A first-order matrix RF cavity with exact phase dependence.
Parallel capable? : yes
GPU capable? : yes
Back-tracking capable? : yes
cavity Q (for cavity that charges up to given voltage from 0)
phase reference number (to link with other time-dependent elements)
does cavity change central momentum?
set to 1 for long runs to avoid rounding error in phase
mode for determining fiducial arrival time (light, tmean, first, pmaximum)
include focusing at entrance?
include focusing at exit?
None (default) or SRS (simplified Rosenzweig/Serafini for standing wave)
Number of kicks to use for kick method. Set to zero for matrix method.
arrival time of reference particle
Linearize phase dependence?
Lock phase to given value regardless of bunch centroid motion?
Optionally used to assign an element to a group, with a user-defined name. Group names will appear in the parameter output file in the column ElementGroup
The phase convention is as follows, assuming a positive rf voltage: PHASE=90 is the crest for acceleration. PHASE=180 is the stable phase for a storage ring above transition without energy losses.
The body-focusing model is based on Rosenzweig and Serafini, Phys. Rev. E 49 (2), 1599. As suggested by N. Towne (NSLS), I simplified this to assume a pure pi-mode standing wave.
The CHANGE_T parameter may be needed for reasons that stem from elegant’s internal use of the total time-of-flight as the longitudinal coordinate. If the accelerator is very long or a large number of turns are being tracked, rounding error may affect the simulation, introducing spurious phase jumps. By setting CHANGE_T=1, you can force elegant to modify the time coordinates of the particles to subtract off NTrf , where Ttf is the rf period and N = ⌊t∕Ttf + 0.5⌋. If you are tracking a ring with rf at some harmonic h of the revolution frequency, this will result in the time coordinates being relative to the ideal revolution period, Trf * h. If you have multiple rf cavities in a ring, you need only use this feature on one of them. Also, you can use CHANGE_T=1 if you simply prefer to have the offset time coordinates in output files and analysis.
N.B.: Do not use CHANGE_T=1 if you have rf cavities that are not at harmonics of one another or if you have other time-dependent elements that are not resonant. Also, if you have harmonic cavities, only use CHANGE˙T on the cavity with the lowest frequency.