Elli, Cao

I have moved the AS_Air camera 30cm along the beampath, to optimise this camera location for an SRC gouy phase measurement.  See attached photo.  The camera is now 20cm in front of the beam waist, instead of 10cm behind it.  We now measure 10.4cm between the beamsplitter (to CAM_17) and AS_Air.
  I have left some clamps in place to mark the original position of this camera, so we can move it back quickly if necessary.

OPERATORS NOTE:  The spot position on the AS_Air Camera will now be somewhat different.  Take note during during the intitial alignment stage.  When aligning the BS, the beam now looks brighter on the AS_Air camera.

I have analyzed some initial measurements from the fast polarization photodetectors (from a lock-stretch on Sat 31st Jan: centered around GPS = 1138230306). The channels H1:TCS-IFO_POLZ_P_HWS_OUT and S_HWS_OUT are the respectively powers measured by the P- and S- photodiodes (in Watts - accounting for the dewhitening and response of the photodetectors).

The absolute level of noise of S and P on the table is roughly the same, albeit with distinct differences in the spectra. The relative intensity noise, on the other hand, is an order of magnitude larger in the S- polarization than in P.

Also shown is the coherence between S and P. The fact that the coherence isn't very large indicates that something (either in the interferometer or the output chain after the BS_AR reflection) is injecting more noise on the S- polarization than on the P-polarization. Obviously, this needs a more detailed investigation.

Lastly - the model includes an estimate of the noise in the polarization angle at the AS port (AS_RN) - this is important because it is close to what the OFI will see and convert to intensity noise at the output of the OFI. In the horizontal axis, we're limited by sensing noise above 4Hz.

The DC level of polarization rotation at the OFI, theta_DC, is around 0.09 rad (5.2 deg) in the middle of the lock-stretch. The estimated intensity noise on transmission through the OFI is 2*theta_DC*AS_RN and is shown in the attached spectra.

Power

RIN

Coherence

Polarization induced RIN after the OFI

[Jenne, Sheila]

We measured the drive to the 90MHz distribution amplifier, and gave it a 2dB attenuator so that we are now driving the distribution amp with 10dBm rather than 12dBm.  We re-measured the outputs of the distribution amplifier, and now they were a little over 12dBm.  So, each output of the distribution amplifier got a 2dB attenuator, so each of the demod boards is getting the 10dBm that they want for their local oscillators. 

Subsystem Status

• SEI:  Upgraded ISI Guardian stuff, but HAM2/3 still need to be manually addressed by Operator (toggle GS13 gains via scripts) [Hugh]
• SUS:  Noise in a PR optic narrowed down (Evan), and will be investigated [Richard]
• PSL:  Nothing [Peter]
• Vac/Facility:  beamtube cleaning/sealing, need to fly genie over arms & viewport work (requiring GV soft close) [Bubba/John]

Reviewed work permits.

Items for Tues Maintenance

• Dust Monitor screens & vacuum work
• PSL ISS modification (needs IMC for 2-3hrs), DAQ restart (Kiwamu)
• End Station ESD driver work, re-terminating cables (Fil)
• SUS Noise Evan found investigation (Richard)
• End Station charge measurement 
• Kyle high voltage cabling continues
• Boom lift taken to an end station (Bubba)
• Control Stations Network at LSB TODAY (Bubba)
• 2pm CDS Meeting to happen 
• Clearing out racks in Mechanical Room, so can clear out off-site warehouse

H1 Status this morning

• Noniminal Low Noise since 2:41UTC (10:41pmPST)
• intention bit:  OBSERVING since 2:49UTC
• observatory mode:  "LOGGING"

At around 7:20 beam-sealing work started on the site.  Ken went out to the end stations just after 8am.  Jim took H1 out of OBSERVE to switch Blends & Robert is queued up for BS upconversion work if H1 remains locked.

Looks like Verbal Alarms was alarming a GRB since 23:50UTC.

AS AIR camera still appears to be frozen.

video4 looks like it was re-booted

Appears to have happened ca 2016-02-07 21:00:00 Z.

Stopping and restarting h1cam18 did not fix the problem.

Summary

Varying the DARM offset by a factor of 2 has no effect on the unexplained noise above 70 Hz.

Details

Nominally we run with 20 mA of DCPD sum current, which (with an optical gain of 3.2 mA/pm) corresponds to a DARM offset of 13 pm. I took quiet data (15 minutes at a time) with sum currents varying from 10 to 40 mA, which corresponds to DARM offsets from 9 to 18 pm.

Thanks to the automatic gain scaling that Dan and Stefan installed before O1, no manual gain adjustment is needed either for the DARM loop or the calibrated freerunning channels. At each offset, I remeasured the DARM OLTF just to be sure.

I did not adjust the SRCL feedforward during this test, and indeed the coherence below 70 Hz between DARM and the SRCL control signal is increased at DARM offsets other than 13 pm. At 40 mA sum current, the coherence is >0.3 from 25 to 40 Hz. Therefore, the excess noise below 70 Hz during this test is due almost certainly to the SRCL feedforward becoming mistuned.

As part of the locking sequence, we switch the sensor for the SRM yaw loop from AS B 36I to a combination of AS B 36I and AS A 36I. This is necessary because pure AS B 36I is not a good sensor for SRM alignment at 20+ W of PSL power. Conversely, the combination of A and B is a slightly inferior sensor for SRM alignment at 2 W; one can see that POP90 increases slightly after switching.

So far, we've been doing this switch as part of the 2 W ASC engagement sequence, which (under normal conditions) occurs five minutes or so before increasing the power to 20+ W. However, over the past week, this switch seems to make the interferometer less stable, and tonight alone has caused two lock losses in a row.

Therefore, I moved this sensor switch later, so that it occurs just before increasing the PSL power. So far it's worked twice in a row.

1500 -1520 hrs. local -> To and from Y-mid 

Next over-fill to be Monday, Feb. 8th before 4:00 pm

Started my shift with the IFO locked at NLN for the first ~2.5 hours.  After an EQ knocked us out, this was followed by another ~1.5 hour lock.  This was lost due to commissioning efforts.  Since then, we have been struggling a bit to get past ENGAGE_ASC.  There have been several largish spikes (~1 um/s) in the 0.03-0.1 Hz seismic plot, but only at EY.  Winds are gusting to 30 mph and microseism is trending down.  Evan and I aren't sure what could be causing these spikes, maybe it is wind.  The spikes seem larger than I am used to seeing for winds in this range.

I spent some time this evening measuring OLTFs of our beamsplitter loops and the SRC pointing loops. We might find it helpful to refer back to these measurements when trying to reconstruct the ASC later.

As a reminder, the beamsplitter loops the 36 MHz AS WFS. The SRC pointing loops use the ASC QPD as a sensor, and feed signal to both SR2 and SRM (in such a way as to be decoupled from the 36 MHz SRM loop).

The beamsplitter OLTFs seem pretty straightforward; the UGFs are about 2 Hz for pitch and 3 Hz for yaw.

The SRC pointing loops seem to show complex plant dynamics, so it is difficult to quote a single UGF. There are UGFs ranging from 0.5 Hz to 3 Hz or so. Presumably another UGF in each loop exists at some frequency below the plant dynamics, as with the differential hard loops.

Between Jenne and me, I believe we have either OLTF measurements or step response measurements for all the ASC loops except the four soft loops.

Our first lock in several days was short lived.  Apparently mother nature had other plans.  5.5 EQ near Fiji.

Attached are plots of the ETM charge measurements Betsy took earlier this week.

Carlos, Jim, Dave, Aidan:

Carlos installed an Ubuntu14 boot drive in the h1hwsey computer this afternoon. The old Ubuntu10 HDD was left loose in one of the unused SATA bays if we need to go back to the old OS.

This system is now ready for Aidan and the TCS team to test their latest HWS software. The controls account is setup on this machine, and /data is mounted from h1hwsmsr.

BTW: The DAQ EDCU is running RED because it is not connecting to the missing ETMY HWS channels.

Evan and Kiwamu,

We have been unable to lock the interferometer since this Tuesday (alog 25431). We finally identified and fixed the problem.

It was the cage servo of SR3 which for some reason had a too high control gain and therefore kept feeding sensing noise to the suspension up to 1 Hz. We are happy now.

[Symptoms]

The symptoms were described in Evan's original alog.

In addition, today we noticed that the lock loss in DRMI often happened with a mode hop, indicating that some kind of misalignment was involved. Since the mode hop can be easily triggered by the large optics (i.e. BS, ITMs, PR3 and SR3), we suspected the large optics. Then, we found that we could stably lock PRMI which pointed us to SR3.

[Something happened in this Tuesday]

Trend data showed increase in the pitch motion of SR3. See the attached. The increase of noises occurred at around 4 pm local time of this Tuesday. We have no idea what triggered this situation.

By the way, the UR OSEM seemed as if it had reduced noise, but it turned out that this was due to the 60 Hz power line for some reason decreased at the same time. We then switched off the cage servo to see if it improves the situation. Indeed it did. In fact DRMI was able to lock more stably.

We have checked the damped spectra of the top and bottom stages without the cage servo comparing against the past ones (alog 17781). We did not find any obvious issues with the suspension when the cage servo was off. At this point, we concluded that the problem is in the cage servo code rather than the suspension or its damping system.

[The fix]

We lowered the control gain in the guardian by a factor of 100 which may sound big to some readers, but this gave us a good control time scale of 3 minutes according to a coarse impulse response test.

The resulting spectra at the top and bottom stages seemed as quiet before. So this is good. The code is checked into SVN.

We still don't understand why this happened.

Cao, Ellie, Dave O and Aidan

From llo alog 21927, Aidan found that the ratio between s an p polarizations is higher than expected.  The polarization at the output port has been observed to change over time during lock stretches. In particular the s polarization reduces by 30-50% over the course of 1-2 hours and p polarization slowly increases. Due do various polarization-depenent optical elements in the interferometer, the s-polarization pick up different phase shifts. Excess of p-polarized light may couple to DC readout and introduces excess of noise at the output. Given the time dependent behaviour of the s-polarisation we would expect the DARM noise to change with time if  polarization noise was contributing in a major way to the DARM spectrum. The DARM power spectra were inspected a number of times during post power up to  investigate the dependency of the noise on the polarization  the state of the interferometer.

DARM power spectra from 19Dec15, 26Dec15 and 9Jan16 lock stretches show no apparent changes over time after power up. These lock stretches were during the O1 run and were chosen because the interferometer went to observing mode very quickly after the power was increased. Power spectra are recorded at 0.19 Hz bandwidth, 10 averages. The interferometer went to observing mode at 7, 5 and 2 minutes after power up on 19Dec15, 26Dec15 and 9Jan16 respectively.

There is no clear correlation between the polarization drift and the DARM spectra. Whereas there is a 30%-50% decrease in s-polarization over the course of 1-2 hours after power up, the DARM noise spectra remains stable in the 10 to 70 Hz range.

The DARM spectra also indicates no effect due to thermal lensing as the DARM spectra is very stable during self-heating of the interferometer. Thermal lensing relaxation time is approximately 20 minutes after power up. DARM power spectra after stabilization (occurring at minimum 2 minutes after power up) remains constantst during thermal lensing relaxation period and beyond.

We will be looking into the same problem at Livingston, which has a stronger polarization drift.

Again Masayuki.Nakano reported with Stefan's account

Kiwamu, Masayuki

We measured spectrum of the OMC DCPD signals with a single bounce beam. It would help a noise budget of a DARM signal.

What we did

1. Increase the IMC power
IMC power was increased up to 21W. Also H1:PSL-POWER_SCALE_OFFSET was changed to 21.

2. Turn of the guardian of isc-lock
Requested 'DOWN' to the isc-lock guardian to not do anything during the measurement.

3.Miss align the mirrors
For leading the single bounce beam, all of mirrors were misaligned by requesting 'MISALIGN' to guardians of each mirrors except for ITMX.

4.Aligned the OM mirrors
When we got single bounce beam from IFO, there was no signal from ASC-AS-A, B, C QPDs initially. We aligned OM1,OM2,OM3,OMC suspensions with the playback data of OSEM signals

5.Locked the OMC
The servo gain, 'H1:OMC-LSC_SERVO_GAIN', was set to 10 and master gain of the OMC-ASC was set to 0.1.
The DCPD output was 34 mA.

6.Measurement (without a ISS second loop)
The power spectrum of below channels are measured. Measurement frequency was 1-7kHz and BW was 0.1 Hz. The measured channel was as below.
H1:OMC-DCPD_SUM_OUT
H1:OMC-DCPD_NULL_OUT
H1:PSL-ISS_SECONDLOOP_SUM58_REL_OUT
H1:PSL-ISS_SECONDLOOP_SUM58_REL_OUT was used as the out-of-loop sensor of the ISS.

7.Closed the ISS second loop
The ISS second loop was closed. The sensors used to gain error signal was PD1-4.

8.Measurement (with a ISS second loop)
Same measurement as step5. In addition to that, the coherence function between DCPD-SUM and SECONDLOOP_SUM was measured.

Discussion

I scaled out-of-loop sensor signals of ISS, i.e. the residual intensity noise after the ISS second loop, to the same unit as OMC-DCPD signals. The scaling factor was estimated by dividing the H1:OMC-DCPD_SUM_OUT spectrum (without ISS) by H1:PSL-ISS_SECONDLOOP_SUM58_REL_OUT spectrum (also without ISS) at 100Hz.
I scaled those spectrum both (hereafter 'both' means with and without closing ISS) by same scaling factor.
You can see the DCPD-SUM spectrum, DCPD-NULL spectrum and scaled second loop ISS out of loop sensor signals in attached plots.

The both NULL signals agree with the shot noise of a PD with 34mA signal (cyan curve) above 30Hz, and below that it would be limited by ADC noise.
About the SUM signals, it seems to consistent with the scaled intensity noise above 300 Hz. Also they have some coherence between the intensity noise and the OMC PD signal upper than 300Hz(see another plot). On the other hand, there seems to be some unknown noise below 300 Hz when the second ISS loop was closed.

Possibly this unkown noise might come from the length motion of the OMC. I attached another plot. This plot is the one of same channel(upper) and the OMC error signal with a different servo gain of OMC LSC loop. The error signal and DCPD-SUM signal seem to have similar structure around 100Hz. I haven't any analysis yet because these plots are measred after whitening filter had some trouble and we are planing to do same measurement again with whitening filter.

[Jenne, Cao]

What was once the 90 MHz local oscillator for just the ASAIR 90 WFS now goes to a distribution amplifier box.  3 of the outputs of that board now go to the local oscillator inputs for each of ASAIR_90, AS_A_90 and AS_B_90. The local oscillator inputs want 10dBm each, so we measured the output of the distribution box, and each output was 15dBm.  So, we put 5dB RF attenuators on each spigot.  Next up, we'll lock DRMI and look at phasing.