AT vs elegant MA calculation

[androula.alekou]

Hello,

We are comparing the momentum aperture calculations between AT and elegant.

In elegant we use RF, with SREFFECTS,QEXCITATION=0 but still the obtained MA obtained is different than what we get with AT (black vs red line in attachment).

We think that elegant is calculating the MA around a closed orbit that has no radiation and no RF. When we remove the radiation and RF effect in
AT the plots agree (blue line in attachment).

Can we choose to calculate the MA around the closed orbit with radiation and RF in elegant?

Thank you
Andri

[michael_borland]

Andri,

If you include the &closed_orbit command in your .ele file before the &momentum_aperture command, then elegant will include the effect of the closed orbit.

Also, you may wish to use element-by-element synchrotron radiation, which you can do by setting SYNCH_RAD=1 and ISR=0 on the CSBEND, KQUAD, and KSEXT elements. It's also good to ensure that your rf cavities are in the right locations in the lattice. These two steps will give more accurate results than the common short-cut of using the SREFFECTS element for synchrotron radiation and putting a single RFCA right after it.

I'll be interested to see the comparison with AT when you've tried this.

--Michael