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  1.  Configuration of beamlines
    • LDMX downstream of test beam? Or deflect one or the other? Geometry and magnet constraints on each.
    • Plan to engage Carsten at 4/13 meeting to understand the boundary conditions
  2. Stopper

    • Understand whether Alev's proposed S30XL stopper has large enough aperture to handle spread-out beam, power limitations, and tolerance to localized heating if quads over-focus the beam.  (Tor is following up with Alev)

  3. Define hand-off between different instrumentation sets for low-current tuning
    • ACMs for LESA line spec'ed to 10 nA (design on S30XL (ops?) budget, envisioned to proceed as electrical engineers roll off LCLS-II work)
    • Want a downstream diagnostic in ESA with sufficient resolution to verify bunch charge < 10^3 e at 40 MHz (clarify this)

    • Expect that LDMX can be used at and below this level of current to characterize beam size and current.  
      • First layer of ECAL is key
      • TS and tracker could be used too but provide only 1d information
      • Deeper ECAL layers should be powered down at these multiplicities, to avoid damage to silicon.
    • If new diagnostic is required, should start work this year.
    • Should define these transitions more carefully and seek review from LDMX ECal subsystem experts.  (Want to have a slide on this for "summer 2022" LDMX review)
  4. Modeling of beam and backgrounds (potentially good project for student interested in both accelerator and detector physics).  Includes:

    • Better understand initial beam shaping using spoiler and collimators in A-line

    • Model propagation downstream and generation of beam backgrounds between spoiler and LDMX

    • Backgrounds at the detector, and their impact on physics analysis (on their own and when overlayed with standard events) quads
    • Uniformity of spot size -- and its impact on multi-electron performance of trigger scintillator, veto performance, etc

    • What particles does LDMX receive when beam is on upstream stopper?  (Feeds into hardware design and understanding when DAQ and subsystems should be turned off)