40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log, Page 274 of 344  Not logged in ELOG logo
ID Date Author Typedown Category Subject
  1904   Fri Aug 14 15:20:42 2009 josephbSummaryComputersLinux1 now has 1.5 TB raid drive



nodus was rebooted by Alex at Fri Aug 14 13:53. I launched elogd.

cd /export/elog/elog-2.7.5/
./elogd -p 8080 -c /export/elog/elog-2.7.5/elogd.cfg -D

 It looks like Alex also rebooted all of the control room computers.  Or something.  The alarm handler and strip tool aren't running.....after I fix susvme2 (which was down when I got in earlier today), I'll figure out how to restart those.

 Alex switched the mount point for /cvs/cds on Linux1 to the 1.5 TB RAID array after he finished copying the data from old drives.  This required a reboot of linux1, with all the resulting /cvs/cds mount points on the other computers becoming stale.  Easiest way to fix that he found was to do a reboot of all the control room machines.  In addition, a reboot fest should probably happen in the near futuer for all the front end machines since they will also have stale mount points as well from linux1.

The 1.5 TB RAID array mount is now mounted on /home of linux1, which was the old mount point of the ~300 GB drive.  The old drive is now at /oldhome on linux1.


  1916   Mon Aug 17 02:12:53 2009 YoichiSummaryComputersFE bootfest
Rana, Yoichi

All the FE computers went red this evening.
We power cycled all of them.
They are all green now.

Not related to this, the CRT display of op540m is not working since Friday night.
We are not sure if it is the failure of the display or the graphics card.
Rana started alarm handler on the LCD display as a temporary measure.
  1919   Mon Aug 17 09:52:04 2009 robSummaryGeneralconlogger restarted

I restarted the conlogger on op340m.  This needs to be done when op340m is rebooted--it wasn't done for some reason and so we've lost several days of controls records.

  1920   Mon Aug 17 17:43:11 2009 ranaSummaryGeneralconlogger restarted

Added the conlog directory to the SVN, minus the enormous data directory. We are now free to make changes to the conlog code.

  1921   Mon Aug 17 17:48:49 2009 robSummaryGeneralconlogger restarted


I restarted the conlogger on op340m.  This needs to be done when op340m is rebooted--it wasn't done for some reason and so we've lost several days of controls records.

 I added a cronjob on op340m to check every half-hour if the conlog is running, and if not, restart it. 

  1923   Tue Aug 18 14:24:43 2009 YoichiSummaryPSLReference Cavity Inspection
Rana, Koji, Yoichi

To see why the reflected beam from the RC is distorted, we took out
the periscope and the iris in front of the RC. The periscope mirrors
had some gunk and dusts on them. We blew nitrogen air onto them to
remove the dust. Since the gunk did not come off with the air, we
wrapped a Q-tip with lens cleaning paper soaked in Methanol, and wiped
the surface of the mirrors. We did this because it was hard to remove
the mirrors from the periscope (they were in a spring loaded mirror
holders. The springs were too strong to safely remove them without
damaging the mirrors).

Looking into the RC from the front mirror revealed nothing obstructing
in the path.

After the cleaning, we put the periscope back and observed the direct
reflection from the cavity (not locked). It was still distorted
exactly like before.

So we did some tests.
First we injected He-Ne to the RC. It turned out that multiple
reflections from the optical window (not AR coated for He-Ne) made it
almost impossible to investigate anything with He-Ne. But this
observation made us to suspect maybe one side of the window is not AR

We placed the periscope about 50cm away from the RC and injected the
beam from an angle, so that we can observe the direct reflection.

First, we checked the shape of the beam leaving the periscope. It was good.
We then observed the reflected beam from the RC. It was also good, no distortion.
We made sure that it was really the reflection from the mirror, not from the window
as follows.
We measured the separation between the in coming beam to the cavity and the reflected beam
at two locations. From this, we can guess where the two beams intersect (the reflection point).
The estimated reflection point was far inside the RC enclosure, indicating that it was really
reflection from the front mirror of the RC.
Since we did not see any other reflection beam, we concluded that the AR coating of the window
is good.

We checked the direct reflection beam shape with several different incident angles, but the
beam shape was always good.

We put back the periscope to the original position. This time, we put a high reflectivity mirror
after the output mirror of the periscope. The beam coming out of the circulator (PBS) had a good
circular shape. But still if we let the beam reflected by the cavity, the beam shape is distorted.
Something must be happening in the RC. Unfortunately, we could not figure out what it is.

We put everything back to the original configuration, except for the iris, and the RC alignment
was already good (surprise). After Koji's final tweak, the FSS is now doing fine, but still
the reflected beam is ugly.
  1933   Fri Aug 21 17:28:50 2009 Kevin, ranaSummaryPEMMagnetic Field Measurements Around the Lab

This goal of this test was to measure and map the AC (at 60 Hz) and DC magnetic fields around the interferometer. I've attached the final products which were drawn up with Google SketchUp.

The notes on the maps make them more or less self explanatory: for each numbered point there's an X, Y, and Z measurement produced by the magnetometer. For the AC numbers I measured the Peak-to-Peak value, while for the DC I simply measured the Mean. The magnetometer's axes were always oriented about the same way, with the X arrow on the magnetometer pointing north. I tried to keep variables such as the lights constant as much as possible (they were all on for most measurements, with the exception of a few noted DC ones) and all measurements had the top of the magnetometer at about 32 inches.  The map is pretty close to scale and all the walls and numbered locations were measured out (though the location of objects and the laser tubes is somewhat estimated). I added "landmarks" in the room, which were pretty much the laser tubes, computer racks, and ISC tables.

For each laser room measurement I also took a screenshot using the oscilloscope as a means of recording the shape of the wave for each measurement. Ch1 corresponds to the X value, Ch2 to the Y, and Ch3 to the Z. The screenshots are numbered 1-29 corresponding to the numbers on the map. The zip folders containing the screenshots can be found on the wiki:  PEM:Magnetometers

I should also mention that there is no point #24 and accordingly no 24 screenshot. I realized after I was done that I had messed up the location of that one and instead of risking bad data decided to just remove it.

I decided on the location of the points mainly based on the location of outlets in the room (since I had to plug in the oscilloscope for the AC numbers to set it to 60 Hz). After an initial pass of the room, I went back and filled in some of the larger gaps by moving the magnetometer as far as I could while the oscilloscope remained plugged in to the wall. I used the same points for DC numbers.

Prior to measuring the laser room, I measured the field in other rooms as well. I have

  • AC numbers and screenshots for the control room and the adjoining office room.

  • DC numbers for the entry room and the office room, not including the control room. The X-axis arrow is pointed south (instead of north) for these numbers.

These numbers were sort of a warm up for me to figure out the process and how I would go about recording my data. Since they're not in really important locations and aren't guaranteed to be accurate, I decided not to map them, though the screenshots are still on this Dell Inspiron 1300 Laptop and the measurements in my notebook.

Here are the settings I used on the oscilloscope for all measurements (I merely changed the Vertical Coupling between DC and AC depending on what I was measuring):

  • Impedance: 1M ohms

  • Bandwidth: Full

  • Probe Setup: Voltage 1X

  • Trigger Type: Edge

  • Trigger Coupling: DC

  • Fast Trig: Normal

  • Trigger Mode: Auto

  • Trigger Source: AC Line

  • Acquire Mode: 512 Average

 The notebook that I used contains some additional info that I didn't include in the map, most importantly more precise descriptions of where each of the points is located and the measured distance between each of them (as well as slight changes I made to my measured distances in order to make the room a rectangle; the changes are slight enough that they shouldn't have any real effect on the data).

Since Kevin used our 3-axis Bartington Fluxgate magnetometer, we can guess that we can convert his voltage measurements (below) into magnetic field
by using the manual's guess of 10 uT /V or 10 V/Gauss. This is probably ok at the factor of 2 level, but one day we should calibrate it with a coil.

The punchline is that the DC fields in the lab are roughly what we expect from the Earth's field plus the rebar in our floors: ~1 Gauss. The 60 Hz fields are ~50-500 nT peak-peak.

  1934   Fri Aug 21 17:49:47 2009 YoichiSummaryComputersUpgrade FE conceptual plan
I started to draw a conceptual diagram of the upgraded FE system.
(It takes some time to load the page for the first time)

Some places, tips will pop up when you stop the cursor over an object.
You can also click on the LSC block to see inside.

This is just a start point, so we should add more details.
The source of the diagrams are in the svn:

I used yEd (http://www.yworks.com/en/products_yed_about.html) to make
the drawings. It is Java, so works on many platforms.
  1941   Tue Aug 25 03:30:23 2009 YoichiSummaryWIKI-40M UpdateGreen lock and phase noise
While Koji and I were discussing about the green laser lock, we wondered if the common motion of the cavity mirrors,
which won't be suppressed by the green laser servo, will cause any problem to the locking.

Since the common motion of the cavity mirrors is equivalent to the change of the path length from the laser to the
input mirror, it will show up as a phase noise in the error signal.
Unfortunately, since we inject the green laser from the end mirror, this phase noise has opposite sign for the
PSL and the green laser.

I calculated the magnitude of the phase noise using an extremely rough estimate of the common motion of the mirrors.
It is explained in the 40m wiki.

The result plot is attached.
(Probably the seismic noise I used is an over estimate.)
  1942   Tue Aug 25 11:02:39 2009 ranaSummaryPSLTemperature Box

The PSL Temperature Box (D980400-B-C, what kind of numbering scheme is that?) modified at LHO/LLO ~8 years ago to have better resolution on the in-loop temperature sensors.

I haven't been able to find a DCN / ECN on this, but there's an elog entry from Hugh Radkins here.  I'm also attaching the PDF of the latest drawing (circa 2000) from the DCC.

The schematic doesn't show it, but I am guessing that the T_SENSE inputs are connected to the AD590 chips, and that 4 of these are attached somehow to the RefCav can. IF this is true, I don't understand why there are input resistors on the LT1125 of U1; the AD590 is supposed to be a current source ?

Peter King is supposed to be coming over to work on this today so whoever spots him should force/cajole/entice him to elog what he's done. Film him if necessary.


I also think R1-8 should be swapped into metal film resistors for stability. The datasheet says that it puts out 1 uA/K, so the opamps put out 10 mV/K.

J8 and JP1 should be shorted to disable both the tidal and VME control input. Both are unused and a potential source of drift.

  1956   Thu Aug 27 13:42:08 2009 ranaSummaryPSLReference Cavity Temperature Control: psl.db changes

I made the changes to the psl.db to handle the new Temperature box hardware. The calibrations (EGUF/EGUL) are just copied directly from the LHO .db file (I have rsync'd their entire target area to here).

allegra:c1psl>diff psl.db~ psl.db
< grecord(ai,"C1:PSL-FSS_TIDALOUT")
< {
<       field(DESC,"TIDALOUT- drive to the reference cavity heater")
<       field(DISV,"1")
<         field(SCAN,".5 second")
<       field(DTYP,"VMIVME-3113")
<       field(INP,"#C0 S28 @")
<       field(EGUF,"10")
<       field(EGUL,"-10")
<       field(EGU,"volts")
<       field(LOPR,"-10")
<       field(AOFF,"0")
< }
<         field(EGUF,"285.675")
<         field(EGUL,"-214.325")
>         field(EGUF,"67.02")
>         field(EGUL,"7.96")
<         field(EGUF,"726.85")
<         field(EGUL,"-1273.15")
>         field(EGUF,"75.57")
>         field(EGUL,"12.31")
<         field(EGUF,"726.85")
<         field(EGUL,"-1273.15")
>         field(EGUF,"75.57")
>         field(EGUL,"12.31")
< grecord(ai,"C1:PSL-FSS_TIDALINPUT")
< {
<       field(DESC,"TIDALINPUT- tidal actuator input")
<       field(DISV,"1")
<         field(SCAN,".5 second")
<       field(DTYP,"VMIVME-3123")
<       field(INP,"#C0 S3 @")
<       field(EGUF,"10")
<       field(EGUL,"-10")
<       field(EGU,"volts")
<       field(LOPR,"-10")
<       field(AOFF,"0")
< }
> grecord(ai,"C1:PSL-FSS_TIDALINPUT")
> {
>       field(DESC,"TIDALINPUT- tidal actuator input")
>       field(DISV,"1")
>         field(SCAN,".5 second")
>       field(DTYP,"VMIVME-3123")
>       field(INP,"#C0 S3 @")
>       field(EGUF,"10")
>       field(EGUL,"-10")
>       field(EGU,"volts")
>       field(LOPR,"-10")
>       field(AOFF,"0")
> }
> grecord(ai,"C1:PSL-FSS_TIDALOUT")
> {
>       field(DESC,"TIDALOUT- drive to the reference cavity heater")
>       field(DISV,"1")
>         field(SCAN,".5 second")
>       field(DTYP,"VMIVME-3113")
>       field(INP,"#C0 S28 @")
>       field(EGUF,"10")
>       field(EGUL,"-10")
>       field(EGU,"volts")
>       field(LOPR,"-10")
>       field(AOFF,"0")
> }
<         field(HOPR,"0.010")
<         field(LOPR,"-0.010")
>         field(HOPR,"2")
>         field(LOPR,"0")

  1958   Thu Aug 27 16:14:28 2009 steveSummaryOMCburned photodiode

Old -pre 6/2009  LLO DCPD 3 mm od GTRAN photodiode

  1967   Fri Sep 4 16:09:26 2009 josephbSummaryVACRebooted RGA computer and reset RGA settings

Steve noticed the RGA was not working today.  It was powered on but no other lights were lit.

Turns out the c0rga machine had not been rebooted when the file system on linux1 was moved to the raid array, and thus no longer had a valid mount to /cvs/cds/.  Thus, the scripts that were run as a cron could not be called.

We rebooted c0rga, and then ran ./RGAset.py to reset all the RGA settings, which had been reset when the RGA had lost power (and thus was the reason for only the power light being lit).


Everything seems to be working now.  I'll be adding c0rga to the list of computers to reboot in the wiki.

  1978   Tue Sep 8 20:15:33 2009 rana, jenneSummaryPSLRC temperature servo: Heater Voltage noise

We measured the voltage noise of the heater used to control the RC can temperature. It is large.


The above scope trace shows the voltage directly on the monitor outputs of the heater power supply. The steps are from the voltage resolution of the 4116 DAC.

We also measured the voltage noise on the monitor plugs on the front panel. If these are a true representation of the voltage noise which supplies the heater jacket, then we can use it to estimate the temperature fluctuations of the can. Using the spectrum of temperature fluctuations, we can estimate the actual length changes of the reference cavity.

I used the new fax/scanner/toaster that Steve and Bob both love to scan this HP spectrum analyzer image directly to a USB stick! It can automatically make PDF from a piece of paper.

The pink trace is the analyzer noise with a 50 Ohm term. The blue trace is the heater supply with the servo turned off. With the servo on (as in the scope trace above) the noise is much much larger because of the DAC steps.

  1993   Fri Sep 18 16:26:02 2009 steveSummaryPSLNeslab chiller is OK

Rob found puddles of water very close to the chiller during lunch time. We raised the unit and took the side cover off. All surfaces were dry and the water level in the tub normal.

Later on we discovered that one of the Vons distilled water bottle was leaking. Jenne and I checked for excess amount of condensing water droplets inside the MOPA box.

On the bare,not insulated tubing and valve are loaded with droplets of water. Relative humidity is 44% at 24 C and HEPA filter speed set to 80 V in the enclosure.


  1999   Thu Sep 24 20:17:05 2009 ranaSummaryLSCComparison of Material Properties for the new RFPD Mounts
  Steel Brass Aluminum Delrin
Density (kg/m^3) 7850 8500 2700 1420
CTE (ppm/C) 12 19 23 100




200 110 69 2
Color grey gold light silver any


  2043   Fri Oct 2 15:24:29 2009 sanjit, ranaSummaryIOOmcwfs centered

we set the offsets for the MCWFS DC and for the MCWFS demod outputs and then turned off the lights put the MZ at half fringe and then centered the spots on the MCWFS heads.

The MCREFL beam looks symmetric again and the MC REFL power is low. 

  2064   Wed Oct 7 11:18:40 2009 kiwamuSummaryElectronicsracks of electronics


I took the pictures of all racks of electronics yesterday, and then uploaded these pictures on the wiki.


You can see them by clicking "pictures" in the wiki page.


  2070   Thu Oct 8 20:18:56 2009 KojiSummaryGeneralArm cavity loss

Last night (Oct 07), I ran armLoss script in order to obtain the latest numbers for the arm cavity loss.
Here is the summary

<<X arm>>
Measured arm reflectivity R_cav:
0.875 +/- 0.005
Estimated round trip loss L_RT: 157ppm +/- 8ppm
Estimated finesse F: 1213+/-2
Data Points: 34

<<Y arm>>
Measured arm reflectivity R_cav:
0.869 +/- 0.006
Estimated round trip loss L_RT: 166ppm +/- 8ppm
Estimated finesse F: 1211+/-2
Data Points: 26








TE=10ppm, LE=L_RT/2, RE=1-TE-LE
tE=Sqrt(TE), rE=Sqrt(RE)

TF=0.005, LF=L_RT/2, RF=1-TF-LF
tF=Sqrt(TF), rF=Sqrt(RF)

rcav = -rF +(tF^2 rE)/(1-rF rE)
R_cav = rcav^2

F = pi Sqrt(rF rE)/(1-rF rE)


  2071   Thu Oct 8 21:32:59 2009 KojiSummaryGeneralRecycling cavity loss

I looked at the data of the day before yesterday (Oct 06) to know how much is the recycling gain.

X arm: (TRX_PRecycled) / (TRX_PRMmisaligned) * T_PRM = 83.1/0.943*0.07 = 6.17
Y arm: (TRX_PRecycled) / (TRX_PRMmisaligned) * T_PRM = 99.2/1.017*0.07 = 6.83

==> G_PR = 6.5 +/- 0.5     (oh...this estimation is so bad...)

From the recycling gain and the arm cavity reflectance, one can get the loss in the recycling cavity.

G_PR = T_PRM  / (1-Sqrt(R_PRM * (1-L_PRC)*R_cav))^2

==> loss in the recycling cavity L_PRC: 0.009+/-0.009
       (About 1% loss is likely in the recycling cavity)


<<X arm>>
Measured arm reflectivity R_cav: 0.875 +/- 0.005
Estimated round trip loss L_RT: 157ppm +/- 8ppm
Estimated finesse F: 1213+/-2

<<Y arm>>
Measured arm reflectivity R_cav:
0.869 +/- 0.006
Estimated round trip loss L_RT: 166ppm +/- 8ppm
Estimated finesse F: 1211+/-2


  2094   Thu Oct 15 01:21:31 2009 ranaSummaryCOCThermal Lensing in the ITM

Thermal lensing formula:


from (T090018 by A. Abramovici (which references another doc).

In the above equation:

w        1/e^2 beam radius

k        thermal conductivity (not the wave vector) = 1.3 W / m/ K

alpha    absorption coefficient (~10 ppm/cm for our glass)

NP       power in the glass (alpha*NP = absorbed power)

dn/dT    index of refraction change per deg  (12 ppm/K)

d        mirror thickness (25 mm for all of our SOS)

I'm attaching a plot showing the focal length as a function of recycling cavity power for both our current MOS and future SOS designs.

I've assumed a 10 ppm/cm absorption here. It may actually be less for our current ITMs which are made of Heraeus low absorption glass - our new ITMs are Corning 7980-A (measured to have an absorption of 13 ppm/cm ala the iLIGO COC FDD). I expect that our thermal lens focal length will always be longer than 1 km and so I guess this isn't an issue.

  2097   Thu Oct 15 09:23:07 2009 steveSummaryLockingnever had it so good

Awesome 5 hrs of locking  Rob!

  2100   Thu Oct 15 17:12:00 2009 ranaSummaryLockingnever had it so good


  2101   Fri Oct 16 03:16:50 2009 rana, robSummaryLSCfunny timing setup on the LSC

While measuring the Piezo Jena noise tonight we noticed that the LSC timing is setup strangely.

Instead of using the Fiber Optic Sander Liu Timing board, we are just using a long 4-pin LEMO cable which comes from somewhere in the cable tray. This is apparent in the rack pictures (1X3) that Kiwamu has recently posted in the Electronics Wiki. I think all of our front ends are supposed to use the fiber card for this. I will ask Jay and Alex what the deal is here - seems like to me that this can be a cause for timing noise on the LSC.

We should be able to diagnose timing noise between the OMC and the LSC by putting in a signal in the OMC and looking at the signal on the LSC side. Should be a matlab script that we can run whenever we are suspicious of this. This is an excellent task for a new visiting grad student to help learn how to debug the digital control system.

  2104   Fri Oct 16 13:25:18 2009 KojiSummaryLSCfunny timing setup on the LSC

Could be this.



We should be able to diagnose timing noise between the OMC and the LSC by putting in a signal in the OMC and looking at the signal on the LSC side. Should be a matlab script that we can run whenever we are suspicious of this. This is an excellent task for a new visiting grad student to help learn how to debug the digital control system.


  2118   Mon Oct 19 14:48:15 2009 rana, robSummaryElectronicspiezo jena measuring box
Attached is the schematic of the Piezo Jena driver measuring box made in a Pomona box:
                2.2 uF
In ----o-------- | | --------o-------- Out
       |                     |
       _                     |
       _  1uF                R  7.5 kOhms
       |                     |
       |                     |
      GND                   GND
The 1 uF cap is there to simulate the piezo and the 2.2 uF and 7.5k resistor ac couple the signal for the spectrum analyzer. They give a ~10 Hz corner frequency.
  2130   Wed Oct 21 16:18:12 2009 SteveSummarySAFETYLIGO Safety Officers visited the 40m

David Nolting, chief LIGO Safety Officer and his lieutenants from LLO and LHO paid homage to the 40m lab this morning.

They give us a few recommendation: update safety documents, move optical table from the front of ETMX-rack and label-identify absorbent plastics on enclosure windows-doors.

We'll correct these short comings ASAP


  2137   Fri Oct 23 09:13:45 2009 steveSummaryVACRGA scan

Pump down #66 is 435 days old. RGA scan is normal. New maglev is fine. New UPS is in place but not hooked up to communicate.

V1 has bare minimum interlock. Pirani vacuum gauges  PTP1 and PRP do not communicate with readout system.

There is no emergency dial out in case of vacuum loss.  Our existing vacuum dedicated desk top computer is dead.

New cold cathodes, Pirani gauges and gauge controller should be added.

In general: vacuum system needs an upgrade !


  2157   Wed Oct 28 17:20:21 2009 ranaSummaryCOCETM HR reflectivity plot

This is a plot of the R and T of the existing ETM's HR coating. I have only used 1/4 wave layers (in addition to the standard 1/2 wave SiO2 cap on the top) to get the required T.

The spec is a T = 15 ppm +/- 5 ppm. The calculation gives 8 ppm which is close enough. The calculated reflectivity for 532 nm is 3%. If the ITM reflectivity is similar, the signal for the 532 nm locking of the arm would look like a Michelson using the existing optics.


  2231   Tue Nov 10 21:46:31 2009 ranaSummaryComputersTest Point Number Mapping


I found this interesting entry by Rana in the old (deprecated) elog : here

I wonder if Rolf has ever written the mentioned GUI that explained the rationale behind the test point number mapping.

I'm just trying to add the StochMon calibrated channels to the frames. Now I remember why I kept forgetting of doing it...

 As far as I know, the EPICS channels have nothing to do with test points.

  2247   Thu Nov 12 02:02:18 2009 ranaSummaryLSCArm Locking with no feedback to the ETM or ITM


1) Turn off feedback to ETMY (the ETMY button on the LSC screen).

2) Put a 1 into the YARM->MC2 output matrix element on the LSC screen.

3) Turn off FM6 (comb), FM7 (0.1:10) on the MC2_MCL filter bank. This is to make the IOO-MCL loop more stable and to reduce the IOO-MCL low frequency gain.

4) Set the MC2-LSC gain to 0.5, turn the output ON, turn ON FM4 & FM5 & FM6 of the MC2-LSC filter bank.

5) Turn on the input of MC2-LSC and the arm should now lock.

6) After locking, set the MC2-MCL gain to zero. Hopefully with a few second ramp time.


(A comment by KA - c.f. this entry )

  2283   Tue Nov 17 15:54:34 2009 ranaSummaryPEM40 days of weather

the inside temperature is alarming at the red level today - should check if the HIHI value is set correctly

  2286   Tue Nov 17 21:10:35 2009 ranaSummaryElectronicsBusby Low Noise Box: Photos and Upgrades


It looked like the Busby Low Noise Box had too much low frequency noise and so I upgraded it. Here is a photo of the inside - I have changed out the 0.8 uF AC coupling cap with a big, white, 20 uF one I found on Rob's desk.

The Busby Box is still working well. The 9V batteries have only run down to 7.8V. The original designer also put a spare AD743 (ultra low current FET amp) and a OP27 (best for ~kOhm source impedances) in there.

Here's the noise after the fix. There's no change in the DC noise, but the AC noise is much lower than before:


I think that the AC coupled noise is higher because we are seeing the current noise of the opamp. In the DC coupled case, the impedance to ground from the input pins of the opamp is very low and so the current noise is irrelevant.

The change I implemented, puts in a corner frequency of fc = 1/2/pi/R/C = 1/2/pi/10e3/20e-6 = 0.8 Hz.

Overall, the box is pretty good. Not great in terms of current noise and so it misses getting an A+. But its easily a solid A-.

  2288   Wed Nov 18 00:38:33 2009 ranaSummaryElectronicsVoltage Noise of the SR560's OUTPUTs (the back panel)

I've measured the voltage noise of the SR560's lead acid battery outputs; they're not so bad.

Steve ordered us some replacement lead-acid batteries for our battery powered pre-amps (SR560). In the unit he replaced, I measured the noise using the following setup:

SR560                              Busby Box

(+12V/GND) -------------AC Input      Out  ----------------   SR785

The SR785 was DC coupled and auto-ranged. The input noise of the SR785 was measured via 50 Ohm term to be at least 10x less than the SR560's noise at all frequencies.


Its clear that this measurement was spoiled by the low frequency noise of the Busby box below 10 Hz. Needs a better pre-amp.

  2304   Fri Nov 20 00:18:45 2009 ranaSummaryCamerasVideo MUX Selection Wiki page

Steve is summarizing the Video Matrix choices into this Wiki page:



Price: < 5k$

Control: RS-232 and Ethernet

Interface: BNC (Composite Video)

Please check into the page on Monday for a final list of choices and add comments to the wiki page.

  2314   Mon Nov 23 16:28:12 2009 steveSummaryCamerasVideo swicher options


Steve is summarizing the Video Matrix choices into this Wiki page:



Price: < 5k$

Control: RS-232 and Ethernet

Interface: BNC (Composite Video)

Please check into the page on Monday for a final list of choices and add comments to the wiki page.

 Composite video matrix switchers with 32 BNC in and 32 BNC channels out are listed.

  2406   Sun Dec 13 20:50:45 2009 ranaSummaryIOOMach Zender Calibration

I ramped the MZ PZT (with the loop disabled on the input switch) to calibrate it. Since the transmission has been blocked, I used the so-called "REFL" port of the MZ to do this.

The dark-to-dark distance for the MZ corresponds to 2 consecutive destructive interferences. Therefore, that's 2 pi in phase or 1 full wavelength of length change in the arm with the moving mirror.

Eyeballing it on the DTT plot (after lowpassing at 0.1 Hz) and using its cursors, I find that the dark-to-dark distance corresponds to 47.4 +/- 5 seconds.

So the calibration of the MZ PZT is 88 +/- 8 Volts/micron.

Inversely, that's a mean of 12 nm / V.

why am I calibrating the MZ? Maybe because Rob may want it later, but mainly because Koji won't let me lock the IFO.

Apparently, we haven't had a fast channel for any of the MZ board. So I have temporarily hooked it up to MC_DRUM at 21:13 and also turned down the HEPA. Now, let's see how stable the MZ and PMC really are overnight.

EDIT: it railed the +/- 2V ADCwe have so I put in a 1:4 attenuator via Pomona box. The calibration of MC_DRUM in terms of MZ_PZT volts is 31.8 cts/V.

So the calibration of MC_DRUM1 in meters is: 0.38 nm / count

  2407   Sun Dec 13 23:18:09 2009 ranaSummaryIOODisplacement noise on the PSL table

For the Laser Gyro, I wondered how much mechanical noise we might get with a non-suspended cavity. My guess is that the PMC is better than we could do with a large ring and that the MZ is much worse than we could do.

Below 5 Hz, I think the MZ is "wind noise" limited. Above 10 Hz, its just ADC noise in the readout of the PZT voltage.

  2436   Mon Dec 21 01:14:08 2009 ranaSummaryElectronicsNoise measurement of the Rai Weiss FET preamp box

 I shorted the input to the box and then put its output into the SR560 (low noise, G = 100, AC). I put the output of the SR560 into the SR785.

*** BTW, the 2nd channel of the SR785 is kind of broken. Its too noisy by a factor of 100. Needs to go back for repair once we get started in the vac.

The attached PNG shows its input-referred noise with the short.

The picture shows the inside of the box before I did anything. The TO-5 package metal can is the meaty super dual-FET that gives this thing all of its low noise power.


In the spectra on the right are two traces. The BLUE one is the noise of the box as I found it. The BLACK one is the noise after I replaced R1, R6, R7, & R10 with metal film resistors.

The offset at the output of the box with either an open or shorted input is +265 mV.

I think we probably should also replace R2, R3, & R1, but we don't have any metal film resistors lower than 100 Ohms in the kit...but hopefully Steve will read this elog and do the right thing.

  2452   Sat Dec 26 19:22:13 2009 KojiSummaryGeneralMode coupling of two astigmatic beams

In this note, amplitude and power couplings of two astigmatic (0,0)-th order gaussian modes are calculated.

  2499   Sun Jan 10 23:22:56 2010 JenneSummaryGeneralScattering Measurements of 35W Beam Dumps

On Friday, Rana and I measured the scatter coming from the 35W beam dumps.

(These are the ones with big aluminum heat sinks on the back that kind of look like little robots with 2 legs...inside the horn is a piece of polished silicon at Brewster's Angle.)



For the measurement, we used the Scatterometer setup at the 40m on the small optical table near MC2. 

We used a frequency of 1743 Hz for the Chopper, and this was also used as the reference frequency for the SR830 Lock-In Amplifier. 

The settings on the Lock-In were as follows:

Input A


AC coupled

Floating input

"Low Noise"

Time Constant = 1sec

'Scope reading Output A, Output A set to 'Display', and A's display set to "R" (as in magnitude).

Sensitivity changed throughout the experiment, so that's quoted for each measurement.



White Paper Calibration - white paper placed just in front of Beam Dump.  Sensitivity = 500microVolts.  Reading on 'scope = 7V

Laser Shuttered.  Sensitivity = 500microVolts. 'scope reading = 9mV.

Black Glass at Beam Dump location.  Sensitivity = 500microVolts.  Reading on 'scope = 142mV.   (DON'T touch the glass....measure the same setup with different sensitivity)

Black Glass at Beam Dump location (Not Touched since prev. measurement). Sensitivity = 10microVolts. Reading on 'scope = 6.8V

Laser Shuttered. Sensitivity = 10microVolts. 'scope Reading = 14mV +/- 10mV (lots of fluctuation).

Black Glass Wedge Dump at Beam Dump location. Sensitivity = 10microVolts. 'scope = 100mV.

Beam Dump with original shiny front plate. Sensitivity = 10microVolts.  'scope railing at 11V

Beam Dump with front plate removed. Sensitivity = 10microVolts. 'scope reading = 770mV

Beam Dump, no front plate, but horn's opening surrounded by 2 pieces of Black Glass (one per side ~1cm opening), BG is NOT flush with the opening...it's at an angle relative to where the front plate was.  Sensitivity = 10microV. 'scope = 160mV +/- 20mV.

Beam Dump, no front plate, only 1 piece of Black Glass. Sensitivity = 10microV. 'scope reading = 260mV.

Beam Dump, no front plate, 2 pieces of Black Glass, normal incidence (the BG is flush with where the front plate would have been). Sensitivity = 10microV. 'Scope reading = ~600mV



Using our calibration numbers (Black Glass measured at 2 different sensitivities, not touching the setup between the measurements), we can find the calibration between our 2 different sets of measurements (at 500microV and 10microV), to compare our Beam Dump with regular white paper. 

BG at 500uV was 142mV.  BG at 10uV was 6.8V.    6.8V/0.142V = 47.9 

So the white paper, which was measured at 500uV sensitivity, would have been (7V * 47.9) = 335 V in 10uV sensitivity units. 

This is compared to the BG wedge dump at 10uV sensitivity of 100mV, and the Beam Dump reading of 770mV, and the Beam Dump with-black-glass-at-the-opening reading of 160mV.

So our Silicon/Steel horn dump is ~8x worse than a Black Glass wedge and (335 / 0.77) = 435x better than white paper.

We used regular white paper as a calibration because it has a Lambertian reflectance. For some general idea of how to do these kinds of scatter measurements, you can look at this MZ doc.

Assuming that our white paper had a BRDF of (1/pi)/steradian, we can estimate some numbers for our setup:

Sensitivity (signal with the laser shuttered) = (0.02 / 335 / pi) = 2 x 10^-5 / sr.   This is ~3x worse than the best black glass surfaces.

Our wedge = (0.1 / 335 / pi) = 1 x 10^-4 / sr.  Needs a wipe.

Our Silicon-Steel Horn = (0.75 / 335 / pi) = 7 x 10^-4 / steradian.

Our measurements were all made at a small angle since we are interested in scatter back along the incoming beam. We were using a 1" lens to collect the scatter onto a PDA55. The distance from the beam to the center of the lens was ~2" and the detector's lens was ~20" from the front of the horn. So that's an incident angle of ~3 deg.


* It seems that any front plate other than Black Glass is probably worse than just having no front plate at all.

* If we put in a front plate, it shouldn't be normal to the incident beam.  Black Glass at normal incidence was almost at the same level as having no front plate. So if we're going to bother with a front plate, it should be about 30deg or 40deg from where the original front plate was.

* No front plate on the Dump is about 7x a Black Glass wedge dump.

* The silicon looks like it might have some dust on it (as well as the rest of the inside of the horn).  We should clean everything.  (Maybe with deionized nitrogen?)

* We should remeasure the Beam Dump using polished steel at a small (30-40deg) angle as the front plate. 



 * Photos taken with the Olympus camera, which has its IR blocker removed.

* In the photo you can see that we have a lot of reflection off of the horn on the side opposite from the silicon.

* The 2nd picture is of the scatterometer setup.

  2507   Tue Jan 12 09:14:52 2010 steveSummaryGeneralScattering Measurements of 35W Beam Dumps


 What was the power level, polarization and beam size at beam trap?

  2511   Tue Jan 12 14:28:01 2010 steveSummaryEnvironmentlab temp of 7 years



Rana noticed that recently the temperature inside the lab has been a little bit too high. That might be causing some 'unease' to the computers with the result of making them crash more often.

Today I lowered the temperature of the three thermostats that we have inside the lab by one degree:
Y arm thermostat: from 71 to 70 F
X arm thermostat: from 70 to 69 F
Aisle thermostat: from 72 to 71 F.

For the next hours I'll be paying attention to the temperature inside the lab to make sure that it doesn't go out of control and that the environment gets too cold.

 Today the lab is perceptibly cooler.

The temperature around the corner is 73 F.


  2514   Thu Jan 14 11:44:06 2010 josephbSummaryComputersMemory locations for TST model for ITMY

The main communications data structure is RFM_FE_COMMS, from the rts/src/include/iscNetDsc40m.h file.  The following comments regard sub-structures inside it.  I'm looking at all the files in /rts/src/fe/40m to determine how the structures are used, or if they seem to be unnecessary.

The dsccompad structure is used in the lscextra.c file.  I am assuming I don't need to add anything fo the model for these.  They cover from 0x00000040 to 0x00001000.

FE_COMMS_DATA is used twice, once for dataESX (0x00001000 to 0x00002000), and once for dataESY (0x00002000 to 0x00003000).

Inside FE_COMMS_DATA we have:

status and cycle which look to be initialized then never changed (although they are compared to).

ascETMoutput[P,Y], ascQPDinput are all set to 0 then never used.

qpdGain is used, and set by asc40m, but not read by anything.  It is offset 114, so in dataESX its 4210 (0x00001072), and in dataESY its (0x00002072)

All the other parts of this substructure seem to be unused.

daqTest, dgsSet, low1megpad,mscomms seem unused.

dscPad is referenced, but doesn't seem to be set.

pCoilDriver is a structure of type ALL_CD_INFO, inside a union called suscomms, inside FE_COMMS_Data, and is used.  In this structure, we have:

extData[16], an array of DSC_CD_PPY structures, which is used.  Inside extData we have for each optic (ETMY has an offset of 9 inside the extData array):

Pos is set in sos40m.c via the line pRfm->suscomms.pCoilDriver.extData[jj].Pos = dsp[jj].data[FLT_SUSPos].filterInput;   Elsewhere, Pos seems to be set to 1.0

Similarly, Pit and Yaw are set in sos40m, except with FLT_SUSPitch and FLT_SUSYaw, and being set elsewhere to 1.1, 1.2.  However, these are never applied to the ETMX and ETMY optics (it goes through offests 0 through 7 inclusive). 

Side is set 1.3 or 1.0 only, not used.

ascPit , ascYaw, lscPos are read by the losLinux.c code, and is updated by the sos40m.c code. For ETMY, their respective addresses are: 0x11a1c0, 0x11a1c4, 0x11a1c8.

lscTpNum, lscExNum, seem to be initialized, and read by the losLinux.c, and set by sos40m.c.

modeSwitch is read, but looks to be used for turning dewhitening on and off. Similarly dewhiteSW1R is read and used. 

This ends the DSC_CD_PPY structure.

lscCycle, which is used, although it seems to be an internal check.

dum is unused.

losOpLev is a substructure that is mostly unused.  Inside losOpLev, opPerror, opYerror, opYout seem to be unused, and opPout only seems ever to be set to 0.

Thats the end of ALL_CD_INFO and pCoilDriver.

After we have itmepics, itmfmdata, itmcoeffs, rmbsepics,...etymyepics, etmyfmdata,etmycoeffs which I don't see in use.

We have substructure asc inside mcasc, with epics, filt, and coeff char arrays. These seem to be asc and iowfsDrv specific.

lscIpc, lscepics, and lscla seems lsc specific,

The there is lscdiag struct, which contains v struct, which includes cpuClock, vmeReset, nSpob, nPtrx, nPtry don't seem to be used by the losLinux.c.

The lscfilt structure contains the FILT_MOD dspVME, which seems to be used only by lsc40m.

The lsccoeff structure contrains the VME_COEF pRfmCoeff, which again seems to only interact in the lsc code.

Then we have aciscpad, ascisc, ascipc, ascinfo, and mscepics which do not seem to be used.

ascepics and asccoeff are used in asc.c, but does not seem to be referenced elsewhere.

hepiepics , hepidsp, hepicoeff, hepists do not appear to be used.







  2535   Thu Jan 21 10:09:27 2010 KojiSummaryIOOPhotos of the optical tables

I made a wiki page dedicated for the photos of the optical tables.
The current layouts were uploaded.


  2539   Thu Jan 21 15:16:16 2010 josephb, kojiSummaryComputersMegatron used to lock Y arm

We succeeded in having a stable single arm (Y) lock using Megatron to replace c1iscey.

Now the lock with megatron is pretty easy. Really. It's very cool.

As we saw the oscillation of the YARM servo, we temporalily increased the gain of TRY filter by a factor of 2 (0.003->0.006). Also decreased the gain of YARM servo by the factor of  2 (1->0.5). This makes the servo gain reduced by a factor of 4 in total. This change seemed to come from the change of the ADC/DAC range.

We finally fixed the hi-gain pd transmission communications from Megatron to the c1lsc by tracking down the correct RFM memory location (which is unhelpfully labeled as a qpd channel in both losLinux and lsc40.m).  The memory location is 0x11a1e0, and is refered to as qpdData[3].

  2583   Tue Feb 9 17:18:45 2010 josephbSummaryComputersLocking Y arm successful with fully replaced front-end for ITMY

We were able to lock the Y-arm using Megatron and the RCG generated code, with nothing connected to c1iscey.

All relevant cables were disconnected from c1iscey and plugged into the approriate I/O ports, including the digital output.  Turns out the logic for the digital output is opposite what I expected and added XOR bitwise operators in the tst.mdl model just before it went out to DO board.  Once that was added, the Y arm locked within 10 seconds or so.  (Compared to the previous 30 minutes trying to figure out why it wouldn't lock).

  2584   Tue Feb 9 17:51:48 2010 JenneSummaryIOOInput Mode Matching Telescope design is complete

The upgrade's input mode matching telescope design is complete.  A summary document is on the MMT wiki page, as are the final distances between the optics in the chain from the mode cleaner to the ITMs.  Unless we all failed kindergarden and can't use rulers, we should be able to get very good mode matching overlap.  We seem to be able (in Matlab simulation land) to achieve better than 99.9% overlap even if we are wrong on the optics' placement by ~5mm.  Everything is checked in to the svn, and is ready for output mode matching when we get there.

  2588   Wed Feb 10 23:44:56 2010 KojiSummaryCOCPhase Map Analysis

In the middle of the last month, Kiwamu and I went to Garilynn's lab to measure the phase maps of the new ITMs and SRMs.

Analysis of the phase map data were posted on the svn directory:

The screen shots and the plots were summarized in a PDF file. You can find it here:

The RoCs for all of the PRMs are turned out to be ~155m. This is out of the spec (142m+/-5m) although the actual effect is not understand well yet..

These RoCs are almost independent from the radus of the assumed gaussian beam.
In deed, I have checked the dependence of the RoC on the beam spot position, and it turned out that the RoCs vary only little.
(In the SRMU01 case, for example, it varies from 153.5m to 154.9m.)
The beam radius of 3mm was assumed. The RoCs were calculated 20x20mm region around the center of the mirror with a 2mm mesh.

  2645   Sun Feb 28 16:45:05 2010 ranaSummaryGeneralPower ON Recovery
  1. Turned ON the RAID above linux1.
  2. Hooked up a monitor and keyboard and then turned ON linux1.
  3. After linux1 booted, turned ON nodus - then restarted apache and elog on it using the wiki instructions.
  4. Turned on all of the control room workstatiions, tuned Pandora to Johnny Cash, started the auto package updater on Rosalba (517 packages).
  5. Started the startStrip script on op540m.
  6. turned on RAID for frames - wait for it to say 'SATA', then turn on daqctrl and then fb40m and then daqawg and then dcuepics
  7. turned on all the crates for FEs, Sorensens, Kepcos for LSC, op340m, mafalda was already on
  8. fb40m again doesn't mount the RAID again!
  9. I turned on fb40m2 and that fixes the problem. The fb40m /etc/vfstab points to, not the JetStor IP address.
  10. I plugged in the Video Switch - its power cord was disconnected.
  11. FEs still timing out saying 'no response from EPICS', but Alberto is now here.

Sun Feb 28 18:23:09 2010

Hi. This is Alberto. Its Sun Feb 28 19:23:09 2010

  1. Turned on c1dcuepics, c0daqctrl and c0daqawg. c0daqawg had a "bad"status on the daqdetail medm screen. The FEs still don't come up.
  2. Rebooted c1dcuepics and power cycled c0daqctrl and c0daqawg. The problem is still there.
  3. Turned on c1omc. Problem solved.
  4. Rebooted c1dcuepics and power cycled c0daqctrl and c0daqawg. c0daqawg now good. The FE are coming up.
  5. Plugged in the laser for ETMY's oplev
  6. Turned on the laser of ETMX's oplev from its key.

 Monday, March 1, 9:00 2010 Steve turns on PSL-REF cavity ion pump HV at 1Y1

ELOG V3.1.3-