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LIGO- G040XXX-00-D EMC Upgrade Progress Overview M. Zucker 30 July 2004

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Text of LIGO- G040XXX-00-D EMC Upgrade Progress Overview M. Zucker 30 July 2004

No Slide TitleApproved/funded: Phase I (power, grounding, digital containment)
Replace switching power supplies w/linears (L1, H1, H2)
Segregate digital (+ telcom, video) from analog by rack (L1, H1, H2)
Reform DC power, signal and safety grounding* (L1 Ex, L1 Ey)
Shielded VME crates, EMI filters, cabling (L1 Ex, L1 Ey)
Shielded EMC racks, cabling, feedthroughs (L1 Ex, L1 Ey)
Shielded/alternative/new wave cross-connects* (L1 Ex, L1 Ey)
Ancillary resolutions (all implemented)
Improved analog protocols for new designs (HEPI, FSS, ISS, RFPD, etc.)
EMC planning and testing integrated in design & prototype process
EMC testing part of commissioning at observatories
Incorporate lessons learned while propagating to H1, H2
Evaluate results before designing Phase II (analog shielding/repackaging, sensor & driver isolation)
LATER ADDITION: Move to separate room for acoustic isolation
*Substantial design evolution since 11/02
M. Zucker
Pro:
VERY FAST switchover!
Con:
M. Zucker
RF shielding demands contiguous grounding, no gaps
60 Hz & audio ground loops require ground isolation, “star” grounding; but inductance makes ground useless for RF
Isolation transformers help but introduce safety grounding issue
MZ proposed frequency-dependent “hybrid grounding”
2003 electrical code permits balanced power
60 Hz power for instrumentation supplied through balanced transformer; ground is defined at center tap of secondary (connected to technical earth grid)
No induced currents in ground => no “ground” potentials
Now used widely in audio studios
Pro:
Signal and shield grounds can generally be connected without interference, forming good RF shield coverage without ground loops (but breaking loops is now safe too)
Extreme isolation from power grid noise, facilities, vacuum equipment, etc.
Con:
MUST power ALL loads, test instruments etc. from balanced power; random wall plug not just a ground loop any more, but DAMAGE
M. Zucker
M. Zucker
M. Zucker
M. Zucker
Parting shots
Work is about 6 months behind schedule; limited by both available manpower & opportunities (commissioning gaps)
Switchover speed has been optimized to limit downtime
Offline building and wiring as much as possible
Moving to a separate space decouples build from ongoing commissioning
Some issues/concerns still in work:
Circuit loading by RFI feedthrough capacitances
Connector reliability
Evaluation still in progress (some prelim. results to show)
Corner station move scheduled week of LSC, shakedown expected to take the rest of August
M. Zucker