NOTE: This entry is related to 22847 and 22959
This entry is a summary of the 3rd and 4th harmonic frequencies of the QUAD suspensions violin modes. The frequency identification was done through 2 stages;
1) First looking at a 1mHz resolution spectrum of channel H1:OMC-DCPD_SUM_OUT_DQ on 10800 seconds from 2015-10-28 12:00:00 (before the test mass injections described in 22959), total of 20 averages and 50% overlap. See plots attached. This gave a first approximate value of the frequencies.
3rd harmonics (32 modes identified): Attached file: '3rd_Harmonics_from_Spectrum.txt'
4th harmonics (30 modes identified): Attached file: '4th_Harmonics_from_Spectrum.txt'
2) Second, feed the above frequencies to a line tracker (iWave) for a more accurate identification and over different data. In particular 21 hours of data with detector in Observing mode and with damping filters turned off, from 2015-10-21 21:30:00
3rd harmonics (22 modes identified, notice that the reason for the smaller number of modes being identified is the automation applied to the line tracker in order to be able to process the big number of modes being tracked over a long data stream. For this reason the line tracker sometimes locked to the wrong mode of higher amplitude and or was not able to separate modes of high amplitude and proximity. The number of modes identified may improve by more targetted application of the tracker): Attached file: '3rd_Harmonics_from_LineTracker.txt'
4th harmonics (25 modes identified): Attached file: '4th_Harmonics_from_LineTracker.txt'
For reference, here are the compilations of tentative 3rd/4th quad harmonic frequencies from 104.5 hours of early O1 data, using 0.5-mHz binning: Q 1456.1793 1.109279e-18 ******* Q 1456.8448 4.093626e-19 ***** Q 1461.4125 3.152596e-19 ***** Q 1461.7318 1.663059e-17 ********** Q 1461.8627 2.275449e-19 ***** Q 1462.0311 9.120542e-17 ************ Q 1462.3129 1.442451e-16 ************* Q 1462.5991 1.951920e-18 ******* Q 1463.0994 1.613099e-17 ********** Q 1467.4759 9.898746e-18 ********* Q 1467.9648 1.940260e-16 ************* Q 1470.3809 7.576511e-17 ************ Q 1470.8263 1.099916e-16 ************* Q 1471.9279 1.821525e-16 ************* Q 1472.4505 9.761998e-17 ************ Q 1472.5268 7.321176e-18 ********* Q 1474.0800 1.401120e-16 ************* Q 1475.0976 3.710737e-17 *********** Q 1475.2510 2.168896e-16 ************** Q 1476.3779 4.452248e-18 ******** Q 1478.1701 2.011867e-16 ************* Q 1478.6459 2.489583e-18 ******** Q 1482.5840 6.298267e-16 *************** Q 1484.0765 3.847696e-16 ************** Q 1484.4293 7.193998e-18 ********* Q 1484.5241 2.194240e-16 ************** Q 1484.5731 1.033684e-17 ********** Q 1484.6685 2.331379e-16 ************** Q 1922.9259 4.402502e-18 ******** Q 1923.6124 2.213001e-17 *********** Q 1923.8550 3.272046e-18 ******** Q 1923.8610 1.089465e-17 ********** Q 1924.6739 2.196115e-17 *********** Q 1924.9150 1.129535e-17 ********** Q 1926.2402 9.830786e-17 ************ Q 1927.4652 5.627035e-18 ********* Q 1927.4662 5.627035e-18 ********* Q 1928.4620 1.166487e-17 ********** Q 1929.3128 2.991775e-18 ******** Q 1931.5738 2.536072e-18 ******** Q 1932.1391 1.111758e-17 ********** Q 1932.3359 3.306404e-17 *********** Q 1932.6117 3.029987e-17 *********** Q 1940.3232 3.044162e-18 ******** Q 1940.6643 2.881532e-17 *********** Q 1941.3501 9.968986e-17 ************ Q 1942.1270 1.072596e-18 ******* Q 1942.1751 6.163310e-17 ************ Q 1942.3900 6.222474e-17 ************ Q 1943.7780 1.641306e-17 ********** Q 1944.1332 3.131086e-18 ******** Q 1946.7318 4.684879e-17 ************ Q 1947.7089 1.957731e-18 ******* Q 1954.4574 1.942626e-17 ********** Q 1955.9208 2.102610e-17 ********** Q 1957.3347 3.023210e-17 *********** Q 1959.0215 4.312900e-17 *********** where the 2nd number is the inverse-noise-weighted average displacement ASD, and the asterisks are a crude log-scale depiction of the ASD value. This table is a subset of this earlier alog attachment: https://alog.ligo-wa.caltech.edu/aLOG/uploads/21982_20150926195339_Lines_H1-CAL-DELTAL-EXT_O1-week1.txt Although the frequencies are given to 0.1 mHz precision, I have seen them vary in the past by as much as a few mHz over months time scales.
Thank you Keith. I was aware of this frequency list however I noticed that several modes were missing. In principle if mode frequencies do not overlap then we should expect 32 modes per harmonic. In my manual check of the 3rd harmonic frequencies I identified 32 frequency candidates with a few others of small amplitude. In comparison with your list I can confirm that your list misses several 3rd harmonic modes:
There are two very close modes at 1463.097 and 1463.101 Hz, your list only identifies one mode from this pair at 1463.0994Hz. Also your list misses the mode at 1472.217Hz.
In relation to the 4th harmonic: Your list shows a repeat peak at 1927.465Hz, although it assigns a 1 mHz difference between the 2 peaks the amplitude is identical so it looks as if it is actually a single peak.
Notice that the main reason of my analysis is not just to identify the violin mode frequencies but to actually measure their Q (through exponential decay) which I will report in another aLog which I am writting at the moment.
UPDATE ON ORIGINAL ENTRY:
Some of the peaks I originally identified as 3rd and 4th harmonics from the 1mHz resolution spectrum plots are not violin modes, as verified after careful analysis of their exponential decay with a line tracker (iWave).
3rd harmonic identified modes: 30 with Spectrum of 1mHz resolution, the line tracker locked properly to only 25.
4th harmonic identified modes: 26 with Spectrum of 1mHz resolution, the line tracker locked properly to only 25.
For completion I provide next the frequencies of the identified modes, on a table of 3 columns, the first column are the frequencies given by Keith, the second column are the frequencies as per the 1mHz spectrums shown in this entry and the third column are the median frequency tracked by a line tracker on 21 hours of data. The zeros are missing information from each list:
Keith_table 1mHz_res_spectrum Line_tracker_21hours_data
1.0e+03 *
1.456179300000000 1.456180344722471 1.456177151198640
1.456844800000000 1.456847712651581 1.456842618595428
1.461412500000000 1.461413707108750 1.461409317387718
1.461731800000000 1.461733620917401 1.461732469282266
1.461862700000000 1.461861606048793 1.461859532596437
1.462031100000000 1.462032270322383 1.462031865574721
1.462312900000000 1.462313909933999 1.462313301797892
1.462599100000000 1.462599872305624 1.462596623730558
1.463099400000000 1.463097080131224 1.463096689345246
0 1.463100546759006 1.463100039151534
1.467475900000000 1.467476228900213 1.467475846153371
1.467964800000000 1.467965366395409 1.467964868969873
1.470380900000000 1.470381699013083 1.470380789546349
1.470826300000000 1.470827285183412 1.470826225123052
1.471927900000000 1.471929276656110 1.471928631371064
0 1.472217057788634 1.472216372878212
1.472450500000000 1.472451085888389 1.472450299085779
1.472526800000000 1.472528816242792 0
1.474080000000000 1.474080396944674 1.474079862541953
1.475097600000000 1.475099020030272 1.475097416001178
1.475251000000000 1.475252651191380 1.475251394384721
1.476377900000000 1.476379150480257 0
1.478170100000000 1.478170077745102 1.478169573722027
1.478645900000000 1.478646456410533 0
1.482584000000000 1.482587879011576 1.482585385731902
1.484076500000000 1.484082047455499 1.484077440343936
1.484429300000000 1.484431224630876 0
1.484524100000000 1.484525638863272 1.484525699339724
1.484573100000000 1.484573390876472 0
1.484668500000000 1.484669984871669 1.484668763161195
1.922925900000000 1.922927022647360 1.922925588791648
1.923612400000000 1.923613112500675 1.923612097950808
1.923855000000000 1.923855111277119 1.923854588725318
1.923861000000000 1.923862018275805 1.923861256988942
1.924673900000000 1.924674100071188 1.924673358918374
1.924915000000000 1.924915873423103 1.924914735873632
1.926240200000000 1.926241192663720 1.926240582396548
1.927465200000000 1.927466117175330 1.927465533945791
1.927466200000000 0 0
1.928462000000000 1.928465010303079 1.928461858686449
1.929312800000000 1.929315906067996 1.929312798521826
1.931573800000000 1.931575488954602 1.931573475268973
1.932139100000000 1.932140403468284 1.932139817442099
1.932335900000000 1.932335886291686 1.932335653144635
1.932611700000000 1.932611738162179 1.932612502374920
1.940323200000000 1.940327437428355 1.940322842326236
1.940664300000000 1.940668395302165 1.940663844123977
1.941350100000000 1.941355862583405 1.941349656248626
1.942127000000000 0 0
1.942175100000000 1.942176424197661 1.942174876991754
1.942390000000000 1.942391628419225 1.942390477296026
1.943778000000000 1.943779225301499 1.943777686818187
1.944133200000000 1.944135400000000 0
1.946731800000000 1.946734993919390 1.946732788506648
1.947708900000000 0 0
1.954457400000000 1.954461746453794 1.954459288744910
1.955920800000000 1.955924562578534 1.955921817650888
1.957334700000000 1.957335449254732 1.957335075248596
1.959021500000000 1.959024110148374 1.959023577426715