Evan, Matt, Lisa

We took ~25 min of undisturbed data starting at Jul 31 2015 09:21:13 UTC , after the MICH FF improvement (and  all the changes described earlier  implemented), with the interferometer locked in low noise ~ 65 Mpc (according to SensMon).

We saw a big glitch during this period (~9:28), a huge one right before (~9:18, right after the mich tuning was done), and another one at the end of the undisturbed period. 

We went back to commissioning mode as Evan is starting some noise injections for his noise budget.

Commissioning Team

For the meeting tomorrow, here is a list with the things that we changed this week, and they are now part of the baseline locking sequence:


1) more aggressive cut-off in MICH, to reduce coherence with DARM above 50 Hz (log 20020 );

2) more aggressive cut-offs in the  ASC_AS_A / AS_AS_B --> OM1 / OM2 centering loops (from 100 Hz to 20 Hz) to remove some coherence with those signals reported by Bruco;

3) more aggressive cut-offs in the OMC SUS alignment loops ( log 20087 ) to remove unwanted OMC length motion which was observed to cause fringe wrapping by Josh et al (log 20079 );

4) heroic modification of the DHARD loops (both PITCH and YAW) during the locking sequence, aimed to make the transition to REFL/TR and carm offset reduction more stable by increasing the phase margin of this loop, which was kind of poor and was seen to cause several lock losses in the past (log 20084 ); these loops have now high ugfs (~ 5 Hz) and >30 degrees phase margin.  Note that the ASC work is not done yet: tomorrow we will add cut off filters, and attack CHARD. Also, we haven't yet succeeded in turning off the ITMs optical levers, which are still on;

5) modification of the ISS loop to improve phase/gain margin (log 20088  and log 20088 );

6) IMC WFS --> PSL PZT loop to reduce ~300 Hz peaks in DARM ( log 20051 );

7) found and fixed a sneaky ramp time problem which was causing the switch from ESD ETMX --> ETMY to fail repeatedly (log 20076 ), Jenne got a BIG PLUS for this one;

8) added an offset to PR3 during the CARM offset reduction to counteract the wire heating ( log 20055 )

9) the Guardian usercode has been modified to speed up the locking sequence ( log 20055 ), and improve IMC_LOCK;

The interferometer has been happily locked in low noise at ~ 65 Mpc for nearly 2 hours with all the above changes implemented, and the Guardian has been updated. 

10) (Later edit) Evan just optimized the MICH feed forward, and he reduced the MICH coupling between 30 and 50 Hz; the sensitivity is now better in that region. 

Other things in our to-do-list for tomorrow:

1) More alignment work (cut-offs and CHARD)

2) Test the whole sequence again to check robustness

3) Track down the TMSX weirdness (log 20078)

4) Noise investigations and injections for noise budget

Sudarshan, Matt

The new ISS filter was seen to oscillate at ~1MHz with no input signal.  This was fixed by adding 50pF cap into the feedback of the output opamp.  This cap, in combination with the 10k resistor, puts a pole at 300kHz, which is fine for this loop.  The second loop is currently closed (with the IFO at high power) and appears to be working properly.

Evan, Matt, Josh S. (in spirit)

The OMC ASC  loops now have 0.5Hz cut-off to remove unwanted OMC length motion (see plot).  This change is intended to reduce the OMC SUS velocity so that we don't get fringes in DARM.

The filters are in OMC-ASC_{POS, ANG}_{X, Y} loops (see screenshot), and do not appear to cause stability problems (because the UGFs are below 100mHz) with the MASTER_GAIN up to 0.2, though some gain peaking is observed at this gain.  The normal operating gain is 0.1.

Jenne, Matt, Sheila, Evan, Stefan, Lisa

Tonight we reworked DHARD YAW. We started with a new filter desgin, which avoids inverting any thing in the plant (our old design had just the 2-3Hz resonances inverted).  The first screenshot shows the new control filter (which is in FM6).  This filter gives us significantly better phase margin than we had before.  We engage it in the state DARM WFS (right after transitioning to RF DARM) with a gain of 50, and leave the gain at 50 as the optical gain increases until the state CARM_5PM, where we reduce it by a factor of 2.  This is because the sensor noise is too large at high CARM offsets to run with the final bandwidth.  The attached screen shot shows the open loop gain at some different arm powers.  We are not currently using a boost, but we think that we should be able to turn on the soft boost in FM3 (boostMS).  

We also restored the DHARD PIT gain changes durring the CARM offset reduction that we found alst night, they seem to work fine.

After a half hour at 24 Watts with the new loop on and no ITM oplev damping, we saw a pitch instability ring up (about 6:55 UTC July 31st).  This was fixed by turning back on the ITM PIT oplev damping.  The oplev damping is back in the guardian for now.  

Matt, Evan

Why do the TMSX RT and SD OSEMs have such huge spikes at 1821 Hz and harmonics? These spikes are about 4000 ct pp in the time series. In comparison, the other OSEMs on TMSX are 100 ct pp or less (F1 and LF shown for comparison).

Also attached are the spectra and time series of the corresponding IOP channels.

A little piece of script, deModMonitor.py, which helps you monitoring demodulated signals, is available at 

/opt/rtcds/userapps/release/isc/h1/scripts/demodMonitor.

An example of how this code can be used is TCS_deModMonitor.py and run_TCS_deModMonitor.sh. The main purpose is to monitor how omc dcpd's response w.r.t. intensity noise (, or frequency noise or src length noise) changes when we heat up the compensation plates. A sinusoidal excitation is generated using Chris Wipf's awg module and injected to PSL-ISS_TRANSFER1_INJ. The code then reads out OMC DCPD's demodulated signal every certain amount of time and records the data to a txt file. In case that the code needs to be terminated during a measurement, it will catch ctrl+c and turn off the excitation.

The code is designed s.t. it should be able to used in a general demodulating-monitoring process.

Josh, Daniel Vander-Hyde, Kimberly Mercado

Summary

To decrease uncertainty in calculation of actuation function correction factor, kappa_A, sensing function correction factor, kappa_C, and CC pole frequency, f_c, we've recently increased calibration line amplitudes to give SNR of 100 with 10s FFT (see LHO alog #19792). Earlier Kiwamu posted his investigation of CC pole frequency over the last weekend in LHO alog comment #19988. In this alog we show kappa_A, kappa_C and f_c calculated according to the method described in T1500377-v3 for the same time interval (2015-07-25 00:00 UTC to 2015-07-27 UTC, when GRD-ISC_LOCK_STATE_N >= 501, 1 min FFTs).

Statistical uncertainties of kappa_A, kappa_C and f_c within 1.5 hours time interval highlighted with green are:

Xctrl(34.7) and PcalX(33.1), std(kappa_A) = +/- 0.45 % (1 sigma)
PcalX(325.1), std(kappa_C) = +/- 1.12 % (1 sigma); std(f_c) = +/- 5.20 Hz (1 sigma)
PcalY(331.9), std(kappa_C) = +/- 1.43 % (1 sigma); std(f_c) = +/- 5.55 Hz (1 sigma)
PcalX(534.7), std(kappa_C) = +/- 0.70 % (1 sigma); std(f_c) = +/- 2.08 Hz (1 sigma)
PcalY(540.7), std(kappa_C) = +/- 0.78 % (1 sigma); std(f_c) = +/- 2.68 Hz (1 sigma)

Notice that kappa_C and f_c on the left subplots were calculated from low SNR 325.1 Hz and 331.9 Hz Pcal lines set by Evan (see LHO alog comment #19823). Calculation of these parameters using higher SNR 534.7 Hz and 540.7 Hz Pcal lines (right subplots) gave less noisy results.

Details

C_0, D_0 and A_0 were taken from LHO ER7 DARM model.

To make kappa_C calcluations consistent between results from 4 Pcal lines, a manual correction to phases of Pcal lines that correspond to 130us of time advance was applied. On the plot we report only changes in f_c by subtracting mean value of about 300 Hz. In order to receive an absolute value of f_c using this method, we must take into account exact time delay/advance of PCAL RXPD channel w.r.t. DARM_ERR; possibly a frequency independent phase shift (however we do now know any reason for that); and the DARM model TFs at the reference time, C_0, D_0 and A_0.

Plots of 1 min FFT dewhitened calibration line amplitudes and phases are given below.

Calibration line uncertainties in DARM_ERR readout in a 1.5 hours interval (highlighted with green color) are as follows:

Xctrl( 34.7) = 2.2000e-01 (+/- 0.00 %); Derr( 34.7) = 2.9738e-10 (+/- 0.15 %)
PcalX( 33.1) = 2.4587e-02 (+/- 0.00 %); Derr( 33.1) = 3.0817e-10 (+/- 0.26 %)
PcalX(325.1) = 1.0724e-01 (+/- 0.00 %); Derr(325.1) = 2.0593e-10 (+/- 1.48 %)
PcalY(331.9) = 9.3791e-02 (+/- 0.01 %); Derr(331.9) = 2.0150e-10 (+/- 1.55 %)
PcalX(534.7) = 7.1100e-01 (+/- 0.00 %); Derr(534.7) = 5.8223e-10 (+/- 0.52 %)
PcalY(540.7) = 6.3845e-01 (+/- 0.01 %); Derr(540.7) = 5.8948e-10 (+/- 0.45 %)

P.S.

After today's calibration telecon we've changed calibration lines that will be used for estimation of kappa_A, kappa_C and f_c to (see LHO alog #20063):

• PCALY 36.7 Hz, SNR ~100;
• DARM_CTRL 37.3 Hz, SNR ~90;
• PCALY 331.9 Hz, SNR~100;
• PCALY 1083.7 Hz, SNR~40;

We are also planning to add an ESD line close to low frequency PCALY line and another high frequency low SNR PCALX line at 3001.3 Hz after completing power budget investigations of PCALX module.

Sheila's alog from last night (20055) indicated that they were seeing locklosses during the transition to the ETMY ESD again.   After some investigation, I believe that I have found and solved the problem, so hopefully we won't see those anymore.

The problem was that the SUS-ETMY_L3_LOCK_L gain was being set to zero in the COIL_DRIVERS state (one state before the LOWNOISE_ESD_ETMY state) while there was a large ramp time in the filter bank (input was off at this time, although output was on).  There is no timer or wait time after this.  In the next state (LOWNOISE_ESD_ETMY), the ramp time is explicitly set to zero, and then the gain is set to zero.  However, since the gain had already been set to zero with a long ramp time, and EPICS doesn't acknowledge a write command if the value isn't going to change, the gain was still slowly ramping to zero over 10 seconds.  The LOWNOISE_ESD_ETMY state assumed that the gain had been immediately set to zero, so it turns on the input immediately.  This is sending large signals out, which are also getting sent up the chain to the L2 and L1 stages. 

To solve this, in the COIL_DRIVERS state where the gain is first set to zero, I first set the ramp time to zero (the ramp time is already explicitly set to seconds immediately before the big ETMX->ETMY transition at the end of the LOWNOISE_ESD_ETMY state).  The input is off at this time, so we should not see a difference at this state.  The DOWN state actually turns off the input and turns off the gain, so I'm not sure why the gain is ever non-zero before the LOWNOISE_ESD_ETMY state.  Even if I don't find where the gain is set to a non-zero value between the DOWN state and the LOWNOISE_ESD_ETMY state, this problem is now (hopefully) solved.   

DQ Shift Summary: July 25-26

(See the DQ shift wiki page  for more details.)

There were two long analysis-ready segments in this shift:

Sat Jul 25 22:23:58 to Sun Jul 26 02:23:45 (4 hours)

Sun Jul 26 10:13:36 to Sun Jul 26 23:10:22 (12.9 hours!)

Overall the locks were very clean. Here are the main data quality notes:

• The glitch rate was low and steady!
• The loudest glitches came from the ETMY DAC saturations -- see alog 19937
• Several loud glitches between 100-400 Hz (related to PSL periscope?) occured throughout the locks (a couple per hour)
• Glitches at 60 Hz every ~70-80 minutes, found by hveto to be correlated with the ETMY suspension. (H1:SUS-ETMY_M0_DAMP_L_IN1_DQ)
• Upconversion around the first harmonics of the violin modes is higher than it has been in the past; these nonstationary features have been a problem for the burst search.
• Loud, short-duration low frequency glitches ("blip glitches") are still present. (A few per hour)

Based on discussions during the Calibration Committee call today, we decided to eliminate the 157.9 Hz low-SNR calibration line.

We switched off the excitation which was in the OSC2 position.

So we are now driving at 36.7 with SNR of about 100 for calculating the actuation correction, kappa_A (see LIGO-T1500377), and 331.9 Hz with SNR of ~100 for calculating the sensing correction, kappa_C, and f_c, the cavity pole.

We are also driving at 1083.7 Hz with an SNR of about 40.

All SNRs quoted are with 10-second FFTs.

As soon as we inspect and tune up the Xend Pcal, we plan to start an excitation at 3001.3 Hz with a relatively low SNR (all that we can achieve at this high frequency).

LLO will run lines spaced within 1-2 Hz of hte LHO lines.

This is our current plan for the Pcal lines for the O1 run.

Kyle, Gerardo

0900 hrs. local 

Added 1.5" O-ring valve in series with existing 1.5" metal valve at Y-end RGA pump port -> Valved-in pump cart to  RGA -> Valved-in Nitrogen calibration bottle into RGA -> Energized RGA filament -> Valved-out and removed pump cart from RGA -> Valved-in RGA to Y-end 

???? hrs. local 

Began faraday analog continuous scan of Y-end 

1140 hrs. local 

Isolated NEG pump from Y-end -> Began NEG pump regeneration (30 min. ramp up to 250C, 90 min. soak, stop heat and let cool to 150C) 

1410 hrs. local 

Valved-in NEG pump to Y-end 

1430 hrs. local 

Valved-out Nitrogen cal-gas from Y-end

1440 hrs. local 

Valved-in Nitrogen to Y-end -> Stop scanning