View source for Special Meeting LV Cable Strategy Summary 9/22/21

PARTICIPANTS: Bogdan, Carlos, Emmanuel, Thi, Vladimir, Tanja


'''PRACTICAL IMPLEMENTATION CABLING'''

* Discussion of advantages/disadvantages of two options

::* [https://wiki.jlab.org/cuawiki/images/2/2a/NPS_PMt_PCB.pdf Slides]

* Found suitable connector with 6 pins for option with connector at back
::* HV
::* Ground
::* Signal

* Problem: Flat cables interfere with HV cables --> shift connectors

* Horizontal back chaining with shifted connectors
::* less work than connector on side, but more risky during assembly/disassembly
::* Three issues - most problematic: interference with HV cables

* Discussion about if one can cut connector
::* need only three pins
::* can cut, but not likely to resolve interference with HV cables

* Alternative: connector on the side
::* less risky
::* requires more work - have to make additional cables etc.
::* requires fabrication of 1000 flat cables and ~30 other cables - time estimate: ~3 weeks
::* PCB design time estimate: ~3 months (expect ready early 2022)

* Decision: go with connector on side as less risky and should have enough time to complete the work in parallel with PCBs

* '''Action item''':
::* write to DSG and ask if available to take on cable fabrication task
::* provide information on connector and placement to Fernando

* Discussion: additional grounding PMT shield
::* '''action item''': investigate how this may be realized


'''DISCUSSION ON LV POWER DISTRIBUTION - FROM 9/18 EMAIL DISCUSSION''' 

* [https://wiki.jlab.org/cuawiki/images/e/eb/Notes_on_LV_Power_Distribution.pdf Link to Fernando's Notes]
::* assessment is that the choice of a single cable per divider or per column/row is predicated on the ease of fabrication and installation, not on power or on cable losses.

* Another item to consider relates to the choice of connector for the single pin GND of the PMT shield, if implemented. Suggestion: have a single pin connector facing the same way as the other connectors for ease of maintenance: the 5-pin connector for HV and signal on top of the PCB, the 6-pin LV connector on the bottom and the single pin GND shield connector (bottom or top). 
::* this single pin connector concerns the grounding of the mumetal shield of the PMT - no decision was made as to how to implement it: connect all the shields on the detector or connect each shield to a GND pin on each divider.
::* Adding this pin connector to the PCB is reasonable and we should consider its location, orientation. Any suggestions about connector preferences would also be very helpful.
::* Just to be clear, the LV distribution cabling and grounding is fine as is with the 6 conductor flat cable.
::* good idea to ground the mu-metal shielding, but probably not through the dividers.

* The shielding is made of 36 vertical and 30 horizontal plates. Most likely one single ground cable is enough for the whole system, but if we want to be on the safe side we could ground each plate individually (so 36+30 cables, but not 1080, like the dividers). Also, it would be preferable to avoid the divider area for that, so that the PMTs can be removed more easily for maintenance.
::*[CMC: Shielding needs were later clarified during the meeting on 9/22. We'll try to ground each individual mu-metal tube around the PMTs to the ground of the voltage divider]

'''NEXT MEETING: NPS MEETING ON THURSDAY 30 SEPTEMBER AT 9AM ET'''