I am installing an OSA on the AP table and it's ongoing.
I am leaving some stuff scattered on the AP table and I will resume the work after I come back.
1) The REFL165 has been replaced onto the AS table.
2) When the PD interface cable is attached the PD shows a DC out put of 6mV and does not respond to a flash light. I changed the PD interface port in the LSC rack by swapping the other end of the cable with an unused (Unidentified PD) interface cable, The PD is working fine after that. There could be a problem with some binary switch state on the PD interface where the REFL165 cable was plugged in earlier.
I've measured the input signal to the seismic box from seismometer Guralp 1. The spectrum of the signal in the "input +" (TP 1) is
The spectrum below 1 Hz is ~250 uV/sqrt(Hz). As the input is differential, then the input voltage is 0.5 mV/sqrt(Hz). The spectrum of the "output +" signal (TP 2) is
So the gain at ~ 1Hz is ~20. I've measured the transfer function between the "input +" and "output +" (TP1 and TP2) for all 9 circuits
The channels 1-6 are of new modification and have gain ~20 at the frequencies 0.2 - 100 Hz. Below 0.2 Hz the gain is reduced. 100 Hz - cut off frequency of the low-pass filters. Meanwhile channels 7-9 (old configuration) have much more gain and 10_50 Hz filters work here.
The coherence between "input +" and "output +" (TP1 and TP2) for 9 circuits is
We can see that channel VERT 3 is very bad. For others coherence is lost below 0.2 Hz. The spectrum analyzer noise measured is ~1000 times less then the signal at these frequencies. I'll pay more attention to this loss of coherence at low frequencies. Something is noisy.
The transfer function and current noise were measured. The location of the peak shifts with the amount of incident light power (RF or DC). The TF was measured at an incident 1064nm light power of 0.4 mW which produced a DC output voltage of 14 mV => DC photocurrent of 0.28 mA.
Many of the effects that Koji noted in the previous characterization are still present.
In addition I observed a shift of the peak towards lower frequencies as the RF power supplied to the AM Laser (Jenne Laser) is increased. This could create a dependance of the demodulation phase on incident RF power.
The plots are attached below.
To determine the amount of RF power in the AM laser beam at various RF drive levels I measured the RF power out of the Newfocus 1611 PD while driving the AM laser with a Marconi. During this measurement the DC output was 2.2V. With the DC transimpedance of 10^4 and a sensitivity of 0.8 A/W we have carrier power as 0.275 mW (-5.6 dBm). [Incidentally the measured carrier power with a power meter is about 0.55 mW. Why this discrepancy?]
Estimation of the signal strength at the REFL165 PD:
From the 40m Sensing Matrix for DRFPMI we see that the signal strength at REFL165 in CARM is about 5x10^4 W/m. Since we expect about 0.1nm of linear range in CARM length we expect about 0.05 mW of RF power. If the (DC) carrier power is about 10 mW at the photodiode (18mW is about the max we can have since the max power dissipation is 100 mW in the diode) then the RF : DC power ratio is 5x10^-3 => -23 dB
As this is lower than the power levels at which the PD transfer function was determined and where we noted the distorsion and shift of the resonance peak, it is likely that these effects may not be seen during the normal operation of the interferometer.
The shift due to the carrier power level (DC) change may still however pose a problem through a changing demodulation phase.
I placed the OSA (Optical Spectrum Analyzer) on the AP table and this OSA will monitor the REFL beam.
Tomorrow I will do fine alignment of the OSA.
- a new 90% BS in the REFL path for limiting the REFL beam power
- Squeezed the ABSL (ABSolute length Laser) path
- Modification of the AS OSA path
Power Spectral Density plot using PyNDS, comparing 5 fast data channels for ETMX.
Is there any stuff to install, etc? Y'know, for those of use who don't really know how to use computers and stuff....
No new stuff for these computers. Everything should be installed already.
The actual temperature of the Xend laser is 0.02 C higher than anticipated based on the formula in elog 3759. Both the PSL and the Xend laser are at their nominal diode currents (2.100 A for the PSL, 2.003 A for Xend), so the curves should be used as they are. The PSL temp (when the slow servo offset is ~0) is 31.71 C. Using curve 2 from elog3759, the Xend laser should be 37.78, which I found was +10 counts on the Xgreen slow servo offset.
Right now the Xend laser is at 37.80 C, and the beat is around 30 MHz. This is +80 counts on the Xgreen slow servo. +60 counts gave me ~80 MHz. When (a few minutes ago) the MC unlocked and relocked, it came back to a slightly different place, so the temp of the Xend laser had to go up a few 10's of counts to get the same beat freq. Right now the PSL slow servo offset is 0.076 V.
The HP8591E is set with ResBW=100kHz, Ref Level= -39dBm (so I'm not attenuating my input signal!). The largest peak I see for the beatnote is -66dBm. The nose floor around the peak is -83dBm. Trace (trace button!) A is set to MaxHoldA, and Trace B is set to ClearWriteB, so B is giving me the actual current spectrum, while A is remembering the peak value measured, so it's easier to see if I went past the peak, and just didn't see it on the analyzer.
Also, I went back and realigned the beams earlier, to ensure that there was good overlap both near the BS which combines the PSLgreen and Xgreen beams, and at the PD. The overlap I had been looking at was okay, but not stellar. Now it's way better, which made the peak easier to see. Also, also, the waveplate after the doubling oven on the PSL table is still rotated so that I get max power on the Xgreen side of things, and not much at all on the Ygreen side. I'll need to rebalance the powers, probably after we make sure we are seeing the beatnote with the BeatBox.
Lay a cable from the BBPD to the BeatBox in 1X2, make the BeatBox do its thing.
Use the dichroic locking to do a sweep of the Xarm.
I've moved GUR1 seismometer from MC2 to the working tables in order not to disturb the MC while working with the seismometer box. The new place for the GUR1 for a few days is near the printer, cables and blue boxes. I've cleaned all mess and wires from the floor, so that seismometer now looks like that
I've connected 2 inputs of the N/S 1 circuit of the seismometer box with a 50 Ohm resistor and measured the noise at the output. The comparison with the seismic signal is
The noise increased at 0.5 Hz and is pretty big. This might explain the loose of coherence at low frequencies.
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.
This is because spectrum analyzer did not plot the real noise spectrum at the first few points at low frequencies. I've remeasured the noise at 1mHz - 3Hz at "output -" (TP9) and compared it to the seismometer signal
The noise seems to be much less then the signal. I've measured the noise several times and once I got a huge amount of noise
I made another measurement in some time and got the low noise again. A circuit might have a bad contact somewhere.
The plan is to change AD620 adjustable resistor (R2) from 5.49kOhm to 500Ohm to increase the gain from 20 up to 200.
I've replaced R2 resistor that adjusts the gain of the AD620 amplifier. Previous value 5491Ohm, new value 464Ohm, so the gain should increase up to ~200-250. Only at the N/S 1 circuit!
LISO simulation of the circuit transfer function and noise are
LISO predicts gain ~45-46 dB = 200 and noise at the level of 10uV at 1Hz. The transfer function and noise measured are
The noise measured is 5 times higher then predicted by LISO. Though I described AD620 as an ordinary amplifier with 49.9kOhm resistor connecting output and inverted input. I specified the noise spectrum 10 nV and 1/f corner frequency 30 Hz. In the AD620 datasheet noise spectrum is 10 - 100 nV depending on the gain. However, the gain is 200 and noise spectrum should be 10 nV. May be in reality it is not the case. It also possible that the noise model used by LISO is not valid for AD620 as it is not an ordinary operational amplifier.
Today I've attended the laser safety seminar.
I've put the seismometer box back to the 1x1, Guralp is back under MC2. When the seismometer is not plugged in, the noise is
Now, I'm going to collect some data from GUR 1 and MC_F and see if the problem with adaptive filter (increasing errror while decreasing mu) will be gone.
I realigned the steering mirrors for the PMC. The trans value went up from 0.79 to 0.83.
The misalignment was largely in the pitch direction.
PZT1 started railing in the pitch direction and because of this TRY doesn't go more than 0.7. I will leave it as it is for tonight.
Tomorrow I will shift the alignment of the MC to make the PZT1 happier.
PZT1, the one with Koji's custom mid-HV driver (#5447), is getting degraded.
The OSA for the REFL beam is now fully functional.
The only thing we need is a long BNC cable going from the AP table to the control room so that we can monitor the OSA signal with an oscilloscope.
The attached picture shows how they look like on the AP table. Both AS and REFL OSAs are sitting on the corner region.
A long BNC cable was installed and now the REFL OSA signal is happily shown on an oscilloscope in the control room.
I checked the laser powers on the AP table and confirmed that their powers are low enough at all the REFL photo diodes.
When the HWP( which is for attenuating the laser power with a PBS) is at 282.9 deg all of the REFL diodes receives about 5 mW.
This will be the nominal condition.
If the HWP is rotated to a point in which the maximum laser power goes through, the diodes get about 10 mW, which is still below the power rate of 18 mW (#6339).
I used the Coherent power meter for all the measurements.
The table below summarizes the laser powers on the REFL diodes and the OSA. Also the same values were noted on the attached picture.
nominal power [mW]
(when HWP is at 282.9 deg)
expected max power [mW]
(when HWP is at a point where the max power goes through)
[Alex / Den]
I've encountered a problem that C1:PEM-SEIS_GUR1_X_IN1 is saved in the int format. It turned out that inside the code the signal is also in the int format. It is not just a saving error. It should not be so as ADC works at 64k and the model runs at 2k.
Why? There is a bug somewhere in the generation of the code. c1pem.c looks suspicious to Alex because there is a mismatch in the ADC numbers with the simulink model.
Solution: upgrade to 2.4 version - most probably it was fixed there. If not, Alex will handle this problem.
I have slightly shifted the MC beam pointing to relax the PZT1 PITCH. As a result the TRY value went to 0.97 in a first lock trial.
However another issue arose:
The polarity for controlling the PZT1 PITCH seems to have flipped for some reason.
Since it is still sort of controllable, I am leaving it as it is.
If I remember correctly, sliding the PZT1 pitch value to the positive side brought the beam spot upward in the AS CCD. But now it moves in the opposite way.
Also the ASS feedback looks tending to push the PZT1 pitch to the wrong direction.
I am not 100 % sure if the polarity really flipped, but this is my current conclusion.
Tomorrow I will shift the alignment of the MC to make the PZT1 happier.
I wrote an RAM simulation script ... it calculates the LSC signal offset and the operation point offset depending on the RAM modulation index.
Configuration : RAM is added on optC1, by the additional Mach-Zehnder ifo before the PRM.
Both are for PRCL sweep result. Note that REFL33I is always almost zero. Next step: Check the LSC matrix with matrix at the offset operation point.
This a kind of self record...
We need an RF setup at POP to extract 22 and 110 MHz components separately.
I am planning to work on this in the daytime on Tuesday.
AS55Q and AS55I signals. AS55Q is around zero while AS55I has a large offset which is about the signal amplitude. It is likely because of the RAM?
[Keiko / Kiwamu]
Update on the MICH characterization:
On the right figure, you see the non-zero operation points even when RAM mod index = 0. Apparently they come from non-zero loss of the model. (Each mirror of 50ppm loss was assumed).
Has default inmat:
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.
As par Kiwamu's request, RF filters for POP22 and POP110 were installed. They are not really nice. We need to replace it with more fancy electronics.
More to come later.
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.
The Xgreen PD now has a cable going over to the beatbox. Once beatbox characterization is done I can re-find the beat, and we can do some stuff with the beatbox.
The PEM model has been modified now to include a block called 'JIMS' for the JIMS(Joint Information Management System) channel processing. Additionally I added test points inside the BLRMS blocks that are there. These test points are connected to the output of the sqrt function for each band. I needed this for debugging purposes and it was something Jenny had requested.
The outputs are taken out of the RMS block and muxed, then demuxed just outside the JIMS block. I was unable to get the model to work properly with the muxed channel traveling up or down levels for this. Inside the JIMS block the information goes into blocks for the corresponding seismometer channel.
For each seismometer channel the five bands are processed by comparing to a threshold value to give a boolean with 1 being good (BLRMS below threshold) and 0 being bad (BLRMS above threshold). The boolean streams are then split into a persistent stream and a non-persistent stream. The persistent stream is processed by a new library block that I created (called persist) which holds the value at 0 for a number of time steps equal to an EPICS variable setting from the time the boolean first drops to zero. The persist allows excursions shorter than the timestep of a downsampled timeseries to be seen reliably.
The EPICS variables for the thresholds are of the form (in order of increasing frequency):
The EPICS variables for the persist step size are of the form:
I have set all of the persist values to 2048 (1 sec.) for now. The threshold values are currently 200,140,300,485,340 for the GUR1X bands and 170,105,185,440,430 for the GUR1Y bands.
The values were set using ezcawrite. There is no MEDM screen for this yet.
PEM model was restarted at approx. 11:30 Mar. 7 2012 PST.
The RF separator installed comprises of the Minicircuits filters cascaded as in the figure below.
This has one input and 4 output ports for 11, 22, 30-60, and 110MHz signal.
As seen in this entry #6167, we have 22 and 110MHz signals together with 11, 44, 66MHz signals.
They may be demodulated via a harmonic characteristic of the mixers. (Remeber mixers are not multipliers.)
Of course the big concern is the impedance matching for those signals as usual.
The 2nd attachment shows measured impedance of the circuits with all of the ports terminated.
From the complex impedance, we can calculate the reflection coefficient. The 44 and 110MHz
components look correctly matched while the others seems largely reflected.
This certainly is not a nice situation, as the reflection can make the amplifier next to the PD unhappy
(although the reflected power is tiny in our case).
In our case more eminent problem is that the amplitude of the 22MHz signal can vary depending on the cable length by
factor of 10 in amplitude. (c.f. VSWR on the 2nd attachment.)
The transmission to each port was measured. The separation of the signals looks good. But the attenuation of the
targetted signals (i.e. insertion losses) are qulitatively consistent with the impedance. Again these losses are depend
on the cable length.
I swap an OSA at PSL and OSA at REFL. It was because the PSL-OSA had a better resolution, so we place this better one at REFL. The ND filter (ND3) which was on the way to REFL OSA was replaced by two BSs, because it was producing dirty multiple spots after transmitting.
This is the calibrated MICH noise budget on Mar 5. There was a sharp peak at 1Hz and a blob on 3 Hz. The demod phase was adjusted for AS55Q.
Just a quick report on the REFL OSA.
The attached plot below shows the raw signal from the REFL OSA which Keiko installed in this afternoon.
When the data was taken the beam on the REFL OSA was a direct reflection from PRM with the rest of the suspended mirrors misaligned.
One of the upper and lower 11 MHz sidebands is resolved (it is shown at 0.12 sec in the plot) while the other one is still covered by the carrier tail.
The 55 MHz upper and lower sidebands are well resolved (they are at 0.06 and 0.2 sec in the plot).
One of the oscilloscopes monitoring the OSA signals in the control room has a USB interface so that we can record the data into a USB flash memory and plot it like this.
I'm puzzled why the 11MHz peak can be such high considering 1.7~2 times smaller the modulation depth.
This is the MICH noise budget on 6th March. 1Hz peak got a bit better as the BS sus control gain was increased.
I noticed that NDS2 was not running on mafalda as it should be. Instead, there were a couple of zombie MEDMs using up 99% of the CPU. I killed the zombies and have run the 'build channel list' script. When it finished, I tried to restart the nds server, but got the following error in the log file. Email has been dispatched to JZ.
mafalda:logs>less nds2-mafalda-201203072111.logConfiguring from file: nds2.confAllow list: ALLterminate called after throwing an instance of 'std::runtime_error' what(): Insufficient arguments
I was also wondering about the same thing, comparing with what Mirko obtained before with the same OSA ( #5519).
We measure the REFL OSA spectrum when (1) direct reflection from the PRM (2) CR lock at PRC (3) SB lock at PRC. When CR lock, both SBs are reflected from the PRC and when SB lock (ref line), some SB is sucked by PRM and looked lower than the other two lines.
Here is the recent two noise budgets of MICH, with the old measurement by Jenne. The most latest Mar 6 data is quite close to the old data, even better around 20-30 Hz. Probably some scattering source was improved?
Some updates on the locking activity:
I disabled the feedback to the PZT1 PITCH in the Y arm dithering scripts so that it won't push the beam away from the good point.
Currently one has to do a manual alignment only for the PZT PITCH but the rest of DOFs are still able to be automatically aligned with the script.
The polarity for controlling the PZT1 PITCH seems to have flipped for some reason.
Optical spectrum analyzers like the Attachment made by Coherent , Meles Griot- CVI and Spectral Product are all discontinued.
The 40m have Coherent models C240 analyzer with controller C251 Their Finesse measured in 2004: sn205408 F302, sn205409 F396,
Jenne borrowed Jan's Meles Griot model 13SAE006, Peter King has the same model. FSR 300 MHZ, finnees 200 minimum
We tried to measure the sensing matrix for MICH and PRCL last night. They look too much mixed as we expect... the matrix may be posted later. We suspect the IX and IY of the MICH excitation is not balanced very well, although Kiwamu adjusted that about two weeks ago, and it is mixing the dof. We'll try to balance it again, ans see the matrix.
Over-sized local laser emergency switch was held by large C clamp at the south end. This was replaced by a smaller one and it is mounted with magnets.
The Innolight laser was turned off, while the interlock was wired.
DAQ reload/restart was performed at about 1315 PST today. The previous ini file was backed up as c1pem20120309.ini in the /chans/daq/working_backups/ directory.
I set the following to record:
The two JIMS channels at 2048:
[C1:PEM-JIMS_CH1_DQ] Persistent version of JIMS channel. When bit drops to zero indicating something bad (BLRMS threshold exceeded) happens the bit stays at zero for >= the value of the persist EPICS variable.
[C1:PEM-JIMS_CH2_DQ] Non-persistent version of JIMS channel.
And all of the BLRMS channels at 256:
Names are of the form:
On monday I intend to look at the weekend seismic data to establish thresholds on the JIMS channels.
256 was the lowest rate possible according to the RCG manual. The JIMS channels are recorded at 2048 because I couldn't figure out how to disable the decimation filter. I will look into this further.