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Next: CSRCSBEND Up: Element Dictionary Previous: CLEAN

CSBEND

A canonical kick sector dipole magnet.
Parallel 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
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   double 0.0 error rotation about incoming longitudinal axis
N_KICKS   long 4 number of kicks
NONLINEAR   long 1 include nonlinear field components?
SYNCH_RAD   long 0 include classical synchrotron radiation?
EDGE1_EFFECTS   long 1 include entrace edge effects?
EDGE2_EFFECTS   long 1 include exit edge effects?
EDGE_ORDER   long 1 order to which to include edge effects
INTEGRATION_ORDER   long 2 integration order (2 or 4)
EDGE1_KICK_LIMIT   double -1 maximum kick entrance edge can deliver

A canonical kick sector dipole magnet.
Parameter Name Units Type Default Description
EDGE2_KICK_LIMIT   double -1 maximum kick exit edge can deliver
KICK_LIMIT_SCALING   long 0 scale maximum edge kick with FSE?
USE_BN   long 0 use b$<$n$>$ instead of K$<$n$>$?
B1 $1/M$ double 0.0 K1 = b1*rho, where rho is bend radius
B2 $1/M^{2}$ double 0.0 K2 = b2*rho
B3 $1/M^{3}$ double 0.0 K3 = b3*rho
B4 $1/M^{4}$ double 0.0 K4 = b4*rho
ISR   long 0 include incoherent synchrotron radiation (scattering)?
SQRT_ORDER   long 0 Order of expansion of square-root in Hamiltonian. 0 means no expansion.
USE_RAD_DIST   long 0 If nonzero, overrides SYNCH_RAD and ISR, causing simulation of radiation from distributions, optionally including opening angle.
ADD_OPENING_ANGLE   long 1 If nonzero, radiation opening angle effects are add if USE_RAD_DIST is nonzero.





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 fourth order.

One pitfall of symplectic integration is the possibility of orbit and path-length 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 on-axis particle by tracking. Using INTEGRATION_ORDER=4 is recommended to reduce the number of required kicks.

Normally, one specifies the higher-order components of the field with the K1, K2, K3, and K4 parameters. The field expansion in the midplane is $B_y(x) = B_o * (1 + \sum_{n=1}^4\frac{K_n\rho_o}{n!}x^n)$. By setting the USE_bN flag to a nonzero value, one may instead specify the b1 through b4 parameters, which are defined by the expansion $B_y(x) = B_o * (1 + \sum_{n=1}^4\frac{b_n}{n!}x^n)$. 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.

Edge effects are included using a first- or second-order matrix. The order is controlled using the EDGE_ORDER parameter, which has a default value of 1. N.B.: if you choose the second-order matrix, it is not symplectic.

Note about split dipoles: elegant can internally split dipoles into several pieces, which the user can control using the element_divisions parameter of the run_setup namelist, or using the divide_elements command. In splitting dipoles, elegant simply substitutes a series of dipoles with the length and angle divided by the appropriate factor. ``Interior'' edge effects (i.e., between split pieces) are automatically turned off.

The user may also split dipoles into pieces in the lattice definition. E.g., suppose one wanted to split the following dipole: 

B1: SBEN,L=0.5,ANGLE=0.5,E1=0.5,E2=0.5
One could do this easily using 
B1PART: SBEN,L=0.1,ANGLE=0.1,E1=0.5,E2=0.5
B1: line=(5*B1PART)
The edge effects are turned off for the edges between successive B1PART elements. This is done only for successive dipoles with the same name and when there are no intervening elements.

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.

next up previous
Next: CSRCSBEND Up: Element Dictionary Previous: CLEAN
Robert Soliday 2007-04-02