Status of LCGT and CLIO Masatake Ohashi ICRR

Status of LCGT and CLIO Masatake Ohashi (ICRR, The University of of TOKYO) and LCGT, CLIO collaborators TAUP 2007 Sendai, Japan 2007/9/12 TAUP 2007 Sendai Japan 2007/09/12

Contents • LCGT Outline • Status of LCGT – Interferometer Design – Sapphire Mirror and its Suspension – Cryostat and Cooling Technique • Status of CLIO – Present Status as a proto-type of LCGT • Summary TAUP 2007 Sendai Japan 2007/09/12

Large-scale Cryogenic Gravitational wave Telescope （LCGT） 180 Mpc TAUP 2007 Sendai Japan 2007/09/12 illustration: KAGAYA

LCGT Outline • It is 3 km Fabry-Perot interferometer with power recycling and broadband RSE. • Main mirrors made of sapphire are cooled at 20 K. • It is built at underground site in Kamioka Mine. • Two independent interferometers are installed. • The main target is the coalescence of Binary Neutron Starｓ at 180 Mpc. TAUP 2007 Sendai Japan 2007/09/12

LCGT on LIGO Web Next generation IFO from Japan TAUP 2007 Sendai Japan 2007/09/12

Merit of Underground site Seismic activity of Kamioka Mine The point is that Quiet ! at least 100 m below land surface is necessary to prevent wind effect. Seismic activity of city area TAUP 2007 Sendai Japan 2007/09/12

Interferometer Design TAUP 2007 Sendai Japan 2007/09/12

Interferometer Design - Over View 1 - • Detector parameters Mirror Laser Nd: YAG laser (1064 nm) Injection lock + MOPA Power : 150 W Main Interferometer Broad band RSE configuration Baseline length : 3 km Beam Radius : 3 -5 cm Arm cavity Finesse : 1550 Power Recycling Gain : 11 Signal Band Gain : 15 Stored Power : 771 k. W Signal band : 230 Hz Vacuum system Beam duct diameter : 100 cm Pressure : 10 -9 Torr Sapphire substrate + mirror coating Diameter : 25 cm Thickness : 15 cm Mass : 30 kg Absorption Loss : 20 ppm/cm Temperature : 20 K Q = 108 Loss of coating : 10 -4 Final Suspension + heat link with 4 Sapphire fibers Suspension length : 40 cm Fiber diameter : 1. 5 mm Temperature : 16 K Q of final suspension : 108 TAUP 2007 Sendai Japan 2007/09/12

Interferometer Design - Over View 2 - Main IFO : 3 km IFO Input optics : Two MCs, Modulators, MMT Output optics: OMC, Photo detectors TAUP 2007 Sendai Japan 2007/09/12

Interferometer Design 3 km arm - Layout 1 - Center room for IFO-1 Center room for IFO-2 3 km arm Two IFOs share the vacuum pipes TAUP 2007 Sendai Japan 2007/09/12

Interferometer Design - RSE - • Merit of RSE High-finesse cavity and moderate PRG Easier to realize high power in cavities Smaller transmission light in optics Flexible optimization for GW sources Main reason for LCGT Independent adjustment of power in cavities and signal band Narrow-band observation (optional) Absorption in sapphire substrates Heat absorption : 20 ppm/cm x 15 cm = 300 ppm Cooling power : 1 W for each mirror Laser power on BS should be less than ~1 k. W (safety factor 3) TAUP 2007 Sendai Japan 2007/09/12

Sapphire Mirror TAUP 2007 Sendai Japan 2007/09/12

Sapphire Mirror - Absorption - Laser light absorption is important factor for cooling. LCGT requirement : substrate 20 ppm/cm (-> 250 m. W) coating 1 ppm (-> 40 m. W) We need high quality sapphire substrate. TAUP 2007 Sendai Japan 2007/09/12

Sapphire Mirror - Mechanical Quality Factor - Over 108 is obtained TAUP 2007 Sendai Japan 2007/09/12

Sapphire Mirror Loss Angle - Dissipation of the Coating film - Temperature [K] Dissipation is almost independent of Temperature TAUP 2007 Sendai Japan 2007/09/12

Sapphire Mirror Thermal Expansion - Temperature [K] Thermal expansion is negligible at cryogenic temperature. TAUP 2007 Sendai Japan 2007/09/12

Cryogenic Techniques TAUP 2007 Sendai Japan 2007/09/12

Cryogenic Technique - Estimated Heat Generation in the Mirror substrate : Sapphire Suspension rods : Sapphire ・ q=290 m. W Safety factor T=20 K TAUP 2007 Sendai Japan 2007/09/12 Design

Cooling method by a cryocooler TAUP 2007 Sendai Japan 2007/09/12

Seismic Noise Attenuation TAUP 2007 Sendai Japan 2007/09/12

Seismic Attenuation System (SAS) • Inverted pendulum – 30 m. Hz • 3 cascaded GAS filter – 500 m. Hz • Test mass suspension – triple pendulum TAUP 2007 Sendai Japan 2007/09/12

Suspension Point Interferometer (SPI) - Background and Purpose - TAUP 2007 Sendai Japan 2007/09/12

Schedule and Budget 2008 2009 2010 2011 2012 2013 2014 130 M$ without salary and maintenance LCGT proposal is submitted to the Ministry of Education and Science （MEXT) as one of recommended projects of the University of TOKYO. But LCGT will not start at 2008. We will retry next year. TAUP 2007 Sendai Japan 2007/09/12

CLIO TAUP 2007 Sendai Japan 2007/09/12

Cryogenic prototype for LCGT

Overview of CLIO TAUP 2007 Sendai Japan 2007/09/12

Cryostat for an end mirror TAUP 2007 Sendai Japan 2007/09/12

Cooling test and achieved temperature 63 K 8. 8 K 12. 9 K 45 K TAUP 2007 Sendai Japan 2007/09/12

Cooling summary Inline end Inline near Per arm end Per arm near Cooling time 176 hour start 07/06/22, 10: 00 174 hour start 07/06/22, 10: 00 164 hour start 07/04/27, 11: 05 193 hour start 07/08/16, 12: 30 Mirror temp Heat in the suspension Heat at the 1 st cooling 2006/02 13. 5 K 40 m. W N/A 13. 4 K 36 m. W N/A 12. 5 K 62 m. W#1 116 m. W 13. 8 K 29 m. W 109 m. W #1; No shield for radiation from the outer shield at 63 K. TAUP 2007 Sendai Japan 2007/09/12

Low vibration PT refrigerator by KEK and SUMITOMO TAUP 2007 Sendai Japan 2007/09/12

Cryogenic suspension TAUP 2007 Sendai Japan 2007/09/12

Heat Transfer 300 K Radiation from window of Gate Valve warms mirrors Serious Problem for cooling Mirror (20 K) Radiation shield (40 K) 300 K Radiation ( straying ) Gate Valve (300 K) Good Heat Transfer, Baffles, … TAUP 2007 Sendai Japan 2007/09/12

Radiation Shields TAUP 2007 Sendai Japan 2007/09/12

Cooling procedure STEP 3 cooling mirror alignment Cooling shortens suspension by 2 mm STEP 1 cooling mirror alignment STEP 4 cooling mirror alignment STEP 2 cooling mirror alignment TAUP 2007 Sendai Japan 2007/09/12

Expected Noise Spectrum at 20 K Current best (300 K) Target sensitivity (20 K) Resonance of suspension system TAUP 2007 Sendai Japan 2007/09/12

Noise budget for CLIO (300 K) Cooling TAUP 2007 Sendai Japan 2007/09/12

Thermal noise reduced by cooling ? Thermal Noise of Aluminum Wires YES ! TAUP 2007 Sendai Japan 2007/09/12

CLIO Stability Akutsu’s POSTER TAUP 2007 Sendai Japan 2007/09/12

SUMMARY • We will submit LCGT budget request for FY 2009 again next year. • Cryogenic prototype CLIO was completed. Now in commissioning phase. • We demonstrated to operate interferometer with cryogenic mirrors, but careful heat transfer is necessary for cooling. TAUP 2007 Sendai Japan 2007/09/12

European Plan TAUP 2007 Sendai Japan 2007/09/12

Interferometer Design - Layout 2 - Baffle for LCGT Specification of LCGT Tube diameter 1000 mm Mirror diameter 250 mm Mirror distance 600 mm Mirror offset 340 mm -11 m/Hz 1/2@30 Hz Seismic motion 1 x 10 Estimated scattered light noise -21 m/Hz 1/2@30 Hz (Safety factor=7) 4. 2 x 10 (for one mirror) Baffle design Number: 45 x 2 for one arm Height: 35~50 mm Integration Surface: DLC coatings Diamond-Like Carbon (DLC) coatings Each reflection Surface roughness: Ra=20 nm Outgassing : lower than SS 316 with baking Reflectivity: 5% for -p polarization at 45 deg. 1/10 45 TAUP 2007 Sendai Japan 2007/09/12