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Entry  Mon Mar 6 12:34:30 2017, johannes, Summary, ASS, ASS light injection scenarios 
    Reply  Mon Aug 21 20:11:25 2017, johannes, Summary, General, Loss measurements plan 
       Reply  Mon Aug 21 21:26:41 2017, gautam, Summary, General, Loss measurements plan 
          Reply  Tue Aug 22 16:56:54 2017, johannes, Summary, General, AS laser existing components inventory 
             Reply  Mon Aug 28 23:22:56 2017, johannes, Update, PSL, PSL table auxiliary NPRO aom_switching_zoomin.pngaom_switching_zoomout.pngaom_switching_mini_zoomin.pngaom_switching_mini_zoomout.png
                Reply  Tue Aug 29 20:04:09 2017, rana, Update, PSL, PSL table auxiliary NPRO 
                   Reply  Tue Aug 29 21:36:59 2017, johannes, Update, PSL, PSL table auxiliary NPRO isomet_mini_1st_zoomout.pngisomet_mini_0th_zoomout.png
                      Reply  Tue Sep 5 23:13:44 2017, johannes, Update, PSL, PSL table auxiliary NPRO PSL_IR.pdfpsl_aux_laser.pdf
                         Reply  Thu Sep 7 23:09:00 2017, johannes, Update, PSL, PSL table auxiliary NPRO 3200-1113_200_switching_PD10A_zoomin.png3200-1113_200_switching_PD10A_zoomout.png
                            Reply  Mon Sep 11 12:40:32 2017, johannes, Update, PSL, PSL table auxiliary NPRO psl_aux_laser2.svg.pngPSL_IR2.png
Message ID: 13235     Entry time: Mon Aug 21 20:11:25 2017     In reply to: 12869     Reply to this: 13236
Author: johannes 
Type: Summary 
Category: General 
Subject: Loss measurements plan 

There are three methods we (will soon) have available to evaluate the round-trip dissipative losses in the arms that do not suffer from the ITM loss dominance:

  • DC reflection method:
    • Compare reflected light levels from [ITM only] vs [arm cavity on resonance]
  • Basler CCDs:
    • Infer large (or small) angle scatter loss with calibrated CCDs
  • Reflection ringdowns:
    • Need AS port light injection, principle is similar to DC method but better (?)


The DC method comparing reflectivities has been used in the past and is relatively easy to do. After the recent vacuum troubles the first step should be to re-perform these as CDS permits (needs some ASS functionality and of course the MC to behave). It wouldn't hurt to know the parameters this depends on, aka mode overlap and modulation depths with better certainty. Maybe the SURF scripts for mode-spectroscopy can be applied?


With the new CCD cameras calibrated, pre-vent we can determine the magnitude of the large-angle scatter loss (assuming isotropic scatter) of ETMX and possibly ETMY. Can we look past ETMX/ETMY from the viewports? Then we can probably also look at the small angle scatter of ITMX and ITMY. If not, once we open one of the chambers there's the option of installing mirrors as close as possible to the main beam path. The easiest is probably to look at ITMX, since there is plenty of space in the XEND chamber, and the camera is already installed.


This requires a lot of up-front work. We decided to use the spare 200mW NPRO. It will be placed on the PSL table and injected into an optical fiber, which terminates on the AS table. The again free space beam there needs to be sort-of mode-matched into the SRC ("sort-of" because mode-spectroscopy). We want to be able to phaselock this secondary beam to the PSL with at least a couple kHz bandwidth and also completely extinguish the beam on time-scales of a few microseconds. We will likely need to purchase a few components that we can salvage from other labs, I'm still going through the inventory and will know more soon (more detailed post to follow). We need to settle for the polarization we want to send in from the back.


Tentative Schedule (aggressive)

Week Aug 21 - Aug 27:

  • Update mode-overlap estimates
  • Obtain current DC refl estimates
  • Spatial profile of auxiliary NPRO
  • Fiber setup concept; purchasing
  • CCD software prep work

Week Aug 28 - Sep 3:

  • Re-evaluate modulation indices if necessary
  • Optical beat AS Port Auxiliary Laser (ASAL) - PSL
  • PLL setup
  • CCD large angle prep work

Week Sep 4 - Sep 10:

  • PLL CDS integration
  • Amplitude-modulation preparation
  • CCD large angles

Week Sep 11 - Sep 17:

  • Fiber-injection
  • AS table preliminary mode-matching
  • Faraday setup
  • CCD small angle prep work

Week Sep 18 - Sep 24:

  • ASAL amplitude switching
  • CCD small angles

Week Sep 25 - Oct 1:

  • AS port ringdowns


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