Hi! I'm trying to do slow extraction simulations from a synchrotron using elegant and got a little confused by the behaviour of the limit_in_4d flag to the bunched_beam command. What I actually want to do is to create something like a KV beam in the transverse planes. To this end, I choose "uniform-ellipse" as distribution type for x and y. The transverse hard edge emittances are asymmetric, ex=50um, ey=8um (well, it's a hadron machine). When I set limit_in_4d=0, I get the expected ellipses in (x,xp) and (y,yp), and sddsanalyzebeam reproduces these values. However, the beam distribution in (x,y) is a rectangle, where I would want a flat ellipse. Therefore, I tentatively limit_in_4d=1. But this changes the emittances of the distribution: sddsanalyzebeam now reports ex=32um and ey=14um. I tried to figure out how the limit_in_4d works from the documentation unsuccessfully.
So here are my questions:
- Am I missing something essential?
- What exactly does limit_in_4d=1 do?
- Is it possible to create a KV beam using the bunched_beam command after all?
Best regards, David