Elegant users forum

Hello Michael,

As you know, in ERL after a arc of length n*lambda+lambda/2 there must be deceleration.

In our case, we are using 9 cell cavity. I split up the cavity so that there is proper phase and a one module will give 25 MeV energy. It works fine. But after that arc the cryomodule again increases the beam energy.

Is it due to phase? I mean, I've to add something that it will change the phase by 180 and decrease the beam energy.

Thank you.
Aamna

Aaaman,

The key is to realize that elegant general treats every instance of an element (e.g., "linA1") as an independent entity. If the element is an RFCA that is used several times, each RFCA is independently phased to the beam so as to have phase value given in the element definition. In light of this, there are two ways to accomplish what you want:
* Define different RFCA elements for the acceleration and deceleration stage. In this case, you explicitly put in the desired accelerating or decelerating phase.
* A assign a unique positive PHASE_REFERENCE value to each RFCA. Elegant will record the time at which the beam passes the first instance of each RFCA (e.g., linA1, linA2) and use that to phase the first RFCA to the value given by the PHASE parameter. Subsequent instances of the same RFCA will be locked in phase to the first one, so the actual phase will differ from the PHASE value according to the time of flight and rf frequency. This is the best approach. I've modified your file to indicate what I mean.

By the way, in making your movie, you'll get better results by putting the -graph=dot option on sddsplot.

--Michael

Thank you!

Aamna