Issue with beam-beam and ion pymask

[skostogl]

Comparing the footprints computed with MADX and SixTrack for ions, there is a good agreement without beam-beam. However, when including HO collisions in 1 IP, it seems that there is no head-on tune spread in the sixtrack footprint while it is clearly observed in the MADX footprint.

[giadarol]

Hi Sofia, is the code you are running available on GitHub? I could give it a try.

[sterbini]

Hi all,

Sofia found a solution for the moment (tested with HO, she is going to test it with the LRs too).
The point is how to deal with the weak particle charge (in Pb case +82). The BB force in 6track seems to consider always the weak bb charge 1. So our present strategy, is to edit the pymask, and to use the strength-ratio of the 4D and 6D BB EXPERT BLOCK to scale up it taking into account the

• slicing, already coded
• the rescaling due to the BBB variation , already coded but perhaps it should be moved on the strong beam charge
• the weak particle charge, to be coded.

For completeness I copy&paste the BB EXPERT block syntax

[rdemaria]

Please add an issue in SixTrack! It should handle the charge correctly

[skostogl]

updated plot