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Entry  Wed Oct 4 17:38:25 2017, gautam, Update, LSC, FS725 for Marconi stabilization 
    Reply  Thu Oct 5 18:40:27 2017, gautam, Update, LSC, FS725 for Marconi stabilization IMG_7617.JPGIMG_7619.JPGIMG_7618.JPG
       Reply  Fri Oct 6 00:25:45 2017, rana, Update, LSC, FS725 for Marconi stabilization 
Message ID: 13362     Entry time: Thu Oct 5 18:40:27 2017     In reply to: 13357     Reply to this: 13363
Author: gautam 
Type: Update 
Category: LSC 
Subject: FS725 for Marconi stabilization 

[steve, gautam]

  1. We installed the FS725 on the shelf inside the PSL enclosure - see Attachment #1.
  2. We ran a long BNC cable (labelled "GPS 1pps" on both ends) from 1X7 to the PSL enclosure - this was to pipe the 1PPS signal from the GPS timing unit (EndRun Technologies Tempus LX) rear panel (50 ohm output according to the datasheet) to the 1PPS input of the FS725 (high impedance). See Attachments #2. Note that the 1pps output was already tee'd on the rear panel. One port of the tee was unused (this now goes to the FS725) while the other was going to the 1PPS input of the Master Timing Sequencer (D050239), so I decided that there was no need to tee the 1pps input of the FS725 with a 50ohm terminator. In a few minutes, the Rb standard indicated that it was locked to its internal reference, and also to the external 1pps input (see Attachment #1). 
  3. We ran a long BNC cable (labelled "Rb 10MHz" on both ends) from the 10MHz output of the FS725 (50 ohm output impedance),  in the PSL enclosure to the rear BNC "FREQ_STD IN/OUT" BNC connector of the Marconi (1kohm input impedance). Changed the frequency reference setting on the Marconi to "External Direct". The FS725 datasheet recommends terminating the load with a 50ohm inline terminator, I have not yet done this (see Attachment #3). Is it appropriate to use a Balun (FTB-1-1) here? This would avoid ground loops between the Marconi and the FS725, and also make the load seen by the FS725 50ohms
  4. Found that there was an unused long cable from the PSL enclosure to the 1X2 electronics rack. We re-purposed this to drive the AOM driver via the DAC output in 1Y2. The cable is labelled "AOM driver" on both ends. This was to facilitate measurement of the coupling of laser intensity noise to AS55_Q in a DRMI lock.
  5. Removed 2 long cables between 1X7 and 1X2 that weren't connected to anything.
  6. Re-arranged the DC bench supply on the shelf in the PSL enclosure, whose only purpose seems to be to supply 12V to a fan attached to the rear of the PSL NPRO controller. Seems to be a waste of space! The fan was momentarily disconnected but has since been reconnected and is spinning again.
  7. Removed a couple of unused power cables from the mess on the shelf in the PSL enclosure. Also removed an unused Sony Video Squential Switcher YS-S6 from the PSL enclosure. 
Quote:

I've located the Stanford Research FS725 Rb reference unit. The question is where to put it. This afternoon Steve and I put it inside the little electronics rack next to 1X3, but in hindsight, this probably isn't such a great place for a timing reference as there are a bunch of Sorensen power supplies in there (and presumably the accompanying harmonics from these switching supplies). 

The unit itself was repaired in 2015, and powering it on, it locked to the internal reference within a few minutes as prescribed in the manual. 

 

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