|FDSN code||Z5 (2016-2016)||Network name||Vibration measurement at the MROI Inner Beam Combining Area technical slab, instrument optical tables and Delay Line Area (Vibration measurement at the MROI lab)|
|Start year||2016||Operated by|
|End year||2016||Deployment region||
The MRO Interferometer is currently under construction at the Magdalena Mountains, part of the Cibola National Forest in NM. Part of the interferometer project is the Beam Combining Area (BCA) where very sensitive instrumentation resides. It is crucial for the success of the observatory that this instrumentation perform within tight requirements under different environmental conditions, including vibration disturbances. Other areas of concern is the Delay Line Area (DLA) where precision trolleys carrying optical mirrors run by up to 200 meters length within evacuated aluminum pipes and deliver light to the BCA. The goal for this vibration measurement at the MROI are:  To characterize the vibrations in the inner BCA at floor level and on the surfaces of two optical tables;  To use these data to see how ground vibrations couple into the inner BCA optical tables; and  To use these date to see what vibrational noise any equipment mounted on the BCA optical tables (e.g the beam compressors) will be subject to. FREQUENCY RANGE OF INTEREST: We are concerned about vibrations in roughly the 2 Hz - 250 Hz frequency range. DIRECTIONS: It is necessary to measure vibrations in all three orthogonal directions (x,y,z) and it would help if we chose to orient, say, the x direction to be along the delay line direction. TYPICAL MOTIONS OF INTEREST: We are worried about motions of order 20nm occurring over timescales of order 20ms. Note that 20nm is the sort of OPD difference that matters for interferometry, and 20ms is the near-infrared coherence time. SENSITIVITY REQUIRED: 20nm of motion occuring in 20ms corresponds to a velocity of 1 micron/second. MEASUREMENT CONDITIONS: It would be good to make recordings: (a) With the HVAC running (as it would presumably be during a real observation) but with no other disturbances; (b) With the HVAC off (as it would presumably *not* be during a real observation) and with no other disturbances; and (c) As for (b) but perhaps with someone walking in the outer BCA building. The overall measurement time frame suggest may take no more than one week. Anticipated location for measuring vibration (install sensors) are: - Inside the Inner BCA: (a) - On the top surface of the metrology optical table; (b) - On the top surface of the beam relay system optical table; (c) - On the floor, in between the metrology and the beam relay system optical tables; (d) - On the floor, where the fringe tracker optical table will reside in the future. - Inside the DLA: (e) - On the floor, near the anchor bolts where the Delay Line pipes are installed. In case enough sensors are not available, we propose the following order of priority: (c), (a), (d), (b) and (e).
|Digital Object Identifier (DOI)||10.7914/SN/Z5_2016|
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