RIght! Overview out of the way - now comes the trivial first bit

Step 1: Beam out of the laser - this will be tricky, but we'll see what we can actually measure in this set-up. Can't get the Beamscan head any closer to the laser and using a lambda/2 plate + polariser to control power until the Faraday isolator is in place. Using 1 inch separation holes as reference points for now - need better resolution later, but this is fine for now and gives an idea of where things need to go on the bench. The beam is aligned to the 3rd row up (T) for all measurements, the Beamscan spits out diameters (measuring only the 13.5% values) so convert as required to beam radius and the beam is checked to ensure a reasonable Gaussian profile throughout.

Position A1_13.5%_width A2_13.5%_width

(bench) (um mean) (um mean)

32 2166.1 1612.5

31 2283.4 1708.3

30 2416.1 1803.2

29 2547.5 1891.4

27 2860.1 2070.3

26 2930.2 2154.4

25 3074.4 2254.0

24 3207.0 2339.4

OK. As expected, this measurement is in the linear region of the beampath - i.e. not close to the  waist position and beyond the Rayleigh length) so it pretty much looks like two straight lines. There's no easy way to get into the path closer to the laser, so reckon we'll just need to infer back from the waist after we get a lens in there. Attached the plot, but about all you really need to get from this is that the beam out of the laser is very astigmatic and that the vertical axis expands faster than the horizontal.

Not terribly exciting, but have to start somewhere.

Step 2: Getting the beam through the Faraday isolator (FI).

Started out with an f=100mm lens at position 32,T on the bench which gave a decent looking waist of order 100 um in the right sort of position for the FI, but after checking the FI specs, it's limited to 500W/cm^2. In other words, if we have full power from the laser passing into it we'd need a beam width of more than 211 um. Solution? Use an f=150mm lens instead and don't put the FI at the waist. I normally don't put a FI at a waist anyway, for assorted reasons - scattering, thermal lensing, non-linear magnetic fields, the sharp changing of the field components in an area where you want as constant a beam as possible.  Checked with others to make sure they don't do things differently around these parts… Koji says it doesn't matter as long as it passes cleanly through the aperture. So… next step is inserting the Faraday.

The beam profiles in vertical and horizontal around the FI position with the f=150mm lens in place are attached. Note that the FI will be going in at around 0.56m.

Additional:

I fired up some old waistplotter routines, and set the input conditions as the measured waist after the lens and used that to work out what the input waist is at the laser. It may not be entirely accurate, but it /will/ be self consistent later on.

Vertical waist      = 105.00 um at 6.282 cm after laser output (approx)

Horizontal waist = 144.63 um at 5.842 cm after laser output (approx)

Definitely astigmatic.

Step 3: Inserting FI and un-eliptical-ification of the beam

The FI set up on it's mount and the beam passes through it - centrally through the apertures on each side. Need to make sure it doesn't clip and also make sure we get 93% through (datasheet specs say this is what we should achieve). We will not achieve this, but anything close should be acceptable.

Setting up for minimum power through the FI is HWP @125deg.

Max is therefore @ 80deg

Power before FI = 544 mW

Power after FI =     496 mW (after optimising input polarisation)

Power dumped at input crystal = 8.6mW

Power dumped at input crystal from internal reflections etc = 3.5mW

Power dumped at output crystal on 1st pass = approx 8mW

OK. that gives us a 90.625% transmission and a 20.1mW absorption/unexplained loss.

Well - OK. The important part about isolators isn't their transmission, it's about how well they isolate. Let's see how much power gets ejected on returning through the isolator…

Using a beam splitter to pick off light going into and returning from the FI. A 50/50 BS1-1064-50-1025-45P. And using a mirror near the waist after the FI to send the beam back through. There are better ways to test the isolation performance of FI's but this will suffice for now - really only want to know if there's any reasonable isolation at all or if all of the beam is passing backwards through the device.

Power before BS = 536 mW (hmmn - it's gone down a bit)

Power through BS = (can't access ejected on first pass)

Power through FI = 164 mW (BS at odd angle to minimise refractive effect so less power gets through)

Power lost through mirror = 8.3mW (mirror is at normal incidence so a bit transmissive)

Using earlier 90.6% measurement as reference, power into FI = 170.83 mW

So BS transmission = 170.83/536 = 0.3187

BS reflectivity therefore = 1 - 0.3187 = 0.6813

Power back into FI = Thru FI - Thru mirror = 155.7 mW

Power reflected at BS after returning through FI = 2.2mW

Baseline power at BS reflection from assorted internal reflections in FI (blocked return beam) = 1.9mW

Note - these reflections don't appear to be back along the input beam, but they *are* detectable on the power meter.

Actual power returning into FI that gets reflected by BS = 0.3 mW

(note that this is in the fluctuating noise level of measurement so treat as an upper limit)

Accounting for BS reflectivity at this angle, this gives a return power = 0.3/0.6813 = 0.4403 mW

Reduction ratio (extinction ratio) of FI =  0.4403/155.7 = 0.00282

Again - note that this upper limit measurement is as rough and ready as it gets. It's easy to optimise this sort of thing later, preferable on a nice open bench with plenty of space and a well-calibrated photodiode. It's just to give an idea that the isolator is actually isolating at all and not spewing light back into the NPRO.

Next up… checking the mode-matching again now that the FI is in place. The beam profile was scanned after the FI and the vertical and horizontal waists are different...

Step 3b: Non-circular? We can fix that...

A quick Beamscan sweep of the beam after the Faraday:

Position A1_13.5%_width A2_13.5%_width

(bench) (um mean) (um mean)

25.8 503.9 478.8

25 477.5 489.0

24 447.1 512.4

21 441.6 604.5

20 476.3 645.4

19 545.4 704.1

18 620.3 762.8

OK. It looks not too bad - doesn't look too different from what we had. Note that the x axis is in local table units - I found this useful for working out where things were relative to other things (like lenses and the FI) - but it means the beam propagates from right to left in the plot. in other words, the horizontal waist occurs first and is larger than the vertical waist. Also - they're not fitted curves - they're by-eye, best guesses and there's no solution for the vertical that doesn't involve offsets... discussion in a later part of the thread.

Anyway! The wonderful thing about this plot is that the horizontal and vertical widths cross and the horizontal focussing at this crossing point is shallower than the vertical. This means that we can put a lens in at the crossing point and rotate it such that the lens is stronger in the horizontal plane. The lens can be rotated until the effective horizontal focal length is right to fix the astigmatism.

I used a 200mm lens I had handy - a rough check sweeping the Beamscan quickly indicated should be about right though. Adjusting the angle until the beam size at a distant point is approx circular - I then move the profiler and adjust again. Repeat as required. Now… taking some data. with just that lens in:

Position A1_13.5%_width A2_13.5%_width

(bench) (um mean) (um mean)

24 371.7 366.1

21 360.3 342.7

20 447.8 427.8

19 552.4 519.0

18 656.4 599.2

17 780.1 709.9

16 885.9 831.1

Well now. That looks quite OK. Fit's a bit rubbish on vertical but looks like a slight offset on the measurement again.

The angle of the lens looks awful, but if it's stupid and it works then it isn't stupid. If necessary, the lens can be tweaked a bit more, but there's always more tweaking possible further down the line and most of the astigmatic behaviour has been removed. It's now just a case of finding a lens that works to give us a 50 um beam at the oven position...

Step 4: Matching into the oven

Now that the astigmatism is substantially reduced, we can work out a lens solution to obtain a 50um waist *anywhere* on the bench as long as there's enough room to work with the beam afterwards. The waist after the Faraday and lens is at position 22.5 on the bench. A 50 mm lens placed 18 cm after this position (position 14.92 on the bench) should give a waist of 50 um at  24.57 cm after the waist (position 12.83 on the bench). This doesn't give much room to measure the beam waist in though - the Beamscan head has a fairly large finite size… wonder if there's a slightly less strong lens I could use…

OK. With a 66 mm lens at 23 cm (position 13.45 on the bench) after the waist we get a 50 um waist at 31.37 cm after the waist (position 10.15 on the bench). 

Closest lens I found was 62.9mm which will put the 50um point a bit further towards the wall, but on the X-arm the oven is at position 8.75 ish. So anything around there is fine.

Using this lens and after a bit of manual fiddling and checking with the Beamscan, I figured we needed a close in, fine-grained measurement so set the Beamscan head up on a micrometer stage Took a whoie bunch of data around position 9 on the bench:

Position A1_13.5%_width A2_13.5%_width

(mm) (um mean) (um mean)

-15 226.8 221.9

-14 210.9 208.3

-13 195.5 196.7

-12 181.0 183.2

-11 166.0 168.4

-10 154.0 153.1

-9 139.5 141.0

-8 127.5 130.0

-7 118.0 121.7

-6 110.2 111.6

-5 105.0 104.8

-4 103.1 103.0

-3 105.2 104.7

-2 110.9 110.8

-1 116.8 117.0

0 125.6 125.6

0 125.6 125.1

1 134.8 135.3

2 145.1 145.6

3 155.7 157.2

4 168.0 168.1

5 180.5 180.6

6 197.7 198.6

7 211.4 209.7

8 224.0 222.7

9 238.5 233.7

10 250.9 245.8

11 261.5 256.4

12 274.0 270.4

13 291.3 283.6

14 304.2 296.5

15 317.9 309.5

And at this point the maximum power available at the oven-waist is 298mW. With 663mW available from the laser with a desired power setting of 700mW on the supply. Should make sure we understand where the power is being lost. The beam coming through the FI looks clean and unclipped, but there is some stray light around.

Position A1_13.5%_width A2_13.5%_width

(bench) (um mean) (um mean)

7 868.5   739.9

6 1324 1130

5 1765 1492

4 2214 1862

The plot looks pretty good, but again, there looks to be an offset on the 'fitted' curve. Taking a couple of additional points further on to make sure it all works out as the beam propagates. I took a few extra points at the suggestion of Kiwamu and Koji - see the zoomed out plot.  The zoomed in plot has by-eye fit lines - again, because to get the right shape to fit the points there appears to be an offset. Where is that coming from? My suspicion is that the Beamscan doesn't take account of the any background zero offsets when calculating the 13.5% and we've been using low power when doing these measurements - very small focussed beams and didn't want to risk damage to the profiler head.

Decided to take a few measurements to test this theory. Trying different power settings and seeing if it gives different offset and/or a changed width size

7 984.9 824.0 very low power

7 931.9 730.3 low power

7 821.6 730.6 higher power

7 816.4 729.5 as high as I'm comfortable going

Trying this near the waist…

8.75 130.09 132.04 low power

8.75 106.58 105.46 higher power

8.75 102.44 103.20 as high as it can go without making it's saturated

So it looks like offset *is* significant and the Beamscan measurements are more accurate with more power to make the offsets less significant. Additionally, if this is the case then we can do a fit to the previous data (which was all taken with the same power setting) and simply allow the offset to be a free parameter without affecting the accuracy of the waist calculation. This fit and data coming to an e-log near you soon.

Of course, it looks from the plots above (well... the code that produces the plots above) that the waist is actually a little bit small (around 46um) so some adjustment of the last lens back along the beam by about half a cm or so might be required.

 I went through the entries.

1. Give us a photo of the day. i.e. Faraday, tilted lens, etc...

2. After all, where did you put the faraday in the plot of the entry 4466?

3. Zoomed-in plot for the SHG crystal show no astigmatism. However, the zoomed out plot shows some astigmatism.
How consistent are they? ==> Interested in seeing the fit including the zoomed out measurements.

I strain relieved RF cables labeled 33 MHZ LO and 166 MHZ to EOM at 1X2  This is a temporary setup for the 11 MHZ

The coax N  bulkheads connectors are mounted on the plastic front panel now.

 OK. Taking these completely out of order in the easiest first...

2. The FI is between positions 27.75 and 32 on the bench - i.e. this is where the input and output apertures are. (corresponds to between 0.58 and 0.46 on the scale of those two plotsand just before both the vertical and horizontal waists) At these points the beam radius is around 400um and below, and the aperture of the Faraday is 4.8mm (diameter).

1. Photos...

Laser set up - note the odd angles of the mirrors. This is where we're losing a goodly chunk of the light. If need be we could set it up with an extra mirror and send the light round a square to provide alignment control AND reduce optical power loss...

Faraday and angled lens - note that the lens angle is close to 45 degrees. In principle this could be replaced with an appropriate cylindrical lens, but as long as there's enough light passing through to the oven I think we're OK.

3. Fitting... coming soon once I work out what it's actually telling me. Though I hasten to point out that the latter points were taken with a different laser power setting and might well be larger than the actual beam width which would lead to astigmatic behaviour.

Right. Fitting to the data. Zoomed out plots first. I used the general equation f(x) = w_o.*sqrt(1 + (((x-z_o)*1064e-9)./(pi*w_o.^2)).^2)+c for each fit which is basically just the Gaussian beam width parameter calculation but with an extra offset parameter 'c'

Vertical fit for zoomed out data:

Coefficients (with 95% confidence bounds):

       c =   7.542e-06  (5.161e-06, 9.923e-06)

       w_o =   3.831e-05  (3.797e-05, 3.866e-05)

       z_o =       1.045  (1.045, 1.046)

Goodness of fit:

  SSE: 1.236e-09

  R-square: 0.9994

The doubling oven is now ready to go for the Y arm. The PPKTP crystal is mounted in the oven:

Note - the crystal isn't as badly misaligned as it looks in this photo. It's just an odd perspective shot. I then closed it up and checked to make sure the IR beam on the Y bench passes through the crystal. It does. Just need to tweak the waist size/position a bit and then we can actually double some frequencies!

Last bit of oven matching for now.

I moved the lens before the oven position back along the beam path by about 1cm - waist should be just above position 9 in this case. Note - due to power-findings from previous time I'm maximising the power into the head to reduce the effect of offsets.

From position 9:

Position A1_13.5%_width A2_13.5%_width

(mm) (um mean) (um mean)

-1 121.1 123.6

0 112.5 113.8

1 106.4 106.1

2 102.9 103.4

3 103.6 103.6

4 106.6 107.4

5 111.8 112.5

6 118.2 120.1

7 126.3 128.8

8 134.4 137.1

9 143.8 146.5

10 152.8 156.1

11 163.8 167.1

12 175.1 176.4

13 186.5 187.0

14 197.1 198.4

15 210.3 208.9

16 223.5 218.7

17 237.3 231.0

18 250.2 243.9

19 262.8 255.4

20 274.7 269.0

21 290.4 282.3

22 304.3 295.5

23 316.7 303.1

Note - had to reduce power due to peak saturation at 15mm - don't think scale changed, but be aware just in case. And saturated again at 11. And again at 7. A little bit of power adjustment each time to make sure the Beamscan head wasn't saturating. Running the fit gives...

OK. The fit is reasonably good. Residuals around the area of interest (with one exception) are <+/- 2um and the waists are 47.5um (vertical) and 50.0um (horizontal) at a position of 9.09 on the bench. And the details of the fitting output are given below.

-=-=-=-=-=-=-=-=-=-=-=-

Vertical Fit

cf_ =

     General model:

       cf_(x) = w_o.*sqrt(1 + (((x-z_o)*1064e-9)./(pi*w_o.^2)).^2)+c

     Coefficients (with 95% confidence bounds):

       c =   5.137e-06  (4.578e-06, 5.696e-06)

       w_o =   4.752e-05  (4.711e-05, 4.793e-05)

       z_o =        1.04  (1.039, 1.04)

cfgood_ = 

           sse: 1.0699e-11

       rsquare: 0.9996

           dfe: 22

    adjrsquare: 0.9996

          rmse: 6.9738e-07

-=-=-=-=-=-=-=-=-=-=-=-

Horizontal Fit

cf_ =

     General model:

       cf_(x) = w_o.*sqrt(1 + (((x-z_o)*1064e-9)./(pi*w_o.^2)).^2)+c

     Coefficients (with 95% confidence bounds):

       c =    3.81e-06  (2.452e-06, 5.168e-06)

       w_o =   5.006e-05  (4.909e-05, 5.102e-05)

       z_o =        1.04  (1.04, 1.04)

cfgood_ = 

           sse: 4.6073e-11

       rsquare: 0.9983

           dfe: 22

    adjrsquare: 0.9981

          rmse: 1.4471e-06

We now have green light at the Y end. 

The set-up (with careful instructions from Kiwamu) - setting up with 100mW of IR into the oven.

Input IR power = 100mW measured.

Output green power = 0.11mW

(after using 2 IR mirrors to dump IR light before the power meter so losing a bit of green there light too)

And it's pretty circular-looking too. Think there might be a bit more efficiency to be gained near the edges of the crystal with internal reflections and suchlike things but that gives us an UGLY looking beam.  Note - the polarisation is wrong for the crystal orientation so used a lambda/2 plate to get best green  power out.

Efficiency is therefore 0.11/100 = 0.0011 (0.11%) at 100mW input power.

Temperature of the oven seems to be around 35.5degC for optimal conversion.

Took a picture. Ta-dah! Green light, and lots more where that came from! Well... about 3x more IR available anyway.

We ripped out all of the old AS, PLL, and REFL paths, green, orange, and cyan respectively on the old AP table layout photo:

• AS (green): had already been re-purposed by putting a ThorLabs diode right after the first steering mirror.   Everything downstream of that has been removed.
• PLL (orange): everything removed.
• REFL (cyan): CCD was left in place, so everything upstream of that was not touched.  Everything else was removed, including all of the REFL detectors.
• OMCT (purple): previously removed
• OMCR (blue): left in place, but the diode and CCD are not connected (found that way).
• MCT (magenta): previously removed.
• IMRC (red): untouched

All optics and components were moved to the very south end of the SP table.

We also removed all spurious cables from the table top, and from underneath, as well as pulled out no-longer-needed power supplies.

Every so often things just work out. You do the calculations, you put the lenses on the bench, you manually adjust the pointing and fiddle with the lenses a bit, you get massive chunks of assistance from Kiwamu to get the alignment controls and monitors set up and after quite a bit of fiddling and tweaking the cavity mirror alignment you might get some nice TEM_00 -like shapes showing up on your Y-arm video monitors.

So. We have resonating green light in the Y-arm. The beam is horribly off-axis and the mode-matching, while close enough to give decent looking spots, has in no way been optimised yet. Things to do tomorrow - fix the off-cavity-axis problem and tweak up the mode-matching... then start looking at the locking...

 Locked!

The Y-arm can now be locked with green light using the universal PDH servo. Modulation frequency is now 277kHz - chosen because it seems to produce smaller offsets due to AM effects

To lock, turn on the servo, align the system to give nice circular-looking TEM_00 resonances, and wait for a good one. It'll lock on a decent mode for a few seconds and then you can turn on the local boost and watch it lock for minutes and minutes and minutes.

The suspensions are bouncing around a bit on the Y-arm and the spot is quite low on the ETMY and a little low on ITMY, but from this point it can be tweaked and optimised.

I spent some time tracking down the AS beam which had vanished from the AP table. Eventually, by dramatically mis-aligning SRM, PRM and ITMY, returning BS to its Jan 1st PITCH and YAW values and tweaking the ITMX alignment [actual values to follow], I was able to get an AS beam out onto the AP table. I verified that it was the prompt reflection off ITMX by watching it move as I changed the YAW of that optic and watching it stay stationary as I changed the YAW of ITMY.

Jamie and I then steered the beam through a 2" PLCX-50.8-360.6 lens and placed the RF PD (AS55) at the focus. Additionally, we installed the AS camera to observe the leakage field through a Y1S steering mirror (as shown in the attached diagram).

Currently the PD has power but the RF and DC outputs are not connected to anything at the moment.

Atm 2 by Steve

OK… the Y-arm may be locked with green light, which was the goal, and this is all good but it's not yet awesome. Awesome would be locked and aligned properly and quiet and optimised. So...  in order to assist in increasing the awesome-osity, here are a few stream-of-consciousness thoughts and stuff I've noticed and haven't had time to fix/investigate or have otherwise had pointed out to me that may help...

Firstly, the beam is not aligned down the centre of the cavity. It's pretty good horizontally, but vertically it's too low by about 3/4->1cm on ETMY. The mirrors steering the beam into the cavity have no more vertical range left, so in order to get the beam higher the final two mirrors will have to be adjusted on the bench. Adding another mirror to create a square will give more range AND there will be less light lost due to off 45degree incident angles. When I tried this before I couldn't get the beam to return through the Faraday, but now the cavity is properly aligned this should not be a problem.

A side note on alignment - while setting cameras and viewports and things up, Steve noticed that one of the cables to one of the coils (UL) passes behind the ETMY. One of the biggest problems in getting the beam into the system to begin with was missing this cable. It doesn't fall directly into the beam path if the beam is well aligned to the cavity, but for initial alignment it obscures the beam - this may be a problem later for IR alignment.

Next, the final lambda/2 waveplate is not yet in the beam. This will only become a problem when it comes to beating the beams together at the vertex, but it WILL be a problem. Remember to put it in before trying to extract signals for full LSC cavity locking.

Speaking of components and suchlike things, the equipment for the green work was originally stored in 3 plastic boxes which were stored near the end of the X-arm. These boxes, minus the components now used to set up the Y-end, are now similarly stored near the end of the Y-arm.

Mechanical shutter - one needs to be installed on the Y-end just like the X-end. Wasn't necessary for initial locking, but necessary for remote control of the green light on/off.

Other control… the Universal PDH box isn't hooked up to the computers. Connections and such should be identical to the X-arm set-up, but someone who knows what they're doing should hook things up appropriately.

More control - haven't had a chance to optimise the locking and stability so the locking loop, while it appears to be fairly robust, isn't as quiet as we would like. There appears to be more AM coupling than we initially thought based on the Lightwave AM/PM measurements from before. It took a bit of fiddling with the modulation frequency to find a quiet point where the apparent AM effects don't prevent locking. 279kHz is the best point I've found so far. There is still a DC offset component in the feedback that prevents the gain being turned up - unity gain appears limited to about 1kHz maximum. Not sure whether this is due to an offset in the demod signal or from something in the electronics and haven't had time left to check it out properly yet. Again, be aware this may come back to bite you later.

Follow the bouncing spot - the Y-arm suspensions haven't been optimised for damping. I did a little bit of fiddling, but it definitely needs more work. I've roughly aligned the ETMY oplev since that seems to be the mass that's bouncing about most but a bit of work might not go amiss before trusting it to damp anything.

Think that's about all that springs to mind for now…

Thanks to everyone at the 40m lab for helping at various times and answering daft questions, like "Where do you keep your screwdrivers?" or "If I were a spectrum analyser, where would I be?" - it's been most enjoyable!

Y-end PDH electronics.

The transfer function of the Y-end universal PDH box:

AS port ITMX YAW  range where AS beam was visible = [-1.505, -1.225] - these extrema put the beam just outside of some aperture in the system -> set ITMX YAW to -1.365

ITMX PITCH range = [-0.7707, -0.9707] -> set to ITMX PITCH to -0.8707

To understand the situation of the ADC cabling at the LSC rack I looked around the rack and the cables.

The final goal of this investigation is to have nice and noise less cables for the ADCs (i.e. non-ribbon cable)

Here is just a report about the current cabling.

(current configuration)

At the moment there is only one ribbon-twisted cable going from 1Y2 to 1Y3. (We are supposed to have 4 cables).

At the 1Y2 rack the cable is connected to an AA board with a 40 pin female IDC connector.

At the 1Y3 rack the cable is connected to an ADC board with a 37 pin female D-sub connector.

The ribbon cable is 28AWG with 0.05" conductor spacing and has 25 twisted pairs (50 wires).

(things to be done)

 - searching for a twisted-shielded cable which can nicely fits to the 40 pin IDC and 37 pin D-sub connectors.

 - estimating how long cable we need and getting the quote from a vendor.

 - designing a strain relief support

I've just installed the new control room machine: "pianosa".   It is a replacement for the old sun machine "op440m" [0].

Hardware:

• dual dual-core Intel Core i7-2600 CPU @ 3.40GH, hyperthreaded to provide 8 effective cores
• 16G memory (4x 4G dimms)
• nVidia GF108 GeForce GT 430

It's now running Ubuntu 10.04 LTS 64bit.  Unfortunately, the default 10.04 kernel is 2.6.32, which does not support pianosa's apparently very new network adapter, which is (from lspci):

00:19.0 Ethernet controller: Intel Corporation 82579LM Gigabit Network Connection (rev 04)

To get around this I temporarily added a PCI nic so that I could get on the network.  I then added the Ubuntu kernel team PPA archive and installed linux-image-2.6.38-2, which is new enough to have the needed network driver, but not completely bleeding edge:

sudo add-apt-repository ppa:kernel-ppa/ppa
sudo apt-get update
sudo apt-get install linux-image-2.6.38-2-generic linux-headers-2.6.38-2-generic

Once the built in nic was working I removed the temporary one.  Everything seems to be working fine now.

I have not yet done any configuration to integrate pianosa into the CDS network.  I'll do that tomorrow.

[0] op44m has been moved into the control room rack next to linux1, in headless mode.  If there is still a need to run scripts that only run on solaris, op440m can still be accessed via ssh as normal.  Hopefully we can fully decommission this machine soon.

[1] https://launchpad.net/~kernel-ppa/+archive/ppa

We found a stray unused heliax cable running from the LSC rack 1Y2 to a point between the cabinets 1X3 and 1X4. This cable will need to be redirected to the AS table in the new scheme.   It is labled C1LSC-PD5  The current situation has been updated as seen in the layout below

The Martian wireless bridge has the ethernet cable inserted in the wrong connector.

It should be inserted to one of the four port. Not in the "INTERNET" connector.

Once the connector has been changed, the martian net as well as the internet became accessible from the laptops.

 I was charge with making a Non-Inverting Op Amp Low Pass Feedback circuit for Jenne, which may somehow be integrated into a seismometer project she's working on.

Circuit diagram is attached. Calculations show that R1, R2 and C have the following relationship: if R1=10^n, R2=10^(n+1), C=10^(-n-4). For the particular circuit being modeled by the transfer function, R1=100 Ohm, R2=1k Ohm, and C=1uF.

Attached also is the circuit's Bode plot, showing frequency versus gain and phase, respectively. The frequency versus gain graph is true to what the circuit was calculated to generate: a gain of +20 and a cutoff frequency at 200Hz. Not sure what's going on with the frequency verus phase plot.

The attached plot shows the 30 day trend of the MC3 UL PD signal. The signal dropped to zero at some point but now it is close to the level it was a few weeks ago. There still could be a problem with the cable.

The rest of the MC1,2,3 PD signals looked ok.

Building on what was posted previously

The configuration has now evolved into an Inverting Op Amp Feedback Low Pass Filter circuit.

Had to change out some components to satisfy conditions: R1=1k Ohm, R2=10k Ohm, C=0.1uF. These were changed in order to decrease the magnitude of the current passing through the op amp by a factor of 10 (10V supplied through the R1 resistor yields about 10mA). The configuration itself was changed from non-inverting to inverting in order to get the frequency vs. gain part of the Bode plot to continue to decrease across higher frequencies instead of leveling off around 4kHz.

 Having finished the bulk of the work for the LPF itself ( see here ), I have begun trying to design the seismometer box to Jenne's specifications.

Currently looking into what the voltage buffer amplifier might look like for this.

Suggestions/corrections would be much appreciated!

I installed 'glue' on Rossa, Allegra, and Rosalba.  This is a Python module that includes a facility for LIGO_LW XML files.  Oddly, I couldn't find the glue package on Pianosa.

New right angle PVC front panel with SMA bulkhead connectors are in place. The connections are still lose. It is ready for Suresh to finalise his vision on it.

I am tuning the notch filters for the bounce modes in the suspensions, starting with the ITMs and ETMs.  I'll do the MCs, the PRMs, and the SRMs next.

I noticed that the filter for ITMX (in the file C1SUS.txt, the module ITMX_SUSPOS, the selection BounceRoll) that the filter was composed of two bandstops (and a constant gain).  It looked like this:

ellip("BandStop",4,1,40,11.4,12.2)ellip("BandStop",4,1,40,16.7,17.5)gain(1.25872)

Valera said that one of these was for the roll mode and the other for the bounce mode.  However, looking at the spectra that Kiwamu and I made this week, I don't perceive a resonance between 11.4 and 12.2 Hz.  So, we're taking a guess that this was for a mode that has moved due to new pendulum designs.  For many of the suspensions, in the free swinging test we noticed a line around 23 Hz; we thought we might as well re-use one of these elliptical filters to avoid exciting this line.  Of course, if this line does *not* result from excitation of an uncontrolled degree of freedom, this will not help and could be detrimental.  When we talk to Valera again, we can review this decision and at that point we might decide just to take out that bandstop.

ITMX is done.  I'll continue tomorrow.  I've attached closed-loop spectra for before the tuning (itmx-before.pdf) and after (itmx-after.pdf).

(Update: the following day, I took closed loop spectra with (itmx-withbounceroll.pdf) and without (itmx-nobounceroll.pdf) the bandstops.  It looks like the bandstops made the bounce mode slightly worse, but the roll mode slightly better.)

I tuned the ITMY bandstops -- 'before' and 'after' spectra attached.  Note that the after the tuning, the bounce mode at ~16 Hz is about twice as quiet!

However, notice that in the 'before' plot the roll mode at about 23.5 Hz did not show up at all, whereas it is quite prominent in the 'after' plot.  I was concerned that this line could have been a result of placing the bandstop there, so I made another plot with the BounceRoll filter turned off.  Sure enough, the 23.5 Hz line is still there.  So I'm not crazy: the roll mode did start acting up at some time between my 'before' and 'after' plot, but not as a result of the tuning.

I have updated the /opt/rtcds paths to reflect the new specification of the CDS aLIGO code release procedures document.

Path to RTS:  /opt/rtcds/caltech/c1/core/release

This is where the advLigoRTS front-end code generator is checked out.  The "release" directory is a link to the svn branch from which we are currently running ("trunk" by default).

This used to be at /opt/rtcds/caltech/c1/core/advLigoRTS

Path to userapps: /opt/rtcds/caltech/c1/userapps/release

This is where the cds_user_apps code is checked out.  cds_user_apps is where all of the front-end models, medm screen, scripts, etc. will live.  The "release" directory is a link to the svn branch from which we are currently running ("trunk" by default).

This was most recently at /opt/rtcds/cds_user_apps

Yesterday we found that MC3 OSEM LL PD did not have a sensible signal - the readback was close to zero and it was making MC move around. I disabled the PD LL so that the damping is done with just three face plus side PDs. There still no signal from MC3 LL PD today. It needs debugging.

The schematic for the seismometer box from this last time  has been updated...

Koji was helpful for coming up with a general diagram for the voltage buffer amplifier, which has now been added to the configuration pictured below.

The only thing that remains now before I try to plot it with Eagle/LISO is to pick an op amp to use for the voltage buffer itself. Someone suggested THS4131 for that (upon Googling, it hit as a "high speed, low noise, fully-differential I/O amplifier"). It looks good, but is it the best option?

[Valera / Kiwamu]

It was because of a loose connection. Pushing the connector solved the issue.

We really have to think about making reliable connections and strain reliefs.

[Valera / Kiwamu]

The pointing of the incident beam to the interferometer has been jumping frequently.

Due to this jump the lock of the Y arm didn't stay for more than 2 min.

We turned off the strain gauge loop of PZT2-YAW and PZT2-PITCH, then the spot motion became solid and the Y arm locking became much more robust.

I tuned the bounce and roll mode bandstops for ETMY, although it was difficult for me to tell if there was improvement with the bandstops on relative to the bandstops off because it seemed like the bounce and roll modes were being excited intermittently.  I'll take spectra with the filters both on and off during an evening next week.

cd /opt/rtcds/caltech/c1/userapps
rm -rf trunk
svn update --depth=files trunk
svn update --depth=empty trunk/{CDS,ISI,ISC,PSL,SUS}
svn update trunk/{CDS,ISI,ISC,PSL,SUS}/{c1,common}

As of RCG version 2.1, recorded channels use the suffix "_DQ", instead of "_DAQ".  I just rebuilt and installed the c1lsc model, which changed the channel names, therefore hosing the old daq channel ini file.  Here's what I did, and how I fixed it:

$ ssh c1lsc
$ cd /opt/rtcds/caltech/c1/core/trunk
$ make c1lsc
$ make install-c1lsc
$ cd /opt/rtcds/caltech/c1/scripts
$ ./startc1lsc
$ cd /opt/rtcds/caltech/c1/chans/daq
$ cat archive/C1LSC_110517_152411.ini | sed "s/_DAQ/_DQ/g" >C1LSC.ini
$ telnet fb 8087
daqd> shutdown

c1sus and c1auxey crashed, required hard reboot

For some reason, we found that c1sus and c1auxey were completely unresponsive.  We went out and gave them a hard reset, which brought them back up with no problems.

This appears to be related to a very similar problem report by Kiwamu just a couple of days ago, where c1lsc crashed after editing the C1LSC.ini and restarting the daqd process, which is exactly what I just did (see my previous log).  What could be causing this?

I added a lockin to the LSC model, and added it's corresponding control to the LSC screen.  Here's is what I added to the LSC model:

On the left are the froms from the normalized RF PD outputs. Those go into a matrix, whose single row goes into the lockin signal input. The clock output from the lockin goes into the LSC output matrix (last row).

Here is what I added to the LSC master screen:

I also modified the lockin overview screen:

I think this new screen looks a lot cleaner.  Maybe we could start using this one as a template for lockin screens.

 This is OK....but, the input matrix should come from the same place as the regular input matrix: i.e. it should be just another row like CARM, DARM, etc. rather than have its own screen.

Also, I think a nice mod to all the matrices would be if the ORANGE triangle was only visible when there's a signal flowing through it.

Last Saturday the POY55 RFPD (see this entry) was installed on the ITMY optical bench for the trial of the DRMI locking.

Since the amount of the light coming into the diode is tiny, the DC monitor showed ~ 3 mV even when the PRC was locked to the carrier.

In order to amplify the tiny RF signal from the photo diode a ZHL amplifier was installed next to the RFPD. The RF amp is sitting on delrin posts for insulation from the table.

The DC Transimpedance of POP55 was increased from 50 Ohm to 10010 Ohm. There is the offset of 46mV. This should be cancelled in the CDS.

The top-level subsystem subdirectories in the cds_user_apps source repository were renamed today to be all lower case.  This required checking out the new directory and updating all of the model links in /opt/rtcds/caltech/c1.  Here is how I updated the cds_user_apps working tree:

cd /opt/rtcds/caltech/c1/userapps
mv trunk{,.bak}
svn update --depth=files trunk
svn update --depth=empty trunk/{cds,isi,isc,psl,sus}

I then fixed the links in the /opt/rtcds/caltech/c1/core/release/src/epics/simLink directory:

for link in $(find . -maxdepth 1 -type l); do ln -sf $(readlink $link | tr [:upper:] [:lower:]) ; done

A couple of things had to be cleaned up:

• /opt/rtcds/caltech/c1/userapps/trunk/cds/c1/models/c1uct.mdl was linked in, but that model doesn't seem to exist anymore, so I removed the link.
• a couple of things were linked from /opt/rtcds/caltech/c1/userapps/trunk instead of /opt/rtcds/caltech/c1/userapps/release, so I fixed those links.
• /opt/rtcds/caltech/c1/userapps/release/cds/test/models/llo/l1isctest.mdl was not checked out, so I checked it out and fixed the link (this model should really be named something different if it is of common use, or we plan on using it at the 40m).

!!!CHECK IN MODEL CHANGES!!!

Today I found three models that were modified, but not checked in to the SVN repository:

M       sus/c1/models/lib/sus_single.mdl
M       isc/c1/models/c1lsc.mdl
M       isc/c1/models/c1mcp.mdl

I checked in the c1lsc model, since I think it was just the change that Kiwamu made in http://nodus.ligo.caltech.edu:8080/40m/4749.  I left the others, since I have no idea what they are or who made them.

Please please please remember to commit your model changes to the SVN after you're done.  This is particularly important for important models, such as c1lsc.  If you don't check in your changes I can pretty much guarantee that at some point you will loose them.

 You're absolutely right.  That was a brain-fart oversight.  I fixed the model so that the input from the lockin comes from another output row in the RFPD input matrix.  I then fixed the C1LSC medm screen accordingly:

This is obviously much simpler and more straight-forward.

A future improvement would be to modify the DCPD input matrix to be able to route those signals to the lockin as well.  This is actually currently possible since the DCPD input matrix is just a subset of the full input matrix, but it's not available via medm yet.

 I went ahead and added the lockin output to the DCPD input matrix.