Message on 'pianosa':
Failed to fetch http://ppa.launchpad.net/drgraefy/nds2-client/ubuntu/dists/lucid/main/binary-amd64/Packages.gz 404 Not Found
Sorry, that was an experiment to see if I could set up a general-use repository for the NDS packages. I've removed it, and did an update/upgrade.
Since lately the alignment of the input beam to the interferometer has changed, I went checking the alignment of the beam on the photodiodea. They were all fine except for pd9, that is AS DD 199. Here the DC is totally null. The beam seems to go right on the diode but the scope on the PD's DC output shows no power. This is really strange and bad.
After inspecting PD9 with the viewer and the cards, the beam looks like it is aligned to the photodiode althought there is no signal at the DC output of the photodetector. So I checked the spectrum for PD9_i and Q (see attachments) and it seems that those channels are actually seeing the beam. I'm going to check the alignemtn again and see the efefct on the spectra to make sure that the beam is really hitting the PD.
I measured noise level of the phase tracker by inputting constant frequency RF signal from marconi.
Measured frequency noise was ~2 Hz/rtHz @ 100 Hz. It's not so good.
What I did:
1. Unplugged 11MHz marconi and put RF signal to the beatbox from this. Frequency and amplitude I put are 100 MHz and -3 dBm.
2. Measured spectra of phase tracker outputs, C1:ALS-BEATX_FINE_PHASE_OUT, C1:ALS-BEATY_FINE_PHASE_OUT.
3. Calibrated using the factor I measured (elog #8199).
4. Put marconi back to orignal settings.
- According to Schilt et al., this noise level is not so good.
- By changing the delay-line cable length or optimizing whitening filter etc., we can improve this.
I swept the frequency of RF input to the beatbox to calibrate and check linearity range of phase tracker.
Calibration factors are;
C1:ALS-BEATX_FINE_PHASE_OUT 52.1643 +/- 0.0003 deg/MHz
C1:ALS-BEATY_FINE_PHASE_OUT 51.4788 +/- 0.0003 deg/MHz
There was systematic error to the linearity check, but at least, calibration factor changes less than 50 % in the frequency range of 10 MHz to more than 500 MHz.
What I did:
Used network analyzer(Aligent 4395A) to sweep the frequency RF input to the beatbox and getdata of phase tracker signal. I swept from 10 Hz to 500 MHz with 501 points in 50 sec. This sweep is slow enough considering we could lock the 40m arms (typical speed of a mirror is 1 um/s, so bandwidth of the phase tracker should be more than 1 um/sec / 40 m * 3e14 Hz = 75 MHz/s).
RF amplitude was set to be -3 dBm and splitted into BEATX and BEATY.
Plots for BEATX and BEATY are below;
- Considering delay line length is ~30m, expected calibration factor is;
2*pi*l/v = 2*pi * 30 m / (2e8 m/s) = 0.94 rad/MHz = 54 deg/MHz
so, this calibration is reasonable.
- Since frequency sweep of network analyzer is not continuous, phase tracker output is like steps with some ringdown. This makes some systematic error for checking linearity. I'm planning to do slower sweep or continuous sweep. Also, the phase tracker seems like he can exceed 500 MHz.
I measured openloop transfer function of the phase tracking loop for the first characterization of phase tracker.
What is phase tracker:
See elog #6832.
For ALS, we use delay-line frequency discriminator, but it has trade-off between sensitivity and linear range. We solved this trade-off by tacking the phase of I/Q signals.
Figure below is the current diagram of the frequency discriminator using phase tracker.
OLTF of phase tracking loop:
Below. UGF at 1.2 kHz, phase margin 63 deg for both BEATX and BEATY. Phase delay can be clearly explained by 61 usec delay. This delay is 1 step in 16 KHz system.
Note that UGF depends on the amplitude of the RF input. I think this should be fixed by calculating the amplitude from I/Q signals.
BEAT(X|Y)_PHASE_GAIN were set to 300, and I put -3dBm 100 MHz RF signal to the beatbox during the measurement.
Other measurements needed:
- Linear range: By sweeping the RF input frequency and see sensitivity dependence.
- Bandwidth: By measuring transfer function from the modulation frequency of the RF input to phase tracker output.
- Maximum sensitivity: Sensitivity dependence on delay-line length (see PSL_Lab #825).
- Noise: Lock oscillator frequency with phase tracker and measure out-of-loop frequency noise with phase tracker.
- Sensitivity to amplitude fluctuation: Modulate RF input amplitude and measure the sensitivity.
We found that our phase tracker noise is currently limited by the noise introduced in DAQ.
We confirmed that the frequency noise was improved from 2 Hz/rtHz to 0.4 Hz/rtHz by increasing the gain of the whitening filter.
The whitening filters should definitely be refined.
What we did:
1. Put constant frequency RF input to the beatbox from Marconi and measured noise spectrum of the beatbox output(BEATX I) after the whitening filter with a spectrum analyzer. Noise floor level was ~0.2 Hz/rtHz at carrier frequency range of 15-100 MHz. Calibration factor of the beatbox output was ~380 mV/MHz.
2. Measured noise spectrum of C1:ALS-BEATX_FINE_I_OUTPUT(figure below). The noise floor didn't change when there was RF input of 100 MHz from Marconi(blue) and DAQ input was terminated (green). Also, C1:ALS-BEATX_FINE_I_IN1(which is before unwhitening filter) showed a flat spectrum. These show our spectrum is limited by DAQ noise, which is introduced after the whitening filter.
3. We increased the gain of whitening filter by x20 to show frequency noise performance can be improved by better whitening filter(red). But we can not use this setup as the other quadrature will be saturated by a too much gain at DC. Thus we need to carefully consider the signal level and the gain distribution of the whitening filters.
- Better whitening filters. The current one consists of zero 1 Hz and pole 10 Hz with DC gain of 5 using SR560.
- Better beatbox. We can increase the RF input power to the mixer and unify the preamplifier and the whitening filter in the box.
[Koji, Jenne, Yuta]
We put phase tracker in FINE loop for ALS. We checked it works, and we scanned Y arm by sweeping the phase of the I-Q rotator.
From the 8 FSR scan using FINE (30 m delay line), we derived that Y arm finesse is 421 +/- 6.
What we did:
1. We made new phase rotator because current cdsWfsPhase in CDS_PARTS doesn't have phase input. We want to control phase. New phase rotator currently lives in /opt/rtcds/userapps/trunk/isc/c1/models/PHASEROT.mdl. I checked that this works by sweeping the phase input and monitoring the IQ outputs.
2. We made a phase tracker (/opt/rtcds/userapps/trunk/isc/c1/models/IQLOCK.mdl) and included in c1gcv model. Unit delay is for making a feed back inside the digital system. Currently it is used only for BEATY_FINE (Simulink diagram below). We edited MEDM screens a little accordingly.
3. Phase tracking loop has UGF ~ 1.2 kHz, phase margin ~50 deg. They are enough becuase ALS loop has UGF ~ 100 Hz. To control phase tracking loop, use filter module C1:ALS-BEATY_FINE_PHASE (with gain 100). Sometimes, phase tracking loop has large offset because of the integrator and freedom of 360*n in the loop. To relief this, use "CLEAR HISTORY."
4. Locked Y arm using C1:ALS-BEATY_FINE_PHASE_OUT as an error signal. It worked perfectly and UGF was ~ 90 Hz with gain -8 in C1:ALS-YARM filter module.
5. Swept phase input to the new phase rotator using excitation point in filter module C1:ALS-BEATY_FINE_OFFSET. Below is the result from this scan. As you can see, we are able to scan for more than the linear range of FINE_I_IN1 signal. We need this extra OFFSET module for scanning because BEATY_FINE_I_ERR stays 0 in the phase tracking loop, and also, error signal for ALS, output of PHASE module, stays 0 in ALS loop.
6. We analyzed the data from 8FSR scan by FINE with phase tracker using analyzemodescan.py (below). We got Y arm finesse to be 421 +/- 6 (error in 1 sigma). I think the error for the finesse measurement improved because we could done more linear sweep using phase tracker.
Next things to do:
- Phase tracker works amazingly. Maybe we don't need COARSE any more.
- Install it to X arm and do ALS for both arms.
- From the series of mode scan we did, mode matching to the arm is OK. There must be something wrong in the PRC, not the input beam. Look into PRC mode matching using video capture and measuring beam size.
FYI and FMI
Phase tracker UGF is Q_AMP * G * 2 PI / 360 where Q_AMP is the amplitude of the Q_ERR output and G is the gain of the phase tracker.
For example: Q_AMP = 270, G = 4000\ => UGF = 1.9kHz
A comment :
Since the LSC RFPD have a long cable of more than 6 m, which rotates a 33 MHz signal by more than 360 deg, so the delay has always existed in everywhere.
The circuit you measured is a part of the delay existing in the LSC system, but of course it's not a problem as you said.
In principle a delay changes only the demodulation phase. That's how we treat them.
RA: Actually, the issue is not the delay, but instead the dispersion. Is there a problem if we have too much dispersion from the RF filter?
Two extender plates ready for cleaning. The existing optical table tops have 38" OD. Using two of these the OD will be 44"
[Steve / Kiwamu]
An attenuator, consisting of two HWPs and a PBS, has been installed on the PSL table for the MC low power state.
Those items allow us to reduce the amount of the incident power going into the MC.
We haven't decreased the power yet because we still have to measure the arm lengths.
After we finish the measurement we will go to the low power state.
We have adjusted the polarization after the last HWP using another PBS. Now it is S-polarizing beam.
After the installation of the attenuator the beam axis has changed although we were immediately able to lock the MC with TEM00 mode.
I touched two steering mirrors on the PSL table to get the transmitted power of MC higher. At the moment the transmitted power in MC_TRANS is at about 30000 cnts.
The attached picture is the setup of the attenuator on the PSL table.
[Suresh / Kiwamu]
The incident beam power going into MC was decreased down to 20 mW by rotating the HWP that we set yesterday.
A 10% beam splitter which was sitting before MCREFL_PD was replaced by a perfect reflector so that all the power goes into the PD.
And we confirmed that MC can be still locked by increasing C1IOO-MC_REFL_GAIN. Some modifications in the Autolocker script need to be done later.
Also we opened the aperture of the MC2F camera to clearly see the low power beam spot.
WE ARE READY FOR THE VENT !!
Power after the EOM = 1.27 W
Power after the HWPs and PBS = 20.2 mW
Power on MCREFL = 20 mW (MC unlocked)
MCREFL_DC = 0.66 V (with MC locked)
After we finish the measurement we will go to the low power state.
Cold cathode gauge just turned on.
Slow pump down _pd68 has reached the vacuum normal state. CC4_Rga region is pumped now. The RGA is still off.
Precondition to this pump down: 129 days at atm, ITMs replaced. MMT, oplev and other components were removed from BSC, ITMCs. New MMT mirrors are in. IOO_access_connector was out. The end chambers were not opened.
This is to facilitate the summary page config fines to be pulled from nodus in a scripted way, without being asked for authentication. If someone knows of a better/more secure way for this to be done, please let me know. The site summary pages seem to pull the config files from a git repo, maybe that's better?
I found that several linux libraries have been moved around and disabled today. In particular, I see a bunch of new stuff in apps/linux/ and ezca tools are not working.
Also found that someone has pulled the power cable to the function generator I was using to set the VCO offset. This is the one on top of the Rb clocks. Why?? Why no elog? This is again a big waste of time.
Password for nodus and all control room workstations has been changed. Look for new one in usual place.
We will try to change the password on all the RTS machines soon. For the moment, though, they remain with the old passwerd.
We will need to order a few things for our final setup.
I've updated the parts list to be an excel document and included every single part we will need. This is ony a first draft so it will probably be updated in the future. I also made a mistake in hole sizing for the front panel so I've updated it and attached it as well (second attachment).
Edit: re-attached the EX can panel fpd file so that everything is in one place
Got this 1U box from the Y arm that we could potentially use (attachment 1). It doesn't have handles on the front but I guess we could attach them if necessary. Attachment 2 is a switch that could be used instead of a light up switch, but now we need to add LEDs on the front panel that indicate that the switch is functional. Attachment 3 is a terminal block that we can use to attach the 16 gage wire to since it is thick and attaching it directly to the board would be difficult. If this is alright to use then I'll change up my designs for the front panel and PCB to accomodate these parts.
The outside particle counts for 0.5 micron are 3 million this morning at 9am. Low clouds, foggy condition with low inversion layer.
This makes the 40m lab 30-50K
I just turned on the HEPA filter at the PSL enclosure.
Please, leave it on high
I moved the mobile HEPA filter from ITMX's north door to ITMX-ISCT and covered it up with a merostate tent to accommodate the aluminum foil particle measurement on June 5
It lowered the 40m baseline counts by about a factor of 3 of 0.5 micron and a factor of 2 of 1.0 micron.
The HEPA filter is sweeping the floor and blowing the particles upwards. The MET ONE counter is on the top of the IOOC looking south at ~75 degrees upward.
The San Gabriel mountain has been on fire for 6 days. 144,000 acres of beautiful hillsides burned down and it's still burning. Where the fires are.
The 40m lab particle counts are more effected by next door building-gardening activity than the fire itself.
This 100 days plot shows that.
How can we improve the cleanliness of the 40m IFO room 104 ? May be Mario Batali crocs if you chief chef of the lab likes it. We can do more effective things.
Atm 1 is showing the lab air quality dependence on outside air measured at the top of the IOO chamber. This made me to measure the differential pressure between lab and out side.
Properly sized air conditioner is over pressurizing it's room by 0.05 [" Water] like clean assembly room.
The 40m at Vertex location is barely getting pressurized to 0.01 " W
The control room is OK with 0.04 " W but it's air quality is very bad! It is 10x worse at 0.5 micron than IFO room.
Every entry from well pressurized control room into barely pressurized IFO pumps dirty air to our "clean room."
This door should be closed.
The drill- room entry is ideal because it is using the same air conditioner as the main lab, therefore it has cleaner air.
Things to do: seal holes of CES walls, seal paint wall at south end so it will shed less, replace gas kits on doors.
I have plugged the cable tray space entering the control room above Rosalba.
Probably more important is to establish quantitatively how particle counts affects the lock acquisition or noise in the interferometer.
We don't want to adopt a "Sky is Falling" mentality as was done previously in LIGO when people were trying to outlaw burritos and perfume.
Dust monitor counts and human noses do not correlate well with the interferometer's nose.
When the vacuum system is closed, we might check to see if particle counts correlate with losses in the PMC or excess scatter on the ISC tables. If not, we should move on to other concerns.
I played with the particle counter this morning. Now it's running and reading the correct numbers on the old COCHECKLIST.adl medm screen.
However, it can not be seen with dataviewer.
Koji just rebooted the frame builder and the problem was solved.
The MET#1 particle counter was moved from CES wall at ITMX to PSL enclousure south west corner at 11am.
The HEPA filter speed at the Variac was turned down to 20V from 40
This counter pumps air for 1 minute in every 20 minutes. Soft foam in bags used to minimize this shaking as it is clamped.
The logging script is multiplying by 100 instead of 10 !
Some one turned up the PSL HEPA rotation voltage from 20 V to 33 ( 120V Variac ) and X-arm AC set temp lowered to 68F
Effects at 12" height from optical table :
1.0, 0.5 & 0.3 micron particle count goes to zero and temperature fluctuaion increased
Rotation speed voltage was set to 30V
Jeff is still working on the filter banks.
South end flow bench and both clean room assembly flow benches measured zero counts for 0.3 and 0.5 micron size particales.
The counting efficiency of 0.5 micron is 100%
0.3 micron particles / cf min
0.5 micron particles / cf min
The PSL HEPA performance was measured at the center of the table with MET ONE #3
ETMY end ThinkPad "paola" could not reboot due to "Fan Error". It seems that it is the failure of the CPU fan. I really needed a functional laptop at the end for the electronics work, I decided to open the chassis. By removing the marked screws at the bottom lid, the keyboard was lifted. I found that the CPU fan was stuck because of accumulated dust. Once the fan was cleaned, the laptop starts up as before.
I finished designing the PCBs for the VME crate back sides (see attached). The project files live on the DCC now at https://dcc.ligo.org/LIGO-D1700058. I ordered a prototype quantity (9) of the PCB printed and bought the corresponding connectors, all will arrive within the next two weeks. See also attached the front panels for the Acromag DAQ chassis and Lydia's RF amplifier unit (the lone +24V slot confuses me: I don't see a ground connector?). On the Acromag panel, six (3x2) of the DB37 connectors are reserved for VME hardware, two are reserve, and I filled the remaining space with general purpose BNC connectors for whatever comes up.
The amplifier unit should use the three pin dsub connectors (3w3?) that we use on many of the other units for DC power, and preferably go through the back panel. You can leave out the negative pin, since you just need +24 and ground.
This is already how it's hooked up. The hole on the from that says +24 V is for an indicator light.
Somebody changed the settings on painosa without elogging anything about it. Why does this keep happening? I thought the point of the elog was to communicate. I think there are sufficient number of problems in the lab without me having to manually reset the control room workstation settings every week. Please make an elog if you change something.
Overnight, the pressure increased from 247 uTorr to 264 uTorr over a period of 30000 seconds. Assuming an IFO volume of 33,000 liters, this corresponds to an average leak rate of ~20 uTorr L / s. It'd be interesting to see how this compares with the spec'd leak rates of the Viton O-ring seals and valves/ outgassing rates. The two channels in the screenshot are monitoring the same pressure from the same sensor, top pane is a digital readout while the bottom is a calibrated analog readout that is subsequently digitized into the CDS system.
We allowed the pumpdown to continue until reaching 9e-4 torr in the main volume. At this point we valved off the main volume, valved off TP2 and TP3, and then shut down all turbo pumps/dry pumps. We will continue pumping tomorrow under the supervision of an operator. If the system continues to perform problem-free, we will likely leave the turbos pumping on the main volume and annuli after tomorrow.
The pressure of the main volume increased from ~1mtorr to 50mtorr for the past 24 hours (86ksec). This rate is about x1000 of the reported number on Jan 10. Do we suspect vacuum leak?
Overnight, the pressure increased from 247 uTorr to 264 uTorr over a period of 30000 seconds. Assuming an IFO volume of 33,000 liters, this corresponds to an average leak rate of ~20 uTorr L / s.
I looked into this a bit today. Did a walkthrough of the lab, didn't hear any obvious hissing (makes sense, that presumably would signal a much larger leak rate).
Attachment #1: Data from the 30 ksec we had the main vol valved off on Jan 10, but from the gauges we have running right now (the CC gauges have not had their HV enabled yet so we don't have that readback).
Attachment #2: Data from ~150 ksec from Friday night till now.
Interpretation: The number quoted from Jan 10 is from the cold-cathode gauge (~20 utorr increase). In the same period, the Pirani gauge reports a increase of ~5 mtorr (=250x the number reported by the cold-cathode gauge). So which gauge do we trust in this regime more? Additionally, the rate at which the annuli pressures are increasing seem consistent between Jan 10 and now, at ~100 mtorr every 30 ksec.
I don't think this is conclusive, but at least the leak rates between Jan 10 and now don't seem that different for the annuli pressures. Moreover, for the Jan 10 pumpdown, we had the IFO at low pressure for several days over the chirstmas break, which presumably gave time for some outgassing which was cleaned up by the TPs on Jan 10, whereas for this current pumpdown, we don't have that luxury.
Do we want to do a systematic leak check before resuming the pumpdown on Monday? The main differences in vacuum I can think of are
This entry by Steve says that the "expected" outgassing rate is 3-5 mtorr per day, which doesn't match either the current observation or that from Jan 10.
We can pump down (or vent) annuli. If this is the leak between the main volume and the annuli, we will be able to see the effect on the leak rate. If this is the leak of an outer o-ring, again pumping down (or venting) of the annuli should temporarily decrease (or increase) the leak rate..., I guess. If the leak rate is not dependent on the pressure of the annuli, we can conclude that it is internal outgassing.
Folks were complaining that they were getting zeros whenever they tried to open fast channels in DTT or Dataviewer. It turned out that the problem was that all available test points were in use in the c1lsc model:
There is a limit to how many test points can be open to a single model (in point of fact I think the limit is on the data rate from the model to the frame builder, not the actual number of open test points). In any event, they was all used up. The grid at the bottom right of the C1LSC GDS screen was all full of non-zeros, and the FE TRATE number was red, indicating that the data rate from this model had surpassed threshold.
The result of this overbooking is that any new test points just get zeros. This is a pretty dumb failure mode (ideally one would not be able to request the TP at all with an appropriate error message), but it is what it is. This usually means that there are too many dtt/dataviewers left with open connections.
We tried killing all the open processes that we could find that might be holding open test points, but that didn't seem to clear them up. Stuck open test points is another known problem. Referencing the solution in #6968 I opened the diag shell and killed all test points everywhere:
controls@pianosa:~ 0$ diag -l -z
Set new test FFT
NDS version = 12
supported capabilities: testing testpoints awg
diag> tp clear * *
test point cleared
Two out of the four over-head fluorescent lights in the X end of the interferometer were flickering today.