A canonically-integrated straight dipole magnet, assumed to have multipoles defined in Cartesian
coordinates.
Parallel capable? : yes
GPU capable? : no
Back-tracking capable? : yes
Parameter Name | Units | Type | Default | Description |
L | M | double | 0.0 | arc length (not chord 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 |
TILT | RAD | double | 0.0 | rotation about incoming longitudinal axis |
YAW | RAD | double | 0.0 | rotation about vertical axis through entrance point |
HGAP | M | double | 0.0 | half-gap between poles |
FINT1 | double | 0.0 | edge integral for entrance |
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FINT2 | double | 0.0 | edge integral for exit |
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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) |
FSE | double | 0.0 | fractional strength error |
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FSE_DIPOLE | double | 0.0 | fractional strength error of dipole component |
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FSE_QUADRUPOLE | double | 0.0 | fractional strength error of quadrupole component |
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ETILT | RAD | double | 0.0 | error rotation about incoming longitudinal axis |
N_KICKS | long | 4 | number of kicks |
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INTEGRATION_ORDER | short | 4 | integration order (2 or 4) |
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SYSTEMATIC_MULTIPOLES | STRING | NULL | input file for systematic multipoles |
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CCBEND continued
A canonically-integrated straight dipole magnet, assumed to have multipoles defined in Cartesian coordinates.
Parameter Name | Units | Type | Default | Description |
EDGE_MULTIPOLES | STRING | NULL | input file for systematic entrance/exit edge multipoles |
|
EDGE1_MULTIPOLES | STRING | NULL | input file for systematic entrance edge multipoles. Overrides EDGE_MULTIPOLES. |
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EDGE2_MULTIPOLES | STRING | NULL | input file for systematic exit edge multipoles. Overrides EDGE_MULTIPOLES. |
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RANDOM_MULTIPOLES | STRING | NULL | input file for random multipoles |
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SYSTEMATIC_MULTIPOLE_FACTOR | double | 1 | Factor by which to multiply systematic and edge multipoles |
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RANDOM_MULTIPOLE_FACTOR | double | 1 | Factor by which to multiply random multipoles |
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REFERENCE_ORDER | short | 0 | Reference order for multipole errors. Overridden by value in multipole files, if those are given. |
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MIN_NORMAL_ORDER | short | -1 | If nonnegative, minimum order of systematic and random normal multipoles to use from data files. |
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MIN_SKEW_ORDER | short | -1 | If nonnegative, minimum order of systematic and random skew multipoles to use from data files. |
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MAX_NORMAL_ORDER | short | -1 | If nonnegative, maximum order of systematic and random normal multipoles to use from data files. |
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MAX_SKEW_ORDER | short | -1 | If nonnegative, maximum order of systematic and random skew multipoles to use from data files. |
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SYNCH_RAD | short | 0 | include classical, single-particle synchrotron radiation? |
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CCBEND continued
A canonically-integrated straight dipole magnet, assumed to have multipoles defined in Cartesian coordinates.
Parameter Name | Units | Type | Default | Description |
ISR | short | 0 | include incoherent synchrotron radiation (quantum excitation)? |
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ISR1PART | short | 1 | Include ISR for single-particle beam only if ISR=1 and ISR1PART=1 |
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USE_RAD_DIST | short | 0 | If nonzero, overrides SYNCH_RAD and ISR, causing simulation of radiation from distributions, optionally including opening angle. |
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ADD_OPENING_ANGLE | short | 1 | If nonzero, radiation opening angle effects are added if USE_RAD_DIST is nonzero. |
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OPTIMIZE_FSE | short | 1 | Optimize strength (FSE) to obtain the ideal deflection angle. |
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OPTIMIZE_DX | short | 1 | Optimize x offset to obtain centered trajectory. |
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OPTIMIZE_FSE_ONCE | short | 0 | If nonzero, the FSE offset is optimized only once, even if relevant parameters are changed. |
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OPTIMIZE_DX_ONCE | short | 0 | If nonzero, the x offset is optimized only once, even if relevant parameters are changed. |
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COMPENSATE_KN | short | 0 | If nonzero, K1 and K2 strengths are adjusted to compensate for the changes in FSE needed to center the trajectory. |
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EDGE_ORDER | short | 3 | Gives order of edge effects. Does not affect edge multipoles. |
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DX_DY_SIGN | short | 1 | Prior to 2020.4, the sign of DX and DY was reversed for ANGLE<0. For backward compatibility, this is retained. Set this field to a positive value to use a consistent convention. |
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CCBEND continued
A canonically-integrated straight dipole magnet, assumed to have multipoles defined in Cartesian coordinates.
Parameter Name | Units | Type | Default | Description |
VERBOSE | short | 0 | If nonzero, print messages showing optimized FSE and x offset. |
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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 |
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This element provides a symplectic straight-pole, bending magnet with the exact Hamiltonian in Cartesian coordinates. The quadrupole, sextupole, and other multipole terms are defined in Cartesian coordinates. The magnet at present is restricted to having rectangular ends with symmetric entry and exit. This is quite different from CSBEND, where the edge angles are user-defined and where the field expansion is in curvilinear coordinates. Strictly speaking, CSBEND is only valid when the dipole is built with curved, beam-following poles.
Integration of particles in CCBEND is very similar to what’s done for KQUAD, KSEXT, and KOCT. The only real difference is that coordinate transformations are performed at the entrance and exit to orient the incoming central trajectory to the straight magnet axis. In addition, the fractional strength error is adjusted to ensure that the outgoing central trajectory is correct.
By default, two adjustments are made at start-up and whenever the length, angle, gradient, or sextupole term change:
One can block the re-optimization of these parameters by setting OPTIMIZE_FSE_ONCE and OPTIMIZE_DX_ONCE to 1. Note also that the optimization is performed with all error-defining parameters (DX, DY, DZ, FSE, and ETILT) set to zero.
Edge angles and edge effects
The edge angle treatment in CCBEND is relatively simple, consisting of a vertical focusing effect with momentum dependence to all orders. Also included are edge pseudo-sextupoles (due to the body K1 term) and pseudo-octupoles (due to the body K2 term). The user may also specify edge multipoles using the EDGE_MULTIPOLE parameter.
Multipole errors
Multipole errors are specified for the body and edge in the same fashion as for the KQUAD element. The reference is the dipole field by default, but this may be changed using the REFERENCE_ORDER parameter.
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
The CCBEND element does not support splitting. Important: Users should not attempt to split CCBEND elements by hand, since this will not result in the correct geometry entering and exiting the various parts.
Matrix generation
elegant will use tracking to determine the transport matrix for CCBEND elements, which is needed for computation of twiss parameters and other operations. This can require some time, so elegant will cache the matrices and re-use them for identical elements.
CENTER