Problems on using FTRFMODE

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WEI-HOU
Posts: 31
Joined: 01 Mar 2018, 08:20

Problems on using FTRFMODE

Post by WEI-HOU » 08 Jun 2023, 18:58

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
Posts: 1927
Joined: 19 May 2008, 09:33
Location: Argonne National Laboratory
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Re: Problems on using FTRFMODE

Post by michael_borland » 14 Jun 2023, 11:32

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
Posts: 31
Joined: 01 Mar 2018, 08:20

Re: Problems on using FTRFMODE

Post by WEI-HOU » 15 Jun 2023, 18:37

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
Posts: 1927
Joined: 19 May 2008, 09:33
Location: Argonne National Laboratory
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Re: Problems on using FTRFMODE

Post by michael_borland » 15 Jun 2023, 18:45

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
Posts: 31
Joined: 01 Mar 2018, 08:20

Re: Problems on using FTRFMODE

Post by WEI-HOU » 16 Jun 2023, 12:04

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
Posts: 1927
Joined: 19 May 2008, 09:33
Location: Argonne National Laboratory
Contact:

Re: Problems on using FTRFMODE

Post by michael_borland » 16 Jun 2023, 13:12

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
Posts: 31
Joined: 01 Mar 2018, 08:20

Re: Problems on using FTRFMODE

Post by WEI-HOU » 16 Jun 2023, 18:33

Hello Michael,

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

Regards
Wei Hou

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