Just curious -- it's my impression that the point of "upgrading the timing system to the new V3 firmware" was to reprogram all timing system hardware's LED lights so as to not blink every second or two, because we suspect that those LEDs are somehow coupling into the IFO and causing 1 to 2 Hz combs in the interferometer response. 

The I/O chassis, IRIG-B, comparators, and RF amplifiers are a huge chunk of the timing system. Do we think that this majority will be enough to reduce the problem to negligible, or do we think that because the timing master and fanouts -- which are the primary and secondary distributors of the timing signal -- are still at the previous version that we'll still have problems?

With the I/O chassis timing upgrade we removed the separate power supply form the timing slaves on the LSC in the corner and both EX and EY ISC chassis.  Hopefully the timing work will eliminate the need for the separate supplies.

Could you clarify that last comment? Was yesterday's test of changing the LED blinking pattern
done in parallel with removal of separate power supplies for timing and other nearby electronics?



 

To clarify Jeff's comment: testing on separate power supplies was done by Brynley Pearlstone, and information on that can be found in his alog entries. Per his work, there was significant evidence that the blinking LEDs were related to the DARM comb, but changing power supplies on individual timing cards did not remove the comb. This motivated changing the LED logic overall to remove blinking.

I'm not sure whether the upgrades done so far will be sufficient to fix the problem. Maybe Robert or others have a better sense of this?

Notable alog entries from Bryn:
https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=25772
https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=25861
https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=27202

I have gone through and manually compared FScan spectrograms and
normalized spectra for the 27 magnetocometer channels that are
processed daily: https://ldas-jobs.ligo-wa.caltech.edu/~pulsar/fscan/H1_DUAL_ARM/H1_PEM/fscanNavigation.html,
to look for changes following Tuesday's timing system intervention,
focusing on the lowest 100 Hz, where DARM 1-Hz (etc.) combs are worst.

Because of substantial non-stationarity that seems to be typical,
it's not as straightforward as I hoped it would be to spot a change
in the character of the spectra. I compared today's generated FScans (July 20-21)
to an arbitrary choice two weeks ago (July 6-7).

But these six channels seemed to improve w.r.t. narrow line proliferation:

H1_PEM-CS_MAG_EBAY_LSCRACK_X_DQ
H1_PEM-EX_MAG_EBAY_SUSRACK_X_DQ
H1_PEM-EX_MAG_EBAY_SUSRACK_Y_DQ
H1_PEM-EX_MAG_EBAY_SUSRACK_Z_DQ
H1_PEM-EY_MAG_EBAY_SUSRACK_X_DQ
H1_PEM-EY_MAG_VEA_FLOOR_X_DQ  (before & after figures attached)

while these four channels seemed to get worse w.r.t. narrow lines:

H1_PEM-EX_MAG_VEA_FLOOR_Z_DQ
H1_PEM-EY_MAG_EBAY_SEIRACK_X_DQ
H1_PEM-EY_MAG_EBAY_SEIRACK_Y_DQ
H1_PEM-EY_MAG_EBAY_SEIRACK_Z_DQ

In addition, many of today's spectrograms show evidence of broad
wandering lines and a broad disturbance in the 40-70 Hz band
(including in the 2nd attached figure).

Weigang Liu has results in for folded magnetometer channels for UTC days July 18 (before changes), July 19-20 (overlapping with changes) and July 21 (after changes):

Compare 1st and 4th columns of plots for each link below.

CS_MAG_EBAY_SUSRACK_X - looks slightly worse than before the changes
CS_MAG_EBAY_SUSRACK_Y - periodic glitches higher than before
CS_MAG_EBAY_SUSRACK_Z - periodicity more pronounced as than before

CS_MAG_LVEA_VERTEX_X -  periodic glitches higher than before
CS_MAG_LVEA_VERTEX_Y -  periodic glitches higher than before
CS_MAG_LVEA_VERTEX_Z -  periodic glitches higher than before

EX_MAG_EBAY_SUSRACK_X - looks better than before
EX_MAG_EBAY_SUSRACK_Y - looks better than before
EX_MAG_EBAY_SUSRACK_Z - looks slightly worse than before

EY_MAG_EBAY_SUSRACK_Y  - looks slightly better after changes
EY_MAG_EBAY_SUSRACK_Z - looks the same after changes
(Weigang ran into a technical problem reading July 21 data for EY_MAG_EBAY_SUSRACK_X)

A summary of links for these channels from ER9 and from this July 18-21 period can be found here.