= Optical Platform Suspension =

Each in-vacuum optical table for the 40 m test masses is an optical breadboard with a diameter of 38 inches.
We plan to place a single stage suspended breadboard on top of this existing table to get 1 additional stage of seismic isolation. We will need 4 of these to cover each test mass.

  * VOPO style suspension
     * Attach a structure (poles or a frame) on the existing breadboard
     * The structure supports vertical blades
     * Wires are attached on the vertical blades
     * A breadboard is suspended from the vertical blades

  * Breadboard 
     * Thickness
     * Internal resonances: modes/frequencies

  * Blade spring
     * Load weight (total weight of the load, max load)
     * constrained layer damping of blade modes ?
     * What about just using 3 little coil springs to mount the breadboard from underneath rather than use blades? Then its more like an extra layer of the stack.

  * Counter balance

  * Vibration isolation
     * Requirement: 30x reduction for f = 10-100 Hz
     * pendular modes should be 0.2-0.45 Hz or 1.5-2.5 Hz to avoid SOS resonances.

  * Active control
    * Sensor (What, how many, how sensitive, range, noise)
    * Actuators (Coil Magnet, requirement, strength, Vertical, Horizontal )
    * Electronics (Feedthru)
    * Control system
    * does it need to be active or can we use resonant eddy current damping?

  * Utility structures 
    * EQ stops
    * Safety (Blades/Wires)

  * Active VS Passive approach
    * Active
       * Pros
         * ...
       * Cons
         * ...

    * Passive
       * Pros
         * ...
       * Cons
         * ...