thin-gap vs fieldmap

[kevin]

Thank you for your previous explanation.

Following your suggestion, we updated the GAP definition by providing all four parameters related to the transit time factor, i.e.:

βs, Ts, T′, and T″.

In our current setup, we assign:

βs: calculated from the synchronous particle energy at each gap
Ts: obtained from our field data
T′ = 0
T″ = 0

However, even after explicitly providing all four parameters in this form, we still observe no change in the simulation results (e.g., output energy and beam dynamics quantities), compared to the case where these parameters were not fully specified.

To further verify this, we also performed tests by significantly modifying Ts (for example, reducing it by a large factor), but the results remained unchanged.

Therefore, we would like to ask:

Under which conditions are βs, Ts, T′, and T″ actually taken into account in the GAP model?
Is there any specific setting, option, or calculation mode in TraceWin that enables or disables the use of these TTF-related parameters?

[Didier]

Do you speak about Tracking ? because in envelope if you beam is at Bs, oviously nothing will change

[kevin]

Yes, we are using multi-particle tracking (PARTRAN mode) rather than envelope calculations.

[Didier]

Ok, I see, in tracking mode, see Tom Wangler's book, it's much more complexe and 4 parameters must be set to a non null value.

[gwhitlock71]

Yes, we are using multi-particle tracking (PARTRAN mode) rather than envelope calculations.

kevin, quick one... when you cut Ts by a large factor in PARTRAN, did the output energy really come out identical to the last digit? Or is it just teh plot that looks the same, wich can happen when the gap voltage is dwarfing everything else. Also what did you actually put in for T' and T'', because Didier said they cant be zero in tracking and yours are both 0 as far as i can tell.