TUXB —  Tuesday Oral Parallel B   (25-May-21   11:00—12:00)
Chair: C. Vaccarezza, INFN/LNF, Frascati, Italy
Paper Title Page
TUXB01 A 3 MeV All Optical Terahertz-Driven Electron Source at Tsinghua University 1294
 
  • H. Xu, Y.-C. Du, W.-H. Huang, R.K. Li, C.-X. Tang, L.X. Yan
    TUB, Beijing, People’s Republic of China
 
  Funding: Science Challenge Project No.TZ2018005
Efficient acceleration and manipulation of high-brightness electron beams using terahertz waves in a compact setup has been recently a hot research topic in acceleration community. Previous works have achieved multi-MV/m acceleration gradient and dozens of keV energy gain while leaving room for further improvements in the high-energy regime. Here, we experimentally demonstrate whole-bunch acceleration and cascaded terahertz-driven acceleration of a relativistic beam with a record energy gain of 204 keV. A terahertz-driven all-optical electron source is now under development, which hold great potential for terahertz-driven ultrafast electron diffraction and related scientific discoveries.
* Xu, H., Yan, L., Du, Y. et al. Cascaded high-gradient terahertz-driven acceleration of relativistic electron beams. Nat. Photonics (2021). https://doi.org/10.1038/s41566-021-00779-x
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXB01  
About • paper received ※ 19 May 2021       paper accepted ※ 01 June 2021       issue date ※ 10 August 2021  
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TUXB02
Precision Control of Plasma Wakefields for Highly Efficient and Energy-Spread-Preserving Electron Acceleration  
 
  • S. Schröder, S. Bohlen, L.A. Boulton, R.T.P. D’Arcy, S. Diederichs, J.M. Garland, P. Gonzalez-Caminal, A. Knetsch, C.A. Lindstrøm, G. Loisch, A. Martinez de la Ossa, J. Osterhoff, K. Poder, L. Schaper, B. Schmidt, B. Sheeran, G.E. Tauscher, S. Wesch, J.C. Wood, J. Zemella
    DESY, Hamburg, Germany
  • L.A. Boulton
    USTRAT/SUPA, Glasgow, United Kingdom
  • J. Chappell
    UCL, London, United Kingdom
 
  Plasma-wakefield accelerators driven by intense particle beams promise to significantly reduce the size of future high-energy facilities. These applications require an energy-efficient acceleration process with a well-controlled energy spectrum, both of which can be achieved simultaneously by tailoring the plasma wakefield. A prerequisite for such control of the wakefield is its precise measurement. Here we discuss a new measurement technique that enables femtosecond-level sampling of the longitudinal electric fields and that is particularly powerful due to its operational simplicity*. Using this method, we experimentally demonstrated optimal beam loading in a nonlinear electron-driven plasma accelerator by wakefield flattening at the few-percent level**. Bunches were accelerated at a gradient of 1.3 GV/m and with an energy-transfer efficiency of (42±4)% while preserving per-mille energy spreads with full charge coupling. These results open the door to the high-quality operation of future plasma accelerators through precise control of the acceleration process.
* S. Schröder, et al. Nat Commun 11, 5984 (2020)
** C.A. Lindstrøm, et al. Phys. Rev. Lett. 126, 014801 (2021)
 
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TUXB03
Recent results and future perspectives for high-quality electron beams from plasma accelerators  
 
  • R. Pompili
    INFN/LNF, Frascati, Italy
 
  Next-generation plasma-based accelerators can push electron bunches to gigaelectronvolt energies within centimeter distances. So far, several experiments have demonstrated high gradient and succesfull beam acceleration but the resulting beam quality, in terms of energy spread and emittance, is still lower than the state-of-the-art conventional accelerators. Several proof-of-principle experiments have recently demonstrated very promising results thanks to contribution from different scientific communities with different expertise (lasers, rf-accelerators, plasma). These findings will significantly impact the optimization of the acceleration module and its implementation in forthcoming compact machines for user-oriented applications. An overview of these recent achievements and of the recent results obtained in the framework of the EuPRAXIA collaboration will be presented and discussed in this talk.  
slides icon Slides TUXB03 [6.431 MB]  
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TUXB04 Fabrication and Tuning of a THz-Driven Electron Gun 1297
 
  • S.M. Lewis, A.A. Haase, J.W. Merrick, E.A. Nanni, M.A.K. Othman, S.G. Tantawi
    SLAC, Menlo Park, California, USA
  • S.M. Lewis
    Fermilab, Batavia, Illinois, USA
 
  Funding: This work was supported by the Department of Energy Contract No. DE-AC02-76SF00515 (SLAC) and by NSF Grant No. PHY-1734015.
We have developed a THz-driven field emission electron gun and beam characterization assembly. The two cell standing-wave gun operates in the pi mode at 110.08 GHz. It is designed to produce 360 keV electrons with 500 kW of input power supplied by a 110 GHz gyrotron. Multiple gun structures were electroformed in copper using a high precision diamond-turned mandrel. The field emission cathode is a rounded copper tip located in the first cell. The cavity resonances were mechanically tuned using azimuthal compression. This work will discuss details of the fabrication and tuning and present the results of low power measurements.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXB04  
About • paper received ※ 18 May 2021       paper accepted ※ 22 June 2021       issue date ※ 14 August 2021  
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TUXB05
Intense Channeling Radiation as a Tool for a Hybrid Crystal-Based Positron Source for Future Colliders  
 
  • L. Bandiera, A. Mazzolari, M. Romagnoni, A.I. Sytov
    INFN-Ferrara, Ferrara, Italy
  • L. Bomben, V. Mascagna
    INFN MIB, MILANO, Italy
  • G. Cavoto
    INFN-Roma, Roma, Italy
  • I. Chaikovska, R. Chehab
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  • D. De Salvador
    Univ. degli Studi di Padova, Padova, Italy
  • L.G. Foggetta
    INFN/LNF, Frascati, Italy
  • E. Lutsenko, M. Prest
    Università dell’Insubria & INFN Milano Bicocca, Como, Italy
  • M. Soldani
    Università degli Studi di Ferrara, Ferrara, Italy
  • V.V. Tikhomirov
    INP BSU, Minsk, Belarus
  • E. Vallazza
    INFN-Trieste, Trieste, Italy
 
  There is a strong need for intense positron sources for future colliders. A crystal-based hybrid positron source could be an alternative to conventional sources based on the e- conversion into e+ in a thick target. The basic idea of the hybrid source is to split the e+ converter into a gamma-quanta radiator plus a gamma-to-positron converter*. In such a scheme an e- beam crosses a thin axially oriented crystal with emission of "channeling radiation", characterized by a considerably larger amount of photons w.r.t. standard bremsstrahlung**. The net result is an increase in the number of e+ produced at the converter target. In the hybrid scheme, only photons reach the converter, thereby reducing the Peak Energy Deposition Density (PEDD) in the target. Here we present the results of a test conducted at the DESY TB with 5.6 GeV e- interacting with a W crystal. A huge enhancement in the radiated energy and in the photon emission has been recorded and reproduced with Monte Carlo simulations***. This study is relevant for the design of the FCC-ee positron source. Indeed, through Monte Carlo, we also investigated the best parameters of the crystal radiator suited for the FCC-ee e+ source.
* R. Chehab et al. PAC’89,10.1109/PAC.1989.73147
** X.Artru et al. NIMB 266 (2008) 3868
*** A. Sytov, V. Tikhomirov, L. Bandiera PRAB 22 (2019) 064601
 
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TUXB06
High Transformer Ratio Plasma Wakefield Acceleration and Current Profile Reconstruction Using Emittance Exchange  
 
  • R.J. Roussel
    Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
  • G. Andonian, A. Deng, C.E. Hansel, G.E. Lawler, W.J. Lynn, R. Robles, J.B. Rosenzweig, K. Sanwalka
    UCLA, Los Angeles, California, USA
  • S. Baturin
    Northern Illinois University, DeKalb, Illinois, USA
  • M.E. Conde, D.S. Doran, G. Ha, J.G. Power, J. Seok, C. Whiteford, E.E. Wisniewski
    ANL, Lemont, Illinois, USA
 
  Funding: This work is supported by the Department of Energy, Office of High Energy Physics, under Contract No. DESC0017648.
To overcome limits on total acceleration achievable in plasma wakefield accelerators, specially shaped drive beams can be used to increase the transformer ratio, implying that the drive beam deceleration is minimized in comparison with acceleration obtained in the wake. We report the results of a nonlinear PWFA, high transformer ratio experiment using high-charge, longitudinally asymmetric drive beams in a plasma cell. An emittance exchange process is used to generate variable drive current profiles, in conjunction with a long (multiple plasma wavelength) witness beam. The witness beam is energy-modulated by the wakefield, yielding a response that contains detailed spectral information in a single-shot measurement. Using these methods, we generate a variety of beam profiles and characterize the wakefields, directly observing beam-loaded transformer ratios up to 7.8. Further, a spectrally-based current reconstruction technique, validated by 3D particle-in-cell simulations, is introduced to obtain the drive beam profile from the decelerating wakefield data.
 
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TUXB07 High-Current H₂⁺ Beams from a Compact Cyclotron using RFQ Direct Injection 1301
 
  • D. Winklehner, J.M. Conrad, D. Koser, J. Smolsky, L.H. Waites
    MIT, Cambridge, Massachusetts, USA
 
  Funding: This work was supported by NSF grants PHY-1505858 and PHY-1626069.
For the IsoDAR neutrino experiment, we have developed a compact and cost-effective cyclotron-based driver to produce high current beams (cw proton beam currents of >10 mA at 60 MeV). This is a factor of 4 higher than the current state-of-the-art for cyclotrons and a factor of 10 compared to what is commercially available. All areas of physics that call for high cw currents can greatly benefit from this result; e.g. particle physics, medical isotope production, and energy research. This increase in beam current is possible in part because the cyclotron is designed to include and use vortex-motion, allowing clean extraction. Such a design process is only possible with the help of high-fidelity codes, like OPAL. Another novelty is the use of an RFQ embedded in the cyclotron yoke to bunch the beam during axial injection. Finally, using H2+ relieves some of the space charge constraints during injection. In this paper, we will give an overview of the project and then focus on the design and simulations of the cyclotron itself. We will describe the physics, computational tools, and simulation results. At the end, we will describe how we are including machine learning in the simulations.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXB07  
About • paper received ※ 27 May 2021       paper accepted ※ 22 July 2021       issue date ※ 31 August 2021  
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