Reports until 14:15, Thursday 08 December 2016
LHO VE (DetChar)
kyle.ryan@LIGO.ORG - posted 14:15, Thursday 08 December 2016 - last comment - 09:50, Friday 09 December 2016(32367)
Need DetChar to scrutinize data 

We have a diagnostic setup at BSC8 that we need to run for several consecutive days.  This setup utilizes rotating shaft vacuum pumps that have the potential of effecting the IFO data.  Prior to the start of O2, we had Robert S. monitor the IFO signal(s) while it was locked and in "Low Noise" both with the pumps on and also off, i.e. we did "on/off" tests (see alog entry 31802).  Additionally, and on more than one occasion, we had ran these for several consecutive days during which the IFO experienced long lock stretches at good sensitivity.  As such, we were hoping that someone could examine the pertinent IFO data during the following two time segments to look for any evidence of these pumps running.  In both cases, the pumps in question were running continuously:  


November 24th, 0230 UTC to November 29th, 1800 UTC and

December 5th, 1900 UTC to December 7th, 0035 UTC.
Comments related to this report
keith.riles@LIGO.ORG - 20:48, Thursday 08 December 2016 (32374)DetChar
Link 

Attached is a zipped tar file of spectral comparisons for the two pump-on periods cited
and for an intervening pump-off period. Since I don't know what the pump frequency
is supposed to be, I'm not sure where to focus attention, but I'm not seeing gross differences
other than higher 60-Hz harmonics in both pump-on periods (is that expected from
the pumps?), along with the overall greater excitation / upconversion of violin modes and
the presence of  "silent" calibration lines at 22.3 and 30.1 Hz in the first pump-on period. 

Here are the FScanned data intervals used:

pumpon-1 -- 23.5 hours of SFTs collected between Nov24th, 0230 UTC and Nov 29th, 1800 UTC
pumpon-2 -- 11.5 hours between Dec 5th, 1900 UTC and Dec 7th, 0035 UTC
pumpoff -- 78 hours between Nov 30, 14:00 UTC and Dec 5th, 14:00 UTC

If there are particular frequencies where I should be expecting disturbances,
let me know and I'll do some zooming.
Non-image files attached to this comment
keith.riles@LIGO.ORG - 09:50, Friday 09 December 2016 (32390)
Link 

Kyle informed me offline that the pumps run at 1720 RPM (28.667 Hz) 
with small turbos running at 90,000 RPM (1500 Hz). Attached are zooms
of bands around the first four harmonics 28.667 Hz (band sizes increase
linearly with harmonic number) and around 1500 Hz. I don't see anything
jumping out at me in any of the low-frequency bands that indicates an 
artifact restricted to pump-on times. 

The region around 1500 Hz is harder to interpret because of different average 
quad violin mode excitations and associated up-conversion.

Fig 1 - 28.5-28.8 Hz
Fig 2 - 57.0-57.6 Hz
Fig 3 - 85.5-86.4 Hz
Fig 4 - 114.0-115.2 Hz
Fig 5 - 1480-1520 Hz
Images attached to this comment