Using the data from May 17th lock strech where spherical power was stable and the calculation method from alog16558 and alog16579, the estimate power absorbed by ITMX was 390 +/- 40 parts per billion (agrees with what has been previously calculated in alog16603).

The primary source of uncertainty comes from assuming 10% uncertainty in the arm power.

As Kiwamu suggested, I used 3.1% (measured value) for PRM transmissivity instead of 2.97% which is vender's value.

The arm buildup = 1233 cts, recycling gain = 38, CR power to PRC = 19W, power stored in the arm = 102360W, and the absorbed power = 40 mW. Yields the absorbtion in the ITMX coating to be 390 +/- 40 ppb.