A simulation of a singlepass broadband or functionally specified longitudinal impedance.
Parallel capable? : yes
GPU capable? : no
Backtracking capable? : no
Parameter Name  Units  Type  Default  Description 
CHARGE  C  double  0.0  Deprecated—use CHARGE element 
BROAD_BAND  long  0  broadband impedance? 

RA  Ohm  double  0.0  shunt impedance, Ra=V/P 
RS  Ohm  double  0.0  shunt impedance (Rs=Ra/2) 
Q  double  0.0  cavity Q 

FREQ  Hz  double  0.0  frequency (BROAD_BAND=1) 
ZREAL  STRING  NULL  <filename>=<x>+<y> form specification of input file giving real part of impedance vs f (BROAD_BAND=0) 

ZIMAG  STRING  NULL  <filename>=<x>+<y> form specification of input file giving imaginary part of impedance vs f (BROAD_BAND=0) 

BIN_SIZE  S  double  0.0  bin size for current histogram (use 0 for autosize) 
N_BINS  long  128  number of bins for current histogram 

MAX_N_BINS  long  0  Maximum number of bins for current histogram 

WAKES  STRING  NULL  filename for output of wake 

WAKE_INTERVAL  long  1  interval in passes at which to output wake 

WAKE_START  long  0  pass at which to start to output wake 

WAKE_END  long  9223372036854775807  pass at which to stop to output wake 

AREA_WEIGHT  long  0  use areaweighting in assigning charge to histogram? 

INTERPOLATE  long  0  interpolate wake? 

SMOOTHING  long  0  Use SavitzkyGolay filter to smooth current histogram? 

SG_ORDER  long  1  SavitzkyGolay filter order for smoothing 

SG_HALFWIDTH  long  4  SavitzkyGolay filter halfwidth for smoothing 

ZLONGIT continued
A simulation of a singlepass broadband or functionally specified longitudinal impedance.
Parameter Name  Units  Type  Default  Description 
REVERSE_TIME_ORDER  long  0  Reverse timeorder of particles for wake computation? 

FACTOR  double  1  Factor by which to multiply impedance. 

START_ON_PASS  long  0  The pass on which the impedance effects start. 

RAMP_PASSES  long  0  Number of passes over which to linearly ramp up the impedance to full strength. 

HIGH_FREQUENCY_CUTOFF0  double  1  Frequency at which smoothing filter begins. If not positive, no frequency filter smoothing is done. Frequency is in units of Nyquist (0.5/binsize). 

HIGH_FREQUENCY_CUTOFF1  double  1  Frequency at which smoothing filter is 0. If not given, defaults to HIGH_FREQUENCY_CUTOFF0. 

BUNCHED_BEAM_MODE  long  1  If nonzero, then do calculations bunchbybunch. 

START_BUNCH  long  1  In bunched beam mode, if nonnegative, starting bunch number for computations 

END_BUNCH  long  1  In bunched beam mode, if nonnegative, ending bunch number for computations 

ALLOW_LONG_BEAM  long  0  Allow beam longer than covered by impedance data? 

GROUP  string  NULL  Optionally used to assign an element to a group, with a userdefined name. Group names will appear in the parameter output file in the column ElementGroup 

This element allows simulation of a longitudinal impedance using a “broadband” resonator or an impedance function specified in a file. The impedance is defined as the Fourier transform of the wake function
 (167) 
where i = , W(t) = 0 for t < 0, and W(t) has units of V∕C.
For a resonator impedance, the functional form is
 (168) 
where R_{s} is the shunt impedance in Ohms, Q is the quality factor, and ω_{r} is the resonant frequency.
When providing an impedance in a file, the user must be careful to conform to these conventions. In addition, the units of the frequency column must be Hz, while the units of the impedance components must be Ohms. At present, elegant does not check the units for correctness.
Other notes:
Bunchedmode application of the impedance is possible using speciallyprepared input beams. See Section 6 for details. The use of bunched mode for any particular ZLONGIT element is controlled using the BUNCHED_BEAM_MODE parameter.
Explanation of <filename>=<x>+<y> format: Several elements in elegant make use of data from external files to provide input waveforms. The external files are SDDS files, which may have many columns. In order to provide a convenient way to specify both the filename and the columns to use, we frequently employ <filename>=<x>+<y> format for the parameter value. For example, if the parameter value is waveform.sdds=t+A, then it means that columns t and A will be taken from file waveform.sdds. The first column is always the independent variable (e.g., time, position, or frequency), while the second column is the dependent quantity.
ZTRANSVERSE