A canonical kick sector dipole magnet.
Parallel capable? : yes
GPU capable? : yes
Backtracking capable? : yes
Parameter Name  Units  Type  Default  Description 
L  M  double  0.0  arc length 
ANGLE  RAD  double  0.0  bend angle 
K1  1∕M^{2}  double  0.0  geometric quadrupole strength 
K2  1∕M^{3}  double  0.0  geometric sextupole strength 
K3  1∕M^{4}  double  0.0  geometric octupole strength 
K4  1∕M^{5}  double  0.0  geometric decapole strength 
K5  1∕M^{6}  double  0.0  geometric 12pole strength 
K6  1∕M^{7}  double  0.0  geometric 14pole strength 
K7  1∕M^{8}  double  0.0  geometric 16pole strength 
K8  1∕M^{9}  double  0.0  geometric 18pole 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 poleface curvature 
H2  1∕M  double  0.0  exit poleface curvature 
HGAP  M  double  0.0  halfgap between poles 
FINT  double  0.5  edgefield integral 

FINT1  double  1  edgefield integral. If negative, use FINT. 

FINT2  double  1  edgefield integral. If negative, use FINT. 

DX  M  double  0.0  misalignment 
DY  M  double  0.0  misalignment 
DZ  M  double  0.0  misalignment 
XKICK  RAD  double  0.0  horizontal steering angle (approximate) 
YKICK  RAD  double  0.0  vertical steering angle (approximate) 
FSE  double  0.0  fractional strength error of all components 

FSE_DIPOLE  double  0.0  fractional strength error of dipole component 

CSBEND continued
A canonical kick sector dipole magnet.
Parameter Name  Units  Type  Default  Description 
FSE_QUADRUPOLE  double  0.0  fractional strength error of quadrupole component 

ETILT  RAD  double  0.0  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? 

SYNCH_RAD  short  0  include classical, singleparticle synchrotron radiation? 

EDGE1_EFFECTS  short  1  If nonzero, determines the method used to include entrance edge effects. 

EDGE2_EFFECTS  short  1  If nonzero, determines the method used to include exit edge effects. 

EDGE_ORDER  short  1  order to which to include edge effects 

INTEGRATION_ORDER  short  4  integration order (2 or 4) 

EXPAND_HAMILTONIAN  short  0  If 1, Hamiltonian is expanded to leading order. 

EDGE1_KICK_LIMIT  double  1  maximum kick entrance edge can deliver 

EDGE2_KICK_LIMIT  double  1  maximum kick exit edge can deliver 

KICK_LIMIT_SCALING  short  0  scale maximum edge kick with FSE? 

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∕M^{2}  double  0.0  K2 = b2/rho 
CSBEND continued
A canonical kick sector dipole magnet.
Parameter Name  Units  Type  Default  Description 
B3  1∕M^{3}  double  0.0  K3 = b3/rho 
B4  1∕M^{4}  double  0.0  K4 = b4/rho 
B5  1∕M^{5}  double  0.0  K5 = b5/rho 
B6  1∕M^{6}  double  0.0  K6 = b6/rho 
B7  1∕M^{7}  double  0.0  K7 = b7/rho 
B8  1∕M^{8}  double  0.0  K8 = b8/rho 
XREFERENCE  M  double  0.0  reference x for interpretation of fn values 
F1  double  0.0  Fractional normal field error fn=bn*xr/n!, adds to K1 or b1. 

F2  double  0.0  Fractional normal field error fn=bn*xr/n!, adds to K2 or b2. 

F3  double  0.0  Fractional normal field error fn=bn*xr/n!, additive. 

F4  double  0.0  Fractional normal field error fn=bn*xr/n!, additive. 

F5  double  0.0  Fractional normal field error fn=bn*xr/n!, additive. 

F6  double  0.0  Fractional normal field error fn=bn*xr/n!, additive. 

F7  double  0.0  Fractional normal field error fn=bn*xr/n!, additive. 

F8  double  0.0  Fractional normal field error fn=bn*xr/n!, additive. 

G1  double  0.0  Fractional skew field error. 

G2  double  0.0  Fractional skew field error. 

G3  double  0.0  Fractional skew field error. 

G4  double  0.0  Fractional skew field error. 

G5  double  0.0  Fractional skew field error. 

CSBEND continued
A canonical kick sector dipole magnet.
Parameter Name  Units  Type  Default  Description 
G6  double  0.0  Fractional skew field error.  
G7  double  0.0  Fractional skew field error. 

G8  double  0.0  Fractional skew field error.  
ISR  short  0  include incoherent synchrotron radiation (quantum excitation)? 

ISR1PART  short  1  Include ISR for singleparticle beam only if ISR=1 and ISR1PART=1 

SQRT_ORDER  short  0  Ignored, kept for backward compatibility only. 

USE_RAD_DIST  short  0  If nonzero, overrides SYNCH_RAD and ISR, causing simulation of radiation from distributions, optionally including opening angle. 

ADD_OPENING_ANGLE  short  1  If nonzero, radiation opening angle effects are added if USE_RAD_DIST is nonzero. 

PHOTON_OUTPUT_FILE  STRING  NULL  output file for photons, if USE_RAD_DIST=1 

PHOTON_LOW_ENERGY_CUTOFF  eV  double  0.0  Lower limit of photon energy to output. 
REFERENCE_CORRECTION  short  0  If nonzero, reference trajectory is subtracted from particle trajectories to compensate for inaccuracy in integration. 

TRACKING_MATRIX  short  0  If nonzero, gives order of trackingbased matrix up to third order to be used for twiss parameters etc. If zero, 2ndorder analytical matrix is used. 

CSBEND continued
A canonical kick sector dipole magnet.
Parameter Name  Units  Type  Default  Description 
FSE_CORRECTION  short  0  If nonzero, FSE is adjusted to compensate for edge effects when EDGE1_EFFECTS or EDGE2_EFFECTS = 2 

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 provides a symplectic bending magnet with the exact Hamiltonian. For example, it retains all orders in the momentum offset and curvature. The field expansion is available to eighth order.
One pitfall of symplectic integration is the possibility of orbit and pathlength errors for the reference orbit if too few kicks are used. This may be an issue for rings. Hence, one must verify that a sufficient number of kicks are being used by looking at the trajectory closure and length of an onaxis particle by tracking. Using INTEGRATION_ORDER=4 is recommended to reduce the number of required kicks.
As of version 28.0 and later, the REFERENCE_CORRECTION feature is available to compensate for errors inherent in the numerical integration of the trajectories. In particular, depending on the number of kicks used, as well as the bending radius and angle, an onaxis particle may emerge from the element with a nonzero trajectory and a pathlength error. With REFERENCE_CORRECTION set to a nonzero value, these errors are subtracted from the coordinates of all particles. There are some pitfalls to using this feature: first, one may not realize that the number of kicks is too small to provide good results, since the output trajectory of the central particle will always be (nearly) identically zero. Second, in a magnet with a gradient or other field nonuniformities, a particle may emerge centered on the ideal trajectory yet still see the impact of the gradient, sextupole, etc. For these reasons, this feature should be used with caution and only when the residual trajectory is large enough to cause problems.
Higherorder field components
Normally, one specifies the higherorder components of the field with the Kn, with n = 1 through 8. The field expansion in the midplane is B_{y}(x) = B_{o} * (1 + ∑ _{n=1}^{8}x^{n}). By setting the USE_bN flag to a nonzero value, one may instead specify the bn parameters, which are defined by the expansion B_{y}(x) = B_{o} * (1 + ∑ _{n=1}^{8}x^{n}). This is convenient if one is varying the dipole radius but wants to work in terms of constant field quality.
Setting NONLINEAR=0 turns off all the terms above K_1 (or b_1) and also turns off effects due to curvature that would normally result in a gradient producing terms of higher order.
The EXPANSION_ORDER parameter controls the order of the expansion of the nonlinear fields, so that terms are limited to x^{i } y^{j } with i + j ≤EXPANSION_ORDER. By default, when EXPANSION\_ORDER=0, the expansion order is set automatically, as follows: If the highest nonzero multipole order (specified by Kn, Bn, Fn, or Gn) is n (with n = 1 being quadruople), then the expansion order is set to n + 3. However, the expansion order is never automatically set to less than 4, unless all the multipole terms are zero, in which case the expansion always yields a constant. Since the number of polynomial terms increases like the square of the expansion order, using many multipole terms can significantly increase run time. The maximum value for the expansion order is 10.
Edge angles and edge effects
Some confusion may exist about the edge angles, particularly the signs. For a sector magnet, we have of course E1=E2=0. For a symmetric rectangular magnet, E1=E2=ANGLE/2. If ANGLE is negative, then so are E1 and E2. To understand this, imagine a rectangular magnet with positive ANGLE. If the magnet is flipped over, then ANGLE becomes negative, as does the bending radius ρ. Hence, to keep the focal length of the edge 1∕f = tanE_{i}∕ρ constant, we must also change the sign of E_{i}.
Several models are available for edge (or fringe) effects. Which is used depends on the settings of the EDGE_ORDER, EDGE1_EFFECTS, and EDGE2_EFFECTS parameters EDGE1_EFFECTS controls entrance edge effects while EDGE2_EFFECTS controls exit edge effects, as follows:
Radiation effects
Incoherent synchrotron radiation, when requested with ISR=1, normally uses gaussian distributions for the excitation of the electrons. Setting USE_RAD_DIST=1 invokes a more sophisticated algorithm that uses correct statistics for the photon energy and number distributions. In addition, if USE_RAD_DIST=1 one may also set ADD_OPENING_ANGLE=1, which includes the photon angular distribution when computing the effect on the emitting electron.
Adding errors
When adding errors, care should be taken to choose the right parameters. The FSE and ETILT parameters are used for assigning errors to the strength and alignment relative to the ideal values given by ANGLE and TILT. One can also assign errors to ANGLE and TILT, but this has a different meaning: in this case, one is assigning errors to the survey itself. The reference beam path changes, so there is no orbit/trajectory error. The most common thing is to assign errors to FSE and ETILT. Note that when adding errors to FSE, the error is assumed to come from the power supply, which means that multipole strengths also change.
Splitting dipoles
When dipoles are long, it is common to want to split them into several pieces, to get a better look at the interior optics. When doing this, care must be exercised not to change the optics. elegant has some special features that are designed to reduce or manage potential problems. At issue is the need to turn off edge effects between the portions of the same dipole.
First, one can simply use the divide_elements command to set up the splitting. Using this command, elegant takes care of everything.
Second, one can use a series of dipoles with the same name. In this case, elegant automatically turns off interior edge effects. This is true when the dipole elements directly follow one another or are separated by a MARK element.
Third, one can use a series of dipoles with different names. In this case, one must also use the EDGE1_EFFECTS and EDGE2_EFFECTS parameters to turn off interior edge effects.
CSRCSBEND