[Steve / Kiwamu]
Since the oplevs were the ones we haven't carefully tested, so the oplevs need to be checked.
This checking is also a part of the suspension optimizations (see the minutes of the last 40m meeting).
In this work Steve will check two things for all the oplevs :
1. Noise level including the dark noise, electrical noise and ADC noise to just make sure that the noise are blow the signal levels below ~ 30Hz.
2. The spectra of the signals to make sure there are no funny oscillations and unexpected structures
To check the things listed above, we take two kinds of oplves' spectra :
1. "dark noise" when the He-Ne beam is blocked.
2. "signals" when the optics are damped by only OSEMs
We did these checks on the BS oplev today (see the last entry).
All of them are fine, for example the dark noise (including electrical noise and ADC noise) are below the signal levels.
And no oscillation peak was found. Steve will go through all of the oplevs in this way.
Healthy BS oplev
[Jenne / Kiwamu]
Last night we modified the locking scripts, that were called from C1IFO_CONFIGURE.adl, to adapt them to the new "PRCL" and "SRCL" convention.
So far they work fine and quitted dumping some error messages about inexistence of these channel names.
P.S. The locking scripts have been summarized on the 40m wiki
- Now the power and signal recycling cavity lengths are named "PRCL" and "SRCL" in stead of three letter names without "L".
We should change the locking script to accomodate these changes.
Summary of the week ending July 10th. Number of elog entries = 21
+ The cutoff frequency of the high pass filters for the damping were set to 30Hz.
+ Turned off all the BounceRoll filters.
+ The BS oplev was checked and seemed healthy.
+ All the measred data of the LSC whitening filters were fit.
+ All the zpk parameters are recorded on the wiki.
+ The setup completed.
+ The freqeucy-lock of the ABSL laser was achieved with UGF of ~ 40kHz.
+ The temperature of the ABSL laser was adjusted to be 47.25 deg
+ The I-P curve of the ETMY laser was measred.
+ The current set point is 1.8 [A], which used to be 1.5 [A], corresponding to the output of power of 197 [mW] and 390 [mW] respectively.
Summary of the week ending July 17th. Number of elog entries = 20
Summary of the week ending July 24th. Number of elog entries = 45
* Check of LSC WF switching
-> some were switching, but the majority were not.
* Ran activateDQ.py for seeting some DQ channels of Oplevs
* Turned ON all the offset buttons on the OL1, etc.
* Rebuilt and restarted c1msc, c1sus, c1scx and c1scy as an update.
* ETMY's shadow sensors look bad. Unknown noise below 3 Hz, which is higher than the usual floor by factor of 10.
* The frequency lock was down.
* The laser power into the RFPD had been too big, so it was reduced
* Seismometers were connected to the AA-board on 1X6
* Most of the channels were acquired to the ADC, but some were not.
- Mode Cleaner
* Gain of quadrants were checked.
* Due to the SUS model update, the MC locking trigger hasn't worked correctly. This was fixed by changing ioo.db file
* Virtual box was installed on Rossa. Altium is now available on Rossa.
[Suresh / Kiwamu]
It looks like something wrong with Makefile.
We ran make c1ioo -- this was successful every time. However make install-c1ioo doesn't run.
The below is the error messages we got.
make: Entering directory `/opt/rtcds/caltech/c1/core/branches/branch-2.1'
Please make c1ioo first
Then we looked at Makefile and tried to find what was wrong. Then found the sentence (in 36th line from the top) saying
if test $(site)no = no; then echo Please make $$system first; exit 1; fi;\
We thought the lack of the site-name specification caused the error.
So then we tried the compile it again with the site name specified by typing
in the terminal window.
It went ahead a little bit further, but it still doesn't run all through the Make commands.
Through some locking exercise I found that several things are degrading.
Remember the interferometer is like a cat, so we have to feed and take care of her everyday. (Otherwise the cat will be dead !)
Locking of the Arms :
Locking of PRM :
The vent will start from 1 st of August ! !
The vent will start from 1 st of August !
++++ Task List for the vent preparation ++++
+ Preparation of beam dumps (Jamie / Steve)
+ Health check of shadow sensor and measurement of the cross-coupling (Steve)
+ Measurement of the arm Lengths and estimation of the required precision (Kiwamu)
+ Alignment of the Y green beam (Suresh)
+ Alignment of the incident beam axis (Jenne)
+ Measurement of the MC spot positions (Suresh)
+ Loss measurement of the arm cavities (Kiwamu / volunteers)
++++ Task List for the post-vent activity ++++
+ 3f RFPDs (Koji / Rana)
+ EOM resonant circuit (Kiwamu)
+ Sophistication of the LSC model (Yoichi)
+ DRMI commissioning (Keiko / Anamaria)
A new offset-zeroing script has been developed and it is ready to run.
The motivation is to replace the old zeroing script called offset by a better one because this old script somehow failed to revert the gain settings on a given filter bank.
The new script, named offset2, does the same job, but uses tdsavg instead of using ezcaservo. So it doesn't screw up the gain settings.
Additionally the structure of the script is much simpler than the old offset script, and fewer ezca-functions.
I will modify some scripts which use the old offset script so that all the offset-zeroing is done by offset2.
Useful scripts are listed on the 40m wiki
[Nicole / Jamie / Rana / Kiwamu]
The X arm and Y arm have been locked.
The settings for the locking were stored on the usual IFO_CONFIGURE scripts, so anybody can lock the arms.
In addition to that Nicole, Jamie and Rana re-centered the beam spot on the ETMY_TRANS camera and the TRY PD.
The next step is to activate the C1ASS servo and align the both arms and beam axis.
Xarm locking notes:
* Changed TRX gain from -1 to -0.02. Without this 50x reduction the arm power was not normalized.
* Had to fix trigger matrix to use TRX for XARM and TRY for YARM. Before it was crazy and senseless.
* Lots of PZT alignment. It was off by lots.
* Yarm trans beam was clipping on the steering mirrors. Re-aligned. Needs to be iterated again. Be careful when bumping around the ETMY table.
* YARM gain was set to -2 instead of -0.2. Because the gain was too high the alignment didn't work right.
ALWAYS HAVE an OPEN DATAVIEWER with the standard ARM channels going when doing ANY INTERFEROMETER WORK.
THIS IS THE LAW.
Last night I aligned the incident beam axis and the Yarm by touching the PZT mirrors and the suspensions.
I didn't estimate how good they were aligned, but I guess the Y arm is now ready for the Y green light.
Next : Y green alignment and the MC spots measurement / alignment.
++ Motivation ++
Prior to the coming vent we want to have the Y arm, incident beam axis and Y green light aligned so that we can align some necessary optics in the chamber.
Also alignment of the incident beam will allow us to re-position the incident beam alignment monitor (i.e. IPPOS and IPANG).
Our plan was to first align the Y arm using the ASS system and then align the Y green light to the Y arm.
++ what I failed ++
First I was trying to measure the spot positions on the MC mirrors to make me sure the beam axis has/hasn't changed.
Also I was going to align the MC suspensions to have nice spot position on each suspension using the MCASS system
because this will help us checking the beam clearance in the Faraday and perhaps re-positioning of the Faraday during the coming vent.
But essentially I failed and eventually gave up because MCASS didn't work. It seems that MCASS needs some modifications in the scripts.
Then, to make me feel better I moved on to the Y arm and beam axis alignment.
++ what I did ++
I tried using C1ASS to align the incident beam and suspensions on the Y arm, but it didn't work.
However the drive signals from ASS and its demodulated signals looked fine. Only the feedback did not work correctly.
Every time I enabled the feedback paths, the arm just lost the lock. Something is wrong in the feedback paths.
Then I started to align the cavity by my hands while looking at the demodulated signal from each LOCKIN module.
I aligned the things until each demodulated signal fluctuates around zero.
At the end the beam spots on the ETMY and ITMY camera looked well-aligned and the transmitted light became larger by a factor of 2ish.
The servos of C1ASS for the Y arm and the beam axis alignments were fixed.
Now we can correctly run the Y arm ASS from the C1IFO_CONFIGURE window as usual.
The sign of some control gains had been flipped for some reasons, so I changed them to the correct signs.
Next : Health-check for the X arm ASS, the loss measurements.
Since we will measure (and hopefully adjust) the spot positions on the MC suspensions prior to the vent, MCASS is necessary for it.
Here is the MCASS status so far:
+ Valera worked on MCASS on the last February, and basically no progress after he left.
+ The MCASS model had been completed in C1IOO.mdl.
+ He made some useful scripts, including mcassup, mcassOn/Off, senseMCdecenter, senseMCmirrro and senseMCdofs.
Summary of those scripts can be found in his entry #4355.
+ We haven't closed the MCASS loops.
+ The control filters are still blank.
+ We haven't put any elements on the input and output matrices.
+ Some parameters for the dithering oscillators and demodulation systems were properly set.
So we can get the demodulated signals by simply running mcassUp and mcassOn. (This essentially corresponds to the A2L measurement.)
+ The PIT motions are driven at 10, 11 and 12 Hz for MC1, 2 and 3 respectively. For YAW, the frequencies were chosen to be 11.5, 12.5 and 13.5 Hz.
+ Some medm windows were prepared but not as refined as that of ASS.
+ Valera performed a measurement of the spot positions by using MCASS. The results are summarized in #4660.
+ We made an estimation about the beam clearance on the Faraday based on the measured spot positions (#4674)
So, it seems we should be able to at least measure the spot positions soon by using his scripts.
The X arm ASS was also fixed. So both X and Y arm ASS are now back to normal.
Now we can align the arms any time from the buttons on the C1IFO_CONFIGURE window.
The reason why the servo didn't work was that the sign of some control gains had been flipped.
This was exactly the same situation as that in the Y arm ASS (#5067).
I modified the script armloss so that the channel names in the script are properly adopted to the new CDS.
Additionally I disabled the ETMX(Y)_tickle command in the script.
The tickle command puts some offsets on the LSC signal to let the arms pass through a fringe until it gets locked, but apparently we don't need it because the arms are loud enough.
A brief check showed that the script ran fine.
I will measure the loss on the X and Y arm cavity tomorrow.
I think you made a simple mistake in your diagram -- the mixer must be replaced by a summer circuit. Otherwise you cannot do the PDH lock.
Required arm length = 37.7974 +/- 0.02 [m]
This is a preliminary result of the estimation of the Arm length tolerance.
I did the measurement of the arm loss on both X and Y arm by running the armLoss script.
The results will be posted later.
Status update for the vent preparation:
The punchline is : We can not open the chamber on Monday !
##### Task List for the vent preparation #####
(not yet) Low power MC
(not yet) Measurement of the arm lengths
(not yet) Alignment of the Y green beam (#5066)
(not yet) Measurement of the MC spot positions
(80% done) Estimation of the tolerance of the arm length (#5076)
(done) Preparation of beam dumps (#5047)
(done) Health check of shadow sensors and the OSEM damping gain adjustment (#5061)
(done) Alignment of the incident beam axis (#5073)
(done) Loss measurement of the arm cavities (#5077)
I made some attempts to measure the current length of the arm cavities by using the mass-kicking technique.
However unfortunately I am running out my energy to complete the measurement,
so I will finish the measurement at some time today.
I still have to set an appropriate kick amplitude. Right now I am injecting AWG into ETMY_LSC_EXC at 0.2 Hz with amplutde of 400 cnts.
I guess it needs a little bit more amplitude to get more psuedo-constant velocity.
Volunteers are always welcome !
The procedure was well-described in entry #555 by Dr.Stochino.
Here is just an example of the time series that I took today showing how the time series looks like.
The beam axis of the Y green light has been aligned.
Now I can see TEM00 mode is flashing on the ETMY camera.
-- (What I will do tonight)
The next step is to refine some electronics in the PDH loops to get the green light locked to the Y arm cavity.
If the beam isn't locked, I guess the in-vac-work will be so difficult because of the low intensity of the green light.
According to a brief check on the circuits, a low pass filter after the demodulation mixer is in a sad situation.
It doesn't pass any signals and in fact it behaves more like an absorber.
On the other hand, the modulation system looks fine to me because I was able to see the 270 kHz sideband converted into AM due to the fringing.
Summary of the week ending July 31st. Number of elog entries = 53
+ ETMY-LR sensor looked strange. Something wrong.
+ Responses from the DC alignment bias to the shadow sensors and the oplevs were checked.
--> ETMY shows the response with the opposite sign. Wired.
+ ETMY shadow sensors were examined in terms of the spectra.
--> WF, AA and ADC noise looks reasonably low and not high enough to explain the low frequency noise.
+ Adjusted all the OSEM gains
+ MICH noise budget is ongoing. WF filter needs to be greater than 21 dB to have dark noise of the PD greater than ADC noise
+ The arms became lockable
+ modified and re-ran activateDQ.py.
+ c1iscex crashed for unknown reasons and we physically rebooted it.
- ALS (Fiber experiments)
+ PMC trans is sampled for the fiber beat-note measurement on the PSL table.
+ The beat-note signal between PSL and X end laser were obtained.
+ Some optics in the ETMY table were rearragend to have the Y green light aligned.
- ACS / ASS
+ incident beam axis has changed a lot.
+ X arm and Y arm ASS were reactivated.
---> The sign of some of the control gains had been wrong.
+ The incident beam axis and X/Y arm were re-aligned
+ Some medm screens fixed.
+ Adjustment of the demodulation phase on each quadrant on WFS1 and WFS2 are done.
+ The sensing matrix (from optics to WFS sensors) were measured.
+ c1pem was modified
+ plugged a seismometers to ADC through an AA board.
--> channels are coming to the digital land
- Preparation for the invac work
+ 7 pieces of beam traps are available
+ Tolerance of the arm length is estimated to be +/- 2 cm.
+ ABSL is injected into the reference cavity. some flashing happened but no locking.
+ eddited the psl.db file to set EGUF and EGUL
+ turned RefCav heater and servo back on
I succeeded in locking the green light to the Y arm cavity, but it wasn't so robust. Something is unhealthy in the electronics.
I am leaving the Y green system as it is because I already can see a plenty of the green light flashing in the BS chamber.
So just a flashing of the green light is good enough for the in-vac-work.
The next step is to refine some electronics in the PDH loops to get the green light locked to the Y arm cavity.
The vent will take place on Wednesday.
Plan for Tuesday :
(Morning) Preparation of necessary items for the low power MC (Steve / Jamie)
(Daytime) Measurement of the MC spot positions (Suresh)
(Daytime) Arm length measurement (Jenne)
(Nighttime) Locking of the low power MC (Kiwamu / Volunteers)
Plan for Wednesday :
(Early morning) Final checks on the beam axis, all alignments and green light (Steve / Kiwamu / Volunteers )
(Morning) Start the vent (Steve)
(daytime-nighttime) Taking care of the Air/Nitrogen cylinders (Everybody !!)
Status of the vent preparation :
(ongoing) Measurement of the arm lengths
(ongoing) Measurement of the MC spot positions
(done) Alignment of the Y green beam (#5084)
I have updated the 40m public calender.
Main change :
+ The vent starts from 3rd of August
+ Keiko and Anamaria (LSU) come from 13th of August
The measurement of the spot positions on the MC mirrors are DONE.
Surprisingly the spot positions are not so different from the ones measured on May.
We used Valera's script senseMCdecenter to estimate the spot positions ( see his entry).
It returns so many EPICS error messages and sometime some measured values were missing. So we had to throw away some of the measurements.
Anyways we gave the resultant ASCII file to Valera's matlab file sensmcass.m to get the actual amount of off-centering in milli-meter.
The attached file is the resultant plot from his matlab code.
An attenuator, consisting of two HWPs and a PBS, has been installed on the PSL table for the MC low power state.
Those items allow us to reduce the amount of the incident power going into the MC.
We haven't decreased the power yet because we still have to measure the arm lengths.
After we finish the measurement we will go to the low power state.
We have adjusted the polarization after the last HWP using another PBS. Now it is S-polarizing beam.
After the installation of the attenuator the beam axis has changed although we were immediately able to lock the MC with TEM00 mode.
I touched two steering mirrors on the PSL table to get the transmitted power of MC higher. At the moment the transmitted power in MC_TRANS is at about 30000 cnts.
The attached picture is the setup of the attenuator on the PSL table.
The incident beam power going into MC was decreased down to 20 mW by rotating the HWP that we set yesterday.
A 10% beam splitter which was sitting before MCREFL_PD was replaced by a perfect reflector so that all the power goes into the PD.
And we confirmed that MC can be still locked by increasing C1IOO-MC_REFL_GAIN. Some modifications in the Autolocker script need to be done later.
Also we opened the aperture of the MC2F camera to clearly see the low power beam spot.
WE ARE READY FOR THE VENT !!
Power after the EOM = 1.27 W
Power after the HWPs and PBS = 20.2 mW
Power on MCREFL = 20 mW (MC unlocked)
MCREFL_DC = 0.66 V (with MC locked)
After we finish the measurement we will go to the low power state.
An important rule during the in-vac work :
Do not change the incident axis of the X and Y green beams.
Because of the air flows and unusual pressure in the chambers, the DC alignment of the suspensions become less reliable in terms of the beam pointing reference.
The green beams will be considered as references during the vent.
The vacuum system is coming up to atm. The vent was started with slow N2 flow.
Tomorrow's main goal is : let the both X and Y green light come out from the chambers.
Plan of the in-vac work for tomorrow :
- Removal of the access connector and the BS north door, starting from 9:00 AM. (requires 6 people)
- If necessary, align ITMs and ETMs to get the green light nicely flashing / locked.
- Take pictures of the BS and IOO table before installing / repositioning some optics.
- Repositioning of the green periscope in the BS chamber to let the Y green light go through it.
- Steer some green mirrors on the IOO table to let the Y green light come out from the chamber.
- Steer some green mirrors on the BS table to let the X green light come out from the chamber.
- Put some beam traps on the BS table
- Leveling of the BS table. (Do we need to level the IOO table ? it will change the spot positions on the MC mirrors somewhat)
- Take pictures again.
- Extra jobs : if we still have some more times, lock MC and check the beam clearance at the Faraday. Also check some possible beam clippings for the IR beam.
- Close the chamber with the light doors.
- Softball game at 6:30 PM.
[Jamie, Jenne, Suresh, Steve, Koji, Kiwamu]
We got two green beams coming out from the chambers !
Summary of today's invac work :
- removed the access connector and the BS north door
- realigned the X and Y arm to the green beams.
- installed a HWP on the ETMY table to rotate the polarization of the green beam to P.
- repositioned the first periscope on the BS table.
- repositioned the second periscope on the IOO table.
- steered some green mirrors on the IOO and OMC chamber to let the Y green beam come out to the PSL table.
- installed a PBS in front of the first periscope to spatially overwrap two green beams.
- adjusted the incident angle of the PBS to maximize the power of the Y green beam, which is transmitted through it.
- steer two mirrors on the BS table to align the X green beam
- installed two beam dumps, one is near the PBS to eliminate a ghost in the X green beam, and the other is on the back side of IPPOS/ANG pick off window.
- closed the doors.
When steering the final green mirror on the OMC table, accidentally we changed the alignment of the MC incident mirror.
So the alignment of the incident beam going into MC has changed, and we haven't re-aligned it yet.
During we were installing the PBS on the BS table, we found that the allowable incident angle for the Y beam is about ~ 55 deg, which maximizes the amount of the transmitted Y green.
Since the PBS had been considered to be 45 deg incident in our optical layout, this required several modifications in the green mirrors.
To have a clear X green beam path going into the PBS, we had to slide the PBS and periscope to the West.
The periscope is now sitting on the very edge of the BS table, and in fact ~ 20% of the bottom plate of the periscope is already sticking out.
Also since 30% of the area of the PBS's post is on a hole, which is somehow for the stack, we had to use three dog clamps instead of a folk clamps to make the contact tight.
Today's main mission is : adjustment of the arm length
+ Open the ETMX(Y) door, starting from 9:00 AM
+ Secure the ETMX(Y) test mass by tightening the earthquake stops.
+ Move the ETMX(Y) suspension closer to the door side
+ Inspect the OSEMs and take pictures before and after touching the OSEMs.
+ Level the table
+ Adjust the OSEM positions
+ Move the ETMX(Y) suspension to have designed X(Y)arm length
+ Level the table again
+ Align the ETMX(Y) such that the green beam resonate
There is a page on the 40m wiki explaining the procedure.
Additionally there are several old elogs about the cross-coupling minimization, which can be useful for us:
 "SUS ranking from measured data", iLog by Osamy (Aug.22 2005)
 "TF from position to sensors for ETMX ", iLog by Osamu (Aug.25 2005)
 "Further OSEM tweaking", iLog by Rana (Oct.3 2006)
We need a plan how to minimize cross coupling in the OSEMs now
Also, according to Steve, there will be some crane guys for fixing the Y end crane issue (#5124) Monday morning.
a film crew will be here Monday morning. They are slated to be here from 8am to 12:30pm or so.
The X green beam has been realigned to compensate the effect of the ETMX repositioning.
After the alignment we became able to lock the 00 mode with the X green beam.
For the alignment:
spot position on the ETMX mirror = within ~ 1 cm. This number is strictly constrained by a homemade aluminum iris that Jamie put last Friday.
spot position on the ITMX mirror = unknown, but looks pretty good on the CCD camera.
spot position on the PSL table = ~ 1 mm downward from what it used to be. The horizontal alignment is perfect.
The X green beam again became a reference of the beam axis.
The ETMX suspension tower is in a good place.
Kiwamu will work on the green alignment over the weekend. Assuming everything works out, we'll try the same procedure on ETMY on Monday.
Since ETMY have been showing some strange behaviors we deeply inspect the ETMY suspension.
Here is a brief review of the ETMY suspension and a brief status update of the inspection so far.
The inspection is still ongoing.
(Review : How wrong ?)
First of all, let us summarize what were the observed phenomena on the ETMY suspension :
1. unknown low frequency noise covering frequency range from 0.1 to 3 Hz in all of four face sensors (#5025, #5029).
2. LR sensor showed a very broad bounce peak at ~ 17 Hz (#5025).
3. The sign of some of the sensors are flipped.
4. The control gains had to be higher than those of ETMX by 10-100 (#5025).
(Status update : Noise spectra)
Currently the ETMY suspension is sitting on the north side of the table for the inspection.
We took dark noise of the OSEMs when the OSEMs were taken off from the tower and put on the table.
The plot below is an example of the LR sensor spectra. Note that the whitening filters have been always ON.
The black curve is the dark noise when the sensor was off from the tower.
The blue curve is the free swinging spectrum newly taken today.
The red curve is the free swinging spectrum (damped spectrum ?) on 25th of July, this was still in vacuum.
The dark noise is below the free swinging spectrum from 0.2 - 30 Hz, which looks reasonable
The most interesting thing is that the free swinging spectrum became better in low frequency (below 3 Hz)
from the one measured in vacuum.
It needs more investigation to answer the reason why it happened.
Note that before we moved the tower to the current position, we looked at the OSEM-magnets relations, and found nothing was touching.
[Rana / Jenne / Kiwamu]
The ETMY suspension tower is currently sitting on the north side of the table for some inspections.
The adjustment of the OSEMs is ongoing.
(What we did)
+ Taken out two oplev mirrors, Jamie's windmill and a lemo patch panel.
+ Put some pieces of metal as makers for the original place
+ Put some makers on the distance of dLY = -25.49 cm = -10.04 inch from the original place (see the 40m wiki).
The minus sign means it will move away from the vertex.
+ Brought the ETMY suspension tower to the north side to do some inspections
+ Did some inspections by taking the noise spectra (#5141)
+ Adjusted the OSEM range and brought the magnets on the center of the OSEM holders by rotating and translating the OSEMs
+ During the work we found the proper PIT and YAW gains were about -5, which are the opposite sign from what they used to be.
+ Trying to minimize the cross couplings
JD: There is still some funny business going on, like perhaps the LR magnet isn't quite in the OSEM beam. We leave the optic free swinging, and will continue to investigate in the morning.
Summary of the week ending Aug 8th. Number of elog entries = 56
+ The vent started Wednesday morning
+ Repositioning of the green periscopes and associated mirrors are done.
+ Got both of the green beams coming out from the chambers
+ Moved the ETMX suspension tower by -8.09 inch (away from vertex)
+ Fixed the alignment of the ETMX CCD mirrors
+ Recovered the X green beam axis for the latest ETMX position
+ oplev centered prior to the vent
+ ETMY_TRANS_QPD didn't respond at all, needs to be fixed
+ Old MZ PD (InGaAs 2mm, @29.5MHz) has been modified for REFL33.
The 11MHz notch circuit is at the amp side instead of the diode side. This is ready for the installation
+ REFL165 PD has been made from the old 166MHz PD.
+ IPPOS has been sick since 19th of July, 2011
+ IPANG is clipped on a pick-up mirror on the ETMY table. QPD itself is healthy.
+ The spot positions on the MC mirrors were measured prior to the vent.
The results are almost the same as before within a few percent difference expect for the MC2 yaw.
+ An attenuator, consisting of two HWPs and a PBS, has been installed on the PSL table for the MC low power state.
+ a 10% BS in front of the MCREFL_RFPD was replaced by a perfect reflector for the low power mode.
+ The incident power for MC was decreased to 20 mW
+ The beam axis going to MC was misalgned due to the attenutor.
Then the beam was aligned by touching two steering mirrors on the PSL table
+ MC is able to be locked in air. The reflection DC goes from 1.4 to 0.13 V when the MC is locked.
+ With the mass-kicking technique, the arm lengths were measured.
Xarm = 37.5918 m, Yarm = 37.5425 m.
- Green locking
+ Y green beam is aligned to the Y arm
+ Locking of the Y green is not robust, it needs to be revisited
+ Wiener Filtering was applied on the data collected from the X-arm for a duration of 1500 seconds.
+ The hazardous waste people are moving chemicals around outside our door, and have roped off our regular front door.
+ The horizontal trolley drive of the east end crane stopped working. It will be fixed.
We will move on to the vertex region today.
The goal of the vertex region work is to get the pick-off beams out the chambers, including POX/Y and POP.
The work will be in parallel to the ETM woks.
The first step will be : lock and align MC with the IR beam.
I believe that the 17 Hz broad structure on SIDE is just because of a bad rotational angle of the SIDE OSEM.
The same structure had been observed on the EMTY_UR, and the structure became narrower after we repositioned/rotated the OSEM yesterday.
My guess is that the SIDE OSEM is now in a place where the OSEM is quite sensitive to the bounce mode
and creating the broad structure due to a bi-linear coupling between the bounce mode and low frequency signals.
There is something defintely wrong with the side sensor. It might be the electronics as it also has this problem with it slow channel readings (my previous elog today).
I modified a set of the automated MC locking scripts which are dedicated for the low power MC.
Currently there are three scripts like the usual MC locking scripts:
(1)mcup_low_power, (2) mcdown_low_power and (3) autolockMCmain40_low_power.
I ran those scripts on op340m as usual and so far they are running very well. The lock acquisition is quite repeatable.
I hope theses scripts always bring the lock condition to the same one and hence the LOCKIN signals don't change by every lock.
- To run the script
log into op340m and run autolockMCmain40m_low_power
And the MC settles into a new position when the MC-PSL servo loop was disturbed by random denizens in the lab. Requiring us to start over again.
The spot positions on the MC mirrors were adjusted by steering the MC mirrors, resulting in 1 mm off-centering on each optic.
One of the requirements in aligning the MC mirrors is the differential spot positions in MC1 and MC3.
It determines the beam angle after the beam exists from MC, and if it's bigger than 3 mm then the beam will be possibly clipped by the Faraday (#4674).
The measured differential spot positions on MC1 and MC3 are : PIT = 0.17 mm and YAW = 1.9 mm, so they are fine.
(Measurement and Results)
Suresh and I aligned the MC cavity's eigen axis by using MCASS and steering the MC mirrors.
Most of the alignment was done manually by changing the DC biases
because we failed to invert the output matrix and hence unable to activate the MCASS servo (#5167).
Then I ran Valera's script to measure the amount of the off-centering (#4355), but it gave me many error messages associated with EPICS.
So a new script newsensedecenter.csh, which is based on tdsavg instead of ezcaread, was made to avoid these error messages.
The resultant plot is attached. The y-axis is calibrated into the amount of the off-centering in mm.
In the plot each curve experiences one bump, which is due to the intentional coil imbalance to calibrate the data from cnts to mm (#4355).
The dashed lines are the estimated amount of off-centering.
For the definition of the signs, I followed Koji's coordinate (#2864) where the UL OSEM is always in minus side.
After the beam spots on MC1 and MC3 were close to the actuation nodes (<1mm away)
We tried adjusting the OSEMs on PRM, but we didn't complete it due to a malfunction on the coils.
The UL and LL coils are not working correctly, the forces are weak.
Tomorrow we will look into the satellite box, which is one of the suspects.
During the adjustment we found that the POS excitation force was unequal in each sensor.
At the beginning we thought it's because of the difference of the sensitivity in each OSEM due to the bad OSEM orientations.
However it turned out that it comes from the actual force imbalance on each coil.
We checked the force of each coil by putting an offset (-2000 cnts) in each output digital filter and looked at the OSEM signals in time series.
The UL and LL coils are too weak and the responses are almost buried in the noise of the OSEMs in time series.
We briefly checked some analog electronics and found the DAC, AI board and deWhitening board were healthy.
We were able to see the right amount of voltage from the monitor pin on the front panel of the coil driver.
So something downstream are suspicious, including the satellite box, feedthrough and coils.
- - -
Although the coil issue, it could be worth trying to check the input matrix.
Excited all optics - -
Fri Aug 12 03:34:12 PDT 2011
Adjustment of the PRM OSEMs are done. The coils turned out to be healthy.
The malfunction was fixed. It was because the UL OSEM was too deeply inserted and barely touching the AR surface of the mirror.
+ Excited POS at 6.5 Hz with an amplitude of 3000 cnts by the LOCKIN oscillator.
+ Looked at the signal of each sensor in frequency domain.
+ Maximized the excitation peak for each of the four face OSEMs by rotating them.
+ Minimized the excitation peak in the SIDE signal by rotating it.
+ Adjusted the OSEM translational position so that they are in the midpoint of the OSEM range.
(POS sensitivity check)
From the view point of the matrix inversion, one thing we want to have is the equally sensitive face sensors and insensitive SIDE OSEM to the POS motion.
To check the success level of today's PRM adjusment, I ran swept sine measurements to take the transfer function from POS to each sensor.
The plots below are the results. The first figure is the one measured before the adjustment and the second plot is the one after the adjustment.
As shown in the plot, before the adjustment the sensitivity of OSEMs were very different and the SIDE OSEM is quite sensitive to the POS motion.
So PRM used be in an extremely bad situation.
After the adjustment, the plot became much better.
The four face sensors have almost the same sensitivity (within factor of 3) and the SIDE is quite insensitive to the POS motion.
I am leaving all of the suspensions free swinging. They will automatically recover after 5 hours from now.
Excited all optics
Sat Aug 13 02:08:07 PDT 2011
FYI : I ran a combination of two scripts: ./freeswing && ./opticshutdown
I guess the ETMY suspension is still fine. Their OSEM DC voltage and the free swinging spectra look healthy.
It could be a failure in the initial guess for fitting.
I'm no longer convinced that ETMY is healthy. I can't fit the peaks to get the input matrix.
Excited all optics
Sun Aug 14 20:22:33 PDT 2011