KAGRA Logbook

MIF (ITF Control)

yutaro.enomoto - 21:38 Monday 06 May 2019 (8818)

Alignment of X arm and Y arm cavities: Consistency between two arms

[Yokozawa, Enomoto]

= Summary =
We tried to align the main beam so that the beam resonates in X arm and Y arm cavities at the same time.
As a result, we could not make the beam spot positions on both ITMs centered at the same time.
That implies the relative height of two ITMs are different by ~ 1-2 cm.
Need more investigation.

= What we did =
- put all the suspensions back to the position known to be good.
- aligned the X arm cavity using the green X beam while confirming the beam spot positions on ITMX/ETMX were centered.
- aligned the main beam to X arm cavity by using PR2 and IMMT2. Here the alignment up to PR3 was fixed

- aligned the Y arm cavity using the green Y beam while confirming the beam spot positions on ITMY/ETMY were centered.
- aligned the main beam to Y arm cavity by using BS, but the IR transmission did not reach the level we had achieved last time, meaing the alignment of the main beam to Y arm was not good.
- moved ITMY/ETMY randomly to maximize the IR transmission, but this was not successful.

- aligned BS by using the baffle PDs in EYA, to fix the alignment of BS.
- aligned ITMY so that the main beam reflection from ITMY came back to REFL table, by comparing that from ITMX, to fix the alignment of ITMY.
- aligned ETMY so that the IR transmission of Y arm was maximized.
- moved ITMY/ETMY slightly. Here the alignment of the main beam to Y arm cavity itself seemed fine, but the transmission was low (~60 % of what we had achieved last time).
- confirmed that the beam spot position at ITMY was too high with this alignment condition, which probably explains why the transmission was too low.
(the pics of the beam spot positions on ITMX and ITMY are attached)

= Next move =
- compromise the beam spot position on ITMX a bit, and see if that on ITMY gets better and become acceptable or not.
- measure the height of both ITMs. If ITMX is too high or ITMY is too low, change the height of them.

Images attached to this report

Comments to this report:

shinji.miyoki - 16:29 Tuesday 07 May 2019 (8822)

I found that the temperature in IXV constantly increased by ~0.6C (22.2 -> 22.8) for the recent 2 months.
While, the temp in IYV is almost constant around 24.5C.

I am afraid the situation change of type-A for IXV due to this temp change.

In IXV room, there are four commercial dryers operated on 7 th May.
Furuta-san stopped one of them to monitor the change of temp in IXV.

I will report one day change of temp tomorrow.

shinji.miyoki - 16:48 Tuesday 07 May 2019 (8823)

The temp in IYV experienced drastic temperature change around 13th Feb 2019 from 27.5 - > 25 during several days and, after that, it decreased by 0.5 C for several months to 24.5.

The final mechanical position adjustment for ITMY Type-A was done before or after Feb 13th 2019 ??

shinji.miyoki - 17:03 Wednesday 08 May 2019 (8824)

I guess there were some activities and FFU operation in IXYV both for height check of ITMs.
So, the temperature in IXYV was now moving toward the equilibrium temperature now.

I will report the temps again tomorrow.

shinji.miyoki - 13:40 Friday 10 May 2019 (8837)

Temp in IXV became 22.4 C. The one dryer (larger one) off could adjust temp by 0.4 C.

yutaro.enomoto - 20:09 Thursday 16 May 2019 (8890)

= I am happy with the current beam spot positions on both ITMs =

[Stefan, Yutaro]
As entitled. After the height adjustment work by VIS team, we aligned the main beam to X arm and Y arm.
The attachment shows the spot position on ITMX (1st) and ITMY (2nd). I would say it's acceptable for now.
(3rd one is ITMX spot with green)

Images attached to this comment

takashi.uchiyama - 20:38 Monday 20 May 2019 (8909)

Toshikazu Suzuki

Suzuki-sama measured height of ITMX/Y by auto level.

ITMX is -0.9mm from the duct center,
ITMY is +0.5mm from the duct center,

Before height adjustment,
ITMX was +5.2mm from the duct center.
ITMY was -6.0mm from the duct center.

So that
ITMX was moved -6.1mm by the height adjustment works.
ITMY was moved +6.5mm by the height adjustment works.

ITMX is +5.8mm from the beam line measured by Telada-san.
ITMY is -2.0mm from the beam line measured by Telada-san.

yoshinori.fujii - 12:11 Tuesday 21 May 2019 (8916)

Then it sounds strange;
based on the LVDT sensors of ITMX, although the adjusted amout was about 2.1mm according to klog#8871, the actual adjusted amount looked like 6.1mm (klog#8990).
-- I'm not quite sure if this means that the measured/used calibration factors of GASs are not useful anymore.
-- At least about the calibration factors of the BF-damper LVDTs, there was no chance to take any mistakes on the calibration-factor measurement (since the factors were measured via KAGRA DAQ system).
-- The adjusted amount measured by the GAS-filters was consistent with the amount measured by the BF-LVDTs (not exactly though).
-- Did we change any parameters on the LVDT boards after the calibration work?
-- Was the height of ITMX truely changed by 6.1 mm?
-- In any case, *NOT* believing that the *_ITMX*_DAMP_GAS_IN is aligned to [um] for now might help us. sorry for this unconvenience.