We have now reduced the power being input to the MC from 1.25W to 10mW, and changed out the MC refl BS for a mirror.
The power was reduced via the PBS we introduced in Entry 7295.
While we were in there, we took a look at the AS beam, which was looking clipped on the monitor. Jenne felt that it appears that the clipping seems to be occurring inside the vacuum, possibly on the faraday. This will be investigated during the vent.
I stopped the regular MC autolocker and told the crontab to startup the low power Mc autolocker on op340m. Also, since we now have the new MC2 transmission setup, the power that gets to the 'regular' MC trans PD is lower, so I've lowered the lock threshold to 50 counts, from 100 counts.
We installed a Half Wave Plate -> Polarized Beam Splitter -> Half Wave Plate in the PSL beam line, immediately after the EOM, to be used for attenuating the beam when we vent, as in Entry 6892.
It was illuminating to discover that the optics labeled QWP0-1064-10-2 are indeed half wave plates, instead of quarter wave plates as QWP suggests.
The PBS transmits "P"/Horizontal polarization, but the beam coming from the EOM is "S"/Vertically polarized, and we want to keep that, since we do not want the beam attenuated quite yet.
So, we use the HWP to rotate the P from the EOM to S, so that the majority of the power passes through the PBS. The second HWP then rotates the transmitted S back into P, which continues to the mode cleaner. When we want to attenuate, we will simply rotate the first HWP to change the proportion of S polarized light that will pass straight through the PBS and towards the mode cleaner.
After setting the proper HWP angles, we aligned the PBS via minimizing the MC reflection.
Since we have not yet attenuated the power, we have not yet changed the BS for the MC reflection, since this would damage the PD. The beam splitter will be changed out for a 100% reflectivity mirror to increase the power to the PD when we do.
Before we did this, I centered PSL POS and ANG, which gives us a reference of where the PSL beam was good when the MC spots were ~centered. There had been a beam dump blocking them, possibly from the last time we put in the power attenuator optics. This beam dump was moved a little to be out of the way of the PSL QPDs, and the PBS placed closer to the lens after the EOM, so that the PBS reflected beam is dumped. However, we should not remove that razor dump when we remove the attenuation optics, since it is also dumping a stray IR beam from the PSL QPD pickoff windowd.
I have turned of the high voltage supplies for PZT1 and PZT2. The OMC PZT high voltage supplies were already off, since we aren't really using them currently.
I have closed the PSL shutter, but have not put in a manual extra beam dump yet.
All systems go for vent!
Steve - EricQ will be here around 8am to help with the vent.
Let's see if the ripples observed in the MC ringdown can be due to tilt motion of the mirrors.
The time it takes to produce a phase shift corresponding to N multiples of 2*pi is given by:
t = sqrt(2*N*lambda/(L*omega_T^2*(alpha_1+alpha_2)))
L is the length of the MC (something like 13m), and alpha_1, alpha_2 are the DC tilt angles of the two mirrors "shooting into the long arms of the MC" produced by the MC control with respect to the mechanical equilibrium position. omega_T is the tilt eigenfrequency of the three mirrors (assumed to be identical). lambda = 1.064e-6m;
The time it takes from N=1 to N=2 (the first observable ripple) is given by: tau1 = 0.6/omega_T*sqrt(lambda/L/(alpha_1+alpha_2))
The time it takes from N=2 to N=3 is given by: tau2 = 0.77*tau1
First, we also see in the measurement that later ripples are shorter than early ripples consistent with some accelerated effect. The predicted ripple durations tau seem to be a bit too high though. The measurements show something like a first 14us and a late 8us ripple. It depends somewhat on the initial tilt angles that I don't know really.
In any case, the short ripple times could also be explained if the tilt motions start a little earlier than the ringdown, or the tilt motion starts with some small initial velocity. The next step will be to program a little ringdown simulation that includes mirror tilts and see what kind of tilt motion would produce the ripples exactly as we observe them (or maybe tilt motion cannot produce ripples as observed).
Isn't it just a ringing of the intracavity power as you shifted the laser frequency abruptly?
Hmm. I don't know what ringing really is. Ok, let's assume it has to do with the pump... I don't see how the pump laser could produce these ripples. They have large amplitudes and so I always suspected something happening to the intracavity field. Therefore I was looking for effects that would change resonance conditions of the intracavity field during ringdown. Tilt motion seemed to be one explanation to me, but it may be a bit too slow (not sure yet). Longitudinal mirror motion is certainly too slow. What else could there be?
Laser frequency shift = longitudinal motion of the mirrors
Ok, so the whole idea that mirror motion can explain the ripples is nonsense. At least, when you think off the ringdown with "pump off". The phase shifts that I tried to estimate from longitudinal and tilt mirror motion are defined against a non-existing reference. So I guess that I have to click on the link that Koji posted...
Just to mention, for the tilt phase shift (yes, there is one, but the exact expression has two more factors in the equation I posted), it does not matter, which mirror tilts. So even for a lower bound on the ripple time, my equation was incorrect. It should have the sum over all three initial tilt angles not only the two "shooting into the long arms" of the MC.
I've been helping Steve vent this morning. The following things were done (from Steve's logbook):
(At this point, I took over the air canisters, while Steve made preparations around the lab.
With the 5th cylinder, we began approaching 1 atm, so we slowed the regulator down to 5psi. Around 750 torr, Steve opened VV1 to air.
According to Steve, we will be at atmospheric pressure at ~12:30pm.
ANTS ALERT please watch out for ants. We have them in the control room.
The power has been increased to 20mW. We got the 10mW number from the linked elog entry above. However, after venting we were having problems locking the MC. Upon investigating past elog posts, we found that 20mW was actually the power used in the past. The MC will now autolock.
ETMX appears to be fine. It was stuck to its OSEMs in the usual way. I touched it and it dislodged and is now swinging freely. Damping loops have been re-engaged.
The biggest reason why we could not lock the MC was that the beam was not properly hitting the MC REFL diode.
Now the MC REFL DC is about ~0.1 and 1.2 when the MC is and is not locked.
We increased the power according to the quantitative analysis of the intracavity power in this earlier entry
Autolocker script for the low power MC was modified so that the initial VCO gain is 3 in stead of 10.
The 2 steps of super boost were also enabled again.
Today we prepared our experimental setup to take a cavity scan of the input mode cleaner, which we want to measure in the next day or so. Attached is a diagram of our setup.
What we want to do is to inject a set of sidebands into the PSL and sweep their frequency from 32-45 MHz (a range just over one fsr of the mode cleaner- vfsr=11MHz). We will measure the power transmitted out of the MC using a photo-diode and demodulate this signal with our input signal from the Marconi. From this we should be able to see the resonant frequencies of the carrier and the higher order modes.
One aspect we spent some time thinking about; whether we would be able to inject a signal into an EOM given the EOM and the Marconi are not perfectly impedance matched. Based on Kiwamu’s previous e-log entries designing the EOM, we decided that injecting a signal in 32-45 MHz region at 15dBm is similar to injecting the 29.5MHz sideband (at the same power level with very similar input impedance.) Fingers crossed we don’t blow anything up first week on the job.
The technique is based on detection of the beating between the resonant carrier and a resonant higher order mode.
This means that the beat signal is cancelled out if the transmitted beam is integrated over the entire beam.
Thus, you may want to introduce intentional clipping (or cutting a half of the beam with a razor blade).
Ref: LIGO DCC G080467: Precise Measurements on Longitudinal and Transverse Mode Spacings of an Optical Cavity using an Auxiliary Laser
I am quite curious on the measurement as I am going to do the same measurement for the aLIGO OMC.
I am interested in seeing the statistical evaluation on the precision of the measurement.
[Jenne, Suresh, with support from Jamie and Koji]
MC spots measured, MC1, MC3 no change.
No clipping going through Faraday.
Beam hitting to the right of center of PZT1. It was translated sideways so we are now hitting it on the center. Knobs adjusted so we hit center of MMT1.
Beam totally obscured by Faraday on the way to MMT2. MMT2 moved north, so that we clear the Faraday by more than a beam diameter. MMT1 knobs adjusted to hit center of MMT2.
MMT2 knobs adjusted to hit center of PZT2.
PZT2 didn't have enough range with knobs, so we loosened it, pointed then adjusted with knobs so we're hitting center of PRM.
We need to check spot centering on PRM with camera tomorrow.
Suresh checked that we're not clipped by IP ANG/POS pickoff mirrors, but we haven't done any alignment of IP ANG/POS.
Tomorrow: Open ITMX door. Check with Watek that we're hitting center of PRM. Then look to see if we're hitting center of PR2. Then, continue through the chain of optics.
I think we should NOT do any adjustment of IP ANG/POS now. We should in fact try to recover them when doing the PRM spot centering
The motivation for removing the ITMX door was so that the scatter measurement team could check alignment of the new viewing mirror next to ETMX. After discussion today we decided that everything can be done at the X end. They can inject a probe beam into the ETMX chamber, bounce it off of ITMX and align the viewing mirror with the reflection. So we'll leave ITMX door on for now.
We should, however, inspect the situation ITMY and make sure we have good clearance in the Y arm part of the Michaelson. Koji previously expressed suspicion that we might have clipping on the southern edge of the POY steering mirror, so we need to check that out.
Koji and I discussed the situation for getting camera face views of BS and PRM. Koji said the original idea was to see if we could install something at the south-east view port of ITMX chamber. Steve also suggested utilizing the "ceiling" camera mounted on the top of the IOO chamber.
End X tasks:
1,PRM spot can be viewed directly from the window south-east of ITMX chamber. I can easy set up the mobile- Watek for this reason or you can just use an IR viewer.
Remember, we have 2 SOS centering targets ready to use , that Rana was suggesting.
2, PR2 spot centering can be viewed directly through window north-west of ITMX.
3, We should put back the BS view pick-up mirror for the vertical camera on the BS chamber and adjust its upper pick-up.
4, The BS centering can be viewed with the mobile-Watek placed inside the BS chamber immediately.
Earthquake m4.1 test for ETMX and moves ITMX. ITMX-LR sensor 0.3V
We have done some work at ETMX today. We installed the baffle and placed two mirrors on the table.
The baffle position/orientation still needs to be checked more thoroughly to make sure that the beam will pass through the center of the baffle hole.
One of the two mirrors will stay on the table as pickoff. The other is only temporarily installed for alignment purposes. Later today we will shoot a laser into the chamber that will reflect off one of these mirrors towards the center of ITMX, then go back to the pickoff mirror next to ETMX and hopefully make it through the viewport.
To place the pickoff mirror, we had to move the "cable rack" next to ETMX a few inches towards the back of the table.
I must say that I am not at all happy with the baffle situation. It is currently completely blocking our camera view of the ETMX face. Here's a video capture of the ETMX face camera:
The circle is the baffle hole, through which we can see just the bottom edge of the test mass. I don't think whatever benefit the baffle gives out weights the benefit of being able to see the spot on the mirror.
This afternoon we will try to adjust the baffle, and maybe the camera view mirror, to see if we can get a better shot of the center of the TM. If we can see the beam spot through the hole we can probably live with it. If not, I think we should remove the baffle.
The baffle has been moved away from ETMX towards the edge of the table (in fact, it is a little beyond the edge). It is also rotated so that its long edge is horizontal. In this way it was possible to center the baffle hole with respect to the optical axis, but also make it possible that the camera looks over the baffle.
We have tried to get an alignment beam from view port -> ETMX pick-off ->ITMX-> back to EX. This work was pretty much unsuccessful though. We could see the green laser scattering around ITMX, but there was no good way to know when the beam hit ITMX. So tomorrow we will find a better way to check where the beam is hitting at ITMX and finish the alignment of the scattering pick-off mirror.
Today tried to take our first cavity scan. We unplugged the 55MHz sideband input from the RF combiner on the PSL table, and connected a network analyser instead. Using the network analyzer we injected a 12dBm signal (swept from 32MHz to 45MHz) through the RF combiner into the EOM to create our swept sidebands. We measured the MC cavity response by looking at the signal comming out of the RF photodiode on the MC2 table. I replaced the BNC cable connected to the RF PD with a longer BNC cable that could reach our network analyzer next to the PSL table. Riju will post a diagram of our setup.
We didn't see the expected carrier resonances when we performed a cavity scan. The light incident on the RF PD is around 0.7micro Watts and we are still thinking about whether this is strong enough to see our signal above the noise. We also want to work out what the strength of our swept sidebands is. We will attempt to do a 'real' cavity scan tomorrow.
I tightened as many of the dog clamps on the bottom of the BS, ITMX and ITMY chambers as I could find. I used a torque wrench at 45 ft-lbs. Some of the bolts of the dogs were too long, and I couldn't find an extender thing to accommodate the bolt so I could reach the nut. None of the bolts moved that I was able to reach.
Steve, we're not doing final final alignment today (we will do it tomorrow), so please go around and double-check my work by checking all of the dogs first thing in the morning. Thanks.
We placed the Watek camera on the SE viewport of the ITMX chamber, and focused it on the face of PRM. We are not able to see any scattered light transmitted through the PRM, so this camera was an ineffective way to try to check spot centering on the PRM. Jamie placed one of the new targets on the PRM cage - see his elog for details.
To get more use of the camera, we need to mount it on something, at the 5.5 inch beam height, and then cover that something with clean foil so we can place the camera on the table, in the beamline in various places. We also need to carefully wrap the cables in foil so the don't dirty anything inside.
Jamie and Koji pointed out that we need to be doing the in-vac alignment with the PZTs at the center of their ranges. Also, we confirmed that they were set to "closed loop off", so the strain gauges were not supplying any feedback.
PZT1 was set to 0 for both pitch and yaw, since it has a very limited range of motion right now, so 0 is close enough.
For PZT2, Koji and I moved the slider in pitch and yaw, and watched the LCD output monitor on the PZT driver at the bottom of 1Y3. We saw the value on the LCD change between slider values +4 to -6 for PZT2 yaw, so it is set to -1 as the center. We saw the value on the LCD change between slider values -4 to +5 for PZT2 pitch, so it is set to +0.5 as the center. Beyond these slider values (the sliders all go -10 to +10), the LCD value didn't change, either at 0, or at the maximum.
Since PZT1 doesn't really move, this shouldn't affect any of the alignment work that Suresh and I did last night, although we should quickly confirm tomorrow. On the agenda for tomorrow is adjusting PZT2 such that we hit the center of PR2 (and hopefully that will also put us through the center of the PRM target, if the alignment was done well enough last time), so it's okay that we have only now set it to the center of its range.
We installed beam targets on PRM and BS suspension cages.
On both suspensions one of the screw holes for the target actually houses the set screw for the side OSEM. This means that the screw on one side of the target only goes in partial way.
The target installed on BS is wrong! It has a center hole, instead of two 45 deg holes. I forgot to remove it, but it will obvious it's wrong to the next person who tries to use it. I believe we're supposed to have a correct target for BS, Steve?
The earthquake stop screws on PRM were too short and were preventing installation of the PRM target. Therefore, in order to install the target on PRM I had to replace the earthquake stops with ones Jenne and I found in the bake lab clean room that were longer, but have little springs instead of viton inserts at the ends. This is ok for now, but
We checked the beam through PRM and it's a little high to the right (as viewed from behind). Tomorrow we're going to open ITMX chamber so that we can get a closer look at the spot on PR2.
The two eye target for the BS is in the clean tool box. It actually has irises.
The alignment of the pick-off mirror near ETMX is done. Everything turned out to be easy once we realized that there is no sense getting the alignment laser (going through viewport to pick-off to ITMX) back to ETMX. It is only necessary to hit ITMX somehow, since this makes sure that there is one scattered beam that will make it from ITMX to pick-off through viewport.
After the auxiliary optic (that we never used in the end) was removed again, we levelled the optical table.
So in the current setup, we can have small-angle scattering measurements on ITMX and large-angle scattering measurements on ETMX.
Almost all chamber dog clamps on the floor checked. There are a few exception where it is impossible to to get to the nut.
Only the OOC nuts turned little bit. So our elastomer discs are holding up well. This means that the chamber anchoring to the floor is good.
Koji, Riju, Elli
This morning Koji discovered that the 55MHz input into the RF combiner that I disconnected yesterday wasn't terminated properly, so it was reflecting power back into the amplifier in the signal generation unit. We turned off the signal generation unit and checked that the amplifier was still working properly- it was. A 50 ohm terminator was attached to the end of the 55MHz cable so that it is now terminated properly.
When we tried to turn the signal generator box back on we discovered the switch is broken (the box will only stay on while you hold down the on switch) and will need to be replaced. In order to create the 29.5MHz sidebands to lock the mode cleaner, we bypassed the signal generation unit which won't stay on (unplugging '29.5 MHZ out' cable from the frequency generation unit), and instead sent a 0.39V 29.5MHz signal from a function generatior into 'RF input' on the 'RF AM Stabiliser' board.
We also increased the power coming exiting the PSL table and going into the cavity from 11 microwatts to 20 microwatts by adjusting the polariser at the end of the table slightly. The power has been set to 20 microwatts using the polariser a few days ago but had drifted down since then.
Steve and Eric
Placed pick up mirror for BS face and PRM back. I will ask Jamie to clamp it.
There will be an other camera set up to view the face of PRM
It is essential we take a look at the ringdown data for all measurements made so far to figure out what must be done to track the source of these notorious ripples. I've attached the plot for the same showing the decay time to be the same in all cases. About the ripples; it seems unlikely to both Jan and me that the ripples are some electronic noise because the ripples do not follow any common pattern or time constant. We have discussed with Koji about monitoring the frequency shift, the input power to the MC and also try other methods of shutting down the pump to track their source as the next steps.
The SOS centering target is 1.9 mm lower than it should be!
The hole is 10mm for the ~6 mm beam
The power switch of the frequency source was mechanically broken. I replace it with the spare in Kiwamu's treasure box.
I think this replaced new one also had the same problem before, we basically have to find an alternative switch.
The problem is too much friction between the metal housing and the plastic button. I have lubricated the button with
I have checked that the 55MHz output still have the output of 25dBm after a 5m BNC cable. (nominal: 27dBm)
I could not test it with the MC as the chambers have already been closed with the light doors.
Elog re: Friday's work
Adjusted PZT2 so we're hitting the center of PR2.
Noticed that the beam centering target is too low by a few mm, since the OSEM set screw holes that it mounts to are lower than the center line of the optic. This meant that while we were hitting the center of PR2, the beam was half clipped by PRM's centering target. We removed the target to confirm that the beam is really centered on PR2.
Checked the beam on PR3 - it looked fine. There had been concern last week that PR2 was severely pitched forward, but this turns out to be an effect of the PRM centering target being too low - shoot the beam downward to go through the hole, beam continues downward to hit the bottom of PR2, so beam is falling of the bottom of PR3. But when we actually centered the beam on PR2, things looked fine on PR3.
Checked that the beam approximately goes through the beam splitter. Again, the targets are too low, and these 45 deg targets' holes are smaller than the 0 deg targets, so we don't see any beam going through the target, since the beam is hitting the target higher than the hole. The beam looked left/right like it was pretty close to the hole, but it was hard to tell since the angle is bad, and I'm not infinitely tall. We should check again to make sure that the beam is going through properly, and we're not clipping anywhere. I'll need help from a height-advantaged person for this.
Checked that the beam is hitting the center of the ITMY, as best we can see by using an IR card at the back of the optic. We didn't try reaching around to put a target on the front side.
We were debating whether it would be worth it to open ETMY this week, to check that the beam transmitted through the BS hits the center of ETMY.
We also took a quick look around the AS optics, but since that depends on BS/ITMX alignment, we weren't sure how to proceed. We need a plan for this part. All suspended optics were restored to their last good alignment, but we haven't tried locking MICH or anything to confirm that the alignment.
To do list: Check no clipping on ITMY table of beam between BS and ITMY, clipping on POY optics. Also, oplev is clipping on cable holder thing on the table - this needs to be moved. .....other?
We need a plan for the rest of the week. I want to be closing the heavy doors on Friday at the latest. Please add to / comment on this list!
* Lock MICH to get BS, ITMs aligned well
* Check if beam is hitting center of ITMs.
* Check for clipping around BS
- Use Watek in-vac to look at beam at all 4 BS ports - make sure no clipping going into BS, after BS in the michelson, or the AS port
* Try to get arms to flash??
* Prepare glass beam dumps??
* IPPOS / IPANG - make sure beam gets out of chambers (this may require opening ETMY)
* Jan take photos of ETMX scattering setup
* Manasa take in-vac photos of all tables, for table layouts
* Jan / Manasa viewport transmission
* Install glass beam dumps?
* If ETMY open, install glass baffle
* Check table levelling one last time on all tables.
* Close all heavy doors. (Access connector, ITMX, ITMY, BS, ETMX, ETMY? )
* Drag wipe test masses
* Start at ~10am?
Mon (if not Fri)
* Start pumping
* Jan/Manasa - Measure transmission of viewport at ETMX
I adjusted the PMC alignment this morning, brought the transmission up to 0.83V.
After the lunch meeting, we found the the MC transmission was higher than recently seen. Turned out the HWP had drifted, causing 30mW to be input to the MC. I adjusted it back down to 20mW.
Opened ETMY, beam was high and to the right (if you look at the face of ETMY). Tried walking beam up, since just doing PZT2 caused clipping at the BS before we got to the correct spot on ETMY. Moved PZT1, then PZT2, to translate beam, but we couldn't get far enough without starting to fall off of PZT2. Put PZT1 approx. back where it was. Jamie tapped on the top of PR3 (tip tilt just before BS), and then did some compensation with PZT2 to get the beam through the BS target to the center of ETMY.
The beam is very dim at ETMY. We ended up holding the big IR card with holes such that one of the holes was near the center of the optic, in front of the cage. Then one person turned off all the room lights so we could see the beam, another person moved PZT2 and PR3, then lights person turned on and off the lights so we could compare beam position with hole position. A total pain, but it ended up working better than just trying to follow the beam with a card.
We clearly need a better plan for adjusting the tip tilts in pitch, because utilizing their hysteresis is ridiculous. Koji and Steve are thinking up a set of options, but so far it seems as though all of those options should wait for our next "big" vent. So for now, we have just done alignment by poking the tip tilt.
Tomorrow, we want to open up the MC doors, open up ETMY, and look to see where the beam is on the optic. I am concerned that the hysteresis will relax over a long ( >1hour ) time scale, and we'll loose our pointing. After that, we should touch the table enough to trip the BS, PRM optics, since Koji is concerned that perhaps the tip tilt will move in an earthquake. Jamie mentioned that he had to poke the tip tilt a pretty reasonable amount to get it to change a noticeable amount at ETMY, so we suspect that an earthquake won't be a problem, but we will check anyway.
After doing all of that, we adjusted IPANG so that the beam gets out of the vacuum envelope. The beam must squeeze between the wall of the black beam tube and a lens for the oplev, so there is a very, very limited amount of space. The eventual new tables will be very helpful for alleviating this, but for now we must live with it. Even though it is pretty squishy right at the edge of the table, with the new layout we should think about giving IPANG a little more space. Basically, if there is any Yaw motion, the beam going to the QPD will be clipped, and we may get confusing info. We moved some of the IPANG optics that are on the end transmission table so the beam is centered on the optics while it just makes it through the space between the wall and the lens. The spot was centered on the IPANG QPD.
We still need to check on IPPOS, but it is always easier than IPANG.
We discovered that the 45deg SOS beam targets are awesome, especially the ones with the irises. The plain hole ones have very small holes relative to our beam size, so they are much more useful for the MC optics (which they were designed for). The 45deg targets were made such that the target holes do not line up with the mounting holes. This is good, since the mounting holes are lower than the center of the optic. I don't think ericQ and I realized that on Friday, so it's probable that we had installed the target upside-down. We still need to remake the 0deg targets for the next vent.
Jamie dogged down the new 'bathroom mirror' that lets us see BS and PRM on the same camera view. He also adjusted some of the masses on the BS table to relevel the table. We need to (at some point) rename the AS_SPARE camera to something like BS_PRM, since we plugged the new camera into the AS_SPARE port on the videoswitch.
tl;dr: Input beam adjusted so we're hitting center of ETMY. IPANG coming out of vacuum, QPD centered. Need better tip tilt in-situ adjustment capability.
Since the EOM's signal combiner (splitter backwards) is frequency-independent, Koji and Jamie (in the proper turn off, turn on order) put the 55MHz signal back to the EOM, and put the MC mode scan input to the 11MHz port. This way we can lock the Michelson tomorrow, and we don't have to keep switching cables around when Riju wants to take some scans.
* Hit center of ETMY, using input optics, PR3.
* Get IPANG out of vac, center QPD.
* AM: Riju do MC mode scans
* Starting right after 40m meeting, if not before: Lock MICH to get BS, ITMs aligned well
* Check if beam is hitting center of ITMX.
- Use Watek to look at beam at all 4 BS ports - make sure no clipping going into BS, after BS in the michelson, or the AS port
- Use some old in-vac mirrors to direct beam out the BS door. Cameras are waiting near BS chamber.
* IPPOS - make sure beam gets out of chamber
* Install glass baffle at ETMY. Jan maybe install baffle at one of ITMs.
I'm very unhappy with the tip-tilts right now. The amount of hysteresis is ridiculous. I have no confidence that they will stay pointing wherever we point them. It's true I poked the top more than it would normally move, but I don't actually believe it wouldn't move in an earthquake. Given how much hysteresis we're seeing, I expect it will just drift on it's own and we'll loose good pointing again.
And as a reminder, IPPOS/ANG don't help us here before the tip-tilts are in the PRC after the IP pointing sensors.
I think we need to look seriously at possible solutions to eliminate or at least reduce the hysteresis, by either adding weight, or thinner wire, or something.
We really need something better to replace the access connector when we're at air. This tin foil tunnel crap is dumb. We can't do any locking in the evening after we've put on the light doors. We need something that we can put in place of the access connector that allows us access to the OMC and IOO tables, while still allowing IMC locking, and can be left in place at night.
It is in the shop. It will be ready for the next vent. Koji's dream comes through.
Can we see the full design? If we can't lock the mode cleaner with this thing on then it's really of no use. We want it to be equivalent to the light doors, but allow us to keep the mode cleaner locked. That's the most important aspect.
It also needs to be wide enough that the MMT beam can go through, so that we can not only lock the MC, but also work on the rest of the IFO.
[EricQ, Jenne, brains of other people]
Checked at ETMY that the pointing hadn't changed a whole lot. Jamie and Koji pointed out that we were half falling off of the IPANG QPD. Adjusted PZT2 sliders so that we were again centered on IPANG's QPD. Before we close up, we'll want to put the sliders back to their nominal positions, and use the knobs to hit IPANG, but this is equivalent and fine for now. The tip tilts don't seem to have moved much overnight, since the beam drift on both IPANG and ETMY was fixed simultaneously with PZT2 (recall, IPANG picked off before tip tilts exist in the beam path). This left us hitting the center of ETMY. We moved ETMY sliders to make the reflected beam hit the center of ITMY (same spot position as transmitted beam from BS). Then moved ITMY to get prompt reflection to hit same spot on ETMY as original primary beam from BS. Checked at ITMY that we didn't need to move ETMY anymore. (Actually, I forget how many iterations we did, but in the end, all of the reflections that we can find are co-located on the test masses.)
Align BS so we're hitting the center of ETMX
Tap / readjust ITMX OSEM which is at 0.3 to get it back to the center of its range
Align ITMX to lock MICH
Check no clipping on POX / POY optics, no clipping around BS
Check PRM, SRM alignment (what exactly do we want to do here? Try to lock PRMI / SRMI?)
Get IPPOS out of vac
Fix clipped ITMY / SRM oplev
Install 'black' glass beam dumps - forward-going POP beam, 2 places in BS chamber (check old elog from Jenne/Yuta for the places).
Get green spots co-located with IR spots on ETMs, ITMs, check path of leakage through the arms, make sure both greens get out to PSL table
The Y-End green beam was roughly aligned by the steering mirrors for the green beam.
I couldn't understand the Y-End green setup as the PD was turned off and the sign of the servo was flipped. Once they are fixed, I could lock the cavity with the green beams.
After a long alignment session, TEM00 was found. The alignment of the green beam has not been optimized.
Looking at the spot position at ETMY OSEM holders (not by the ccd image), it seems that the cavity mode is not at the center of the mirrors.