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Entry  Thu Apr 21 18:18:42 2022, yehonathan, Update, BHD, POX Alignment POX11_alignment.png
    Reply  Thu Apr 28 17:45:53 2022, Anchal, Update, BHD, POX Beam issues PXL_20220429_002703686.jpg
       Reply  Sat Apr 30 13:29:33 2022, Paco, Update, BHD, POX Beam issues --- fixed, ASL alignment on vertex chamber 
          Reply  Mon May 2 17:51:30 2022, Anchal, Update, BHD, POX Beam aligned on RFPD, YARM locked 
Message ID: 16818     Entry time: Thu Apr 28 17:45:53 2022     In reply to: 16799     Reply to this: 16821
Author: Anchal 
Type: Update 
Category: BHD 
Subject: POX Beam issues 

[Anchal, Paco]

We investigated the low power issue with POX11 photodiode.

  • We used a power meter to confirm that above 12 uW of power is reaching the ITMX oplev table.
  • But the power reaching the photodiode was only 3 uW, because the 2 steering mirrors used were discarding half of the light. These mirrors were taken from former POP setup and are probably BS or meant for different incidence angle/polarization.
  • We used flashlight to test that the photodiode gives a response, so it is not dead.
  • We also put in a db15 breakout board in line to the PD and confirmed that power input is correct, temperature is nominal, enable is ON, and DC out is responsive to flashlight.
  • So we decided to redo the path with Y1-45P 1inch mirrors. I found two such mirrors in the lab.
  • When setting up the path again, I realized that the beam shape is not even. I took a photo of the beam on the card (see attachment 1) and indeed the POX beam that is coming to the table is half clipped.
  • So tomorrow, we'll open the chamber and find out where this is happening. For now, I've setup a nominal path to the POX11 photodiode, but we'll tune it after we get a clear POX beam on the table.
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PXL_20220429_002703686.jpg
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