Zach and Koji
We measured uncalibrated angle-to-length coupling using tdssine and tdsdmd.
We made a simple shell script to measure the a2l coupling.
- Opened the IMC/OMC light door.
- Saw the large misalignment mostly in pitch. Aligned using MC2 and MC3.
- Locked the MC in the low power mode. (script/MC/mcloopson AND MC length gain 0.3->1.0)
- Further aligned MC2/3. We got the transmission of 0.16, reflection of 0.2
- Tried to detect angle-to-length coupling so that we get the diagnosis of the spot positions.
- Tried to use ezcademod. Failed. They seems excite the mirror but returned NaN.
- We used tdssine and tdsdmd instead. Succeeded.
- We made simple shell script to measure the a2l coupling. It is so far located users/koji/100421/MCspot
- We blocked the beam on the PSL table. We closed the chamber and left.
Koji and Kevin measured the vertical beam profile of the Innolight 2W laser at one point.
This data was taken with the laser crystal temperature at 25.04°C and the injection current at 2.092A.
The distance from the razor blade to the flat black face on the front of the laser was 13.2cm.
The data was fit to the function y(x)=a*erf(sqrt(x)*(x-x0)/w)+b with the following results.
Reduced chi squared = 14.07
x0 = (1.964 +- 0.002) mm
w = (0.216 +- 0.004) mm
a = (3.39 +- 0.03) V
b = (3.46 +- 0.03) V
razor height (mm) Voltage (V)
Back in Gainesville in 1997, I learned how to do this using the chopper wheel. We had to make the assumption that the wheel's blade was moving horizontally during the time of the chop.
One advantage is that the repetitive slices reduces the random errors by a lot - you can trigger the scope and average. Another advantage is that you can download the average scope trace using USB, floppy, or ethernet instead of pencil and paper.
But, I never analyzed it in enough detail to see if there was some kind of nasty systematic error.
Good fit. I assumed sqrt(x) is a typo of sqrt(2).
x0 = (1.964 +- 0.002) mm
w = (0.216 +- 0.004) mm
a = (3.39 +- 0.03) V
b = (3.46 +- 0.03) V
I updated the default FILTER.adl file located in /home/controls/cds/advLigo/src/epics/util/ on megatron. I moved the yellow ! button up slightly, and fixed the time string in the upper right.
The attached plot shows the spectra of the 3 Z axes of the 3 seismometers we have (this data is from ~20Aug2009, when the Ranger was in the Z orientation) in Magenta, Cyan and Green, and the noise of each of the sensors in Red, Blue and Black. The noise curves were extracted from the spectra using the Huddle Test / 3 Corner Hat method. The Blue and Black traces which are just a few points are estimates of the noise from other spectra. The Blue points come from the Guralp Spec Sheet, and the Black comes from the noise test that Rana and I did the other day with the Ranger (elog 2223).
I'm not really happy with the black spectra - it looks way too high. I'm still investigating to see if this is a problem with my calibration/method....
So, as it turns out (surprise), I'm a spaz and forgot a 2*pi when calibrating the Guralp noise spectra from the spec sheet. I noticed this when redoing the Huddle Test, and comparing my Spec Sheet Guralp noise with Rana's, which he shows in elog 2689. When going from m/s^2, the units in the spec sheet, I just tilted the line by a factor of frequency. Koji pointed out that I needed a factor of 2*pi*f. That moves the Guralp spec line in the plot in elog 2237 (to which this entry is a reply) down by ~6, so that my measured noise is not, in fact, below the spec. This makes things much more right with the world.
In other news, I redid the Huddle analysis of the 2 Guralp seismometers, ala Rana's elog 2689. The difference is now we are on the granite slab, with soft rubber feet between the floor and the granite. We have not yet cut holes in the linoleum (which we'll do so that we're sitting directly on the 40m's slab).
Rana> this seems horrible. Its like there's a monster in there at 6-7 Hz! Either the seismos are not centered or the rubber balls are bad or Steve is dancing on the granite slab again.
What kind of fit did you use? How are the uncertainties in the parameters obtained?
Joe and I started working on the new LSC FE control today. We made a diagram of the system in Simulink, but were unable to compile it.
Joe checked out the latest CDS software out of their new SVN and put it somewhere (perhaps his home directory).
We then copied the directory with the .mdl files and the CDS parts library into our real Simulink Model Directory:
Use this and not someplace in Alex or Rob's home directory !
Joe will put in more details on Monday once he figures out how to build the new stuff. Basically, we decided not to support multiple versions of the CDS real time code here. We'll just stay synced to the latest stable ~versions.
I exported the current version of the LSC FE into our public_html/FE/ area on nodus where we will put all of the self-documenting FE diagrams:
To make a web setup like this, you just use the "Export to Web" feature from the top-level Simulink diagram (e.g. lsc.mdl). Choose the following options:
Note: in order to get the web page to work, I had to change the apache httpd.conf file to allow AddType file overriding. Here's the term cap of the diff:
nodus:etc>diff httpd.conf httpd.conf~
< ServerAdmin email@example.com
> ServerAdmin firstname.lastname@example.org
< AllowOverride FileInfo
The vertical beam profile of the Innolight 2W laser was measured at eight points along the axis of the laser.
These measurements were made with the laser crystal temperature at 25.04°C and the injection current at 2.091A. z is the distance from the razor blade to the flat black face of the front of the laser.
The voltage from a photodiode was measured for the razor at a number of heights. Except for the first two points, one scan was made with the razor moving down and a second scan was made with the razor moving up. This data was fit to
y = a*erf(sqrt(2)*(x-x0)/w) + b with the following results:
The values for w and its uncertainty were estimated with a weighted average between the two scans for the last six points and all eight points were fit to
w = w0*sqrt(1+(z-z0)2/zR2) with the following results:
chi^2/ndf = 17.88
w0 = (0.07 ± 0.13) mm
z0 = (-27 ± 121) mm
zR = (65 ± 93) mm
It looks like all of the data points were made in the linear region so it is hard to estimate these parameters with reasonable uncertainty.
1. The vertical axis should start from zero. The horizontal axis should be extended so that it includes the waist. See Zach's plot http://nodus.ligo.caltech.edu:8080/40m/2818
2. Even if you are measuring only the linear region, you can guess w0 and z0, in principle. w0 is determined by the divergence angle (pi w0/lambda) and z0 is determined by the linear profile and w0. Indeed your data have some fluctuation from the linear line. That could cause the fitting prescision to be worse.
3. Probably the biggest reason of the bad fitting would be that you are fitting with three parameters (w0, z0, zR) instead of two (w0, z0). Use the relation ship zR= pi w0^2/lambda.
LSC Plant Model. That is all.
Once you made a CDS model, please update the following wiki page. This will eventually help you.
LSC Plant Model. That is all.
The SVN checkout was done on megatron. It is located under /home/controls/cds/advLigoRTS
So, to compile (or at least try to) you need to copy the .mdl file from /cvs/cds/caltech/cds/advLigo/src/epics/simLink to /home/controls/cds/advLigoRTS/src/epics/simLink on megatron, then run make SYS in the advLigoRTS directory on megatron.
The old checkout from CVS exists on megatron under /home/controls/cds/advLigo.
I scanned the temperature of the crystal oven on Friday night in order that we can find the optimal temperature of the crystal for SHG.
The optimal temperature for this crystal was found to be 36.2 deg.
The crystal is on the PSL table. The incident beam on the crystal is 27.0mW with the Newport power-meter configured for 1064nm.
The outgoing beam had 26.5mW.
The outgoing beam was filtered by Y1-45S to eliminate 1064nm. According to Mott's measurements, Y1-45S has 0.5% transmission for 1064nm, while 90% transmission for 532nm. This means I still had ~100uW after the Y1-45S. This is somewhat consistent with the offset seen in the power-meter reading.
First, I scanned the temperature from 28deg to 40deg with 1deg interval.The temperature was scaned by changing the set point on the temperature controller TC-200.The measurements were done with the temperature were running. So, the crystal may have been thermally non-equilibrium.
Later, I cut the heater output so that the temperature could be falling down slowly for the finer scan. The measurement was done from 38deg to 34deg with interval of 0.1deg with the temperature running.
I clearly see the brightness of the green increase at around 36 deg. The data also shows the peak centered at 36.2deg. We also find two lobes at 30deg and 42deg. I am not sure how significant they are.
To fix a problem one of the models was having, I checked the CVS version of the Bitwise.pm file into the SVN (located in /home/controls/cds/advLigoRTS/src/epics/util/lib), which adds left and right bit shifting funtionality. The yec model now builds with the SVN checkout.
Also while trying to get things to work, I discovered the cdsRfmIO piece (used to read and write to the RFM card) now only accepts 8 bit offsets. This means we're going to have to change virtually all of the RFM memory locations for the various channels, rather than using the values from its previous incarnation, since most were 4 bit numbers. It also means it going to eat up roughly twice as much space, as far as I can tell.
Turns out the problem we were having getting to compile was nicely answered by Koji's elog post. The shmem_daq value was not set to be equal to 1. This caused it to look for myrimnet header files which did not exist, and caused compile time errors. The model now compiles on megatron.
[Edit by KA: 4 bit and 8 bit would mean "bytes". I don't recall which e-log of mine Joe is referring.]
Talked with Jay briefly this morning.
We are due another 1-U 4 core (8 CPU) machine, which is one of the ones currently in the test stand. I'm hoping sometime this week I can convince Alex to help me remove it from said test stand.
The megatron machine we have is definitely going to be used in the 40m upgrade (to answer a question of Rana's from last Wednesday's meeting). Thats apparently the only machine of that class we get, so moving it to the vertex for use as the LSC or SUS vertex machine may make sense. Overall we'll have the ASS, OMC, Megatron (SUS?), along with the new 4 1-U machines, for LSC, IO, End Y and End X. We are getting 4 more IO chassis, for a total 5. ASS and OMC machine will be going without full new chassis.
Speaking of IO chassis, they are still being worked on. Still need a few cards put in and some wiring work done. I also didn't see any other adapter boards finished either.
I tried Koji's suggestions for improving the fit to the vertical beam profile; however, I could not improve the uncertainties in the fit parameters.
I started retaking the data today with the same laser settings used last time and noticed that the photodiode was saturating. We were using an ND 4.0 neutral density filter on the photodiode. Koji and I noticed that the coating on the filter was reduced in the center and added an additional ND 0.6 filter to the photodiode. This seemed to fix the photodiode saturation.
I think that the photodiode was also saturating to a lesser extent when I took the last set of data. I will take another vertical beam profile tomorrow.
[Edit by KA: Metallic coating started being evaporated and the ND filters reduced their attenuation. We decided to use absorptive one as the first incident filter, and put a thinner one behind. This looked fine.]
Give me the plot of the fit, otherwise I am not convinced.
Kiwamu and Koji
The PRM/SRM were balanced with the standoffs. We glued them to the mirror.
This was the last gluing so far until we get new PRM/ETMs.
The mode profile of Gaussian beams in our PPKTP crystals was calculated.
I confirmed that the Rayleigh range of the incoming beam (1064 nm) and that of the outgoing beam (532 nm) is the same.
And it turned out that the waist postion for the incoming beam and the outgoing beam should be different by 13.4 mm toward the direction of propagation.
These facts will help us making optical layouts precisely for our green locking.
The result is shown in the attached figure, which is essentially the same as the previous one (see the entry).
The horizontal axis is the length of the propagation direction, the vertical axis is the waist size of Gaussian beams.
Here I put x=0 as the entering surface of the crystal, and x=30 mm as the other surface.
The red and green solid curve represent the incoming beam and the outgoing beam respectively. They are supposed to propagate in free space.
And the dashed curve represents the beams inside the crystal.
A trick in this calculation is that: we can assume that the waist size of 532 nm is equal to that of 1064 nm divided by sqrt(2) .
If you want to know about this treatment in detail, you can find some descriptions in this paper;
"Third-harmonic generation by use of focused Gaussian beams in an optical super lattice" J.Opt.Soc.Am.B 20,360 (2003)"
I thought that the micrometer I was using to move the razor through the laser beam was metric; however, it is actually english.
After discovering this mistake, I converted my previous measurements to centimeters and fit the data to
w = sqrt(w0^2+lambda^2*(z-z0)^2/(pi*w0)^2) with the following results:
reduced chi squared = 14.94
z0 = (-4.2 ± 1.9) cm
w0 = (0.013 ± 0.001) cm
Beginning last week, I have been helping Koji with some of the IO work that must be done for the 40m upgrade. The first thing he asked me to do is to help with the alignment of the MC.
As I understand, it became apparent that the IFO beam was not centered on all (or any) of the MC mirrors, which is disadvantageous for obvious reasons. We are trying to correct this, using the following strategy:
Using the results of these measurements, it is possible to evaluate the components of a block-diagonal matrix M which relates the tilt-to-displacement coupling of each DOF to each mirror's misalignment in that degree, i.e.,
a = M x
with a a 6-dimensional vector containing the coupling of each degree of freedom to the length of the cavity and x a 6-dimensional vector containing the angular misalignments of each. Due to orthogonality of pitch and yaw, M will take the form of a 6x6 matrix with two non-zero 3x3 blocks along the diagonal and zero matrices on the off-diagonal blocks.
The idea is to isolate components of M by moving one mirror at a time, solve for them, then find the inverse M-1 that should give us the required angular adjustments to obtain the beam-centered ideal cavity mode.
In theory, this need only be done once; in practice, our measurement error will compound and M will not be accurate enough to get the beams exactly centered, so we will have to iterate.
NOTE: The fact that we are adjusting the three cavity mirrors to obtain the ideal mode means that we will necessarily tarnish our coupling into the cavity. Once we have adjusted the mirrors once, we will need to re-steer the input beam and center it on the REFL diode.
Status: This process has been completed once through step 5. I am in the process of trying to construct the matrix for the first adjustment.
Restarted the elog with the script as it was down.
I have worked out the first set of adjustments to make on the MC mirrors (all angle figures are in units of the increments on the control screen)
Using the method described in the previous post, I obtained the following matrix relating the angle-to-length coupling and the angular deviations. In the following matrix, Mij corresponds to the contribution of the jth degree of freedom to the ith A-to-L coupling, with the state vector defined as xi = (MC1P, MC2P, MC3P, MC1Y, MC2Y, MC3Y), where each element is understood as the angular deviation of the specific mirror in the specific direction from the ideal position, such that x = 0 when the cavity eigenmode is the correct one and the beams are centered on the mirrors (thus giving no A-to-L coupling regardless of the components of M).
-0.2843 -0.4279 -0.1254 0 0 0
-0.8903 -0.4820 -0.6623 0 0 0
0.5024 0.0484 -0.0099 0 0 0
0 0 0 0.1145 -0.1941 -0.3407
0 0 0 0.0265 1.5601 0.2115
0 0 0 0.1015 0.1805 -0.0103,
giving an inverse
0.0003 -0.0001 0.0020 0 0 0
-0.0031 0.0006 -0.0007 0 0 0
0.0018 -0.0018 -0.0022 0 0 0
0 0 0 -0.0013 -0.0015 0.0117
0 0 0 0.0005 0.0008 -0.0008
0 0 0 -0.0037 -0.0010 0.0044
The initial coupling vector is then acted on with this inverse matrix to give an approximate state vector x containing the angular misalignments of each mirror in pitch and yaw. The results are below:
Would it be possible to write about the technique on a wiki page as you get measurements and results?
I used the Mathematica CurveFit package that we use in Ph6/7 to make the fits for the beam profile data. I wrote two functions that use CurveFit shown in the attachment to make the fits to the error function and square root.
Sure. I figured I would put up a How-To if it works.
Koji, Steve, and Kevin looked into calibrating the Wilcoxon accelerometers. Once calibrated, the accelerometers will be used to monitor the motion of the PSL table.
We want to use the shaker to shake each accelerometer and monitor the motion with an OSEM. We will make a plate to attach an accelerometer to the shaker. A flag will also be mounted on this plate.The OSEM will be mounted on the table next to the shaker and positioned so that the flag can block the LED light as the plate moves up and down. We will then measure the motion of the accelerometer as it is shaken from the OSEM signal. The OSEM signal will be calibrated by keeping the plate and the flag still and moving the OSEM down along the flag a known distance with a micrometer.
Awhile back we had requested a feature for the RCG code where a single file would define a memory location's name as well as its explicit hex address. Alex told me it had been implemented in the latest code in SVN. After being unable to find said file, I went back and talked to him and Rolf. Rolf said it existed, but had not been checked into the SVN yet.
I now have a copy of that file, called G1.ipc. It is supposed to live in /cvs/cds/caltech/chans/ipc/ , so I created the ipc directory there. The G1.ipc file is actually for a geo install, so we'll eventually make a C1.ipc file.
The first couple lines look like:
There are also section using ipcType IPC:
Effectively the ipcNum tells it which memory location to use, starting with 0x2000 (at least thats how I'm interpreting it. Every entry of a given ipcType has a different ipcNum which seems to be correlated to its description (at least early on - later in the file many desc= lines repeat, which I think means people were copy/pasting and got tired of editing the file. Once I get a C1.ipc file going, it should make our .mdl files much more understandable, at least for communicating between models. It also looks like it somehow interacts with the ADCs/DACs with ipcType PCI, although I'm hoping to get a full intro how to use the file tomorrow from Rolf and Alex.
I've added a diagram in the wiki under IFO Upgrade 2009-2010->New CDS->Diagram section Joe_CDS_Plan.pdf (the .svg file I used to create it is also there). This was mostly an exercise in me learning inkscape as well as putting out a diagram with which lists control and model names and where they're running.
A direct link is: CDS_Plan.pdf
- Checked the SRM/PRM balancing after the gluing.
- The mirrors were removed from the suspensions for baking.
- Bob is going to bake them next week.
The spot positions on the MC mirrors were measured with coil balance gains.
The estimated spot positions from the center of the MC1 and MC3 are as followings:
MC1H = +0.29 mmMC1V = -0.43 mmMC3H = +1.16 mmMC3V = -0.68 mm
The cordinates are described in the figure
As far as the cavity mirrors are aligned to the incident beam, spots on the MC1 and MC3 tell us the geometry of the incident beam.
Note that spot position on the MC2 is determined by the alignment of the MC1 and MC3, so it does not a big issue now.
The calibration between the coil balance and the spot position are described in the previous entry.
MC Trans: 0.18
MC Refl: 0.12-0.13
MC Trans: 0.18
MC Refl: 0.12-0.13
(subtract 1, then multiply 10.8mm => spot position.)
Deviations of the MC spot from the center of the mirrors were measured.
1) The vertical deviation looks easy being adjusted as they are mostly translation. They are ~0.5mm too high.
The distance from SM2 to MC is 1.8m. Thus what we have to do is
rotate SM2 Pitch in CW knob by 0.25mrad.
1 turn steers the beam in 10mrad. So 0.25mrad is 1/40 turn (9deg)
2) The horizontal deviation is more troublesome. The common component is easily being adjusted
but the differential component (i.e. axis rotation) involves large displacement of the beam
at the periscope sterring mirrors.
(MC3H - MC1H) / 0.2 m * 1.8 m = 8 mm
The beam must be moved in 8mm at the periscope. This is too big.
We need to move the in-vac steering mirror IM1. Move SM2Yaw in 7mrad. This moves the spot on IM1 by 5mm*Sqrt(2).
Then Move Im1 Yaw such that we see the resonance.
For the alignment adjustment, try to maximize the transmission by MC2 Yaw (cavity axis rotation) and SM2Y (beam axis translation)
Actual move will be:
- Move IM1Y CCW (assuming 100TPI 1.5 turn in total...half turn at once)
- Compensate the misalignment by SM2Y CW as far as possible.
- Take alignment with MC2Y and SM2Y as far as possible
This operation will move the end spot something like 15mm. This should be compensated by the alignment of MC1Y at some point.
Actually, I tried some tweaks of the input steering to get the beam being more centered on the MC mirrors on Saturday evening.
I made a mistake in the direction of the IM1Y tuning, and it made the horizontal spot position worse.
But, this also means that the opposite direction will certainly improve the horizontal beam angle.
Rotate IM1Y CCW!!!
The current setting is listed below
MC1H = +1.15 mm
MC1V = -0.13 mm
MC3H = +0.80 mm
MC3V = -0.20 mm
MC1H = +1.15 mm
MC1V = -0.13 mm
MC3H = +0.80 mm
MC3V = -0.20 mm
Lessons learned on the beam spot centering (so far)
The spot position on MC2 can be adjusted by the alignment of the mirror while maintaining the best overlapping between the beam and the cavity axes.
In general, there are two methods:
1) Use the cavity as a reference:
Move the MC mirrors such that the cavity eigenmode hits the centers of the mirrors.
-> Then adjust the incident beam to obtain the best overlapping to the cavity.
2) Use the beam as a reference:
Move the incident beam such that the aligned cavity has the spots at the centers of the mirrors.
-> Then adjust the incident beam to obtain the best spot position while the cavity mirrors keep tracking
the incident beam.
Found the method 1) is not practical.
This is because we can move the eigenmode of the cavity only by very tiny amount if we try to keep the cavity locked.
How much we can move by mirror alignment is smaller than the waist radius or the divergence angle.
For the MC, the waist radius is ~2mm, the divergence angle is 0.2mrad. This means the axis
translation of ~1mm is OK, but the axis rotation of ~4mrad is impractical.
Also it turned out that adjustinig steering mirror to the 10-m class cavity is quite difficult.
A single (minimum) touch of the steering mirror knob is 0.1mrad. This already change the beam position ~0.1mm.
This is not an enough resolution.
Method 2) is also not so easy: Steering mirrors have singular matrix
Indeed! (Remember the discussion for the IMMT)
What we need is the pure angle change of 4mrad at the waist which is ~2m distant from the steering mirror.
This means that the spot at the steering mirror must be moved by 8mm (= 4mrad x 2m). This is the result of the
nearly-singular matrix of the steering mirrors.
We try to avoid this problem by moving the in-vac mirror (IM1), which has somewhat independent move.
The refl beam path also has the big beam shift.
But once the vacuum manifold is evacuated we can adjust very little angle.
This can also be a good news: once the angle is set, we hardly can change it at the PSL side.
Talked with Jay briefly today. Apparently there are 3 IO chassis currently on the test stand at Downs and undergoing testing (or at least they were when Alex and Rolf were around). They are being tested to determine which slots refer to which ADC, among other things. Apparently the numbering scheme isn't as simple as 0 on the left, and going 1,2,3,4, etc. As Rolf and Alex are away this week, it is unlikely we'll get them before their return date.
Two other chassis (which apparently is one more than the last time I talked with Jay), are still missing cards for communicating between the computer and the IO chassis, although Gary thinks I may have taken them with me in a box. I've done a look of all the CDS stuff I know of here at the 40m and have not seen the cards. I'll be checking in with him tomorrow to figure out when (and if) I have the the cards needed.
I've updated the LSC and IFO models that Rana created with new shared memory locations. I've used the C1:IFO- for the ifo.mdl file outputs, which in turn are read by the lsc.mdl file. The LSC outputs being lsc control signals are using C1:LSC-. Optics positions would presumably be coming from the associated suspension model, and am currently using SUP, SPX, and SPY for the suspension plant models (suspension vertex, suspension x end, suspension y end).
I've updated the web view of these models on nodus. They can be viewed at: https://nodus.ligo.caltech.edu:30889/FE/
I've also created a C1.ipc file in /cvs/cds/caltech/chans/ipc which assigns ipcNum to each of these new channels in shared memory.
I got around to actually try building the LSC and IFO models on megatron. Turns out "ifo" can't be used as a model name and breaks when trying to build it. Has something to do with the find and replace routines I have a feeling (ifo is used for the C1, H1, etc type replacements throughout the code). If you change the model name to something like ifa, it builds fine though. This does mean we need a new name for the ifo model.
Also learned the model likes to have the cdsIPCx memory locations terminated on the inputs if its being used in a input role (I.e. its bringing the channel into the model). However when the same part is being used in an output role (i.e. its transmitting from the model to some other model), if you terminate the output side, it gives errors when you try to make.
Its using the C1.ipc file (in /cvs/cds/caltech/chans/ipc/) just fine. If you have missing memory locations in the C1.ipc file (i.e. you forgot to define something) it gives a readable error message at compile time, which is good. The file seems to be being parsed properly, so the era of writing "0x20fc" for block names is officially over.
Ottavia was moved this afternoon from the control room into the lab, adjacent to Mafalda in 1Y3 on the top shelf. It has been connected to the camera hub, as well as the normal network. Its cables are clearly labeled. Note the camera hub cable should be plugged into the lower ethernet port. Brief tests indicate everything is connected and it can talk to the control room machines.
The space where Ottavia used to be is now temporarily available as a good place to setup a laptop, as there is keyboard, mouse, and an extra monitor available. Hopefully this space may be filled in with a new workstation in the near future.
Koji and Zach
We improved the beam axis rotaion on the MC. We still have 3mrad to be corrected.
So far we lost the MC Trans spot on CCD as the beam is now hitting the flange of the window. We need to move the steering mirror.
To do next:
- MC2 spot is too much off. Adjust it.
- Rotate axis for 3mrad more.
- Adjust Vertical spot position as a final touch.
- Incident beam had 7mrad rotation.
- Tried to rotate in-vac steering mirror (IM1) in CCW
- After the long struggle the beam from PSL table started to hit north-east side of IM1 mount.
- Moved the IM1. All of the beam (input beam, MC Trans, MC Refl) got moved. Chaotic.
- Recovered TEM00 resonance. MC Trans CCD image missing. The beam axis rotation was 8.5mrad.
Even worse. Disappointed.
- We made a strategic plan after some deliberation.
- We returned to the initial alignment of Saturday only for yaw.
Not at once, such that we don't miss the resonance.
- Adjusted SM2Y and IM1Y to get reasonable resonance. Then adjusted MC2/3 to have TEM00 lock.
- Measured the spot positions. The axis rotation was 4.8mrad.
- Moved the spot on IM1 by 7mm by rotating SM2Y in CCW - ((A) in the figure)
- Compensated the misalignment by IM1Y CCW. ((B) in the figure)
Used a large sensor card with puch holes to see the spot distribution between the MC1 and MC3.
- Fine alignment by MC2/MC3. Lock to TEM00. The beam axis rotation was 3mrad.The beam axis translation was 3mm.
- This 3mm can be Compensated by IM1Y. But this can easily let the resonance lost.
Put the sensor card between MC1/MC3 and compensated the misalignment by MC3 and MC1.
Note: You match the returned spot from the MC2 to the incident beam by moving the spot deviation by MC3,
the spot returns to the good position on MC1. But the angle of the returned beam is totally bad.
This angle deviation can be adjusted by MC1.
Note2: This step should be done for max 2mm (2mrad) at once. As 2mrad deviation induces the spot move on the MC2 by an inch.
- After all, what we get is
MC1H = -0.15 mmMC1V = -0.33 mmMC3H = +0.97 mmMC3V = -0.33 mm
This corresponds to the axis rotation of 3mrad and the beam axis translation of 0.8mm (to north).
Here's the (calibrated) transimpedance of the new REFL55 PD.
T(55.3) / T_(11.06) = 93 dB
Ben, Steve, and Koji
Ben came to the 40m and hooked up a cable to the main interlock service.
We have tested the interlock and confirmed it's working.
[Now the laser is approved to be used by persons who signed in the SOP.]
The RC, PMC, and MZ were unlocked during the interlock maneuver.
Now they are relocked.
Zach and Koji,
MC1H = -0.12mm
MC1V = -0.13mm
MC2H = -0.15mm
MC2V = +0.14mm
MC3H = -0.14mm
MC3V = -0.11mm
MC1H = -0.12mm
MC2H = -0.15mm
MC2V = +0.14mm
MC3H = -0.14mm
MC3V = -0.11mm
The aperture right before the vacuum window has been adjusted to the beam position. This will ensure that any misalignment on the PSL table can have the correct angle to the mode cleaner as far as it does resonate to the cavity. (This is effectively true as the small angle change produces the large displacement on the PSL table.)
If we put an aperture at the reflection, it will be perfect.
Now we can remove the MZ setup and realign the beam to the mode cleaner!
- The beam axis rotation has been adjusted by the method that was used yesterday.
Differential: SM2Y and IM1Y
Common: SM2Y only
- We developped scripts to shift the MC2 spot without degrading the alignment.
These scripts must be upgraded to the slow servo by the SURF students.
- These are the record of the alignment and the actuator balances
C1:SUS-MC1_PIT_COMM = 2.4005
C1:SUS-MC1_YAW_COMM = -4.6246
C1:SUS-MC2_PIT_COMM = 3.4603
C1:SUS-MC2_YAW_COMM = -1.302
C1:SUS-MC3_PIT_COMM = -0.8094
C1:SUS-MC3_YAW_COMM = -6.7545
C1:SUS-MC1_ULPIT_GAIN = 0.989187
C1:SUS-MC1_ULYAW_GAIN = 0.987766
C1:SUS-MC2_ULPIT_GAIN = 0.985762
C1:SUS-MC2_ULYAW_GAIN = 1.01311
C1:SUS-MC3_ULPIT_GAIN = 0.986771
C1:SUS-MC3_ULYAW_GAIN = 0.990253
I suggest "ITF" for the model name.
After munching analytical models, simulations, measurements of photodiodes I think I got a better grasp of what we want from them, and how to get it. For instance I now know that we need a transimpedance of about 5000 V/A if we want them to be shot noise limited for ~mW of light power.
Adding 2-omega and f1/f2 notch filters complicates the issue, forcing to make trade-offs in the choice of the components (i.e., the Q of the notches)
Here's a better improved design of the 11Mhz PD.
The accelerometer power supply / preamp board has been OFF because of exciting new accelerometer measurements. It's now on, so watch out and make sure to turn it back off before plugging / unplugging accelerometers.
I added a noise model of the SR560 to the LISO opamp.lib. This assumes you're using it in G=100, low-noise mode. The voltage noise is correct, but I had to guess on the current noise because I didn't measure it before. Lame.
This can be compared with the noise that we measure when locking it down...
For reasons unknown, the seismic spectra posted above Rosalba has been wrong since ~January when it was first posted. The noise that we were claiming was waaaay lower than is really possible.
Rana and I checked the calibrations, and the numbers in DTT for the Ranger and the Guralp are correct (it's unknown what was being used at the time of the bad plot) - Cal for the Guralp is 3.8e-9 m/s, and for the Ranger is 1.77e-9 m/s.
Something is funny with the accelerometer calibration. Hopefully Kevin's investigation will sort it out. Their calibration used to be 1.2e-7 m/s^2 , but it was changed to be 7e-7 m/s^2 to match the noise level of the accelerometers with the seismometers at ~10Hz. We need to go through the calibration carefully and figure out why this is!
Posted above Rosalba for easy reference, and attached below, is the new seismic spectra. The black trace is when the Ranger's mass is locked down, and the teal circle markers indicate the Guralp Spec-Sheet Noise Floor.
** Rana says> the y-axis in Jenne's plot is (m/s)/sqrt(Hz). The Guralp has a velocity readout bandwidth of 0.03-40 Hz, so we would have to modify the calibration to make it right in those frequencies. I believe the Ranger cal has the correct poles in it. The huge rise at low frequencies is because of the 1/f noise of the SR560.
This should be better. It should also have larger resonance width.