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[[Technical_Board_Meeting_Mar_12,_2024 | Technical Board Meeting March 12, 2024 ]] <<   >> TBD

Online:  see email

=Agenda=
* Target Chamber Vacuum Isolation - differential pumping alternative [https://moller-docdb.physics.sunysb.edu/cgi-bin/DocDB/private/ShowDocument?docid=1287 slides]
* [https://moller.jlab.org/wiki/index.php/Technical_Board_Meeting_Oct_23,_2023 Previous Meeting] on target window design

=Minutes=
*Dave proposes a differential pumping approach to isolating the target vacuum. 
* The advantages would be:
** no need to service during the experiment.  The current estimate is that a window would need to be replaced every SAD. 
** reduced background for the experiment.  (The current window increases the aluminum background by a factor of about 50%. )
* Dave has estimated that the adapter spool piece connecting to the target chamber could hold two 13mm D apertures about 30cm apart, sufficient to separate the target 1e-6 Torr from 2 mTorr in spectrometer region.  This would require a 200 l/s pump on the adapter piece.
* In this case, with the vacuum spaces connected, Dave would need to be DA/SO for the entire pressure system, from the target to the dump window.
* The differential pumping solution would require a comprehensive review of components (sensors, etc) in the spectrometer region all the way to the dump window, to verify that there are no ignition sources. Such a review requires a list of components from the spectrometer design time, and about a week of Dave's time.
** Dave points out that the requirements for the window are reduced if the spectrometer is shown to be compatible with hydrogen service.  In particular, the frequency for changes could be reduced, improving ALARA performance.  For this reason, conducting the review is a valuable exercise even if the window design is used. 
** The final safety review of the target will also be informed by this review, regardless of the window design.  So this review is probably required in any case. 
* It will be possible to retrofit to a window from the differential pumping configuration, if needed (for example, if the spectrometer pressure is too high).


Next step:
* Mike will get a list of components throughout the pressure region to Dave.
* Dave will go through this list of evaluate suitability for hydrogen service.
* This review will be useful in any case, for future reviews or for potentially simplifying the Al window requirements.  
* The case for the differential pumping can be re-evaluated after this first step is done. 
* Other aspects to consider:
** the spectrometer SRD specifies a nominal vacuum of 10 mTorr, but  <0.1 Torr as an upper limit.   Presumably a larger pump would be required.
** Cip and Kent will check that the proposed dimensions and locations of the differential pump orifices are compatible with physics requirements.

=Attendance=

Invited to attend:
* Kent Paschke, Chair (MOLLER Scientific Coordinator)
* Mark Pitt (Deputy Spokesperson, MOLLER-NSF Project Coordinator)
* Ruben Fair (DOE Project Manager)
* Klaus Dehmelt (Deputy DOE Project Manager)
* Dave Meekins  (L2 CAM: Target)
* Mike Dion (L2 CAM: Spectrometer)
* Ciprian Gal  (L2 CAM: Infrastructure)
* Silviu Covrig (Working Group Convener: Target)

Unable to attend:
* Robin Wines (Project Engineer)
* Krishna Kumar (MOLLER Spokesperson)