Recent Progress in BMAD Calculations
of Effects of Parasitic Crossings


26 August 2004



Recent progress has been made in implementing the simulation of parasitic crossings and the beam-beam interaction in BMAD calculations for CESR lattices. The calculations are done in the weak/strong scenario, originally intended for calculations of electron injection efficiencies. Such work was done by the 2004 REU student Jamie Antonelli together with summer employee David Kettler. They showed that the lattice used for CESRC exhibited the horizontal tune crossing the half integer for positron bunch currents exceeding 3 mA. Recently, a scheme to weight individual positron bunches was devised in order to calculate the effects of various bunch configurations, such as the 8x4 configuration employed for the CHESS running. Results for tune variations, maximum beta function values, and orbit variations are shown below for each electron bunch.

The first plot shows results for the CHESS lattice 20040820_1445 tested at the end of the recent machine studies period. It shows that in the 8x4 positron bunch configuration, the maximum horizontal beta value in the ring for electron bunch 5 depends strongly on the positron bunch current. This bunch is therefore omitted in the following plots. Plots 2-7 show the results for maximum beta values, tunes, and orbit variations for this lattice. The orbit plots show the difference in orbits for positron bunch currents of 0.2 and 10.0 mA/bunch. Plot 8 investigates the effect on the vertical orbit further, by repeating this plot with the vertical separator kicks doubled. Indeed the difference in orbit is reduced, so the orbit wave is likely engendered by the BBI at the North IP. The final six plots show the (incomplete) results now being obtained for the CESRC lattice hibetainj_20040628_v01.



Creation date: 08/26/04.