Sextupole elements

[hsayed]

Hi Micheal,

I'm trying to understand how Elegant could be used to correct chromaticity for a ring.
I would like to know how the following Elegant elements would affect chromaticity of a ring, and how differently they would if they all do.

SEXT with zero length
KSEXT with zero length
MULT with zero length ( in the manual it is mentioned that it can not be used for chromaticity. I wonder why?)

SEXT with none-zero length
KSEXT with none-zero length
MULT with none-zero length ( in the manual it is mentioned that it can not be used for chromaticity. I wonder why?)

Thanks
Hisham

[michael_borland]

Hisham,

In order to affect the chromaticity, the SEXT or KSEXT element must have non-zero length. If you need a zero length element, set L=1e-12 or some other very small number. The K2 value is then K2L/L.

If you are planning to do tracking, you should use KSEXT, since SEXT is not symplectic.

MULT elements do not affect the chromaticity only because I haven't coded it. It is on my list of things to do.

--Michael

[hsayed]

Thanks Michael

How about KQUSE ? does the sextupole filed (K2) affect Elegant chromaticity calculations ?

[michael_borland]

Hisham,

Yes, the KQUSE element will affect chromaticity computations. Both the quadrupole and sextupole components contribute.

--Michael