- We labeled the cables to be disconnected
- The following stuffs have been removed from the PSL table
- The OMC power supply cable was visited.
- We put thick and long optical poles
Nancy notified me that the elog crashed. It was fixed.
I restarted elog, but it kept crashing. Some of the entries on Aug 6th caused the trouble.
I tried to refresh the pictures in entries 3376, 3377, 3378. Still it kept crashing.
I started to dig into the elog file itself. (/cvs/cds/caltech/elog/elog-2.7.5/logbooks/40m/100806a.log)
FInally I found that there was some invalid reply links in the entry 3379.
Date: Fri, 06 Aug 2010 19:29:59 -0700
Reply to: 3379
In reply to: 3379
Date: Fri, 06 Aug 2010 19:29:59 -0700
Reply to: 3379
In reply to: 3379
The entry is refering this entry itself. That is weird. So I deleted the reply-to and in-reply-to lines.
Then elogd got happy.
In fact, 3379 was a dupulication of 3380, so I deleted this entry.
Jenne asked us to keep th MC locked and let the seismometers happy through this weekend.
Note that the work at the control room and the desks are no problem as far as you are quiet.
Nancy told Jenne and me that she finished the work and reverted the WFS to the old state at 4:30AM.
She could not make the elog as it has been crashed.
MC and old MC WFS looks working as usual.
From 6:40AM to 9:40AM the oscillation of the PMC looks present.
At 10:30AM I reduced the gain of the PMC from +15dB to +13dB.
The WFS and QPD servos were working. That was great.
Everything was fine except for the time series plots.
I could not get what story you are telling with the time series.
(e.g. your's are good or bad or anything)
Some photos are attached in this entry. All of the photos found in the picasa album (click the slideshow)
We wanted to characterize the PSL table before the work before its lifting up.
We put a set of three-axis Wilcoxon accelerometers on the ground and another set on the PSL table through the weekend.
- The data at 9th Aug 00:00(UTC) is used. This was Sunday 5PM in the local time.
- The freq resolution was 0.01Hz. The # of avg was 50.
- The accelerometer signals were calibrated by the value 1.2e-7 V/(m/s^2). We use this absolute value of the spectrum for the comparison purpose.
- The accelerometers were aligned to North(X), East(Y), and Up(Z). There was the coherence observed from 2~20Hz.
The transfer functions are valid only this frequency region although we still can set the lower bound of them.
- The transfer functions in the horizontal directions show huge peaks at around 20Hz. The Q of the peaks are ~30 to ~100.
The vertical transfer function shows somewhat lower peak at around 50Hz with Q of ~10.
- The low resonant freq and the high Q of the horizontal mode comes from the heaviness of the table.
- We are going to raise the table. This will usually mean that we get the lower resonant freq. This is not nice.
- So, the decision to use 6 tripods rather than 4 was right.
- The steel tripods are expected to give both more rigidity and more damping than the chep-looking hollow Newport legs.
- Concrete grouting of the tripods will also lower the effective height and will benefit for us.
Katharine, Sharmila, Gopal, Kiwamu, Jenne, Aidan, Steve, and Koji
A guy from the carpenter shop has done the drilling work in the morning.
In the afternoon we wrapped the central part of the interferometer with plastic sheets in order to avoid the dusts from the tile ripping that will happen tomorrow.
This sounds very relieving although this could be a lower bound of the number.
Why didn't you use the output on the PD which just give us the direct observation of your so-called SCR.
Ed: I meant time series of the PD output
So the SCR is calculated by the ratio of the FFT'd DC and the 5 Hz signal. Using the CCD, I obtained the SCR to be 0.075 ± 0.01. Previously, we expected our SCR to be 0.09 as in the previous e-log entry.
Jenne and Koji
Last week Jenne has put the accelerometers on and under the PSL table immediately after the plastic sheets were removed.
So I took the same measurement as I did on 9th Aug.
Here is the comparison of the vibrational performance of the table before and after the modification.
Basically the table is now stiffer and more damped than it was before.
We don't find any eminent structure below (at least) 70Hz.
This result is obtained despite elevating of the table.
1) Attachment 1
For the horizontal comparison (top), it is clearly seen that the large resonant peak at 20Hz was eliminated.
At least the new resonances went up to 70-90Hz region. Y is basically equivalent to X.
For the vertical comparison (bottom), it is clearly seen that the resonant peaks at around 50 & 70Hz were eliminated.
At least no new resonance is seen.
2) Attachment 2
All-in-one plot for the measurement --- spectra, coherences, transfer functions --- after the upgrade. I put the same plot for the one before the upgrade.
I am feeling that it is ok to carefully make new holes and threads as far as the holes do not penetrate the plate.
The thickness of the plate can be measured by the four holes at the corners.
1. I can not see whether the attaching surface is flat or not.
It should have ~1mm step to avoid "the legs" of the laser at the four corners.
Otherwise we will have ~0.5mm space between the block and the laser
and will squish this gap by the screws => cause the deformation of the block and the laser.
2. The countersinks for the M4 screws can be much deeper so that we can use the existing M4 screws.
In any case, the long M4 screws are not rigid and also not common.
To test out this website - emachineshop.com, Jenne and I are designing some of the mounts for the new beam height.
It took me a few hours to figure out how to do it, but the software is easy enough for simple stuff. This is a brass mount with M4 clearance holes which are countersunk and a lip so that it can be dogged down to the table.
Yeah, this looks nice.
And I also like to have something I have attached. This is "HOZAN P-90", but we should investigate American ones
so that we can cut the wires classified by AWG.
I found this very interesting German maker of cool cable cutting tools. It's called Jokari.
We should keep it as a reference for the future if we want to buy something like that, ie RF coax cable cutting knives.
I have reviewed the suspension model of C1SUS and refined it.
It is comaptible to the current one but has minor additions.
Brilliant! This is the VERY way how the things are to be conquered!
The RefCav is locked and aligned. I changed the fast gain sign by changing the jumper setting on the TTFSS board. The RefCav visibility is 70%. The FSS loop ugf is about 80 kHz (plot attached) with FSS common gain max out at 30 dB. There is about 50 mW coming out of the laser and a few mW going to RefCav out of the back of the PMC. So the ugf can be made higher at full power. I have not made any changes to account for the PMC pole (the FSS is after the PMC now). The FSS fast gain was also maxed out at 30 dB to account for the factor of 5 smaller PZT actuation coefficient - it used to be 16 dB according to the (previous) snap shot. The RefCav TRANS PD and camera are aligned. I tuned up the phase of the error signal by putting cables in the LO and PD paths. The maximum response of the mixer output to the fast actuator sweep of the fringe was with about 2 feet of extra cable in the PD leg.
I am leaving the FSS unlocked for the night in case it will start oscillating as the phase margin is not good at this ugf.
Two SOS suspensions for the ETMs were disassembled and packed for cleaning and baking by Bob.
These suspensions have been stored on the X end flow bench long years, and looked quite old.
They have some differences to the modern SOSs.
- The top suspension block is made of aluminum and had dog clamps to fix the wires.
- The side bars are not symmetric: the side OSEM can only be fixed at the right bar (left side in the picture).
- EQ stops were made of Viton.
- One of the tower bases seems to have finger prints (of Mike Zucker?).
I found that the OSEM plates had no play. We know that the arrangement of the OSEMs gets quite difficult
in this situation. Therefore the holes of the screws were drilled with the larger drill.
We decided to replace all of the screws to the new ones as all of the screws are Ag plated and got corroded
by silver sulfide (Ag2S). I checked our stock in the clean room. We have enough screws.
The day before yesterday, I was cleaning a flow bench in the clean room.
I found that one SOS was standing there. It is the SRM suspension.
I thought of the nice idea:
- The installed PRM is actually the SRM (SRMU04). It is 2nd best SRM but not so diiferent form the best one.
==> Use this as the final SRM
- The SRM tower at the clean room
==> Use this as the final PRM tower.
==> The mirror (SRMU03) will be stored in a cabinet.
- The two SOS towers will be baked soon
==> Use them for the ETMs
This reduces the unnecessary maneuver of the suspension towers.
Net switch mumbo-jumbo:
Although Rana is going to buy a replacement for the Netgear Switch for martian, I opened the lid of the Netgear as the fan already have stopped working.
Also the lid of the other network switch for GC (Black one) was opened as it has a broken fan and a noisy half-broken fan.
I have asked Steve to buy replacement fans. These would also be the replacement of the replacement.
During the work, it seemed that I accidentally toggled the power supply of linux1. It lead lengthy fsck of the storage.
This is why all of the machines which rely on linux1 got freezed. linux1 is back and the machines looked happy now.
If you find any machine disconnected from the network, please consult with me.
The Netgear Network Switch in the top shelf of Nodus' rack has a broken fan. It is the one interfaced to the Martian network.
The fan must have broken and it is has now started to produce a loud noise. It's like a truck was parked in the room with the engine running.
Also the other network switch, just below the Netgear, has one of its two fans broken. It is the one interfaced with the General Computer Side.
I tried to knock them to make the noise stop, but nothing happened.
We should consider trying to fix them. Although that would mean disconnecting all the computers.
Zach> Nodus seemed to be working fine again, and I was browsing the elog with no
Zach> problem. I tried making an entry, but when I started uploading a file it
Zach> became unresponsive. Tried SSHing, but I get no prompt after the welcome
Zach> blurb. ^C gives me some kind of tcsh prompt (">"), which only really
Zach> responds to ^D (logout). Don't know what else to do, but I assume someone
Zach> knows what's going on.
By gracefully rebooting nodus, the problem was solved.
It (">") actually was the tcsh prompt, but any commands with the shared or dynamic link libraries looked unfunctional.
I could use
to browse the directory tree. The main mounted file systems like /, /usr, /var, /cvs/cds/caltech looked fine.
I was afraid that the important library files were damaged.
in order to flush the file systems.
These should run even without the libraries as mount must properly work even before /usr is mounted.
They indeed did something to the system. Once I re-launch a new login shell, the prompt was still ">"
but now I could use most of the commands.
/, /usr, /var, /cvs/cds/caltech
I have rebooted by usual sudo-ing and now the services on nodus are back to the functional state again.
# nodus was working in the evening at around 9pm. I even made an e-log entry about that.
# So I like to assume this is not directly related to the linux1 incident. Something else could have happened.
svn is back after starting apache on nodus.
I am guessing that the NFS file system hangup may have caused some machines to get into an awkward state. We may be best off doing a controlled power cycle of everything...
mafalda is up now.
I found that the cable for mafalda (the sole red cable) had a broken latch.
The cable was about falling off from the switch. As a first-aid, I used this technique to put a new latch, and put it into the switch.
Now I can logged in it. I did not rebooted it.
How much current do you need for each voltages?
GE-82 was the only PNP transister I could find in the lab. It's too old but we just like to confirm any other components are still functioning.
Similarly, we can confirm the functionality of the other components by skipping those current boost transisters,
if we don't need more than 30mA.
It was a bit difficult to comprehend the result.
Is it good? or bad? Have you seen the thermal effect? or not?
- Put linear lines to show the visibility of the cavity.
- Calibrate the incident power and make another plot to show the visibility (%) vs the incident power (W).
We wanted to see thermal effects on the PMC.
What I did yesterday:
Changed the current of the NPRO from 2A to 0.8A and measured the power of the reflected/transmitted light from the PMC when locked.
I also measured the power of the reflected light when PMC is not locked (It supposed to be proportional to the output power of the laser).
At several points of the laser current, I could'nt lock the PMC very well. The power of the reflected/transmitted light depend on the offset voltage of the PZT.
When the laser power was weak(~<0.9A), the power of reflected/transmitted light changed periodically(~ several minutes).
Both Rolf and Alex (at least his elbow) together visited the 40m to talk with Joe for the CDS.
40m is the true front line of the CDS development!!!
[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.
The network cables for the Martian network were moved to the new Netgear switch from the old one which had the broken fan.
The martian machines look happy so far.
Above the new switch we have the GC network switch. The two fans of it were also broken. The fans were replaced.
They are now quiet and I am quite satisfied.
I removed some old equipment from the rack outside the control room and stacked them next to the filing cabinets in the control room. I also mounted the new Netgear switch in the rack.
From the plot, you observed the reduction of the output power only by 1% between 25deg to 45deg.
This does not agree with the reduction from 2.1W to 1.6W.
Is there any cause of this discrepancy?
The measurement was made by attenuating the roughly 2W laser beam by a stack of two Neutral Density filfers and then measuring the transmitted light with the PDA36A photodetector. This was because both the power meters used in the past were found to have linear drifts in excess of 30% and fluctuations at the 10% level.
- Steve is working on the storage shelf for those optics.
- PRMU002 was chosen as it has the best RoC among the three.
We've put the old PRM and SRM (which were living in a foil house on the cleanroom optical table) into Steve's nifty storage containers. Also, we removed the SRM which was suspended, and stored it in a nifty container. All 3 of these optics are currently sitting on one of the cleanroom optical tables. This is fine for temporary storage, but we will need to find another place for them to live permanently. The etched names of the 3 optics are facing out, so that you can read them without picking them up. I forgot to note the serial numbers of the optics we've got stored, but the old optics are labeled XRM ###, whereas the new optics are labeled XRMU ###.
Koji chose for us PRMU 002, out of the set which we recently received from ATF, to be the new PRM. Suresh and I drag wiped both sides with Acetone and Iso, and it is currently sitting on one of the rings, in the foil house on the cleanroom optical table.
We are now ready to begin the guiderod gluing process (later tonight or tomorrow).
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?
I cleaned up the scattered tools, optics, and mounts of the PSL table. I gathered those stuffs at the two coners.
At the end of the work I scanned the table with an IR viewer. (This is mandatory)
I put some beam block plates to kill weak stray beams.
One thing I like to call the attention is:
Particularly, there was no beam block at the forward rejection side of the first PBS where we dump the high power beam.
This is cool though the projector is flashing the blue screen alternately.
I gave the dual head video card (ATI RADEON something) to Yuta a month ago.
It is on the top of Zita. This would make the things more fun.
Yuta has also successfully set up zita to run the projector, so we should clear our some of the boxes and bookshelves in that area so that the projection can be larger.
We found the beat at 1064nm. T(PSL)=26.59deg, T(X-end)=31.15deg.
The X-end laser was moved to the PSL table.
The beating setup was quickly constructed with mode matching based on beam profile measurements by the IR cards.
We used the 1GHz BW PD, Newfocus #1611-FS-AC.
As soon as we swept the Xtal temp of the X-end laser, we found the strong beating.
[Koji / Suresh]
We worked on the 1064 beating a bit more.
- First of all, FSS and FSS SLOW servo were disabled not to have variating Xtal temp for the PSL.
- The PSL Xtal temp (T_PSL) was scanned from 22deg-45deg while we search the Xtal temp (T_Xend) for the Xend laser to have the beat freq well low (f<30MHz).
The pumping current for each laser was I_PSL = 2.101 [A] and I_Xend = 2.000 [A]
For a certain T_PSL, we found multiple T_Xend because the freq of the laser is not a monotonic function of the Xtal temperature. (see the innolight manual).
T_Xend to give us the beating was categorized in the three sets as shown in the figure. The set on "curve2" is the steadiest one. (Use this!)
The trends were quite linear but the slope was slightly off from the unity.
- T_PSL was scanned to see the trend of the PMC output.
The PMC was sometimes locked to the mode with lower transmission (V_PMCT ~ 3.0V).
When T_PSL ~ 31deg we consistently locked the PMC at higer transmission (V_PMCT ~ 5.3V).
At the moment we decided the operating point of T_PSL = 32.25 deg, V_PMCT = 5.34, where we found the beat at T_Xend=38.28deg.
- We cleaned up the PSL table more than how it was. Returned the tools to their original places.
The X-end laser was shut down and was left on the PSL table.
Kiwamu can move the X-end laser to the Xend and realign it.
Then we should be able to see the green beating quite easily.
- What is the actual photocurrent for the beam1 and beam2? We don't care how much power do you have before the BS, but care how much current do you have on the PD.
- How much is the visibility? There is mismatching of the beams. i.e. The beam diameter looked quite different. Also the beams are not TEM00 but have fringes probably comes from the TT mirrors. You maybe able to measure the visibility by the DC output, making the beat freq go through df=0 slowly.
- What is the measured gain of the RF amp? Does it include the voltage division by the output/input impedance?
The signal level of the observed peak was -48dBm.
However I was expecting it is like -28dBm with some ideal assumptions.
There may be a 20dB unknown loss which sounds big to me.
I was assuming the parameters are like:
A = 0.39 [A/W] (assuming 90% quantum efficiency at 532nm)
Z = 240 [V/A]
P1 = 17 uW (measured by Newport power meter)
P2 = 30 uW (measured by Newport power meter)
G_RF = 23 dB
Q1. Suppose the laser beam has a certain (i.e. arbitrary) polarization state but contains only TEM00. Also suppose the PSB is perfect (reflect all S and transmit all P). What results do you expect from your expereiment?
Q2. Suppose the above condition but the PBS is not perfect (i.e. reflects most of S but also small leakage of P to the reflection port.) How are the expected results modified?
Q3. In reality, the laser may also contain some thing dirty (e.g. deporarization in the laser Xtal, higher order modes in a certain polarization but different from the TEM00's one, etc). What actually is the cause of 170mW rejection from the PBS? Can we improve the transmitted power through the PBS?
Q4. Why is the visibility for the lambda/4 with 330deg better than the one with 326deg? Yes, as I already explained to Kevin, I suppose it was caused by the lack of the data points in the wider angle ranges.
I measured the reflected power from the PBS as a function of half wave plate rotation for five different quarter wave plate rotations.
The optimum angles that minimize the reflected power are 330° for the quarter wave plate and 268° for the half wave plate.
The following data was taken with 2.102 A laser current and 32.25° C crystal temperature.
For each of five quarter wave plate settings around the optimum value, I measured the reflected power from the PBS with an Ophir power meter. I measured the power as a function of half wave plate angle five times for each angle and averaged these values to calculate the mean and uncertainty for each of these angles. The Ophir started to drift when trying to measure relatively large amounts of power. (With approximately 1W reflected from the PBS, the power reading rapidly increased by several hundred mW.) So I could only take data near the minimum reflection accurately.
The data was fit to P = P0 + P1*sin^2(2pi/180*(t-t0)) with the angle t measured in degrees with the following results:
where V is the visibility V = 1- P_max/P_min. These fits are shown in attachment 1. We would like to understand better why we can only reduce the reflected light to ~150 mW. Ideally, we would have V = 1. I will redo these measurements with a different power meter that can measure up to 2 W and take data over a full period of the reflected power.
[Suresh / Koji]
The MC mirrors are aligned. Now the flashing of the resonances are visible on the MC2 CCD
although the modematching seemed pretty poor.
- The incident power was adjusted to be ~20mW by rotating HWP after the laser source.
The power before the window of the chamber was ~450mW. Where are those missing 1.5W?
- We checked the spot on the last two steering mirrors and the incident beam on MC1.
The beam was too much off from the center of the 1st steering mirror. It was also hitting 1cm north of the MC1.
We adjusted the steering mirrors such that the incident and reflected beams are symmetrically visible at the MC1 tower.
- The MC mirrors are aligned. We first tried to use only MC2 and MC3. And then we used MC1 too as the spot on the MC2 was too high.
- We saw some TEM00 flashes but with many other modes flashing. We checked the beam diameter on the PSL table and on the MC REFL.
The latter one looked twice large as the former one. We concluded the beam is diverging.
- We closed the tank and decided to work on the mode matching tomorrow.
ELOG reverted to 2.7.5 due to editing difficulties
- /cvs/cds/caltech/elog/start-elog.csh reconfigured to launch 2.7.5
- /cvs/cds/caltech/elog/elog is linked to ./elog-2.7.5
- logbook dir of 2.8.0 was copied in the dir of 2.7.5. The old and obsolete 2.7.5 was discarded.
ELOG restarted with 2.8.0 again.
- moved elog-2.8.0/script dir to elog-2.8.0/script.orig
- copied elog-2.7.5/script to elog-2.8.0/script
- /cvs/cds/caltech/elog/start-elog.csh reconfigured to launch 2.8.0
- /cvs/cds/caltech/elog/elog is linked to ./elog-2.8.0
- logbooks on 25th and 26th were copied from 2.7.5 to 2.8.0.
ZHL-32A is a high power (well..., actually middle power) amplifier with the max output power of +29dBm (~1W!).
It seems to be overkill.
Your signal is so small so you don't need ZHL-32A, but can use small amp which we may have somewhere in the lab.
And the description:
"RF amplifier ZHL-32A has around +28dBm gain at 80MHz"
The unit is wrong.
For green locking, we are planning to feedback frequency differential signal to ETM suspension for the final configuration.
We don't have ETM suspension control system right now, so we are going to feedback the signal to X-end laser frequency for a test.
We have two loops for the servo;
1. coarse locking using frequency counter, feeding back to the laser temperature
2. using VCO, feeding back to the laser PZT
Today, we checked frequency counter SR620 and see how to get the small beat note signal(-48dBm; see elog #3771).
What we did:
1. Using Marconi(RF signal generator), put RF signals to SR620 and see how small signal SR620 can see.
It depends on the frequency. For 80MHz signal, you need more than about -9dBm.
Since we are going to lock the frequency difference between X-end and PSL to 80MHz, we need at least +40dBm amp before putting the signal into SR620.
RF amplifier ZHL-32A has around +28dBm gain at 80MHz, so we need 2 of them.
2. Marconi -> ZHL-32A -> ZHL-32A -> SR620 and see how small 80MHz signal SR620 can see.
Around -68dBm. This should be enough.
3. SR620 has "STRIP CHART" output on the rear panel. The output voltage is proportional to the mean frequency of the input.
The output range is 0-8V. So in order to get 4V for 80MHz, set SCALE to 20MHz.
- find green beat again and see if SR620 can see it with double ZHL-32A configuration
The standoff glued. The incandescent lamp set for curing the epoxy.
Jenne and Suresh did the balancing job. The next job was to glue it.
They ran out of the clear epoxy, and tried to use the grey epoxy which we used on the other suspensions for the upgrade.
They found that the solution A with grey color one was dried out and grainy.
We made a test piece of the grey epoxy (mixed with the solution B) in order to see the glue is still usable or not.
After the PMA party, we found that the glue was not stiffening but brittle. We judged that the grey epoxy is no longer useful.
Steve found a pack of Vac Seal in the chemical fridge. We decided to use this one for the gluing of the standoff.
After the gluing, we set an incandescent lamp to make the glue warm.
Finally, we wrapped the suspension tower with Al foils and turned the HEPA fans again.
- The PBS alignment increased the transmitted power
- The first faraday and the PMC EOM were realigned.
- The transmission of the PMC increased from ~5.4V to ~6.5V.
Thus we need to pay attention to the incident beam power on to the MC
so that it does not exceed the power of 20-40mW.
Kevin will give us the detail of the work.
Neglecting the digital anti-imaging filter makes the discrepancy. You must take into account your digital filter twice.
I attached the slides I made during my visit for March LVC '09. P.5 would be useful.
[time delay of the CDS] (left, middle)
The time delay gets larger with frequency. The time delay seems to be -175 usec at DC.
However, the gain seems a little different from my expectation(feCoeff4x). So, there are maybe other filters I don't know.
I neglected TF of upsampling this time.
Actually, 123.5usec is almost exactly twice of 1/16384Hz.
Because of the loop, we have 1/16384Hz delay. I wonder where we do have the delay.
In order to understand the behaviour of the system can I ask you to test the following things?
1) What are the delay without IOPs with fsampl of 16k, 32k, 64k?
2) What are the delay with IOP with fsampl of 32k, 64k?
TF agreed well with 2-time feCoeff4x and CDS time delay was -123.5 usec.
Today we found the green beam from the end was totally missing at the vertex.
- What we found was very weak green beam at the end. Unhappy.
- We removed the PBS. We should obtain the beam for the fiber from the rejection of the (sort of) dichroic separator although the given space is not large.
- The temperature controller was off. We turned it on again.
- We found everything was still misaligned. Aligned the crystal, aligned the Faraday for the green.
- Aligned the last two steering mirrors such that we hit the approximate center of the ETMX and the center of the ITMX.
- Made the fine alignment to have the green beam at the PSL table.
The green beam emerged from the chamber looks not so round as there is a clipping at an in-vac steering.
We will make the thorough realignment before closing the tank.
Wow! Great guys!!
Can I expect to see the spectra of the frequency counter output with and without the servo?
RA: I think the SBP-70 is a bad idea. It limits the capture range. So does the SHP-25. You should instead just use a DC-block; the SR620 should work from 1-200 MHz with no problems.
Also, we have to figure out a better solution for the DAC at the ends: we cannot steal the QPD gain slider in the long run and the 4116 DAC at the ends has all 8 channels used up. Should we get the purple box for testing or should we try to use the fast DAC in the EX IO chassis as the actuator?
- Removed MCT optics in the IMC chamber
- Rotated MC1 and MC3 in clock-wise to debias the YAW bias offsets (-5V and -8V to -1.5V and -0.5V).
- Adjusted insertion of the MC1 OSEMs so as to have the outputs of about 1.0V.
- Locked to TEM00. Trying to get the beams at the center of the mirror using Yuta's A2L.
As MC2 Trans mon QPD is temporary removed for fixing, we needed a reference for the MC alignment.
I replaced the 10% pick-off in the MCREFL path to the HR mirror.
Now the MCREFL DC with MC unlock is ~2.2, while it is ~0.29 in lock.
i.e. The visibility is 87%.
This means that the MCWFS were disabled for the moment.
It didn't make sense in several points.
1. Is the Faraday aperture really 3mm? The beam has the gaussian radius of ~1.5mm. How can it be possible to go through the 3mm aperture?
2. Why the MC3-FT distance is the matter? We have the steering mirror after MC3. So we can hit the center of the Faraday.
But if we have VERTICAL TILT of the beam, we can not hit the center of the Faraday entrance and exit at the same time.
That would yield the requirement.
3. If each coil has 5% variance in the response, variance of the nodal point (measured in % of the coil imbalance) by those four coils will be somewhat better than 5%, isn't it?