Particles fly off to huge trajectories - any ideas?
Posted: 08 Jun 2022, 05:13
Hello everyone,
I've been running some runs where I externally drive a bunch using EVKICK. Most runs are fine, but sometimes I'll see a run where there is a really big jump in the Y-size. I presume with confidence this is numerical? (No Touschek elements etc; this is just a standard synchrotron lattice using SYNCH_RAD, ISR=1 and a CAV element).
To be clear what happens, I plotted the result in Y-plane of phase-space. It seems most of the bunch behaves entirely fine, except for one particle which shot out to mm of orbit! Naturally, if I remove any outliers (IE: particles over 3 STDs away from the mean) I get a normal behaving pattern. What is more unusual is that this effect happens within one turn! The other colours on the graph refer to some other runs. The orange one is one that behaves just fine. The green one has a similar problem, but the extent to which particles shoot off is far less - but still noticeable when looking at the aggregate statistics. I should say that while I'm running quite sparse particle runs (but with full tracking) this doesn't stop the point that certain particles have extremely unusual behaviour.
Is there a way to ensure this doesn't happen? How much can we trust the simulations if I just remove outliers?
I've been running some runs where I externally drive a bunch using EVKICK. Most runs are fine, but sometimes I'll see a run where there is a really big jump in the Y-size. I presume with confidence this is numerical? (No Touschek elements etc; this is just a standard synchrotron lattice using SYNCH_RAD, ISR=1 and a CAV element).
To be clear what happens, I plotted the result in Y-plane of phase-space. It seems most of the bunch behaves entirely fine, except for one particle which shot out to mm of orbit! Naturally, if I remove any outliers (IE: particles over 3 STDs away from the mean) I get a normal behaving pattern. What is more unusual is that this effect happens within one turn! The other colours on the graph refer to some other runs. The orange one is one that behaves just fine. The green one has a similar problem, but the extent to which particles shoot off is far less - but still noticeable when looking at the aggregate statistics. I should say that while I'm running quite sparse particle runs (but with full tracking) this doesn't stop the point that certain particles have extremely unusual behaviour.
Is there a way to ensure this doesn't happen? How much can we trust the simulations if I just remove outliers?