Jan 24 2024

Action items from last time

• Gabriel will work w/ ME to confirm the R28 cathode insert hole size/shape, i.e. post the shop print,
• Gabriel/Max will decide on prototypical R30-4 parameters like that of the R28 cathode insert (hole, cone shape, lip shape) at CEBAF, then Gabriel will generate the corresponding CST model, and Alicia will include this in her comparison with (R28 & R30 @ z=19cm optics match-point),
• Gabriel will look at testing a cylindrically symmetric CST model against Max's POISSON model to confirm differences, intending to confirm that the differences are just 2-D vs. 3-D, nothing else,
• Alicia will continue to develop bands of acceptance parameters at Z=19cm, where parameters refers to the beam/optics parameters acceptable/typical for the CEBAF injector (implicitly meaning up to max current),
• Max and Alicia will continue to develop and experimental match-point for the purpose of comparison between measurement and model; as mentioned above a simulation match-point at Z=19cm has already been found in a drift free region after the gun,
• Max will provide some sets of optics optimized cathode parameters (hole=fixed, cone shape, lip shape) to Gabriel, so he may generate a detailed CST model to explore max E-field strengths at surfaces/triple-points,
• Max will take the lead to develop the table of parameters with uncertainties which will be used in the simulations (GPT/CST), these will be used to develop allowable tolerances in fabrication/assembly so we can with high likelihood end up within Alicia's acceptance bands,

Updates

• Alicia
• Max and Gabriel
  • Resolved discrepancy related to different definition of hole diameter: now we consistently use the dimensions from the T-cathode drawing
  • Correct cathode position for field map export/import relative to particle start coordinates is important; this changes with cathode recess
  • CST field maps tend to be unphysical close to cathode if export boundaries do not align with mesh cells, causing sensitivity to step size in exported file
• Carlos
  • The 25 deg Pierce cathode front end piece from the GTS spherical electrode gun (R30-1, Yan's thesis) was measured by SRF's Coordinate-Measurement Machine (CMM).
  • Findings:
    • Pierce angle design: 25 deg. Measured: 24.4 deg.
    • Cathode hole diameter to extrapolation of conical edge: Design: 0.432 inches = 10.97 mm. Measured: 0.467 in = 11.86 mm
    • Drawing and CMM findings can be found in the SharePoint folderhere

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