I finally got a script working to step the alignment offsets on the IMC mirrors and record the transmitted power drop with MC2trans and IM4trans QPDs. 

The idea behind this was to compare the quadratic function for power drop with misalignment with the theoretical function, giving us a means of accurately calibrating the alignment offsets.

The reason I'm interested in calibrating these offsets accurately is for beam jitter measurements using the coupling from jitter to RIN in transmission of a misaligned IMC [see e.g. LHO aLOG entry 8190]. The coupling factor is determined by the slope of the quadratic function, so we can't calibrate jitter measurements made in this way any better than we can calibrate the DC alignment offset.

The first attached plot shows the normalized transmitted power obtained for each individual mirror DOF, from both IM4trans QPD and MC2trans QPD, over "intended" alignment offset. Also included is a plot of the normalized transmitted power from a Finesse model of the IMC over "real" misalignment offset. From these plots we can see that in general the alignment offsets actually applied to the MC mirrors are larger than the intended alignment offsets. However, the measured data is not always symmetric (especially for IM4). This could be due to clipping at the QPDs. The centering on IM4trans is not as good as the centering on MC2trans, so I would be more confident in the numbers from MC2trans.

I fitted a quadratic function P=A(x-h)^2+k to each of the curves. The calibration is then done by scaling the alignment offsets applied to the actual suspensions by sqrt(Amodel/Adata). The second attached plot shows each DOF again, but this time with the x-axis scaled for the measured data to fit the model. I used the scaling factors calculated from MC2trans data since the centering on this QPD was better. For the most part I'd say the data matches the model well after this scaling.

These scaling factors are:

I would propose to include these scaling factors in the calibration of the MC mirror offsets.

The script can be run again at any time to check for any possible changes in e.g. the OSEM coil driver gains over time. It might be beneficial to take more data points at some point too, but the script takes 15mins or so to run as it is (mainly due to the time given for optics to settle between changes of offset). Another improvement would be to step MC1 and MC3 pitch over a larger range, since the transmitted power is actually fairly insensitive to these DOFs. Both these things can be edited in the top few lines of the script.

In case anyone is interested in running this script in future, it is located at opt/rtcds/userapps/release/ioo/h1/scripts/imc/pfulda/IMC_align_calibrate.py

Be sure to run the mcWFSrelieve script located in opt/rtcds/userapps/release/ioo/h1/scripts/imc/ first though!

I attach the analysis scripts here too, including the measured data, Finesse model and results, and other functions used.

Stefan, Lisa

Now that the mirrors move less and the arm cavity locks stably, we want to actually measure the frequency noise between the red and green.

When trying to do the green CARM hand off, we found that we didn't have a signal. 
We tracked it down to a bad alignment between the green beam from the SHG and the one from the arm.
We used Sheila's numbers  as reference: the beat note was supposed to be around 28 mV, it was just a few mV. We realigned the green arm beam on ISCT1, and we brought the beat note back to about 22 mV. 

I tried to add back the Beckhoff channels and then remove the ones that I thought were updating too frequently. It still seemed to be updating too much (from watching H1:CDS-CONLOG_QUEUE_SIZE). I reverted back to the list without the Beckhoff channels.

Sheila, Paul

Yesterday while in the PSL we aligned the Thorlabs PDA55 known as IO_AB_PD_3. This PD sees the beam picked off from the main beam after the EOM by the wedge IO_MB_WG1. The PD was already on the table and connected to the DAQ, but the final steering mirror steering onto it was not present. The post was in place (labelled as IO_MB_WG1, though I think this should be labeled IO_AB_W1) but there was no mirror mount on top. I borrowed a HR turning mirror already mounted that I found in the IO shelf in the PSL ante-room and mounted this on the post and aligned the beam onto the PD. 

The design actually calls for this PD to be placed behind a window (IO_AB_W1), but I did not find this window so I left it in reflection from an HR mirrror as a temporary setup.

The power incident on the PD was 1.17mW, and it gave a DC reading of 5.56V. The PDA55 switchable gain was at its lowest setting (1.5E4).

This roughly makes sense: using the previously estimated PDA55 responsivity of 0.325A/W we get an expected voltage of 0.325A/W * 1.5E4 V/A * 1.17E-3 W = 5.8V. This looks like the responsivity is a little lower than the other PDA55 (IO_AB_PD_1), so I adjusted the responsivity in the LSC DCPD medm screen until the voltage and power matched the measurement. The channel H1:PSL-EOM_A_DC_POWER is now calibrated in mW incident on this PD. I don't know the pick off fraction of that wedge exactly, so if anyone wants to calibrate it in terms of power leaving the EOM it might be best to measure the main beam power on the PSL table before the IO power control stage.

1: Pilot unit beam diverter was replaced with a production unit.

IR high reflector on the old diverter was put in the new one, but we removed a translucent-ish black glass and installed a standard black glass.

2. TMS ISC table + telescope was reattached to the top mass and suspended.

Some circus of putting the tele+table on a bench and then picking it up from the opposite side was necessary due to space constraint under the test end. As a result, one Genie lift is right now trapped between the roll up door side of the clean room and the TMS/ETM. I hope this doesn't bother others.

One of the TMS tele F2 mirror clamp was pressed against the tele lift tooling when we're lowering the tele/table.

After the tele/table was freed and was suspended, I inspected F2 mirror. All clamps were still touching the mirror, and all ball point contacts (three from the side and three from the back) were all touching the mirror sourface also. Looks good.

3. Fall protection wire and temporary alignment stabilization tooling were installed.

4. For tomorrow: Cable up QPDs, picos and beam diverter, balance the entire structure, and completely free up everything.

That could be a day's job. After that, we need IAS to measure the position of the TMS input aperture. We need to find the right tooling for that at EX lab. The one we used for EX probably doesn't work as EY is a pilot unit and it has somewhat different screw hole locations, so we need to find the old tooling.

Evan, Paul

Yesterday we took beam size measurements on ISCT of the beam directly reflected from ITMY. I didn't get around to processing the data until later, hence the late post.

The results were: ITMY direct reflected beam size = 2329um (x-axis), 2398um (y-axis)

As expected, the ITMY direct relfected beam size is smaller than the ITMX direct reflected beam size, but only by 6% or so. I will check against my model to see if the difference in sizes makes sense quantitatively, though the unknown non-thermal lens in ITMY may make it difficult to draw a strong conclusion from this.

I attach again plots of the ASD of the beam spot centroid position and radius throughout the first 60 seconds of logging.

Craig Conley and Rick Savage

We rotated the in-vacuum periscope structure, installed the stabilizing slides, slid it down to close to its final location, then installed the center target for final alignment (see attached photo).

We are ready for the final alignment with the help of IAS.  We plan to do this work on Friday.  We have some clean tools staged outside the cleanroom on a clean cart (covered with foil).

Jax, Daniel

We installed the differential frequency difference divider and PLL in R1. It is cabled up but still waiting for power.

The turn on of the ITMX ISI is currently one button.  Please use level 3 on the command page.

The blends are TCrappy on Stage1 all dofs; Stage2 has 100mHz on X & Y, 250mHz elsewhere.  There may be more optimization for Stage2 or maybe not.  As long as the no isolation position and the Target remain close, the one button up should continue.  Otherwise, well you know the drill.

Hats off to Jim & RichM.

Rich, Jim and Hugh

The ETMX BSC-ISI is running a level 2 controller (~25Hz UUG) with low frequency blend filters (~40Mhz stage 1 and ~250mHz on stage 2)

We were to able to turn on the level three controllers mostly due to an excessive amount of 60Hz pick in the GS13s and L4Cs, this needs to get looked

 We still need to finalize the tilt decoupling

I have been hesitating to post this result as I am getting a calculation which doesn't agree with the measurement. (Also this is kind of a side track of the PRMI commissioning)

I did a back of envelope calculation of how large Michelson optical gain we would get at REFLAIR_A_RF45 with PRM misalgined. Currently, I am getting a dubious estimation which is 4 times smaller than what was measured on 31st of January (see alog 9698). I expected it to be 1.7e9 W/m while the measurement claimed 6.8e9 W/m. For those who are insterested in the detail, I am attaching my caculation.

Any suggestion is welcom. As usual, there must be a stupid reason. Thank you.

Andres R. & Jeff B.

    We finished cabling and suspended H1-SR2. The masses appear to be hanging correctly as no BOSEM adjustments were necessary to center the flags. After confirming the 50% light positioning of the BOSEMs, we started the Phase 3A transfer functions.     

- PSL Check done: Watchdogs look good, ref cav is locked but doesn't look clean and the FSS is resonant at 8:55 AM PT but only locked since 7:50 AM PT. Sheila D was notified.

- ACB work in the West Bay

- TMS work at EY

- Electrical inspector on site to meet with Richard M.

- HAM4 SR2 work

Scott, Mark, Mitchell

Today with Apollo's help we were able to suspend the ACB from the solid stack to begin the balancing process. After correcting an assembly error on my part we successfully hung the baffle. For reasons still unknown the baffle is bottomed out with the documented payload added. After removing 5lbs of mass the baffle box was still mostly bottomed out. I am currently in discussions with Mike Vargas and Scott Shankle about this issue.  

I updated all ODC strings, as well as the bitmask and string scripts in cds/h1/scripts:
h1setODCbitmask
h1setODCbitstrings

SVN revision 7038

[Rich Hugh Arnaud]
When activating the ISI level 3 controllers the boost filter of level 2 under FM9 would be enabled (instead of level 3 boost under FM8). This was due to a simple error that we modified from the python script running behind the "isolate" command.

line 350 of script BSCISItool under

/opt/rtcds/userapps/release/isi/common/scripts/

was modified from :

    if ($control_level eq 3) {@commands = ("ALL OFF DECIMATE OUTPUT INPUT FM4 FM5 FM6 ON") x $num_dofs, @boost_commands = ("FM9 ON") x $num_dofs; }

to

    if ($control_level eq 3) {@commands = ("ALL OFF DECIMATE OUTPUT INPUT FM4 FM5 FM6 ON") x $num_dofs, @boost_commands = ("FM8 ON") x $num_dofs; }

the script was comitted under the svn revision 7037

I've made some plots of the currently loaded filters on ITMX BSC-ISI

  I used the program plot_current_blend_filters.m from  /ligo/svncommon/SeiSVN/seismic/BSC-ISI/Common/

 which reads the foton file and plots out the filters (thank you Ryan)

  I only plotted out the low pass filters assuming that the high pass filters are appropriately complementary

   A few comments

  A filter name that starts with "T" means that the T240 will be part of the blend

   LP filters that go flat at high frequencies are not recommended, so for instance the Stage 1 X  40mHz and T100mHz N0.44 are bad filters and will get replaced

  The "best"  we have been using the TCrappy filters which are what the blend filters are tuned to

Stage 1 RX  TCrappy == TLLO

  Z = X = Y

  RX = RY = RZ

(Sheila, Alexa)

1. We wanted to re-visit the EX PLL shot noise measurement we had previously done.

• From the direct output of the pre-ampifier we measured the beatnote signal to be -33dB at 39.8MHz with 100 Hz BW
• The RF spectrum analyzer had a noise floor of -126dbm with 100 Hz BW (no attenuation)
• From the direct output of the pre-amp with the BBPD blocked, we measured an electronic noise of -118dbm at 100 Hz BW from the PD
• With the fiber blocked we measured noise of -114dBm at 100 Hz BW
• We meaured the power at the BBPD to be 5.8mW with a DC reading of 1.04V --> .52mA at the PD. We calibrated the PD responsivity to be .09 A/W
• To confirm we were measuring shot noise, we increased the optical power by a factor of 2, and saw that the noise with the fiber blocked increased to -111dBm at 100 Hz BW. We expected this increase, so are confident we were measuring shot noise.

2. WIth the EX PLL locked, the arm cavity well aligned, and the green beam flashing, we looked at the PDH error signal out of the demod IMON and measured the peak-to-peak of the signal to be 230mVpp

3. We went on to investigate the fringe wrapping we saw in the PDH amplitude spectrum at the error point. With the arm locked, we only saw a slight difference in the spectrum with the HEPA fans on or off (Sheila will attach pictures). There did not seem to be fringe wrapping, and the acoustic noise seemed minimal. I will look at the PDH shot noise again when I can misalign ITMX and see if the fringe wrapping is still there..