IPAC2014 - Classification: 03 Particle Sources and Alternative Acceleration Techniques / A16 Advanced Concepts

Paper	Title	Page
TUPME044	Planned High-brightness Channeling Radiation Experiment at Fermilab's Advanced Superconducting Test Accelerator	1457
	B.R. Blomberg, D. Mihalcea, H. Panuganti, P. Piot Northern Illinois University, DeKalb, Illinois, USA C.A. Brau, B.K. Choi, W.E. Gabella, B.L. Ivanov, M.H. Mendenhall Vanderbilt University, Nashville, Tennessee, USA C.W. Lynn Swarthmore College, Swarthmore, Pennsylvania, USA P. Piot, T. Sen Fermilab, Batavia, Illinois, USA W.S. Wagner Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Radiation Physics, Dresden, Germany
	Funding: Work supported by the DARPA Axis program under contract AXIS N66001-11-1-4196 In this contribution we describe the technical details and experimental setup of our study aimed at producing high-brightness channeling radiation (CR) at Fermilab’s new user facility the Advanced Superconducting Test Accelerator (ASTA). In the ASTA photoinjector area electrons are accelerated up to 40-MeV and focused to a sub-micron spot on a ~40 micron thick carbon diamond, the electrons channel through the crystal and emit CR up to 80-KeV. Our study utilizes ASTA’s long pulse train capabilities and ability to preserve ultra-low emittance, to produce the desired high average brightness.
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TUPME047	SINBAD - A Proposal for a Dedicated Accelerator Research Facility at DESY	1466
	R.W. Aßmann, C. Behrens, R. Brinkmann, U. Dorda, K. Flöttmann, B. Foster, J. Grebenyuk, I. Hartl, M. Hüning, Y.C. Nie, J. Osterhoff, A. Rühl, H. Schlarb, B. Schmidt DESY, Hamburg, Germany M. Groß, B. Marchetti, F. Stephan DESY Zeuthen, Zeuthen, Germany F.J. Grüner, B. Hidding, A.R. Maier Uni HH, Hamburg, Germany F.X. Kärtner, B. Zeitler CFEL, Hamburg, Germany A.-S. Müller, M. Schuh KIT, Karlsruhe, Germany
	A new, dedicated accelerator research facility SINBAD (Short INnovative Bunches and Accelerators at DESY) is proposed. This facility is aimed at promoting two major goals: (1) Short electron bunches for ultra-fast science. (2) Construction of a plasma accelerator module with useable beam quality. Research and development on these topics is presently ongoing at various places at DESY, as add-on experiments at operational facilities. The two research goals are intimately connected: short bunches and precise femtosecond timing are requirements for developing a plasma accelerator module. The scientific case of a dedicated facility for accelerator research at DESY is discussed. Further options are mentioned, like the use of a 1 GeV beam from Linac2 for FEL studies and the setup of an attosecond radiation source with advanced technology. The presently planned conversion of the DORIS storage ring and its central halls into the SINBAD facility is described. The available space will allow setting up several independent experiments with a cost-effective use of the same infrastructure. National and international contributions and proposals can be envisaged.
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TUPME048	Injection of a LWFA Electron Bunch in a PWFA Driven by a Self-modulated-proton-bunch	1470
	P. Muggli MPI, Muenchen, Germany L.D. Amorim IST, Lisboa, Portugal S. Karsch MPQ, Garching, Munich, Germany N.C. Lopes, J. Vieira Instituto Superior Tecnico, Lisbon, Portugal
	The AWAKE experiment recently approved at CERN will study the acceleration of an externally injected electron bunch in a plasma wakefield accelerator (PWFA) driven by a self-modulated proton bunch. We study the possibility of injecting a bunch created by a laser-driven plasma wakefield accelerator (LWFA). We consider a first plasma source used for self-modulation of the drive bunch and a gas discharge source for acceleration of the collinearly injected bunch. The LWFA produces an electron bunch very short when compared to the PWFA wavelength and with relatively large current, possibly allowing for loading of the wakefields. Short length and high current lead to a small final energy spread. Co-linear injection preserves the incoming bunch quality and insures trapping and acceleration of the whole bunch. The energy of the LWFA electron bunch can easily exceed the trapping energy and can be produced over only a few millimeters gas-jet plasma driven by a laser of relatively modest power by today’s standards. We explore the parameter space suitable for this injection scheme that is more compact, simpler to implement and more suitable for injection in the mm-size accelerator structure.
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TUPME052	Enhanced Laser Ion Acceleration based on Near-Critical Density Plasma Lens	1483
SUSPSNE023	use link to see paper's listing under its alternate paper code
	Y.X. Geng, J.E. Chen, L.R.F. Li, Y.H. Li, Q. Liao, C. Lin, L.H.Y. Lu, Y.R. Lu, H. Wang, X.Q. Yan, Z.X. Yuan, S. Zhao, W.B. Zhao, Y.Y. Zhao, K. Zhu, B.Y. Zou PKU, Beijing, People's Republic of China
	The laser prepulse has large effect on ion acceleration driven by high power laser pulse. Recently, simulations show that with proper prepulse parameters, a near critical density pre-plasma can be generated in the front target. When the main laser pulse propagating in this pre-plasma, it can experience transverse Self-focusing, longitudinal profile steepening and prepluse cleaning at the same time, meaning its quality is spontaneously improved by this “plasma lens”.The effects can greatly improve the energy coupling efficiency of laser pulse into accelerated ions. A 3mJ Ti-Sapphire laser system has been built at PKU in order to experimentally study the pre-pulse effect on a solid target. Fluid simulation show that, after hundreds of picoseconds radiated with this laser pulse, the pre-plasma in front of the target will expand to near critical density with tens of micron scale length, which is suitable as a plasma lens to improve the ion acceleration. A laser interferometer system is built to measure the scale length and density evolution of plasma and the optimum condition of the pre-plasma has been searched using both Aluminum target and home-made DLC target. H.Y.Wang et al, Laser shaping of a relativistic intense, short Gaussian pulse by a plasma lens, PRL, 107,265002, 2011
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TUPME053	Study of the Energy Modulated Electron Cyclotron Resonance Ion Source for the Coupled RFQ-SFRFQ Cavity	1486
	W.L. Xia, J.E. Chen, S.L. Gao, Z.Y. Guo, Y.R. Lu, S.X. Peng, Z. Wang, X.Q. Yan, J. Zhao, K. Zhu PKU, Beijing, People's Republic of China
	The coupled RFQ and SFRFQ cavity has been manufactured and tested recently. According to the beam dynamic design, the input He⁺ beam within 120° phase width is designed for the cavity to achieve over 98% transmission efficiency. An energy modulated electron cyclotron resonance (ECR) ion source was proposed and simulated. To achieve the 1% energy modulation on the 30keV direct current (DC) beam, two simplified RF power feeding structures for beam bunching were studied. The simulations show positive results as well as the bunched beam is achieved by the energy modulated ECR ion source.
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TUPME054	Influence of a Vacuum Gap on a Bunch Wakefield in a Circular Waveguide Filled up with Dielectric	1489
	T.Yu. Alekhina, A.V. Tyukhtin, V.V. Vorobev Saint-Petersburg State University, Saint-Petersburg, Russia
	Analysis of electromagnetic field of a particle bunch intersecting several boundaries in a dielectric waveguide is important for the wakefield acceleration technique and other problems of accelerator physics. In previous works we investigated the case of a single boundary in a waveguide. Now we study the electromagnetic field of the bunch moving in a dielectric circular waveguide and crossing a vacuum cavity. The main attention is given to the case when wakefield (Cherenkov radiation) is generated in dielectric. The behavior of the total field depending on distance and time is explored numerically. Analytical estimations are made as well. Influence of the vacuum gap on the wakefield is considered for different lengths of the gap. It is clarified conditions when the vacuum gap does not practically influence on the wakefield. It is noted that the quasi monochromatic wave (the Cherenkov transition radiation) generated in the vacuum region can be used for restoration of the field in the area after the gap. This effect can be achieved for some optimal parameters of the problem. T.Yu. Alekhina, A.V. Tyukhtin, Phys. Rev. ST-AB, v.15, 091302 (2012); T.Yu. Alekhina, A.V. Tyukhtin, Phys. Rev. ST-AB, v.16, 081301 (2013).
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TUPME055	Room-temperature Burst-mode GHz and THz Pulse-train Photoinjector	1492
SUSPSNE022	use link to see paper's listing under its alternate paper code
	F.H. Chao, C.H. Chen, K.Y. Huang, Y.-C. Huang, Y.C. Wang, M.H. Wu NTHU, Hsinchu, Taiwan P.J. Chou NSRRC, Hsinchu, Taiwan
	A photoinjector usually generates an electron pulse with few ps pulse duration repeating at 10-100 Hz. The low-pulse rate limits the data rate in a number of applications. Although high-repetition-rate operation is possible from a superconducting accelerator, the high cost and complexity of a superconducting system prevent it from being widely used. In this paper, we present our study toward a burst-mode GHz/THz pulse train photoinjector operating at room temperature. For the GHz operation mode, we self-develop a driver laser system, generating tens of laser pulses at 2.856 GHz in an adjustable 5-10 ns temporal envelope repeating at 10 Hz. Upon illuminating the photocathode with the driver laser, our S-band photoinjector (supported by Tsing Hua University, Beijing) is to generate a GHz electron pulse train with the same temporal structure as that of the driver laser pulses. For the THz operation mode, we illuminate the photocathode with two lasers, one being a typical UV gun-driver laser at 260 nm and the other being a mid-infrared laser at 100 THz. The UV laser induces photoemission and the infrared laser gates the emission current at 100 THz by virtue of the Schottky effect.
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TUPME056	Improving Ion and Electron Beam Characteristics within LA³NET	1495
	C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom C.P. Welsch The University of Liverpool, Liverpool, United Kingdom
	Funding: This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 289191. Lasers are widely used at accelerator and light source facilities for beam generation, acceleration and optimization. Research within LA³NET focuses on laser-based particle sources (photo injectors and laser ion sources), laser acceleration, and laser-based beam diagnostics. This project was recently selected as a ‘success story’ by the European Commission for its research achievements. This paper presents selected numerical and experimental results. From HZDR results of electron transport simulations in their new SRF gun II cavity, super-conductive solenoid and downstream accelerators are shown. The results from optimization studies into asymmetric grating structures obtained at the University of Liverpool are also presented, along with initial results from studies into novel diagnostics for high intensity proton beams at CERN and low energy electron beams at KIT. Finally, the events organized by the consortium to date and future plans are summarized.
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TUPME058	The Argonne Wakefield Accelerator (AWA): Commissioning and Operation	1503
	M.E. Conde, S.P. Antipov, D.S. Doran, W. Gai, C.-J. Jing, C. Li, W. Liu, J.G. Power, J.Q. Qiu, J.H. Shao, C. Whiteford, E.E. Wisniewski ANL, Argonne, Illinois, USA S.P. Antipov, C.-J. Jing, J.Q. Qiu Euclid TechLabs, LLC, Solon, Ohio, USA S. Cao IMP, Lanzhou, People's Republic of China C. Li, J.H. Shao TUB, Beijing, People's Republic of China E.E. Wisniewski Illinois Institute of Technology, Chicago, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-06CH11357. The commissioning of the upgraded AWA facility is well underway. The new L-band electron gun has been fully commissioned and has been successfully operated with its Cesium Telluride photocathode at a gradient of 80 MV/m. Single bunches of up to 100 nC, and bunch trains of four bunches with up to 80 nC per bunch have been generated. The six new accelerating cavities (L-band, seven cells, pi mode) have been RF conditioned to 12 MW or more; their operation at 10 MW brings the beam energy up to 75 MeV. Measurements of the beam parameters are presently underway, and the use of this intense beam to drive high gradient wakefields will soon follow. One of the main goals of the facility is to generate RF pulses with GW power levels, corresponding to accelerating gradients of hundreds of MV/m and energy gains on the order of 100 MeV per structure.
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TUPME059	Longitudinal Bunch Shaping with a Double Dogleg based Emittance Exchange Beam Line	1506
	G. Ha, M.E. Conde, W. Gai, C.-J. Jing, K.-J. Kim, J.G. Power, A. Zholents ANL, Argonne, Illinois, USA M.-H. Cho, G. Ha, W. Namkung POSTECH, Pohang, Kyungbuk, Republic of Korea C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA
	Funding: Work supported by High Energy Physics, Office of Science, US DOE. A new program is under development at Argonne National Laboratory (ANL) to use an emittance exchange (EEX) beamline to produce longitudinally shaped electron bunches. While the ultimate goal is to generate triangular shapes for high transformer ratio wakefield acceleration we are also exploring, in general, the capability of the double dogleg EEX beamline to control the bunch shape. We are studying effects that degrade the quality of the longitudinal current profile including: non-uniform particle distribution, emittance, the deflecting cavity thick-lens effect, 2nd order effects, space charge effects and coherent synchrotron radiation effects. We will present the double dogleg EEX beamline layout and the diagnostic design as well as give a progress report on the experimental status of the program.
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TUPME060	Simulation Analysis on Micro-Bunched Density Modulation from a Slit-Masked Chicane	1509
	Y.-M. Shin, P. Piot, C.R. Prokop Northern Illinois University, DeKalb, Illinois, USA D.R. Broemmelsiek, E.R. Harms, A.H. Lumpkin, J. Ruan, J.C.T. Thangaraj Fermilab, Batavia, Illinois, USA
	Funding: This work was supported by the DOE contract No. DEAC02-07CH11359 to the Fermi Research Alliance LLC. Pre-bunching a beam at a resonance condition with an accelerating structure vastly improves performance of beam-driven accelerators and undulators since it enhances a beam-wave coupling. We plan to test a slit-mask micro-buncher at the chicane of Fermilab-ASTA 50 MeV beamline in the effort of advanced accelerator research. With the chicane design parameters (bending angle (alpha) of 18 degree, R56 ~ - 0.18 m, and bending radius of ~ 0.78 m), analytic model showed that a slit-mask with W (period) = 900 um and a (aperture width) = 300 um (30 % transparency) generates 100 um spaced micro-bunches with 5 ~ 6 % correlated energy spread. Two kinds of combined beamline simulation, CST-PS+Impact-Z and Elegant+Shower, including space charge and CSR effects, showed that a 900 um spaced, 300 um wide slits placed in the middle of chicane splits 20 pC – 1 nC bunches into ~ 100 um spaced micro-bunches. It is possible that a further optimization of mask design creates sub-100 fs micro-bunches, which is currently under development. [1] NIM A 375, 597 (1996) [2] PRL 101, 054801 (2008) [3] Y.-E Sun, P. R. G. Piot, FEMILAB-CONF-08-408-APC * ASTA: Advanced Superconducting Test Accelerator
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TUPME061	Ultra-High Gradient Beam-Driven Channeling Acceleration in Hollow Crystalline Media	1512
	Y.-M. Shin, T. Xu Northern Illinois University, DeKalb, Illinois, USA G. Flanagan Muons, Inc, Illinois, USA E.R. Harms, J. Ruan, V.D. Shiltsev Fermilab, Batavia, Illinois, USA
	Since the recent discovery of the Higgs boson particle, there is an increasing demand in Energy Frontier to develop new technology for a TeV/m range of acceleration gradient. The density of charge carriers, ~ 10²⁴ – 10²⁹ m^-3, of crystals is significantly higher than that of a plasma gas, and correspondingly in principle wakefield gradients of up to 0.1 - 10 TV/m are possible. Our simulations (VORPAL and CST-PIC) with Fermilab-ASTA* beam parameters showed that micro-bunched beam gains energy up to ~ 70 MeV along the 100 um long channel under the resonant coupling condition of the plasma wavelength, ~ 10 um. Also, with lowering a charge, electron bunches channeling through a high-density plasma medium have higher energy gain in a hollow channel than in a uniformly filled cylinder, which might be attribute to lower scattering ratios of the tunnel structure. The numerical analysis implied that synthetic crystalline plasma media (e.g. carbon nanotubes) have potential to mitigate constraint of bunch charges required for beam-driven acceleration in high density plasma media. The channeling acceleration** will be tested at the ASTA facility, once fully commissioned. * ASTA: Advanced Superconducting Test Accelerator ** [1] T. Tajima and M. Cavenago, PRL 59, 13(1987) [2] P. Chen and R. Noble, SLAC-PUB-7402(1998) [3] V.Shiltsev, Physics Uspekhi 55, 965(2012)
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WEOAB03	Linear Electron Acceleration in THz Waveguides	1896
	E.A. Nanni, W.S. Graves, K.-H. Hong, W.R. Huang, F.X. Kärtner, KR. Ravi, L.J. Wong MIT, Cambridge, Massachusetts, USA A. Fallahi, F.X. Kärtner CFEL, Hamburg, Germany R.J.D. Miller DESY, Hamburg, Germany G. Moriena University of Toronto, Toronto, Ontario, Canada
	Funding: Supported by DARPA N66001-11-1-4192, CFEL DESY, DOE DEFG02-10ER46745, DOE DE-FG02-08ER41532, ERC Synergy Grant 609920 and NSF DMR-1042342. We report the first experimental demonstration of linear electron acceleration using an optically generated single cycle THz pulse centered at 0.45 THz. 7 keV of acceleration is achieved using 10 microJ THz pulses in a 3 mm interaction length. The THz pulse is produced via optical rectification of a 1.2 mJ, 1 micron laser pulse with a 1 kHz repetition rate. The THz pulse is coupled into a dielectric-loaded circular waveguide with 10 MeV/m on-axis accelerating gradient. A 25 fC input electron bunch is produced with a 60 keV DC photo-emitting cathode. The achievable accelerating gradient in the THz structures being investigated will scale rapidly by increasing the IR pulse energy (100 mJ - 1 J) and correspondingly the THz pulse energy. Additionally, with recent advances in the generation of THz pulses via optical rectification, in particular improvements to efficiency and generation of multi-cycle pulses, GeV/m accelerating gradients could be achieved. An ultra-compact high-gradient THz accelerator would be of interest for a wide variety of applications.
	Slides WEOAB03 [7.185 MB]
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Paper

Title

Page

Planned High-brightness Channeling Radiation Experiment at Fermilab's Advanced Superconducting Test Accelerator

1457

B.R. Blomberg, D. Mihalcea, H. Panuganti, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
C.A. Brau, B.K. Choi, W.E. Gabella, B.L. Ivanov, M.H. Mendenhall
Vanderbilt University, Nashville, Tennessee, USA
C.W. Lynn
Swarthmore College, Swarthmore, Pennsylvania, USA
P. Piot, T. Sen
Fermilab, Batavia, Illinois, USA
W.S. Wagner
Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Radiation Physics, Dresden, Germany

Funding: Work supported by the DARPA Axis program under contract AXIS N66001-11-1-4196
In this contribution we describe the technical details and experimental setup of our study aimed at producing high-brightness channeling radiation (CR) at Fermilab’s new user facility the Advanced Superconducting Test Accelerator (ASTA). In the ASTA photoinjector area electrons are accelerated up to 40-MeV and focused to a sub-micron spot on a ~40 micron thick carbon diamond, the electrons channel through the crystal and emit CR up to 80-KeV. Our study utilizes ASTA’s long pulse train capabilities and ability to preserve ultra-low emittance, to produce the desired high average brightness.

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TUPME047

SINBAD - A Proposal for a Dedicated Accelerator Research Facility at DESY

1466

R.W. Aßmann, C. Behrens, R. Brinkmann, U. Dorda, K. Flöttmann, B. Foster, J. Grebenyuk, I. Hartl, M. Hüning, Y.C. Nie, J. Osterhoff, A. Rühl, H. Schlarb, B. Schmidt
DESY, Hamburg, Germany
M. Groß, B. Marchetti, F. Stephan
DESY Zeuthen, Zeuthen, Germany
F.J. Grüner, B. Hidding, A.R. Maier
Uni HH, Hamburg, Germany
F.X. Kärtner, B. Zeitler
CFEL, Hamburg, Germany
A.-S. Müller, M. Schuh
KIT, Karlsruhe, Germany

A new, dedicated accelerator research facility SINBAD (Short INnovative Bunches and Accelerators at DESY) is proposed. This facility is aimed at promoting two major goals: (1) Short electron bunches for ultra-fast science. (2) Construction of a plasma accelerator module with useable beam quality. Research and development on these topics is presently ongoing at various places at DESY, as add-on experiments at operational facilities. The two research goals are intimately connected: short bunches and precise femtosecond timing are requirements for developing a plasma accelerator module. The scientific case of a dedicated facility for accelerator research at DESY is discussed. Further options are mentioned, like the use of a 1 GeV beam from Linac2 for FEL studies and the setup of an attosecond radiation source with advanced technology. The presently planned conversion of the DORIS storage ring and its central halls into the SINBAD facility is described. The available space will allow setting up several independent experiments with a cost-effective use of the same infrastructure. National and international contributions and proposals can be envisaged.

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TUPME048

Injection of a LWFA Electron Bunch in a PWFA Driven by a Self-modulated-proton-bunch

1470

P. Muggli
MPI, Muenchen, Germany
L.D. Amorim
IST, Lisboa, Portugal
S. Karsch
MPQ, Garching, Munich, Germany
N.C. Lopes, J. Vieira
Instituto Superior Tecnico, Lisbon, Portugal

The AWAKE experiment recently approved at CERN will study the acceleration of an externally injected electron bunch in a plasma wakefield accelerator (PWFA) driven by a self-modulated proton bunch. We study the possibility of injecting a bunch created by a laser-driven plasma wakefield accelerator (LWFA). We consider a first plasma source used for self-modulation of the drive bunch and a gas discharge source for acceleration of the collinearly injected bunch. The LWFA produces an electron bunch very short when compared to the PWFA wavelength and with relatively large current, possibly allowing for loading of the wakefields. Short length and high current lead to a small final energy spread. Co-linear injection preserves the incoming bunch quality and insures trapping and acceleration of the whole bunch. The energy of the LWFA electron bunch can easily exceed the trapping energy and can be produced over only a few millimeters gas-jet plasma driven by a laser of relatively modest power by today’s standards. We explore the parameter space suitable for this injection scheme that is more compact, simpler to implement and more suitable for injection in the mm-size accelerator structure.

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TUPME052

Enhanced Laser Ion Acceleration based on Near-Critical Density Plasma Lens

1483

SUSPSNE023

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

Y.X. Geng, J.E. Chen, L.R.F. Li, Y.H. Li, Q. Liao, C. Lin, L.H.Y. Lu, Y.R. Lu, H. Wang, X.Q. Yan, Z.X. Yuan, S. Zhao, W.B. Zhao, Y.Y. Zhao, K. Zhu, B.Y. Zou
PKU, Beijing, People's Republic of China

The laser prepulse has large effect on ion acceleration driven by high power laser pulse. Recently, simulations show that with proper prepulse parameters, a near critical density pre-plasma can be generated in the front target. When the main laser pulse propagating in this pre-plasma, it can experience transverse Self-focusing, longitudinal profile steepening and prepluse cleaning at the same time, meaning its quality is spontaneously improved by this “plasma lens”.The effects can greatly improve the energy coupling efficiency of laser pulse into accelerated ions. A 3mJ Ti-Sapphire laser system has been built at PKU in order to experimentally study the pre-pulse effect on a solid target. Fluid simulation show that, after hundreds of picoseconds radiated with this laser pulse, the pre-plasma in front of the target will expand to near critical density with tens of micron scale length, which is suitable as a plasma lens to improve the ion acceleration. A laser interferometer system is built to measure the scale length and density evolution of plasma and the optimum condition of the pre-plasma has been searched using both Aluminum target and home-made DLC target.
H.Y.Wang et al, Laser shaping of a relativistic intense, short Gaussian pulse by a plasma lens, PRL, 107,265002, 2011

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TUPME053

Study of the Energy Modulated Electron Cyclotron Resonance Ion Source for the Coupled RFQ-SFRFQ Cavity

1486

W.L. Xia, J.E. Chen, S.L. Gao, Z.Y. Guo, Y.R. Lu, S.X. Peng, Z. Wang, X.Q. Yan, J. Zhao, K. Zhu
PKU, Beijing, People's Republic of China

The coupled RFQ and SFRFQ cavity has been manufactured and tested recently. According to the beam dynamic design, the input He⁺ beam within 120° phase width is designed for the cavity to achieve over 98% transmission efficiency. An energy modulated electron cyclotron resonance (ECR) ion source was proposed and simulated. To achieve the 1% energy modulation on the 30keV direct current (DC) beam, two simplified RF power feeding structures for beam bunching were studied. The simulations show positive results as well as the bunched beam is achieved by the energy modulated ECR ion source.

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TUPME054

Influence of a Vacuum Gap on a Bunch Wakefield in a Circular Waveguide Filled up with Dielectric

1489

T.Yu. Alekhina, A.V. Tyukhtin, V.V. Vorobev
Saint-Petersburg State University, Saint-Petersburg, Russia

Analysis of electromagnetic field of a particle bunch intersecting several boundaries in a dielectric waveguide is important for the wakefield acceleration technique and other problems of accelerator physics. In previous works we investigated the case of a single boundary in a waveguide*. Now we study the electromagnetic field of the bunch moving in a dielectric circular waveguide and crossing a vacuum cavity. The main attention is given to the case when wakefield (Cherenkov radiation) is generated in dielectric. The behavior of the total field depending on distance and time is explored numerically. Analytical estimations are made as well. Influence of the vacuum gap on the wakefield is considered for different lengths of the gap. It is clarified conditions when the vacuum gap does not practically influence on the wakefield. It is noted that the quasi monochromatic wave (the Cherenkov transition radiation) generated in the vacuum region can be used for restoration of the field in the area after the gap. This effect can be achieved for some optimal parameters of the problem.
* T.Yu. Alekhina, A.V. Tyukhtin, Phys. Rev. ST-AB, v.15, 091302 (2012);
T.Yu. Alekhina, A.V. Tyukhtin, Phys. Rev. ST-AB, v.16, 081301 (2013).

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TUPME055

Room-temperature Burst-mode GHz and THz Pulse-train Photoinjector

1492

SUSPSNE022

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

F.H. Chao, C.H. Chen, K.Y. Huang, Y.-C. Huang, Y.C. Wang, M.H. Wu
NTHU, Hsinchu, Taiwan
P.J. Chou
NSRRC, Hsinchu, Taiwan

A photoinjector usually generates an electron pulse with few ps pulse duration repeating at 10-100 Hz. The low-pulse rate limits the data rate in a number of applications. Although high-repetition-rate operation is possible from a superconducting accelerator, the high cost and complexity of a superconducting system prevent it from being widely used. In this paper, we present our study toward a burst-mode GHz/THz pulse train photoinjector operating at room temperature. For the GHz operation mode, we self-develop a driver laser system, generating tens of laser pulses at 2.856 GHz in an adjustable 5-10 ns temporal envelope repeating at 10 Hz. Upon illuminating the photocathode with the driver laser, our S-band photoinjector (supported by Tsing Hua University, Beijing) is to generate a GHz electron pulse train with the same temporal structure as that of the driver laser pulses. For the THz operation mode, we illuminate the photocathode with two lasers, one being a typical UV gun-driver laser at 260 nm and the other being a mid-infrared laser at 100 THz. The UV laser induces photoemission and the infrared laser gates the emission current at 100 THz by virtue of the Schottky effect.

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TUPME056

Improving Ion and Electron Beam Characteristics within LA³NET

1495

C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

Funding: This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 289191.
Lasers are widely used at accelerator and light source facilities for beam generation, acceleration and optimization. Research within LA³NET focuses on laser-based particle sources (photo injectors and laser ion sources), laser acceleration, and laser-based beam diagnostics. This project was recently selected as a ‘success story’ by the European Commission for its research achievements. This paper presents selected numerical and experimental results. From HZDR results of electron transport simulations in their new SRF gun II cavity, super-conductive solenoid and downstream accelerators are shown. The results from optimization studies into asymmetric grating structures obtained at the University of Liverpool are also presented, along with initial results from studies into novel diagnostics for high intensity proton beams at CERN and low energy electron beams at KIT. Finally, the events organized by the consortium to date and future plans are summarized.

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TUPME058

The Argonne Wakefield Accelerator (AWA): Commissioning and Operation

1503

M.E. Conde, S.P. Antipov, D.S. Doran, W. Gai, C.-J. Jing, C. Li, W. Liu, J.G. Power, J.Q. Qiu, J.H. Shao, C. Whiteford, E.E. Wisniewski
ANL, Argonne, Illinois, USA
S.P. Antipov, C.-J. Jing, J.Q. Qiu
Euclid TechLabs, LLC, Solon, Ohio, USA
S. Cao
IMP, Lanzhou, People's Republic of China
C. Li, J.H. Shao
TUB, Beijing, People's Republic of China
E.E. Wisniewski
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-06CH11357.
The commissioning of the upgraded AWA facility is well underway. The new L-band electron gun has been fully commissioned and has been successfully operated with its Cesium Telluride photocathode at a gradient of 80 MV/m. Single bunches of up to 100 nC, and bunch trains of four bunches with up to 80 nC per bunch have been generated. The six new accelerating cavities (L-band, seven cells, pi mode) have been RF conditioned to 12 MW or more; their operation at 10 MW brings the beam energy up to 75 MeV. Measurements of the beam parameters are presently underway, and the use of this intense beam to drive high gradient wakefields will soon follow. One of the main goals of the facility is to generate RF pulses with GW power levels, corresponding to accelerating gradients of hundreds of MV/m and energy gains on the order of 100 MeV per structure.

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TUPME059

Longitudinal Bunch Shaping with a Double Dogleg based Emittance Exchange Beam Line

1506

G. Ha, M.E. Conde, W. Gai, C.-J. Jing, K.-J. Kim, J.G. Power, A. Zholents
ANL, Argonne, Illinois, USA
M.-H. Cho, G. Ha, W. Namkung
POSTECH, Pohang, Kyungbuk, Republic of Korea
C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA

Funding: Work supported by High Energy Physics, Office of Science, US DOE.
A new program is under development at Argonne National Laboratory (ANL) to use an emittance exchange (EEX) beamline to produce longitudinally shaped electron bunches. While the ultimate goal is to generate triangular shapes for high transformer ratio wakefield acceleration we are also exploring, in general, the capability of the double dogleg EEX beamline to control the bunch shape. We are studying effects that degrade the quality of the longitudinal current profile including: non-uniform particle distribution, emittance, the deflecting cavity thick-lens effect, 2nd order effects, space charge effects and coherent synchrotron radiation effects. We will present the double dogleg EEX beamline layout and the diagnostic design as well as give a progress report on the experimental status of the program.

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TUPME060

Simulation Analysis on Micro-Bunched Density Modulation from a Slit-Masked Chicane

1509

Y.-M. Shin, P. Piot, C.R. Prokop
Northern Illinois University, DeKalb, Illinois, USA
D.R. Broemmelsiek, E.R. Harms, A.H. Lumpkin, J. Ruan, J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA

Funding: This work was supported by the DOE contract No. DEAC02-07CH11359 to the Fermi Research Alliance LLC.
Pre-bunching a beam at a resonance condition with an accelerating structure vastly improves performance of beam-driven accelerators and undulators since it enhances a beam-wave coupling. We plan to test a slit-mask micro-buncher at the chicane of Fermilab-ASTA 50 MeV beamline in the effort of advanced accelerator research. With the chicane design parameters (bending angle (alpha) of 18 degree, R56 ~ - 0.18 m, and bending radius of ~ 0.78 m), analytic model showed that a slit-mask with W (period) = 900 um and a (aperture width) = 300 um (30 % transparency) generates 100 um spaced micro-bunches with 5 ~ 6 % correlated energy spread. Two kinds of combined beamline simulation, CST-PS+Impact-Z and Elegant+Shower, including space charge and CSR effects, showed that a 900 um spaced, 300 um wide slits placed in the middle of chicane splits 20 pC – 1 nC bunches into ~ 100 um spaced micro-bunches. It is possible that a further optimization of mask design creates sub-100 fs micro-bunches, which is currently under development.
*[1] NIM A 375, 597 (1996)
[2] PRL 101, 054801 (2008)
[3] Y.-E Sun, P. R. G. Piot, FEMILAB-CONF-08-408-APC
** ASTA: Advanced Superconducting Test Accelerator

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TUPME061

Ultra-High Gradient Beam-Driven Channeling Acceleration in Hollow Crystalline Media

1512

Y.-M. Shin, T. Xu
Northern Illinois University, DeKalb, Illinois, USA
G. Flanagan
Muons, Inc, Illinois, USA
E.R. Harms, J. Ruan, V.D. Shiltsev
Fermilab, Batavia, Illinois, USA

Since the recent discovery of the Higgs boson particle, there is an increasing demand in Energy Frontier to develop new technology for a TeV/m range of acceleration gradient. The density of charge carriers, ~ 10²⁴ – 10²⁹ m^-3, of crystals is significantly higher than that of a plasma gas, and correspondingly in principle wakefield gradients of up to 0.1 - 10 TV/m are possible. Our simulations (VORPAL and CST-PIC) with Fermilab-ASTA* beam parameters showed that micro-bunched beam gains energy up to ~ 70 MeV along the 100 um long channel under the resonant coupling condition of the plasma wavelength, ~ 10 um. Also, with lowering a charge, electron bunches channeling through a high-density plasma medium have higher energy gain in a hollow channel than in a uniformly filled cylinder, which might be attribute to lower scattering ratios of the tunnel structure. The numerical analysis implied that synthetic crystalline plasma media (e.g. carbon nanotubes) have potential to mitigate constraint of bunch charges required for beam-driven acceleration in high density plasma media. The channeling acceleration** will be tested at the ASTA facility, once fully commissioned.
* ASTA: Advanced Superconducting Test Accelerator
** [1] T. Tajima and M. Cavenago, PRL 59, 13(1987)
[2] P. Chen and R. Noble, SLAC-PUB-7402(1998)
[3] V.Shiltsev, Physics Uspekhi 55, 965(2012)

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WEOAB03

Linear Electron Acceleration in THz Waveguides

1896

E.A. Nanni, W.S. Graves, K.-H. Hong, W.R. Huang, F.X. Kärtner, KR. Ravi, L.J. Wong
MIT, Cambridge, Massachusetts, USA
A. Fallahi, F.X. Kärtner
CFEL, Hamburg, Germany
R.J.D. Miller
DESY, Hamburg, Germany
G. Moriena
University of Toronto, Toronto, Ontario, Canada

Funding: Supported by DARPA N66001-11-1-4192, CFEL DESY, DOE DEFG02-10ER46745, DOE DE-FG02-08ER41532, ERC Synergy Grant 609920 and NSF DMR-1042342.
We report the first experimental demonstration of linear electron acceleration using an optically generated single cycle THz pulse centered at 0.45 THz. 7 keV of acceleration is achieved using 10 microJ THz pulses in a 3 mm interaction length. The THz pulse is produced via optical rectification of a 1.2 mJ, 1 micron laser pulse with a 1 kHz repetition rate. The THz pulse is coupled into a dielectric-loaded circular waveguide with 10 MeV/m on-axis accelerating gradient. A 25 fC input electron bunch is produced with a 60 keV DC photo-emitting cathode. The achievable accelerating gradient in the THz structures being investigated will scale rapidly by increasing the IR pulse energy (100 mJ - 1 J) and correspondingly the THz pulse energy. Additionally, with recent advances in the generation of THz pulses via optical rectification, in particular improvements to efficiency and generation of multi-cycle pulses, GeV/m accelerating gradients could be achieved. An ultra-compact high-gradient THz accelerator would be of interest for a wide variety of applications.

Slides WEOAB03 [7.185 MB]

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