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  12801   Sun Feb 5 21:56:50 2017 LydiaUpdateIMC29.5 MHz stabilizer box replacement

Since the "stablizer box" doesn't really need to stabilize, it just needs to amplify, I decided to replace it with an off the shelf amplifier we already had, ZHL-2. I worked on getting it set up today, but didn't connect anything so that people have a chance to give some feedback. 

  • The gain we expect is 18 dB, and the maximum output with 1dB of compression is 29 dBm. To avoid compression, I'm aiming for ~26 dBm output, so ~8 dBm input. We measured the output of the source to be 12.8 dBm before, so I attached a 5dB attenuator to the input side of the amplifier. 
  • Across the 24V power input and the ground pin, I soldered a 100 uF, 50V electrolytic capacitor and a .27 uF, 50V metal film capacitor. Note that unlike the other similar amplifiers we have, the ground and +24 pins are separated (see image on datasheet). I wasn't sure if that changed what to do so I just found comparable caps to the ones that were there on another model. 
  • I twisted and soldered wires to the +24 and ground, making sure they were long enough to reach the clips where the power from the Sorensens gets split up. I placed the amplifer in the rack on top of the RF distribution box and ziptied the power cable in place. 
  • I connected a splitter to the output of the amplifier. Should I use a 10dB coupler instead, to maximize the power to the EOM?

So, I think the remaining thing to do is to connect the splitter to ASC out and to the line to the EOM, the +24V supply to the amplifier, and the 29.5 MHz input to the attenuator. I wanted to wait on this to get confiration that the setup is OK. Eventually we can put all of this in a box. 

Also, I noticed that in the clear cabinet with the Sorensens next to this rack, the +24 V unit is not supplying any voltage and has a red light that says "OVP." 

  12807   Tue Feb 7 12:01:10 2017 LydiaUpdateIMC29.5 MHz stabilizer box replacement

I tested the amplifier with the Agilent network analyzer and measured 19.5 dB of gain between 29 and 30 mHz. The phase only changed by 1 degree over this same 1 MHz span. Since everything seems to be in order I'll hook it up this afternoon, unless there are any objections

  12809   Tue Feb 7 17:00:55 2017 LydiaUpdateIMC29.5 MHz stabilizer box replacement

I set everything up and connected it as shown on the block diagram attached to the previous entry, with the exception of the DC power. This is becuase there is no place open to connect to on the DIN rail where the DC power is distributed, so the +24V power will have to be shut off to the other equipment in 1X1 before we can connect the amplifier. (The amplifier is in 1X2, but the DC power distribution was more accessible in 1X1.) I also added 3 new +24 V clips with fuses despite needing only one, so next time we need to connect something new it's not such a hassle. 

The RF distribution box where the 29.5 MHz signal originates should not be turned on until the amplifer has DC power. Since we may have a power interruption tomorrow, the plan is to wait until things are shut down in preparation, and then shut off anyhting else necessary before connecting the new clips on the rail to the existing ones. 

  12816   Fri Feb 10 02:14:10 2017 gautamUpdateIMC29.5 MHz stabilizer box replacement

Lydia finished up installing the new RF amplifier, and will elog the details of the installation.

I wanted to try and measure the IMC OLG to compare against my Simulink model. So I went about performing a few checks. Summary of my findings:

  1. The amplifier seems to be working fine. I checked powers at the input, output to EOM and output to distribution box (that serves the various LOs) first with a 30dB attenuator at the input, and subsequently with the design choice of 5dB attenuator at the input. Everything seemed in order.
  2. I installed a 30 dB attenuator at the MC REFL PD input to the demod board since my (rough) calculations suggested that our modifications would have resulted in the RF beat power between carrier and sideband increasing in power by ~27dB.
  3. I then opened the PSL shutter and tried locking the IMC - with manual tweaking of the various gains, I was able to lock.
  4. But getting to this point took me a while so I couldn't get an OLG measurement in.

TBC tomorrow, I'm leaving the PSL shutter closed and the RF source off for tonight...

  12817   Fri Feb 10 11:41:43 2017 LydiaUpdateIMC29.5 MHz stabilizer box replacement

To install the replacement amplifier, I did the following:

  • Mounted the amplifier in a 2U chassis, with a metal plate between the amplifier and the bottom of the box. The plate is separated from the box and the amplifier with 2 sets of Nylon screws. I did it this way to make use of the holes that were already in the chassis bottom and just drill holes into a plate instead. 
  • Cannibalized mounting brackets and back panel from old ALS Beatbox. The back panel has an on/off switch and a 3W3 feedthrough for power. 
  • Made a power cable to reach from the 1X1 fuse blocks to the back panel of my box. Goes up through the top of the rack and then back down. 
  • Installed the chassis in the rack. The lid is currently off and there is no front panel yet. 
  • Changed the +5dB attenuator to +30 to be able to check things first before supplying a way stronger signal. 
  • Installed 4 new +24 V fuse blocks on the adjacent rack (1X1). 
    • Put the new fuses on the DIN rail and wired them together. Connected the new power cable to one of them. 
    • Blocked PMC transmission and made sure all RF sources in 1X1 and 1X2 were turned off
    • Turned off the + 24 V and -24 V Sorensens, trying to keep them fairly balanced as I turned them to 0. 
    • At this point Rana suggested I turn off the other DC power supplies in the rack, which I did.
    • Connected the new fuse blocks to the existing +24 V ones. Note that they are not contiguous but they follow the color code and will be labeled. 
    • I'm only using one of the new +24 outputs, but I made more for future use to minimize the number of times we have to turn the power off. 
  • Connected the output of the amplifier to the EOM, and the coupled signal to the distribution box (which splits it and sends it to the demod boards). 
  • Turned on the power switch and checked that the amplifier was in fact getting 24 V. 
  • Connected the input from the 29.5 MHz source and measured the power coming from the amplifier. I measured -12 dBm instead of the expected ~0 dBm, but Gautam was able to see the expected power later, so maybe something just wasn't connected right.
  • Double checked the power coming into the amplifier, which was consistent with earlier measurements at about 12.8 dBm. 


Still to be done:

  • Label/relabel several things (fuse blocks, back panel, etc) 
  • Current label on +24 Sorensen needs to be updated
  • Order front panel and install
  • Install power indicator lights on front and back 
  • Readjust gains (analog and digital) to use full signal output and measure (hopefully) improved WFS performance
  • Insert bi-directional coupler and measure modulation depth and reflections from EOM
  12819   Fri Feb 10 13:24:28 2017 ranaUpdateIMC29.5 MHz stabilizer box replacement

To remind myself about how to put filter caps on the mini-circuits RF Amps, I looked at Koji's recent elog. Its mostly about op-amps, but the idea holds for us.

We want a big (~100 uF) electrolytic with a 50V rating for the +24V RF Amp. And then a 50V ceramic capacitor of ~0.1 uF close to the pins. Remember that the power feed through on the Mini-circuits case is itsself a capacitive feedthrough (although I guess its a ~100 pF).

Later, we should install in this box an active EMI filter (e.g. Vicor)

  12755   Wed Jan 25 15:41:29 2017 LydiaUpdateIMC29.5 MHz modulation depth measurement plan

[Lydia, gautam]

To measure the modulation depth of the 29.5 MHz sideband, we plan to connect a bidirectional coupler between the EOM and the triple resonant circuit box. This will let us measure the power going into the EOM and the power in the reflection. According to the manual for the EOM (Newport 4064), the modulation depth is 13 mrad/V at a wavelength of 1000 nm. Before disconnecting these we will turn off the Marconi.

Hopefully we can be gentle enough that the EOM can be realigned without too much trouble. Before touching anything we'll measure the beam power before and after the EOM so we know what to match after.

If anyone has an objection to this plan, speak now or we will proceed tomorrow morning.

  12756   Wed Jan 25 17:30:03 2017 KojiUpdateIMC29.5 MHz modulation depth measurement plan

I'm afraid that the bidirectional coupler, designed to be 50ohm in/out, disturbs the resonant circuit designed for the EOM which is almost purely capacitive.

One possible way could be to measure the transfer function using the active FET probe from the triple resonant input to the output with the EOM attached.

Another way: How about to measure the reflection before the resonant circuit? Then, of course, there is the triple resonant interface circuit between the power combiner and the EOM. This case, we will see how much power is consumed in EOM and the resonant circuit. Then we can use the previous measurement to see the conversion factor between the power consumption to the modulation depth. Kiwamu may give us his measurement.

  12758   Wed Jan 25 19:39:07 2017 gautam UpdateIMC29.5 MHz modulation depth measurement plan

Just collecting some links from my elog searching today here for easy reference later.

  • EOM datasheet: Newfocus 4064 (according to this, the input Impedance is 10pF, and can handle up to 10W max input RF power).
  • An elog thread with some past measurement details: elog 5339. According to this, the modulation depth at 29.5 MHz is 4mrad. The EOM's manual says 13mrad/V @1000nm, so we expect an input signal at 29.5MHz of 0.3V(pk?). But presumably there is some dependance of this coefficient on the actual modulation frequency, which I could not find in the manual. Also, Kiwamu's note (see next bullet) says that the EOM was measured to have a modulation depth of 8 mrad/V
  • A 2015 update from Kiwamu on the triple resonant circuit: elog 11109. In this elog, there is also a link to quite a detailed note that Kiwamu wrote, based on his analysis of how to make this circuit better. I will go through this, perhaps we want to pursue installing a better triple resonant circuit...

I couldn't find any details of the actual measurement technique, though perhaps I just didn't look for the right keywords. But Koji's suggestion of measuring powers with the bi-directional coupler before the triple resonant circuit (but after the power combiner) should be straightforward. 

  12767   Fri Jan 27 21:25:11 2017 LydiaUpdateIMC29.5 MHz modulation depth

[gautam, Lydia]

We set out to measure the 29.5 MHz power going to the EOM today but decided to start by looking at the output of the RF AM stabilizer box first. We wanted to measure the AM noise with a mixer, so we needed to know the power it was giving. We looked at the ouput that goes to the power combiner on the PSL table and found it was putting out only -2.0 dBm (~0.5 Vpp)! This was measured by taking a spectrum with the AG4395 and confirmed by looking on a scope.

To find out if this could be adjusted, we found an old MEDM screen (/opt/rtcds/caltech/c1/medm/c1lsc/master/C1LSC_RFADJUST.adl) and moved the 29.5 MHz EOM Mod Index Adjust slider while measuring the voltage coming in to the MOD CONTOL connection on the front of the AM stabilizer box. Moving the slider from 0 to 10 changes the input voltage linearly from -10 V to 10 V measured with a DMM at the cross-connects as we couldn't find an appropriate adapter for the LEMO cable. The 29.5 MHz modulation only appeared for slider values between 0 and 5, after which it abruptly shuts off. However, changing the slider value between 0 and 5 (Voltage from -10 to 0) does not change the amplitude of the output.

This seems like a problem; further investigation into the AM stabilizer box is neccessary. This DCC document outlines how to test the box, but we can't find a schematic. Since we don't have any mixers that can handle signals as small as -2 dBm, we gave up trying to measure the AM noise and will attempt to measure that and the reflection power from the EOM + resonant circuit once this problem has been diagnosed and fixed.

GV: After some digging, I found the schematic for the RF AM stabilization box (updated wiki and added it to the 40m document tree). According to it, there should be up to +22dBm of RF AM stabilized output to the EOM available, though we measured -2dBm yesterday, and could not vary this level by adjusting the EPICS voltage value. Neglecting losses in the cabling and the power combiner on the PSL, this translates to a paltry 0.178Vrms*0.6*8mard/Vrms ~ 0.85 mrad of modulation depth (gain at 29.5 MHz of the triple resonant circuit taken from this elog)... I think we need to pull this 1U chassis out and debug more thoroughly...


  12768   Sat Jan 28 01:25:51 2017 gautamUpdateIMC29.5 MHz modulation depth

Some more details of our investigation:

  1. Here is a spectrum of the signal to the power combiner on the PSL table, measured on the output of the RF AM Stabilization box.

    Perhaps these sidebands were the ones I observed while looking at the input to the WFS demod board.
  2. The signal looked like a clean sinusoid when viewed on an oscilloscope with input impedance set to 50ohms. There were no sharp features or glitches in the time we observed, except when the 29.5 MHz MEDM slider was increased beyond 5, as noted by Lydia.
  3. We couldn't find a schematic for this RF AM Stabilization servo, so we are not sure what RF output power to the EOM we should expect. Schematic has since been found.
  4. I measured the power level at the input side (i.e. from the crystal) and found that it is ~12dBm, which seems reasonable (the front panel of the box housing the 29.5 MHz oscillator is labelled 13dBm). The schematic for the RF AM stabilization box says we should expect +10dBm at the input side, so all this points to a problem in the RF AM stabilization circuit...
  5. There is an attenuator dial on the front panel of the said RF AM stabilization servo that allows one to tune the power to the LO input of the WFS. Right now, it is set to approximately 7dB of attentuation, which corresponds to -12dBm at the WFS demod board input. I did a quick check to see if turning the dial changed the signal level at the LO input of the WFS board. The dial moves in clicks of 1dB, and the RF power at the LO input of the demod board increased/decreased by ~1dBm for each click the dial was rotated (I only explored the region 3dB-11dB of atttentuation). So it should be possible to increase the LO level to the WFS demod boards, is there any reason we shouldn't increase this to -8bBm (~0.25Vpp into 50ohms, which is around the level Koji verified the mixer to be working well at)?
  6. There were a couple of short ribbon cables which were just lying around on top of the cards in the eurocrate, Koji tells me that these were used as tester cables for checking the whitening filters and that they don't serve any purpose now. These have been removed.
  7. Added a button to IMC MEDM screen to allow easy access to the MEDM screen with slider to control the 29.5MHz modulation depth - though as mentioned in Lydia's elog, at the moment, this slider has no effect on the 29.5MHz power level to the EOM...
  2801   Thu Apr 15 14:47:28 2010 steveUpdateElectronics25MHZ oscillation of HP4195A

The 1979 vintage RF spectrum analyzer HP4195A  sn2904J01587 shipped out  for repair today to http://www.avalontest.com

It has a 25 MHZ oscillation when you go  below 150 MHZ in your sweep....atm1 with the larger amplitude shows this 25 MHZ

Atm2 is displaying  full sweep-sign scans from 1 to 500 MHZ.....here one can clearly see the three segment of the scan:

1, large amplitude 25 MHZ oscillation dominating the spectrum up to 150 MHZ

2, the mid section from 150 MHZ  to 300 MHZ with medium size amplitude is normal

3, from 300 MHZ to 500 MHZ the amplitude is decreasing.......showing the disadvantage of using a 300 MHZ oscilloscope




  16211   Thu Jun 17 22:19:12 2021 KojiUpdateElectronics25 HAM-A coil driver units delivered

25 HAM-A coil driver units were fabricated by Todd and I've transported them to the 40m.
 2 units we already have received earlier.
The last (1) unit has been completed, but Luis wants to use it for some A+ testing. So 1 more unit is coming.

  12660   Fri Dec 2 16:40:29 2016 gautamUpdateIMC24V fuse pulled out

I've pulled out the 24V fuse block which supplies power to the AOM RF driver. The way things are set up on the PSL table, this same voltage source powers the RF amplifiers which amplify the green beatnote signals before sending them to the LSC rack. So I turned off the green beat PDs before pulling out the fuse. I then disconnected the input to the RF driver (it was plugged into a DS345 function generator on the PSL table) and terminated it with a 50 ohm terminator. I want to figure out a smart way of triggering the AOM drive and recording a ringdown on the scope, after which I will re-connect the RF driver to the DS345. The RF driver, as well as the green beat amplifiers and green beat PDs, remain unpowered for now...

  623   Wed Jul 2 13:56:10 2008 Rob, Yoichi, JohnUpdateLocking24.5 Hz resonance
Work continues on trying to reduce the CARM offset using dc signals from PO_DC. Got up to arm powers of
~35 last night.

We found that progress was stymied by an oscillation around 24 Hz. This oscillation was clearly visible
in the intensity of the light at REFL, PO and TrX.

Initially we suspected that this oscillation was due to an instability in the CARM loop. We attempted to
solve the problem by tuning the crossover frequncy of the AO and MC_L paths and shaping the MC_L loop to
reduce the impact of the 24 Hz noise.

After some quick tests we found that the 24 Hz signal was present even when dc CARM was used. It appears
that the peak is in fact due to a SOS mechanical resonance. We currently suspect a roll mode.

We're going to check that PRC, MICH and DARM have filters to attenuate the 24 Hz line. We'll also look at the
SUS_POS bandstop filters to see where they are centred.

The ISS was behaving strangely again. Constantly saturated at 5dB of gain. Someone needs to look a this.
  6359   Mon Mar 5 20:31:33 2012 KojiUpdateLSC22/110MHz path for POP

This a kind of self record...

We need an RF setup at POP to extract 22 and 110 MHz components separately.

I am planning to work on this in the daytime on Tuesday.

  6366   Tue Mar 6 22:23:04 2012 KojiUpdateLSC22/110MHz path for POP


 As par Kiwamu's request, RF filters for POP22 and POP110 were installed. They are not really nice. We need to replace it with more fancy electronics.
More to come later.


  6374   Wed Mar 7 15:56:36 2012 KojiUpdateLSC22/110MHz path for POP

The RF separator installed comprises of the Minicircuits filters cascaded as in the figure below.
This has one input and 4 output ports for 11, 22, 30-60, and 110MHz signal.
As seen in this entry #6167, we have 22 and 110MHz signals together with 11, 44, 66MHz signals.
They may be demodulated via a harmonic characteristic of the mixers. (Remeber mixers are not multipliers.)


 Of course the big concern is the impedance matching for those signals as usual.
The 2nd attachment shows measured impedance of the circuits with all of the ports terminated.
From the complex impedance, we can calculate the reflection coefficient. The 44 and 110MHz
components look correctly matched while the others seems largely reflected.
This certainly is not a nice situation, as the reflection can make the amplifier next to the PD unhappy
(although the reflected power is tiny in our case).

In our case more eminent problem is that the amplitude of the 22MHz signal can vary depending on the cable length by
factor of 10 in amplitude. (c.f. VSWR on the 2nd attachment.)

The transmission to each port was measured. The separation of the signals looks good. But the attenuation of the
targetted signals (i.e. insertion losses) are qulitatively consistent with the impedance. Again these losses are depend
on the cable length.



  8192   Wed Feb 27 20:50:41 2013 ManasaUpdateLSC22/110MHz path for POP

[Yuta, Manasa]

Modified POP path.

1. Removed temporary POP DC and the BS 50 (elog)
2. Introduced a 95% BS after the POP steering mirrors (95% of the signal goes to PD10CF used for POP22 and 5% goes to POP camera)
3. Output of PD10CF goes to the LSC rack through POP110 heliax cable.
4. The PD output at the LSC rack  goes through a DC block to separate DC from RF.


We could not find a power supply slot for the amplifiers on the LSC rack. We had to put a temporary power supply in contradiction to our 'no temporary power supply' policy.

  8397   Tue Apr 2 23:14:02 2013 ranaUpdateLSC22/110MHz path for POP


We could not find a power supply slot for the amplifiers on the LSC rack. We had to put a temporary power supply in contradiction to our 'no temporary power supply' policy.

 After 1 month, its hard to imagine that this could not have been fixed by putting in a proper fuse and fuse block. I will remove this tomorrow if I still find it this way in the bottom of the rack.

There are also 2 Sorensen switching supplies in the bottom of the LSC rack (with all of our sensitive demod boards). These should also be moved over to the old 'digital' LSC rack tomorrow for the post meeting lab cleanup.

Use fuse blocks with fuses with appropriate ampacity.

  2925   Wed May 12 23:31:17 2010 AlbertoUpdate40m Upgrading216 MHz resonance in the POY11 PD killed
It turned out that the resonance at 216 MHz in the 11MHz PD that I showed in the elog entry 2902 was casued by an instability of the of the MAX4107 opamap' feedback loop.
As the datasheet of the opamp shows, the close-loop gain has a peak at about 200-250MHz, in presence of even small capacitive loads.
In my case, perhaps either the capacitance of the BNC cables plugged to the RF output of the PD box, or the shunt capacitance of the circuit parts after the opamap (traces and resistors) might have introduced capacitance at the output of the amplifier.
LISO had failed in predicting the resonance because it has only ideal transfer functions of the opamps. In particular the open-loop gain of the opamaps in the library is just a function with a simple pole.
At RF frequencies the output impedances of the opamp starts having a non-negligible inductance that interacts with the load capacitance, generating a typical LC-circuit resonance.
In cases like this, such effect can be mitigated by introducing an "isolating" resistor at the output of the opamp.
So I did that and modified the circuit as in this simplified schematic here:

The choice of 100 Ohm for the isolating resistor was mainly empirical. I started with 10, then 20 and 50 until I got a sufficient suppression of the resonance. Even just 10Ohm suppressed the resonance by several tens of dB.



In that way the gain of the loop didn't change. Before that, I was also able to kill the resonance by just increasing the loop gain from 10 to 17.  But, I didn't want to increase the closed-loop gain.

One thing that I tried, on Koji's suggestion, was to try to connect the RF output of the PD box to an RF amplifier to see whether shielding the output from the cable capacitance would make the resonance disappear: It did not work.

  2926   Thu May 13 05:06:43 2010 ranaUpdate40m Upgrading216 MHz resonance in the POY11 PD killed


 This idea was tried before by Dale in the ~1998 generation of PDs. Its OK for damping a resonance, but it has the unfortunate consequence of hurting the dynamic range of the opamp. The 100 Ohm resistor reduces the signal that can be put out to the output without saturating the 4107.

I still recommend that you move the notch away from the input of the 4107. Look at how the double notch solution has been implemented in the WFS heads.

  13544   Fri Jan 12 20:35:34 2018 Udit KhandelwalSummaryGeneral2018/01/12 Summary
  1. 40m Lab CAD
    1. Worked further on positioning vacuum tubes and chambers in the building.
    2. Next step would be to find some drawings for optical table positions and vibration isolation stack. Need help with this! 
  2. Tip Tilt Suspension (D070172)
    1. Increased the length of side arms. The overall height of D070172 assembly matches that of D960001.
    2. The files are present in dropbox in [40mShare] > [40m_cad_models] > [TT - Tip Tilt Suspension]
  12055   Wed Mar 30 16:40:24 2016 ericqUpdateLSC2016 vs 2010

I haven't found any data files for the DARM spectrum of the previous generation of 40m, but with some GIMP-fu, I have plotted Monday's spectrum (green) on top of one of the figures from Rob's thesis.

  9730   Mon Mar 17 10:50:58 2014 steveUpdatesafety2014 annual crane certification




 We had our annual safety inspection today.  Our SOPs are outdated. The full list of needed correction will be posted tomorrow.


The most useful found was that the ITMX-ISCT ac power is coming  from 1Y1 rack. This should actually go to 1Y2 LSC rack ?

 Please test this so we do not create more ground loops.

 Annual crane inspection is scheduled for 8-11am Monday, March 17, 2014


The control room Smart UPS has two red extension cords that has to be removed: Nodus and Linux1

 KroneCrane Fred inspected and certified the 3 40m cranes for 2014. The vertex crane crane was load tested at fully extended position.

  4651   Fri May 6 10:20:00 2011 steveSummarySAFETY2011 safety audit

The emphasis of this annual safety audit  was on  safe  electrical housekeeping on March 3, 2011

Safety audit correction list for the electric shop:

1, install breaker panel door in room 101
2, install conduit- AC out let in the east arm for USB camera table and
    south arm for maglev- external fan
3, replace AC cord to south end work bench and door alarm
4, trace breaker of 1Y4

Requested completion date: 3-28-2011 at estimated cost $1,500.
All recommendations  for improvement were done by April 1, 2011
We thank the participants for making the 40m a safer  place to work.
  1620   Fri May 22 01:27:14 2009 peteUpdateSUS200 days of MC3 side

Looks like something went nuts in late April.  We have yet to try a hard reboot.

  547   Fri Jun 20 01:38:55 2008 ranaUpdatePEM20 day Weather
Yoichi showed me that its possible to make PNG images from PS using GS:
gs -sDEVICE=png16m -sOutputFile=foo.png bar.ps
  10899   Wed Jan 14 02:11:07 2015 ranaSummaryTreasure2-loop Algebra Loopology

I show here the matrix formalism to calculate analytically the loop TF relationships for the IMC w/ both FSS actuators so that it would be easier to interperet the results.

The attached PDF shows the Mathematica notebook and the associated block diagram.

In the notebook, I have written the single hop connection gains into the K matrix. P is the optical plant, C is the Common electronic gain, F is the 'fast' NPRO PZT path, and M is the phase Modulator.

G is the closed loop gain matrix. The notation is similar to matlab SS systems; the first index is the row and the second index is the column. If you want to find the TF from node 2 to node 3, you would ask for G[[3,2]].

As examples, I've shown how to get the FAST gain TF that I recently made with the Koji filter box as well as the usual OLG measurement that we make from the MC servo board front panel.

  16464   Thu Nov 11 00:11:39 2021 KojiSummarySUS2" to 3" sleeve issue

Yehonathan and Tega found that the new PR3 and SR3 delivered in 2020 is in fact 3/4" in thickness (!). Digging the past email threads, it seems that the spec was 10mm but the thickness was increased for better relieving the residual stress by the coatings.

There are a few issues.

1. Simply the mirror is too thick for the ring. It sticks out from the hole. And the mirror retainers (four plastic plates) are too far from the designed surface, which will make the plates tilted.

2. The front side of the mirror assembly is too heavy and the pitch adjustment is not possible with the balance mass.

Some possible solutions:

- How about making the recess deeper?
In principle this is possible, but the machining is tricky because the recess is not a simple round hole but has "pads" where the mirror sits. And the distance of the retainer to the thread is still far.
And the lead time might become long.

- How about making new holes on the ring to shift the clamp?
Yes it is possible. This will shift the mirror assembly by a few mm. Let's consider this.

- How about modifying the wire blocks?
Yes it is equivalent to shift the holes on the ring. Let's consider this too.

1. How to hold the mirror with the retainer plates

[Attachment 1] The expected distance between the retainer plate and the threaded hole is 13.4mm. We can insert a #4-40 x L0.5" stand off (McMaster-Carr 91197A150, SUS316) there. This will make the gap down to 0.7mm. With a washer, we can handle this gap with the plate. Note that we need to use vented & silver plated #4-40 screws to hold the plates.

[Attachment 2] How does this look like when the CoM is aligned with the wire plane? Oh, no... the lower two plates will interfere with the EQ stops and the EQ stop holders. We have to remove them. [Attachment 3]
We need to check with the suspension if the EQ stop screws may hit the protruded optics and can cause chipping/cracking.

2. Modifying the wire block

[Attachment 4] The 4x thru holes of the wire block were extended to be +/-0.1" slots. The slots are too long to form ovals and produce thin areas. With the nominal position of the balance mass, the clamp coordinates are y=1.016 (vertical) and z=-2.54mm (longitudinal).
==> The CoM is 0.19mm backside (magnet side) and 0.9134 mm lower from the wire clamping points. This looks mathematically doable, but the feasibility of the manufacturing is questionable.

[Attachment 5] Because the 0.1" shift of the CoM is large, we are able to make new #2-56 thread holes right next to the original ones. The clamp coordinates are y=1.016 (vertical) and z=-2.54mm (longitudinal).
==> The CoM is 0.188mm backside (magnet side) and 0.9136 mm lower from the wire clamping points. With the given parameters, the expected pitch resonant frequency is 0.756Hz

My Recommendation

- Modify the metal ring to shift the #2-56 threads by 0.1"

- The upper two retainer plates will have #4-40 x 0.5" stand off. Use vented Ag-coated #4-40 screws.

- The lower two are to be removed.

- Take care of the EQ stops.

- Of course, the best solution is to redesign the holder for 3/4" optics. Can we ask Protolab for rapid manufacturing???

Why did we need to place the mass forward to align the 1/4" thick optic?

We were supposed to adjust the CoM not to have too much adjustment. But we had to move the balance mass way too front for the proper alignment with a 1/4" thick optic. Why...?
This is because the ring was designed for a 3/8" thick optic... It does not make sense because the depth of the thread holes for the retainer plate was designed for 1/4" optics...

When the balance mass is located at the neutral position, the CoM coordinate is

x 0.0351mm (x+: left side at the front view)
y 0.0254mm (y+: vertical up)
z 0.4493mm (z+: towards back)

So, the CoM is way too behind. When the balance mass was stacked and the moved forward (center of the axis was moved forward by 0.27"), the CoM coordinate is (Attachment 6)

x 0.0351mm
y 0.0254mm
z 0.0011mm

This makes sens why we had to move the balance mass a lot for the adjustment.

  16296   Wed Aug 25 08:53:33 2021 JordanUpdateSUS2" Adapter Ring for SOS Arrived 8/24/21

8 of the 2"->3" adapter rings (D2100377) arrived from RDL yesterday. I have not tested the threads but dimensional inspection on SN008 cleared. Parts look very good. The rest of the parts should be shipping out in the next week.

  16364   Wed Sep 29 09:36:26 2021 JordanUpdateSUS2" Adapter Ring Parts for SOS Arrived 9/28/21

The remaining machined parts for the SOS adapter ring have arrived. I will inspect these today and get them ready for C&B.

  820   Mon Aug 11 00:58:31 2008 ranaUpdatePEM2 years of temperature trend
The PSL RMTEMP alarmed again because it says the room temperature is 19.5 C. Steve said in
an earlier log entry that this is a false alarm but he didn't say why he thought so...

I say that either the calibration of the RMTEMP channel has drifted, the setpoint of the HVAC
has shifted, or there's a drift in the RMTEMP channel. I don't know what electronics exactly
are used for this channel so not sure if its susceptible to so much drift.

However, since the Dust Monitor (count_temp) shows a similar temperature decline in the
last two years I am inclined to blame the HVAC system.

The attached plot shows 2 years of hour-mean trend.
  821   Mon Aug 11 09:39:29 2008 ranaUpdatePEM2 years of temperature trend
Steve and I went around and inspected and then adjusted the thermostats and humidostats.

All the thermostats were set at 70F in 2005 by Steve. We adjusted the ones on the arms up to 72F
and set the one on the wall west of the framebuilder up to 74F (this area was consistently colder
than all the others and so we're over-correcting intentionally).
  5783   Wed Nov 2 10:41:47 2011 steveUpdateGeneral2 spare heliax at the LSC rack

They were traced and labeled. One goes to 1X2 and the other to AS-ISCT. They are Andrew Heliax 1/4" od. made by CommScone,  model number FSJ1-50A

  16778   Thu Apr 14 10:18:35 2022 PacoSummaryBHD2 in oplev mirrors incompatible with LMR2V

[Paco, JC]

We realized the 2 in oplev mirrors (Thorlabs BB2-E02) for ITMYOL, SRMOL, and BSOL, are 0.47 in thick, while the LMR2V fixed mount is 0.46 in deep, even without taking the retaining ring into account. After a brief exchange with Koji, and Ian, we decided to glue the mirrors onto the mounts using Torr Seal (a vac compatible epoxy). They are curating in the clean room and should be ready to install in about 2 hours.

  3622   Wed Sep 29 16:56:36 2010 yutaUpdateVAC2 doors opened

(Steve, Koji, Joe, Kiwamu, Yuta)

 The vent was started on Monday, and finished on Tuesday.
 We were to open the doors on Tuesday, but we couldn't because the vertex crane got out of order.
 Now the crane was fixed, and so we opened the doors today.

What we did:

 We opened the north side of the BS chamber and the west side of the ITMX chamber.
 Now, the light doors are put instead.

  2744   Wed Mar 31 16:55:05 2010 josephbUpdateComputers2 computers from Alex and Rolf brought to 40m

I went over to Downs today and was able to secure two 8 core machines, along with mounting rails.  These are very thin looking 1U chassis computers. I was told by Rolf the big black box computers might be done tomorrow afternoon.  Alex also kept one of the 8 core machines since he needed to replace a hard drive on it, and also wanted to keep for some further testing, although he didn't specify how long.

I also put in a request with Alex and Rolf for the RCG system to produce code which includes memory location hooks for plant models automatically, along with a switch to flip from the real to simulated inputs/outputs.


  9691   Wed Mar 5 11:33:10 2014 KojiSummaryLSC2 arm ALS->LSC transition - road map

Step by step description of transition from 2arm ALS to Common/Differential LSC for FPMI

- Step 0: Place the frequencies of the arm green beams at the opposite side of the carrier green.

- Step 1: Activate stablization loops for ALSX and ALSY simultaneously.
  (Use LSC filter modules for the control. This still requires correct handling of the servo and filter module triggers)

- Step 2: Activate stablization loops for ALS Common and Differential by actuating ETMX and ETMY

- Step 2 (advanced): Activate stabilization loops for ALS Common by actuating MC2 and ALS Differential by ETMX and ETMY

- Step 3: Transition from ALS Common to 1/SQRT(TRX)+1/SQRT(TRY). Make sure that the calibration of TRX and TRY are matched.
  The current understanding is that the offset for 1/SQRT(TRX)+1/SQRT(TRY) can't be provided at the servo filter. Figure out
  what is the correct way to give the offsets to the TR signals.

- Step 4: Lock Michelson with AS55Q and then POP55Q (PD not available yet) or any other PD, while the arms are kept off-resonant using ALS.

- Step 5: Reduce the TR offsets. Transition to RF CARM signals obtained from POP55I or REFL11I in the digital land.

- Step 5 (advanced): Same as test6 but involve the analog common mode servo too.

- Step 6: Transition from ALS Differential to AS55Q

Independent test: One arm ALS (To be done everyday)

- ALS resonance scan

- Measurement of out-of-loop displacement (or frequency) stability 

- Check openloop transer function

Independent test: Common Mode servo for one arm

- Reproduce Decmber CM servo result of transition from one arm ALS to CM servo
  Insert 1/sqrt(TRY) servo in between?

- How can we realize smooth transition from ALS to POY11?

  6851   Fri Jun 22 02:21:57 2012 JenneUpdateGreen Locking2 arm ALS - Success!!!!

[Yuta, Jenne]

We locked both arms using the ALS system simultaneously!  Hooray!

Video of spectrum analyzer during lock acquisition of both beats is attached.

Jamie is super awesome, since he fixed us up a beatbox speedy-quick.  Thanks Jamie!!  speedy_gonzales-5257.jpg


1:  Aligned PSL green optics

     1.1:  We added an amplifier of ~20dB after the X beat PD (more Xgreen power on the PSL table so the signal was ~3dB higher than Y, so required less amplification).  The ~24dB amplifier is still in place after the Y beat PD.  Both beat signals go to a splitter after their amplifiers.  One side of each splitter goes to one of the channels on the beatbox.  The other side of each splitter goes to a 3rd splitter, which we're using backwards to combine the 2 signals so we can see both peaks on the spectrum analyzer at the same time.

2:  Found both beat notes

     2.1:  Y beat was easy since we knew the temps that have been working for the past several days

     2.2:  X beat was more tricky - the last time it was locked was the end of February (elog 6342)

         2.2.1:  We found it by adjusting the PSL laser temp nearly the full range - DC Adjust slider was at 8.8V or so (Y beat was found with the slider at ~1.1V tonight)

          2.2.2:  We then walked the beat around to get the PSL temp back to "normal" by moving the PSL temp, then compensating with the Xend laser temp, keeping the beatnote within the range of the spectrum analyzer.

          2.2.3:  Fine tuned the temps of all 3 lasers until we had 2 peaks on the analyzer at the same time!!

       Yend - measured Temp=34.14 C, thermal Out of Slow servo=29820

       Xend - displayed temp=39.33 C, thermal Out of Slow servo=5070

      PSL - displayed temp=31.49 C, Slow actuator Adjust=1.100V

3:  Locked both arms using ALS!!

     3.1:  We were a little concerned that the Xarm wasn't locking.  We tried switching the cables on the beatbox so that we used the old channels for the Xarm, since the old channels had been working for Y.  Eventually we discovered that the input of the filter module for ETMX's POS-ALS input was OFF, so we weren't really sending any signals to ETMX.  We reverted the cabling to how it was this evening when Jamie reinstalled the beatbox.

          3.1.1:  We need to sort out our SUS screens - Not all buttons in medm-land link to the same versions of the SUS screens!  It looks like the ALS screen was modified to point the ETMY button to a custom ETMY SUS screen which has the ALS path in the POS screen, along with LSC and SUSPOS.  There is no such screen (that I have found) for ETMX.  The regular IFO_ALIGN screen points to the generic SUS screens for both ETMY and ETMX, so we didn't know until Yuta searched around for the filter bank that the ALS input for ETMX was off.  We just need to make sure that all of the screens reflect what's going on in the models.

     3.2:  See the video attached - it shows the beat peaks during locking!!! (how do I embed it? right now you have to download it)

          3.2.1:  First you will see both peaks moving around freely

          3.2.2:  Then X arm is locked briefly, then unlocked

          3.2.3: Y arm is locked, steadily increasing gain

          3.2.4:  X arm is locked, so both arms locked simultaneously

          3.2.5:  Yuta clicked a button, accidentally unlocking the Xarm

4:  The transmission of the X arm was not so great, and both of our green beams (although X green especially) were no longer nicely aligned with the cavities.  Yuta tried to align the X arm to the X green, but it's bad enough that we really need to start over with the whole IFO alignment - we leave this until tomorrow.  Since we didn't have any good IR transmission, we didn't bother to try to find and hold the Xarm on IR resonance using ALS, so we didn't measure a POX out of loop residual cavity motion spectrum.  Again, tomorrow. 

  6852   Fri Jun 22 03:37:42 2012 KojiUpdateGreen Locking2 arm ALS - Success!!!!

Are these correct?

1. It is a nice work.

2. This is not locking, but stabilization of the both arms by ALS.

3. We now have the phase trackers for both arms.

4. There is no coarse (i.e. short) delay line any more.

5. The splitters after the PDs are reducing the RF power to Beat-box.
Actually there are RF monitors on Beat-box for this purpose, but you did not notice them.

6. c1ioo channel list
has to be updated.

7. Video can be uploaded to Youtube as Mike did at http://nodus.ligo.caltech.edu:8080/40m/6513

  6853   Fri Jun 22 10:52:18 2012 yutaUpdateGreen Locking2 arm ALS - Success!!!!

Answers to questions from Koji.

Are these correct?

1. It is a nice work.

Correct, of course!

2. This is not locking, but stabilization of the both arms by ALS.


3. We now have the phase trackers for both arms.


4. There is no coarse (i.e. short) delay line any more.

Correct. No coarse, only fine delay line (30m) with the phase tracker.

5. The splitters after the PDs are reducing the RF power to Beat-box.
Actually there are RF monitors on Beat-box for this purpose, but you did not notice them.

Oh, yes. But distance between beatbox and spectrum analyzer in the control room is longer than distance between BBPD on PSL table and the spectrum analyzer. We were too lazy to do cabling, but maybe we should.

6. c1ioo channel list 
has to be updated.

Yes, we will.

7. Video can be uploaded to Youtube as Mike did at http://nodus.ligo.caltech.edu:8080/40m/6513

We didn't, but we can.

  3295   Mon Jul 26 20:30:35 2010 JenneUpdateSUS2 Tip Tilts suspended and balanced

[Koji, Jenne]

We were on Team Cleanroom, while Kiwamu and Alberto were on Team Chamber.  Team Cleanroom suspended and balanced 2 Tip Tilts this afternoon.

One of the TTs that was suspended today is the one which was broken on Friday (see elog 3278).  We resuspended it using the regular 0.0036" diameter wire (91um).  We balanced it using the HeNe oplev, and then set it aside.  This TT has serial number 2.

We noticed that, like the previous 2 TT suspensions (this one before it was broken, and the one actually installed in the BS chamber on Friday, which is #3), there seems to be a little bit of hysteresis in the pointing.  The difference comes if we poke the top of the mirror holder and observe the place the reflected beam spot comes to rest at, and if we poke the bottom of the mirror holder.  The beam spot stays a little higher when we poke the top vs. when we poke the bottom. 

To combat this, we tried suspending our second TT of the day (the one that Kyung Ha and I had half finished) using thinner wire for the mirror holder.  We used the 0.0017" diameter wire (43um) that is used for the SOSes.  Unfortunately, it still seems like there is a similar hysteresis.  The thin-wire TT has serial number 4.

While working on TT4, we recalled that we have to include rubber dampers for the vertical blade springs.  Oooops!  We used some of the leftover #4-40 screws with viton tips that Zach and Mott had made for Earthquake stops to damp the vertical resonance of the blades.  We measured the Q factor by flicking the blades up or down.  We changed the oplev setup to be a shadow sensor setup, and watched the ringdown of the vertical mode on the 'scope.  We counted #cycles/time = frequency, and the t(1/2) time for the exponential ringdown to calculate the Q.  For the shadow sensor, we positioned the QPD in line with the initial HeNe beam, and placed the edge of the mirror holder clamp partially in the beam, so the beam was partly occluded.  When the mirror shook up and down, more or less of the beam was blocked, and we could see this power fluctuation on the 'scope.

Using the formula Q = pi  f0 T1/2 / ln(2) = 4.53 f0 T1/2, where T1/2 is the the time it takes for the amplitude to decay by half, we measured a Q of 31 for the vertical mode with no damping, and a Q of 14 with damping.  Koji confirmed the calculation and put it into wiki.

We need to go through the other TTs that have been assembled and give them their rubber dampers.


  2574   Fri Feb 5 14:31:46 2010 JenneUpdateSUS2 SOS towers assembled

[Jenne, Kiwamu]

The 2 SOS towers for the ITMs have been assembled, and are on the flow bench in the cleanroom.  Next up is to glue magnets, dumbells, guiderods and wire standoffs to the optics, then actually hang the mirrors.


  4830   Fri Jun 17 00:17:26 2011 ranaConfigurationElectronics2 RFPDs sent to LLO

Koji and I found 2 RFPD boxes to send to LLO. We've put them onto Steve's desk to be overnighted to Valera.

One of them is our old 21.5 MHz gold box RFPD from the FSS (which we don't use). The other one is a 2mm gold box one which was previously tuned for 66 MHz.


They shipped out on Friday

  1349   Tue Mar 3 11:39:50 2009 OsamuDAQComputers2 PCs in Martian

 Kiwamu and I brought 2 SUPER MICRO PCs from Willson house into 40m.

Both PCs are hooked up into Martian network. One is named as bscteststand for BSC which has been set up by Cds people and another one is named kami1 for temporary use for CLIO which is a bland new, no operating installed PC. This bland new PC will be returned Cds or 40m once another new PC which we will order within several days arrives.

IP address for each machine is and respectively.

We have installed CentOS5.2 into the new PC.

  7385   Fri Sep 14 01:18:51 2012 ranaUpdateCOC2 Layout Changes

After looking at the in-vacuum layout I think we should make two changes during the next vent:

1) Reduce the number of mirrors between the FI and its camera. We install a large silvered mirror in the vacuum flange which holds the Faraday cam (in the inside of the viewport). That points directly at the input to the Faraday. We get to remove all of the steering mirror junk on the IO stack.

2) Take the Faraday output (IFO REFL) out onto the little table holding the BS and PRM Oplevs. We then relocate all 4 of the REFL RFPDs as well as the REFL OSA and the REFL camera onto this table. This will reduce the path length from the FI REFL port to the diodes and reduce the beam clutter on the AS table.

  7398   Mon Sep 17 18:04:01 2012 SteveUpdateCOC2 Layout Changes


After looking at the in-vacuum layout I think we should make two changes during the next vent:

1) Reduce the number of mirrors between the FI and its camera. We install a large silvered mirror in the vacuum flange which holds the Faraday cam (in the inside of the viewport). That points directly at the input to the Faraday. We get to remove all of the steering mirror junk on the IO stack.

2) Take the Faraday output (IFO REFL) out onto the little table holding the BS and PRM Oplevs. We then relocate all 4 of the REFL RFPDs as well as the REFL OSA and the REFL camera onto this table. This will reduce the path length from the FI REFL port to the diodes and reduce the beam clutter on the AS table.

 There is just so much room on this table.

  3960   Sat Nov 20 02:25:30 2010 yutaUpdateCDS2 LOCKINs for suspension models

(Suresh, Koji, Yuta)

  No AWG. No tdssine.
  ...... LOCKIN!

What we did:
  1. Added 2 LOCKINs for c1sus model.
   Currently, we cannot put cdsOsc in a subsystem.
   So, we put LOCKINs just for BS for a test.
   The signal going into LOCKIN can be anything. For now, we just put a matrix for selecting the signal and connected the input signals to the ground.

   See the following page for the current simlink diagram of c1sus model.

  2. Edited MEDM screens. (see Attachment #1)

  We succeeded in putting 2 LOCKINs and exciting BS.
  During the update, we might destroyed things. For example, fb status is red in GDS screens.
  We will wait for Joe to fix them.

 - Fix cdsOsc and put LOCKINs for all the other optics
 - Come up with a good idea what to do with this LOCKIN. Remember, LOCKIN is not just a replacement for excitation points.
 - Enhance an oscillator so that we can put a random noise

  3314   Wed Jul 28 18:24:57 2010 JenneUpdateGreen Locking2 Green Periscopes have mirrors, aligned

[Koji, Jenne, Kiwamu]

This is to describe the work that went on in the Cleanroom today.  Kiwamu's entry will detail the tidbits that happened in the chamber.

We engraved the periscope mounts with the mirror info for the mirrors which were placed in the periscope.  We also engraved the barrels of the optics with their info, for posterity.  Koji carefully put the mirrors into the periscopes.  Since we have wedged optics, the goal was to have the front HR surface of the mirror parallel to the plane of the mount, and leave a bit of space behind one side of the optic (if we just pushed the optic fully in, the HR surface wouldn't be flat, and would send the beam off to the left or right somewhere).  Once the mirrors were mounted in the periscopes, we checked the vertical levelness of the outcoming beam.  For the first periscope (the one which has been installed on the BS table), the beam was deflected upward (2.5)/32 inches over 55inches.  This corresponds to a 1.4mRad vertical deflection.  The second periscope (which will eventually be installed on the OMC table) had a deflection of 1/32 over 55inches, or 0.6mRad.  We did not check the side-to-side deflection for either of the periscopes.

We also engraved one more DLC mount with mirror info, and put a mirror into the mount.  This is one of the optics that was placed onto the BS table today, which Kiwamu will describe.

We removed TT#3 from the BS chamber so that it could have rubber vertical dampers installed, and be characterized.  For future reference, the #'s of the Tip Tilts refers to the serial number of the suspension block piece, which forms the top horizontal bar of the frame. 

ELOG V3.1.3-