Minutes March 24th, 2009
Present: Gianluigi Arduini, Fritz Caspers, Elias Métral, Nicolas Mounet, Federico Roncarolo, Benoit Salvant, Bruno Spataro, Carlo Zannini, Bruno Zotter.
Agenda
- Benoit Salvant
"Simulations of SPS BPH, and update of ZBASE " (slides, minutes)
- Carlo Zannini
"Status of particle studio simulations" (slides, minutes)
Minutes
Presentation by Benoit:
- Elias mentioned it is expected for any structure that Xquad = -Yquad. Although this is the case when the bunch is there, this is not true anymore in the simulations of the BPH and BPV. To be followed up.
- Elias also said that R/Q in transverse should be given in Ohm/m^2, and not only in Ohm/m. This probably explains the non linear behaviour observed.
- Federico and Benoit should check which standard is used to get the R/Q. The factor 2 may come from there.
- Issue from PS DFT => Mentioned to and followed by CST. Should be solved in the new version.
- New simulations with “slotline pick-up” => In principal this is a structure which has a pretty high R/Q.
- Procedure to have the computation done correctly to obtain the wake function for HEADTAIL May be we could contact Burkhardt Doliwa for SPS MKE kicker simulations he made in the past (collaboration after GSI workshop in 2006)
- Pros/cons of Particle Studio / Microwave Studio discussed.
- Comment from Bruno Zotter => Change HEADTAIL to have triangle or Gaussian distributions instead of rectangular ones. May be a student could look at it.
Presentation by Carlo:
- The cylindrical shape with losses has been tested by CST and they also did not reach convergence with very high number of mesh (that we can not reach here). Particle Studio has not been optimised for such structures.
- The factor ~ 4.2 discrepancy between theory and simulations has also been identified in the mode 1 of the longitudinal wake. The same factor in the transverse wake is only a consequence. It is important to note that a very small contribution of the longitudinal wake (1% of mode 0) is responsible for the transverse wake.
- The longitudinal and transverse mode 0 and 1 were explicitly derived from the assumption of flat chambers, yokoya factors that are valid for longitudinal mode 0 and transverse mode 1, and Panofsky Wenzel. It is interesting to notice the linear dependence of the longitudinal wake mode 1 with the source charge. Is this dependence confirmed by theory?
- Next steps include exposing the issue to CST at PAC in Vancouver (it was already explained over the phone). We could also check the steps to obtain the wake from the longitudinal electric field, but after that, it will be rather hard to investigate further on this topic... Elias mentioned one of his main objectives is to get the correct quadrupolar contribution for the kickers. Fritz reminded to be careful with the abusive use of electric boundary conditions for all materials.
AOB
- Discussions
Author: Benoit Salvant CERN
AB/ABP-LIS