Choose timezone
Your profile timezone:
FCC-ee tuning meeting
→
Europe/Zurich
FCC-ee tuning meeting
#############################################
Tessa, Emittance tuning with dipoles b2 and b3 errors.
b2 of +-4e-4 and b3 of 2e-4 errors added to ARC dipoles (IR dipoles are excluded here) and chromaticity shift is left uncorrected.
Without dipole errors all seeds converge while with dipole errores only 80 seeds out of 99 converged. Achieved emittance values are very similar with and without the dipole errors. The issue was the need of extra tuning time and the 19 seeds run out of CPU time. In summary dipole errors are not of concern for tuning to achieve emittances (DA and other parameters not checked) although it requires more tuning steps.
########################################
Esmaeil, Impact of dipole b3
b3 considered is -4e-4, larger than nominal value of -2e-4. Error is added to all dipoles, including IR dipoles.
MADX is slow: Is there a way to make parallel calculations?
The b3 errors casue 1st order chromaticity change of 20 units and about 10% change on second order chromaticity.
In ttbar lattice: sigmay=50nm, sigmax=2 um, so the on-momentum DA obtained is large.
Correcting chromaticity makes DA=0.
DA is computed with ELEGANT (issues with symplecticity probably as quads and sextupoles are thick) for 512 turns.
The definition of dipole in ELEGANT gives a different chromaticity than MADX, ~-10 units.
In next steps the discrepancy in chroma needs to be addressed. All arc sextupoles should be used to correct chroma. A symplectic tracking should be used in ELEGANT to avoid potential issues.
Simone requests that chromaticity sextupoles are labeled so everyone uses same families.
There are minutes attached to this event.
Show them.