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 * Temperature stability of GAS filters. (Fabian.)  * --(Temperature stability of GAS filters. (Fabian.) )--

Describe KAGRA/Subgroups/VIS/TypeB/PaperTODOlist here.


  • Fabian did a bit of a mess in defining sections and subsections in the sensors part. (Fabian or Mark).
  • Figures are scientifically good but ugly. (Fabian).
  • Let's use Type-B, Type-C, etc. with the hyphen and follow Mark's acronym style for everything else.

To Do list for the Type-B paper

Author list (Fabian)

  • Paste the appropriate KAGRA's full author list. The merged 2018-2019 author list has been updated with the changes reported by Panwei. The link is (Fabian.)

  • Write Rikako's name in the paper. (Fabian.)

  • Check Panwei's status and write him in case he's not a collaborator. We're reporting his OSEM sensitivity measurements.

  • Write to Rikako. We're reporting her damper ring measurements.There's a process of approval for including her which we already know about.

  • Kozu-kun is part of the author list; so we don't have to do anything.


  • Update status of KAGRA with respect to O3 (Fabian or Mark).
  • Say KAGRA is an underground facility in order to take advantage of the low seismicity (Fabian or Mark).
  • Say it employs cryogenic test masses; include a reference (Fabian or Mark).
  • Write more suitable text in the introduction (Fabian or Mark).
  • Copy in this manuscript the remaining sections from the previous version (Fabian).

Vibration isolation systems in KAGRA

  • Write about the advantages of going underground from a quantitative point of view: the ground motion amplitude is between 10 and 100 times smaller than at surface sites. Provide a citation. (Fabian or Mark.)
  • Point out the requirements on the optics' motion. See the table already in the paper.
  • Say something about the primary (60 mHz) and secondary (150-200 mHz) microseismic peaks and maybe explain seasonal variations. (Fabian under Miyo-kun's supervision.)

The mechanical system

  • The text was mostly done by Mark.

  • We require to harmonize what's been written already. (Mark or Fabian.)
  • Decent 3D-CAD figures are required. (Hirata-san.)
  • Produce a 3D-CAD cartoon in which the optical table is not floating (Hirata-san).
  • Add values of the resonance frequencies (Fabian or Mark.)

Sensors and actuators for control


  • Brief description of the anatomy of the OSEMs.

  • Produce a nicer figure. (Fabian.)
  • Typical OSEM sensitivity measured when locking the target. These are Panwei's measurements.

  • Typical measuring range according to all the units used in BS, SR2, SR3 and SRM.

  • Typical calibration value. (Fabian, klog 4189.)
  • Produce a nicer plot (Fabian).
  • Write the figure caption (Fabian).
  • Write a couple of sentences about the coil-magnet actuator and cite Mark’s document and Michimura-san’s paper whose data is already in the bibtex file. (Mark.)


  • Typical sensitivity measured when locking the target.

  • Typical measuring range.

  • Typical calibration value (Fabian, 4153).
  • Produce a nicer plot (Fabian).
  • Write the figure caption (Fabian).
  • Analyze SRM LVDT sensitivity data and add a comment here if necessary (Fabian).

Optical lever

  • Brief description of the oplev.

  • Brief description of diagonalization procedure.

  • Where the displacement calibration comes from: relativeposition of components measured with ruler, dimensions given by the 3D-CAD, QPD displacement calibration and comparison with IP displacement.

  • Typical extent of coupling after diagonalization.

  • Typical measuring range.

  • Write the diameter of the beam determines the linear range of the QPD as a beam displacement sensor. (Fabian.)
  • Point out that the oplev is expected to be limited by the seismic motion. (Fabian.)
  • Say it is not easy to measure directly the oplev sensitivity but it is possible to set an upper limit to the optic rms displacement and velocities. (Fabian.)

Inertial sensors

  • Add and modify whatever is in the other version of the paper (Fabian).
  • Brief description of what a geophone is.

  • Brief explanation of the calculation of the noise determining the sensitivity.

  • Say that below the resonant frequency the noise goes as f^-{3.5} and explain the reason. (Fabian.)
  • Produce a nicer plot. (Fabian.)
  • Briefly say how they were calibrated against a calibrated seismometer.

  • Say the noise was measured using three channel correlation analysis.

  • Say we are in the process of finding out the reson of discrepancy betwwen the predicted and measured sensitivity.

Rigid body model of suspension (Mark)

Write relatively brief description.

Control and performance

Control topology

Copy and modify whatever Terrence wrote already. (Fabian.)

Performance at low frequencies (Fabian)

  • Magnetic damper ring. Include Rikako and Enzo’s measurements. (Fabian and Enzo.)
  • Temperature stability of GAS filters. (Fabian.)

  • Long term stability of optic position measured by oplev. (Fabian.)
  • Damping time of resonant motion with the control system on and off. (To be mesured by Fabian on May.)

  • Optic residual displacement and velocity rms measured with the oplev in a day with good weather; show coherence with seismometer on ground.

  • Describe the control system used:
    • –Say that due to time constrains and to unidentified noise sources it wasn’tpossible to implement inertial damping.
    • –IP: LVDT position control and damping.
    • –F0: LVDT position control and damping.
    • –F1: LVDT position control and damping.
    • –BF: LVDT position control and damping.
    • –IM OSEMs: position control from oplev and damping from the OSEMs readout.
    • –Oplev: position control acting on IM and damping o the mirror.

Performancer at high frequencies (Fabian)

This is a mixture of things to write and a TO DO list for Fabian. Not everything has to be in the paper.

  • In the case of the IPLVDTs calculate the displacement sensitivity in L,T and Y. (For the calculation not for the paper.)

  • In the case of the IP geophones calculate the displacement sensitivity in L, T and Y. (For the calculation not for the paper.)

  • In the case of the IM OSEMs calculate the displacement sensitivity in L, T, V, R, P and Y. (For the calculation not for the paper.)
  • Inertial damping and reduction of the effect of the microseismic peak.
    • Explain the selection of the blending filter in terms of the geophone noise below the resonance frequency. (Cite Takanori.)
    • Choose the blending frequency according to the following:
      • Frequency at which the geophone noise equals the LVDT noise.
      • Figure of merit: reduction of the microseismic motion induced on the mirror with the inertial damping.
      • Figure of merit: The geophone injected noise at low frequencies should not be too large.
  • Describe the control system used in the calculation:
    • IP: LVDT position control and inertial damping.
    • F0: LVDT rolled-off position control and damping of the whole vertical chain.
    • F1: LVDT rolled-off position control.
    • BF: LVDT rolled-off position control.
    • IM OSEMs: off.
    • Oplev: off.
    • Check the contribution of the wavefront sensor in Takanori’s thesis.
  • Calculated expected performance within IFO observation band including injectedcontrol noise and comparison with requirement. (Fabian.)

TO DO list for Enzo: damper ring performance

Not all the items are to appear in the paper. Some of them are for general information. In order to avoid loading too much work on Enzo, Fabian will write the text fr the paper with the information provided by him.

  • Compile a list of useful klog entries about the damper ring.
  • Where's Rikako's presentation?
    • There was a presentation at NAOJ about her project: here

  • Did Rikako write a report?
    • There is no formal report, but it has all the info that we need: here I can tidy it up in the following days.

  • Which mode does the damper ring aims to damp?
    • It damps the torsion mode of the whole chain. f = 55mHz
  • What was the criteria for choosing the ring position,
    • Damping time?
      • Yes. The first criteria was to have a damping time below 60 s.This damping time corresponds to the damper ring at about 4 mm over the nominal position.
    • Was the motion damped but not critically or overdamped?
      • The motion was damped. To be more precise, the damping ratio was in all measurements below 1, so it is underdamped. For example, for a damping time of 30 s the damping ratio is 0.096[-].
  • Describe in an itemized way the procedure for finding the suitable position of the damper ring. For example:
    • We moved the damper ring to ZZZ position moving KKK components.
    • At a position XXX we excited the YYY mode usng VVV actuators and measured the damping time with the oplev.
    • We used a least-square fit to data or any other fancier method.
  • Explain the presence of residual motion at other frequencies that the oplev also senses and the damper ring does not damp. Remember Brazil!

    • I have started writing the section of the Magnetic damper which includes the topics covered above: here

  • Produce a plot with the results of different tests. It doesn't have to beautiful but understandable.
  • Provide raw data for a beautiful plot.

TO DO list for Hirata-san: 3D-CAD views

The task requires reading and provide beautiful 3D-CAD views according to the content.

  • Check what Fabian has produced in the past here. Some of it may be useful. Decide which ones are suitable if any.

  • I have been using PNG format.
  • Whole chain with chamber.
  • Whole chain without chamber. (In the figure we currently have, which was produced by Fabian, the optical table is not in the right place!)
  • IP.
  • GAS filter.
  • IM/IRM.
  • Optic/RM.

KAGRA/Subgroups/VIS/TypeB/PaperTODOlist (last edited 2020-06-15 13:07:43 by fabian.arellano)