10.50 LRWAKE—Long-range (inter-bunch and inter-turn) longitudinal and transverse wake

Long-range (inter-bunch and inter-turn) longitudinal and transverse wake
Parallel capable? : yes
GPU capable? : no
Back-tracking capable? : no






Parameter Name UnitsType Default

Description






INPUTFILE STRINGNULL

name of file giving Green function






TCOLUMN STRINGNULL

column in INPUTFILE containing time data






WXCOLUMN STRINGNULL

column in INPUTFILE containing horizontal dipole Green function






WYCOLUMN STRINGNULL

column in INPUTFILE containing vertical dipole Green function






WZCOLUMN STRINGNULL

column in INPUTFILE containing longitudinal Green function






QXCOLUMN STRINGNULL

column in INPUTFILE containing horizontal quadrupole Green function






QYCOLUMN STRINGNULL

column in INPUTFILE containing vertical quadrupole Green function






FACTOR double 1

factor by which to multiply wakes






XFACTOR double 1

factor by which to multiply longitudinal wake






YFACTOR double 1

factor by which to multiply horizontal dipole wake






ZFACTOR double 1

factor by which to multiply vertical dipole wake






QXFACTOR double 1

factor by which to multiply horizontal quadrupole wake






QYFACTOR double 1

factor by which to multiply vertical quadrupole wake






TURNS_TO_KEEP long 128

number of turns of data to retain






RAMP_PASSES long 0

Number of passes over which to linearly ramp up the wake to full strength.






LRWAKE continued

Long-range (inter-bunch and inter-turn) longitudinal and transverse wake






Parameter NameUnitsType Default

Description






GROUP stringNULL

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 provides serial and parallel modeling of long range, multi-bunch, multi-pass, non-resonant wakes. Resonant wakes can be modeled using the *RFMODE elements, while short-range wakes are modeled with WAKE, TRWAKE, ZLONGIT, ZTRANSVERSE, and RFCW.

For the LRWAKE element, the beam is assumed to be bunched and wakes are computed bunch-to-bunch. The long-range wake is assumed to be constant within any single bunch.

To use this element, the beam has to be prepared in a special way so that elegant can recognize which particles belong to which bunches. See Section 6 for details. Given a properly prepared beam, the algorithm works as follows.

To use LRWAKE, the user provides the wakes (functions of t) in an SDDS file. These wakes may extend over an arbitrary number of turns, with the user declaring how many turns to actually use as part of the element definition. However, they should be zero within the region occupied by a single bunch, to avoid double-counting with the true short-range wake. (Note that the above sums include the self-wake.) Similarly, the short-range should be zero for times comparable to the bunch spacing.

Note that the quadrupole wakes are in some cases related to the dipole wakes by constant numerical factors [48]. In such a case, one may name the same column for QXCOLUMN (QYCOLUMN) and WXCOLUMN (WYCOLUMN) and then specify QXFACTOR (QYFACTOR) appropriately.

LSCDRIFT