Output from frequency_map doesn't agree with tracking

[Teresia]

Hi,

I am trying to construct an ILMatrix using the output from frequency_map to get the tune and and amplitude-dependent tune shifts from tracking, but the output I get doesn't agree with what I expect or what I get by doing a FFT on the output from track.

To test I tried running frequency_map for one step using only a small amplitude in both x and y. I expected to get tunes close to what I get from track and a path length close to the circumference of the machine. This is the output:

x y nux nuy s
m m m/pass
---------------------------------------------------------------------------
1.000000e-12 1.000000e-12 1.896258e-01 2.776528e-01 5.611217e+02

However, running track gives me the s/pass 561.571 m (which agrees with the circumference) and the tunes 0.1916 and 0.2804.

Is frequency_map doing something different than track that might explain this? I thought the frequency map was just running tracking for particles with different initial amplitudes, but perhaps the code is doing something more complex than this?

Best regards,

Teresia

[michael_borland]

Teresia,

The most common cause of this would be using too few kicks on the CSBEND and KQUAD elements. This can cause tune errors, but also path-length errors (due to CSBEND). Try increasing the N_KICKS parameters.

--Michael