Parameter Name | Units | Type | Default | Description |
L | ![]() |
double | 0.0 | length |
VOLT | ![]() |
double | 0.0 | peak voltage |
PHASE | ![]() |
double | 0.0 | phase |
FREQ | ![]() |
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 | 1 | number of kicks to use. Set to zero for matrix method. | |
DX | ![]() |
double | 0.0 | misalignment |
DY | ![]() |
double | 0.0 | misalignment |
T_REFERENCE | ![]() |
double | -1 | arrival time of reference particle |
LINEARIZE | long | 0 |
Linearize phase dependence? |
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 , where
is the rf period and
. If
you are tracking a ring with rf at some harmonic
of the revolution
frequency, this will result in the time coordinates being relative to
the ideal revolution period,
. 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.