This information is based on the cumulative spectrum of recent lock stretches (9/18-9/26, computed from Fscan SFTs with spec_avg_long), plus Fscan magnetometer data.
0.997698 Hz
- Worst comb at present
- Previously noted in ER9
- Higher in DARM 9/24-9/26 than 9/18, 9/23
- Appears in CS mags and is fairly steady there (based on available Fscan data since April).
1.0 Hz
- Present in CS, EX, EY magnetometers
0.5 Hz odd harmonics (AKA 1 Hz with 0.5 Hz offset)
- Looking better! Weaker than ER9 by a factor of ~5-10 (varies across spectrum). Improvement presumably due to timing system LED reprogramming.
- Hoping for more improvements as IO chassis timing slaves are put back on alternate power supplies.
1.0 Hz with 0.998889 offset (new)
- Very close to 1 Hz comb, but distinct peaks are visible
0.987987 Hz (new)
- Present in EX magnetometers
- Increases on 9/11/16 in magnetometers
Attached plots:
- 1: LSC-DARM_OUT_DQ cumulative spectrum with the noted combs highlighted
- 2-4: Representative (SUSRACK) magnetometer channels at CS, EX, EY with combs highlighted
- 5-6: Plots showing 0.5 Hz odd harmonics improvement between ER9 and present
Minor edit: offset on 4th comb mentioned has too many significant figures. Should be rounded to ~0.9989 (+/- 0.0005).
Update on the 0.996798 Hz: this comb appears in magnetometer channels between Feb 3rd and 4th*. After looking at the alogs for surrounding date range, Robert suspected the HWS as a potential source. We checked TCS-ITMX_HWS_RCXCLINKSWITCH and saw a switch on, which corresponded neatly with the date of the comb's appearance in magnetometer channels. Robert has also previously noted near-1Hz combs associated with the HWS in the CS. Richard says that the HWS can be placed on a separate power supply in the near future, which will hopefully clear this up.
*edit, typed wrong date