Quadrupole shifts beam phase?

[hendrik.haehnel]

Dear Didier,
we found some weird behaviour in TraceWIn. This arbitrary example only has a drift section, a triplet and two buncher gaps.

Somehow, the beam center phase is shifted in the Quadrupole. Is this just some numerical error for this edge case (not a realistic case)? Or is there some bug?

Code: Select all

DRIFT 15 50
DRIFT 25 50
QUAD 8 100 18
DRIFT 5 18
QUAD 10 -100 18
DRIFT 5 18
QUAD 8 100 18
DRIFT 5 15
DRIFT 5 15
GAP 400 -90 15
DRIFT 28 15
GAP 400 -90 15
DRIFT 5 15
END

Image of the envelope (phase shifted in Quadrupole)

envelope.png (18.51 KiB) Viewed 1193 times

Project file attached below.

Best regards,
Hendrik

[Didier]

Dear Hendry,

Considring your very low beam energy, the transverse dispersion becomes non-negligible. Try with a very small transverse emittance to see that the effect disappears.

phase.png (2.72 KiB) Viewed 1176 times

Regards,

Didier

[hendrik.haehnel]

Tank you, you are absolutely correct. I should have thought of that.

Best regards,
Hendrik