aLIGO LHO Logbook

H1 DetChar

ansel.neunzert@LIGO.ORG - posted 12:20, Monday 11 December 2023 (74740)

Overview of combs in recent monthly Fscan spectra

This is a big-picture overview of combs in recent months.

Data and methods

"Relative priority" is a new metric documented in G2302324 (Athena Baches, Abby Wang, and Nick Baker). It is not finalized-- in fact these values differ slightly from the version in the linked presentation due to bug fixes-- and should be understood as (a) having arbitrary units, (b) reflecting the general importance of spectra artifacts to CW searches, and (b) being useful only for comparing artifacts in similar data sets-- for example, it should not be used to compare artifacts from monthly spectra and ones from weekly spectra. In this case it is used to compare and rank combs across monthly spectra.

Monthly August, October, and November Fscan spectra and their auto-generated lines lists were used. I skipped September because I still need to troubleshoot some issues with the lines list for that month.

Main messages

The 9.47-8 Hz combs are still the worst offenders, even considered individually.
The near-1Hz and near-5Hz combs, likely due to HWS, are quite problematic.
- A useful comparison point is the recently-mitigated 1.66 Hz comb. Considered together, the HWS combs are likely worse for CW searches (much worse if you just look at October as a reference point, but in that case the comparison comb was only intermittently present due to ongoing testing.)
The good news: we have been making progress on a good fraction of the highest-priority combs.

Details

Key

Color-coding and letter labels convey identical information.

A	9.47-8 Hz comb triplet. (70219) Duplicate entries likely due to frequency shifts, which have been observed for this comb (72323) Cause unknown.
B	1.66 Hz comb related to OM2 heater driver and variations which appeared during testing in October. Now mitigated. (72967)
C	near-1Hz and near-5Hz combs recently associated with HWS (74614, 74617)
D	near-30 Hz comb. Cause unknown.
E	set of near-100Hz combs with various offsets. Cause unknown
no tag	Entries that are not persistent over multiple months.

August

Ranking	Comb spacing	Comb offset	Relative priority	Label
1	9.47425	0	46	A
2	9.47539	0	45	A
3	1.6611234	0	44	B
4	9.480545	9.48	39	A
5	4.9842174	0	22	C
6	29.969515	0	17	D
7	99.998456	70.029	5	E
8	6.64457	1.659	5
9	99.99846	29.9695	5	E
10	99.99864	0	5	E
11	99.99844	89.909	2	E
12	99.99846	0	2	E
13	199.9969	10.09	1	E

October

Ranking	Comb spacing	Comb offset	Relative priority	Label
1	9.475416	0	43	A
2	9.474265	0	43	A
3	9.48057	0	42	A
4	9.480574	0	39	A
5	0.996787	0	32	C
6	4.98425	0	30	C
7	1.10864403	0	23	B
8	29.969514	0	15	D
9	1	0	6
10	99.99846	29.9694	5	E
11	99.998644	0	5	E
12	99.99846	70.029	4	E
13	99.99845	10.09	2	E
14	99.99845	0	2	E

November

Ranking	Comb spacing	Comb offset	Relative priority	Label
1	9.47429	0	47	A
2	9.4754423	0	34	A
3	9.480612	0.0003	34	A
4	9.475456	9.4748	33	A
5	0.996785	0	32	C
6	4.984252	0	29	C
7	29.96951	0	15	D
8	28.44192	9.48	8
9	0.12332754	0.1166	8
10	0.1233334	0.0614	7
11	47.4031	28.4417	6
12	1	0	6
13	99.998458	70.029	4	E
14	99.99846	29.9694	4	E
15	99.99844	0	2	E
16	99.99844	89.9088	2	E
17	8.426278	5.5594	1