KAGRA Logbook

[Aso, Miyo, Arai]

1. The adjustment of IM OSEM V2, V3

1.1 The way of fixing the optical bench

To solve the problem as mentioned in 6186, we adjusted the position of IM OSEM V. First, we had to fix the optical bench because we can only access the PRM from side flanges and it's difficult to keep balance without touching or standing on optical bench. But, fixing the optical bench with only screws cannot guarantee the sliding of optical bench. So, we fixed the optical bench with jacks and C clamps. To put the jacks, we removed the screws and spacers. Then we put four jacks and supported the optical bench. Also, we used the C clamps between the optical bench and inner flame.

1.2 The OSEMs we adjusted : IM V2, V3

We checked the signals (i.e. IM_OSEMINF_V1_INMON) after tilting Pitch and rechecked that IM OSEM V2, V3 are out of linear range as is yesterday. So we entered in the PRM chamber (with clean shoes) and adjusted V2 and V3. We fixed IRM and then IM, then adjusted OSEM.

2. The adjustment of BF GAS by using fishing rod of BF GAS

We also tried to solve the problem that BF GAS may touch with something. We checked the signal of BF_LVDTINF_GAS_INMON and found that BF may touch the EQ stop. So we looked the past trend data(see the attached figure) and found the current position of BF GAS is different from nomimal position which is on around 2017/10. We moved BF GAS by fishing rod to nominal position(BF_LVDTINF_GAS_INMON:1000 to 5000). Now BF GAS seems to be freely swinging.

3. Tommorrow's schedule

Because we moved BF GAS very much, IM OSEM V is out of range again now. So we will re-adjust IM OSEM tommrrow. The procedure is as same as today.