Overview

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Task description

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Some working assumptions

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To avoid misunderstandings …

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Suspension Thermal Noise

  Boosted aLIGO Quad with 1.2m long last stage and 160kg test masses.

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Suspension Thermal Noise

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Suspension R&D

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Newtonian Noise

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Used seismic from:

Newer data from LLO

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New data from LLO seem to suggest that Strawman red underestimates the GGN level by about a factor 2. Work in progress!

Seismic barrages

  2D finite-difference time-domain simulations for barrages of 40x40m.

  Attenuation of seismic by about a factor 2.

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Coating Brownian noise

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Increasing the beam size

  Assume an increase of beam size by a factor 1.6.

  Keep aspect ratio of test masses as it is => 160kg.

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Optical coatings with reduced thermal noise

 Continued improvement of tantala coatings.   Loss related to local atomic structure of material

 High-temperature annealing of coatings.   Heat treatment in the range of 500-1000 degrees centigrade

 Amorphous silicon as a high-index coating material   n=3.5 => quarter-wave layer is thinner. In addition need fewer layers.   Potential improvement = 4.6   Requires change of laser wavelength

 Crysatalline coatings (AlGaAs)

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Khalili cavities

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Khalili cavities

 Extremely hardware intensive.

 Lots of technical challenges:   Thermal lensing   Cavity stability   Control

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Thermal lensing in K-cavity

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Waveguide mirrors

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Quantum noise

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Squeezing losses

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= 9% in total

Cavity losses in literature

Assuming losses are independent of cavity length

Speedmeter an alternative?

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Strawman Red Costs

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Overview

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 For details please see document on the DCC:

 https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=78100

Stefan Hild Slide 26 Strawman Caltech, Jan 2012