[Manasa, Evan]

Manasa and I are trying to get the AS beam onto the AS camera with a focusing lens. Currently, the mirror immediately preceding the camera has been removed and the camera and lens are sitting directly behind the BS.

Results of the Razor Blade Beam Scan

The horizontal blade test measured the beam intensity as a razor blade passed in between it and a power meter from the left side of the beam (negative x values) until blocking it. The resulting function, found through least-squares regression of the error function, calculates a beam height of 3.6 mm +/- 16 mm. However, the function has a chi-squared value of 3.2, so that value may not be accurate.

The vertical blade test measured beam intensity as a razor moved from below the beam (negative x values) until blocking it. This function, found the same way as above, calculates a beam width of 2.8mm +/- 9.6 mm, and has chi-squared value of 0.77.

Both data sets have a y-error of 0.5 micro-Watts, and an x-error of 0.127 mm. The Python code used to analyze the data and plot the results is attached.

We conducted a beam scan on the AP table of the AS beam. We used a lens to focus the beam onto a power meter, and slowly moved a razor blade across the beam using a micrometer, vertically and horizontally both in front of and behind the beam. We also had to block the beam next to the AS beam in order to do this, but is unblocked now. Mike will begin curve fitting the data to try and see if there is a different spot size given by the x-axis vs. the y-axis, and if the lens has any effect.

 [ericq, mikej, some input from zach]

After realigning the MC, the measurement was repeated this afternoon. This time, however, we isolated the beam from ITMY by misaligning ITMX. The beam looked somewhat elliptical to me, and Mike should have fits up tonight. Afterwards, ITMX was returned to the position I found it in, and the PMC shutter and access connector were closed. (Sorry about last night!)

**EDIT:** Mixed up X and Y. Beam is 3.5844 mm tall and 2.7642 mm wide

14.112 hundredths of an inch in the vertical direction

3.5844 millimeters

10.883 hundredths of an inch in the horizontal direction

2.7642 millimeters

Plots and error bars to come soon.

[Jenne, Gabriele]

We aligned MICH (first locked Yarm, but didn't optimize since we don't have TRY, then locked Xarm, then aligned MICH), but there was no beam on AS55.  We went out to check, and the beam was almost not hitting the small steering mirror between AS55.  We adjusted the BS splitting the beam between camera and PD, and got the beam back on AS55. We could then lock MICH.

We also futzed with the REFL55 phase to get PRCL stuff in I, and MICH stuff in Q.  The procedure was to align PRMI, then kick PRM in pos, and adjust the phase so we got signal mostly in I after the kick.  We started at the original value of 60deg, but are leaving it at -20deg.

[ericq, lydia, gautam]

IMC realignment, Arm dither alignment

• We started today by re-locking the PMC (required a c1psl restart), re-locking the IMC and then locking the arms
• While trying to dither align the arms, I could only get the Y arm transmission to a maximum of ~0.09, while we are more used to something like 0.3 when the arm is well aligned this vent
• As it turns out, Y arm was probably locked to an HOM, as a result of some minor drift in the ITMY optical table leveling due to the SOS tower aperture being left in over the weekend

ITMY chamber

• We then resolved to start at the ITMY chamber, and re-confirm that the beam is indeed centered on the SRM by means of the above-mentioned aperture
• Initially, there was considerable yaw misalignment on the aperture, probably due to the table level drifting because of the additional weight of the aperture
• As soon as I removed the aperture, eric was able to re-dither-align the arms and their transmission went back up to the usual level of ~0.3 we are used to this vent
• We quickly re-inserted the aperture and confirmed that the beam was indeed centered on the SRM
• Then we removed the aperture from the chamber and set about inspecting the beam position on OM1
• While the beam position wasn't terribly bad, we reasoned that we may as well do as good a job as we can now - so OM1 was moved ~0.5 in such that the beam through the SRM is now well centered on OM1 (see Attachment #1 for a CAD drawing of the ITMY table layout and the direction in which OM1 was moved)
  
• Naturally this affected the beam position on OM2 - I re-centered the beam on OM2 by first coarsely rotating OM1 about the post it is mounted on, and then with the knobs on the mount. The beam is now well centered on OM2
• We then went about checking the table leveling and found that the leveling had drifted substantially - I re-levelled the table by moving some of the weights around, but this has to be re-checked before closing up... 

BS/PRM chamber

• The beam from OM2 was easily located in the BS/PRM chamber - it required minor yaw adjustment on OM2 to center the beam on OM3
• Once the beam was centered on OM3, minor pitch and yaw adjustments on the OM3 mount were required to center the beam on OM4
• The beam path from OM3 to OM4, and OM4 to the edge of the BS/PRM chamber towards the OMC chamber was checked. There is now good clearance (>2 beam diameters) between the beam from OM4 to the OMC chamber, and the green steering mirror in the path, which was one of the prime clipping candidates identified on Friday

OMC chamber

• First, the beam was centered on OM5 by minor tweaking of the pitch and yaw knobs on OM4 (see Attachment #2)
• Next, we set about removing the unused mirror just prior to the window on the AP table (see Attachment #3). PSL shutter was closed for this stage of work, in order to minimize the chance of staring directly into the input beam!
• Unfortunately, we neglected checking the table leveling prior to removing the optic. A check after removing the optic suggested that the table wasn't level - this isn't so easy to check as the table is really crowded, and we can only really check near the edges of the table (see Attachment #3). But placing the level near the edge introduces an unknown amount of additional tilt due to its weight. We tried to minimize these effects by using the small spirit level, which confirmed that the table was indeed misaligned
• To mitigate this, we placed a rectangular weight (clean) around the region where the removed mirror used to sit (see Attachment #3). Approximately half the block extends over the edge of the table, but it is bolted down. The leveling still isn't perfect - but we don't want to be too invasive on this table (see next bullet point). Since there are no suspended optics on this table, I think the leveling isn't as critical as on the other tables. We will take another pass at this tomorrow but I think we are in a good enough state right now. 
• All this must have bumped the table quite a bit, because when we attempted re-locking the IMC, we noticed substantial misalignment. We should of course have anticipated this because the mirror launching the input beam into the IMC, and also MMT2 launching the beam into the arms, sits on this table! After exploring the alignment space of the IMC for a while, eric was able to re-lock the IMC and recover nominal transmission levels of ~1200 counts. 
• We then re-locked the arms (needed some tip-tilt tweaking) and ran the dither again, setting us up for the final alignment onto OM6
• OM5 pitch and yaw knobs were used to center the beam on OM6 - the resulting beam spot on OMPO-OMMTSM and OM6 are shown in Attachment #4 and Attachment #5 respectively. The centering on OMPO-OMMTSM isn't spectacular, but I wanted to avoid moving this optic if possible. Moreover, we don't really need the beam to follow this path (see last bullet in this section)
• Beam path in the OMC chamber (OM5 --> OMPO-OMMTSM --> OM6 --> window was checked and no significant danger of clipping was found
• Beam makes it cleanly through the window onto the AP table. We tweaked the pitch and yaw knobs on OM6 to center the beam on the first in-air pick off mirror steering the AS beam on the AP table. The beam is now visible on the camera, and looks clean, no hint of clipping
• As a check, I wondered where the beam into the OMC is actually going. Turns out that as things stand, it is hitting the copper housing (see Attachment #6, it's had to get a good shot because of the crowded table...). While this isn't critical, perhaps we can avoid this extra scatter by dumping this beam?
• Alternatively, we could just bypass OMPO-OMMTSM altogether - so rotate OM5 in-situ such that we steer the beam directly onto OM6. This way, we avoid throwing away half (?) the light in the AS beam. If this is the direction we want to take, it should be easy enough to make the change tomorrow

In summary...

• AS beam has been centered on all steering optics (OM1 through OM6)
• Table leveling has been checked on ITMY and OMC chambers - this will be re-checked prior to closing up
• Green-scatter issue has to be investigated, should be fairly quick..
• In the interest of neatness, we may want to install a couple of beam dumps - one to catch the back-reflection off the window in the OMC chamber, and the other for the beam going to the OMC (unless we decide to swivel OM5 and bypass the OMC section altogether, in which case the latter is superfluous)

C1SUSAUX re-booting

• Not really related to this work, but we couldn't run the MC relief script due to c1susaux being unresponsive
• I re-started c1susaux (taking care to follow the instructions in this elog to avoid getting ITMX stuck)
• Afterwards, I was able to re-lock the IMC, recover nominal transmission of ~1200 counts. I then ran the MC relief servo
• All shutters have been closed for the night

I touched steering mirrors for AS and REFL at AP table.
AS beam and REFL beam now hits cameras at center and their respective PDs.

What I did:
  1. Aligned Y arm and X arm.

  2. Locked FPMI and aligned BS + X arm by minimizing ASDC (DC output of the AS55 PD, C1:LSC-ASDC_OUT reached ~ -1.43).

  3. Put -2V offset to the OMC stage 2 in yaw to avoid AS clipping. The offset is currently given by SRS DS345 on AUX_OMC_NORTH rack.

  4. Misaligned ETMs, locked MI in the bright fringe. Maximized ASDC (C1:LSC-ASDC_OUT reached ~ 1.22) by aligning 2 mirrors right after the vacuum chamber. This also centered beam spot on the AS camera.

  5. Locked MI in the dark fringe. Maximized REFLDC (DC output of the REFL55 PD, C1:LSC-REFLDC_OUT reached ~ 2.5) by aligning 2 mirrors after the vacuum chamber. Beam spot on the REFL camera was centered, too.

AS:

REFL:

In Attachment 1, I give a plan for the proposed path of AS beam into the IMC WFS heads to use them temporarily as AS WFS. Paths shown in orange are the existing MC REFL path, red for the existing AS path, cyan for the proposed AS path, and yellow for the existing IFO refl path.  We plan to overlap AS beam to the same path by installing the following new optics on the table:

• M1 will be a new mirror mounted on a flipper mount reflecting 100% of AS beam to SW corner of the table.
• M2 will be a new fixed mirror for steering the new AS beam path to match with MC WFS path.
• M3 will be the existing beamsplitter used to pick off light for MC refl camera. We'll just mount this on a flipper so that it can be removed from the path. Precaution will be required to protect the CCD from high intensity MC reflection by putting on more ND filters.
• The AS beam would need to be made approximately 1 mm in beam width. The required lenses for this would be placed between M1 and M2.

I request people to go through this plan and find out if there are any possible issues and give suggestions.

PS: Thanks JC for the photos. I got it from foteee google photos. It would be nice if these are also put into the 40m wiki page for photos of optical tables.

RXA: Looks good. I'm not sure if ND filters can handle the 1 W MC reflection, so perhaps add another flipper there. It would be good if you can measure the power on the WFS with a power meter so we know what to put there. Ideally we would match the existing power levels there or get into the 0.1-10 mW range.

I've completed the beam redirection path for AS beam to WFS heads in a nominal way. By that I mean that all mirrors (M1, M2, M3, and M4) are now in their final positions and we will need to install one or two lenses to collimate the beam to match the mode that the WFS path is expecting as it has it's on the focusing lens before the photodiodes. For this last part, I think the fasted way would be to profile the beam and calculate the correct lens and position rather than trial and error as the beam intensity is very low for estimating the beam size by eye.

IMC WFS state: Flip M1 and M2 down.

AS WFS state: Flip M1 and M2 up.

I measured the expected beam profile by WFS photodiodes by measuring the beam when mode cleaner was unlocked from the point where beam is picked for WFS. See attachment 1 for beam details. z=0 is the point in the path where AS beam will merge.

For measuring the beam profile of AS beam, I had to focus it using a lens. I picked up a 360.6 mm ROC lens and placed it at z=-67 inch point. Then I profiled the beam at some comfortable section of the path and fitted it. with reverse z-axis. Using this method, I can place the lens back and obtain the original beam back. Attachment 2 shows this fitting process and identification of the original beam profiles. I plotted the AS beam profiles again in attachment 3 and saved them for seeding mode matching effort later. Note that we don't want to be super accurate here, so I did not do any error analysis, just wanted to finish this fast. Also pardon me for the bad quality plots, I did not want to learn Matlab plotting to make it beautiful.

Note: There is significant astigmatism in both IMC reflection beam and AS beam. This could be due to beam going through far off-center on lens. Something to keep in mind, again this measurement is not ideal in terms of precision but this large an astigmatism could not be due to measurement error.

Next:

• Identify correct len(s) and their positions
• Align the AS beam to WFS heads
• Test the full signal chain.

I completed the mode matching calculation today and found good solution with 360.6 mm ROC PLCX lens at -1.2 m from z=0 point. I placed the lens there today and aligned all mirrors to get centered beam on both WFS PDs when the flipper mirrors are flipper up. This alignment would probably require tweaking everying we flip the mirrors as the flipper mirrors do not come back to same position usually.

I mounted the modified WFS boards 111B and 112B next to the whitening filter boards of existing WFS. Now to switch over, onewould need to transfer the 8 RF lemo cables and the 2 IDE ribbon cables.

I'm working on rtcds model to read AS WFS data and handle it separately. I'll keep a WPICS binaruy switch to switch between IMC WFS or AS WFS. I need to figure out some build issues on this work still.

Model and medm changes

After incrementally doing the model changes, I found out that the model was failing to build because of creation of a subsystem. If I just kept all divertor blocks out in the main model instead of in a single subsystem, the compilation works. Maybe the reason is because RCG can only take subsystems at base level which have top_names attribute. But I did nto test this, I just went with what works.

In summary, I added a new subsystem in c1ioo model called AWS (stands for Antisymmetric Wavefront Sensors). This subsystem and IOO subsystem receive teh WFS RF demodulated signals based on a single binary switch named C1:IOO-SEL_WFS_IMC_OR_AS. Value 0 connects the subsystem IOO to the inputs and value 1 connects AWS to the inputs. There is a switch on the left edge in the WFS screens now to select between the two.

Inside the AWS, the WFS I/Q phase rotation is done and then it goes into one of the two subsystems called AWS-XARM or AWS-YARM for using the AS for either XARM or YARM. THis is based on a single binary switch called C1:AWS-SEL_ARM_X_OR_Y. Value 0 selects output to XARM and value 1 selects output to YARM. There is a switch near top left of  C1AWS_XARM_WFS_MASTER.adl and C1AWS_YARM_WFS_MASTER.adl screens. I copied these screens from C1IOO_WFS_MASTER.adl, so they have same structure. See attachment 1. Any edits should be made to /opt/rtcds/caltech/c1/medm/c1ioo/master/C1AWS_XARM_WFS_MASTER.adl and simply run python opt/rtcds/caltech/c1/medm/c1ioo/master/createYARMWFSscreensFromX.py to create teh YARM screen from it.

Along with this, models c1scy and c1scx were edited also to take in IPC directly from c1ioo instead of going through RFM. We should phase out use of RFM eventually and directly connect all IPC connections with the ends.

First tests

[Anchal, Yuta]

After the model is up and running, we flipped the WFS path to use AS beam. I switched the 8 RF outputs of the WFS from IMC WFS boads to AS WFS boards and switched the IDC connectors to WFS. Attachment 2 shows teh photo in this flipped state. Then we misaligned both ITMX and ETMX. First simple test was to check if we see the YARM PDH error signal when YARM was flashing. And indeed we saw that on all 16 channels. So next we locked YARM and injected 311 Hz line with 300 counts amplitude at ETMY. We looked for this peak in the Q channels of WFS outputs and adjusted all phases to 0.1 degrees to minimize Q signal to the noise floor. For WFS2 case, teh SNR is bit higher due to more power than WFS1 and their phase angle might be adjusted to even better degree but we did not got for it.

Then I used C1AWS_XARM_WFS_MASTER.adl>!Actions>Correct WFS RF offsets button to remove offsets in all the RF demodulated signals. I have set this button to use /opt/rtcds/caltech/c1/Git/40m/scripts/RFPD/resetOffsets.py script.

At this point, we are ready to see if we have WFS sensitivity but I need to work on other projects today and Yuta and Paco took over interferometer for 60 Hz noise hunting.

[koji, ian, tega, paco]

With the remote/local assistance of Tega/Ian last friday I made changes on the c1sus model by connecting the C1:ASC model outputs (found within a block in c1ioo) to the BS and PRM suspension inputs (pitch and yaw). Then, Koji reviewed these changes today and made me notice that no changes are actually needed since the blocks were already in place, connected in the right ports, but the model probably just wasn't rebuilt...

So, today we ran "rtcds make", "rtcds install" on the c1ioo and c1sus models (in that order) but the whole system crashed. We spent a great deal of time restarting the machines and their processes but we struggled quite a lot with setting up the right dates to match the GPS times. What seemed to work in the end was to follow the format of the date in the fb1 machine and try to match the timing to the sub-second level. This is especially tricky when performed by a human action so the whole task is tedious. We anyways completed the reboot for almost all the models except the c1oaf (which tends to make things crashy) since we won't need it right away for the tasks ahead. One potential annoying issue we found was in manually rebooting c1iscey because one of its network ports is loose (the ethernet cable won't click in place) and it appears to use this link to boot (!!) so for a while this machine just wasn't coming back up.

Finally, as we restored the suspension controls and reopened the shutters, we noticed a great deal of misalignment to the point no reflected beam was coming back to the RFPD table. So we spent some time verifying the PRM alignment and TT1 and TT2 (tip tilts) and it turned out to be mostly the latter pair that were responsible for it. We used the green beams to help optimize the XARM and YARM transmissions and were able to relock the arms. We ran ASS on them, and then aligned the PRM OpLevs which also seemed off. This was done by giving a pitch offset to the input PRM oplev beam path and then correcting for it downstream (before the qpd). We also adjusted the BS OpLev in the end.

Summary; the ASC BS and PRM outputs are now built into the SUS models. Let the AS WFS loops be closed soon!

Addenda by KA
- Upon the RTS restarting,

• Date/Time adjustment
sudo date --set='xxxxxx'
• If the time on the CDS status medm screen for each IOP match with the FB local time, we ran
  rtcds start c1x01
  (or c1x02, etc)
• Every time we restart the IOPs, fb was restarted by
  telnet fb1 8083
> shutdown
  and restarted mx_stream from the CDS screen because these actions change the "DC" status.

- Today we once succeeded to restart the vertex machines. However, the RFM signal transmission did fail. So the end two machines were power cycled as well as c1rfm, but this made all the machines in RED again. Hell...

- We checked the PRM oplev. The spot was around the center but was clipped. This made us so confused. Our conclusion was that the oplev was like that before the RTS reboot.

[anchal, paco]

We picked up AS WFS comissioning for daytime work as suggested by gautam. In the end we want to comission this for the PRFPMI, but also for PRMI, and MICH for completeness. MICH is the simplest so we are starting here.

We started by restoromg the MICH configuration and aligning the AS DC QPD (on the AS table) by zeroing the C1:ASC-AS_DC_YAW_OUT and C1:ASC-AS_DC_PIT_OUT. Since the AS WFS gets the AS beam in transmission through a beamsplitter, we had to correct such a beamsplitters's aligment to recenter the AS beam onto the AS110 PD (for this we looked at the signal on a scope).

We then checked the rotation (R) C1:ASC-AS_RF55_SEGX_PHASE_R and delay (D) angles C1:ASC-AS_RF55_SEGX_PHASE_D (where X = 1, 2, 3, 4 for segment) to rotate all the signal into the I quadrature. We found that this optimized the PIT content on C1:ASC-AS_RF55_I_PIT_OUT and YAW content on C1:ASC-AS_RF55_I_YAW_OUTMON which is what we want anyways.

Finally, we set up some simple integrators for these WFS on the C1ASC-DHARD_PIT and C1ASC-DHARD_YAW filter banks with a pole at 0 Hz, a zero at 0.8 Hz, and a gain of -60 dB (similar to MC WFS). Nevertheless, when we closed the loop by actuating on the BS ASC PIT and ASC YAW inputs, it seemed like the ASC model outputs are not connected to the BS SUS model ASC inputs, so we might need to edit accordingly and restart the model.

For the photodetector frequency response project, I finished the construction of our baluns chassis and mounted it in rack 1Y1 (1st picture).

After consulting with Jenne, I mounted the fiber launcher for REFL165 on the AS table such that it would not cause an obstruction. I aligned the launcher using a multimeter to monitor the DC output of REFL165, but looking at the data I got, it seems I need to do a better alignment/focusing job to get rid of a bunch of noise.

 [Eric, Alex]

We added our reference photodetector (Newport 1611, REF DET) to the southern edge of the AS table, as pictured. The detector's power supply is located under the southwest corner of the table, as pictured. We have connected the detector to its power supply, and will connect the detector's fiber input and RF output tomorrow.

EDIT: this is about the RFPD frequency response setup...

[Eric, Alex]

For the RFPD frequency response project, we routed the fiber that will connect our REF DET (on the AS table) to our 1x16 optical splitter (in the OMC_North rack), as pictured. (The new fiber is the main one in the picture, which ends at the right edge near REF DET) Note that we secured the fiber to the table in two places to ensure the fiber would remain immobile and out of other optical paths already in place.

At 2:00 we plan to run fiber from our laser module (in rack 1Y1) to our 1x16 optical splitter (in the OMC_North rack) and measure the power output at one of the splitter's output ports. We plan to keep the output power limited to less than 0.5 mW per optical splitter output.

[Eric, Alex]

We decided that the POY Table would be a better home for our REF DET (Newport 1611 FC-AC) than the AS Table. We moved the PD to the POY Table (1st attachment) and routed a fiber from our 1x16 Optical Splitter in the OMC_North rack to the POY Table. REF DET's power supply is now located under the POY table (2nd attachment). We left the fiber described in the previous post on the AS Table.

Afterwards, we hooked a fiber up to our laser module to test it (3rd attachment). The laser was not being distributed, just going to one fiber with a power meter at its end. Everything turns out, but we realized we need to read the power supply's manual before continuing. 

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

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

I was going to lock MICH, but I don't see anything on dataviewer for either AS55Q or ASDC.  I went out onto the table, and there is beam on the diode, but no mV out on a voltmeter connected to the DC monitor point.  I shine a flashlight, and still I see 0.0mV.  So, something is up with AS55, but since the michelson is aligned right now, I'm not going to mess with the PD.  I won't lock MICH, I'll just move on.  Koji is taking a look at the diode, but if he doesn't get it figured out tonight, we can take a closer look after we pump down.

 Never mind.  I was using an LED flashlight, which doesn't emit light that the PD is sensitive to.  A regular flashlight gives plenty of signal on the DC out. 

Using an SR560 with 30Hz low pass and gain of 100, it was pretty easy to align the light on the PD. 

Koji calculates in his head that there is about 6 microwatts of light incident on the PD, which is not a lot of light. Our SNR may be kind of lame for locking right now.

 Adaptive filtering was applied to MC and X,Y arms at the same time. I used a very aggressive (8 order) butterworth filter at 6 Hz as an AI filter for MC not to inject noise to ARMS as was done before

Mu for MC was 0.2, downsample = 16, delay = 1. I was able to subtract 1 Hz. Stack subraction is not that good as for arms but this is because I used only one seismometer for MC that is under the BS. I might install accelerometers under MC2.

EDIT, JCD, 18Feb2013:  Den remembers using mu for the arms in the range of 0.01 to 0.1, although using 0.1 will give extra noise.  He said he usually starts with something small, then ramps it up to 0.04, and after it has converged brings it back down to 0.01.

 I actuate on ETMY for YARM and ETMX for XARM. For now I did adaptive filtering for both arms at the same time. I used the same parameters for xarm as for yarm.

I've notched 16 Hz resonance because it has high Q and I need to think more how to subtract it using FIR filter or apply IIR.

I'll try MC stabilazation method.

I have uploaded ARBCAV v3.0 to the SVN. The major change in this release, as I mentioned, is the input/output handling. The input and output are now contained in a single 'model' structure. To define the cavity, you fill in the substructure 'model.in' (e.g., model.in.T = [0.01 10e-6 0.01]; etc.) and call the function as:

model = arbcav(model);

Note: the old syntax is maintained as legacy for back-compatibility, and the function automatically creates a ".in" substructure in the output, so that the user can still use the single-line calling, which can be convenient. Then, any individual parameter can be changed by changing the appropriate field, and the function can be rerun using the new, simpler syntax from then on.

The function then somewhat intelligently decides what to compute based on what information you give it. Using a simple option string as a second argument, you can choose what you want plotted (or not) when you call. Alternatively, you can program the desired functionality into a sub-substructure 'model.in.funct'.

The outputs are created as substructures of the output object. Here is an example:

>> th = 0.5*acos(266/271) *180 /pi;

OMC.in.theta = [-th -th th th];

OMC.in.L = [0.266 0.284 0.275 0.271];

OMC.in.RoC = [1e10 2 1e10 2];

OMC.in.lambda = 1064e-9;

OMC.in.T = 1e-6 * [8368 25 8297 33];

OMC.in.f_mod = 24.5e6;

>> OMC

OMC = 

    in: [1x1 struct]

>> OMC = arbcav(OMC,'noplot')

Warning: No loss given--assuming lossless mirrors 

> In arbcav at 274 

OMC = 

         in: [1x1 struct]

        FSR: 2.7353e+08

        Lrt: 1.0960

    finesse: 374.1568

    buildup: 119.6956

         df: [1000x1 double]

      coefs: [1000x4 double]

        HOM: [1x1 struct]

>> OMC.HOM

ans = 

      f: [1x1 struct]

    pwr: [1x1 struct]

>> OMC.HOM.pwr

ans = 

    carr: [15x15 double]

     SBp: [15x15 double]

     SBm: [15x15 double]

Some other notes:

• The annoying Mdo.m has been internalized; it is no longer needed.
• For the next release, I am working on including:
  • Finite mirror thickness/intracavity refractive elements - If, for god knows what reason, you decide to put a mirror substrate within a cavity 
  • Mode overlap - Calculating the overlap of an input beam to the cavity
  • Mode matching - Calculating a mode matching telescope into the cavity for some defined input beam
  • Anything else?

I have added lots of information to the help header, so check there for more details. As always, your feedback is greatly appreciated.

 The uncoated bi-concave lens was replaced by AR coated one: KBC 037 -100 AR.14 resulting 35% count increase on qpd

I've packaged an AP1053 in a Thorlabs box. The gain and the input noise level were measured. It has the gain of ~10 and the input noise of ~0.6nV/rtHz@50MHz~200MHz.

Details

AP1053 was soldered on Thorlabs' PCB EEAPB1 (forgot to take a picture). The corresponding chassis is Thorlabs' EEA17. There is a 0.1uF high-K ceramic cap between DC and GND pins. The power is supplied via a DC feedthru capacitor (Newark / Power Line Filter / 90F2268 / 5500pF) found in the WB EE shop. The power cable has a connector to make the long side of the wires detachable. Because I did not want to leave the RF signal path just mechanically touched, the SMA connectors were soldered to the PCB. As the housing has no access hole, I had to make it at one of the sides.

The gain of the unit was measured using the setup shown in the upper figure of Attachment 2. When the unit was energized, it drew the current of about 0.1A. The measued gain was compensated by the pick off ratio of the coupler (20dB). The gain was measured with the input power of -20, -10, 0, 10, and 15dBm. The measurement  result is shown in Attachment 3. The small signal gain was actually 10dB and showed slight degradation above 100MHz. At the input of 10dB some compression of the gain is already visible. It looks consistent with the specification of +26.0dBm output for 1dB compression above 50MHz and +24.0dBm output below 50MHz.

The noise level was characterized with the setup shown in the bottom figure of Attachment 3. The noise figure of the amplifier is supposed to be 1.5dB above 200MHz and 3.5dB below 200MHz. This is quite low and the output noise of AP1053 can not be measured directly by the analyzer. So, another LN amplifier (ZFL-500HLN) was stacked. The total gain of the system was measured in the same way as above. The measured noise level was ~0.7nV/rtHz between 50MHz and 200MHz. Considering the measurement noise level of the system, it is consistent with the input referred noise of 0.6nV/rtHz. I could not confirm the advertized noise figure of 1.5dB above 200MHz. The noise goes up below 50MHz. But still 2nV/rtHz at 3MHz. I'd say this is a very good performance.

                   Sad situation

    The anti-symmetric port

spider webs fly in the wind

MCRefl is absent, it is under investigation. I removed a bunch of hardware and note all spare optics along the edges.

Access to the north side of the PSL table is blocked by the    8" beam guard. This opens the beam pathways between them.

Please remember to cover the optical tables !

Before we install the REFL 3f PDs I made a drawing of the current table layout, since there has been no update lately. Once I've incorporated the two extra PDs (now seen sitting bottom left), I will update the drawing and post in the wiki as well.

On Wednesday (21st) night, I checked the AP table as I wanted to try PRMI locking. 
It was difficult to work with the table as there were so many unnecessary components on it.
Also the beams went through complicated paths as they have funny angles. 

So I decided to clean up of IMC REFl WFS, IFO REFL, and IFO AS paths.
I found that the AS beam was highly astigmatic as the beam went through a (too-much-) tilted lens.
I made several blocked optical paths for REFL and AS for future extension of the detection system.

The current status of the table was uploaded below.

The optical spectrum analyzers and the aux NPRO were left untouched but they should be moved
somewhere (either on the table or outside) which does not disturb the other optical paths.
 

After the cleaning, I started locking PRMI. I could lock PRMI stably. But I could not figure out how
the intra-cavity mode looked like as I did not have the POP camera. The power recycling
gain was not quantitatively evaluated as I did not have POP and I wasn't sure how the beam was aligned at POX/POY.

We need to know:

- Quantitative evaluation of the beam shape in the PRC

- Quantitative evaluation of the power recycling gain

Some obvious things to be fixed

- The POX whitening filters seem not switching. This issue should be checked at the circuit module itself and at the BIO.

- The POX beam is not well focused on the PD. This was particularly clear when PRMI was locked with carrier.

- The POP beam is going nowhere. We need POP55 and POP CCD for diagnoses.

I haven't checked ITMY table.

I blocked the  AP table's south west 10" ID port since it is obsolete with the new layout.

Reminder: items on the enclosure self can fall down in an earthquake. I moved oscilloscope and heavy calorimeter head from the edge of the cliff.

The most up to date pictures of the AP table and ETMX table that Steve took have been uploaded to the relevant page on the wiki. It seems like the wiki doesn't display previews of jpg images - by using png, I was able to get the thumbnail of the attachment to show up. It would be nice to add beam paths to these two images. The older versions of these photos were moved to the archive section on the same page.

I measured the power in various beams on the AP table to check and see if any beam is having too much power. 

I am uploading two pics one is in the "high power state" and the other is the "low power state".   High power in the MC REFL PD occurs when the MC is unlocked.  In addition the WFS also will see this  hike in power. We wish to make sure that in either state the power levels do not exceed the max power that the PDs can tolerate.

Low Power state: MC locked, PRM not aligned.                                                   High Power state: MC unlocked,  PRM aligned.

New stage can hold the correct polarization.

DRAWING CORRECTION:  Post block height was lowered to be 1.88" from 2.0"

The new stage missed the right height by ~2 mm.

Even if I completely bottom out the (New Focus 9071) 4-axis stage, its not short enough. So I removed the AOM from the beam and re-aligned into the PMC.

Steve, please get the aluminum piece remachined to go down by 2.5 mm so we can have some height adjustment room.

Also, the turning mirror mount just after the EOM and before the AOM is a U-100 and we want it to be a Suprema for stability - let's not forget to swap that after Steve gets the mount fixed.

Edit/manasa/ Data has not been fit correctly in here. A proper fit will follow this elog.

Proper fits and numbers are here :elog

Earlier last week I had tried to measure the AOM ringdown and concluded I could not make one.

I was proved wrong and I was able to make a measurement. I am still not sure why I was not able to make the measurement earlier with the very same settings and configuration.

What I did:

I gave the AOM a 0-1V modulation input using the signal generator (50 ohm feedthrough bnc was used to impedance match the AOM driver's modulation input). For the measurement here I used a 1Hz square wave. I used a 300MHz oscilloscope to look at the falling edge of the ringdown PD output installed.

I recorded a few ringdown samples. To get a quick number, I fit one such sample to find the AOM switching time as 1.48us (Plot attached). 

i reconnected the AOM driver to the AOM in the main beam path (it was hijacked for the AOM in the AUX laser path for Anjali's MZ experiment). I also temporarily hooked up the AOM to a CDS channel to facilitate some swept-sine measurements. This was later disconnected. The swept sine will need some hardware to convert the bipolar drive signal from the CDS system to the unipolar input that the AOM driver wants (DTT swept sine wont let me set an offset for the excitation, although awggui can do this).