TUZBB —  Tuesday Parellel Session 6   (03-Sep-19   14:00—16:00)
Chair: E. Prebys, UCD, Davis, California, USA
Paper Title Page
TUZBB1
Physics of the MBA Lattice  
 
  • R.R. Lindberg
    ANL, Lemont, Illinois, USA
 
  Funding: Supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
Multi-bend achromat (MBA) lattices were proposed more than 25 years ago as a way to reduce the emittance of third generation storage rings by 1-2 orders of magnitude, and thereby increase the x-ray brightness by a similar factor. However, it wasn’t until the recent advances in compact magnets and vacuum pumping, pioneered by MAX-IV and CERN, respectively, that MBA lattices could be considered as the basis for a light source. Now, there are many projects around the world that employ an MBA lattice to achieve an emittance well below 1 nm. I will begin by briefly reviewing how the MBA lattice can achieve an ultra-low emittance. Then, I will proceed to discuss how the essential physics of the MBA drives its design, and how that in turn impacts the physics. For example, its requirement for strong magnets leads to a small dynamic aperture and physically small vacuum chambers, which in turn impacts impedance and collective effects. I will try to illustrate this interplay with advances made by many other projects, but will inevitably favor the recent progress of the APS-Upgrade project, where we are targeting a 42-pm design for hard x-rays.
 
slides icon Slides TUZBB1 [2.799 MB]  
 
TUZBB2 Reaching Low Emittance in Synchrotron Light Sources by Using Complex Bends -1
TUPLM30   use link to see paper's listing under its alternate paper code  
 
  • G.M. Wang, J. Choi, O.V. Chubar, Y. Hidaka, T.V. Shaftan, S.K. Sharma, V.V. Smaluk, C.J. Spataro, T. Tanabe
    BNL, Upton, New York, USA
  • N.A. Mezentsev
    BINP SB RAS, Novosibirsk, Russia
 
  All modern projects of low-emittance synchrotrons follow Multi-Bend Achromat approach*. The low emittance is realized by arranging small horizontal beta-function and dispersion in the bending magnets, the number of which varies from 4 to 9 magnets per cell. We propose an alternative way to reach low emittance by use of a lattice element that we call "Complex Bend"**, instead of regular dipole magnets. The Complex Bend is a new concept of bending magnet consisting of a number of dipole poles interleaved with strong alternate focusing so as to maintain the beta-function and dispersion oscillating at very low values. The details of Complex Bend, considerations regarding the choice of optimal parameters, thoughts for its practical realization and use in low-emittance lattices, are discussed.
* MBA: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.495.2446&rep=rep1&type=pdf
** Complex Bend: Phys. Rev. Accel. Beams 21, 100703 (2018)
 
slides icon Slides TUZBB2 [8.348 MB]  
 
TUZBB3 Precise Beam Velocity Matching for the Experimental Demonstration of Ion Cooling With a Bunched Electron Beam -1
 
  • S. Seletskiy, M. Blaskiewicz, K.A. Drees, A.V. Fedotov, W. Fischer, D.M. Gassner, R.L. Hulsart, D. Kayran, J. Kewisch, K. Mernick, R.J. Michnoff, T.A. Miller, G. Robert-Demolaize, V. Schoefer, H. Song, P. Thieberger, P. Wanderer
    BNL, Upton, New York, USA
 
  The first ever electron cooling based on the RF acceleration of electron bunches was experimentally demonstrated on April 5, 2019 at the Low Energy RHIC Electron Cooler (LEReC) at BNL. The critical step in obtaining successful cooling of the Au ion bunches in the RHIC cooling sections was the accurate matching of average longitudinal velocities of electron and ion beams corresponding to a relative error of less than 5·10-4 in the e-beam momentum. Since the electron beam kinetic energy is just 1.6 MeV, measuring the absolute e-beam energy with sufficient accuracy and eventually achieving the electron-ion velocity matching was a nontrivial task. In this paper we describe our experience with measuring and setting the e-beam energy at LEReC.  
slides icon Slides TUZBB3 [1.335 MB]  
 
TUZBB4 Space Charge Study of the Jefferson Lab Magnetized Electron Beam -1
SUPLM23   use link to see paper's listing under its alternate paper code  
 
  • S.A.K. Wijethunga, J.R. Delayen, G.A. Krafft
    ODU, Norfolk, Virginia, USA
  • J.F. Benesch, F.E. Hannon, C. Hernandez-Garcia, G.A. Krafft, M.A. Mamun, M. Poelker, R. Suleiman, S. Zhang
    JLab, Newport News, Virginia, USA
 
  Magnetized electron cooling could result in high luminosity at the proposed Jefferson Lab Electron-Ion Collider (JLEIC). In order to increase the cooling efficiency, a bunched electron beam with high bunch charge and high repetition rate is required. We generated magnetized electron beams with high bunch charge using a new compact DC high voltage photo-gun biased at -300 kV with alkali-antimonide photocathode and a commercial ultrafast laser. This contribution explores how magnetization affects space charge dominated beams as a function of magnetic field strength, gun high voltage, laser pulse width, and laser spot size.  
slides icon Slides TUZBB4 [12.577 MB]  
 
TUZBB5 Transverse Ion Beam Emittance Growth Due to Low Frequency Instabilities in Microwave Ion Source Plasma -1
SUPLM10   use link to see paper's listing under its alternate paper code  
TUPLM31   use link to see paper's listing under its alternate paper code  
 
  • C. Mallick, M. Bandyopadhyay, R. Kumar
    Institute for Plasma Research, Bhat, Gandhinagar, India
 
  The ion source is accompanied by the generation of low frequency (LF) plasma instabilities (PI). Its signature is also visible in high current heavy ion beam required for any accelerator. These LFs affect the profile of the ion beam in transverse phase-space. These issues are investigated in detail by measuring the emittance of beam. Beam oscillations are extracted from the transverse emittance data by taking Fast Fourier Transform (FFT) of it. PI frequencies are identified in the measured electromagnetic emission from the plasma, in which these frequencies appeared as sidebands around pump frequency 2.45 GHz. The PI components i.e.,ion acoustic (IA) and ion cyclotron (IC) waves are also visible in the FFT spectra. Low and high frequency oscillations in the beam are 476 kHz and ~1.3 MHz respectively. These two groups of frequencies also exist within the PI induced IA (238 - 873 kHz) and IC (1.29 - 1.3 MHz) frequency ranges. The measured emittance (rms-normalized) in horizontal and vertical phase-space varies from 0.002-0.098 𝜋 mm mrad and 0.004-0.23 𝜋 mm mrad respectively. PI induced beam oscillation is the reason behind such broad transverse emittance growth.
Reference
’S. Kumar et al.,Phys. Rev. Accel. Beams 21, 093402 (2018)’
’R. D’Arcy et al., Nucl. Instrum. Methods Phys. Res. A 815 7(2016)’
’L. Groening et al., Phys. Rev. Lett. 113, 264802 (2014)’
 
slides icon Slides TUZBB5 [5.911 MB]  
 
TUZBB6 Nonlinear Tune-Shift Measurements in the Integrable Optics Test Accelerator -1
SUPLM11   use link to see paper's listing under its alternate paper code  
TUPLM32   use link to see paper's listing under its alternate paper code  
 
  • S. Szustkowski, S. Chattopadhyay
    Northern Illinois University, DeKalb, Illinois, USA
  • S. Chattopadhyay, A.L. Romanov, A. Valishev
    Fermilab, Batavia, Illinois, USA
  • N. Kuklev
    University of Chicago, Chicago, Illinois, USA
 
  Funding: US Department of Energy, Office of High Energy Physics, General Accelerator Research and Development (GARD) Program
The first experimental run of Fermilab’s Integrable Optics Test Accelerator (IOTA) ring aimed at testing the concept of nonlinear integrable beam optics. In this report we present the preliminary results of the studies of a nonlinear focusing system with two invariants of motion realized with the special elliptic-potential magnet. The key measurement of this experiment was the horizontal and vertical betatron tune shift as a function of transverse amplitude. A vertical kicker strength was varied to change the betatron amplitude for several values of the nonlinear magnet strength. The turn-by-turn positions of the 100 MeV electron beam at twenty-one beam position monitors around the ring were captured and used for the analysis of phase-space trajectories.
 
slides icon Slides TUZBB6 [12.880 MB]