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A method for Killing the parametric instabilities dead

A method for Killing the parametric instabilities dead. Eric Black, Riccardo DeSalvo, Andri Gretarsson, Calun Torrie Parametric instability workshop Pasadena August 23 2005. Getting rid of mirror resonances. Using simulations and Levin’s recipe Calum Torrie and Andri Gretarsson

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A method for Killing the parametric instabilities dead

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  1. A method for Killing the parametric instabilities dead Eric Black, Riccardo DeSalvo, Andri Gretarsson, Calun Torrie Parametric instability workshop Pasadena August 23 2005 LIGO-G050461-00-R

  2. Getting rid of mirror resonances • Using simulations and Levin’s recipe Calum Torrie and Andri Gretarsson • applied pressure on the mirror surface using: • A) A mesa beam profile and Ansys • B) A Gaussian profile and a semi analytic calculation • Looked for null action areas on the mirror outer surface on which to apply a damper to kill mirror resonances • These studies were made to eliminate the mirror resonance peaks in the sensitivity curve and to design heavy composite masses LIGO-G050461-00-R

  3. TN neutral band, Calun • A clear no action band is present (<<%) LIGO-G050461-00-R

  4. TN neutral band, Andri Null action band <10-4 effect LIGO-G050461-00-R

  5. Damping allowances • Loss is 10-4 on the neutral ring and limited on a small mass fraction • => can tolerate 103 ~ 104 losses without TN performance degradation • effective damping on mirror modes LIGO-G050461-00-R

  6. Damper design • Heat shrunk 1x5 mm aluminum ring LIGO-G050461-00-R

  7. Getting rid of mirror resonances • The null action band has less than a percent surface strain energy density than the laser spot area • A soft aluminum damping ring can be applied in this area • A moderately high mechanical quality mirror can be obtained without dissipation for the beam profile action LIGO-G050461-00-R

  8. Testing the idea • Tests to be performed in the TNI on existing TNI mirrors • Application of a ring does not damage the mirror • Measurement of the Q factors and TN performance before and after application of the ring will fully determine the effectiveness and the TN cost of the ring. • The measurement will test the feasibility of composite masses with an optical mass wedged inside an inertial donut mass LIGO-G050461-00-R

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