40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
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ID Date Authorup Type Category Subject
  9579   Mon Jan 27 21:36:35 2014 ericq UpdateGeneralVent so far

After turning the slow FSS threshold down, the mode cleaner stays locked enough to do other things. We were able to align the tip tilts to the y-arm such that we were able to get some flashes in what looks like a TM00-ish mode. (It was necessary to align the PRM such that there was some extra power circulating in the PRC to be able to see the IR flashes on the ITMY face camera) This is enough to convince us that we are at least near a reasonable alignment, even though we couldn't lock to the mode. 

The x-arm was in a hairier situation; since the green beam wouldn't flash into any modes, we don't even know that a good cavity axis exists. So, I used the green input PZTs to shine the green beam directly on the earthquake stops on the ITMX cage, and then inferred the PZT coordinates that would place the green beam roughly on the center of ITMX. I moved the ETMX face camera such that it points at the ETMX baffle. I tried looking for the retroreflected green spot to no avail. Hopefully tomorrow, we can get ourselves to a reasonably aligned state, so we can begin measuring the macroscopic PRC length. 

  9583   Tue Jan 28 22:24:46 2014 ericq UpdateGeneralFurther Alignment

[Masasa, ericq]

Having no luck doing things remotely, we went into the ITMX chamber and roughly aligned the IR beam. Using the little sliding alignment target, we moved the BS to get the IR beam centered on ITMX, then moved ITMX to get good michelson fringes with ITMY. Using an IR card, found the retroflection and moved ETMX to make it overlap with the beam transmitted through the ITM. With the PRM flashing, X-arm cavity flashes could be seen. So, at that point, both the y-arm and x-arm were flashing low order modes. 

  12302   Thu Jul 14 22:29:57 2016 ericq UpdateGeneralETMX guide rod gluing / ETMY Magnet gluing

The pickle puckers came off ETMY cleanly yes ETMY now rests in the ring holder, under a glass jar, with all of its magnets.

We removed the guiderod gluing fixture from ETMX without any apparent damage to the fixture arm, optic, or guiderod epoxy joint. 

I started measuring some distances on the optic for the side magnet gluing, but am not sure of it yet. So, I didn't manage to start the gluing today. 

  12305   Fri Jul 15 16:23:51 2016 ericq UpdateGeneralGluing setbacks

[ericq, Lydia]

Here is a picture of the ETMX guide rod post-gluing. There is unfortunately a fair amount of excess. The "tab" is the result from the epoxy travelling along the finger of the fixture arm that held the guide rod.

We set out to glue the previously remove ETMX side magnet, and set up the fixture to do so. For ETMX we needed 3 mm of shimming on the thick side, and 6mm on the thin side.

However, while cleaning the magnet+dumbbell base of epoxy residue, I broke the dumbbell off of the magnet no

We then fetched the spare side magnet that Steve had been holding onto. While cleaning it, it was dropped and dissapeared from this plane of existence nono

So, instead of gluing a side magnet today, we are gluing the existing magnet and dumbbell back together:

Sadly, this used up the last of our EP30.nonono

Though Koji had the foresight to order more(yes), it will not arrive until Monday/Tuesday, so no side magnet gluing until then.frown

  12372   Thu Aug 4 14:21:21 2016 ericq UpdateComputer Scripts / ProgramsWeb things mostly back online

The nodus restart caused a bit of downtime. The apache configuration files were accidentally deleted the other day, so elog/svn/wikis were just holding on in memory; this fact was unfortunately not elogged. 

Things should be up and running again, except for the 8080->8081 elog redirection which I haven't been able to figure out.

I will also set up the NFS backup to include nodus configuration files from now on

  12373   Thu Aug 4 15:00:40 2016 ericq UpdateComputer Scripts / ProgramsWeb things mostly back online

Nodus' /export and /etc directories are now being backed up at /cvs/cds/caltech/nodus_backup

They will be rsync'd over as part of the nightly tape backups (scripts/backup/rsync.backup)

  12382   Sun Aug 7 14:53:39 2016 ericq UpdateSUSETMX Standoff gluing was successful

I came in to check on ETMX. I freed the earthquake stops, and found that the OSEMS were reasonably, but not perfectly, centered. Turning on the damping, I found that the pitch balance is biased slightly downwards at about ~0.5mrad, which is acceptable. 

As another check for how much we moved the standoff while gluing, we can look at the spectra of the OSEMS while the mirror is free swinging, and see if/how the resonance frequencies have moved around. As Gautam previously mentioned, the pitch frequency is even softer than we expected from the thicker ruby standoff alone. This is due to the excess glue around the guide rod forcing us to position the standoff even lower to have good contact with the optic's barrel. In the plot below, the design yaw/pit/pos frequencies are the dashed lines, and the measured frequencies are the solid lines. 

[The plot is not in spectral density units, so that the peak heights reflect real units of motion at each resonance frequency. Data and code used to generate the plot is attached] 

  Yaw Pitch Pos Side
Design frequencies from T000134: 0.773 Hz 0.856 Hz 1.001 Hz  
ETMX Measurement in-air 2010 0.828 Hz 1.04 Hz 0.908 Hz 0.949 Hz
Pre-gluing 0.785 Hz 0.709 Hz 0.949 Hz 0.975 Hz
Post-gluing 0.789 Hz 0.705 Hz 0.953 Hz 0.984 Hz

According to the calculations from ELOG 12316, this pitch frequency implies the support point is 0.317mm lower than the design value of 0.985mm. (However, this is just an approximation and does not include the fact that each standoff is at a different height.)

Nevertheless, this difference is frequency is not so large that the dynamics of the suspension will be qualitatively changed in some important way; really, the pitch frequency is just ~1.5dB lower. So, I deemed our standoff gluing a success, removed the optic from the suspension, and placed it in an optic holding ring after giving the top of the barrel a gentle drap wipe with some iso. At this point, I used the microscope to look at the ruby standoff groove. As far as I can tell, no glue has invaded the groove - it looks sharp as ever. (whew)

I also wiped the wire with acetone and easily removed the glue droplets. However, I noted that (as is the case for ETMY) the wire is deformed at the points where it was in contact with the standoffs. I wonder if we should re-suspend with new wire, or accept the current deformed wires.

In any case, we can now move on to air baking the ETMX tower and gluing the stray magnet back onto ETMY.

Attachment 1: ETMX_resonances.pdf
ETMX_resonances.pdf
Attachment 2: ETMX_SUSspectra.zip
  7388   Fri Sep 14 16:39:14 2012 ericq, jenneUpdateGeneralFirst In Vac Picture

After much fussing, we got a picture of MMT1 with the beam.

Using the iris doesn't seem feasible. Since it has to be significantly separated from the optic, it is hard to judge whether it is centered, especially in yaw.

It took ~30 min to get this picture. Comments on whether this kind of picture is good enough are welcomed, since there are many more to be taken.

Attachment 1: mmt1.jpg
mmt1.jpg
  10363   Mon Aug 11 21:03:48 2014 ericq, ranaSummaryIOOMC demod measurement

We measured the TF of the MC Demod board today.

We set the Marconi to +3dBm and drove the PD IN port of the demod board, starting at 29.5 MHz. Then we looked at the beat signal amplitude in the output of the demod board. So this is a transfer function but with mag only. Plots from Q below.

Rana took the demod board out and took pictures of it. Inside, the post mixer low pass is a SCLF-5 from mini-circuits. This has a lot of cutoff down low. Since the purpose of this filter is only to cutoff the 2f-1f and the 3f-2f products, we need to have a lot of attenuation at 29.5 MHz. One day, we may want to re-instate that notch for the (3*f1- f_MC) beat frequency, but for now we want stability.

So, I recommend that we (Steve) get 3 each of the SCLF-10 and SCLF-10.7 from Mini-Circuits Tuesday morning. Maybe we can put them into a spare board?

Also, we should probably remove the 140kHz:70kHz lead filter which is in the MC servo board. Its out of date. I think it would be fine for us to get a 7-15 kHz UGF for the CM servo and the MC can basically do that already. Mainly we want to fix the high frequency shape to get more stability.

After the measurements and photos, we had to reset the MCWFS offsets to get the WFS to not break the lock. Seems very sensitive to offsets. Hopefully Andres will give us a new Gouy phase telescope.

  10935   Fri Jan 23 14:25:03 2015 evanUpdateCDSNew netgpib scripts for SR785

Does netgpibdata/TFSR785 work at the 40m currently? I rsynced the netgpibdata directory to LHO this morning to do some measurements, but I had to modify a few lines in order to get it to call the SR785 functions properly. My version is attached.

Attachment 1: TFSR785.zip
  228   Wed Jan 9 10:47:15 2008 frickeUpdateComputersethernet wiring in office/control room
The electrical people have been here for three days, installing ethernet cables and drops in the 40m office area, in the old conduits where there was power and 10base2. Soon we will have reliable ethernet connections, instead of relying on switches hanging from the ceiling, etc!
  9575   Sat Jan 25 21:09:16 2014 gabrieleHowToLSCProcedure to measure PRC length

I know the drawing is wrong. I put random distances, not realistic ones, and I did not try to get something close to reality. Once we put the measured distances, the drawing should (hopefully) be correct.

  12063   Tue Apr 5 11:42:17 2016 gaericqutamUpdateendtable upgradeTABLE REMOVAL

There is currently no table at the X end!

We have moved the vast majority of the optics to a temporary storage breadbord, and moved the end table itself to the workbench at the end. 

Steve says Transportation is coming at 1PM to put the new table in.

  8684   Wed Jun 5 20:45:19 2013 gautamUpdateGeneralITMx Oplev Fixed

Quote:

 (Manasa)

The ITMx Oplev was misaligned. Switched the ITMx Oplev back on and fixed the alignment.

EDIT, JCD:  This is totally my fault, sorry.  I turned it off the other day when I was working on the POP layout, and forgot to turn the laser back on.  Also, I moved the fork on the lens directly in front of the laser (in order to accommodate one of the G&H mirrors), and I nudged that lens a bit, in both X and Y directions (although very minimally along the beam path).  Anyhow, bad Jenne for forgetting to elog this part of my work.

 [Jenne, Gautam]

It turned out that the earlier fix was not really a fix, because there was some confusion as to which of the two lenses Jenne moved while working, and while Manasa and I were re-aligning the beam, we may have moved the other lens.

Subsequently, when we checked the quadrant sum, it was low (in the region of 20), even though OPLEV_PERROR and OPLEV_YERROR were reasonably low. We called up a 30 day trend of the quadrant sum and found that it was typically closer to 4000. This warranted a visit to the table once again. Before going to the table, we did a preliminary check from the control room so as to make sure that the beam on the QPD was indeed the right one by exciting ITMx in pitch (we tried offsets of 500 and -500 counts, and the spot responded as it should). ITMx oplev servo was then switched off.

At the table, we traced the beam path from the laser and found, first, that the iris (I have marked it in one of the photos attached) was practically shut. Having rectified this, we found that the beam was getting clipped on the first steering mirror after the laser (also marked in the same photo, and a second photo showing the clipping is attached). The beam isn't very well centred on the first lens after the laser, which was the one disturbed in the first place. Nevertheless, the path of the entering beam seems alright. The proposed fix, then, is as follows;

  1. Use the existing iris and a second one to mark the path of the entering beam.
  2. Make the necessary adjustments (i.e. move the lens immediately after the laser and the first steering mirror after the laser) such that the direction of the entering beam is unchanged, and the clipping and centering problems are resolved. 

Back in the control room we noticed that the quadrant sum had gone up to ~3500 after opening out the iris. The OPLEV_PERROR and OPLEV_YERROR counts however were rather high (~200 counts in pitch and ~100 counts in yaw). Jenne went back to the table and fixed the alignment such that these counts were sub-10, and the quadrant sum went up to ~3800, close to the trend value. 

At the time of writing, the beam is still not centred on the lens immediately after the laser and is still getting clipped at the first steering mirror. Oplev servo back on.

Photos

 An overview

ITMx_overview.JPG

 

The clipping

ITMx_clipping_.JPG

  8688   Fri Jun 7 17:12:46 2013 gautamUpdateGeneralProjector - lightbulb replaced

Quote:

Quote:

Update: We don't have our BIG screen 

There was no light from the projector when I came in this morning. I suspected it might have to do with the lifetime of the bulb. But turning the projector OFF and ON got the projector working....but only for about 10-15 seconds. The display would go OFF after that. I will wait for some additional help to dismount it and check what the problem really is.

 

 

  • Shipping Estimate Friday June 7, 2013 - Monday June 10, 2013
    Delivery Estimate: Wednesday June 12, 2013 - Monday June 17, 2013 by 8:00pm
  • Lampedia Projector Lamp for VIEWSONIC PRO8200 / PRO8300
    Sold by: Lampedia

 [manasa, gautam]

-the replacement lamp arrived a while back.

-the old lamp has been switched out, it had 3392 lamp hours on it.

-new lamp installed, projector mounted back up, and lamp hours reset to zero. there is a lingering odour of something burning, not sure what it is or if it is in any way connected to the new lamp. old lamp disposed in the hazardous waste bin. the big screen is back online.

  8735   Thu Jun 20 20:46:16 2013 gautamUpdateIOOWFS debugging-QPD debugging

 

 I wanted to make sure that the QPD map on the C1IOO_MC_TRANS_QPD.adl screen corresponded to the actual physical quadrants on the photodiode at the MC2 table. We turned MC_WFS_OUT  OFF before fiddling around with a red laser pointer to try and map the quadrants.

I initially verified the correspondence between the various quadrants and the text-fields displaying the outputs using PV_Info. I found that there was good agreement in this respect. So for instance, field adjacent to the quadrant marked "1" on the C1IOO_MC_TRANS_QPD.adl screen had the following input channel: IOO_MC_TRANS_SEG1_INMON. The filter banks were empty and there was just an overall gain on -1 on all four channels. The channels leading to the filter-banks were the 'right' ones: quadrant 1 for the top bank, then quadrants 2,3 and 4 down.

Next, a red laser pointer was used to map the quadrants. Here, there was some disagreement between the physical quadrants and the map on the C1IOO_MC_TRANS_QPD.adl screen, which is summarised in the attached image-the whole thing is sort of rotated 180degrees about the centre. 

The interpretation of the figure is as follows:

quadrant 1 on screen QPD=bottom right quadrant on QPD

quadrant 2 on screen QPD=top right quadrant on QPD

quadrant 3 on screen QPD=top leftt quadrant on QPD

quadrant 4 on screen QPD=bottom left quadrant on QPD

MC_WFS_OUT was turned back ON.

 

 

 MC2_QPD-map.png

 

 

  8745   Tue Jun 25 12:42:16 2013 gautamUpdateGeneralSerial-interface with Doubling Oven at Y end

Summary 

I have been working on setting up a serial-link with the temperature controller of the PPKPT crystal doubling oven at the Y-end for some time now. The idea was to remotely tune the PID gains of the controller and get temperature data. The device used to serially interface with the temperature controller is a Raspberry Pi model B, which is connected to the temperature controller by means of a USB to serial adaptor with a PL2303 chip. I installed the interface this morning, and have managed get talking with the doubling oven. I am now able to collect time-series data by ssh-ing to the Raspberry Pi from the control room. I will use this data to manually tune the PID gains for now, though automatic tuning via some script is the long-term goal.

 

Details 

The temperature controller for the doubling oven is a Thorlabs TC200, and supports serial communication via the RS232 protocol by means of a female DB9 connector located on its rear panel. I have hooked up the Raspberry Pi to this port by means of a USB-Serial adaptor that was in one of the cabinets in the 40m control room. After checking the Martian Host Table, I assigned the Raspberry Pi the static IP 192.168.113.166 so that I could ssh into it from the control room and test the serial-link. This morning, I first hooked up the Raspberry pi to an ethernet cable running from rack 1Y4 to make sure I could ssh into it from the control room. Having established this, I moved the raspberry pi and its power supply to under the Y-endtable, where it currently resides on top of the temperature controller. I then took down the current settings on the temperature controller so that I have something to revert to if things go wrong: these are

Set-Point:                           35.7 Celcius

Actual Temperature:          35.8

P-gain:                                 250

I-gain:                                 60

D-gain:                                25

TUNE:                                  ON

I then connected the Pi to the temperature controller using the serial-USB cable, and plugged the ethernet cable in. Rebooted the Pi and ssh-ed into it from the control room. I first checked the functionality of the serial-link by using terminal's "screen" feature, but the output to my queries was getting clipped on the command line for some reason (i.e. the entire output string wasn't printed on the terminal window, only the last few characters were). Turns out this is some issue with screen, as when I tried writing the replies to my queries to a text file, things worked fine. 

At present, I have a python script which can read and set parameters (set-point temperature, actual temperature, PID gains)on the controller as well as log time-series data (temperature from the temperature sensor as a function of time )to a text file on the Pi. As of now, I have only checked the read functions and the time-series logger, and both are working (some minor changes required in the time-series function, I need to get rid of the characters the unit spits out, and only save the numbers in my text-file). 

For the time-being, I plan to apply a step to the controller and use the time-series data to manually tune the PID parameters using MATLAB. I am working on a bunch of shell scripts to automate the entire procedure.

  8746   Tue Jun 25 19:18:07 2013 gautamConfigurationendtable upgradeplan of action for PZT installation

  This entry is meant to be a sort of inventory check and a tentative plan-of-action for the installation of the PZT mounted mirrors and associated electronics on the Y-endtable. 

Hardware details:

  •  PZT mounts are cleaned and ready to be put on the end-tables.
  • The PZTs being used are PI S-330.20L Piezo Tip/Tilt Platforms. Each endtable requires two of these. The input channels have male single-lemo connectors. There are 3 channels on each tip/tilt platform, for tilt, yaw and a bias voltage.
  • The driver boards being used are D980323 Rev C. Each board is capable of driving 2 piezo tip/tilt platforms. I am not too sure of this but I think that the SMA female connector on these boards is meant to be connected with the bias voltage from our Kepco high-voltage power supplies. The outputs on these boards are fitted with SMB female connectors, while the piezo tip/tilt platforms have male single-lemo connectors. We will have to source cables with the appropriate connectors to run between the end-table and rack 1Y4 (see below). The input to these boards from the DAC will have to be made with a custom ribbon connector as per the pin out configuration given in the circuit drawing.
  • High-voltage power supply: KEPCO BHK 300-130 MG. This will supply the required 100V DC bias voltage to the piezo tip/tilts via the driver board. Since each board is capable of driving two piezos, we will only need one unit per end-table. The question is where to put these (photo attached). It doesn't look like it can be accommodated in 1Y4 (again photo attached) and the power cable the unit came with is only about 8ft long. If we put these under the end-tables, then we will need an additional long (~10m) cable to run from these to the driver boards at 1Y4 carrying 100 V. 
  •  We will need long (~10m by my rough measurement at the X and Y ends) cables to run from rack 1Y4 to the endtable to drive the piezos. These will have to be high-voltage tolerant (at least to 100V DC) and should have SMB male connectors at one end and female single-lemo connectors at the other. I have emailed 3 firms (CD International Technologies Inc., Stonewall Cables, and Fairview Microwave) detailing our requirements and asking for a quote and estimated time for delivery. We will need 6 of these, plus another cable with an SMA connector on one end and the other end open to connect the 100V DC bias voltage from the high voltage power supply to the driver boards (the power supply comes with a custom jack to which we can solder open leads). We will also possibly need ~3m long lemo-to-?(I need to check what the input connector for the data acquisition channels) cables for the monitoring channels, I am not sure if these are available, I will check with Steve tomorrow.

Other details:

  • I have attached a wiring diagram with the interconnects between various devices at various places and the type of connectors required etc. The error signal will the the transmitted green light from the cavity, and there is already a DQ channel logging this information, so nothing additional wiring is required to this end.
  • Jamie had detailed channel availability in elog 8580. I had a look at rack 1Y4, and there were free DAC channels available, but I am not sure as to which of the ones listed in the elog it corresponds to. In any case, Jamie did mention that there are sufficient channels available at the end-stations for this purposes, but all of these are fast channels. What needs to be decided is if we are going ahead and using the fast channels, or if we need to find slow DAC channels. 
  • I spoke to Koji about gluing the mirrors to the PZTs, and he says we can use superglue, and also to be sure to clean both the mirror and the tip/tilt surfaces before gluing. In any case, all the other hardware issues need to be sorted out first before thinking about gluing the mirrors.

High-Voltage Power Supply

photo_3.JPG

 

Situation at rack 1Y4

 

photo_4.JPG

 Wiring diagram

ASC_schematic.pdf

  8755   Wed Jun 26 11:45:06 2013 gautamUpdateGeneralPID tuning-Doubling Oven at Y end

 

Summary

Having established the serial link between the Doubling oven at the Y-end and the Raspberry pi, I wanted to use this interface to collect time-series from the oven after applying a step function in an effort to measure the transfer function of the oven. The idea was that knowing the transfer function of the oven, I could use some simple PID tuning rules like the Ziegler-Nichols rule or put everything in SIMULINK and find the optimal PID gains. However, I am unable to extract the oven transfer function from the time series data collected.

Methodology:

Last night, between 920pm and 940pm I applied a step function to the doubling oven by changing the setpoint of the controller from 35.7 Celsius to 39 Celsius (having checked elog 3203 to get an idea of a 'safe' step to apply). I then used the Pi to collect time series data for 6 minutes, then returned the set-point back to 35.7 Celsius, and took another time-series to make sure things were back to normal. Having gotten the time series data, I attempted to fit it using some exponentials which I derived as follows:

oven-loop.pdf

 

I couldn't think of a way to get the laplace transform of the time-series data collected, so I approximated the oven transfer function as a system with a one simple pole i.e. G(s)=K/(1+Ts), where K and T are parameters that characterise the oven transfer function. I then plugged in the above expression for Y(s) into Mathematica (knowing X(s)=constant/s, and H(s) = 250 + 60/s +25s from the PID gains) and did an inverse laplace transform to find a y(t) with two unknown parameters K and T to which I could fit the time-series data.

Results:

The time-series data collected via the Pi after applying the step was this:

Time_series.png

 The inverse laplace transform from mathematica yielded the following (formidable!) function (time, the independent variable, is x, and the fitting parameters are a=K and b=T where K and T are as described earlier):

 

(39*(exp(x*(1/(2*(25*a - b)) - (125*a)/(25*a - b) - sqrt(1 - 500*a+ 56500*a^2 + 240*a*b)/(2*(25*a - b)))) - exp(x*(1/(2*(25*a - b)) - (125*a)/(25*a - b) + sqrt(1 - 500*a + 56500*a^2 + 240*a*b)/(2*(25*a - b)))))*a)/sqrt(1 - 500*a + 56500*a^2 + 240*a*b)

My best attempts to fit this using MATLAB's cftool have given me useless fits:

 fit_attempt.png

I tried changing the start-points for the fitting parameters but I didn't get any better fits.

To Do:

  1. Explore other fitting options.
  2. Try and find a way to Laplace transform the time-series data so I can do the fitting in the s-domain.
  3. I have some tweaking to do as far as the python scripts on the pi are concerned.
  4. I have to get the current temperature readings onto one of the unused Y-arm EPICS channels, and log that data ~ once every 10 seconds.

Misc Remarks:

  1. The time-series data has a 'stepped' appearance because of the resolution of the temperature sensor: it is 0.1 Celsius.
  2. The sampling rate of the data-acquisition is limited; right now, I wait for 0.15 seconds after sending the command word to the controller before reading the data. When I set the wait-period any lower than this, I get errors. This has to be investigated more as I feel I should be able to get better sampling with the advertised baudrate of 115200, but in any case, it looks like it is sufficient for our purposes.

 

  8758   Wed Jun 26 19:02:38 2013 gautamUpdateGeneralITMx Oplev (not quite?) Fixed

 

Summary:

Steve and I tried to fix the Oplev situation detailed in elog 8684, today afternoon. We have come up with a fix which needs to be adjusted, possibly completely overhauled depending on whether the mirror steering the return beam to the QPD is blocking the POX beam coming out. 

Details:

  • ITMx Oplev servo was first turned off.
  • It turns out we were hitting the wrong pair of Oplev steering mirrors inside the chamber. The incident beam was hitting a mirror meant for IR light (see sketch below) and not the intended first steering mirror. We pretty much redid the entire alignment (we used a pair of irises initially to set up a reference path) so as to hit the right pair of mirrors inside the chamber. At the end of today's efforts, the beam is reasonably well centered on both the intended mirrors, and there is not as much scattered light. 

Situation in the chamber: the black line is meant to indicate what was happening, the red is indicative of the present path.

 

oplev_chamber.pdf

  • The Oplev laser was installed in 2011 (October 13,2011 to be precise), and the quality of the beam coming out of the laser was pretty bad (the cross section was badly distorted even before it hit any optics). Steve thought this laser had reached the end of its lifetime, so we replaced the laser with a new one. Output power of this new laser has yet to be measured. The power-supply for the laser was also dodgy so we switched that out as well, and installed a new power supply. New laser and power supply are working satisfactorily. The old power supply will be checked with another laser tomorrow to gauge its status.
  • The cross-section of the beam from the new Oplev laser was deemed satisfactorily circular and we centred it on the first of the two lenses in the beam-path. We are getting 2.81 mW of power from the new laser.
  • In order to hit the right pair of Oplev steering mirrors while avoiding the clipping the beam on the tip-tilt/PR2 suspension, we had to sort of widen the angle of the beam going in, and so both steering mirrors, as well as the second lens in the beampath were shifted around. I have attached before and after pictures of the layout on the table. We adjusted things till the beam is reasonably well centred on both steering mirrors inside the chamber.
  • Because of the changed beam-path, the return Oplev beampath also changed, and so we had to move the steering mirror directing the return beam to the QPD as well. In its new position, it may be clipping the POX beam.
  • The beam is not getting clipped anywhere on the table now. It is also well centered on the two lenses in its path.
  • We placed two irises marking the new path so that we have a reference if the alignment needs to be changed again.
  • Turned ITMx Oplev servo back on.

Other stuff:

  1. The higher--power new laser means that the QPD sum is now ~6000counts (up from ~3500). The power in the return beam is 143.5 uW, which is ~5% of the power of the input beam.
  2. We centred the spot on the QPD, though when we excited ITM in yaw, the spot doesn't quite move horizontally, rather, it moves somewhat diagonally
  3. I turned the lights off, blocked the beam and measured the zero-current counts for the various QPD quadrants. These were all less than 1.5, and I reset these values on the ITMx Oplev screen according to my measurements.
  4. While viewing the spot of the Oplev beam on the ITMx face, we noticed that there were two spots, one less bright than the other. Steve suspects that this is because of multiple reflections from the chamber window.
  5. The status of the POX beam has to be verified (i.e is it getting clipped by the steering mirror for the return beam?)
  6. There was a Thorlabs PD on the table which had a green power LED. Jenne had asked me to cover this LED up, which I did with bits of tape.

Plan of action:

  • The spot size at the QPD is right now about 3mm. We may want to improve this by moving the first of the two lenses in the beam-path (there is not a whole lot of room to maneuvering the second lens.
  • Jenne just aligned and locked the X-arm, and doesn't think that the POX beam is being blocked, but I will verify this sometime tomorrow.

 

BEFORE

photo_1.JPG

 

AFTER

photo_2.JPG 

 

  8770   Thu Jun 27 18:11:53 2013 gautamUpdateGeneralITMx Oplev-POX looks beam okay

 

 Jenne just aligned the X arm and I got a chance to check the status of the POX beam coming out of the chamber. Turned the Oplev servo off so that the red beam could be blocked, turned all the lights off, and had a look at the beam in the vicinity of the mirror steering the Oplev-out beam to the QPD with an IR view-card. The beam is right now about half a centimeter from the pitch knob of the said mirror, so its not getting clipped at the moment. But perhaps the offending mirror can be repositioned slightly, along with the Oplev QPD such that more clearance is given to the POX beam. I will work this out with Steve tomorrow morning. 

  8777   Thu Jun 27 23:01:39 2013 gautamUpdateGeneralITMx Oplev-servo gains adjusted

 

 With rana's input, I changed the ITMx oplev servo gains given the beam path had been changed. The pitch gain was changed from 36 to 30, while the yaw gain was changed from -25 to -40. Transfer function plots attached. The UGF is ~8Hz for pitch and ~7Hz for yaw.

I had to change the envelope amplitudes in the templates for both pitch and yaw to improve the coherence. Above 3Hz, I multiplied the template presets by 10, and below 3Hz, I multiplied these by 25.

 

pitch-plot.pdf

 

yaw-plot.pdf

  8784   Fri Jun 28 13:10:28 2013 gautamUpdateGeneralITMx Oplev-servo gains adjusted

 

 As mentioned in elog 8770, I wanted to give the POX beam a little more clearance from the pick-off mirror steering the outcoming oplev beam. I tweaked the position of this mirror a little this morning, re-centred the spot, and checked the loop transfer function once again. These were really close to those I measured last night (UGF for pitch ~8Hz, for yaw ~7Hz), reported in elog 8777, so I did not have to change the loop gains for either pitch or yaw. Plots attached.

 pitch-plot_copy.pdf

 

yaw-plot_copy.pdf

  8789   Tue Jul 2 00:25:14 2013 gautamUpdateGreen LockingUniversal PDH box tuning

 [Koji, Annalisa, Gautam]

Annalisa noticed that over the weekend the Y-arm green PDH was locked to a sideband, despite not having changed anything on the PDH box (the sign switch was left as it was). On friday, we tried turning on and off some of the filters on the slow servo (C1ALS_Y_SLOW) which may have changed something but this warranted further investigation. We initially thought that the demodulation phase was not at the optimal value, and decided to try introducing some capacitances in the path from the function generator to the LO input on the universal PDH box. We modelled the circuit and determined that significant phase change was introduced by capacitances between 1nF and 100nF, so we picked out some capacitors (WIMA FKP) and set up a breadboard on which to try these out.

After some trial and error, Koji dropped by and felt that the loop was optimized for the old laser, the various loop parameters had not been tweaked since the new laser was installed. The following parameters had to be optimized for the new laser;

  • Servo gain
  • LO frequency
  • LO modulation depth
  • Demodulation phase

The setup was as follows: 

  • PDH box error signal to Oscilloscope CH1
  • Green PD output to Oscilloscope CH2
  • No capacitor between Function Generator and the PDH box
  • 0.1Hz triangle wave (30 counts amplitude) applied to ETMY via awggui (so as to sweep the cavity and see stronger, more regular TEM00 flashes)

The PDH error signal did not have very well-defined features, so Koji tweaked the LO frequency and the modulation depth till we got a reasonably well-defined PDH signal. Then we turned the excitation off and locked the cavity to green. The servo gain was then optimized by reducing oscillations in the error signal. Eventually, we settled on values for the Servo Gain, LO frequency and modulation depth such that the UGF was ~20kHz (determined by looking at the frequency of oscillation of the error signal on an Oscilloscope), and the PDH signal had well-defined features (while the cavity was unlocked). The current parameters are

  • LO frequency: 205.020 kHz
  • modulation depth: 0.032 Vpp

We then proceeded to find the optimal demodulation phase by simulating the circuit with various capacitances between the function generator and the PDH box (circuit diagram and plots attached). The simulation seemed to suggest that there was no need to introduce any additional capacitance in this path (introducing a 1nF capacitance added a phase-lag of ~90 degrees-this was confirmed as the error-signal amplitude decreased drastically when we hooked up a 1nF capacitor on our makeshift breadboard). In the current configuration, the LO is connected directly to the PDH box.

 

Misc Points:

  • The phase shifter in the PDH box is not connected: the IC in the box, JSPHS-26, is designed for operation in the range 18-26MHz. If necessary, an all-pass-filter could be introduced, with a tuneable rheostat to adjust the phase for our frequency range. Right now, turning the knob marked "LO phase angle" on the front panel doesn't do anything. The mixer on the PDH board is also not used for the same reason.
  • PSL shutter was closed sometime earlier this evening, because we suspected some IR light was reaching the Green PD on the y-endtable, and was influencing the error signal. Its back open now.
  • Useful information about the old y-end laser relevant to selecting the right LO frequency, modulation depth, and servo gain can be found here and in elog 2746 and subsequent replies, though the details of how the measurement were made aren't entirely clear. The idea is that the characteristics of the piezoelectric element in the laser has some characteristics which will determine the optimal LO frequency, modulation depth and servo gain.

 

To Do:

Now that we are reasonably confident that the loop parameters are optimal, we need to stabilise the C1ALS_Y_SLOW loop to stabilise the beat note itself. Appropriate filters need to be added to this servo.

 

Circuit Diagram: 50 ohm input impedance on the source, 50 ohm output impedance seen on the PDH box, capacitance varied between 1nF and 100nF in steps.

circuit.pdf

Plots for various capacitances: Gold-green trace (largest amplitude) direct from LO, other traces at input to PDH box.

model.pdf

  8800   Wed Jul 3 21:19:04 2013 gautamConfigurationendtable upgradeplan of action for PZT installation

 This is an update on the situation as far as PZT installation is concerned. I measured the required cable (PZT driver board to PZT) lengths for the X and Y ends as well as the PSL table once again, with the help of a 3m long BNC cable, just to make sure we had the lengths right. The quoted cable lengths include a meter tolerance. The PZTs themselves have cable lengths of 1.5m, though I have assumed that this will be used on the tables themselves. The inventory status is as follows.

  1. Stuff ordered:
    • RG316 LEMO 00 (female) to SMB (female) cables, 10 meters - 6pcs (for the Y-end)
    • RG316 LEMO 00 (female) to SMB (female) cables, 11 meters - 6pcs (for the X-end)
    • RG316 LEMO 00 (female) to SMB (female) cables, 15 meters - 8pcs (6 for the PSL, and two spares)
    • RG316 SMA (male) to open cables, 3 meters - 3pcs (1 each for the X end, Y end and PSL table, for connecting the driver boards to the 100V DC power supply)
    • 10 pin IDC connectors for connecting the DAC interface to the PZT driver boards 
  2. Stuff we have:
    • 40 pin IDC connectors which connect to the DAC interface
    • PZT driver boards
    • PZT mounts
    • Twisted ribbon wire, which will be used to make the custom ribbon to connect the 10 pin IDC to the 40 pin IDC connector

I also did a preliminary check on the driver boards, mainly to check for continuity. Some minor modifications have been made to this board from the schematic shown here (using jumper wires soldered on the top-side of the PCB). I will have to do a more comprehensive check to make sure the board as such is functioning as we expect it to. The plan for this is to first check the board without the high-voltage power supply (using an expansion card to hook it up to a eurocrate). Once it has been verified that the board is getting powered, I will connect the high-voltage supply and a test PZT to the board to do both a check of the board as well as a preliminary calibration of the PZTs.

To this end, I need something to track the spot position as I apply varying voltage to the PZT. QPDs are an option, the alternative being some PSDs I found. The problem with the latter is that the interfaces to the PSD (there are 3) all seem to be damaged (according to the labels on two of them). I tried connecting a PSD to the third interface (OT301 Precision Position Sensing Amplifier), and hooked it up to an oscilloscope. I then shone a laser pointer on the psd, and moved it around a little to see if the signals on the oscilloscope made sense. They didn't on this first try, though this may be because the sensing amplifier is not calibrated. I will try this again. If I can get one of the PSDs to work, mount it on a test optical table and calibrate it. The plan is then to use this PSD to track the position of the reflected beam off a mirror mounted on a PZT (temporarily, using double sided tape) that is driven by feeding small-amplitude signals to the driver board via a function generator. 

 

Misc

The LEMO connector on the PZTs have the part number LEMO.FFS.00, while the male SMB connectors on the board have the part number PE4177 (Pasternack)

Plan of Action:

  • The first task will be to verify that the board is working by the methods outlined above.
  • Once the board has been verified, the next task will be to calibrate a PZT using it. I have to first identify a suitable way of tracking the beam position (QPD or PSD?)
  • I have identified a position in the eurocrate at 1Y4 to install the board, and I have made sure that for this slot, the rear of the eurocrate is not hooked up to the cross-connects. I now need to figure out the exact pin configuration at the DAC interface: the bank is marked 'DAC Channels 9-16' (image attached) but there are 40 pins in the connector, so I need to map these pins to DAC channels, so that when making the custom ribbon, I get the pin-to-pin map right.

DAC_bank.png

 

The wiring scheme has been modified a little, I am uploading an updated one here. In the earlier version, I had mistaken the monitor channels as points from which to log data, while they are really just for debugging. I have also revised the coaxial cable type used (RG316 as opposed to RG174) and the SMB connector (female rather than male).

ASC_schematic.pdf 

 

 

 

 

  8804   Mon Jul 8 13:45:19 2013 gautamConfigurationendtable upgradeDriver board verification

With the help of an expansion card,  I verified that the + 15V and + 24V from the eurocrate in the slot I've identified for the PZT driver boards are making their way to the board. The slot is at the right-most end of the eurocrate in 1Y4, and the rack door was getting in the way of directly measuring these voltages once I hooked up the driver board to the expansion card. So I just made sure that all the LEDs on the expansion card lit up (indicating that the eurocrate is supplying + 5, + 15 and + 24V), and then used a multimeter to check continuity between the expansion card and the driver board outside of the eurocrate. The circuit only uses + 15V and + 24V, and I checked for continuity at all the IC pins marked with these voltages on the schematic.

Since the whole point of this test was to see if the slot I identified was delivering the right voltages, I think this is sufficient. I will now need to fashion a cable that I can use to connect a DC power supply to the PZT driver boards so that these can be tested further.

The high voltage points (100V DC) remain to be tested.

  8809   Tue Jul 9 11:37:37 2013 gautamUpdateCDSset up for testing DAC Interface-board pin outs

The bank marked channel 9-16 is free, but the connector is a 40 pin IDC and I need to know the exact pin-out configuration before I can set about making the custom ribbon cable that will send the control signals from the DAC card to the PZT driver board. 

The DAC interface board on rack 1Y4 seems to be one of the first versions of this board, and has no DCC number anywhere on it. Identical modules on other racks have the DCC number D080303, but this document does not exist and there does not seem to be any additional documentation anywhere. The best thing I could find was the circuit diagram for the ADL General Standards 16-bit DAC Adapter Board, which has what looks like the pin-out for the 68 pin SCSI connector on the DAC Interface board. Koji gave me an unused board with the same part number (D080303) and I used a multimeter and continuity checking to make a map between DAC channels, and the 40 pin IDC connector on the board, but this needs to be verified (I don't even know if what is sitting inside the box on 1Y4 is the same D080303 board).

Jenne suggested making a break-out cable to verify the pin-outs, which I did with a 40-pin IDC connector and a bit of ribbon wire. The other end of the ribbon wire has been stripped so that we can use some clip-on probes and an oscilloscope to verify the pin-outs by sending a signal to DAC channels 9 through 16 one at a time. On the software side, Jenne did the following:

  • Restarted the mx_stream on c1iscey  (unrelated to this work)
  • 8 Excitation points added in the simulink model on c1scy 
  • Model compiled and installed

We have not restarted c1scy yet as Annalisa is working on some Y-arm stuff right now. We will restart c1scy and use awggui to perform the test once she is done.

 Pink edits by JCD

  8811   Tue Jul 9 12:01:20 2013 gautamUpdateCDSset up for testing DAC Interface-board pin outs

 

 Jenne just rebooted c1scy and daqd on the framebuilder. We will do the actual test after lunch.

  8814   Tue Jul 9 18:44:37 2013 gautamUpdateCDSDAC Interface Board-Pin Outs

  Summary:

The pin-outs for the DAC interface board have been determined.

Details:

  • I used a temporary break-out cable (pic attached) and connected the 40pin IDC connector on this to the DAC interface board at 1Y4.
  • I had a hypothetical pin-out map which was to be verified. So I connected pairs of ribbon wire to an oscilloscope in the configuration which I believed to be correct, and then used awggui to send a 3Hz, 10000 count sine-wave to the corresponding channel via the excitation points set up earlier.
  • I verified that the correct waveform showed up on the scope screen. I then tried sending the same signal to another DAC channel and verified that there were no accidental shorts/bad connections. The signal was fairly noisy, but this was probably because of the makeshift connections.
  • Repeated the above for all 8 channels in the bank marked 9-16 on the DAC interface board.

Turns out that my deductions using the D0902496 wiring diagram, a spare D080303 DAC to IDC adaptor and a multimeter were correct! The pin outs as determined by this test are sketched in the graphic below.

To Do:

  •  Now that the pin-outs have been determined, I need to go about making the custom ribbon that will connect the 40pin IDC on the DAC interface board to the 10-pin IDC on the PZT driver board. Because there is a pair of wires that will have to be 'skipped' while going from the 40-pin to the 10 pin IDC (corresponding to the pair not-connected between two DAC channels on the 40-pin IDC), this may be tricky.

Misc:

The excitation points added to the simulink model are still there, I plan on keeping it as such till I finish installation of the boards as they will be useful for testing purposes.

 

Pin-Outs of the DAC to IDC Adaptor (D080303) inside the "DAC Interface Box at 1Y4":

DAC_Interface_Board_Pin-out.pdf

 

Makeshift break-out ribbon cable:

 

break-out_ribbon.JPG

 

 

  8817   Wed Jul 10 01:27:44 2013 gautamUpdateGreen LockingY-end Green PDH open-loop transfer function

 [Annalisa, gautam]

Summary:

We have measured the open-loop transfer function of the Y-end green PDH loop. From the measurement, the loop UGF is ~12kHz.

Details:

We have been trying to measure this transfer function for some time now, and playing around with various points of injecting the excitation and measuring the output. Koji helped arrive at one that actually worked, and the scheme used to make this measurement is shown in the sketch below. The SR785 signal analyzer was used to make the measurement, while an SR560 preamp was used to sum the output from the PDH box (PZT-OUT) and the excitation, with this sum being delivered to the auxiliary laser PZT via a pomona box that sums the servo output and the signal from the LO. The transfer function measurement made was a1/a2 w.r.t the sketch attached.

  • The swept-sine measurement was done from high to low frequencies, as the open-loop gain was expected to be high at low frequencies.
  • After some trial and error, we realised that the excitation amplitude on the SR785 can be varied continuously during the course of a swept sine measurement using the dial on the front panel. We started out with a 1mVpp signal at the high end of the frequency sweep (~102kHz, the upper limit on the SR785) and went up to 17mVpp at ~30Hz). These values were determined by trial and error, and were approximately the maximum that did not kick the loop out of lock/into a higher order mode.

Remarks:

  • As per this paper, the expected bandwidth of this loop is expected to be ~30kHz, while the measured UGF was more like 11.7kHz. Perhaps we can get this closer to the expected 30kHz by increasing the servo gain. The measurement shown was done with the servo gain knob on the Universal PDH box set to ~7.86. We tried two other values, ~8.2 and 10 (this was the limit on the knob), but the UGF first increased to ~13kHz (for the 8.2 gain), and then decreased to ~5kHz with a gain of 10. Not sure why this was, but it can be looked into further. 
     

Set-up to measure Y-end Green PDH transfer function:

Green_PDH_measurement.pdf

 

Measured Open Loop Transfer Function:

Y-end_Green_PDH.pdf

  8823   Wed Jul 10 22:41:06 2013 gautamConfigurationendtable upgradePZT Driver Board

 I did the following with the PZT Driver Board: 

 

  •  With an expansion card attached to the driver board, I used an Agilent E3620A power supply to verify that the 15V and 24V supplies were reaching the intended ICs. It turns out that the +24 V supply was only meant to power some sort of on-board high voltage supply which provided the 100V bias for the PZTs and the MJE15030s. This device does not exist on the board I am using, jumper wires have been hooked up to an SMA connector on the front panel that directly provides 100V from the KEPCO high voltage supply to the appropriate points on the circuit.

  •  All the AD797s as well as the LT1125CS ICs on the board were receiving the required +15V.

      

The next step was to check the board with the high-voltage power supply connected.

 

  •  The output from the power supply is drawn from the rear output terminal strip of the power supply via pins TB1-2 (-OUT) and TB1-7 (+OUT). I used a length of RG58 coaxial cable from the lab and crimped a BNC connector on one end, and stripped the other to attach it to the above pins.

  •  There are several options that can be configured for the power supply. I have left it at the factory default: Local sensing (i.e. operating the power supply using the keypad on the front of it as opposed to remotely), grounding network connected (the outputs of the power supply are floating), slow mode, output isolated from ground.

  • I was unsure of whether the grounding network configuration or the 'positive output, negative terminal grounded' configuration was more appropriate. Koji confirmed that the former was to be used so as to avoid ground loops. When installed eventually, the eurocrate will provide the ground for the entire system.
  • I then verified the output of the HV power supply using a multimeter from 2V up to 150V.
  • I then connected the high voltage supply to the PZT driver board with a BNC-SMA adaptor, set, for a start, to output 30V. Ensured that the appropriate points on the circuit were supplied with 30V.

 

I then hooked up a function generator in order to simulate a control signal from the DAC. The signal was applied to pin 2 of the jumpers marked JP1 through JP4 on the schematic, one at a time. The signal applied was a 0.2 Vpp, 0.1 Hz sine wave.

 

 

 

  •  The output voltage was monitored both using a DMM at the SMB output terminals, and at the monitor channels using an oscilloscope. The outputs at both these points were as expected.
  • There are 4 potentiometers on the board, which need to be tuned such that the control output to the piezos are 50V when the input signal is zero (as this corresponds to no tilt). The gain of the amplifier stage (highlighted in the attached figure) right now is ~15, and I was using 30V in place of 100V, so an input signal of 2V would result in the output saturating. This part of the circuit will have to be tuned once again after applying the full 100V bias voltage. 
  • Koji suggested decreasing the gain of the amplifier stage by switching out resistor R43 (and corresponding resistor in the other 3 stages on the board) after checking the output range of the DAC so that possibility of unwanted saturation is minimised. I need to check this and will change the resistors after confirming the DAC output range. 
  • The potentiometers will have to be tuned after the gain has been adjusted, and with 100V from the high-voltage DC power supply. 

  

To Do:

 

  • Switch out resistors
  • Tune potentiometers with 100V from the HV supply
  • Verify that the output from the board after all the tuning lies in the range 0-100V for all possible input voltages from the DAC.
  • Once the output voltage range has been verified, the next step would be to connect a PZT to the board output, affix a mirror to the tip/tilt, and perform some sort of calibration for the PZT. 

HV_Amplifier.pdf

 

 

 

 

 

 

  8832   Thu Jul 11 23:50:57 2013 gautamConfiguration PZT Driver Board-changes made

 Summary:

Continued with tests on the PZT driver board. I made a few changes to replace defective components and also to modify the gain of the HV amplifier stage. I believe the board has been verified to be satisfactory, and is now ready for a piezo to be connected, tested and calibrated.

Changes made:

  • I tested the board with the full 100V bias voltage today, working my way up from 30V in steps of about 20V and verifying the output at each stage.
  • In order to deliver 100V to the board, it was necessary to change the maximum current limit on the KEPCO supply, which is set at default at ~1.6 mA. The KEPCO power supply placed near rack 1X2 (which I believe was used to power a piezo driver board) is labelled 150V, 12 mA, though I found that the board only drew 7mA of current when the power supply output 100V. I have set the limit to 10 mA for the time being.
  • The potentiometer in the third stage (R44 in the schematic) was faulty so I replaced it with another 100K potentiometer, which was verified to work satisfactorily.
  • We expect the DAC output to supply a voltage to the input of the PZT driver board in the range -10V to 10V. Today, I verified this by using my temporary break-out cable. I hooked this up to the DAC at 1Y4 and output a 3 Hz sine wave with amplitude of 32000 counts (the maximum) on channel 9. The output as observed on an oscilloscope (image attached) was a 10Vpp sinusoid, confirming the above hypothesis. As mentioned in my previous elog, the gain of the high-voltage amplifier stage is ~15, which would mean the output would saturate if the input were to be >6V. I have changed the gain of all 4 stages (M1-pitch, M1-yaw, M2-pitch and M2-yaw) to ~4.85 by swapping the 158k resistors (R43, R44, R69 and R70 in the schematic) for 51k resistors. 
  • It was necessary to change the value of the biasing potentiometers after the change in gain so that 0 input voltage once again provided 50V at the output, as required by the PZTs for there to be no tilt. This was done and verified. This biasing voltage now is ~10.4V in all four stages.
  • Having adjusted the gain, I tested the circuit over the expected full range of the input voltage from the DAC (from -10V to 10V) from the DS345 function generator (0.05Hz sinusoid). I monitored the output using a multimeter, as the monitor channels were peaking at ~7V, which was above the limit for the oscilloscope I was using. It was verified for all four channels that the output was between 0 V and 100 V (the safe range quoted in the datasheet for the tip-tilts, for this range of input voltages. So I think we are ready to connect a PZT to the board and conduct further tests, and calibrate the PZT. 

Pending Issues:

  • Koji pointed out that there has to be an anti-imaging filter stage between the DAC output and the filter stage, which I had not considered till this point.Another subtle point is that the DAC output is differential while the driver boards have a single-ended input, which means we effectively lose half the range of the PZTs. 
  • A suitable candidate is the D000186-rev D. Some information about the present state of this board is detailed in this elog. This board also solves the problem of the differential vs single input as the input to the AI board is differential while the output is single-ended. Koji has given me one of the boards he had collected. 
  • Some changes will have to be made to this version of the board in order to make it compatible with the existing DAC. I will first have to measure the power spectrum of the DAC output to verify that the AI boards need notches at 64k and 128k. The existing notches are at 16k and 32k, and once the DAC power spectrum has been verified, I hope to affect the necessary changes by switching out the appropriate capacitors on the existing board. 
  • The AI board is an extra element which I have now added to an updated wiring diagram, attached.

Revised Wiring Diagram:

ASC_schematic.pdf

 

DAC Max. Output Trace on Oscilloscope

 

DAC_Max_output.JPG

 

 

 

  8845   Mon Jul 15 11:51:18 2013 gautamConfigurationendtable upgradeDAC at 1Y4-Max Output and Power Spectrum

 Summary:

I measured the maximum output of the DAC at 1Y4 as well as its power spectrum. The results are as follows (plots below):

  • Maximum amplitude of differential output: + 10V.
  • Power spectrum has a peak at 64 kHz.

Therefore, the gain of the high-voltage amplification stage on the PZT driver boards do not need to be changed again, as the required output range of 0-100V from the DAC board was realised when the input voltage ranged from -10V to +10 V w.r.t ground. The AI board converts the differential input to a single ended output as required by the driver board.

I will now change some resistors/capacitors on the AI board such that the position of the notches can be moved from 16k and 32k to 64k and 128k.

Procedure:

 Max. amplitude measurement

My previous measurement of the maximum output amplitude of the DAC was flawed as I made the measurement using a single channel of the oscilloscope, which meant that the negative pin of the DAC channel under test was driven to ground. I redid the measurement to avoid this problem. The set up this time was as follows:

  • Positive pin of DAC connected to channel 1 of oscilloscope using break out cable and mini-grabber probe
  • Negative pin of DAC connected to channel 2 of oscilloscope
  • Grounds of channels 1 and 2 connected (I just hooked the mini-grabbers together)
  • Measurement mode on oscilloscope set to channel 1 - channel2
  • Used excitation points set up earlier to output a 3 Hz sine wave with amplitude of 32000 counts from channel 9 of the DAC. 

The trace on the oscilloscope is shown below;

max_amp.JPG

So with reference to ground, the DAC is capable of supplying voltages in the range [-10V 10V]. This next image shows all three traces: positive and negative pins of DAC w.r.t ground, and the difference between the two.

max_amp_all_channels.JPG

 Power spectrum measurement

 

I used the SR785 to make the measurement. The set up was as follows:

  • Positive pin of DAC to A-input of SR560
  • Negative pin of DAC to B-input of SR560
  • A-B output to Channel 1 input A of the SR785
  • SR785 configured to power spectrum measurement

Initially, I output no signal to the DAC, and obtained the following power spectrum. The peak at 65.554 kHz is marked.

DACOffPowerSpec.pdf

I then re-did the measurement with a 200 Hz (left) and 2000 Hz(right), 1000 counts amplitude (I had to change the Ch1 input range on the SR785 from -18dBm to -6dBm) sine wave from channel 9 of the DAC, and obtained the following. The peaks at ~64 kHz are marked.

DACOnPowerSpec.pdf    DAC2kPowerSpectrum.pdf

Now that this peak has been verified, I will work on switching out the appropriate resistors/capacitors on the AI board to move the notches from 16k and 32k to 64k and 128k. 

  8848   Mon Jul 15 15:54:20 2013 gautamConfigurationendtable upgradeDAC at 1Y4- Power Spectrum -with the right units

Quote:

We need the unit of the voltage power spectrum density to be V/sqrt(Hz).
Otherwise we don't understand anything / any number from the plot.

 I redid the measurement with the appropriate units set on the SR785. Power spectral density plots for no output (top), 500Hz, 1000 counts amplitude sine wave (middle) and 2000Hz, 1000 counts amplitude (bottom) are attached, with the right unit on the Y-axis.

 

DACOffPSD.pdf

 

DAC500PSD.pdf

 

DAC2000PSD.pdf

  8853   Mon Jul 15 17:59:31 2013 gautamConfigurationendtable upgradeDAC at 1Y4- Power Spectrum -6.4kHz bandwidth

Quote:

Those 'peaks' for the oscillations seem ridiculously broad.  I think you should look again, really quickly, with smaller bandwidth at, say, the 2kHz oscillation, to make sure it looks reasonable.

 I did just this, and it looks okay to me:

DAC-6.4_kHz_BW_PSD.pdf

  8857   Tue Jul 16 14:51:09 2013 gautamConfigurationendtable upgradeAI Board-D000186-Modified notches

 I tried shifting the notch frequencies on the D000186-revision D board given to me by Koji. The existing notches were at ~16 kHz and ~32 kHz. I shifted these to notches at ~64 kHz and ~128 kHz by effecting the following changes (see schematic for component numbering) on Channel 8 of the board-I decided to check things out on one channel before implementing changes en masse:

  • R6 and R7 replaced with 511 ohm smts
  • R8 replaced with 255 ohm smt
  • R14 and R15 replaced with 549 ohm smts
  • R16 replaced with 274 ohm smt

=> New notches should be at 66.3 kHz and 131.7 kHz.

I then measured the frequency response of the modified channel using the SR785, and compared it to the response I had measured before switching out the resistors. The SR785 only goes up to 102 kHz, so I cannot verify the 128 kHz notch at this point. The position of the 64 kHz notch looks alright though. I think I will go ahead and switch out the remaining resistors in the evening.

Note 1: These plots are just raw data from the SR785, I have not tried to do any sort of fitting to poles and zeros. I will do this at some point. 

Note 2: All these smts were taken from Downs. Todd helped me locate the non-standard value resistors. I also got a plastic 25-pin D-sub backshells (the spares are in the rack), with which I have fashioned the required custom ribbon cables (40 pin IDC to 25 pin D-sub with twisted ribbon wire, and a short, 10pin IDC to 10pin IDC with straight ribbon wire).

D000186_Frequency_Response.pdf

  8873   Thu Jul 18 19:09:08 2013 gautamConfigurationendtable upgradeQPD Calibration for PZT Calibration

Summary 

I have been working on setting up a QPD which can eventually be used to calibrate the PZT, and also orient the PZT in the mount such that the pitch and yaw axes roughly coincide with the vertical and horizontal.

The calibration constants have been determined to be:

X-axis: -3.69 V/mm

Y-axis: -3.70V/mm

Methodology:

I initially tried using the QPD setup left behind by Chloe near MC2, but this turned out to be dysfunctional. On opening out the QPD, I found that the internal circuitry had some issues (shorts in the wrong places etc.) Fortunately, Steve was able to hand me another working unit. For future reference, there are a bunch of old QPDs which I assume are functional in the cabinet marked 'Old PDs' along the Y-arm. 

I then made a circuit with which to read out the X and Y coordinates from the QPD. This consists of 4 buffer amplifiers (one for each quadrant), and 3 summing amplifiers (outputs are A+B+C+D = sum, B+C-A-D = Y-coordinate, and A+B-C-D = X-coordinate) that take the appropriate linear combinations of the 4 quadrants to output a voltage that may be calibrated against displacement of the QPD. 

The output from the QPD is via a sub-D connector on the side of the pomona box enclosing the PD and the circuitry, with 7 pins- 3 for power lines, and 4 for the 4 quadrants of the QPD. It was a little tricky to figure the pin-out for this connector, as there was no way to use continuity checking to map the pins to quadrants. Therefore, I used a laser pointer, and some trial and error (i.e. shine the light on a given quadrant, and check the sign of the X and Y voltages on an oscilloscope) to map the pin outs. Steve tells me that these QPDs were made long before colour code standardisation, but I note here the pin outs in any case for future reference (the quadrant orientations are w.r.t the QPD held with all the circuitry above it, with the active surface facing me):

Red= +Vcc

Black= -Vcc

Green = GND

Blue = Upper Left Quadrant

White = Upper Right Quadrant

Purple = Lower Left Quadrant

Grey = Lower Right Quadrant

Chloe had noted that there was some issue with the voltage regulators on her circuit (overheating) but I suspect this may have been due to the faulty internal circuitry. Also, she had used 12 V regulators. I checked the datasheet of the QPD, Op-Amp LF347 (inside the pomona box) and the OP27s on my circuit, and found that they all had absolute maximum ratings above 18V, so I used 15V voltage regulators. The overheating problem was not a problem anymore.

I then proceeded to arrange a set up for the calibration (initially on the optical bench next to MC2, but now relocated to the SP table, and a cart adjacent to it). It consists of the following:

  • He-Ne laser source
  • Y2 2-inch mirror (AR and HR coated for 532nm) glued onto the PZT and mounted on a machined Newport U100P  - see this elog for details.
  • QPD mounted on a translational stage whose micrometers are calibrated in tenths of an inch (in the plots I have scaled this to mm)
  • A neutral density filter (ND = 2.0) which I added so that the QPD amplifier output did not saturate. I considered using a lens as well to reduce the spot size on the QPD but found that after adding the ND filter, it was reasonably small.
  • High-voltage power supply (on cart)
  • Two SR power supplies (for the PZT driver board and my QPD amplifier
  • SR function generator
  • Laser power source
  • Two oscilloscopes
  • Breadboard holding my QPD amplifier circuit

Having set everything up and having done the coarse alignment using the mirror mount, I proceeded to calibrate the X and Y axes of the QPD using the translational stage. The steps I followed were:

  • Centre spot on QPD using coarse adjustment on the mirror mount: I gauged this by monitoring the X and Y voltage outputs on an oscilloscope, and adjusted things till both these went to zero.
  • Used the tilt knob on the translational stage to roughly decouple the X and Y motion of the QPD.
  • Kept Y-coordinate fixed, took the X-coordinate to close to its maximum value (I gauged this by checking where the voltage stopped changing appreciably for changes in the QPD position.
  • Using this as a starting point, I moved the QPD through its X range, noting voltage output of the X-coordinate (and also the Y) on an oscilloscope.
  • Repeated the procedure for the Y-coordinate.
  • Analysis follows largely what was done in these elogs. I am attaching the script I used to fit an error function to the datapoints, this is something MATLAB should seriously include in cftool (note that it is VERY sensitive to the initial guess. I had to do quite a bit of guessing).

The plots are attached, from which the calibration values cited above are deduced. The linear fits for the orthogonal axis were done using cftool. There is some residual coupling between the X and Y motions of the QPD, but I think this os okay my purposes. 

My next step would be to first tweak the orientation of the PZT in the mount while applying a small excitation to it in order to decouple the pitch and yaw motion as best as possible. Once this is done, I can go ahead and calibrate the angular motion of the PZT in mrad/V.

 

                                                            X-Axis                                                                                                                                Y-axis                                                

QPD-XCalib.pdf  QPD-YCalib.pdf

 

 

Attachment 3: Error_Function_Fitting.zip
  8874   Thu Jul 18 20:20:52 2013 gautamConfigurationendtable upgradeFirst mirror glued to PZT and mounted in modified mounts

 

 Yesterday, I mounted the first PZT in one of the modified mounts, and then glued a 2-inch Y2 mirror on it using superglue.

Details:

-The mirror is a 2-inch, Y2 mirror with HR and AR coatings for 532 nm light.

-The AR side of the mirror had someone's fingerprint on it, which I removed (under Manasa's guidance) using tweezers wrapped in lens cleaning paper, and methanol.

-Before gluing the mirror, I had to assemble the modified mount. Manasa handed over the remaining parts of the mounts (which are now in my newly acquired tupperware box along with all the other Piezo-related hardware). I took the one labelled A, and assembled the holder part. I then used one of the new mounts (2.5 inches, these are with the clean mounts in a cardboard box in the cupboard holding the green optics along the Y-arm) and mounted the holder on it. 

-Having assembled the mount, I inserted the piezo tip-tilt into the holder. The wedge that the machine shop supplied is useful (indeed required) for this. 

-I then cleaned the AR surface of the mirror and the top-surface of the tip-tilt. 

-The gluing was done using superglue which Steve got from the bookstore (the remaining tube is in the small fridge). We may glue the other mirror using epoxy. I placed 4 small drops of superglue on the tip-tilt's top surface, placed the mirror with its AR face in contact with the piezo, and applied some pressure for a short while until the glue spread out fairly evenly. I then left the whole setup to dry for about half an hour.

-Steve suggested using a reference piece (I used two small bolts) to verify when the glue had dried.

-Finally, I attached the whole assembly to a base.

Here it is in action in my calibration setup (note that it has not been oriented yet. i.e. the two perpendicular axes of the piezo are for the time being arbitrarily oriented. And maybe the spreading of the glue wasn't that even after all...):

Piezo-mirror.jpg

 

Sidenote:

Yesterday, while setting stuff up, I tested the piezo with a 0.05 Hz, 10Vpp input from the SR function generator just to see if it works, and also to verify that I had set up all my electronics correctly. Though the QPD was at this point calibrated, I did observe periodic motion of both the X and Y outputs of my QPD amp! Next step- calibration... 

  8875   Thu Jul 18 21:12:58 2013 gautamConfigurationendtable upgradeAI Board-D000186-All channels modified

 

 I carried some further modifications and tests to the AI Board. Details and observations here:

  • I switched out the resistors for all the remaining 7 channels, using the same substitutions as detailed here
  • I then verified that the modified transfer function for all 8 channels using the SR785. I did not collect data for all the channels as netgpib was taking ages, but I did use the cursor on the screen to verify the position of the first notch at ~64 kHz. I noticed that all the channels did not have the lowest point of the notch at the same frequency. Rather, (at least on the screen), this varied between 63kHz and 67kHz. I would put this down to component tolerance. Assuming 5% tolerance shifts the theoretical notch frequency from 66268 Hz to 63112 Hz. 
  • After verifying the transfer functions, I went to 1Y4 and plugged the AI board into the eurocrate. I then connected the input of the AI board to the DAC output using my custom ribbon cable. Next, I used the excitation points set up earlier to send a 1 kHz, 32000 counts amplitude sine wave through the channels one at a time. I monitored the output using an oscilloscope and the LEMO monitor channels on the front panel of the board.
  • I found that the single-ended output of the AI board swings between -10 V and 10 V (w.r.t ground, oscilloscope trace attached). This is good because this is the range of input voltage to the PZT driver boards required to realize the full actuation range of the PZTs.
  • I also verified that the connections on the custom ribbon cable are correct (channel map was right) and that there were no accidental shorts (I checked other channels' output monitor while driving one channel). 

I think the board is okay to be used now.

AI_Board_Output.jpg

 

  8877   Thu Jul 18 23:34:40 2013 gautamConfigurationendtable upgradeCoarse adjustment of PZT axes orientation in mount

 I have managed to orient the PZT in the mount such that its axes are approximately aligned with the vertical and the horizontal. 

In the process, I discovered that the 4 screws on the back face of the PZT correspond to the location of the piezoelectric stacks beneath the tip-tilt platform. The PZT can therefore be oriented during the mounting process itself, before the mirror is glued onto the tip-tilt platform.

In order to verify that the pitch and yaw motion of the mirror have indeed been roughly decoupled, I centred the spot on the QPD, fed to the 'pitch' input of the PZT driver board (connected to channel 1 of the PZT) a 10 Vpp, 1 Hz sine wave from the SR function generator (having turned all the other relevant electronics, HV power supply etc ON. The oscilloscope trace of the output observed on the QPD is shown. The residual fluctuation in the Y-coordinate (blue trace) is I believe due to the tilt in the QPD, and also due to the fact that the PZT isnt perfectly oriented in the mount.

It looks like moving the tip-tilt through its full range of motion takes us outside the linear regime of the QPD calibration. I may have to rethink the calibration setup to keep the spot on the QPD in the linear range if the full range is to be calibrated, possibly decrease the distance between the mirror and the QPD. Also, in the current orientation, CH1 on the PZT controls YAW motion, while CH2 controls pitch.

Oscilloscope Trace:

Yellow: X-coordinate

Blue: Y-coordinate

PZT_out_waveform.jpg

  8883   Fri Jul 19 22:51:40 2013 gautamConfigurationendtable upgradeSecond mirror glued to PZT and mounted

 

I mounted the second PZT in a modified mount, and then glued a 1-inch Y2 mirror on it using superglue.

 Details:

-The mirror is a Laseroptik 1-inch, Y2 mirror with HR and AR coatings for 532 nm light.

-The procedure for mounting the mirror was the same as detailed in elog 8874. This time, I tried to orient the Piezo such that the four screws on the back face coincided with the horizontal and vertical axes, as this appeared to (somewhat) decouple the pitch and yaw motion of the tip-tilt on the first PZT.

-One thing I forgot to mention in the earlier elog: it is best to assemble the mount fully before inserting the tip-tilt into it and gluing the mirror to the tip-tilt. In particular, the stand should be screwed onto the mount before inserting the tip-tilt into the holder, as once it is in, it will block the hole through which one can screw the stand onto the mount. 

-I have placed the mirror on the SP table along with the rest of my QPD/Piezo calibration setup. I will attempt to calibrate this second PZT once I am done with the first one. 
 
Here is an image of the assembly:
Piezo-mirror_2.JPG

 

 

 

 

 

 

 

  8884   Fri Jul 19 23:35:31 2013 gautamConfigurationendtable upgradePreliminary Calibration of PZT

 I recalibrated the QPD today as I had shifted its position a little. I then identified the linear range of the QPD and performed a preliminary calibration of the Piezo tip-tilt within this range.

 


Details:

-I recalibrated the QPD as I had shifted it around a little in order to see if I could move it to a position such that I could get the full dynamic range of the piezo tilt within the linear regime of the QPD. This proved difficult because there are two reflections from the mirror (seeing as it is AR coated for 532nm and I am using a red laser). At a larger separation, these diverge and the stray spot does not bother me. But it does become a problem when I move the QPD closer to the mirror (in an effort to cut down the range in which the spot on the QPD moves). In any case, I had moved the QPD till it was practically touching the mirror, and even then, could not get the spot motion over the full range of the PZTs motion to stay within the QPD's linear regime (as verified by applying a 20Vpp 1Hz sine wave to the PZT driver board and looking at the X and Y outputs from the QPD amplifier. 

-So I reverted to a configuration in which the QPD was ~40cm away from the mirror (measured using a measuring tape).

-The new calibration constants are as follows (see attached plots):

X-Coordinate: -3.43 V/mm
Y-Coordinate: -3.41 V/mm


-I then determined the linear range of the QPD to be when the output was in the range [-0.5V 0.5V]. 

-Next, at Jenne's suggestion, I decided to do a preliminary calibration of the PZT within this linear range. I used an SR function generator to supply an input voltage to the PZT driver board's input (connected to Channel 1 of the piezo). In order to supply a DC voltage, I set a DC offset, and set the signal amplitude to 0V. I then noted the X and Y-coordinate outputs, being sure to run through the input voltages in a cyclic fashion as one would expect some hysteresis. 

-I did this for both the pitch and yaw inputs, but have only superficially analysed the latter case (I will put up results for the former later). 

 


Comments:

-There is indeed some hysteresis, though the tilt seems to vary linearly with the input voltage. I have not yet included a calibration constant as I wish to perform this calibration over the entire dynamic range of the PZT. 

 

-There is some residual coupling between the pitch and yaw motion of the tip tilt, possibly due to its imperfect orientation in the holder (I have yet to account for the QPD's tilt).

 

-I have not included a graphical representation here, but there is significantly more pitch to yaw coupling when my input signal is applied to the tip-tilts pitch input (Channel 2), as compared to when it is input to channel 1. It is not clear to me why this is so.

 

-I have to think of some smart way of calibrating the PZT over its entire range of motion, keeping the spot in the QPD's linear regime throughout. One idea is to start at one extreme (say with input voltage -10V), and then perform the calibration, re-centering the spot to 0 on the QPD each time the QPD amp output reaches the end of its linear regime. I am not sure if this will work, but it is worth a shot. The other option is to replace the red laser with a green laser (from one of the laser pointers) in the hope that multiple reflections will be avoided from the mirror. Then I will have to recalibrate the set up, and see if I can get the QPD close enough to the mirror such that the spot stays within the linear regime of the QPD. More investigation needs to be done.


Plots:

QPD Calibration Plots:
QPD-XCalib.pdf            QPD-YCalib.pdf

 

 

Piezo tilt vs input voltage plots:

 

                                                          Yaw Tilt                                                                                                                                         Pitch Tilt

Piezo_Yaw_Calib-in_QPD_linear_range-Yaw_tilt.pdf               Piezo_Yaw_Calib-in_QPD_linear_range-Pitch_tilt.pdf 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  8900   Tue Jul 23 04:07:48 2013 gautamUpdateCDSExcitation points set up on c1scx

 

 In light of recent events and the decision to test the piezo tip-tilts for green beam steering on the X-end table, I have set up 8 excitation points to channels 8 through 15 of the DAC on c1scx (as was done earlier for the DAC at 1Y4 with Jenne's help) in order to verify that the pin-outs of the DAC interface board. I have not yet compiled the model or restarted the computer, and will do these tomorrow, after which I will do the test. The channels are named YYY_CHAN9 etc. 

 

 

 

 

  8909   Tue Jul 23 16:47:01 2013 gautamUpdateCDSExcitation points set up on c1scx

 I just compiled and installed the model with the excitation points on c1scx and then restarted framebuilder. The channels I set up are now showing up in the awggui dropdown menu. I will do the tests on the DAC channels shortly.

Just to keep things on record, these are the steps I followed:

  • opened the model c1scx (path: /opt/rtcds/userapps/release/sus/c1/models) with MATLAB
  • Added 8 excitation points and saved the model. A copy has been saved as c1scx.mdl.r2010b because of the recent upgrade to r2013a. 
  • ssh to c1iscex (computer running the model c1scx). 
  • Entered the following sequence of commands in terminal: rtcds make c1scx ,  rtcds install c1scx , rtcds start c1scx 
  • ssh to framebuilder, and restarted the framebuilder by entering telnet fb 8088   and then   shutdown.
  8911   Tue Jul 23 19:38:58 2013 gautamUpdateCDSCharacterisation of DAC at 1X9

 

 I just finished carrying out the same checks for the DAC at 1X9 (with channels 9 through 16 that are unused as of now) as those I had done for the DAC at 1Y4, as the hardware prep up till now was done with the characterisation of the DAC at 1Y4. Conclusions:

  • The accessible range of output voltage are -10 V to +10V w.r.t ground --> No change needs to be made to the gain of the HV amplifier stage on the PZT Driver Board
  • The pin-outs of the DAC Adaptor Board at 1X9 is identical to that at 1Y4 --> Custom ribbons do not need to be modified.
  • The PSD of the DAC output has a peak at 64 kHz --> Notches on AI Board do not need to be moved again.

I will now proceed to install various pieces of hardware (AI Board, PZT driver board, HV Power Supply and cabling) at 1X9, while not making the connection to the PZTs till I receive the go ahead. 

  8912   Tue Jul 23 20:41:40 2013 gautamConfigurationendtable upgradeFull range calibration and installation of PZT-mounted mirrors

 Given that the green beam is to be used as the reference during the vent, it was decided to first test the PZT mounted mirrors at the X-endtable rather than the Y-endtable as originally planned. Yesterday, I prepared a second PZT mounted mirror, completed the full range calibration, and with Manasa, installed the mirrors on the X-endtable as mentioned in this elog. The calibration constants have been determined to be (see attached plots for aproximate range of actuation):

M1-pitch: 0.1106 mrad/V

M1-yaw: 0.143 mrad/V

M2-pitch: 0.197 mrad/V

M2-yaw: 0.27 mrad/V


Second 2-inch mirror glued to tip-tilt and mounted:

  • The spot sizes on the steering mirrors at the X-end are fairly large, and so two 2-inch steering mirrors were required.
  • The mirrors already glued to the PZTs were a CVI 2-inch and a Laseroptik 1-inch mirror.
  • I prepared another Laseroptik 2-inch mirror (45 degree with HR and AR coatings for 532 nm) and glued it to a PZT mounted in a modified mount as before.
  • Another important point regarding mounting the PZTs: there are two perforated rings (see attached picture) that run around the PZT about 1cm below the surface on which the mirror is to be glued. The PZT has to be pushed in through the mount till these are clear of the mount, or the actuation will not be as desired. In the first CVI 2-inch mirror, this was not the the case, which probably explains the unexpectedly large pitch-yaw coupling that was observed during the calibration [Thanks Manasa for pointing this out]. 

Full range calibration of PZT:

Having prepared the two steering mirrors, I calibrated them for the full range of input voltages, to get a rough idea of whether the tilt varied linearly and also the range of actuation. 

Methodology:

  • The QPD setup described in my previous elogs was used for this calibration. 
  • The linear range of the QPD was gauged to be while the output voltage lay between -0.5V and 0.5V. The calibration constants are as determined during the QPD calibration, details of which are here.
  • In order to keep the spot always in the linear range of the QPD, I stared with an input signal of -10V or +10V (ie. one extreme), and moved both the X and Y micrometers on the translational stage till both these coordinates were at one end of the linear range (i.e -0.5V or 0.5V). I then increased the input voltage in steps of ~1V through the full range from -10V to +10V DC. The signal was applied using a SR function generator with the signal amplitude kept to 0, and a DC offset in the range -5V to 5V DC, which gave the desired input voltages to the PZT driver board (between -10V DC and 10V DC).
  • When the output of the QPD amp reached the end of the linear regime (i.e 0.5V or -0.5V), I moved the appropriate micrometer dial on the translational stage to take it to the other end of the linear range, before continuing with the measurements. The distance moved was noted. 
  • Both the X and Y coordinates were noted in order to investigate pitch-yaw coupling.

Analysis and remarks:

  • The results of the calibration are presented in the plots below. 
  • Though the measurement technique was crude (and maybe flawed because of a possible z-displacement while moving the translational stage), the calibration was meant to be rough, and I think the results obtained are satisfactory. 
  • Fitting the data linearly is only an approximation, as there is evidence of hysteresis. Also, PZTs appear to have some drift, though I have not been able to quantify this (I did observe that the output of the QPD amp shifted by an amount equal to ~0.05mm while I left the setup standing for an hour or so).  
  • The range of actuation seems to be different for the two PZTs, and also for each degree of freedom, though the measured data is consistent with the minimum range given in the datasheet (3.5 mrad for input voltages in the range -20V to 120V DC). 

 

PZT Calibration Plots

The circles are datapoints for the degree of freedom to which the input is applied, while the 'x's are for the other degree of freedom. Different colours correspond to data measured with the position of the translational stage at some value.

                                            M1 Pitch                                                                                             M1 Yaw

M1_Pitch_calib.pdf     M1_Yaw_calib.pdf

 

                                              M2 Pitch                                                                                        M2 Yaw 

M2_Pitch_calib.pdf     M2_Yaw_calib.pdf

 



Installation of the mirrors at the X-endtable:

The calibrated mirrors were taken to the X-endtable for installation. The steering mirrors in place were swapped out for the PZT mounted pair. Manasa managed (after considerable tweaking) to mode-match the green beam to the cavity with the new steering mirror configuration. In order to fine tune the alignment, Koji moved ITMx and ETMx in pitch and yaw so as to maximise green TRX. We then got an idea of which way the input pointing had to be moved in order to maximise the green transmission.

 

Attachment 5: PI_S330.20L.pdf
PI_S330.20L.pdf
  8932   Mon Jul 29 13:39:25 2013 gautamConfigurationendtable upgradePZT Driver Board-further changes

 

 

I have updated the schematic of the D980323 PZT driver boards to reflect the changes made. The following changes were made (highlighted in red on the schematic):

  • Gain of all four HV amplifier stages changed from ~15 to ~5 by swapping 158k resistors R43, R44, R69 and R70 for 51k resistors.
  • Electrolytic 10 uF capacitors C11, C12, C29 and C31 swapped for 470pF, 500V mica capacitors.
  • Fixed resistor in voltage divider (R35, R40, R59 and R64) replaced with 0 ohm resistors so as to be able to apply a bias of -10V to the HV amplifier
  • The DC-DC Series components, which I think were originally meant to provide the 100V DC voltage, have been removed.
  • The path between the point at which +100V DC is delivered and jumpers J3 and J6 has been shorted (bypassing R71 and R11 for J3, R73 and R12 for J6).
  • Tantalum capacitors C38 and C39 have been replaced with electrolytic capacitors (47 uF, 25V). One of the original tantalum capacitors had burned out when I tried installing the board in the eurocrate, shorting out -15V to ground. At Koji's suggestion, I made this switch. The AD797s do not seem to be oscillating after the switch.


I have also changed the routing of the 100V from the HV power supply onto the board, it is now done using an SMA T-connector and two short lengths of RG58 cable with SMA connectors crimped on.

The boards are functional (output swings between 0 and 100V as verified with a multimeter for input voltages in the range -10V to +10V applied using a function generator.

 



Revised schematics:

D980323-C-modified.pdf

D980323-C-modified-pg2.pdf

 

 

 

  8935   Mon Jul 29 21:57:45 2013 gautamConfigurationendtable upgradeHardware installed at 1X9

 The following hardware has been installed on rack 1X9;

  • KEPCO high voltage power supply (kept in a plastic box at the bottom of the rack, with the 3m SMA cable carrying 100V running along the inside side wall of the rack). The HV supply has not been connected to the driver board yet.
  • AI board D000186 installed in top eurocrate. The board does not seem to fit snugly into the slot, so I used a longish screw to bolt the front panel to the eurocrate.
  • PZT driver board D980323 installed in top eurocrate adjacent to the AI board.
  • Six 11m SMB-LEMO cables have been laid out from 1X9 to the endtable. I have connected these to the PZT driver board, but the other end (to the PZTs) is left unconnected for now. They have been routed through the top of the rack, and along the cable tray to the endtable. All the cables have been labelled at both ends. 


I have also verified that the AI board is functional in the eurocrate by using the LEMO monitoring points on the front panel.


The driver boards remain to be verified, but this cannot be done until we connect the HV supply to the board. 

 

 

  8942   Tue Jul 30 19:40:47 2013 gautamConfigurationendtable upgradeDAC-PZT Driver Board Output Signal Chain Tested

 

 [Alex, Gautam]

The signal chain from the DAC output to the output of the PZT driver board (including the HV supply) has been verified. 

I had installed the two boards in the eurocrate yesterday and laid out the cables from 1X9 to the endtable. The output of the AI board had been verified using the monitor port on the front panel, but the output from the PZT driver board was yet to be checked because I had not connected the HV supply yesterday.

When I tried this initially today, I was not getting the expected output from the monitor channels on the front panel of the PZT driver board, even though the board was verified to be working. Alex helped debug the problem, which was identified as the -15V supply voltage not making it onto the board.

I changed the slot the board was sitting in, and used a long screw to bolt the board to the crate. Both the AI board and the PZT driver board seem to be slightly odd-sized, and hence, will not work unless firmly pushed into the eurocrate and bolted down. This would be the first thing to check if a problem is detected with this system. 

In any case, I have bolted both boards to the eurocrate, and the output from the PZT driver board is as expected when I sent a 10Vp sine wave out from the DAC. I think the cables can now be hooked up to the PZTs once we are pumped down.

  8943   Tue Jul 30 19:44:05 2013 gautamConfigurationendtable upgradeSecond mirror glued to PZT and mounted

 

 I have glued a fourth mirror to a PZT (using superglue) and inserted it into a modified mount. This is to be used together with the 1-inch Laseroptik mirror I had glued a couple of weeks back at the Y-endtable. I will be calibrating both these mirrors tonight such that these are ready to put in as soon as we are pumped down.

The mirror was one of those removed from the X-endtable during the switch of the steering mirrors. It is a CVI 2-inch mirror, with HR and AR coatings for 532 nm. 

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