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ID Date Author Typeup Category Subject
  7302   Tue Aug 28 19:06:32 2012 KojiMetaphysicsRingdownripples

Isn't it just a ringing of the intracavity power as you shifted the laser frequency abruptly?

Quote:

Let's see if the ripples observed in the MC ringdown can be due to tilt motion of the mirrors.

The time it takes to produce a phase shift corresponding to N multiples of 2*pi is given by:

t = sqrt(2*N*lambda/(L*omega_T^2*(alpha_1+alpha_2)))

L is the length of the MC (something like 13m), and alpha_1, alpha_2 are the DC tilt angles of the two mirrors "shooting into the long arms of the MC" produced by the MC control with respect to the mechanical equilibrium position. omega_T is the tilt eigenfrequency of the three mirrors (assumed to be identical). lambda = 1.064e-6m;

The time it takes from N=1 to N=2 (the first observable ripple) is given by: tau1 = 0.6/omega_T*sqrt(lambda/L/(alpha_1+alpha_2))

The time it takes from N=2 to N=3 is given by: tau2 = 0.77*tau1

etc

First, we also see in the measurement that later ripples are shorter than early ripples consistent with some accelerated effect. The predicted ripple durations tau seem to be a bit too high though. The measurements show something like a first 14us and a late 8us ripple. It depends somewhat on the initial tilt angles that I don't know really.

In any case, the short ripple times could also be explained if the tilt motions start a little earlier than the ringdown, or the tilt motion starts with some small initial velocity. The next step will be to program a little ringdown simulation that includes mirror tilts and see what kind of tilt motion would produce the ripples exactly as we observe them (or maybe tilt motion cannot produce ripples as observed).

 

  7303   Tue Aug 28 19:21:37 2012 janoschMetaphysicsRingdownripples

Hmm. I don't know what ringing really is. Ok, let's assume it has to do with the pump... I don't see how the pump laser could produce these ripples. They have large amplitudes and so I always suspected something happening to the intracavity field. Therefore I was looking for effects that would change resonance conditions of the intracavity field during ringdown. Tilt motion seemed to be one explanation to me, but it may be a bit too slow (not sure yet). Longitudinal mirror motion is certainly too slow. What else could there be?

Quote:

Isn't it just a ringing of the intracavity power as you shifted the laser frequency abruptly?

Quote:

Let's see if the ripples observed in the MC ringdown can be due to tilt motion of the mirrors.

The time it takes to produce a phase shift corresponding to N multiples of 2*pi is given by:

t = sqrt(2*N*lambda/(L*omega_T^2*(alpha_1+alpha_2)))

L is the length of the MC (something like 13m), and alpha_1, alpha_2 are the DC tilt angles of the two mirrors "shooting into the long arms of the MC" produced by the MC control with respect to the mechanical equilibrium position. omega_T is the tilt eigenfrequency of the three mirrors (assumed to be identical). lambda = 1.064e-6m;

The time it takes from N=1 to N=2 (the first observable ripple) is given by: tau1 = 0.6/omega_T*sqrt(lambda/L/(alpha_1+alpha_2))

The time it takes from N=2 to N=3 is given by: tau2 = 0.77*tau1

etc

First, we also see in the measurement that later ripples are shorter than early ripples consistent with some accelerated effect. The predicted ripple durations tau seem to be a bit too high though. The measurements show something like a first 14us and a late 8us ripple. It depends somewhat on the initial tilt angles that I don't know really.

In any case, the short ripple times could also be explained if the tilt motions start a little earlier than the ringdown, or the tilt motion starts with some small initial velocity. The next step will be to program a little ringdown simulation that includes mirror tilts and see what kind of tilt motion would produce the ripples exactly as we observe them (or maybe tilt motion cannot produce ripples as observed).

 

 

  7304   Tue Aug 28 20:23:54 2012 KojiMetaphysicsRingdownripples

Laser frequency shift = longitudinal motion of the mirrors

Ringing: http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-20-24-2463

Quote:

Hmm. I don't know what ringing really is. Ok, let's assume it has to do with the pump... I don't see how the pump laser could produce these ripples. They have large amplitudes and so I always suspected something happening to the intracavity field. Therefore I was looking for effects that would change resonance conditions of the intracavity field during ringdown. Tilt motion seemed to be one explanation to me, but it may be a bit too slow (not sure yet). Longitudinal mirror motion is certainly too slow. What else could there be?

 

  7305   Wed Aug 29 09:35:03 2012 janoschMetaphysicsRingdownripples 2

Ok, so the whole idea that mirror motion can explain the ripples is nonsense. At least, when you think off the ringdown with "pump off". The phase shifts that I tried to estimate from longitudinal and tilt mirror motion are defined against a non-existing reference. So I guess that I have to click on the link that Koji posted...

Just to mention, for the tilt phase shift (yes, there is one, but the exact expression has two more factors in the equation I posted), it does not matter, which mirror tilts. So even for a lower bound on the ripple time, my equation was incorrect. It should have the sum over all three initial tilt angles not only the two "shooting into the long arms" of the MC.

Quote:

Laser frequency shift = longitudinal motion of the mirrors

Ringing: http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-20-24-2463

Quote:

Hmm. I don't know what ringing really is. Ok, let's assume it has to do with the pump... I don't see how the pump laser could produce these ripples. They have large amplitudes and so I always suspected something happening to the intracavity field. Therefore I was looking for effects that would change resonance conditions of the intracavity field during ringdown. Tilt motion seemed to be one explanation to me, but it may be a bit too slow (not sure yet). Longitudinal mirror motion is certainly too slow. What else could there be?

 

 

  7356   Fri Sep 7 00:08:10 2012 janoschMetaphysics baffle clipping loss

With a curvature radius of about 57m for the ETMs, flat ITMs at the beam waist, and using 39m for the arm lengths, one finds that the beam radius at the ETMs is about 5.3mm. The clipping power loss of a 5.3mm beam through a 20mm radius baffle hole would be less than a ppm of a ppm if the beam was perfectly centered. If the baffle hole had 15mm radius, the clipping loss would be 0.01ppm. If the baffle hole had 10mm radius, the loss would be 810ppm. The loss values are calculated using the formula of the  "Gaussian beam" Wikipedia article, "Power through an aperture" section. So I did not check if that one is ok.

  8376   Fri Mar 29 19:56:02 2013 GabrieleMetaphysicsLSCLock of PRMI on sidebands

I finally managed to get long stretches of PRMI lock, up to many minutes. The lock is not yest very stable, it seems to me that we are limited by some yaw oscillation that I could not trace down. The oscillation is very well visible on POP.

Presently, PRCL is controlled with REFL55_I, while MICH is controlled with AS55_Q. This configuration is maybe not optimal from the point of view of phase noise couplings, but at least it works quite well. I believe that the limit on the length of locks is given by the angular oscillation. I attach to this entry few plots showing some of the lock stretches. The alignment is not optimal, as visible from a quite large TEM01 mode at the dark port.

Here are the parameters I used:

MICH gain -10   PRCL gain -0.1

Normalization of both error signal on POP22_I with factor 0.004

Triggering on POP22: in at 100, out at 20 for both MICH and PRCL.

POP55 demodulation phase -9

MICH and PRCL control signal limits at 2000 counts

 

There is a high frequency (628 Hz) oscillation going on when locked (very annoying on the speakers...), but reducing the gain made the lock less stable. I could go down to MICH=-1.5 and PRCL=-0.02, still being able to acquire the lock. But the oscillation was still there. I suspect that it is not due to the loops, but maybe some resonance of the suspension or payload (violin mode?). There is still some room for fine tuning...

Lock is acquired without problems and maintained for minutes.

Have a nice week-end!

Attachment 1: lock_prmi5.pdf
lock_prmi5.pdf
Attachment 2: lock_prmi6.pdf
lock_prmi6.pdf
Attachment 3: lock_prmi7.pdf
lock_prmi7.pdf
Attachment 4: oscillation.pdf
oscillation.pdf
Attachment 5: lock_prmi8.pdf
lock_prmi8.pdf
  8380   Mon Apr 1 09:25:35 2013 JenneMetaphysicsLSCLock of PRMI on sidebands

[Gabriele, Jenne]

I put a notch in FM10 for both MICH and PRCL at 628Hz, to try to prevent us from exciting the mode that Gabriele saw on Friday.  Since those filter banks were all full, I have removed an ELP50 (ellip("LowPass",4,1,40,50)).  I write it down here, so we can put it back if so desired.

  9028   Mon Aug 19 10:16:15 2013 PicassoMetaphysicsTreasureoutsider art

 ranasglory.png

  9192   Thu Oct 3 02:46:58 2013 ranaMetaphysicsPEMUSGS Furlough

ObamaCare_GOP.png

  10278   Sat Jul 26 14:45:33 2014 GabrieleMetaphysicsASCResponse of POP QPD

 Koji asked me to perform a simulation of the response of POP QPD DC signal to mirror motions, as a function of the CARM offset. Later than promised, here are the first round of results.

I simulated a double cavity, and the PRC is folded with parameters close to the 40m configuration. POP is extracted in transmission of PR2 (1ppm, forward beam). For the moment I just placed the QPD one meter from PR2, if needed we can adjust the Gouy phase. There are two QPDs in the simulation: one senses all the field coming out in POP, the other one is filtered to sense only the contribution from the carrier field. The difference can be used to compute what a POP_2F_QPD would sense. All mirrors are moved at 1 Hz and the QPD signals are simulated:

pop_qpd_all.png

This shows the signal on the POP QPD when all fields (carrier and 55 MHz sidebands) are sensed. This is what a real DC QPD will see. As expected at low offset ETM is dominant, while at large offset the PRC mirrors are dominant. It's interesting to note that for any mirror, there is one offset where the signal disappears.

pop_qpd_carrier.png

This is the contribution coming only from the carrier. This is what an ideal QPD with an optical low pass will sense. The contribution from the carrier increases with decreasing offset, as expected since there is more power.

pop_qpd_sb.png

Finally, this is what a 2F QPD will sense. The contribution is always dominated by the PRC mirrors, and the ETM is negligible.

The zeros in the real QPD signal is clearly coming from a  cancellation of the contributions from carrier and sidebands.

The code is attached.

Attachment 4: foldeddoublecavity.mist
classname FoldedDoubleCavity

# parameters
const Pin  1                # input power
const Lprc 6.752            # power recycling cavity length
const d_BS_PR3 0.401        # folding mirror distances
const d_PR2_PR3 2.081
const d_PRM_PR2 1.876
const c 299792458           # speed of light
const fmod 5*c/(4*Lprc)     # modulation frequency, matched to Lprc
... 51 more lines ...
Attachment 5: pop_qpd.m
% compile simulation class
clear classes
m = MIST('foldeddoublecavity.mist');

% create simulation object
s = FoldedDoubleCavity(8);

% set angulat motion
s.PRM.setMotionShape('pitch');
s.PR2.setMotionShape('pitch');
... 85 more lines ...
  10357   Fri Aug 8 19:42:59 2014 JenneMetaphysicsGeneralkitchen sink flooding

 When I got back to the lab, there was enough water that it was seeping under the wall, and visible outside. Physical plant says it will take an hour before they can come, so I'm getting dinner, then will let them in.

  10358   Fri Aug 8 20:22:12 2014 JenneMetaphysicsGeneralkitchen sink water off

Quote:

 When I got back to the lab, there was enough water that it was seeping under the wall, and visible outside. Physical plant says it will take an hour before they can come, so I'm getting dinner, then will let them in.

 The guy from physical plant came, and turned off the water to the kitchen sink.  He is putting in a work order to have the plumbers come look at it on Monday morning.  It looks like something is wrong with the water heater, and we're getting water out of the safety overpressure valve / pipe.

The wet things from under the sink are stacked (a little haphazardly) next to the cupboards.

  11369   Mon Jun 22 14:21:42 2015 SteveMetaphysicsTreasureJenne and Den graduated

Last supper before departing at  "Grazie" El Portal. All the best on your journey!

Attachment 1: ls.jpg
ls.jpg
  12342   Wed Jul 27 15:03:02 2016 sisyphusMetaphysicsSUSBroken wire

While tightening the bolts on the ETMX wire clamp, the wire broke. All four face magnets broke off. 

Fortunately, no pieces were lost.

  12343   Wed Jul 27 16:56:47 2016 ranaMetaphysicsSUSBroken wire

For the rest of this vent, at least, we need to start using the EQ stops more frequently. Whenever the suspension is being worked on clamp the optic. When you need it to be free back off the stops, but only by a few hundred microns - never more than a millimeter.

Best to take our time and use the stops often. With all the magnets being broken off, its not clear now how many partially cracked glue joints we have on dumbells which didn't completely fall off.

  12764   Fri Jan 27 19:40:03 2017 ranaMetaphysicselogword wrapping & large images

"Why does the word wrapping not work in our browsers with ELOG?" I sometimes wonder. Some of the elogs are fine, but often the 40m one has the text run off the page.

I found that this is due to people uploading HUGE images. If you need to do this, just use the shrink feature in the elog compose window so that we only have to see the thumbnail at first. Otherwise your 12 MP images will make it hard to read everyone else's entries.

  12776   Tue Jan 31 15:08:13 2017 ericqMetaphysicsCDSMinute Trend Koan

A novice was learning at the feet of Master Daqd. At the end of the lesson he looked through his notes and said, “Master, I have a few questions. May I ask them?”

Master Daqd nodded.

"Do we record minute trends of our data?"

"Yes, we record raw minute trends in /frames/trend/minute_raw"

"I see. Do we back up minute trends?"

"Yes, we back up all frames present in /frames/trend/minute"

"Wait, this means we are not recording our current trends! What is the reason for the existence of seperate minute and minute_raw trends?

“The knowledge you seek can be answered only by the gods.”

"Can we resume recording the minute trends?"

Master Daqd nodded, turned, and threw himself off the railing, falling to his death on the rocks below.

Upon seeing this, the novice was enlightened. He proceeded to investigate how to convert raw minute trends to minute trends so that historical records could be preserved, and precisely when Master Daqd started throwing himself off the mountain when asked to record minute trends.

  14265   Fri Nov 2 09:47:57 2018 SteveMetaphysicsTreasureZojirushi is dead

     It took at least ten years to rust away. crying

Attachment 1: DSC01773.JPG
DSC01773.JPG
Attachment 2: zoji.JPG
zoji.JPG
  14271   Mon Nov 5 15:55:39 2018 SteveMetaphysicsTreasureZojirushi is dead

We have no coffee machine.

We are dreaming about it

We still do not have it.

Attachment 1: zoji.JPG
zoji.JPG
  14272   Tue Nov 6 09:45:32 2018 aaronMetaphysicsTreasureZojirushi is dead

New all organic machine.

  16485   Wed Nov 24 17:13:31 2021 YehonathanMetaphysicsGeneralToilet tank broken

The toilet tank in the big bathroom stopped refilling. I contacted PPService@caltech.edu and put up an "Out of Order sign".

  16487   Tue Nov 30 11:03:44 2021 YehonathanMetaphysicsGeneralToilet tank broken

a plumber came in yesterday and fixed the issue.

Quote:

The toilet tank in the big bathroom stopped refilling. I contacted PPService@caltech.edu and put up an "Out of Order sign".

 

  64   Mon Nov 5 22:24:38 2007 Andrey, SteveOmnistructureVACPumping down goes smoothly

We (Steve and Andrey) started pumping down at 3.25PM today. At 9 PM we turned off the rotary pump, and turned on turbomolecular pumps.

By 10.10PM we reached the pressure 1 milliTorr, and the current status is "Vacuum Normal". We leave the turbopumps on for the night, and as it is pretty late for Steve, we are going home.

P.S. Steve was very displeased with the standard selection of "Type" of messages, he would like to extend that list.
  79   Wed Nov 7 14:01:31 2007 waldmanOmnistructureOMCFrequency and Intensity noise
One of the biggest problems I had using the PZT to lock was excessive noise. I did a little noise hunting and found that the problem was the cable running from the rack to the laser fast input. As a reminder, the laser has a 4 MHz / volt fast input. We require about 300 MHz to go one FSR, so there is a Thorlabs HV box between at the NPRO fast input which takes 0-10 V -> 0-150 V. The 150 V HV range is worth about 600 MHz of NPRO frequency.

OLD SETUP: Single side of DAC differential (10 Vpp) -> 9V in series with 10 kOhm -> 10 kOhm input impedance of Thorlabs HV -> NPRO

We used the single side of the DAC differential because we didn't have a differential receiver. This turned out to be a bad idea because the cable picks up every 60 Hz harmonic known to man kind.

NEW SETUP: Digital conditioning -> DAC differential (digitally limited to 0 - 1 V) -> SR560 in A-B mode gain 10 (0 - 10 V output)-> Thorlabs HV -> NPRO.

This has almost no 60 Hz noise and works much, much better. Moral of the story, ALWAYS USE DIFFERENTIAL SIGNALS DIFFERENTIALLY !

Note that I may be saturating the SR560 with 10 V output, Its spec'd for 10 Vpp output with 1 VDC max input. I don't know whether or not it can push 10 V out....
  86   Fri Nov 9 00:01:24 2007 waldmanOmnistructureOMCOMC mechanical resonances (Tap tap tappy tap)
[Pinkesh, Aidan, Sam]

We did a tap-tap-tappy-tap test of the OMC to try to find its resonances. We looked at some combination of the PDH error signal and the DCPD signal in a couple of different noise configurations. The data included below shows tapping of the major tombstone objects as well the breadboard. I don't see any strong evidence of resonances below the very sharp resonance at 1300 Hz (which I interpret as the diving board mode of the breadboard). If I get free, I 'll post some plots of the different breadboard resonances you can excite by tapping in different places.

(The "normalized" tapping response is abs(tap - reference)./reference.)
Attachment 1: Fig1.png
Fig1.png
Attachment 2: Fig2.png
Fig2.png
Attachment 3: Fig4.png
Fig4.png
Attachment 4: Fig2.pdf
Fig2.pdf
Attachment 5: Fig1.pdf
Fig1.pdf
Attachment 6: Fig4.pdf
Fig4.pdf
Attachment 7: ResonanceData.zip
  99   Wed Nov 14 07:48:38 2007 nornaOmnistructureOMCOMC Cable dressing
[Snipped from an email]

1) Last Friday Pinkesh and I set the OMC up with only the top three OSEMs and took a vertical transfer function. We had removed the other OSEMs due to difficulty of aligning all OSEMs with the weight of the bench etc bringing the top mass lower than the tablecloth can accommodate. See attached TF.Clearly there are extra peaks (we only expect two with a zero in between) and my belief is that at least some of them are coupling of other degrees of freedom caused by the electrical wiring. Pinkesh and I also noticed the difficulty of maintaining alignment if cables got touched and moved around. So.....

2) Yesterday Dennis and I took a look at how much moving a cable bundle around (with the peak shielding) changed the DC alignment. In a not too precise experiment ( using HeNe laser reflecting off the bench onto a surface ~ 1 metre away) we saw that we could reposition the beam one or two mm in yaw and pitch. This corresponds to ~ one or two mrad which is ~ the range of the OSEM DC alignment. We discussed possibility of removing the cabling from the middle mass, removing the peak and taking it from the bench directly to the structure above. I asked Chub if he could make an equivalent bundle of wires as those from the two preamps to see what happens if we repeat the "moving bundle" experiment. So...

3) Today Chub removed the cabling going to the preamps and we replaced it with a mock up of wire bundle going directly from the preamps to the structure above. See attached picture. The wires are only attached to the preamp boxes weighted down with masses but the bundle is clamped at the top. We repeated the "wiggle the bundle" test and couldnt see any apparent movement ( so maybe it is at most sub-mm). The cable bundle feels softer.

The next thing Chub did was to remove the second bundle ( from photodiodes, heater, pzt) from its attachment to the middle mass and strip off the peek. It is now also going to the top of the structure directly. The whole suspension now appears freer. We discussed with Dennis the "dressing " of the wires. There are some minor difficulties about how to take wires from the bright side to the dark side, but in general it looks like that the wires forming the second "bundle" could be brought to the "terminal block" mounted on the dark side and from there looped up to the top of the structure. We would have to try all this of course to see the wiring doesnt get in the way of other things (e.g. the L and R OSEMs). However this might be the way forward. So...

4) Tomorrow Pinkesh and I will check the alignment and then repeat the vertical transfer function measurement with the two bundles as they are going from bench to top of structure. We might even do a horizontal one if the middle mass is now within range of the tablecloth.
We can then remove preamp cables completely and lay the second bundle of cables on the optical bench and repeat the TFs.

The next thing will be to weigh the bench plus cables. This will allow us to
a) work out what counterbalance weights are needed - and then get them manufactured
b) firm up on how to handle the extra mass in terms of getting the masses at the correct height.

And in parallel Chub will work on the revised layout of cabling.

Looking a little further ahead we can also get some stiffness measurements made on the revised bundle design ( using Bob's method which Alejandro also used) and fold into Dennis's model to get some sanity check the isolation.

I think that's it for now. Comments etc are of course welcome.

Norna
Attachment 1: OMC-11-13-07_011.jpg
OMC-11-13-07_011.jpg
Attachment 2: VerticalTrans.pdf
VerticalTrans.pdf VerticalTrans.pdf VerticalTrans.pdf VerticalTrans.pdf
  114   Mon Nov 19 14:19:25 2007 steveOmnistructurePEMjackhammer
The construction personal successfully jackhemmered a fence around the "Drever's parking slot"
There is no parking space available close by
Attachment 1: jackhammer.jpg
jackhammer.jpg
Attachment 2: jackhammer2.jpg
jackhammer2.jpg
  122   Mon Nov 26 10:17:31 2007 steveOmnistructureSUSetmy sus damping restored
20 days plot is showing etmy loosing damping 4 times.
I zoomed in with each event. Three of them could of been triggered
by garbage loading just outside. However attachment 2 plot demonstrating that small earthquake or seismic event
did not tripped etmy damping.
The fourth event was preceded by a 4-5 hrs of continous rise of the rms motion at C1:SUS-ETMY_LLPD_VAR
Attachment 1: etmyrms20d.jpg
etmyrms20d.jpg
Attachment 2: etmyrmseq.jpg
etmyrmseq.jpg
  129   Wed Nov 28 08:47:29 2007 steveOmnistructureVACrga is out of order
The rga is not working since Nov 10
The controller is broken.
pd65-m-d23
Attachment 1: pd65d23.jpg
pd65d23.jpg
  139   Thu Nov 29 11:10:54 2007 robOmnistructureVACRGAlogger sleeping
Without the RGA controller responding, the RGAlogger script just hangs. Rather than fix it, I just put it to sleep by commenting out the line in op440m crontab file. Once we get it running again, we'll move the cronjob to op340m.
  153   Sun Dec 2 17:37:33 2007 ranaOmnistructureComputersNetwork Cabling in the Office
We all know that we've spent many integrated man hours trying to figure out why our network connections
in the office area don't work. Usually its because of the bad hub around the Tobin/Osamu desk.

I pried open some of the wall conduit today and it looks pretty easy to fish cables through. I think
its time we finally did that. It may be a little disruptive, but I propose we get Larry to come over
and figure out what needs to happen for us to get regular 100 Mbit ports on the walls. These can
then all go over and get connected to a switch in the rack that holds linux1.

Opinions / comments ?
  179   Fri Dec 7 11:33:24 2007 waldmanOmnistructureOMCPZT wiring
The 2 pin LEMO connector has got an unmarked pin and a pin marked by a white half-circle.
The unmarked pin is connected to the side of the PZT attached to the mirror.
The marked pin is connected to the side of the PZT attached to the tombstone.
  188   Wed Dec 12 16:22:22 2007 albertoOmnistructureElectronicsLC filter for the RF-AM monitor circuit
In the LC configuration (see attached schematic) the resonant frequency is tuned to one of the peak of our RF-AM monitor and it is amplified by a factor equal to the Q of the filter. As I wrote in one of the last elog entries, we would like amplifications of about 10-30 dB in order to have negligible couplings. Such values are obtained only with small capacitances (few or less pF). The drawback is relatively large inductance (uH or more) which has inevitably low Self Resonant Frequencies (SRF - the resonant frequencies of the RLC circuit usually associated with an actual inductor - ~ MHz). Even before, one limit is also the input impedance of the RF amplifier. Quality factors > 1 require megaohms, far from the 50 ohms in the MiniCircuit amplifiers Iím using now. So, if we plan to use these even for the final design of the circuit, we have to abandon the LC configuration.
For this same reason the only way I could get the expected responses from my several test boards was with a 10 megaohm input probe (see attachment for the measurement with and without probe). Assuming that impedance, I found these as the best trade-offs between the attenuation requirements and the values of the inductors for respectively the peaks at 33, 66,133, 166,199 MHz:
26uH, 6.6u, 20u, 73u, 16u
If we could find inductor with these values and high SRF the configuration should work. The problem is I couldnít find any. Above a few uH they all seem to have SRF ~ MHz.
That is why I switched to the Butterworth. This should work despite the input impedance of the amplifier and with much smaller inductances. I made a totally new test circuit, with surface mount components. I think I still have to fix some things in the measurements but (this time I got rid of the simulator I was using earlier and designed a new configuration with new values from the Horowitzís tables) it seems I have the expected peaks. More soon.
Attachment 1: TF_LC_filter_10pF_1.8uH_scope_probe.png
TF_LC_filter_10pF_1.8uH_scope_probe.png
Attachment 2: TF_LC_filter_10pF_1.8mH_no_probe.png
TF_LC_filter_10pF_1.8mH_no_probe.png
Attachment 3: LC_filter_schematic.png
LC_filter_schematic.png
  190   Thu Dec 13 12:05:36 2007 albertoOmnistructureElectronicsThe new Butterworth seems to work quite well
It works better probably because of the small inductors I'm using this time.
The peak is at 30 MHz because I didn't have the precise elements to get 33.

The bandwidth and the Q could be improved by adding one or two more order to the filter and trying to better match the low-pass' resonant frequency with the high-pass'.

Also I have to see if it could work at 166 and 199 MHz as well.
Attachment 1: TF_New_Butterworth_12-Nov-2007_TF.png
TF_New_Butterworth_12-Nov-2007_TF.png
Attachment 2: Bultervverth2.png
Bultervverth2.png
  200   Wed Dec 19 11:31:01 2007 steveOmnistructurePEMaircond filter maintenance
Jeff is working on all air condiontion units of the 40m lab
This we do every six months.
Attachment 1: acfilters6m.jpg
acfilters6m.jpg
  272   Sat Jan 26 02:08:53 2008 JohnOmnistructureLSCFibres
There is now a fibre running from the SP table to the ISCT at the Y-end. In the coming days I will try to mode match the beam from this fibre into the arm through ETMY. To achieve this I will be altering the optical layout of this table.
  310   Tue Feb 12 13:53:27 2008 robOmnistructureVACReturn of the RGA

The new RGA head was installed a few days ago. I just ran the RGAlogger script to see if it works, which it does. I also edited the crontab file on op340m to run the RGAlogger script every night at 1:25 AM. It should run tonight.
Attachment 1: RGA-080212.png
RGA-080212.png
  365   Fri Mar 7 19:04:39 2008 steveOmnistructurePSLlaser pointer
Green laser pointer was found in my desk.
I blamed Rana for not returning it to me after a conference talk.
It is surprisingly bright still.
I will bring sweets for Wednesday meeting.
  453   Sat Apr 26 11:21:15 2008 ajwOmnistructureComputersbackup of /cvs/cds restarted
The backup of /cvs/cds (which runs as a cron job on fb40m; see /cvs/cds/caltech/scripts/backup/000README.txt) 
has been down since fb40m was rebooted on March 3.
I was unable to start it because of conflicting ssh keys in /home/controls/.ssh .
With help from Dan Kozak, we got it to work with both sets of keys
( id_rsa, which allows one to ssh between computers in our 113 network without typing a password,
 and backup2PB which allows the cron job to push the backup files to the archive in Powell-Booth).

It still goes down every time one reboots fb40m, and I don't have a solution.
A simple solution is for the script to send an email whenever it can't connect via ssh keys
(requiring a restart of ssh-agent with a passphrase), but email doesn't seem to work on fb40m.
I'll see if I can get help on how to have sendmail run on fb40m.
  464   Mon May 5 11:04:30 2008 robOmnistructureComputersNetwork setup

Mafalda was not connected to the network, and so our DMF-based seisBLRMS has not been running for ~1 week. I traced this to a broken ethernet cable connecting mafalda to the network switch in the rack next to the B&W printer. This cable has a broken connector at the switch side, which means it can't stay connected if there's any tension. It needs to be replaced.
  483   Fri May 16 17:27:55 2008 AndreyOmnistructureGeneralToilets are broken, do not use them !!!

Both toilets in 40-meter were constantly flushing, the leaking water was on the floor inside of the restrooms, so

BOTH RESTROOMS ARE CLOSED TILL MONDAY


I have heard the constant loud sound of flushing water, opened the door, and was unpleasantly surprised because all the floor was under the layer of water and the toilets were constantly flushing. I called security at X5000, a plumber came in and told that a team of plumbers needs to repair the flushing system after the weekend. The plumber today just shut off the flushing water, wiped off the floor and told not to use the restrooms in the weekend. We should expect a team of plumbers on Monday.

Sinks are working, so you can wash your hands.
  780   Fri Aug 1 11:51:15 2008 justingOmnistructureComputersadded /cvs/cds/site directory
I added a /cvs/cds/site directory. This is the same as is dicsussed here. Right now it just has the text file 'cit' in it, but eventually the other scripts should be added. I'll probably use it in the next version of mDV.
  885   Tue Aug 26 09:58:59 2008 steveOmnistructureCOCETMX is #03
This is the picture of ETMX from the upper south west viewport
Attachment 1: etmx-d40posg_012.jpg
etmx-d40posg_012.jpg
Attachment 2: etmx03.jpg
etmx03.jpg
  888   Tue Aug 26 18:19:16 2008 ranaOmnistructureElectronicsResistor Noise at the 40m
As Stefan points out in his recent ISS ilog entries at LLO, Daniel Sigg recently wrote a
recommendation memo on resistor and capacitor
choices: T070016.

While working on the PMC I have had to use leaded resistors and wondered about the noise. As it turns
out we have the RN series of 1/4 W resistors from Stackpole Electronics. The RN series are
metal film resistors (datasheet attached); metal film is what Sigg recommends for lowest flicker
noise.

So we are OK for using the Stackpole 1/4 W leaded resistors in low noise circuits.
Attachment 1: SEI-RN_RNM.pdf
SEI-RN_RNM.pdf SEI-RN_RNM.pdf
  1038   Fri Oct 10 00:34:52 2008 robOmnistructureComputersFEs are down

The front-end machines are all down. Another cosmic-ray in the RFM, I suppose. Whoever comes in first in the morning should do the all-boot described in the wiki.
  1039   Fri Oct 10 10:20:42 2008 AlbertoOmnistructureComputersFEs are down

Quote:

The front-end machines are all down. Another cosmic-ray in the RFM, I suppose. Whoever comes in first in the morning should do the all-boot described in the wiki.


Yoichi and I went along the arms turning off and on all the FE machines. Then, from the control room we rebooted them all following the procedures in the wiki. Everything is now up again.

I restored the full IFO, re-locked the mode cleaner.
  1040   Fri Oct 10 13:57:33 2008 AlbertoOmnistructureComputersProblems in locking the X arm
This morning for some reason that I didn't clearly understand I could not lock the Xarm. The Y arm was not a problem and the Restore and Align script worked fine.

Looking at the LSC medm screen something strange was happening on the ETMX output. Even if the Input switch for c1:LSC-ETMX_INMON was open, there still was some random output going into c1:LSC-ETMX_INMON, and it was not a residual of the restor script running. Probably something bad happened this monring when we rebooted all the FE computers for the RFM network crash that we had last night.

Restarting the LSC computer didn't solve the problem so I decided to reboot the scipe25 computer, corresponding to c1dcuepics, that controls the LSC channels.

Somehow rebooting that machine erased all the parameters on almost all medm screens. In particular the mode cleaner mirrors got a kick and took a while to stop. I then burtrestored all the medm screen parameters to yesterday Thursday October 9 at 16:00. After that everything came back to normal. I had to re-lock the PMC and the MC.

Burtrestoring c1dcuepics.snap required to edit the .snap file because of a bug in burtrestore for that computer wich adds an extra return before the final quote symbol in the file. That bug should be fixed sometime.

The rebooting apparently fixed the problem with ETMX on the LSC screen. The strange output is not present anymore and I was able to easily lock the X arm. I then run the Align and the Restore full IFO scripts.
  1070   Wed Oct 22 20:50:30 2008 AlbertoOmnistructureComputersGPS
Today I measured the GPS clock frequency at the output of CLOCK_MON in a board on the same crate where the c1iool0 computer is located. The monitor was connected with a BNC cable to the 10MHz reference input of the frequency counter on top of that rack, where it was used to check the 166MHz coming from one of the Marconi.

The frequency was supposed to be 10MHz but I actually measured 8 MHz. I tracked down the GPS input cable to the board and it turned out to come from one of the 1Y7 rack. Here it was connected to a board with a display that was showing corrupted digits, plus some leds on the front panel were red.

I'm not sure the GPS reference is working properly.
  1075   Thu Oct 23 18:45:18 2008 AlbertoOmnistructureComputer Scripts / ProgramsPython code for GPIB devices developed for the Absl length experiment
I wrote two Python scripts for my measurement that can be also used/imitated by others: sweepfrequency. py and HP8590.py. The first is is the one that we run by a Python interpreter (just typing "python <name script> <parameters>"from the terminal). It manages the parameters that we have to pass it for the measurement and calls the second one, HP8590.py which actually does most of the job.

Here what it does. It scans the frequency of the Marconi and, for each step, searches the highest peak in the Spectrum Analyzer (which is centered 50 KHz around the frequency of the Marconi). It then associates the amplitude of the peak to the frequency of the Marconi and write the two number in two columns of a file.
The file name, the GPIB-to/LAN interface IP address, the frequency range, the frequency step amplitude and the number of measures we want it to average for each step, are all set by the parameters when we call sweepfrequency.py.
More details are in the help of the function or just looking at the header of the code.

I guess that one can perform other similar measurement just with little changes in the code so I think it could turn out useful to anyone else.
Attachment 1: HP8590.py
# This function provides the measuremeent of the peak amplitude on the spectrum analyzer
# HP8590 analyzer while sweeping the excitation frequency on the function generator.
#
# Alberto Stochino 2008

import re
import sys
import math
from optparse import OptionParser
from socket import *
... 55 more lines ...
Attachment 2: sweepfrequency.py
## sweepfrequency.py [-f filename] [-i ip_address] [-a startFreq] [-z endFreq] [-s stepFreq] [-m numAvg]
#
## This script sweeps the frequency of a Marconi local oscillator, within the range
## delimited by startFreq and endFreq, with a step set by stepFreq. An arbitary
## signal is monitored on a HP8590 spectrum analyzer and the scripts records the
## amplitude of the spectrum at the frequency injected by the Marconi at the moment.

## The GPIB address of the Marconi is assumed to be 17, that of the HP Spectrum Analyzer to be 18

## Alberto Stochino, October 2008
... 51 more lines ...
  1135   Fri Nov 14 17:41:50 2008 JenneOmnistructureElectronicsSweet New Soldering Iron
The fancy new Weller Soldering Iron is now hooked up on the electronics bench.

Accessories for it are in the blue twirly cabinet (spare tips of different types, CD, and USB cable to connect it to a computer, should we ever decide to do so.

Rana: the soldering iron has a USB port?
Attachment 1: newSolderingIron.JPG
newSolderingIron.JPG
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