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Message ID: 1290     Entry time: Fri Aug 9 16:00:14 2013
Author: tara 
Type: Notes 
Category: NoiseBudget 
Subject: noise hunting 

I measured the slope of the error signal for ACAV path to be 200 kHz/V. This will be used for calibration the error point noise to frequency noise.

 See some details about the error signal's slope and calibration in psl:562.

THe setup for ACAV path is

  • Input power to the cavity 1 mW.
  • RF power on marconi for the driver = 13dB, to 4-way splitter then 14.75 MHz resonant EOM.
  • The error point noise was measured at COMMON channel out1 on RCAV TTFSS.

Next: Measure the slope at RCAV path, measure error noise from both loops, compare to beat signal.

 


Plan for opening the chamber:

I'm certain that the beam reflected from the window that overlaps with the reflected beam from the cavity going to the RFPD causes a lot of noise. This should show up in the error noise. So to avoid the reflection from the window, I have open the chamber to turn the cavity axis a bit. I need to:

  • calculate how much the cavity has to be turned if we will dump the beam at the lens for the RFPD.
  • see if the beam path is still ok for the rotated cavities.
  • Replace the cavity mount wall. The current one is too short due to the mistake in the design. I needed to use  nuts to raise the height, see pic.  Without the gap on the side, temperature control between the two cavities will be better due to smaller coupling. The walls will be ready on Monday, I might need a day or two to clean and bake them before the installation.
  • use screws to hold the cavities down firmly, instead of resting on four point supports.
  • I don't plan to replace the AD590s on the thermal shield. This will take too much work to remove the feed through, fix the cable. Otherwise, we can just slide the stack half way out of the chamber for replacing the wall and rotating the cavities. Plus, we can use beat signal as an error signal for Temp control.

 

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