Research and Development for Large-Scale Cryogenic Gravitational Wave Telescope (LCGT)

Norikatsu MioDepartment of Advanced

Materials Science,University of Tokyo

Contents

What is LCGT ?Key technologies to LCGTR&D activities for LCGTSummary

LCGT： Japanese future project

3-km interferometer at Kamioka mineCryogenic system to reduce thermal noise

Budget for LCGT has not been approved!

Optical Design of LCGT

Noise budget

N1∝N∝

LCGT ： quantum-noise-limited sensitivity

Key technologies to LCGT

Cryogenic mirrors Cooling technology (Next talk)

Operation of cryogenic interferometerCLIO: 100-m cryogenic interferometer (ICRR)

High-power laser100-W Nd:YAG laser (U-Tokyo)

etc

Cryogenic laser interferometer observatory: CLIO

100-m cryogenic interferometer detector in Kamioka

Kamioka Observatory

CLIO＆KLIS

Optical layout of CLIO

Locked-Fabry-Perot-type interferometer

Target sensitivity of CLIO

Laser: Nd:YAG

1064nm, 2W

Finesse: 7500

Mirror: Sapphire

20 K, 1.8 kg, Q ~108

SQL　at 100 Hz

CLIO Photos

Entrance

Arm tunnel

Center room

Vacuum pipe

Kamioka laser interferometric strainmeter: KLIS

100-m laser interferometric strainmeter

High-power laser

Quantum-noise limited sensitivityAchieve the required detection level

Cooling capabilityAbsorbed power < refrigerating power

1kW at BS of interferometerRecycling gain of 10 and input optics efficiency of 33% are assumed

Necessary laser power => 300W

Design of laser system

LD-pumped Nd:YAG laser system (1.06µm)100-W Master-Slave Injection Lock laser

Master(2W)->1st Slave (10W)->2nd Slave 100WSaturated power amplifier (100W->300W)

Second slave laser and amplifier

Under development P > 100WStanford (USA) (slab)Laser Zentrum Hannovor (Germany) (rod)Adelaide (Australia) (slab)U-Tokyo+Mitsubishi (Japan) (rod)

High-quality & high-power laser

Thermal birefringence compensation

Uniform pumpingby diffusive reflector

Two rods and rotatorBy Mitsubishi

Laser module

Nd:YAG rods rotator Diffusive reflector +LD

Linear cavity configuration

Convex mirrors （Curvature: 20cm)R=85％ Output couplerP =60 W and M2 =1.12

Ring cavity configuration

PreliminaryTotal output power: 39 W (Self-injection)

Double-module cavity for 100-W output power

Ring cavity with two laser modulesSecond module will be installed, next year

Summary

R&D activities for Japanese future project, LCGT are on going in Japan.CLIO & KLIS are being constructed in Kamioka mine; KLIS can be operated.100-W prototype laser system for LCGT is being developed.