10.82 RFCA—A first-order matrix RF cavity with exact phase dependence.

A first-order matrix RF cavity with exact phase dependence.
Parallel capable? : yes
GPU capable? : yes
Back-tracking capable? : yes






Parameter Name UnitsType Default

Description






L M double 0.0

length






VOLT V double 0.0

peak voltage






PHASE DEGdouble 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 short 0

does cavity change central momentum?






CHANGE_T short 0

set to 1 for long runs to avoid rounding error in phase






FIDUCIAL STRINGNULL

mode for determining fiducial arrival time (light, tmean, first, pmaximum)






END1_FOCUS short 0

include focusing at entrance?






END2_FOCUS short 0

include focusing at exit?






BODY_FOCUS_MODEL STRINGNULL

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 short 0

Linearize phase dependence?






LOCK_PHASE short 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 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.

RFCW