Elegant users forum

I did a tracking of a simple lattice ,but the normalized emittance changed.Is this a bug? Can you have a look

These are the files

It's not a bug, but rather a result of the fact that you plotted the uncorrected emittance and have dispersion in the system. The uncorrected emittance is defined as
ex = sqrt{ <x^2> <xp^2> - <x*xp>^2 }

If there is dispersion (e.g., following a dipole magnet), then this quantity can grow.

If you plot the corrected emittance (ecx or ecnx), you get a different picture. For the corrected emittance, we make the transformation
x -> x - delta*etax
xp -> xp - delta*etaxp
prior to computing the emittance.

As you can see in the attached plot, ecnx is nearly constant. It isn't exactly constant because of chromatic aberrations from the quadrupoles.

--Michael