We recovered the LO beam on the BHD port. To do this, we first tried reverting to a previously "good" alignment but couldn't see LO beam hit the sensor. Then we checked the ITMY table and couldn't see LO beam either, even though the AS beam was coming out fine. The misalignment is likely due to recent changes in both injection alignment on TT1, TT2, PR2, PR3, as well as ITMX, ITMY. We remembered that LO path is quite constrained in the YAW direction, so we started a random search by steering LO1 YAW around by ~ 1000 counts in the negative direction at which point we saw the beam come out of the ITMY chamber
We proceeded to walk the LO1-LO2 in PIT mostly to try and offload the huge alignment offset from LO2 to LO1 but this resulted in the LO beam disappearing or become dimmer (from some clipping somewhere). This is WiP and we shall continue this alignment offload task at least tomorrow, but if we can't offload significantly we will have to move forward with this alignment. Attachment #1 shows the end result of today's alignment.
The following that went unnoticed from yesterday were recovered today:
1. ETMX and ETMY 'misalign' scripts weren't running. Troubleshooting showed slow machines c1auxex and c1auxey weren't responding. The machines were reset.
2. PRM oplev gains were zero. Gain values were set looking back at the burt files.
3. X end PZT power supplies were turned ON and set to 100V.
4. X end doubler temperature was reset to the last optimal value on elog (36.35 deg).
Some hitches that should be looked into:
1. Check: ASS for X arm seems not quite doing its job. ETMX has to be moved using sliders to obtain maximum TRX and the arm alignment was seen to be drifting.
2. Check: Status of other slow machines and burt restore whichever needs one.
ETMX ASC output was turned off for whatever reason. Switched it on, ASS is fine.
We both happened to come by today to fix things up.
When I arrived, the PMC was locked to a 01 mode, which I fixed. The PMC transmission is still worryingly low. MC locked happily.
ETMX was getting odd kicks, the kind where a DC shift would occur suddenly, and then go away a few moments later. I turned off all dynamic coil outputs, and looked at the MON output of the SOS driver with a scope to try and see if the DAC or dewhitening was glitching, but didn't see anything... Meanwhile, Jenne fiddled with the TTs until we got beams on POP and REFL. (EDIT, JCD: Useful strategies were to put an excitation onto TT2, and move TT1 until the scattered beam in the chamber was moving at the excitation frequency, Find the edges of TT2 by finding where the scattered light stops seeing the excitation, and center the beam on TT2. By then, I think I saw the beam on the PRM face camera. Then, put a temporary camera looking at the face of PR2. Using TT2 to center here got us the beam on the POP camera.)
We then walked PRM and the TTs around to keep those two camera beams and get the PRM oplev beam back on its QPD. At this point, ITMX was misaligned (by us), and ITMY aligned to get some recycled flashes into the Y-arm. Y-arm was locked to green, and we poked TTs to get better IR flashes. Misaligning PRM, we had Y-Arm flashes of ~0.7. From there, the michelson and then X-arm were roughly aligned. Both arms were seeing flashes of about 0.7, and the MICH fringes on the AS port look nice.
Frustratingly, the SUS->LSC communication for TRY and TRX isn't working, and could not be fixed by any combination of model or front-end restarting... Thus we haven't been able to actually lock the arms and run ASS. THIS IS VERY FRUSTRATING.
Additionally, at the point where we were getting light back into the Yarm, the ITMX that were seen on Friday were happening again, tripping the watchdog. Also, something in the Yarm cavity is getting intermittently pushed around, as can be seen by the green lock suddenly wandering off. All of these suspension shenanigans seem to be independent of oplev damping.
It troubles me that this whole situation is fairly similar to the last time we lost the input pointing (ELOG 10088)
In any case, we feel that we have gotten the IFO alignment to a lockable state.
It's great that you guys found the beam.
Yes, ITMX kick and lost communication for TRY were the motivation of my CDS rebooting.
[Steve Koji Kiwamu]
- The storage on linux1 and linux1 itself (with this order) were turned on at 10:30am
- Kiwamu restored the vacuum system
=> opened V4, started TP1 (maglev) and opened V1.
The pressure went downfrom 2.5 mTorr to the normal level in about 20 minutes.
- A regular fsck of linux1 was completed at 5pm
- Nodus was turned on. Mounting /cvs/cds succeeded
- The control room computers were turned on
- The rack power for FB turned on, FB and megatron started.
- HVs on 1X1 were turned on. The are not vacuum HV, but used only in the air
- Turned on the RF generation box and the RF distribution box
- burtrestore slow machines (c1psl, c1susaux, c1iool0, c1iscaux, c1iscaux2, c1auxex, c1auxey)
Found the Marconi for the 11 MHz source had been reset to its default.
=> reset the parameters. f = 11.065910 MHz (see #5530) amp = 13 dBm.
Interferometer became lockable. I checked the X/Y arm lock, and MICH lock, they all are fine.
I failed to start Rana's favorit anciant desktop computer at the vac rack. He has to baby this old beast just a little bit more.
Vacuum status: Vac Normal was reached through Farfalla: Rga was switched back to IFO and and Annuloses are beeing pumped now.
V1 was closed for about a day and the pressure reached ~2.8 mTorr in the IFO. This leakrate plus outgassing is normal
The ref cavity 5000V was turned on.
The only thing that has to be done is to restart the RGA. I forgat to turn it off on Friday.
As it turns out Steve is not crazy in this particular instance: the vacuum computer, linux3 , has some issues. I can login just fine, but trying to open a terminal makes the CPU rail and the RAM max out and eventually the machine freezes.
Under KDE, I can open a terminal OK as root, but if I then try a 'su controls', the same issue happens. Let's wait for Jamie to fix this.
Restarted Apache on nodus using Yoichi's wiki instructions. SVN is back up.
The following is a message from the LIGO 40m Chief Recycling Officer:
Please get up off your (Alignment Stabilization Servo)es and recycle your bottles and cans! There is a recycling bin in the control room. Recent weeks have seen an increase in number of bottles/cans thrown away in the regular garbage. This is not cool.
Going off some discussion we had at lunch today, here is my current knowledge of the state of cavity lengths.
Acknowledging that Koji changed the sideband modulation frequency recently, the ideal cavity lengths are (to the nearest mm):
We when last hand measured distances, after moving PR2, we found:
However, when I looked at the sideband splitting interferometrically, I found:
This is only 5mm from the hand measured value, so we can believe that the SRC length is between 5 and 6 cm too long. I'm building a MIST model to try and see what this may entail.
Com'on. This is just a 60ppm change of the mod frequency from the nominal. How can it change the recycling cav length by more than a cm?
This describes how the desirable recycling cavity lengths are affected by the phase of the sidebands at non-resonant reflection of the arms.
If we believe these numbers, L_PRC = 6.7538 [m] and L_SRC = 5.39915 [m].
Compare them with the measured numbers
You should definitely run MIST to see what is the optimal length of the RCs, and what is the effect of the given length deviations.
Koji correctly points out that I naïvely overlooked various factors. With a similar analysis to the wiki page, I get:
This means that:
Next step is to see how this may affect our ability to sense, and thereby control, the SRC when the arms are going.
MIST simulations and plots are in the attached zip.
I looked at the data of the day before yesterday (Oct 06) to know how much is the recycling gain.
X arm: (TRX_PRecycled) / (TRX_PRMmisaligned) * T_PRM = 83.1/0.943*0.07 = 6.17
Y arm: (TRX_PRecycled) / (TRX_PRMmisaligned) * T_PRM = 99.2/1.017*0.07 = 6.83
==> G_PR = 6.5 +/- 0.5 (oh...this estimation is so bad...)
From the recycling gain and the arm cavity reflectance, one can get the loss in the recycling cavity.
G_PR = T_PRM / (1-Sqrt(R_PRM * (1-L_PRC)*R_cav))^2
==> loss in the recycling cavity L_PRC: 0.009+/-0.009
(About 1% loss is likely in the recycling cavity)
Measured arm reflectivity R_cav: 0.875 +/- 0.005
Estimated round trip loss L_RT: 157ppm +/- 8ppm
Estimated finesse F: 1213+/-2
Measured arm reflectivity R_cav: 0.869 +/- 0.006
Estimated round trip loss L_RT: 166ppm +/- 8ppm
Estimated finesse F: 1211+/-2
I put all three seismometers and all six accelerometers together in the foam box with peanuts. Three of the accelerometers are facing in the x-direction and three are in the y-direction. Both Guralps are aligned on the NS axis and the Ranger is pointing vertically.
**EDIT: The accelerometers are in the x and z directions, not x and y. Sorry, I was sleepy when I wrote this.**
One of the accelerometers was refusing to show anything, and after a few hours of checking connections and swapping cables, I discovered that someone had unplugged the cable from the ADC. A quick glance in the dataviewer shows that the channel has been unplugged since about 3 in the afternoon on August 8th (Saturday). So... obviously all the accelerometer measurements made with that channel since then did not actually get recorded. Yay.
Anyway, as of 2:45, everything is working and taking data. Clearly we're not getting a full night's worth... hopefully that's okay.
I noticed that our current suspension damping loops for the new SOS were railing the DAC outputs. The reason being that cts2um module has not been updated for most optics and thus teh OSEM signal (with the new Sat Amps) is about 30 times stronger. That means our usual intuition of damping gains is too high without applying correct conversion cts2um filter module. I reduced all these gains today and nothing is overflowing the c1su2 chassis now. I also added two options in the "!" (command running drop down menu) in the sus_single medm screens for opening ndscope for monitoring coil outputs or OSEM inputs of the optic whose sus screen is used.
I am using a PDA255 photodiode to measure the power outputted by the NPRO beam on the PSL table. (I'm going to then use a network analyzer to measure the amplitude response of the PZT to being driven at a range of frequencies. I'll detect the variation in in response to changing the driving frequency using this PDA255.)
The PDA255 has an active area of 0.8mm^2 and a maximum intensity for which the response is linear of 10mW/cm^2. This means that a beam I focus on the PD must have a power less than 0.08 mW (and even less if the spot size is smaller than the window size).
I used a power meter to measure the beam power and found it was 0.381 mW.
The second polarizing beam splitter in the setup transmits most of the beam power, but reflects 0.04 mW (according to the power meter). I'm going to place the photodiode there in the path of the reflected beam.
We aligned both the reference cavity and the PMC, each by looking at their Trans PD on Davaviewer, and adjusting the two steering mirrors to maximize the transmission power. We got a pretty good amount of improvement for the ref cav, but since the PMC hasn't decayed a whole lot, we got a much smaller amount of improvement.
After Alberto and I worked on aligning the reference cavity, Rob asked the important and useful question: what is the visibility of the reference cavity. This helps tell us if we're optimally aligned or not even close.
I did a scan of the ref cav temperature, using /scripts/PSL/FSS/SLOWscan, but there seems to be no real signal is C1:PSL-FSS_RFPDDC. As shown in Alberto's 200-day plot, it does change sometimes, but if you zoom in on the flat parts, it seems like it's not really reading anything meaningful. I did a cursory check-out of it, but I'm not 100% sure where to go from here: There are (as with all of these gold-box PDs) 3 outputs: a ribbon cable (for ADC purposes I think), an SMA for the RF signal, and a BNC for the DC signal. The photodiode is clearly working, since if you stick the Lollypop in front of the PD, the cavity unlocks. I plugged a 'scope into the DC BNC, and it also behaves as expected: block the beam and the signal goes down; unblock the beam and the signal goes up. Something of note is that this readout gives a positive voltage, which decreases when the beam is blocked. However, looking at the dataviewer channel, nothing at all seems to happen when the beam is blocked/unblocked. So the problem lies somewhere in the get-signal-to-DAQ path. I unplugged and replugged in the ribbon cable, and the value at which the channel has been stuck changed. Many days ago, the value was -0.5, for the last few days it's been -1.5, and after my unplug/replug, it's now back to ~ -0.5 . The other day Alberto mentioned, and made the point again today that it's a little weird that the PD reads out a negative voltage. Hmm.
we have a tester cable, but you don't want it. Instead the problem is probably at the cross-connect. The D-cable goes to a cross-connect and you can probe there with a voltmeter. If the signal is good there, trace it to the ADC. Also trend for several years to see when this happened - Yoichi may know the history better.
Also, we still need to complete the FSS RFPD task list from last year.
I called in the reinforcements today. Ben came over and we looked all around at all of the cross-connects and cables relating to the FSS. Everything looks pretty much okey-dokey, except that we still weren't getting signal in the DataViewer channels. Finally we looked at the psl.db file, which indicates that the C1:PSL-FSS_RFPDDC channel looks at channel 21 of the ADC cross connect thing. We followed the cable which was plugged into this, and it led to a cable which was disconnected, but laying right next to the Ref Cav refl PD. We plugged this into the DC out SMA connection of the photodiode (which had not been connected to anything), and suddenly everything was mostly golden again in dataviewer land. RFPDDC_F now has a signal, but RFPDDC is still flat.
Even though this seems to be working now, it's still not perfect. Rob suggested that instead of having this SMA cable going from the photodiode's DC out, we should take the signal from the ribbon cable. So I'm going to figure out which pin of the D-connector is the DC out, and take that from the cross connect to the ADC cross connect. This will help avoid some persnickity ground loops.
I turned the RefCav heater and servo back on a couple days ago. At first it was stabilizing again at a low setpoint, but in reality the right temperature (~40 C). After fixing the in-loop signal offsets, the setpoint now correctly reflects the actual temperature.
Jenny is going to calibrate the sensors using some kind of dunking cannister next week.
Unfortunately, it seems that the large power supply which is used for the heater is dead. Or maybe I don't remember how to use it?
The AC power cord was plugged in to a power strip which seems to work for IO chassis. We also tried swapping power strip ports.
We checked the front panel fuses. The power one was 3 Ohms and the 'bias' one was 55 Ohms. We also checked that the EPICS slider did, in fact, make voltage changes at the bias control input.
Non of the front panel lights come on, but I also don't remember if that is normal.
Have those lights been dead a long time? We also reconnected the heater cable at the reference cavity side.
Rana and I
1) took the temperature sensors off the reference cavity;
2) wrapped copper foil around the cavity (during which I learned it is REALLY easy to cut hands with the foil);
3) wrapped electrical tape around the power terminals of the temperature sensors (color-coded, too! Red for the out of loop sensor, Blue for the first one, Brown for the second, Gray for the third, and Violet for the fourth. Yes, we went with an alphabetical coding system, excluding the out of loop sensor);
4) re-wrapped the thermal blanket heater;
5) covered the ends of the cavities with copper, ensuring that the beam can enter and exit;
6) took pretty pictures for your enjoyment!
We will see if this helps the temperature stabilization of the reference cavity.
The end of the reference cavity, with a lovely square around the beam.
The entire, well-wrapped reference cavity!
From the trend, it seems that the Reference Cavity's temperature servo is working fine with the new copper foil. I was unable to find the insulating foam anywhere, but that's OK. We'll just get Frank to make us a new insulation with his special yellow stuff.
The copper foil that Steve got is just the right thickness for making it easy to form around the vacuum can, but we just have to have the patience to wrap ~5-10 more layers on there. We also have to get a new heater jacket; this one barely fits around the outside of the copper wrap. The one we have now seems to have a good heating wire pattern, but I don't know where we can buy these.
I also turned the HEPA's Variac back down to the nominal value of 20. Please remember to turn it back up to 100 before working on the PSL.
This is the trend so far with the copper foil wrapping. According to Megan's calculation, we need ~1 mm of foil and the thickness of each layer is 0.002" (1/20th of a mm), so we need ~20 layers. We have ~5 layers so far.
As you can see the out-of-loop temperature sensor (RCTEMP) is much better than before. We need another week to tell how well the frequency is doing -
the recent spate of power cycles / reboots of the PSL have interrupted the trend smoothness so far.
I wrapped another ~3 layers onto there. It occurs to me now that we could just get some 2mm thick copper plates made to fit over the stainless steel can.
They don't have to completely cover it, just mostly. I also took the copper circles that Steve had made and marked them with the correct beam height
and put them on Steve's desk. We need a 1" dia. hole cut into these on Monday.
To compensate for the cooling during my work, I've set the heater for max heating for 1 hour and then to engage the temperature servo.
I also noticed the HEPA VARIAC on the PSL was set to 100. Please set it back to 20 after completing your PSL work so that it doesn't disturb the RC temperature..
This evening we measured the noise spectrum of the reference cavity PD used in the FSS loop. From that we estimated the transimpedance and found that the PD is shot-noise limited. We also found a big AM oscillation in correspondence of the FSS modulation sideband which we later attenuated at least in part.
Some more words about the RFAM: I noticed that there was an excess RFAM by unlocking the RC and just looking at the RF out with the 50 Ohm input of the scope. It was ~100 mVp-p! In the end our method to minimize the AM was not so sensible - we aligned the waveplate before the EOM so as to minimize the p-pol light transmitted by the PBS cube just ahead of the AOM. At first, this did not minimize the RFAM. But after I got angry at the bad plastic mounting of the EOM and re-aligned it, the AM seemed to be small with the polarization aligned to the cube. It was too small to measure on the scope and on the spectrum analyzer, the peak was hopping around by ~10-20 dB on a few second timescale. Further reduction would require some kind of active temperature stabilization of the EOM housing (maybe a good SURF project!).
For the EOM mount we (meaning Steve) should replace the lame 2-post system that's in there with one of the mounts of the type that is used in the Mach-Zucker EOMs. I think we have spare in the cabinet next to one of the arms.
After the RFAM monkeying, I aligned the beam to the RC using the standard, 2-mirror, beam-walking approach. You can see from the attached plot that the transmission went up by ~20% ! And the reflection went down by ~30%. I doubt that I have developed any new alignment technique beyond what Yoichi and I already did last time. Most likely there was some beam shape corruption in the EOM, or the RFAM was causing us to lock far off the fringe. Now the reflected beam from the reference cavity is a nice donut shape and we could even make it better by doing some mode matching! This finally solves the eternal mystery of the bad REFL beam (or at least sweeps it under the rug).
At the end, I also fixed the alignment of the RFPD. It should be set so the incident angle of the beam is ~20-40 deg, but it was instead set to be near normal incidence ?! Its also on flimsy plastic legs. Steve, can you please replace this with the new brass ones?
I was aware of a problem on those units since I acquired the data. Then it wasn't totally clear to me which were the units of the data as downloaded from the Agilent 4395A, and, in part, still isn't.
It's clear that the data was in units of spectrum, an not spectral density: in between the two there is a division by the bandwidth (100KHz, in this case). Correcting for that, one gets the following plot for the FSS PD:
Although the reason why I was hesitating to elog this other plot is that it looks like there's still a discrepancy of about 0.5dBm between what one reads on the display of the spectrum analyzer and the data values downloaded from it.
However I well know that, I should have just posted it, including my reserves about that possible offset (as I'm doing now).
Teflon feet removed and heavy brass-delrin pd base installed. Ref-cavity reflected light remains to be beautiful doughnut shape on camera.
Summary: This afternoon we managed to get the temperature control of the reference cavity working again.
We bypassed the MINCO PID by connecting the temperature box error signal directly into EPICS.
We couldn't configure the PID so that it worked with the modified temperature box so we decided to just avoid using it.
Now the temperature control is done by a software servo by using the channel C1:PSL-FSS_MINCOMEAS as error signal and driving C1:PSL-FSS_TIDALSET (which we have clip-doodle wired directly to the heater input).
We 'successfully' used ezcaservo to stabilize the temperature:
ezcaservo -r C1:PSL-FSS_MINCOMEAS -s 26.6 -g -0.00003 C1:PSL-FSS_TIDALSET
We also recalibrated the channels:
with Peter King on the phone by using ezcawrite (EGUF and EGUL) but we didn't change the database yet. So please do not reboot the PSL computer until we update the database.
More details will follow.
I made the changes to the psl.db to handle the new Temperature box hardware. The calibrations (EGUF/EGUL) are just copied directly from the LHO .db file (I have rsync'd their entire target area to here).
allegra:c1psl>diff psl.db~ psl.db
< field(DESC,"TIDALOUT- drive to the reference cavity heater")
< field(SCAN,".5 second")
< field(INP,"#C0 S28 @")
< field(DESC,"TIDALINPUT- tidal actuator input")
< field(SCAN,".5 second")
< field(INP,"#C0 S3 @")
> field(DESC,"TIDALINPUT- tidal actuator input")
> field(SCAN,".5 second")
> field(INP,"#C0 S3 @")
> field(DESC,"TIDALOUT- drive to the reference cavity heater")
> field(SCAN,".5 second")
> field(INP,"#C0 S28 @")
[HV pulse] ----+ +-->-- [PD2]
->--[HWP]->-- [EOM] -->-- [PBS] --<->-- [QWP] --<->-- [Reference Cavity] -->-- [PD1]
We succeeded in getting the reflected green beam from both ITMY and ETMY.
After we did several things on the end table, we eventually could observe these reflections.
Now the spot size of the reflection from ITMY is still big ( more than 1 cm ), so tomorrow modematching to the 40m cavity is going to be improved by putting mode matching telescopes on right positions.
An important thing we found is that, the beam height of optics which directly guides the beam to the cavity should be 4.5 inch on the end table.
(what we did)
* Aidan, Kevin and Kiwamu set the beam to be linearly polarized by rotating a QWP in front of the Innolight. This was done by monitoring the power of the transmitted light from the polarizer attached on the input of the Faraday of 1064 nm. Note that the angle for QWP is 326.4 deg.
* We put some beam damps against the rejected beam from the Faraday
* To get a good isolation with the Faraday we at first rotated the polarization of the incident beam so to have a minimum transmission. And then we rotated the output polarizer until the transmission reaches a minimum. Eventually we got the transmission of less than 1mW, so now the Faraday should be working regardless of the polarization angle of the incident beam. As we predicted, the output polaerizer seems to be rotated 45 deg from that of the input.
* Rana, Koji and Kiwamu aligned the PPKTP crystal to maximize the power of 532 nm. Now the incident power of 1064 nm is adjusted to 250mW and the output power for 532 nm is 0.77mW. Actually we can increase the laser power by rotating a HWP in front of the Faraday.
* We injected the green beam to the chamber and aligned the beam axis to the ETMY without the modematching lenses, while exciting the horizontal motion of the ETM with f=1Hz from awg. This excitation was very helpful because we could figure out which spot was the reflection from the ETM.
* Once we made the reflected beam going close to the path of the incident beam, we then put the modematching lenses and aligned the steering mirrors and lenses. At this time we could see the reflected beam was successfully kicked away by the Faraday of 532 nm.
* Koji went to ITMY chamber with a walkie-talkie and looked at the spot position. Then he told Rana and Kiwamu to go a right direction with the steering mirrors. At last we could see a green beam from ITM illuminating the ETM cage.
* We excited the ITMY with f=2Hz vertically and aligned the ITM from medm. Also we recovered a video monitor which was abandoned around ETMY chamber so that we could see the spot on the ETM via the monitor. Seeing that monitor we aligned the ITM and we obtained the reclection from the ITM at the end table.
* We also tried to match the mode by moving a lens with f=400mm, but we couldn't obtain a good spot size.
I could not understand this operation. Can you explain this a bit more?
It sounds different from the standard procedure to adjust the Faraday:
1) Get Max transmittion by rotating PBS_in and PBS_out.
2) Flip the Faraday 180 deg i.e. put the beam from the output port.
3) Rotate PBS_in to have the best isolation.
Now I know why Rana was wearing his bright green pants yesterday. It is nice to see the green beam in the 40m IFO again. It calls for celebration!
I stopped AWG 1Hz drive of ITMYs (south-arm) I still see unblocked beams at the ETMYs table. We have plenty of cleaned razor beam traps to be used. Please block Faraday rejects etc