Ed, Jason, PK
Eearlier this afternoon the ISS AOM Diffracted power was up to ~39%. Reason, still unknown except for folks were in the enclosure working on FSS. Peter King set the refsignal to -2.5V and brought the diff power to ~8.5%. It's seems stable for now. We'll see.
Nutsinee, Elli
We have aligned EX HWS to within ~+/-5cm from the ETMX image plane. This is as good as we can get with the current level of motion in the HWS images. To locate the image plane more acurately, the next step is to understand why there is this variation in the HWS images.
The distances on the HWS path are now:
L1-L2: 610mm (unchanged)
L2-L3: 877mm
L3-HWS: 1593mm
To do this we applied a 0.05mHz, 2microrad yaw excitation to the M0 optic align filter bank, and looked at the motion of the x centroid in the HWS images. We moved L3 51mm towards L2, the HWS 57mm away from L3, and mirrors M7 and M8 each 80mm to the right to the lengthen L3 to HWS path. We also adjusted the pitch of ALS-BS 1 to lower the beam on HWS-M1, which was clipping slightly.
See the attached pdf with L4C and IPS TFs from LHO and LLO--look at title and legend. Main interest here is above 10hz. We are looking into why.
The filter switch widget in the SDF doesn't jive with diff list. See attached. There is no setting difference but the widget suggests there is.
Are you sure that channel is being monitored (monitor bit set to 1)?
Yes, this popped up when Jim was doing some blend tests.
Firefox became too slow to start from controls account. That's because Jamie's firefox script copied all cache files (over 900Mb) and thumbnail files (over 600 Mb) to a temporary directory each time firefox was launched.
That's not all Jamie's fault, because firefox people changed the cache file naming convention in the past ('cache2' instead of 'Cache').
Anyway, Jamie's script was changed such that '[Cc]ache*' and 'thumbnail*' are excluded from rsync, and now firefox starts in a second or two. Also I deleted all caches and thumbnails. The size of firefox controls profile folder was reduced from about 1.7GB to 73MB.
Jamie's script is necessary for controls account because of the lock file management of firefox. Without the script, only one workstation at any given time can launch firefox as controls without manually deleting lock file.
Summary:
Elli and Nutsinee measured the current state of the ETMX HWS layout and the behaviour of a beam transmitted through it. From this I was able to solve for unknown distances in the layout and produce a new optical solution that will image the ETM onto the HWS with the existing lenses.
Diagnosis:
Elli and Nutsinee made some measurements of the ETMX HWS yesterday to determine the conjugate plane. We started with the following measurements:
Also, we know the following measurements of the transmon telescope (Data from T0900385 - v06 and G1100873):
This list of values allows us to calculate the ABCD matrix propagating the beam from the ETM to the HWS.
Elli and Nutsinee injected a 2 urad oscillation into ETMX YAW at 0.05Hz. This results in a peak-to-peak oscillation of 8 urad on the reflected beam (pk-pk multiples by a factor of 2, reflection multiplies by another factor of 2). They then measured the pk-pk oscillation of the centroid of the return beam on the HWS in pixels, where 1 pixel = 12 um, for different positions on the HWS. At the conjugate plane, this should be zero.
These numbers didn't jive with the nominal optical layout. The only real uncertainty was the distance "Secondary mirror to HWS Lens L1". So, using the values that for the oscillations, I readjusted this value in the ABCD matrix, modeled the expected centroid oscillations and compared the measured oscillations. "Secondary mirror to HWS Lens L1" = 5728mm gave a result that agreed to better than 1%.
New Optical Solution:
So now that we "know" the values for all distances, I re-solved for an optical solution that would image the ETM onto the HWS with a demagnification of -20.5x with the existing lenses. The new values are:
The calculations are attached.
Diagnosis calculation
New solution calculation
XorYDist = (nominal) + (unknownX) = 5.273m + 0.455m
An Fscan of H1:CAL-DELTAL_EXTERNAL_DQ during the April 2 lock is here: https://ldas-jobs.ligo-wa.caltech.edu/~pulsar/fscan/H1_DUAL_ARM/H1_DUAL_ARM_HANN/H1_DUAL_ARM_HANN/fscans_2015_04_02_06_00_02_PDT_Thu/H1_CAL-DELTAL_EXTERNAL_DQ/fscanH1_CAL-DELTAL_EXTERNAL_DQ_H1_1111928417_1112014818.html (Clink on the "old" button to see the plots.) The Fscans are used to look for lines in the data. A 4 Hz comb is still seen in the power versus frequency spectra, and a number of wandering lines are seen in the time-frequency spectrograms.
Rick, Evan
This evening we went into the PSL and examined OLTF of the FSS.
Since we want to increase the FSS gain, but cannot turn the common gain slider up any further, we looked for other ways to squeeze more gain out of the loop.
Rick had the idea to try to increase the error signal slope by adjusting the demod phase using the delay line. Indeed, we were able to increase the loop gain uniformly by 3 dB. The phase remained more or less unchanged below 700 kHz.
We now have a UGF of about 350 kHz with 50° of phase. The gain margin is about 3 dB.
Delay line switch positions (up/down) are as follows:
| Delay (ns) | Old | New |
| 1/16 | D | D |
| 1/8 | D | U |
| 1/4 | D | U |
| 1/2 | D | U |
| 1 | D | U |
| 2 | D | U |
| 4 | D | U |
| 8 | U | D |
| 16 | U | U |
| 1/16 | D | D |
| 1/8 | D | D |
| 1/4 | D | D |
| 1/2 | D | D |
| 1 | U | D |
| 2 | U | D |
| 4 | U | D |
| 8 | D | D |
| 16 | D | D |
| Total | 32.9 ns | 40.0 ns |
So the phase change at 21.5 MHz is 56°. That seems like quite a lot, so perhaps we should take a closer look at the error signal with the FSS unlocked to make sure it's reasonable.
Also, on the manual FSS MEDM screen, we found that the TEST2 enable/disable button didn't really work; we seemed to get a sensible transfer function no matter what.
Peter K, Jeff B, Evan H
We did some FSS diagnostics today in and around the PSL:
Originally there was 14.5 dBm of 21.5 MHz drive going into the delay line, and 8.1 dBm coming out (and thus going to the EOM). So we have won back almost 6 dB of drive to the EOM. That's roughly consisent with the extra headroom we now have on the common gain slider.
However, I do not understand why we had to adjust the fast gain after removing the delay line. With 26 dB common and 15 dB fast, we saw a broad peak in the transfer function around 50 kHz or so, and we increased the fast gain to 21 dB to suppress it. So perhaps removing the delay line shifted the crossover frequency.
A new OLTF is attached (at 26 dB of common gain), along with the error signal and cavity sweeps that we took (which are now outdated).
Using data (scope_7.csv) in the above attachment, we find that the PSL NPRO PZT actuation coefficient is 1.3 MHz/V [ = 21.5 MHz / (7.11 V + 9.09 V)].
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.
I should mention that last night when the LVEA was in laser hazard, we were able to use the DC centering loops to center the beam on WFS A and B with good jitter suppression. This was with the HAM door open and the purge air on -- so, whatever has changed with OM1, we can actuate on the mirror well enough to center the beam even in the noisiest environment.
For reference, when the OM1 optic was changed at LLO, we observed no change in the TFs (see LLO aLOG entry 15167).
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.
Just attaching images associated with this work.
1) SR3 Oplev laser currently installed is Sl. No. 199
2) The binary switch state for setting gain and whitening. Currently there is just 3dB of gain and no whitening
3) power spectra of adc noise floor and sum signal to show that the signal is atleast ten times larger than the noise floor at all frequencies of interest
It seems there is a discrepancy between the SR3 pitch slider and the SR3 oplev motion. I move the pitch slider by what I think is 0.5 µrad, and the oplev reports that SR3 moves by 0.2 µrad. Not sure about yaw.
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
Here's a picture of the HAM6 table as viewed from the end (East) door. The new CC wafer is now inbetween the sea of mirrors/BDs/TTs.
