L4C seismometers number 23 and 25 have been removed due to their proximity to the during-vent storage location for the HAM6 doors. 

I have not removed #21, but if it is at all in the way, please feel free to do so.  It is a passive instrument, so all that is needed is unplugging the DB9 connection that is within ~12 inches of the sensor, and then lever the sensor off the epoxy.  The sensor and cooler can be stored next to any other out-of-the-way sensor, and I will re-install them once the vent is complete.

A supplymental observation in addition to LHO ALOG 28820 was that we found (at least) one more epoxy delamination in the decomissioned OMC. The sympton is similar to the one found in the 3rd OMC last week ([LHO ALOG 28714])

Looks like a problem started around 9am.  Could not find anything glaring at the chamber but a CPS rack may have been disturbed with the activity nearby.  HEPI is ISoalted and the ISI is DAMPED.  Don't see anything unexpected in the Spectrum.  We'll start with CPS rack cycling and then more explicit wiring chasing.

Attached is the in-the-loop frequency noise spectrum with the common gain at 16 and fast
gain at 9.  With these settings, UGF = 418 kHz, with a phase margin of ~48 deg.  If the
common gain is pushed higher, the UGS is ~860 kHZ with a phase margin of ~15 deg.  However
at this point the loop is very touchy.




Jason/Peter

Summary:

High power beam path in HAM6 was carefully inspected using flashlights and so-called green lanterns. Some of the OMC shroud panels were removed and the OMC was pulled out of the chamber.

Some damages and contaminations were found.

1. One of the OMC cavity mirrors on PZT was found to have a large defect very close the center. From the picture it seems as if the defect is a ring or a disk, the size of which is comparable to that of the beam. Hopefully this is the main cause of our problem.
2. OMC TRANS steering mirror had a big particulate at around the center. This might have made the OMC trans video look worse.
3. A big crater in one of the black glass panels for the V-shaped beam dump receiving the beam diverter reflection of the OMC REFL. The other panel had the evaporated glass "coated" all over.
4. Much smaller, but obvious, damage on another V-shaped beam dump that receives the reflection of 90:10 BS downstream of the beam diverter.
5. A crater above the entrance beam hole for the OMC shroud. It seems as if some large power came out of SRM when OMs were totally misaligned in PIT.

HAM6 didn't look particularly clean, there were some particulates on OM mirrors for example but they were all far from the center.

Note that all of the above except 2. could have been prevented if the fast shutter was working.

No other problem was identified.

Corey will post some of the pictures.

Fixing things:

We will proceed to replace the OMC as planned.

OMC TRANS steering mirror was removed from the Siskiyou mirror holder, particulate was removed on the table using Top Gun, and First Contact was applied. Later the mirror will be installed back in the mirror holder. This way we don't need to worry about the alignment.

V-dump glasses were replaced on the spot.

We might replace the damaged shroud panel if we have a new one and if the cleaning can be done fast, otherwise we might just leave it there.

Other things to note:

We also visually inspected low-power beam path and found nothing suspicious.

AS for the OMC mirror damage, speculation of me and Koji is that we had a particulate contamination of some kind when the large power hit the OMC as the fast shutter was not working.

Using the Fieldfox N9912A we inspected both ends of the Y2-8 HV Cable.  We used a Velocity of Propagation (VP) of 0.59 and turned on Low Pass (LP) filter for our testing.  We did not see anything with the LP filter off.

From Y2-8, we measured 256.5m to the end of the cable at the Y end station, no aberrations on the trace.

From the Y end station, we measured 256.5m to the end of the cable at Y2-8 but we also noted a blip at approximately 17.9m from the Y end station connector.  This blip did not exist on the scan from the Y2-8 connector.  I believe there may be a kink in the cable at the junction box leading out of the Y end station.

We also spotted some wildlife trying to get into the clean room area.

Gerardo M., Marc P.

J. Kissel, K. Venkateswara, M. Ross, J. Driggers

We've built the control infrastructure for the newly installed Compact BRS. This stuff now lives in the h1ngn (the Newtonian Noise model on the h1oaf computer) front-end model. The control scheme follows the diagram as described in T1600325. Screen shots of the various models attached.

Also, because the DAC_0 card on the OAF machine is shared with the (we think the H1 Only) AUDIO infrastructure in the h1oaf model, we've also modified that model aesthetically to indicate that this DAC card is shared.

The models have been successfully compiled and committed to the userapps svn repo here,
/opt/rtcds/userapps/release/isc/h1/models/
h1ngn.mdl
h1oaf.mdl

Measured 167.3W at the output of the high power oscillator.  162.5W at the input to the pre-modecleaner
with the ISS off.

    The diffracted power versus offset slider position was measured.  Combined with the power out of the
laser, this gave the percentage diffracted power.  The free-running peak-to-peak power fluctuations
measured by the ISS photodiodes as reported by a trend of the PDB EPICS was 0.2Vpp with a mean value of
8.3V.  So the 0.1Vp fluctuations represent ~1.2%.

    Allowing for some margin, we wish to diffract 2%.  2% of 162.5W is 3.25W.  With the digital support
loop on, this corresponds to an offset slider of ~2.5.

    The polynomial fit calculating the percentage diffraction was: 220.159x**2 - 97.169x + 11.293.
This was changed to match the measurements done earlier to day to: 97.6751x**2 - 63.548x + 11.458.  The
MEDM screen now correctly reports the amount of light diffracted by the ISS AOM.



Jason/Peter

Bubba, Chandra, Gerardo, Kyle

HAM 6 took one hour to vent to atmosphere, The north & south doors were removed before lunch. GV 5 & 7 were soft closed prior to vent. Attached is vent pressure plot from today and also from April, for comparison.

NOTE: in addition to powering off all HV in HAM 6, we also powered down the ITM HV.

Y2-8 ion pump not operational 

[Betsy, Koji] @Bonding lab

The OMC is sit in the bonding lab for curing of the epoxy. Otherwise, it is ready to be moved to the chamber side.

- 3rd OMC optics cleaning

Attachment 1:
We applied FirstContact cleaning of the optical surfaces. The optical side of the breadboard was wiped with IPA-soaked cloth (without touchting the optics).
The FCs will be left until the OMC is brought to the chamber side.

- PD replacement

Attachment 2:
The original OMC DCPDs were replaced with the new high QE DCPDs. The PDs at the BS transmission and reflection sides are from the PD cage A slot 3 (A3) and A4, respectively. They correspodns to the PD serials B1-01 and B1-16. The final testing at Caltech showed the QEs of 0.980 and 0.981 respectively.

The FirstContact seals are attached on the PD apertures to prevent particulates come into the PD surfaces.

- Mounting blacket bonding reinforcement

Attachment 3:
We added a glass prism to reinforce the bonding of one of the mounting blackets on the top (suspension) side of the OMC breadboard. A small amount of glue residue form the existing bond was removed by a razor blade to clean the place for the new prism. As small amount of glue as possible was applied to have round glue foot print, particularly on the glass-glass joint. The glue on the Invar-glass joint looks round. The glue on the glass-glass joint looks square inspite of our effort (We really don't think it is an issue). A steel block was added to hold the prism until the epoxy is cured.

I was bit again by buzilla bug 1013. The changes I made yesterday (alog28775 =) did not take effect since the change was in common code and I forgot to restart the nodes. I ended up restarting all of the SEI configuration nodes, but really only had to do all of the BSCs. No harm, everything came back nicely.

Illuminators for ETMx and ETMy have been turned off for PCal camera work.

This is in reponse to LLO alog 27053  : " .....  Would be helpful if DetChar can tell us if the OL lasers have been glitchy in the last several months.  ...."

Summary:

I dont think the ITMX laser is mode hopping.  I did not notice any step like changes in the SUM signal, though it is hard to tell due to the periodic pulses.  

The latter can be fixed by tweaking the PID setttings of temperature controller and its set point, I think.

Both ITM oplevs have large resonances at ~60 and ~90 Hz. These are much attenuated in ETMs.  The mounting of ITM oplevs could perhaps be examined to see if there is something out of place.   

QPD Sum calibration:

  At the laser wavelength 632 nm, Si QPD efficiency is ~0.35 A/W; Transimpedance=10kOhm according to D1100290 ; Differential Ouput gives x2 ; 16bit-ADC gives (2^16)/20 counts/V;  

  Using these factors : 1mW of incident light on the QPD would give us ~23k counts.  Since ETMX, ITMX and ITMY oplevs  have 18dB, 21 dB and 15 dB whitening gain,

the incident power on these QPDs is

And 1/4 of that per quadrant !!   

Kiwamu, Nutsinee

A code is scheduled to run at 9 pm tonight. The code will power up CO2 to 1.3W and power it back down to 0W after 6 hours. Please do not touch ITM optics.

I started to look into a faster ASC UIM to TOP stage offloading.

The DC gain ratio of the DRIVEALIGN filter outputs is about PUM:TOP = 23:20000 (pitch) and 30:20000 (yaw). There is a slight mismatch between the optics, but that seems to be taken care of with the CAL filter (FM1 in M0_LOCK).

With that gain ratio, and with FM1, FM4 and FM5 on in the MO_LOCK banks, the current x-over between TOP and PUM is about 0.002Hz (pitch) and 0.0029Hz (yaw).

This is very low. I verified that with 10x the gain in all 4 soft loops (gain=0.45 instead of 0.045) and 10x the offloading gain to top, the soop[s still seem stable. I believe the reason we are not running with that during the angaging these loops tax the SRC loops.

I added 0Hz:0.1Hz AC couplers into the L2 DRIVEALIGN P2P and Y2Y banks, as well as 0.002Hz:0.1Hz lead filters into Mo DRIVEALIGN P2P  banks ( 0.0029Hz:0.1Hz lead filters for Y2Y). These filters were successfully engaged in full lock. Somewhere however the guardian turns up the offloading gain by 10dB, making these filters unstable... So for now they are not in guardian.

Unfortunately, the pwer-up is still failing randomly. Not sure whether that's the 40mph wind, the numerous locked-down hepi's or the increased noise on RF DARM.