The WFS demod phases were adjusted this afternoon. The WFS loops were successfully closed.

This was needed because the RF phase rotated for some reason a week ago (see alog 7181).

The new demod settings :

H1:IMC-WFS_A_SEG1_PHASE_R = -90
H1:IMC-WFS_A_SEG2_PHASE_R = -17
H1:IMC-WFS_A_SEG3_PHASE_R = -27
H1:IMC-WFS_A_SEG4_PHASE_R = 22
 

H1:IMC-WFS_B_SEG1_PHASE_R = 15
H1:IMC-WFS_B_SEG2_PHASE_R = -34
H1:IMC-WFS_B_SEG3_PHASE_R = 28.5
H1:IMC-WFS_B_SEG4_PHASE_R = -81

The adjustment :

As usual I hooked up a function generator to EXC_A of the IMC servo board at the floor to excite the longitudinal signal. I set it to be 6 Hz and 4 Vp-p. I had to put such a big signal because the IMC locking loop had a big gain at around this frequency. Looking at diaggui I rotated the demod phases so that a peak at the excitation frequency in the Q signals becomes as small as possible. Roughly speaking all of them needed to be rotated by 95 degrees. This is consistent with what I saw in the length signal (see alog 7181). By the way I took a look at the length demod signal and confirmed that the RF phase stayed the same.

Notes on the control loops :

I enabled FM1, which is a 10 dB flat gain, in all six degrees of freedom. These are the ones we disabled in order to empirically avoid an oscillation at around 0.1 Hz when we were adjusting the demod phase on July 18th (which was not alogged unfortunately). A current screenshot of the IMC WFS control is attached. Besides the demod phases and FM1, everything stays the same. After all these settings I ran /opt/rtcds/userapps/release/ioo/h1/scripts/imc/mcwfsrelieve to offload the control signals to the static offset in H1IMC-MCX_PIT where X can be 1, 2 or 3.

Replaced check valves on control air compressors at Y mid and end stations.  Work is complete and air system is restored.

[Daniel, Sheila, Kiwamu]

 As a preparation for the ISCTEY migration we went down to EY this morning and cleaned up the exterior cables, some measurement devices and etc.

The light pipes, which had been attached between the ISCTEY enclosure and the viewports on the BSC6 chamber, were also removed. The viewports are now protected by the yellow cover with the lexan guilotine in. The ISC equipments were brought to the squeezer area and some of those beloging to the EE shop were put back to the shop. We removed all the loose parts from the inside of the enclosure so that nothing will move during the transportation.

The belows are pictures of the ISCTEY enclosure taken after the cleaning.

The IMC alignment seems stable in a time scale of a week even with no WFSs activated.

The screen shot below is a trend of 6 days for the reflected and transmitted light of the IMC. There is no obvious power drop (or increment), indicating that the IMC alignment was stable.

It has been approximately 6 days since we disabled the WFSs alignment control for the IMC (see alog 7181). Note that the transmitted light became more stable when Rick activated the ISS in the last Thursday.

Last week, we finally received new 6" Mirrors from Newport (part# 60D20ER.2).  These are the ones we were waiting for to use as the F1 mirror for the EX TMS (we've tried a gang of other various 6" mirrors which all had their own unique ugliness).  aLOG of the Inspection was last week, but I wasn't able to post photos due to ResourceSpace being down.  

Inspection photos of both mirrors are here.

J. Kissel, A. Pele 

In prep for the shutdown of EY, we've ramped down and turned off all active control requests from BSC6. HPI-BSC6, ISI-BSC6, SUS-ETMY, and SUS-TSMY have all been ramped down, and are now with their master switch turned off.

Over the weekend I tested recruiting the IMC cavity feedback to simultaneously damp the MC2 longitudinal DOF. It is possible to make a cavity controller damp a the longitudinal modes of a suspension of 3 or more stages if three rules of thumb are met:

1. Cavity feedback exists below the top mass for at least 2 of the stages. Those are M2 and M3 here.
2. The feedback on the stages below the top mass have unity gain frequencies (UGFs) greater than the longitudinal resonances. The highest mode in this case is 2.75 Hz.
3. The damping increases as the UGF of the highest stage below the top mass decreases towards the highest frequency longitudinal mode. Here the M2 UGF decreases towards the 2.75 Hz longitudinal mode.

This is part of the more general global damping scheme described in G1200774. Global damping is intended to both isolate OSEM sensor noise from the cavity degrees of freedom and decouple the damping design from the control of the optics.

Parameters for this test:
1. The IMC was locked with feedback to MC2 M2 and M3. 
2. There was also ~10 kHz feedback to the laser frequency, but this was unimportant for this test. 
3. The MC2 M1 longitudinal (MC2_M1_DAMP_L) damping was off. 
4. The varying parameter is the gain on the M2 feedback loop (MC2_M2_LOCK_L). The gain was set to 4 different values [0.03, 0.06, 0.12, 0.3], corresponding to M2 UGFs at [3.3, 4.0, 6.0, 14.7] Hz respectively. 0.03 is the default gain.

The M3 loop was not adjusted. Its gain was left at -1000. Fortunately, the existing IMC cavity control was designed with oodles of phase margin, making it relatively easy to adjust the M2 gain by an order of magnitude without redesigning any filters (except for the addition of a 41 Hz notch filter for stability as described in 7257).

See the three attached figures.

1. IMCCavityRingdown.pdf shows the impulse response of the cavity at these different M2 UGFs. The impulse was applied to the M1 stage. Note that the Q of the top mass is a strong function of the M2 UGF, and is positively correlated with it. The magnitudes of the curves in this plot were normalized because they are naturally different since the cavity has differing loop gains with the differing UGFs.

2. MC2M1Ringdown.pdf is structured exactly like IMCCavityRingdown.pdf except the M1 response is shown rather than the cavity response. The results here are the same, the M1 Q drops with the M2 UGF. The curves here are not normalized, since we are not looking at a stage with cavity feedback (no changing loop gains at this stage to effect our scaling).

3. MC2M1toM1TFs.pdf shows longitudinal transfer function measurements on M1 (MC2_M1_TEST_L_EXC to MC2_M1_DAMP_L_IN1). Like the previous two plots, a curve is shown for each UGF case. Here we see again, but in the frequency domain, that the Qs of M1 decrease with M2 UGF. For reference, the transfer function without cavity control or L and P damping (other damping on) is plotted in green. This reference shows clearly how much the cavity control influences the top mass dynamics.


More general comments:

1.  In general, if cavity feedback is applied to the two stages below the top mass in a 3 or more stage pendulum, and that feedback has UGFs beyond the longitudinal modes, some longitudinal damping will be observed. However, by carefully placing the UGF of the stage right below the top mass near that mode, one can maximize the damping provided by the cavity. In this way, no noisy top mass longitudinal damping is required for the pendulum that receives this cavity feedback. The loss in loop gain by dropping this UGF can be compensated for by increasing the UGF at a lower stage.

2. Note, if the cavity feedback is sent to each pendulum in the cavity equally, all longitudinal modes seen by that cavity are damped by the cavity feedback. There are then undamped longitudinal modes not seen by the cavity (or more precisely seen weakly). However, this can be overcome by damping these modes by recombining the OSEM sensors into a global coordinate system orthogonal to the cavity as discussed by G1200774.


Some more nitty gritty measurement details:

1. The impulse is applied at the M1 L stage with MC2_M1_TEST_L_EXC. DTT was used for this by filtering its native impulse excitation through a filter with two poles at 10 Hz. The 10 Hz roll-off is greater than the longitudinal modes, so the ringing response should be true to an impulse. However, it is also smoothed out enough that the otherwise extremely tall and short excitation will excite the suspension and not saturate the DAC.

2. I left the cavity pretty much as I found it when I was done. i.e. the MC2 M1 L damping was turned back on, and the MC2_M2_LOCK_L gain was set back to 0.03. The one exception is that I left a 41 Hz notch filter in place in MC2_M2_LOCK_L at filter module 5 since the cavity seems to be more robust with it there. aLog 7259 describes the notch more fully. The IMC cavity was still locked when I left.

3. The MATLAB code that generates these plots is found at 
.../sus/trunk/HSTS/Common/FilterDesign/H1MC2_CavityControlTest_27July2013.m

Nobody can understand this alog unless he/she is familiar with https://dcc.ligo.org/LIGO-T1100603-v1 , but the basic message is that we're OK, some problem was identified in the mechanical/optical design of the installation tooling but a new procedure was developed to work around it.

At first things weren't good.

• We had the new F1 steering mirror from Newport, which was orders of magnitude better than anything from the past.
• Telescope path was aligned using two auto collimators, AC1 looking from the primary (i.e. the arm) side and AC2 from the secondary (i.e. the ISC table) side. Note that AC2 is installed on the telescope plate using a specially machined class-B sleeve that ensures that the  auto collimator barrel contacts with the inside surface of the sleeve by two lines.
• For laser injection, two irises were installed, one inside the telescope path and the other on the injection table ("pedestal" in the case of Hanford).
  • The first iris was centered using AC2.
  • The second one was set up after flipping the direction of AC2 inside the sleeve mentioned before.
  • Then the injected beam was centered on the irises using video cameras.
• An 8-inch flat mirror was placed downstream of the primary mirror and the angle was set up using AC1.
• We injected the laser beam and started analyzing the return beam.
• We saw a huge astigmatism/ellipticity in the return beam.
  • All flat mirrors (FM1, FM2 and 8" retro mirror) were rotated and exonerated.

After putting a clean wipe on the primary and taking a picture of the IR beam position, it turned out that the beam had a huge offset like an inch or more. This shouldn't have been the case since the procedure is designed specifically to prevent such a thing from happening. Anyway, we should use IR-sensitive DSLR camera  to determine the beam position on the primary.

On further investigation it turned out that flipping AC2 in the sleeve was not a good idea. When we removed the 8" reflector in front of AC1, in the view of AC1 the iris on the injection table was totally off centered by half inch or so, though it was quite well centered in the view of the flipped AC2.

Apparently AC2's optical axis depends on the direction the AC is inserted into the sleeve. The angle repeatability of this sleeve was not that good to start with in the past, maybe that alone explains this, or maybe the AC2's optical axis is not quite colinear with the barrel. Regardless of the real cause, we changed the procedure such that the iris on the injeciton table is set up by AC1.

After this change, the beam shape started to look reasonable. We were able to tune the telescope in such a way that the errors are spread in two directions, and we're already good (see attached).

However, after the tuning is done, the beam is still off-centered on the primary by half inch or so. After Cheryl took the picture of the beam position on the iris in the telescope path, it seems that it is off-centered by maybe 0.5mm or so even though it looked perfectly centered using video cameras. Since the magnification of the telescope is 20, this agrees with the beam position on the primary (half inch = 12.7mm).

We will center the injected beam on two irises using IR camera, tighten all of the actuator tensioning screws for the mirror holders (which, sadly, will change the alignment), make an adjustment if necessary, take the last scan and we'll move to the mating of the telescope and the ISC table.

There appears to be a gain change somewhere in the IMC cavity control sensing chain from where it was last February. See the attached pdf. The first two pages show the measured MC2 M2 loop gain against the model. The first is before correcting the cavity sensing gain, the second is after. The 3rd and 4th pages are structured the same way but for the MC2 M3 loop gain. After adjusting the gain by this 1.36 factor, the measurements agree much better.

The gain of 1.36 was calculated by measuring the difference in the gain between the model and the measurements in the M3 loop gain. The model had about 1.36 times more gain than the measurements. So in the model I reduced the gain of the signal entering the M3 locking filter by this much. This scales the M2 loop as well since the M2 locking filter input is the output of the M3 locking filter (distributed hierarchy). The result is much better agreement between the modeled loop gain and measured loop gain for both M2 and M3.

The data in the attached pdf are from measurements done by Jeff Kissel and myself from last Friday in log 7255. The measurements in that log and this one are plotted against a model developed by Jeff and discussed in DCC doc G1300111. Note that the measurements agree well with the model in G1300111. The cavity locking loops have changed a bit since G1300111 was posted last February, but that is taken into account in the updated model for these current measurements (/ligo/svncommon/SusSVN/sus/trunk/HSTS/Common/FilterDesign/IMCmodel_H1_MC2_M2M3hierarchicalfeedback_26July2013.m). So it is not clear to me where this gain change may have come from.

Forgot to mention -- because of the suspicion that the transmitted input mode cleaner noise is dominated by coil driver noise, I switched H1 SUS MC1, MC2, and MC3 coil drivers into their lowest noise state (State Request 2 on M1/Top "LP ON", State 3 on M2 and M3 "Acq OFF, Lp ON). They had been in their highest-drive-strength (and therefore most noisy) state. 

Sadly, since I couldn't get the arm cavity locked on Red, I couldn't reproduce the measurement -- and we lose the arm cavity tomorrow. A chorus of sad trombones plays in unison. 

While increasing the cavity feedback gain on H1:SUS-MC2_M2_LOCK_L from 0.3 to 0.12 I noticed a 40.91 Hz (measured in DTT with a BW of 0.01) line slowly ringing up. Modeling of the IMC locking control suggested that the cavity should have robust stability, even at the 4 times higher gain at M2. The MSTS model predicts a roll bounce mode at 40.37 Hz, so a good bet is that is what this is. There were similar problems with cavity feedback at LASTI.

I installed a 20 dB, Q 20 notch filter at 40.91 Hz to reduce the ring up in filter module 5 of H1:SUS-MC2_M2_LOCK_L. The name of the filter is notch41Hz. At a gain of 0.12 the cavity now seems much happier. I committed the updated H1SUSMC2.txt file to the svn.

J. Kissel, A. Pele, B. Shapiro, J. Warner

In attempts to measure/calibrate the ETMY actuation function from each stage to the arm cavity with high precision (using the Red/Green beat-note when locked on Red), why tried again to get the Green/Red light locked in the arm cavity. However, we failed to get the arm locked. Queue sad trombone -- we lose the end station first thing Monday morning.

Why we think we failed:
- For some reason we couldn't figure out, ISI-ITMY would not isolate at either level 2 or level 3.
    In order to assist long term studies, we decided to isolate to level 2 tonight. ISI-ETMY and ISI-BS came up just fine.
    - Checked that CPS offsets were in the right place
    - Followed the detailed instructions (many times).
    - Trips on bringing up Stage 1 (on the actuators, since we disabled the inertial sensors during the turn on process).
    No dice. Both levels were functional and stable yesterday.

- Poor alignment of the IFO
    - After noodling around with SUS-BS, SUS-PR3, and SUS-TSMY and getting H1:ALS-Y_REFL_B_LF_OUT_DQ no lower than 11000, I realized that, though the ISI-ITMY offsets are small, the table may not be in exactly the right good place I had last night when both ISI-ETMY and ISI-ITMY isolated. After tweaking the ITM alignment, the REFL_B came down to 9000-10000. However, I could not get H1:ALS-C_COMM_A_DEMOD_RFMON to ever go above -29 dBm -- the most I could get was -30 dBm (though this was true last night as well). Further, at some point of the alignment of ITM, I was able to get the REFL_B signal to "bottom out," in that the characteristic 0.4 [Hz] QUAD motion would disappear. So... maybe I'm on the hairy edge of a diode some where?

Where/How it fails: at the end of the CARM_handoff script, and it blows the reference cavity (and subsequently the mode cleaner). 
- During some of the lock losses, the RefCav would take a few minutes to catch lock again, so I thought the IMC Gaurdian was fighting the RefCav, as Stefan / Rick / Kiwamu had diagnosed yesterday. So, I'd switched the IMC Gaurdian to manual for a bit, and the RefCav would come up fine ... but this may just be a red herring.
- Also, I remember Kiwamu / Alexa having trouble with getting past the stage of the CARM_handoff because of the issues with demod phase rotation of the IMC vs. input polarity of the IMC Common Mode Board.


So, we leave the HIFO-Y in a rather sorry state tonight. Note that the red light is still flashing in the arms; I'm not sure what effect this has on the green cavity performance.

Cavities Locked: Input Mode Cleaner, Arm on Green 
Chamber    HEPI                                   ISI                               SUS
HAM1       Locked                                 n/a                               n/a
HAM2       Floating, Alignment Offsets Only       Level 2 Isolated                  MC1, MC3, PRM damped Level 1.5; PR3 damped Level 1.0
HAM3       Floating, Alignment Offsets Only       Level 2 Isolated (eLIGO Blends)   MC2, PR2 damped Level 1.5 
BS         Level 2 Isolated (Position Locked)     Level 2 Isolated                  BS damped Level 2.0
ITMY       Locked                                 Damping Only                      ITMY damped Level 2.1
ETMY       Level 2 Isolated (Position Locked)     Level 2 Isolated                  ETMY damped Level 2.1, TMSY damped Level 2.0


Tonight's BSC-ISI Level 2 is brought to you by:
Blends at ST1 "750mHz" and ST2 "250mHz"
GND to ST1 STS2 Sensor Correction is OFF
ST1 to ST2 T240 Sensor Correction is OFF
ST0 to ST1 HEPI L4C Feed-Forward is ON (with "FF01_2" filters)
The Input Gains for the L4Cs and GS13s are OFF (I *think* this means they're in low -gain mode). They're ON for the T240s.

These are measurements of the loop gain transfer function of the IMC cavity loops running on MC2. The first pdf shows the loop gain transfer function on M2, the second is the loop gain transfer function on M3. Note the good agreement with the model.

The UGF of M2 is about 3.2 Hz
The UGF of M3 is about 6.5 Hz

The data for the M2 plot live in
/sus/trunk/HSTS/H1/MC2/Common/Data/2013-07-26_H1IMC_M2-M3_Crossover_OLGTF_TF_Export
The data for the M3 plot live in
/sus/trunk/HSTS/H1/MC2/Common/Data/2013-07-26_H1IMC_MCL-MCF_Crossover_OLGTF_TF_Export

The matlab function that makes these plots is
/ligo/svncommon/SusSVN/sus/trunk/HSTS/Common/FilterDesign/IMCmodel_H1_MC2_M2M3hierarchicalfeedback_26July2013.m

Work on OSB Optics Lab – Andres Medinas
Testing HLTS PR3 (Transfer Functions) – Arnaud
Work on LVEA (by the beam splitter) – Richard
Doing Testing on the IMC (Running TFs) – Jeff K.
Taking equipments to End X – Justin
Finished TFs on IMC – Jeff K.

J. Kissel, B. Shapiro

We're trying to compare measurements of the input mode cleaner loop crossovers to a model, and got stuck because the userapps repository's copy of the H1LSC.txt filter file was out of date. We've copied over the latest version of the file from
/opt/rtcds/lho/h1/chans/H1LSC.txt
into the userapps repo here
/opt/rtcds/userapps/release/isc/h1/filterfiles/H1LSC.txt
and committed the new version. Note that there were many more differences between the chans version and the userapps version, most likely associated with all of the HIFO-Y work.

We really need to make the chans copy of every foton file a soft-link to the userapps repo version for every foton file. Currently, this is only true for the SUS, a few IOP, and the ISCEY filter file.

Also -- the LSC model is still running with an IMC block in its top level, so even though the channel names for the IMC filters are, for example H1:IMC-L, there is not foton file called "H1IMC.txt," as one would expect. Instead, its filters are buried in the H1LSC.txt file.

J. Kissel, H. Paris, A. Pele, B. Shapiro

After spending all afternoon getting all the chambers up into their best (local) performance, I've used Stefan's instructions to lock the Y ARM on Red. So easy -- even I could do it! Thanks to all of those who've written scripts to automate the ALS and IMC :-). Interestingly, and I forgot to ask about it, but there's no need to run any down script when the lock is lost. One just runs the two scripts again (assuming your Beam Splitter alignment remains good).

OK, I wrote the aLOG too soon. There have been several lock stretches, and the ISI-BS has tripped. I detailed time line is written below, for as long as I stayed here.

Here's the configuration of the SEI/SUS during these stretched:

Cavity Lock: 
Chamber    HEPI                                   ISI                               SUS
HAM1       Locked                                 n/a                               n/a
HAM2       Floating, Alignment Offsets Only       Level 2 Isolated                  MC1, MC3, PRM damped Level 1.5; PR3 damped Level 1.0
HAM3       Floating, Alignment Offsets Only       Level 2 Isolated (eLIGO Blends)   MC2, PR2 damped Level 1.5 
BS         Level 2 Isolated (Position Locked)     Level 3 Isolated*                 BS damped Level 2.0
ITMY       Locked                                 Level 3 Isolated                  ITMY damped Level 2.1
ETMY       Level 2 Isolated (Position Locked)     Level 3 Isolated                  ETMY damped Level 2.1, TMSY damped Level 2.0

* I noticed ISI-BS had tripped around 2:53 UTC, but it may have been down for some time. I didn't bother bringing it back up, 'cause I didn't want to blow the cavity lock. Or another three hours.

All Optical Levers are well centered.

All BSC-ISIs have been brought up to the configuration outlined in LHO aLOG 7226, but just for posterity, this means:
Level 3 Isolation Filters
Blends at ST1 "T250mHz" and ST2 "250mHz"
GND to ST1 STS2 Sensor Correction is ON (The corner station ISIs are both using the beer-garden STS2)
ST1 to ST2 T240 Sensor Correction is ON
ST0 to ST1 HEPI L4C Feed-Forward is ON (with "FF01_2" filters)
The Input Gains for the L4Cs and GS13s are OFF (I *think* this means they're in low -gain mode). They're ON for the T240s.

----------
Time Line (all times UTC, Jul 25 2013)
2:27 Locked on Red
2:46 Lost Red Lock
2:47 Regained Red Lock
    2:50 Glitch in CARM_IN1!
    2:53 Noticed ISI-BS had tripped. All other ISIs are still fully operational
    2:57 Glitch in CARM_IN1!
3:00 Lost Red Lock
3:06 Regained Red Lock
    3:11:23 Glitch in CARM_IN1! 
    3:24:47 Glitch in CARM_IN1!
3:27 We begin to ignore the IFO and go home, be cause there's enough data in the can to get a 0.01 [Hz] measurement in the past (assuming those glitches don't spoil the spectra)... but may the lock last through the night!

The attached plot shows a measurement of the ETMY from the ISI L witness sensor to the cavity displacement against the quad model from the suspension gnd L input to the test mass L output. Overall there is good agreement except for the factor of about 1.5 between the model and measurement (the model is greater).

relevant details:

The quad model is the MATLAB struct variable susModel in 
/ligo/svncommon/SusSVN/sus/trunk/QUAD/Common/FilterDesign/MatFiles/dampingfilters_QUAD_2013-06-14_Level2p1_RealSeismic_model.mat

The data was collected starting at GPS time 1058680016 based on Jeff Kissel's log 7194. This time was set to be some arbitrary short time after Jeff's recorded time of when the cavity was set at GPS time 1058670016. The state of the IFO at this time is given by that log, 7194, though the state of the ISI isolation at that time is questionable based on the ASDs and trend data of that time. 

The measured transfer function comes from the DTT export file: 
/ligo/svncommon/SusSVN/sus/trunk/QUAD/H1/ETMY/Common/Data/2013-07-23_CavityTFMeasurements_TF
There is a corresponding coherence file
/ligo/svncommon/SusSVN/sus/trunk/QUAD/H1/ETMY/Common/Data/2013-07-23_CavityTFMeasurements_Coh
These files are exported from the DTT file
/ligo/svncommon/SusSVN/sus/trunk/QUAD/H1/ETMY/Common/Data/2013-07-23_CavityTFMeasurements.xml
This TF and coherence data was exported in the following order:

1.  H1:SUS-ETMY_M0_ISIWIT_L_DQ to H1:ALS-Y_REFL_CTRL_OUT_DQ
2.  H1:SUS-ETMY_M0_ISIWIT_L_DQ to H1:SUS-ETMY_L3_OPLEV_PIT_OUT_DQ
3.  H1:SUS-ETMY_M0_ISIWIT_L_DQ to H1:SUS-ETMY_L3_OPLEV_YAW_OUT_DQ
4.  H1:SUS-ETMY_M0_ISIWIT_T_DQ to H1:ALS-Y_REFL_CTRL_OUT_DQ
5.  H1:SUS-ETMY_M0_ISIWIT_T_DQ to H1:SUS-ETMY_L3_OPLEV_PIT_OUT_DQ
6.  H1:SUS-ETMY_M0_ISIWIT_T_DQ to H1:SUS-ETMY_L3_OPLEV_YAW_OUT_DQ
7.  H1:SUS-ETMY_M0_ISIWIT_V_DQ to H1:ALS-Y_REFL_CTRL_OUT_DQ
8.  H1:SUS-ETMY_M0_ISIWIT_V_DQ to H1:SUS-ETMY_L3_OPLEV_PIT_OUT_DQ
9.  H1:SUS-ETMY_M0_ISIWIT_V_DQ to H1:SUS-ETMY_L3_OPLEV_YAW_OUT_DQ
10. H1:SUS-ETMY_M0_ISIWIT_R_DQ to H1:ALS-Y_REFL_CTRL_OUT_DQ
11. H1:SUS-ETMY_M0_ISIWIT_R_DQ to H1:SUS-ETMY_L3_OPLEV_PIT_OUT_DQ
12. H1:SUS-ETMY_M0_ISIWIT_R_DQ to H1:SUS-ETMY_L3_OPLEV_YAW_OUT_DQ
13. H1:SUS-ETMY_M0_ISIWIT_P_DQ to H1:ALS-Y_REFL_CTRL_OUT_DQ
14. H1:SUS-ETMY_M0_ISIWIT_P_DQ to H1:SUS-ETMY_L3_OPLEV_PIT_OUT_DQ
15. H1:SUS-ETMY_M0_ISIWIT_P_DQ to H1:SUS-ETMY_L3_OPLEV_YAW_OUT_DQ
16. H1:SUS-ETMY_M0_ISIWIT_Y_DQ to H1:ALS-Y_REFL_CTRL_OUT_DQ
17. H1:SUS-ETMY_M0_ISIWIT_Y_DQ to H1:SUS-ETMY_L3_OPLEV_PIT_OUT_DQ
18. H1:SUS-ETMY_M0_ISIWIT_Y_DQ to H1:SUS-ETMY_L3_OPLEV_YAW_OUT_DQ
19. H1:SUS-ITMY_M0_ISIWIT_L_DQ to H1:ALS-Y_REFL_CTRL_OUT_DQ
20. H1:SUS-ITMY_M0_ISIWIT_L_DQ to H1:SUS-ITMY_L3_OPLEV_PIT_OUT_DQ
21. H1:SUS-ITMY_M0_ISIWIT_L_DQ to H1:SUS-ITMY_L3_OPLEV_YAW_OUT_DQ
22. H1:SUS-ITMY_M0_ISIWIT_T_DQ to H1:ALS-Y_REFL_CTRL_OUT_DQ
23. H1:SUS-ITMY_M0_ISIWIT_T_DQ to H1:SUS-ITMY_L3_OPLEV_PIT_OUT_DQ
24. H1:SUS-ITMY_M0_ISIWIT_T_DQ to H1:SUS-ITMY_L3_OPLEV_YAW_OUT_DQ
25. H1:SUS-ITMY_M0_ISIWIT_V_DQ to H1:ALS-Y_REFL_CTRL_OUT_DQ
26. H1:SUS-ITMY_M0_ISIWIT_V_DQ to H1:SUS-ITMY_L3_OPLEV_PIT_OUT_DQ
27. H1:SUS-ITMY_M0_ISIWIT_V_DQ to H1:SUS-ITMY_L3_OPLEV_YAW_OUT_DQ
28. H1:SUS-ITMY_M0_ISIWIT_R_DQ to H1:ALS-Y_REFL_CTRL_OUT_DQ
29. H1:SUS-ITMY_M0_ISIWIT_R_DQ to H1:SUS-ITMY_L3_OPLEV_PIT_OUT_DQ
30. H1:SUS-ITMY_M0_ISIWIT_R_DQ to H1:SUS-ITMY_L3_OPLEV_YAW_OUT_DQ
31. H1:SUS-ITMY_M0_ISIWIT_P_DQ to H1:ALS-Y_REFL_CTRL_OUT_DQ
32. H1:SUS-ITMY_M0_ISIWIT_P_DQ to H1:SUS-ITMY_L3_OPLEV_PIT_OUT_DQ
33. H1:SUS-ITMY_M0_ISIWIT_P_DQ to H1:SUS-ITMY_L3_OPLEV_YAW_OUT_DQ
34. H1:SUS-ITMY_M0_ISIWIT_Y_DQ to H1:ALS-Y_REFL_CTRL_OUT_DQ
35. H1:SUS-ITMY_M0_ISIWIT_Y_DQ to H1:SUS-ITMY_L3_OPLEV_PIT_OUT_DQ
36. H1:SUS-ITMY_M0_ISIWIT_Y_DQ to H1:SUS-ITMY_L3_OPLEV_YAW_OUT_DQ

Note, the cavity signal H1:ALS-Y_REFL_CTRL_OUT_DQ is calibrated in Hz. The ISI witness signals are calibrated in nm. The calibration of the optical levers is unknown.

The measured transfer function was scaled by multiplying it by 
7.0982e-12 [m/Hz] / 1e-9 [nm/m] = 0.0070982 [m^2 / (nm Hz)]
The 7.0982e-12 [m/Hz]  comes from
lambda*L/c
where lambda = (1064e-9 / 2) [m], for the green light wavelength
L = 4000 [m], for the arm length
c = 299792458 [m/s], for the speed of light

To date and the best of my knowledge, the only measurements of the 18-bit DAC noise have been those performed by J. Heefner, documented in T0900338, where the DAC noise is quoted as 150 [nV/rtHz] (and flat in the frequency band he probed). We'd learned from eLIGO (lessons by Tobin, myself,Matt, and Nic) that a DAC's noise floor changes when excitation is present, so Jay had measured the DAC noise while injecting a single-frequency line at ~100 [Hz], and then measured the high-frequency asymptote (his plots are on a linear x axis, without a grid so one can really only see the results above 100 Hz).

In the interest of suspension performance in the 0.1-10 [Hz] band where cavities are currently sensitive to their optic's motion, I've now characterized the noise in detail at low-frequency (0.05-1e3 [Hz], with focus on 0.05-50 [Hz] band), using a realistic output spectrum as the requested voltage. The results are attached and described below. Since the results are clearly non-linear, we may need to try different input spectra (working a little harder than I did to balance the SR785 range vs. noise) to really understand it. Naturally, we should also develop a model of the quantization noise, to see if we can differentiate this from just bad, non-linear electronics noise. Finally, we should also perform this same measurements on a 16-bit DAC.

Note that, by default, the user-model-to-IOP-model exchange is done with zero-padding, as has become the default configuration for all models.

--------
Plots and Captions

2013-07-21_2119_H1SUSMC2_DACOutput_ModeCleanerLocked_ASDs.pdf
During a fully functional Input Mode Cleaner lock, this is the output voltage requested of the DAC at all three stages. The spectra seen at the TOP/M1 stage is totally confusing to me, so I ignored it, as it was distracting to this study to try and figure out. More on that to come later. As such, (and also informed by the input range vs. noise floor of the SR785 at these frequencies), I chose the Middle / M2 stage spectra as my representative spectra.

experimentalsetup.pdf
Diagram of how the experiment was set up. For this study, I commandeered the H1 SUS QUAD Test Stand. This is a fully-production quality test stand, running up-to-date software, and up to which nothing is hooked, so it was the perfect test bed. The Pomona box that was used to switch between output channels (borrowed from MIT) was a easy, convenient way to grab the signals, keeping them shielded, without having to mess with the usual breakout boards and clip leads -- a set up usually fraught with excess unwanted noise.

2013-07-21_H1SUSQUADTST_DACNoise.pdf The Results
PG1: Here is the digitally requested spectrum, calibrated into voltage out of the AI filter (i.e. cts at the COILOUTF_??_EXC point, multiplied by the gain of the DAC, 20 / 2^18 [V/ct]). It is compared with the measurement noise floor (for the low-frequency, 0.05 - 50 [Hz] band, with -10 [dBVpk] SR785 input range), and the measured DAC noise with no digital output requested. The "traveling notches" in the requested drive are used to carve out at the DAC noise without disrupting the main frequency content of the signal. Note that because of SR785 range vs. noise issues, I sent out a requested signal with a factor of 10 less RMS voltage at 1e-2 [Vrms]. This is compared with the M2 stage (with 1e-1 [Vrms]) and 

PG2 - 4:
The measured DAC noise output at the AI chassis for 3 DAC channels. We see, rather obviously that none of the notches below 10 [Hz], indicating a several elevated DAC noise floor. I've included a quick by-eye fit to the noise, which indicates that the DAC noise is 6e-6 * (10 [Hz] / f) [V/rtHz], with this excitation. 

Notes:
- Even though the SR785 measurement is focused on the 0.05 - 50 [Hz] band, the full spectrum out to several [kHz] is requested during all measurements.
- It's unclear to me why the shape and level of the DAC noise changes when I switch to the higher measurement band (10 to 810 [Hz]). Since I saw the DAC noise floor after the natural 100 [Hz] roll-off of the output spectra while retaining the 30 [Hz] notch (and it was Sunday at 8pm), I didn't bother traveling the notch any further, and therefore only have one measurement for each channel in this band.

-----------
Details:
The template for the mode cleaner output request spectra can be found here:
${SusSVN}/sus/trunk/HSTS/H1/MC2/Common/Data/2013-07-21_2119_H1SUSMC2_DACOutput_ModeCleanerLocked_ASDs.xml

The input spectra is defined by the following AWGGUI Foton String which filtered white ("uniform") noise:

amplitude  = 100000 to get 1e-2 [Vrms]

zpk([1.3;1.3;1.3;1.3;1.3;1.3],[0.3;0.3;0.3;0.3;0.3;0.3],1,"n")ellip("LowPass",4,1,80,100)
notch(0.47,10,200)notch(0.5,10,200)notch(0.52,10,200)
notch(0.9,10,200)notch(1,10,200)notch(1.1,5,200)
notch(4.7,10,200)notch(5,10,200)notch(5.2,5,200)
notch(10,5,200)notch(11,5,200)notch(12,2.5,200)
notch(30,5,200)notch(32,5,200)notch(34,2.5,200)
I'm *sure* there's a more elegant way of defining it, but ... so it goes.

The captured digital output spectra templates can be found here:
${SusSVN}/sus/trunk/QUAD/H1/QUADTST/Common/Data/18Bit_DACNoise_2013-07-21/
2013-07-21_H1SUSQUADTST_DACNoise_COILOUTF_AvgASDw0p45-0p5-0p55HzTipleNotch_ASDs.xml
2013-07-21_H1SUSQUADTST_DACNoise_COILOUTF_AvgASDw0p9-1-1p1HzTipleNotch_ASDs.xml
2013-07-21_H1SUSQUADTST_DACNoise_COILOUTF_AvgASDw4p5-5-5p5HzTipleNotch_ASDs.xml
2013-07-21_H1SUSQUADTST_DACNoise_COILOUTF_AvgASDw10-11-12HzTipleNotch_ASDs.xml
2013-07-21_H1SUSQUADTST_DACNoise_COILOUTF_AvgASDw30-32-34HzTipleNotch_ASDs.xml


The raw SR785 data files can be found here:
${SusSVN}/sus/trunk/QUAD/H1/QUADTST/Common/Data/18Bit_DACNoise_2013-07-21/SCRN*.TXT
with a key to what each number means in
${SusSVN}/sus/trunk/QUAD/H1/QUADTST/Common/Data/18Bit_DACNoise_2013-07-21/2013-07-21_MeasNotes.txt

The data is analyzed, and plots are produced with the following script:
${SusSVN}/sus/trunk/QUAD/H1/QUADTST/Common/Scripts/plot18bitdacnoise_20130721.m  

Daniel Halbe, Josh Smith, Jess McIver

Summary: strong, semi-periodic transient ground motion is propagating up the SEI platforms and down the suspension stages at ETMY. Cause of the ground motion is not yet determined. Effect on the HIFOY signal is not yet evaluated. 

Glitching in the top stage of the ETMY BOSEMs was first identified by Daniel Halbe (see Spectrogram_SUS_Longitundinal_M0_BOSEM_July2.png). These glitches are seen in all DOFs of the suspensions and seismic isolation platforms, have an irregular periodicity of about every 10-20 minutes, a duration of a few minutes, a central frequency of 3-5 Hz, an amplitude in Stage 1 T240s of the ISI on the order of a thousand nm/s (~ um/s) away from baseline noise, and have been occurring since at least June 12, 2013. They are not seen in ITMY suspensions channels. 

For a table that traces these glitches across each DOF and up the stages of seismic isolation to the top stage of the suspension, see: https://wiki.ligo.org/DetChar/HIFOYETMYglitching > Normalized spectrograms (PSD) of the periodic glitches for 1 hour 10 min

Daniel also found them in the lower stage ETMY OSEMs: https://wiki.ligo.org/DetChar/SpectrogramsOfH1AllMassQuadSUSETMY

And Josh Smith traced them to excess ground motion using a representative top stage BOSEM channel (see EMTY_top_stage_BOSEM_pitch_correlation_to_excess_ground_motion.png). 

These glitches have a strong correlation with local ground motion and significant correlation with ground motion near the vault. There appears to be faint correlation with ground motion near MX and the LVEA that merits further investigation.  
(See the normalized spectrogram Top_stage_BOSEM_ETMY_longitudinal_glitching.png and compare to normalized spectrograms Ground_motion_PEM_{location}_spectrogram.png of the same time period)

For additional plots of ground motion at various locations around the ifo during these glitches, see again: https://wiki.ligo.org/DetChar/HIFOYETMYglitching
(If you are unable to see some of the plots on this page, please see the instructions under 'Normalized spectrograms (PSD) of the periodic glitches for 1 hour and 10 min'). 

Note that the reported units of counts are incorrect for all plots (a bug in ligoDV) - these channels are calibrated to nm/s for inertial sensors or to um for BOSEMs and OSEMs.