Vacseal in the freezer. It could have been expired sooooo many years ago, We need some cure testing.

Can you release the part numbers of the ordered components (and how/where to use them), so that we can incorporate them into the CAD model?

Yes,

For the thin optics adapter design, we want Peek 1/4-20 screw (part # 98885A131) to replace the lower back long EQ stop. On it, we will have a Peek washer (part # 93785A600) fastened between two Peek nuts (part #98886A813).

For the thick optics adapter design, we want Peek 1/4-20 screw (part # 98885A131) to replace both the upper and lower back EQ stop. On the upper stop, we need a single Peek nut (part #98886A813).

I will cure-test the Vacseal.

 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.

For the upcoming vent, we'd like to rotate the SOS towers to correct for the large YAW bias voltages used for DC alignment of the ITMs and ETMs. We could then use a larger series resistance in the DC bias path, and hence, reduce the actuation noise on the TMs. 

Today, I used the calibrated Oplev error signals to estimate what angular correction is needed. I disabled the Oplev loops, and drove a ~0.1 Hz sine wave to the EPICS channel for the DC yaw bias. Then I looked at the peak-to-peak Oplev error signal, which should be in urad, and calibrated the slider counts to urad of yaw alignment, since I know the pk-to-pk counts of the sine wave I was driving. With this calibration, I know how much DC Yaw actuation (in mrad) is being supplied by the DC bias. I also know the directions the ETMs need to be rotated, I want to double check the ITMs because of the multiple steering mirrors in vacuum for the Oplev path. I will post a marked up diagram later. 

Steve is going to come up with a strategy to realize this rotation - we would like to rotate the tower through an axis passing through the CoM of the suspended optic in the vertical direction. I want to test out whatever approach we come up with on the spare cage before touching the actual towers.

Here are the numbers. I've not posted any error analysis, but the way I'm thinking about it, we'd do some in air locking so that we have the cavity axis as a reference and we'd use some fine alignment adjust (with the DC bias voltages at 0) until we are happy with the DC alignment. Then hopefully things change by so little during the pumpdown that we only need small corrections with the bias voltages.

Some remarks:

1. Why the apparent difference between ITMs and ETMs? I think it's because the bias path resistors are 400 ohms on the ETMs, but 100 ohms on the ITMs. 
2. If we want the series resistance for the bias path to be 10 kohm, we'd only have ~800 urad actuation (for +10V DC), so this would be an ambitious level of accuracy. 

The SOS centering target is 1.9 mm lower than it should be! 

The hole is 10mm for the  ~6 mm beam

The SOS coil drivers (Atm2) were moved from 1X1 to 1Y2 location. Is this the best place to locate the  IOO Tip-Tilt steering that will replace the PJ-PZT ?

See 40m wiki T-T

One of the possibilities that we see a large low-frequency digital noise is due to Foton. I've checked the SOS coefficients that saves Foton with a Matlab coefficients. I used a 3 order low-pass cheby1 filter cheby1("LowPass",3,0.1,3) 

In matlab I generated SOS model using 3 approaches 

[A,B,C,D]=cheby1(3,0.1,3/1024) % create SS form

[sos,g]=ss2sos(A,B,C,D)  % convert to SOS form

[z, p, k]=cheby1(3,0.1,3/1024) % create ZPK form

[sos,g]=zp2sos(z,p,k)  % convert to SOS form

[b, a]=cheby1(3,0.1,3/1024) % create TF form

[sos,g]=tf2sos(b,a)  % convert to SOS form

As this is a 3 order filter, in the SOS representation we'll get 2 by 6 SOS - matrix. It is presented below. In each matrix place there 4 numbers - from the Foton file and obtained using these 3 methods.

GAIN

1.582261654653329e-07

1.582261654653329e-07

1.582261654653329e-07

1.582261655030947e-07

SOS-MATRIX

1              1.0000000000000000      #           0                                              #       1      #         -0.9911172660954457     #       0

1              1.0005663179617605      #           0                                              #       1      #         -0.9911172660954457     #       0

1              1.0000000000000000      #           0                                              #       1      #         -0.9911172660954457     #       0

1              0.9999894976396830      #           0                                              #       1      #         -0.9911172660997303     #       0

############################################################################################################

1              2.0000000000000000      #          1.0000000000000000         #       1      #        -1.9909750803252266      #      0.9911175825477769

1              1.9994336820732397      #          0.9994340026283055         #      1       #       -1.9909750803252262       #     0.9911175825477765

1              2.0000000000000000      #          1.0000000000000000         #      1       #       -1.9909750803252262       #     0.9911175825477765

1              2.0000105023603174      #          1.0000105024706190         #      1       #       -1.9909750803209423       #     0.9911175825434912

It seems that smth analog to zp2sos is used in Foton. We can see that due to representation error we have derivations in the 4 and 6 digits for SS and TF forms. This means that a pretty big mistake can run due to digital transforms even using double precision as in the Matlab test.

Alex Ivanov said that he'll fix that single precision problem and in the 2.5 release we won't have any FLOAT variables. Though we still do not understand how that variables declared as FLOAT can cause filter calculations. 

Atm 1, It's right arm is perfect.

Atm 3-4, The left one has bended (dropped) end.

Atm 2, Our ruby wire stanoffs will fit the jig. Ruby OD 1.27 mm vs. old Aluminum OD 1.0 mm. Length ruby 6.4 mm vs Al 4.8 mm

Atm 5, The fixture translation stages are a bit loooose. Careful use of the micrometer is needed to be precise

Betsy agreed that the 40m will keep SOS fixtures.

[Yehonathan, Paco]

We put away most items used / involved in SOS assembly and characterization. Many were stored in the left-most cabinet in the clean area. The OpLev test setup and optics were stored in the upper cabinets above the microscope area, and several screws and other general components were collected in clean bags or wrapped in foil, labeled and put away.

I opened the packages send from Syracuse.

- The components are not vacuum clean. We need C&B.
- Some large parts are there, but many parts are missing to build complete SOSs.

- No OSEMs.
- Left and right panels for 6 towers
- 3 base blocks
- 1 suspension block
- 8 OSEM plates. (1 SOS needs 2 plates)

- The parts looks like old versions. The side panels needs insert pins to hold the OSEMs in place. We need to check what needs to be inserted there.

- An unrelated tower was also included.

Two SOS suspensions for the ETMs were disassembled and packed for cleaning and baking by Bob.

These suspensions have been stored on the X end flow bench long years, and looked quite old.

They have some differences to the modern SOSs.

- The top suspension block is made of aluminum and had dog clamps to fix the wires.
- The side bars are not symmetric: the side OSEM can only be fixed at the right bar (left side in the picture).
- EQ stops were made of Viton.
- One of the tower bases seems to have finger prints (of Mike Zucker?).

I found that the OSEM plates had no play. We know that the arrangement of the OSEMs gets quite difficult
in this situation. Therefore the holes of the screws were drilled with the larger drill.

We decided to replace all of the screws to the new ones as all of the screws are Ag plated and got corroded
by silver sulfide (Ag₂S). I checked our stock in the clean room. We have enough screws.

Important note: Use stainless screws in aluminum / Silver-plated screws in stainless
There exists some study about galling: LIGO-G020394-00-D

Stress Relieved 0.0017"  Music Wire  CFW P/N: CFW2035025,   Made 08-17-2016                                

GBL (grams breaking load )         

UTS (ultimate tensile strength)                                 

YTS (yield tensile strength) 

ELONG (elongation)  

0.0017" OD., 500ft steel music wire ordered. Pictures of the existing roll are below. It will be on 8" OD. spool too.

The wire will arrive in 1-2 weeks. It is a new production. Brad Snook of Ca Fine Wire was suprised that we are still using the 13 years old wire.  Oxidation is an issue with iron contained steel wire.

He would not give me a shelf life time on it. He recommended to check the strenght of it before usage. It passed with safety factor of 2 just recently.

In the future we'll store the new spool in oxigen free nitrogen environment..

We have indeed seen numerous tarnished/rusty points along the wires, and just tried to choose lengths free of any of these. I wonder if this can explain the brittleness/ease with which we've been breaking it. My feeling is that we should use the newer wire if feasible.

Not really true that it passed. That's just an arbitrary margin. Best to throw away all the old wire. We have no quantitative estimate of what the real torque should be. Its just feelings.

[Jenne, Diego]

The EPICS freeze that we had noticed a few weeks ago (and several times since) has happened again, but this time it has not come back on its own.  It has been down for almost an hour so far. 

 So far, we have reset the Martian network's switch that is in the rack by the printer.  We have also power cycled the NAT router.  We have moved the NAT router from the old GC network switch to the new faster switch, and reset the Martian network's switch again after that.

We have reset the network switch that is in 1X6.

We have reset what we think is the DAQ network switch at the very top of 1X7.

So far, nothing is working.  EPICS is still frozen, we can't ping any computers from the control room, and new terminal windows won't give you the prompt (so perhaps we aren't able to mount the nfs, which is required for the bashrc).

We need help please!

[EricQ]

EricQ suggested it may be some NFS related issue: if something, maybe some computer in the control room, is asking too much to chiara, then all the other machines accessing chiara will slow down, and this could escalate and lead to the Big Bad Freeze. As a matter of fact, chiara's dmesg pointed out its eth0 interface being brought up constantly, as if something is making it go down repeatedly. Anyhow, after the shutdown of all the computers in the control room, a  reboot of chiara, megatron and the fb was performed.

[Diego]

Then I rebooted pianosa, and most of the issues seem gone so far; I had to "mxstream restart" all the frontends from medm and everyone of them but c1scy seems to behave properly. I will now bring the other machines back to life and see what happens next.

[Diego, Jenne]

Everything seems reasonably back to normal:

Notes:

• the machines in the control room have been rebooted;
• the c1iscey frontend now behaves;
• I saw on nodus, which remained up and running the whole time, a bunch of   nfs: server chiara is not responding, timed out  messages, belonging to the freezing time; it may be that the sync option for the nfs share is too resource demanding, or some other network issue;
• the FSS was doing strange stuff and the MC couldn't recover the lock; the MCautolocker script wasn't running because of the lock loss of the MC and the lack of communication between the machines; so we did a sudo initctl start MCautolocker on megatron and recovered the MC too.

SP table has been a mess because Q and I had let our SURF leave without cleaning up.

I cleaned up the SP table, put things back where they belong and did some sorting. I will put back the optomechanics where they belong sometime later.

For now, check out the SP table next time you are looking for a Y1  or lens or BS.

This morning I found that there was no light on the SPOB PD. I went looking at the photodetector and I found that the shutter in front of it was closed.

I switched the shutter driver from n.c. to n.o. which had the effect of opening it.

I guess we inadvertently closed the shutter with Rana when last week we were tinkering with the ITMY  camera.

The free swinging test was successful. I ran the input matrix diagonalization code (/opt/rtcds/caltech/c1/Git/40m/scripts/SUS/InMAtCalc/sus_diagonalization.py) on theSR2 free-swinging data collected last night. The logfile and results are stored in /opt/rtcds/caltech/c1/Git/40m/scripts/SUS/InMAtCalc/SR2 directory. Attachment 1 shows the power spectral density of the DOF basis data (POS, PIT, YAW, SIDE) before and after the diagonalization. Attachment 2 shows the fitted peaks.

1.09

0.914

0.622

0.798

-0.977

1.249

0.143

-1.465

-0.359

0.378

0.552

-1.314

-0.605

1.261

0.118

0.72

0.403

0.217

0.534

3.871

The new matrix was loaded on SR2 input matrix and this resulted in no control loop oscillations at least. I'll compare the performance of the loops in future soon.

[Jenne, Annalisa]

SR2 is flipped, and reinstalled.  We did that before lunch, and we're about to go in and work on SR3 and PR3.

EDITS / Notes:

I set dog clamps to have a reference position of where the tip tilt was, then I removed SR3 from the chamber.  Once out, I followed the same procedure I used for PR2 during the last vent - I removed the whole suspension (top mount, wires, optic) from the cage, and laid it down flat.  Then I loosened the set screw which pushes on the teflon nudge, removed the mirror, inspected it, and put it back in, with the HR side facing the back side of the ring.  Then I replaced the suspension system in the cage, and put the mirror back into the chamber. 

When I loosened the teflon nudge at the top of the mirror holder ring, the optic seemed to fall down a tiny bit.  I think this implies that the HR surface of the optic did not used to be parallel to the front face of the mirror holder ring.  When I put the suspension back onto the cage, the pitch balancing was very bad.  We checked the level of the table that I had the cage on, and it was miraculously pretty level, so I did the pitch balancing out of the chamber. 

Also, during my quick inspection of the mirror (not thorough, just using room lights), I noticed a small fleck of lint near the edge of the optic on the HR surface.  The HR surface is now on the outside of the SRC, but we should still blow at the optic with the ionized nitrogen to get it off.

I did not think to check the fine-tuning alignment of SR2....Koji did that after lunch (which I will elog about in a separate elog).

After the first flipping, X/Y arms were aligned and locked. Then the ASS aligned the arms.

SR2 is set to go through a free swinging test at 3 am tonight. We have used this script (Git/40m/scripts/SUS/InMatCalc/freeSwing.py) reliably in the past so we expect no issues, it has a error catching block to restore all changes at the end of the test or if something goes wrong.

To access the test, on allegra, type:

Then you can kill the script if required by Ctrl-C, it will restore all changes while exiting.

Yesterday afternoon, I went back into the BS chamber, and flipped both PR3 and SR3. Now all of the recycling cavity folding mirrors have been flipped.

For PR3, I followed the same procedure as SR2, setting a reference position, removing the optic, flipping it, etc.  When I put it back in, I realized that since this has a 41 degree angle of incidence, the beam going to the BS had translated north by ~1cm.  After some fiddling, Koji pointed out that the 2 degree wedge probably had a more significant effect than just the HR surface having moved back a small amount.  Anyhow, we adjusted PR3 such that we were going through the BS aperture, as well as the ITMY aperture. 

During the flip of PR3, Annalisa and I noticed that the arrow on the barrel of the LaserOptik mirrors also indicates the thickest part of the wedge.  This is opposite of our SOS optics, where the arrow's position on the barrel indicates the thinnest part of the wedge.  For both PR3 and SR3, I kept the arrow on the same side of the optic as it was originally.

I then flipped SR3, following again the same procedure.  PR3 I had done a tiny bit of pitch rebalancing, although I think it was unneccessary, since it is within what we can do with the poking/hysterisis method.  SR3 I did not do any pitch rebalancing.  With PR3 aligned at least to the ITM, Koji and I aligned SR3 and SR2 so that the AS beam was hitting the center of all the SRC optics.  We also adjusted the steering mirrors after the SRM to get the beam centered on PZT3, the last optic on the BS table, which launches the beam over to the OMC chamber.  We scanned around a bit by turning the PZT's knobs, but we were unable to see the AS beam on the camera. 

We have implemented an SR560-based ISS loop using the AOM on the PSL table. This is a continuation of the work in 40m:9328.

We dumped the diffracted beam from the AOM onto a stack of razor blades. This beam is not terribly well separated from the main beam, so the razor blades are at a very severe angle. Any alternatives would have involved either moving the AOM or attempting to dump the diffracted beam somewhere on the PMC refl path. We trimmed the RF power potentiometer on the driver so that with 0.5 V dc applied to the AM input, about 10% of the power is diverted from the main beam.

We ran the PMC trans PD into an AC-coupled SR560. To shape the loop, we set SR560 to have a single-pole low- pass at 300 Hz and an overall gain of 5×10⁴. We take the 600 Ω output and send it into a 50 Ω feed-through terminator; this attenuates the voltage by a factor of 10 or so and thereby ensures that the AOM driver is not overdriven.

The AOM driver's AM input accepts 0 to 1 V, so we add an offset to bias the control signal. The output of the 50 Ω feedthrough is sent into the 'A' input of a second SR560 (DC coupled, A − B setting, gain 1, no filtering). Using a DS345 function generator, a 500 mV offset is put into the 'B' input (the function generator reads −0.250 V because it expects 50 Ω input). The 50 Ω output of this SR560 is sent into the AOM driver's AM input.

A measurement of suppressed and unsuppressed RIN is attached. We have achieved a loop with a bandwidth of a few kilohertz and with an in-loop noise suppression factor of 50 from 100 Hz to 1 kHz. This measurement was done using the PMC trans PD, so this spectrum may underestimate the true RIN.

 A small followup measurement. Here are spectra of the MC trans diode with and without the ISS on. The DC value of the diode (in counts) changed from 17264.2 (no ISS) to 17504.3 (with ISS), but I didn't account for this change in the plot.

There is a small inkling of benefit between 100Hz and 1kHz. Above about 100Hz, the RIN is suppressed to about the noise level of this measurement. Below 100Hz there is no change, which probably means that power fluctuations are introduced downstream of the AOM, which argues for an outer-loop ISS down the road.

Atm #2 is in units of RIN.

 I have disconnected the cable from the SR560 to LSC -ch8 for 15minutes this morning. It is moved from the floor to the top of the chambers as preparation for 40m tour. The SR560 seems to be overloading.

The  ISS servo is off according to the MEDM screen. Why MC-T plot showing zero?  The MC was happy yesterday.

Gautam and Steve,

All 3 show the same noise level ~80 nV / rt Hz at 1 kHz as shown. Batteries ordered to be replaced in the top 2

We'll do more measurement to see how can we get to 4 nV / rt Hz  specification level.

these are not the SR785 settings that you're looking for

To get low noise measurements on the SR785, you have to have the input range set to -50 dB, not +20 dB. Its not within the powers of commercial electronics ADCs to give you a 10 nV noise floor with +10 V input signals. The SR560 has an input referred noise of 5 nV/rHz, so the output noise should be 5e-9 x 500 = 2.5 uV/rHz. Your picture shows it giving 1 uV RMS, so you also need to use the PSD units.

I brought a bunch of SR560s over for repair from Bridge labs. This unit, picture attached (SN 49698), appears to still not be retaining charge. I’ve brought it back. 

I have ordered some LSK389A (in both the SOIC-8 and TO-71 packages) to replace the SR560's default front end FET pair (NPD5565).

I'm going to rework s# 00619 once these new FETs come in. Also ordered 100 of the SOIC-8 to DIP-8 adapter boards from Digikey.

This plot shows the current performance compared to the Rai Low Noise box. I expect the FETs should let us get to ~1.5 nV/rHz with the SR560.

I replaced the NPD5565 with a LSK389 (SOIC-8 with DIP adapter). There was a noise reduction of ~30%, but not nearly as much as I expected. I wonder if I have to change the DC bias current on these to get the low noise operation?

https://photos.app.goo.gl/hsMwsif7NLscsgpx1

<p>I purchased some more of these from DigiKey. These parts are currently in the EE shop. These are replacements for the NDP5565 part of the SR560.</p>

I had to go through five SR560s in the lab yesterday evening to find one that had the expected 4 nV/rtHz input noise and worked on battery power. To confirm that the batteries were charged, I left 4 of them plugged in overnight. Today, I confirmed that the little indicator light on the back is in "Maintain" and not "Charge". However, when I unplug the power cord, they immediately turn off.

One of the units has a large DC output offset voltage even when the input is terminated (though it is not present with the input itself set to "GND" rather than DC/AC). Do we want to send this in for repair? Can we replace the batteries ourselves?

yes, both problems can be fixed. Usually we just order some spare lead-acid batteries from SRS (Steve may have some spare ones somewhere). The DC offset often comes from a busted FET input. I bought 50 of those at one point - they're obsolete. Its also possible to replace the input stage with any old FET pair.

I'll handle the one with the offset if you leave it on my desk.

I borrowed SR785 to measure AA, AI noise and TF.

 The 785 analyzer in the 40 had a wonky hard to read screen. I was hoping that a new white CRT would fix all the problems. 

I installed a white CRT, which didn't fix the wonkyness, but I adjusted the CRT position, brightness, focus settings to make the screen somewhat more readable.

BEFORE:

AFTER:

If we want to send the thing in for service to fix the wonkyness, we should probably hold on to the old CRT because they will probably replace the whole screen assembly and we'll lose our white screen.

When Juan and I were working on the suspension measurement, I found that CHA didn't settle down well.

I inspected and found that CHA's + input seemed broken and physically flaky. For Juan's measurements, I plugged + channels (for CHA/B) and used - channels as an input. This seemed work but I wasn't sure the SR functioned as expected in terms of the noise level.

We need to inspect the inputs a bit more carefully and send it back to SRS if necessary.

How many SR785's do we have in the lab right now? And the measurement instruments like SR785 are still the heart of our lab, please be kind...

I am using SR785 Spectrum Analyzer now and also tomorrow. 
I will put it back on Sunday. If anyone needs it during the weekend,
please just take it and I can reset it by myself later. Thanks.

A poor lonely SR785 was found this morning roaming around in the lab in evident violation of the fundamental rule which requires all the equipment on carts to be brought back inside the lab right after use.

The people and the professors related to the case should take immediate action to repair for their misdeed.

In preparation for later today evening. The TT alignment wasn't visibly disturbed.

I'm working near 1X5 and there is an SR785 adjacent to the electronics rack with some cabling running along the floor. I plan to continue in the evening so please leave the setup as is.

During the course of this work, I noticed the +15V Sorensen in 1X6 has 6.8 A of current draw, while Steve's February2018 label says the current draw is 8.6A. Is this just a typo?

Steve: It was most likely my mistake. Tag is corrected to 6.8A

I'm still in the process of electronics characterization, so the SR785 is still hooked up. MC3 coil driver signal is broken out to measure the output voltage going to the coil (via Gainx100 SR560 Preamp), but MC is locked.

SN 46,795 of 2003 is back.

The unit was repaired and returned to the 40m. Now, with a DMM, I measure a DC offset value that is ~1% of the AC signal amplitude. I measured the TF of a simple 1/20 voltage divider and it looks fine. In FFT mode, the high frequency noise floor levels out around 5-7nV/rtHz when the input is terminated in 50 ohms.

I will upload the repair documents to the wiki.

In this morning, we have disconnected SR785 which was in front of 1X2 rack, to measure a Hall sensor noise.

After a while, we put back SR785 and re-connected as it has been.

But the display setup might have been changed a little bit.