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Reports until 18:20, Friday 20 April 2018
H1 SQZ
sheila.dwyer@LIGO.ORG - posted 18:20, Friday 20 April 2018 - last comment - 11:10, Thursday 26 July 2018(41572)
green aligned to OPO, more mode matching measurements

Nutsinee, Sheila

This morning Nutsinee and I measured the beam profile arriving in HAM6 from the squeezer, before OM1.  

Then we improved the alignment of the 532 beam into the OPO, the power in the 1st order mode is now about 5% of the power in the 00 mode.  Nutsinee saved scan data for the 532 beam.  

Then we placed an aperture on the far side on HAM6 in the seed path, and removed the translation stage lens from the translation stage.  We measured the beam profile in a few locations after ZM1, which seems to be agreeing with the model that Dan and Thomas have.  We repalced the lens and checked that the beam still comes back to HAM6 on the OMC side. 

Lastly we measured the distance from the beam diverter to the LVEA wall is 137.5 inches. 

More details about the measurements are coming soon.

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sheila.dwyer@LIGO.ORG - 11:10, Thursday 26 July 2018 (43084)
Link

Hoacun, Sheila

Distances from periscope/table/wall/beam diverter:

  • Attached is a PDF that Terry sent to Haocun with measured distances in chamber, including that ZM1 to the beam diverter is 37 inches.  The beam diverter to wall distance above combined with the distances in Terry's notebook imply that the beam diverter is 201.5 inches from the LVEA wall.  
  • After the chamber was closed, we moved the table closer to the chamber.  Hoacun and I just measured the distance from the mark on the floor that Hugh and TJ made in April, and we see that the table has moved closer to the chamber by 14.5 inches.  The edge of the table is now 87 inches from the LVEA wall and the top periscope mirror is 80 inches from the wall.  (This agrees with Terry's notebook)
  • So, the top periscope mirror is now 114 inches from the beam diverter or 2.9 meters from the beam diverter.

 Measurements of seed mode in chamber: 

  • Measurements for the lens solution that we left installed when we pumped down is here: 41683, the third plot shows that the measured horizontal waist of the seed beam is 556 um at 3.52m from SRM and the vertical waist is 571um at 3.53m from SRM. 
  • Using the finesse model that Dan Brown +T Vo updated with squeezer info, (here, lines 582 + info about squeezer around line 650), the distance from ZM1 to SRM is 4.36m.  
  • So the information we want for mode matching to the homodyne is that the beam waist is 556 um at 0.84meters from ZM1, which is 0.095m before the beam diverter. 
  • (Other mode matching information from before we did our lens swap is in alogs 41504 and 41521).  

Conclusion:

The seed waist is 556um at 0.095meters before the beam diverter, or 3 meters from the top periscope mirror.

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