Filter exclude particles above xRMS

[Zhaoliangchao]

In the beam parameter page, one can choose using filter or not to abandon the halo particles.
My question is how does it work? If we set "exclude all particles above 4xRMS', what does it mean? How many particles are abandoned?

[Didier]

Dear Zhaoliangchao,

If you select 4xRMS, the emittance is calculated including all particles, then all particles above 4xRMS are excluded, then the RMS emittance is calculated again taking these exclusions into account. Then all the particles above 4xRMS are excluded again and the RMS emittance is calculated again, and so on. It's an iterative process that generally takes 3 or 4 passes to converge, but it's very effective for really freezing a emittance value, particularly for beams with a lot of halo.

Usual method for analysing emittance measurements.

Regards,

Didier

[Zhaoliangchao]

Can we know the final number of particles excluded or included? Like 'select visible particles ', the particle number is shown below the figure.

[Didier]

Dear Zhao,

I added in particle distribution plot the possibilité to select particle outside elipse calculated with filtered methode and also then number of selected particle is now print at the bottom of the windows (see bellow)

plot.png (151.33 KiB) Viewed 1506 times

Regards,

Didier