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Entry  Sat Sep 19 23:59:22 2020, anchal, Summary, ALS, ALS noise budget update ALS_nb_ExtraPoles.pdfALS_controls.yamlALS_nb_Kiwamus_Values.pdfALS_controls_Kiwamus_Values.yamlALS_simulink_model.svg
    Reply  Sun Sep 20 23:12:13 2020, rana, Summary, ALS, ALS noise budget update 
       Reply  Tue Sep 22 00:14:43 2020, anchal, Summary, ALS, ALS noise budget update ALS_NoiseBudgetUpdate.pdfALS_controls.yaml
          Reply  Tue Sep 22 12:14:42 2020, rana, Summary, ALS, ALS noise budget update 
             Reply  Wed Sep 23 11:13:49 2020, anchal, Summary, ALS, ALS noise budget update ALS_NoiseBudgetUpdate.pdfALS_controls.yaml
                Reply  Wed Oct 7 16:56:23 2020, anchal, Summary, ALS, ALS noise budget update - Updated AUX PDH Loop values Extract_X_AUX_PDH_Model.zipALS_NoiseBudgetUpdate.pdf
                   Reply  Thu Oct 8 11:59:52 2020, rana, Summary, ALS, ALS noise budget update - Updated AUX PDH Loop values 
                      Reply  Fri Oct 9 18:32:14 2020, anchal, Summary, ALS, ALS noise budget update - Updated AUX PDH Loop values 
                         Reply  Wed Oct 14 17:03:55 2020, anchal, Summary, ALS, ALS noise budget update - Added whitening filter for ADC ALS_NoiseBudgetUpdate.pdf
Message ID: 15593     Entry time: Tue Sep 22 00:14:43 2020     In reply to: 15589     Reply to this: 15594
Author: anchal 
Type: Summary 
Category: ALS 
Subject: ALS noise budget update 

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
Attachment 1: ALS_NoiseBudgetUpdate.pdf  149 kB  Uploaded Tue Sep 22 01:27:36 2020  | Hide | Hide all
ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf
Attachment 2: ALS_controls.yaml  2 kB  Uploaded Tue Sep 22 01:34:18 2020  | Hide | Hide all
# -----------------------------------------------------------------------------
# AUX
# -----------------------------------------------------------------------------
## Cavity Pole
C_AUX:
  p: 1.8883e+04
  k: 1.1865e+05

H_AUX:
  z: 0
... 106 more lines ...
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