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[[Technical_Board_Meeting_Jan_23,_2024 | Technical Board Meeting January 23, 2024 ]] <<   >> TBD

Online:  see email

=Agenda=
* GEM Rotator Design, GEM Rotator Stand procurement [https://virginia.box.com/s/m62x3634rdp4u0h8o9ynbn02lp8o15jw slides]  [Chandika Annaswatta]

=Minutes=
'''Summary:'''
* A recommendation is sought regarding the planned purchase of the GEM rotator support stands.  This includes stock 80/20 bars, front and side plates, associated stock and custom mounting plates, bolts, and alignment cartridges. 
** There was some uncertainty about whether the alignment cartridges should be inluded, only because it wasn't clear if they are in NSF or DOE scope.  This will be worked out separately and isn't the concern of the TB.  
* The board recommends that the procurement should proceed, after an assembly plan has been discussed among the experts in the Detector Mechanics meeting and deemed sufficiently detailed to assure that assembly is possible. 
**  Discussion also led to the conclusion that the chain-drive motor assembly might be best located on Beam Right, rather than Beam Left.  This isn't included in the TB recommendation, but it was understood that this would be considered before procurement of relevant parts. 
** There were a number of other important questions raised, about the mounting of the linear translation rails and GEM assemblies and about tolerances in the support stand.  The components in this procurement are thought to be independent of the answers to those questions. 


'''Discussion Notes:'''
* Bob Michaels: what limits the angular velocity and acceleration of the rotator wheel?  Chankida Annasiwatta: PLC controller for chain-drive motor.  Stepper motors used for linear translators.
* Ruben Fair: inquired about the intended use of the rotation.  Dave Armstrong: described the use to position GEMS during calibration tracking runs, with multiple positions needed to cover full acceptance.
* Mark Pitt: inquired about ferrous materials concerns with motor  DA: described the rather complete ferrous materials studies performed by Eric King in consultation with DA and CA. 
* Vladimir: inquired about installation of GEM frames.  DA: Described installation as a manual lifting and postion by technicians in a sky-lift, not using the overhead crane.  This was enough information at this stage for Vladimir's installation planning.
* Yury Kolomensky: inquired about tolerances.  DA: not critical as long as pieces mechanically can be assembled, except the alignment legs.  (Additional comments on this below).  Yury points out that the specific quote was from a low cost machining service with suspect quality, so using shops that will meet tolerance may cost more than estimate. 
* Dustin McNulty: Inquires about the Beam Left placement. This area will be crowded with cabling from HVMAPS etc. Ciprian Gal agrees that the motor will be more accessible if Beam Right. CA thinks this is just a mirror swap of the mounting assembly (a change, but easy to do) and no other changes required. It was understood that this would be considered and decided before that hardware is purchased. 
* CG also asks if a prototype of the GEM mounting frame will be purchased.  DA answers that there are plans, but it isn't part of this specific request. 
* RF asks about the resonant frequency threshold of 10 Hz.  The design frequency (10.5 Hz) isn't far above it.  
** CA points out that 20 Hz was original suggested, but was too difficult to achieve, and 10 Hz was ulimately decided as a minimum threshold.  
** Larry Bartoszek describes this threshold as based on experience. 
** This base modal frequency is distinct from the 0.1g acceleration used the seismic analysis. 
* Kent Paschke asks about the effect of cable runs, which add weight that is leveraged off of the rotator wheels. CA responds that the weight is low, and is shown to be a small effect in static analysis.  
** These were not included in modal analysis. 
* Larry Bartoszek: asks about getting all the bolts in place in the assembly plan. This follows an earlier discussion, and CA answers that the concerns raised earlier were addressed. 
* LB asks about GEM assembly being installed into the translation rail assembly.  He raises concerns about ease of installation and alignment necessary to avoid binding. Ideas about reconfigurating the planned installation steps were floated. This discussion was deferred to a Detector Mechanics meeting, as it did not seem to impact the planned procurement under discussion. 
* LB also discussed rotation wheels. Questions were asked about alignment of the wheels during assembly, along with some other details of the design. These questions will be discussed further in Detector Mechanics meetings, but it was established that they do not need to be resolved before the requsted procurement, as the major pieces of the support frame will be the same in any case. 
* Ryan Biraben: recommends that a detailed installation plan be developed to assure that there are no interferences with assembly steps.  This was discussed to some degree, and the decision made that such a plan should be discussed in the Detector Mechanics meeting before procurement. 
* DA noted that there was a plan for test assembly at W&M. The urgency of the procurement was to have pieces in hand when manpower is available to start test assembly.

=Attendance=

TB membership
* 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)
* Juliette Mammei  (Executive Board International Representative)
* Mark Jones  (Hall A Leader)
* David Armstrong (Elected Executive Board Member)
* Paul A Souder (Elected Executive Board Member)
* Robin Wines (Project Engineer)
* 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)
* Dustin McNulty  (Working Group Convener: Integrating Detectors)
* Nilanga Liyanage  (Working Group Convener: Tracking Detectors)
* Jim Napolitano (Working Group Convener: Polarimetry)
* Yury Kolomensky (Working Group Convener: Physics Extraction)
* Larry Bartoszek (presenter)
* Ryan Biraben (designer)
* Mike Dion (L2 CAM: Spectrometer)
* Silviu Covrig (Working Group Convener: Target)
* Caryn Palatchi  (Working Group Convener: Polarized Beam)
* Paul King  (Working Group Convener: DAQ) 
* Rakitha Beminiwattha (Working Group Convener: Simulations)

Additional Experts:
* Chandika Annasiwatta 
* Larry Bartoszek
* Ryan Biraben