jeffrey.kissel@LIGO.ORG - posted 16:14, Wednesday 05 March 2014 - last comment - 16:34, Wednesday 05 March 2014(10552)
H1 SUS ETMX UIM/L1 Coils Balanced
J. Kissel Following the same procedure outlined in LHO aLOGs 9453 and 9079, and similar to results from LHO aLOG 10493, with virtually the same demod parameters (only the amplitude was decreased from 1.25e5 to 1.2e5 [ct]) I balanced the coils on the UIM stage of H1 SUS ETMX. The final balanced gains in the L1_COILOUTF bank are H1 SUS ETMX L1 Channel Balanced COILOUTF Gain UL -0.966 LL +1.004 UR +0.996 LR -1.034 The precision is still within +/- 0.5%; the ground motion while tuning the gains was not much better than yesterday, even though I tried several configurations of the ISI. See details of balanced vs. unbalanced signal SNR in comments below. This balancing has reduced the L3 P and Y caused by a L1 pringle excitation at 4 [Hz] by DOF Reduction Factor @ 4.0 [Hz] P > 11.9 (peak below the noise, and totally incoherent) Y > 57.6 (peak below the noise, and totally incoherent) The attachment shows the result from which these values were obtained, comparing the optical lever ASD at 4 [Hz] driven from L2 at the same amplitude for both balanced and unbalanced configurations. Important note -- I found and was foiled by finding the L1_COILOUTF_UR gain sign set to Found Expected L1 UL - - L1 LL + + L1 UR - + L1 LR - - where expected comes from T1200015, and E1000617. Note these signs are exactly opposite from the PUM, because the UIM uses BOSEMs and the PUM uses AOSEMs, whose coils are wound in a different direction. Thus, the same magnet polarities are compensated by opposite signs. I did a cursory check on the other three QUADs, and the same mistake is there too. This might just be a systematic, copy and paste error that we've propagated every where, and didn't notice until now because we haven't needed to use the UIM.
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Comments related to this report
Measurement Details
-------------------
Coil Driver Configuration:
State = 1
I was able to get plenty of SNR leaving the coil driver in the state I found it.
Demodulator filters used:
SIG band pass: BP4.0Hz = butter("BandPass",2,3.5,4.0)
DEMOD I & Q low-pass: CLP50mHz = cheby1("LowPass",2,3,0.05)
Demodulator Drive Parameters
Freq [Hz] Amp [ct] Sin [ct] Cos [ct]
4.0 120000 10000 10000
4.0 120000 10000 10000
SEI Configuration:
HPI: Level 1 Isolation, "Pos" position sensor only blend filters
ST1: Level 2 Isolation, "TCrappy" blend filters (in all DOFs)
ST2: Level 2 Isolation, "TCrappy" blend filters (in all DOFs)
Note -- Sebastien had informed us that the Level 3 isolation filters and ST1-ST2 Sensor Correction are unstable for the time being, so I stuck with the above configuration.
Resulting Demod Phases:
Measured using a 200 second average (shorter than yesterday) of the demodulated signals, i.e.
tdsavg 200 H1:SUS-ETMX_LKIN_P_DEMOD_I_OUT H1:SUS-ETMX_LKIN_P_DEMOD_Q_OUT H1:SUS-ETMX_LKIN_Y_DEMOD_I_OUT H1:SUS-ETMX_LKIN_Y_DEMOD_Q_OUT
H1 ETMX L2
Demod Phase [deg] Unbalanced Value [ct] Balanced Value [ct]
P 79 I +1.933 pm ~0.75 -0.103 pm ~0.75
Q -0.072 pm ~0.75 -0.060 pm ~0.75
Y 78 I +5.181 pm ~0.75 -0.012 pm ~0.75
Q 0.148 pm ~0.75 0.078 pm ~0.75
note that the quote pm values are the by-eye, peak-to-peak amplitude of the demodulated signal which oscillates with a ~25 sec period. I qoute values to a much higher precision because I'm averaging over 200 seconds.
To perturb the PIT or YAW balancing by 1%:
/ligo/svncommon/SusSVN/sus/trunk/Common/PythonTools/perturbcoilbalance_fourosem.py H1 ETMX L2 [PIT/YAW] 0.01
Exact balanced values:
Measured using a simple command line caget, i.e.
caget H1:SUS-ETMX_L2_COILOUTF_UL_GAIN H1:SUS-ETMX_L2_COILOUTF_LL_GAIN H1:SUS-ETMX_L2_COILOUTF_UR_GAIN H1:SUS-ETMX_L2_COILOUTF_LR_GAIN
H1 ETMX L1
Coil COILOUTF Gain
UL -0.965868
LL +1.003680
UR +0.995864
LR -1.003386
Of course, these values are set at arbitrary precession, they're rounded to the values quoted in the main entry (a) because the measurement uncertainty is no better than 0.5%, and (b) the MEDM screen does not display out to higher precession, so further precision would not be visible.