10.17 CSRCSBEND—Like CSBEND, but incorporates a simulation of Coherent Synchrotron radiation.

Like CSBEND, but incorporates a simulation of Coherent Synchrotron radiation.
Parallel capable? : yes
GPU capable? : yes
Back-tracking capable? : yes






Parameter NameUnitsType Default

Description






L M double0.0

arc length






ANGLE RADdouble0.0

bend angle






K1 1∕M2double0.0

geometric quadrupole strength






K2 1∕M3double0.0

geometric sextupole strength






K3 1∕M4double0.0

geometric octupole strength






K4 1∕M5double0.0

geometric decapole strength






K5 1∕M6double0.0

geometric 12-pole strength






K6 1∕M7double0.0

geometric 14-pole strength






K7 1∕M8double0.0

geometric 16-pole strength






K8 1∕M9double0.0

geometric 18-pole strength






E1 RADdouble0.0

entrance edge angle






E2 RADdouble0.0

exit edge angle






TILT RADdouble0.0

rotation about incoming longitudinal axis






H1 1∕M double0.0

entrance pole-face curvature






H2 1∕M double0.0

exit pole-face curvature






HGAP M double0.0

half-gap between poles






FINT double0.5

edge-field integral






DX M double0.0

misalignment






DY M double0.0

misalignment






DZ M double0.0

misalignment






FSE double0.0

fractional strength error






ETILT RADdouble0.0

error rotation about incoming longitudinal axis






N_KICKS long 4

number of kicks






ETILT_SIGN short 1

Sign of ETILT relative to TILT. -1 is the old convention prior to 2020.5






NONLINEAR short 1

include nonlinear field components?






LINEARIZE short 0

use linear matrix instead of symplectic integrator?






SYNCH_RAD short 0

include classical, single-particle synchrotron radiation?






CSRCSBEND continued

Like CSBEND, but incorporates a simulation of Coherent Synchrotron radiation.






Parameter Name UnitsType Default

Description






EDGE1_EFFECTS short 1

include entrance edge effects?






EDGE2_EFFECTS short 1

include exit edge effects?






EDGE_ORDER short 1

order to which to include edge effects






INTEGRATION_ORDER short 4

integration order (2 or 4)






BINS long 0

number of bins for CSR wake






BIN_ONCE short 0

bin only at the start of the dipole?






BIN_RANGE_FACTOR double 1.2

Factor by which to increase the range of histogram compared to total bunch length. Large value eliminates binning problems in CSRDRIFTs.






SG_HALFWIDTH short 0

Savitzky-Golay filter half-width for smoothing current histogram. If less than 1, no SG smoothing is performed.






SG_ORDER short 1

Savitzky-Golay filter order for smoothing current histogram






SGDERIV_HALFWIDTH short 0

Savitzky-Golay filter half-width for taking derivative of current histogram. Defaults to SG_HALFWIDTH (if positive) or else 1.






SGDERIV_ORDER short 1

Savitzky-Golay filter order for taking derivative of current histogram






TRAPAZOID_INTEGRATION short 1

Select whether to use trapazoid-rule integration (default) or a simple sum.






OUTPUT_FILE STRINGNULL

output file for CSR wakes






OUTPUT_INTERVAL long 1

interval (in kicks) of output to OUTPUT_FILE






CSRCSBEND continued

Like CSBEND, but incorporates a simulation of Coherent Synchrotron radiation.






Parameter Name UnitsType Default

Description






OUTPUT_LAST_WAKE_ONLY short 0

output final wake only?






STEADY_STATE short 0

use steady-state wake equations?






IGF short 0

use integrated Greens function (requires STEADY_STATE=1)?






USE_BN short 0

use b<n> instead of K<n>?






EXPANSION_ORDER short 0

Order of field expansion. (0=auto)






B1 1∕M double 0.0

K1 = b1/rho, where rho is bend radius






B2 1∕M2double 0.0

K2 = B2/rho






B3 1∕M3double 0.0

K3 = B3/rho






B4 1∕M4double 0.0

K4 = B4/rho






B5 1∕M5double 0.0

K5 = B5/rho






B6 1∕M6double 0.0

K6 = B6/rho






B7 1∕M7double 0.0

K7 = B7/rho






B8 1∕M8double 0.0

K8 = B8/rho






ISR short 0

include incoherent synchrotron radiation (quantum excitation)?






ISR1PART short 1

Include ISR for single-particle beam only if ISR=1 and ISR1PART=1






CSR short 1

enable CSR computations?






BLOCK_CSR short 0

block CSR from entering CSRDRIFT?






DERBENEV_CRITERION_MODE STRINGdisable

disable, evaluate, or enforce






PARTICLE_OUTPUT_FILE STRINGNULL

name of file for phase-space output






PARTICLE_OUTPUT_INTERVAL long 1

interval (in kicks) of output to PARTICLE_OUTPUT_FILE






SLICE_ANALYSIS_INTERVAL long 0

interval (in kicks) of output to slice analysis file (from slice_analysis command)






CSRCSBEND continued

Like CSBEND, but incorporates a simulation of Coherent Synchrotron radiation.






Parameter Name UnitsType Default

Description






LOW_FREQUENCY_CUTOFF0 double -1

Highest spatial frequency at which low-frequency cutoff filter is zero. If not positive, no low-frequency cutoff filter is applied. Frequency is in units of Nyquist (0.5/binsize).






LOW_FREQUENCY_CUTOFF1 double -1

Lowest spatial frequency at which low-frequency cutoff filter is 1. If not given, defaults to LOW_FREQUENCY_CUTOFF1.






HIGH_FREQUENCY_CUTOFF0 double -1

Spatial frequency at which smoothing (high-frequency cutoff) 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

Spatial frequency at which smoothing (high-frequency cutoff) filter is 0. If not given, defaults to HIGH_FREQUENCY_CUTOFF0.






CLIP_NEGATIVE_BINS short 1

If non-zero, then any bins with negative counts after the filters are applied have the counts set to zero.






WAKE_FILTER_FILE STRINGNULL

Name of file supplying wakefield filtering data.






WFF_FREQ_COLUMN STRINGNULL

Name of column supplying frequency values for wakefield filtering data.






WFF_REAL_COLUMN STRINGNULL

Name of column supplying real values for wakefield filtering data.






CSRCSBEND continued

Like CSBEND, but incorporates a simulation of Coherent Synchrotron radiation.






Parameter Name UnitsType Default

Description






WFF_IMAG_COLUMN STRINGNULL

Name of column supplying imaginary values for wakefield filtering data.






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






For a discussion of the method behind this element, see M. Borland, “Simple method for particle tracking with coherent synchrotron radiation,” Phys. Rev. ST Accel. Beams 4, 070701 (2001) and G. Stupakov and P. Emma, SLAC LCLS-TN-01-12 (2001).

Recommendations for using this element. The default values for this element are not the best ones to use. They are retained only for consistency through upgrades. In using this element, it is recommended to have 50 to 100 k particle in the simulation. Setting BINS=600 and SG_HALFWIDTH=1 is also recommended to allow resolution of fine structure in the beam and to avoid excessive smoothing. It is strongly suggested that the user vary these parameters and view the histogram output to verify that the longitudinal distribution is well represented by the histograms (use OUTPUT_FILE to obtain the histograms). For LCLS simulations, we find that the above parameters give essentially the same results as obtained with 500 k particles and up to 3000 bins.

In order to verify that the 1D approximation is valid, the user should also set DERBENEV_CRITERION_MODE = ‘‘evaluate’’ and view the data in OUTPUT_FILE. Generally, the criterion should be much less than 1. See equation 11 of [20].

In order respects, this element is just like the CSBEND element, which provides a symplectic bending magnet that is accurate to all orders in momentum offset. Please see the manual page for CSBEND for more details about features not related to CSR.

Splitting dipoles: Splitting dipoles with continuation of CSR effects is possible provided the dipole sections (all of which must have the same name) are either consecutive or separated only by MARK, WATCH, or LSCDRIFT elements. The LSCDRIFT elements must have L=0 and should have LEFFECTIVE set to the length of the upstream dipole segment. This allows simulating LSC and CSR within a single dipole.

CSRDRIFT