1. ILC DR instability simulations
CMAD a tracking and e-cloud beam instability parallel code (M.P. SLAC)
Taking MAD(X) optics file at input, thus tracking the beam in a real lattice and applying the interaction beam-electron cloud over the whole ring
refined simulations: finding density thresholds 1.7e11 e/m3 for DCO4 and 3.5e11 e/m3 for DSB3
DC04 lattice: 6.4 km ring
DSB3 lattice: 3.2 km ring
(M. Pivi, SLAC)

2. Tune shift DCO4
CMAD

3. Tune shift DCO4
No cloud

4. Tune shift DCO4
1.2e10 e/m3

5. Tune shift DCO4
1.2e11 e/m3

6. Tune shift DCO4
CMAD
All combined

7. 2006 Recommendation

8. Base for Recommendation
By March we were asked to give a recommendation on the reduction of the ILC DR circumference to 3 km while maintaining the same 6ns bunch spacing and address the electron cloud instability
We have used 3 simulation codes ECLOUD, POSINST (CLOUDLAND) to predict the build-up and 1 code CMAD to predict the beam instability threshold for the 6km and 3km Damping Rings, namely DCO4 and DSB3. The codes are currently used for CesrTA simulations.
Simulations were performed by the international collaboration in particular at Frascati, Cornell, LBNL and SLAC, from September 2009 to March 2010. 8

9. Recommendation
Summary: given the same current and bunch distance we expect similar or even higher instability threshold for the shorter ring
With respect to RDR baseline, the risk level to adopt a reduced 3km Damping Ring while maintaining the same bunch spacing is low. 9

10. Wrap up simulation results by next Webex meeting
In preparation for recommendation of ILC Damping Ring length, proposing a Webex meeting before LCWS10:
Tuesday March 23