The box is electrically isolated from the optical bench.
Underneath the box there are four rubber legs and two Delrin plates (black and white) on the top of the box.
As everyone knows this box is a prototype, so I will make another nicer box with a PCB in this November.
I measured the open loop transfer function of the 80MHz VCO's PLL while locking it to Marconi.
This measurement is for a health check and a characterization of the PLL
The transfer function looks good, it agrees with the designed filter shape.
The frequency of Marconi is set to 79.5MHz which is the center frequency of the VCO.
The signal from Marconi is mixed down with the VCO signal at a mixer ZLW-3SH.
Then the demodulated signal goes to a 80MHz LPF to cut off high frequency components.
And it goes through a control filter which has 1Hz pole and 40Hz zero (see this entry).
The 80MHz LPF, the controls filter, the VCO and the RF amplifier are all built in the box.
In order to measure the open loop transfer function I inserted SR560 before the 80MHz LPF.
Using T-splitters the input and the output of SR560 are connected to a spectrum analyzer SR785.
Exciting the system using a source channel of SR785, I measured the open loop transfer function.
The unity gain frequency was measured to about 20 kHz.
It agrees with the designed filter shape (though the gain factor is a little bit underestimated).
Apparently there is a phase delay at high frequency above 10kHz, but it is okay because the phase margin is quite acceptable up to 100kHz.
However I found that the control range was quite narrow.
The PLL was able to be kept in only +/- 1MHz range, this fact was confirmed by shifting the frequency of Marconi during it's locked.
I will post another elog entry about this issue.
Marconi power = 6dBm
VCO power after RF amp. = -0.6 dBm
Marconi frequency = 79.5 MHz
Phase detection coefficient = 0.4 V/rad (measured by using an oscillo scope)
Bad; there should be a passive ~1 MHz LP filter between the mixer and anything that comes after. The SR560 + mixer does not equal a demodulator.
For Yuta's business, I intentionally misaligned the wideband EOM slightly to Yaw direction. Good luck.
It should show a big AM component at photo detectors.
I touched only the top right knob on the EOM mount and tweaked it by exactly 2 turns in counterclockwise direction.
The hold-in range of the PLL must be greater than +/- 4MHz in order to bring the arm cavity to its resonance.
(Hold-in range is the range of frequencies over which the PLL can track the input signal.)
However as I mentioned in the past elog (see this entry), the PLL showed a small hold-in range of about +/- 1MHz which is insufficient.
In this entry I explain what is the limitation factor for the hold-in range and how to enlarge the range.
(Requirement for hold-in range )
We have to track the frequency of the green beat signal and finally bring it to a certain frequency by controlling the cavity length of the arm.
For this purpose we must be able to track the beat signal at least over the frequency range of 2*FSR ~ +/- 4MHz.
Then we will be able to have more than two resonances, in which both the end green and the PSL green are able to resonate to the arm at the same time.
And if we have just two resonances in the range, either one of two resonances gives a resonance for both IR and green. At this phase we just bring it to that frequency while tracking it.
Theoretically this requirement can be cleared by using our VCO because the VCO can drive the frequency up to approximately +/- 5MHz (see this entry)
The figure below is an example of resonant condition of green and IR. The VCO range should contain at least one resonance for IR.
(In the plot L=38.4m is assumed)
However the measured hold-in range was about +/- 1MHz or less. This is obviously not large enough.
According to a textbook, this fact is easily understandable.
The hold-in range is actually limited by gains of all the components such as a phase detector's, a control filter's and a VCO's gain.
Finally it is going to be expressed by,
[hold-in range] = G_pd * G_filter * G_vco
[hold-in range] = G_pd * G_filter * G_vco
At the PD (Phase Detector which is a mixer in our case) the signal does not exceed G_pd [V] because it appears as G_pd * sin(phi).
When the input signal is at the edge of the hold-in range, the PD gives its maximum voltage of G_pd to maintain the lock.
Consequently the voltage G_pd [V] goes through to G_filter [V/V] and G_vco [Hz/V].
This chain results the maximum pushable frequency, that is, hold-in range given above equation.
In our case, the estimated hold-in range was
[hold-in range] ~ 0.4 [V] * 3 [V/V] * 1 [MHz/V]
[hold-in range] ~ 0.4 [V] * 3 [V/V] * 1 [MHz/V]
= 1.2 [MHz]
This number reasonably explains what I saw.
In order to enlarge the hold-in range, increase the gain by more than factor of 5. That's it.
* reference  "Phase-Locked Loops 6th edition" Rolan E. Best
In order to enlarge the hold-in range I modified the control filter and increased the gain by factor of 25 in the PLL.
It successfully enlarged the range, however the lock was easily broken by a small frequency change.
So I put a low frequency boost (LFB) and it successfully engaged the PLL stiffer.
Now it can maintain the lock even when the frequency disturbance of about 1MHz/s is applied.
(enlargement of the hold-in range)
I modified the control filter by replacing some resistors in the circuit to increase the gain by factor of 25.
- R18 390 [Ohm] => 200 [Ohm]
- R20 1000 [Ohm] => 5000 [Ohm]
- R41 39 [Ohm] => 10 [Ohm]
This replacement also changes the location of the pole and the zero
- pole 1.5 [Hz] => 0.3 [Hz]
- zero 40 [Hz] => 159 [Hz]
Note that this replacement doesn't so much change the UGF which was about 20 kHz before.
It becomes able to track the input frequency range of +/- 5MHz if I slowly changes the frequency of the input signal.
However the PLL is not so strong enough to track ~ 1 kHz / 0.1s frequency step.
(make the PLL stiffer : a low frequency boost)
One of the solution to make the PLL stiffer is to put a boost filter in the loop.
I used another channel to more drive the VCO at low frequency. See the figure below.
The 80MHz VCO box originally has two input channels, one of these inputs was usually disabled by MAX333A.
This time I activated both two input channels and put the input signal to each of them.
Before signals go to the box, one of the signal path is filtered by SR560. The filter has G=20000, pole=0.3Hz. So it gives a big low frequency boost.
Once the PLL was achieved without the boost, I increased the filter gain of SR560 to 20000 because locking with the boost is difficult as usual.
I maximized the laser power by rotating the HWP after the NPRO.
If someone works on the MC locking, one should decrease it again.
Stabilizing the beat note frequency using Yuta's temperature servo (see this entry)
I was able to acquire the PLL of 80MHz VCO to the real green signal.
Some more details will be posted later.
Since we are going to lock the MC today, I aligned it back to the default place.
For Yuta's business, I intentionally misaligned the wideband EOM slightly to Yaw direction.
I checked the slow servo and the PLL of 80MHz VCO using the real green beat note signal.
The end laser is not locked to the cavity, so basically the beat signal represents just the frequency fluctuation of the two freely running lasers.
The PLL was happily locked to the green beat note although I haven't fedback the VCO signal to ETMX (or the temperature of the end laser).
It looks like we still need some more efforts for the frequency counter's slow servo because it increases the frequency fluctuation around 20-30mHz.
(slow servo using frequency counter)
As Yuta did before (see his entry), I plugged the output of the frequency counter to an ADC and fedback the signal to the end laser temperature via ezcaservo.
The peak height of the beat note is bigger than before due to the improvement of the PMC mode matching.
The peak height shown on the spectrum analyzer 8591E is now about -39dBm which is 9dB improvement.
The figure below is a spectra of the frequency counter's readout taken by the spectrum analyzer SR785.
When the slow temperature servo is locked, the noise around 20-30 mHz increased.
I think this is true, because I was able to see the peak slowly wobbling for a timescale of ~ 1min. when it's locked.
But this servo is still useful because it drifts by ~5MHz in ~10-20min without the servo.
Next time we will work on this slow servo using Aidan's PID control (see this entry) in order to optimize the performance.
In addition to that, I will take the same spectra by using the phase locked VCO, which provides cleaner signal.
(acquisition of the PLL)
In order to extract a frequency information more precisely than the frequency counter, we are going to employ 80MHz VCO box.
While the beat note was locked at ~ 79MHz by the slow servo, I successfully acquired the PLL to the beat signal.
However at the beginning, the PLL was easily broken by a sudden frequency step of about 5MHz/s (!!).
I turned off the low noise amplifier which currently drives the NPRO via a high-voltage amplifier, then the sudden frequency steps disappeared.
After this modification the PLL was able to keep tracking the beat signal for more than 5min.
(I was not patient enough, so I couldn't stand watching the signal more than 5min... I will hook this to an ADC)
I disconnected the yellow GPIB box from the backside of HP3563A (classic analyzer),
and connected it to AG4395A (network analyzer), which is the official place for it.
As I said in the past entry (see this entry), there was unknown loss of about 20dB in the beat detection path.
So I started fully characterizing the beat detection path.
Today I measured the frequency response of the wideband RFPD using the Jenne Laser.
Since all the data were taken by using a 1064nm laser, the absolute magnitudes [V/W] for 532nm are not calibrated yet.
I will calibrate the absolute values with a green laser which has a known power.
The data were taken by changing the bias voltage from -150V to 0V.
The shape of the transfer function looks quite similar to that Hartmut measured before (see the entry).
It has 100MHz bandwidth when the bias voltage is -150V, which is our normal operation point.
Theoretically the transfer function must keep flat at lower frequency down to DC.
Therefore for the calibration of this data, we can use the DC signal when a green beam with a known power is illuminating the PD.
As a part of the characterization works, I measured the spectra of the RFPD noise as well.
The noise is totally dominated by that of the RFPD (i.e. not by an RF amplifier).
I am going to check the noise curve by comparing with a LISO model (or a simple analytical model) in order to make sure the noise is reasonable.
The red curve represents the dark noise of the RFPD, which is amplified by a low noise amp, ZFL-1000LN.
The blue curve is a noise of only ZFL-1000LN with a 50 Ohm terminator at its input.
The last curve is noise of the network analyzer AG4395A itself.
It is clear that the noise is dominated by that of RFPD. It has a broad hill around 100MHz and a spike at 16MHz.
Gain of ZFL-1000LN = 25.5 dB (measured)
Applied voltage to ZFL-1000LN = +15.0 V
Bias voltage on PD = -150 V
We found that two of three PZT mirrors are at wrong place in the chambers.
Therefore we have to move these PZT mirrors together with their connections.
Here is a diagram for the current situation and the plan.
Basically mirror (A) must be associated to the output beam coming out from the SRM, but it was incorrectly put as a part of the input optics.
Similar to that, mirror (C) must belong to the input optics, but it is incorrectly being used as a part of OMC stuff.
Therefore we have to swap the positions of mirror (A) and mirror (C) as shown in the diagram above.
In addition to the mirror immigration, we also have to move their cables as well in order to keep the right functions.
We took a look at the length of the cables outside of the chambers in order to check if they are long enough or not.
And we found that the cables from c1asc (green line in the diagram) is not long enough, so we will put an extension D-sub cable.
I installed and activated Altium, a PCB design software, on the Windows machine M2.
With Altium I am going to design the triple resonant circuit for the broadband EOM.
[Joe, Suresh, Kiwamu]
We will fully install and run the new C1LSC front end machine tomorrow.
And finally it is going to take care of the IOO PZT mirrors as well as LSC codes.
During the in-vac work today, we tried to energize and adjust the PZT mirrors to their midpoints.
However it turned out that C1ASC, which controls the voltage applying on the PZT mirrors, were not running.
We tried rebooting C1ASC by keying the crate but it didn't come back.
The error message we got in telnet was :
memory init failure !!
We discussed how to control the PZT mirrors from point of view of both short term and long term operation.
We decided to quit using C1ASC and use new C1LSC instead.
A good thing of this action is that, this work will bring the CDS closer to the final configuration.
(things to do)
- move C1LSC to the proper rack (1X4).
- pull out the stuff associated with C1ASC from the 1Y3 rack.
- install an IO chasis to the 1Y3 rack.
- string a fiber from C1LSC to the IO chasis.
- timing cable (?)
- configure C1LSC for Gentoo
- run a simple model to check the health
- build a model for controlling the PZT mirrors
We tried installing C1LSC but it's not completely done yet due to the following issues.
(1) A PCIe optical fiber which is supposed to connect C1LSC and its IO chasis is broken at a high probability.
(2) Two DAC boards (blue and golden board) are missing.
We will ask the CDS people at Downs and take some more of those stuff from there.
( works we did )
- took the whole C1ASC crate out from the 1Y3 rack.
- installed an IO chasis to the place where C1ASC was.
- strung a timing optical fiber to the IO chasis.
- checked the functionality of the PICe optical fiber and found it doesn't work.
Fig.1 c1asc taken out from the rack Fig.2 IO chasis installed to the rack
Fig.3 PCIe extension fiber (red arrow for an obvious bended point)
I uploaded some pictures taken in the last and this week. They are on the Picasa web albums.
in vac work [Nov. 18 2010]
in vac work [Nov 23 2010]
CDS work [Nov 24 2010]
This morning I opened the chambers and started some in-vac works.
As explained in this entry, I swapped pzt mirror (A) and (C) successfully.
The chambers are still open, so don't be surprised.
(today's missions for IOO)
- cabling for the pzt mirrors
- energizing the pzt mirrors and slide them to their midpoint.
- locking and alignment of the MC
- realignment of the pzt mirrors and other optics.
- letting the beam go down to the arm cavity
As a result of the vacuum work, now the IR beam is hitting ETMX.
The spot of the transmitted beam from the cavity can be found at the end table by using an IR viewer.
Last night I found that the response of ITMX against the angle offsets were strage.
Eventually I found a loose connection at the feedthrough connectors of ITMX chamber.
So I pushed the connector hard, and then ITMX successfully became normal.
It looked like someone had accidentally kicked the cable during some works.
This bad connection had made unacceptable offsets in the OSEM readout, but now they seem fine.
We finished the installation of ETMX into the chamber.
In order to clear the issue of the side OSEM, we put a spacer such that the OSEM can tilt itself and accommodate the magnet.
Though we still don't fully understand why the side magnet is off from the center.
Anyway we are going to proceed with this ETMX and perform the REAL green locking.
(what we did)
- took the ETM tower out from the chamber, and brought it to the clean room again.
- checked the rotation of the ETM by using a microscope. It was pretty good.
The scribe lines at the both sides are at the same height within the diameter of the scribe line.
- checked the height of the ETM by measuring the vertical distance from the table top to the scribe line. This was also quite good.
The height is correctly 5.5 inch within the diameter of the scribe line.
- checked the magnet positions compared with the OSEM holder holes.
All the face magnets are a little bit off upward (approximately by 1mm or less).
The side magnet is off toward the AR surface by ~ 1-2mm.
(yesterday we thought it was off downward, but actually the height is good.)
- raised the position of the OSEM holder bar in order to correct the miscentering of the face magnets.
Now all the face magnets are well centered.
- brought the tower back to the chamber again
- installed the OSEMs
We put a folded piece of aluminum foil in between the hole and the side OSEM as a spacer.
- leveled the table and set the OSEMs to their mid positions.
- slided the tower to place
I succeeded in locking the end green laser to X arm with the new ETM.
Though the lock is still not so stable compared to the previous locking with the old ETM. Also the beam centering is quite bad now.
So I will keep working on the end green lock a little bit more.
Once the lock gets improved and becomes reasonably stiff, we will move onto the corner PLL experiment.
- beam centering on ITMX
- check the mode matching
- revise the control servo
[Suresh and Kiwamu]
We aligned the green beam to the X arm cavity more carefully.
Now the green beam is hitting the centers of ETMX, ITMX and BS.
Also we confirmed that the green beam successfully comes out from the chamber to the PSL table.
(what we did)
- opened the BS, ITMX and ETMX chambers.
- checked the positions of the beam spots on ITMX, BS and ETMX
The spot position on ETMX was fine,
But at BS and ITMX, the spots were off downward.
We decided to move the beam angle by touching a steering mirror at the end green setup.
- changed the beam axis by touching the steering mirror at the end station.
- checked the spot positions again, they all became good. It looks the errors were within ~ 1mm.
- moved the position of a TT, which is sitting behind the BS, by ~10mm, because it was almost clliping the beam.
- aligned the green optics
- got the beam coming out from the chamber.
[Joe and Kiwamu]
We added some more DAQ channels on c1sus.
We wanted to try diagonalizing the input matrices of the ITMX OSEMs because the motion of ITMX looked noisier than the others
So for this purpose we tried adding DAQ channels so that we can take spectra anytime.
After some debugging, now they are happily running.
(DAQ activation code)
There is a code which activates DAQ channels written by Yuta in this October.
If you just execute this code, it is supposed to activate the DAQ channels automatically by editing C1AAA.ini files.
However there were some small bugs in the code, so we fixed them.
Now the code seems fine.
(reboot fb DAQ process)
When new DAQ channels are added, one has to reboot the DAQ process running on fb.
To do this, log in to a certain port on fb,
telnet fb 8088
telnet fb 8088
Then the process will automatically recover by itself.
After doing the above reboo job, we found tpman on C1IOO got down.
We don't fully understand why only C1IOO was affected, but anyway rebooting of the c1ioo front end machine fixed the problem.
I moved the Pynds package from Yuta's local directory to the public place.
Now the package is living under :
Also I added the PATH on cshrc.40m, so you don't have to setenv every time.
(This package can not run on non-64bit linux)
Typing "import nds" on python allows you to use the nds functions.
Quote from Yuta's past entry
3. I installed pyNDS to /cvs/cds/caltech/users/yuta/pynds
I found that all the front end machine showed the red light indicators of DAQ on the XXX_GDS_TP.adl screens.
Also I could not get any data from both test points and DAQ channels.
First I tried fixing by telneting and rebooting fb, but it didn't help.
So I rebooted all the front end machines, and then everything became fine.
I am leaving ITMX and ETMX freely swinging, so that later I can take the spectra and diagonalize the input matrices.
Please don't restore the watchdogs until tomorrow morning.
The input matrix of ITMX has been diagonalized.
The evaluation of this diagonalisation will be done tonight by freely swinging ITMX again.
(Somehow I couldn't get any data for ETMX from the DAQ channels. I will try it again tonight.)
For solving the matrix, I used Yuta's python code called inmartixoptimizer.py.
I took the transfer functions of UL->UR, UL->LL and UL->LR as described in this entry.
In the measurement, the frequency bin was set to 0.001 Hz and the data were 50 times averaged on dtt.
Here is the new input matrix.
[[ 0.87059649 1.14491977 1.07992057 0.90456317]
[ 0.64313916 0.55555661 -1.44997325 -1.35133098]
[ 1.13979571 -1.19186285 -0.89606597 0.77227546]]
This matrix should give a better performance than before.
The oplevs have been installed on ITMX and ETMX.
Now the oplev servos are running.
The lock of the green beam became more stable after the oplevs were activated.
(what I did)
- opened the ITMX and ETMX chamber.
- rearranged the oplev mirrors in the vacuum chambers so that we can have the reflected oplev beam coming out from the viewport.
At the ITMX table, I put the oplev mirrors approximately on the designed places.
- aligned the beam on the optical benches
- strung a ribbon cable at the 1X9 rack.
This cable connects the oplev interface board and the ADC blue golden board.
- modified c1scx simulink model.
Since the model didn't have proper connections to the ADC channels, I added four ADC channels and plugged them into oplev servo in the model.
- relaunched the c1scx code after building and installing it.
- activated the oplev servos. Amazingly the default gains did work (i.e. all the gain = 1)
- after aligning X arm to the green beam, I did final centering of oplev beams
- - - - - ADC connection for ETMX oplev signals :
ADC0_24 = segment_1
ADC0_25 = segment_2
ADC0_26 = segment_3
ADC0_27 = segment_4
Tonight, swing again.
Please do not restore the watchdogs until tomorrow (Dec.9) morning.
[Koji, Osamu and Kiwamu]
We found that the ETMX free swinging spectra showed a strange resonant frequencies.
We are going to inspect the suspension today.
In a ideal case the SOS (Small Optic Suspension) is supposed to have the following resonant frequecies.
(Although we didn't carefully identify which corresponds to which)
f_POS ~ 0.98 Hz
f_PITCH ~ 0.66 Hz
f_YAW ~ 0.8 Hz
f_SIDE ~ 0.99 Hz
However ETMX showed the following resonant frequencies.
f_POS ~ 0.91 Hz
f_PITCH ~ 0.7 Hz
f_YAW ~ 0.93 Hz
f_SIDE ~ 1.0 Hz
Especially f_YAW looks pretty high. Also the others are not at the right frequencies.
So we are suspicious that something wrong is happening on the ETMX suspension.
We checked the ETMX suspension and found the UR OSEM was close to the magnet.
So we rotated the UR OSEM so that it won't touch the magnet any more.
We will check the resonant frequencies again by taking the spectra.
In fact the ETMX stacked when we applied a big angular offset to Yaw direction.
This was because that the magnet was actually touching the UR OSEM.
The earthquake stops were fine, they weren't touching the test mass.
Also we looked at the wire and the standoffs, they seemed fine.
We aligned the beam axis pointing down to both X and Y arm.
Now the beams are hitting the centers of both ETMX and ETMY.
Amazingly Osamu made X arm flashing by aligning the cavity.
- opened almost all the chambers except for the MC2 chamber.
- locked and aligned the MC.
We set Marconi to the right frequency, which had been set to the default values, probably due to the power outage in the last weekend.
Also we found a DAC cable disconnected from the IO chassis of c1sus. So we connected it in order to damp the MC suspensions.
- aligned MMT2 and PZT2 in order to let the beam go through the center of PRM.
- checked the beam centering at the two TTs (PR2, PR3).
- rotated PR3 to make the beam go through the centers of both ITMY and BS at the same time.
- tried finding the beam spot at the ETMY chamber, and successfully found it.
To see such faint beam spot, we used an IR viewer.
In addition to that, we put a large piece of aluminum foil as a screen in the chamber.
- aligned the beam to the center of ETMY by tweaking the PZT mirror (SM2).
- aligned the BS so that the reflected beam at the BS goes through the center of ITMX.
- tried finding the beam spot at the X end, and successfully found it hitting the wall in the chamber.
- aligned the BS in order to let the beam hit the center of ETMX.
- tried aligning ETMX and ITMX to the beam.
Eventually we made the X arm flashing.
However the flash was a bit too weak to completely align the cavity.
(plan for tomorrow)
- reinstall some steering mirrors into the BS chamber
- check and neutralize PZT1
- alignment of IP_ANG
[Jenne, Koji and Kiwamu]
We finished a coarse alignment of IP_ANG.
The beam for IP_ANG successfully reached to the ETMY chamber and is ready for the final alignment.
(Additionally we again tried looking for a resonance for TEM00 in the X arm, but we obtained only flashes of some higher order modes.)
--- what we did
* installed the steering mirrors for IP_ANG and IP_POS.
* checked PZT1 if it worked correctly or not. It was healthy.
* neutralized and realigned PZT1.
* flipped a window, which is standing before PRM, because the wedged side of the window was at wrong side.
* realigned PZT2 and checked the spot positions on the TTs.
* repositioned more carefully the TTs and aligned them to the correct angles.
* aligned the beam to the center of both the BS and ITMY by rotating the last TT.
* aligned the beam more precisely by tweaking PZT2 while looking at the spot at the Y end.
The beam is still hitting the center of ETMY.
* aligned the steering mirror for IP_ANG while looking at the spot at the Y end.
In fact IP_ANG is visible with a card.
* aligned the BS by looking at the spot on ITMX.
* covered ETMX with aluminum foil, and made a ~1cm hole on the foil as a target.
The hole was placed on the center of ETMX.
* more precisely aligned the BS by looking at the spot on the aluminum foil.
The spot was clearly visible on CCD monitor.
* aligned the ITMX by looking at a spot on the foil. The spot represented the beam reflected by ITMX back to ETMX.
* saw flashes on the foil but couldn't make it TEM00 because it was difficult to see any flashes on the surface of either ETMX or ITMX.
It means the flashes are visible only when the beam is hitting some scattering surface.
The mirror surface of the test masses are less lossy than that of the old test masses ??
I found that a few connections in the simulink model of c1scx was incorrect, so I fixed them correctly.
It had been a mystery why we had to put a funny matrix on ETMX (see this entry).
But now we don't have to do such a voodoo magic because the problem was solved.
Now the damping of ETMX is happily running with an ordinary output matrix.
I looked at the wiring diagram of the ETMX suspension (it's on Ben's web page) and confirmed that the coils are arranged in order of UL, LL, UR, LR.
But then I realized that in our simulink model they had been arranged in order of UL, UR, LL, LR.
So UR and LL had been swapped incorrectly !
So I just disconnected and plugged them into the right outputs in the simulink model.
I rebooted c1iscex in order to reactivate c1scx front end code.
After rebooting it, I changed the output matrix to the usual one, then everything looked okay.
(actually it's been okay because of the combination of the wrong connections and the funny matrix).
The alignment of the ITMs and the PRM has been done.
As a result their reflections now come out at the REFL port successfully.
The vacuum work is going on well as we scheduled at the last meeting.
(plan for tomorrow)
- installation of ETMY
- installation of OSEMs on ETMY
- alignment of the beam to the center of ETMY
- alignment of the ETMY to the beam
- final alignment of IP_ANG
- setting up the oplev for ETMY
- replace one of the steering mirrors at the RFEL path by a 0 deg mirror (see here).
- setting up POX/POY (if there are time)
- aligned the PRM tower such that the reflected beam goes back to exactly the same path as that of the incoming beam.
- leveled the ITMY table because the OSEMs of ITMY had been completely out of range.
- aligned the ITMY and ITMX in order to let the reflections back to REFL.
- with a help from Osamu, we put a CCD camera, which actually had been used as OMC_T, just after the view port on the AP table.
- looking at the CCD monitor we were able to see the reflected lights from the ITMs. (In fact sensor cards didn't help looking for the lights.)
- playing with the alignment of the ITMs, we easily obtained Michelson fringes, which were also visible on the CCD monitor.
[Zach and Kiwamu]
We installed the new ETMY tower and successfully aligned the beam to the center of ETMY.
Also we finished the final alignment of IP_ANG.
(what we did)
- took the old ETM out from the chamber and put it on the flow bench at the X end.
- with a help from Joe and Osamu, we brought the new ETM and put it roughly on place.
- did a fine positioning of ETMY.
- covered the ETM tower with a large peace of aluminum foil in order to see the spot on a video monitor.
- stoled a compact video monitor that was sitting on the PSL table since we don't have any monitors at the Y end.
- made a ~1cm hole on the foil as a target for the beam.
- steered PZT1 in order to correct the beam position on ETMY. This is done by looking at the spot on the video monitor.
- steered IPANG_SM1 to let the beam hit a steering mirror in the ETMY chamber which Koji installed recently.
Now we have IP_ANG coming out from the viewport of the ETMY chamber.
[Koji, Oasmu and Kiwamu]
We made the following progresses :
(1) installation of the last TT called SR2.
(2) fixing an earthquake stop issue on the BS
(3) fixing a clipping of beams at the dark port
(earthquake stops on the BS)
- When we were aligning the BS, we found that the BS showed funny behaviors.
For example a kick on LR didn't shake LRSEN, and a big DC angular offset (~ 8 in the medm screen ) was needed to keep a horizontal beam axis in the reflection.
We checked all the earthquake stops and found two suspicious earthquake stops at right bottom side.
They looked like slightly touching the BS. So we moved them further away from the BS.
Then the problem had gone. We doublechecked the health by kicking, applying an angular offset and so on.
We found transmitted/reflected beams from the BS to the dark port was clipped at the BS tower.
We moved the BS tower by ~1cm and realigned the rotation of the BS tower.
We also found the beam spots on the two TTs, PR2 and PR3, were offcentered. Especially the beam spot on PR3 was almost on the edge of the mirror.
Probably this was because we touched PZT1 when aligning the beam to the Y end.
So it means, it is not a good idea to align the beam to the end only by steering PZT1. We should use PR2 and PR3 as well when we align the beam to the Y end.
We realigned them such that the beam hits the center of PR2, PR3 and ETMY.
We worked on some more vacuum businesses. Today we finished did the following works:
- alignment of the POX mirrors
- alignment of the POP1 and POP2 mirrors
- installation of OSEMs onto SRM
- alignment of the SRM tower
(alignment of POP mirrors)
Since a beam on the POP path was quite too weak to see even by IR viewers, we used a He-Ne laser to imitate the real beam instead.
We injected the He-Ne beam from an optical bench to the chamber, and made it go through the PRM and PR2 by using some steering mirrors.
The pin assignment was flipped in a way of mirror image due to the extension cables which cause a mirroring.
So we made mirroring connectors to flipp them back to the correct pin assignment, and plugged the mirroring connectors in between the feedthrough of the BS chamber and the SRM satellite box.
This is a picture showing how they are connected now.
I made some efforts in order to damp ETMY, however it still doesn't happily work.
It looks like something wrong is going on around the whitening filters and the AA filter borad.
I will briefly check those analog parts tomorrow morning.
- - -(symptom)
Signs of the UL and the SD readouts are flipped, which I don't know why.
At the testpoints on the analog PD interface board, all the signs are the same. This is good.
But after the signals go through the whitening filters and AA filters, UL and SD become sign-flipped.
I tried compensating the sign-flips by changing the sign by means of the software, but it didn't help the damping.
In fact the suspension got crazy when I activated the damping. So I have no idea if we are looking at exactly right readouts or some sort of different signals.
- - -(fixing DAC connector)
I fixed a connector of the DAC ribbon cable since the solderless connector was loosely locked to its cable.
Before fixing this connector I couldn't apply voltages on some of the coils but now it is working well.
[Koji and Kiwamu]
We did some more vacuum works today. It is getting ready to pump down.
(what we did)
- alignment of the POY mirrors. Now the beam is coming out from the ITMY chamber successfully
- leveling of the tables (except for the IOO and OMC chamber)
- realigned the beam axis down to the Y arm because the leveling of the BS table changed the alignments.
- installed IP_POS mirrors
- aligned the green beam and made it overlap with IR beam path.
- repositioned green steering mirrors since one of them are too close to the dark beam path
Last Saturday I succeeded in damping the ETMY suspension eventually.
This means now ALL the suspensions are happily damped.
It looked like some combination of gains and control filters had made unstabie conditions.
I actually was playing with the on/off switches of the control filters and the gain values just for fun.
Then finally I found it worked when the chebyshev filters were off. This is the same situation as Yuta told me about two months before.
Other things like the input and the output matrix looked nothing is wrong, except for the sign flips at ULSEN and SDSEN as I mentioned in the last entry (see here).
So we still should take a look at the analog filters in order to make sure why the signs are flipped.
[Jenne and Kiwamu]
At first we prepared the following stuff:
* isopropyl alcohol
* lens papers
* cleaned scissors
Then we cut the lens papers into the half by the scissors such that the long side can remain.
This is because that the SOSs have relatively narrow spaces at their optic surfaces for putting a piece of paper.
We did vertical and horizontal wiping using the lens paper and appropriate amount of isopropyl alcohol.
Each wiping (vertical and horizontal) requires two or three times trials to appropriately remove dusts.
Amount of isopropyl:
* vertical 15 [ul]
* horizontal 10 [ul]
In addition to this, we also used the ionizer gun for blowing big dusts and fiber away from the surface.
Before wiping them, all the test masses had small dusts uniformly distributed on the HR surfaces.
Especially ETMX was quite dirty, many small spots (dusts) were found when we shined the surface with the fiber illuminator.
ETMY was not so bad, only a couple of small dusts were at around the center. ITMX/Y had several dusts, they were not as dirty as ETMX, but not cleaner than ETMY.
After we wiped them, we confirmed no obvious dusts were around the centers of the optics. They looked pretty good !
I stopped the pumping at 9:30 pm. Now we are at 29 torr.
How to stop pumping:
1, close RV1 manual valve with torque wheel
2, close V3
3, turn off roughing pumps RP1 & RP3
4, disconnect metal hose connection to butterfly valve
I gave a christmas present to a doubling oven who has been sitting on the PSL table.
The below is a picture of the present I gave. It's a base plate for the doubling oven, made from a block of aluminum, and black-anodized.
The size and the shape are nicely tailored for the combination of the Newfocus kinematic mount and the Covesion oven.
The design had been done by using Solid Works 2010
Here is a picture before he got the present.
Now he looks pretty happy.
Found exactly the same error messages at the end of the log file.
This was the error today:
GET /40m/ HTTP/1.1
User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:126.96.36.199) Gecko/20100401 Firefox/3.6.3
Cookie: elmode=threaded; __utma=65601905.411937803.1291369887.1291369887.1291369887.1; __utmz=65601905.1291369887.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); SITESERVER=ID=4981c5fd42ae53c9c9e0980f2072be4f
I replaced the final steering mirror (Y1-1037-45-S) in the zig-zag path on the PSL table by a 0 deg mirror Y1-1037-0.
With a sensor card I confirmed the transmission reduced a lot after the replacement.
As we expected, the replacement of the mirror caused a mis-alignment of the incident beam axis to the MC, so I compensated it by touching the angle of the mirror a little bit.
After the alignment of the mirror, the MC is still resonating at TEM00.
We will check the spot positions more accurately by A2L technique.
- Y1-45S has 4% of transmission. Definitively we like to use Y1-0 or anything else. There must be the replaced mirror.
I think Suresh replaced it. So he must remember wher it is.