 | (129) |
To use this, one must set STANDING_WAVE=0 (the default). One must also have N_KICKS≥ 10.
An rf cavity with exact phase dependence, first order in transverse coordinates.
Parallel capable? : yes
GPU capable? : yes
Back-tracking 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 | short | 0 | does cavity change central momentum? |
|
| CHANGE_T | short | 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 | short | 0 | include focusing at entrance? |
|
| END2_FOCUS | short | 0 | include focusing at exit? |
|
| STANDING_WAVE | short | 0 | Use standing-wave cavity model instead of default traveling wave? |
|
| BODY_FOCUS_MODEL | STRING | NULL | None (default), SRS or TW1. |
|
| 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.
Body focus models: By default, no body focusing (i.e., focusing along the cavity) is included. Two options are included:
|
| (129) |
To use this, one must set STANDING_WAVE=0 (the default). One must also have N_KICKS≥ 10.
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. Failure to follow these rules can result in wrong results and crashes.
RFCW