Friday morning before increasing the ITF input power from 17 W to 20 W we have turned on the DAS to observe the effect on the ITF.
We have applied the same power on both DASs:
9.11 UTC-> DAS ON (P_innerRing=90 mW, P_outerRing=180mW)
We observed a fast improvement of the gain and then a decrease that suggested an excessive power applied to the DAS.
9.26 UTC-> DAS OFF
9.38-> DAS ON (P_innerRing=50 mW, P_outerRing=100mW)
9.56-> DAS OFF
In this case no important changes in the gain behaviour has been observed.
From the data it seems that the working point is between the 2 DAS power values.
Due to the VPM failures the tests have been suspended to allow increasing the YAG power up to 20 W.
New tests will be performed with P ITF=25 W.