1. Kazuaki Kuroda On behalf of LCGT Collaboration
Status of LCGT project
Kazuaki Kuroda
On behalf of LCGT Collaboration
3rd ET
23-November, 2010

2. Objective of LCGT
LCGT plans to take part in the race of the first　detection of gravitational wave – Its uniqueness may lead to the basis of the third generation detector
It is also expected to play a key station in Asia in the worldwide GW network
Adv. LIGO and Adv. Virgo have similar sensitivity. GEOHF will cover high frequency region.

3. Target GW Sources of LCGT
1. Coalescence of neutron star binaries
2. Coalescence of black hole binaries
3. Core collapse of massive stars
4. Rotation of pulsar
Higher priority
Existing neutron star binaries in our Galaxy
PSR B
PSR B
PSR J
PSR J
PSR J
quasi-mode
oscillation
coalescence
chirp signal
-300Hz
-1kHz
msec

4. Sensitivity of LCGT and future improvement
This figure will be revised
soon by new design

5. ＬＣＧＴ in World-wide GW Network
１）Increase the large baseline length （20 ms time flight among North America, Europe and Asia）
２）Widen the sensitivity pattern
Adding LCGT to L/H-L/L-Virgo, the whole sky coverage is realized
33% coverage
100% coverage
By global network
@B. Schutz(Fujihara seminar, May 2009)

6. Characteristics of LCGT
The interferometer of LCGT belongs to the second and half generation detector
operated underground environment
utilizing cryogenics
Cryogenic leaves the optical design of LCGT rather conservative
Traditional size of the beam (no need of larger optics)
Less thermal lens effect (no need of TCS system on main mirror)
Less serious optical instability
New advanced technologies arising from cryogenic mirror system
Mirror exposed to room temperature wall
Quiet refrigerator system is needed

7. The merit of underground At Kamioka low frequency noise is less than TAMA site by 30 times.
20m Prototype detector installed
The seismic noise of Mitaka is
equivalent to continuous blast-
ing in Kamioka underground.

8. Merit of Underground 20m prototype interferometer was moved
from Mitaka to Kamioka underground in 1998
Blue: at Mitaka
Red: underground Kamioka
Green: limit by isolation system
Displacement spectrum m/RHz Hz

9. Achieved sensitivity by TAMA
Almost all noise sources that limit TAMA sensitivity have been recognized.
Low frequency region of TAMA sensitivity is limited by up-conversion noise

10. Cryogenic mirror was established by several basic experiments.
Cooling test
Cryogenic mirror was established
by several basic experiments.
Contamination test
Mechanical Q test
Original schematic diagram of cryo-mirror

11. Quiet Refrigerator system with anti-vibration system
Cryostat used in CLIO
at the factory of Toshiba
(in 2003)

12. Heat radiated by cold surface was Not correctly considered in design
Heat reflected by cold surface
was correctly calculated
by simulation, which coincided well
with experiment
This is utilized in LCGT

13. Achieved thermal noise limit by CLIO
Mirror suspension thermal
--inversely proportional to f 2.5
Thermal noise limit by eddy
current damping between actuator
magnets and metal solenoid holder
--inversely proportional to f 2
This thermal limit at room
temperature was broken
by cryogenics in March, 2010
Displacement noise 1/√Hz
Mirror thermal
Frequency

14. Quality selection device of sapphire substrate
In order to cope with large optical loss of sapphire substrate,
quality selection of sapphire pieces has been developed.
LIGO sapphire substrate, 250mm in diameter
29kg lent by the courtesy of LIGO.
Auto scanning birefringence device

15. Initial and baseline LCGT
Initial LCGT without cryogenic mirror will be operated by October, 2014, in order to show an engineering result (First Step that should be fulfilled)
The initial LCGT forms the main part of Baseline LCGT (except recycling and cryogenics)
Synthesized silica for the initial LCGT mirror and sapphire for the baseline LCGT
Since cryostats cannot be physically installed after the initial LCGT, the main bodies of cryostats are installed at the first stage
Tall anti-vibration system may be installed in the first phase

16. LCGT Organization for Construction

17. LCGT: Time line (Budget)
We will hear the final decision at the end of 2010.

18. Optical design of LCGT (main part)
These main parameters determine
backbone of optical configuration and
reachable sensitivity
Beam radius 3cm
Beam radius 3cm

19. Design parameters
In order to attain the sensitivity to catch the event at ~250Mpc,
we need ~800kW optical power (~400 kW each cavity) to reduce
shot noise.
Thermal noise of the mirror, coating of the mirror, and
suspension need to be suppressed by cryogenic temperature,
20K. Mechanical losses of these parts are required to satisfy
this thermal noise limit; they are10-8, 4X10-4, 10-8
Final sensitivity is
limited by quantum noises
in the observation frequency
band, 230Hz. Radiation
pressure noise is determined
both by the optical power
and by mass, 30kg.
800kW

20. Design of Vacuum system (Center room)①

21. Three types of anti-vibration system
Type A) SAS(GASF 3stage)+cryo-sus: ITMX, ITMY, ETMX, ETMY
Type B) SAS(GASF 2stage)+non-cryo: BS, PR2, PR3, SR2, SR3, MC2F, MC2E
Type C) STACK+2stages: MC1F, MC1E, MMT, PD
2 m
2 m m
4.3 m
1-2 m
3 m

22. Data Analysis
It is difficult to detect burst wave events by a single detector
Coherent observation gives more fruitful result
It is natural to promote data-sharing in the world-wide GW observation network
We have experienced data taking & analysis by TAMA and CLIO
Need to find flexible way to satisfy requirements of both program and science

23. Projects underground at Kamioka
LCGT is planed to be built underground at Kamioka, where the prototype CLIO detector is placed.

24. Schedule of LCGT coincides with the original GWIC roadmap
Edited in November, 2009
Construction schedule

25. International collaborations with other projects
Attachment agreed under existing MOU between ICRR (represents LCGT Collaboration) and LIGO laboratory
Manpower, software & technique exchanged
MOU with Attachment between VIRGO (EGO + Virgo Collaboration) and ICRR is now on process to be signed
MOU between ICRR and GEO people is also conceived

26. Summary
LCGT has been partially funded (June, 2010) to promote fundamental physics by GW detection
LCGT is expected to play a key role in the worldwide GW network with adv. LIGO, adv. Virgo and possible other observatories
LCGT will become a prototype model of ET
Researchers who are interested in the gravitational wave astronomy and LCGT from overseas are welcome to LCGT