Mitchell, Camilla
We added a borrowed a LIGO-E1900393 dual reflecting mirror in frount of the HWS ITMX CCD after Dan found we were coupling 1064nm into our Hartmann signal alog 65734. This should be (>60% Transmissive) at 790nm and reflect >99% 532 and 1064nm.
We couldn't see the beam returning from the ITM so aligned the mirror using the CCD image of the dots and placed the beam dump by eye. The mirror slightly displaced the CCD image but we didn't change the beam steering unitl we've tested how well this filter works. Started with average pixel value 84 and after adding mirror had avg. pixel value 69 so ~83% HWS beam transmitted. Took new references and left camera setting at sync freq 1Hz.
Measured power out of SLED fiber collimators to be 0.8mW in 790nm for ITMX and 0.19mW in 840nm for ITMY. This has gone down significantly since February (alog 61892) where ITMX had 2.3mW and ITMY had 1.3mW. I will plan to replace the IY SLED soon.
This mirror has really reduced the coupling of IR into the spherical power. Yay! You could previously see the TOTAL_PIXEL_VALUE increase by >20% with power up. But now it barely changes above the noise. See attached plot. We will not change the pointing of this HWS beam onto the CCD, it is central enough. See yesterday's ring heater test- alog 65960.
