Elegant users forum

Dear Michael and collaborators,

I would like to find the periodic envelopes (sigmax,sigmay) of an electron beam in a beamline. The beam is subject to the space charge kicks given by "&insert_sceffects". For this reason, I believe I cannot use the twiss output with "matched=1". I was thinking of using the optimization procedure by varying the initial conditions (alphas and betas) as optimization variables and the optimization terms given by the difference between the starting and final envelopes and slopes. As far as I know, there doesn't appear to be a way to use the initial Twiss parameters of a beam as the optimization variables. All the examples use magnet strengths for this purpose. Is there a way to vary the initial Twiss parameters inside an optimization block ?

I thank you in advance,

regards, Santiago Bernal (U. of Maryland)

Santiago,

Elegant can only optimize things that are parameters of beamline elements. So the way to do this is using the TWISS element, which allows transforming the twiss values.

Assuming your beamline is called BL, then you'd add to your lattice file the following lines:
INTW: twiss
BLT: (INTW,BL)

You can now use parameters BETAX, ALPHAX, ETAX, etc of INTW in optimization_variable commands.

To ensure periodicity, you would add optimization_term commands to make, e.g., "INTW.BETAX" and "betax" (the final value) equal.

--Michael