Technical Board Meeting May 22, 2023

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Technical Board Meeting April 24, 2023 << >> Monday, June 12



  • Sieve collimator design and optics calibration docdb:1122 - Dave Armstrong


The final design of the hole pattern on the sieve collimator was presented by David Armstrong.

  • This is the same as was presented at recent a Simulation WG meeting and the Collaboration meeting. Slides in DocDB are linked above. In short summary:
    • the thickness of the sieve blocker has been demonstrated
    • it has been shown from the remoll simulation that the hole pattern is measurable at the GEM chamber location using the solid targets at the expected positions;
    • each hole is visible in at least one GEM rotation position;
    • a reconstruction matrix has been developed that provides sufficient precision across all sieve holes;
    • deviations of the magnetic field at the limit of specified tolerance for the coil positions are discoverable in optics calibration using this hole pattern;
    • the pattern will be given as (r,phi) or (x,y) coordinates. The tolerance on hole position is not extremely high, but the locations must be well measured.

A number of points were raised in discussion.

  • The coordinate system must be carefully conveyed along with the dimensions. (Upstream vs downstream face, beam left vs beam right, to avoid a gross misunderstanding.)
  • The precision of mounting, reproducibility after insertion, and alignment procedures need consideration. It was pointed out that the MIT scope explicitly includes the alignment systems, and that the SRD describes the requirement for the sieve alignment. (These do not directly impact the sieve construction.)
  • Just to clarify the pathway for information: the final hole pattern will be transmitted by David through the spectrometer project (Juliette, Mike Dion, also KK and Kent). Dion as the contract Tech Rep will transmit this to MIT.
  • It was pointed out that past practice suggests that late changes to sieve holes are often requested. A "blank" sieve, held back to be built to a new hole pattern, would be prohibitively expensive in this case. It was also pointed out rotating this sieve by pi/7 would allow an entirely blank slate, if a late change were needed. (This would obviously create complications with mounting and water flow, so isn't clear if it is possible). The optics working group asserts that we do not need to plan for the late change, but are confident to move ahead with this design.

Summary: after reviewing this presentation and following the recent presentation at other collaboration meetings, the Technical Board expressed no reservations about moving ahead with purchase of the sieve collimator. This advice will be passed on to project management, after a brief hold to allow some post-meeting email exchanges and discussions to complete.



  • Kent Paschke, Chair (MOLLER Scientific Coordinator)
  • Mark Pitt (Deputy Spokesperson, MOLLER-NSF Project Coordinator)
  • Juliette Mammei (Executive Board International Representative)
  • Mark Jones (Hall A Leader)
  • David Armstrong (Elected Executive Board Member)
  • Robin Wines (Project Engineer)
  • Dave Meekins (L2 CAM: Target)
  • Mike Dion (L2 CAM: Spectrometer)
  • Carl Zorn (L2 CAM: Detectors)
  • Ciprian Gal (L2 CAM: Infrastructure)
  • Robert Michaels (L2 CAM: DAQ)
  • Vladimir Berdnikov (L2 CAM: Installation)
  • Dustin McNulty (Working Group Convener: Integrating Detectors)
  • Paul King (Working Group Convener: DAQ)
  • Nilanga Liyanage (Working Group Convener: Tracking Detectors)
  • Jim Napolitano (Working Group Convener: Polarimetry)
  • Yury Kolomensky (Working Group Convener: Physics Extraction)


  • Krishna Kumar (MOLLER Spokesperson)
  • Jim Fast (DOE Project Manager)
  • Jessie Butler (Deputy DOE Project Manager)
  • Michael Gericke (MOLLER-CFI Project Coordinator)
  • Paul A Souder (Elected Executive Board Member)
  • Silviu Covrig (Working Group Convener: Target)
  • Caryn Palatchi (Working Group Convener: Polarized Beam)
  • Rakitha Beminiwattha (Working Group Convener: Simulations)