|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||double||0.0||beam charge (or use CHARGE element)|
|FACTOR||double||1||factor to multiply wake by|
|N_BINS||long||128||number of bins for current histogram|
||Use Savitzky-Golay filter to 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 central momentum?|
||allow beam longer than wake data?|
||Number of passes over which to linearly ramp up the wake to full strength.|
|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 input file for this element gives the longitudinal Green function, 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.
A positive value of results in energy loss. A physical wake function should be positive at .
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).
The algorithm for the wake element is as follows:
ALLOW_LONG_BEAMis nonzero). In the latter case, that part of the beam that is furthest from is ignored for computation of the wake.
SMOOTHINGis nonzero, smooth the arrival time histogram.
CHANGE_P0is nonzero, change the reference momentum of the beamline to match the average momentum of the beam.