Lumped simulation of synchrotron radiation effects (damping and quantum excitation) for rings.
Parallel capable? : yes
GPU capable? : no
Back-tracking capable? : no
x damping partition number
y damping partition number
momentum damping partition number
reference equilibrium x emittance
reference equilibrium y emittance
reference equilibrium fractional momentum spread
reference fractional momentum change per turn due to SR (negative value)
reference momentum (to which other reference values pertain)
fraction of implied SR effect to simulate with each instance
include damping, less rf effects?
include quantum excitation?
include average losses?
cutoff (in sigmas) for gaussian random numbers
include orbit offsets in tracking (see below)?
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
This element is intended for storage ring modeling only and provides a fast alternative to element-by-element modeling of synchrotron radiation. It should be used with care because the results will not necessarily be self-consistent. This is particularly an issue when there is dispersion at the location of the SREFFECTS element.
There are several types of storage ring simulation in which one may want to use this element:
The major parameters (JX, JY, EXREF, SDELTAREF, DDELTAREF, and PREF) can be supplied explicitly by the user, or filled in by elegant if the twiss_output command is given with radiation_integrals=1.
In explicit initialization, the user supplies the quantities EXREF, EYREF, SDELTAREF, DDELTAREF, and PREF. These are, respectively, the reference values for the x-plane emittance, y-plane emittance, fractional momentum spread, energy loss per turn, and momentum. The first four values pertain to the reference momentum. JX, JY, and JDELTA may also be given, although the defaults work for typical lattices.
In automatic initialization, the user turns on the radiation integral feature in twiss_output, causing elegant to automatically compute the above quantities. This will occur only if PREF=0. The COUPLING parameter can be used to change the partitioning of quantum excitation between the horizontal and vertical planes. Because the radiation integrals computation in twiss_output pertains to the horizontal plane only, the user must supply either EYREF or COUPLING if non-zero vertical emittance is desired.
The user may elect to turn off some aspects of the synchrotron radiation model. These should be changed from the default values with care!
There are a number of caveats that must be observed when using this element.
This issue can be resolved by placing the SREFFECTS element next to the rf cavity and setting INCLUDE_OFFSETS=0. Since the average momentum change is zero from the two elements, no additional betatron motion will be generated. Optionally, one can also use many SREFFECTS elements at equivalent locations in the lattice, which will decrease the magnitude of the effect.