LIGO Document E1300411-v1
- This PEM upgrade proposal was first submitted 7/30/2012 by David S. & Eric G. for R&D evaluation, as T1200260-v2. Since this isn't strickly speaking R&D, it was rejected as an R&D proposal; The funds should be allocated from LHO & LLO "maintenance and upgrade" funds. On October 22, 2012 David Shoemaker asked that the proposal be removed from R&D consideration, with the intent that it be added to the operations Liens list, M1300166. However this was never done. We (Dennis C., Eric G., David S., Stan W., Valera F., Peter F., Rana A., Rolf B.) all agree that technically it is worthy of pursuing. However none of the comments from the R&D review have been addressed in this more recent ECR E1300411.
6/19/2013 approved by Dennis Coyne with the following CAVEATS, QUESTIONS & COMMENTS:
CAVEATS: Only the proposal in sections 1 through 5 of T1200221-v1 is approved (additional magnetometers and accelerometers which have been costed), contingent upon addressing the questions/comments listed below. The "additional upgrades and projects" listed in section 6 require costing (and another ECR) before they can be reviewed.
1) Need some estimate of how it will be wired into the CDS system. The presumed spare ADC channels should be identified and checked to be in appropriate locations, so that we are sure that we don't need more investment in DAQ channels, chassis, power supplies, etc. Where are the spare channels? What is the required sampling rate? Are the AA filters appropriate and the +/- 20V ADC range appropriate for these new sensors? Should the cost include new AA and/or new ADCs? What about pre-amps for the accelerometers - are these needed? Bottom line: need to see the full picture for signal handling.
2) We're not really keen on:
a) putting accelerometers on the test mass optical levers - at least not without some prior investigations of optlev vibrations.
b)We don't see why it is useful to have one axes accelerometers on the in air tables that don't have the beam in the low noise mode (ISCT1/ISCT6/TRX/TRY). The table vibration is not a problem for the lock acquisition or the power up.
3) The count is for exactly the number of sensors proposed with no spares. If we rely upon these sensors for vetos, then we should consider having some spares on hand. Perhaps the sparing approach can be evaluated after the efficacy of each sensor is determined during initial commissioning.
4) Why does the proposed plan have considerably more sensors at LHO than LLO? (e.g. 52 accelerometers at LHO and only 43 at LLO). Is LHO a testbed to determine if these additional sensors are worth the investment? Will the sensors be re-allocated between the two observatories once commissioning determines which locations/sensors are best for PEM monitoring/vetoing?
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