1. Ryutaro Takahashi (National Astronomical Observatory of Japan) Vibrtion isolation system for KAGRA The 6th Korea-Japan workshop on KAGRA NAOJ, 20-21 June, 2014

2. Contents 1. Configuration 2. R&D Status Test of the payload prototype Test of the payload prototype Test of the bottom filter prototype Test of the bottom filter prototype 3. Summary

3. 1. Configuration

4. Top Filter (TF) Inverted Pendulum (IP) Standard Filter (SF) Filter1~3 in Type-A Filter1 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 Attenuation System SAS(Type-A/B)

5. Overview of KAGRA Vibration Isolation System Type-A: for cryogenic mirrors Type-B: for room temperature mirrors Type-Bp: simpler Type-B Type-C: for small optics

6. Type-A CRY- PAY IP SFSF TF BF

7. Type-B Outer frame IP SFSF PAY B TF BF

8. Type-Bp SFSF PAY B BF BP

9. Type-C Stack BP B

10. 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

11. 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.

12. TM RM IM 60 cm Intermediate mass (IM) was fixed to a frame, suspending: Test mass (m TM = 10.7 kg) by Tungsten wires (d = 0.2 mm) Recoil mass (m RM = 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

13. Transfer function of the TM-RM by J. V. van Heijningen

14. The legend describes the position of the flag along the optic axis. The sensitivities were calculated from the slope of each curve. Photodiode LED 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

15. Flag misalignment ( mm )Slope ( V / mm )Error (%)R 1.00-6.296-13.80.997 0.500-6.746-7.60.996 0.250-6.948-4.90.996 0.000-7.3040.00.996 -0.250-7.3230.30.996 -0.500-7.6304.50.996 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

16. Test of the bottom filter prototype Function: final vertical filter Dimension:  730 x 272h Weight: 99kg Blades: Marasing steel x3 Load: 48.6kg Aimed frequency: 0.4Hz One vertical position sensor: LVDT One vertical actuator: voice coil Attitude control: two motors for pitch, one motor for yaw

17. Aging process Daido Steel MAS-1: 480 ℃, 4h Aubert & Duval Marval 18: 435 ℃, 100h Maraging steel for GAS blade

18. G&MATC Optimum load [kg]47.650.2(5% up) Working height [mm]64.564.5 Frequency [Hz]0.40.7→0.3 Measurement of resonant frequencies

19. 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