Agenda/Minutes of the VIS Meeting on 2019/6/7

2019/6/7 13:30 -

Participants:

Progress report

Site work schedule: [[|XLSX]]

[Fujii with Yamada-kun, Ushiba-san]

Comb-damping filter box was installed and worked properly.
Coil balancing work at TM/IM/MN-stage, ongoingklog#9077
Tuned the GAS filter control (IY).
- loops were closed but somehow 238Hz line was observed in GAS-LVDT. Not sure why.
Checked the GAS filter controls (EX, EY).
Measured the transfer functions from IM to TM (IX, IY, EX, EY).
- All oplev TF (MNexc, IMexc, TMexc) in P/Y was measured.
- Remaining is the TFs measured by IX-TMLoplev, since the L-oplev is not installed.
- PS TF will be measured with larger amplitude.
modeling the measured mechanical TFs and tuning damping filters of the payloads.
Compared the spectra of the type-A suspensions at IP, BF, MNoplev and TMoplev etc, w/ inertial damping and w/ LVDT damping (and w/o damping. this was done only for ITMX). Note (to be summarized)
- It looked that current inertial damping at ITMX injected noise at lower frequency than 0.1Hz.
- This raised the 80mHz-Yaw-mode more effectively, compared to LVDT-damping at IP-stage.
- Now LVDT damping is implemented at ITMX.
started looking for (better) blending of 80mHz damping.
At ITMY, in the TF measurement campaign, it was found that the payload seemed to touch to frame; the BF-excited TFwas not as expected klog39126.

See Klog 9064
SRM IP L and T is blended at ~110 mHz (partially optimized by gradient descent, stopped after 10 iterations, then manually adjusted.) while IP Y is blended at 260 mHz (Lucia's old filter). The stability test was carried over the past weekend with inertial damping and all other stages on. The system seems stable.
To study to performance of the inertial damping, I improvised an OL windshield for SRM.
Another round of diagonalization was carried just because we have better sensitivity.
With IP LVDT damping and other controls on, the residual motion is as follows 9086:

RMS Displacement:

RMS Velocity:

I measured the residual motion with inertial damping, inertial damping without LVDT DC, normal damping without LVDT DC. Results are pretty similar.
I modified the optimization algorithm to allow fine learning. The cost plateaued after ~300 iterations and the blending frequency was at 78.6 mHz. I tried implementing this blending filter but the system went unstable.

The calibration, diagonalization for IP geophones was done.
I measured and fit noise floor for LVDTs and geophones.
I found that the IP geophones have a much higher noise level than those from SRM. (1 order of magnitude higher, see 9088)
This explains why the optimization result of the blending filter converges much quicker than that of SRM, because the geophone noise level limits the blending frequency to be at ~ 130 mHz.
However, when the system went unstable when the blending filter was implemented. I should try a higher blending frequency or manually adjusting the blending filter to have a proper shape.

Help commisioning.
Somehow design better cost functions which could help limiting the blending frequency and changing the shape of the blending filter effectively.
Inertial damping and OL windshield for BS and (SR3, if haven't done already).
Type B Operation Manual.
A more pleasant VIS Status Monitor.

Found that the PRM IM is touching during MISALIGNED state. I added the YAW offset on BF so that the offset in IM YAW is reduced.
Implemented the Oplev DC control for IM for all PRs. The TM Oplev control, which has gain from about 0.2-1 Hz damps the resonance, while the IM oplev control has gain only below 0.1 Hz. (for YAW, IM oplev also damps the lowest resonant mode.)
- PR3 was kicked during the control test, but fortunately PR3 comes to the good condition. (Previously the IM OSEMs are at the edge of the linear range, but now it comes almost at the middle.)
- The guardian is also updated for the ALIGNED state. The target values for the DC control are automatically obtained from the K1:VIS_PR*_GOOD_OPLEV_(PIT/YAW) that is also used in the commissioning tool.
Ready to change the BF control so that BF GAS loop has gain at DC. The resonance is damped only by IM V OSEMs. (Good to reduce the GAS LVDT coupling noise.)

=== OMMT & OSTM (Takahashi)===

[Sato]

Took out the MC suspension from TAMA. Transported it to the clean room in the ATC.
Designed the modification parts for the OSTM.

Engineering run on 6/8
Introductory materials (on basic stuff that is required for gravitational wave interferometry, especially for KAGRA). Not just for VIS, we should encourage other subgroups to do this as well for narrowing the knowledge gap between subgroups and, more importantly, to help beginners (like Terrence) to get up to speed with the current status of KAGRA.
DAQ channel list : List
Removable filter banks
- Type-Bp: K1:VIS-PR*_TEST Type-B: K1:VIS-SR*_TM_OSEM, K1:VIS-SR*_IP_GEOWHITEN (filter function will be required in the future? can be replaced to test points?)

On 2019/6/14(Fri)