Phase offset between field maps [SOLVED]

[Didier]

Dear Wai-Ming,

I agree with everything you wrote, except "the

RF phase" does NOT depend on the length of the fieldmap.

Whichever option you choose for parameter#10, if you set a synchronous phase value, the RF phase will necessarily depend on the field in the cavity, i.e. minimally on its length.

In your example if you change "A2: field_map 100 134 -30 10 0 0.1 0 0 A2_78_134 1" by "A2: field_map 100 120 -30 10 0 0.1 0 0 A2_78_134 1"

The RF phase is obviously not the same!

Regards,

Didier

[wtam]

Dear Didier,

I have a clarification for myself through more testing.

Please understand the background of this post that I have attached two different projects (.ini) and two sets of fieldmaps. The fieldmaps are the same except for the zero padding which make one longer in z than the other. I use different drift lengths to accommodate for the zero padding, i.e. the z location of the E-fields (you can consider it as the gaps) is exactly the same in the two different projects. I have tested it again and the result is that when setting parameter10=1, the RF phase does NOT depend on the length of the fieldmap. The way you tried it would of course change the RF phase.

I am attaching the graphics again to better explain the above.

The result makes sense to me because in the linac vision, the RF phase should not depend on zero padding if the acceleration is the same (same amplitude and same location). I was confused by Nicholas's statement, but I believe he might have misunderstood my question.

Best regards,
Wai-Ming