To continue trying to understand how OM2 is improving range, I compared some recent sqz / no-sqz times with hot/cold OM2. So far, I still see the optical gain reduction with hot OM2 (i.e. cold OM2 is better >kHz), and the improvement in low-frequency noise with hot OM2 (~30-300 Hz?).
- Sept 2023, different OM2 temps for no-sqz / sqz darm (maybe most interesting plot).
- The bottom plot shows the ASD ratio of DARM with cold/hot OM2, where cold/hot ratio > 1 implies that DARM noise with OM2 hot is better than with it cold (i.e. measured darm with hot om2 is less noisy there than with cold om2).
- Same plot but including the same traces from July (adding to LHO:71533) ****
- And sqz/no-sqz at the various OM2 temps.
****Caveat regarding the calibration: I am simply plotting GDS-CALIB_STRAIN_NOLINES for these various times, but this is not the most accurate for the traces before September, as I did not use any corrections to GDS for those times.
I'm interested in this because OM2 was re-heated this week LHO:72967 after having been off for some time, possibly off since ~8/29. If we assume OM2 was cold on bad sqz night following 9/10, LHO:72796, and OM2 was hot & thermalized for today's 9/21 no-sqz time due to IO chassis power issues impacting HAM7 ISI LHO:73026 (reasonable to assume OM2 is hot; the remaining thermister 1 shows a plateau in temperature today) -- then we have some long quiet stretches to compare. For the sqz subtraction (ie, sqz dB as a function of frequency), last done with hot om2 on 8/2 for many sqz angles 72565, these long quiet sqz/no-sqz stretches are super useful. I'm still working on more IFO modelling to be more confident in quantum noise parameters as a function of OM2.
For reference, Camilla helped find the following sqz quiet times, building on the OM2 times used before in LHO:71533. A full dictionary of times used for plotting is attached.
'cold OM2 4':{ # bad sqz night @ https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=72796
'no sqz': {
'gps start': 1378445718,
'gps stop' : 1378446918
},
'FDS': {
'gps start': 1378440000,
'gps stop' : 1378441800
}},
'hot OM2 4':{ # OM2 got cold sometime https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=72967
# these hot sqz/no-sqz times are from 9/21 when ham7 isi tripped for several hours, https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=73020
'no sqz': {
'gps start': 1379340154,
'gps stop' : 1379345854
},
'FDS': {
'gps start': 1379324600,
'gps stop' : 1379328200
}},
I think it's okay to assume OM2 was cold for the sqz data I pulled from 9/10-9/11. I checked trends of AS port alignments over the past 2 months which includes intentional OM2 cycling, and zoomed in from the past 1 month with an un-monitored temperature cycling.
From the same times Daniel found in 72970, that is on Tuesday 8/29, we see about the same alignment shifts that Elenna saw in 70886 from changing OM2 temperature.
Looking at the trends, the alignment shifts with OM2 temps seem reasonably reproducible; I put a green box around trends which seemed the most correlated (i.e. OM1, 2, 3 and OMC SUS alignments).
