|BIN_SIZE||double||0.0||bin size for current histogram (use 0 for autosize)|
|N_BINS||long||20||number of bins for current histogram|
||don't affect the beam until this pass|
||use "Symm" columns from URMEL output file?|
|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 0, cutoff frequency. Modes above this frequency are ignored.|
|OUTPUT_FILE||STRING||NULL||Output file for voltage in each mode.|
|FLUSH_INTERVAL||long||1||Interval in passes at which to flush output data.|
||Number of passes over which to linearly ramp up the impedance to full strength.|
|RESET_FOR_EACH_STEP||long||1||If nonzero, voltage and phase are reset for each simulation step.|
||If nonzero, induced voltage from present turn does not affect bunch. Short range wake should be included via WAKE or ZLONGIT element.|
|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|
This element simulates a set of beam-driven dipole modes in a cavity using the fundamental theorem of beam loading and phasor rotation. It 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_DATAis 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).
Normally, the field dumped in the cavity by one particle affects trailing particles in the same turn.
However, if one is also using a
ZTRANSVSE element to simulate the short-range wake of the cavity, this would be double-counting.
In that case, one can use
LONG_RANGE_ONLY=1 to suppress the same-turn effects of the