Technical Board Meeting April 24, 2023

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Technical Board Meeting April 10, 2023 << >> Technical Board Meeting May 22, 2023



  • Nilanga Liyanage - GEM Prototypes Docdb:1054
  • Mike Dion - Modification of SAM type to accommodate Bellows 7 Docdb:1052
  • Discussion of future agenda topics


  • Nilanga Liyanage discussed the GEM prototype chamber
    • Full size chamber prototype has been built and tested at UVa with cosmic ray and x-ray gun source
    • small changes to allow close fit with scintillator detectors, make gas and electrical connectors compatible with rotator frames, also fixing grounding error for readout card.
    • will also need a new readout card to avoid the first few channels of each chip, which become very noisy with long cables
    • Additional change to reduce number of gas inlet/outlets was tested with the prototype chamber
    • this chamber is now at JLab for further cosmic testing on SBS cosmic GEM stand
    • Discussion of radiation length, which totals to 0.91% R.L. This is thought to be a low technical risk - Nilanga has built thinner chambers, and chambers with larger surface area, and experience suggests these are safely robust. Simulations have shown this thickness does not significantly degrade tracking or measurement of the scattered flux distribution.
    • With the exclusion of the noisy channels, cable lengths of 30-40m will be possible while maintaining sufficient signal and noise control. 30m is expected to be needed. Patches are possible without degrading performance.
    • Based on these results, an order will be placed for all components under NSF support, which will get into the queue at CERN and with the company making the frames. A new readout card with the required channels removed will be delivered first from this order, and used to construct a second prototype. Assuming successful results from the 2nd prototype, the remaining readout cards will be manufactured. Other components will be manufactured without waiting for this last check.
    • It is expected that materials will be received within about 4 months of ordering, and it will take about 10 months after delivery to complete construction.
    • SBU will order components when allowed in CD2.
    • The Technical Board endorses this plan, and agrees the order should proceed.
      • The SBU order is expected to follow closely the components purchased by UVa. If the principals (Dave, Carl, Nilanga, and Klaus) feel that SBU has significant changes, they will return to discuss with the TB.
      • Results from the 2nd UVa prototype and from the first SBU prototype (when completed and tested) will be shared with the TB.
  • Bellow 7 (Mike Dion)
    • Mike reported that bellows 7, a hydroformed, inconel bellows, was received from Hyspan. The welds look excellent, and it passed vacuum test at the vendor and again on receipt at JLab.
    • This bellows is about 1.5" shorter than the design of 22".
    • Hyspan refers to a bellows specification definition EJMA which no one at JLab has or has access to. The bellows section (purchased from another vendor by Hyspan to be welded for completed component) should have been long enough, so it isn't clear how this ended up too short. One possibility would be inelastic deformation occurred during testing, but no specific information to suggest this.
    • The TB agreed the proposed design modification was appropriate, so this component can be accepted for use.
    • A short discussion of the constraining rods raised the concern that such rods might be a tight fit at Bellows 5, which has to fit below the charged particle acceptance but outside the detector pipe. Kent will follow up with Eric Sun to include any constraining rods in the simulation geometry.
  • We should expect a meeting on the next TB timeslot (Thursday, May 4 at 9am EDT) to discuss TB issues in advance of the May 5-6 Collaboration Meeting.


  • Kent Paschke, Chair (MOLLER Scientific Coordinator)
  • Krishna Kumar (MOLLER Spokesperson)
  • Mark Pitt (Deputy Spokesperson, MOLLER-NSF Project Coordinator)
  • Michael Gericke (MOLLER-CFI Project Coordinator)
  • Juliette Mammei (Executive Board International Representative)
  • David Armstrong (Elected Executive Board Member)
  • Mike Dion (L2 CAM: Spectrometer)
  • Carl Zorn (L2 CAM: Detectors)
  • Ciprian Gal (L2 CAM: Infrastructure)
  • Vladimir Berdnikov (L2 CAM: Installation)
  • Caryn Palatchi (Working Group Convener: Polarized Beam)
  • 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)


  • Jim Fast (DOE Project Manager)
  • Jessie Butler (Deputy DOE Project Manager)
  • Mark Jones (Hall A Leader)
  • Paul A Souder (Elected Executive Board Member)
  • Robin Wines (Project Engineer)
  • Dave Meekins (L2 CAM: Target)
  • Robert Michaels (L2 CAM: DAQ)
  • Silviu Covrig (Working Group Convener: Target)
  • Rakitha Beminiwattha (Working Group Convener: Simulations)