gravitational wave detector Yuta Michimura Department of Physics, - - PowerPoint PPT Presentation

Science with even smaller scale space gravitational wave detector

Yuta Michimura

Department of Physics, University of Tokyo

November 28, 2019 Ando Lab Seminar

Contents

• Introduction
• Deci-hertz GW astronomy
• How to proceed with DECIGO
• Recap of F-DECIGO plan (60 km, 2 kg)
• Concept
• Science cases (including dark matter)
• FF-DECIGO plan (100 m, 100 g)
• Background
• Concept
• Science cases (especially stochastic background)
• Possibility of longer arms
• Summary

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Deci-hertz GW Astronomy

• Even more interest

after the dawn of GW astronomy

• Intermediate-mass BH
• IMRIs
• White dwarf binary

and Type Ia SNe

• Stochastic background
• Dark matter search

(Ultralight boson from BH superradiance)

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arXiv:1908.11375

Detectors We Usually Discuss

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B-DECIGO LISA

Cosmic Explorer Einstein Telescope aLIGO KAGRA

LISA: https://perf-lisa.in2p3.fr/ TianQin: arXiv:1902.04423 (from Yi-Ming Hu) B-DECIGO: PTEP 2016, 093E01 (2016) KAGRA: PRD 97, 122003 (2018) aLIGO: LIGO-T1800044 ET: http://www.et-gw.eu/index.php/etdsdocument CE: CQG 34, 044001 (2017)

TianQin

Other Proposals

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• There are so many proposals in deci-hertz band

(this is not a complete list at all!)

Zoo of Proposals

• DECIGO CQG 28, 094011 (2011)
• ALIA arXiv:1907.11305 (post LISA, 500,000 km)
• BBO CQG 23 4887 (2006) (post LISA, 50,000 km)
• TOBA PRL 105, 161101 (2010) (10m torsion bar)
• GEOGRAWI arXiv:1111.2576 (73,000 km LISA) -> gLISA arXiv:1608.04790
• GADFLI arXiv:1111.3708 (73,000 km LISA)
• LAGRANGE arXiv:1111.5264 (660,000 km LISA)
• OMEGA white paper (2011) (1,000,000 km LISA)
• SAGE arXiv:1811.04743 (Sagnac interferometer)
• AMIGO arXiv:1709.05659
• MAGIS arXiv:1711.02225 (atom interferometer)
• Taiji arXiv:1807.09495 (almost LISA)
• INO arXiv:1809.10317 (optical lattice clocks)
• SAGE arXiv:1907.03867 (atom interferometer or atomic clocks)
• TianGO arXiv:1908.06004 (100 km, 10 kg Michelson with squeezing)
• DO arXiv:1908.11375 (1e8 m LISA, Voyage2050)
• SOGRO IJMPD 28, 1940001 (2019) (superconducting)

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Comparison of Proposals

• Wei-Tou Ni, IJMPD 25, 1630001 (2016)
• Almost every proposal is LISA-type

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How to Proceed with DECIGO?

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• There’s a high possibility that DECIGO require

international collaboration

• But almost all the other proposals are LISA-type
• Fabry-Pérot type pathfinder is necessary to show

the feasibility, and we might be the only ones who think it is necessary

• We want to do it quick and yet we want to do some

science → Small-scale mission (公募型小型) Launch with Epsilon rocket 150億円

Meeting on Nov 21, 2019 @ JAXA

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• Akutsu-san, Izumi-san, Ito-san, Shoda-san, me
• Meeting to define DECIGO mission

やばいものリスト

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• Fabrication and handling of large mirror
• Telescope
• Inside or outside of the cavity ?
• Adaptive optics ?
• Inertial sensor and thruster
• Length sensing and control vs orbit
• Link acquisition
• Force / acceleration noise requirement

やばいものリスト

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• Fabrication and handling of large mirror
• Telescope
• Inside or outside of the cavity ?
• Adaptive optics ?
• Inertial sensor and thruster
• Length sensing and control vs orbit
• Link acquisition
• Force / acceleration noise requirement

→ Some part can be demonstrated with small-scale mission

Recap of F-DECIGO Concept

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• Minimum success:

Formation flight demonstration

• Full success:

End-to-end demonstration of the sensitivity Force noise evaluation

• Extra success:

Multi-wavelength GW observation Intermediate mass BH search

• Use already-demonstrated

parameters

F-DECIGO Designed Sensitivity

• 60 km, 2 kg, finesse 10, 10 mW, 4e-15 N/rtHz

13

B-DECIGO LISA TianQin

F-DECIGO Horizon Distance

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B-DECIGO LISA TianQin

CE ET aLIGO

GW150914 GW170817

Optimal direction and polarization SNR threshold 8

z=10 z=1

KAGRA

O1 and O2 binaries plotted

F-DECIGO

IMBH search upto z~1

F-DECIGO Science Cases

• First real IMBH search

48 event/year (SNR>8, optimistic)

• H. Shinkai+, ApJ 835, 276 (2017)
• Estimate merger time and location of BNS

For 1.4 Msun-1.4 Msun @ 40 Mpc, ~100 sec and 103 deg2 precision is possible But SNR is around 2

• H. Takeda+,

PRD 98, 022008 (2018)

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week day hour ISCO week day hour ISCO week day hour ISCO Observation from a month before the merger Median over the angles

Dark Matter Search also Possible

• Axion search with polarization measurement
• K. Nagano, T. Fujita, YM, I. Obata, PRL 123, 111301 (2019)
• Vector DM which couples to B-L charge
• A. Pierce+, PRL 121, 061102 (2018)
• Sensitivity not very good

16 aLIGO DECIGO F-DECIGO LISA Equivalence principle tests F-DECIGO CAST

Cosmic Explorer DECIGO aLIGO

SN1987A

• 4e-15 N/√Hz force noise (Residual gas of 1e-6 Pa)

Demonstrated by LISA Pathfinder

PRL 120, 061101 (2018)

• 2 kg mirror and housing, vacuum tank

Similar to LISA Pathfinder

• 60 km arm length

GRACE-FO demonstrated 200 km Link acquisition is also demonstrated

PRL 123, 031101 (2019)

Technical Feasibility

17 DECIGO requirement is 1e-16 N/√Hz GFO proof mass is 72 g

• April 2019: C-DECIGO (10 km, 10 kg) proposal at Ando

Group Midterm Seminar (slide)

• May 2019: C-DECIGO (10 km, 10 kg) proposal at FF

meetup (slide)

• > downgraded to F-DECIGO (10 km, 2 kg) to reduce mass
• Sep 2019: Refined F-DECIGO plan (60 km, 2 kg) assuming

LPF-level force noise and focusing on applying to 公募型小 型 at JPS meeting (slide)

• Nov 2019: 60 km, 2 kg plan presented at DECIGO

workshop (slide), Letter of Intent to 公募型小型

• > 100 m and 100 g plan (Let’s call it FF-DECIGO) was

proposed from the limitation of Epsilon rocket and actuation dynamic range

History of Iterations

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• 180 kg / satellite @ 800 km altitude would be

realistic to launch with Epsilon (previously we are

thinking of 350 kg / satellite @ 1800 km)

• 25 kg package with 72 g proof mass was used for

GRACE-FO and probably similar for small-scale mission

• Relative acceleration from J2 term being too much

in geocentric orbit

Why 100 m and 100 g

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Arm length J2 coefficient Earth gravity constant Earth radius Orbital altitude

• Relative force from J2 is constant if m*L=const.
• m*L = 100 g * 100 m gives 4e-8 N from J2
• Force noise requirement 4e-15 N/rtHz
• Dynamic range 107 should be within our reach

(~109 with good analog circuits)

Relative Force from J2 Term

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6400 km 800 km 1800 km

60 km * 2 kg detector at 1800 km → 2e-4 N from J2 100 m * 100 g detector at 800 km → 4e-8 N from J2

Calculation done with T. Ito’s code

• If orbital altitude and dynamic range is given,

achievable strain sensitivity can be calculated

• You cannot win by increasing m or L !!!

J2 Term and Sensitivity

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with altitude 800 km and dynamic range 107

dynamic range

• Focus on the demonstration of formation flying and

the demonstration of the end-to-end demonstration as a gravitational wave detector

• By (kind of) giving up GW detection

FF-DECIGO Concept

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• Finesse can be higher than F-DECIGO, upto

radiation pressure noise being ~4e-15 N/rtHz

FF-DECIGO Finesse

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Shot noise

1e-21/rtHz 5e-22/rtHz

FF-DECIGO

F-DECIGO B-DECIGO

Assumed mirror g-factor = 0.3 diameter/thickness = 5 wavelength 515 nm

• 100 m, 100 g, finesse 1000, 10 mW, 4e-15 N/rtHz

FF-DECIGO Designed Sensitivity

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FF-DECIGO

TOBA

B-DECIGO LISA TianQin

FF-DECIGO Horizon Distance

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B-DECIGO LISA TianQin

CE ET aLIGO

GW150914 GW170817

z=10 z=1

KAGRA

F-DECIGO FF-DECIGO TOBA

• IMBH probably O(10-8) event / year
• Dark matter search worse than F-DECIGO
• Upper limit to stochastic GW background

FF-DECIGO Science Case

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Data from Y. Kuwahara

FF-DECIGO

• Worth a try if we can do faster than LISA, TianQin

and 3G (and SOGRO etc.)

Comparison with Other Proposals

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B-DECIGO LISA TianQin FF-DECIGO

• Improvement by many orders of magnitude

Comparison with Prototypes

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TorPeDO prototype Phase 3 TOBA Prototype TOBAs

Phase 1 Phase 2 Phase 2.5 Cryo

Data from T. Shimoda

LISA Pathfinder 1.96 kg, 38 cm

• Sensitivity and horizon distance scales linearly with

arm length if intra-cavity power is constant

• Can be longer

upto ~2 km

from diffraction loss

Possibility of Longer Arms

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Shot noise

1e-21/rtHz 5e-22/rtHz

FF-DECIGO

F-DECIGO B-DECIGO

and J2 term is somehow OK

• Assume mode-match is designed for 100 m and

arm length is changed in orbit

• Sensitivity scales almost linearly upto ~1 km with

larger g-factor

Mode-Match Degradation

30 Only mode mismatch Including diffraction loss Compensation could be possible with adaptive optics and mode match tuning

• F-DECIGO (60 km, 2 kg) might not be possible but

FF-DECIGO (100 m, 100 g) could be possible with Epsilon-class mission

• Considering J2 term, if altitude and dynamic range

is fixed, achievable strain sensitivity can be calculated and you cannot win by increasing the mirror mass or arm length

• Almost no chance of FF-DECIGO detect

gravitational waves, but still it can search for stochastic GW background with unpreceded sensitivity at ~1 Hz

• Changing the arm length in orbit sounds feasible

Summary

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