Rick S., Jason O., Matt H., Ed M., and Jeff B.

Went into the PSL today and performed a few maintenance tasks (work permit #5039).

1) Measured PSL power at several points in the beam path:

• 33w - between M1 & M2 (just outside of the front end)
• 26w - reflected from PMC
• 27.2w - incident light on PMC
• 24.4w - downstream of the EOM (in the IO section of the PSL table)
• 24.9w - PMC transmitted

• 67.5mW – upstream of the FSS AOM
• 54.5 mW - Single pass power, upstream of M25 (81%)
• 36.3mW - Double pass power, upstream of FSS EOM (66%, 54%)
• 33.7mW – At top of periscope mirror, incident on RefCav

3) Measured voltage of RefCav REFL PD (H1:PSL-FSS_RFPD_DC_OUTPUT):

• 299mV – With FSS RefCav unlocked
• 165mW – With FSS RefCav locked
  • This is too high, giving a RefCav visibility of only 45%!

Once again the RefCav Trans PD (TPD) has begun to drift down.  Was set to ~1.6V on 1/5/2015 (see alog 15871) and today is reading ~0.9V.  Therefore we adjusted the RefCav alignment by adjusting the vertical and horizontal of the top periscope mirror.  Measured voltages at the RefCav REFL PD.

• Vertical adjustment dropped RefCav to 83mV
• Horizontal adjustment dropped RefCav to 65mV

After adjustment (and locking of adjustment screws):

• RefCav REFL PD - 300mV (with FSS RefCav unlocked)
• RefCav REFL PD - 60mV (with FSS RefCav locked)
  • This gives a FSS RefCav visibility of 80%, which is better.  Per Rick S. this should closer to 98%, so some more work to do here, but is good enough for now and we were running out time in our maintenance window.
• RefCav TPD - 1.63V (H1:PSL-FSS_TPD_DC_OUTPUT)
• RefCav transmitted power - 19.1mW

Will keep an eye on this as the RefCav transmitted power seems to drift down suddenly.  We’re not sure what’s causing this apparent alignment drift.  All the measured powers leading up to the RefCav were close to those measured during the 1/5/2015 adjustment, but the RefCav TPD was still reading ~44% less.

4) We also measured the UGF of the FSS:

• UGF: 200kHz, phase margin 35 deg
  • According to Rick S. this should be closer to 600kHz, so we have some work to do here.
• At 500kHz: -6dB, phase margin 58 deg 

5) For Daniel, we adjusted power at IO PD (IO-AB-PD3-DC) to 3.3V by turning up the PD gain by 3 clicks and adding a ND filter to the PD (see Daniel's earlier alog).

6) We are now storing the 2 3IFO PMCs in the NW corner of the PSL LAE on a cart, with their lids off.

Summary:

Looking at ITMx HWS data from full interferometer locks on 7 Feb and 9 Feb, here are some estimates of ITMx coating absorption:   500(150) parts per billion measured on Feb 7,  9 Feb: 430(130) ppb measured on Feb 9.  For reference, Livingston measured 140-200 ppb coating absorption on the ITMs, see log 14634.

Method:

-HWS measures spherical power.  The raw data was multiplied but a factor of 0.00326 in dataviewer to account for magnification of the image, which gives Spherical power in diopters.   The change in the spherical power before and after the interferometer drops lock was ~5*1(0.02) microdiopters both days.  The measurements were averaged over a few minutes.

-The shperical power is related to absorbed power by 1.06(0.3) mW/microdiopter (log 14634) which means ~5mW power was absorbed.

-On 7 Feb 10.4 kW was in the x-arm, on 9 Feb 11.5 kW was on x-arm (calculated as per alog 16579).  I've assumed 10% uncertainty on this power, but perhapse that is too small.

[absorption in ppb]=[absorbed power]/[locked arm power] *1e9

Datasets and code are saved in /ligo/home/eleanor.king/HWSreadouts.

Jeff restarted ETMX SUS, but this didn't solve the decimation problem reported in alog 16511.

All models on h1oaf0 stopped running just before 1:00 PM PST with ADC timeout errors.  Had to kill the user models and restart the IOP model to recover timing, then the user models were restarted.

Richard, Filiberto

Late last week I noticed the current meter for the Ham4 and Ham5 +-24V ISI DC supplies that feed the coil drivers were oscillating at about 1Hz and 0.5amps.  Today we connected a meter to the output lines of the supply and systematically shut down the ISI system starting with the Ham4 moving to Ham5.  First step was using guardian to take the system to READY state.  We then shut off the outputs using the watchdogs.  The oscillation remained until we shut off the 2nd Ham5 coil driver.  The system was brought back up and the oscillation was gone.  Re-engaged the software had guardian take it back to isolation.  Still no oscillation present.  I will check the power on this system during the week to see if it goes back into oscillation.    There was no obvious problem with the HAM isolation during this time.  If the oscillation returns we will power the HAM 5 electronics down first to see if this corrects the problem.

The h1nds1 NDS server has been reconfigured to serve past data from the same disk systems as h1nds0.  The /trend/minute_raw data has been renamed, and is being copied to /frames/trend/minute_raw because the /trend file system is nearly full.  The h1fw1 is still writing minute_raw files, so there will still be a redundant source for the files.

Added 26 channels. Removed 105 channels.

No Issues at restart, no impact on HEPI Platform.

SDF updated, foton file committed to svn.

The PSL team has installed an ND filter in front of the IO photodiode measuring the power after the EOM. Now we have about 3V. I adjusted the calibration to give us 21W. Old alog at 16437. I added the power readbacks to the IMC overview screen as well.

Summary:

ETMX M0 stage was pushed towards the reaction chain so the F1 flag comes out of the BOSEM. It got slightly better, BOSEM reading changed from  7300 to 8300.

Reaction chain was pushed away from the test mass chain so that L1 and L2 stages don't get too close to the test mass chain.

We don't know yet if this made any change to the damping etc.

Details:

Due to a huge pit offset we need to align ETMX (it was large before the vent, but it got worse after), F1 flag is too much into the coil, and supposedly that is one of the reasons why the PIT damping is not that good. In the first attachment, you can see the BOSEM reading of F1 to be about 7300 (ideally this is 16000 or so).

I gave the top stage a length push such that the test mass chain is pushed away from the top face BOSEMs, and gained about 1000 counts in F1 BOSEM. With this offset the coil outputs should still have some headroom even if you misalign the ETMX to point to baffle PDs.

One drawback of this is that the test mass chain is pushed towards the reaction chain, which is fine under a normal circumstances, except that Sheila tells that misaligning the reaction chain of ETMX affected the actuation behavior of L1 and/or L2. I'm worried that something is close to touching, and pushing flags further into OSEMs doesn't sound like a good idea.

So I gave a length offset to the reaction chain, pulling it back from the test mass chain.

In the second screen shot you can see that I gave offsets to L2L, L2Y and L2P drivealign matrix rather than M0_LOCK_L because of a very small DC gain of the latter, and because it's somewhat more convenient than to give length offset to TEST_L and compensate the misalignment caused by that by using alignment sliders.

If this makes no negative impact on locking, the offset could be moved to TEST_L and sliders.

Reaction chain offset H1:SUS-ETMX_R0_TEST_L_OFFSET was set to -100k. I can go further easily, but I left some headroom so the reaction mass could be misaligned when fringe wrapping between the test mass and the reaction mass is observed.

After these, M0_OSEMINF_F1_INMON changed from 7300 to 8250, L1 LL from 6700 to 7000, L2 UL from 7100 to 7500.

I took a very very quick top P2P TF of the test mass chain for before(blue)/after(red) comparison and I see no ill effect (but no difference means no change in the PIT sensing). This comparison was done without oplev damping.

ETMx and ETMy ring heater chassis have been turned on.  I have copied the ITM calibration settings (except for resistance values) over to the ETMs.  I breifly turned each heater on and off again, they are drawing the right ammount of power.  All of the ring heaters are requesting 0W (ie no heating) right now.

Looking at the tidal feedback signals during the 2 hour lock shows:

1. The calibration of ALS-Y_REFL_SLOW is too small by a factor of 2. In Fig. 1 we see the green REFL_FAST signals running out of range near ~7.5µm. This is corresponds to the full VCO range of 1MHz and is correct. The same is true for X_REFL_SLOW, but the corresponding Y_REFL_SLOW shows a signal roughly half the size. The calibration is the same but the ALS common mode board have different gains in the input and VCO path. The X-arm board uses -7dB and 0dB, respectively, whereas the Y-arm board uses -13dB and +6dB. The Y-arm board should have the same gain as X.
2. When the Y-arm tidal servo is switched to red lock, the HEPI feedback runs away slowly, see Fig 2. This is due to the fact that the integrator for the slow Y-arm feedback is holding at its last position, but no feedback is applied to either the ESD or the common tidal. Either the common tidal feedback needs to enabled or the integrator bled off.
3. The calibration gains for the common tidal feedback was missing. The MC_F signal is calibrated in kHz and sent to the VCO. With a double passed AOM the gain factor becomes 0.5µm * 1/(2*37.5kHz) ~ 0.007 µm/kHz.
4. Driving HEPI to a positive offset seems to lead to a negative MC_F. Meaning, one should be able to just copy the MC_F value into the COMM_ERR offset field.

Script:

#!/usr/bin/python
import ezca
Ezca=ezca.Ezca("H1:")
while True:
    val=Ezca['IMC-F_OUT16']
    Ezca['LSC-X_COMM_ERR_OFFSET']=val
    Ezca['LSC-Y_COMM_ERR_OFFSET']=val

Alexa Dan Evan Lisa Sheila

Today the ETMY bounce mode was ringing up during our many lock attempts.  We rediscovered Nic's work to damp this mode using DARM feedback to the pitch drive of ETMY L2.  We have been able to damp the mode while hanging out in ALS_DIFF, but progress is slow.  We suspect that the high noise floor of DARM when locked on ALS_DIFF is limiting our ability to damp the mode.  Transitioning to RF DARM may let us damp the mode more quickly, but this carries it's own inconvenience.

Anyways the way to damp the mode is to enable ETMY L2 DAMPDARM MODE1 --> PIT, with FM1-3 turned on.  (FM3 is a 206dB gain stage, I have never seen so many dB in one place before.)  With the bounce mode very high we had to reduce the overall filter gain to -0.04 to keep the SUS L2 drive from saturating.  (Nic recommends -1, probably this is good once the mode has damped a little.)

 - Dan as Sheila

Evan, Lisa, Sheila, Dan, Alexa, Kiwamu

Summary

With DARM on ASAIR_RF45_Q and CARM on analog REFLAIR_RF9_I at zero CARM offset, we were able to transition the DRMI 3f signals from REFLAIR_B to the 1f POPAIR_B signals. 

The locking sequence is scripted in the guardian up until this point.

Details

By exciting PRM, we adjusted the demod phase of POPAIR_B_RF9 and POPAIR_B_RF45. In both cases we maximized the I signals, and found 66.6º and -30º for RF9 and RF45 respectively. Then, we excited PRM, SRM, and BS at 137 Hz, 137 Hz, and 53 Hz respectively.  The folder /ligo/home/alexan.staley/Public/Spectra_3F2POP contains the DTT files, which have the power spectra for all the POPAIR_B signals, as well as transfer functions to the respective REFLAIR_B signals. The input matrix is as follows:

When locked with the POP signals, we measured all three loops and found that they were all at the appropriate UGFs with good phase.

This morning, the IMC had a difficulty in relocking it.

It turned out that most of the IMCASC DOFs had accumulated some large offsets which had pushed the alignment so bad that it was not able to catch a 00-mode. This was due to the fact that we had turned on both the offsets (e.g. IMC-DOF_1_P_OFFSET) and the integrators, which off course simply accumulated the offset in the up front even when the IMC was unlocked. I disabled all the offsets as they are not necessary for now.

On Nov 7 I added smoothing to the terribly noisy channels generating the differential pressure.  I revert these back to no smoothing.