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Thermal Compensation Initial Results Dave Ottaway Mike Smith, Phil Willems, Cheryl Vorvick, Gerado Moreno, Ken Mason, Stefan Ballmer and Daniel Sigg. ?. Initial LIGO Thermal Compensation Concept. CO 2 Laser. ZnSe Viewport. Over-heat pattern Inner radius = 4cm Outer radius =11cm.
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Thermal Compensation Initial Results Dave Ottaway Mike Smith, Phil Willems, Cheryl Vorvick, Gerado Moreno, Ken Mason, Stefan Ballmer and Daniel Sigg LIGO Laboratory
? Initial LIGO Thermal Compensation Concept CO2 Laser ZnSe Viewport Over-heat pattern Inner radius = 4cm Outer radius =11cm Over-heat Correction Under-heat Correction Inhomogeneous Correction • Image target onto the TM limits the effect of diffraction spreading • Modeling by Phil Willems suggests a centering tolerance of 10 mm required LIGO Laboratory
Thermal Compensation Implementation LIGO Laboratory
Thermal Compensation Projector Annulus Mask Central Heat Masks No Masks • Intensity variations across the images due to small laser spot size • Modeling suggests that this should not be an issue • Projection optics work well • Images taken at 1 Watt CO2 Power (AOM distortion above 3 W) LIGO Laboratory
Thermal Compensation Controls LIGO Laboratory
PRM Results – Mode Images AS Port No Heating 30 mW 60 mW 90 mW 120 mW 150 mW 180 mW Carrier LIGO Laboratory
PRM Results –Sideband build-up • Max ~90 mW • 30 mW Steps • Wavefront sensing controlled PRM LIGO Laboratory
PRM Optical Gain during heating LIGO Laboratory
Full Interferometer Results • Lock interferometer at 1 Watt • Apply 90 mW Common central heating • Started to reduce central heating • Max with 45 mW heating, then reduce heating to 22.5 mW • No change in AS_DC ???? LIGO Laboratory
Summary of Results State SPOB GSB -------------------------------------------------------------------------------- State 2 cold 85 7.0 State 2 hot (90 mW CO2) 152 12.5 State 2 max (tRM / (1 - rRM rM rITM))2 14 -------------------------------------------------------------------------------- State 4 cold 160 13 State 4 warm (0.8W input) 190 16 State 4 hot (2.3W input, no TCS) 240 20 State 4 hot (0.8W input, 45mW CO2) 320 26.5 State 4 max (tRM / (1 - rRM rM))2 30 -------------------------------------------------------------------------------- LIGO Laboratory
Asymmetric Heating • Maximum achieved with 120 mW on single ITM • SPOB build-up is the same as common heating LIGO Laboratory
PRM Asymmetric Heating – Optical Gain LIGO Laboratory