Problems on using FTRFMODE

[WEI-HOU]

Hello,

I encountered the following problem when using FTRFMODE for multi-bunch simulations.

"error: No available particle for RF cavity fiducilization"

I tried setting the factor for FTRFMODE to be very small and it still occurred.
My bunch length is about 2ps, and I set BIN_SIZE=0.3ps and N_BINS=200 to cover the entire beam.

Were my parameters wrong?

Thank you.

[michael_borland]

The problem is that you have CHANGE_T=1 on your RFCA elements. This can only be used if all rf elements (including RFMODE, TRFMODE, etc.) are harmonically-related. Since that isn't the case, it introduces a problem with propagation of the rf phasors for *RFMODE elements.

--Michael

[WEI-HOU]

Hello Michael,

Thank you for your clarification.

I also notice that 'pCetnral0' in Twiss output does not change, and therefore Twiss outputs are wrong.
Is there a way to fix this problem?

Regards
Wei-Hou

[michael_borland]

Wei-Hou,

Yes, you need to remove the following statement:

Code: Select all

&alter_elements name=*, type=RFCA, item=CHANGE_P0, value = 0 &end

You have CHANGE_P0=1 in the lattice file, which is what you want to keep.

--Michael

[WEI-HOU]

Hello Michael,

According to this thread, viewtopic.php?f=12&t=1117

Isn't CHANGE_P0 has to be zero in order to be used together with the momentum profile that was first obtained with single bunch tracking?
Thanks.

Regards
Wei Hou

[michael_borland]

Wei-Hou,

Sorry, I didn't notice that you were loading an energy profile.

There does seem to be a bug in the twiss computation for this case. I'll fix it for the next release. The tracking results should be fine.

--Michael

[WEI-HOU]

Hello Michael,

Yes, Twiss parameters of the beam ( betaxBeam, etc) looks fine.
Thanks, keep me posted.

Regards
Wei Hou