Author: Gai, W.
Paper Title Page
MOPMB037 Beam Position Monitor Design for Dielectric Wakefield Accelerator In THz Range 171
 
  • Q. Gao, H.B. Chen, J. Shi
    TUB, Beijing, People's Republic of China
  • W. Gai
    ANL, Argonne, Illinois, USA
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
 
  Dielectric based collinear wakefield accelerator have been broadly selected for the THz accelerator due to its simplicity. In order to move the THz accelerators from the current exploratory research into the practical phase, certain common accelerator components are indispensable. Beam Position Monitor (BPM) is one of them. However, most of conventional BPM techniques are hardly scaled down to THz regime. Here we propose a BPM design which uses the dominant dipole mode excited in the dielectric wakefield accelerators to extract information of the beam position.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB037  
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TUOBB01 Demonstration of Current Profile Shaping using Double Dog-Leg Emittance Exchange Beam Line at Argonne Wakefield Accelerator 1065
 
  • G. Ha, M.-H. Cho, W. Namkung
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • M.E. Conde, D.S. Doran, W. Gai, G. Ha, K.-J. Kim, W. Liu, J.G. Power, Y.-E. Sun, C. Whiteford, E.E. Wisniewski, A. Zholents
    ANL, Argonne, Illinois, USA
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • P. Piot
    Fermilab, Batavia, Illinois, USA
 
  Emittance exchange (EEX) based longitudinal current profile shaping is the one of the promising current profile shaping technique. This method can generate high quality arbitrary current profiles under the ideal conditions. The double dog-leg EEX beam line was recently installed at the Argonne Wakefield Accelerator (AWA) to explore the shaping capability and confirm the quality of this method. To demonstrate the arbitrary current profile generation, several different transverse masks are applied to generate different final current profiles. The phase space slopes and the charge of incoming beam are varied to observe and suppress the aberrations on the ideal profile. We present current profile shaping results, aberrations on the shaped profile, and its suppression.  
slides icon Slides TUOBB01 [5.032 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUOBB01  
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TUPMY031 Estimation and Suppression of Aberrations in Emittance Exchange based Current Profile Shaping 1615
 
  • 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
 
  The longitudinal current profile manipulation has been explored for many applications including THz radiation, FEL and advanced acceleration schemes. Especially, collinear dielectric wakefield accelerations require a microbunch shaping for a high transformer ratio. We have studied aberrations from the emittance exchange based current profile shaping to preserve the high transformer ratio. All second order aberration terms in the double dog-leg emittance exchange beam line are discovered. Aberration patterns from each aberration sources like second order terms, space-charge, and CSR and their effect on the transformer ratio are estimated analytically. These aberration sources and corresponding patterns are confirmed using a particle tracking code GPT. Simple methods to suppress each aberration will be presented too. All calculation in this work is done with a double dog-leg emittance exchange beam line.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMY031  
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TUPMY036 Drive Generation and Propagation Studies for the Two Beam Acceleration Experiment at the Argonne Wakefield Accelerator 1629
SUPSS029   use link to see paper's listing under its alternate paper code  
 
  • N.R. Neveu, M.E. Conde, D.S. Doran, W. Gai, G. Ha, C.-J. Jing, W. Liu, J.G. Power, D. Wang, C. Whiteford, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  • S.P. Antipov, C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • G. Ha
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • N.R. Neveu
    IIT, Chicago, Illinois, USA
  • D. Wang
    TUB, Beijing, People's Republic of China
 
  Funding: Work supported by by the U.S. Department of Energy under contract No. DE-AC02-06CH11357.
Simplified staging in a two beam accelerator (TBA) has been accomplished at the Argonne Wakefield Accelerator (AWA) facility. This layout consists of a drive beamline and witness beamline operating synchronously. The drive photoinjector linac produces a 70 MeV drive bunch train of eight electron bunches (charge per bunch between 5-40 nC) that pass through decelerating structures in each TBA stage. The witness linac produces an 8 MeV witness bunch that passes through the accelerating structures in each TBA stage. Recent effort has been focused on improving the uniformity of the UV laser pulses that generate the bunch trains. Current work at the AWA is focused on the transition from simplified staging to full staging. A kicker will be designed and installed to direct bunch trains to one TBA stage only. Preliminary calculations and simulation results are presented.
 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMY036  
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TUPOW014 Simulation of High Resolution Field Emission Imaging in an rf Photocathode Gun 1769
 
  • J.H. Shao, H.B. Chen, J. Shi, X.W. Wu
    TUB, Beijing, People's Republic of China
  • S.P. Antipov, C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • W. Gai
    ANL, Argonne, Illinois, USA
  • F.Y. Wang
    SLAC, Menlo Park, California, USA
 
  Precisely locating field emission (FE) emitters on a realistic surface in rf structures is technically chal-lenging in general due to the wide emitting phase and the broad energy spread. A method to achieve in situ high resolution FE imaging has been proposed by using solenoids and a collimator to select electrons emitted at certain phases. The phase selection criterion and imaging properties have been studied by the beam dynamics code ASTRA. Detailed results are presented in this paper.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW014  
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TUPOW015 Experiment of High Resolution Field Emission Imaging in an rf Photocathode Gun 1772
 
  • J.H. Shao, H.B. Chen, J. Shi, X.W. Wu
    TUB, Beijing, People's Republic of China
  • S.P. Antipov, S.V. Baryshev, C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • M.E. Conde, W. Gai, G. Ha, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  • F.Y. Wang
    SLAC, Menlo Park, California, USA
 
  The first in situ high resolution field emission (FE) imaging experiment has been carried out on an L-band photocathode gun test stand at Argonne Wakefield Accelerator facility (AWA). Separated strong emitters have been observed to dominate the field emission. Field enhancement factor, beta, of small regions on the cathode has been measured with the imaging system. It is shown that most strong emitters overlaps with the high beta regions. The post surface examinations reveal the origins of ~75% strong emitters overlap with the spots where rf breakdown have occurred. Detailed results are presented in this paper.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW015  
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TUPOW018 Tunable High-Intensity Electron Bunch Train Production Based on Nonlinear Longitudinal Space Charge Oscillation 1782
SUPSS016   use link to see paper's listing under its alternate paper code  
 
  • Z. Zhang, H.B. Chen, Y.-C. Du, W.-H. Huang, J. Shi, X.L. Su, C.-X. Tang, Q.L. Tian, D. Wang, W. Wang, L.X. Yan, L.M. Zheng, Z. Zhou
    TUB, Beijing, People's Republic of China
  • W. Gai
    ANL, Argonne, Illinois, USA
 
  High peak current electron bunch trains with tunable terahertz (THz) spacing are produced and measured experimentally. An initial picosecond periodic modulation in the temporal profile of a relativistic electron beam is magnified by the longitudinal space charge forces. As opposed to trying to reduce its smearing effect for large beam current, we take advantages of the nonlinear space charge oscillation through controlling the plasma phase advance. The spacing of the bunch train can be varied continuously either by tuning the velocity bunching of a radio-frequency gun or by tuning the compression of a downstream magnetic chicane. The narrow-band μJ-level THz radiation from the bunch train are also measured with tunable central frequency of the spectral from ~0.5 THz to 1.6 THz. The bunch train measurements are consistent with the particle tracking simulations.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW018  
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WEPOY025 High Power RF Generation From a W-Band Corrugated Structure Excited by a Train of Electron Bunches 3040
SUPSS062   use link to see paper's listing under its alternate paper code  
 
  • D. Wang, C.-X. Tang
    TUB, Beijing, People's Republic of China
  • S.P. Antipov, C.-J. Jing, J.Q. Qiu
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • M.E. Conde, D.S. Doran, W. Gai, G. Ha, G. Ha, W. Liu, J.G. Power, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
 
  We report on the generation of multi-megawatt peak RF power at 91textGHz, using an ultrarelativistic electron bunch train to excite electromagnetic fields in a high-impedance metallic corrugated structure. This device can be used as a power source for high gradient acceleration of electrons. To achieve precise control of the wakefield phase, a long range wakefield interferometry method was developed in which the RF energy due to the interference of the wakefields from two bunches was measured as a function of the bunch separation.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY025  
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WEPOY026 Simulation and Measurement of the Beam Breakup Instability in a W-band Corrugated Structure 3044
 
  • D. Wang, C.-X. Tang
    TUB, Beijing, People's Republic of China
  • S.P. Antipov, C.-J. Jing, J.Q. Qiu
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • M.E. Conde, D.S. Doran, W. Gai, G. Ha, W. Liu, J.G. Power, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
 
  The corrugated wakefield structure has wide application in electron beam energy manipulation and high frequency RF radiation generation. The transverse wakefield which cause beam breakup (BBU) instability is excited when the drive beam is not perfectly centered through the structure. Here we report on the numerical and experimental investigation of the BBU effect in a W-band corrugated structure, for both cases of short range wakefield and long range wakefield. In the numerical part we develop a point to point (P2P) code that allows rapid and efficiency simulations of the beam dynamics effect by wakefield, which is based on the the particle-wake function coupled dynamics equation of motion. And the experimental measurements of BBU effect are found to be in good agreement with the simulations.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY026  
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THPOR036 Updates on the Sliding Contact Cooling ILC Positron Source Target Development 3865
 
  • W. Liu, D.S. Doran, R.A. Erck, G.R. Fenske, W. Gai, V.J. Guarino
    ANL, Argonne, Illinois, USA
 
  The R&D of the baseline positron source target for ILC is still ongoing after TDR due to the uncertainty of rotating vacuum seal and water cooling system of the fast spinning target wheel. Different institutes around the globe have proposed different approaches to tackle this issue. A spinning target wheel system with sliding contact cooling has been proposed by ANL. The proposed system eliminated the needs of rotating vacuum seal by using magnetic torque coupler to drive the solid spinning wheel target. The energy deposited from positron production process is taken away via cooling pads sliding against the spinning wheel. A full size test wheel has been built and some initial tests have been done with promising outcomes. Results of these tests are presented in this paper along with a plan for developing a prototype.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR036  
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THPOW021 Generation of Homogeneous and Patterned Electron Beams using a Microlens Array Laser-Shaping Technique 3983
SUPSS020   use link to see paper's listing under its alternate paper code  
 
  • A. Halavanau, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • D.R. Edstrom, P. Piot, J. Ruan, J.K. Santucci
    Fermilab, Batavia, Illinois, USA
  • W. Gai, G. Ha, J.G. Power, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  • G. Ha
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • G. Qiang
    TUB, Beijing, People's Republic of China
 
  Funding: Northern Illinois University - US DOE contract No. DE-SC0011831. Fermilab - US DOE contract No. DE-AC02-07CH11359. The Argonne wakefield facility - US DOE contract No. DE-AC02-06CH11357.
In photocathodes the achievable electron-beam parameters are controlled by the laser used to trigger the photoemission process. Non-ideal laser distribution hampers the final beam quality. Laser inhomogeneities, for instance, can be "amplified" by space-charge force and result in fragmented electron beams. To overcome this limitation laser shaping methods are routinely employed. In the present paper we demonstrate the use of simple microlens arrays to dramatically improve the transverse uniformity. We also show that this arrangement can be used to produce transversely-patterned electron beams. Our experiments are carried out at the Argonne Wakefield Accelerator facility.
 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW021  
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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 icon Slides FRXCB01 [11.937 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-FRXCB01  
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