40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log, Page 3 of 326  Not logged in ELOG logo
ID Date Author Typeup Category Subject
  8306   Mon Mar 18 13:10:19 2013 KojiBureaucracyAuxiliary lockingYend table upgrade - go fetch NPRO from ATF

1) Annalisa is going to start  working on mode profiling and beat note search for the old MOPA NPRO.

2) In the meantime, Manasa is working on the end table items. This will be reviewed by KA in the afternoon.

The laser at ATF is moved to the 40m when the status of 1) and 2) is determined by KA to be reasonable.

We also make the beat note measurement for the ATF laser too.
 

  8308   Mon Mar 18 20:13:18 2013 AnnalisaBureaucracyAuxiliary lockingYend table upgrade - go fetch NPRO from ATF

Quote:

1) Annalisa is going to start  working on mode profiling and beat note search for the old MOPA NPRO.

2) In the meantime, Manasa is working on the end table items. This will be reviewed by KA in the afternoon.

The laser at ATF is moved to the 40m when the status of 1) and 2) is determined by KA to be reasonable.

We also make the beat note measurement for the ATF laser too.
 

Today I installed mirrors to steer the pick-off from the main laser beam in a more free part of the PSL table and make the beat note measurement between it and the NPRO.

At the beginning I took the beam from the harmonic separator after the doubling crystal, and I was going to bring it in a less full part of the table . At the end I realized that there was already a beam steered up to a more free part of the table, and the beam is taken from the transmission of the PMC.

Tomorrow I'm going to use that beam to find the beat note with the NPRO.

I also removed almost all the steering  optics that I used on the ITMY table to send the auxiliary beam for ABSL through the window parallel to the POY beam. The most important thing is that I removed the BS, which was on the same path of the POY beam (see elog 8257).

 

  8319   Wed Mar 20 16:45:59 2013 ManasaBureaucracyAuxiliary lockingFetched NPRO from ATF

[Koji, Annalisa, Manasa]

NPRO with controller from ATF joins the 40m. We have put it on the POY table where we plan to use it for ABSL.

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  10312   Thu Jul 31 21:59:25 2014 KojiBureaucracyGeneralAnts

Don't leave your food on tables and desks!

Also I put the souvenir chocolates in the microwave, just in case.

Attachment 1: P7316690.JPG
P7316690.JPG
  11096   Wed Mar 4 00:50:36 2015 ranaBureaucracyTreasureTransitioned DARM to AS55Q, some other work

Just in case there was some confusion, the champagne on my desk is not to be opened before I get back, no matter how many signals are transitioned to RF.

  11346   Fri Jun 5 11:59:59 2015 ericqBureaucracyGeneralMaintenance Tasks, IFO upgrades

At wednesday's meeting, Rana, Koji, Steve, and I started making a list of maintenence tasks that should be done/checked on a regular basis. The actual scheduling of these has not yet been considered. They include:

  • N2 Tank pressure / cylinder replacement
  • Headlamp, walkie talkie battery recharge
  • Workstation software updates
  • Coffee bean and filters
  • Multimeter battery levels
  • Sorensen DC power supply voltage settings and current draws
  • UPS' status (Vacuum, NFS host, workstations)
  • SR560s, battery powered scopes plugged in
  • Rack Fuses intact
  • Take pictures of electronics racks, optical tables
  • Replace PSL HEPA filter

Next, we brainstormed work that can be done to improve the interferometer performance, and what order/precedence they should take. 

In the end, it was decided that the plan for the next few weeks was to focus on improving the ALS noise levels, and, more importantly, seeking to make the performance more consistent. We need to know what is limiting us, and what we extent we can expect to improve things. To this end, I am working on reviving a ALS noise budget; using the noise budget from the green locking paper to inform a simulinkNB kind of thing.

Here are all of the items we listed during this brainstorming session.

Some near-term/priority tasks are:

  • Installing the accelerometers near MC1 and 2
  • Installing green steering PZT mirrors at the Y end table, commission dither alignment
  • Improving the X end green mode matching
  • ALS noise budgeting
  • Upgrade the realtime system to RCG v2.9

More down the line, other things we thought about were:

  • Cleanup of bench power supplies (FSS box has one, where else?)
  • Fixing the ETMX suspension issues 
  • Upgrade SOS suspension code to the appropriate aLIGO block
  • Upgrade to the green PDH electronics
  • Understanding / tuning the FSS servo laser PZT vs. PC crossover
  • Undestanding / tuning the 11MHz vs 55MHz modulation phase
  • Replacing the slow vxworks machines with the Acromag setup Aiden has set up for the CTN lab
  • QPD upgrade
  • New/better green beatbox
  • Finalize the manifestation of the IR beat control (Freq counter vs. fast DFD)
  • Explore the idea of using an analog output of the ALS beatbox as fast input to the CM board
  • Replace triple resonant EOM driving circuit with double resonant one
  • X end table layout/enclosure upgrade
  12828   Tue Feb 14 10:43:06 2017 gautamBureaucracyEquipment loanEquipment to Cryo Lab

PZT Buzzer Box (Thorlabs HV Supply + Manual + 2*PZT Buzzers) ---> Cryo Lab (Brittany + Aaron)

  12872   Tue Mar 7 15:17:19 2017 SteveBureaucracyGeneralproperty tag

Property tag found.

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property_tag.jpg
  13456   Tue Nov 28 17:27:57 2017 awadeBureaucracyCalibration-RepairSR560 return, still not charging

I brought a bunch of SR560s over for repair from Bridge labs. This unit, picture attached (SN 49698), appears to still not be retaining charge. I’ve brought it back. 

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image.jpg
  13923   Wed Jun 6 17:22:23 2018 KojiBureaucracyGeneralSalvaged junk from yend

While Keerthana and johannes were working at the end, I made a little cleaning at the yend. I salvaged large amount of hardware inclding optics, optomechanics. We all together should work on returning them to appropriate locations.

Attachment 1: DSC_0661.JPG
DSC_0661.JPG
  13949   Tue Jun 12 14:47:37 2018 gautamBureaucracyGeneralUnlabelled components from EX moved to SP table and labelled

Steve mentioned two unlabelled optics were found at EX, relics from the Endtable upgrade.

  • One was a 1" 45 deg p-pol optic (Y1-1025-C-45P), it looks a bit scratched.
  • The other was a Beam Sampler (BSF10-C).

These are now labelled and forked down on the SP table.

  13950   Tue Jun 12 15:32:15 2018 SteveBureaucracyGeneralSalvaged junk from Xend

Koji's collection of Yend components put away. I cleaned up the  Xend bench today.

Loadcells, leveling wedge mounts  and related items placed under flowbench cabinet next to Guralp staff.

 

  13970   Fri Jun 15 08:09:15 2018 SteveBureaucracyGeneralcleaning up at the PSL enclousure

The cabeling was cleaned up a little bit yesterday morning. The upper back side is still massy.

Attachment 1: before.jpg
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after.jpg
Attachment 3: back_side.jpg
back_side.jpg
  14170   Mon Aug 20 14:04:53 2018 johannesBureaucracyEquipment loanTwo C30642G PDs removed

EDIT: After discussing with Koji and checking the existing M2ISS PDs I put the two C30642G back and took two C30665GH (active diameter: 3mm) diodes. Only one of this type remains in storage.

I removed two C30642G photodiodes from the stash for the new M2ISS hardware and updated the wiki page accordingly.

  14174   Tue Aug 21 17:32:51 2018 awadeBureaucracyEquipment loanOne P-810.10 Piezo Actuators element removed

I've taken a PI Piezo Actuator (P-810.10) from the 40m collection. I forgot to note it on the equipment checklist by the door, will do so when I next drop by.

  14553   Fri Apr 19 09:42:18 2019 KojiBureaucracyGeneralItem borrowing (40m->OMC)

Apr 16, 2019
Borrowed two laser goggles from the 40m. (Returned Apr 29, 2019)
Apr 19, 2019
Borrowed from the 40m:
- Universal camera mount
- 50mm CCD lens
- zoom CCD lens (Returned Apr 29, 2019)
- Olympus SP-570UZ (Returned Apr 29, 2019)
- Special Olympus USB Cable (Returned Apr 29, 2019)

 

  14555   Fri Apr 19 12:06:31 2019 awadeBureaucracyElectronicsBorrowed Busby Box May 19th 2019

I've borrowed the Busby Box for a day or so.  Location: QIL lab at Bridge West.

Edit  Sat Apr 20 21:16:46 2019 (awade): returned.

  14565   Wed Apr 24 11:22:59 2019 awadeBureaucracyEquipment loanBorrowed Zurich HF2LI Lock in Amplifer to QIL

Borrowed Zurich HF2LI Lock in Amplifer to QIL lab Wed Apr 24 11:25:11 2019.

  14822   Thu Aug 1 13:55:34 2019 DuoBureaucracyEquipment loanGpib module taken to QIL lab

vanna --> QIL.

gautam 20190804: The GPIB module + power supply were returned to me by Duo ~5pm today at the 40m.

  15544   Fri Aug 28 11:41:23 2020 gautamBureaucracysafetyCrane inspection 2020

Mr Fred Goodbar of Konacrane was in the lab 830am-1130am today. All three cranes in the VEA were inspected, loaded with 450lb test weights, and declared in good working condition and safe to use.

  1. Apparently, the clackity noise heard when running the crane at the south end is a known problem - the crane was opened up and inspected sometime in the past, and no obvious cause was found. This is not expected to affect the usability of the crane.
  2. The travel speed of the cranes is slow - but this is apparently intentional, on the request of Steve V.

The interferometer subsystems appear normal after the inspection. 

  1   Wed Oct 17 18:46:33 2007 ranaConfigurationGeneraleLog Change
This is the first entry in the new 40m eLog.

Its GWs or bust now! Big grin



[Hnull][/Hnull]
  20   Fri Oct 26 21:48:40 2007 waldmanConfigurationOMCFiber 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
  • 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
Some of these exist at 056 already
  21   Sat Oct 27 19:00:44 2007 waldmanConfigurationOMCHanging, 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.
  22   Sun Oct 28 03:03:42 2007 ranaConfigurationIOOThree 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).

Frequencies:
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.
  26   Mon Oct 29 12:20:15 2007 waldmanConfigurationOMCChanged 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.
  27   Mon Oct 29 23:10:05 2007 waldmanConfigurationOMCLost in DAQspace
[Pinkesh, Sam]

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.
Attachment 1: SS.pdf
SS.pdf
Attachment 2: SS.gif
SS.gif
  30   Tue Oct 30 13:58:07 2007 ajwConfigurationIOOMC Ringdowns
Here's a quick fit-by-eye to the latter part of the data from tek00000.xls.

The prediction (blue) is eqn 41 of
http://www.ligo.caltech.edu/docs/P/P000017-A.pdf

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.
Attachment 1: CavityRingdown.png
CavityRingdown.png
Attachment 2: CavityRingdown.m
% CavityRingdown.m
% Eqn 41 of 
% "Doppler-induced dynamics of fields in Fabry–Perot
% cavities with suspended mirrors", Malik Rakhmanov (2000).
% http://www.ligo.caltech.edu/docs/P/P000017-A.pdf

clear all

% read in ringdown timeseries:
at = importdata('tek00000.csv');
... 121 more lines ...
  40   Wed Oct 31 15:22:59 2007 robConfigurationIOOMode 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.
Attachment 1: MCtf.pdf
MCtf.pdf
  45   Thu Nov 1 11:45:30 2007 tobinConfigurationIOOMode 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.
  67   Tue Nov 6 10:42:01 2007 robConfigurationIOOmode cleaner locked
Increased the power exiting the PSL by turning the half-wave plate after the MOPA, opened the PSL shutter, and aligned the mode cleaner to the input beam. It wasn't that hard to find the beam with the aperture open all the way on the MC2 camera. The transmitted power is now 2.9 arbitrary units, while the input power is 1.2 arbitrary units. Not sure yet if that's an increase or decrease in efficiency, since no one posted numbers before the vent. Also turned on the input-steering PZTs and saw a REFL beam on the camera.
  70   Tue Nov 6 15:37:34 2007 robConfigurationSUSrampdown script
/cvs/cds/caltech/scripts/SUS/rampdown.pl is now in the crontab for op340m, running every half-hour at 15&45. It checks the suspension watchdog trip levels, and reduces them by 20 if they are above 150.
  71   Tue Nov 6 16:48:54 2007 tobinConfigurationComputersscopes on the net
I configured our two 100 MHz Tektronix 3014B scopes with IP addresses: 131.215.113.24 (scope0) and 113.215.113.25 (scope1). Let the scripting commence!

There appears to be a Matlab Instrument Control Toolbox driver for this scope.
  72   Tue Nov 6 18:18:15 2007 tobinConfigurationComputersI broke (and fixed) conlogger
It turns out that not only restart_conlogger, but also conlogger itself checks to see that it is running on the right machine. I had changed the restart_conlogger script to run on op340, but it would actually silently fail (because we cleverly redirect conlogger's output to /dev/null). Anyway, it's fixed now: I edited the conlogger source code where the hostname is hardcoded (blech!) and recompiled.

On another note, Andrey fixed the "su" command on op440m. It turns out that the GNU version, in /usr/local/bin, doesn't work, and was masking the (working) sun version in /bin. Andrey renamed the offending version as "su.backup".
  73   Tue Nov 6 23:45:38 2007 tobinConfigurationComputerstektronix scripts!
I cooked up a little script to fetch the data from the networked Tektronix scope. Example usage:

linux2:scripts>tektronix/tek-dump scope0 ch1 foo.csv

"scope0" is the hostname of the scope, "ch1" is the channel you want to dump, and "foo.csv" is the file you want to dump it to. The script is written in Python since Python's libhttp gave me less trouble than Perl's HTTP::Lite.
  74   Wed Nov 7 00:51:33 2007 andrey, rob, tobinConfigurationIOOMC ringdowns
We completed several ringdown measurements this afternoon; Andrey is currently processing the data.
  77   Wed Nov 7 10:55:21 2007 ajwConfigurationComputersbackup script restarted
Following the reboot of computers on 10/31/07, the backup script required restart (which unfortunately "can't" be automated because a password needs to be typed in). I restarted, following the instructions in /cvs/cds/caltech/scripts/backup/000README.txt and verified that it more-or-less worked last night (the rsync sometimes times out; it gets through after a couple of days of trying.)
  78   Wed Nov 7 13:54:44 2007 robConfigurationIOOMode Cleaner transfer function
I performed the same procedure described here, and re-measured the transfer function of the mode cleaner to see the effect of the drag-wiping. The results are attached in a pdf. We don't seem to have done any damage, but the improvements are barely measurable.

WhatThenNow
pole frequency3.789kHz3.765kHz
loss per optic99ppm91ppm
finesse14601470
trans86.7%87.7%
Attachment 1: mctf.pdf
mctf.pdf
  80   Wed Nov 7 14:05:59 2007 tobinConfigurationIOOMC ringdown
Modeling the mode cleaner as a simple cavity with all losses lumped together, we expect the cavity power to be
attenuated by a factor (1-L) after each interval (2l/c)=1/fsr. Therefore we can get the cavity loss L
(including power lost through transmission) from the ringdown time constant tau as:

L = 1 - exp[ - 1/(tau * fsr) ]

From this we have to subtract the 2000 ppm transmission for each of MC1 and MC3, and divide by three to spread
the losses across the three optics.

I get 168 ± 39 ppm loss per optic based on a very simple exponential fit to the tails (t>0) of four of Andrey's data files.

By comparison, I get 154 ± 37 ppm from Rana's data files from before the vent.
  84   Thu Nov 8 15:57:53 2007 tobinConfigurationPSLshelf removed
I removed the sheet metal shelf from the PSL enclosure, for easier access to the ISS.

ISS investigations ongoing.
  85   Thu Nov 8 18:44:01 2007 tobinConfigurationPSLISS
Tobin, Rob

With the Sense PD blocked, I adjusted the offset trim of the fourth stage in the ISS servo until the current shunt signal was zeroed. After this adjustment, we are able to crank the ISS gain all the way up to 30 dB without CS saturations (provided the HEPA is turned down to a very quiet level), getting about 35kHZ UGF at that gain setting. However, the current shunt mean value was still enormous.

Examining the current shunt signal on a fast scope, we saw an enormous (>2Vpp) 3.6 MHz sawtooth signal. Going up the chain of op-amps, we found that U1, as measured at the "Filter Out" testpoint, is oscillating wildly at 12 MHz (680 mVpp).
  89   Fri Nov 9 17:33:33 2007 robConfigurationPSLISS

The 3.7 MHz is actually on the light. It's the beat between the 29.5 MHz sidebands and the 33.2 MHz sidebands. There are pads in the ISS PCB for a filter to notch this frequency--John is working on it.

I also found a 1.2 ND filter on the lens which focuses the beam on the ISS diodes. I replaced it with a 0.6 ND filter, which brought the ISS DC level (on the screen) up to ~4.2 (it saturates at 5). Once John finishes the filter we should be able to crank up the gain.
  90   Fri Nov 9 21:36:14 2007 robConfigurationPSLFSS
rob, rana

We looked at the FSS a bit today. The most we could get out of it with the gain sliders was a UGF of around 95kHz. After a bit of tweaking the waveplate after the AOM, this got up to ~115kHz. We should be able to get at least 500kHz. This system needs a fair amount of work.
  95   Mon Nov 12 15:05:49 2007 robConfigurationPSLFSS

Spent a bit of time fiddling with the FSS again today. In a not-particularly-systematic manner, I raised the input-side of the 21.5MHz PC, adjusted the half-wave plate in front of it, touched up the RC alignment and the alignment onto the transmitted and reflected diodes. This got us a ~15% increase in
transmitted light, and I was able to push the UGF to 140kHz with the common gain slider at 30dB and the FAST gain slider at 22dB. The next options include adjusting the AOM setup, mode matching into the RC, and just increasing the pickoff fraction right from the getgo.
  118   Tue Nov 20 13:06:57 2007 tobinConfigurationComputerslinux1 has new disk
Alex put the new hard disk into linux1 along with a fresh install of linux (CentOS). The old disk was too damaged to copy.

Alex speculates that the old disk failed due to overheating and that linux1 could use an extra fan to prevent this in the future.
  124   Tue Nov 27 15:45:08 2007 robConfigurationPSLFSS loop

It's unclear (to me, at least) what was the end result of the FSS path tweaking before Thanksgiving. Today I measured the open loop gain, and it was still around 100kHz, even with the gain sliders maxed out, but it looked really crappy with a sharp cutoff around the UGF. Then, on a lark, I pushed around the "Input Offset Adjust" slider, which sums an offset into the signal coming out of the mixer. By moving this slider to 7V, I got the UGF to 500kHz with 45 deg of phase. That would be fine, and we could go offset hunting, but the same thing happens if one puts in a large negative value! I don't really understand what's going on, but it seems like weirdness in the electronics. Unfortunately the web interface to the conlog is not running (presumably because the `new' linux1 doesn't have its apache server running) and my command line conlog efforts have been stymied. So, I don't know what the historical settings of this offset are, but zero is definitely not a good setting right now. Here's a snapshot:

FSS
UGF: 500kHz
CG : 24dB
FG : 19dB
input offset: 7V
Phase Adjust: 1.09V
Phase Button: 0
RF Amp Adjust: 7.38V

margins:
phase: 45 deg
gain: 8dB
Attachment 1: FSSsmall.jpg
FSSsmall.jpg
  125   Tue Nov 27 15:47:17 2007 robConfigurationIOOMC loop
After the FSS running pretty quick, I checked the MC loop. I used TPA 1&2.

MC loop
UGF: 70kHz
Input Gain: 29dB
Boost Level: 2
phase: 40 deg
Attachment 1: MCsmall.jpg
MCsmall.jpg
  126   Tue Nov 27 16:18:58 2007 robConfigurationIOOMC loop
Reduced the common gain to 22dB in the mcup script, so that the WFS would not blow the lock. The above measure of the OLG was done without the mcWFS running, so may be a low estimate as compared to when the alignment is perfect.
  132   Wed Nov 28 16:46:28 2007 ranaConfigurationComputersscientific linux 5.0
I tried installing Scientific Linux on Tiramisu. The installation process was so bad (really)
that I quit after 15 minutes. Its back to booting Ubuntu as if nothing had ever happened. Let
us never speak of Scientific Linux again.
  133   Wed Nov 28 17:15:26 2007 ranaConfigurationSUSETMY damping / watchdogs
Steve has noted that ETMY was often tripping its watchdog. I saw this again today.

So I checked the damping settings. Someone had set the SIDE gain to +1. The gain which gives
it a Q of ~10 is +10. I set the SIDE gain to +20. I checked and the ETMX gain is -16 so now
they're at least similar. I have updated the snapshot to reflect the new value.

Hopefully now it will be more well behaved.
  137   Wed Nov 28 21:51:52 2007 tobinConfigurationPSLISS
I replaced the front-end differential receivers for the ISS's "inner-loop" sensor and monitor diode inputs with lower-noise THS4131's (formerly THS4151's). I verified operation by taking the transfer function from the "PD+" and "PD-" inputs (separately) to the testpoint following the differential receiver; the surgery appears successful.

I measured the dark spectra at the ISS's DC PD BNC ports and found a noise floor of ~ 16 nV/rtHz, compared with a floor of ~ 22 nV/rtHz last week. This seems to add up, assuming the DC PD port has 0dB gain: the 4131 has a rated noise of 1.3 nV/rtHz and the 4151 a noise floor of 7.6 nV/rtHz, a difference of 6 nV/rtHz. The other change made in that time was to add a larger power supply bypass capacitor in the PD.

There are two of the old 4151 chips still on the ISS board on the two "outer-loop" channels that we don't use. If I dig up any more 5131's I will replace these too for completeness.

There is currently no light on the ISS diodes; I'm not sure where it's intended to come from.
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