I had some issues with the Debian GUI which I thought would be solved upon reboot.
I restarted the machine but the boot sequence would get stuck at the cvs/cds mounting.
To get access to the command line prompt I edited the Grub script by adding init=/bin/bash to the end of the line that start with the word linux and booting.
This allowed me to access root with reading permission. To get writing permission I ran
mount -n -o remount,rw /
then, I commented out the cvs/cds line in /etc/fstab and booted. This brought back the normal debian GUI.
However, we were unable to manually mount cvs/cds. The problem seems to be that rossa got disconnected from the network. Switching port on the network switch and using a different network cable didn't seem to help.
Currently, rossa is bootable but there is no network access.
Compared the network settings between some of the machines.
It seemed that we can write network settings into /etc/network/interfaces. (Comment lines omitted)
iface lo inet loopback
iface lo inet loopback
pianosa has the same content, but I found chiara has much more elaborated lines. So I decided to put the details there.
iface lo inet loopback
iface eno1 inet static
iface lo inet loopback
iface eno1 inet static
And just in case ifup was ran
$ sudo /sbin/ifup eno1
$ sudo /sbin/ifup eno
This made rossa connected to the wired network as rebooted.
So reactivated the NFS line in /etc/fstab
Rebooting pianosa brought it back to the nominal operation. Victory.
I looked at the Acromag situation of c1psl to prepare for the PSL air flow speed sensor.
Someone clever did a great job of binding all the spare channels into DB37s.
The pin-outs and channel assignments are all listed in a Google spreadsheet. The link can be found on the following wiki page.
https://wiki-40m.ligo.caltech.edu/CDS/SlowControls/c1psl (Click "Feedthrough wiring with test status")
According to the spreadsheet, we are supposed to have
For now, we can hook up the sensors via a DB37 breakout or even just a connector. If we have many cables coming in the future, we can make a breakout 1U unit.
I went to /cvs/cds/caltech/target and found some folders for apparently old targets.
They were tarballed (.tar.gz) and the folders were removed.
I don't know why we have c1auxey and c1auxey1. And it seems that c1auxey1 is the new one???
We should remove some of them from the autoburt request files.
If there is any unexpected error let me know so that I can revert.
The raw frame file is stored in /frames at fb. Before the disk space is flooded, the wiper script deletes the old raw frame files.
I wonder what the state of the wiper script is.
There are wiper scripts (wiper.pl) in /opt/rtcds/caltech/c1/target/fb and /opt/rtcds/caltech/c1/target/daqd, but they no longer seemed to be in use.
I went around the machines and found a service on fb
controls@fb1:~ 0$ sudo systemctl status rts-daq_wiper
● rts-daq_wiper.service - Remove old frame files to reclaim space for the new frame files
Loaded: loaded (/etc/systemd/system/rts-daq_wiper.service; static; vendor preset: enabled)
Active: inactive (dead) since Fri 2023-08-04 20:00:27 PDT; 9min ago
Process: 5355 ExecStart=/opt/rtcds/caltech/c1/scripts/daq_wiper -d /frames -t 2.5 (code=exited, status=0/SUCCESS)
This python version of the wiper script (/opt/rtcds/caltech/c1/scripts/daq_wiper) is running since the last year.
According to the explanation found in the script, the trend data is kept saved, while the raw data is kept deleted to save the specified amount of space (0.25TB it says).
I think this is the configuration we want. So the script was left untouched.
[JC, Koji, Yuta, Hiroki]
When we tried to measure the spectrum of C1:LSC-DARM_IN2 with the diaggui, the following error was occured and were not able to measure the spectrum:
"Unable to obtain measurement data"
We solved this issue by clearing the test points in c1lsc with the following commands:
diag> tp clear 42 *
"42" corresponds to the DCUID of c1lsc and "*" specifies all the test points.
Details of Clear command: tp clear node# tp#
node# = dcu# of the RTS (see CDS status screen to find the DCU #)
tp# (see CDS status screen to find the TP #)
- I made a basic description on a wiki page: https://wiki-40m.ligo.caltech.edu/CDS/DolphinSwitch
- Investigation crashed c1lsc/c1sus/c1iscex/c1sus2. Well, it's time to test the dolphin fencing. It seemed successful.
- Rebooted the crashed machines. I accidentally rebooted nodus, but Apache and elog were restarted.
- Burtrestoring to 18:19 snapshots. I suffered from the zero alignment gain issue, but the two arms are aligned and locked.
During the crash, I tried to reboot c1sus2 while the others were running. I actually did not install the script. It seems that it has been there since 2022 Sep.
Here is the instruction:
./dolphin_ix_port_control.sh --disable 192.168.113.40 #
./dolphin_ix_port_control.sh --enable 192.168.113.40 #
rtcds stop --all
rtcds start --all
We can improve the process and the location of the script, but this is a good progress I suppose.
I came to the lab to see the recovery work from the power glitch this morning 8:15AM. All CDS seems up. The suspensions are somewhat aligned. Some of them were not damped. The oplevs were off. Radhika is working on the recovery of the FP arms.
I noticed that FSS Slow servo is not working. I always forget what is the right way to turn it on. Here is the summary:
How to turn on FSSSlow (2023 Sept version)
sudo systemctl enable FSSSlow
sudo systemctl start FSSSlow
sudo systemctl status FSSSlow
● FSSSlow.service - Script to run the PID temperature control servo for the PSL
Loaded: loaded (/opt/rtcds/caltech/c1/Git/40m/scripts/PSL/FSS/FSSSlow.service; enabled; vendor pre
Active: active (running) since Fri 2023-09-08 17:10:52 PDT; 1s ago
Main PID: 2088 (python3)
Tasks: 6 (limit: 4674)
└─2088 /usr/bin/python3 /opt/rtcds/caltech/c1/Git/40m/scripts/PSL/FSS/PIDLocker.py PIDConf
Sep 08 17:10:52 megatron systemd: Started Script to run the PID temperature control servo for the
Dolphin Fencing technique
I believe that the dolphin emits some glitches to the other hosts during the host machine shutting down and starting up.
However, if the dolphin is disabled, that FE process will not run.
Therefore, we need some technique:
./dolphin_ix_port_control.sh --disable 192.168.113.40 2
sudo reboot; exit
./dolphin_ix_port_control.sh --enable 192.168.113.40 2
Thermal lensing formula:
from (T090018 by A. Abramovici (which references another doc).
In the above equation:
w 1/e^2 beam radius
k thermal conductivity (not the wave vector) = 1.3 W / m/ K
alpha absorption coefficient (~10 ppm/cm for our glass)
NP power in the glass (alpha*NP = absorbed power)
dn/dT index of refraction change per deg (12 ppm/K)
d mirror thickness (25 mm for all of our SOS)
I'm attaching a plot showing the focal length as a function of recycling cavity power for both our current MOS and future SOS designs.
I've assumed a 10 ppm/cm absorption here. It may actually be less for our current ITMs which are made of Heraeus low absorption glass - our new ITMs are Corning 7980-A (measured to have an absorption of 13 ppm/cm ala the iLIGO COC FDD). I expect that our thermal lens focal length will always be longer than 1 km and so I guess this isn't an issue.
In addition to the main mirrors (PRM, SRM) we will also have fold mirrors (called PR1, PR2, SR1, SR2). I am curious to see if we can get away with just using commercial optics; I think that the CVI Y1S coatings may do the trick.
The above plots show the reflectivities v. wavelength. I've asked the sales rep to give us specs on the reflectivity v. angle. I bet that we can guess what the answer will be from these plots.
This is a plot of the R and T of the existing ETM's HR coating. I have only used 1/4 wave layers (in addition to the standard 1/2 wave SiO2 cap on the top) to get the required T.
The spec is a T = 15 ppm +/- 5 ppm. The calculation gives 8 ppm which is close enough. The calculated reflectivity for 532 nm is 3%. If the ITM reflectivity is similar, the signal for the 532 nm locking of the arm would look like a Michelson using the existing optics.
[Koji, Jenne, Alberto, Steve, Bob]
ETMX has been drag wiped.
Around 2:45pm, after the main IFO volume had come up to atmospheric pressure, we removed both doors to the ETMX chamber. Regular procedures (wiping of O-rings with a dry, lint-free cloth, covering them with the light O-ring covers, etc.) were followed. Koji took several photos of the optic, and the rest of the ETMX chamber before anything was touched. These will be posted to the 40m Picasa page. Steve and Koji then deionized the optic.
Koji removed the bottom front earthquake stop, and clamped the optic with the remaining earthquake stops.
The clean syringes were prepared: These are all glass and metal (nothing else) medical syringes. The size used was 100microliters. Earlier today, we had prepared our solvents in small little beakers which had been baked over the weekend. Brand new glass bottles of Acetone and Isopropyl Alcohol were opened, and poured into the small beakers. To make sure we have enough, we have 3 ~10ml beakers of each Acetone and Isopropyl.
We started with Acetone. The syringe was filled completely with acetone, then squirted onto a kimwipe. This was repeated ~twice, to ensure the syringe was well rinsed. Then the syringe was filled a little past the 100 microliter mark. Koji held a piece of lens cleaning paper to ETMX and used an allen wrench underneath the optic to help guide the paper, and keep it near the optic (of course, the only thing in actual contact with the optic was the lens paper). In one smooth shot, the plunger of the syringe was pressed all the way down. (This is a bit tricky, especially when the syringe is totally full. You have to squeeze it so the plunger moves fairly quickly down the barrel of the syringe to get a good arc of liquid. The goal is to shoot all of the solvent to the same place on the lens paper, so that it makes a little circle of wetness on the paper which covers the coated part of the optic. The amount of solvent used should be balanced between having too little, so that the paper is dry by the time it has been wiped all the way down, and too much such that there is still a residue of liquid on the optic after the paper has been removed.) The target was to hit the optic just above the center mark (the oplev was on, so I went for just above the red oplev dot). Immediately after applying the liquid onto the paper, Koji slowly and smoothly pulled down on the lens paper until it came off of the bottom of the optic. The acetone was repeated, for a total of 2 acetone wipes. Because acetone evaporates very quickly, more acetone is used than isopropyl. The optimal amount turned out to be ~115 microliters of acetone. It is hard to say exactly how much I had on the second wipe, because the syringe is not marked past 100 microliters. On the first wipe, with about 105 microliters, the lens paper was too dry at the bottom of the optic.
We then switched to Isopropyl. A new syringe was used, and again we rinsed it by filling it completely with isopropyl, and emptying it onto a kimwipe. This was repeated at least twice. We followed the same procedure for applying liquid to the optic and wiping the optic with the lens paper. On the first try with isopropyl, we used 100 microliters, since that was the preferred amount for acetone. Since isopropyl evaporates much slower than acetone, this was determined to be too much liquid. On the second isopropyl wipe, I filled the syringe to 50 microliters, which was just about perfect. The isopropyl wiping was done a total of 2 times.
After wiping, we replaced the front bottom earthquake stop, and released the optic from the other earthquake stops' clamping. The OSEM values were checked against the values from the screenshots taken yesterday afternoon, and were found to be consistent. Koji took more photos, all of which will be placed on the 40m Picasa page.
We visually inspected the optic, and we couldn't see anything on the optical surface of the mirror. Koji said that he saw a few particulates on some horizontal surfaces in the chamber. Since the optic seemed (at least to the level of human vision without a strong, focused light) to be free of particulates on the optical surface to start with, the suspense will have to remain until we button down, pump down, and try to lock the IFO to determine our new finesse, to see if the wiping helped any substantial amount.
We replaced the regular, heavy door on the inner side of the ETMX chamber (the side closer to the CES building), and put only a light door on the outer side of the chamber (the side closer to the regular walkway down the arm). We will look at the spectra of the OSEMS tomorrow, to confirm that none of the magnets are stuck.
We commence at ~9am tomorrow with ETMY.
* The LED lights are awesome. It's easy to use several lights to get lots of brightness (more than we've had in the past), and the chamber doesn't get hot.
* We should get larger syringes for the acetone for the large optics. It's challenging to smoothly operate the plunger of the syringe while it's so far out. We should get 200 microliter syringes, so that for the acetone we only fill them about half way. It was noticeably easier to apply the isopropyl when the syringe only had 50 microliters.
* It may be helpful to have a strong, focused optical light to inspect the surface of the mirror. Rana says that Garilynn might have such an optical fiber light that we could borrow.
Jenne, Kiwamu, Alberto, Steve, Bob, Koji
We wiped ETMY after recovery of the computer system. We take the lunch and resume at 14:00 for ITMX.
Detailed reports will follow.
Jenne, Kiwamu, Koji, Alberto, Steve, Bob
ITMX was wiped without having to move it.
After 'practice' this morning on ETMY, Kiwamu and I successfully wiped ITMX by leaning into the chamber to get at the front face.
Most notable (other than the not moving it) was that inspection with the fiber light before touching showed many very small particles on the coated part of the optic (this is versus ETMY, where we saw very few, but larger particles). The after-wiping fiber light inspection showed many, many fewer particles on the optical surface. I have high hopes for lower optical loss here!
[Kiwamu, Jenne, Alberto, Steve, Bob, Koji]
We finished wiping of four test masses without any trouble. ITMY looked little bit dusty, but not as much as ITMX did.
We confirmed the surface of the ITMX again as we worked at vertex a lot today. It still looked clean.
We closed the light doors. The suspensions are left free tonight in order to check their behavior.
Tomorrow morning from 9AM, we will replace the door to the heavy ones.
This plot shows the Transmission for 532 and 1064 nm as a function of the thickness of the SiO2 layer.
i.e. the thickness is constrained so that the optical thickness of the SiO2 and Ta2O5 pair is always 1/2 of a wavelength.
The top layer of the mirror is also fixed in this plot to be 1/2 wave.
This plot shows the result for 17 pairs. For 16 pairs, we are unable to get as low as 15 ppm for the 1064 nm transmission.
In the middle of the last month, Kiwamu and I went to Garilynn's lab to measure the phase maps of the new ITMs and SRMs.
Analysis of the phase map data were posted on the svn directory:
The screen shots and the plots were summarized in a PDF file. You can find it here:
The RoCs for all of the PRMs are turned out to be ~155m. This is out of the spec (142m+/-5m) although the actual effect is not understand well yet..
These RoCs are almost independent from the radus of the assumed gaussian beam.
In deed, I have checked the dependence of the RoC on the beam spot position, and it turned out that the RoCs vary only little.
(In the SRMU01 case, for example, it varies from 153.5m to 154.9m.)
The beam radius of 3mm was assumed. The RoCs were calculated 20x20mm region around the center of the mirror with a 2mm mesh.
X Arm: 0.875 +/- 0.005
Y Arm: 0.869 +/- 0.006
[Jenne, Kiwamu, with moral support from Koji, and loads of advice from Steve and Bob]
New upgrade ITMX (ITMU03) has it's guiderod & standoff glued on, as step 1 toward hanging the ITMs.
1. Make sure you have everything ready. This is long and complicated, but not really worth detail here. Follow instructions in E970037 (SOS Assembly Spec), and get all the stuff in there.
2. Set optic in a 'ring stand', of which Bob has many, of many different sizes. They are cleaned and baked, and in the cleanroom cupboard on the bottom just behind the door. We used the one for 3" optics. This lets you sit the optic down, and it only rests on the bevel on the outside, so no coated surface touches anything.
3. Drag wipe the first surface of the optic, using Isopropyl Alcohol. We used the little syringes that had been cleaned for the Drag Wipe Event which happened in December, and got fresh Iso out of the bottle which was opened in Dec, and put it into a baked glass jar. The drag wipe procedure was the same as for the December event, except the optic was flat on the bench, in the ring holder.
4. Turn the optic over.
5. Drag wipe the other surface.
6. Align the optic in the guiderod gluing fixture (Step 3 in Section 3.2.1: Applying Guide Rod and Wire Standoff of E970037).
7. Set guiderod and standoff (1 guiderod on one side, 1 standoff on the other, per instructions) against the side of the optic.
8.a. Use a microscope mounted on a 3-axis micrometer base to help align the guiderod and standoff to the correct places on the optic (Steps 4-5 of Section 3.2.1). This will be much easier now that we've done it once, but it took a looooooong time.
8.b. We put the optic in 180deg from the way we should, based on the direction of the wedge angle in the upgrade table layout (wedge angle stuff used a "Call a Friend" lifeline. We talked to Koji.) The instructions say to put the guiderod and standoff "above" the scribe lines in the picture on Page 5 of E970037 - the picture has the arms of the fixture crossing over the scribe lines. However, to make the optic hang correctly, we needed to put the guiderod and standoff below the scribe lines. This will be true as long as the arrow scribe line (which marks the skinniest part of the optic, and points to the HR side) is closest to you when the optic is in the fixture, the fixture is laying on the table (not standing up on end) with the micrometer parts to your right. We should put the other ITM into the fixture the other way, so that the arrow is on the far side, and then we'll glue the guiderod and standoff "above" the scribe lines. Mostly this will be helpful so that we can glue in exactly the places the instructions want us to.
8.c. The biggest help was getting a flashlight to help illuminate the scribe lines in the optic while trying to site them in the microscope. If you don't do this, you're pretty much destined to failure, since the lights in the cleanroom aren't all that bright.
8.d. The micrometer mount we were able to find for the microscope has a max travel of 0.5", but the optic is ~1" thick. To find the center of the optic for Step 5 in the guiderod and standoff alignment we had to measure smaller steps, such as bevel-to-end-of-scribe-line, and length-of-scribe-line then end-of-scribe-line-to-other-bevel. Thankfully once we found the total thickness and calculated the center, we were able to measure once bevel-to-center.
9. Apply glue to the guiderod and standoff. We made sure to put this on the "down" side, which once the optic is hung, will be the top of the little rods. This matches the instructions as to which side of the rods to apply the glue on. The instructions do want the glue in the center of the rod though, but since we put the optic in the fixture the wrong way, we couldn't reach the center, so we glued the ends of the rods. We will probably apply another tiny dab of glue on the center of the rod once it's out of the fixture, perhaps while the magnet assemblies are being glued.
10. We didn't know if the airbake oven which Bob showed us to speed up the curing of our practice epoxy last night was clean enough for the ITM (he was gone by the time we got to that part), so for safety, we're leaving the optic on the flow bench with a foil tent (the foil is secured so there's no way it can blow and touch the optic). This means that we'll need the full curing time of the epoxy, not half the time. Maybe tomorrow he'll let us know that the oven is in fact okay, and we can warm it up for the morning.
Jenne and kiwamu
We have glued the dumbbells to the magnets that will be used for the ITMs
We made two sets of glued pair of the dumbbell and the magnet ( one set means 6 pairs of the dumbbell and the magnet. Therefore in total we got 12 pairs. )
You can see the detailed procedure we did on the LIGO document E990196.
Actually we performed one different thing from the documented procedure;
we made scratch lines on the surface of the both dumbbells and magnets by a razor blade.
According to Steve and Bod, these scratch make the strength of the glues stronger.
Now the dumbbell-magnet pairs are on the flow bench in the clean room, and supported by a fixture Betsy sent us.
- - notes
On the bench the left set is composed by magnets of 244 +/- 3 Gauss and the right set is 255 +/- 3 Gauss.
This work happened on Friday, after Nodus and the elog went down....
The guiderod and standoff for ITMY were epoxied, and left drying over the weekend on the flow bench under a foil tent. The flow bench was off for the weekend, so we made tents which hopefully didn't have any place for dust to get in and settle on the mirrors.
There is a small chance that there will be a problem with glue on the arm of the fixture holding the guiderod to the optic. Kiwamu and I examined it, and hopefully it won't stick. We'll check it out this afternoon when we start getting ready for gluing magnets onto optics this afternoon.
The magnets + dumbbell standoffs have been glued to ITMX. We're waiting overnight for them to dry.
Since I broke one of the magnet + dumbbells on the ITMY set, we've glued another dumbbell to the 6th magnet, and it should be ready for us to glue to ITMY tomorrow, once ITMX is dry and out of the fixture. This doesn't put us behind schedule at all, so that's good.
We had been concerned that there might be a problem with the arm of the guiderod fixture being glued to ITMY, but it was fine after all. Everything is going smoothly so far.
Zach and Mott are almost prepared to start cutting the viton for the earthquake stops. We need 2 full sets by Wednesday morning, when we expect to begin hanging the ITMs.
This is going to be a laundry list of the mile markers achieved so far:
* Guiderod and wire standoff glued to each ITMX and ITMY
* Magnets glued to dumbbells (4 sets done now). ITMX has 244 +- 3 Gauss, ITMY has 255 +- 3 Gauss. The 2 sets for SRM and PRM are 255 +- 3 G and 264 +- 3 G. I don't know which set will go with which optic yet.
* Magnets glued to ITMX. There were some complications removing the optic from the magnet gluing fixture. The way the optic is left with the glue to dry overnight is with "pickle picker" type grippers holding the magnets to the optic. After the epoxy had cured, Kiwamu and I took the grippers off, in preparation to remove the optic from the fixture. The side magnet (thankfully the side where we won't have an OSEM) and dumbbell assembly snapped off. Also, on the UL magnet, the magnet came off of the dumbbell (the dumbbell was still glued to the glass). We left the optic in the fixture (to maintain the original alignment), and used one of the grippers to glue the magnet back to the UL dumbbell. The gripper in the fixture has very little slop in where it places the magnet/dumbbell, so the magnet was reglued with very good axial alignment. Since after the side magnet+dumbbell came off the glass, the 2 broke apart, we did not glue them back on to the optic. They were reattached, so that we can in the future put the extra side magnet on, but I don't think that will be necessary, since we already know which side the OSEM will be on.
* Magnets glued to ITMY. This happened today, so it's drying overnight. Hopefully the grippers won't be sticky and jerky like last time when we were removing them from the fixture, so hopefully we won't lose any magnets when I take the optic out of the fixture.
* ITMX has been placed in its suspension cage. The first step, before getting out the wire, is to set the optic on the bottom EQ stops, and get the correct height and get the optic leveled, to make things easier once the wire is in place. Koji and I did this step, and then we clamped all of the EQ stops in place to leave it for the night.
* The HeNe laser has been leveled, to a beam height of 5.5inches, in preparation for the final leveling of the optics, beginning tomorrow. The QPD with the XY decoder is also in place at the 5.5 inch height for the op lev readout. The game plan is to leave this set up for the entire time that we're hanging optics. This is kind of a pain to set up, but now that it's there, it can stay out of the way huddled on the side of the flow bench table, ready for whenever we get the ETMs in, and the recoated PRM.
* Koji and Steve got the ITMX OSEMs from in the vacuum, and they're ready for the hanging and balancing of the optic tomorrow. Also, they got out the satellite box, and ran the crazy-long cable to control the OSEMs while they're on the flow bench in the clean room.
Koji and I discovered a problem with the small EQ stops, which will be used in all of the SOS suspensions for the bottom EQ stops. They're too big. :( The original document (D970312-A-D) describing the size for these screws was drawn in 1997, and it calls for 4-40 screws. The updated drawing, from 2000 (D970312-B-D) calls for 6-32 screws. I naively trusted that updated meant updated, and ordered and prepared 6-32 screws for the bottom EQ stops for all of the SOSes. Unfortunately, the suspension towers that we have are tapped for 4-40. Thumbs down to that. We have a bunch of vented 4-40 screws in the clean room cabinets, which I can drill, and have Bob rebake, so that Zach and Mott can make viton inserts for them, but that will be a future enhancement. For tonight, Koji and I put in bare vented 4-40 screws from the clean room supply of pre-baked screws. This is consistent with the optics in our chambers having bare screws for the bottom EQ stops, although it might be nicer to have cushy viton for emergencies when the wire might snap. The real moral of this story is: don't trust the drawings. They're good for guidelines, but I should have confirmed that everything fit and was the correct size.
First, the easy story: SRM got it's guiderod & standoff glued on this evening. It will be ready for magnets (assuming everything is sorted out....see below) as early as tomorrow. We can also begin to glue PRM guiderods as early as tomorrow.
The magnet story is not as short.....
Problem: ITMX and ITMY's side magnets are not glued in the correct places along the z-axis of the optic (z-axis as in beam propagation direction).
ITMX (as reported the other day) has the side magnet placement off by ~2mm. ITMX side was glued using the magnet fixture from MIT and the teflon pads that Kiwamu and I improvised.
It was determined that the improvised teflon pads were too thin (maybe about 1m thick), so I took those out, and replaced them with the teflon pads stolen from the 40m's magnet gluing fixture. (The teflon pad from the MIT fixture and the ones from the MIT fixture are the same within my measuring ability using a flat surface and feeling for a step between them. I haven't yet measured with calipers the MIT pad thickness). The pads from the 40m fixture, which were used in the MIT fixture to glue ITMY side last night were measured to be ~1.7mm thick.
Today when Koji hung ITMY, he discovered that the side magnet is off by ~1mm. This improvement is consistent with the switching of the teflon pads to the ones from the 40m fixture.
We compared the 40m fixture with the one from MIT, and it looks like the distance from the edge of where the optic should sit to the center of the hole for the side magnet is different by ~1.1mm. This explains the remaining ~1mm that ITMY is off by.
We should put the teflon pads back into the 40m fixture, and only use that one from now on, unless we find an easy way to make thicker teflon pads for the fixture we received from MIT. (The pads that are in there are about the maximum thickness that will fit). I'm going to use my thickness measurements of SRM (taken in the process of gluing the guiderods) to see what thickness of pads / what fixture we want to actually use, but I'm sure that the fixture we found in the 40m is correct. We can't use this fixture however, until we get some clean 1/4-28 screws. I've emailed Steve and Bob, so hopefully they'll have something for us by ~lunchtime tomorrow.
The ITMX side magnet is so far off in the Z-direction that we'll have to remove it and reglue it in the correct position in order for the shadow sensor to do anything. For ITMY, we'll check it out tomorrow, whether the magnet is in the LED beam at all or not. If it's not blocking the LED beam enough, we'll have to remove and reglue it too.
Why someone made 2 almost identical fixtures, with a 1mm height difference and different threads for the set screws, I don't know. But I don't think whoever that person was can be my friend this week.
We removed the old SRM and PRM from their cages, and are temporarily storing them in the rings which we use to hold the optics while baking. Steve will work on a way to store them more permanently.
We then hung the new SRM (SRMU03) and new PRM (SRMU04) in the cages. We were careful not to break the wires, so the heights will not have changed from the old heights.
The optics have not been balanced yet. That will hopefully happen later this week.
While trying to set up the SIS-FFT to use our new ITM phase maps, I noticed that the surface of our ITMs looks pretty good actually (even compared to the aLIGO pathfinder optic map on the AIC wiki). I'm attaching it here for your viewing pleasure.
The code to plot it has been added to the SVN in the PhaseMaps/mat directory.
Kiwamu and Koji
We have visited GariLynn's lab to make a calibration of the metrology interferometer.
The newly calibrated value is
RoC(SRMU01) = 153.3+/- 1.6 [m]
This is to be compared with the specification of 142m +/- 5m
Although the calibration deviation from the previous value was found to be 1.3%, it is far from explaining the curvature difference between the spec (142m) and the measured value.
The previous measurements of the SRM curvatures showed larger RoCs by ~10% compared with the spec.
It can be caused by the mis-calibration of the pixel size of the CCD in the metrology interferometer.
In order to confirm the calibration value, an object with known dimension should be measured by the instrument.
We've got a flat blank optic from "Advanced Thin Film" together with a metalic ring.
The ring has been attached on the blank optic with 3 fragments of a double sided tape.
The RoC of SRMU1 was also measured in order to obtain "the radius of curvature of the day".
The calibration process is as follows:
Because of the calibration error, we measured too long RoC. The same day, we measured the curvature of SRMU01 as 155.26 m.
The newly calibrated value is
RoC(SRMU01) = 153.3+/- 1.6 [m]
This is the value to be compared with the specification of 142m +/- 5m
[Kiwamu, Yuta, Koji]
We went to the new metrology lab at Downs subbasement (Rm014) in order to measure the phase map of the delivered PRMs.
It's brand-new. So we had to measure the reference phase map, calibration as well as the phase map of our mirrors (3 PRMs and 1 spare SRM). It took a whole day...
Calibration of the phase map interferometer was calculated for the data on Oct 8th, 2010.
The calibration value is 0.1905 mm/pixel.
This is slightly smaller than the assumed value in the machine that is 0.192mm/pixel.
This means that the measured radii of curvature must be scaled down with this ratio.
(i.e. RoC(new) = RoC(old) / 0.1922 * 0.19052)
Our tagets of the phasemap measurement are:
1. Measure the figure errors of the mirrors
2. Measure the curvature of the mirrors
The depth of the mirror figure is calibrated by the wavelength of the laser (1064nm).
However, the lateral scale of the image is not calibrated.
Although Zygo provides the initial calibration as 0.192 mm/pixel, we should measure the calibration by ourselves.
We found an aperture mask with a grid of holes with 2mm diameter and 3mm spacing (center-to-center).
Take the picture of this aperture and calibrate the pixel size. The aperture is made of stainless and makes not interference
with the reference beam. Thus we put a dummy mirror behind the aperture. (UPPER LEFT plot)
As the holes are aligned as a grid, the FFT of the aperture image shows peaks at the corresponding pitches. (UPPER MIDDLE plot)
As the aperture was slightly rotated, the grids of the peaks are also slanted.
We can obtain the spacing of the peak grids. How can we can that values precisely? I decided to make an artificial mask image.
The artificial mask (LOWER LEFT plot) has the similar FFT pattern (LOWER MIDDLE plot). The inner product of the two
FFT results (i.e. Sum[abs(fft1) x abs(fft2)]), quite a large value is obtained if the grid pitch and the aperture angle agrees between those images.
Note that the phase information was discarded. The estimated grid spacing of the artificial mask can be mathematically obtained.
The grid pitch and the angle were manually set as initial values. Then the parameters to give the local maximum was obtained by fminsearch of Matlab.
UPPER RIGHT and LOWER RIGHT plots show the scan of the evaluation function by changing the angle and the pitch. They behave quite normal.
The obtained values are
Grid pitch: 15.74 pixel
Angle: 1.935 deg
As the grid pitch is 3mm, the calibration is
3 mm / 15.74 pixel = 0.1905 mm/pixel
A spherical surface can be expressed as the following formula:
z = R - R Sqrt(1-r2/R2) (note: this can be expanded as r2/(2 R)+O(r3) )
Here R is the RoC and r is the distance from the center. This means that the calibration of r quadratically changes the curvature.
We have measured the RoC of the spare SRM. We can compare the RoCs measured by this new metrology IFO and the old one,
as well as the one by Coastline optics.
I have made a summary web page for the 40m upgrade optics.
I made a bunch of RoC calculations along with the phase maps we measured.
Those are also accommodated under this directory structure.
Probably.... I should have used the wiki and copy/paste the resultant HTML?
After looking at the in-vacuum layout I think we should make two changes during the next vent:
1) Reduce the number of mirrors between the FI and its camera. We install a large silvered mirror in the vacuum flange which holds the Faraday cam (in the inside of the viewport). That points directly at the input to the Faraday. We get to remove all of the steering mirror junk on the IO stack.
2) Take the Faraday output (IFO REFL) out onto the little table holding the BS and PRM Oplevs. We then relocate all 4 of the REFL RFPDs as well as the REFL OSA and the REFL camera onto this table. This will reduce the path length from the FI REFL port to the diodes and reduce the beam clutter on the AS table.
There is just so much room on this table.
1) Mirror mount holder for "large silvered mirror" inside of the 8" OD tube vacuum envelope.
I took the two 'flat' 2" mirrors over to Downs and Garilynn showed me how to measure them with the old Wyko machine.
The files are now loaded onto our Dropbox folder - analysis in process. From eyeball, it seems as if the RoCs are in the neighborhood of ~5 km, with the local perturbations giving ~10-15 km of curvature depending upon position (few nm of sage over ~1 cm scales)
Koji's matlab code should be able to give somewhat more quantitative answers...
Ed: Here you are. "0966" looks good. It has RoC of ~4km. "0997" has a big structure at the middle. The bump is 10nmPV (KA)
Summary: After today's meeting, Gabriele and I looked into the arm loss situation, to see if we should really believe the losses that had been suggested by my previous measurements. We made some observations that we're not sure how to explain, and we're thinking about other ways to try and estimate the losses to corroborate previous findings.
We first looked to see if the ASS had some effective offset, leaving the alignment not quite right. Once ASS'd, we twiddled each arm cavity mirror in pitch and yaw to see if we could achieve higher transmission. We could not, so this suggested that ASS works properly.
We then looked at potential offsets in the Xarm loop. We found that an input offset of 25 counts increased the transmission, but only very slightly. With this offset adjusted, we confirmed the qualitative observation that locking/unlocking the xarm causes a much bigger change in ASDC than doing the same with the harm.
However, we noted that the ASDC data (which is the DC value of the AS55 RFPD) was quite noisy, hovering around 50 counts. Looking at the c1lsc model, we found that we were looking at direct ADC counts, so the signal conditioning was not so great. We went to the LSC rack and stole the SR560 that had been hooked up as a REFLDC offsetter, and used it to give ASDC a gain of 100, and a LP at 100Hz, since we only care about DC values. We then undid the gain in the input FM; and this calmed the trace down a fair bit. The effects due to each arm locking/unlocking was still consistent with previous observations.
At this point, we looked at the arm transmission and ASDC signals simultaneously. Normally, when misaligning a cavity, one would expect the reflected power to rise and the transmission to fall.
However, we saw that when misalignment the Yarm in yaw in either direction, or the Xarm in one direction, both the IR transmission and ASDC would fall. This initially made us think of clipping effects.
So, we checked out the AS beam situation on the AP table. On a card, the beam looks round as we could tell, and the beam spot on AS55 was nice and small. (We tweaked its steering a little bit in pitch to put it at the center of the "falling-off" points) The reflection and transmission falling effect remained.
At this point, we're not really sure what could be causing this effect. After the reflected beams recombine at the BS, the output path is common, so it's strange that this odd effect would be the same for both arms.
Lastly, we discussed other ways that we may be able to see if the Xarm really has ~500ppm loss. Since its transmission is ~1.4%, Gabriele estimated that we may be able to see a ~300Hz difference in the arm cavity pole frequency between the two arms, based on the modification of the cavity finesse due to loss. Since we don't currently have the AOM set up to inject intensity noise, we talked about using frequency noise injection to measure the arm cavity poles, though this would be coupled with the IMC pole, but this could hopefully be accounted for.
Yutaro left detailed slides for his loss map measurement
Steve sent 4 of our 1" diameter G&H HR mirrors to Josh Smith at Fullerton for scatter testing. Attached photo is our total stock before sending.
Antonio/Gautam are now developing a more up to date Finesse model of our recycling cavities to see what we can have there before our power recycling gain or cavity geometric stability is compromised. Expect that we will here a progress report on the model on Wednesday.
I've been working on putting together a Finesse model for the current 40m configuration. The idea was to see if I could reproduce a model that is in agreement with what we have been seeing during the recent DRFPMI locks. With Antonio and EricQs help, I've been making slow progress in my forays into Finesse and pyKat. Here is a summary of what I have so far.
Having put together the .kat file (code attached, but this is probably useless, the new model with RC folding mirrors the right way will be what is relevant), I was able to recover a power recycling gain of ~7.5. The arm transmission at full lock also matches the expected value (125*80uW ~ 10mW) based on a recent measurement I did while putting the X endtable together. I also tuned the arm losses to see (qualitatively) that the power recycling gain tracked this curve by Yutaro. EricQ suggested I do a few more checks:
Conclusion: It doesn't look like I've done anything crazy. So unless anyone thinks there are any further checks I should do on this "toy" model, I will start putting together the "correct" model - using RC folding mirrors that are oriented the right way, and using the "ideal" RC cavity lengths as detailed on this wiki page. The plan of action then is
Sidenote to self: It would be nice to consolidate the most recent cavity length measurements in one place sometime...
Having played around with a toy finesse model, I went about setting up a model in which the RC folding mirrors are not flipped. I then repeated the low-level tests detailed in the earlier elog, after which I ran a few spatial mode overlap analyses, the results of which are presented here. It remains to do a stability analysis.
Overview of model parameters (more details to follow):
Results (general note: positive RoC in these plots mean a concave surface as seen by the beam):
Next step is to carry out a stability analysis...
I think you should use the current actual PRC & SRC cavity lengths as measured, as it would be simplest to simply replace the folding mirror optics without changing the macroscopic lengths / optic positions. (EDIT: Gautam rightly points out that we have to move things around regardless, since our current lengths include propagation through the folding mirror subtrates)
Moreover, the recycling cavity lengths you posted are not the right "ideal" lengths to use, as they do not account for the complex reflectivities of the sidebands off of the arm cavities (I have made this mistake myself). See this 40m wiki page for details.
In short, given our current modulation frequency, the ideal lengths to use would be:
These are the lengths that the recycling cavity optics were positioned for (though we did not achieve them perfectly). If you do a finer PRC/SRC length scan around the DRFPMI resonance of your model, you would presumably see some undesired sideband splitting.
In a previous elog, I demonstrated that the RoC mismatch between ETMX and ETMY does not result in appreciable degradation in the mode overlap of the two arm modes. Koji suggested also checking the effect on the contrast defect. I'm attaching the results of this investigation (I've plotted the contrast, rather than the contrast defect 1-C).
Details and methodology
Attachment #1 shows the result of this scan (as mentioned earlier, I plot the contrast C and not the contrast defect 1-C, sorry for the wrong plot title but it takes ~30mins to run the simulation which is why I didn't want to do it agian). If the RoC of the spare ETMs is about 54m, the loss in contrast is about 0.5%. This is in good agreement with this technical note by Koji - it tells us to expect a contrast defect in the region of 0.5%-1% (depending on what parameter you use as the RoC of ETMY).
It doesn't seem that switching out the current ETM with one of the spare ETMs will result in dramatic degradation of the contrast defect...
That sounds weird. If the ETMY RoC is 60 m, why would you use 57.6 m in the simulation? According to the phase map web page, it really is 60.2 m.
This was an oversight on my part. I've updated the .kat file to have all the optics have the RoC as per the phase map page. I then re-did the tracing of the Y arm cavity mode to determine the appropriate beam parameters at the laser in the simulation, and repeated the sweep of RoC of ETMX while holding RoC of ETMY fixed at 60.2m. The revised contrast defect plot is attached (this time it is the contrast defect, and not the contrast, but since I was running the simulation again I thought I may as well change the plot).
As per this plot, if the ETMX RoC is ~54.8m (the closer of the two spares to 60.2m), the contrast defect is 0.9%, again in good agreement with what the note linked in the previous elog tells us to expect...
So, it seems that changing the ETMX for one of the spares will change the contrast defect from ~0.1% to 0.9%. True? Seems like that might be a big deal.
That is what the simulation suggests... I repeated the simulation for a PRFPMI configuration (i.e. no SRM, everything else as per the most up to date 40m numbers), and the conclusion is roughly the same - the contrast defect degrades from ~0.1% to ~1.4%... So I would say this is significant. I also attempted to see what the contribution of the asymmetry in loss in the arms is, by running over the simulation with the current loss numbers of 230ppm for Yarm and 484ppm for the X arm, split equally between the ITMs and ETMs for both cases, and then again with lossless arms - see attachment #1. While this is a factor, this plot seems to suggest that the RoC mismatch effect dominates the contrast defect...