Elegant users forum

Hi all,

I want to simulate IBS using the IBScatter element, but I would like to do it using ILMatrix to speed up the computations. However, I would also like to include coupling in the simulation and I am not really sure about the best way to do that.

I have attempted to introduce coupling in my lattice by giving a tilt to the quadrupoles and then calculate the ILMatrix using twiss_output, but if I have understood the manual correctly the output from twiss_output is only valid for negligible coupling and therefore the ILMatrix will not include the coupling correctly?

I have also understood from the examples that the parameters for ILMatrix could instead be determined from tracking, which might mean that this would include the coupling? Or is it the case that the ILMatrix element cannot include coupling and it has to be introduced into the simulation in some other way?

Anyone else that have attempted this and found a working solution?

Best regards,

Teresia

Teresia,

At present, ILMATRIX doesn't have good support for coupling. One can adjust the TILT parameter to introduce x-y coupling, but it is hard to figure out just how much tilt to introduce. I suppose one could look at the oscillation beating between x and y, in comparison to a simulation with element-by-element tracking. One could also insert an EMATRIX element with appropriately-tuned off-diagonal elements. This might be possible by comparing the matrix (determined by tracking with analyze_map) in two cases: (1) with your full lattice that includes skew quadrupoles, tilts, etc. (2) ILMATRIX plus EMATRIX.

If you try any of these suggestions, please let us know how they work.

--Michael

Thank you, Michael.

I was actually thinking about the TILT parameter and if that could possibly be used to get coupling. For my purpose I don't think it is so important to be able to figure out beforehand what the tilt should be since I just want to set it so I get a certain equilibrium vertical emittance including IBS. As long as the simulation is fast enough trial-and-error should work.

I will try your suggestions and let you know if I found something that works.

Best regards,

Teresia