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 Fri Feb 14 17:40:27 2020, anchal, DailyProgress, ISS, Installed ISS on both paths using SR560s 
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 Sat Feb 15 18:57:43 2020, rana, DailyProgress, ISS, Installed ISS on both paths using SR560s
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Thu Feb 20 17:42:23 2020, rana, DailyProgress, ISS, Installed New ISS on both paths using SR560s
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Sun Feb 23 18:19:32 2020, rana, DailyProgress, ISS, Installed New ISS on both paths using SR560s
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Fri Feb 28 14:00:11 2020, anchal, DailyProgress, ISS, Installed New ISS on both paths using SR560s - PROBLEM
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Sun Mar 1 16:34:31 2020, rana, DailyProgress, ISS, Installed New ISS on both paths using SR560s - PROBLEM
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Mon Mar 2 16:48:12 2020, anchal, DailyProgress, ISS, Follow-up, porbalem stopped happening, OLTF plot.
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Message ID: 2542
Entry time: Thu Feb 20 17:42:23 2020
In reply to: 2539
Reply to this: 2544
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| Author: |
rana |
| Type: |
DailyProgress |
| Category: |
ISS |
| Subject: |
Installed New ISS on both paths using SR560s |
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I've installed new ISS consisting of one SR560 per path.
ISS SR560 Details:
| Path |
Input Coupling |
Invert |
High Pass Roll off (dB/octave) |
High Pass Corner (Hz) |
Low Pass Roll off (dB/octave) |
Low Pass Corner (Hz) |
Gain Mode |
Gain |
Output Impedance (Ohms) |
| North |
AC |
No |
6 |
300 |
6 |
300 |
Low Noise |
5x103 |
600 |
| South |
AC |
Yes |
6 |
300 |
6 |
300 |
Low Noise |
1x104 |
600 |
Measurements:
- I took transfer function by exciting at port B and using mode A-B on the SR560.
- The transfer function was measured as Actuation Signal (output of SR560) over Error Signal (input to SR560).
- This transfer function should be equal to open-loop gain over the SR560 transfer function.
- So, I took another measurement of the transfer function of SR560 itself not connected to the loop.
- This gave me total open-loop transfer function.
- I used
 as the transfer function of EOAM in units of relative intensity change per V (1/V).
- I used the coupling factor (See CTN:2528) and DC power level of the laser after transmission to get the detector transfer function in units of V.
- Using the above, I calculated the plant transfer function for each path and then used that to calculate the closed-loop transfer function.
- To compare, I also calculated noise suppression before and after switching on ISS.
- These two separate methods match very well. At 300 Hz, intensity noise is suppressed by 40 dB.
- There is no other witness detector after transmission to use as an out-of-loop photodiode, neither is there any space to put a new one.
- There is oscillation happening at UGF fo around 40 kHz in both paths. I can work on it if this looks like a problem in the final beatnote or if it seems to saturate FSS loops. Currently, I saw nothing alarming.
Data |
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