Reports until 13:55, Tuesday 24 December 2013
H1 SUS (SUS)
keita.kawabe@LIGO.ORG - posted 13:55, Tuesday 24 December 2013 - last comment - 14:25, Tuesday 24 December 2013(9079)
BS M2 coil balancing done

I saw no sign of real work in BS M2 coil balancing, I had some time, no SUS person was around, so I started doing it manually.

Coil gains before/after the adjustment:

  Before After
H1:SUS-BS_M2_COILOUTF_UL_GAIN 1.23 1.01
H1:SUS-BS_M2_COILOUTF_LL_GAIN -1.23

-0.985

H1:SUS-BS_M2_COILOUTF_UR_GAIN -1.23 -1.015
H1:SUS-BS_M2_COILOUTF_UR_GAIN 1.23 0.99

Seems like the balance was not that bad anyway. I removed funny overall factor of 1.23 as I and Jeff Kissel agreed last week.

Comments related to this report
keita.kawabe@LIGO.ORG - 14:25, Tuesday 24 December 2013 (9080)

What was done:

H1:SUS-BS_LKIN settings and filters were done newly by me as the existing things didn't make sense. You need to excite pringles mode, S/N is poor, so you want to bring the frequency low-ish to make the motion larger, and the integration time should be very long.

  OSC_FREQ OSC_CLKGAIN OSC_SINGAIN OSC_COSGAIN DEMOD_SIG FM1 DEMOD_PHASE DEMOD_I and Q FM1
H1:SUS-BS_LKIN_P 2.9

100000 (somewhat smaller than 132k counts)

100 (doesn't matter as far as P and Y

SINGAIN and COSGAIN are the same).

100 Bandpass for 3Hz

30 (adjusted to

maximize I phase)

0.01Hz elliptic LPF

H1:SUS-BS_LKIN_Y

2.9 Doesn't matter at all 100 100 Bandpass for 3Hz 140

0.01Hz elliptic LPF

H1:SUS-BS_M2_LKIN2OSEM matrix element P Y
UL 1 0
LL -1 0
UR -1 0
LR 1 (was originally -1) 0

The above LKIN2OSEM matrix will excite the pringle mode, and the idea is to read the OPLEV signal after the lock in and minimize the output. Note that the optic moves in YAW when the're is a PIT imbalance because of the pringle excitation. When you see YAW signal you change PIT balance etc.

The first plot show you what S/N to expect. Left is before the adjustment, right is after.

The second plot is the time series of the lockin output during the adjustment. The first big jump at about t=-50min is the start of the excitation, and I left it for some time, made the first adjustment at t=-40, left it for some time and made the second adjustment at t=-35 min.

It's nice if somebody automates this.

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