LIGO Document T1800013-v1

ITM03 LHO ITMx post O2 inspection

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T - Technical notes
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A feature was found at the location predicted by TCS. This feature is highly absorbing. This feature was present in the scans of the optic as received from the coater.
No other absorbers over 20 ppm were found in the center 60 mm of the optic.

Rough estimate of circulating power in O2 at LHO is 150-200kW in the arms. This leads to a peak intensity of ~ 33-44W/mm^2. - A. Brooks

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Hi Gari,

Certainly the mirror wouldn't have seen more than 200 kW. We were running at about 100 kW during O1 with 25W into the vacuum. However, the power recycling gain dropped significantly (~20%) as we tried to increase to 50W input to the vacuum, so the circulating power in the arms probably wasn't usually more than about 160 kW. Often the recycling gain was even lower than that, so even less circulating power. There was one time that I accidentally clicked a button, and the power into the vacuum went as high as 62W, and then immediately came back down, but I'd guess that the total power was still less than 200 kW, and for a very brief time.

I hope that's helpful. If you need a more precise number, I can try to look more carefully at some of our data.


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