Author: Beaudoin, B.L.
Paper Title Page
MOOBS3 Bunch-End Interpenetration During Evolution to Longitudinal Uniformity in a Space-Charge-Dominated Storage Ring 22
 
  • T.W. Koeth, B.L. Beaudoin, S. Bernal, I. Haber, R.A. Kishek, P.G. O'Shea
    UMD, College Park, Maryland, USA
  
  The University of Maryland Electron Ring is a facility for study of the novel physics that occurs as intense space-charge-dominated beams that are transported over long distances. An example presented here is the role of space-charge longitudinal expansion and bunch-end interpenetration in the relaxation of a coasting bunch towards uniformly filling the ring. By comparing experiment to simplified longitudinal simulations the relaxation process is shown to be largely independent of details of the transverse dynamics. However, to get detailed agreement it was found necessary to include the consequences of transverse current loss. Since the AC coupled diagnostics lose information on any DC current loss, a novel beam knockout technique was developed to recover this information.  
slides icon Slides MOOBS3 [2.501 MB]  
 
MOODS1 Space-Charge Effects in Bunched and Debunched Beams 85
 
  • B.L. Beaudoin, S. Bernal, K. Fiuza, I. Haber, R.A. Kishek, T.W. Koeth, P.G. O'Shea, M. Reiser, D.F. Sutter
    UMD, College Park, Maryland, USA
  
  Funding: This work is funded by the US Dept. of Energy Offices of High Energy Physics and High Energy Density Physics, and by the US Dept. of Defense Office of Naval Research and Joint Technology Office
The University of Maryland Electron Ring (UMER) is a machine designed to study high-intensity beam physics. With the application of axial fields to the bunch ends, we are able to keep a beam with an injected tune shift of 1.0, bunched over multiple turns. This is feasible with the application of tailored fields to optimally match the space-charge self-fields while minimizing the excitation of longitudinal space-charge waves. With this scheme, we have been able to extend the number of turns at the University of Maryland Electron Ring (UMER) by a factor of ten. Without the use of longitudinal focusing, head and tail effects begin to dominate, especially with the higher current beams. Time resolved measurements of the peak correlated energy spread have shown in some cases a change in the overall spread of 1.8% for the 0.6 mA beam, from the injected beam energy. 		 
slides icon Slides MOODS1 [2.834 MB]  
 
WEP050 Advances in Modeling the University of Maryland Electron Ring 1585
 
  • R.A. Kishek, B.L. Beaudoin, S. Bernal, M. Cornacchia, K. Fiuza, I. Haber, T.W. Koeth, P.G. O'Shea, D.F. Sutter, H.D. Zhang
    UMD, College Park, Maryland, USA
  
  Funding: Work funded by the US Dept. of Energy Offices of Fusion Energy Sciences and High Energy Physics, and by the Dept. of Defense Office of Naval Research and the Joint Technology Office.
The University of Maryland Electron Ring (UMER) is a research accelerator designed to operate with extreme space charge. The existence of high-precision experimental measurements of tune, dispersion, chromaticity, response matrix elements, and other parameters*, **, *** has prompted a revision of the models used to describe the machine. Due to the low energy (10 keV) of the electrons, the dipole and quadrupole magnets used are air-core printed-circuit coils whose fields we calculate using a Biot-Savart solver. Different levels of approximations for the magnetic fields have been developed. We present simulation results from the particle-in-cell code WARP, and from the accelerator code, ELEGANT. These are compared both against simpler models as well as experimental results. The improved modeling has significantly reduced the discrepancies between simulation and experiment.
* D.F. Sutter, et al., Proc. PAC 2009
** C. Wu, et al., Proc. PAC 2009
*** S. Bernal, et al., Proc. AAC 2010 		 
 
WEP101 Smooth Approximation of Dispersion with Strong Space Charge 1665
 
  • S. Bernal, B.L. Beaudoin, T.W. Koeth, P.G. O'Shea
    UMD, College Park, Maryland, USA
  
  Funding: This work is funded by the US Dept. of Energy Offices of High Energy Physics and High Energy Density Physics, and by the US Dept. of Defense Office of Naval Research and Joint Technology Office.
We apply the Venturini-Reiser envelope-dispersion equations* to a continuous beam in a uniform focusing/bending lattice to study the combined effects of linear dispersion and space charge. Within this simple model we investigate the scaling of average dispersion and the effects on beam dimensions; we also introduce a generalization of the space-charge intensity parameter and apply it to the University of Maryland Electron Ring (UMER) and other machines. In addition, we present results of calculations to test the smooth approximation by solving the Venturini-Reiser original equations and also through simulations with the code ELEGANT.
*M. Venturini and M. Reiser, Phys. Rev. Lett. 81, 1, p. 96, 6 July 1998 		 
 
WEP102 Current Dependent Tune Shifts in the University of Maryland Electron Ring UMER 1668
 
  • D.F. Sutter, B.L. Beaudoin, S. Bernal, M. Cornacchia, R.A. Kishek, T.W. Koeth, P.G. O'Shea
    UMD, College Park, Maryland, USA
  
  Funding: Work supported by the U.S. DOE Offices of High Energy Physics and Fusion Energy Sciences and by the U.S. DOD Office of Naval Research and Joint Technology Office.
The shift in betatron tunes as a function of space charge has been studied in many accelerators and storage rings. Because of its low operating energy (10 keV, γ = 1.02) and wide range of beam currents (0.6 to 100 mA, corresponding respectively to predicted incoherent tune shifts of 1.2 to 5.2), the University of Maryland electron ring (UMER) provides a unique opportunity to study space charge driven tune shifts over a wide parameter space. Comparisons of predictions and measurements are presented, including a discussion of special factors such as the magnetic penetration of the vacuum chamber walls.