I'm driving C1:SUS-ITMX_OLYAW and PIT_EXC with amplitude 0,1-0.3 while taking transfer funtions of oplev.

The transfer functions are normal. However I noticed that the LL osem is not responding to this excitations

Healthy sensor respons should be like Atm3

Frank pointed out to me that I had dumbly forgotten to include the voltage reference's noise. The LT1031 has an output noise level of ~125 nV/rHz above 10 Hz or so, and this at least makes the estimate much closer. I had also not included an extra LT1125 stage between the reference and the other stages. I guess I was tired.

The estimate is now within a factor of a few of the measured level, and it has roughly the right shape. Around 1 Hz, it looks like the measured data begin to roll up away from the model, though it's tough to say due to the effect of the AC coupling on the analyzer less than a decade below. If there is indeed extra noise here, Frank thinks it could be due to resistor current noise.

I'll switch one or two out for nicer ones and see if things change.

OL_YAW transfer functions are here.

 I had two PHDs helping me to overlap the EXML files in DTT. We failed. This job requires professorial help.

These observations of the OSEMs  were taken while taking transfer functions of oplev YAW at excitation amplitude 0.1

 Atm1,  C1:SUS-ETMX_SENSOR_SIDE cross coupling

Atm2,   C1:SUS-ITMX_SENSOR_LL   not excitable

Atm3-4,   BS and PRM  insensitive

Good OSEM list: ITMY, ETMY and SRM

I worked on the OSEM box a little more today, with the hopes of reducing the measured output current noise. I succeeded, at least modestly. It turns out that most of the noise was indeed caused by the crappy resistors.

Below is the circuit for one of the 5 LEDs. The output of the op-amp structure directly after the LT1031 reference is split between 5 stages identical to the structure on the right. I have shown just one (UR) for clarity. The various measurement points are explained below.

I started from the beginning of the circuit, directly after the LT1031, to make sure that the excess noise seen the other day wasn't just from a noisy reference. Below is the measured output voltage noise along with the LISO estimate. Clearly, the LT1031 is performing to spec (as it should, since it's a new part that I just put in). Note that the apparent better-than-spec performance at low frequencies is just from the AC coupling, which I needed due to the high DC level.

Since the reference was in order, the next step was to switch out some of the crappy old resistors for nicer thin-film ones. In case anyone is interested, Frank has done some detailed investigation of excess 1/f current noise in resistors. I measured the voltage noise level at the point labeled "inter-stage measurement" above, first without any modifications and then after swapping the old 10k resistors (R1 & R2) out for nice Vishay thin-film ones. There is clearly a big improvement, and the modified circuit essentially agrees with LISO now down to 1 Hz. Below this, it looks like there could still be an issue.

I wanted to see what the improvement was in the overall output current noise of the system, so I went about measuring the current noise as I had the other day (by measuring the voltage noise across R55 and dividing by the resistance). The performance was already better than the old measurement, but not at the LISO level. So, I replaced the current-setting resistors (R54 & R55)---which were actually 3 parallel resistors on a single pad in each case---by nice Vishay ones, as well. I didn't have any that were close to the original resistance of ~287 ohms, so I put three 1k ones in parallel. This of course shifts the resistance up to 333 ohms, but that only causes a ~16% change in current. I was sure to convert voltage noise into current noise with this new resistance, though.

With this change, the total output current noise is now very close to the LISO estimate as well down to ~1 Hz.

Some notes:

• First, I apologize for the noise margin at higher frequencies. I redid the higher frequency measurements with an SR560 as a preamp, but I must have screwed up the calibration because the data don't match up quite right with the LF measurements. It was clear while I was taking them that they followed the LISO trace.
• There still seems some excess noise below 1 Hz. It could be that the noisy resistors in the parallel stages were somehow still contaminating the cleaned-up channel. I'll look into this more soon.

Finally I found a company who can do Koji's improved  -hard to make-  specification on ruby or sapphire wire standoff.

NOT POLISHED excimer laser cut, wire groove radius R 0.0005" + - 0.0002"

$250 ea at 50 pieces of order

ITMX, PRM and BS watchdogs are tripped. They were restored.

Stable MC was disabled so I can use MC_REFL 1 W beam to measure green glass .

While Kiwamu and I were trying to investigate the the vertex glitches we were noticing excess noise in ITMX, which Kiwamu blamed on some sort of bad diagonalization.  Sure enough, the ITMX input matrix is in the default state [0], not a properly diagonalized state.  Looking through the rest of the suspensions, I found PRM also in the default state, not diagonalized.

We should do another round of suspension diagonalization.

Kiwamu (or whoever is here last tonight): please run the free-swing/kick script (/opt/rtcds/caltech/c1/scripts/SUS/freeswing) before you leave, and I'll check the matrices and update the suspensions tomorrow morning.

[0]

This reminds me that the whole Dr. SUS situation never got taken care of. Where I left off, I was having issues pulling 40m data with NDS2 (which is what all the diagonalization scripts use).

What is the deal with 40m+NDS2? If it is till no-go, can we have a consensus on whether this is too important to wait for? If so, I will rewrite the scripts to use NDS and we can upgrade to NDS2 once we can prove we know how to use it.

 Oplev transfer functions PIT UGF were optimized to be at 2-3 Hz with 60 degree minimum phase margin by adjuting oplev gains.

Additional Notes by KI:

• The PRM oplev has a tailored 3.3 Hz resonant gain in order to calm down a wobble during the lock acquisitions.
• Also in the PRM oplev a 35 Hz elliptic cut-off filter wasn't  activated at the time when Steve measured it.
• In both ITMs, elliptic cut-off filters seem to have higher corner frequencies compered with the others.
  
  • I guess these settings are from the old days.
• ETMs and ITMs have whitening filters while the rest of the suspensions don't.
  • Without the whitening filters, normally the signals above 30 Hz are covered by some electrical noises or perhaps He-Ne laser intensity noise (#5630).
    • This is why we usually use the 35 Hz elliptic filters to roll off the control noises.
  • Since the ETMs and ITMs have whitening filters they potentially can have slightly higher corner frequencies in the elliptic filters.
    • Of course the corner frequencies need to be re-designed in terms of the amount of noise injection to the longitudinal motion.
      

 All suspentions were restored and MC locked. PRM side osem  RMS motion was high.

Atm2, Why the PRM is 2x as noisy as the SRM ?

Somehow the angular stability of the central part have not been so great.

Also the angular motions look fluctuating a lot and they seem to be related with the glitches.

I took the oplev spectra when the PRMI is locked and unlocked to see whether if something obviously crazy is going on or not.

They seem ok to me except that the PRM pitch shows an extra bump at around 2-3 Hz when the PRMI is locked. But I don't think it's prominent.

- The attached files show the oplev spectra. When the PRMI is locked the PRM and both ITMs are under the length control.

(red) pitch when PRMI is locked

(blue) yaw when PRMI is locked

(orange) pitch without any length controls

(cyan) pitch without any length controls

 The BS and the PRM have 3.3 Hz resonant gain filters that kill the phase margins.

 Green welding glass 7" x 9"   shade #14 with 40 mm hole and mounting fixtures are ready to reduce scatter light on SOS

PEEK 450CA shims and U-shaped clips  will keep these plates damped.

[Suresh, Jamie]

Suresh and I opened up and checked out the eLIGO tip-tilts assemblies we received from LLO. There are two, TT1 and TT2, which were used for aligning AS beam into the OMC on HAM6. The mirror assemblies hang from steel wires suspended from little, damped, vertical blade springs. The magnets are press fit into the edge of the mirror assemblies. The pointy flags magnetically attach to the magnets. BOSEMS are attached to the frame. The DCC numbers on the parts seem to all be entirely lies, but this document seems to be close to what we have, sans the vertical blade springs: T0900566

We noticed a couple of issues related to the magnets and flags. One of the magnets on each mirror assembly is chipped (see attached photos). Some of the magnets are also a bit loose in their press fits in the mirror assemblies. Some of the flags don't seat very well on the magnets. Some of the flag bases are made of some sort of crappy steel that has rusted (also see pictures). Overall some flags/magnets are too wobbly and mechanically unsound. I wouldn't want to use them without overhauling the magnets and flags on the mirror assemblies.

There are what appear to be DCC/SN numbers etched on some of the parts.  They seem to correspond to what's in the document above, but they appear to be lies since I can't find any DCC documents that correspond to these numbers:

TT1: D070176-00 SN001
  mirror assembly: D070183-00 SN003
TT2: D070176-00 SN002
  mirror assembly: D070183-00 SN006

 I don't know what tripped the PRM watchdog, but it was unhappy.  I manually moved the sliders on the IFO align screen away from the positions of the save file before turning on the damping, to make sure that I wouldn't be sending oodles of power to the REFL port, since the ND filter is still removed.  So PRM is damped now, but misaligned.

Has default inmat:

PRM, ITMX

Has fancy inmat:

BS, ITMY, SRM (but side is non-fancy), ETMX, ETMY, MC1, MC2, MC3

So it's likely that the MICH problems (giganto 1Hz peak) Keiko and Kiwamu were seeing last night had to do with ITMX having the non-optimized input matrix.  I'll try to figure out where the data from the last freeswing test is, and put in a fancy diagonalized matrix.

 We found that that bounce (16.1 Hz) and roll (23.5 Hz) modes on the ITMX were much higher than on the ITMY. After some checking, it seems that the bandstop filters for the

SUSPOS, SUSPIT, SUSYAW, and SUSSIDE loops are set to the correct frequencies. However, the OLPIT and OLYAW had not been set correctly. I have copied the SUS filters into the OL filterbanks and reloaded all the filter banks. Attached are the comparison of old, bad, OL with the SUS ones.

The same cockamamie situation was there for the BS & ITMY as well. Although we still don't have the roll mode frequencies listed in the mechanical resonances wiki, I have guessed that the ITMY roll frequency is the same as the ITMX, since they have nearly the same bounce frequency. OL filters for the BS & ITMY are now at the right frequency (probably). Keiko is on top of fixing things for the other optics.

I think this whole notching adventure was in Leo's hands several months ago, but WE forgot to point him at the OLs in addition to the SUS. I blame Kiwamu 50% for not supervising him and Koji by 45% for not supervising Kiwamu. The other 5% goes to someone else. You know who you are.

Here are the OSEM spectrum of MICH suspensions (BS, IX, IY). Bounce and Roll modes are shown on 16 and 23 Hz. The filters for them has been checked.

keiko, kiwamu, Rana

The BS SIDE damping gain seemed too low. The gain had been 5 while the rest of the suspensions had gains of 90-500.

I increased the gain and set it to be 80.

I did the "Q of 5" test by kicking the BS SIDE motion to find the right gain value.

However there was a big cross coupling, which was most likely a coupling from the SIDE actuator to the POS motion.

Due to the cross coupling, the Q of 5 test didn't really show a nice ring down time series. I just put a gain of 80 to let the Q value sort of 5.

I think we should diagonalize the out matrices for all the suspensions at some point.

All oplev qpd quadrons were zeroed by offset  in blocked dark condition.

[Rana / Kiwamu]

 We put some elements in the BS output matrix to mitigate the actuator coupling from SIDE to POS.

As a result the degree of the coupling reduced by a factor of 2 or so.

Rana did the "Q of 5" test on the SIDE damping servo after putting the elements and set the gain to be 40.

The attached screen shot is the new elements that we put in the suspension output matrix.

(How to)

• Excite the SIDE motion by AWG at 3 Hz.
• Monitor the POS signal in DTT
• Try some numbers in the matrix elements until the peak at 3 Hz in the POS signal is minimized

To start the optical lever filter design, I looked into the noise on ITMY. It should be similar to the other arm cavity optics since they have the same whitening electronics.

The RED/BLUE are with loops open. The MAGENTA/CYAN with loops closed. Looks good; the bandwidth is a few Hz and there is not much peaking,

To figure out the contribution from the dark noise I misaligned the ITMY until the sum on the QPD went to zero. Then I took the spectra of the OL{1,2,3,4}_OUT signals (they all looked the same).

To normalize them properly I took OL4, multiplied it by 2 to account for the incoherent sum of 4 channels and then divided by the nominal SUM (which was 14685 counts). I've left the OL3 un-normalized to show the ratio.

From this plot it seems that the dark noise is not a problem at any frequency (no need to amplify for the new ADCs).

I'm going to use the open loop spectra to design the optimal feedback control. The file is saved as /users/rana/dtt/ITMY_OL-120325.xml

 Conclusion: There is no need to silver plate the SS plunger at the torque level we hold the OSEMs

Mike Gerfen will be done with 50 pieces by April 4 and he will give them to Bob for cleaning. They should be cleaned and baked in a jig so the springs would be compressed for better venting.

There's a beam dump after the HeNe on the BS oplev table, since the IPPOS measurement optics (steering mirrors) are in the way of the oplev beams. 

Don't enable the BS or PRM oplevs!!!!  We'll post a notice in the elog when the oplevs are back to normal. 

Self, remember to disable the oplevs manually if they come on with any restore scripts.

I tried to figure out what can add noise below 0.5 Hz to the MC_F. I compared MC1, MC2, MC3 suspos, suspit, susyaw and susside positions with damping (black curves) and without (red curves). Local damping is fine.

Then I compared MC1, MC2, MC3 suspos, suspit, susyaw and susside positions with WFS on (black curve) and off (red curve). WFS add noise to MC1 and MC3 measured by osems (MC2 is fine though). WFS should change osem readings but is it a correct way to do this below 0.5 Hz (?) It looks like just a flat noise. Need to think about the conclusion.

    WFS servo is moving the MC mirror angles to minimise TEM01 and TEM10 modes within the MC cavity.    This means it will compensate not only for angular noise in the mirrors but also for the PSL beam pointing fluctuations.  So the extra "noise" we see when WFS loops are on is because they are active below the WFS UGF of about 2 Hz.  Also if the HEPA airflow is above 20% (of its max), the PSL beam jitter (caused by the airflow) will add broadband noise into the WFS servo loops and this will show up in the OSEM signals.  See elog 5943 for details.

It's been a while since I think anyone has done it, and several optics were pretty far from centered, so I centered all of the oplevs except for SRM.

I am confident about my arm alignment, MICH and PRC (so BS, ITMX, ITMY, PRM, ETMX and ETMY), but I wasn't sure if I was getting SRC right, so I didn't touch the SRM's oplev.

Suresh removed all of the IPPOS measurement optics, so there was nothing blocking the BS and PRM oplevs.

However, the PRM oplev was ridiculously bad, and I don't know how long it's been that way.  Some of the optics shooting the beam into the chamber weren't optimally aligned, so the beam coming out of the chamber was hitting the lowest edge of the optic mount, for the first optic the beam encountered.  I adjusted the mirror launching the beam into the chamber by a teeny bit, so that the outcoming beam was ~horizontal and hitting the center of the first steering mirror in pitch.  I had to move that steering mirror a little to the right (if you are staring at the HR face of the mirror), to get the beam to come close to the horizontal center of the optic.  Then I proceeded to do normal oplev alignment.

Also, I've noticed lately that ITMX is noisier than all the other optics.  It's kind of annoying.  The sensor RMS values reported for the ITMX watchdogs for UL and LL are rarely below 2, and are often (~70% of the time?) above 3.  The SD RMS is a normal 1-ish.

[Jenne, MikeJ]

The ETMY oplev quad sum was ~0, so we went to investigate.  The power supply was dead.  Keying it on and off didn't fix things, and it was certainly getting power since the front indicator light was flickering.  We replaced it with a different power supply, and the oplev is back.

Also, the Y-green AUX laser was off, presumably from the power outage a while back.  I turned it back on.

EDIT JD:  The first power supply we used didn't work....the oplev was on for a few minutes, then went off again.  We switched to one of the new (still JDSU) power supplies from Edmund Optics, and it's been happily working for at least an hour now.

And has the temp controller of the green been recovered too? (Push enable button)

 Just now, yes.

[Jenne/Den/Koji]

We locked Xarm/Yarm and manually alignmed ITMX/ITMY/BS/ETMX/ETMY/PZT1/PZT2.

ITMY OPLEV was largely misaligned ==> The beam was centered on the QPD.

----

Then we aligned PRM using SB locking PRMI.

We noticed that OPLEV servo does not work. It made the PRM just noiser.

We went into the PRM table and found that the OPLEV beam was clipped in the vacuum chamber.
We tried to maximize the reflected beam from the window by touching the steering mirrors at the injection side.

Then the reflected beam was introduced to the center of the QPD.

After the alignment, the OPLEV QPD SUM increased to 4000ish from 200ish.
According to the OPLEV trend data, this is a nominal value of the QPD SUM.

Now the OPLEV servo does not go crazy.

 --

BS OPLEV beam was centered on the QPD.

I'm still not super happy with the low power level of the ETMX oplev, so I went to investigate.

This is a 3-year plot.  The first ~year in the plot, the oplev sum is ~15000 cts, and in the most recent year, it's ~1000 cts.  A new HeNe was installed in May 2011 (elog 4686), with an output of 2.6mW, after the old one had died.  When the new one was installed, Steve said that it was giving ~1400 counts, so maybe 1000 isn't too, too embarrassing.  There is, however, a lens on the injection side, which is AR coated for 1064.  The power before this lens (measured with the Ophir, set to 632nm) was ~2.6mW.  The power after this lens was ~1.5mW.  Now THAT is embarrassing.  I'm adding replacing that lens to the to-do list (elog 6595), although I don't want to do it until such a time (maybe in an hour, maybe in a few days?) when I've got the Xarm locked / aligned, so I can nicely re-center the oplev.  UPDATE:  The lens is a KBC 037 (-100) lens, and the sticker on the lens mount says coated for 1064.  We don't have any KBC037's in the visible lens kits, so we need to get one before I can do this replacement (PURCHASED 10pm).

There is an elog (elog 5004) from July 2011, which mentions that these channels have not been saved for a long time, so that's why there's the year-long gap. 

Since Den wasn't able to fix c1sus (make it talk to the framebuilder) before he left a few hours ago, I decided to do some housekeeping rather than actual locking. 

I wrote new save / misalign / restore scripts for all of the suspended optics on the C1IFO_ALIGN screen.  Adding save / restore versions for the mode cleaner optics should be quick and easy.  Now when you use the ! button for each optic, it points you to the new scripts.  I still have the burt capabilities there, but the restore script has the burt-restore line commented out.

Functionality:

SAVE:  burt-save the PIT_COMM and YAW_COMM values, as well as write those values and the date to a text file.

MISALIGN:  Turn off oplevs, move 100 steps of 0.01 in the "+" direction.

RESTORE: Move ~100 steps toward the saved value, until you're within 0.001 of the saved value (step size is "saved val" minus "current val" divided by 100).  Then just write the saved value to the slider (otherwise if the slider were touched between the last "save" and the restore, we might not be able to step precisely to the value we want). Turn oplevs back on.

Scripts are in the same place the old ones used to live:  ...../caltech/c1/medm/c1ifo/cmd/   New scripts are C1IFO_OPTIC(save/restore/misalign)_soft.cmd

I'm checking this one off of the to-do list.

Good things:  (a) I remembered / re-learned / just plain learned a lot about scripting.  (b) the optics are now walked slowly over to their misaligned state, and slowly walked back.  The past regime had the optics suddenly kicked over by a lot, sometimes enough to trip / come close to tripping watchdogs, which was never good.

Bad things: it took a long time.  Now it's bedtime.

ETMY sus damping restored.

ETMX sus damping restored

Guralp 1  is on the south side of IOO chamber

 The typical sign of a dying gas laser is that it glows for a few minutes only. The power supplies are fine.

Two new  JDS - Uniphase 1103P lasers ( NT64-104 )  arriving on Monday, May 21

 The uncoated bi-concave lens was replaced by AR coated one: KBC 037 -100 AR.14 resulting 35% count increase on qpd

 Yesterday I swapped in new He/Ne laser with output power 3.5 mW  The return spot on qpd is large ~6mm in diameter and 20,500 counts

The spot size reduction require similar layout as ETMX oplev.

I've terminated input to AA filters and measured signal to coils C1:SUS-MC3_??COIL_OUT.

I compared this noise to the signal when OSEM are connected to ADC.

I made BNC -> LEMO board such that all LEMOs have the same signal equal to BNC signal. I provided excitation of 50 mV as white noise to the input of the AA filter and measured coherence between excitation and MC3 coil driver. The path is

AA -> ICS 110 -> Pentium -> Pentek -> AI -> Univ Dewhitening -> Coil Driver

As all inputs have the same signal, matrices that recombine the signals should not affect coherence. But what I got for coherence between AA IN / Dewhitening OUT is

AA IN -> COIL DRIVER IN transfer function for MC3

I've provided excitation to the AA input, the same for all OSEM channels. In the digital domain coherence between C1:SUS-MC3_ULSEN_INMON / C1:SUS-MC3_ULCOIL_INMON and other channels OSEM -> COIL is 1 starting from 0.1Hz.

The only thing left to understand is why the coherence AA IN / COIL DRIVER IN measured in the analog domain is not 1 in the frequency range 0.1 - 1 Hz. It does not look like just SRS noise. I've connected Ch 1 and 2 to the source, coherence is close to 1.

 The oplev path is relayed and the spot size on the qpd is reduced. I still have to clean up and replace "Miki Mouse" lens holder.

There was no IP-ANG coming out of the chamber at this time!

 Flipped the sign on the ETMY oplev servo gain, since it was wrong.  (It was "-" for both, now it is "+" for both)

For some reason the state of the oplevs is completely different for almost every suspension.  They have different sets of filters in the bank, and different filters engaged.  wtf?  How did this happen?  Is this correct?  Do we expect that the state of the oplevs should be different on all the different suspensions?  I wouldn't have thought so.

I discovered this because the PRM is unstable with the oplevs engaged.  I don't think it was yesterday.  Is something hidden changing the oplev settings?

 As of February 23, 2012 when oplev PIT and YAW transfer functions were taken

 Its a good question, but the answer is yes. At some level all of the OL servos should be different to handle the different mechanical resonances of the suspension as well as the optical table's acoustic noise and the different noise requirements for the difference optical cavities.

However, it would be better to have the same basic structure and then one or two customization filters.

What not to do:

The PRM oplev servo was left on and it was driving this oscillation overnight.

 Oplev servo turned off and sus damping restored. What is kicking up the PRM?