Parameter Name | Units | Type | Default | Description |
FILENAME | STRING | NULL | input file | |
BIN_SIZE | ![]() |
double | 0.0 | bin size for current histogram (use 0 for autosize) |
N_BINS | long | 20 | number of bins for current histogram | |
RIGID_UNTIL_PASS | long | 0 |
don't affect the beam until this pass | |
USE_SYMM_DATA | long | 0 |
use "Symm" columns from URMEL output file? | |
DX | ![]() |
double | 0.0 | misalignment |
DY | ![]() |
double | 0.0 | misalignment |
XFACTOR | double | 1 | factor by which to multiply shunt impedances | |
YFACTOR | double | 1 | factor by which to multiply shunt impedances | |
CUTOFF | ![]() |
double | 0.0 | If ![]() |
OUTPUT_FILE | STRING | NULL | Output file for voltage in each mode. | |
FLUSH_INTERVAL | long | 1 | Interval in passes at which to flush output data. | |
RAMP_PASSES | long | 0 |
Number of passes over which to linearly ramp up the impedance to full strength. |
This element is similar to TRFMODE, but it allows faster simulation of more than
one mode. Also, the mode data is specified in an SDDS file. This file can be
generated using the APS version of URMEL, or by hand. It must have the following
columns and units:
USE_SYMM_DATA
is non-zero, then ShuntImpedanceSymm is used. The latter is the full-cavity shunt
impedance that URMEL computes by assuming that the input cavity used
is one half of a symmetric cavity.
The file may also have the following columns:
N.B.: Unlike TRFMODE, FTRFMODE does not include the longitudinal field that, strictly speaking, must also be excited. Generally this is a very small effect. It will be added in a future version.
In many simulations, a transient effect may occur when using this element because, in the context of the simulation, the impedance is switched on instantaneously. This can give a false indication of the threshold for instability. The RAMP_PASSES parameter should be used to prevent this by slowly ramping the impedance to full strength. This idea is from M. Blaskiewicz (BNL).