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Sat Sep 19 23:59:22 2020, anchal, Summary, ALS, ALS noise budget update    
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Sun Sep 20 23:12:13 2020, rana, Summary, ALS, ALS noise budget update
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Tue Sep 22 00:14:43 2020, anchal, Summary, ALS, ALS noise budget update 
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Tue Sep 22 12:14:42 2020, rana, Summary, ALS, ALS noise budget update
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Wed Sep 23 11:13:49 2020, anchal, Summary, ALS, ALS noise budget update 
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Wed Oct 7 16:56:23 2020, anchal, Summary, ALS, ALS noise budget update - Updated AUX PDH Loop values 
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Thu Oct 8 11:59:52 2020, rana, Summary, ALS, ALS noise budget update - Updated AUX PDH Loop values
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Fri Oct 9 18:32:14 2020, anchal, Summary, ALS, ALS noise budget update - Updated AUX PDH Loop values
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Wed Oct 14 17:03:55 2020, anchal, Summary, ALS, ALS noise budget update - Added whitening filter for ADC
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Message ID: 15593
Entry time: Tue Sep 22 00:14:43 2020
In reply to: 15589
Reply to this: 15594
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Author: |
anchal |
Type: |
Summary |
Category: |
ALS |
Subject: |
ALS noise budget update |
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This is not a reply to comments given to the last post; Still working on incorporating those suggestions.
Trying out a better filter from scratch
Rana suggested looking first at what needs to be suppressed and then create a filter suited for the noise from scratch. So I discarded all earlier poles and zeros and just kept the resonant gains in the digital filter. With that, I found that all we need is three poles at 1 Hz and a gain of 8.1e5 gives the lowest RMS noise value I could get.
Now there can be some practical reasons unknown to me because of which this filter is not possible, but I just wanted to put it here as I'll add the actual noise spectra into this model now.
Few questions:
- What anti-aliasing filters are used in ALS?
- Is the digital delay fixed to a constant upper limit or is it left to change as per filters? I have already used a 470 us delay (modeled with Pade 4th order approximation).
- I could not find a good place where channel names are listed with corresponding meaning. Where can I find them?
- Is there a channel which keeps a record of lock status? In short, how do I find the in-lock times
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# -----------------------------------------------------------------------------
# AUX
# -----------------------------------------------------------------------------
## Cavity Pole
C_AUX:
p: 1.8883e+04
k: 1.1865e+05
H_AUX:
z: 0
... 106 more lines ...
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