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RFCA

A first-order matrix RF cavity with exact phase dependence.
Parallel capable? : yes
Parameter Name Units Type Default Description
L $M$ double 0.0 length
VOLT $V$ double 0.0 peak voltage
PHASE $DEG$ double 0.0 phase
FREQ $Hz$ double 500000000 frequency
Q   double 0.0 cavity Q (for cavity that charges up to given voltage from 0)
PHASE_REFERENCE   long 0 phase reference number (to link with other time-dependent elements)
CHANGE_P0   long 0 does cavity change central momentum?
CHANGE_T   long 0 set to 1 for long runs to avoid rounding error in phase
FIDUCIAL   STRING NULL mode for determining fiducial arrival time (light, tmean, first, pmaximum)
END1_FOCUS   long 0 include focusing at entrance?
END2_FOCUS   long 0 include focusing at exit?
BODY_FOCUS_MODEL   STRING NULL None (default) or SRS (simplified Rosenzweig/Serafini for standing wave)
N_KICKS   long 0 Number of kicks to use for kick method. Set to zero for matrix method.
DX $M$ double 0.0 misalignment
DY $M$ double 0.0 misalignment
T_REFERENCE $S$ double -1 arrival time of reference particle
LINEARIZE   long 0 Linearize phase dependence?
LOCK_PHASE   long 0 Lock phase to given value regardless of bunch centroid motion?
GROUP   string NULL 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 $N T_{rf}$, where $T_{tf}$ is the rf period and $N = \lfloor t/T_{tf}+0.5\rfloor$. 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, $T_{rf}*h$. 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.


next up previous
Next: RFCW Up: Element Dictionary Previous: REMCOR
Robert Soliday 2014-03-21