Ryutaro TakahashiRyutaro Takahashi(National Astronomical Observatory of Japan)(National Astronomical Observatory of Japan)

Vibrtion isolation system fVibrtion isolation system for KAGRAor KAGRA

The 6th Korea-Japan workshop on KAGRANAOJ, 20-21 June, 2014

ContentsContents

1.1. ConfigurationConfiguration

2.2. R&D StatusR&D Status• Test of the payload prototypeTest of the payload prototype• Test of the bottom filter prototypeTest of the bottom filter prototype

3.3. SummarySummary

1. Configuration

Top Filter (TF)

Inverted Pendulum (IP)

Standard Filter (SF)Filter1~3 in Type-AFilter1 in Type-B

Bottom Filter (BF)

Test Mass (TM)Recoil Mass (RM)

Pre-isolator (PI)

Payload (PAY)

Filter chain

Intermediate Mass (IM)Intermediate Recoil Mass (IRM)

Seismic AttSeismic Attenuation Syenuation Sy

stemstemSASSAS

(Type-A/B)(Type-A/B)

Overview of KAGRA Vibration Isolation System

Type-A: for cryogenic mirrorsType-B: for room temperature mirrorsType-Bp: simpler Type-BType-C: for small optics

Type-A

CRY-PAY

IP

SF

TF

BF

Type-BType-B

Outer frame

IP

SF

PAY

BB

TF

BF

Type-Bp

SF

PAY

BB

BF

BP

Type-C

Stack

BP

BB

•Test of the pre-isolaor prototype was finished in Kashiwa (ICRR).

•Test of the payload prototype is under going in Mitaka (NAOJ).

•Test of the bottom filter prototype was finished in Mitaka (NAOJ-ATC)

•Full prototype test using TAMA300 will be started.

2. R&D Status

Test of the payload prototype

•Main parts were assembled once to confirm the dimensions each other.•Transfer functions of TM-RM system was measured.•Position sensors are tested and improved.

TM

RM

IM

60 cm

Intermediate mass (IM) was fixed to a frame, suspending:

• Test mass (mTM = 10.7 kg) by Tungsten wires (d = 0.2 mm)

• Recoil mass (mRM = 20.4 kg) by Tungsten wires (d = 0.6 mm)

Control the TM by 4 Optical Sensor and Electro-Magnetic actuators (OSEMs).

OSEMs were diagonalized to the virtual directios (x, pitch, yaw)

Test mass (TM) and Recoil mass (RM)

60 cm

Transfer function of the TM-RM

by J. V. van Heijningen

The legend describes the position of the flag alongthe optic axis.

The sensitivities were calculated from the slope of each curve.

PhotodiodeLED

The horizontal axis describes the position of the flag as it

moves either in or out of the OSEM.

Calibration of OSEM

by F. E. Pena Arellano

Flag misalignment ( mm ) Slope ( V / mm ) Error (%) R

1.00 -6.296 -13.8 0.9970.500 -6.746 -7.6 0.996

0.250 -6.948 -4.9 0.9960.000 -7.304 0.0 0.996-0.250 -7.323 0.3 0.996-0.500 -7.630 4.5 0.996

When using the calibration calculated at the middle plane, this OSEM offers a 5% error

within the range [ - 0.500 , + 0.250 ] mm along the optic axis.

In the linear range of each curve a straight line was fitted.

• Number of data points: 9

• Measurement range: [ - 0.400 , + 0.400 ] mm from the

centre (9 mm in the scale of this example).

Calibration of OSEM

by F. E. Pena Arellano

Test of the bottom filter prototype

Function: final vertical filterDimension: 730 x 272hWeight: 99kgBlades: Marasing steel x3Load: 48.6kgAimed frequency: 0.4Hz

One vertical position sensor: LVDTOne vertical actuator: voice coilAttitude control: two motors for pitch,

one motor for yaw

Aging process•Daido Steel MAS-1: 480 , 4h℃•Aubert & Duval Marval 18: 435 , 100h℃

Maraging steel for GAS blade

G&M ATCOptimum load [kg] 47.6 50.2 (5% up)Working height [mm] 64.5 64.5Frequency [Hz] 0.4 0.7→0.3

Measurement of resonant frequencies

Four kinds of vibration isolation system are used in KAGRA.

The OSEMs on RM were diagonalized and the transfer functions of TM-RM system were measured.

The new optics in the OSEM offered 5% error in the range of 0.75mm.

The production process of the GAS blade was estblished with new maraging steel and shorter aging time.

3. Summary