KAGRA Logbook

MIF (General)

shinji.miyoki - 22:22 Tuesday 29 September 2020 (15127)

7 FFU in IYC made glitch noise !!

[Nakano, Tanaka, Yamamoto, Akutsu, Miyoki(remote), Yokozawa(remote) ]

The commissioning team suffered from unknown glitch noises that swinged a lot IYC mirror at several ? micro radian !!

They doubted the IYC-C cooler (near IYC clean booth) and FFUs operation today in the corner station because they contain motors and consumm current a lot.

Consequently, IYC-C cooler was innocent, however, the total current increase of FFUs beside KOACHs in IYC clean booth was guilty.

5 FFUs are set bothside of KOACHs. So total number is 10. 3 (of these 10) FFUs operation seemed not to generate hazardous glitch, however, more FFUs operation enlarge glitches more and more. So, they decided to operate 3 FFUs. Actually, the number of FFUs was increased from 3 to 7 today.

The decreased heat (0.18 x 4 ~ 0.72 kW) was easily compensated with power up of delongi heaters near BS.

C-HT01:25C/L5 1.2kW -> ~1.5W) near BS

C-HT02:26C/L5 (1.2kW -> ~1.5kW) near PR2

In tha past. IFO operation with all FFUs operation was realized. So, something became wrong during last one year. Miyoki will ask Yoshimura-san to check the operation circuit controller for FFUs in IYC clean booth.

Anyway, we will stop FFU and cooler operation anymore until the RSE trial will end.

Comments to this report:

kenta.tanaka - 23:20 Tuesday 29 September 2020 (15128)

After FFU investigation, Akutsu san changed the voltage of oplev laser from AC to DC and then we turned on the all FFU whether the glitch disappear. Unfortunatly, the glitch is observed. That is, Oplev voltage is innocent as for thi case.

we added the timeseries of oplev signal. untill -100sec, it is when all FFU turn on. from -100 sec, it is only three FFU turn on. As you can see, There are many glitches in the signals until -100 sec. From -100 sec, there seems to be no glitch.

we don't find out why FFU causes such glitch or how many FFUs cause Anyway, we turn on only three FFU.

Images attached to this comment

kenta.tanaka - 0:20 Wednesday 30 September 2020 (15131)

After glitch investigation. we checked the sideband signal (POP90 I). This is fig. 1 Blue line means the spectra when PRMI was locked on 5/19 23:06 (UTC). Red line is the one after turn on only three FFU.

As you can see, from 1 Hz to 10 Hz, the spectra got lower. This seems to be because the glich disappear.

Images attached to this comment

masayuki.nakano - 1:38 Wednesday 30 September 2020 (15132)

Several comments:

The spectra Kenata shows are the ones when the PRMI was locked exactly same configuration: arm are misaligned, lock with 3f signal.
He wrote the control signal has not been changed from the privious ones, but it is not true. The control signal has been reduced, and it means that the suspension motion was reduced as reported before (15114)
The POP90I corresponds to the build-up sideband power. So, once the longitudinal motion has been suppressed enough by PRCL loop, this signal shows how stable the PRMI is in sense of angular motion. From June (blue), the POP90 fluctuation got much less, which indicates that the suspension angular motion (PRs, BS and ITMs) are reduced by the modification of the control loop. This reduction is not related to glitch issue.

takaaki.yokozawa - 10:17 Wednesday 30 September 2020 (15137)

I checked the reproducibility of the IYC glitch by FFUs.

Actually, I can find the glitch when "some" FFUs turned on or off, but NO reproducibility nor rules can be found.

Also, I checked the FFUs environment(Sound, vibration), I could not find anything.

That implys power consumption issue or related thing (Maybe not FFU trouble)

I backed three FFU operation now.

Images attached to this comment

shinji.miyoki - 0:02 Thursday 01 October 2020 (15143)

I will also ask Nihon Air Tech that is the productor of this FFU control box.