lisa.barsotti@LIGO.ORG - posted 16:00, Saturday 01 August 2015 - last comment - 18:34, Saturday 01 August 2015(20131)
High frequency excess noise is ~0.6 times shot + dark noise
Evan, Lisa This entry is to clarify the fact that the impact of this excess of high frequency noise is actually bigger than the coherence with the ASC channels suggests, as it can clearly be seen by comparing OMC NULL and SUM. For example, around 2 kHz, the discrepancy in the noise floor between OMC SUM (total noise) and OMC NULL (shot + dark noise) is about 15%, so corresponding to a noise which is 0.6 times shot + dark. The attachment shows OMC SUM/NULL in H1 at low noise (left) compared to L1 (right). So, the message is that we are looking for something quite big here..
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Maybe not surprising, this noise is not stationary from lock to lock. Last night the noise was lower than the night before (first plot: compare OMC SUM green trace with red trace; NULL was the same in both locks).
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