FRXBA —  Friday Parallel Session 1   (06-Sep-19   08:30—10:00)
Chair: J.G. Power, ANL, Lemont, Illinois, USA
Paper Title Page
Review of Recent Advances in Cooling Techniques  
  • S. Nagaitsev
    Fermilab, Batavia, Illinois, USA
  Beam cooling plays an important role in future electron-ion colliders. The talk will review recent advances in cooling techniques. It will especially discuss variants of electron cooling such as e.g., coherent and micro-bunched electron cooling. Other cooling technique, e.g. optical stochastic cooling will also be presented.  
slides icon Slides FRXBA1 [8.086 MB]  
Diverse Beam Profile Shapings Through Nonlinear Focusing of Multipole Magnets in a Beam Transport Line  
  • Y. Yuri, T. Yuyama
    QST/Takasaki, Takasaki, Japan
  • M. Fukuda
    RCNP, Osaka, Japan
  It is well-known that the transverse intensity distribution of a charged-particle beam can be made approximately uniform through the nonlinear focusing force using multipole (mainly, octupole) magnets in a beam transport line. This fact indicates that the proper use of multipole magnets enables the diverse beam profile shapings that cannot be achieved by common linear focusing, such as quadrupole magnets. We have, therefore, investigated the feasibility of the beam profile shaping (other than uniform profiles) by means of nonlinear focusing. Recently, we have experimentally demonstrated the formation of an ion beam with a hollow transverse distribution using octupole and sextupole magnets. It has been found that the hollow beam has a steep peak at the radial edge and that its cross-sectional shape varies diversely depending on the order and strength of the applied multipole magnets. In the presentation, the first experimental result of the hollow-beam formation will be reported together with the theoretical analysis of the behavior of a nonlinear-focused beam. Moreover, other unique beam profiles obtained through the nonlinear force of the multipole magnets will also be shown.  
slides icon Slides FRXBA2 [4.108 MB]  
FRXBA3 Applications and Opportunities for the Emittance Exchange Beamline -1
  • G. Ha, M.E. Conde, J.G. Power
    ANL, Lemont, Illinois, USA
  • M. Chung, J. Seok
    UNIST, Ulsan, Republic of Korea
  Funding: This work is supported by the U.S. Department of Energy, Offices of HEP and BES, under Contract No. DE-AC02-06CH11357.
Emittance exchange (EEX) provides a powerful method of controlling the longitudinal phase space using the relatively simpler methods of transverse control. An EEX beamline was installed at the Argonne Wakefield Accelerator (AWA) facility in 2015. Several experiments important to the wakefield acceleration, such as a high transformer ratio from shaped bunches, have already been demonstrated. We are currently developing several applications of the EEX beamline including temporal profile shaping, THz radiation generation, time-energy correlation control, diagnostic uses of EEX etc. We will present the on-going EEX program for longitudinal phase space control taking place at the AWA facility, and discuss recently discovered new opportunities.
slides icon Slides FRXBA3 [6.809 MB]  
Maximizing 2-D Beam Brightness Using the Round to Flat Beam Transformation in the Ultralow Charge Regime  
SUPLM02   use link to see paper's listing under its alternate paper code  
  • F.W. Cropp V, P.E. Denham, J. Giner Navarro, E.T. Liu, P. Musumeci
    UCLA, Los Angeles, USA
  • N. Burger, L. Phillips
    PBPL, Los Angeles, USA
  • A.L. Edelen, C. Emma
    SLAC, Menlo Park, California, USA
  Funding: This work is supported by the United States National Science Foundation award PHY-1549132 (the Center for Bright Beams)
We seek to maximize the 2-D beam brightness in an RF photoinjector operating in an ultralow charge (<1 pC) regime by implementing the FBT. Particle tracking simulations suggest that in one dimension, normalized projected emittances smaller than 5 nm can be obtained at the UCLA Pegasus facility with up to 100 fC beam charge. A tunable magnetic field is put on the cathode. Three skew quadrupoles are used to block-diagonalize the beam matrix and recover the vastly different eigenemittances as the projected emittances. Emittance measurement routines, including grid-based, pepperpot-based and quad scan routines, have been developed for on-line calculation of the 4-D beam matrix and its eigenemittances. Preliminary measurements are in agreement with simulations and indicate emittance ratios larger than 10 depending on the laser spot size on the cathode. Fine tuning the quadrupole gradients for the FBT has a significant effect on the 2-D beam brightness. We have made concrete steps toward computer minimization and machine learning optimization of the quadrupole gradients in order to remove the canonical angular momentum from the beam and achieve the target normalized projected emittances.
slides icon Slides FRXBA4 [3.056 MB]  
FRXBA5 The Role of Laser Shaping in Microbunching Instability Suppression and Seeded X-Ray Free Electron Emission -1
SUPLM09   use link to see paper's listing under its alternate paper code  
  • J. Tang, S. Carbajo, F.-J. Decker, Z. Huang, J. Krzywiński, R.A. Lemons, W. Liu, A.A. Lutman, G. Marcus, T.J. Maxwell, S.P. Moeller, D.F. Ratner, S. Vetter
    SLAC, Menlo Park, California, USA
  Microbunching instability (MBI) driven by collective effects in an accelerator is known to be detrimental for the performance of X-ray free electron lasers. At the Linac Coherent Light Source (LCLS), laser heater (LH) system was installed to suppress the microbunching instability by inducing a small amount of slice energy spread to the electron beam. The distribution of the induced energy spread greatly effects MBI suppression and can be controlled by shaping the transverse profile of the heater laser. In this paper, we present theoretical and experimental results on utilizing a Laguerre-Gaussian 01 Mode (LG01) laser at LCLS to obtain better suppression of the instability. We demonstrate experimentally that Gaussian-shaped energy distribution is induced by LG01 mode LH and final microbunching gain is better suppressed. We finally discuss the role of LH spatial shaping in soft X-ray self-seeded (SXRSS) FEL emission and demonstrate that this LH configuration is capable of generating high spectral brightness FEL pulses.  
slides icon Slides FRXBA5 [3.160 MB]