...was down.  Have restarted it.

I think I have finally found a Mode Matching solution for our new Input Mode Matching Telescope!  And after looking at the layout diagram with Koji and Raffaele, it seems like all of the optics will fit into the chambers / onto the tables (not true as of last week). 

3. RoCMMT1 is -5m
   RoCMMT2 is 8m,
   with the MMTs 1.89m apart.
   This is a 1.6x telescope.
   MMT2 is 2.2641m from the PRM
   MMT1 is 2m from MC3.
   The Condition Number for this optical chain is 89219047.5781.

This layout is very similar to the one that Koji posted on the wiki yesterday:  Upgrade09/Optical Layout.  The difference is that I want to move MMT1 ~20cm closer to the MC13 table, so just on the other side of the main red beam that goes directly to PRM.  There is plenty of space there, so it should be all good.  The tricky bit is that the flat steering mirrors fit into things now while they are piezos, but they will be trickier to fit if we make them into Tip Tilts.  But I have full faith in Koji's amazing optical table layout skills, that he can make it happen. 

Unless there are major objections, I think this is the MMT that we're going to go with. (So speak now or forever hold your peace.)  The angle between tilt and translation isn't quite what we'd like it to be (at ~18deg), but it's not too terrible.  And we still have 99.5% overlap which is very important.

I am in the way to get a reasonable optical layout.
Please calculate the final results with the following conditions.

"Result" =
- mode overlapping with astigmatism
- alignment matrix (m/rad, rad/rad) for Pitch and Yaw
- alignment orthogonality
- sensitivity of the mode overlapping to the perturbations
  * histgram
  * individual scan of the optic positions

Optics chain: MC3 - SM1(flat) - MMT1(f=-5m) - MMT2(f=+8m) - SM2(flat) - PRM

Incident angles: SM1 24deg, MMT1 3deg, MMT2 1deg, SM2 44.5deg

Distances:
MC3 HR - SM1: 884mm
SM1 - MMT1: 1058.2mm
MMT1 - MMT2: 1890mm
MMT2 - SM2: 2007.9mm
SM2 - PRM HR: 495.6mm

It has ~200mm deviation from the solution. I can move only MMT1 for final optimization.
Give us the numbers if it can improve the performance.
Note that this move changes SM1-MMT1 and MMT1-MMT2 simultaneously.

Koji just found the emergency exit door unlocked again.  NOT GOOD.

We have determined that if you use the emergency door to enter the lab, it leaves the door unlocked, unless you go back outside and deliberately lock it.  This means that someone has been using the emergency exit as a regular entrance. 

It's fine to leave by that door, but you should make a habit of entering through the regular door.  Using the back door as an entrance is a special case situation, when they have the main door blocked.

The emergency lamps above the exit sign on the NW entrance to the control room are on. I tried opening and closing the door, but it remains on. Probably nothing to worry about, but noting here anyway.

It happened before too. Doesn't it say it has occasional self-testing or something?

True - it is now not on anymore.

When I came into the lab this morning, I noticed that both N2 tanks were empty. I had swapped one on Friday (4-16-21) before I left the lab. Looking at the logs, the right tank (T2) sprung a leak shortly shortly after install. I leak checked the tank coupling after install but did not see a leak. There could a leak further down the line, possibly at the pressure transducer.

The left tank (T1) emptied normally over the weekend, and I quickly swapped the left tank for a full one, and is curently at ~2700 psi. It was my understanding that if both tanks emptied, V1 would close automatically and a mailer would be sent out to the 40m group. I did not receive an email over the weekend, and I checked the Vac status just now and V1 was still open.

I will keep an eye on the tank pressure throughout the day, and will try to leak check the T2 line this afternoon, but someone should check the vacuum interlocks and verify.

Installed T2 today, and leaked checked the entire line. No issues found. It could have been a bad valve on the tank itself. Monitored T2 pressure for ~2 hours to see if there was any change. All seems ok.

I checked out what happened on c1vac. There are actually two independent monitoring codes running:

1. The interlock service, which monitors the line directly connected to the valves.
2. A seaparate convenience mailer, running as a cronjob, that monitors the tanks.

The interlocks did not trip because the low-pressure delivery line, downstream of the dual-tank regulator, never fell below the minimum pressure to operate the valves (65 PSI). This would have eventually occurred, had Jordan been slower to replace the tanks. So I see no problem with the interlocks.

On the other hand, the N2 mailer should have sent an email at 2021-04-18 15:00, which was the first time C1:Vac-N2T1_pressure dropped below the 600 PSI threshold. N2check.log shows these pressures were recorded at this time, but does not log that an email was sent. Why did this fail? Not sure, but I found two problems which I did fix:

• One was that the code was checking the sensor on the low-pressure side (C1:Vac-N2_pressure; nominally 75 PSI) against the same 600 PSI threshold as the tanks. This channel should either be removed or a separate threshold (65 PSI) defined just for it. I just removed it from the list because monitoring of this channel is redundant with the interlock service. This does not explain the failure to send an email.
• The second issue was that the pyN2check.sh script appeared to be calling Python 3 to run a Python 2 script. At least that was the situation when I tested it, and this was causing it to fail partway through. This might well explain the problem with no email. I explicitly set python --> python2 in the shell script.

The code then ran fine for me when I retested it. I don't see any further issues.

The right N2 tank had a bad/loose valve and did not fully open. This morning the left tank was just about empty and the right tank showed 2000+ psi on the gauge. Once the changeover happened the copper line emptied but the valve to the N2 tank was not fully opened. I noticed the gauges were both reading zero at ~1pm just before the meeting. I swapped the left tank, but not in time. The vacuum interlocks tripped at 1:04 pm today when the N2 pressure to the vacuum valves fell below 65psi. After the meeting, Chub tightened the valve, fully opened it and refilled the lines. I will monitor the tank pressures today and make sure all is ok.

There used to be a mailer that was sent out when the sum pressure of the two tanks fell <600 psi, telling you to swap tanks. Does this no longer exist?

I've uploaded the schematic and PCB PDF for End DAC Adapter Unit D2100647.

Please review the design.

• CH1-8 SUS actuation channels.
  • 5CHs out of 8CHs are going to be used, but for future extensions, all the 8CHs are going to be filled.
  • It involves diff-SE conversion / dewhitening / SE-diff conversion. Does this make sense?
• CH9-12 PZT actuation channels. It is designed to send out 4x SE channels for compatibility. The channels have the jumpers to convert it to pass through the diff signals.
• CH13-16 are general purpose DIFF/SE channels. CH13 is going to be used for ALS Laser Slow control. The other 3CHs are spares.

The internal assembly drawing & BOM are still coming.

Both green beatnotes have been found with nominal amplitudes. (X: -30dBm Y: -20dBm), at temperatures which don't seem to be prone to mode hopping. 

X = 42.64, Y ~40.15

Both arms can lock on ALS, but as Koji mentioned in ELOG 11334, the ALS noise seems anomalously high. 

Details

The temperatures I posted in the previous log ended up not being so useful. To find the right end laser temperatures, I looked at the IR beatnotes on the control room analyzer out to 1GHz, and swept around the SLOW_SERVO2_OFFSET channels to change the laser temperature. During this time, the end green shutters were closed, the PSL shutter was closed, the FSS slow servo was off, and the FSS_SLOWDC was set to 0.0. (The green PSL shutter had to be open, because the IR beat fiber is coupled after it.)

For each arm, I found three temperatures where an IR beat could be observed; as Koji mentioned on Wednesday, we should use the middle mode. For each of the arms, scanning around from the middle to move the beat by +-1GHz did not cause a mode hop - the beat stayed visible on the scope. Once I found a real IR beat for the X arm, I took at look at the RF output of the X BBPD, and found my alignment from the other night was actually pretty good; I made a minor touch up to maximize the green beat. 

For the AUX X innolight, I was able to find the actual temperature of the laser crystal when at the correct point, remove the digital offset, and return to the same temperature with the controller front panel dial. This temperature is 42.64 degrees Celcius. There is no diode temperature control on the unit, as far as I could tell, but the maximum green transmitted power through the X arm is about the same as it's ever been, around GTRX=0.5. 

My motivation for doing this was that I always have problems remembering the historical typical values for the digital temperature offset. It seems much cleaner to me to set things up such that a beat is visible "at the origin" (i.e. FSS_SLOWDC=0 and SLOW_SERVO2_OFFSET=0) I suppose that this will also depend on what mode of the PMC we're locked to. During my time working today, its been locked near the middle of its range, currently sitting at 145V. 

However, for the AUX Y lightwave, I was a little perplexed to find that moving the the laser crystal setpoint around does not apear to change the real laser temperature at all. Thus I could not offload the digital offset in the same way. Aditionally, the lightwave controller does not have the same temperature measuring accuracy as the innolight, even with the back panel voltage readout that is hooked up to the multimeter that lives under the optical table. The best I can tell is around 40.1-40.2 degrees C. Y_SLOW_SERVO2_OFFSET of -10690 counts gives a beat <100MHz at FSS_SLOWDC=0. This is actually very close to the previous operating point, so the same mode seems to still work. 

The arms now easily lock on ALS, albeit with higher noise. With arms locked on ALS, POX and POY show >1kHz rms noise.  

I gave the PRFPMI locking script a few tries, but it's having problems keeping the PRMI locked. The ALS is a few times noisier than usual, and I haven't revisited the validity of the PRC angular feedforward, so I'm not so surprised. 

[Manasa, Masayuki]

- Motivation

For PRMI + 2arm, we tried to make the ALS control noise better. As this entry we had huge 60 Hz comb noise in PDH loop of YARM.

So we tried to figure out the problem and fix it.

- What we did

We checked which power supply the staff in Y-end are connected to, and change some of them to connect to 1Y4 AC power supply from wall AC. What we changed was
1.Main end laser
2.He-Ne laser
3.Green REFL PD

We checked error signal of PDH control and compared before and after. The 60 Hz peak get better from -80 dBVpk to -90 dBVpk. Also I attached the plot of XARM, privious YARM (the data of Yesterday night), and current YARM ALS in-loop noises. The RMS of ALS in-loop noise of Y-arm get better by factor of 2. However, even the 60 Hz comb noise get better than before, RMS get worse by comb noise. 

We would like to make these noise better at least until these noises don't affect to RMS, so we should continue to check.

Control signal measurement of end PDH control

The Yarm ALS wasn't robust. Yesterdays night, we found that suspension kicked by something and that was the reason why the end PDH control lost lock. To make sure that the PDH loop itself is robust, I measured control signals of End PDH loops. When the gain inclease, the peak at UGF appeared and become unstable. Both arms does not seems unstable before the peaks appear.

 Xarm PDH servo gain optimization

I optimized the x end PDH servo gain with measuring OLTF. Now the servo gain is 5.0. UGF is around 10 kHz and phase margin is 40 degree.

Also I measured out of loop noise. I locked the arm using IR PDH, and measure the ALS error signal. The high frequency noise become better.

19:00~ Start working on the electronics bench

The following units were tested and ready to be installed. These are the last SUS electronics units and we are now ready to upgrade the end SUS electronics too.

40m End ADC Adapter Unit D2100016 / 2 Units (S2200001 S2200002)

40m End DAC Adapter Unit D2100647/ 2 Units (S2200003 S2200004)

These are placed on Tega's desk together with the vertex DAC adapters

0:30 End work

 [Manasa, Diego]

This is our first time touching tables for Frequency Offset Locking. 

The goal was to couple the 1064nm that leaks after the SHG crystal and couple it into the fiber before we run it along the length of the arm. 

The fiber has been mounted at the end but there is no light coupled into the fiber as yet.

In the process, the following were done:

1. ETMY oplev servo disabled. This was enabled after the work.
2. NPRO laser power was reduced so that nothing gets burnt accidently while putting things on the table. This was also reset after the work.

The arms could be locked to green and IR after the work. So I am hoping today's work will not affect locking.

[Paco, Yuta]

Prep for closing and pump down.

• Aligned IFO to maximize DC levels.
  • YARM (flashing peak 0.05 with PRM misaligned), XARM (flashing peak 0.06 with PRM misaligned), PRC (PRY flashing -30 @ POPDC, offset -70 and REFL DC 270), SRC (SRY flashing -30 @ POPDC, offset -70), BHD.
• GTRY clipping
  • We tried moving the alignment of PR3, PR2, ETMY, ITMY to reduce clipping and retain IR flashing. We found it kind of difficult, so we only used the unclipped GTRY temporarily to improve the input YAUX injection after which the YAUX locked. We then restored the clipping in favor of the IR beam alignment.
• PR3 position
  • PR3 seems to be +1 inch away towards East, nominally placed along North-South, and offset in YAW.
• Aligned OPLEVs to center at around Mon May 23 13:20:32 2022
• Snapshot of all cameras in the control room around Mon May 23 13:24:51 2022

[Chub, JC, Jordan, Yuta, Yehonathan, Paco]

Closed in the following order:

• IMC chamber
• OMC chamber
• BS chamber
• ITMY chamber
• ITMX chamber

[Yuta, Paco]

After closing the heavy doors, we tried to have GTRY less clipped using PR2, PR3, ITMY and ETMY. During this adventure, we also aligned GRY injection beam by hand. Rotating a waveplate for GRY injection made GRY locking stably at GTRY of ~0.3.

We were able to get the latest SVN checkout (revision 2009), working with the c1x00 (IOP) and c1vgl models at the new X end on the c1iscex machine.

We were unable to get it working yesterday, and as far as we can tell, the only significant change was a reboot of the c1sus machine.  Before the reboot, it did not look like there were any conflicting models running on the c1sus machine, but apparently something was preventing the models on c1iscex from running properly.

Other simulated plant models still need to have their shared memory location blocks updated to the new type.

Now that we have proved we still can get the end model running, we are moving onto the c1sus machine.

The spot on the IPANG QPD was checked. The spot is higher than the center and South side of the lens.
Some photos are found below.

The spot on the IPANG steering mirrors in the ETMY chamber was also checked.
It is clipped at the top of the steering mirror. (See attachment 4)
So basically the spot is about 1" above the center of the mirror.

 After the vent, the IPang spot position on the steering mirrors on the Yend table moved approximately by 1 inch down.

Inside the chamber, the spot position is in the center of the steering mirror. (difficult to take a picture because the PSL beam power has been reduced)

 Mounts:

1. No more mounts using the 1" dia. pedestal / fork technology.
2. No more mounts using the 1/2" post / post holder technology. Both of these are loose, weak, and cause noise.
3. All steerable mirror mounts which carry the important sensing beams should use steel mounts (e.g. Polaris from Thorlabs). Aluminum mirror mounts are not to be used.
4. The mounts must be mounted to a 3/4" steel post (these are the custom ones we used in the PSL; Steve should get some more of them made).
5. The post is then mounted on an aluminum base (The BA2 or BA3 (2" x 3" aluminum) from Thorlabs is OK. The 1" x 3" ones are not). These must be fastened to the table using 2 screws, each with a SS washer.

I think Steve is trying to align the end transmission QPDs, since the arms are locked nicely right now.  I noticed that the QPDX pitch and yaw signals were digital zeros.  A quick look determined that the QPDX matrix to go from 4 quadrants to 3 degrees of freedom had been filled in for the POS row, but not pitch and yaw.  So, I copied the QPDY matrix over to QPDX (so the ordering of the rows and columns is assumed to be the same). 

Hopefully this will get us close to centered, but I suppose we ought to check really which quadrant is which, by shining a laser pointer at each quad at each end.

 I have modified the ETM suspension models to include a schmidt triggering block, so that we can choose between using the high gain low power Thorlabs PD and the low gain high power QPD. 

The Thorlabs high gain PD signal is used as the signal to trigger on, so we need to put appropriate thresholds in.

If things are "triggered", that will imply that the Thorlabs PD is seeing a lot of power, so we should be using the QPD SUM channel instead.  There is a "choice" block after the trigger block, to do this switching.

Since the LSC model will only see the output of this choice block, the gain that is currently in C1:LSC-TR[X or Y]_GAIN should be moved to the end SUS model.  We also need to find the correct gain for the QPD sum channels so that they are also normalized to "1" for single arm full power so that we can smoothly go between the 2 diodes.

Rana has promised to make screens, and write scripts for the switching stuff.

I just upgraded the EndRun Technologies Tempus LX GPS receiver timing unit, and it seems to have fixed all the problems.  

Thanks to Steve for getting the info from EndRun.  There was indeed a bug in the firmware that was fixed with a firmware upgrade.

I upgraded both the system firmware and the firmware of the GPS subsystem:

Tempus LX GPS(root@Tempus:~)-> gntpversion 
Tempus LX GPS 6010-0044-000 v 5.70 - Wed Oct 1 04:28:34 UTC 2014
Tempus LX GPS(root@Tempus:~)-> gpsversion 
F/W 5.10 FPGA 0416
Tempus LX GPS(root@Tempus:~)->

After reboot the system is fully functional, displaying the correct time, and outputting the correct IRIG-B data, as confirmed by the VME timing unit.

I added a wiki page for the unit: https://wiki-40m.ligo.caltech.edu/NTP

Steve added this picture

 My full effort to get the optical table enclosure ready for the lab has failed today.

What I did: cut IR thermashield sheets to size for sides and top and sandwitched them beetween 1" and 1/4" acrylic.

                   The carpenter shop recut the bottom o -ring groove to 0.250" wide and 0.150" deep.

                   O-ring was cut and installed. So this was ready to go lab.

                  NO, I realized that the liner yellow acrylic was not cut correctly. It was larger than 1" wall.

                 The shop is cutting them down to fit and I have to resize IR shields

As discussed at the 40m meeting: Koji, Manasa and Steve

We are planning to remove the whole 4'x2' optical table ETMY-ISCT with optics as it is tomorrow morning.
This way I can start placing the new 4'x3' table and acrylic enclosure in place.

I will be removing all cables on the ETMY endtable and labeling them today before we remove the table tomorrow morning. If there is anything else that should be done before the swapping which we might have not considered, elog it and we'll have it all done.

Also,I've attached the updated inventory.

THE INVENTORY FOR ETMY ENDTABLE.

We definitely need the polaris mirror mounts and cylindrical lenses. As for the rest, we can still go ahead and do the swapping without them.

Does "Ready (in stock)" for the base plates mean in stock at the company, or in hand and already here in the lab?

For the 2" mirror mounts, are we planning on making a decision soon, or a long time in the future....i.e. is this something that should go in the temporary solution column?

For the mode matching and collimating lenses, do we actually have the ones you want in our lens kits?  A lot of those kits are half empty.

I'm set on the mission to get the new bigger endtables setup for the auxiliary green laser; now that the tables are already here.

I want to have everything documented in this same thread for future reference. It has been a pain trying to filter relevant elogs. I'll be working on the layout redesign one at a time....starting with the ETMX end.

This is the simplest cartoon layout of  ETMX endtable (not the actual table layout):

I have been searching through the elogs for the beam parameters measured earlier. I'm assuming they would not have changed much and will make calculations based on them.

However, we will have to change a few not-so-good mounts and include/exclude some optics.

P.S. HR (steer) are necessary steering mirrors and HR are just folding mirrors for the drawing.

I am currently putting together all components so that they are ready to go on the table once leveling and installation of shield box is done. All dirty optics were drag wiped. These are stored in the cupboard along the Y arm.
I could not find the fiber coupling mount on the old endtable. Also the harmonic separator that reflects the trans beam to PDs and camera is labelled Y1-1064 (??) and I don't know what's the deal with this.
I am nearly 70% done with assembling…so the ex-endtable is almost empty.

Yet to do:
1. Mount 2" optics
2. Hunt, gather and mount appropriate lenses

Points I did not notice earlier:
We need some good 2" lens mounts and also order 2" lenses for IPANG and trans beam.

With reference to measurements made earlier: elog, 

Beam parameters for Innolight 1W NPRO are:

w_x0 = 160 um 

w_y0 = 181.1 um

z_0x = -9.17 cm

z_0y = -10.19 cm

The beam is clearly elliptical.  We will introduce an additional pair of cylindrical lenses to circularize the beam before it enters the faraday.

I made calculations for the beam divergence ratio and checked with thor labs catalogue of cylindrical lenses to find pairs that will match the ratio. 

I propose to use lenses with focal lengths f₁ = 22.2 mm and f₂ = 25 mm. The beam diameter after the lenses will be d_x = 164.05 um and d_y = 163.19 um.

These fs are too short.

I have attached the possible layout of the optics on the new ETMX endtable. More optics have been added when compared to the early cartoon layout considering that we need additional steering mirrors for reasons like: the table height in and out-of vac are different and several mounts have restricted movement in certain degrees of freedom. 

As you can see, there is enough room for filters and other last time additions that may arise.

I will proceed with calculations based on the distances from the CAD drawing and the spec of the optics if there are no comments or suggestions about the layout.

 

For convenience, I would include a steering mirror in front of the TRX PD.  Also, don't we usually have lenses in the oplev paths?  Also, also, do we need lenses in front of the green refl and TRX PDs?  Do you have a place in mind for the shutter?  Is there a way to compactify the layout a little bit, so that even if the lenses are different for each table, the general layout for both ETMX and ETMY is the same (with an empty space on ETMX where IPANG belongs on ETMY)?  I'm sure it is, since you've talked to Steve about this, but just to check: is the green refl PD far enough away from the edge of the table to accommodate the fancy new box?

• I don't like the idea to place the cylindrical lenses right in front of the laser.
  This design requires the CLs to be tilted to avoid direct reflections going into the laser.
  It is also required that they are made of UV fused silica to avoid thermal lensing.
   
• Instead, move the CLs after the farday while we keep L1, HWP, QWP after the laser.
  L1 should be UV fused silica lens. I should be placed with slight tilt.
  It is preferrable to place CLs after the faraday at somewhere the beam is not too small.
   
• The HWP before the SHG can be moved to downstream of the steering mirrors as they can change the poralization.
  (Probably I am too paranoic.)
   
• Why don't you use the harmonic separator right after the SHG crystal in stead of relying on an arbitrary transmission of the 532nm mirrors?
   
• I am not confident about such a "nice" separation angle of the returning beam from the green faraday.
  Confirm the separation angle on the actual setup.
  The beams split in the polarizer rather than in the air like in your diagram.
  Then because of this small angle separation, the pick-off mirror may have a bit more critical distance than you indicated.
  (I could be wrong.)
• I don't think the green faraday is IO-5-532-HP. It should be IO-?-532-LP.
  Rotate the tilt aligner 180deg so that we can easily access to the adjusting screws
   
• The green PDA36A path needs more length and probably a focusing lens too.
   
• After the PLCX lens, the beam is big (w=3mm) everywhere. Don't you want to use 2" mirrors and mounts?
   
• We eventually will install steering PZTs for the green.
  On which mirrors do you want to install the PZTs? Do you have enough spare space for them?
   
• The mount indicated "HS" is one of the trickiest mounts on the table as the big beam goes through the mirror.
  Probably you want to use 2" suprema mount with correct chirality.
   
• How is the power budget of the IR trans path? Which is the low power PD and which is the high power PD?
  What's the transimpedance of them? Where is the crossover?
  How much power does go into the CCD? Is it a reasonable amount?
   
• The IR transmon beam is even larger than the green beam (w=5mm). 
  You definitely need a lens to shrink the beam. But we don't want to have the QPD and the CDD at the focus.
   
• As Jenne pointed out, having a steering mirror for the IR PDA36A is a good idea.
  But do you really want to use the Si PD for the IR tmonitor?
• I feel I don't want to have the pair of steering mirrors in the oplev incident path. One is enough.
  We should be able to accommodate optional mode-matching lenses in the incident path.
  We definitely don't want to have any lens in the returning path of the oplev.

I have updated the layout to fix all the issues brought up. The last couple of 2" green steering mirrors will hold the PZTs for input steering. I will update with the list of optical components that we will be ordering for this layout. The ETMY endtable layout will be similar to this one, except that we will have IPANG setup at the empty space in the right top corner.

I measured the beam profile of the Alberto laser (that will be the ETMY end laser) as I found the data inconsistent with the measurements done earlier.

Method

The laser was set to nominal current (ADJ =0) and the output measured 330mW. I used a 99% BS and measured the beam profile of the transmitted light at several points along propagation using Beamscan. I am attaching the data and matlab script for the fit for future reference.

The TRY path on the end table is temporarily in place to help IFO locking.
The Y arm transmission was steered to get TRY back on the PD and the camera. I found that TRY is a couple of inches off in yaw at the end table (comparing to the CAD layout and the earlier layout) and I believe it is because of the changes in input pointing.
I've used a Y1 mirror to steer the Y transmission to an R98% BS. The reflected beam falls on PDA520 and the transmitted beam is steered to the camera. The earlier normalization of TRY is no more valid as the power distribution at the PD has changed.

Temporary  acrylic wind guard added between enclosure and ETMY transmission window to help IFO locking

 Endtable upgrade - timeline and progress chart. End table upgrade wiki page updated.

 Drawing of customized mount for endtable doubler crystal (PV40+PVP2+NP9071) modified and updated on the endtable upgrade wiki page.

I started populating the end table; the TRY path to start with. I found that I need to redo the cables/electronics layout around the table as we have only one cable feedthrough hole with the new box right now. I need another hand with this and will have Annalisa help me tomorrow.

P.S. I misaligned PRM and restored ETMY to get TRY flashes. I tweaked ETMY to see strong TEM00 flashes.

Old slider positions on medm screen in case we need to restore them:

        TT1    TT2     ITMY    ETMY

P   -1.3586  0.8443   0.9114   -3.7693

Y   0.3049   1.1507  -0.2823  -0.2761

[Den, Annalisa, Manasa]

The Alberto laser was moved from the PSL table. The height of the heat sink rendered a beam height of only 3 inches. I did not want to deal with changing beam height at the table. So, we went ahead and used the old heat sink. I used the beam scan to make measurements of the beam width to match my mode-matching calculations and found some mismatch with the measurements done earlier. So I will measure the beam width again before alignment.

I will also have to change the layout because of the supporting posts that have come up with the new box. Annalisa is doing a COMSOL model to check what the thickness of these supporting posts should be so that the box stays stiff.

Assembly progress:

1. ETMY oplev setup has been put together. Because of the shift in the TRY path, I had to modify the oplev path on the table as well.

2. Green laser setup coming together:
    (i) Used a HWP after the NPRO to convert s-polarization to p-polarization. (Verified by introducing a PBS after the HWP and then removed later).
    (ii) Lens focuses the beam into the Faraday.
    (iii) Used steering mirrors to align the beam to the faraday. With 320mW before the Faraday, I was able to get 240mW after the output aperture. The spec sheet for the faraday specifies a 93% transmission; but what I measure is only 75%.

I started to put together optics at the endtable. I am attaching the layout with the green blocks showing the optics that are assembled and will not be moved henceforth unless somebody contradicts.

1. Power after HWP = 314mW
    Power before faraday = 310mW
    Power after faraday = 300mW (the power loss while aligning the faraday earlier was due to the AR coating on the focusing lens before the faraday - it was AR coated for visible and that accounted to the power lost)

2. Since we do not know the length of TGG inside faraday, I measured the beam profile after the faraday so that I can trace the beam without any errors to calculate exact mode matching solutions.

3. The NPRO beam seems to be obviously elliptical as seen on the IR card and also from beam profile measurement. So we cannot skip including cylindrical lenses in the layout.

I have updated the waists (W)  and beam diameters (D) at 1064nm optics on the endtable.

I am not able to locate the characteristics of QPD-Y and oplev PD and hence took the beam diameter to be half of the detector surface area to determine their positions.

Beam diameter on PDA520 used for TRY was calculated using the transimpedance and responsivity of the PD from an old elog in 2004.