FODO Cell Example

[EZoni]

Based on discussions with @jlvay and @cemitch99, we would like to compare three different variations of a YAML file defining a FODO cell example and discuss with the community which one(s) may be preferred, as far as PALS is concerned. For the choice of parameters, we used the ImpactX example described here.

1. Option consistent with PALS, as is:

   Lattice:
     - Branch: fodo
   BeamLine:
     name: fodo
     line:
       - item:
           Element:
             name: drift1
             kind: Drift
             length: 0.25
       - item:
           Element:
             name: quad1
             kind: Quadrupole  
             length: 1.0
             MagneticMultipoleP:
               Kn1: 1.0
       - item:
           Element:
             name: drift2
             kind: Drift  
             length: 0.5
       - item:
           Element:
             name: quad2 
             kind: Quadrupole
             length: 1.0
             MagneticMultipoleP:
               Kn1: -1.0
       - item:
           Element:
             name: drift3
             kind: Drift
             length: 0.5 

2. Option without item and Element, using element's name as identifier:

   Lattice:
     - Branch: fodo
   BeamLine:
     name: fodo
     line:
       - Drift1:
           kind: Drift
           length: 0.25
       - Quad1:
           kind: Quadrupole  
           length: 1.0
           MagneticMultipoleP:
             Kn1: 1.0
       - Drift2:
           kind: Drift  
           length: 0.5
       - Quad2:
           kind: Quadrupole
           length: 1.0
           MagneticMultipoleP:
             Kn1: -1.0
       - Drift3:
           kind: Drift
           length: 0.5 

3. Option without item and Element, using element's kind as identifier:

   Lattice:
     - Branch: fodo
   BeamLine:
     name: fodo
     line:
       - Drift:
           name: drift1
           length: 0.25
       - Quadrupole:
           name: quad1
           length: 1.0
           MagneticMultipoleP:
             Kn1: 1.0
       - Drift:
           name: drift2
           length: 0.5
       - Quadrupole:
           name: quad2
           length: 1.0
           MagneticMultipoleP:
             Kn1: -1.0
       - Drift:
           name: drift3
           length: 0.5 

[DavidSagan]

@EZoni The problem is what is displayed does not show how things will work with more complex constructions. Can you modify this to show how these options will work with elements defined outside the BeamLine as well as with element inheritance, repetition, and sublines? Thanks.

[jlvay]

@DavidSagan . Here is an attempt with inheritance and repetition using Option 2:

Lattice:
  - Branch: fodo
BeamLine:
  name: fodo
  line:
    - Drift1:
        kind: Drift
        length: 0.25
    - ap1:
        kind: Aperture
        ApertureP:
           x_limit: [-0.03, 0.04]
    - Quad1:
        kind: Quadrupole  
        length: 1.0
        MagneticMultipoleP:
          Kn1: 1.0
    - Drift2:
        kind: Drift  
        length: 0.5
    - ap2:
        kind: Aperture
        inherit: ap1
        ApertureP:
           y_limit: [-0.02, 0.05]
    - Quad2:
        kind: Quadrupole
        length: 1.0
        MagneticMultipoleP:
          Kn1: -1.0
    - Drift3:
        kind: Drift
        length: 0.5 
Beamline:
  name: full_line
  line:
    - fodo:
        repetition: 3

[DavidSagan]

Another option would be to just get rid if item:

Element:
   name: quad1
     kind: Quadrupole  
     length: 1.0
     MagneticMultipoleP:
       Kn1: 1.0

Lattice:
  - Branch: fodo

BeamLine:
  name: fodo
  line:
    - Element:
          name: drift1
          kind: Drift
          length: 0.25
    - Element:
         - Inherit: quad1
         - name: quad1_A
         - length: 2.0
    - Element:
          repetition: 2
          direction: -1
          name: drift2
          kind: Drift  
          length: 0.5
    - Element:
          name: quad2 
          kind: Quadrupole
          length: 1.0
          MagneticMultipoleP:
            Kn1: -1.0

Beamline:
  name: full_line
  line:
    - BeamLine:
        name: fodo
        repetition: 3
    - Element:
          name: drift3
          kind: Drift
          length: 0.5 

[DavidSagan]

Also I suspect that lattices will generally use element definitions separate from the beam lines. So to rewrite your first example:

Element:
   name: drift1
   kind: Drift
   length: 0.25

Element:
   name: quad1
   kind: Quadrupole  
   length: 1.0
   MagneticMultipoleP:
       Kn1: 1.0

Lattice:
  - Branch: fodo
  - 
BeamLine:
  name: fodo
  line:
    - item: drift1
    - item: quad1
    - item: drift2
    - item: quad2

[jlvay]

For your last two examples, I would propose:

Element:
  name: Q1
  ...

BeamLine:
  line:
    - Q1:
         repetition: 3
         direction: -1
         placement:
            offset: 37.5
            base_item: thingA
            from_point: EXIT_END

and

Element:
   name: drift1
   kind: Drift
   length: 0.25

Element:
   name: quad1
   kind: Quadrupole  
   length: 1.0
   MagneticMultipoleP:
       Kn1: 1.0

Lattice:
  - Branch: fodo

BeamLine:
  name: fodo
  line:
    - drift1
    - quad1
    - drift2
    - quad2

[jlvay]

Option 4:

Lattice:
  - Branch: branch_name
      beamline: fodo

BeamLine: fodo
  line:
    - Drift: drift1
        length: 0.25
    - Quadrupole: quad1
        length: 1.0
        MagneticMultipoleP:
          Kn1: 1.0
    - Drift: drift2
        length: 0.5
    - Quadrupole: quad2
        length: 1.0
        MagneticMultipoleP:
          Kn1: -1.0
    - Drift: drift3
        length: 0.5 

[jlvay]

Drift: drift1
   length: 0.25

Quadrupole: quad1
   length: 1.0
   MagneticMultipoleP:
       Kn1: 1.0

Lattice:
  - Branch: branch_name
      beamline: fodo

BeamLine: fodo
  line:
    - drift1
    - quad1
    - drift2
    - quad2

[jlvay]

@campa-consortium/pals-contributors

Here is a more complex example:

Quadrupole: thingA
  length: 1.0
  MagneticMultipoleP:
    Kn1: -1.0

Quadrupole: thingB
  length: 1.0
  MagneticMultipoleP:
    Kn1: 1.0

Marker: thingC

BeamLine: subline1
  zero_point: thingC
  line:
    - thingA
    - thingB
    - thingC      

BeamLine: inj_line
  multipass: True
  length: 37.8
  line:
    - thingA
    - thingB  
        placement:
          offset: 0.1
          to_point: ENTRANCE_END
          base_item: thingA
          from_point: EXIT_END
    - Drift: drift1      # This item contains an is reversed.
        direction: -1
        length: 1.
        repetition: 3    # This iterated three times
    - subline1     
        placement:
          offset: 0.1
          to_point: ZERO_POINT
          base_item: drift1
          from_point: EXIT_END

This more complex example shows that the new syntax is viable (did not encounter any showstopper). Hence, the team will go forward and implement it unless there is any serious concern. Please let us know ASAP of any concern or objection.