oops, forgotten the third attachment...
here it is
# Resonant RF diode front end
I read a few datasheets of the C30642GH photodiode that we're going to use for the 11 and 55 MHz. Considering the values listed for the resistance and the capacitance in what they define "typical conditions" (that is, specific values of bias voltage and DC photocurrent) I fixed Rd=25Ohms and Cd=175pF.
Then I picked the tunable components in the circuit so that we could adjust for the variability of those parameters.
Finally with LISO I simulated transfer functions and noise curves for both the 11 and the 55MHz photodiodes.
I'm attaching the results and the LISO source files.
Use 10 Ohms for the resistance - I have never seen a diode with 25 Ohms.
p.s. PDFs can be joined together using the joinPDF command or a few command line options of 'gs'.
Jenne and Koji
We successfully hung ITMX on the SOS. Side magnet is ~2mm off from the center of the OSEM. ITMX aligned using the QPD. The OSEMs changes the alignment. It looks that something magnetic is inside the OSEM PD or LED.
Reguled ITMY side magnet.
Cleaned up the lab for the safety inspection.
The brand new OSEM LED and PD can be picked up with a weak magnet. These ferrous metals of LEDs and PDs will be magnetized by sitting in the sus next to the
magnets for years. I hanged optics with new OSEMs and never saw this effect before.
We have to demagnetize them.
The OSEM LEDs and PDs from Honeywell have always had some ferromagnetic material in them. These are the same OSEMs we had since 2000.
You must be thinking of the really old 20th century plastic OSEMs.
We need to do a new huddle test of the Guralps for the Wiener filtering paper. The last test had miserable results.
I tried to use recent data to do this, but it looks like we forgot to turn the Guralp box back on after the power outage or that they're far off center.
So instead I got data from after the previous power outage recovery.
I tried to use our usual Wiener filter method to subtract Guralp1-Z from Guralp2-Z, but that didn't work so well. It was very sensitive to the pre-weighting.
Instead I used the new .m file that Dmass wrote for subtracting the phase noise from his doubling noise MZ. That worked very well. It does all of the subtraction in the frequency domain and so doesn't have to worry about making a stable or causal filter. As you can see, it beats our weighted Wiener filter at all frequencies.
The attached plot shows the Guralp spectra (red & green), the residual using time-domain Wiener filtering (black) and the Dmass f-domain code (yellow).
As soon as Jenne brings in her beer cooler, we're ready to redo the Huddle Test.
Since we're going to open the MC1 tank tomorrow, I've moved the MC1 accelerometers and the Guralp over to underneath MC2 for the vent. I'll reconnect them later.
I've put both Guralps next to the Ranger and connected them to the breakout box. The data is now good.
I found that the Ranger was not centered and so it was stuck (someone kicked it in the last 2 weeks apparently). I recentered the mass according to the procedure in the manual. Its now moving freely.
In order to do a better huddle test, I increased the gain of the Ranger's SR560 preamp to 100 from 10 and put it on the low noise setting. I also enabled a 2x lowpass at 3 kHz for no good reason.
I couldn't find what the actual value of the gain of the Guralp breakout box is, but I assume its 10. With this assumption the calibrations are this:
Guralp: 800 V/(m/s) * 10 (V/V) * 16384 cts/V => 7.63e-9 (m/s)/count (0.03 - 40 Hz)
Ranger: 345 V/(m/s) * 100 (V/V) * 16384 cts/V => 1.77e-9 (m/s)/count (above 1Hz)
To account for the fact that I am not damping the Ranger with an external damping resistor, I have changed the calibration poles and zeros: in DTT we now use 2 poles @ 0 Hz and a complex pair at 1 Hz:
G = 1.77e-9
Poles = 0, 0
Zeros = 0.15 0.9887
I think that the Guralp gain is too high by a factor of 2. To really do this right, we should attach a known voltage to the input pins of the Guralp breakout and then read off the amount of counts.
I put Jenne's cooler over the seismometers. Kiwamu put the copper foil wrapped lead brick on top of the cooler to hold it down. I also put another (unwrapped) lead brick on top of the Guralp cables outside of the cooler. Frank gave me a knife with which I cut a little escape hole in the bottom of the cooler lip for the Guralp cables to sneak out of.
They are sandblasting at CES: our particle counts are very high. DO NOT OPEN CHAMBER!
Looks like the GUR2_X signal is bad. Jenne says that we need to center it mechanically before the signals will become useful again. Maybe Steve will do this - instructions are in the manuel ?
This is the spectra and coherence from a quiet time last night. I've lowered the Guralp cal by a factor of 2 to account for the fact that the gain in the breakout box is actually 20 and not 10 as I previously said.
The AD620 stage in the front part has a gain of 10 and then there's a single-to-differential stage in the output which gives us a gain of 2. The DTT cal in counts is now 3.8e-9 (m/s)/count.
The second plot shows the Guralp and Ranger signals at the ADC input (converted from counts to Volts for usefulness). The thick grey line is the expected noise of the Guralp breakout box
(mainly the AD620) propagated to the ADC (via multiplication by 2). It looks like the preamp board should not be a problem as long as we can reach the AD620 limit.
So the excess noise in the Guralp is not the fault of the preamp, but more likely the mounting and insulation of the seismometers.
Recent status of SOSs:
We completed one of the suspension (ITMY).
ITMX: 6 Magnets, standoffs, and guide rod glued / balance to be confirmed / needs to be baked
ITMY: 6 Magnets, standoffs, and guide rod glued / balance confirmed / needs to be baked
SRM: 6 Magnets, one standoff, and guide rod glued, / waiting for the release from the gluing fixture.
PRM: one standoff, and guide rod glued / waiting for the magnet gluing.
We think we solved all the problems for hanging the suspensions.
--- Magnet gluing fixture ---
--- Suspending the mirror ---
The elog was down and I ran the restart script.
I used some recent better data to try for better Z subtraction.
Dmass helped me understand that sqrt(1-Coherence) is a good estimate of the theoretical best noise subtraction residual. This should be added to DTT. For reference the Jan statistic is the inverse of this.
This should get better once Steve centers the Guralps.
Do not open IFO vacuum envelope today! They are sandblasting again at CES
Guralp 2 centered.The mass position offsets are: E-W 0.05V, N-S 0V, Z 0.4V
Guralp 1: E-W -0.1V, N-S -0.25V, Z 0V measured, not adjusted
The GUR2_X channel has an offset. See plot below when seismometers are disconnected. This offset has to be removed.
NOTE: this huddle is on bad-soft ground-lenoleum tile from prehistoric Flintstone age
MC1 and MC3 seem to have kept themselves together, but all the other optics' watchdogs tripped.
Some of the suspensions got watchdog tripped -> enabled -> damped.
The MC mirrors got slightly misaligned.
The oplev plots clearly show the alignment effect of this eq.
Someone adjusted the Guralp2 mass position last night??
Last night (Mar 17) I checked the PLL setup as Mott have had some difficulty to get a clean lock of the PLL setting.
Now the beating signal is much cleaner and behave straight forward. I will add some numbers such as the PD DC output, RF levels, SR560 settings...
Last night (Mar 17) I checked the PLL setup as Mott had some difficulty to get a clean lock of the PLL setting.
I also had noticed the progressive change of the aux NPRO alignment to the Farady.
I strongly agree about the need of a good and robust PLL.
By modifying the old PDH box (version 2008) eventually I was able to get a PLL robust enough for my purposes. At some point that wasn't good enough for me either.
I then decided to redisign it from scratch. I'm going to work on it. Also because of my other commitments, I'd need a few days/1 week for that. But I'd still like to take care of it. Is it more urgent than that?
We use the current PLL just now, but the renewal of the components are not immediate as it will take some time. Even so we need steady steps towards the better PLL. I appreciate your taking care of it.
I checked the setup further more.
Now I have significant fraction of beating (30%) and have huge amplitude (~9dBm).
The PLL can be much more stable now.
It looks like Steve used a GND-12V supply to power the Guralp through the little breakout box (the box is for checking the centering of the mass). This is BAD. The Guralps want +/- 12V.
We centered all of the channels on Gur2, and checked the channels on Gur1, so we'll see how they're feeling after a while.
This trend of the last 200 days shows that GUR2 has been bad forever...until now anyways.
I went and double-checked and aligned the styrofoam cooler at ~5:00 UTC. It was fine, but we really need a better huddling box. Where's that granite anyway?
Here's the new Huddle Test output. This time I show the X-axis since there's some coherence now below 0.1 Hz.
You'll also notice that the Wiener filter is now beating the FD subtraction. This happened when I increased the # of taps to 8000. Looks like the noise keeps getting lower as I increase the number of taps, but this is really a kind of cheat if you think about it carefully.
From this morning, now in calibrated units, and with the Güralp self noise spec from the Güralp manual.
We are going to set the waist size to 0.1 mm for the beam going through the triple resonant EOM on a new PSL setup.
When we were drawing a new PSL diagram, we just needed to know the waist size at the EOM in order to think about mode matching.
This figure shows the relation between the waist size and the spot size at the aperture of the EOM.
The x-axis is the waist size, the y-axis is the spot size. It is clear that there is a big clearance at 0.1 mm waist size. This is good.
Also it is good because the waist size is much above the damage threshold of the EO crystal (assuming 1W input).
The attached file is the python code for making this plot.
You don't need a lengthy code for this. It is obvious that the spot size at the distance L is minimum when L =
zR, where zR is the Rayleigh range. That's all.
Then compare the spot size and the aperture size whether it is enough or not.
It is not your case, but if the damage is the matter, just escape to the large zR side. If that is not possible
because of the aperture size, your EOM is not adequate for your purpose.
There was more jackhammering this morning just about 20 ft north-west of the beamsplitter chamber, outside.
It looks like the PLL drifted alot over the weekend, and we couldn't get it back to 9 dBm. We switched back to the new focus wideband PD to make it easier to find the beat signal. I replaced all the electronics with the newly fixed UPDH box (#17) and we aligned it to the biggest beat frequency we could get, which ended up being -27 dBm with a -6.3V DC signal from the PD.
Locking was still elusive, so we calculated the loop gain and found the UGF is about 45 kHz, which is too high. We added a 20 dB attenuator to the RF input to suppress the gain and we think we may have locked at 0 gain. I am going to add another attenuator (~6 dB) so that we can tune the gain using the gain knob on the UPDH box.
Finally, attached is a picture of the cable that served as the smb - BNC adaptor for the DC output of the PD. The signal was dependent on the angle of the cable into the scope or multimeter. It has been destroyed so that it can never harm another innocent experiment again!
We have managed to lock the PLL to reasonable stability. The RF input is attenuated by 26 dBm and the beat signal locks very close to the carrier of the marconi (the steps on the markers of the spectrum analyzer are coarse). We can use the marconi and the local boost of the pdh box to catch the lock at 0 gain. Once the lock is on, the gain can be increased to stabilize the lock. The locked signals are shown in the first photo (the yellow is the output of the mixer and the blue is the output to the fast input of the laser. If the gain is increased too high, the error signal enters an oscillatory regime, which probably indicates we are overloading the piezo. This is shown in the second photo, the gain is being increased in time and we enter the non-constant regime around mid-way through.
Tomorrow I will use this locked system to measure the PZT response (finally!).
This is the first touch to the MC mirrors after the earthquake on 16th.
So far, I have aligned in Yaw such that the yaw peak is minimized.
This seal is good for daily use- operation only. The IFO has to be sealed with light metal doors every night so ants and other bugs can not find their way in.
Our janitor Kevin is mopping the hole IFO room floor area with 5% ant killing solution in water in order to discourage bugs getting close to our openings of the vented chamber.
You may be sensitive to this chemical too. Do not open chamber till after lunch.
Old control room air condition failed yesterday around noon. It was blowing 80-85F hot air for about 2-3 hours at racks 1Y4-7 and the entry room 103
I found the elog down and I restarted it.
Then, after few seconds it was down again. Maybe someone else was messing with it. I restarted an other 5 times and eventually it came back up.
After realigning and getting the lock today, I tried to add in the SR785 to measure the transfer function. As soon as I turn on the piezo input on the PDH box, however, the lock breaks and I cannot reacquire it. We are using an SR650 to add in the signal from the network analyzer and that has worked. We also swapped the 20 dB attenuator for a box which mimics the boost functionality (-20 dB above 100 Hz, 0 dB below 6Hz). I took some spectra with the SR750, and will get some more with the network analyzer once Alberto has finished with it.
The SR750 spectra is posted below. The SR750 only goes up to 100 kHz, so I will have to use the network analyzer to get the full range.
I spent some time trying to understand how touching the metal cage inside or bending the PCB board affected the photodiode response. It turned out that there was some weak soldering of one of the inductors.
Matt and Koji:
We closed the light doors of the chambers.
We are leaving the PLL as it is locked in order to see the long term stability. And we will check the results in early morning of tomorrow.
DO NOT disturb our PLL !!
(what we did)
After Mott left, Matt and I started to put feedback signals to the temperature control of NPRO.
During doing some trials Matt found that NPRO temperature control input has an input resistance of 10kOhm.
Then we put a flat filter ( just a voltage divider made by a resistor of ~300kOhm and the input impedance ) with a gain of 0.03 for the temperature control to inject a relatively small signal, and we could get the lock with the pzt feedback and it.
In addition, to obtain more stable lock we then also tried to put an integration filter which can have more gain below 0.5Hz.
After some iterations we finally made a right filter which is shown in the attached picture and succeeded in obtaining stable lock.
Now some pedestals, mirrors and lenses are left on the PSL table, since we are on the middle way to construct a PLL setup which employs two NPROs instead of use of PSL laser.
So Please Don't steal any of them.
Can I please get the network analyzer back?
Hartmut suggested a possible explanation for the way the electronics transfer function starts picking up at ~50MHz. He said that the 10KOhm resistance in series with the Test Input connector of the box might have some parasitic capacitance that at high frequency lowers the input impedance.
Although Hartmut also admitted that considering the high frequency at which the effect is observed, anything can be happening with the electronics inside of the box.
Matt checked it in this morning and he found it's been locked during the night.
The same thing happening again. The intermittent offset upstream of the seismometer that never got fixed.
The granite plate and ball bearings are in. I will place seismometers on it.
In this afternoon, Mott and I tried to find a beat note between two NPROs which are going to be set onto each end table for green locking.
At first time we could not find any beats. However Koji found that the current of innolight NPRO was set to half of the nominal.
Then we increased the current to the nominal of 2A, finally we succeeded in finding a beat note.
Now we are trying to lock the PLL.
P.S. we also succeeded in acquiring the lock
I upgraded the old REFL199 to the new REFL55.
To do that I had to replace the old photodiode inside, switching to a 2mm one.
Electronics and optical transfer functions, non normalized are shown in the attached plot.
The details about the modifications are contained in this dedicated wiki page (Upgrade_09 / RF System / Upgraded RF Photodiodes)