BRS software crashed on the 25th, so today I went to EX to restrart the code. I kept the damper commented out, so the damper is currently OFF. I will turn it back on when it seems like it will be calm down at EX for a bit (vac team is down there right now).

Within a min afer a lockloss, the ISI ETMY ST1/2 WDs tripped. The medm said that it was ST1 T240 and the plots showed a slow drift to the WD trip level (plot attached). HEPI moved 170 um after lockloss before tidal began to bleed down. A further investigation is ongoing by the SEI team.

CDS: EE shop work to prep for Ring Heater installation
PSL: Wants to tweak PR3 OpLev at first available opportunity
FAC: Continued beam tube cleaning Y-Arm   
VAC: Moving pump cart to End-X for weekend long RGA bake out

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

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