I have updated the correction filter for the dtt DARM spectra that are projected in the wall and screens in the control room. I hope Evan will like it.
This does not affect the CAL-CS or GDS calibrations. This is only for display purpose in diaggui.
[The DARM spectra]
Here is a comparison of the newly corrected and previous DARM spectra.
As shown in the attached screenshot, the high frequency excess wing that has been shown above 3 kHz is now gone. The noise level at around 7 kHz now seems a bit too low compared with the f-shaped GWINC curve (shown in green). This maybe a real calibration error because I have applied the best and latest knowledge about the sensing chain for correcting the spectrum.
The correction filter is made by a matlab script:
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/PreER8/H1/Scripts/ControlRoomCalib/H1DARM_FOM_correction.m
This script creates a text file which contains the correction filter in [freq, dBmag, phasedeg] format from 1 Hz to 7444 Hz. The text file can be found at
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/PreER8/H1/Scripts/ControlRoomCalib/DARM_FOM_calibration.dat
Both script and text files are checked in to the svn. Also I updated the latest FOM dtt template, H1_DARM_FOM_20150722.xml so that it now uses the new correction filter.
[Corrections newly included]
Here is a list of what I newly included.
-
Analog anti-aliasing filter
- See this plot from alog 17951
-
Unconmpensated OMC DCPD poles
- See this plot from alog 18037
-
True zpk([355], []) cavity pole, instead of zpk([355], [7000]) in the IIR filter
- See some discussion in G1501013
Note that the previous correction was made only from the IOP down sampling filter and the numerical whitening zpk([1,1,1,1,1], [100,100,100,100,100]) which are still included in the new correction.
For those of us who like to look at the DCPD streams, I modified the script to also produce the appropriate correction TF (using the uncompensated preamp poles, the AA filter, and the downsampling filters only).
There is still a little bit of sloping at high frequencies, even in the null stream (which we expect to be flat above 100 Hz). Maybe the AA model needs to be tuned?
I happened to come across this code again to reproduce the calibration correction filter for O1. I then found some bugs in the code which are now fixed.
-
The code was looking at the latest foton filter
- Now it looks at an archived filter from Sep.10.2015
-
The code was picking up a wrong filter module (FM2 instead of FM1) for whitening filter of DELTAL_EXTERNAL.
- Now it looks for FM1.
-
Also, the ascii version of the filter (DARM_FOM_calibration.dat) was also dur to the above errors.
- I reproduced and saved it in svn.
- The code is saved to SVN.