PMC locked manually and PRM sus damping restored.
Fire alarm went off several minutes ago. Talked to security and they said there was no fire. It beeped twice again just now. No one has been working on the IFO today.
The EOM upstream of the PMC is used as the phase corrector for the FSS/IMC servo. It is also used to apply the 35.5 MHz PDH RF sidebands for the PMC locking. There is a Pomona box which is used to merge the two signals onto a single cable for the EOM.
Does this circuit make sense to anyone?
This LHO log indicates that EPICS slow down could be due to NFS activity. Could we make some trend of NFS activity on Chiara and then see if it correlates with EPICS flatlines?
I wonder if our EPICS issues frequency is correlated to the Chiara install.
However, the one that was recovered from the ATF lab is no longer locking to the Rubidium reference frequency, although it was locked at the time we disconnected it from the ATF lab. I emailed the support staff at SRS, who seem to think that either the internal oscillator has drifted too far, or the Rb lamp is dead. Either ways, it needs to be repaired. They suggested that I run a check by issuing some serial commands to the unit to determine which of these is actually the problem, but I've been having some trouble setting up the serial link - I will try this again tomorrow.
The Rubidium standard we had sent in for repair and recalibration has come back. I checked the following:
However, I am still having trouble setting up a serial communications link with the FS725 with a USB-serial adaptor - I've tried with a Raspberry Pi and my Mac (using screen to try and connect), and also using one of the old Windows laptops lying around on which I was able to install the native software supplied by SRS (still using the USB-serial adaptor to establish connection though). Could it be that the unit is incompatible with the USB-serial adaptor? I had specifically indicated in the repair request that this was also a problem. In any case, this doesn't seem to be crucial, though it would have been nice for diagnostics purposes in the future...
I've stored the repaired FS725 inside the electronics cabinet (marked "Eletronics Modules") for now (the other unit was returned to Antonio in W. Bridge some weeks ago).
I think there should be a scientifically based aveluation of the ETMY enclosure so we can make the ETMX better.
Meanwhile I'm counting pieces to move on with the south end table cover.
When I came in this afternoon, I saw that the PZT voltage to the PMC had railed. Following the usual procedure of turning the servo gain to zero and adjusting the DC offset, I got the PMC to relock, but the PMCR level was high and the alignment looked poor on the control room monitor. So I tweaked the input alignment on the PSL till I felt it was more reasonable. The view on the control room monitor now looks more like the usual state, and the "REFL (V)" field on the PMC MEDM screen now reads 0.02-0.03 which is the range I remember it being in nominally.
Two mechanical and two sticdky traps were set to catch univited visitor.
Absolutely no food or food remains into inside garbage cans!!!!!!!!!!!!!!!!!!!!!!!!!
A small rat / large mouse just ran through the control room. Ugh.
I'll finish up the beat / frequency noise parts of the diagnosis tomorrow later, but I've done some investigation of the AUX X laser RIN.
I placed a PDA255 at one of the rejected beams from the PBS on the downstream side of the IR faraday, making sure the power didn't saturate the PD. I measured the RIN on a SR785, and simultaneously looked at the signal on a 100MHz scope.
The RIN has a very strong dependence on the laser diode current, and no noticable dependence on the crystal temperature or the presence of the PDH modulation / temperature control cables. Here are some traces, note that "nominal" current up until recently was 2.0A.
When adjusting the diode current, a peak beings to appear in the tens of kHz, eventually noticible in the DC power trace on the scope. The point at which this occurs is not fixed.
At all times, I saw a strong intensity fluctuation at around 380-400kHz on the scope whose amplitude fluctuated a fair amount (at least 75mVrms over Vdc=6.5V, but would often be 2 or 3 times that).
I didn't look at the frequency noise while doing this, because the WiFi at the X end was too slow, I'll do more tomorrow in the daytime.
Here's how we should diagnose the EX laser:
I've not updated the MEDM screens to reflect the two new paths yet, but will do so soon. It also remains to install appropriate filters for the servo path that takes the frequency readout as the input.
A few more related changes:
I've set up two IPC channels that take the output from the digital frequency counters and send them to the end front-ends (via the RFM model). A summary of the steps I followed:
I've set things up such that we can select either the "PZT IN" or the frequency counter as the input to the slow servo, via means of a EPICS variable called "FC_SWITCH" (so C1:ALS-X_FC_SWITCH or C1:ALS-Y_FC_SWITCH). If this is 0, we use the default "PZT IN" signal, while setting it to 1 will change the input to the slow servo to be the frequency readout from the digital frequency counter. I've not updated the MEDM screens to reflect the two new paths yet, but will do so soon. It also remains to install appropriate filters for the servo path that takes the frequency readout as the input.
Tangentially related to this work: I've modified the FC library block so that it outputs frequency in MHz as opposed to Hz, just for convenience..
We were not able to fix the excess frequency noise of the AUX X laser by the usual laser diode current song and dance. Unfortunately, this level of noise is much too high to have any realistic chance of locking.
We're leaving things back in the IR beat -> phase tracker state with free running AUX lasers, on the off chance that there may be anything interesting to see in the overnight data. This may be limited by our lack of automatic beatnote frequency control. (Gautam will soon implement this via digital frequency counter). I've upped the FINE_PHASE_OUT_HZ_DQ frame rate to 16k from 2k, so we can see more of the spectrum.
For the Y beat, there is the additional weird phenomenon that the beat amplitude slowly oscillates to zero over ~10 minutes, and then back up to its maximum. This makes it hard for the phase tracker servo to stay stable... I don't have a good explanation for this.
With the IR beats going to the nominal ALS channels as Gautam left them, we're able to measure the free running frequency noise of the end AUX lasers.
Specifically, the end shutters are closed, leaving the AUX lasers free running. The IR beats then consist of this free running light beating with the PSL light, and the ALS phase trackers give a calibrated frequency noise spectrum. I've stabilized the PSL light by locking the laser to the Y arm via MC2 acutation, so the free running AUX laser noise should dominate by a lot above the suspension resonances. This also has the benefit of giving me the use of the CAL'd Y arm displacement as a sanity check.
At this point in time, it looks like the X laser is close to 10x noisier than the Y laser, though it does seem to be at the rule-of-thumb "10kHz/rtHz at 100Hz" level.
Since there are a few hours to go before the locking efforts tonight, I've temporarily borrowed the channels used to read out the green beat frequency, and have hooked them up to the broadband IR PDs in the FOL box on the PSL table. I've used the network analyzer in the control room to roughly position the two beatnotes. I've also turned the green beat PDs back on (since the PSL shutter has to be open for the IR beat, and there is some green light falling on these PDs, but I've terminated the outputs).
So this needs to be switched back before locking efforts tonight...
Forgot to submit this yesterday...
While we were trying to get the X-arm locked to IR using MC2, frame-builder mysteriously crashed, necessitating us having to go down to the computer and perform a hard reboot (after having closed the PSL shutter and turning all the watchdogs to "shutdown"). All the models restarted by themselves, and everything seems back to normal now..
c1sus and c1ioo were restarted. PMC locked.
I have added a new cron job in pcdev1 at CIT using the 40m shared account. This will run the /home/40m/DetectorChar/bin/cleanarchive script one minute past midnight on the first of every month. The script removes GWsumm archive files older than 1 month old.
I noticed what I thought was excessive movement of the beam spot on ITMX and ETMX on the control room monitors, and when I checked the CDS FE status overview MEDM screen, I saw that c1scx and c1asx had crashed. I ssh-ed into c1iscex and restarted both models, and then restarted fb as well. However, the DAQ-DCO_C1SCX_STATUS indicator remains red even after restarting fb (see attached screenshot). I am not sure how to fix this so I am leaving it as is for now, and the X arm looks to have settled down.
To get C1PEM data back into the frames, I removed the new BLRMS blocks, recompiled, reinstalled, re-enabled it in daqd, restarted.
We still really want more headroom in our framebuilder situation.
Based on calibration measurement I have done (elog 11785, 11831), I updated calibration factors of oplevs on medm screen as follows. Not to change loop gain oplev servo, I also changed oplev servo gain.
After making sure that the upper UGFs were properly in place, I saved these settings to the SDF files. Thanks Yutaro!
Here's something to ponder.
Our online MCL feedforward uses perpendicular vertex T240 seismometer signals as input. When designing a feedforward filter, whether FIR Wiener or otherwise, we posit that the PSD of the best linear subtraction one can theoretically achieve is given by the coherence, via Psub = P(1-C).
If we have more than one witness input, but they are completely uncorrelated, then this extends to Psub = P(1-C1)(1-C2). However, in reality, there are correlations between the witnesses, which would make this an overestimate of how much noise power can be subtracted.
Now, I present the actual MCL situation. [According to Ignacio's ELOG (11584), the online performance is not far from this offline prediction]
Somehow, we are able to subtract much more noise at ~1Hz than the coherence would lead you to believe. One suspicion of mine is that the noise at 1Hz is quite nonstationary. Using median [C/P]SDs should help with this in principle, but the above was all done with medians, and using the mean is not much different.
Thinking back to one of the metrics that Eve and Koji were talking about this summer, (std(S)/mean(S), where S is the spectrogram of the signal) gives an answer of ~2.3 at that peak at 1.4Hz, which is definitely in the nonstationary regieme, but I don't have much intution into just how severe that value is.
So, what's the point of all this? We generally use coherence as a heuristic to judge whether we should bother attempting any noise subtraction in the first place, so I'm troubled by a circumstance in which there is much more subtraction to be had than coherence leads us to believe. I would like to come up with a way of predicting MISO subtraction results of nonstationary couplings more reliably.
I've attached the results from my measurements of the noise characteristics of the Y-end auxiliary PDH system.
The following spectra were measured, in the range DC-1MHz:
In order to have good spectral resolution, the frequency range was divided into 5 subsections: DC-200Hz, 200Hz-3.4kHz, 3.4kHz-16.2kHz, 10kHz-100kHz, 100kHz-1MHz. The first three are measured using the SR785, while the last two ranges are measured with the Agilent network analyzer. The spectrum of the mixer output with its input terminated was quite close to the analyzer noise floor - hence, this was measured with an S560 preamplifier set to a gain of 100, and subsequently dividing the ASD by 100. To convert the Y-axis from V/rtHz to Hz/rtHz, I used two conversion factors: for the analyzer noise floor, PD dark noise, mixer noise and in-loop error signal, I made an Optickle simulation of a simple FP cavity (all parameters taken from the wiki optics page, except that I put in Yutaro's measured values for the arm loss and a modulation depth of 0.21 which I estimated as detailed here), and played around with the demodulation phase until I got an error signal that had the same qualitative shape as what I observed on an oscilloscope with the arms freely swinging (feedback to the laser PZT disabled). The number I finally used is 45.648 kHz/V (the main horns were 800mV peak-to-peak on an oscilloscope trace, results of the Optickle FP cavity simulation shown in Attachment #2 used to calibrate the X-axis). For the servo noise spectrum and in-loop control signal, I used the value of 2.43 MHz/V as determined here.
I'm not sure what to make of the strong peaks in the mixer noise spectrum between ~60Hz and 10kHz - some of the more prominent peaks are 60Hz harmonics, but there are several peaks in between as well (these have been confusing me for some time now, they were present even when I made the measurement in this frequency range using the Agilent network analyzer. My plan is to repeat these measurements for the Xend now.
Two companies are willing to make the ruby grooves and the third one is still working on their quote.
The price is ~$100 each. The cost goes down 10% if we order 50 instead of 30 pieces.
How many should we get ?
After the discussions at the Wednesday meeting, I redid this measurement using a sinusoidal excitation summed at the error-point of the PDH servo as opposed to a DC offset. From the data I collected, I measured the actuator gain to be 2.43 +/- 0.04 MHz/V. This is almost half the value we expect, I'm not sure if I'm missing something obvious.
Yutaro left detailed slides for his loss map measurement
(45.1,16) => (200,3.5)
(85.6,8) => (222,3.0)
(26,-16) => (140,-3.0)
(31,-21) => (143,-4.5)
(110,8) => (122,7.2)
(81,-11) => (147,-6)
(159,15) => (239,10)
(174,-21) => (226,-16)
Attached is the plot of relation between the average arm round trip loss and power recycling gain. 2 % loss due to PR3 AR reflection is taken into account.
Can I ask you to make a plot of the power recycling gain as a function of the average arm loss, indicating the current loss value?
I took PR3 AR reflectivity and calculated PRG (PR3 is flipped and so AR surface is inside PRC).
As shown in attached figure, which shows AR specification of the LaserOptik mirror (PR3 is this mirror), AR reflectivity of PR3 is ~0.5 %. Since resonant light in PRC goes through AR surface of PR3 4 times per round trip, round trip loss due to this is ~2 %. Then I got
PRG = 7.8.
To check if the strange behavior of ASDC is caused by SR2/SR3 or not, I did the following measurement:
ASDC measures the power of the light reflected by ITMX. POXDC measures the power of the light reflected by ITMX and SRM successively. Then I varied the angle of ITMX in YAW direction and compared the behaviors of ASDC and POXDC.
The results are shown in Attachments 1-3.
As you can see in these figures, the strange up-and-down behavior appeared ONLY in ASDC. Therefore, the cause of this behavior exists between AS table and SRM (I had confirmed that the angle of SRM did not affect ASDC).
And this behavior is fringe-like, as can be seen in the figures (there seems to be 3 "peaks" and 2 "valleys"), so the cause could be interference between main path and not good AR reflection at a mirror after SRM before AS table (I suspect a mirror is flipped mistakenly).
I did additional tests for the strange behavior of ASCD. ETMY, ETMX and ITMY were misaligned so that only light reflected by ITMX went into AS port. I had done similar measurement before with ITMY YAW varied.
Attachment 1 shows how ASDC level changed when ITMX PIT varied.
Attachment 2 shows how ASDC level changed when ITMX YAW varied.
Attachment 3 shows how the power of light measured by a power meter just after the AS view port varied when ITMX YAW varied.
Comparing 1 & 2, we can say that this behavior is not unique to YAW direction.
From 2 & 3, we can say something strange is happening inside the chamber.
NDS2 and the usual ports so that we can use optimus as a comsol server.
I don't think there are any other ports we need open, but I could be wrong. Let me know if I broke something you need!
I spent this afternoon trying to debug fb1, with very little to show for it. We're back to running from fb.
The first thing I did was to recompile EPICS from source, so that all the libraries needed by daqd were compiled for the system at hand. I compiled epics-3.14-12-2_long from source, and installed it at /opt/rtapps/epics on local disk, not on the /opt/rtapps network mount. I then recompiled daqd against that, and the framecpp, gds, etc from the LSCSoft packages. So everything has been compiled for this version of the OS. The compilation goes smoothly.
There are two things that I see while running this new daqd on fb1:
The mx stream connection between the front ends and the daqd is flaky. Everything will run fine for a while, the spontaneously one or all of the mx_stream processes on the front ends will die. It appears more likely that all mx_stream processes will die at the same time. It's unclear if this is some sort of chain reaction thing, or if something in daqd or in the network itself is causing them all to die at the same time. It is independent of whether or not we're using multiple mx "end points" (i.e. a different one for each front end and separate receiver threads in the daqd) or just a single one (all front ends connecting to a single mx receiver thread in daqd).
Frequently daqd will recover from this. The monit processes on the front ends restart the mx_stream processes and all will be recovered. However occaissionally, possibly if the mx_streams do not recover fast enough (which seems to be related to how frequently the receiver threads in daqd can clear themselves), daqd will start to choke and will start spitting out the "empty blocks" messages that are harbirnger of doom:
Aborted 2 send requests due to remote peer 00:30:48:be:11:5d (c1iscex:0) disconnected
00:30:48:d6:11:17 (c1iscey:0) disconnected
mx_wait failed in rcvr eid=005, reqn=182; wait did not complete; status code is Remote endpoint is closed
disconnected from the sender on endpoint 005
mx_wait failed in rcvr eid=001, reqn=24; wait did not complete; status code is Remote endpoint is closed
disconnected from the sender on endpoint 001
[Wed Dec 9 18:40:14 2015] main profiler warning: 1 empty blocks in the buffer
[Wed Dec 9 18:40:15 2015] main profiler warning: 0 empty blocks in the buffer
[Wed Dec 9 18:40:16 2015] main profiler warning: 0 empty blocks in the buffer
My suspicion is that this time of failure is tied to the mx stream failures, so we should be looking at the mx connections and network to solve this problem.
There's possibly a separate issue associated with writing the second or minute trend files to disk. With fair regularity daqd will die soon after it starts to write out the trend frames, producing the similar "empty blocks" messages.
[Eric Q, Gautam, Koji]
We went through the network connections to produce the mapping of the instruments.
Gautam summarized the notes into a spread sheet. See attachments.
We didn't find any irregular connections except for the connection of NETMGR port of c1ioo to Martian Network.
This cable was removed.
Glitches are gone. Rga scan is good
I measured the PZT actuator gain for the Lightwave NPRO at the Y-end to be 3.6 +/- 0.3 MHz/V. This is somewhat lower than the value of 5 MHz/V reported here, but I think is consistent with that measurement.
In order to calibrate the Y-axis of my Aux PDH loop noise budget plots, I wanted a measurement of the end laser actuator gain. I proceeded to measure this as follows:
The attached plot shows the measured data. The X-axis is shown after the conversion mentioned in the last bullet point. The error bars are the standard deviations of the averaging at each DC offset.
I estimated power recycling gain with the results of arm loss measurement.
From elog 11818 and 11857, round trip losses including transmittivity of ETM of Y arm and X arm (let us call them and ) are 229+13.7=243 ppm and 483+13.7=495 ppm, respectively.
How I calculated:
I used the following formula.
Amplitude reflectivity of an arm cavity :
(see elog 11816)
Amplitude reflectivity of FPMI :
With power transmittivity of PRM and amplitude reflectivity of PRM , power recycling gain is
I assumed , , and , and then I got
PRG = 9.8.
Since both round trip losses have relative error of ~ 4 % and PRG is proportional to inverse square of up to the leading order of it, relative error of PRG can be estimated as ~ 8 %, so PRG = 9.8 +/- 0.8.
According to elog 11691, which says TRX and TRY level was ~125 when DRFPMI was locked, power recycling gain was at the last DRFPMI lock.
Measured PRG is lower than PRG estimated here, but it is natural because various causes such as mode mismatch between PRC mode and arm cavity mode, imperfect contrast of FPMI, and so on could decrease PRG, which Eric suggested to me.
Added on Dec 9
If were as small as , PRG would be 16.0. PRC would be still under coupled.
The noise floor of the Rga scan is glitching less today
I've done a couple things to try and make nodus a little more secure. Some have worried that nodus may be susceptible to being drafted into a botnet, slowing down our operations.
1. I configured the ssh server settings to disallow logins as root. Ubuntu doesn't enable the root account by default anyways, but it doesn't hurt.
2. I installed fail2ban. Function: If some IP address fails to authenticate an ssh connection 3 times, it is banned from trying to connect for 10 minutes. This is mostly for thwarting mass brute force attacks. Looking at /var/log/auth.log doesn't indicate any of this kind of thing going on in the past week, at least.
3. I set up and enabled ufw (uncomplicated firewall) to only allow incoming traffic for:
Here I explain usage of my scripts for loss map measurement. There are 7 script files in a same directory /opt/rtcds/caltech/c1/scripts/lossmap_scripts. With these scripts, round trip loss of an arm cavity with the beam spot on one mirror shifted to 5x5 (option: 3x3) points is measured. You can choose on which cavity you measure, the beam spot on which mirror you shift, and maximum shift of the beam spot in vertical and horizontal direction.
To start measurement from the beginning
Run the following command in an arbitrary directory and you will get several text files including the result of loss map measurement:
> python /opt/rtcds/caltech/c1/scripts/lossmap_scripts/lossmap.py [maximum shift in mm (PIT)] [maximum shift in mm (YAW)] [arm name (XorY)] [mirror name (E or I)]
Optionally, you can add "AUTO" at the end of the above command. Without "AUTO", you will be asked if the dithering has already settled down or not after each shift of the beam spot and you can let the scripts wait until the dithering settles down sufficiently. If you add "AUTO", it will be judged if the dithering has settled down or not according to some criteria, and the measurement will continue without your response to the terminal.
The files to be created in the current directory by the scripts are:
- lossmapETMX1-1.txt # [POX power (locked)] / [POX power (misaligned)]
- lossmapETMX1-2.txt # standard deviation of [POX power (locked)] / [POX power (misaligned)]
- lossmapETMX1-3.txt # TRX
- lossmapETMX1-1_converted.txt # round trip loss (ppm) calculated from lossmapETMX1-1.txt
- lossmapETMX1-1_converted_sigma.txt # standard deviation of round trip loss calculated from 1-1.txt and 1-2.txt
- lossmapETMX_result.txt # round trip loss and its error in a clear form.
The name of the files would be "lossmapITMY1-1.txt" etc. depending on which mirror you have chosen.
To restart measurement from a certain point
Run the following command in a directory containing "lossmap(mirror name)1-1.txt", "lossmap(mirror name)1-2.txt" and "lossmap(mirrorname)1-3.txt" which are created by previous not-completed measurement:
> python /opt/rtcds/caltech/c1/scripts/lossmap_scripts/lossmap.py [maximum shift in mm (PIT)] [maximum shift in mm (YAW)] [arm name (XorY)] [mirror name (E or I)] [restart point (PIT)] [restart point (YAW)]
You can also add "AUTO".
How to designate the restart point:
Matrix elements of output of this measurement procedure are characterized by a pair of two numbers as the following shows.
(-1,-1) -> (-1,-0.5) -> (-1,0) -> (-1,0.5) -> (-1,1)
(-0.5,1) <- (-0.5,0.5) <- (-0.5,0) <- (-0.5,-0.5) <- (0.5,-1)
(0,-1) -> (0,-0.5) -> (0,0) -> (0,0.5) -> (0,1)
(0.5,1) <- (0.5,0.5) <- (0.5,0) <- (0.5,-0.5) <- (0.5,-1)
(1,-1) -> (1,-0.5) -> (1,0) -> (1,0.5) -> (1,1)
Please write the numbers that correspond to the matrix element you want to restart at. Arrows show the order of sequence of measurement. About the correspondence between the matrix elements and real position on the ETMY and ETMX, see elog 11818 and 11857, respectively.
This script will overwrite the files (~1-1.txt etc.) so it is safer to make backup of the files before you run this script.
Some notes on the scripts and measurement
- Calibration has been done only for ETMs, i.e. for ITMs unit of [maximum shift] is not mm, but the values written in [maximum shift] equal to the maximum offsets added just after demodulation of ASS loop (ex. C1:ASS-YARM_ITM_PIT_L_DEMOD_I_OFFSET).
- It should be checked before doing measurement if the following parameters are correct or not.
POXzero (L47 in lossmapx.py and L52 in lossmapx_resume.py: the value of C1:LSC-POXDC_OUTPUT when no light injects into POXPD.)
POYzero (L45 in lossmapy.py and L50 in lossmapy_resume.py: the value of C1:LSC-POYDC_OUTPUT when no light injects into POYPD.)
mmr (L11 in lossmap_convert.py: (mode matching carrier power)/(total power))
Tf (L12 in lossmap_convert.py; transmittivity of ITM)
Tetm (L13 in lossmap_convert.py: transmittivity of ETM in ppm)
- Changing n (L50 in lossmap.py) from 5 to 3, the grid points will be 3x3 changed from the default value of 5x5. If 3x3, the matrix elements are characterized by
(-1,-1) -> (-1,0) -> (-1,1)
(0,1) <- (0,0) <- (0,-1)
(1,-1) -> (1,0) -> (1,1)
similarly to the case of 5x5.
- You can copy the directory lossmap_scripts anywhere in controls and use it. These scripts will work as long as all the 7 scripts exist in a same directory.
I changed the snapshot file for ASS, /opt/rtcds/caltech/c1/scripts/ASS_DITHER_ON.snap as follows:
L124 > C1:ASS-XARM_ETM_PIT_GAIN 1 -5.000000000000000e-02
=> C1:ASS-XARM_ETM_PIT_GAIN 1 -1.500000000000000e-02
L128> C1:ASS-XARM_ETM_YAW_GAIN 1 5.000000000000000e-02
=> C1:ASS-XARM_ETM_YAW_GAIN 1 1.500000000000000e-02
The purpose of this change is to avoid the oscillation when the dithering of X arm is running.
A question to Jamie: although the new framebuilder prototype still had the same problem with trend writing, can it handle this higher testpoint/DQ channel load?
The new fb1 daqd was also crashing even without the trend writing enabled. I'm not sure how much that's affected by the load, though, e.g. it might be able to handle the extra load fine but then die because of some other issue not related to the number of channels being acquired.
We should schedule some time this week to work on fb1 some more.
CC1 and CC2 are working again. Why did they start working again ?
On the day before yesterday and in this morning, I measured loss map of ETMX. I reported the method I used to change the beam spot on ETMX below.
Round trip loss was measured for 5 x 5 points. The result is below.
455.4 +/- 21.1 437.1 +/- 21.8 482.3 +/- 21.8 461.6 +/- 22.5 507.9 +/- 20.1
448.4 +/- 20.7 457.3 +/- 21.2 495.6 +/- 20.2 483.1 +/- 20.8 472.2 +/- 19.8
436.9 +/- 19.3 444.6 +/- 19.7 483.0 +/- 19.5 474.9 +/- 20.9 498.3 +/- 18.7
454.4 +/- 18.7 474.4 +/- 20.6 487.7 +/- 21.4 482.6 +/- 20.7 487.0 +/- 19.9
443.7 +/- 18.6 469.9 +/- 20.2 482.8 +/- 18.7 480.9 +/- 19.5 486.1 +/- 19.2
The correspondence between the loss shown above and the beam spot on ETMX is shown in the attached figure. In the figure, "up" and "right" indicate direction of shift of the beam spot when you watch it via the camera (ex. 455.4 ppm corresponds to the highest and rightest point in the view via the camera).
This result is consistent withe previous result of 561.19 +/- 14.57 ppm ericq got with ASDC and reported in elog 10248 if the discussion I reported in 11819 is taken into account. Elog 11819 says in short that the strange behavior of ASDC could give us 60-70 ppm error.
The reason why the error is larger than that of the measurement for ETMY is that the noise of POX is larger than that of POY. But I am not sure to what extent the statistical error needs to be reduced.
How I shifted the beam spot on ETMX:
Basically, the method was same as one used for Y arm. Different point is: for Y arm we have two steering mirrors TT1&2, but for X arm we have only one steering mirror BS. Then in order to shift incident beam so that the beam spot on ITMX does not change, I ran the dithering of X arm as well as that of Y arm and added offsets to both dither loops that caused same amount of shift on ETMX and ETMX. Thanks to the symmetry between X arm and Y arm, the dithering of Y arm ensured that the beam spot on ITMX was unchanged as well as that of ITMY. The idea of this method is schematically shown in Attachment 2.
The calibration of how much the beam spot shifted is based on the results of elog 11846 . The offset was [-15,-7.5,0,7.5,15]x[-5,-2.5,0,2.5,5] for pitch and yaw, respectively.
Since removing c1pem from the daqd master file, daqd has not crashed. I suppose we're running into the stability issue that motivated us to disable some of the other models (IOPs, RFM, etc.) during the RCG upgrade.
I added 1 line to one of the ASS scripts, UNFREEZE_DITHER.py like this:
L29> ez.cawrite('C1:ASS-'+dof+'_GAIN', 0)
The reason why I added this is: without this line, C1:ASS-'+dof+'_GAIN become larger that 1.0, which is nomial value, if you UNFREEZE DITHER when the dither is already running or C1:ASS-'+dof+'_GAIN is not 0.0.
I glanced at the summary pages and noticed that, since Friday around when we first loaded up the new BLRMS parts, daqd has crashing very frequently (few times per hour).
I'm going to comment out the c1pem lines from the daqd master file for tonight, and see if that helps.
I don't know if just running "modprobe" will work or not, because I didn't try it... When the same problem happens again, we can try just running "modprobe" first.