We've run into a problem with our attempts to get the LCS control back up and running.
As reported previously, the Dolphin fiber connection between c1lsc and c1sus appears to be dead. Since we have no replacement fiber, the solution was to move the c1lsc machine in to the 1X4 rack, which would allow us to use one of the many available short Dolphin cables, and then use a long fiber PCIe extension cable to connect c1lsc to it's IO chassis. However, the long PCIe extension cable we got from Downs does not appear to be working with our setup. We tested the cable with c1sus, and it does not seem to work.
We've run out of options today. Tomorrow we're going to head back to Downs to see if we can find a cable that at least works with the test-stand setup they have there.
The bad Dolphin was still bad when tested with a connection between c1sus and the Dolphin swtich.
I'm headed over to Downs to see if we can resolve the issue with the PCIe extension fiber.
After moving the c1lsc computer to 1X4, then connecting c1lsc to it's IO chassis in 1Y3 by a fiber PCIe extension cable, everything is back up and running and the status screen is all green. c1lsc is now directly connected to c1sus via a short copper Dolphin cable.
After lunch we will do some more extensive testing of the system to make sure everything is working as expected.
The PMC trans power was a little low (0.77V or so). I tweaked up the input pointing and now we're getting about 0.875V transmitted.
We are now locking the arms reliably, with reasonable transmitted power. We zeroed the LSC offsets with script, since they were apparently not being reset with either the overall burt restore or the arm restore scripts.
We have lost a bit of power through the mode cleaner. However, we have opted not to tweak it up just yet, so that we don't have to realign to the arms.
The WFS2 sensor head had a damaged Quadrant PIN diode (YAG-444-4A). This has been replaced by a YAG-444-4AH which has a responsivity of 0.5 A/W.
The responsivity of each quadrant was measured at normal incidence. A diagram of the set up with the relevant power levels is attached. The precision of these measurement is about 5% . Largely because the power levels measured are sensitive to the position of the laser beam on the power meter sensor head (Ophir with ND filter mask taken off). Putting the mask back on did not solve this problem.
The incident power was 0.491mW of which about 0.026mW was reflected from the face of the QPD. The beam was repositioned on the QPD to measure the response of each quadrant. In each case the beam was positioned to obtain maximum DC output voltage from the relevant quadrant. A small amount of spill over was seen in the other quadrants. The measurements are given below
To measure these DC outputs of from the sensor-head a breakout board for the 25-pin D-type connector was used as in the previous measurements. The results are given below
WFS2 Quantum Efficiency measurement
The measured responsivity agrees with the specification from the manufacturer. It is to be noted that the previous QPD is reported to have a slightly smaller responsivity 0.4 A/W at 1064 nm. The data sheet is attached.
Since the new QPD may have a slightly different capacitance the RF transfer function of the WFS2 needs to be examined to verify the location of the resonances.
[Larisa and Jenne]
A few weeks ago (on the 28th of January) I had tried to measure the quantum efficiency of one quadrant of the WFS as a function of angle. However, Rana pointed out that I was a spaz, and had forgotten to put a lens in front of the laser. Why I forgot when doing the measurement as a function of angle, but I had remembered while doing it at normal incidence for all of the quadrants, who knows?
Anyhow, Larisa measured the quantum efficiency today. She used WFS2, quadrant 1 (totally oil-free), since that was easier than WFS1. She also used the Jenne Laser (with a lens), since it's more stable and less crappy than the CrystaLasers. We put a 50 Ohm terminator on the RF input of the Jenne Laser, since we weren't doing a swept sine measurement. Again, the Ophir power meter was used to measure the power incident on the diode, and the reflected power, and the difference between them was used as the power absorbed by the diode for the quantum efficiency measurement. A voltmeter was used to measure the output of the diode, and then converted to current as in the quote below.
Still on the to-do list: Replace the WFS2 diode. See if we have one around, otherwise order one. Align beams onto WFS so we can turn on the servo.
QE = (h*c)/(lambda*e) * (I/P)
Where I = (Volts from Pin1 to GND)/2 /500ohms
P = Power from laser - power reflected from diode.
h, c, e are the natural constants, and lambda is 1064nm.
Also, I/P = Responsivity
Larissa is going to put her data and plots into the elog shortly....
Quantum Efficiency Measurement:
I refer to Jamie's LHO elog for the equation governing quantum efficiency of photodiodes: LHO 2 Sept 2009
The information I gathered for each quadrant of each WFS was:  Power of light incident on PD (measured with the Ophir power meter),  Power of light reflected off the PD (since this light doesn't get absorbed, it's not part of the QE), and  the photo current output by the PD (To get this, I measured the voltage out of the DC path that is meant to go to EPICS, and backed out what the current is, based on the schematic, attached).
I found a nifty 25 pin Dsub breakout board, that you can put in like a cable extension, and you can use clip doodles to look at any of the pins on the cable. Since this was a PD activity, and I didn't want to die from the 100V bias, I covered all of the pins I wasn't going to use with electrical tape. After turning down the 100V Kepco that supplies the WFS bias, I stuck the breakout board in the WFS. Since I was able to measure the voltage at the output of the DC path, if you look at the schematic, I needed to divide this by 2 (to undo the 2nd op amp's gain of 2), and then convert to current using the 499 Ohm resistor, R66 in the 1st DC path.
I did all 4 quadrants of WFS1 using a 532nm laser pointer, just to make sure that I had my measurement procedure under control, since silicon PDs are nice and sensitive to green. I got an average QE of ~65% for green, which is not too far off the spec of 70% that Suresh found.
I then did all 8 WFS quadrants using the 1064nm CrystaLaser #2, and got an average QE of ~62% for 1064 (58% if I exclude 2 of the quadrants....see below). Statistics, and whatever else is needed can wait for tomorrow.
Problem with 2 quadrants of WFS2?
While doing all of this, I noticed that quadrants 3 and 4 of WFS2 seem to be different than all the rest. You can see this on the MEDM screens in that all 6 other quadrants, when there is no light, read about -0.2, whereas the 2 funny quadrants read positive values. This might be okay, because they both respond to light, in some kind of proportion to the amount of light on them. I ended up getting QE of ~72% for both of these quadrants, which doesn't make a whole lot of sense since the spec for green is 70%, and silicon is supposed to be less good for infrared than green. Anyhow, we'll have to meditate on this. We should also see if we have a trend, to check how long they have been funny.
I would like to announce my confusion with regard to the MICH noise budget, in hopes that someone else has some inspiration.
If you tilt your head sideways, you will notice that in this plot (totally uncalibrated, as yet), the BLACK trace, which is my white-light measurement of the AS55 shot noise is above the AS55Q noise when the Michelson is locked (true only at low frequency). You will also notice that the same appears to be true for the Whitening Filter + Antialiasing Filter + ADC noise (GRAY trace). Since Black, Gray, Pink and Green should all have the same calibration factor (a constant), calibrating the plot will not change this. Brown and Blue are the MICH_OUT (aka MICH_CTRL) for dark and bright fringes, respectively.
I measure 58mV at the DC out of the AS55 PD when the Michelson is locked on the bright fringe. This (assuming DC transimpedance of 50ohms) gives 1.16mA of DC photo current.
So. What is going on here? Am I totally confused??
In other news, assuming (which I'm not 100% confident about right now) that these traces are vaguely correct, the Michelson is limited by shot noise above ~20Hz. This is...good? We want to be shot noise limited. Do we want to be limited at such a low frequency?
(Also, yes I can calibrate the plot to m/rtHz, but no, I won't tonight because something is funny with my calibration for the free running noise and I'll fix it tomorrow.)
Hey, Jenne. I think there are a couple of things. First, you're missing a PD dark noise measurement, which would be useful to see.
But I think the main issue is that it sounds like all of your closed loop measurements are done with the in-loop PD. This means that everything will be suppressed by the loop gain, which will make things look like they have a noise lower than the actual noise floor.
[Jenne / Kiwamu]
We spent approximately an hour for the weekly Wednesday cleaning.
This time we moved onto an area where a desk and optics shelf reside along the Y arm.
We will continue cleaning up there in the next time too.
After talking with Steve, I had a look at the PEM's AA board, to see what the problem was.
Steve said the symptom he had noticed was that the Kepco power supplies which supply the +\- 5 V to the AA board were railing at their current limits as soon as he plugged the board in. Also, he smelled smoke.
I started with the power supplies, and saw that the 2 individual supplies each had a dV=5V, and that the one labeled +5V had the red wire on the + output of the power supply, and the black wire on the - output. The supply labeled -5V had the orange wire on the -output of the power suppy, and the black wire on the + output. Normally, you would expect that the 2 black wires are also connected together, and perhaps also to ground. But at least together, so that they share a common voltage, and you get +\- 5V. However these 2 power supplies are not connected together at all.
This implies that the connection must be made on the AA boards, which I found to be true. It seems a little weird to me to have that common ground set at the board, and not at the power supplies, but whatever. That's how it is.
The problem I found is this: The keyed connectors were made backward, so that if you put them in "correctly" according to the key, you end up shorting the +5V to the -5V, and the 2 black wires are not connected together. You have to put the keyed connectors in *backwards* in order to get the correct wires to the correct pins on the board. See the attached pdf figure.
Since these are internal board connections, and they should not ever be changed now that Steve has put in the adapter thing for the SCSI cable, I'm just leaving them as-is. Steve is going to write in huge letters in sharpie on the board how they're meant to be connected, although since this problem wasn't caught for many many years, maybe it won't ever be an issue again. Also, we're going to move over to the new Cymac system soon-ish. However, whomever made the power cable connector from the box to the board for this AA board was lazy and dumb.
After putting the connectors on the way they needed to be, Steve and I powered up the board, hooked up the SCSI cable in the back, and put a constant voltage (~1.3VDC battery) across various different channels, and confirmed that we could see this voltage offset in Dataviewer. (Kiwamu is hoarding both of our SRS function generators, so we couldn't put in a low freq sine wave like I normally would). Everything looked okie dokie, so I'll check the regular PEM channels tomorrow.
Steve will re-install the board in the rack in the morning.
As seen in the photo, the board has a strange bulge on the board,
and the color of the internal line around the bulge got darkened.
I don't trust this board any more. We should switch to the alternative one.
- I was investigating the SUS whitening issue.
- I could not find any suspension which can handle the input whitening switch correctly.
- I went to 1X5 rack and found that both of the two binary output boxes were turned off.
As far as I know they are pulling up the lines which are switched by the open collector outputs.
- I tried to turn on the switch. Immediately I noticed the power lamps did not work. So I need an isolated setup to investigate the situation.
- The cables are labelled. I will ask steve to remove the boxes from the rack.
- I went to 1X5 rack and found that both of the two binary output boxes were turned off.
As far as I know they are pulling up the lines which are switched by the open collector outputs.
I shut down damping to the Vertex optics and removed Binary IO Adapter chassy BO0 and BO1
About a week ago I discussed the BO0's power indicator lights with Kiwamu. They were not on or they were blinking on-off.
I put screws into ps connectors in the back, but it did not helped.
- We found the reason why some of the LEDs had no light. It was because the LEDs were blown as they were directly connected to the power supply.
The LEDs are presumably designed to be connected to a 5V supply (with internal current-limiting resistor of ~500Ohm). The too much current
with the 15V (~30mA) made the LED blown, or the life-time of them shorter.
- Jamie removed all of the BO modules and I put 800Ohm additional resister such that the resultant current is to be 12mA.
The LEDs were tested and are fine now.
- The four BO boxes for C1SUS were restored on the rack. I personally got confused what should be connected where
even though I had labeled for BO0 and BO1. I just have connected CH1-16 for BO0. The power supplies have been connected only to BO0 and BO1.
- I tested the whitening of PRM UL sensor by exciting PRM UL sensor. The transfer function told us that the pendulum response can be seen
up to 10-15Hz. When the whitening is on, I could see the change of the transfer function in that freq band. This is good.
So the main reason why I could not see theis was that the power supply for the BOs were not turned on.
- I suppose Jamie/Joe will restore all of the BO boxes on the racks tomorrow. I am going to make a test script for checking the PD whitenings.
ITMY sus damping restored.
[Suresh / Kiwamu]
We did the following things :
- Took the LightWave NPRO out from the MOPA box
- Temporarily took out the laser controller which has been connected to the Y end laser.
- Put the LightWave on AP table and plugged the laser controller and confirmed that it still emits a beam
[Things to be done]
- measure the beam profiles and power
- get a laser controller, which will be dedicated for this laser, from Peter King
[Background and Motivation]
The PRC and SRC length have to be precisely measured before the vent.
In order to measure those absolute length we are going to use the Stochino technique, which requires another laser to scan the cavity profiles.
The LightWave NPRO laser in the MOPA box was chosen for the Stochino laser because it has a large PZT range of 5 MHz/V and hence allows us to measure a wider frequency range.
The laser in the MOPA box had been connected to home-made circuits, which are not handy to play with. So we decided to use the laser with the usual laser controller.
Peter King said he has a LightWave laser controller and he can hand it to us.
Until we get the controller from him we do some preparations with temporary use of the Y end laser controller.
I have installed a new binary output module in ETMY, where there was none previously. It is installed, powered (with working LEDs), hooked up (to the binary output card and the cross connect), but it hasn't been fully tested yet.
I also re-installed the binary output module in ETMX, with newly modified power-indicator LEDs.
Both modules are fully installed, but they have not yet been fully tested to confirm that they are indeed switching the whitening and de-whitening filters.
Some updates of the LSC screen
- Signal amplitude monitor for the PD signals (--> glows red for more than 1000)
- Kissel Buttons for the main matrices
- Trigger display at the output of the DOF filters
- Signal amplitude monitor for the SUS LSC output (--> glows red for more than 10000)
ADC Over flow monitor is showing some unknown numbers (as ADCs are handled by IOPs).
I asked Joe for the investigation (and consideration for the policies)
ETMX sus damping restored
In order to install the BO module in 1X2, I need to shut down all DC power to the 1X1 and 1X2 racks.
All power has been restored to the 1X1 and 1X2 racks. The modecleaner is locked again.
I have also hooked up the binary output module in 1X2, which was never actually powered. This controls the whitening filters for MC WFS. Still needs to be tested.
Here is my work plan for this week:
1) Help Steve clean small table for experiment
2) Remove aluminum base from TT suspension
3) Mount shaker onto table base
4) Mount horizontal slider onto table base
5) Connect TT suspension, shaker, and horizontal slider
1) Begin building circuit for displacement photosensors
2) Calibrate photosensor using linear regions of power versus distance curves
3) Circuit box for photosensors?
The I-P curve of the LightWave NPRO (M126-1064-700), which was taken out from the MOPA box, was measured. It looks healthy.
The output power can go up to about 1 W, but I guess we don't want it to run at a high power to avoid any further degradation since the laser is old.
X-axis is the current read from the display of the controller. Y-axis is the output power, directly measured by Coherent PM10.
The measurement was done by changing the current from the controller.
[Things to be done]
Hmm. Was the current within the operating range? (i.e. Is it a 700mW laser or a 1W one?)
You can obtain the nominal operating current from the old EPICS values (or some elog entries).
Note that NPROs are designed to be healthy only at around the nominal pumping power
(i.e. thermal gradient, and thermal lensing of the crystal, etc.)
Be aware that this laser should be used under the old SOP. So the appropriate interlocking is mandatory.
And probably we need to modify the SOP such that it reflects the latest situation.
The I-P curve of the LightWave NPRO, which was taken out from the MOPA box, was measured. It looks healthy.
Put the serial numbers into the elog. So we can identify the laser and controller in the future.
The old days the NPRO ( inside the MOPA ) was running ~1.7A 500 mW
There was a rogue, undocumented, gateway process running on NODUS since ~4 PM. This guy was broadcasting channels back into the Martian and causing lockups in the IOO controls. I did a kill -9 on its process.
Someone will pay for this.
The small optical bench (next to the MC-2 Chamber and the tool box tower) has been cleared of the misc. object previously on it, cleaned, and leveled (after much calibration X___X).
PLEASE, PLEASE, PLEASE do NOT MOVE OR HIT THE TABLE! It was incredibly painful to level.
This is how leveling the table made me feel...
VERY SAD...so do not move please!
The shaker has already been moved to the table and the amplifier for my shaking experiment is located behind the table (not on the table, as to prevent scratching).
I used a matlab code written by Koji to analyse the transimpedance and current noise data of REFL55. The details are in the attached pdf file.
Resonance is at 55.28 MHz:
Q of 4.5, Transimpedance of 615 Ohms
shot noise intercept current = 1.59 mA
current noise =21 pA/rtHz
Notch at 110.78 MHz:
Q of 54.8 Transimpedance of 14.68 Ohms.
REFL55 was modified. The noise level confirmed. The PD is now ready to be installed.
Kevin's measurement report told us that something was wrong with REFL55 PD. The transimpedance looked OK, but the noise level was terrible (equivalent to the shotnoise of 14mA DC current).
Rana and I looked at the circuit, and cleaned up the circuit, by removing unnecessary 11MHz notch, 1k shunt resister, and so on.
I made a quick characterization of the PD.
The transimpedance ws measured as a function of the frequency. The resonance was tuned at 55MHz. The notch was tuned at 110MHz in order to reject the second harmonics. The transimpedance was ~540V/A at 55MHz. (For the calibration, I believed the DC transimpedance of 50V/A and 10000V/A for the DC paths of this PD and #1611, respectively, as well as the RF impedance (700V/A0 of #1611.
Output noise levels were measured with various amount of photocurrent using white light from a light bulb. The measurement was perforemed well above the noise level of the measurement instruments.
The measured output noise levels were converted into the equivalent current noise on the PD. The dark noise level agrees with the shot noise level of 1.5mA (i.e. 22pA/rtHz). In deed, the noise level went up x~1.5 when the photocurrent is ~1.4mA.
1.The aim is the laser frequency stabilisation of PSL and AUX.
2.As a first step we want to couple some of the AUX laser beam into a single mode optical fibre and route the fibre to the PSL table.
3.The position of the optical fibre on the ETMY table is shown by the coupler in the attached picture. The yellow lines show the new scheme we want to implement.
4.WHAT WE DID TODAY.
40m surfs: Nicole Ing, Iswita Saikia and Sonali Mohapatra received 40m specific safety training today.
There were small pieces of glass, remnants of a fluorescent tube, which were lying around on the ETMY end table for a while now. We picked up the larger pieces by hand and used the HEPA filtered vacuum cleaner to pick up the remaining glass and dust on the table.
The Lightwave NPRO power supply which is being shared between the AS table and the ETMY table has been shifted back to the ETMY table.
The current to the laser is set at 1.5A. The laser output is 200mW at this current level.
Last night I was making a script which will measure the sensing matrix using the realtime LOCKIN module.
The script is a kind of expansion of Jamie's one, which measure the asymmetry, to more generic purpose.
It will shake a suspended optic of interest and measure the response of each sensor by observing the demodulated I and Q signals from the LOCKIN module.
I will continue working on this.
- made a function that drives the LOCKIN oscillator and get the data from the I and Q outputs.
- checked the function with the MICH configuration.
ITMX, ITMY and BS were shaken at 100 Hz and at different time.
Then the response of AS55_Q showed agreement with what I got before for the actuator calibration (see this entry).
It means the function is working fine.
I am now measuring the sensing matrix in the DRMI configuration.
A goal of tonight is to measure the sensing matrix as a test of the script.
The result will be updated later.
What I did today.
1. Collimation of a beam.
2. Coupling of the IR light at the ETMY table to a fibre.
Peter King came over to the 40m with a laser controller and gave it to us.
We will test it out with the LightWave NPRO, which was used for MOPA.
This is the new hot air station for the 40m lab.........
The sensing matrix was measured in the DRMI configuration for the first time.
The measurement was done by an automatic script and the realtime LOCKIN module built in the c1lsc model.
The resultant matrix is still too primitive, so I will do some further analysis.
(Measurement of sensing matrix)
The quantities we want to measure are the transfer functions (TFs) from displacement (or change in optical phase) of each DOF to sensors in unit of [counts/m].
So essentially the measurement I did is the same as the usual TF measurement. The difference is that this measurement only takes TFs at a certain frequency, in this case 283 Hz.
The measurement goes in the following order :
(1) Lock DRMI
(2) Shake an optic of interest longitudinally with an amplitude of 1000 counts at 283.103 Hz, where no prominent noise structures are present in any spectra of the sensor signals.
(3) Put a notch filter at the same frequency of 283.103 Hz in each DOF (MICH, PRC and SRC) to avoid unwanted suppression due to the control loops.
(This technique is essentially the same as this one, but this time the control loops are shut off only at a specific frequency )
The notch filter I put has a depth of 60 dB and Q of 20. The filter eats the phase of ~10 deg at 200 Hz, which still allow servos to run with a high UGF up to 200Hz.
(4) Take the output signal from a signal port of interest (i.e. REFL11_I, etc.,) and then put it into the realtime LOCKIN module.
(5) Measure the resultant I and Q signals coming out from the LOCKIN module.
(6) Repeat the procedure from (2) through (5) for each optic and sensor.
Again, the resultant sensing matrix is still primitive, for example the optic-basis should be converted into the DOF basis.
The values listed in the matrix below is the absolute values obtained by operation of sqrt( I^2 + Q^2) plus the polarity according to the output from I and Q of LOCKIN.
Therefore they still contain the actuator response, which is not desired. i will calibrate them into [counts/m] later by using the calibration factor of the actuator responses.
All the raw data showed the relative phase between I and Q either ~ 127 deg or ~ -53 deg.
In my definition, the one has 127 deg is plus polarity and the one has -53 deg is minus polarity.
Technically speaking the polarity depends on the polarity of the actuator and also the direction of the actuator against the DOFs.
Without any excitation the absolute values fluctuated at about 10-4 - 10-5, so the excitation amplitude was big enough to observe the sensing matrix.
Though, I still need to estimate the statistical errors to make sure the SNR is reasonably big.
Fig.1 Measured sensing matrix from optic to sensors.
(Things to be done)
- convert the optic-basis (i.e. BS, ITMs, PRM and SRM) to the DOF-basis (i.e. MICH, PRC and SRC) so that the matrix is understandable from point of view of the interferometer control.
- estimate the optimum demodulation phase for each DOF at each sensor port.
- add some statistical flavors (e.g. error estimations and so on.)
- edit the script such that it will keep watching the ADC overflows and the coherence to make sure the measurement goes well.
- add some more signal ports (e.g. REFL55, POY55 and etc.)
- compare with an Optickle model
I have shifted the Jenne laser back to the small table where we do RF PD characterisation (RFPD table). I found several 25pin D-type connector cables, connected them in tandem and am using that to power the WFS2 sensor head at the RFPD table.
The set up is ready for looking at the RF response of the WFS sensors. Will continue tonight.
June 22-June 24:
1.Coupling light into fibre at the ETMY.
2.Routing of the fibre to the PSL table.
June 27-June 30:
1.PSL optical table layout sketching.
2.Combining the PSL beam with fibre output onto a BS and then superpose them on a New Focus 1611 PD.
July 5-July 8:
1.Conversion of the PD output to voltage using MFD(Mixer Frequency Discriminator).
2. Report writing.
July 7: 5:00 pm: 1st Report Due.
July 11-July 22:
1.Locking Y-arm to PSL.
2.Setting up the feedback loop using the MFD output as the error signal and acting on the AUX laser frequency.
July 25-Aug 5:
1.Y-Arm cavity characterisation.
Measurement of the transmission of IR and green light through the cavity.
To obtain FSR, Finesse,Loss of the Cavity, Visibility, Transverse Modes(g-factor, astigmatism), Reflectivity, Q-factor.
3.Report and abstract writing.
Aug 1: 5:00 pm: 2nd Report and absract due.
Preparation for talk and seminar.
I was trying to measure the sensing matrix in the PRMI configuration, but basically gave up.
It is mainly because the lock of PRMI wasn't so stable and it didn't stay locked for more than a minute.
It looked like an angular motion fluctuated a lot around 1- 3 Hz. The beam spot on the AS camera moved a lot during the lock.
I have to figure out who is the bad suspension and why.
All the suspensions are bad until you fix them. But, ... there is a script which can be used to diagnose them today:
Access to the north side of the PSL table is blocked by the 8" beam guard. This opens the beam pathways between them.
Rod Luna picked up these computers for Larry Wallace yesterday: Dell Inspiron 530, Dell Dimension 4600 and SunBlade 1000
For some reasons foton's deafault sample rate is NOT correct when it runs on the CentOS machines.
It tries to setup the sample rate to be 2048 Hz instead of 16384 Hz until you specify the frequency.
To avoid an accidental change of the sample rate,
running foton on CentOS is forbidden until any further notifications.
Run foton only on Pianosa.
Additionally I added an alias sentence in cshrc.40m such that people can not run foron on CentOS (csh and tcsh, technically speaking).
Below is an example of raw output when I typed foron on a CentOs machine.
DO NOT use foton on CentOS
We have fixed the counts-to-micron (cts2um) calibration for the suspension sensor filters. Each suspension sensor filter bank (e.g. ULSEN) has a "cts2um" calibration filter. These have now been set with the following flat gains:
40 V 10^3 um um
-------- * -------- = .36 --
2^16 cts 1.7 V ct
The INMTRX was also fixed with proper element values:
This was done for all core optic suspensions (BS, PRM, SRM, ITMX, ITMY, ETMX, ETMY).
I recorded a burt snapshot of these settings: /opt/rtcds/caltech/c1/burt/autoburt/snapshots/2011/Jun/23/21:40
I found the PMC unlocked. Koji noticed that the FSS Slow Actuator Adjust was railed at the positive end of the slider. I set it close to zero, and relocked the PMC. The FSS slow loop servo is doing its thing, and the PMC and MC are now locked.
I found some DQ channels (e.g. SENSOE_UL and etc.) for C1SUS haven't been activated, so I ran activateDQ.py.
Then I restarted daqd on fb as usual. So far the DQ channels look working fine.
The I-P curve was measured again, but this time in a lower current range of 1.0-1.9 [A].
The plot below is the latest I-P curve.
Based on the measurement and some thoughts, I decided to run this laser at about 1.8 [A] which gives us a middle power of ~ 360 [mW].
In the 40m history, the laser had been driven at 2.4 [A] in years of approximately 2006-2009, so it's possible to run it at such a high power,
but on the other hand Steve suggested to run it with a smaller power such that the laser power doesn't degrade so fast.
The laser controller handed from PK (#4855) was used in this measurement.
The nominal current was tuned to be 1.8 [A] by tuning a potentiometer on the laser head (see page.18 on the manual of LWE).
There was a huge bump around 1.4 [A] and sudden power drop at 1.48 [A] although I don't know the reason.