Carried out some noise injections while violin modes were being damped. Analysis will follow. Times below
ASC-DC3_Y_EXC
butter("BandPass",8,0.5,5)zpk([],[1.5+i*2.59808;1.5-i*2.59808;1.5+i*2.59808;1.5-i*2.59808;1.5+i*2.59808;1.5-i*2.59808],1,"n")
ampl 10
start PDT: 2023-07-17 12:12:25.248450 PDT
UTC: 2023-07-17 19:12:25.248450 UTC
GPS: 1373656363.248450
stop PDT: 2023-07-17 12:14:28.217030 PDT
UTC: 2023-07-17 19:14:28.217030 UTC
GPS: 1373656486.217030
ampl 30
start PDT: 2023-07-17 12:15:09.156033 PDT
UTC: 2023-07-17 19:15:09.156033 UTC
GPS: 1373656527.156033
stop PDT: 2023-07-17 12:19:34.343574 PDT
UTC: 2023-07-17 19:19:34.343574 UTC
GPS: 1373656792.343574
DHARD_Y_EXC
resgain(0.22, 2,14)resgain(0.48,3,20)resgain(2.5,8,15)cheby1("BandPass", 6,1, 0.05,3)gain(2000)zpk([1],[0.1],1,"n")
ampl 0.6
start PDT: 2023-07-17 12:25:39.173166 PDT
UTC: 2023-07-17 19:25:39.173166 UTC
GPS: 1373657157.173166
stop PDT: 2023-07-17 12:30:06.552000 PDT
UTC: 2023-07-17 19:30:06.552000 UTC
GPS: 1373657424.552000
ampl 1.0
start PDT: 2023-07-17 12:30:58.643632 PDT
UTC: 2023-07-17 19:30:58.643632 UTC
GPS: 1373657476.643632
resgain(1.2,5,10)resgain(0.22,3,20)resgain(0.45,2,22)resgain(2.2, 1.5,23)
cheby1("BandPass",6,1,0.08,3)gain(1000)zpk([1],[0.1],1,"n")
ampl 1.0
start PDT: 2023-07-17 12:37:54.797826 PDT
UTC: 2023-07-17 19:37:54.797826 UTC
GPS: 1373657892.797826
I had some time to try a DHARD_Y injection, with only a few iterations at imprving the noise shape, and not enough averages. Still, the results are promising and I got a first go at the DHARD_Y plant.
The measurement needs to be improved around 2.6-3 Hz to esolve the shape of the peak / bump there
Witth the noise injection on ASC-DC3_Y, I could determine that the DC centering loops does not limit the DHARD_Y noise: the coherence we normally see below a few Hz is due to DHARD and DC3/DC seeing the same beam motion.
The first plot shows a comparison of DHARD_Y, DARM and DC3_Y with and without noise injection. The second plot shows the DC3_Y noise projection into DHARD_Y, using the transfer function measured during noise injection.
This also implies that the DC centering loops are not responsible for the 2.6 Hz peak