PSL Status: 
SysStat: All Green, except VB program offline & LRA out of range 
Output power: 32.4w  
Frontend Watch: Green
HPO Watch: Red

PMC:
Locked: 5 days, 2 hours, 3 minutes
Reflected power:    2.1w
Transmitted power: 22.8w 
Total Power:       24.9w 

ISS:
Diffracted power: 9.2%
Last saturation event: 0 days, 0 hours, 24 minutes 

FSS:
Locked: 0 days, 0 hours, 24 minutes
Trans PD: 1.384v
 

DarkhanT, RickS

We found that the DARM_CTRL excitation line reverted to old values on 7/31 (last Friday) at about 11:13 PDT, 18:13 UTC.  Perhaps this was the result of an errant BURT restore, but we didn't find a record of one in a quick survey of the aLog.

When we set the lines last week (see this link), we didn't update the SDF (our bad!).

Today, we reset the frequency of the DARM_CTRL line and adjusted the amplitude to give us SNR ~100.  We also adjusted the amplitude of the Pcal lines to adjust their SNRs to be near the design values.

The updated settings are:

Wanted to know before Tuesday whether there were any reservoir level=>accumulator problems.  All reservoir levels are unchanged.  No HEPI maintenance tomorrow.

Late entry from last Tuesday's SUS front end restarts, here are the results of the 18bit DAC AUTOCALs performed by the IOP model. One card fails autocal, two take an addtional 1.2S to complete.

h1susb123

H1 was locked when I got in, so I brought ISC_LOCK to DOWN to get some locking practice.

It went up to CARM_ON_TR before stopping and notifying  of "No IR in arms".

Sheila mentioned in a log a few weeks back to go to manual and then go back to the state PREP_TR_CARM, but that did not solve the issue and broke lock when I went back to CARM_ON_TR.

Brought it back up and got the same notification, and then I did exactly what I did last time.

While it was going up and down the last few times I was investigating some of the work the commissioners did last night, and I ended up using SDF to switch back some of the changes from alog20146

At this point I got Jenne involved and she worked hard trying to figure it out while I went to a training.

When Evan came in he admitted that he had forgotten to turn back on the Input to the H1ALS-C_REFL_DC_BIAS filter module.

This seemed to have solved the issue.

This filter module is not being monitored, so I added it to the SDF monitor and Jenne added it to the Guardian.

All seems to be good now, made it to COIL_DRIVERS before a commissioner accidentally lost lock.

Log Times – The time stamp on the headers of aLOG entries are in Local Time. After much discussion, the times in body of the log entries should be entered in UTC time, with a note to that effect. Example: “restarted XYZ at 15:45 UTC”.

Betsy is giving operator training on the SDF system at 10:00 in the control room.

The New LIGO Web page has launched.
 
Prep work for the Tuesday maintenance window: 
   Sub Systems are coordinating planned updates
   CDS: will swap a switch on the End-Y UIM Coil Driver
   VAC: will be regenerating the NEG pump at End-X
   FAC: will be moving several crates to Mid-X    

Matt E and I were talking about the broadband noise that is showing up coherently in the OMC DC readout, increasing the noise by 15% or something above shot noise, at frequencies above ~80 Hz. The observation is that this noise increases as the input power is increased (i.e., the watts/rtHz on the OMC DC PDs goes up with higher input power). Amplitude noise on one or more RF sidebands is a plausible source of this noise (not a new idea), and we wanted to suggest specific tests be done to look for RF sideband noise. For example:

• measure the amplitude noise on the 9 MHz and 45 MHz signals coming out of the RF distribution amplifiers in the LVEA that drive the IO EOM (not sure if there are any active devices between these distribution amps and the modulator crystal)
• measure the (AM) noise on the light reflected from the OMC, in full lock (if possible); this light has most of the carrier removed, so any AM on the RF sidebands should be relatively larger than in the OMC transmitted beam (the OMC REFL beam is typically blocked by a beam diverter in low noise, I guess; if the diverter is opened the beam should go to two QDPs in HAM6, if they are aligned)
• measure the RF sideband noise by locking the OMC to one of these sidebands (in DRMI, e.g.); I understand Stefan made an attempt at this already for a 45 MHz sideband -- ?
• of course if the new EOM driver is installed then you could try reducing the modulation index after transitioning to low-noise

There have been some questions about how to run the HWS code.

The HWS code runs on one of three HWS computers, we have one at each end station and one at the corner station.  I have set up a tmux session to run the HWS code constantly at the corner station.  If the code is running, the heartbeat will flash on the TCS HWS ITMX/Y medm screens, and the seidel aberrations will update once a second on the HWS ITMX/Y CODE screen.  To take a measurement using the HWS, in addition to having thr HWS code running, you also need to turn on the RCX link framegrabber power, the Dalsa 1M60 Camera power, and the Superluminescent diode (SLED) power switched on the HWS medm screen.  To increase the lifetime of the SLED and to avoid injecting 1Hz noise into the PEM channels (we are working on filters on the camera power supply to fix this one), we are leaving the HWS hardware off if we are not using it.

If you want to stop or restart the corner station code for some reason, you can ssh into the cornerstation hws computer:

>>    ssh -X controls@h1hwsmsr

and attach to the tmux session

>>    tmux attach

This webpage (http://www.dayid.org/os/notes/tm.html) has a list of tmux commands.  We are running two sessions, one for ITMX and one for ITMY.  Go to the relevant session, go to the folder ~/temp, and run the HWS code with the command

>>    Run_HWS_H1ITMX  (or ITMY....)

There was a persistent excitation in:

H1:ALS-C_REFL_DC_BIAS_EXC

on h1lsc.  This was presumably from an awg process left running by Evan on operator1 workstation.

I killed ALL testpoints on h1lsc (dcuid 10):

jameson.rollins@operator1:~ 0$ diag -l -z
supported capabilities: testing  testpoints  awg 
diag> tp clear 10 *
test point cleared
diag>

I took down the IFO at 717 PST for locking training. The insiral range shows that it was locked for over 12 hours. Awesome!

Based on measurements of the DARM OLTF and the EY PUM/test crossover that Jeff and I took last week, we can estimate the current value of the EY ESD actuation coefficient. It is 1.45×10⁻¹⁰ N/V², with a 20 % uncertainty. This is an 80 % increase compared to the previous value (0.8×10⁻¹⁰ N/V²) which was measured at the end of May.

This number mostly relies on the crossover measurement, since above 10 Hz, the effect in the OLTF of changing the actuation coefficient is largely the same as changing the optical gain. Additionally, this number requires us to assume a number for the PUM actuation coefficient. Here I assume that it has not changed since the May calibration (i.e., I use 7.0×10⁻¹³ m/ct at dc).

Note that the modeled crossover doesn't really agree well with the measurement above 80 Hz. More investigation is required, particularly since during ER7 we already knew there was an issue with the DARM model around 10 Hz. (This discrepancy is why I say the uncertainty in the coefficient is no better than 20 %.)

To generate this number, I took Jeff's ER7 calibration script and made a version (H1DARMXO.m) that models the crossover. Both scripts (and the parameters file for the July 25 measurement) live in the CalSVN under Runs/PreER8/H1/Scripts/DARMOLGTFs. All parameters were left the same as their ER7 values except for the optical gain (I use 1.0×10⁶ ct/m), the DARM pole (I use 330 Hz), and the EY L3 drive strength (I use 11×10⁻¹⁵ m/ct at dc). By tuning the L3 drive strength to match the measured crossover, we can extract the ESD actuation coefficient, assuming the rest of the L3 signal chain has been well-characterized. This is how I get the number quoted above.

The 80 % increase is sort of consistent with the 70 % increase that we saw when retuning the L3 digital gain post-vent. Strictly speaking, that was a measurement of the relative strengths of EX and EY. However, the DARM OLTF (with the retuned EY L3 gain) stayed roughly the constant before and after the vent, indicating that this 70% increase really is a change in EY.

Evan, Stefan

Using a line at 6409.7Hz we found a null in the frequency noise coupling. Thus we took the REFL_9 to OMC_DCPD_A transfer function (plot 1).
This is a nice modelling challenge - thus we spend some time calibrating it in meaningful units.

Calibration:
 - OMC_DCPD_9 (H1:IOP-LSC0_MADC0_TP_CH12):
   - This is just a copy of the filters in the PDA filter module, plus the 13.7kHz 17.8kHz poles from preamp (alog 17647). We did not take into account the AA board, but it should be the same for both channels:
   - G=8.63151e-07
   - P=0.87, 7.689, 7.689
   - Z=10.07, 78.912, 90.642, 13700, 17800
 - REFL9 (H1:IOP-LSC0_MADC1_TP_CH28):
   - The gain is 2900V/WattsRF (see alog 10661) x (12dB whitening) x 1638.4cts/V, plus a z=1,p=10Hz whitening filter (again, no AA board compensation)
   - G=5.2867e-08 = 1/(2900*3.9811*1683.4)
   - P=1
   - Z=10

Plot 2 shows the 9 OMC_DCPD traces during heating, calibrated in A/rtHz

The xml template is in LIGO-T1500414
https://dcc.ligo.org/T1500414

The broadband level below 8kHz didn't change, but the structure around 15kHz disappeared... (Compare to alog 19856)

Attached is a plot of the frequency noise in OMC_PDC_A at six different times during the thermal tuning. There is a significant drop in frequency noise coupling. However the feature that changes most drastically is the carrier 10-mode resonance at 5.1kHz. Thus some of this might be alignment induced effects.

Plot 2 has three more traces with even more heating.

This is a brief update of the current situation of the ISS 2nd loop.

• It successfully lowers intensity noise.
• The resonant peaks of the periscope mirror mount, which would contribute significantly to DARM, can be pushed to more than a factor of 10 below the current DARM floor, in 20-2k Hz band.

[Contribution to DARM]

Here are estimation of the contribution of intensity noise to DARM with and without closing the 2nd loop:

The left plot is an estimation without the 2nd loop closed, and the right plot with the 2nd loop closed. The estimation was done by measuring the coupling transfer function from the ISS 2nd loop PD array to the DARM error point and propagating the measured spectra of the ISS array via the measured transfer function to DARM displacement. As you can see, when the 2nd loop is open, it pollutes the DARM spectrum in 100- 400 Hz. Though it looks like I am missing a factor of two or so for some reason in order for the intensity noise to be dominant in the DARM spectrum as observed.

As shown in the right plot, the loop suppresses intensity noise and pushes it to a point more than a factor of 10 apart from the DARM noise floor. This is good. One thing I noticed is that the spectral shape of intensity noise changed depending on whether the 2nd loop was closed or not. For example, the left plot clearly shows structure in 100 - 400 Hz band in the estimated contribution of intensity noise while the right plot does not show the structure. I am still studying what is going on, but it seems like it is from some kind of readout noise of the PD array which covered the real spectral shape.

Also, I attach a measured coupling from the PD arrays to DARM displacement [meters/RIN].

As shown, it is on the order of 3-4 x 10^-14 [meters/cnts]. By the way, meters, I refer here is unsuppressed DARM displacement. The measurement was done by injecting swept sine at  H1:PSL-ISS_TRANSFER1_INJ with the 2nd loop intentionally disabled in order to get high coherence. The interferometer was locked fully in low noise and a PSL power was at 24 W at around 8:40 PT of July 31st.

[Suppression]

As mentioned above, the suppressed noise does not make sense. They look as if they are covered by some kind of readout noise.  Nevertheless, it is evident that the suppression at 300 Hz is approxiamtely a factor of 60 as expected. Good. Later, Stefan and I undid the anti-whitening in the measured spectra in order to check whether the signals were above ADC noise or not -- they were above ADC noise by a factor of 10 or so. Also, I believe that the structure in 10-20 Hz is some scattering induced noise which Gabriele reported before (for example, alog 15198).

[Next to do]

* Modeling of the measured intensity noise coupling. 

* Figure out the read out noise.

Kiwamu, Stefan, Evan

We are trying to minimize the coupling of frequency and intensity noise into DARM by tuning the central heating on the IX CP.

The following excitations have been set up:

• Frequency excitation at 6409.7 Hz. 40 ct excitation into ALS-C_REFL_DC_BIAS (FM gain 1, all filters off). This goes into input 1A of the summing node board with a slider gain of 0 dB. We use LSC demodulator #1.1 to demodulate the signal in OMC DCPD sum.
• Intensity excitation at 2202.7 Hz. 40 ct excitation into PSL-ISS_TRANSFER1_INJ (FM gain 1, all filters off). This goes into the error point of the inner ISS loop. The outer ISS loop is off. We use LSC demodulator #2.1 to demodulate the signal in OMC DCPD sum.
• SRCL excitation at 748.7 Hz. 5000 ct excitation into SRM via LSC lockin oscillator #3. We use LSC demodulator #3.1 to demodulate the signal in OMC DCPD sum.
• Additionally, Stefan set up a broadband, analog frequency noise injection from 3 kHz to 30 kHz into input #2 of the common-mode board. This must be reverted in order to relock the interferometer.

The amplitudes were chosen so that each line has an SNR of 50 or so in OMC DCPD sum with a 10 s FFT. Each demodulator demodulates OMC DCPD sum at the appropriate frequency, and then lowpasses I and Q with a 100 mHz, 4th-order butterworth.

At 2015-08-03 01:19:45 Z we changed the IX CP heating power from 0.23 W to 0.36 W.

At 2015-08-03 02:57:25 Z we changed the IX CP heating power from 0.36 W to 0.53 W.

At 2015-08-03 04:26:20 Z we changed the IX CP heating power from 0.53 W to 0.41 W.

Additionally:

• At 2015-08-03 03:26:30 Z we turned off the broadband frequency noise injection.
• At 2015-08-03 03:45:50 Z we closed the outer loop of the ISS.