KAGRA Logbook

With Kokeyama-san and Miyoki-san,

We updated the current REFL WFS optical layout to the one with 2000 mm lens as described in 10335. However, the layout at the REFL table was a little bit different from what was drawn in the figures in 10335. This makes following Eleonora's design a bit difficult. And since we didn't bother to move the CCD, we improvised by removing LNS1,2,3 in figure 1 in 10335 and put a 2000 mm lens in that path. We then measured the beam profile with the configuration as described below:

to ccd --------------\--------------------- from viewport, periscope, etc

<-> 2000 mm lens

~50 cm

steering mirror \------------------------------------------- to beam profiler

-> zero distance reference

We first measured the beam profile with a BS in between the lens and the steering mirror. Then we noticed that if we remove the BS, the beam size changes. So, we measured again without the BS.

The beam profile and the new positions of the PZT steering mirrors and the QPDs are shown in the attached figure and below.

positions:

QPD1 = 1.5677311924168056 m,

QDP2 = 1.7985434776193914 m,

steering mirror 1 = 0.9677312750639899 m,

steering mirror 2 = 1.1985434896754559 m

results:

guoy phase difference x = 1.617762923329441 rad,

guoy phase difference y = 1.8438525346500985 rad,

beam size QPD1 x = 274.310023645134 um,

beam size QPD1 y = 290.02866419545754 um,

beam size QPD2 x = 290.02866419545754 um,

beam size QPD2 y = 285.2910657528782 um,

actuation range QPD1 = 600 um,

actuation range QPD2 = 600 um

We will design the optical layout later.