PSL Table doors were open, and the laser shutter was closed.
Doors have been closed, laser has been opened.
Sorry, that was me; taking some photos of the PSL and EX mirrors.
We found the PSL laser switched off. Looking at the wall StripTool, it looks like this happened about 4 hours ago. Gautam was working at and around the PSL table, and I suspect he accidently ran into the Big Red Button.
We turned the laser back on.
As part of the ongoing effort to try and calibrate the PMC DAQ channels into physical units, I tried to get a calibration for the PSL NPRO PZT actuator gain. In order to do this, I selected "Blank" on the PMC servo MEDM screen such that there was no feedback signal to the PMC PZT for length control. Then I used the summing box right before the PSL PZT to inject a ~1Hz triangular wave, 4Vpp. This was sufficient to sweep the NPRO frequency over 70MHz such that both sidebands and the carrier go through resonances in the PMC cavity. I then simultaneously monitored the applied triangular wave voltage and the PMC error signal (using the single pin LEMO connector on the front panel) on an oscilloscope. Analysis is underway, but a quick look at one measurement suggests a PZT actuator gain of ~1.44MHz/V, which is close to what we expect for the Innolight NPROs. The idea is to use this calibration to convert the DQ channels into physical units.
Details + plots + error analysis to follow...
By sweeping the laser frequency and looking at the PMC PDH error signal, I have determined the 2W Mephisto Innolight PZT actuator gain to be 1.47 +/- 0.04 MHz/V.
An example of the data used to calculate the actuator gain (left), and the spread of the calculated actuator gain (right - error bars calculated assuming 5e-4 s uncertainty in the sideband zero-crossing interval, and using the error in the slope of the linear fit to the sweep voltage):
This will now allow calibration of the PMC DAQ channels into Hz.
GV 4 April - The y-axis of the lower plot in Attachment #1 has mis-labelled units. It should be [V], not [MHz/V].
good cal. I wonder if this data also gives us a good measurement of the cavity pole or if the photo-thermal self-locking effect ruins it. You should look at the data for the positive sweeps and negative sweeps and see if they give the same answer for the cavity poles. Also, maybe we can estimate the PMC cavity pole using the sidebands as well as the carrier and see if they give the same answer?
At around 10:30AM today morning, the PSL mysteriously shut off. Steve and I confirmed that the NPRO controller had the RED "OFF" LED lit up. It is unknown why this happened. We manually turned the NPRO back on and hte PMC has been stably locked for the last hour or so.
There are so many changes to lab hardware/software that have been happening recently, it's not entirely clear to me what exactly was the problem here. But here are the observations:
Steve says that this kind of behaviour is characteristic of a power glitch/surge, but nothing else seems to have been affected (I confirmed that the X and Y end lasers are ON).
The particle counter on the 40m PSL was removed. The package was made together with the OMC lab particle counter (see the packing list below).
The kit was picked up by Radhika for a python code to read out the numbers.
=== Packing List ===
I was looking into why we don't have any light on the PSL pointing QPDs, and it turns out that it has been this way since ~June 29th 2012. I need to look back in the elog to see what was going on on the PSL table that day, but I suspect it has something to do with Yuta and I, working on the beat setup, since this is all very near that area.
Attached is a plot of the loss of signal on the QPDs.
We lost IP POS on the same day as we lost the PSL pointing. See 2nd attachment. The _S_Calc is the sum, and it almost looks like the light got near the edge of the diode and just kept falling off until it was gone. The sum started getting lower on May 16th, and then was gone on June 29th.
So far I've gone back as far as Jan 2012, but I still haven't found any data where we *did* have light on IP ANG. Sad.
UPDATE, UPDATE (like P.P.S.): June 29th was the day of the vent...see elog 6895.
I used existing BNC cables running from the PSL table to the PSL rack and reassigned them to the PSL Shutter and PMC transmission PD channels.
The PSL shutter turned out to be a sinking channel. Jordan reconnected the PSL shutter wires to a sinking BIO Acromag. Channel list is updated.
Both channels have been tested to be working as expected.
gautam add on about EPICS:
P.S - there is a problem we noticed - if the modbus process is started with the local subnet not having a fixed IP address, then all the EPICS channels will not be responsive. The way to fix this is to run the following sequence of commands:
With the Acromag chassis now permanently installed, we tested the C1PSL channels going over the channel list one by one, excluding the IMC channels which Gautam is taking responsibility for (the servo board itself is also in question).
The strategy is to check the response of input channels to specific output channels for expected behaviour whenever is possible.
We marked on the channel list spreadsheet the status of the channels that were tested.
In more detail
PMC Servo Card
Unlocked the PMC by switching C1:PSL-PMC_SW1. Tweaked C1:PSL-PMC_RAMP and observed a change in C1:PSL-PMC_PZT.
We misaligned MC1 to get a measurable signal in WFS channels. NDScoped the corresponding C1:IOO-WFS*_SEG*_I&Q channels and observed a change in those channels in response to switching the attenuation on and off.
The signals were compared to previous values for consistency. Then they were unplugged from the Acromag chassis to confirm their values went to 0 and returned to the same values after being reconnected.
Fri Feb 03 19:57:20 2012
Fri Feb 03 20:25:19 2012 : Aligned all SUS to center their OL beams
Fri Feb 03 20:29:21 2012: Aligned all SUS to make OL_PIT = 0.5
About 3.5 hours ago, all the PSL wall StripTool traces "flatlined", as happens when we had the EPICS freezes in the past - except that all these traces were flat for more than 3 hours. I checked that the c1psl slow machine responded to ping, and I could also telnet into it. I tried opening the StripTool on pianosa and all the traces were responsive. So I simply re-started the PSL StripTool on zita. All traces look responsive now.
The PMC was unlocked when I came in ~10mins ago. The wall StripTool traces suggest it has been this way for > 8hours. I was unable to get the PMC to re-lock by using the PMC MEDM screen. The c1psl slow machine responded to ping, and I could also telnet into it. But despite burt-restoring c1psl, I could not get the PMC to lock. So I re-started c1psl by keying the crate, and then burt-restored the EPICS values again. This seems to have done the trick. Both the PMC and IMC are now locked.
Unrelated to this work: It looks like some/all of the FE models were re-started. The x3 gain on the coil outputs of the 2 ITMs and BS, which I had manually engaged when I re-aligned the IFO on Monday, were off, and in general, the IMC and IFO alignment seem much worse now than it was yesterday. I will do the re-alignment later as I'm not planning to use the IFO today.
This was me. I restarted the front ends when I was getting the MX streams working yesterday. I'll try to me more conscientious about logging front end restarts.
PSL Shutter closed / MC Autolocker disabled / PSL mechanical shutter closed / Laser injection current turned to zero / Laser turn off (red button) / Laser key turned off
The laser stat before the shutdown:
- LD Temp A: Set 22.07 (Untouched)
- LD Temp B: Set 21.03(Untouched)
- Laser Injection Current: Dial 9.53, Actual 2.100 -> Dial was moved to zero upon shutting down
- Laser Crystal Temp: Dial 3.34 (untouched) Set 30.57 Actual 30.60 (Untouched)
PSL Table covering
- Because of the so many cables going up and down, sealing the PSL table with the metalized sheet was not easy. Therefore, the sheets have been just softly laid above the optics. (Attachment 1)
- The largest sheet which covers the east half of the table was taped to the table at the bottom, so that the air from the chimneys (see below) does not come up to the table
- The large dust could come from the opening of the enclosure during the filter replacement. So it was considered to be easier to seal the openings. (Attachment 2)
- Of course, the HEPAs are going to be tested after the maintenance work. It means that vent paths were needed so that the seals do not explode with the pressure (together with dust).
- Thus, the tubes of the sheets are attached to the seals to form "chimneys" for guiding the airflow beneath the table. (Attachment 2/3/4)
- This configuration was not meant to be sufficiently strong for a continuous run of the fans. Long running of the HEPAs may cause the failure of the seal tapes.
Therefore the HEPA test should be done with a low flow rate and/or a short period of high flow.
- Once the work has been done, all the sheets should be carefully removed without scattering the fallouts onto the optics.
I also located the (possible) HEPA filters in the lab. (Attachments 1~3)
Oh! This is NO-NO! We can't place anything in front of the mains breakers. (Attachment 2)
I relocated the objects (Attachment 3)
I made a wiki entry for the PSL table diagram under the PSL directory on the 40mHomePage. I tried to use the ImageLink macro to use a resized (smaller) version of the diagram as a link to the full image, which it is designed to do if there is no target given, but it didn't seem to work. Instead, I had to create a second page that had the full-sized diagram, and I used ImageLink with a smaller version to link to that page.
The inventory that is shown is clearly incomplete. Part of this is due to the fact that many labels were either missing or impossible to read without touching stuff. For those components with labels missing, I tried to infer what they were to the best of my knowledge, but I wasn't able to for all of them. In true wiki spirit, everyone is encouraged to fill in any additional information they might have on these components.
Thanks. I love this. Could you also put the original file that is editable for future modification by anyone?
Do you mean the diagram or the inventory? The diagrams are online as attachments (small versions on the main "PSL Table Diagram" page and large versions on the linked pages). The inventory is easily editable on the wiki itself. It's just rendered in table form using the CSV parse utility for "comma-separeted values" (though you actually need to use semicolons, for reasons unknown).
Diagram. I don't want to say PNG is an editable format for this purpose...
You have the PPT, PDF or any drawing format to create this diagram.
Diagram. I don't want to say PNG is an editable format for this purpose...
You have the PPT, PDF or any drawing format to create this diagram.
Good news and bad news. For the MOPA diagram, which I did recently, I have GIMP file with separate layers for the background image, ray traces, and labels. Unfortunately, I didn't realize that this was the best way to do it until I had done most of the ray tracing for the main diagram, so, although I have that file in GIMP as well, only the labels are on a separate layer. If this is a major issue I can do the tracing again. The other thing is that the original files are quite large: 17.3 MB for the MOPA, and 64.1(!) MB for the main diagram. Let me know what you think.
Some photos are attached in this entry. All of the photos found in the picasa album (click the slideshow)
I put the PSL telescope in place, and started coupling to it.
Unfortunately, I was only able to couple about 55 uW into the "fiber coupler" (read: fiber coupled splitter). See picture below:
Additionally, I'm not sure why this is, but both of the splitters we ordered don't split equally, but to 90% and 10% in each output port.
We also found that, since we aren't using the fibers we originally intended to, the specs are a little different, and the waist we're trying to have at the collimator face is now 283 um.
I used the free software called 'ABCD' for Mac to construct this mode matching solution for going from the PMC to the IMC.
After getting it close by eye, I plugged the initial guess into Matlab and let it optimize the distances. I then plugged this into 'ABCD'
to get the exact solution. ABCD doesn't actually optimize anything; it just makes a nice table and graphically plots the solution.
The part numbers for these lenses are:
In a manner similar to the now classic 'Mode Matching from PMC to IMC' entry, I have calculated the lenses and positions needed to match the 2W NPRO beam into the PMC.
The added complication is that we also want to have a reasonable beam size to get into the Faraday and the AOM. It seems that this should be possible using one lens.
After the beam comes out of the AOM, there's another lens to match to the PMC. Its possible to do this with more lenses, but this is just an effort to minimize the number
of surfaces in the beam.
Thoughts on where to take the pickoff for the SHG for the PSL-green? We discussed today at the meeting the possibility of putting a 90/10 beam splitter right after the PMC, so that the green team would get somewhere between 100-200mW.
I moved the epics IOC server process for the single Acromag ADC that monitors the PSL signals from megatron to c1auxex2.
First, I disabled the legacy support on all channels as explained in elog 13565. Then I copied the files npro_config.cmd and NPRO.db from /opt/rtcds/caltech/c1/scripts/Acromag to /cvs/cds/caltech/target/c1psl2/ following the pattern of the old Motorola machines and the new c1auxex2. I had to make some edits for correct paths and expanded the epics records to the standard we're using for ETMX.
I then added a service to systemd on c1auxex2 that runs the epics IOC for the Acromag PSL channels: /etc/systemd/system/modbusPSL.service. No more tmux on megatron.
Running two IOCs on a signle machine at the same time did not produce any errors and seems fine so far.
//edit Manasa// Harry will update this elog with before/after pictures of the table and power of the 1064nm rejected beam from the SHG.
While making these measurements, I reduced the Y end laser power (decreasing the current) so that we could use the beam profiler without burning anything and then brought it back up to the nominal power after the measurements were done.
We wanted to take measurements of "waists" of the PSL and AUX (Y-Arm) so I can then design a telescope to couple both into fibers for use in FOL.
For both lasers, PSL and AUX, I measured the profile of the dumped red (1064nm) beams coming out of the second harmonic generators, as this is the light that we will be using in FOL.
The power in the beam I measured from the PSL was 87.5 mW, and the power in the measured beam at the end table was 96 mW (when reduced from nominal power).
I used the beam profiler to take measurements of spot size at multiple points along the optical axis of both lasers.
An issue with these measurements was space constraints. In other words, there was no room on either table for a translation stage to hold the Profiler. I used a tape measure to determine Z-Coordinates. However, especially in the case of the AUX laser, parallax error caused uncertainty in my position measurements, which I would estimate at plus and minus 1.5cm.
I then fit these data using ALM to determine waist size and location for use in telescope design.
Z = 0 in the PSL graph is the face of the first mirror in the beam path, and in the AUX graph Z = 0 is the face of the SHG.
My measurement of the PSL gave:
X Waist = 43um at z = 6.8mm, as measured from the face of the SHG.
Y Waist = 44um at z = 6.8mm, as measured from the face of the SHG.
AUX Measurements gave:
X Waist = 44um at z = -3.1mm from the SHG face
Y Waist = 36um at z = -3.6mm from the SHG face
Find attached alm files in .zip
Movement on the Tables
In order to facilitate the measurements, we needed to move some things around, as pictured below.
On the PSL table, we installed a steering mirror after the Green filtering mirror, which is immediately after the SHG output, in addition to appropriate beam dumps.
At the end table, we removed some unused optics, as well as a PD, which were in the way . //edit// manasa: We removed IPANG (which has no light on it) and the associated steering optics.
Either tonight or tomorrow morning, I will use these data to design coupling telescopes for the PSL and AUX light.
Tomorrow, I will couple both lasers to fibers, and hopefully finish assembling the optics for FOL
Earlier today, we did a bunch of stuff to see if we could improve the situation with the excess ALS-X noise. Long story short, here are the parameters that were changed, and their initial and final values:
X-end laser diode temperature: 28.5 degrees ---> 31.3 degrees
X-end laser diode current: 1.900 A ---> 1.942 A
X-end laser crystal temperature: 47.43 degrees ---> 42.6 degrees
PSL crystal temperature: 33.43 degrees ---> 29.41 degrees
PSL Diode A temperature: 21.52 degrees ---> 20.75 degrees
PSL Diode B temperature: 22.04 degrees ---> 21.3 degrees
The Y-end laser temperature has not yet been adjusted - this will have to be done to find the Y-beatnote.
Unfortunately, this does not seem to have fixed the problem - I was able to find the beatnote, with amplitude on the network analyzer in the control room consistent with what we've been seeing over the last few days, but as is clear from Attachment 1, the problem persists...
Some details not directly related to this work:
Is the black ref spectrum from this year or from May of 2015 or ?
I wonder if the noise is a bunch of fast spikes or if its a true broadband rumble. Maybe we can tell by looking at the analog DFD or PLL outputs?
Found the IR beatnote between PSL and Y end laser.
Since our goal was to find the beatnote ASAP to recover ALS, I ignored the fine details in alignment. I will revisit the setup to make some improvements in the near future.
1. Coupled the PSL IR beam leaking after the doubler into the fiber. We have only 10% coupling into the fiber at the PSL table right now (6mw); but this will be improved once I get a suitable translation stage for the telescope.
2. PSL IR --> PM980 fiber --->50-50 fiber beam splitter ---> 50-50 fiber beam combiner
AUX Y ---> PM980 fiber ---> 50-50 fiber beam combiner
The output port of the fiber beam combiner is connected to the fiber coupled broadband RF PD.
3. The RF output of the PD when connected to a spectrum analyzer shows a beatnote of -50dBm. The small amplitude of the beatnote is due to the laser power being attenuated before coupling into the fiber to keep the PD safe.
Attached is photo of how the setup is put on the PSL table. We will put all the stuff in a box once the X setup is also in place.
Green beatnotes recovered.
It was just a matter of aligning the arm greens and PSL greens on the PSL table. I suppose something knocked the PSL alignment out of whack... I was also able to simultaneously see the green beatnote and IR beatnote respond to Yend laser temperature.
Locked arms on POX/POY, checked RMS of ALS-BEAT[X/Y]_FINE_PHASE_OUT_HZ channels.
These seem fine. Locked CARM and DARM on ALS, found IR resonances.
ALS is back in business
The attached plot shows 2 day trends of the PMC and MC reflected and transmitted power, the PSL POS/ANG QPD signals, and the temperature measured by the dust counter.
The power step in the middle of the plot corresponds to Koji/Jenne PMC realignment yesterday.
It looks like everything is following the day/night temperature changes.
The attached plot shows 7 day trends of the MC and PMC power levels, PSL QPDs, and temperature. The MC stayed locked for ~40 hours over the weekend. The temperature swings were somewhat smaller over the past couple of days but one should remember to turn the PSL HEPA down after working on the table. Steve turned the HEPA flow from 100% down to 20% on Thursday and posted the reminder signs on the PSL enclosure.
We aligned the PSL green optics so that the PSL green beam and Y arm green beam interfere. 2 beams are now hitting the Y arm beat PD. The DC level from the beat PD is about 13 mV.
We didn't try to see the beat signal for today, because the temperature of the doubling crystal seemed funny. We need to look into it tommorow.
Currently, the temperature control is enabled and the set point is 36.9 deg C, but the temperature is stuck at 33.0 deg C.
I checked a broken QPD, which was placed for PSL angle monitor, and finally I cocluded one segment of the quadrant diode was broken.
The broken segment has a offset voltage of -0.7V after 1st I-V amplifier. It means the diode segment has a current offset without any injection of light.
Tomorrow I will check a new QPD for replacement.
Kakeru and Kiwamu
We placed a QPD on the PSL bench for PSL angle monitor.
As we mentioned before, old QPD which used to be placed is broken.
And we put broken QPD into the "photodiodes" box under the soldering table.
Today I tuned the periscope on the PSL table to align the beam to the Mode Cleaner. With the Wave Front Sensor control off, I minimized the reflection from the MC and maximized the transmission. While doing that I also checked that the transmitted beam after the MC didn't lose the alignment with the interferometer's main Faraday isolator.
In this way, I've got a reflection, as read from the MC_REFLPD_MC, of about 0.6. Then I centered the WFS on the AS table. After that the WFS alignment control brought the reflection to 0.25 and a nice centered bull-eye spot showed on the monitor.
More PSL progress.
The new laser was raised to a 4 inch beam height using basically the most randomly thrown together method possible. (It'll work just fine for aligning things, but we seriously need to get a nice block made.) The PMC and the nice Osamu-mirror mount to go into the PMC also have temporary risers, so we'll need to replace them with the real deal as soon as we get things back from the shop.
So far we've got (1) the lens after the laser, (2) a Half Wave Plate (no quarter wave plate yet), (3) steering mirror that will go after the EOM, (4) 2 steering mirrors to get into the PMC, in addition to all of the stuff that we did the other day. With all of this stuff we've got the beam hitting the 1st PMC mirror. We still don't have the EOM and AOM in the beam path however.
To get the rough alignment that we did, we turned on the new 2W NPRO, operating at the minimum power we could see on a card. We turned it off after use, so it is still off. Steve, we left the cable for the interlock sitting on the PSL table on the NW corner....can you please hook it up tomorrow? Also, after the interlock is installed we should go back to regular running laser hazard mode.
Koji and I inspected and photographed the laser after opening up its case. I then drilled the clearance holes in the 4 corners and tapped holes for 1/4-20. I was careful to tap with the laser sideways, to avoid shavings getting into the laser and suctioned out as much of the pieces as I could. The laser is now mounted on some bad 1/4-20 based NewFocus style pedestals. The riser block can now be made with 1/4-20 through holes and the laser will sit on its for corner feet. We'll make the base aluminum to avoid differential CTE based stress in the laser base.
We checked the level of the laser. With the new mounting the beam is level to within ~1 mrad and has a 4" beam height.
I've mounted the Faraday Rotator from the old MOPA. It has 8-32 mounting holes (who's shafts are curiously not parallel). We need an aluminum block of the proper height (2 3/4" ??) to make a permanent solution.
I've also mounted the thin-film polarizer. This works well, but it also needs a block machined to get the mounting to be less Mickey Mouse.
Pockel Cell for phase correction and 35.5 MHz PMC modulation
The EOM is mounted as before on the angle bracket to align it for P-pol light. The beam now goes cleanly through there. No further mounting hardware required.
The 2 lenses in the 'mode matching telescope' between the laser and the PMC are in place, but not placed with any accuracy.
By sheer luck, I saw the PMC flashing in the TEM27 mode without any alignment from me. Next step is to get the lens positions tuned and then do the beam scan on the beam going towards the PMC to verify the approximate mode matching. This is all crude, but I just want to get the beam going into the vacuum as fast as possible.
I realigned the PSL beam going into the MC.
The MC beam was realigned so as to maximise the power in the MC. I minimised the MC_RFPD_DCMON dial on the MC_ALIGN screen while adjusting the two zig-zag mirrors at the end of the PSL table.
I found the PSL beam into the MC off in pitch by large amount. I readusted the PSL beam for optimal coupling.
The beam had shifted on the WFS as well. So I recentered the DC signal on the WFS with the MC unlocked. However both the DC and RF signals on the WFS shift when we lock the MC. This ought to indicate sub-optimal coupling of PSL into MC. But instead, if we were to reduce these offsets on the WFS by adjusting the MC axis it leads to higher reflected power from the MC.
The current plan is to retain these RF offsets and lock the WFS with a DC offset in the servo filters.
The MC coupling had become re-shittified. As we need transmitted MC light for the RAMmon, I realigned the input beam to the MC. (Jenne said that the MC mode itself should be well aligned, so I just used the zigzag on the PSL). MC_REFL is now ~0.5-0.6.
Of course, looking at the MC transmission os the important thing, but I wonder if maybe we should also monitor the beam before it goes into the MC just to see if its the fault of the MC-WFS or not. In the bad old MZ days, I remember that the MC mirror alignment would drastically change the post-MC RAM.
It requires another PD/demod set, but may be illuminating in the end.
Also, can someone please add some channels to EPICS which calibrate the RAM channels into RAM units?
I noticed that the beam centering on the WFS had changed over night and the MC_TRANS_SUM was about 40k counts. When well aligned this SUM is around 50-55k counts. So PSL coupling into MC was suboptimal. It was not clear whether the MC shifted or the PSL beam shifted. So I looked at the PSL ANG and POS QPDs.
The plots above show the gradual drift of the PSL beam in vertical direction during the last 8hrs or so. But the last bit shows the adjustments I had to make to reobtain optimal alignment. And these adjustments are not undoing the drift! This would indicate that the MC axis has also shifted during the same time period.
[ Kevin and Kiwamu ]
We made the setup for the green PLL stuff on the PSL table.
Now the two green beams are happily going to the RFPD.
Tomorrow we try to catch the beat note signal
- - - what we did
* took the two light doors out from the OMC and the MC chamber in order to let the green light go through there.
* using aluminum foils we covered the space between the OMC and the MC chamber in order to protect from dust
* aligned the steering mirrors inside of the chamber because the height of the green light coming out from the chamber had been a little bit low at the PSL table.
* at the PSL table we put several steering mirrors and a beam splitter which combines the two green lights
* installed Hartmut's RFPD and applied -150V bias on it.
* put a lens on each path of the green beam in order to make the beam size approximately the same at the RFPD
* closed the light doors
- - - Notes
* At the beginning, an output signal from the RFPD was pretty small ( less than 1mV at DC ), so I replaced a feedback resistor that was 241 Ohm by 24 kOhm.
As a result the signal became about 10mV when the green lights go into the PD.
* Actually the power of the green beams are so weak.
I measured them by using a Newport power meter, it said something like 4 uW for both of the green lights.
One of the reasons is that the transmitted light from the PMC which generates one of the green lights is already weak. It's about 480 mW ( while more than 600 mW was reflected by the PMC ! ).
I am going to make sure if these numbers are reasonable or not.