Elegant users forum

Dear Michael,

I am a little confused about definition of time of the RFDF element. According to the manual, the kick of the RFDF is of form F=ecB0 cos (wt+phi). What is the physical meaning of t appearing in this formula?
Is it the time it takes a particle to arrive at the RFDF from the start of the beam line (where time is set to be t=0)? Based on this possibility, I tried to set the total phase (wt+phi) of the kick, say to zero (for on-crest kick), but it failed. It even gives me the same kicks (i.e., the same total phases) after I change the length of the beam line preceding the RFDF.
So I am clueless about the time of the RFDF and can not control the total phase of the RFDF in a way I want, specially in multiple passes. Could you let me know how the ELEGANT defines t?

Thanks as always,

Gunn

Gunn,

As with all rf elements, elegant determines an offset to the phase so that the user-specified PHASE parameter holds for the fiducial particle on the first arrival of the beam at the element. Hence, changing the position of the element in the beam line won't change the phase. The actual equation should be cos(omega*(t-t0) + phi), where t is the particle arrival time, t0 is the fiducial arrival time, and phi is the user-specified phase.

One thing to note in rings is that you must set the frequency precisely. A ballpark number is not sufficient since elegant doesn't make any assumptions that cavities are near revolution harmonics.

--Michael