WEXBA —  Wednesday Parallel Session 1   (04-Sep-19   08:30—10:00)
Chair: P. Piot, Northern Illinois University, DeKalb, Illinois, USA
Paper Title Page
WEXBA1
Beam Dynamics Measurements with New Generation BPMs  
 
  • B. Podobedov
    BNL, Upton, New York, USA
 
  Due to state-of-the-art NSLS-II beam position monitors, combined with advanced signal-processing techniques, we are now able to measure the difference between the betatron tunes of two (or more) bunches stored in the ring with the accuracy better than 10-6. For bunches of unequal charge this allows us to precisely determine the transverse kick factors. By applying local bumps, or, for in-vacuum undulators (IVUs), by varying the gap, we can also precisely measure the impedance of individual ring components. Since the tunes of unequally charged bunches are measured simultaneously, this reference method is virtually immune to machine drifts, as well as other systematic errors. For instance, in our IVU measurements vs. undulator gap, we can accurately determine current-dependent tuneshifts two orders of magnitude smaller than the tuneshift induced by the natural focusing of the undulator. Other examples of measurements performed with similar, or related, techniques include single-shot measurements of tune-shift with amplitude as well as non-invasive lattice characterization during user operations.  
slides icon Slides WEXBA1 [6.184 MB]  
 
WEXBA2 Recent Results and Opportunities at the IOTA Facility -1
 
  • A.L. Romanov, D.R. Broemmelsiek, K. Carlson, D.J. Crawford, N. Eddy, D.R. Edstrom, J.D. Jarvis, V.A. Lebedev, S. Nagaitsev, J. Ruan, J.K. Santucci, V.D. Shiltsev, G. Stancari, A. Valishev, A. Warner
    Fermilab, Batavia, Illinois, USA
  • S. Chattopadhyay, S. Szustkowski
    Northern Illinois University, DeKalb, Illinois, USA
  • Y.K. Kim, N. Kuklev, I. Lobach
    University of Chicago, Chicago, Illinois, USA
 
  The Integrable Optics Test Accelerator (IOTA) was recently commissioned as part of the Fermilab Accelerator Science and Technology (FAST) facility. The IOTA ring was briefly operated with electrons at 47 MeV followed by a 6-months run with 100 MeV electrons. The main goal of the first run was to study beam dynamics in the integrable lattices with elliptical nonlinear magnets and in the quasi-integrable case with profiled octupole channel. The flexibility of the IOTA ring allowed a wide range of complementary studies, such as experiments with a single electron; studies of fluctuations in undulator radiation and operation with low emittance beams. Over the next year the proton injector will be installed and two runs carried out. One run will be dedicated to the refinement of nonlinear experiments and another will be dedicated to the proof-of-principle demonstration of Optical Stochastic Cooling.  
slides icon Slides WEXBA2 [13.793 MB]  
 
WEXBA3 CSR Phase Space Dilution in CBETA -1
SUPLM17   use link to see paper's listing under its alternate paper code  
 
  • W. Lou, G.H. Hoffstaetter, D. Sagan
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • C.E. Mayes
    SLAC, Menlo Park, California, USA
 
  CBETA, the Cornell BNL ERL Test Accelerator, will be the first multi-turn Energy Recovery Linac (ERL) with SRF accelerating cavities and Fixed Field Alternating gradient (FFA) beamline. While CBETA gives promise to deliver unprecedentedly high beam current with simultaneously small emittance, Coherent Synchrotron Radiation (CSR) can pose detrimental effect on the beam at high bunch charges and short bunch lengths. To investigate the CSR effects on CBETA, we used the established simulation code Bmad to track a bunch with different parameters. We found that CSR causes phase space dilution, and the effect becomes more significant as the bunch charge and recirculation pass increase. Potential ways to mitigate the effect involving varying phase advances are being investigated.  
slides icon Slides WEXBA3 [7.109 MB]  
 
WEXBA4
Comparison of Numerical Methods for the Calculation of Synchrotron Radiation From Electrons  
 
  • F.Y. Li, B.E. Carlsten, R. Garimella, C. Huang, T.J. Kwan
    LANL, Los Alamos, New Mexico, USA
 
  The phenomenon of synchrotron radiation from electrons is at the core of modern accelerator based light sources. While synchrotron radiation in the far field has been well established, the self-consistent beam dynamics due to the near-field synchrotron radiation becomes increasingly important as high-brightness beams and coherent light sources are developed. Since it is difficult to diagnose the near fields in experiments, accurate and efficient numerical methods are essential to the design of these light sources. Here, we investigate several existing methods for the calculation of the radiation near fields, including the finite difference method, the Lienard-Wiechert method and a novel near-field method. We compare the accuracy and efficiency of these methods in both 1D and multi-dimensions, for both steady-state and dynamic beam trajectories, both radiation field and space charge field, as well as for both coherent and incoherent fields. We also discuss a self-similarity feature in the synchrotron radiation that can be exploited to improve the calculation.
Work supported by the LDRD program at LANL.
 
slides icon Slides WEXBA4 [8.567 MB]