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40m Log |
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Thu Mar 18 10:46:51 2010, Koji, Update, ABSL, PLL reconstructed
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Thu Mar 18 12:27:56 2010, Alberto, Update, ABSL, PLL reconstructed
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Thu Mar 18 13:40:35 2010, Koji, Update, ABSL, PLL reconstructed
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Thu Mar 18 21:42:26 2010, Koji, Update, ABSL, PLL reconstructed
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Mon Mar 22 22:11:26 2010, Mott, Update, ABSL, PLL reconstructed
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Mon Mar 22 23:37:32 2010, Mott, Update, ABSL, PLL reconstructed 
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Tue Mar 23 18:44:46 2010, Mott, Update, ABSL, PLL reconstructed
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Wed Mar 24 03:58:18 2010, kiwamu, matt, koji, Update, Green Locking, leave PLL locked
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Wed Mar 24 04:22:51 2010, kiwamu, matt, Update, Green Locking, two NPRO PLL
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Wed Mar 24 14:52:02 2010, Alberto, Update, Green Locking, two NPRO PLL
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Wed Mar 24 15:59:59 2010, kiwamu, matt, Update, Green Locking, leave PLL locked
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Thu Mar 25 17:29:48 2010, kiwamu, mott, Update, Green Locking, PLL two NPROs
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Message ID: 2680
Entry time: Thu Mar 18 12:27:56 2010
In reply to: 2679
Reply to this: 2681
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Author: |
Alberto |
Type: |
Update |
Category: |
ABSL |
Subject: |
PLL reconstructed |
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Quote: |
Last night (Mar 17) I checked the PLL setup as Mott had some difficulty to get a clean lock of the PLL setting.
- I firstly found that the NPRO beam is not going through the Faraday isolator well. This was fixed by aligning the steering mirrors before the Faraday.
- The signal from the RF PD was send to the RF spectrum analyzer through a power splitter. This is a waist of the signal. It was replaced to a directional coupler.
- Tee-ing the PZT feedback to the oscilloscope was producing the noise in the laser frequency. I put the oscilloscope to the 600Ohm output of the SR560, while connectiong the PZT output to the 50Ohm output.
- In addition, 6dB+6dB attenuators have been added to the PZT feedback signal.
Now the beating signal is much cleaner and behave straight forward. I will add some numbers such as the PD DC output, RF levels, SR560 settings...
Now I am feeling that we definitely need the development of really clean PLL system as we use PLL everywhere! (i.e. wideband PD, nice electronics, summing amplifiers, stop poking SR560, customize/specialize PDH box, ...etc)
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I also had noticed the progressive change of the aux NPRO alignment to the Farady.
I strongly agree about the need of a good and robust PLL.
By modifying the old PDH box (version 2008) eventually I was able to get a PLL robust enough for my purposes. At some point that wasn't good enough for me either.
I then decided to redisign it from scratch. I'm going to work on it. Also because of my other commitments, I'd need a few days/1 week for that. But I'd still like to take care of it. Is it more urgent than that? |