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Dear elegant users and experts,

I want to simulate a clystron failure in a linac including the misfocusing in the following quads.

The idea was to run these simulations using the correct fiducialization in the run_control command. I can see different Twiss functions at the end of the beam line thus the focusing seems to be different, but the beam center energy in the *cen file is still the same.

I would be very grateful if you could help me with this problem because I'm not sure if I chose the right settings for these kind of simulations and I don't have any expirience with the fiducialization option in the run_control command.

The elegant files are attached to this post.

Thank you in advance!
Best, Matthias

Matthias,

To use fiducialization, you need to track at least two steps. The first step fiducializes, while the second tracks the real beam. I modified your .ele file to reflect this.

The energy offset will appear not in pCentral, which is the reference momentum, but in Cdelta = (<p>-pCentral)/pCentral.

Also, since the energy deviations are so large it is best to use KQUAD and CSBEND in place of QUAD and SBEN. The modeling for KQUAD and CSBEND is good to all orders in energy deviation, whereas QUAD (SBEN) is only good to 3rd (2nd) order. I've attached a modified file. You may want to play with the N_KICKS values to ensure that the results are converged.

--Michael

Dear Michael,

thank you for your answer and for the modified files! I have one more question concerning the number of steps. You wrote that I need at least 2 steps but in the modified file you wrote:

&run_control
n_indices = 1,
reset_rf_for_each_step = 0
first_is_fiducial = 1
n_steps = 1
&end

I guess it has to be n_steps = 2 or did I misunderstand this point?

Best,
Matthias

Matthais,

My mistake. I forgot that when fiducialization is invoked, elegant automatically adds a step without the user asking.

--Michael

Dear Michael,

thanks for you help!

Best, Matthias