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 Name	Units	Type	Default	Description

L	M	double	0.0	arc length

ANGLE	RAD	double	0.0	bend angle

K1	1∕M²	double	0.0	geometric quadrupole strength

K2	1∕M³	double	0.0	geometric sextupole strength

K3	1∕M⁴	double	0.0	geometric octupole strength

K4	1∕M⁵	double	0.0	geometric decapole strength

K5	1∕M⁶	double	0.0	geometric 12-pole strength

K6	1∕M⁷	double	0.0	geometric 14-pole strength

K7	1∕M⁸	double	0.0	geometric 16-pole strength

K8	1∕M⁹	double	0.0	geometric 18-pole strength

E1	RAD	double	0.0	entrance edge angle

E2	RAD	double	0.0	exit edge angle

TILT	RAD	double	0.0	rotation about incoming longitudinal axis

H1	1∕M	double	0.0	entrance pole-face curvature

H2	1∕M	double	0.0	exit pole-face curvature

HGAP	M	double	0.0	half-gap between poles

FINT		double	0.5	edge-field integral

DX	M	double	0.0	misalignment

DY	M	double	0.0	misalignment

DZ	M	double	0.0	misalignment

FSE		double	0.0	fractional strength error

ETILT	RAD	double	0.0	error rotation about incoming longitudinal axis

N_SLICES		long	4	Number of slices (full integrator steps).

N_KICKS		long	4	number of kicks. Deprecated. Use N_SLICES

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?


Parameter Name	Units	Type	Default	Description

LINEARIZE		short	0	use linear matrix instead of symplectic integrator?

SYNCH_RAD		short	0	include classical, single-particle synchrotron radiation?

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, 4, or 6)

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


Parameter Name	Units	Type	Default	Description

TRAPAZOID_INTEGRATION		short	1	Select whether to use trapazoid-rule integration (default) or a simple sum.

OUTPUT_FILE		STRING	NULL	output file for CSR wakes

OUTPUT_INTERVAL		long	1	interval (in kicks) of output to OUTPUT_FILE

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∕M²	double	0.0	K2 = B2/rho

B3	1∕M³	double	0.0	K3 = B3/rho

B4	1∕M⁴	double	0.0	K4 = B4/rho

B5	1∕M⁵	double	0.0	K5 = B5/rho

B6	1∕M⁶	double	0.0	K6 = B6/rho

B7	1∕M⁷	double	0.0	K7 = B7/rho

B8	1∕M⁸	double	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		STRING	disable	disable, evaluate, or enforce

PARTICLE_OUTPUT_FILE		STRING	NULL	name of file for phase-space output


Parameter Name	Units	Type	Default	Description

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)

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		STRING	NULL	Name of file supplying wakefield filtering data.

WFF_FREQ_COLUMN		STRING	NULL	Name of column supplying frequency values for wakefield filtering data.


Parameter Name	Units	Type	Default	Description

WFF_REAL_COLUMN		STRING	NULL	Name of column supplying real values for wakefield filtering data.

WFF_IMAG_COLUMN		STRING	NULL	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.

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