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Reports until 19:10, Monday 13 February 2017
H1 ISC
sheila.dwyer@LIGO.ORG - posted 19:10, Monday 13 February 2017 (34112)
Jitter measurements

Here are some old measurements of the jitter coupling I measured by exciting the IMC PZT and measuring noise in DARM and IM4 trans.  

While T0900142 doesn't directly have transfer functions to compare these measurements to, but Kiwamu has been working on simulations that we can use directly.  Based on the strain given at the top of page 2 of T0900142, including a factor of 10 safety, the requirement is that the jitter signal should be less than 1.2e-21 m/rtHz at 100 Hz.  These measurements show a coupling of around 5e-13 m/fractional amplitude at IM4. If we used these measurements to make a requirement, it would be about 2e-9 fractional amplitude in the 01 or 10 mode at IM4 per rt Hz at 100 Hz, or about 50 times more stringent than the requirement shown in figure 1 of T0900142.  It looks like the couplings in the requirements document are either flat above 100 Hz or decreasing, where our measured coupling continues to increase as f at higher frequencies. 

Based on the accousitc injections in Anamaria's log, the LLO coupling at 100 Hz is similarly worse than what is calculated in the requirements document.  

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