| ID |
Date |
Author |
Type |
Category |
Subject |
|
660
|
Fri Jul 11 20:16:01 2008 |
Eric | DAQ | Cameras | Taking data from the GC 750 Camera |
Mafalda has been set up with a background process to constantly take data from the GC 750 camera (at the end of the x-arm) for the weekend. This camera will otherwise be inoperable until then.
In the small chance that this slows either Mafalda or the network to a crawl, the process to kill should have PID 26265. |
|
661
|
Fri Jul 11 23:55:25 2008 |
alan | Update | Locking | RF common mode at zero offset |
| Quote: | rob, john, yoichi
Last night we succeeded in reducing the CARM offset to zero.
|
Congratulations! Well done! I look forward to hearing the details and further progress! |
|
662
|
Sat Jul 12 23:28:31 2008 |
rana | Update | PSL | PMC needs help |
As everyone has noticed recently, the PMC seems to have a PZT problem. It often zooms
of to one of its rails after locking as if the PZT range has decreased dramatically.
WE should check this on Monday by disabling the FSS and applying a slow triangle wave to
the NPRO frequency. The PMC will track this frequency change and this will allow us to
diagnose its problems.
If it has real problems, I have a spare in W. Bridge which we can swap in temporarily.
The attached plot shows 3 years of trend; looks like it went bad in summer of last year.
This also seems to be the cause of our ISS saturation problems: lowering the gain of the PMC
even slightly increased the intensity noise enough to cause saturation. Increasing the gain
even slightly increased the intensity noise enough to cause saturation due to PMC servo oscillation. |
| Attachment 1: Untitled.png
|
|
|
663
|
Sun Jul 13 17:19:29 2008 |
rana | Summary | PSL | MOPA SLOWM Calibration |
John, Rana
We first unlocked the FSS and ramped the SLOW actuator. With the PMC locked we observed the PMC PZT voltage
as a function of SLOWM (SLOW loop actuator voltage). We believed this to be ~1-5 GHz / V. Since this is
not so precise we then ran a slow (2 min. period) triangle wave into the slow actuator and looked at the
ref cav transmission peaks to calibrate it.
Plot is attached>
We assume that the reference cavity length = 203.2 mm then the FSR = 737.7 MHz. So looking at the plot
and using our eye to measure the SLOWM calibration is 1054 +/- 30 MHz/V. This is probably dominated by
our eye method.
Note: we tried to get the length from T010159-00-R (Michele, Weinstein, Dugolini). In that doc,
the length used is 203.3 mm whereas its 203.2 mm in the PSL FDD (?). The calculation of the FSR is also
incorrect (looks like they used c = 299460900 instead of 299792458 m/s). We took the length from the PSL FDD
(T990025-00-D) but not the FSR, since they also did not find the right value of 'c'. I guess that the speed
of light just ain't what it used to be. |
| Attachment 1: SLOWDCcalibration.png
|
|
|
664
|
Sun Jul 13 22:39:16 2008 |
John | Summary | General | Edited medm screens |
I've edited the FSS and PMC screens so that red boxes are shown around the appropriate slider if a gain or offset is not within the limits defined in C1PSL_SETTINGS_SET.adl
With the current setting of 0 V the FSS input offset is red. According to the settings screen the nominal value is 0.3 +/- 0.050. Are there any objections to editing the nominal value?
I changed the LockMC screen so that red boxes are not shown when the up/down scripts are not running; when they are active you should see a green box. |
|
665
|
Mon Jul 14 00:36:19 2008 |
John | Summary | PSL | Slow sweep of laser temp - PMC PZT response |
John, Rana
Follow up to # 663
Top trace: C1: PSL-PMC_PZT
Middle: C1: PSL-FSS_SLOWDC
Bottom: C1: PSL-PMC_PMCTRANSPD
The only calibration I could find for the PMC PZT (LLO e-log Sep 3 2003 - 23 MHz/V) predicts 31V for an FSR. I did a rough calibration and got our FSR to be around 210 V. I assumed 713 MHz for an FSR and applied this calibration (~3.4 MHz/ V) to the PZT data.
In terms of volts per metre our PZT gives 2.54 nm/ V whereas the LLO PZT is 17.16 nm/ V. |
| Attachment 1: SlowTsweep.png
|
|
|
666
|
Mon Jul 14 10:57:00 2008 |
Koji | Frogs | Environment | Someone at 40M sent LHO water of life |
Someone at the 40m sent Mike@LHO a pound of peets coffee with the name of Koji Arai.
It was a good surprise! Thanks, we will enjoy it!
I will return to Pasadena next week. See you then. |
|
667
|
Mon Jul 14 12:43:07 2008 |
John | Summary | Computers | Restarted fb40m, tpman and c1ass |
|
|
668
|
Mon Jul 14 19:15:43 2008 |
Alberto | Update | General | abs cavity length measurement experiment |
Lately I've been dealing with the alignment of the interferometer to have a good beam spot at the AS port. Today the alignment script kept failing because of computer problems (failure of the frame builder) and also because the IFO was probably too far from the range where the automatic alignment works.
An other problem I keep having with the alignment of the optics on the AP table is with multiple reflection beams of the NPRO beam at the Farady.
Although I believe that now the two beams are quite well aligned, I don't see any reflection of the secondary beam from the IFO anymore.
It's like the more I try to improve the alignment, the worse I get from the beam matching. I'll keep working on this. |
|
669
|
Mon Jul 14 21:34:10 2008 |
Alberto | Update | General | abs cavity length measurement experiment |
| Quote: | Lately I've been dealing with the alignment of the interferometer to have a good beam spot at the AS port. Today the alignment script kept failing because of computer problems (failure of the frame builder) and also because the IFO was probably too far from the range where the automatic alignment works.
An other problem I keep having with the alignment of the optics on the AP table is with multiple reflection beams of the NPRO beam at the Farady.
Although I believe that now the two beams are quite well aligned, I don't see any reflection of the secondary beam from the IFO anymore.
It's like the more I try to improve the alignment, the worse I get from the beam matching. I'll keep working on this. |
Realigning the OSA I also had to move a little bit the mirror that reflects the IFO beam of at the AS port in order to raise the beam height. This had the effect of changing the position of the AS spot on the camera and on the monitors.
Tonight with John, we made sure that the AS beam was still aligned to the PD. |
|
670
|
Tue Jul 15 09:47:09 2008 |
steve | Update | PEM | lab temps and particles |
All air condtion units were serviced last Friday.
AC filters are trying to control our particle counts but they have no capacity to match bad Pasadena conditions.
IFO room filters at CES were really clean.
Air make up filters inside and outside were dirty.
They showed the construction effect.
Control room and clean assembly units needed all filters replaced.
Note: the PSL-FSS_RCTEMP droped o.1C when enclouser HEPAs were turned back on
The RC temp controller should be better than that! |
| Attachment 1: temps24d.jpg
|
|
|
671
|
Tue Jul 15 10:09:42 2008 |
Eric | DAQ | Cameras | Did anyone kill the picture taking process on Mafalda? |
| Did anyone kill the process on Mafalda that was taking pictures of the end mirror of the x-arm last Friday? I need to know whether or not it crashed of its own accord. |
|
672
|
Tue Jul 15 10:24:57 2008 |
steve | Update | PSL | PMC temp & pzt voltage |
The PMC pzt HV was happy with no HEPA temp stability.
Can we thermally insulate the pmc ? |
| Attachment 1: pmctemp.jpg
|
|
|
673
|
Tue Jul 15 11:47:56 2008 |
Jenne | DAQ | PEM | Accelerometer channels in ASS Adapt MEDM screen |
Jenne, Sharon
We have traced which accelerometers correspond to which channels in the C1ASS_TOP MEDM screen.
Accelerometer Channel
------------- --------------------------
MC1-X C1:ASS-TOP_PEM_2_ADAPT_IN1
MC1-Y C1:ASS-TOP_PEM_3_ADAPT_IN1
MC1-Z C1:ASS-TOP_PEM_4_ADAPT_IN1
MC2-X C1:ASS-TOP_PEM_5_ADAPT_IN1
MC2-Y C1:ASS-TOP_PEM_6_ADAPT_IN1
MC2-Z C1:ASS-TOP_PEM_7_ADAPT_IN1
SEISMOMETER C1:ASS-TOP_PEM_1_ADAPT_IN1 |
|
674
|
Tue Jul 15 12:23:22 2008 |
Jenne | Update | General | MC2 Watchdog tripped |
Alberto, Jenne
Mode Cleaner was unlocked. We checked, and found that MC2's watchdog was tripped. It didn't look like anything bad was going on, so we turned the optic back on, and tried to relock the MC. It looks like the Mode Cleaner is now locked, but the lock bit on the LockMC screen is still red. I don't know what's up. |
|
675
|
Tue Jul 15 12:44:08 2008 |
John | Summary | Locking | DRFPMI with DC readout |
Rob, John
Last night, despite suspect alignment, we were again able to reduce the CARM offset to zero using
the RF signal.We were also able to transfer to dc readout taking calibrated spectra in both states.
DC readout shows a marked improvement over RF above ~1kHz but introduces some noise around 100Hz.
Broadband sensitivity appears to be more than ten times worse than previously. The calibration
being used remains to be confirmed.
Engaging the ETMY dewhitening caused lock to be lost. We'll check this today. The OMC alignment loops
may also need some attention.
We looked at REFL_166 as a candidate for CARM, at present POX still looks better.
The DARM filters were modified to reduce excess noise around 3Hz. Updating filter coefficients does
not cause loss of lock. |
|
676
|
Tue Jul 15 19:15:57 2008 |
rana | Summary | SUS | ETMX Dewhitening characterization |
Since the boys found that the ETM dewhitening transient was kicking the IFO out of lock we
decided to investigate.
First, we wrote a script to diagnose and then tune the DC gain of the dewhitening filters'
digital compensation filter (a.k.a. FM9 or SimDW). It is in the scripts/SUS/ directory
and is called dwgaintuner. It puts in an offset on each coil's DAC channel and
then reads back the Vmon on the coil driver with the DWF on and off. It reports the ratio of these
voltages which you can then type into the FM9/SimDW filter's gain field. We learned that the
difference between the analog DWF path and the bypass path was ~3% (which is consistent with
what you expect from the use of 1% resistors). We need to repeat this for all of the rest of
the suspended optics except for MC1 and MC3.
This Vmon method is better than what's used at the sites so we will export this new technology.
The attached plot shows some switching transients with only the local damping on:
BLUE: Output of filter bank during an FM9 turn off. This is the transient which goes to the DAC.
The transients are mostly of the same magnitude as this.
RED: This is the input of the filter module during another such transient.
GREEN: Tried another switch; this time I filtered the time series in DTT by typing the SimDW into
the Triggered Time Series filter field. This should be simulating what comes out of the
output of the DW board - to convert to volts multiply by 15/32768.
PURPLE: Same kind of filtering as the GREEN, but with also a double 30 Hz highpass to remove the low
frequency damping control signals. You can see that the total transient is only ~5 counts
or ~1 mV at the coil driver output. This is comparable to the relative offset in the bypass
and filter paths.
|
| Attachment 1: etmx-dw-transient.pdf
|
|
|
677
|
Wed Jul 16 09:27:17 2008 |
steve | Update | ALARM | PSL-FSS_RMTEMP alarm is false |
Morning alarm sound is good for people who does not drink coffee.
Our 40m alarm is on every morning.
Those whom are not here in the morning thinks that this beeping sound is inspirational.
Would someone change this sound into less punishing form, like mockingbird chirp....
The C1PSL_SETTINGS.adl (40mm PSL Settings ) indicating that
C1:PSL-FSS_INOFFSET (Input Offset Adjust ) should be 0.3 +-0.05 V (red warning tag )
Alarm Handler: 40M pointing to yellow grade warning of PSL-FSS_RMTEM
This is a false alarm.
Two years trend of these channels are here: |
| Attachment 1: frmtemp2y.jpg
|
|
|
678
|
Wed Jul 16 10:50:55 2008 |
Eric | Summary | Cameras | Weekly Summary |
Finished unwrapping, cleaning, baking, wrapping, wrapping again, packing, and shipping the baffles.
Attempted to set up the Snap software so that it could talk directly to EPICS channels. This is not currently working due to a series of very strange bugs in compiling and linking the channel access libraries. Alex Ivanov directed Joe and me to a script and makefile that are similar to what we're trying to do and it may solve our problem, but at the moment this still doesn't work. We're currently using a workaround that involves making unix system calls to ezca command line tools, but this is too hacky to leave in the final program.
Attempted to fit Josh's PZT voltage vs power plot of the OMC (from about a year ago) to lorentzians in order to try to develop fitting tools for more recent data. This isn't working, due to systematic error distorting the shapes of the peaks. Good fits can be obtained by cutting the number of points to a very small number around the peak of resonance, but this leads to such a small percentage of the peak being used that I don't trust these results either. (In the graph (shows the very top of the tallest peak): blue is Josh's original data, green is a fit to this peak using the top 66% of the peak and arbitrary, equal values for the error on each point, red is Josh's data averaged over bins of size 0.005, teal is a fit to these bins where the error on each point is the standard deviation of each bin, and magenta is a fit to these same bins, except cropped to the top ~10% of the peak, x-axis is voltage, y-axis is transmission power). Rana suggested that I take my own sweeps of the PMC using scripts that are already written: I'm currently figuring out where these scripts are and how to use them without accidently breaking something.
We've begun running the Snap software for long periods of time to see how stable it is. Currently, its only problem appears to be that it memory leaks somewhat: it was up 78% memory usage after a little over an hour. It doesn't put much strain on the computer, using only ~20% CPU. Stress put on the network from the constant transfer of images from the camera to the computer is not yet known. |
| Attachment 1: AttemptedPeakFit3.tiff
|
|
679
|
Wed Jul 16 11:00:15 2008 |
Masha | Update | Auxiliary locking | improving ADC input for the mach zehnder setup and completely unrelated happenings |
For most of last week, the SURFs + Jenne were helping Mike and Ken with "stray light control for
Enhanced LIGO", i.e. cleaning and baking many many baffles which will catch scattered light in the
interferometer.
Otherwise, the two channels of the Mach Zehnder which will be used to measure fibre noise were
balanced, which should reduce the effect of laser amplitude noise in phase noise detection. I have
set up two digital channels to collect time series data from the two photodiodes and took some
preliminary noise measurements. I will be using Matlab to combine the signals as to directly measure
the phase noise, and I wrote some Matlab code to speed up this process: loading the files,
manipulating time series data, and converting into frequency domain. Currently I am building a
filter that will attenuate the signal at frequencies below 1Hz and amplify at higher frequencies in
order to whiten the spectra and reduce ADC noise. |
|
680
|
Wed Jul 16 11:26:47 2008 |
Max Jones | Update | | This Week |
Baffles.
I got a battery for the magnetometer today which is slightly too large (~2 mm) in one dimension. Not sure what I'm going to do.
I'm attempting to calibrate the magnetometer but I'm having a hard time calibrating the axis that I cannot simply put through a coil parallel to the coils length. I have attempted to use the end fields of the solenoid but the measurements from the magnetometer are significantly different from the theoretical calculations.
I would appreciate suggestions. - Max. |
|
681
|
Wed Jul 16 15:59:04 2008 |
josephb, Eric | Configuration | Cameras | PMC trans camera path |
In order to reduce saturation, we placed a Y1 plate (spare from the SP table) in transmission just before the GC650 camera looking at the PMC transmision. The reflection (most of the light) was dumped to a convient razor blade dump. We also removed the 0.3 and 0.5 ND filters and placed them in the 24 hour loan ND filter box.
Good exposure values to view are now around 3000 for that camera. |
|
682
|
Wed Jul 16 16:28:14 2008 |
josephb | Configuration | Computers | Fixed IP address on Switch |
Realized today that the change I made back on June 30th to the switch was to the wrong switch. I had disabled the DHCP setting and mislabeled the switch in the control room (which seems to not have affected anything).
I've turned DHCP back on and labeled it correctly using the Netgear "Smartwizard discovery" program. |
|
683
|
Wed Jul 16 16:59:07 2008 |
Alberto | Update | General | Aligment |
| I think the two beams are aligned again - they both pass the Faraday, they match at the irises and all along the optical path on the AP table. Although the NPRO beam does not show up at the AS port. |
|
684
|
Wed Jul 16 17:36:51 2008 |
John | DAQ | PSL | FSS input offset |
| I changed the nominal FSS input offset to 0 from 0.3. Tolerance remains unchanged at +/-0.05. |
|
685
|
Wed Jul 16 17:51:58 2008 |
Masha | Update | Auxiliary locking | long measurement |
| I'm taking a measurement on the SR785 spectrum analyzer at low frequencies, so I'm going to leave it by the symmetric port table for a while. Please don't move it! |
|
686
|
Wed Jul 16 22:29:05 2008 |
Masha | Update | Auxiliary locking | long measurement |
| Quote: | | I'm taking a measurement on the SR785 spectrum analyzer at low frequencies, so I'm going to leave it by the symmetric port table for a while. Please don't move it! |
all done thanks. |
|
687
|
Thu Jul 17 00:59:18 2008 |
Jenne | Summary | General | Funny signal coming out of VCO |
While working on calibrating the MC_F signal, Rana and I noticed a funny signal coming out of the VCO. We expect the output to be a nice sine wave at about 80MHz. What we see is the 80MHz signal plus higher harmonics. The reason behind the craziness is to be determined. For now, here's what the signal looks like, in both time and frequency domains.
The first plot is a regular screen capture of a 'scope. The second is the output of the SR spectrum analyzer, as seen on a 'scope screen. The leftmost tall peak is the 80MHz peak, and the others are the harmonics. |
| Attachment 1: VCOout_time.PNG
|
|
| Attachment 2: VCOout_freq.PNG
|
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|
688
|
Thu Jul 17 08:30:15 2008 |
steve | Update | PSL | PMC relocked manually |
The PMC pzt HV and the servo gain adj. are railing at max this morning
Why is it on the decreasing side of FSS_RTTEMP slope? |
| Attachment 1: pmc4d.jpg
|
|
|
689
|
Thu Jul 17 12:15:21 2008 |
Eric | Update | PSL | Swept PMC PZT voltage range |
I unlocked the PMC and swept over C1:PSL-PMC_RAMP's full range a couple of times this morning. The PMC should now be relocked and returned
to normal. |
|
690
|
Thu Jul 17 13:08:37 2008 |
John | Summary | LSC | HOM resonances in the arms |
On Tuesday night we attempted to lock the full DRFPMI in the optical spring configuration with the +f2 sideband resonant in the SRC.
Despite having no problems locking on the +f2 in a DRM we couldn't lock the full IFO.
There was some discussion about whether a +f2 higher order mode resonance in the arms could cause this problem.
I calculated the positions of the first six higher order modes for the carrier and all sidebands (using Siegman p 762 (23) with a plus sign).
Plot attached. Colors indicate different frequency components, numbers are the mode index (m+n). Thick lines are fundamental modes of
the sidebands. Heights of HOM indicators have been scaled by 1/(m+n)^2.
It appears that the first order transverse mode of the +166 is indeed partially resonant. We might try to tweak the sideband frequencies a
little to see if this helps us. It would probably be prudent to measure the MC length first.
Numbers used:
L = 38.5750; %average of Alberto's recent measurements elog #556
Retm = 57.375;
f166 = 165.977195e6;
f33 = 33.195439e6; |
| Attachment 1: HOMresonances.png
|
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|
691
|
Thu Jul 17 16:39:58 2008 |
Max Jones | Update | DAQ | Magnetometer Installed |
| Today I installed the magnetometer near the beam splitter chamber. It is located on the BSC chamber at head height on the inner part of the interferometer (meaning I had to crawl under the arms to install it). I don't think I disturbed anything during installation but I think that's it's probably prudent to tell everyone that I was back there just in case. I plan to run 3 BNC cables (one for each axis) from the magnetometer to the DAQ input either tonight or tomorrow. Suggestions are appreciated. - Max. |
|
692
|
Thu Jul 17 20:13:34 2008 |
Yoichi | Update | PSL | PMC alignment/mode matching effort |
I'm working to improve the mode matching of PMC.
Because I noticed that the beam was hitting the aperture of the EOM for PMC, I moved the EOM a little bit to maximize the transmission.
This did not change the alignment to the reference cavity but changed the alignment of the PMC a lot.
So I adjusted it back.
The alignment of the PMC can be easily optimized but the Hermite 02 mode still remains. This means the mode matching is bad.
Moving the lenses by a small amount (a few mm) did not change the height of 02 mode.
I'm planning to move the lenses by a large amount tomorrow. But it will destroy the alignment to the PMC.
So I installed two irises in the beam path after the lenses to remember the alignment roughly.
Right now the PMC transmission is slightly worse than before because the lens positions are not good. |
|
693
|
Fri Jul 18 12:24:15 2008 |
josephb, Eric | Configuration | Cameras | Changed Lenses on GC750 at ETMX |
We removed the giant TV zoom lens and replaced it with a much smaller fixed zoom lens. Currently it views the entire optic. We have another (also small) zoom lens which focuses much better on the spot itself. With how far back the camera is currently placed, neither of these fixed zoom lenses can touch or hit the view port or the chamber while still attached to camera and mount, even using all of the mount's motion range. So this should be less of a safety issue.
Ideally, we'd like to get some images of the full optic (including osems and so forth) with the X-arm locked, and then use the higher zoom lens while still locked, to get images we can use to calibrate the x and y length scales. |
|
694
|
Fri Jul 18 16:57:37 2008 |
Jenne | Update | IOO | Calibrated MC_F |
I have calibrated MC_F. The conversion factor is 137.49 MHz/count.
The calibration data taken is attached, along with a calibrated power spectrum.
On the data plot, the x axis is volts from the C1:IOO-MC_FAST_MON channel, with the calibration between FAST_MON and MC_F = -788.18 volts/count.
The linear term of the fit line = -0.085MHz/volt. Error bars are +/- 1 in the last digit of what the spectrum analyzer gave me for frequency (+/- 0.01MHz).
The net conversion factor is then (-788.18)*(-0.085)*(2) = 137.49 MHz/count. The factor of 2 is because the light passes through the AOM twice.
On the power spectrum,
REF0 and REF1 = MC unlocked, HEPAs on, MC Refl gain = 22
REF2 and REF3 = MC locked, HEPAs on, MC Refl gain = 22
REF4 and REF5 = MC locked, HEPAs on, MC Refl gain = 19
REF6 and REF7 = MC locked, HEPAs off, MC Refl gain = 19 |
| Attachment 1: MC_Fcalib.png
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| Attachment 2: 20080717MC_F-MC_I.pdf
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695
|
Fri Jul 18 17:06:20 2008 |
Jenne | Update | Computers | Computers down for most of the day, but back up now |
[Sharon, Alex, Rob, Alberto, Jenne]
Sharon and I have been having trouble with the C1ASS computer the past couple of days. She has been corresponding with Alex, who has been rebooting the computers for us. At some point this afternoon, as a result of this work, or other stuff (I'm not totally sure which) about half of the computers' status lights on the MEDM screen were red. Alberto and Sharon spoke to Alex, who then fixed all of them except C1ASC. Alberto and I couldn't telnet into C1ASC to follow the restart procedures on the Wiki, so Rob helped us hook up a monitor and keyboard to the computer and restart it the old fashioned way.
It seems like C1ASC has some confusion as to what its IP address is, or some other computer is now using C1ASC's IP address.
As of now, all the computers are back up. |
|
696
|
Fri Jul 18 17:12:35 2008 |
Jenne | Update | IOO | Checking out the MC Servo Board |
[Jenne, Max]
One of the things that Rana thinks that might be causing my MC_F calibration to be off is that the MC Servo Board's filters don't match those on the schematics. Max and I pulled the MC servo board today to check resistor and capacitor values. Alberto needed the Mode Cleaner, so we put the board back before finishing checking values. We will probably pull the board again next week to finish checking the values.
I haven't checked to ensure that the MC still locks, because Yoichi is doing stuff on the PSL table, but I didn't change anything on the board, and hooked all the cables back where they were, so hopefully it's all okay. |
|
697
|
Fri Jul 18 19:15:15 2008 |
Jenne | Update | IOO | Checking out the MC Servo Board |
| Quote: | [Jenne, Max]
I haven't checked to ensure that the MC still locks, because Yoichi is doing stuff on the PSL table, but I didn't change anything on the board, and hooked all the cables back where they were, so hopefully it's all okay. |
I put the PMC back and the MC now locks. |
|
698
|
Fri Jul 18 19:30:20 2008 |
Masha | Update | Auxiliary locking | moving from 40m |
| I will be working in the basement of Bridge probably starting next week; I moved the NPRO laser and some of the optics from my mach zehnder setup on the SP table to Bridge. Thanks for your help! |
|
699
|
Fri Jul 18 19:41:09 2008 |
Yoichi | Update | PSL | PMC PZT investigation |
I measured the HV coming to the PMC PZT by plugging it off from the PZT and hooking it up to a DVM.
The reading of DVM is pretty much consistent with the reading on EPICS. I got 287V on the DVM when the EPICS says 290V.
Then I used a T to monitor the same voltage while it is connected to the PZT. I attached a plot of the actual voltage measured by the DVM vs the EPICS reading.
It shows a hysteresis.
Also the actual voltage drops by more than a half when the PZT is connected. The output impedance of the HV amp is 64k (according to the schematic). If I believe this number, the impedance of the PZT should also be 64k. The current flowing the PZT is 1.6mA at 200V EPICS reading.
The impedance of the PZT directly measured by the DVM is 1.5M ohm, which is significantly different from the value expected above. I will check the actual output impedance of the HV amp later.
The capacitance of the PZT measured by the DVM is 300nF. I don't know if I can believe the DVM's ability to measure C.
I noticed that when a high voltage is applied, the actual voltage across the PZT shows a decay.
The second plot shows the step response of the actual voltage.
The voltage coming to the PZT was T-ed and reduced by a factor of 30 using a high impedance voltage divider to be recorded by an ADC.
The PMCTRANSPD channel is temporarily used to monitor this signal.
After the voltage applied to the PZT was increased abruptly (to ~230V), the actual voltage starts to exponentially decrease.
When the HV was reduced to ~30V, the actual voltage goes up. This behavior explains the weird exponential motion of the PZT feedback signal when the PMC is locked.
The cause of the actual voltage drop is not understood yet.
From the above measurements, we can almost certainly conclude that the problem of the PMC is in the PZT, not in the HV amp nor the read back. |
| Attachment 1: Hysteresis.png
|
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| Attachment 2: StepResponse.png
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|
700
|
Fri Jul 18 19:43:55 2008 |
Yoichi | DAQ | Computers | PSL fast channels cannot be read by dataviewer |
At this moment only the PSL fast channels have trouble.
Rob restarted fb40m, c1IOVME, but no effect. |
|
701
|
Fri Jul 18 23:24:24 2008 |
rob | Update | PSL | PMC PZT investigation |
| Quote: | I measured the HV coming to the PMC PZT by plugging it off from the PZT and hooking it up to a DVM.
The reading of DVM is pretty much consistent with the reading on EPICS. I got 287V on the DVM when the EPICS says 290V.
Then I used a T to monitor the same voltage while it is connected to the PZT. I attached a plot of the actual voltage measured by the DVM vs the EPICS reading.
It shows a hysteresis.
Also the actual voltage drops by more than a half when the PZT is connected. The output impedance of the HV amp is 64k (according to the schematic). If I believe this number, the impedance of the PZT should also be 64k. The current flowing the PZT is 1.6mA at 200V EPICS reading.
The impedance of the PZT directly measured by the DVM is 1.5M ohm, which is significantly different from the value expected above. I will check the actual output impedance of the HV amp later.
The capacitance of the PZT measured by the DVM is 300nF. I don't know if I can believe the DVM's ability to measure C.
I noticed that when a high voltage is applied, the actual voltage across the PZT shows a decay.
The second plot shows the step response of the actual voltage.
The voltage coming to the PZT was T-ed and reduced by a factor of 30 using a high impedance voltage divider to be recorded by an ADC.
The PMCTRANSPD channel is temporarily used to monitor this signal.
After the voltage applied to the PZT was increased abruptly (to ~230V), the actual voltage starts to exponentially decrease.
When the HV was reduced to ~30V, the actual voltage goes up. This behavior explains the weird exponential motion of the PZT feedback signal when the PMC is locked.
The cause of the actual voltage drop is not understood yet.
From the above measurements, we can almost certainly conclude that the problem of the PMC is in the PZT, not in the HV amp nor the read back. |
I'd believe the Fluke's measurement of capacitance. Here's some info from PK about the PZT:
| Quote: |
But the PMC ones were something like
0.750 in. thick x 0.287 in. thick. 2 microns per 200 V displacement,
resonant frequency greater than 65 kHz. Typical capacitance is around 0.66
uF.
|
If the PZT capacitance has dropped by a factor of two, that seems like a bad sign. I don't know what to expect for a resistance value of the PZT, but I wouldn't be surprised if it's non-Ohmic. The 64k is the series resistor after the PA85, not the modeled resistance of the PZT itself. |
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702
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Sat Jul 19 19:39:44 2008 |
rob | Update | PSL | PMC PZT investigation |
| Quote: |
| Quote: | | The 64k is the series resistor after the PA85, not the modeled resistance of the PZT itself. |
Yes. What I meant was that because the measured voltage across the PZT was a half of the open voltage of the HV amp, the DC impedance of the PZT is expected to be similar to the output impedance of the HV amp. Of course, I don't think the DC impedance of a normal PZT should be such low.
I'm puzzled by the discrepancy between this expected DC impedance and the directly measured impedance by the Fluke DVM (1.5M Ohm).
One possibility is that the PZT leaks current only when a high voltage is applied. |
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703
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Sat Jul 19 19:41:56 2008 |
Yoichi | AoG | PSL | The author of the entry 702 is Yoichi not Rob | | I made a mistake. |
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704
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Mon Jul 21 09:52:05 2008 |
Sharon | Update | | Adaptive code changes | | Thanks to Alex, we now save the coefficients of the adaptive filter every cycle. When we choose ENABLE: OFF on the MEDM screen, suppressing the signal to the MC1, we stop and save the last coefficients. When enabling it again, it starts from the last coefficients saved. I will take some measurements today to check how this contributes to the adaptation rate. If you change the number of taps or the number of AUX channels, the coefficients are again set to zero. |
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705
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Mon Jul 21 10:00:42 2008 |
steve | Update | PEM | ifo room temp | Five years of temp trend with 5 C fluctuation. The campus chilled water supply was upgraded ~ 1 year ago.
I requested our thermostats to be calibrated. |
| Attachment 1: temp5y.jpg
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706
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Mon Jul 21 11:54:00 2008 |
Jenne | Update | General | MC Servo Board | I pulled the MC Servo Board again, to check the components that are on the board, and compare them with the schematics. The filters that I'm interested in on the Fast Path haven't been changed. The high pass filters on the Fast Path have been changed.
Component Schematic Actual
--------- --------- ------
C140 10u open
C144 10u open
C149 open a gray Cap. value unknown
C141 10u open
C145 10u open
R97 1.58K 0
R99 open 1130
R103 open 1130
R100 open 0
R104 100 1130
R98 1.58K open
R109 367 365
Board is back in, and MC locks. |
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707
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Mon Jul 21 14:26:11 2008 |
Max | Summary | PEM | Added Channels | The following channels have been added.
Channel Name DAQ port
C1 : PEM-MAG_BSC_X 27
C1 : PEM-MAG_BSC_Y 28
C1 : PEM-MAG_BSC_Z 29
Jenne and I ran the wires from near the beam splitter chamber (as described in a previous elog) to the rack Y7 and plugged the labeled BNC's into ports 27-29. The computer was c0dcu1. John then restarted the frame builder and Alberto and I restarted the front end of c0dcu1 as per the wiki's instructions. The channels seem to be working. - Max. |
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708
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Mon Jul 21 15:52:22 2008 |
steve | Bureaucracy | SAFETY | fire alarms test | The fire alarm test and evacuation drill was successfully completed at 13:45 Wednesday, July 16, 2008
Everybody was on time for the 40m meeting. |
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709
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Mon Jul 21 19:48:57 2008 |
Sharon | Update | | how tp restart C1ASS | How to restart C1ASS:
1. reboot
2. as root: caltech/target/c1ass:> ./startass
3. no need for root: burtgooey
that's it... |
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