• KAGRA
• Subgroups
• VIS
• TypeB
• PaperTODOlist

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

Introduction

The mechanical system

Sensors and actuators for control

Introductory paragraph.

OSEMs

• 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. (Mark.)

LVDTs

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

• 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.

Control and performance

Control topology

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

Performance at low frequencies

• Magnetic damper ring. Include Rikako and Enzo’s measurements. (Fabian and Enzo.)
• Temperature stability. (Fabian.)
• Measured quality factors of resonances with control system on and off. (To be mesured by Fabian after the 1st wave of the pandemic.)
• Damping time of resonant motion with the control system on and off. (To be mesured by Fabian after the 1st wave of the pandemic.)

• 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

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 belowthe 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 mirrorwith the inertial damping.

–Figure of merit: The geophone injected noise at low frequencies should not betoo 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.)