KAGRA Logbook

[YokozaWashimi]

We performed several characterization for PR2 oplevs.
Before this work, we confirmed the IR alignment by locking the Xarm and I asked to Ushiba-san to turn off the damping using TM oplevs.

1. Changing the position of TILT QPD
Because there are so small space between beam splitter for length sensing QPD, we slightly changed the position of TILT QPD.
Now there are some space (We can place the beam profiler, so we may install the cover and filters in future)

2. Setting the length sensing QPD
With adding the oscillation to
K1:VIS-PR2_TM_TEST_P_EXC (0.43 Hz and 30 cnt)
Fig.1. showed the spectrum after setting the length sensing QPD.

3. Measured the calibration factor
TM TILT VER : 1.25 [cnt/mm] (Fig.2.)
TM TILT HOR : -1.29 [cnt/mm] (Fig.3.)
TM LEN HOR : -4.72 [cnt.mm] (Fig.4.)

4. Measured the distance of each optics

d_vb = 115 mm
d_bt = 80 mm
d_bl = 65 mm
d_lm1 = 100 mm
d_m1m2 = 215 mm
d_m2l = 60 mm

5. Measured the beam power
Input : 0.658 mW
TILT QPD : 0.061 mW (15551 cnt with high gain mode)
LEN QPD : 0.120 mW (23729 cnt with high gain made)

6. Measured the beam profile (pdf1 and pdf2)
TILT width major 2.343 mm
TILT width minor 2.154 mm
LEN width major 0.5264 mm
LEN width minor 0.3998 mm
The shape of beam profile of TILT QPD is not so clean, why??