1 / 23

Thermal Compensation in LIGO

Thermal Compensation in LIGO. Rupal S. Amin. LIGO Layout Thermal Aberrations Thermal Issues Compensation Systems Model Closing Remarks. Outline. ETMy. P ower R ecycled M ichelson. Fabry-Perot Cavity. ITMy. Carrier Resonant Sideband pair Non-resonant sideband pair. RM. ITMx.

darice
Download Presentation

Thermal Compensation in LIGO

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Thermal Compensation in LIGO Rupal S. Amin LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  2. LIGO Layout • Thermal Aberrations • Thermal Issues • Compensation Systems • Model • Closing Remarks Outline LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  3. ETMy Power Recycled Michelson Fabry-Perot Cavity ITMy Carrier Resonant Sideband pair Non-resonant sideband pair RM ITMx ETMx BS Optical Layout LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  4. Causes • HEAT GRADIENT • Thermal Lensing • Thermal Expansion • Induced Birefringence • … • Effects • Differential Expansion Cold  Hot  Aberrations Main Laser Beam Thermal Aberrations LIGO-G0900358. Rupal S. Amin GCGW 17 April 2009

  5. PRM Stability Issues • Not stable for RSB • Cavity g-factor > 1 • No containment in cold state • Contrast Defect • Imbalanced thermal lenses increases junk light output Thermal Issues: eLIGO LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  6. Towards 4 km arm Initial Test Mass Pointing optics CO2 laser light TCS Laser Box Thermal Compensation System LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  7. TCS Hardware LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  8. Need a thermal model of the INTERFEROMETER (Dramatic music) Solution for eLIGO LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  9. 1)Comsol FEM of ITMs 0) Matlab 1 2 Interferograms, t(f) results, Power build up, Beam parameters 2) Matlab 3 FINESSE 4 Model: Matlab+Comsol+Finesse LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  10. Comsol Finite Element Analysis • Simulate mirror heating patterns with and without TCS Inputs: Boundary Conditions Substrate Materials Outputs: Deformed Surface Thermally Dependent n Step 1: FEM of ITMs LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  11. Optical interaction only • No mechanical interactions • No radiation pressure Finesse: http://www.rzg.mpg.de/~adf/ Luxor: http://www.aei.mpg.de/~jah/luxor.html Luxor GUI config builder Config file With layout and simple instructions Step 2: In-house sim. code LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  12. LHO AS patterns Mich only Jan 15, 2009 Simulated Interferogram K. Dooley ilog LHO Step 3: FEM + Simulation LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  13. Interferometers require thermal compensation to maintain stability at high power • Thermal model construction in progress • Sensible control signals are needed • Cannot assume that new TCS behave exactly like old TCS Closing LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  14. Special Thanks to • J. Giaime LSU Associate Prof. of Physics • Phil WillemsTCS Group Leader CIT • Aidan Brooks • Cheryl Vorvick • Carl Adams • ViginioSannibale • MohanaMageswaran • NSF grant number: • NSF-PHY-0605496 Thanks to… LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  15. Unexpected TCS induced ASC signals • Due to surface expansion and mirror expansion OSEMs Cold lzr Heated w/ TCS Optical lever response Magnets lzr ~10 mrad Half-story OSEM response Problems with cut and paste LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  16. Common Differential Sideband power build-up iLIGO AS_I In-phase demodulation eLIGO Sideband power build-up? Working on it Problems with cut and paste LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  17. Need to measure mirror absorption ratios Heat and cool interferometer mirrors FEM of drumhead mode freq. evolution Results in frequency shifts f (Hz) f0 fhot Step 1: Model actual heating LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  18. Thermal issues: eLIGO LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  19. Resonant Sideband Imbalance Still Here Problems with cut and paste LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  20. -2003-2004 LHO ilog Indicate poor power build-up PRIOR to mirror replacement Due to excessive thermal lensing Sideband overlap and imbalance NOT controlled -LLO Phase Cam. (A. Gretarsson LLO ilog 2004) Resonant Sideband Build-up Pwr PRM Pwr in S. Ballmer (MIT thesis, 2006) Thermal Issues: iLIGO LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  21. Effects on Strain Sensitivity • Decrease arm cavity gain  Arm length sensing • Decrease PRM carrier gain  Shot noise • Decrease PRM SB gain  Locking and alignment precision • Increase total carrier contrast defect  Shot noise R. Lawrence (MIT Thesis, 2003) Thermal issues: iLIGO LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  22. Objective • Control thermal aberrations with auxiliary lasers • Reduce optical noise • Improve high frequency sensitivity • Reduce down time with pre-heating Thermal Compensation System LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

  23. Result: Absorption ratio for ITMX = 3.5 ppm ITMY = 5 ppm +/- 10% Step 1: Result LIGO-G0900358.Rupal S. AminGCGW 17 April 2009

More Related