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Message ID: 2251     Entry time: Tue Nov 6 13:41:04 2018
Author: anchal 
Type: Summary 
Category: PMC 
Subject: PMC installed on South Path 

Changes:

  • The PMC on the south path has been installed with the PMC servo card on the rack.

  • I added sliders for setting max, min and step size of autolocker scanning in PMC interface medm windows.

  • I used one PLCX-25.4-103.0-UV-1064 and three steering mirrors in front of EOM to mode match with PMC.

  • I laid down new cables for PMC reflection RFPD signals and EOM.

  • I removed the power supply providing 9V to PMC Servo Cards and made a voltage regulator box with LM7809CT which converts 3-pin 18V to two BNC 9V.

  • We are now using external mini-circuits in-line mixers (ZFM-3-S+) and low pass filters (SLP-1.9+) instead of using onboard mixer and filter on PMC servo card and injecting signal through FP1Test input.

  • I mounted the inline hanging mixers and splitters on the rack with LO delay lines inside the rack so there are no hanging parts now.

  • I changed requirements in ALConfig_NPMC.ini and ALConfig_SPMC.ini so that we can inject the signal from FP1Test and autolocker still functions.

  • The HV supply of PMC servo boards was found to be around 180V. We changed it to the designed 160V.

  • Attaching few pics for above changes.

Few numbers:

South PMC Mode matching ~ 70%
Modulation frequency = 14.75 MHz
Modulation Index \approx 0.142 rad
 

Few notes:

  • When aligning to PMC, it is a good idea to keep a white screen infront of transmission and work in dark with IR viewer to get an idea of what is happening.
  • A camera on the back side of PMC also helps when sufficient light starts building up in the cavity.
  • While finding optimum LO delay using the SRS delay box DB64, use the rated 2.5 ns extra lag written in the datasheet.
  • Once maximum swing in PDH error signal is found, check locking once and see if the transmission is good or not. You might be locking to the sideband as the servo locks to one kind of slope only. If you find feeble transmission, just add T/2 delay in the delay box where T is the time period of modulation frequency. This lands you to near right spot.
  • While soldering an SMA connector to the cable, put the heat shrink in first and past it to the cable before proceeding. I made this mistake few times.
Attachment 1: South_PMC_Alignment.jpg  1007 kB  | Hide | Hide all
South_PMC_Alignment.jpg
Attachment 2: NorthAndSouthPMCServoCardsonRack.jpg  501 kB  | Hide | Hide all
NorthAndSouthPMCServoCardsonRack.jpg
Attachment 3: 9VConverter.jpg  474 kB  | Hide | Hide all
9VConverter.jpg
Attachment 4: FGMixersLPFandSplitters.jpg  716 kB  | Hide | Hide all
FGMixersLPFandSplitters.jpg
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