A simulation of a singlepass broadband or functionallyspecified transverse 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? 

RS  Ohm∕m  double  0.0  shunt impedance (Rs=Ra/2=V/(2*P)) 
Q  double  0.0  cavity Q 

FREQ  Hz  double  0.0  frequency (BROAD_BAND=1) 
INPUTFILE  STRING  NULL  name of file giving impedance (BROAD_BAND=0) 

FREQCOLUMN  STRING  NULL  column in INPUTFILE containing frequency 

ZXREAL  STRING  NULL  column in INPUTFILE containing real impedance for x plane 

ZXIMAG  STRING  NULL  column in INPUTFILE containing imaginary impedance for x plane 

ZYREAL  STRING  NULL  column in INPUTFILE containing real impedance for y plane 

ZYIMAG  STRING  NULL  column in INPUTFILE containing imaginary impedance for y plane 

BIN_SIZE  S  double  0.0  bin size for current histogram (use 0 for autosize) 
INTERPOLATE  long  0  interpolate wake? 

N_BINS  long  128  number of bins for current histogram 

MAX_N_BINS  long  0  Maximum number of bins for current histogram 

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 

ZTRANSVERSE continued
A simulation of a singlepass broadband or functionallyspecified transverse impedance.
Parameter Name  Units  Type  Default  Description 
DX  M  double  0.0  misalignment 
DY  M  double  0.0  misalignment 
FACTOR  double  1  Factor by which to multiply x and y impedances. 

XFACTOR  double  1  Factor by which to multiply x impedance. 

YFACTOR  double  1  Factor by which to multiply y impedance. 

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 

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. 

X_DRIVE_EXPONENT  long  1  Exponent applied to x coordinates of drive particles 

Y_DRIVE_EXPONENT  long  1  Exponent applied to y coordinates of drive particles 

X_PROBE_EXPONENT  long  0  Exponent applied to x coordinates of probe particles 

ZTRANSVERSE continued
A simulation of a singlepass broadband or functionallyspecified transverse impedance.
Parameter Name  Units  Type  Default  Description 
Y_PROBE_EXPONENT  long  0  Exponent applied to y coordinates of probe particles 

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 transverse 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
 (169) 
where i = , W(t) = 0 for t < 0, and W(t) has units of V∕C∕m. Note that there is no factor of i in front of the integral. Thus, in elegant the transverse impedance is simply the Fourier transform of the wake. This makes it easy to convert data from a program like ABCI into the wake formalism using sddsfft.
For a resonator impedance, the functional form is
 (170) 
where R_{s} is the shunt impedance in Ohms∕m, 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/m. 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 ZTRANSVERSE element is controlled using the BUNCHED_BEAM_MODE parameter.