New Matlab function atsimplering

[lfarv]

The new function atsimplering creates a simple lattice according to a set of ring properties. A "simple ring" consists of:

• A RF cavity
• a 6x6 linear transfer map
• a detuning and chromaticity element
• a simplified quantum diffusion element which provides the equilibrium emittance, radiation damping and energy loss

It is defined by:

• the nominal energy [eV],
• the ring circumference [m],
• the harmonic number,
• the horizontal tune,
• the vertical tune,
• the RF voltage [V],
• the momentum compaction factor.

plus optional parameters:

• either vertical and horizontal alpha, beta, emittance, or sigma matrix,
• horizontal, vertical and longitudinal damping times,
• energy loss per turn,
• particle,
• lattice name.

It is similar to the python simplering introduced in #643

[simoneliuzzo]

Dear @lfarv @lcarver and @swhite2401 ,

what is the difference with atfastring? The imputs are parameters rather than an AT lattice?

I will try to test it

thank you,

best regards
Simone

[lcarver]

The idea is to be able to generate a ring with only a table of parameters. No initial lattice needed.

[simoneliuzzo]

Dear @lcarver @lfarv and @swhite2401,

if the output is ought to be the same, why having two functions rather than simply adding inputs to atfastring?

For example:
if you give a lattice it will use the lattice. (atfastring)
if you give the parameters it will use the parameters. (atsimplering)
if you give a partial amount of parameters it will use the lattice to get the defaults for the others. (atfastsimplering)

best regards
Simone

[simoneliuzzo]

Dear @lfarv @lcarver and @swhite2401,

do you have a test function checking that the output elements are strictly the same for atfastring(ring) and atsimplering(parameters_of_ring) ?

[lfarv]

if the output is ought to be the same, why having two functions rather than simply adding inputs to atfastring?

@simoneliuzzo
What you propose could be done, though I have doubts on the interest of the "mixed" input. But I'm not pushing for that because:

• generally speaking, I prefer having different functions for different tasks, rather than trying to mix things with ambiguous inputs. Parsing the different possible ways of giving the simplering parameters is already tricky,
• here, the purpose of the two functions is really different: modelling an existing lattice for fastring, creating a new lattice from scratch for simplering,
• if you look in detail, you'll see that the generated lattices are somewhat different: in fastring the damping is included in the linear 6x6 matrix, in simplering it's in the quantdiff element, the quantum diffusion is also treated differently. It's not the ideal solution, it could be possible for fastring to generate the same elements than simplering but not the other way round. So unifying the output needs a modification of fastring. Possible, but it's another topic.

The test you propose is a good idea. But the comparison is not easy because the generated lattice are different, though they should behave the same…

[lcarver]

Looks good to me. Thanks a lot

[lfarv]

@lcarver : I had to solve a conflict with the updated master. Could you approve again? Thanks

@simoneliuzzo : any more comments on this function?

[lfarv]

After solving a conflict with the master branch (Matlab version number), I need another review.
Can @lcarver or @simoneliuzzo approve again?