KAGRA Logbook

MIF (ITF Control)

kiwamu.izumi - 14:44 Wednesday 14 February 2018 (4176)

The interferometer beam still returns to BS from EY after the cryogenic chillers started

Yutaro, Kiwamu,

In this afternoon, we tried searching for the return beam from EY to BS. We successfully found the beam at EX, EY and BS simultaneously.

This is the first confirmation of the return beam after the cryogenic chillers had started (4140).

The optical lever readouts are:

PR2:
- P: 0 urad
- Y: 170 urad
PR3:
- P: -33 urad
- Y: -70 urad
BS:
- P: 150 urad
- Y: 25 urad

Also the IMMTs were within a few 10 urads as read by the optical levers and we didn't try to zero their alignment. The IMC was at the alignment described on 4175.

Comments to this report:

takafumi.ushiba - 15:50 Wednesday 14 February 2018 (4177)

How much was the readout of the EY OpLev while the return beam hit the BS?
Were there any large differences between before and after starting chillers?

kiwamu.izumi - 17:33 Wednesday 14 February 2018 (4179)

Hi Takafumi,

A good question. I forgot to mention that in the original entry. The ETMY optical lever was at

P: +180 urad
Y: +30 urad

In fact, the pitch value of 180 urad is already out of the linear range and therefore not accurate. We need to recenter the QPD again.

Also, at around 11 am in this morning, there was unknown slow drift in the optical lever yaw which lasted for an hour or so. This drift seems to have started right after Miyamoto-kun and company finished the calibration of the length oplev. It is suspicious, but I am not sure if this was the cause for the oplev's inaccuracy.

kiwamu.izumi - 11:29 Thursday 15 February 2018 (4188)

Sorry, I accidentally mixed up the pitch and yaw readouts in the last comment. They should read:

P: + 30 urad
Y: + 180 urad