[S.Nagano, Kokeyama, Nakano, K.Nagano]

Today, we installed RFQPDs for IMC ASC WFS on the IMC REFL table.

Before we put the RFQPDs, the lenses were replaced to a convex, f = 2000 mm, from the piar of convex, f=150 mm, and concave, f = -100 mm, to expand Rayleigh range.
As a result, the Rayleigh range was expanded to 11.8 cm from about 1.5 cm.
In other words, the new beam waist size on IMC WFS pass was measured to be about 200 um in radius.

Then we put the RFQPDs at +/- 11.8 cm from the beam waist position which was located at about 2 m downstream from the lens.
The QPD1 was placed at -11.8 cm and the QPD2 was at +11.8 cm.
This means that the QPD1 and QPD2 detect the light which have Gouy phase of -45 deg and +45 deg, respectively.

Finally, we tested if the QPDs could output DC signal properly to center the light.
At first, we could not get any DC signal from the QPDs.
This was because cabling was wrong.
After the cabling problem was fixed, the DC signal could be output properly and we could center the light on the QPDs seeing their DC signals.

Since we did not have time to test about RF signal used in WFS, the test will be started from tomorrow after some necessary works, such as balancing acctuator efficiency and so on, are done.