Here is the comparison before and after the fix.
Before the work, the UGF was ~40kHz. The phase margin was ~5deg. This caused huge bump of the frequency noise.
After the LO power increase, I had to reduce the MC loop gain (VCO Gain) from 18dB to 6dB. This resulted 4dB (x2.5) increase of the OLTF. This means that my fix increased the optical gain by 16dB (x6.3). The resulting UGF and phase mergin were measured to be 117kHz and 31deg, respectively.
Now I was curious to see if the PMC err shows reasonable improvement when the IMC is locked. Attachment 2 shows the latest comparison of the PMC err with and without the IMC locked. The PMC error has been taken up to 500kHz. The errors were divided by 17.5kHz LPF and 150kHz LPF to compensate the sensing response. The PMC cavity pole was ignored in this calculation. T990025 saids the PMC finesse is 4400 and the cavity pole is 174kHz. If this is true, this also needs to be applied.
1. Now we can see improvement of the PMC error in the region between 10kHz to 70kHz.
2. The sharp peak at 8kHz is due to the marginally stable PMC servo. We should implement another notch there. T990025 suggests that the body resonance of the PMC spacer is somewhere around there. We might be able to damp it by placing a lossy material on it.
3. Similarly, the features at 12kHz and 28kHz is coming from the PMC. They are seen in the OLTF of the PMC loop.
4. The large peak at 36kHz does not change with the IMC state. This does mean that it is coming from the laser itself, or anything high-Q of the PMC. This signal is seen in the IMC error too.
5. 72kHz, 108kHz, 144kHz: Harmonics of 36kHz?
6. Broad feature from 40kHz to 200kHz. The IMC loop is adding the noise. This is the frequency range of the PC drive. Is something in the PC drive noisy???
7. The feature at 130kHz. Unknown. Seems not related to IMC. The laser noise or the PMC noise.
Remaining IMC issues:
Done (Nov 23, 2015) - 29.5MHz oscillator output degraded. Possibly unstable and noisy. Do we have any replacement? Can we take a Marconi back from one of the labs?
Done (Nov 23, 2015) - Too high LO?
- Large 36kHz peak in the IMC
- IMC loop shape optimization
- IMC locking issue. The lock streatch is not long.
- IMC PC drive issue. Could be related to the above issue.
Maybe not relevant - PC drive noise?
Done (Nov 23, 2015) - Check if the attenuator is still there in the input chain
Done (Nov 23, 2015) - Check if the actual LO levels at the 17dBm mixers are reasonable.
- Check if the actual LO levels for the LSC demods are OK too
Well. I thought a bit more and now I think it is likely that this is just the servo bump as you can see in the closed-loop TF.
6. Broad feature from 40kHz to 200kHz. The IMC loop is adding the noise. This is the frequency range of the PC drive. Is something in the PC drive noisy???
The frequency source was fixed. The IMC LO level was adjusted.
IMC is locked => OLTF measured UGF 144kHz PM 30deg.
The trouble we had: the 29.5 MHz source had an output of 6 dBm instead of 13 dBm.
The cause of the issue: A short cable inside had its shield cut and had no connection of the return.
- The frequency source box was dismantled.
- The power supply voltages of +28 and +18 were provided from bench supplies.
- The 29.5 MHz output of 5~6 dBm was confirmed on the work bench.
- The 11 MHz OCXO out (unused) had an output of 13 dBm.
- Once the lid was opened, it was immediately found that the output cable for the 29.5 MHz source had a sharp cut of the shield (Attachment1).
- OK. This cable was replaced. The output of 13 dBm was recovered.
- But wait. Why is the decoupling capacitor on the 29.5 MHz OCXO bulging? The polarity of the electrolytic capacitor was wrong!
- OK. This capacitor was replaced. It was 100 uF 35 V but now it is 100 uF 50 V.
- I further found some cables which had flaky shields. Some of them were twisted. When the panel cable s connected, the feedthroughs were rotated. This twists internally connected cables. Solder balls were added to the connector to reinforce the cable end.
- When the box was dismantled, it was already noticed that some of the plastic screws to mount the internal copper heat sinks for ZHL-2's were broken.
They seemed to be degraded because of the silicone grease. I didn't try to replace all as it was expected to take too much time, so only the broken screws
were replaced with steel screws with shoulder washers at the both side of the box.
- After confirming the circuit diagram, the box was returned to the rack. The 29.5 MHz output of 13 dBm there was confirmed.
In order to check the proper LO level, the IMC demod board was checked. As a short summary, -8dBm is the proper input for the IMC demod board. This was realized when the variable attenuator of the RF AM Stabilizer was set up be -7dB.
Initially, I tried to do the measurement using the extender board. But every board had the issue of +15V not working. After several extender boards were tried, I noticed that the current draw of the demod board burned the 15V line of the extender board.
Then I moved to the work bench. The signals were checked with the 10:1 probe. It's not properly the 50Ohm system, exactly to say.
I found that the LO signals at the mixers have huge distortion as it reaches the nominal 17dBm, and I wondered if ERA-5s were gone. Just in case I replaced the ERA-5s but didn't see any significant change. Then I thought it is due to the mixer itself. The mixer was removed and replaced with a 50Ohm SMD resister. Then the output of the last ERA-5 became sinusoidal, and the level was adjusted to be ~17dBm (4.52 Vpp) when the input power was measured to be -7.7dBm with the RF power meter. Once the mixer was reinstalled, it was confirmed that the waveform becase rectangular like, with the similar amplitude (4.42Vpp).
Now the module was returned to the rack. The RF level at the LO input was adjusted to be -8dBm by setting the attenuator level to be 7dBm.
Once the IMC is locked with this setting, the open loop transfer function was measured. The optical gain seemed almost unchanged compared with the recent nominal. The UGF and PM were measured to be 144kHz and 30deg.
Sorry, I completely forgot to turn the Marconi on...
I didn't finish making the DCC entry for this module yet.
But the attenuators are
- AT1: 10dB. There is a sign that it was 3dB before --- a 3dB chip was also attached on the boardnext to 10dB.
- AT2/3: Removed. They were replaced with 0Ohm resistors.
Currently the input is -8dBm. The input and output of the first ERA-5 are -17dBm and +7dBm, respectively.
Then the input and output of the second ERA-5 are -2dBm and 17dB, respectively.
In order to remove the second amplification stage, the first stage has to produce 26dBm. This is too much for either ERA-5 or any chips that fits on the foot print. If we use low gain but high output amp like GVA-81 (G=10dB, DF782 package), it is doable
Input 0dBm - [ATTN 3] - -3dBm - [ERA-5 G=20dB] - +16~+17dBm - [Circuits -9dB] - +7dBm - [Attn 0dB] - +7dBm - [GVA-81 G=10dB] - +17dBm
I think we should check the conditions of all the LSC demods.
Awwww. I found that the demod board has the power splitter (PSCJ-2-1) with one output unterminated.
This power splitter should be removed.
Uploaded on T1000461 too.
I'm not claiming we need to modify the frequency source immediately as we are not limited by the oscillator amplitude or phase noise.
I just wanted to note something in mind before it goes away quickly.
Alberto's T1000461 tells us that the oscillator and phase noise are degraded by factor of ~3 and ~5 due to the RF chanin.
My diagram is possible removal of up-down situation of the chain.
Maybe more direct improvement would be:
- Removal of two amplifiers out of four. The heat condition of the box is touch thought it is not critical.
- The modification will allow us to have a spare 11MHz channel at 1X2 rack that would be useful for 3f modulation.
T1000461 tells us that the nominal LO input is 2dBm although we don't know what's the LO level is at the mixers in the demod boards.
It wasn't fully mentioned in ELOG 11814.
We checked the PD first and this behavior didn't change after the realignment of the AS55PD.
Yutaro confirmed that this effect is happening in the vacuum chamber.
SLOWDC servo was dead. I followed EricQ's instruction.
MC Autolocker got stack somewhere. I had to go to megatron and kill MC Autolocker.
init relaunched the autolocker automatically, and now it started properly.
Do we need "make" everytime? Do you mean just running "modprobe" didn't work?
[Eric Q, Gautam, Koji]
We went through the network connections to produce the mapping of the instruments.
Gautam summarized the notes into a spread sheet. See attachments.
We didn't find any irregular connections except for the connection of NETMGR port of c1ioo to Martian Network.
This cable was removed.
Can I ask you to make a plot of the power recycling gain as a function of the average arm loss, indicating the current loss value?
Yutaro left detailed slides for his loss map measurement
The next step is to compare this data with the same measurement with the PSL and the AUX laser on the PSL table (or the end Y laser). If these show a lot lower noise level, we can say 1) the x-end laser is malfunctioning and 2) the y-end and AUX laser on the PSL are well low noise.
I configured a new wifi bridge for a GPIB Instruments.
The some facts are described on https://wiki-40m.ligo.caltech.edu/Network
The setting up wasn't so straight forward. I added more details there as a linked page.
One thing I had to do with the martian wifi router was that I had to separate the name of SSIDs for 2GHz and 5GHz networks.
Now the data download from Agilent is super fast!
The first establishing the connection takes the most of the time, and the data transfer takes literary nothing.
controls@pianosa|netgpibdata > time ./netgpibdata -i 192.168.113.167 -d AG4395A -a 10 -f meas01
Connecting to host 192.168.113.167, GPIB 10...
Data will be written into meas01.dat.
Parameters will be written into meas01.par.
Writing measurement data to file...
Writing to the parameter file.
That's a good news. Only quantitative analysis will tell us if it is true or not.
Also we still want to analyze the traffic with the new switch.
On a brighter note, I've only noticed one brief EPICS freeze all night. In addition, the wall StripTools seem totally contiuous since ~4pm, whereas I'm used to seeing some blocky shapes particularly in the seismic rainbow. Could this possibly mean that the old WiFi router was somehow involved in all this?
It is strange that there is no difference between with and without NE, isn't it?
This is the same one as what you got from Steve. But you can find full pages.
jiIn fact, it is one of the most difficult type mode profiling to measure a beam directly out from a laser source.
If you reduce the power by ADJ, this significantly changes the output mode as the pumping power varies temperature gradient of the laser crystal and thus thermal lensing in it. I'd recommend you to keep the nominal power.
If you use a PBS for power reduction, you should increase the transmission ~x10 from the minimum so that you are not dominated by possible junk polarization.
Any transmissive BK7 components where the beam is small can cause thermal lensing. In order to avoid this issue, I usually use two noncoated (or one AR coated) optical windows made of UV fused silica to pick off the beam. Once the beam power is reduced I suppose it is OK to use an additional ND filter in front of the CCD.
Another more reliable method is an old-good knife edge measurement.
I don't think the discrepancy is a serious issue as long as the mode is clean. The mode is determined by the NPRO crystal and is hard to change by anything except for the thermal lensing in the crystal.
And I never succeeded to reproduce the mode listed in the manual.
One thing you'd better to take care is that clipping of the beam produces diffraction. The diffracted beam spreads faster than the nominal TEM00 mode. Therefore the power meter should to be placed right after the razor blade. i.e. As you move the longitudinal position of the razor blade, you need to move the power meter.
800e-6 / 0.225^2 = 0.016
I thought Kiwamu had roughtly 2%/W.
Looks like that's the case. LIGO GC also sent an e-mail that there was a popwer glitch.
I measured the guralp raw outputs and the TFs using the handheld unit and an FFT analyzer.
The handheld unit was connected to each guralp with the same cable which is confirmed t be functional with the Yend Guralp.
The signal for Z, N, and E directions are obtained from the banana connectors on the handheld unit. Each direction has mass, low gain velocity, and high gain velocity output. The PSDs of the signals were measured with an FFT analyzer. The transfer function from the mass signal to the low/high gain signals were also measured for each direction.
The adjustment screw for the E output of the Xend does not work. I had to tilt the Xend Guralp using the leg screws to bring the E signal to zero.
Attachment 1: Raw voltage PSD for all outputs
Attachment 2: Comparison of the low gain vel outputs
- All of the mass output show similar PSDs.
- Low gain velocity outputs shows somewhat similar levels. I still need to check if the output is really the ground velocity or not.
- High gain velocity outputs are either not high gain, broken, or not implemented.
- We need to calibrate the low gain output using signal injection, huddle test, or something else.
Attachment 3: TFs between each mass output and the low or high gain outputs
- TFs between the mass signal and the low vel signals show the similar transfer functions between the channels.
- The high gain outputs show low or no transfer function with regard to the mass signals.
It looks almost OK, but we need a bit sharper picture for both the groove and thw wire.
The alignment of the PMC adjusted on the PSL table: Trans 0.737->0.749
The alignment of the IMC adjusrted on the sliders: Trans 14300->15300
WFS offset has been reset by /opt/rtcds/caltech/c1/scripts/MC/WFS/WFSoffsets
Elogd have been restarted several times today because it died everytime I submit something.
Here is the copy of the log.
I configured three more mini wifi extender. They are ready to use.
We should add these to the host table (I forgot where it is)
Did it again.
PMC Trans ~0.739
IMC Trans ~15000
Gap of the prism from the mirror
Sag: s = R(1-Cos[ArcSin[d/2/R]])
- Mirror curvature sag for 2mm prism (R=37.75mm): s=13um
- Minimum gap: 20um => s=33um => R=15mm
- Nominal gap: 35um => s=48um => R=10mm
- Maximum gap: 50um => s=63um => R=8mm
The second figure shows somewhat realistic arrangement of the pieces
Made a dry run of the in-situ cleaning for a 3inch optic.
Attachment 1: The Al dummy mass is clamped in the suspension cage.
Attachment 2: The front surface was painted. The nominal brush with the FC bottle was used.
Attachment 3: Zoom in of the front surface.
Attachment 4: The back surface was painted.
Attachment 5: The back surface was peeled.
Attachment 6: The front surface was peeled too.
Attachment 7: The peeled layers.
1. To paint a thick layer (particlarly on the rim) is the key to peel it nicely.
2. It was helpful for easier peeling to have mutiple peek tabs. Two tabs were sufficient for ~1" circle.
3. The nominal brush with the bottle was OK although one has to apply the liquid many times to cover such a large area. A larger brush may cause dripping.
4. The nominal brush was sufficiently long once the OSEMs are removed. In any case it is better to remove the OSEMs.
I wanted to know what this Vmon exactly is. D010001 is telling us that the Vmon channels are HPFed with fc=30Hz (Attachment 1). Is this true?
I checked the quiscent noise spectrum of the ITMX UL coil output (C1:SUS-ITMX_ULCOIL_OUT) and the corresponding VMON (C1:SUS-ITMX_ULVmon). (Attachment 2 Ref curves). I did not find any good coherence. So the nominal quiscent Vmon output is carrying no useful information.
Question: How much do we need to excite the coil output in order to see any meaningful signal?
As I excite the ITMX UL coil (C1:SUS-ITMX_ULCOIL_EXC) with uniform noise of 100-300 counts below 0.3Hz, I eventually could see the increase of the power spectrum and the coherence (Attachment 2). Below 0.1 Hz the coherence was ~1 and the transfer function was measured to be -75dB and flat. But wait, why is the transfer function flat?
In fact, if I inject broadband noise to the coil, I could increase the coil output and Vmon at the same time without gaining the coherence. (Attachment 3). After some more investigation, I suspect that this HPF is diabled (= bypassed) and aliasing of the high freq signal is causing the noise in Vmon.
In order to check this hypothesis, we need to visit the board.
Circuit1: It is nice to receive the voltage across the transimpedance resistor with a high impedance buffer (or amplifier), as close to the resister as possible. This amplifier needs to have low numbers for input bias current, input offset current, and input current noise. These current noise becomes the noise of the temperature reading. On the top of that, the input voltage noise of the buffer will be added to the output. The typical noise model can be found in http://www.analog.com/media/en/technical-documentation/application-notes/AN-940.pdf
The good candidates for the buffer is LT1128, ADA4004, OPA140, and LT1012. If the application is not too sensitive to the total noise, OPA604 is a good choise with easier handling.
Circuit2: With the same reason, AD741 is an old generic amp that is not a great choise for this purpose. The current noise is more significant because of the higher transimpedance here. The same noise model as above can be used to analyze the performance.
I started to receive emails from cron every 15min. Is the email related to this? And is it normal? I never received these cron emails before when the sum-page was running.
It seemed something has been done. And I got cron emails.
Then, it seemed something has been done. And the emails stopped.
We obtained two monitors of the same type from Larry.
Ah, thanks. That makes sense. In that case, we should remove the texts "30Hz HPF" from the suspension screens.
Now we just need AA LPFs for these channels, or hook them up to the RT system.
Move the suspension on the south clean bench and make more close inspection. We need to remove the OSEMs.
Then unmount the mirror. Bring it to the clean room and work on the bond removal.
Meanwhile, set up all suspension components inclusing the alignment test setup.
In the evening, I went into the clean room to check how it goes.
- The air around the table is quite warm like a hell. Is this normal?
- I checked how the scattered epoxy spots look like. They were not touching the bath anymore due to evaporation.
- I scraped the spots with the tweezers there. They were easily removed. The particlates on the side barrel were wiped by a wipe with aceton. (Result: Attachment 3)
- Then looked at the other side. I poked the standoff with the tweezer. It was easily removed. I don't think the bond was too weak. Just the area of the bond was so tiny.
- Also residue was scraped by a tweezer and wiped with a cloth. (Attachment 2)
- The removed stand off is in the stainless bowl together with the parts that Eric removed.
- I didn't want to leave the optic in the aceton fume. It was placed on a metal donuts for a 3" optic. (Attachment 4)
- I couldn't find a vacant clean glass jar for the lid. So, a foil hut was built. We should be very careful not to scratch the optic when we remove the hut. (Attachment 5)
- The aceton bath was covered with the foil as it was. (Attachment 6)
Some of the screens are up-to-date, and some are not. Are the errors associated with the screens that failed to get updated?
We replaced the right N2 bottle as it was empty.
Multicolor flash light:
- It seems that the usb port charging doesn't work.
- There is a battery charger on Steve's desk. I set the batteries on it.
White LED flash light:
- I temporarily brought a compatible charger from WB. It's charging two batteries behind the LCD display on my desk.
Handing over message to the next step
ETMX: guide rod gluing (done) -> fixture unmounting side -> fixture setting -> magnet gluing -> suspend -> pitch balance -> ruby gluing -> air bake
ETMY: magnet (done) -> fixture unmounting -> air bake
- A transport setup was made with a donut holder for a 3" optic, glass jar, stain less tray, and a CS Stat zipbag. (Attachment 1)
- The magnets have been glued witht the gluing fixture. (Attachment 2)
- We checked the dimensions of the glued magnet and found that the thicker side has to be raised by 1mm. (We used the fact that the relative distance between the wire groove and the magnet is always the same.)
- The ETMs have 2.5deg wedge and this corresponds to 3.2mm height difference between the left and right edges. This meant that the thinner side had to be raised by 4.2mm.
- We used a 0.9mm Teflon sheet for the thicker side (Attachment 3) and two 2.2mm Teflon pieces for the thinner side (Attachment 4). For stabilization of the fixture, two Teflon tubes with a diameter of ~3mm are inserted to the top and bottom side of the mirror (Attachment 5).
- Mirror orientation in the fixture (Attachment 6).
- It was confirmed that existing UR, LR, and Right SD magnets have the polarity of N facing out, S facing out, and N facing out. And we confirmed that this is consistent with ETMX and the procedure document (E970037)
- Along with the procedure document, we arranged the magnet-dumbbells UL, LL, and Left SD magnets to have S-out, N-out, and N-out. (Attachments 7, 8, and 9)
- In prior to gluing, all three dumbbells surfaces were cleaned by acetone and razor blade scrubbing.
- After the epoxy curing test (see below), the three magnet-dumbbell pairs have been glued on the mirror. A single dub of EP30-2 was applied to each dumbbell surface.
- Attachments 10, 11, and 12 shows how glue is spread at each joint.
Guide rod positioning:
- The longitudinal position of the guide rod was adjusted using the micrometer microscope such that it located at the center of the mirror thickness.
- The guide rod is not long enough to have the edges sticking out from the form of the fixture arm. Therefore only arm finger of the arm held the guide rod.
- The height was adjusted to be 1.73mm (68mil) lower than the mirror scribe line. The mirror is fixed on the fixture upside down. So this bonds the guide rod above the scribe line.
- Then the epoxy was applied to the guide rod. The glue was applied to two edges of the rod, but capillary action spread the glue around the rod. It seemed that the fixture and the rod were connected with the glue. Care should be taken when the fixture is going to be removed. (Attachment 13)
- The top side (in the picture) where the stand-off will come is still relatively kept clean. So it must be OK for the stand off. If there is an issue, we can shave the epoxy with a razor blade.
- EP30-2 tends to fail to get cured. In order to check the mixture is properly made or not, we put a test piece into air bake oven.
- The procedure says, 200F 15min bake show if the glue is in a good shape or not.
- We have the temperature sensor setup on a air bake oven, but it seemed that the indicated temperature there is overestimate.
The heating setting of 2 was enough to show the temp of 100degC although EP30-2 didn't get cured with this setting.
- Our experience says that heater setting of "5" makes the temperature ~90degC. On July 12nd, this setting showed the temp of 90degC. Today (July 13rd) it didn't. In the both cases, the epoxy got cured nicely. So we should use this setting.
Today I took the picture of the glued ruby stand-off. The groove has not been invaded by the epoxy!
We have worked on the FC painting on ITMX and ITMY. We also replaced the OSEM fixing screws with the ones with a hex knob.
This was done except for the SD OSEM as the new screw was not long enough. We left an allen-key version of the screw for the SD OSEM.
All the full-resolution photos can be found on g-photo.
Attachment1: The barrel was pretty dusty. Some dusts were observed on the HR face but it was not so terrible. The barrel and the HR face were blown with the ionized N2 and then wiped with IPA. The face wiping was done n a similar way as the drag wiping.
Attachment2: FC was applied to the HR surface.
Attachment3: The AR surface was also painted with FC. The brush touched the coil holder.
Attachment4: The brush touched the coil holder. Another PEEK tab was applied to remove this FC stain on the metal holder.
Attachment5: This is the result of successful removal of the FC stain.
Attachment6: The OSEM arrangement before removal. We confirmed that the OSEM arrangement was as described on Wiki.
Attachment7/8: The ITMX was obviously a lot dirtier than ITMY. The barrel accumulated dusts.
Attachment9: This is the HR face picture with large dusts on it.
Attachment10: The HR surface was painted with FC.
Attachment11: This is the AR surface with FC painted.