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

LIGO- G040XXX-00-D M. Zucker2 Recap of 11/22/02 EMC Review Approved/funded: Phase I (power, grounding, digital containment) oReplace switching power supplies w/linears (L1, H1, H2) oSegregate digital (+ telcom, video) from analog by rack (L1, H1, H2) oReform DC power, signal and safety grounding* (L1 Ex, L1 Ey) oShielded VME crates, EMI filters, cabling (L1 Ex, L1 Ey) oShielded EMC racks, cabling, feedthroughs (L1 Ex, L1 Ey) oShielded/alternative/new wave cross-connects* (L1 Ex, L1 Ey) oAncillary 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 oIncorporate 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

LIGO- G040XXX-00-D M. Zucker3 Cross-connect Interim Solution Replicate existing open terminal block setup inside separate EMI- sealed enclosure with filtered I/O Pro: oPin-compatible upgrade path, minimum downtime to convert existing system oVERY FAST switchover! oRetains rework flexibility, no new infrastructure required Con: oDoubling of cables and connectors (reliability, loading) oMinimal improvement in intra-rack crosstalk immunity (TBD)

LIGO- G040XXX-00-D M. Zucker4 Grounding system Recall our dilemma: oRF shielding demands contiguous grounding, no gaps o60 Hz & audio ground loops require ground isolation, “star” grounding; but inductance makes ground useless for RF oIsolation transformers help but introduce safety grounding issue oMZ proposed frequency-dependent “hybrid grounding” 2003 electrical code permits balanced power o60 Hz power for instrumentation supplied through balanced transformer; ground is defined at center tap of secondary (connected to technical earth grid) oNo induced currents in ground => no “ground” potentials oNow used widely in audio studios Pro: oSignal and shield grounds can generally be connected without interference, forming good RF shield coverage without ground loops (but breaking loops is now safe too) oExtreme isolation from power grid noise, facilities, vacuum equipment, etc. Con: oMUST power ALL loads, test instruments etc. from balanced power; random wall plug not just a ground loop any more, but DAMAGE

LIGO- G040XXX-00-D M. Zucker5 Balanced power transformer/breaker; tech power drop

LIGO- G040XXX-00-D M. Zucker6 corner sta., feedthru Ey

LIGO- G040XXX-00-D M. Zucker7 Rack I/O filter panel

LIGO- G040XXX-00-D M. Zucker8 Shielded/enclosed VME crates & feedthrough back panels

LIGO- G040XXX-00-D M. Zucker9 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 oOffline building and wiring as much as possible oMoving to a separate space decouples build from ongoing commissioning Some issues/concerns still in work: oCircuit loading by RFI feedthrough capacitances oConnector reliability oOpto-isolated Ethernet links Evaluation still in progress (some prelim. results to show) Corner station move scheduled week of LSC, shakedown expected to take the rest of August