1. Seismic attenuation chains concept, design and advancement status Riccardo DeSalvo for the KAGRA Seismic group JGW-G1201259 September 10, 20121JGW-G1201259 (LIGO-G1200939)

2. KAGRA-SAS design philosophy Use only well tested techniques, Take the best from both Virgo and LIGO examples: – Virgo’s superattenuators/suspensions – LIGO’s OSEMs Gain from the learned lessons: – Passive instead of inertial damping Designed for ease of use and fast lock acquisition September 10, 20122JGW-G1201259 (LIGO-G1200939)

3. Type AType B Filter zero Standard filter Modular design September 10, 2012JGW-G1201259 (LIGO-G1200939)3

4. Dual tunnel solution KAGRA SAS is mounted between two tunnels due to the restrictions of the space reserved for the cryostat Free and safe access to cryostat and seismic chain! September 10, 20124JGW-G1201259 (LIGO-G1200939)

5. The top filter and IP table footed on solid rock Inverted Pendulum table with short legs Large GAS filter Easily accessible No tall structures Better safety September 10, 2012JGW-G1201259 (LIGO-G1200939)5

6. The Type-A KAGRA-SAS Seismic Attenuation System A modern, simplified and improved version of the Virgo Superattenuators Guaranteed performance Eliminate its main defects – GAS replaces MAS filters – damping stage added at top September 10, 20126JGW-G1201259 (LIGO-G1200939)

7. September 10, 20127 Thermal Noise Measured Upper Limit Attenuation measurements. courtesy F. Frasconi JGW-G1201259 (LIGO-G1200939)

8. Improvements over Virgo: damping strategy Mode damping is vital for easy locking of the interferometer One extra filter is added at the beginning of the chain it is coupled with a suspended magnet ring to provide passive Eddy current damping for the attenuation chain yaw and other internal modes. September 10, 20128JGW-G1201259 (LIGO-G1200939)

9. Transversal mode damping seismic noise level of chain’s TM, with/without Eddy current damping September 10, 2012JGW-G1201259 (LIGO-G1200939)9 IP modes Chain modes

10. Lowest mode damping RMS amplitude reduction using shadowmeter on suspension wire September 10, 201210JGW-G1201259 (LIGO-G1200939)

11. Backup damping active seismic attenuation Accelerometers onboard similar to TAMA accelerometers. Improved at AEI and NIKHEF Or feed-forward from ground September 10, 2012JGW-G1201259 (LIGO-G1200939)11

12. KAGRA pre-isolator pedigree The KAGRA SAS pre-isolator was successfully tested in the a-LIGO HAM SAS, further improved at AEI SAS and Virgo-NIKHEF SAS Performs passively the same functions of all three a-LIGO active stages. September 10, 201212JGW-G1201259 (LIGO-G1200939)

13. Secondary optics general concept Used for beam splitter and six recycler mirrors 1500 mm diameter tank Easy access to optics and optical bench from one port without entering Easily Relocatable September 10, 201213JGW-G1201259 (LIGO-G1200939)

14. Attenuation chain Pre attenuator = inverted pendulum + top filter Standard filter with Eddy current damper Bottom filter Intermediate mass and its recoil mass Mirror and its recoil mass Design drawings T1100450T1100450 andD1200818D1200818 September 10, 201214JGW-G1201259 (LIGO-G1200939)

15. The four components of type-B External structure Vacuum tank Attenuation chain Optical bench Also see G1200806G1200806 September 10, 201215JGW-G1201259 (LIGO-G1200939)

16. External structure Mechanically Independent from noisy vacuum tank Magnetic feet to satisfy relocation requirements Also see T1100638T1100638 September 10, 201216JGW-G1201259 (LIGO-G1200939)

17. Canned in 2 sub-units for travel and fast installation September 10, 2012JGW-G1201259 (LIGO-G1200939)17

18. All 19 standard filters produced, assembled & tested. Stored at Akeno September 10, 201218JGW-G1201259 (LIGO-G1200939)

19. SAS Project advancement Design/construction (*) six out of eleven top filters to be completed within 2010/2012 budget September 10, 2012JGW-G1201259 (LIGO-G1200939)19

20. KAGRA- SAS Project status 2010/2012 budget ( ~ 2 M$ including design and manpower) – Completed design of all components – Completed prototypes of all critical components – Built all standard filters (UHV comp. and tested) – Build 6 out of 11 Top filters 2013/2015 budget (t.b.d.) – Complete construction of all SAS and vacuum tanks September 10, 2012JGW-G1201259 (LIGO-G1200939)20