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Technical Board Meeting September 18, 2023 << >> Technical Board Meeting October 30, 2023

Online: see email

Agenda

• Scattering chamber exit window design and lead time [Dave Meekins] Slides
• Effect of Aluminum Scagttering chamber exit window on MOLLER backgrounds Ciprian docdb:1172
• Physics evaluation of Drift pipe end cap design change [Kent] docdb:1171

Minutes

Drift pipe end:

• Drift pipe end cap was "dish" shaped, about 1" thick, to avoid an excessively thick wall. This added cost and schedule concerns, which can be relieved with a flat, 3" thick flange.
• There is a 5" thick wall just upstream of this, at the end of the downstream torus vacuum enclosure.
• Simulations confirm this understanding: the additional thickness at the upstream end of the drift pipe do not add significantly to backgrounds.
• There might even be a very small benefit, but at this level the statistical significance of the simulation is not fully sufficient.

Scattering Chamber Exit Window:

Cip: Physics simulation

• added Al window at the scattering chamber exit
• found that 400micron roughly doubles the total Al contributions from the target windows. The additional contribution is consistent with linear scaling with thickness of the scattering chamber windown
• "deconvolution" results don't degrade, but this is based on assumptions of Al fractions and asymmetries being perfectly known
• In fact, Al corrections will be uncertain at the 10% level due to uncertainty in the Al asymmetry
• Qweak measured APV to 10% (Note in chat: SM coupling known better than this, so this would be a worst-case limit for knowledge of asymmetry.)
• DA: what about uncertainty in rate?
  • rates with gas-filled target are hard to get, since knowing the gas density was difficulty
  • KK: simulation is required, other studies will be possible
  • KK : Be window would be very valuable to have, even if installed later. So we should keep this development alive, even if we got with the Al window to start Run1.

Meekins:

• delivery is not going to be available from previous vendor.
• Materian (now purchased and absorbed into another company) will no longer provide flanges.
  • Al is easy, but Be is difficult
  • Be brazing is possible, (in conversation with WessDel) but this is also challenging to move forward due to inconsistent vendor response.
    • This would require the experiment is accept brazing alloy of zinc/Al
  • Be: better thermal conduction, better cyclic loading, low Z for backgrounds
• Aim to prepare to handle 20psi load if H2 cell failure. 15pse for atmosphere
• Dishing is required, allows for relief of mechanical stress under thermal load
• This design has 10 mils in vacuum window, 25 mils in 3" diameter for accepted scattered particles
• Old window, was about 1 calendar year replacement cycle at 10trips/hr
  • new design is probably much better, but not so clear yet. Now looking at 70k cycles compared to 45k in flat design.
• status: "Its done", this can be built in machine shop.
• May need to make several to meet thickness goals, with reasonably small variation. There are measurement tools to know what we have well.
• KK: Summary from the experiment side: we would prefer Be window to improve physics, but we are ok with this Al design even for full experiment.

Attendance

Present: Kent Paschke, Chair (MOLLER Scientific Coordinator) Krishna Kumar (MOLLER Spokesperson) Mark Pitt (Deputy Spokesperson, MOLLER-NSF Project Coordinator) Ruben Fair (DOE Project Manager) Klaus Dehmelt (Deputy DOE Project Manager) Michael Gericke (MOLLER-CFI Project Coordinator) Mark Jones (Hall A Leader) David Armstrong (Elected Executive Board Member) Dave Meekins (L2 CAM: Target) Carl Zorn (L2 CAM: Detectors) Ciprian Gal (L2 CAM: Infrastructure) Robert Michaels (L2 CAM: DAQ) Vladimir Berdnikov (L2 CAM: Installation) Silviu Covrig (Working Group Convener: Target) Dustin McNulty (Working Group Convener: Integrating Detectors) Paul King (Working Group Convener: DAQ) Jim Napolitano (Working Group Convener: Polarimetry) Eric Sun (joined for technical assistance)

Not attending: Juliette Mammei (Executive Board International Representative)

Paul A Souder (Elected Executive Board Member)
Robin Wines (Project Engineer)

Mike Dion (L2 CAM: Spectrometer) Caryn Palatchi (Working Group Convener: Polarized Beam) Nilanga Liyanage (Working Group Convener: Tracking Detectors) Rakitha Beminiwattha (Working Group Convener: Simulations) Yury Kolomensky (Working Group Convener: Physics Extraction)