L. Xu
TUB, Beijing, People's Republic of China

For the further development of plasma based accelerators, phase space matching between plasma acceleration stages and between plasma stages and traditional accelerator components becomes a very critical issue for high quality high energy acceleration and its applications in light sources and colliders. Without proper matching, catastrophic emittance growth in the presence of definite energy spread may occur when the beam propagating through different stages and components due to the drastic differences of transverse focusing strength. In this paper we propose to use longitudinally tailored plasma structures as phase space matching components to properly guide the beam through stages. Theoretical analysis and full 3-dimensional particle-in-cell simulations are utilized to show clearly how these structures may work in four different scenarios. Very good agreements between theory and simulations are obtained.

Slides MOAC3 [5.534 MB]

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TUYC1

Multi-GeV Electron and Positron Plasma Wakefield Acceleration Results at FACET

S.J. Gessner, E. Adli, J.M. Allen, C.I. Clarke, J.-P. Delahaye, J.T. Frederico, S.Z. Green, M.J. Hogan, N. Lipkowitz, M.D. Litos, M.P. Schmeltz, D.R. Walz, V. Yakimenko, G. Yocky
SLAC, Menlo Park, California, USA
E. Adli
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
M. Downer, R. Zgadzaj
The University of Texas at Austin, Austin, Texas, USA
W. Lu
TUB, Beijing, People's Republic of China
P. Muggli
MPI, Muenchen, Germany

Funding: This work performed [in part] under DOE Contract DE-AC02-76SF00515.
The FACET accelerator test facility at SLAC hosts a new generation of Plasma Wakefield Acceleration (PWFA) experiments. "Two-bunch" experiments have demonstrated high-gradient, highly efficient energy transfer in a plasma wakefield. I will discuss results of follow-up experiments that use a 1.3 meter long plasma to accelerate witness bunch electrons to even higher energies. In a first, we observed multi-GeV acceleration of positrons in a plasma. This is a critical step in demonstrating the applicability of PWFA for High-Energy Physics applications.

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WEPWA001

Electron Beam Transfer Line for Demonstration of Laser Plasma Based Free Electron Laser Amplification

2489

A. Loulergue, M.-E. Couprie, M. Khojoyan, M. Labat, W. Wang
SOLEIL, Gif-sur-Yvette, France
C. Evain
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France

One direction towards compact Free Electron Lasers is to replace the conventional linac by a laser plasma driven beam, provided proper electron beam manipulation to handle the value of the energy spread and of the divergence is done. Applying seeding techniques enables also to reduce the required undulator length. The rapidly developing LWFA are already able to generate synchrotron radiation. With an electron divergence of typically 1 mrad and an energy spread of the order of 1 %, an adequate beam manipulation through the transport to the undulator is needed for FEL amplification. A test experiment for the demonstration of FEL amplification with a LWFA is under preparation in the frame of the COXINEL ERC contract. A specific design of electron beam transfer line following different steps with strong focusing variable strength permanent magnet quadrupoles, an energy de-mixing chicane with conventional dipoles and second set of quadrupoles for further dedicated focusing in the undulator has been investigated. Beam transfer simulations and expected FEL power in the XUV will be presented.

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WEPWA003

Simulations of Electron-Proton Beam Interaction before Plasma in the AWAKE Experiment

2492

U. Dorda, R.W. Aßmann, J. Grebenyuk
DESY, Hamburg, Germany
C. Bracco, A.V. Petrenko, J.S. Schmidt
CERN, Geneva, Switzerland

The on-axis injection of electron bunches in the proton-driven plasma wake at the AWAKE experiment at CERN implies co-propagation of a low-energy electron beam with the long high-energy proton beam in a common beam pipe over several meters upstream of the plasma chamber. The possible effects of the proton-induced wakefields on the electron bunch phase space in the common beam pipe region may have crucial implications for subsequent electron trapping and acceleration in plasma. We present the CST Studio simulations of the tentative common beam pipe setup and the two beam co-propagating in it. Simulated effects of the proton wakefields on electrons are analysed and compared to analytical predictions.

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WEPWA006

Laser Propagation Effects During Photoionization of Meter Scale Rubidium Vapor Source

2499

J.T. Moody, F. Batsch, A. Joulaei, P. Muggli, E. Öz
MPI-P, München, Germany
N. Berti, J. Kasparian
University of Geneva, GAP Biophotonics, Carouge, Switzerland

The baseline AWAKE experiment requires a 10 meter long plasma source with a density of 10¹⁵ cm􀀀^-3 and a density uniformity of 0.2%. To produce this plasma, a temperature stabilized rubidium vapor source is photoionized by a terawatt peak power laser pulse. In this paper we describe the laser pulse evolution within the plasma source including the dispersive, diffractive, and photoionization effects on the laser pulse. These calculations will be experimentally investigated in a meter long heat pipe oven using scaled laser parameters.

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WEPWA007

The AWAKE Proton-driven Plasma Wakefield Experiment at CERN

2502

P. Muggli
MPI-P, München, Germany

Funding: For the AWAKE collaboration
The AWAKE experiment at CERN * aims at studying plasma wakefield generation and acceleration driven by proton bunches. The first experiments will focus on the self-modulation instability of the long (~12cm, rms) proton bunch in the plasma. This instability is used to transform the incoming bunch into a train of short bunches with a period approximately equal to the plasma wavelength, ~1.2mm at a nominal plasma electron density of 7·10¹⁴/cc. These experiments are planned for the end of 2016. Later, low energy (~15MeV) electrons will be externally injected to sample the wakefields and be accelerated beyond 1GeV. The main goals of the experiment will be summarized and the progress with the plasma source, beam diagnostics and injection method will be presented.
* AWAKE Collaboration, Plasma Phys. Control. Fusion 56 084013 (2014)

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WEPWA008

Measuring the Self-modulation Instability of Electron and Positron Bunches in Plasmas

2506

P. Muggli, O. Reimann
MPI-P, München, Germany
E. Adli, V.K.B. Olsen
University of Oslo, Oslo, Norway
J. Allen, S.J. Gessner, S.Z. Green, M.J. Hogan, M.D. Litos, B.D. O'Shea, V. Yakimenko
SLAC, Menlo Park, California, USA
L.D. Amorim
IST, Lisboa, Portugal
G. Andonian, C. Joshi, K.A. Marsh, W.B. Mori, N. Vafaei-Najafabadi, O. Williams
UCLA, Los Angeles, California, USA
N.C. Lopes, L.O. Silva, J. Vieira
Instituto Superior Tecnico, Lisbon, Portugal

The self-modulation instability (SMI) * can be used to transform a long, charged particle bunch into a train of periodically spaced shorter bunches. The SMI occurs in a plasma when the plasma wake period is much shorter than the bunch length. The train of short bunches can then resonantly drive wakefields to much larger amplitude that the long bunch can. The SMI will be used in the AWAKE experiment at CERN, where the wakefields will be driven by a high-energy (400GeV) proton bunch. ** However, most of the SMI physics can be tested with the electron and positron bunches available at SLAC-FACET. *** In this case, the bunch is ~10 plasma wavelengths long, but can drive wakefields in the GV/m range. FACET has a meter-long plasma **** and is well equipped in terms of diagnostic for SMI detection: optical transition radiation for transverse bunch profile measurements, coherent transition radiation interferometry for radial modulation period measurements and energy spectrometer for energy loss and gain measurement of the drive bunch particles. The latest experimental results will be presented.
* N. Kumar et al., PRL 104, 255003 (2010)
** AWAKE Collaboration, PPCF 56 084013 (2014)
*** J. Vieira et al., PoP 19, 063105 (2012)
**** S.Z. Green et al., PPCF 56, 084011 (2014)

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WEPWA026

Loading of a Plasma-Wakefield Accelerator Section Driven by a Self-Modulated Proton Bunch

2551

V.K.B. Olsen, E. Adli
University of Oslo, Oslo, Norway
L.D. Amorim
IST, Lisboa, Portugal
P. Muggli
MPI, Muenchen, Germany
J. Vieira
Instituto Superior Tecnico, Lisbon, Portugal

We investigate beam loading of a plasma wake driven by a self-modulated proton beam using particle-in-cell simulations for phase III of the AWAKE project. We address the case of injection after the proton beam has already experienced self-modulation in a previous plasma. Optimal parameters for the injected electron bunch in terms of initial beam energy and beam charge density are investigated and evaluated in terms of witness bunch energy and energy spread. An approximate modulated proton beam is emulated in order to reduce computation time in these simulations.

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WEPWA033

Characterization of Laser-plasma Accelerated Electron Beam for a Compact Storage Ring

2569

S. H. Park, Y. Cha, Y.U. Jeong, J.S. Jo, H.N. Kim, K.N. Kim, K. Lee, W.J. Ryu, J.S. Shinn, N. Vinokurov
KAERI, Daejon, Republic of Korea
N. Vinokurov
BINP SB RAS, Novosibirsk, Russia

A compact radiation source can be utilized by an electron beam from a Laser-plasma acceleration combined with localized shielding in a small laboratory. The stability of synchrotron radiation in wavelength and power depends on the shot-to-shot jitters of the energy and charge of an electron beam, which is strongly influenced by the plasma density of target and the jitters of a laser beam. With the 30 TW fs laser in KAERI, the optimization for generating the electron beam have done using the different shape of gas nozzle. We also present the pointing stability and the energy spread of the laser-accelerated electron beams.

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WEPWA034

High-charge-short-bunch Operation Possibility at Argonne Wakefield Accelerator Facility

2572

G. Ha, M.-H. Cho, W. Namkung
POSTECH, Pohang, Kyungbuk, Republic of Korea
W. Gai, G. Ha, K.-J. Kim, J.G. Power
ANL, Argonne, Illinois, USA

Originally the drive beam line at Argonne Wakefield Accelerator (AWA) Facility was designed to generate the high charge bunch train. However, we recently installed the double dog-leg type emittance exchange beam line which have two identical dog-leg structures. With this beam line, it is possible to compress the bunch by introducing the chicane or using single dog-leg. Simulation studies have been carried out to confirm the minimum bunch length for each charge and the emittance growth by the coherent synchrotron radiation. We present GPT simulation results to show high-charge-short-bunch operation possibility at AWA facility.

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WEPWA039

The AWAKE Electron Primary Beam Line

2584

J.S. Schmidt, J. Bauche, B. Biskup, C. Bracco, E. Bravin, S. Döbert, M.A. Fraser, B. Goddard, E. Gschwendtner, L.K. Jensen, O.R. Jones, S. Mazzoni, M. Meddahi, A.V. Petrenko, F.M. Velotti, A.S. Vorozhtsov
CERN, Geneva, Switzerland
U. Dorda
DESY, Hamburg, Germany
L. Merminga, V.A. Verzilov
TRIUMF, Vancouver, Canada
P. Muggli
MPI, Muenchen, Germany

The AWAKE project at CERN is planned to study proton driven plasma wakefield acceleration. The proton beam from the SPS will be used in order to drive wakefields in a 10 m long Rb plasma cell. In the first phase of this experiment, scheduled in 2016, the self-modulation of the proton beam in the plasma will be studied in detail, while in the second phase an external electron beam will be injected into the plasma wakefield to probe the acceleration process. The installation of AWAKE in the former CNGS experimental area and the required optics flexibility define the tight boundary conditions to be fulfilled by the electron beam line design. The transport of low energy (10-20 MeV) bunches of 1.25·10⁹ electrons and the synchronous copropagation with much higher intensity proton bunches (3E11) determines several technological and operational challenges for the magnets and the beam diagnostics. The current status of the electron line layout and the associated equipments are presented in this paper.

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WEPWA045

Development of a Spectrometer for Proton Driven Plasma Wakefield Accelerated Electrons at AWAKE

2601

L.C. Deacon, S. Jolly, F. Keeble, M. Wing
UCL, London, United Kingdom
B. Biskup
Czech Technical University, Prague 6, Czech Republic
B. Biskup, E. Bravin, A.V. Petrenko
CERN, Geneva, Switzerland
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 metres in length. To observe 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. Improvements to the baseline design are presented, with an alternative dipole magnet and quadrupole focussing, with the resulting energy resolution calculated for various scenarios. The signal to background ratio due to the interaction of the SPS protons with upstream beam line components is calculated, and CCD camera location, shielding and light transport are considered.

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WEPWA047

Emittance Growth in a Plasma Wakefield Accelerator

2609

Ö. Mete, K. Hanahoe, G.X. Xia
UMAN, Manchester, United Kingdom
M. Labiche
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

The interaction of the witness beam with the surrounding plasma particles and wakefields was studied. The implications of the elastic scattering process on beam emittance and, emittance evolution under the focusing and acceleration provided by plasma wakefields were discussed. Simulations results from GEANT4 are presented in this paper.

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WEPWA048

Design Studies and Commissioning Plans for PARS Experimental Program

2612

Ö. Mete, K. Hanahoe, J. Wright, G.X. Xia
UMAN, Manchester, United Kingdom
M. Dover, M. Wigram, J. Zhang
University of Manchester, Manchester, United Kingdom
J.D.A. Smith
Tech-X, Boulder, Colorado, USA

Funding: Science and Technology Facilities Council and Cockcroft Institute Core Grant
PARS (Plasma Acceleration Research Station) is an electron beam driven plasma wakefield acceleration test stand proposed for VELA/CLARA facility in Daresbury Laboratory. In order to optimise various operational configurations, 2D numerical studies were performed by using VSIM for a range of parameters such as bunch length, radius, plasma density and positioning of the bunches with respect to each other for the two-beam acceleration scheme. In this paper, some of these numerical studies and considered measurement methods are presented.

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WEPWA068

Simulation of Laser Pulse Driven Terahertz Generation in Inhomogeneous Plasmas

2661

C.M. Miao, T.M. Antonsen
UMD, College Park, Maryland, USA
J. Palastro
Icarus Research, Inc., Bethesda, Maryland, USA

Intense, short laser pulses propagating through inhomogeneous plasma can ponderomotively drive THz radiation. Here we consider a transition radiation mechanism (TRM) for THz generation as a laser pulse crosses a plasma boundary. Full format PIC simulations and theoretical analysis are conducted demonstrating that TRM results in low frequency, broad band, coherent THz radiation. The effect of a density ramp is also considered and shown to enhance the radiated energy.

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WEPJE001

Optimal Positron-Beam Excited Plasma Wakefields in Hollow and Ion-Wake Channels

2674

A. A. Sahai, T.C. Katsouleas
Duke ECE, Durham, North Carolina, USA

Funding: DE-SC-0010012, NSF-PHY-0936278
A positron-beam interacting with the plasma electrons drives radial suck-in, in contrast to an electron-beam driven blow-out in the over-dense regime, n_b>n₀. In a homogeneous plasma, the electrons are radially sucked-in from all the different radii. The electrons collapsing from different radii do not simultaneously compress on-axis driving weak fields. A hollow-channel allows electrons from its channel-radius to collapse simultaneously exciting coherent fields *. We analyze the optimal channel radius. Additionally, the low ion density in the hollow allows a larger region with focusing phase. We have shown the formation of an ion-wake channel behind a blow-out electron bubble-wake. Here we explore positron acceleration in the over-dense regime comparing an optimal hollow-plasma channel to the ion-wake channel **. The condition for optimal hollow-channel radius is also compared. We also address the effects of a non-ideal ion-wake channel on positron-beam excited fields.
* S Lee, T Katsouleas, Phys. Rev. E, vol 64, 045501(R) (2001)
** A A Sahai, T Katsouleas, Non-linear ion-wake excitation by ultra relativistic electron wakefields, in review (http://arxiv.org/pdf/1504.03735v1.pdf)

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