Dan, Jeff, Keita, Koji

As part of the closeout activities for the HAM6 work, we have taken TFs for all the suspensions in the chamber.  The OMC-SUS, OM2 and OM3 all checked out fine -- current TFs are the same as the Phase3B measurements that Stuart took last week.

OM1 has changed, mostly in yaw.  The frequencies of the fundamental modes in longitude and pitch have shifted slightly -- this is not surprising since we have slightly changed the mass (the mirror) in the pendulum, and the change is small enough that it doesn't prevent our acceptance of the chamber for closeout.

In yaw, the fundamental mode has split into two high-Q peaks.  The mechanism for how this could happen, while not changing the peak structure in pitch or longitude, is not clear to us.  Rubbing would seem to be ruled out.  The eddy current dampers are a possibility, and the symmetry of the system (two dampers oriented horizontally, aligned to the middle of the optic in the vertical direction) seems to imply that a misalignment of the dampers would primarily couple to yaw.  One leading, somewhat unsatisfying hypothesis is that one of the dampers is too close to the mirror holder, and this is coupling the transverse (side-to-side) mode into yaw.  (But, why not transverse to longitudinal?  And why is this coupling coherent with an excitation in yaw?)  Another idea is that the flags have become misaligned relative to the BOSEMs in just the right way to couple this new mode into yaw.  But, this suffers from many of the same complaints as the first idea.

Regardless of the mechanism, the motion is yaw is well-damped using the local damping loops.  We think this means the motion will not be a problem during low-noise operations, and we are comfortable closing out HAM6.  We can fix it during a subsequent vent.

The attached figures are:

Fig 1 - comparison of OM1 Y-->Y TF with Stuart's measurement from last week.  Note that the Apr 3 measurement was in vacuum, today's measurement is in air with the HAM door on.

Fig 2 - comparison of Y-->Y TF for all OMs (top), comparison of the three DOF TFs for OM1 (bottom).  The bottom panel is meant to illustrate that we are not coupling a pitch or longitudinal mode into yaw.

Fig 3 - comparison of undamped/damped spectra for all OMs.  Dashed references are undamped, solid lines are damped.  Differences between the traces for each OM are due to uncompensated gain differences in the BOSEMs - this has been fixed since the plot was made.  The motion in OM1 yaw, quite large when undamped, is about the same as the other OMs when the damping loops are engaged.

Figs. 4, 5, 6 - A yaw excitation impresses the low-frequency peak onto the other DOFs; the structure is evident in all four BOSEMs; the low-frequency peak is present in a L-->Y TF.

Let's bolt on the door and pump down the chamber.

Nutsinee, Elli

Today we continued work aligning the HWS to the conjugate plane of the ETM at both end-X and end-Y.

End-Y:

We worked on the HWS path on ISCTEY.  (refer to table layout https://dcc.ligo.org/DocDB/0114/D1400241/006/D1400241_ISCTEY_H1_V6.pdf)

According to Aidan's model, the distances between lenses HWS-L2 and L3 and the between L3 and the HWS camera needed to be adjusted.  We moved L3 113mm towards L2 and moved the HWS camera 108mm towards L3. 

To check the location of the ETMy conjugate plane, we applyd a 0.05mHz, 2microrad yaw excitation to H1:SUS-ETMY_M0_OPTICALIGN_Y_EXC, and we measured the pk-pk movement of the beam on the HWS camera  (Refer to script /ligo/home/eleanor.king/HWS_Pictures/HWS_image_plane_X and /ligo/home/eleanor.king/HWS_Pictures//find_image_plane2.m).  This indicated the HWS needed to be moved an additional 30cm towards L3.  To do this, we moved steering mirrors HWS-M2, M3 by 10cm, M4 and M5 by 5cm, which shortened the distance between L3 and the HWS by 30cm.  (We also moved L3 again to maintain the path length between L2 and L3.)

The final distances between optics are:

L1 to L2 610mm

L2 to L3 1079mm

L3 to HWS 734mm

The HWS is sitting on the conjugate plane +/- 5cm.  The HWS images showed a beam that moved around a lot, which stopped us from locating the conjugate plane more precisely than +/- 5cm.  The next step is to find the source of this noise and to move the HWS to within 1cm of the conjugate plane.

End-X:

We moved L2, L3 and the HWS camera so that distances between the lenses are:

L1 to L2 610mm

L2 to L3 928mm

L3 to HWS 1396mm

This should bring the HWS to the image plane of the HWS, but looking at the movement of the beam on  the HWS camera when we applied the 2micro rad yaw to H1:SUS-ETMY_M0_OPTICALIGN_Y_EXC, we calculated we needed to move the HWS by a further 0.5m.  Talking to Aidan, it sounds like L1 is not in the correct position.  The next step is to work out where it needs to be and move it there.

Maybe moot, because it looks like there might be problems with an OM, but the ISI looks ok. I took tf's in DTT, and they look similar to measurements taken under vacuum. HEPI is still locked, not sure of the state of the optics, but the ISI doesn't seem to care much. See attached.

J. Oberling, S. Doravari

With the HAM6 activity closing out, we took advantage of the window and tweaked another laser and swapped it into SR3.  The SN of the new laser is 199.  This was installed in the SR3 optical lever so we will have data for a direct comparison between the stabilized diode laser here at LHO and the fiber-coupled HeNe in use as the LLO SR3 optical lever.  We will begin monitoring this laser tomorrow after it thermally stabilizes overnight so we can perform, if necessary, final tweaks to the laser power to finally stabilize the laser.

Daniel, Jim, Dave:

Following our discovery yesterday that the LSC receive errors of ISC RFM IPC data was zeroed when the ASC computer was removed from the RFM loop, this afternoon we changed the h1asc.mdl model to remove the 16 obsolete RFM channels  to see if that changed the LSC error rate. It did, it has zeroed it. The attached strip tool plot shows the LSC error rate for the 4 ISC RFM channels (2 per end station). The ASC change was made at the 35 minute mark in the 1 hour long X-axis. I have a cron job running on sysadmin0 which clears the errors every minute, the strip tool is updating every 15 seconds.

This is a temporary band-aid fix for the LSC. If we were to put the 16 IPC channels back into the ASC (8 per arm) the error will re-appear. We will attempt to reproduce the error on the DTS and work at a long term solution.

Here are the ASC sender RFM IPC channels which were removed. I verified that no other model is showing RFM receive errors, confirming these are senders with no associated receviers.

H1:ASC_PZT[1,2][X,Y]_[PIT,YAW]_ISCE[X,Y] 8 in total

H1:ASC_ISCE[X,Y]_QPD[1,2]_[PIT,YAW] 8 in total

After the ISC crew were finished, Jim unlocked the ISI and made a small adjustment to it's balance.  I wiped a few of the surfaces of the ISI and chamber that I could reach near the door.  I placed a witness plate on the ISI table in the middle of the sea of ISC mirrors nearest the east side of the table.  Kyle, Gerardo, Bubba and I then tacked the door on with 4 bolts.  Kyle turned off the purge air.  Dan/Keita and Jim are running OM/OMC and ISI TFs to see how we fair for pumping down tomorrow.  We're not yet out of the woods.  TBC...

PS Particle counts at the door interface while the door was going back on was

0.3um  10

0.5um  10

1.0um   0

07:50 Jeff B. to HAM6
08:00 Daniel S. restarting h1lsc model, errors
08:12 Daniel S. restarting h1ecatc1
08:41 Elli and Nutsinee to end Y
09:13 Rick, Travis and Sudarshan to end Y to work on PCAL
09:25 Filiberto and Koji to HAM6 to check grounding
09:31 Rick to end Y
09:34 Peter K. to H2 PSL enclosure
09:38 Hugh de-isolated HEPI on HAM1, going out to check clearances
09:52 Jeff B. to 3IFO storage area to put optics in the desiccant cabinet
10:03 Hugh back
10:12 Betsy to HAM6
10:18 Jeff B. done
10:20 Karen to mid Y, Cris to mid X
10:49 Jeff B. to HAM6 to check on dust monitor reporting low battery alarm
10:55 Jeff B. back, dust monitor plugged back in
11:01 Richard to LVEA to check on Filiberto
11:08 Richard back
11:12 Karen leaving mid Y
11:30 Koji and Filiberto out, found short
11:44 Peter K. out of H2 enclosure
12:12 Greg G. turning on TCS X laser
12:47 Tour in CR
13:18 Elli and Nutsinee back from end Y
13:31 Rick, Travis and Sudarshan back for lunch
13:32 Hugh reisolating HAM1
13:33 Richard to LVEA to look at dewpoint sensor and check on Filiberto
13:50 Elli and Jeff running excitation on etmy
13:54 Jeff and Elli stopping etmy excitation, starting etmx excitation
13:56 Jeff stopping excitation on etmx
14:13 Peter K. transitioning LVEA to laser safe
14:21 Richard to LVEA to look at dewpoint sensor and check on Filiberto
14:36 LVEA transitioned to laser safe
14:42 Richard back
door being tacked on
14:54 Elli and Nutsinee to end X
15:25 Dave restarting ASC model
15:36 Jason and Suresh replacing SR3 optical lever laser

Looking at the RF distribution system for corner and end stations there are only 3 units which show an error:

• The RF divider for the 40MHz indicates a problem with the power supply. After swapping some cables this was traced to the RF Amp concentrator where channel 1 seems busted.
• The RF amplifier for TCS where the field cable is missing.
• The 90MHz LO for ASAIR_B which indicates no signal.

There is also an error associated with the green WFS demodulators where the hardware for the readbacks is still in the works.

When Fil was checking for electrical shorts on HAM6 after the ISC work, he found one of the ISI actuator cabels was shorted to the chamber. Before I went in chamber to unlock and rebalance the ISI, I checked the cable and found that the V3 actuator cable was plugged in upside down. I flipped the cable, Fil checked the pins again, the cable was no longer shorted. 

[Fil, Keita, Dan, Koji]

The ISC tasks in HAM6 was all completed.

Ground short check

FIl and Koji checked the ground short for ISC, SEI, and SUS. We found the shield of the OM1 TT cable had shorting. Also one of the ISI coil driver cables on D4-2B feedthrough had a shorting.

Resoution for the OM1 TT shield shorting

We went to the chamber again and check the shorting for the OM1 TT. The shield for one of the quadrupus cable was touching the table.
After a light touch, the shorting disappeared. We scurptured the shape of the cable such that this shorting won't happen spontaneously and
the beam is not blocked by the cable at the same time.

Picomotor check

The function of the 10 picomotors on HAM6 were checked. They are all good.

Fast shutter function check

The fast shutter test was done and it poped up and down although the response time of the shutter should be checked again
once the beam is back wtih vacuum pressure. Note that we retreated from the chamber to activate the HV for the fast shutter.
And the HV is deactivated again after the test was done.

Beam diverter final test

We doubly checked if the BDs moves or not. We found no problem.

Daniel, Jim, Dave:

Daniel restarted the h1lsc model this morning, but it did not run. The reason is that its safe.snap file is missing from the target's burt directory.

I have created a symbolic link from

/opt/rtcds/lho/h1/target/h1lsc/h1lscepics/burt/safe.snap

to

/opt/rtcds/userapps/release/lsc/h1/burtfiles/h1lsc_safe.snap

The latter file is under SVN control, last modifed Friday 13th March.

I have also noticed that h1calex and h1caley models are also missing their safe.snap files.

GV5 spontaneously hard closed -> ~26 hours after 10psi soft-close -> This valve has done this before at 15psi 

A

Yesterday ran Range of Motion and Linearity Tests.  Took Spectra as well and then ran TFs overnight.

For the ROM, which evaluates based on the free hang position, not from zero, H1- was limited to 0.8mm.  This is not necessarily running into anything as the sensor (IPS) was just running into the sensor max.  In other words, the sensor position could be adjusted (along with the cartesian Isolated-to position) if the true centering of the Actuator could tolerate that.  Also for V4-, it was hitting something and the range was limited to 0.7mm.  I have not investigated this.

The linearity tests are possibly within spec (don't have a number of what that should be) but here V4 is also an outlier having a lesser slope than the others.  See attached, V3 also looks weird here but the range of motion is fine for V3 which drives further than the linearity test so if it is running into something it must be compliant.

The new L4C looks good though.  Attached are Spectra from last October and Yesterday.  I collected Isolated spectra yesterday and the data from October is 'Undamped' but the improved health of this L4C is apparent.  I can get Isolated from a few days ago before the swap.

TFs to come.

[Dan, Ross, Corey, Keita, Koji]

The ISC work for HAM6 was done mostly along with the procedure in this ALOG entry 17631

We first started from the steps which does not require the laser beam, and then moved on the steps with the beam.

Visual inspection of the fast shutter mirror

- The mirror on the fast shutter was checked. We confirmed that the mirror is well intact and did not show any sign of delamination.
i.e. The toaster does not seem to fly.

Beam diverter lubrication with Krytox LVP

- The two beam diverters (BDs) were removed from the table after marking their positions with dog clamps.
  Corey applied Krytox along with the procedure by Matt H.

- The additional mass is added to the moving element to ensure each BD flips to the ends of the moving range.

- The BDs were returned to the HAM6 table. Their positions were aligned in the later process.

- The motion of the BDs were confirmed with EPICS I/F.

QPD cable strain relief

- QPD cable strain relieves (D1101910&D1101911) were installed to AS_C/OMCR_A/OMCR_B DCQPDs.
Now there is no chance for their ferrules to touch metal parts around there.

Transition to Laser Hazard

- The input power at this point was ~3W.

Initial alignment

- Aligned the beam on the AS_C QPD with SR2
- Aligned the beam on the OMC QPDs
- Confirmed the beam is on the WFS QPDs

OM1 mirror replacement

- The hIgh transmission (T=5%) OM1 mirror was removed from the TT suspension.
- The new OM1 mirror with T=800ppm (E1100056 Type02 s/n15) was installed.

- The old and new mirrors were supposed to have the same dimensions. However, the mirror holder faced down significantly.
  This was actually the same situation as it was seen in LLO.

- I don't want to describe the detail of the TT story. In the end, the clamp units on the mirror mounts were shifted towards the face.
  This let us recover the proper alignment of the OM1.

- The alignment slider values were coarsely debiased by aligning the TT suspension structure.
- All the BOSEMs indicated that the flags are too deep inside the BOSEMs. This was fixed.
- We actually debiased the suspension at the end of the procedure again.

- The AS AIR/AS_C pathes were aligned. The beam was faint and we decided to inclease the input power to the IMC up to 7W.
The beam was aligned to hit the AS_AIR periscope mirror. The AS_AIR beam on the ISCT6 table should be aligned.

- The BD for AS_AIR was aligned. The reflection of the BS was also aligned.

90:10 BS insertion

- A 90:10 BS (E1500009) was installed in the OMCR path. In order to accommodate this new optic, the steering mirror just in front of this BS
was moved back towards the OMC. We made sure the beam is hitting the OMCR periscope mirror. This changes the angle of the beam on
the ISCT6 table. Therefore, the OMCR beam on the ISCT6 table should be aligned.
- A V-beamdump is installed for the reflected beam of this BS.
- The OMCR QPD sled path was realigned.

Power budget

- The optical powers at the various places on the table were measured. Also the AS_AIR and OMCR powers on the ISCT6 were measured.
These measurements allows us to estimate the optical powers in the chamber using the ones on the ISCT6 table.

Double checking

- The optical path was traced from the septem windows to the OMC, AS_AIR, AS_WFS, OMCR paths.

- The shutter mirror was lifted manually to see if the reflected beam is still properly dumped.

- Took photos of the table for updating the table layout.

Contamination control

- At the end, the partice level was checked in the HEPA booth. It shows 0 counts for all particle sizes.

Still to do before closing the door

- It should be checked if the picomotors and fast shutter are still working.

- It should be checked if there is any ground shorting.
Note that BDs are shorted on the table. Also the cable harness on the OMC shorts the shields of the OMC QPD/DCPD cables at the OMC breadboard.

The optimal location for  a single version of Krishna’s BRS (intermediate frequency tilt sensor), or, if it would be better to have two of them, depends on the tilt spectrum in the beam direction. We suspected that wind-induced tilt is worse at EY than EX, where the BRS is currently located, because, for typical wind storm directions, the building is being pushed roughly along the beam axis at Y-End and roughly perpendicular at X-End (the tumble weeds usually roll down the Y-Arm). But we aren’t sure whether a single sensor at EY would make sense (e.g. if EY is 10x worse than EX) or if two BRSs would be better.  Since we have only the one BRS, we used the 0.03-0.08 Hz band of STS seismometers to compare the two stations. This frequency band was selected as a proxy for tilt because this band is below the microseismic peak frequency and, in windy conditions, ground motion in this band is usually dominated by tilt. Figure 1 shows the strong correlation between the 0.03-0.08 Hz seismometer band and the tilt measured by the BRS at EX for one wind storm. Each of the small points in the plots in this log represent a 60s average of the wind speed and a 60s fft of the ground motion.

Figure 2 shows 4 months (Aug 15, 2014 - Dec 15, 2014) of the 0.03 to 0.08 Hz beamline seismic band at EY and EX plotted against wind speed measured at EX.  The large red and blue dots show the median of minute points in 2 MPH bins. Dipongkar has plotted the median because large earthquakes, which also appear in this band, would bias the mean. Roughly speaking, for a particular wind speed, the signal at EY is twice the signal at EX when averaged over many storms in 4 months. This data suggests to me that we may want a second BRS at EY rather than moving the sensor from EX to EY, because the difference is, on average, only a factor of 2.

The differences between the stations can change for different wind storms, possibly because of different wind directions. Figure 3 shows the effects of individual storms (each storm is a different color, the same color on both plots) at the two stations. One of the storms produced about 5 times more beam-line tilt at EY than at EX.

Caveat: Getting this data is very time-consuming, so we are putting in this log even though we have obtained only 4 months of data. Dipongkar will continue to increase coverage to include the spring windy period and we will update if necessary.

Robert Schofield, Dipongkar Talukder