||Wed Oct 17 18:46:33 2007
|This is the first entry in the new 40m eLog.|
Its GWs or bust now!
||Thu Oct 18 14:52:35 2007
||Thu Oct 18 15:03:14 2007
||ajw||Routine||General||this is only a test|
||Fri Oct 19 16:11:38 2007
||pkp||Other||OMC||OMC PZT response|
|Sam and I locked the laser to the OMC cavity and looked at the error signal as a function of the voltage applied to the OMC PZT.|
Here are two plots showing the response as a function of frequency from 1 kHz to 100 kHz and another high-res response in the region of 4.5 kHz to 10 kHz.
||Sat Oct 20 11:54:13 2007
||waldman||Other||OMC||OMC and OMC-SUS work|
|[Rich, Chub, Pinkesh, Chris, Sam]|
Friday the 18th was a busy day in OMC land. Both DCPDs were mounted to the glass breadboard and the OMC-SUS structure was rebuilt to the point that an aluminum dummy mass is hanging, unbalanced. The OSEMs have not be put on the table cloth yet, but everything is hanging free. As for the DCPDs, if you recall one beam is 3mm off center from the DCPD tombstone. Fortunately, one DCPD is nearly 3mm offcenter from the case in the right direction, so the errors nearly cancel. The DCPD is too high, so the beam isn't quite centered, but they're close. We'll get photos of the beam positions in someday. Also, the DC gain between the two PDs is, at first glance, different by 15%. DCPD1, the one seen in transmission has 315 mV of signal while DCPD2 has 280 mV. Not sure why, could be because of beam alignment or tolerances in the Preamp or the angle incident on the diode or the QE of the diodes. The glass cans have *not* been removed.
||Mon Oct 22 12:02:59 2007
||ajw||Routine||General||STACIS as microseismic shaker|
|In case we ever want to use our Stacis systems as shakers, check this:|
||Mon Oct 22 19:27:14 2007
||pkp||Other||OMC||PZT calibration/ transfer function.|
|We measured the PZT transfer function by comparing the PZT response of the circuit with the cavity in the loop, with that of the circuit without the cavity in the loop. Basically measure the transfer function of the whole loop with the laser/PZT and Op-amps in it. Then take another measurement of the transfer function of everything else besides the PZT and from both these functions, we can calculate the PZT response. |
The calibration was done by using the error signal response to a triangular wave of volts applied to the PZT. A measurement of the slope of the error signal , which has three zero-crossings as the cavity sweeps through the sidebands, gives us the Volts/Hz response. In order to derive a frequency calibration of the x axis, we assume that the first zero crossing corresponds to the first side band (-29.5 MHz) and the third one corresponds with the other sideband (+29.5 MHz). And then by using the fact that we know the response of the cavity to a constant frequency shift, we can use the Volts/Hz measurement to calculate the Volts/nm calibration. The slope that was calculated was 3.2e-6 V/Hz and using the fact that the cavity is 1 m in length and the frequency is 1064 nm, we get a calibration of 0.9022 V/nm.
||Tue Oct 23 09:01:00 2007
||rana||Other||OMC||PZT calibration/ transfer function.|
|Are you sure that the error signal sweep is not saturated on the top ends? This is usually the downfall|
of this calibration method.
||Tue Oct 23 11:08:20 2007
|There are big brush fires around LA|
40 days plot show no effect in the 40m lab
||Wed Oct 24 01:43:32 2007
||Andrey Rodionov||Other||General||PDF-file -> Will report about first results for XARM during Wednesday meeting |
Here is the pdf-file with some graphs showing first results for XARM optimization.
We will discuss alltogether during our Wednesday meeting which starts at 2.40PM. Probably it would be necessary to project this pdf-file to the big screen,
so someone should bring laptop and probably connect it to the projector. I do not have a laptop.
See you on that meeting.
||Wed Oct 24 08:58:09 2007
||steve||Other||PSL||laser headtemp is up|
|C1:PSL-126MOPA_HTEMP is 19.3C|
Half of the chiller's air intake was covered by loose paper
||Thu Oct 25 00:01:21 2007
||rana||Software Installation||CDS||GEO DV => LIGO DV|
|Martin Hewitson of GEO600 fame has modified the cool GEO DV|
to work with the LIGO NDS system with some NDS advice from Rolf (who's over in Germany this week).
I've moved it onto the 40m CDS system and installed it on the AdhikariLab computer named 'django'. It worked immediately.
I modified the main .m file to include the 40m's NDS server. When you run it you have to include the path to the NDS
client written by Ben Johnson.
The attached is a screenshot of it working on a Mac; it looks as cool on Linux.
Its installed in /cvs/cds/caltech/apps/ligoDV/. In matlab you navigate to that directory and then
type addpath('/cvs/cds/caltech/apps/linux/UNIX_NDS_Client_beta2/') to add the NDS client.
On the Solaris machines, type type addpath('/cvs/cds/caltech/apps/solaris9/UNIX_NDS_Client_beta2/') instead.
Then type ligoDV to start it up. Then click away and have fun.
In the example I've selected
C1:PEM-BS_ACC_EAST_Z and plotted its specgram.
||Thu Oct 25 17:52:45 2007
||waldman||Other||OMC||OMCs with QPDs|
|[Rich, Chub, Pinkesh, Sam]|
Yesterday we got the QPD, OTAS, and PZT cabling harness integrated with the OMC. We found a few things out, not all of them good. The QPDs went on no problem and could be fairly well aligned by hand. We "aligned" them by looking at all four channels of the QPD on the scope and seeing that there is signal. Since the beam is omega = 0.5 mm, this is a reasonable adjustment. We then connected the OTAS connector to the OTAS and found that the heater on the OTAS was bonded on about 30 degrees rotated from its intended position. This rotated the connector into the beam and caused a visible amount of scattering. This wasn't really a disaster until I removed the connector from the heater and broke the heater off of the aluminum parts of the OTAS. Two steps backwards, one step forward. After the OMC, OMC-SUS integration test we will re-bond the heater to the aluminum using VacSeal. In the meantime, the OMC has been moved to Bridge 056 for integration with the OMC-SUS. More on that as we make progress.
||Thu Oct 25 22:02:58 2007
|In light of the SoCal fires, I turned the PSL HEPAs up to 100%.|
||Thu Oct 25 23:35:36 2007
||waldman||Other||OMC||Hang the OMC!|
We tried, convicted and hung the OMC today. The OMC was found guilty of being overweight, and unsymmetrically balanced. The unsymmetry was kind of expected and was corrected with a hefty stack of counterweights positioned over the counterweighting holes. The stacks will be measured at some future date and correctly sized objects machined. The overweightness showed up when the level hanging breadboard was about 5 mm low. This showed up in the board height above the table as well as the OSEM flag positions within their holes. The problem was remedied with a liposuction of the intermediate mass. We removed both small vertical cylinder weights that Chris added, and then we removed the heavy steel transverse weight that can be used to adjust the tip around the long axis (I forgot what its called).
The top of the breadboard ended up about 154 mm off the table. The breadboard is 39 mm thick, and the optics are centered (30 - 12.7) = 17.3 mm below the surface for a as hanging beams height of 154 -39 - 17.3 = 97.7 mm or about an 0.150 inches lower than we were aiming for. Can I get a refund?
We screwed up in multiple ways:
- The slotted disks that capture the wires do not have the alignment bore used to center the wire in the hole
- We didn't correctly route the far field QPD cable so it runs funny
- We didn't have a tool which could be used to get two of the DCPD preamp box mounting screws (which are M3's chub!)
- We don't have the cable clamps to tie off the electrical cables to the intermediate mass
- We don't have any of the cabling from the OMC-SUS top to the rack so we can't test anything
- We haven't uploaded pretty pictures for all to see
We left the OMC partially suspended by the OMC-SUS and partly resting on the installation lab jacks which are currently acting as EQ stops. After we fix the cabling we will more permanently hang it. PS, It looks like the REFL beam extraction will be tricky so we need to get on that....
||Fri Oct 26 09:10:17 2007
||steve||Routine||PEM||PEM &PSL trend|
|The fires are out, lab particle counts are up.|
Psl HEPAs are at 100% and mobel HEPAs are just turned on
20 days plot and 5 hrs plot below
||Fri Oct 26 16:19:29 2007
||Tobin Fricke||Routine||IOO||MC resonances|
|We would like to measure the absorption of the mode cleaner optics. The plan is to repeat <a href="http://ilog.ligo-wa.caltech.edu:7285/mLIGO/Cleaning_the_Mode_Cleaner">Valera's experiment</a> in which we track the MC's thermal resonances to infer their power absorption. Last night Rana and I hooked up a lock-in amplifier to heterodyne the MC servo signal by 28 kHz and piped the output into an ADC using the MC_AO channel. We did not find any resonances.|
Valera recommends we drive the POS of the three MC optics with bandlimited noise to excite the resonances.
||Fri Oct 26 17:34:43 2007
||waldman||Other||OMC||OMC + earthquake stops|
[Chub, chris, Pinkesh, Sam]
Last night we hugn the OMC for the first time and came up with a bunch of pictures and some problems. Today we address some of the problems and, of course, make new problems. We replaced the flat slotted disks with the fitted slotted disks that are made to fit into the counterbore of the breadboard. This changed the balance slightly and required a more symmetric distribution of mass. It probably did not change the total mass very much. We did find that the amount of cable hanging down strongly affected the breadboard balance and may also have contributed to the changing balance.
We also attached earthquake stops and ran into a few problems:
- The bottom plate of the EQ stops is too thick so that it bumps into the tombstones
- The vertical member on the "waist" EQ stops is too close to the breadboard, possibly interfering with the REFL beam
- The "waist" EQ stops are made from a thin plate that doesn't have enough thickness to mount helicoils in
- Helicoil weren't loaded in the correct bottom EQ stops
- The DCPD cable loops over the end EQ stop looking nasty but not actually making contact
However, with a little bit of jimmying, the EQ stops are arrayed at all points within a few mm of the breadboard. Meanwhile, Chub has cabled up all the satellite modules and DCPD modules and Pinkesh is working on getting data into the digital system so we can start playing games. Tonight, I intend to mount a laser in Rana's lab and fiber couple a beam into the 056 room so we can start testing the suspended OMC.
||Fri Oct 26 21:48:40 2007
||waldman||Configuration||OMC||Fiber to 056|
|I set up a 700 mW NPRO in Rana's lab and launched it onto a 50m fiber. I got a few mW onto the fiber, enough to see with a card before disabling the laser. The fiber now runs along the hallway and terminates in rm 056. Its taped down everywhere someone might trip on it, but don't go out of your way to trip on it or pull on it because you are curious. Tomorrow I will co-run a BNC cable and attenuate the NPRO output so it can only send a few mW and so be laser safe. Then we can try to develop a procedure to align the beam to a suspended OMC and lock our suspended cavity goodness.|
Notes to self: items needed from the 40m
Some of these exist at 056 already
- ND10 and ND20 neutral density filter
- EOM and mount set for 4 inch beam height
- Post for fiber launch to get to 4 inch
- Mode matching lens at 4in
- 3x steering mirror at 4in
- RF photodiode at 4in
- Post for camera to 4in
- Light sheild for camera
- Long BNC cable
||Sat Oct 27 19:00:44 2007
||waldman||Configuration||OMC||Hanging, locked OMC with REFL extracted.|
|I got the OMC locked to the fiber output today. It was much more difficult than I expected and I spent about 30 minutes or so flailing before stopping to think. The basic problem is that the initial alignment is a search in 4-dimensional space and there is naturally only one signal, the reflected DC level, to guide the alignment. I tried to eyeball the alignment using the IR card and "centering" the beams on mirrors, but I couldn't get close enough to get any light through. I also tried to put a camera on the high reflector transmission, but with 1.5 mW incident on the cavity, there is only 1.5 microwatts leaking through in the best case scenario, and much, much less during alignment.|
I resolved the problem by placing a high reflector on a 3.5 inch tall fixed mount and picking off the OMC transmitted beam before it reaches the DC diodes. I took the pickoff beam to a camera. The alignment still sucked because even though the beam cleanly transmitted the output coupler, it wasn't anywhere close to getting through the OTAS. To resolve this problem, I visually looked through the back of M2 at M1 and used the IR card to align the beam to the centers of each mirror. That was close enough to get me fringes and align the camera. With the camera aligned, the rest was very easy.
I restored the PDH setup we know and love from the construction days and locked the laser to the OMC with no difficulty. The laser is in Rana's lab so I send the +/- 10V control signal from the SR560 down a cable to 058E where it goes into the Battery+resistor box, the Throlabs HV amplifier, and finally the FAST channel of the NPRO. BTW, a simple experiment sows that about 35 +/- 3 V are required to get an FSR out of the NPRO, hence the Thorlabs HV. The EOM, mixer, splitter, etc is on the edge of the table.
With this specific OMC alignment, ie. the particular sitting on EQ stops, it looks like all of the ghost beams have a good chance of coming clear. I can fit a 2 inch optic in a fixed mount in between the end of the breadboard and the leg of the support structure. A picture might or might not be included someday. One of the ghost beams craters directly into the EQ stop vertical member. The other ghost barely misses M2 on its way down the length of the board. In its current configuration, the many REFL beam misses the leg by about 1.5 inches.
||Sun Oct 28 03:03:42 2007
||rana||Configuration||IOO||Three Way Excitement|
|We've been trying to measure the MC mirror internal mode frequencies so that we can measure|
their absorption before and after drag wiping.
It looked nearly impossible to see these modes as driven by their thermal excitation level;
we're looking at the "MC_F" or 'servo' output directly on the MC servo board.
Today, I set up a band limited noise drive into the 'Fast POS' inputs of the 3 MC coil
driver boards (turns out you can do this with either the old HP or the SR785).
MC1 28.21625 kHz
MC2 28.036 kHz
MC3 28.21637 kHz
I don't really have this kind of absolute accuracy. These are just numbers read off of the SR785.
The other side of the setup is that the same "MC_F" signal is going into the SR830 Lock-In which
is set to 'lock-in' at 27.8 kHz. The resulting demodulated 'R" signal (magnitude) is going into
our MC_AO channel (110B ADC).
As you can see from the above table, MC1 and MC3 are astonishingly and annoyingly very close in
frequency. I identified mirrors with peaks by driving one at a time and measuring on the spectrum
analyzer. I repeated it several times to make sure I wasn't fooling myself; it seems like they
are really very close but distinct peaks. I really wish we had chipped one of these mirrors
before installing them.
Because of the closeness of these drumhead modes, we will have to measure the absorption by making long
measurements of this channel.
||Mon Oct 29 09:16:31 2007
||steve||Routine||VAC||the rga is back|
|We had no filament current since last power glitch of Oct. 8, 2007|
First I thought that the filament was lost, but it was only bad contact.
The rga head pins were oxidized. Rga was turned back on last Friday.
It's temp is 55.3C normal
||Mon Oct 29 09:46:50 2007
||steve||Routine||VAC||vac & pem trend|
|Pumpdown 64 pumped by maglev for 125 days|
Rob, can you tell me, when did the fire start on this plot?
||Mon Oct 29 11:07:22 2007
||waldman||Software Installation||OMC||Software install on OMS|
We spent a little time this morning working on OMS and getting things restarted. A few changes were made. 1) We put openmotif on OMS so that the burtrb doesn't throw that crappy libXm any more. 2) We upgraded OMS to a 32 kHz sampling rate from 2 kHz. All the filters will have to be changed. We also added a PDH filter path to maybe feedback PDH signals cuz that will be cool. Maybe someday I will write up the very cool channel adding procedure.
||Mon Oct 29 12:20:15 2007
||waldman||Configuration||OMC||Changed OMS filters|
|I changed the OMS configuration so that some of the OMC-SUS LED channels go to a breakout box so that we can input the PDH error signal. After lunch, we will try to lock the cavity with a PDH error signal and digital filters. Then its on to dither locked stuff. Note that this LED business will have to be changed back some day. For now, it should be extremely visible because there are dangling cables and a hack job interface lying around.|
||Mon Oct 29 23:10:05 2007
||waldman||Configuration||OMC||Lost in DAQspace|
In setting up a Digital based control of the hanging OMC, we naively connect the Anti-Imaging filter output to an Anti-Aliasing input. This led to no end of hell. For one thing, we found the 10 kHz 3rd order butterworth at 10 kHz, where it should be based on the install hardware. One wonders in passing whether we want a 10 kHz butter instead of a 15 kHz something else, but I leave that for a later discussion. Much more bothersome is a linear phase shift between output and input that looks like ~180 microseconds. It screams "What the hell am I!?" and none of us could scream back at it with an answer. I believe this will require the Wilson House Ghost Busters to fully remedy on the morrow.
||Mon Oct 29 23:25:42 2007
||tobin||Software Installation||CDS||frames mounted|
|I mounted the frames directory on mafalda and linux3. It's intentionally not listed in the /etc/fstab so that an fb crash won't prevent the controls machines from booting. The command to mount the frames directory is:|
mount fb40m:/frames/frames /frames
||Tue Oct 30 00:47:29 2007
|I did a bunch of MC ringdown measurements using the PD that Rob set up. The idea is to put a fast PD (PDA255)|
looking at the transmission through MC2 after focusing by a fast lens. The input to the MC is turned off fast
by flipping the sign of the FSS (Andri Gretarsson's technique).
With the laptop sitting on the MC can, its easy to repeat many ringdowns fast:
- Turn off the MC autolocker. Relock the MC with only the acquisition settings; no boosts
and no RGs. This makes it re-acquire fast. Turn the MC-WFS gain down to 0.001 so that
it keeps it slowly aligned but does not drift off when you lose lock.
- Use low-ish gain on the FSS. 10 dB lower than nominal is fine.
- Setup the o'scope (100 MHz BW or greater) to do single shot trigger on the MC2 trans.
- Flip FSS sign.
- Quickly flip sign back and waggle common gain to get FSS to stop oscillating. MC
should relock in seconds.
Clearly one can scriptify this all just by hooking up the scope to the ethernet port.
Attached are a bunch of PNG of the ringdowns as well as a tarball with the actual data. A sugar
napoleon to whomever can explain the 7 us period of the wiggle before the vent!
||Tue Oct 30 13:58:07 2007
|Here's a quick fit-by-eye to the latter part of the data from tek00000.xls.|
The prediction (blue) is eqn 41 of
T1 = T2 = 0.002. Loss1 = Loss2 = 150 ppm.
MC3 assumed perfectly reflecting.
Velocity = 320 um/s (assumed constant), 2 usec into the ringdown.
OK, there's one little fudge factor in the prediction:
I multiplied D by 2.
||Tue Oct 30 16:55:40 2007
||tobin||Routine|| ||Drag-wiping perfected|
Steve procured an assortment of syringes from the bio storeroom and we practiced drag-wiping the SOS in the flow bench. Using a 50 microliter Hamilton syringe to deliver 16 microliters of methanol seems perfect for drag-wiping the small optics. Drag-wiping in the downward direction seems to work very well, since we can squirt the optic directly in the center, and the (half) piece of kodak lens tissue fits easily between the bottom two earthquake stops.
||Tue Oct 30 19:32:13 2007
||tobin||Problem Fixed||Computers||conlogger restarted|
|I noticed that the conlogger wasn't running. It looks like it hasn't been running since October 11th. I modified the restart_conlogger script to insist that it run on op340m instead of op440m, and then ran it on op340m.|
||Tue Oct 30 20:15:24 2007
Largish (M5.6) earthquake in San Francisco sent our optics swinging.
||Wed Oct 31 08:33:54 2007
||rana||Problem Fixed||SUS||Vent measurements|
|There was a power outage during the day yesterday; whoever was around should post something here about the|
exact times. Andrey and David and Tobin got the computers back up - there were some hiccups which you can
read about in David's forthcoming elog entry.
We restarted a few of the locking scripts on op340m: FSSSlowServo, MCautolocker. Along with the updates
to the cold restart procedures we have to put an entry in there for op340m and a list of what scripts
David tuned up the FSS Slow PID parameters a little; he and Andrey will log some entry about the proper
PID recipe very soon. We tested the new settings and the step response looks good.
We got the MC locking with no fuss. The 5.6 EQ in San Francisco tripped all of the watchdogs and I upped
the trip levels to keep them OK. We should hound Rob relentlessly to put the watchdog rampdown.pl into
the crontab for op340m.
||Wed Oct 31 08:34:35 2007
|In the end, we were unable to get a good scatter measurement just because we ran out of steam. The idea was to get a frame|
grab image of MC2 but that involves getting an unsaturated image.
In the end we settle for the ringdowns, Rob's (so far unlogged) cavity pole measurement, and the MC transmission numbers. They
all point to ~100-150 ppm scatter loss per mirror. We'll see what happens after wiping.
||Wed Oct 31 08:38:35 2007
||rana||Problem Fixed||IOO||MC autolocker|
|The MC was having some trouble staying locked yesterday. I tracked this down to some steps in the last|
half of the mcup script; not sure exactly which ones.
It was doing something that made the FAST of the PSL go to a rail too fast for the SLOW to fix.
So, I broke the script in half so that the autolocker only runs the first part. We'll need to
fix this before any CM locking can occur.
We also need someone to take a look at the FSS Autolocker; its ill.
||Wed Oct 31 09:45:28 2007
||waldman||Other||OMC||Resolution to DAQland saga|
We did a rough accounting for the linear delay this morning and it comes out more or less correct. The 10 kHz 3rd order butterworth AA/AI filter gives ~90 degrees of phase at 6 kHz, or 42 microseconds. Taken together, the two AA and AI filters are worth 80 microseconds. The 1.5 sample digital delay is worth 1.5/32768 = 45 microseconds. The remaining 160 - 125 = 35 microseconds is most likely taken up by the 64 kHz to 32 kHz decimation routine, assuming this isn't accounted for already in the 1.5 sample digital delay.
It remains to be seen whether this phase delay is good enough to lock the laser to the OMC cavity
||Wed Oct 31 10:31:23 2007
||Andrey Rodionov||Routine||VAC||Venting is in progress|
We (Steve, David, Andrey) started venting the vacuum system at 9.50AM Wednesday morning.
||Wed Oct 31 15:02:59 2007
||tobin||Routine||IOO||Mode Cleaner Mode Tracking|
|I processed the heterodyned mode cleaner data yesterday, tracking the three 28 kHz modes corresponding to MC1, MC2, and MC3. Unfortuntately the effect of our MC power chopping is totally swamped by ambient temperature changes. Attached are two plots, one with the tracked mode frequencies, and the other containing dataviewer trends with the MC transmitted power and the room temperature. Additionally, the matlab scripts are attached in a zip file.|
||Wed Oct 31 15:22:59 2007
||rob||Configuration||IOO||Mode Cleaner transfer function|
|I measured the transfer function of the input mode cleaner using a PDA255 and the ISS. First I put the PD in front of the ISS out-of-loop monitor diode and used an SR785 to measure the swept sine transfer function from the Analog IN port of the ISS to the intensity at the PD. Then I moved the PD to detect the light leaking out from behind MC2, using ND filters to get the same DC voltage, and measured the same transfer function. Dividing these two transfer functions should take out the response of the ISS and the PD, and leave just the transfer function of the MC. A plot of the data, along with a single-pole fit, are attached.|
The fit is pretty good for a single pole at 3.79 kHz. There's a little wiggle around 9kHz due to ISS weirdness (as Tobin has not been giving it the attention it requires), but this shouldn't affect this result too much. Using the known MC length of 27.0955m, and assuming that MC1 and MC3 have a power transmissivity of 2000ppm and MC2 is perfectly reflecting, the total round trip loss should be about 300ppm. The fitted finesse is 1460.
||Wed Oct 31 19:26:08 2007
||Andrey Rodionov||Routine||General||Photographs of "Mode-Cleaner Entrance"|
Here are the pictures of "inside the chamber".
||Wed Oct 31 23:55:17 2007
|The 4 QPDs for the OMC have been installed in the 056 at the test setup. All 4 QPDs work and have medm screens located under C2TPT. The breadboard mounted QPDs are not very well centered so their signal is somewhat crappy. But all 4 QPDs definitely see plenty of light. I include light and dark spectra below. QPDs 1-2 are table-mounted and QPD 2 is labeled with a bit of blue tape. QDPs 3-4 are mounted on the OMC. QPD3 is the near field detector and QPD4 is the far field. In other words, QPD3 is closest to the input coupler and QPD4 is farthest.|
Included below are some spectra of the QPDs with and without light. For QPDs 1 & 2, the light source is just room lights, while 3&4 have the laser in the nominal OMC configuration with a few mWs as source. The noise at 100 Hz is about 100 microvolts / rtHz. If I recall correctly, the QPDs have 5 kOhm transimpedance (right Rich?) so this is 20 nanoamps / rtHz of current noise at the QPD.
||Thu Nov 1 01:28:04 2007
||waldman||Other||OMC||First digital lock of OMC|
We locked a fiber based NPRO to the suspended OMC tonight using the TPT digital control system. To control the laser frequency, we took the PZT AI output and ran it on a BNC cable down the hallway to the Thorlabs HV box. The Thorlabs is a singled ended unit so we connected the AI positive terminal only and grounded the BNC to the AI shield. We could get a -6 to 1.5 V throw in this method which fed into the 10 k resisotr + 9 V battery at the input of the HV box. The HV out ran to the NPRO PZT fast input.
We derived our error signal from a PDA255 in reflection with a 29.5 MHz PDH lock. The signal feeds into one of the unused Tip/Tilt AA channels and is passed to the PZT LSC drive through the TPT_PDH1 filter bank. In the PZT_LSC filter we put a single pole at 1 Hz which, together with the phase we mentioned the other night (180 degrees at 3 kHz) should allow a 1 kHz-ish loop. In practice, as shown below, we got a 650 Hz UGF with 45 degrees of phase margin and about 6 dB of gain margin.
The Lower figure shows the error point spectrum with 3 settings. REF0 in blue shows lots of gain peaking at 1.5 kHz-ish, just where its expected - the gain was -40. The REF1 has gain of -20 and shows no gain peaking. The current trace in red shows some gain peaking cuz the alignment is better but it also has included a 1^2:20^2 boost which totally crushes the low frequency noise. We should do a better loop sweep after getting the alignment right so we can see how much boost it will really take.
Just for fun, we are leaving it locked overnight and recording the PZT_LSC data for posterity.
||Thu Nov 1 09:17:27 2007
|Yesterday before vent I could not lock MC, therfore I could not measure the |
transmitted power at MC2
The vent went well. We had lots of help.
We could not find the Nikon D40
PLEASE BORROW THINGS when taking them away
and bring them back promtly.
The laser was turned off for better visibility.
I see clean room frorks laying around here and there.
Please put them away so we do not carry excess particles into the chamber.
||Thu Nov 1 11:45:30 2007
||tobin||Configuration||IOO||Mode cleaner drag-wiping|
|Andrey, Bob, David, John Miller, Rana, Rob, Steve, Tobin|
Yesterday we vented the vacuum enclosure and opened up the chamber containing MC1 & MC3 by removing the access connector between that chamber and the OMC chamber. Rana marked MC1's location with dogs and then slid the suspension horizontally to the table edge for easy drag-wiping access. The optic was thoroughly hosed-down with the dionizer, in part in an effort to remove dust from the cage and the top of the optic. Drag-wiping commenced with Rob squirting (using the 50 microliter syringe) and Tobin dragging (using half-sheets of Kodak lens tissue). We drag-wiped the optic many (~10) times, concentrating on the center but also chasing around various particles and a smudge on the periphery. There remains one tiny speck at about the 7:30 position, outside of the resonant spot area, that we could not dislodge with three wipes.
Today we drag-wiped MC3. First we slid MC1 back and then slid MC3 out to the edge of the table. We disconnected the OSEM cables in the process for accessibility, and MC1 is perched at an angle, resting on a dog. We did not blow MC3 with the deonizer, not wanting to blow particles from MC3 to the already-cleaned MC1. We drag-wiped MC3 only three times, all downward drags through the optic center, with Steve squirting and Tobin dragging. Some particles are still visible around the periphery, and there appears to be a small fiber lodged near the optic center on the reverse face.
Andrey and Steve have opened up MC2 in preparation for drag-wiping that optic after lunch.
||Thu Nov 1 16:34:47 2007
||Andrey Rodionov||Summary||Computers||Limitation on attachment size of E-LOG|
I discovered yesterday when I was attaching photos that it is NOT possible to attach files whose size is 10Mb or more. Therefore, 10Mb or something very close to that value is the limit.
||Thu Nov 1 16:42:48 2007
||Andrey Rodionov||Summary||Environment||End of Daylight Saving Time this weekend|
|Useful information for everyone, as a friendly reminder:|
According to the web-page
this coming weekend there will be the end of Daylight Saving Time.
Clocks will be adjusted backward one hour.
||Thu Nov 1 16:51:33 2007
|If you vant see D40 againn, you leave one plate goulash by N2 tank in morning.|
Vit the good paprikash this time!!!
||Thu Nov 1 19:53:02 2007
||Andrey Rodionov||Bureaucracy||Photos||Tobin's picture|
||Thu Nov 1 19:53:34 2007
||Andrey Rodionov||Bureaucracy||Photos||Robert's photo|
||Thu Nov 1 19:54:22 2007
||Andrey Rodionov||Bureaucracy||Photos||Rana's photo|