Technical Board Meeting Nov 07, 2024
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Technical Board Meeting Sept 4, 2024 << >> Technical Board Meeting Dec 5, 2024
Online: see email
Agenda
Minutes
- KK reminded folks about the overall context: The Al background correction is less than 1% for a total of 250 microns (2 end windows) of Al traversed by the primary beam. The actual Al rate is significantly smaller but the asymmetry is larger for Al. The systematic error on the correction is 10% of itself. So, a 1% is correction is fine. The vacuum separation window could double or triple this correction and at that point the systematic error becomes more important. From the physics point of view, it would be beneficial to avoid having the additional vacuum separation window thickness for the primary beam.
- Dave Meekins went over his slides on the differential pumping concept. They are posted. The idea is to have two 10 to 13 mm diameter holes with a pumping port in between. Even in the worst case situation of the spectrometer vacuum (high end of the requirement), the 10 mm diameter hole is comfortable to maintain the pressure difference required
- Cip and KK followed up with Kent’s slides going over how things would improve and show that the clipping due to multiple scattering and raster is quite a negligible systematic provided the center of the hole is within 1 mm of the beam trajectory for both holes.
- Some discussion ensued about alignment. It was pointed out that the scattering chamber exit flange will be aligned to within 1 mm. The welding specs for constructing the spool piece and aligning the 500 micron foils with the 10-13 mm hole was discussed. It was concluded that centering the holes to within 100-200 microns relative to each other should be possible. This request was explicitly made to be part of the fabrication process. In any case, the manufactured piece would be surveyed so we would know exactly how well lined up the two holes are with respect to the flanges.
- It was communicated that 13 mm would be preferable but if the engineering requirements call for 10 mm, we will live with it. The larger hole will depend on how good the vacuum on the spectrometer side will be. It was pointed out that with a larger hole the alignment requirements can be relaxed.
- The spectrometer team will meet with Dave Meekins to have a more in-depth technical discussion and tie off any loose ends.
- Dave Meekins will communicate the scattering chamber pump specifications so the spectrometer pumps can adhere to similar specs
- The TB formally endorsed pursuing the differential pumping solution to replace the vacuum separation window after concluding that the physics outcome improves and no significant physics downside was identified
Attendence
Ruben, Paul S, KK, David A, Jim N, Paul K, Meekins, Mark, Yury, Vlad, Dion, Kashy, Cip
