1. Sora HEPL Seminar Feb. 11, 2009 @ Stanford Univ. Seiji Kawamura (National Astronomical Observatory of Japan)

2. Outline Gravitational wave DECIGO DECIGO pathfinder Summary Appendix –Displacement noise free interferometer –Juggling interferometer

3. Distortion of space ~ 10 -23 Not yet detected! Predicted by Einstein Emitted from accelerating objects Propagates as tidal distortion of space Gravitational wave

4. GW Sources Neutron star / black hole binaries Supernova Beginning of the universe Etc.

5. 380,000 year (Transparent to radiation) EM 1 sec (Formation of Proton, Neutron) Neutrino How far (old) can we see? Beginning of the universe 13.7 billion year (Now) GW 10 -43 sec (Planck time ）

6. Gravitational wave astronomy

7. Detection of GW by laser interferometer Laser Interfering beam Beam splitter Suspended Mirror Detector

8. The longer arm length gives larger signals! Laser Photodetector Mirror Laser Photodetector Mirror

9. Large-scale detectors LIGO (4 km) VIRGO (3 km) GEO (600 m) TAMA (300 m) CLIO (100 m) LCGT (3 km)

10. Recycling mirror: Increase effective laser power Standard optical configuration Fabry-Perot arm cavity Enhance GW signals

11. Laser Interferometer in Space Signal increased - Due to longer interaction between GW and light - Cancellation of signals at higher frequencies Noise reduced - Lower seismic noise and gravity gradient noise Sensitivity improved at lower frequencies

12. LISA Arm length: 5,000,000km Frequency range: 1 mHz - 0.1 Hz Target Source: White dwarf binary, Giant BH coalescence Optical configuration: Light transponder LISA project

13. What is DECIGO? Deci-hertz Interferometer Gravitational Wave Observatory ( Kawamura, et al., CQG 23 (2006) S125-S131) Bridges the gap between LISA and terrestrial detectors Low confusion noise -> Extremely high sensitivity 10 -18 10 -24 10 -22 10 -20 10 -4 10 4 10 2 10 0 10 -2 Frequency [Hz] Strain [Hz -1/2 ] LISA DECIGO Terrestrial detectors (e.g. LCGT) Confusion Noise moved above LISA band To be moved into TD band

14. Pre-conceptual design Differential FP interferometer Arm length: 1000 km Mirror diameter: 1 m Laser wavelength ： 0.532  m Finesse: 10 Laser power: 10 W Mirror mass: 100 kg S/C: drag free 3 interferometers Laser Photo- detector Arm cavity Drag-free S/C Arm cavity Mirror

15. Why FP cavity? Frequency Strain Radiation pressure noise f -2 Shot noise Shot noise f 1 Transponder type (e.g. LISA) Shot noise Shorten arm length Shot noise f 1 Radiation pressure noise f -2 Transponder type (e.g. LISA) Shorten arm length Implement FP cavity FP cavity type Better best- sensitivity

16. Drag free and FP cavity: compatible? Mirror S/C I S/C II

17. FP cavity and drag free : compatible? Local sensor Thruster Mirror Relative position between mirror and S/C S/C II S/C I

18. Drag free and FP cavity: compatible? Local sensor Thruster Mirror Relative position between mirror and S/C Actuator Interferometer output (GW signal) S/C II S/C I No signal mixture

19. Orbit and constellation (preliminary) Sun Earth Record disk Increase angular resolution Correlation for stochastic background

20. Science by DECIGO (1) Formation of Super- massive BH Frequency [Hz] Strain [Hz -1/2 ] 10 -3 10 -2 10 -1 1 10 10 2 10 3 10 -19 10 -20 10 -21 10 -22 10 -23 10 -24 10 -25 10 -26 (1000 M ◎ z=1) BH binary Coalescence Radiation pressure noise Shot noise 1 cluster

21. Science by DECIGO (2) Frequency [Hz] Strain [Hz -1/2 ] 10 -3 10 -2 10 -1 1 10 10 2 10 3 10 -19 10 -20 10 -21 10 -22 10 -23 10 -24 10 -25 10 -26 5 years NS binary (z=1) Coalescence 3 months Acceleration of Universe ⇓ Dark energy Radiation pressure noise Shot noise 1 cluster

22. Acceleration of Expansion of the Universe NS-NS (z ～ 1) GW DECIGO Output Expansion ＋ Acceleration? Time Strain Template (No Acceleration) Real Signal ? Phase Delay ～ 1sec (10 years) Seto, Kawamura, Nakamura, PRL 87, 221103 (2001)

23. Science by DECIGO (3) Inflation (  GW =2  10 -16 ) Verification of inflation Frequency [Hz] Correlation (3 years) Strain [Hz -1/2 ] 10 -3 10 -2 10 -1 1 10 10 2 10 3 10 -19 10 -20 10 -21 10 -22 10 -23 10 -24 10 -25 10 -26 Radiation pressure noise Shot noise 1 cluster

24. Requirements Acceleration noise should be suppressed below radiation pressure noise –Force noise: DECIGO = LISA/50 (Acceleration noise in terms of h: 1, Distance: 1/5000, Mass: 100) –Fluctuation of magnetic field, electric field, gravitational field, temperature, pressure, etc. Sensor noise should be suppressed below shot noise. –Phase noise: DECIGO = LCGT×10 (Sensor noise in terms of h: 1, storage time: 10) –Frequency noise, intensity noise, beam jitter, etc. Thruster system should satisfy range, noise, bandwidth, and durability.

25. Roadmap 200708091011121314151617181920212223242526 Mission Objectives Test of key technologies Observation run of GW Detection of GW w/ minimum spec. Test FP cavity between S/C Full GW astronomy Scope 1 S/C 1 arm 3 S/C 1 interferometer 3 S/C, 3 interferometer 3 or 4 units DICIGO Pathfinder (DPF) Pre-DECIGO DECIGO R&D Fabrication R&D Fabrication R&D Fabrication

26. DECIGO Pathfinder (DPF) Laser PD Floating Mirrors Drag-free S/C DECIGO DPF 30 cm 1,000 km Shrink the arm length from 1,000 km to 30 cm

27. Conceptual design and Technologies to demonstrate Thruster Local Sensor Floating mirror Stabilization system Laser Actuator Drag-free control system Laser source and stabilization system Control of Fabry-Perot interferometer Launch-lock system

28. Goal sensitivity of DPF

29. Expected sources

30. JAXA ’ s Small science satellite series Plan to launch 3 small satellites between 2011 and 2015 –using next-generation solid rocket booster Reduce time and cost by means of ‘ Standard bus system ’ –Bus weight : ~ 200kg, Bus power : ~ 800W –Downlink ~ 2Mbps, Data storage ~ 1GByte –3-axes attitude control –SpaceWire-based data processing system We submitted a proposal for DPF

31. In June 2007, I attended the LIGO PAC meeting at Caltech, and we were invited to dinner at a Chinese restaurant.

32. We gained momentum! DPF was selected as one of the 4 important mission candidates for small science satellite series run by JAXA/ISAS.

33. DPF S/C Size : 900mm cube Weight : 200kg SAP : 800W Battery: 50AH Downlink : 2Mpbs DR: 1GByte 3N Thrusters x 4 Stabilized Laser Interferometer Module Thruster Control Unit Solar Paddle Interfererometer Control Unit Housing Control Unit Mission Thrusters Central Processing Unit Bus Thrusters Satellite Bus (‘Standard bus’ system) DPF Payload Size : 900mm cube Weight : 100kg Power : 200W Data Rate: 600kbps Mission thruster x16 Power Supply SpW Comm.

34. DPF Mission Outline Orbit: Low-Earth (Altitude 500km), Sun-synchronous orbit (dusk-dawn) Launcher: Single launch by M-V follow-on (solid rocket booster under development) PBS (Post-Boost stage) for fine orbit insertion Launch: 2012 (target) Mission Lifetime: 1 year (nominal) 500km DPF Attitude Control: Gravity-gradient stab. Drag-free control with mission thrusters (Safe hold control by bus thrusters)

35. History and Future 2006 Nov. Submitted a proposal of DPF 2007 Jun. Fortune cookie 2007 Aug. Selected as a Pre-Phase-A mission R&D costs funded 2008 Sep. Submitted Phase-A proposal 2008 Dec. Hearing held for selecting the 2 nd mission 2009 Mar. 2 nd mission will be selected

36. Pre-DECIGO DECIGO Arm length100 km1000 km Mirror diameter30 cm1 m Laser wavelength 0.532  m Finesse3010 Laser power1 W10 W Mirror mass30 kg100 kg # of interferometers in each cluster 13 # of clusters14

37. Sensitivity of Pre-DECIGO S/N~14 for NS-NS@300Mpc, 10-20 events/year

38. Interim organization PI: Kawamura (NAOJ) Deputy: Ando (Kyoto) Executive Committee Kawamura (NAOJ), Ando (Kyoto), Seto (NAOJ), Nakamura (Kyoto), Tsubono (Tokyo), Tanaka (Kyoto), Funaki (ISAS), Numata (Maryland), Sato (Hosei), Kanda (Osaka city), Takashima (ISAS), Ioka (Kyoto) Pre-DECIGO Sato (Hosei) Satellite Funaki (ISAS) Science, Data Tanaka (Kyoto) Seto (NAOJ) Kanda (Osaka city) DECIGO pathfinder Leader: Ando (Kyoto) Deputy: Takashima (ISAS ) Detector Ando (Kyoto) Housing Sato (Hosei) Laser Ueda (ILS) Musya (ILS) Drag free Moriwaki (Tokyo) Sakai (ISAS) Thruster Funaki (ISAS) Bus Takashima (ISAS) Data Kanda (Osaka city) Detector Numata (Maryland) Ando (Tokyo) Mission phase Design phase

39. DECIGO-WG Seiji Kawamura, Masaki Ando, Takashi Nakamura, Kimio Tsubono, Naoki Seto, Shuichi Sato, Kenji Numata, Nobuyuki Kanda, Ikkoh Funaki, Takeshi Takashima, Takahiro Tanaka, Kunihito Ioka, Kazuhiro Agatsuma, Koh-suke Aoyanagi, Koji Arai, Akito Araya, Hideki Asada, Yoichi Aso, Takeshi Chiba, Toshikazu Ebisuzaki, Yumiko Ejiri, Motohiro Enoki, Yoshiharu Eriguchi, Masa-Katsu Fujimoto, Ryuichi Fujita, Mitsuhiro Fukushima, Toshifumi Futamase, Katsuhiko Ganzu, Tomohiro Harada, Tatsuaki Hashimoto, Kazuhiro Hayama, Wataru Hikida, Yoshiaki Himemoto, Hisashi Hirabayashi, Takashi Hiramatsu, Feng-Lei Hong, Hideyuki Horisawa, Mizuhiko Hosokawa, Kiyotomo Ichiki, Takeshi Ikegami, Kaiki T. Inoue, Koji Ishidoshiro, Hideki Ishihara, Takehiko Ishikawa, Hideharu Ishizaki, Hiroyuki Ito, Yousuke Itoh, Nobuki Kawashima, Fumiko Kawazoe, Naoko Kishimoto, Kenta Kiuchi, Shiho Kobayashi, Kazunori Kohri, Hiroyuki Koizumi, Yasufumi Kojima, Keiko Kokeyama, Wataru Kokuyama, Kei Kotake, Yoshihide Kozai, Hideaki Kudoh, Hiroo Kunimori, Hitoshi Kuninaka, Kazuaki Kuroda, Kei-ichi Maeda, Hideo Matsuhara, Yasushi Mino, Osamu Miyakawa, Shinji Miyoki, Mutsuko Y. Morimoto, Tomoko Morioka, Toshiyuki Morisawa, Shigenori Moriwaki, Shinji Mukohyama, Mitsuru Musha, Shigeo Nagano, Isao Naito, Kouji Nakamura, Hiroyuki Nakano, Kenichi Nakao, Shinichi Nakasuka, Yoshinori Nakayama, Kazuhiro Nakazawa, Erina Nishida, Kazutaka Nishiyama, Atsushi Nishizawa, Yoshito Niwa, Yoshiyuki Obuchi, Masatake Ohashi, Naoko Ohishi, Masashi Ohkawa, Norio Okada, Kouji Onozato, Kenichi Oohara, Norichika Sago, Motoyuki Saijo, Masaaki Sakagami, Shin-ichiro Sakai, Shihori Sakata, Misao Sasaki, Takashi Sato, Masaru Shibata, Hisaaki Shinkai, Kentaro Somiya, Hajime Sotani, Naoshi Sugiyama, Yudai Suwa, Rieko Suzuki, Hideyuki Tagoshi, Fuminobu Takahashi, Kakeru Takahashi, Keitaro Takahashi, Ryutaro Takahashi, Ryuichi Takahashi, Tadayuki Takahashi, Hirotaka Takahashi, Takamori Akiteru, Tadashi Takano, Keisuke Taniguchi, Atsushi Taruya, Hiroyuki Tashiro, Mitsuru Tokuda, Yasuo Torii, Morio Toyoshima, Shinji Tsujikawa, Yoshiki Tsunesada, Akitoshi Ueda, Ken-ichi Ueda, Masayoshi Utashima, Yaka Wakabayashi, Hiroshi Yamakawa, Kazuhiro Yamamoto, Toshitaka Yamazaki, Jun'ichi Yokoyama, Chul-Moon Yoo, Shijun Yoshida, Taizoh Yoshino

40. 1st International LISA-DECIGO Workshop Nov. 12-13, 2008 @ ISAS, Sagamihara, Japan Participants: –Danzmann, Heinzel, Gianolio, Jennrich, Lobo, McNamara, Mueller, Prince, Stebbins, Sun, Vitale, … Accomplishments: –Mutual understanding –Kick-off of collaborations –Exposure of the missions to people in the neighboring fields

41. Collaboration with Stanford UV LED discharge for DPF Other R&D for DECIGO

42. Summary DECIGO can detect GWs from the inflation as well as can bring us extremely interesting science. DPF has been selected as one of the important mission candidates for small science satellite series; they plan to launch 3 missions in 5 years starting from 2011.

43. Let DPF fly!

44. Possible breakthrough for 3rd-generation detectors: Displacement-noise free Interferometer Kawamura and Chen, PRL, 93, (2004) 211103 Chen and Kawamura, PRL, 96 (2006) 231102

45. Motivation Displacement noise: seismic Noise, thermal noise, radiation pressure noise Cancel displacement noise  shot noise limited sensitivity Increase laser power  sensitivity improved indefinitely Frequency Sensitivity Displacement noise Shot noise Laser PD Diplacement noise Cancel displacement noise Increase laser power

46. GW and mirror motion interact with light differently Difference outstanding for GW wavelength  distance between masses Mirror motion GW On propagation On reflection Light

47. Cancel motion of objects Motion of A, B, and C cancelled GW signal remains Clock

48. Why is it possible? # of MQ (4) ＞ # of DOF (3) MQ: Measurable quantity DOF: Degree of freedom Therefore a combination of MQs that is free from DOFs exists!

49. Clock noise? Motion: cancelled Clock noise: not cancelled Clock

50. Why? # of DOF (Clock): 3 # of DOF (Displacement): 3 # of MQ: 4 Therefore it is not always possible to make a combination of MQs that is free from all the DOFs!

51. How can we cope with it? d: # of dimensions, N: # of Objects # of DOF (Displacement) ： Nd # of DOF (Clock) ： N # of DOF (Total) ： N(d+1) # of MQ ： N(N-1) If N(N-1)>N(d+1) i.e. N>d+2 A combination of MQs that is free from DOFs exists!

52. Displacement-noise free interferometer Propagation time measurement  interferometer Motion of object  displacement noise of mirrors Clock noise  laser frequency noise

53. Example of DFI Two 3-d bi-directional MZ Take combination of 4 outputs Mirror motion completely cancelled GW signal remains (f 2 )

54. Experiment (Ideal) One bi-directional MZ GW Mirror motion Laser PD GW  Mirror motion Extract

55. Experiment (Practical) EOM used for GW and mirror motion GW Mirror motion Laser PD Laser PD ～～ Simulated mirror motion Simulated GW Ideal Practical

56. Results Mirror motion GW signal Mirror motion cancels out GW signal remains Mirror motion to output Difference GW signal to output Sato, Kokeyama, Ward, Kawamura, Chen, Pai, Somiya, PRL 98 (2007) 141101

57. Possible breakthrough for 3rd-generation detectors: Juggling Interferometer

58. Motivation 10 -8 10 -9 10 -10 10 -11 10 -12 10 -13 10 -14 10 -15 10 -16 10 -17 10 -18 10 -19 10 -20 1 10 100 Frequency [Hz] Displacement [mHz -1/2 ] Seismic noise Pendulum thermal noise Radiation pressure noise Shot noise Limiting the low- frequency sensitivity Lower frequency gives higher GW signals. Suspension thermal noise and seismic noise are huge at low frequencies. What if we can remove suspension? Magnetic levitation is a kind of suspension. Free-fall experiment is just one shot.

59. km-class juggling interferometer 3 km Laser Fiber Laser beam Beam splitter Clamp Mirror Clamp

60. Simple Interferometer Simple Michelson interferometer –FP cavity is not necessary because the sensitivity is limited by displacement noise at low frequencies anyway No fringe lock –Fringe lock is not necessary because intensity noise can be suppressed and no power recycling is necessary

61. Data processing 1 Produce displacement signal (x) from the two PD outputs Displacement Time

62. Noise caused by juggling x: –Longitudinal position on release fluctuates dx/dt: –Longitudinal velocity on release fluctuates –Angular velocity on release fluctuates, which couples with beam off-centering d 2 x/dt 2 : –Above two effects couple with each other x, dx/dt, d 2 x/dt 2 are constant in each segment

63. Data processing 2 In each segment, calculate,, Remove them from the data

64. Loss of GW signal A part of GW signal especially below 1 Hz is lost during the data processing 2. So is a part of any noise. S/N remains the same?

65. S/N degraded below 1 Hz Shot noise after data processing Original shot noise 0.1 1 10 Frequency [Hz] 10 -15 10 -16 10 -17 10 -18 10 -19 10 -20 Displacement [mHz -1/2 ]

66. Juggling interferometer prototype Moving up and down Time Position ~ 2 m ReleaseHold ContinuallyFreely falling ~ 1 sec Clamp ReleaseHold ReleaseHold