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Reports until 10:58, Monday 16 August 2021
H1 AOS
robert.schofield@LIGO.ORG - posted 10:58, Monday 16 August 2021 (59640)
Damping of ITMY Cryobaffle, and installation of nozzle baffles at ITMY reduction flange and in beamsplitter chamber

Figure 1 shows the ITMY cryobaffle damped with Arnaud’s viton dampers. This damping was the main reason for the incursion and should reduce in-band scattering noise by lowering the relative velocity of the baffle.

The first page of Figure 2 shows the nozzle baffles installed at the reduction flange near the ITMX optical levers. The second page of Figure 2 shows before and after installation views from the beam spot on ITMX. The 940 nm illumination and the camera are right at the beam spot to show how reflective objects in ITMY’s field of view are in IR. The nozzle baffles result in only a small reduction in returned light, which is dominated by the annulus around the cryobaffle and a glint from the port at 3:00 that is not eliminated by baffling (more on this later). 

Figure 3 shows before and after installation views from the beamsplitter beamspot of the nozzles that were baffled in BSC2. Again, there is not much of a reduction in the returned IR light. For example, the pictured portion of the wall returns about 10 times as much light as the nozzles did before baffling.

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