Author: Thangaraj, J.C.T.
Paper Title Page
MOOBB01 Transverse-to-longitudinal Emittance-exchange with an Energy Chirped Beam 49
  • J.C.T. Thangaraj, H.T. Edwards, A.S. Johnson, A.H. Lumpkin, T.J. Maxwell, J. Ruan, J.K. Santucci, Y.-E. Sun, R.M. Thurman-Keup
    Fermilab, Batavia, USA
  Emittance exchange has been proposed to increase the performance of free electron lasers by tailoring the phase space of an electron beam. The principle of emittance exchange - where the transverse phase space of the electron beam is exchanged with the longitudinal phase space - has been demonstrated recently at the A0 photoinjector. The experiment used a low charge bunch (250 pC) with no energy chirp. Theory predicts an improvement in the emittance exchange scheme when the incoming beam has an energy chirp imparted on it. The energy chirp helps to overcome the thick lens effect of the deflecting mode cavity and other second order effects that might lead to an incomplete emittance exchange at higher charges. In this work, we report experimental and simulation results from operating the emittance exchange beam line using an energy chirped beam with higher charge (500 pC) at different RF-chirp settings.  
slides icon Slides MOOBB01 [2.338 MB]  
TUPPC094 Experimental Observations of Large-amplitude Solitary Waves in Electron Beams 1377
  • Y. Mo, B.L. Beaudoin, D.W. Feldman, I. Haber, R.A. Kishek, P.G. O'Shea
    UMD, College Park, Maryland, USA
  • J.C.T. Thangaraj
    Fermilab, Batavia, USA
  Funding: Work funded by the US Dept. of Energy Offices of Fusion Energy Sciences and High Energy Physics and Fusion Energy Sciences, and by the Dept. of Defense Office of Naval Research.
The longitudinal dynamics of space charge dominated beams plays an important role in particle accelerators and other applications such as heavy ion fusion and free electron lasers (FELs). All beams are space-charge dominated near the source. Furthermore, the longitudinal profile is not necessarily an ideal mathematical function. By means of experiments on the University of Maryland Electron Ring (UMER), we studied how a perturbation to the line charge density could affect the beam propagation. By varying the initial amplitude of the perturbation, we access nonlinear space charge physics. When starting with large-amplitude perturbations, we have observed, for the first time in charged particle beams, solitary waves for which the nonlinear steepening exactly balances the wave dispersion, leading to persistent waves that preserves their shape over a long distance. This paper presents the results of the soliton experiments, including systematic studies of the dependence of the soliton propagation on beam current, perturbation level and width. The data is compared with theory and simulation.