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AdV-TCS (CO2 laser projector)
Aiello, Fafone, Nardecchia, Rocchi - 17:51 Monday 20 November 2017 (40096) Print this report
CO2 DAS tests with 17 W power

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.

Images attached to this report
Comments to this report:
schaaf, tacca, beuzekom - 19:29 Wednesday 22 November 2017 (40127) Print this report

Attached the intensity images as seen by the phase camera for the DAS test at 17 W input power.

1. figure shows the overlap between 6 MHz USB and carrier on B4. In shaded blue the time when the DAS was on is indicated, the DAS power is noted in the legend as "inner ring/outer ring" in mW. In black vertical lines give the gpstimes of the images described below. The sudden increase after the black line might be due to a power drop of the ring heaters earlier, see image attached in [40096]. The evolution of the overlap seems not to follow the evolution of the gain for this data set. The overlap increases in both stretches were the DAS is turned on while the gain decreases in the first stretch and is stable in the second stretch [40096].

2. figure shows the images on B4, not in chronological order but for increasing power. In particular the 6 MHz USB sideband seems to improve in shape with the DAS on.

3. figure shows the images on B1p, not in chronological order but for increasing power. Here essentially no changes are observed in any of the fields.

4. figure shows the overlaps on B4 for according data stretch. Effect on upper sidebands is more pronounced than on lower sidebands (in agreement with the 2. figure) while the 6 MHz lower sideband seems very stable. The green band gives a typical standard deviation (roughly 0.01).

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