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LOS Absorption Presentation for TCS Group

LOS Absorption Presentation for TCS Group. Rupal S. Amin Tuesday, August 26, 2008. Outline. Motivation Theory Procedure Data Result. Motivation. Question: 1) What do we care about the absorption of the large optics? 2) What is the absorption value?

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LOS Absorption Presentation for TCS Group

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  1. LOS AbsorptionPresentation for TCS Group Rupal S. Amin Tuesday, August 26, 2008 LIGO-G080428-00-L

  2. Outline • Motivation • Theory • Procedure • Data • Result LIGO-G080428-00-L

  3. Motivation • Question: • 1) What do we care about the absorption of the large optics? • 2) What is the absorption value? • Answer: Silica mirrors inside IFO unfortunately absorb resonant laser power. LIGO-G080428-00-L

  4. Motivation • Ans(con’t): Mirrors expand due to temperature changes. Depending on absorption coefficient, mirrors may distort beyond or below design optimum. Cold  Hot  LIGO-G080428-00-L

  5. Motivation • Measuring absorption (especially the ITMS) allows TCS team to build effective absorption models (Mathematica, Matlab, Finesse, SIS) • Correct setup scheme for Enhanced TCS. • So…We need the absorption values of the large Fabry-Perot optics. LIGO-G080428-00-L

  6. Theory • Crude theory • Mirrors have body modes • Finite temperature Brownian motion • Frequencies are thermally dependent • Due to Young’s modulus having a Y(T). • Track body mode frequency evolutions due to DT • Df yields power absorption LIGO-G080428-00-L

  7. Theory • Crude theory • Better theory • We need f and ∆f to determine α* LIGO-G080428-00-L

  8. Procedure • Power Cycle IFO during fully locked state. • Do this over several hours • Save data from fast ASQ sample channels and temperature sensors. • Download GBs of data from LDAS and analyze. LIGO-G080428-00-L

  9. Procedure 4 W 1 W df/f Pwr t LIGO-G080428-00-L

  10. Data • Lock data from 899867714 s • Thermal data: Mirror modes are history dependent LIGO-G080428-00-L

  11. Thermal Resistances and Sources • BSC and contents slow LVEA to ITM interaction time. • Beam tubes: heat source but negligible LIGO-G080428-00-L

  12. Thermal Resistance • Simulation of TM interaction with BSC. Small perturbations lead to simulation problems. LIGO-G080428-00-L

  13. Analysis using raw data LIGO-G080428-00-L

  14. Raw Data (noisy) LIGO-G080428-00-L

  15. Fitting Data Peak = (x0 , Amplitude) G DC based on noise average LIGO-G080428-00-L

  16. Analysis using fitted data LIGO-G080428-00-L

  17. Analysis • ∆f/f for ITMy LIGO-G080428-00-L

  18. Results • Total uncorrected slope = 1.3(3)e-6+/- 1.3e-6 Hz/s • Uncorrected for high power = 4.(43)e-7+/- 3. e-7 Hz/s • Crudely Corrected slope = ? • Refined df/f = Need to do LIGO-G080428-00-L

  19. Ambient temperature f-drift • Crude shift due to temperature fluctuations LIGO-G080428-00-L

  20. Questions? • 1) What is your purpose? • 2) What is your favourite color? LIGO-G080428-00-L

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