Amplitude dependent tune shift

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Amplitude dependent tune shift

Post by Galnander » 18 Nov 2021, 10:59

Dear Michael,

I have a question regarding the calculation of the amplitude dependent tune shift parameters, dnux_dJx, dnux_dJy , dnuy_dJy which are displayed in the twiss output file. We are using these to evaluate the influence from different elements on the non-linear dynamics of the resonant extraction in SIS100 at FAIR/GSI.

Today the calculation of these parameters includes (K)OCT, if leading order only is requested, and (K)SEXT as well as the sextupole component from bending magnets, if higher order computation is requested.

For us it would be useful if the leading order calculation would also include the effects of all other possible octupole components, e.g. from MULT and FMULT elements, as well as the multipole components of the KQUAD elements. In addition, the cubic terms from quadrupole fringe fields are also known to create amplitude dependent tune shift in first orderl, so it would be great if those could be included as well.

Do you see any possibility to extend the calculations of the amplitude dependent tune shift parameters in this way?

Best regards,
Björn Galnander

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