Extent Beam Relevant Reduced Diagnostics

[ax3l]

We need more relevant quantities of accelerator physics in our BeamRelevant reduced diagnostics.

This is important, because we want to talk to accelerator physicists for laser-plasma accelerators and sources. We should for instance add everything we can express with respect to a reference trajectory (straight):

• Divergence
• Beta function (with user-defined s vector - default z)
• Phase advance (with user-defined velocity - default c)
• Twiss parameters
• … we need to check what a good reference element/setup would be with respect to lattice-related parameters.

[ax3l]

@dpgrote @cemitch99 @qianglbl anything missing in the list? :)

[cemitch99]

A few more:

• Beam size in each variable (x,px,y,py,t,pt)
• Centroid offset (from reference particle) in each variable
• Emittance in each dimension (x-px), (y-py), (t-pt)
• Slice diagnostics, such as longitudinal current profile I vs. t

[n01r]

Some of these were implemented in

• #3372 (transverse beta-function)
• #3993 (transverse Twiss alpha)

An additional request is to have these values for only fractions of the beam with respect to beam size. E.g., 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 100%. This would all us to characterize if we have beam halos with much worse quality than the core of the beam.