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ID Date Authorup Type Category Subject
  3265   Thu Jul 22 07:19:56 2010 AlbertoUpdateTreasureMonsters, LNVR, and Phase noise


On Picasa

 "They (shellfish) shall be an abomination to you; you shall not eat their flesh, but you shall regard their carcasses as an abomination." (Leviticus 11:11)

  3269   Thu Jul 22 15:59:29 2010 AlbertoUpdatePSLPSL front end machine


It looks like something wrong happened around the PSL front end.  One of the PSL channel, C1:PSL-PMC_LOCALC, got crazy. 

We found it by the donkey alarm 10 minutes ago.

The attached picture is a screen shot of the PMC medm screen.

The value of C1:PSL-PMC_LOCALC ( middle left on the picture ) shows wired characters. It returns "nan" when we do ezcaread.

Joe went to the rack and powered off / on the crate, but it still remains the same. It might be an analog issue (?)

The problem seems to be a software one.

In any case, Kiwamu and I looked at the at the PMC crystal board and demod board, in search of a possible bad connection. We found a weak connection of the RG cable going into the PD input of the demod board. The cable was bent and almost broken.

I replaced the SMA connector of the cable with a new one that I soldered in situ. Then I made sure that the connection was good and didn't have any short due to the soldering.

  3270   Thu Jul 22 18:18:54 2010 AlbertoUpdatePSLProblem Solved



It looks like something wrong happened around the PSL front end.  One of the PSL channel, C1:PSL-PMC_LOCALC, got crazy. 

We found it by the donkey alarm 10 minutes ago.

The attached picture is a screen shot of the PMC medm screen.

The value of C1:PSL-PMC_LOCALC ( middle left on the picture ) shows wired characters. It returns "nan" when we do ezcaread.

Joe went to the rack and powered off / on the crate, but it still remains the same. It might be an analog issue (?)

The problem seems to be a software one.

In any case, Kiwamu and I looked at the at the PMC crystal board and demod board, in search of a possible bad connection. We found a weak connection of the RG cable going into the PD input of the demod board. The cable was bent and almost broken.

I replaced the SMA connector of the cable with a new one that I soldered in situ. Then I made sure that the connection was good and didn't have any short due to the soldering.

[Alberto, Koji]

By looking at the reference pictures of the rack in the wiki, it turned out that the Sorensen which provides the 10V to the 1Y1 rack was on halt (red light on). It had been like that since 1.30pm today. It might have probably got disabled by a short somewhere or inadvertently by someone working nearby it.

Turning it off and on reset it. The crazy LO calibrated amplitude on the PMC screen got fixed.

Then it was again possible to lock PMC and FSS.

We also had to burtrestore the PSL computer becasue of the several reboots done on it today.

  3285   Sat Jul 24 14:03:19 2010 AlbertoUpdateElectronicsFSS Oscilaltor Phase Noise Measurement

[Rana, Alberto]

Today we measured the phase noise of the oscillator used for the FSS.

The source is a Wenzel crystal at about 21.5MHz that Peter Kalmus built some time ago.

We basically used the same technique that Frank and Megan have been using lately to measure the Marconi's phase noise.

Today we just did a quick measurement but today next week we are going to repeat it more carefully.

Attached is a plot that shows the measurement calibrated for a UGF at about 60 Hz. The noise is compared to that specified by Wenzel for their crystal.

The noise is bigger than that of the MArconi alone locked to the Rubidium standard (see elog entry). We don't know the reason for sure yet.

We'll get back to this problem next week.

  3287   Sun Jul 25 18:47:23 2010 AlbertoUpdateSVNOptickle 40mUpgrade model updated to include short cavity length corrections

I uploaded an updated optickle model of the upgrade to the SVN directory with the optickle models (here).

  3326   Thu Jul 29 22:08:32 2010 AlbertoUpdateSUSMore optics installed on the BS table

[Koji, Steve, Kiwamu, Alberto]

- This afternoon we installed a few new optics on the BS table: GR_PBS, GRY_SM2, GRY_SM1.

- We pulled up the cables so that we had more freedom to move one of the cable towers farther South.

- Then we re-leveled the table. PRM OSEMs were adjusted to be nominal insertions.

- Koji released the earthquake stops on BS but the readout of the OSEMs was apparently frozen on the MEDM screens.
Initially we thought it was a software problem. a nuclear reboot didn't solve it. We spent the following three hours investigating the cause.
Eventually it turned out that the earthquake stops on BS weren't actually fully released.

We opened the tank and accessed to BS. Releasing the earthquake stops in full solved the issue. The OSEMs readout went back to normal.

  3429   Tue Aug 17 09:06:08 2010 AlbertoUpdateelogelog was down

I just restarted the elog after I found it down a few minutes ago.

  3450   Fri Aug 20 16:41:43 2010 AlbertoUpdateElectronicsFrequency Generation Box Assembly Completed

I finished assembling the frequency generation unit for the upgrade. I tested it through to check that the power levels are as expected at the various connection (see attached png, showing in black the design power values, and in red the measured ones).

Because of some modifications made on the design along the construction, I have to recalculate the SNR along the lines.

I can now start to measure phase noise and distortion harmonics.

A document with a description of the design and the results of the characterization measurements will be available in the end.


  3499   Tue Aug 31 17:58:38 2010 AlbertoUpdateElectronicsFSS Frequency Generation Box - Phase Noise

A few weeks ago, on Jul 24, Rana and I measured the phase noise of the FSS frequency box (aka the 'Kalmus Box'). See elog entry 3286.

That time, for some reason, we measured a phase noise higher than we expected; higher than that of the Marconi.

I repeated the measurement today using the SR785 spectrum analyzer. Here is the result:


(The measurement of July 24 on the plot was not corrected for the loop gain. The UGF was at about 30 Hz)

To make sure that my measurement procedure was correct, I also measured the combined phase noise of two Marconis. I then confirmed the consistency of that with what already measured by other people in the past (i.e. Rana elog entry 823 in the ATF elog).

This time the noise seemed reasonable; closer to the Marconi's phase noise, as we would expect. I don't know why it was so bad on July 24.

The shoulder in the Marconi-to-Marconi measurement between 80Hz and 800Hz is probably due to the phase noise of the other Marconi, the one used as LO.

I'm going to repeat the measurement connecting the setup to the DAQ, and locking the Marconi to the Rubidium standard.

Ultimately, the goal is to measure the phase noise of the new Sideband Frequency Generation Box of the 40m Upgrade.

  3501   Wed Sep 1 07:52:27 2010 AlbertoConfigurationElectronicsPMC board unplugged, turned on Sorensen switches on 1Y1 rack

Today I put the FSS frequency box back into the 1Y1 rack.

To power it on, I turned on the 24V and 15V Sorensen switches in the same rack.

The PMC crystal board in the same rack should not be affected (it runs with 10V), but, to make sure it was not powered, I disconnected it from its crate. Since the board was disconnected from the EOM for the PSL table's upgrade, I wanted to avoid having the RF output floating.

We just have to remember to plug it back in, when we need it again.

  3504   Wed Sep 1 08:40:28 2010 AlbertoConfigurationElectronicsPMC board unplugged, turned on Sorensen switches on 1Y1 rack


Today I put the FSS frequency box back into the 1Y1 rack.

To power it on, I turned on the 24V and 15V Sorensen switches in the same rack.

The PMC crystal board in the same rack should not be affected (it runs with 10V), but, to make sure it was not powered, I disconnected it from its crate. Since the board was disconnected from the EOM for the PSL table's upgrade, I wanted to avoid having the RF output floating.

We just have to remember to plug it back in, when we need it again.

 I just turned on the other Sorensen's too in 1Y1.

  3506   Wed Sep 1 11:34:39 2010 AlbertoUpdateElectronicsFSS Box Phase Noise from DAQ

I measured the phase noise of the LO output of the FSS box from the DAQ. I'm attaching the results.

As we expected, the measurement is limited by the internal phase noise of the Marconi.


The measurement was done as shown in this diagram.


  3509   Wed Sep 1 16:29:28 2010 AlbertoUpdateElectronicsFSS Box Phase Noise from DAQ - Measurement setup modified


The differences between this setup and the one used previously is the lack of the 50 Ohm terminator in the mixer output and

that the SR560 readout with the G=100 should come before the first SR560 via T, so as not to be spoiled by the high noise of the G=1 SR560.

I removed the 50 Ohm in-line terminator when I did the measurement with the SR785. The for some reason I was getting more noise, so I removed it.

Now I put it back in and I did the measurement with the DAQ. I also moved the SR560 that amplifies the signal for the DAQ, Tee'ing it with the input of the in-loop SR560.

Now the setup looks like this:


And the phase noise that I measure is this:


Comparing it with the phase noise measured with the previous setup (see entry 3506), you can see that the noise effectively is reduced by about a factor of 2 above 10 Hz.


  3520   Fri Sep 3 11:03:41 2010 AlbertoFrogsElectronicsCable cutting tools

I found this very interesting German maker of cool cable cutting tools. It's called Jokari.

We should keep it as a reference for the future if we want to buy something like that, ie RF coax cable cutting knives.


  3526   Mon Sep 6 10:08:10 2010 AlbertoConfigurationComputersNetgear Network Switch fan broken.

The Netgear Network Switch in the top shelf of Nodus' rack has a broken fan. It is the one interfaced to the Martian network.

The fan must have broken and it is has now started to produce a loud noise. It's like a truck was parked in the room with the engine running.

Also the other network switch, just below the Netgear, has one of its two fans broken. It is the one interfaced with the General Computer Side.

I tried to knock them to make the noise stop, but nothing happened.

We should consider trying to fix them. Although that would mean disconnecting all the computers.

  3529   Mon Sep 6 22:09:11 2010 AlbertoUpdateElectronicsRF Frequency Generation Box heat sink installed and tested

Last week I noticed that the high power amplifiers in the Frequency Generation Box became hot after 2 hours of continuous operation with the lid of the box closed. When I measured their temperature it was 57C, and it was still slowly increasing (~< 1K/hr).
According to the data sheet, their maximum recommended temperature is 65C. Above that their performances are not guaranteed anymore.

These amplifiers aren't properly dissipating the heat they produce since they sit on a plastic surface (Teflon), and also because their wing heat dissipator can't do much when the box is closed. I had to come up with some way to take out their heat.
The solution that I used for the voltage regulators (installing them on the back panel, guaranteeing thermal conduction but electrical isolation at the same time) wouldn't be applicable to the amplifiers.

I discussed the problem with Steve and Koji and we thought of building a heat sink that would put the amplifier in direct contact with the metal walls of the box.
After that, on Friday I've got Mike of the machine shop next door to make me this kind of L-shaped copper heat sink:


On Saturday, I completely removed the wing heat dissipator, and I only installed the copper heat sink on top of the amplifier. I used thermal paste at the interface.

I turned on the power, left the lid open and monitored the temperature again. After 2 hours the temperature of the amplifier had stabilized at 47C.

Today I added the wing dissipator too, and monitored again the temperature with the lid open. then, after a few hours, I closed the the box.
I tracked the temperature of the amplifier using the temperature sensors that I installed in the box and which I have attached to the heat sink.
I connected the box temperature output to C1:IOO-MC_DRUM1. With the calibration of the channel (32250 Counts/Volt), and Caryn's calibration of the temperature sensor (~110F/Volt - see LIGO DOC # T0900287-00-R), the trend that I measured was this:


The heat sink is avoiding the amplifier to overheat. The temperature is now compatible with that of the other component in the box (i.e., crystal oscilaltors, frequency multiplier).
Even with the lid closed the temperature is not too high.

Two things remain untested yet:
1) effect of adding a MICA interface sheet between the heat sink and the wall of the chassis. (necessary for gorund isolation)
2) effect of having all 3 amplifiers on at the same time

I am considering opening air circulation "gills" on the side and bottom of the chassis.

Also we might leave the box open and who ever wants can re- engineer the heat sink.

For posterity.
- Ideally we would like that the heat sink had the largest section area. A brick of metal on top the amplifier would be more effective. Although it would have added several pounds to the weight of the box.
- We need these amplifiers in order to have the capability to change the modulation depth up to 0.2, at least. The Mini-Circuit ZHL-2X-S are the only one available off-the-shelf, with a sufficiently low noise figure, and sufficiently high output power.

  3530   Tue Sep 7 08:56:00 2010 AlbertoUpdateElectronicsFrequency Generation Box Assembly - Phase Noise Measurements

Here are the results of my phase noise measurements on the 7 outputs of the Frequency Generation Box. (BIN=95L applied by DTT). See attached pdf for a higher definition picture.


The plot shows that the phase noise of the 11 MHz outputs (Source, EOM modulation signal, Demodulation signal) is as low as that of the Marconi. The Marconi is limiting my measurement's resolution.

The mode cleaner signal's oscillator (29.5 MHz output, blue trace) is higher than the 11MHz above 1KHz.

The 55MHz signals have all the same phase noise (traces overlapped), and that is higher than the 11 MHz ones from about 100Hz up. i don't know what's going on.

I need to use the spare 11MHz Wenzel crsytal to have a better reference source for the measurement.

  3532   Tue Sep 7 13:31:49 2010 AlbertoUpdateElectronicsRF System - Frequency Distribution Box - Priority Plan

We need a distribution unit in the LSC rack to: 1) collect the demod signals coming from the Frequency Generation Box 2) adjust the power level 3) generate 2nd harmonics (for POP) 4) distribute the demod signals to the single demodulation boards.

The base line plan is the following:


The box can be build up gradually, but the priority goes to these parts:


I need help for this work. I know exactly how to do it, I just don't have the time to do it all by myself.

 Besides the Distribution Box, the demodulation part of the upgrade would still require two steps:

1) upgrade the Band Pass Filters of the demodulation boards (I have all the parts)

2) cabling from the distribution box to the demod board (one-afternoon kind of job)

  3535   Tue Sep 7 15:57:07 2010 AlbertoConfigurationComputersNodus connection not working. Fixed

[Joe, Alberto]

The Nodus connection to the Martian network stopped working after someone switched cables on the Netgear router. Apparently that router doesn't like to have the 23 and 24 ports connected at the same time.

Joe fixed the connection just freeing either the 23 or the 24 port.

  3537   Tue Sep 7 22:21:17 2010 AlbertoConfigurationComputerselog restarted
  3552   Thu Sep 9 12:02:03 2010 AlbertoUpdateElectronicsFrequency Generation Box - Amplitude Noise Measurements

I measured the amplitude noise of the source outputs and the EOM outputs of the Frequency Generation box.

the setup I used is shown in this diagram:


(NB It's important that the cables from the splitter to the RF and LO inputs of the mixers are the same length).

The results of the measurements are shown in the following plot:



1) both Crystals (29.5MHz and 11MHz) have the same noise

2) the 55MHz source's noise is bigger than the 11 MHz (~2x): the frequency multiplication and amplification that happen before it, add extra noise

3) the noise at EOM outputs is ~2x bigger than that of the relative sources


When I have the chance, I'll plot the results of my calculations of expected noise and compare them with the measurements.

  3555   Thu Sep 9 18:53:56 2010 AlbertoConfigurationElectronicsBusby Box, Rai's Box, SR554 in the RF cabinet

I stored the Busby Box, the Rai's Box and the SR554 preamp in the RF cabinet down the Y arm.

  3565   Mon Sep 13 11:40:50 2010 AlbertoUpdateElectronicsFrequency Box Documentation Added to the SVN

I uploaded all the material about the RF frequency Generation Box into the SVN under the path:


I structured the directory as shown in this tree:


I'm quickly describing in a section of the Rf system upgrade document with LIGO # T1000461.

  3572   Tue Sep 14 18:07:41 2010 AlbertoUpdateElectronicsFrequency Box Documentation Added to the SVN

I completed a LIGO document describing design, construction and characterization of the RF System for the 40m upgrade.

It is available on the SVN under https://nodus.ligo.caltech.edu:30889/svn/trunk/docs/upgrade08/RFsystem/RFsystemDocument/

It can also be found on the 40m wiki (http://lhocds.ligo-wa.caltech.edu:8000/40m/Upgrade_09/RF_System#preview), and DCC under the number T1000461.

  3764   Fri Oct 22 18:22:27 2010 AlbertoUpdateElectronicsEpic Takeover


As the suspension work winds down (we'll be completely done once the ETMs arrive, are suspended, and then are placed in the chambers), I'm going to start working on the RF system. 

Step 1: Figure out what Alberto has been up to the last few months.

Step 2: Figure out what still needs doing.

Step 3: Complete all the items listed out in step 2.

Step 4: Make sure it all works.

Right now I'm just starting steps 1 & 2.  I've made myself a handy-dandy wiki checklist: RF Checklist.  Hopefully all of the bits and pieces that need doing will be put here, and then I can start checking them off. Suggestions and additions to the list are welcome.

 There's also a page dedicated to the progress in the PD upgrade process:


There you can find a pdf document with my notes on that.

  3783   Tue Oct 26 07:02:05 2010 AlbertoConfigurationelogELOG 2.8.0 -> ELOG 2.7.5


ELOG reverted to 2.7.5 due to editing difficulties

- /cvs/cds/caltech/elog/start-elog.csh reconfigured to launch 2.7.5

- /cvs/cds/caltech/elog/elog is linked to ./elog-2.7.5

- logbook dir of 2.8.0 was copied in the dir of 2.7.5. The old and obsolete 2.7.5 was discarded.

I think I had the same problem when I switched to 2.75 from 2.65.

Then the problem was FCKeditor.

We should try the solution I put in the elog page of the wiki.


  3893   Thu Nov 11 07:26:03 2010 AlbertoUpdateElectronicsREFL11 Photodiode Not Working


[Koji and Kevin]

I was trying to characterize the REFL11 photodiode by shining a flashlight on the photodiode and measuring the DC voltage with an oscilloscope and the RF voltage with a spectrum analyzer. At first, I had the photodiode voltage supplied incorrectly with 15V between the +15 and -15 terminals. After correcting this error, and checking that the power was supplied correctly to the board, no voltage could be seen when light was incident on the photodiode.

We looked at the REFL55 photodiode and could see ~200 mV of DC voltage when shining a light on it but could not see any signal at 55 MHz. If the value of 50 ohm DC transimpedance is correct, this should be enough to see an RF signal. Tomorrow, we will look into fixing the REFL11 photodiode.

I just wanted to remind you that the most up to date resource about the RF system upgrade, including photodiodes, is the SVN.


There you can find everything: measurements, schematics, matlab scripts to plot and fit, etc. Poke around it to find what you need.
For instance, the schematic of the modified REFL11 photodiode is at:


Because I was doing new things all the time, the wiki is not up to date. But the SVN has all I've got.

  2520   Mon Jan 18 09:44:36 2010 Alberto, BobOmnistructureEnvironmentNo rain water infiltrations so far

It has rained continuously for the last 24 hours. Bob walked through the lab looking for possible water infiltrations. The floor looked dry: no puddles or leaks anywhere so far.

  2971   Fri May 21 16:41:38 2010 Alberto, JoUpdateComputersIt's a boy!

Today the new Dell computer for the GSCS (General SURF Computing Side) arrived.

We put it together and hooked it up to a monitor. And guess what? It works!

I'm totally impressed by how the Windows get blurred on Windows 7 when you move them around. Good job Microsoft! Totally worth 5 years of R&D.

  2490   Fri Jan 8 20:13:49 2010 Alberto, JoBConfigurationComputersThe 40m Kaiser Permanent Reboot Marathon
This morning after Alex and Jo's tinkering with Megatron the RFM network crashed and it brought down also some computers. The effect was that it was not possible to lock the mode cleaner anymore.
A few computers crashed and things didn't come back to their origianl state.
After an endless day of rebooting and fixing problems with the single front ends (in particular with c1susvme1), eventually the mode cleaner got locked again.
Among my weapons I also used the Nuclear Option (TM).
Maybe I'll include more details in a future elog entry.
Anyway, in the end I burtrestored everything to Jan 8 2009 at 9:00.


  1261   Fri Jan 30 17:30:31 2009 Alberto, JosephbConfigurationComputersNew computer Ottavia set up
Alberto, Joseph,

Today we installed the computer that some time ago Joe bought for his GigE cameras. It was baptized "OTTAVIA".

Ottavia is black, weighs about 20 lbs and it's all her sister, Allegra (who also pays for bad taste in picking names). She runs an Intel Core 2 Quad and has 4GB of RAM. We expect much from her.

Some typical post-natal operations were necessary.

1) Editing of the user ID
  • By means of the command "./usermod -u 1001 controls" we set the user ID of the user controls to 1001, as it is supposed to be.

2) Connection to the Martian network
  • Ottavia was given IP address by editing the file /etc/sysconfig/networ-scripts/ifcfg-eth0 (we also edited the netmask and the gateway address as in the Wiki)
  • In linux1, which serves as name server, in the directory /var/named/chroot/var/named, we modified both the IP-to-name and name-to-IP register files 131.215.113.in-addr.arpa.zone and 131.215.11in-addr.martian.zone.
  • We set the file /etc/resolv.conf so that the OS knows who is the name server.

3) Mounting of the /cvs/cds path
  • We created locally the empty directories /cvs/cds
  • We edited the files /etc/fstab adding the line "linux1:/home/cds /cvs/cds nfs rw,bg,soft 0 0"
  • We implemented the common variables of the controls environment by sourcing the cshrc.40m: in the file /home/controls/.cshrc we added the two lines "source /cvs/cds/caltech/cshrc.40m" and "setenv PATH ${PATH}:/cvs/cds/caltech/apps/linux64/matlab/bin/"
  3029   Wed Jun 2 01:47:28 2010 Alberto, KiwamuUpdateIOOmode measurement of new input optics

The mode profile of the new input optics was measured.

Although the distance between each optic was not exactly the same as the design because of narrow space,

we measured the profile after the curved mirror (MMT1) that Jenne and Kevin put in the last week.


(interference from MMT1)

Below is a sketch of the current optical path inside of the chamber.



In the beginning of this measurement, the angle between the incident and the reflection on MMT1 (denoted as theta on the sketch) was relatively big (~40deg) although MMT1 was actually made for 0deg incident.

At that time we found a spatially large interference imposed on the Gaussian beam at the beam scan. This is not good for mode measurement

This bad interference can be caused by an extra reflection from the back surface of MMT1 because the interference completely vanished by removing MMT1  .

In order to reduce the interference we decreased the angle theta as small as possible. Actually we made it less than 10deg which was our best due to narrow space. 

Now the interference got less and the spot looks better.

The picture below shows an example of the beam shape taken by using the beam scan.

Top panel represents the horizontal mode and bottom panel represents the vertical mode.

You can see some bumps caused by the interference on the horizontal mode, these bumps may lead to overestimation of the horizontal spot size .






 The above plot shows the result of the mode measurement.

 Here are the parameter obtained by fitting. The data is also attached as attachment:4

waist size for vertical  w0v [mm]  0.509 +/-0.0237
waist size for horizontal

w0h  [mm]

 0.537  +/- 0.0150
waist position from MMT1 for vertical  xv[m]  -2.91 +/- 0.214
waist position from MMT1 for horizontal xh[m]   -2.90 +/-  0.127

  3046   Thu Jun 3 14:40:28 2010 Alberto, KiwamuUpdateIOOmode measurement of new input optics




For the record, we wanted to check whether the fringes on the beam spot were caused by SM2 (see diagram above). We tried two different mirrors for SM2,

The first was one of the flat, 45 degree ones that were already on the BS table. The last, which is the one currently in place, was inside the plastic box with the clean optics that Jenne left us .

The fringes were present in both cases.

  1166   Tue Dec 2 17:56:56 2008 Alberto, RanaConfigurationPSLMC Alignment
In the attempt to maximize the Mode Cleaner transmission and minimize the reflection from the steering mirrors of the MC periscope, we could not get more ~2 V at the MC Trans PD and ~ 0.5 V at MC REFL_DC. As it turned out from the SUS Drift Monitor, the reason was that the MC optics had been somehow displaced from the optimal position.

After restoring the reference position values for the mirrors and tweaking again the periscope, we got ~3V at the MC TransPD and 0.5V at the reflection.
The beam was then probably clipped at the REFL PD so that we had to adjust the alignment of one of the BS in the transmitted beam path on the AS table.
We also zeroed the WFS PDs, but not before reducing the power from the MZ, for their QPDs not to saturate.

After relocking, the transmission was 3V and the reflection ~0.3V.

The beam isnow centered on the Trans PD and REFL PD and the Mode Cleaner locked. More details on the procedure will follow.
  1883   Mon Aug 10 20:49:13 2009 Alberto, RanaUpdatePSLPMC Mode Matching Lenses Tuning

Rana, Alberto

This afternoon we tried to improve the mode matching of the beam to the PMC. To do that we tuned the positions of the two lenses on the PSL table that come before the PMC.

We moved the first lens back an forth the without noticing any improvement on the PMC transmitted and reflected power. Then we moved the first backwards by about one cm (the order is set according to how the beam propagates). That made the things worse so we moved also the second lens in the same direction so that the distance in between the two didn't change significantly. After that, and some more adjustments on the steering mirrors all we could gain was about 0.2V on the PMC transmission.

We suspect that after the problems with the laser chiller of two months ago, the beam size changed and so the mode matching optics is not adequate anymore.

We have to replace the mode matching lenses with other ones.


  2468   Wed Dec 30 18:01:03 2009 Alberto, RanaUpdateGeneralAll watchdogs tripped this morning


This morning I found all the watchdogs had tripped during the night.

I restored them all.

I can't damp ITMX. I noticed that its driving matrix is all 1s and -1s as the the right values had been lost in some previous burtrestoring.


Rana fixed the problem. He found that the side damping was saturating. He lowered the gain a little for a while, waited for the the damping to slow down the optic and then he brought the gain back where it was.

He also upadted the MEDM screen snapshot.

  1162   Tue Nov 25 18:38:03 2008 Alberto, RobUpdatePSLMC Periscope Alignment
This morning when I came in I found the MC cleaner unlocked and the autolocker script could not lock it. The reflected beam was quite off and showed in the bottom left corner of the IMCR camera. After turning off the WFS locking, I started slightly changing the alignment of the steering mirrors on the MC periscope, waiting for the LSC servo to lock the cavity. It didn't work. At some point I lost the beam from the IMCR camera and that is how someone might have found it when I left it for about one hour.

When I came back and tried again adjusting the steering mirrors, I noticed that the autolocker was working and was trying to lock the cavity. After just a bit of adjustment, the MC got easily locked.

After that, I spent a couple of hours trying to improve the alignment of the periscope to minimize the reflection and maximize the transmission. I started with a transmission of 0.4 V but, despite all the tweaking (I used the technique of turning both yaw knobs at the same time), I couldn't get more than 1.2 V (and 2.4 V at the reflection) if only the LSC servo was on. Looking at the camera, I moved the beam around to look for a more favorable spot but the MC wouldn't lock with the beam in other places. Maybe I could do better or maybe not because the cavity is not aligned. I'm going to try again tomorrow.
  2106   Fri Oct 16 16:44:39 2009 Alberto, SanjitUpdateComputerselog restarted

This afternoon the elog crashed. We just restarted it.

  2477   Tue Jan 5 10:26:32 2010 Alberto, SteveOmnistructureEnvironmentAdded new wall cable-racks

we hung two new WALL cable racks. One is on the pillar next to the Sp table, the other is next to the PSL computer rack.

To do that we had to drill holes in the wall since the simple screws weren't strong enough to keep them up.

One of the racks, the yellow, is dedicated to 4-pin lemos and other thick cables.


  1193   Thu Dec 18 19:15:54 2008 Alberto, YoichiConfigurationSUSMode Cleaner Cavity Alignment

This morning I found the MC locked to the 10 mode. When I locked it on the 00 mode, it was unstable and eventually it always got locked to the wrong mode.

I looked at the Drift Mon MEDM screen, which shows a reference record for position, pitch and yaw of each mirror, and I found that the MC optics were in a different status. Moving the sliders of the mirrors' actuators, I brought them back to the reference position. Then the lock got engaged and it was stable, although the MC reflection from the photodiode, with the wave front sensors (WFS) off, was about 2V. That's higher than the 0.5V the it could get when we aligned the cavity and the input periscope last time.

With the WFS on, the reflection dropped to 0.3V and, so far, the the cavity has been stably locked.

This evening the mode cleaner was again locking on a higher mode so we tweaked the mirrors' actuators by their sliders on the MEDM screen until we improved the reflection to 0.3V.

Then we went inside and, on the AS table, we centered the beam on the wave front sensors.

Now the mode cleaner is locked, the reflection is less than 0.3V and the transmission about 3V, tha is it is in ideal conditions. We'll see if it holds.
  1195   Fri Dec 19 11:29:16 2008 Alberto, YoichiConfigurationMZMZ Trans PD
Lately, it seems that the matching of the input beam to the Mode Cleaner has changed. Also, it is drifting such that it has become necessary to continuously adjust the MC cavity alignment for it to lock properly.

Looking for causes we stopped on the Mach Zehnder. We found that the monitor channel:

which supposedly reads the voltage from some photodiode measuring the transmitted power from the Mach Zehnder, is totally unreliable and actually not related to any beam at all.

Blocking either the MZ input or output beam does not change the channel's readout. The reflection channel readout responds well, so it seems ok.
  3049   Fri Jun 4 11:32:51 2010 Alberto, kiwamuUpdateIOOMC MMT1 Mirror Tests
[Alberto, Kiwamu]
Last Wednesday, we measured the beam profile after the MC mode matching telescope n.1 (MMT1). We found that the reflected beam had an irregular profile when observed with the beam scan. Fringes also appeared on an IR card.
We thought that such effect could be due to interference of the main reflected beam with the beam reflected by the back surface of the mirror.
To test the hypothesis we checked the transmitted and the reflected beams of a spare optic identical to MMT1. (This was the same optic that got dropped during the cleaning/baking process.)
We tested it on the PSL table, using a 200mW beam coming from the new 2W Innolight  laser. To maximize the separation between the two beams, we tested MMT1 at 45 degrees. The setup we used is shown here:
We looked at the beam reflected by MMT1 about 5 meters from the mirror. At that distance the beam spot had a size of about 1-2cm. it didn't look perfectly round, but it showed no fringes, as it had happened with original MMT1 inside the MC chamber.
At the transmission, the second ghost beam due to the back surface reflection (see picture above) was very week. In order to be able to see it on an IR card, we had to increase the laser pumping current from 1A to about 1.5A.
We are now thinking of a way to measure the relative power between the two. The problem is that they run very close to each other and it's not easy to resolve them with a power meter or a photodiode.
  2887   Thu May 6 17:47:01 2010 Alberto, kiwamu, Jc The 3rd (aka The Drigg)OmnistructureTMIMinutes from the Lab Organization Commitee meeting

Today we met and we finally come up with a lot of cool, clever, brilliant, outstanding ideas to organize the lab.

You can find them on the Wiki page created for the occasion.



  1947   Tue Aug 25 23:16:09 2009 Alberto, ranaConfigurationComputerselog moved in to the cvs path

In nodus, I moved the elog from /export to /cvs/cds/caltech. So now it is in the cvs path instead of a local directory on nodus.

For a while, I'll leave a copy of the old directory containing the logbook subdirectory where it was. If everything works fine, I'll delete that.

I also updated the reboot instructions in the wiki. some of it also is now in the SVN.

  8795   Wed Jul 3 11:07:17 2013 AlexSummary Photodetector Characterization

 [Alex, Koji]

We characterized Koji's BBPD MOD for REFL165 (see attachment).

First, we calibrated the Agilent 4395 Network Analyzer (NA) to account for differences in cable features between the Ref PD and Test PD connections. This was done using the 'Cal' softkey on the NA. 

Then we performed transimpedance measurements for the test PD and reference PD relative to the RF output of the NA and relative to each other (see 2nd attachment. Note that the NA's RF output is split and sent to both the IR Laser and the NA's Ref input).

Next, we made DC measurements of the outputs of the photodetectors to estimate the photocurrent distribution of the transimpedance setup (like the 2nd attachment, but with the outputs of the PDs going to a multimeter). By photocurrent distribution, we mean how the beamsplitter and respective quantum efficiencies/generalized impedance/etc. of the PDs influence how much current flows through each PD at with a DC input.

Finally, we measured the output noise as a function of photocurrent (like the 2nd attachment, but with a lightbulb instead of the IR Laser). Input voltages for the lightbulb ranged from 0mV to 6V. Data was downloaded from the NA using netgpibdata from the scripts directory. Analysis is currently in progress; graphs to come soon.


  8806   Mon Jul 8 16:27:49 2013 AlexUpdate Planned rack additions

Alex and Eric

For the photodetector frequency response automation project, we plan to add modules to rack 1y1 as shown in the attached picture (Note: boxes are approximately to scale). 

The RF switch will choose which photodetector's output is sent to the Agilent 4395A Network Analyzer.

The Diode Laser Module is powered by Laser Power Supply, will be modulated by the Network Analyzer and will be output to a 1x16 optical splitter which is already mounted in another rack (not pictured). 

The Transformer Module has not been built yet.

We would like to install the power supply and the laser module tomorrow and will not begin routing fibers and cables until we post a drawing in the elog.

Also, our reference photoreceiver arrived today.


  8829   Thu Jul 11 12:00:50 2013 AlexUpdate Planned rack additions

[Eric, Alex]

We mounted our Laser Module and Laser Power Source in rack 1y1. We plan to add our RF Switch and Transformer Module to the rack, as pictured. (Note: drawn-in boxes in picture are approximately to scale.) Note that the panel of knobs which the gray boxes overlap is obsolete and will soon be removed.

  8849   Mon Jul 15 16:44:46 2013 AlexUpdateOMCOMC North Safety

 [Eric Alex]

We are planning on testing our laser module soon, so we have added aluminum foil and a safety announcement to the door of OMC North. The safety announcement is as pictured in the attachment.

  8850   Mon Jul 15 16:51:37 2013 AlexConfiguration Planned AS Table addition

 [Eric, Alex]

We are planning to add our reference PD to the southern third of the AS Table as pictured in the attachment. The power supply will go under the table.

  8859   Tue Jul 16 17:02:41 2013 Alex ColeConfigurationElectronicsAS Table Additions

 [Eric, Alex]

We added our reference photodetector (Newport 1611, REF DET) to the southern edge of the AS table, as pictured. The detector's power supply is located under the southwest corner of the table, as pictured. We have connected the detector to its power supply, and will connect the detector's fiber input and RF output tomorrow.

EDIT: this is about the RFPD frequency response setup...

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