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WAKE

Longitudinal wake specified as a function of time lag behind the particle.
Parameter Name Units Type Default Description
INPUTFILE   STRING NULL name of file giving Green function
TCOLUMN   STRING NULL column in INPUTFILE containing time data
WCOLUMN   STRING NULL column in INPUTFILE containing Green function
CHARGE $C$ double 0.0 beam charge (or use CHARGE element)
FACTOR $C$ double 1 factor to multiply wake by
N_BINS   long 128 number of bins for current histogram
INTERPOLATE   long 0 interpolate wake?
SMOOTHING   long 0 smooth current histogram?
SG_HALFWIDTH   long 4 Savitzky-Golay filter half-width for smoothing
SG_ORDER   long 1 Savitzky-Golay filter order for smoothing
CHANGE_P0   long 0 change central momentum?
ALLOW_LONG_BEAM   long 0 allow beam longer than wake data?





The input file for this element gives the longitudinal Green function, $W(t)$ versus time behind the particle. The units of the wake are V/C, so this element simulates the integrated wake of some structure (e.g., a cell or series of cells). If you have, for example, the wake for a cell and you need the wake for N cells, then you may use the FACTOR parameter to make the appropriate multiplication. The values of the time coordinate should begin at 0 and be equi-spaced. A positive value of time represents the distance behind the exciting particle.

Use of the CHARGE parameter on the WAKE element is disparaged. It is preferred to use the CHARGE element as part of your beamline to define the charge.

Setting the N_BINS paramater to 0 is recommended. This results in auto-scaling of the number of bins to accomodate the beam. The bin size is fixed by the spacing of the time points in the wake.

The default degree of smoothing (SG_HALFWIDTH=4) may be excessive. It is suggested that users vary this parameter to verify that results are reliable if smoothing is employed (SMOOTHING=1).


next up previous
Next: WATCH Up: Element Dictionary Previous: VMON
Robert Soliday 2002-09-24