problem with CSBEND

[ccwang]

Hi,

Recently, I met a problem with CSBEND. When I set the bending angle "ANGLE=0.0", it seems elegant can't calculate the betatron tune. Does anyone have comment on this? Thanks.

Chinchi

[michael_borland]

Chinchi,

Perhaps your lattice is unstable without the focusing from the bending magnet. I tried an example with a four-dipole chicane and was able to vary the angle from a nonzero value to zero without a problem, but this will be lattice-specific. My example files are attached.

--Michael

[ccwang]

Dear Michael,

Thanks a lot! Actually, I am using CSBEND as a combined quadrupole and sextuple.

QF1: CSBEND, L=0.15, ANGLE=0.0, K1=1.126772404841, &
K2=2.575468751638, FINT=0.0

Is it possible due to including quadrupole and sextupole components?

Best wishes,
Chinchi

[ccwang]

Hi,

I have one more question. When I set FINT=0.0 for my CSBEND, the parameters in the twiss file is not change. It seems strange. Is there any related parameters I should deal with also?

Thanks again.

Chinchi

[michael_borland]

Chinchi,

Actually, having K1 or K2 non-zero will cause a problem when the ANGLE is set to zero. If ANGLE=0, elegant treats the element like a drift space. This is a bug that I'll try to fix in the next release. Meanwhile, you can use the KQUSE element (combined quad/sext) or set angle to a very small, non-zero value.

FINT won't have any effect unless you set HGAP to a non-zero value.

--Michael