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Message ID: 6521     Entry time: Wed Apr 11 17:56:26 2012
Author: Jenne 
Type: Update 
Category: General 
Subject: Summary of things to figure out with the IFO 

Questions:

Power recycling gain

   * It should be ~40, but we observe/measure it to be ~7.  Even if mode matching of ~50% is assumed, gain is calculated to be ~15

   * Would like to measure PR gain independent of mode matching, if possible

Power recycling cavity mode matching

   * Reflectivity of PRMI was measured to be ~50%.  That's pretty high.  What's going on?

   * Even if we're mode matched to the arm, are we appropriately mode matched to the PRC?

Is beam from MC clipped in the Faraday?

   * We had to use MC axis for input pointing since PZTs aren't totally working.

   * Need to measure IPPOS beam for different MC alignments to see if horizontal waist measurement stays constant.

PRM flipped?

   * Not likely, but it can't hurt to confirm for sure.

   * Want to know, since it could give us a different plan for MMT moving than if the PRM is correct.

Thick optic non-normal incidence in IPPO - does this exaggerate astigmatism, which would help explain IPPOS measurement?

Is PRC waist same size / position as arm cavity waist, given the current "known" positions of all the optics?

   * How is this effected by moving the PRM?

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Measurements to take and what information they give us:

IPPOS beam scan, with MC as-is

   * Confirm (or not) IPPOS measurements from last week

IPPOS beam scan with different MC alignments

   * Will tell us about Faraday clipping, if any

AS beam scan, misaligned PRM, misaligned SRM, misaligned ITMX, single bounce from ITMY

   * Can only take this measurement if beam is bright enough, so we'll just have to try

   * Will confirm IPPOS measurement, but includes going through the thick PRM, so can compare to calculated intra-PRC mode

REFL beam scan (already done....is the data satisfactory? If so, no need to redo), single bounce off of PRM

   * Will tell us about the potential PRM flipping

   * Need to compare with calculated mode at REFL port for flipped or non-flipped PRM

Look at POP camera, see 2nd pass through cavity

   * Try to match 1st and 2nd pass.  If they don't match, we're not well matched to PRC mode

Look at beam directly on ETMY cage, then beam from ETM, bounce off ITM, back to ETM cage

   * If the beams are the same size, we're well matched to arm cavity mode

   * Use fancy new frame-grabber.

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MMT code things to calculate, and what information it gives us:

REFL beam path, for PRM flipping comparison

Thick IPPO non-normal incidence - I'm not sure how to do this yet, since I only know how non-normal incidence changes effective radii of curvature, and this is a flat optic, so *cos(theta) or /cos(theta)  won't do anything to an infinite RoC

Compare PRC waist to arm cavity waist, using "known" optic positions

Mode matching sensitivity to MC waist measurements

Mode matching sensitivity to PRM position

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