ID |
Date |
Author |
Type |
Category |
Subject |
|
910
|
Tue Sep 2 09:58:42 2008 |
Yoichi | Configuration | PSL | FSS on an auxiliary loop |
| Quote: | Summary: The FSS is now temporarily disabled. Naturally, the MC won't lock. I will fix it tomorrow morning.
|
Now I removed the power splitters for the aux. reference cavity servo. The FSS is back and the MC locks.
I'm now returning one of the active high-impedance probes to the Wilson house. They need it today.
We are left with only one active probe. If anyone finds another active probe in the 40m lab.,
please let me know (according to Rana we should have one more). |
|
911
|
Tue Sep 2 10:09:03 2008 |
steve | Update | PSL | head temp is cooling down |
The chiller was over flowing this morning.
800 cc of water was removed.
PSL-126MOPA_HTEMP peaked at 20.7 C (normal is 18.7 C) |
|
912
|
Tue Sep 2 14:28:41 2008 |
Yoichi | Update | PSL | FSS EOM driving signal spectra |
Rich advised me to change the +10V input of the FSS crystal frequency reference board from whatever voltage supply we use now to a nice one.
This voltage is directory connected to the signal lines of both LO and RF output amps. Therefore, fluctuations in the voltage directly appear
in the outputs, though DC components are cut off by the AC coupling capacitors.
I changed the source of this voltage from the existing Sorensen one to a power supply sitting next to the rack.
The attached plots shows the difference of the RF output spectra between the two 10V sources.
The low frequency crap is almost gone in the new 10V spectrum.
I tried to increase the FSS gain with the new 10V, but still it goes crazy. I suspect it is because the LO power is too low. |
| Attachment 1: RFDrive1.png
|
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| Attachment 2: RFDrive2.png
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|
|
913
|
Tue Sep 2 22:43:16 2008 |
Yoichi | Configuration | PSL | Updated FSS open loop TF |
Since the LO level of the FSS servo was too low, I replaced the RF oscillator board with a combination of
a Stanford signal generator and an RF amplifier.
Right now, the POY RF amplifier is used for this purpose temporarily.
Now the LO level is about 16dBm. The RF power going into the EOM is attenuated by 20dB from the LO level.
I played with the cable length to get the phase right.
Then I was able to lock the FSS with the new RF signal source.
Attached is the open loop transfer function of the current FSS. Now the UGF is a bit above 200kHz, a factor of 2 improvement.
This gain was achieved with the common gain slider at 13.5dB and the fast gain = 30dB.
With the old RF oscillator board, UGF=100kHz was achieved with the common gain =30dB. Therefore, the increase of the LO gave
us a large signal gain.
Increasing the gain further, again ,makes the PC path crazy.
Rich suggested that this craziness was caused either by the slew rate limit of the PA85 or the output voltage limit of the bypass Op-amp(A829)
is hit.
TO DO:
* Look at the error signal spectrum to see if there is any signal causing the slew rate saturation at high frequencies.
* Find out what the RF signal level for the EOM should be. 20dB attenuation is an arbitrary choice.
* Find out the cross over frequency. Determine where the fast gain slider should be.
etc ... |
| Attachment 1: OPLTF.png
|
|
|
914
|
Wed Sep 3 12:26:49 2008 |
Eric | Summary | Cameras | Weekly Summary |
Finished up simulating the end mirror error in order to test the whether the fitting code still provides reasonable answers despite the noise caused by the defects on the end mirror. The model I used to simulate the defects is far from perfect, but its good enough given the time I have remaining, and I have no reason to believe the differences between it and the real noise would cause any radical changes in how the fit operates. A comparison between a modeled image and a real image is attached. Average error (difference between the estimated value and the real value) for each of the parameters is
For the fit:
Max Intensity: 2767.4 (Max intensities ranged from 8000 to 11000)
X-Position: 0.9401 pixels
X Beam Waist: 1.3406 pixels (beam waists ranged from 35 to 45)
Y-Position: 0.9997 pixels
Y Beam Waist: 1.3059 pixels (beam waists ranged from 35 to 45)
Intensity Offset: 12.7705 (Offsets ranged from 1000 to 4000)
For the center of mass calculation (with a threshold that cut off everything above 13000)
X-Position: 0.0087 pixels
Y-Position: 0.0286 pixels
Thus, the fit is generally trustworthy for all parameters except for maximum intensity, for which it is very inaccurate. Additionally, this shows that the center of mass calculation actually does a much better job than the fit when this much noise is in the image. For the end mirrors, the fit is really only useful for finding beam waist, and even this is not extremely accurate (~3% error). All the parameters for the modeling is on the svn in /trunk/docs/emintun/MatLabFiles/EndMirrorErrorSimulation.txt.
Finished working on the calculations that convert a beam misalignment as measured as a change in the beam position on the two mirrors to a power loss in the cavity. Joe calculated the minimum measurable change in beam position to be around a tenth of a pixel, which corresponds to half a micron when the beam is directly incident on the camera. This gives the ability to measure fractional power losses as low as 2*10^-10 for the 40m main arm cavities. To me, this seems unusually low, though it scales with beam position squared, so if anything else limited the ability to measure changes in the beam position, it would have a large effect on the sensitivity to power losses. Additionally, it scales inversely with length, so shorter cavities provide less sensitivity.
This morning Joe and I tested the ability for the camera code to servo the ITMX in order to change the beam's position on the ETMX. Two major things have been changed since the last time we tried this. First, the calculated beam center that gets output to the EPICS channels now first goes through a transform that converts it from pixels into physical units, and should account for the oblique angle of the camera. The output to the EPICS channels should now be in the form of 'mm from the center of the optic', although this is not very precise at the moment. The second thing that was changed was that the servo was run with a modified servo script that included options to set a minimum, maximum, and slew rate in order to protect the mirrors from being swung around too much. The servo was generally successful: for a given x-position, it was capable of changing the yaw of ITMX so that the position seen on the camera moved to this new location. The biggest problem is that the x and y dimensions do not appear to be decoupled (the transform converting it to physical units should have done this), so that modifying the yaw of the mirror changed both the x and y positions (the y about half as much) as output by the camera. This could cause a problem when trying to servo in both dimensions at once, since one servo could end up opposing the other. I don't know the cause of this problem yet, since the transform that is currently in use appears to be correctly orienting the image. |
| Attachment 1: SimulatedErrorComparison.png
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|
915
|
Wed Sep 3 18:43:19 2008 |
Yoichi | Configuration | Electronics | Two more active probes |
I found two active probes, an HP41800A and a Tektronix P6201.
Thanks John for telling me you saw them before.
Now we have three active probes, wow !
We have to find or make a power supply for P6201.
The manual of the probe is attached. |
| Attachment 1: Tektronix-P6201-active-probe.pdf
|
|
|
916
|
Wed Sep 3 18:45:01 2008 |
Alberto | Configuration | | PD3 gain |
Alberto, Yoichi,
We found that the PD3 servo was unstable with a gain of 1, so we switched it to 0.5 |
|
917
|
Wed Sep 3 19:09:56 2008 |
Yoichi | DAQ | Computers | c1iovme power cycled |
When I tried to measure the sideband power of the FSS using the scan of the reference cavity, I noticed that the RC trans. PD signal was not
properly recorded by the frame builder.
Joe restarted c1iovme software wise. The medm screen said c1iovme is running fine, and actually some values were recorded by the FB.
Nonetheless, I couldn't see flashes of the RC when I scanned the laser frequency.
I ended up power cycling the c1iovme and run the restart script again. Now the signals recorded by c1iovme look fine.
Probably, the DAQ boards were not properly initialized only by the software reset.
I will re-try the sideband measurement tomorrow morning. |
|
918
|
Thu Sep 4 00:38:14 2008 |
rana | Update | PSL | c1iovme power cycled |
Entry 663 has a plot of this using the PSL/FSS/SLOWscan script. It shows that the SB's were ~8x smaller than the carrier.
P_carrier J_0(Gamma)^2
--------- = ------------
P_SB J_1(Gamma)^2
Which I guess we have to solve numerically for large Gamma? |
|
919
|
Thu Sep 4 07:29:52 2008 |
Yoichi | Update | PSL | c1iovme power cycled |
| Quote: | Entry 663 has a plot of this using the PSL/FSS/SLOWscan script. It shows that the SB's were ~8x smaller than the carrier.
P_carrier J_0(Gamma)^2
--------- = ------------
P_SB J_1(Gamma)^2
Which I guess we have to solve numerically for large Gamma? |
P_carrier/P_SB = 8 yields gamma=0.67. |
|
920
|
Thu Sep 4 07:46:10 2008 |
Yoichi | Update | IOO | MC is now happy |
The MC has been locked for more than 12 hours continuously now !
Changes I made yesterday were:
(1) Removed the 20dB attenuator before the EOM.
(2) Reduced the Fast Gain from 21dB to 16dB, which made the PC to be a little bit more loaded (~0.6Vrms).
As Rana pointed out in the meeting, setting the Fast Gain a bit lower may have put the FSS in a stabler state. |
| Attachment 1: MC-lock.png
|
|
|
921
|
Thu Sep 4 10:13:48 2008 |
Jenne | Update | IOO | We unlocked the MC temporarily |
[Joe, Eric, Jenne]
While trying to diagnose some DAQ/PD problems (look for Joe and Eric's entry later), we unlocked the PMC, which caused (of course) the MC to unlock. So if you're looking back in the data, the unlock at ~10:08am is caused by us, not whatever problems may have been going on with the FSS. It is now locked again, and looking good. |
|
922
|
Thu Sep 4 11:33:25 2008 |
josephb, Eric, Jenne | Configuration | Computers | Attempt to increase gain for C1:PSL-ISS_INMONPD_F via 110B |
We were attempting to increase the gain on the channel C1:PSL-ISS_INMONPD_F in preparation to do a scan of the PMC at very low input power.
We started by adding a line to the C1:IOOF.ini file in /cvs/cds/caltech/chans/daq/ under that channel that said "gain=10.0". Before touching anything, the channel was outputting around 4000 counts.
We hit the reconfig button for c1iovme16k, then rebooted c1iovme (which turned out to do nothing) and then the framebuilder, in a method consistent with the wiki. This turned out to put the channel in an odd state, where it was showing very rapid, random spikes, virtually but still around 4000ish counts. We returned the file back to its original format, hit reconfig, and then rebooted the framebuilder. The channel however, was still behaving in the same broken way.
After poking around the PSL table, looking at some direct outputs, we came back and rebooted c1iovme and the framebuilder again, which fixed the channel, such that it was reading out correctly. Taking this as a sign that maybe we should reboot the framebuilder, then c1iovme to get the channel to load changes, we changed the file again to have "gain=10.0". Upon reboot of the framebuilder, the channel was still reading out fine, but at the same level. So we continued with the reboot of c1iovme. This still had no effect on the channel output.
The ini file has been set back at this point, however since Yoichi is working, I'm holding off doing a reconfig and reboot on the framebuilder until later. |
|
923
|
Thu Sep 4 13:48:50 2008 |
Yoichi | Update | PSL | FSS modulation depth |
I scanned the reference cavity with the NPRO temperature (see the attached plot).
The power ratio between the carrier and the sideband resonances is about 26.8.
It corresponds to gamma=0.38.
The RF power fed into the EOM is now 14.75dBm (i.e. 1.7V amplitude). The NewFocus catalog says 0.1-0.3rad/V. So
gamma=0.38 is a reasonable number.
|
| Attachment 1: RCScan.png
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924
|
Thu Sep 4 14:43:58 2008 |
Jenne | Update | PSL | PMC Open Loop Gain |
I have measured the PMC's open loop gain. UGF is 629.7Hz, with a phase margin of 53 degrees.
I injected into FP2 on the front panel, and measured MixOut/Source from 100Hz to 100kHz using the SR785. I did this both when the loop was open, and when the loop was closed (open the loop by enabling FP1, which breaks the loop).
We have 2 transfer functions involved: The actual open loop gain of the PMC servo loop (G1), and the gain between FP2 and the MixerOut monitor point (G2). This gives us:
TF(closed loop) = G2*(1+G1)
TF(broken loop) = G2
G1 = TF(closed)/TF(broken) - 1
This G1 is the final open loop gain, and it is plotted below. |
| Attachment 1: OpenLoopTF04Sept2008.png
|
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|
925
|
Thu Sep 4 16:24:56 2008 |
rana | Configuration | Computers | Attempt to increase gain for C1:PSL-ISS_INMONPD_F via 110B |
| Quote: | We were attempting to increase the gain on the channel C1:PSL-ISS_INMONPD_F in preparation to do a scan of the PMC at very low input power.
|
According to the Wikipedia, certain esoteric mathematical
operations lead to the result that 4000 x 10 > 32768. |
|
926
|
Thu Sep 4 17:03:25 2008 |
Yoichi | Update | PSL | RF oscillator noise comparison |
I measured current spectra of the RF signal going to the FSS EOM.
The attachment compares the spectra between a Stanford signal generator and a Marconi.
I borrowed the Marconi from the abs. length measurement experiment temporarily.
The measurement was done using the signal going to the EOM. That means the spectra include
noise contributions from the RF amp., splitter and cables.
21.5MHz peak was not included because that would overload the ADC and I would have to use a large attenuation.
This means the measurement would be totally limited by ADC noise everywhere except for 21.5MHz.
I noticed that with the Marconi, the FSS is a little bit happier, i.e. the PC path is less loaded
(0.9Vrms with Stanford vs. 0.7Vrms with Marconi). But the difference is small.
Probably the contribution from the 77kHz harmonics in the laser light is more significant (see entry #929).
Also the peaks in the Stanford spectrum are not harmonics of 77kHz, which we see in the FSS error signal.
I returned the Marconi after the measurement to let Alberto work on the abs. length measurement. |
| Attachment 1: RFSpectra.png
|
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|
927
|
Thu Sep 4 17:12:57 2008 |
Yoichi | Update | PSL | FSS open loop TF |
I changed the gain settings of the FSS servo.
Now the Common Gain is 5dB (the last night it was 2dB) and the Fast Gain is 12dB (formerly 16dB).
I measured the open loop TF with this setting (the attachment).
I also plotted the OPLTF when CG=2dB, FG=20.5dB. With this setting, the MC looses lock every 30min.
You can see that the OPLTF is smoother with FG=12dB.
When the FG is high, you can see some structure around 250kHz. This structure is reproducible.
This may be some interruption from the fast path to the PC path through a spurious coupling. |
| Attachment 1: FSS-OPLTFs.png
|
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|
928
|
Thu Sep 4 17:17:03 2008 |
Yoichi | Update | IOO | MC open loop TF |
I measured open loop transfer functions of the MC servo.
The UGF was about 30kHz. Since there was some gain margin at higher frequencies, I increased
the input gain of the MC servo board from 19dB to 22dB. Now the UGF is 40kHz and we have more
phase margin (~30deg). |
| Attachment 1: MC-OPLTF.png
|
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|
929
|
Thu Sep 4 17:44:27 2008 |
Yoichi | Update | PSL | FSS error signal spectrum |
Attached is a spectrum of the FSS error signal.
There are a lot of sharp peaks above 100kHz (the UGF of the servo is about 200kHz).
These are mostly harmonics of 77kHz. They are the current suspects of the FSS slew rate saturation.
I remember when I blocked the light to the PD, these peak went away. So these noises must be
in the light. But I checked it a few weeks ago. So I will re-check it later.
One possible source of the lines is a DC-DC converter in the NPRO near the crystal.
We will try to move the converter outside of the box. |
| Attachment 1: FSS-Error-Spe.png
|
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|
930
|
Thu Sep 4 18:02:34 2008 |
rana, josephb | Configuration | PEM | Accelerometer gains increased by 10 |
We increased the Accelerometer gains by 10 by modifying the C1ADCU_PEM.ini file.
[C1:PEM-ACC_MC1_X]
chnnum=15014
gain = 10
etc.
The plot shows the before and after for one channel. The ADC noise floor is ~10^-2 counts/rHz in this plot so now
we can do much better noise subtraction. |
| Attachment 1: acc.png
|
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|
931
|
Fri Sep 5 08:34:03 2008 |
steve | Update | PSL | MZ locked |
The MC is happy.
The MZ can be locked if you move the slider by hand. |
| Attachment 1: mzhv.jpg
|
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|
932
|
Fri Sep 5 09:56:14 2008 |
josephb, Eric | Configuration | Computers | Funny channels, reboots, and ethernet connections |
1) Apparently the I00-ICS type channels had gotten into a funny state last night, where they were showing just noise, exactly when Rana changed the accelerometer gains and did major reboots. A power cycle of the c1ioo crate and appropriate restarts fixed this.
2) c1asc looks like it was down all night. When I walked out to look at the terminal, it claimed to be unable to read the input file from the command line I had entered the previous night ( < /cvs/cds/caltech/target/c1asc/startup.cmd). In addition we were unable to telnet in, suggesting an ethernet breakdown and inability to mount the appropriate files. So we have temporarily run a new cat6 cable from the c1asc board to the ITMX prosafe switch (since there's a nice knee high cable tray right there). One last power cycle and we were able to telnet in and get it running. |
|
933
|
Fri Sep 5 10:36:34 2008 |
steve | Update | PEM | thermostate setting changed |
Some one changed the thermostat (old control room ) setting behind 1Y6 from 73 to 79F
It should be in the elog.
The temp changed from freezing 20 to sunny 25 C |
|
934
|
Fri Sep 5 15:09:50 2008 |
rana | Update | PEM | thermostate setting changed |
| Quote: | Some one changed the thermostat (old control room ) setting behind 1Y6 from 73 to 79F
It should be in the elog. |
In fact, it is. I demand satisfaction for the injury to my elogging reputation! |
|
935
|
Mon Sep 8 10:57:49 2008 |
steve | Update | IOO | the psl and mc are back to normal |
The alarm handler is silent this morning.
This is almost unbelievably pleasant after two mount of harassment.
The MC did not lose lock for three days.
Atm1: the new fss layout
Atm2: PMC with lead brick
Atm3: 3 days plot |
| Attachment 1: fss.png
|
|
| Attachment 2: pmcbrick.png
|
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| Attachment 3: brick.jpg
|
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|
936
|
Mon Sep 8 13:47:35 2008 |
steve | Update | PEM | thermostate setting changed |
| Quote: |
| Quote: | Some one changed the thermostat (old control room ) setting behind 1Y6 from 73 to 79F
It should be in the elog. |
In fact, it is. I demand satisfaction for the injury to my elogging reputation! |
Thermostate setting was changed from 79F to 77F behind 1Y6 |
|
937
|
Mon Sep 8 15:38:57 2008 |
Yoichi | Configuration | PSL | POY RF amp is back to its original task |
I temporarily fixed the busted ZHL-32A RF amplifier's power connector by simply soldering a cable to the internal circuit and pulling the cable out of the box through a hole for the power connector.
So I released the POY RF amplifier from the temporary duty of serving the FSS RF distribution and put it back to the original task,
so that Rob can finally re-start working on the lock acquisition.
Now the temporarily fixed ZHL-32A is sitting next to the IOO rack along with the power supply and a Stanford signal generator.
Please be careful not to topple over the setup when you work around there. They will be there until Peter's Wentzel RF box arrives. |
|
938
|
Wed Sep 10 08:57:03 2008 |
steve | Update | General | etmy illuminator turned off |
The ETMY illuminator was left on yesterday.
I just turned it off. |
|
939
|
Wed Sep 10 13:28:25 2008 |
Yoichi | Summary | Electronics | IOO rack lost -24V (recovered) |
Alberto, Yoichi
This morning, the MC suddenly started to be unwilling to lock.
I found a large offset in the MC servo board.
It turned out that -24V was not supplied to the Eurocard crate of the IOO rack.
We found two loose cables (violet, that means -24V) around the cross connects with fuses.
We connected them back, and the -24V was back.
The MC locks fine now, and Alberto can continue his arm length experiment. |
|
940
|
Wed Sep 10 19:53:53 2008 |
Alberto | Update | General | abs length experiment |
Update of the last days work on the experiment to measure the absolute length of the cavities.
I'm trying to repeat the same measurement that Koji did on the Y arm, before switching to the X arm.
I switched to the PHD universal box for the PLL control between the main laser and the secondary laser. I found a good gain value for the servo and now I can set the frequency of the beat to any value as long as I do it slowly turning the LO frequency from the knob on the Marconi.
I laid down a 50m BNC cable from the Y end to near the BS chamber, where all the abs length equipment is. I matched the two laser beams changing the alignment of the injection steering mirror at the the dark port on the AP table. I then locked the Y arm cavity. When I first tried to do that, the locking script didn't work because the beam was off of the 'sweet spot' where Rob had set it on Monday. It turned out that aborting the script during one of its previous run, had changed the alignment of the PZT steering mirrors. So with Rob I brought them back near the positions as in the snapshot and then saved a new one with the latest values.
Eventually I could set the beat frequency to the FSR of the arm cavity and saw it in transmission at the ETMY.
Now I'm working on the LabView interface for the GPIB data acquisition board. |
|
941
|
Thu Sep 11 11:29:14 2008 |
josephb | Configuration | Computers | Final netgear switch in place in 1Y2 |
I've placed the final (of 4) Netgear prosafe 24 port switch at the very top of 1Y2. At that location, there are no holes left to screw into, so it has 4 rubber feet and is sitting on the top most signal generator. It has been plugged in and connected to the control room hub with a labeled cat6 ethernet cable.
Its IP address has been set to 131.215.113.253, and has the usual controls password if using the "Smart Wizard Discovery Tool" which comes on the Netgear CD. The CD can be found in the Equipment manuals filing cabinet under Netgear. This program unfortunately only runs on a window PC.
To Do: Fix the C1:ASC ethernet connection which is currently coming straight out the front door and connected to the 1X4 switch (again through the front door). |
|
942
|
Thu Sep 11 14:27:53 2008 |
steve | Bureaucracy | SAFETY | safety training |
| Peter Kalmus received 40m specific safety training last week. |
|
943
|
Thu Sep 11 23:28:35 2008 |
alberto | Update | General | abs cavity length experiment |
| The MC lost lock for some reason not related to either the FSS or the PMC I'm done with my measurement for tonight. I've shut the NPRO beam before leaving. |
|
944
|
Fri Sep 12 11:09:20 2008 |
Alberto | Update | General | abs cavity length experiment |
| I'm leaving the lab for a couple of hours. I shut the NPRO. The interferometer is available to anyone. |
|
945
|
Sat Sep 13 23:13:01 2008 |
Alberto | Update | General | abs cavity length experiment |
| The Y arm was locked all time today but, suddenly, this afternoon it lost lock and since then I've been unable to restore it. I tried unsuccessfully the Restore and the Align scripts several times, although the position of PZT steering mirrors were good (as in the snapshot). I tried things like unlocking/locking the MC, the FSS reference cavity, the PMC but it didn't work. Then I decided to switch to the X arm. Locking it was a piece of cake compare to Y. I'm going to start measuring the FSR of the X arm. |
|
946
|
Sun Sep 14 18:30:32 2008 |
Alberto | Update | General | ABSL: measured X arm |
Today I measured the X arm FSR.
Hi moved the fast PD (Thor Labs PDA255) from the Y end table to the X end table. I had to use a beam splitter to pick out the transmitted beam from the cavity beam and send it to the PD. I did not want to interpose the BS before the TRANS X PD, so I had to move the ETMXT camera to an other place in the table to gain some room. Now the beam that used to go directly to the camera is 50% split and goes also to the PD. I had to put a lens to focus the beam on the PD. The transmitted beam is currently not aligned to the ETMXT camera, I need to fix the alignment of the BS before.
I'm now doing a rough scan of a frequency range 5 times as large as the FSR. I'll post the results soon. |
|
947
|
Sun Sep 14 19:29:07 2008 |
Alberto | Update | General | ABSL: measured X arm |
| Quote: | Today I measured the X arm FSR.
Hi moved the fast PD (Thor Labs PDA255) from the Y end table to the X end table. I had to use a beam splitter to pick out the transmitted beam from the cavity beam and send it to the PD. I did not want to interpose the BS before the TRANS X PD, so I had to move the ETMXT camera to an other place in the table to gain some room. Now the beam that used to go directly to the camera is 50% split and goes also to the PD. I had to put a lens to focus the beam on the PD. The transmitted beam is currently not aligned to the ETMXT camera, I need to fix the alignment of the BS before.
I'm now doing a rough scan of a frequency range 5 times as large as the FSR. I'll post the results soon. |
I'm leaving a long measurement running. I should be back later on. If I won't, whoever wanted to use the interferometer has just to shut the NPRO laser in the AP table. |
|
948
|
Mon Sep 15 14:00:52 2008 |
josephb | Configuration | Computers | 1Y9 Hub and C1asc |
The 1Y9 switch is now using a labeled Cat6 cable in cable trays to connect to the main switch in the offices. In addition, the c1asc cable which had been coming out the door was fixed last Friday, and is now labeled, going out the top and connects to the hub in 1Y2.
Note: Do not connect new ethernet cable from switch to switch without disconnecting the old cable to the rest of the network - this tends to make the Ethernet network unhappy with white flashing alarms. |
|
949
|
Tue Sep 16 10:57:45 2008 |
Yoichi | Configuration | PEM | Particle counter gain |
Summary:
Since we reduced the integration time of the particle counter by a factor of 10, we had to add a gain of 10
to the EPICS channels C1:PEM-count_full and C1:PEM-count_half.
I asked Alex to change it and he did it. I forgot to ask him to change the gain of C1:PEM-count_half. So now only
C1:PEM-count_full has x10 gain.
Detail:
C1:PEM-count_full and C1:PEM-count_half are 'Soft Channel' records in the database (Pcount.db). The values are actually
written into the VAL fields directly by an SNL code Particle.o.
Particle.o reads data from the RS-232C port, to which the particle counter is connected. Then it parses the data and put values
into relevant EPICS channels using channel access. This means we cannot change the gain of the channels by modifying the
database file. For example, ASLO field does not have any effect when the value is directly written into the VAL field.
We had to modify the SNL code. Alex modified Particle.st and the new SNL object file is Particle_x10.o sitting in
/cvs/cds/caltech/target/c1psl/. I modified seq.load so that c1psl loads Particle_x10.o when rebooted.
The source code for the old Particle.st can be found on lesath.ligo.caltech.edu in
/export/CDS/d/epics/apple/Caltech/40mVac/40mVacScipe/dev/src
I asked Alex to disclose the location of the source of the new code.
In order to compile the SNL code into an object file for Motorola CPU by ourselves, we have to call Dave Barker at LHO. |
|
950
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Tue Sep 16 13:04:22 2008 |
Yoichi | Configuration | PEM | C1:PSL-FSS_RMTEMP alarm level changed |
At the request of Steve, I modified the HIGH value of C1:PSL-FSS_RMTEMP from 21.27 to 23.0.
The HIHI is set to 23.50. |
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951
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Tue Sep 16 16:47:01 2008 |
pete | Configuration | PSL | Prototype FSS reference installed |
| After verifying output, I installed the new prototype 21.5 MHz FSS reference (Wenzel crystal oscillator and ZHL-2 amp). Yoichi and I successfully locked the MC, and have left the new reference in place. It's temporarily sitting on the corner of the big black optics table (AP table?). |
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952
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Wed Sep 17 12:55:28 2008 |
rob | Configuration | IOO | MC length |
I measured the mode cleaner length last night:
SR620 Marconi
199178070
165981524 165981725
132785380
33196345
I did the division in Marconi-land, rather than SR620-land.
If someone wants to do this in SR620-land, feel free to do it and post the numbers. |
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953
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Wed Sep 17 12:58:12 2008 |
rob | Update | Locking | bad |
Locking was pretty unsuccessful last night. All the subparts were locked (ARMs, PRM, DRM) and
aligned, but no DRMI+2ARMs locks. The alignment may have drifted significantly by the time I
got around to working the full shebang, however.
We should get back into the habit of clicking the
yellow "Restore last auto-alignment" button when we finish using the interferometer. |
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954
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Wed Sep 17 13:43:54 2008 |
Yoichi | Configuration | PSL | RC sweep going on |
| I'm doing a cavity sweep of the RC. Please leave the IFO untouched until the meeting is over. |
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956
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Wed Sep 17 13:58:36 2008 |
Alberto | Update | General | ABSL: results from the X arm |
Today I repeated the measurement of the FSR on the X arm cavity. The noise in the transmitted power that made the measures fluctuate was much reduced after last night Rob worked on the interferometer. The X arm cavity length is now: (38.4580+/-0.0003)m. I'm attaching a summary of the data I've taken.
I'm now preparing the setup to measure the transverse mode spacing. |
| Attachment 1: Sept17_XarmFSRmeasurement_report.ps
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957
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Wed Sep 17 15:22:31 2008 |
Yoichi | Configuration | PSL | RC sweep going on |
| Quote: | | I'm doing a cavity sweep of the RC. Please leave the IFO untouched until the meeting is over. |
The measurement is still going on.
I will post an entry when it is done.
Thank you for the patience. |
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958
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Wed Sep 17 17:31:24 2008 |
Yoichi | Update | PSL | FSS calibration |
I calibrated the reference cavity error signal with the following procedure.
(1) I disconnected the PC path BNC cable and locked the RC only using the PZT. To do so, I had to insert a 20dB attenuator
in the RF signal path going to the EOM to reduce the gain of the loop sufficiently.
The normal RF level going to the EOM is 17dBm. With the attenuator it is of course -3dBm.
(2) Using the SR785, I injected signal into the Test-IN2 (a sum-amp after the mixer) of the FSS box and measured the TF from the Ramp-IN to the IN1.
When the Ramp-In switch is off, the Ramp-IN port can be used as a test point connected to the PZT drive signal path just before the output.
There is a RC low-pass filter after the Ramp-IN. IN1 is the direct output from the mixer (before the sum-amp).
The attm1 is the measured transfer function along with the fitting by a first order LPF.
From this measurement, the DC transfer function from the applied voltage on the PZT to the error signal is determined to be 163.6 (V/V).
Since the RF level is lowered by 20dB, the cavity gain in the normal operation mode is 10 times larger (assuming that the modulation depth is
linearly proportional to the applied voltage to the EOM).
(3) According to elog:791, the conversion factor from the voltage on the PZT to the frequency change of the NPRO is 11.172MHz/V. Combining this with the
number obtained above, we get 6.83kHz/V as the calibration factor for converting the error signal (mixer output) to the frequency at DC.
Using 38kHz cavity pole frequency, the calibration factor is plotted as a function of frequency in the attm2.
(4) I took a spectrum of the error signal of the FSS and calibrated it with the obtained calibration factor. See attm3.
The spectrum was measured by SR785. I will measure wide band spectra with an RF analyzer later.
TO DO:
1: Use the actual modulation depth difference to extrapolate the calibration factor obtained by with a low RF signal for the EOM.
The cavity sweep was already done.
2: I assumed 38kHz cavity pole. I will measure the actual cavity pole frequency by cavity ringdown.
3: Measure out-of-the-loop spectrum of the frequency noise using PMC and MC. |
| Attachment 1: PZTresp.png
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| Attachment 2: Calibration.png
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| Attachment 3: FreqNoiseSpectrum.png
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959
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Wed Sep 17 17:58:35 2008 |
Yoichi | Configuration | PSL | RC sweep going on |
| The cavity sweep is done. The IFO is free now. |
|
960
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Wed Sep 17 19:13:47 2008 |
Alberto | Update | General | ABSL: status |
I installed the setup for measuring TEM01/10 on the X end table.
I'm leaving. I shut the laser, flipped down the flipper mirror, disconnected the pzt drive signal from the laser.
For Jenne. The power cable for the Guralps' board is now connected to the PDH box on my instruments cart but you can take it. |