Solid works 2010 was installed to m3, an windows machine in the control room.
Have fun !
I improved the mode matching of the incident beam to the doubling crystal on the PSL table.
As a result it apparently got better (i.e. brighter green beam), but it's not the best because now the beam is a little too tightly focused on the crystal.
I am going to work on it again someday after seeing the beat note signal.
- The measured waist sizes are
41.94 [um] for vertical mode
42.20 [um] for horizontal mode
while the optimum waist size is 50 um (see entry #3330).
The plot below shows the beam scan data which I took after improving the mode match.
[ Kevin and Kiwamu ]
We made the setup for the green PLL stuff on the PSL table.
Now the two green beams are happily going to the RFPD.
Tomorrow we try to catch the beat note signal
- - - what we did
* took the two light doors out from the OMC and the MC chamber in order to let the green light go through there.
* using aluminum foils we covered the space between the OMC and the MC chamber in order to protect from dust
* aligned the steering mirrors inside of the chamber because the height of the green light coming out from the chamber had been a little bit low at the PSL table.
* at the PSL table we put several steering mirrors and a beam splitter which combines the two green lights
* installed Hartmut's RFPD and applied -150V bias on it.
* put a lens on each path of the green beam in order to make the beam size approximately the same at the RFPD
* closed the light doors
- - - Notes
* At the beginning, an output signal from the RFPD was pretty small ( less than 1mV at DC ), so I replaced a feedback resistor that was 241 Ohm by 24 kOhm.
As a result the signal became about 10mV when the green lights go into the PD.
* Actually the power of the green beams are so weak.
I measured them by using a Newport power meter, it said something like 4 uW for both of the green lights.
One of the reasons is that the transmitted light from the PMC which generates one of the green lights is already weak. It's about 480 mW ( while more than 600 mW was reflected by the PMC ! ).
I am going to make sure if these numbers are reasonable or not.
The NPRO at the PSL table still can generate 2W laser ! He is still alive.
When I reduced the temperature to 25 deg, the output power increased to 2W successfully.
As Steve wrote down in his last entry (see here), the NPRO output was at 1.6 W currently, which is supposed to be 2W.
We were suspicious about the laser crystal's temperature because the current temperature looks a bit high.
In fact the setpoint of the temperature was 45.9 deg instead of 25 deg that is the previous setpoint.
It turned out that the DC alignment of MC2 from epics doesn't helathily work.
For example, the pitch slider does drive the yaw alignment as well.
Is this somehow related to the unknown MC2 jump happened around September 10th ?? (see the trend below)
I made some KAIZENs (what does kaizen mean ? ) for the PSL green setup.
I replaced the lenses for the modematching of the two green lights at the PSL table, and the beams now look pretty identical.
Also I tuned the temperature setpoint of the doubling crystal and eventually the green light increased to 14 uW at the PSL table.
Once I finish the modification of the RFPD tomorrow, I am going to search for the beat note signal.
( details )
- In-vac green mirrors
I found one of the green steering mirror, which stands at the corner of the MC table, was clipping the green light.
So I steered another mirror, which sends the beam to the clipping mirror after the downward periscope.
I touched also the last steering mirror in the OMC chamber to correct the alignment.
- temperature of the doubling crystal
I took a quick temperature scan in order to find an optimum point for the crystal temperature.
The scan was performed by just turning the heater off after I heated up the crystal up to 40 deg.
Using the NewPort power meter I found the optimum point around 37.3 deg. So I set the temperature to that point.
- mode matching lenses
As written in this entry , Kevin and I had put some lenses to make the two green beam almost the same size at the RFPD.
But today while I was checking these mode-profiles by using a sensor card, I found they were not so matched.
Therefore I replaced these lenses to match them more.
The idea of this replacement is t to let them have a long Rayleigh range, such that they can efficiently and easily interfere because of the flatness of their wave fronts along a distant.
For the green light from the chamber, I put one more lens to form a Keplerian beam shrinker (see here about the Keplerian lens configuration).
They look pretty identical now.
[Yuta, Suresh, Rana and Kiwamu]
The DC alignment problem of MC2 was fixed.
There were some loosely connected cables on the backside of a VME rack which contains the MC2 SOS driver.
We pushed those connectors to make them tightly connected. And then the problem disappeared.
(voltage unbalance on coils)
Before fixing it Yuta opened the satellite box and measured the voltage across the coils using a voltmeter.
At that time UL and LR showed 20 times smaller voltages than that of the other two when we moved the DC alignment slider from min. to max. on the medm screen.
This behavior is exactly consistent with the wired motion of a beam spot which we saw when we were aligning MC2.
(diagnostic using optical lever)
After pushing the connectors, we made an optical lever using a red laser pointer in order to check the actual motion of MC2.
We confirmed that MC2 respond correctly to the alignment slider.
It turned out that the DC alignment of MC2 from epics doesn't helathily work.
For example, the pitch slider does drive the yaw alignment as well.
Still I didn't see any beat note signals..
With a help from Suresh, Yuta and Rana, I tried searching for the green beat note by changing the temperature of the X end NPRO.
The noise level after it goes through an RF amplifier (G=23dB) was about -70dBm at 50MHz.
This noise may cover the beat note signal.
I am going to post some details later.
Last night I tried searching for a beat note signal with two different PD trans impedance gains.
Although I didn't find a beat note signal.
- (1. trans impedance gain = 2400)
I started with a trans impedance resistance of R=2.4k, which is 10 times bigger resistance than the original.
The total PD gain should be about 960 [V/W] theoretically if we assume the responsibility of the PD is 0.4 [A/W].
Then I checked the bandwidth of the RFPD using Jenne laser.
The bandwidth was about 30MHz, which is 3 times narrower than the original. And it agrees with our expectation.
As Koji and I mentioned at the last weekly meeting, the cut off frequency of an RFPD follows inverse square root of the trans impedance resistance R.
where C is a capacitance of the photo diode. (See this)
I was expecting the signal level of -50 dBm / rtHz with a 23dB RF amplifier, assuming the line width of the signal is 10kHz.
- (2. trans impedance gain = 240)
I also tried it with the original trans impedance gain (see this entry).
R = 240 [Ohm]
G = 96 [V/W]
BW = 100 [MHz] (I didn't measure it in this time)
expected signal level = -70 dBm/rtHz
finally we found it !
(notes on signal level)
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.
The expectation was calculated by using the following simple math.
SIGNAL = A x Z x G_RF x sqrt(P1 / 2) x sqrt (P2 / 2)
where A is the responsibility of the PD and Z is the trans impedance gain. G_RF is a gain of the RF amplifier.
The laser powers of green beams, P1 and P2, are divided by 2 due to a beam splitter.
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
(Rana, Koji, Suresh, Yuta, Thanh, Kiwamu)
MC was locked successfully !
Instead of feeding back the signal to the MC length we just injected it to the NPRO pzt with a high voltage (HV) amplifier.
So now we can move on to an in-vac work which needs the main beam to align the stuff.
(mode matching to MC)
Suresh and Thanh (a visitor from ANU) improved the mode matching to the MC.
As written in the entry #3779 the beam after the mode matching lenses were diverging.
It is supposed to converge from 1.7mm radius at the last lens to 1.6 mm radius at the middle point of MC1 and MC2.
They slided the last lens toward the MC to make it more collimated and roughly measured the beam size using a sensor card.
As a fine tuning, they looked at some higher order modes showing up in the MC2 camera, and tried reducing the higher order modes by slightly sliding the last lens.
(assuming the lens position doesn't so much change the alignment)
During the work we removed a steering mirror for green locking because it was on the way of the lens slider.
- - measured optics' distances - -
25.5 cm from 1st lens to the front surface of the EOM
5.5 cm length of the EOM
24.5 cm from the front surface of the EOM to the 2nd lens (concave)
15.5 cm from the 2nd lens to the 1st steering mirror in the zig-zag path
20.5 cm from the steering mirror to the last lens
(preparation for locking)
Rana, Yuta and Koji prepared an old instant amplifier which can produce +/-13V output instead of usual SR560s.
We added an offset (~5V) on the signal to make it within 0-10V which is the input range of the HV amplifier.
If we take SR560, it's probably not sufficiently wide range because they can handle handle only about +/-4V.
We strung a cable from Marconi via the RF stabilizer to the wideband EOM in order to drive the EOM at 24.5MHz.
SInce the EOM doesn't have 50 Ohm input impedance we had to put a 50 Ohm load just before the EOM in order to drive it efficiently.
From a medm screen we set the driving RF amplitude slider (C1:IOO_MCRF_AMPADJ) to 0.0, which provides the maximum RF power on it.
(locking mode cleaner)
At first we unlocked the PMC to see an offset in the error signal without any lights on the MC_REFL PD.
Then we adjusted the offset to zero on the MC servo screen.
At the beginning of the locking the PMC was not stable for some reasons during the MC was locked.
But after increasing the laser power to the MC twice bigger, it looks like the PMC and the MC are quite stable.
I did a health check for a 80MHz VCO box.
I started taking care with the black VCO box, which has been sitting on the SP table and will be used for converting the green beat signal from frequency to voltage.
The circuit in the box basically consists of three parts: low pass filters (LPFs), a VCO and RF amplifiers.
Today I checked the LPF stage. It looks pretty healthy.
Tomorrow I will check the VCO part, especially I am curious about the VCO range.
Since somebody ( surf students ?) removed some resistors, the VCO was just freely running without being applied any voltage.
I put some resistors back on the circuit board by soldering them.
Now the resistors are placed in the same configuration as the original schematic (link to LIGO DCC) except for the wideband signal path, which has a differential input.
I left the wideband path disconnected from the VCO.
(transfer function measurement)
The LPF part in 'external mod' path contains two stages in series:
one is for cutting off demodulated signals above fc=80MHz and the other one is for PLL servo with pole=1Hz, zero=40Hz.
In order to activate this path I shorted 10th pin of the analog switch: MAX333A.
During the transfer function measurement I injected signals to 'external mod' input and took the output signal from a test point pin TP7.
The plot below shows a fitting result of the measured transfer function of the whole LPF stage. I used liso for the fitting.
The measured filter's shape agreed with the design. (though I haven't checked 80MHz cut off)
At the PSL table I aligned the wideband EOM more carefully.
Amplitude modulation (AM) components in the main beam at 29.5MHz were successfully diminished by 24 dB.
Last night when we were locking the MC, we noticed that the reflected light had AM which somewhat disturbes the Pound-Drever-Hall locking of the MC.
So I aligned the wideband EOM to reduce the AM components.
In order to observe AMs I put a photodiode PDA255 whose bandwidth is 50MHz after the wideband EOM.
Before the PD I also put a convex lens together with a stack of ND filters and put a steering mirror to control the beam spot on the PD.
First I aligned the EOM such that the DC voltage from the PD was maximized. This process corresponds to a coarse alignment.
And then I tried reducing a peak at 29.5MHz seen in the spectrum analyzer.
At the beginning the AM peak in the spectrum analyzer was at about -48 dBm.
After the alignment of the EOM it went down below the PD's dark noise floor of -72 dBm.
I checked the alignment also with an IR viewer, it looks quite good.
I calibrated the VCO frequency as a function of the applied input voltage.
The range is approximately +/- 5 MHz, which is large enough to cover the arm's FSR of 3.75MHz.
======== measured parameters ======
center frequency: 79.5 MHz
VCO range: 74MHz - 84MHz
coefficient : 1.22MHz/ V (+/- 2V range)
nominal RF power: -0.66 dBm
(Note: The measurement was done by using Giga-tronics hand-hold power meter.)
P.S. There is a document about the 80MHz VCO box. This may be helpful.
link to LIGO DCC
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.