Study of Phase-Space Tracking of Injected Particles
for Lattice CESR_3S_V2

How does this lattice compare to the result for the 4S lattice?
Does the simulation exhibit the injected e- bunch damping into the stored beam?
What effects are observed over 50k turns?

7 December 2001
JAC
GOAL
Use the phase-space-tracking calculation of the INJTRACK program for the lattice CESR_3S_V2 which is presently in use for HEP running to see how the injected bunch evolves. The latter number of turns is chosen to far exceed the 6500 turns preceding the next injection (inj rep rate of 60 Hz).
This plot shows the positions in horizontal phase space (x [mm], x' [mrad]) of 500 injected electrons from turns 0 (the injection turn) to turn 9. The red contours show the 10-sigma and 1-sigma phase-space ellipses of the stored electron beam. They are calculated using the pre-injection beam position in phase space and the Twiss parameters from the design optics with the pretzel off. The yellow bands indicate the positions of the beampipe walls. Some merging of the injected e- bunch into the stored bunch is observed during these first 9 turns.
A postscript picture with higher resolution is available here.

The corresponding plots for vertical phase space are also available: gif,ps.
So are the plots for longitudinal phase space (dZ [mm], dE/E [%]): gif,ps.
This collection of plots shows the horizontal phasespace distribution for turns 999, 1999, ... 49999. The injected bunch becomes spread out, and does not damp down into the stored beam over so many turns. Some filamentation of the beam is apparent.
The corresponding plots for vertical phase space are here.
The corresponding plots for longitudinal phase space are here.
Conclusions
  • The simulation appears include the effect of the injected bunch merging with the stored beam over the first nine turns in horizontal phase space.
  • The beam does not appear to merge with the stored beam on the scale of so many turns. The horizontal phase space spreads out into a smeared ellipse. The vertical phase space does not evolve with turn number.
  • Some type of filamentation in the horizontal phase space is observed over many thousands of turns. No such effect is observed for the vertical phase space.
  • The longitudinal phase space exhibits an energy spread of a few tenths of a percent and longitudinal oscillations of a few centimeters. These do not change over the entire range of turns studied here.
    Creation date: 7 December 2001