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ID Date Author Type Categoryup Subject
  7207   Thu Aug 16 18:59:18 2012 JenneUpdateSAFETYEmergency Exit door unlocked again

Koji just found the emergency exit door unlocked again.  NOT GOOD.

We have determined that if you use the emergency door to enter the lab, it leaves the door unlocked, unless you go back outside and deliberately lock it.  This means that someone has been using the emergency exit as a regular entrance. 

It's fine to leave by that door, but you should make a habit of entering through the regular door.  Using the back door as an entrance is a special case situation, when they have the main door blocked.

  7285   Mon Aug 27 15:46:55 2012 SteveUpdateSAFETYsafety training

 Rijuparna Chakraborty and Elli Elenora King received 40m specific  basic safety training in the 40mLab

Attachment 1: IMG_1597.JPG
IMG_1597.JPG
  7374   Wed Sep 12 11:33:49 2012 SteveUpdateSAFETYsafety training

Eric Quintero and Mike Jenson received 40m specific basic safety training.

  7467   Wed Oct 3 11:43:33 2012 SteveUpdateSAFETYsafety training

Den Martynov received 40m specific safety training.

  7508   Mon Oct 8 23:58:57 2012 JenneUpdateSAFETYControl room emergency lights came on

[Evan, Jenne]

We were sitting trying to lock MICH (hooooorraaaayy!!!), and the emergency lights above the control room door came on, and then ~1 minute later turned off.  Steve, can you see what's up?

  7559   Tue Oct 16 17:06:47 2012 SteveUpdateSAFETYsafety training

Ayaka Shoda, visiting graduate student received basic 40m specific safety training today

Attachment 1: IMG_1735.JPG
IMG_1735.JPG
  7725   Mon Nov 19 15:58:02 2012 SteveUpdateSAFETYsafety training

Charles Blakemore  our new undergrad help received 40m specific safety training today.

  8009   Wed Feb 6 15:05:18 2013 SteveUpdateSAFETYcameras must be anchord

Cameras must be immediately anchord to avoid a possible collusion with the view port !

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IMG_0070_1.JPG
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IMG_0069_1.JPG
  8026   Thu Feb 7 17:24:13 2013 SteveUpdateSAFETYfire extinguishers checked

The fire department weighted and pressure checked our units today. Surprisingly they found one powder filled can. We can only use HALON  gas in the lab.

 

  8167   Tue Feb 26 09:55:46 2013 SteveUpdateSAFETYEvan receives safety training

Evan got 40m specific safety training today.

  8180   Wed Feb 27 02:52:40 2013 JenneOmnistructureSAFETYBack door unlocked

Did someone unlock the back door by the (unofficial) bike storage lately?  Out of habit, I checked the door behind me while about to leave, and it is unlocked. 

Please recall that if you leave through that door, it should automatically lock behind you (if it was locked already), however if you unlock and enter through the back door, it stays unlocked until someone locks it again.

(Obviously, I'm locking the door before I actually go).

  8240   Wed Mar 6 11:33:09 2013 steveUpdateSAFETYsafety audit 2013

 

                                                 Recommended correction list:

1,  refill- upgrade first aid boxes

2,  maintain 18" ceiling to bookshelf clearance so the ceiling fire sprinklers are not blocked: room 101

3,  label chilled water supply & return valves in IFO room

4,  calibrate bake room hoods annually

5,  update safety sign at fenced storage

 

              40m still to do list:

1,   clean and measure all safety glasses

2,   annual crane inspection is scheduled for 8am March 19, 1013

3,   make PSL encloser shelf earthquake proof

 

Do you see something that is not safe? Add it to this list please.

 

 

Attachment 1: IMG_0010.JPG
IMG_0010.JPG
  8241   Wed Mar 6 16:14:27 2013 SteveUpdateSAFETYsafety training

Chloe Ling, Max Horton and Annalisa Allocca have received basic 40m specific safety training.

Attachment 1: IMG_500.jpg
IMG_500.jpg
  8287   Wed Mar 13 16:04:24 2013 steveUpdateSAFETYlaser safety glasses checked

 All safety glasses were cleaned in soapy water by Bob. I measured their transmission at 1064 nm, 150 mW,  beam diameter 1.5 mm  They are in working order, no transmission.

 Inventory:

10 pieces of KG-5, fit over, from Laser Safety

 4 pieces of KG-5, std size, from Drever Lab, best visibility

 1 piece of KG-5 coated for visible, std size, from Kentek

15 pieces of green-plastic LOTG-YAG, fit over, from UVEX

 7 pieces of green-plastic B-D+S 137, std areo fit, from Sperian

 3 pieces of green-plastic, old Thorlab, fit over

 2 pieces of green-plastic, fit over, from Laservision

 8 pieces of braun- plastic, fit over, for green & IR protection, from UVEX & Thorlabs

Attachment 1: safetyglasseschecked.jpg
safetyglasseschecked.jpg
  8309   Tue Mar 19 10:30:00 2013 steveUpdateSAFETYcrane inspection 2013

 

Professional crane inspector: Fred Goodbar found two small leaks at the Vertex trolley as he was conducting the annual inspection of the 40m cranes.  Otherwise the cranes are in safe condition.

Attachment 1: sippingOIL.jpg
sippingOIL.jpg
Attachment 2: 03191301.PDF
03191301.PDF
  8317   Wed Mar 20 14:52:09 2013 ManasaUpdateSAFETYMC trans RFPD missing

PDA255 at the MC transmission end is missing and whoever had removed it earlier has left the beam undamped.

It could be less than a mW beam...but it is still not acceptable to leave it that way.

On the other note, I have cleared up the unwanted optics from the same table.

MC.png

  8503   Mon Apr 29 08:22:57 2013 SteveUpdateSAFETYsafety training

 

 Albert, our new undergrad work force received 40m specific- basic safety training last week. Please read and sign 40m procedures booklet.

  560   Tue Jun 24 22:43:23 2008 ranaSummarySEIStack TF
Attachment 1: Screenshot.png
Screenshot.png
  1559   Thu May 7 23:34:59 2009 robUpdateSEIseisBLRMS already lost

Can't find hostname 'fb40m'

 

it only lasted a few hours

  1598   Mon May 18 02:18:17 2009 ranaSummarySEIUsing STACIS w/ a good position sensor
WE turned off STACIS a few years ago because we noticed that it was causing noise below a few Hz and making
the overall velocity between the ends higher than with them off. I'm pretty sure they were causing noise
because they use little geophones which are noisy. Below ~0.2 Hz the horizontal geophones are also probably
limited by tilt-horizontal coupling.

Another concept (based on discussion with Brian Lantz and Matt Evans) is to instead put a good position sensor
between the ground and then blue support beam. Since the the STACIS rubber acts like a Q~2 passive resonance at
20 Hz, the whole seismic system (including the blue beams, in-vac tubes, and internal stack) act like a proof
mass of a seismometer.

So, in principle, if we use a very good position sensor and feedback to the STACIS piezo actuators, we can cancel
the ground motion before it enters the stacks. The initial LIGO OSEMs have a noise of 10^-10 m/rHz above 10 Hz
and going up like 1/f below 10 Hz. The AdvLIGO BOSEMs have a noise of ~2x better. Even better, however, are the
UK's EUCLID interferometric OSEMs (developed by Stuart Aston and Clive Speake).

In the attached plot, I show what we can get if we use these EUCLIDs make a ~60 Hz BW feedback loop w/ STACIS.

BLACK   - raw ground motion measured by the Guralp
MAGENTA - motion after passive STACIS (20 Hz harmonic oscillator with a Q~2)
GREEN   - difference between ground and top of STACIS
YELLOW  - EUCLID noise in air
BLUE    - STACIS top motion with loop on (60 Hz UGF, 1/f^2 below 30 Hz)
CYAN    - same as BLUE, w/ 10x lower noise sensor

One of the SURF projects this summer is to put together a couple different sensors like EUCLID to understand the noise.
Attachment 1: stacis40.png
stacis40.png
  1608   Tue May 19 16:08:03 2009 ranaSummarySEIEUCLID
From Stuart Aston, I've attached a picture of the EUCLID position sensor:
Attachment 1: Picture_6.png
Picture_6.png
  3304   Wed Jul 28 01:05:44 2010 ranaUpdateSEIBode Magnitude Plot and Concerns

1) Gravity has to be included because the inverted pendulum effect changes the resonant frequencies. The deflection from gravity is tiny but the change in the dynamics is not. The results are not accurate without it. The z-direction probably is unaffected by gravity, but the tilt modes really feel it.

2) You should try a better meshing. Right now COMSOL is calculating a lot of strain/stress in the steel plates. For our purposes, we can imagine that the steel is infinitely stiff. There are options in COMSOL to change the meshing density in the different materials - as we can see from your previous plots, all the action is in the rubber.

3) I don't think the mesh density directly limits the upper measurement frequency. When you redo the swept-sine using the matlab scripting, use a logarithmic frequency grid like we usually do for the Bode plots. The measurement axis should go from 0.1 - 30 Hz and have ~100 points.

In any case, the whole thing looks promising: we've got real solid models and we're on the merge of being able to duplicate numerically the Dugolini-Vass-Weinstein measurements.

  3306   Wed Jul 28 12:16:03 2010 GopalUpdateSEIBode Magnitude Plot and Concerns

Quote:

1) Gravity has to be included because the inverted pendulum effect changes the resonant frequencies. The deflection from gravity is tiny but the change in the dynamics is not. The results are not accurate without it. The z-direction probably is unaffected by gravity, but the tilt modes really feel it.

2) You should try a better meshing. Right now COMSOL is calculating a lot of strain/stress in the steel plates. For our purposes, we can imagine that the steel is infinitely stiff. There are options in COMSOL to change the meshing density in the different materials - as we can see from your previous plots, all the action is in the rubber.

3) I don't think the mesh density directly limits the upper measurement frequency. When you redo the swept-sine using the matlab scripting, use a logarithmic frequency grid like we usually do for the Bode plots. The measurement axis should go from 0.1 - 30 Hz and have ~100 points.

In any case, the whole thing looks promising: we've got real solid models and we're on the merge of being able to duplicate numerically the Dugolini-Vass-Weinstein measurements.

I made some progress on a couple issues:

1) I figured out how to create log-transfer function plots directly in COMSOL, which eliminates the hassle of toggling between programs.

2) Instead of plotting maximum displacement, which could lead to inconsistencies, I've started using point displacement, standardizing to the center of the top surface.

3) I discovered that the displacement can be measured as a field vector, so the minor couplings between each translational direction (due to the asymmetry in the original designs) can be easily ignored. 

Bode_Disp_MC1_MC3_y.png

  8132   Thu Feb 21 18:10:13 2013 ranaUpdateSEIPump Down misalignments

This plot shows the trend of the OL during the past several hours of roughing pumping.

The big steps at the start of the pump down is NOT due to the pumping, but is instead the "recentering" that Yuta did. Looks like he was unable to find zero on the ETMY.

Some of the rest of the drift is probably just the usual diurnal variation, but there does seem to be some relation to the pumping trend. I guess that the shift of ~0.3 in the ITMX and ITMY pitch is real and pressure related.

We need to figure out how to put the OL calibration factor into the SUS-OL screens.

 

Attachment 1: OL.png
OL.png
  10776   Wed Dec 10 21:05:56 2014 KateUpdateSEIGuralp briefly powered down

 Kate & Jenne

About 2:30 this afternoon, we briefly powered off the Guralp (C1:PEM-SEIS_GUR1_{X,Y,Z}) in order to better align it with the other seismometers along its marked N/S direction. It had been visibly off by a few degrees. 

  12385   Tue Aug 9 13:53:57 2016 babbottUpdateSEIlong Guralp EX cable repaired on the D-sub side

I checked out the cable that I took from you, and all of the connections looked right.  The only thing I did notice was that some of the soldered wires on the 37-pin connector had gotten hot enough to melt their insulation, and potentially short together.  I cut off that connector, and left it on your desk to check out.  I put on a new connector, and checked the pinout.  If the Guralps still doesn't work, we'll have to check out other possibilities.

  12389   Tue Aug 9 19:35:49 2016 ranaUpdateSEIboth Guralp seismometers are functioning and being acquired

After some cable swapping, we now have both Guralp seismometers running and the times series and spectra look similar to each other and motley blushhealthy.


Bean and I took a look at the whole situation today. Ben had nicely fixed the Dsub end of the EX cable (the EY one is still just a sad joke), After installing this newly fixed cable, we still saw no signals. There was some confusion in the control room about using the MED displays to diagnose seismometers: flickering MEDM values cannot be used for this. It would be like checking a pizza box temperature to determine if the pizza is any good.

  1. Although the +/- 12V LEDs on the front panel are dim, we confirmed that the produce 11.94V even when loaded with a seismometer. So its a LED circuit problem not a power problem.
  2. We were able to inject signals into the front panel with a breakout board and see them in DV for Input 1, but not Input 2.
  3. After Ben left, I kept poking around and found that the Guralp chassis output gets broken out into 3x3 BNC cables before going to the PEM BNC panel (and then on to the PEM ADC). This is where the problem was.
  4. The Input #3 BNC cables were connected to the long cables going to the 'GUR2' channels of the PEM. The Input#2 BNC cables were connected to some short BNC cables that were just hanging from the rack. So, somewhere during the debugging of the past N months, someone plugged this in wrong and didn't notice or forgot to switch it back. So all of the tests using DV or DTT or MEDM since that time have been invalid.

 

Tomorrow, Lydia is going to change all of the labels and channel names. The new names will be EX & EY to prevent this kind of huge waste of time with channel name swapping. That means no more illegal names with the label maker, Steve.

From the spectrum you can see that the EX seismometer (GUR2) is still not centered or at least its oscillating at 245 Hz for some reason. This should go away after some power cycling or recentering using the magic wand.

I noticed some anomalies in the mechanical setups at the ends:

  1. Some junk has been stored on top of the EX seismometer. Please never, even temporarily, store your power supplies, tools, or donutsfrown on top of the vibration sensitive sensors. Just put it on the floor and improve your carma.
  2. The EY seismometer has some fishy wires being fished between the can and the rubber seal. This is verboten. That seal must be flush to prevent pressure fluctuations and wires in there will ruin the smooth contact permanently. Temperature sensor wires must go through the grantie block feed-through or else its pointless.
  3. The flimsy insulation on the EY seismo is waay toooo mickey mouse. Real thermal insulation should be done using the yellow foam that Jenne used for the seismo huddle test. This flimsy silvery stuff is OK for making hats and mittens and beer cozy's, but its not research grade foam.
Attachment 1: 1goodday.png
1goodday.png
  12391   Wed Aug 10 10:32:44 2016 SteveUpdateSEIworking Guralps as they are

The saga has started here  We have to give credit to the Boss who fixed it. The seismometers themself are not labeled yet.

Atm6  added on 8-12-2016   EX needed to be centered

Thanks to Max for the nice plost at summery pages

 

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InterfboxOutpFixed.png
Attachment 2: GuralpsCoherences.png
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GurInterfBox.jpg
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EX.jpg
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EY.jpg
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EX_EY.png
  12404   Fri Aug 12 14:37:34 2016 SteveUpdateSEIworking seismometers as they are

2.1 mag earth quake in Norhten Ca

Our seimometers need professorial centering. Related electronics must be checked too.

Quote:

The saga has started here  We have to give credit to the Boss who fixed it. The seismometers themself are not labeled yet.

Atm6  added on 8-12-2016   EX needed to be centered

Thanks to Max for the nice plost at summery pages

 

 

Attachment 1: eq_2.1m_Geysers_CA.png
eq_2.1m_Geysers_CA.png
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eq2.1m_GeysersCA.png
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oscillations.png
  12778   Tue Jan 31 18:51:07 2017 gautamUpdateSEISeismic Rainbow Strip - myths debunked

I've been suggesting that there may be something wonky with the Seismic Rainbow Striptool on the wall for the last couple of weeks. Here are a few things that were verified today.

  1. If you want to restore the StripTools in the control room, just run /opt/rtcds/caltech/c1/scripts/general/startStrip.sh. I have verified as of today that this works, and in future, any changes to channels/limits/colors of traces etc should be reflected in this script.
  2. Though some of the BLRMS bands have looked anomalous over the last few weeks, in particular the 0.3-1Hz band. The attached 120 day trend plot suggests that there hasn't been any dramatic change recently. In fact, looking on the summary pages, Rana noticed that today was an unusually low 0.3-1Hz activity day..
Attachment 1: Seis_BLRMS.png
Seis_BLRMS.png
  12977   Mon May 8 21:53:56 2017 ranaSummarySEIattempt to get seismic BLRMS minute trend

I tried to get some minute trend data today, but was unable to get it from inside or outside the control room using our matlab or python tools.

It seems the NDS2 interface will not work anywhere since it needs our minute trends to be written as frames; in the last version that Jamie left us, our minute trend frame files are not being written since they lead to periodic daqd crashes.

From inside the control room, we can get the minute trend (only with DataViewer). I've attached 30 days of BS_X just to show its real.

We can get the numerical data from the Grace plot window using the menu option Data->Export->ASCII.

You must select all of the 'Write Sets' to get all of the traces in the plot window. The resulting ascii file is not in a great format, but its not terrible.

Attachment 1: BLRMS_trend.png
BLRMS_trend.png
  13505   Fri Jan 5 19:19:25 2018 ranaConfigurationSEIBarry Controls 'air puck' instead of 'VOPO style' breadboard

We've been thinking about putting in a blade spring / wire based aluminum breadboard on top of the ETM & ITM stacks to get an extra factor of 10 in seismic attenuation.

Today Koji and I wondered about whether we could instead put something on the outside of the chambers. We have frozen the STACIS system because it produces a lot of excess noise below 1 Hz while isolating in the 5-50 Hz band.

But there is a small gap between the STACIS and the blue crossbeams that attache to the beams that go into the vacuum to support the stack. One possibility is to put in a small compliant piece in there to gives us some isolation in the 10-30 Hz band where we are using up a lot of the control range. The SLM series mounts from Barry Controls seems to do the trick. Depending on the load, we can get a 3-4 Hz resonant frequency.

Steve, can you please figure out how to measure what the vertical load is on each of the STACIS?

Attachment 1: mm_slm.jpg
mm_slm.jpg
Attachment 2: Screen_Shot_2018-01-05_at_7.25.47_PM.png
Screen_Shot_2018-01-05_at_7.25.47_PM.png
  13526   Wed Jan 10 16:27:02 2018 SteveConfigurationSEIload cell for weight measurement

We could use similar load cells   to make the actual weight measurement on the Stacis legs. This seems practical in our case.

I have had bad experience with pneumatic Barry isolators.

Our approximate max compression loads are 1500 lbs on 2 feet and 2500 lbs on the 3rd one.

Quote:

We've been thinking about putting in a blade spring / wire based aluminum breadboard on top of the ETM & ITM stacks to get an extra factor of 10 in seismic attenuation.

Today Koji and I wondered about whether we could instead put something on the outside of the chambers. We have frozen the STACIS system because it produces a lot of excess noise below 1 Hz while isolating in the 5-50 Hz band.

But there is a small gap between the STACIS and the blue crossbeams that attache to the beams that go into the vacuum to support the stack. One possibility is to put in a small compliant piece in there to gives us some isolation in the 10-30 Hz band where we are using up a lot of the control range. The SLM series mounts from Barry Controls seems to do the trick. Depending on the load, we can get a 3-4 Hz resonant frequency.

Steve, can you please figure out how to measure what the vertical load is on each of the STACIS?

 

Attachment 1: stacis3LoadCells.png
stacis3LoadCells.png
  13570   Tue Jan 23 16:02:05 2018 SteveConfigurationSEIload cells

1500 and 2000 lbs load cells arrived from MIT to measure the vertical loads on each leg.

Quote:

We've been thinking about putting in a blade spring / wire based aluminum breadboard on top of the ETM & ITM stacks to get an extra factor of 10 in seismic attenuation.

Today Koji and I wondered about whether we could instead put something on the outside of the chambers. We have frozen the STACIS system because it produces a lot of excess noise below 1 Hz while isolating in the 5-50 Hz band.

But there is a small gap between the STACIS and the blue crossbeams that attache to the beams that go into the vacuum to support the stack. One possibility is to put in a small compliant piece in there to gives us some isolation in the 10-30 Hz band where we are using up a lot of the control range. The SLM series mounts from Barry Controls seems to do the trick. Depending on the load, we can get a 3-4 Hz resonant frequency.

Steve, can you please figure out how to measure what the vertical load is on each of the STACIS?

 

Attachment 1: stacis3LoadCells.png
stacis3LoadCells.png
Attachment 2: DSC00025.JPG
DSC00025.JPG
Attachment 3: DSC00026.JPG
DSC00026.JPG
  13631   Tue Feb 13 21:22:44 2018 SteveUpdateSEIone load cells tested

Gautam and Steve,

The "called 225 lbs" steel crane load measured right on 102 kg

The trick to the measurment to maintain 1 mm gap to the central cilynder of the load cell.

The lead plate stabilized the large load.


gautam: some additional notes:

  1. the wiring on the Omega controller unit as given to us was wrong - I had to fix this on the D-sub connector in order to get the load cell to work. something to check for the other units.
  2. the main difficulty in doing this calibration run was that the readback is very sensitive to tilts of the load relative to the sensor.
  3. the problem is complicated by the fact that the load cell itself does not have a flat surface - it has a ring that protrudes above the flat face of the cylindrical load cell by a few mm as Steve mentioned.
  4. so in order to measure the weight of our stacks, we have to mitigate this problem and ensure that the full load of the stack is normally incident on the load cell - if the load cell itself is somehow torqued during the measurement because of the distribution of the load on it being uneven, we get an inaccurate measurement.
  5. In this calibration measurement, we think the error is <1% (true mass is 102kg, we measure 104kg on the meter which seems reasonable as the sum of the donut + lead plate)

Attachment 1: as_measured_102kg.jpg
as_measured_102kg.jpg
Attachment 2: sensor.jpg
sensor.jpg
Attachment 3: 1500lbs_load__cell.jpg
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  13806   Wed May 2 10:03:58 2018 SteveHowToSEIpreparation of load cell measurement at ETMX

Gautam and Steve,

We have calibrated the load  cells. The support beams height monitoring is almost ready.

The danger of this measurment that  the beams height changes can put shear and torsional forces on this formed (thin walled) bellow

They are designed for mainly axial motion.

The plan is to limit height change to 0.020" max

0, center oplev at X arm locked

1, check that  jack screws are carrying full loads and set height indicator dials to zero ( meaning: Stacis is bypassed )

2, raise beam height with aux leveling wedge  by 0.010"  on all 3 support point and than raise it an other 0.005"

3, replace levelling wedge with load cell that is centered and shimmed.     Dennis   Coyne pointed out that the Stacis foot has to be loaded at the center of the foot and formed bellow can shear at their limits.

4, lower the support beam by 0.005" ......now full load on the cells

Note: jack screw heights will not be adjusted or  touched.......so the present condition will be recovered

Quote:

We could use similar load cells   to make the actual weight measurement on the Stacis legs. This seems practical in our case.

I have had bad experience with pneumatic Barry isolators.

Our approximate max compression loads are 1500 lbs on 2 feet and 2500 lbs on the 3rd one.

 

 

Attachment 1: loadcellCAL500.pdf
loadcellCAL500.pdf
Attachment 2: 3loadcellwcontr.jpg
3loadcellwcontr.jpg
Attachment 3: loadcellLocation.pdf
loadcellLocation.pdf
Attachment 4: DSC01009.JPG
DSC01009.JPG
Attachment 5: jack_screw.jpg
jack_screw.jpg
Attachment 6: ETMX_NW_foot_STACIS.pdf
ETMX_NW_foot_STACIS.pdf
  13809   Thu May 3 09:56:42 2018 SteveHowToSEIpreparation of load cell measurement at ETMX

[ Dennis Coyne'  precision answer ]

Differential Height between Isolators

According to a note on the bellows drawing (D990577-x0/A), the design life of the bellows at ± 20 minutes rotational stroke is 10,000 cycles. A 20 minute angular (torsional) rotation of the bellows corresponds to 0.186" differential height change across the 32" span between the chamber support beams (see isolator bracket, D000187-x0/B).

Another consideration regarding the bellows is the lateral shear stress introduced by the vertical translation. The notes on the bellows drawing do not give lateral shear limits. According to MDC's web page for formed bellows in this size range the lateral deflection limit is approximately 10% of the "live length" (aka "active length", or length of the convoluted section). According to the bellows drawing the active length is 3.5", so the maximum allowable lateral deflection should be ~0.35".

Of course when imposing a differential height change both torsional and lateral shear is introduced at the same time. Considering both limits together, the maximum differential height change should be < 0.12".

One final consideration is the initial stress to which the bellows are currently subjected due to a non-centered support beam from tolerances in the assembly and initial installation. Although we do not know this de-centering, we can guess that it may be of the order of ~ 0.04". So the final allowable differential height adjustment from the perspective of bellows stress is < 0.08".   Steve:  accumulated initial stress is unknown.  We used to adjust the original jack screws for IFO aligment in the early days of ~1999. This kind of adjustment was stopped when we realized how dangereous it can be. The fact is that there must be unknown amount of accumulated initial stress. This is my main worry but I'm confident that 0.020" change is safe.

So, with regard to bellows stress alone, your procedure to limit the differential height change to <0.020" is safe and prudent.

However, a more stringent consideration is the coplanarity requirement (TMC Stacis 2000 User's Manual, Doc. No. SERV 04-98-1, May 6, 1991, Rev. 1), section 2, "Installation",which stipulates < 0.010"/ft, or < 0.027" differential height across the 32" span between the chamber support beams. Again, your procedure to limit the differential height change to < 0.02" is safe.

Centered Load on the STACIS Isolators

According to the TMC Stacis 2000 User's Manual (Document No. SERV 04-98-1, May 6, 1991, Rev. 1), section 2, "Installation", typical installations (Figure 2-3) are with one payload interface plate which spans the entire set of 3 or 4 STACIS actuators. Our payload interface is unique.

Section 2.3.1, "Installation Steps": "5. Verify that the top of each isolator is fully under the payload/interface plate; this is essential to ensure proper support and leveling. The payload or interface plate should cover the entire top surface of the Isolator or the entire contact area of the optional jack."

section 2.3.2, "Payload/STACIS Interface": "... or if the supporting points do not completely cover the top surface of each Isolator, an interface plate will be needed."

The sketch in Figure 2-2 indicates an optional leveling jack which appears to have a larger contact surface area than the jacks currently installed in the 40m Lab. Of course this is just a non-dimensioned sketch. Are the jacks used by the 40m Lab provided by TMC, or did we (LIGO) choose them? I beleive Larry Jones purchased them.

A load centering requirement is not explicitly stated, but I think the stipulation to cover the entire top surface of each actuator is not so much to reduce the contact stress but to entire a centered load so that the PZT stack does not have a reaction moment.

From one of the photos in the 40m elog entry (specifically jack_screw.jpg), it appears that at least some isolators have the load off center. You should use this measurement of the load as an opportunity to re-center the loads on the Isolators.

In section 2.3.3, "Earthquake Restraints" restraints are suggested to prevent damage from earth tremors. Does the 40m Lab have EQ restraints? Yes, it has

Screw Jack Location

I could not tell where all of the screw jacks will be placed from the sketch included in the 40m elog entry which outlines the proposed procedure.

Load Cell Locations

The sketch indicates that the load cells will be placed on the center of the tops of the Isolators. This is good. However while discussing the procedure with Gautam he said that he was under the impression that the load cell woudl be placed next to the leveling jack, off-center. This condition may damage the PZT stack. I suggest that the leveling jack be removed and replaced (temporarily) with the load cell, plus any spacer required to make up the height difference. Yes

If you have any further question, just let me know.

    Dennis

 

 

Dennis Coyne
Chief Engineer, LIGO Laboratory
California Institute of Technology
MC 100-36, 1200 E. California Blvd.

 

 

 

  13840   Mon May 14 08:55:40 2018 Dennis CoyneHowToSEIpreparation of load cell measurement at ETMX

follow up email from Dennis 5-13-2018. The last line agrees with the numbers in elog13821.

Hi Steve & Gautam,

I've made some measurements of the spare (damaged) 40m bellows. Unfortunately neither of our coordinate measurement arms are currently set up (and I couldn't find an appropriate micrometer or caliper), so I could not (yet) directly measure the thickness. However from the other dimensional measurements, and a measurement of the axial stiffness (100 lb/in), and calculations (from the Standards of the Expansion Joint Manufacturers Association (EJMA), 6th ed., 1993) I infer a thickness of 0.010 inch in . This is close to a value of 0.012 in used by MDC Vacuum for bellows of about this size.

I calculate that the maximum allowable torsional rotation is 1.3 mrad. This corresponds to a differential height, across the 32 in span between support points, of 0.041 in.

In addition using the EJMA formulas I find that one can laterally displace the bellows by 0.50 inch (assuming a simultaneous axial displacement of 0.25 inch, but no torsion), but no more than ~200 times. I might be good to stay well below this limit, say no more than ~0.25 inch (6 mm).

If interested I've uploaded my calculations as a file associated with the bellows drawing at D990577-A/v1.

BTW in some notes that I was given (by either Larry Jones or Alan Weinstein) related to the 40m Stacis units, I see a sketch from Steve dated 3/2000 faxed to TMC which indicates 1200 lbs on each of two Stacis units and 2400 on the third Stacis.

  16783   Mon Apr 18 14:52:47 2022 Ian MacMillanSummarySEISeismic Study of Buildings and Caltech Campus

[Ian, JC]

I want to take measurements of seismic noise at different places on Caltech's campus and in different buildings. I will try to use the accelerometer in my phone for this but first I must calibrate it (Against the 40m accelerometers). 

I placed my iPhone 11 pro next to the seismometers at the 40m MC as seen in Attachment 1.

The calibration from the instrument was done using cts/rthz * 1V/16384cts * 1/ampgain * g/10V * 10m/s^2/g. The ampgain for all was 100.

Next, I took 100 seconds of data on both the iPhone and the three orthogonal Wilcoxon accelerometers.

The ASD for both of the total acceleration is shown in Attachment 2

The ASD for the individual directions acceleration is shown in Attachment 3

The coherence between the individual directions acceleration and the 40m's individual directions is shown in Attachment 4. For this calculation, the 40m data were downsampled to roughly match the phone's sample rate. This coherence is not very good. It should be higher. Because the phone and 40m sensors were picking up the same data as the phone. Because of this I also looked at the coherence between the individual 40m sensors.

In Attachment 5 I look at the coherence between the individual 40m sensors. This should give me a good idea of whether this is some other issue giving me mow coherence. This plot shows that the coherence between the individual 40m sensors is much better than between the phone and the 40m sensors.

Now I wanted to see what kind of data the iPhone could get from real-world tests. I placed it in a number of locations described below and plotted their ASDs in Attachment 6. The locations are thus:

Identifier  Location Notes
QIL QIL Lab in the Sub-basement of west bridge In sub-basement not much activity when taking measurements.
WBSH West bridge sub-basement hallway on floor in hallway no activity around
WB1H West Bridge 1st floor Hall placed on the floor near pillar near stairs to LIGO offices on the ground floor of west bridge
40m desk on my desk at the 40m placed on the desk while people were walking around and I had my feet on the desk. should be noisy

Notice how at the low end the amplitudes follow the relative amplitudes I would expect. QIL and WBSH are the lowest then WB1H is noisier and 40m desk is the noisiest. However, this is only true up until about 0.5 Hz then they all overlap. Since I would expect the 40m desk should be much noisier at all frequencies I suspect that the phone accelerometer is not suitable for measurements higher than 0.5 Hz.

Possible Problems:

One possible problem with my measurement is that my phone was in a leather case. this may have damped out higher frequencies. Also, my phone was not weighed down or bolted to the floor. this stronger connection would make it better at detecting higher frequencies. I could repeat the experiment with no case and a weight on top of my phone.

What's next:

Since I don't think the phone can give me accurate data above 0.5Hz for quiet environments. It may not be suitable for this task. It would seem that the right instrument is the Wilcoxon 731A but it requires an amplifier that I can't track down.

 

I included all the data and code in the zip file in attachment 7

 

Attachment 1: IMG_0513.jpg
IMG_0513.jpg
Attachment 2: tot_acc_cal.pdf
tot_acc_cal.pdf
Attachment 3: indiv_acc_cal.pdf
indiv_acc_cal.pdf
Attachment 4: dec_Coherence.pdf
dec_Coherence.pdf
Attachment 5: 40m_self_Coherence.pdf
40m_self_Coherence.pdf
Attachment 6: tot_acc_testsites.pdf
tot_acc_testsites.pdf
Attachment 7: Calibration.zip
  16798   Thu Apr 21 17:32:35 2022 Ian MacMillanSummarySEISeismic Study of Buildings and Caltech Campus

[Rana, Ian]

We built a power supply for the accelerometer shown in Attachment 1 based on the diagram shown in the Wilcoxon manual and shown in attachment 2. We used a 9V power supply and a capacitor value of 680uF. We did not use a constant current diode. 

When hooked up to an oscilloscope we saw vibrations from hitting our hands on the table but we did not see the same amplitude in the negative and positive directions. For example, when I held the accelerometer and moved it down you would see a dip then a peak as the accelerometer accelerated down then accelerated up when I stopped the down word movement. But weirdly when I did the opposite (moved the accelerometer up the same dip then a peak appeared. This is a little concerning because it should be the opposite. it should be a peak then a dip. This in addition to the seemingly decreased sensitivity in one direction make me think that the accelerometer is broken.

I labeled the box with "might be broken" before I returned it to the cryo lab.

Attachment 1: IMG_1820.jpg
IMG_1820.jpg
Attachment 2: Screen_Shot_2022-04-21_at_5.52.51_PM.png
Screen_Shot_2022-04-21_at_5.52.51_PM.png
  6844   Thu Jun 21 09:01:18 2012 steveUpdateSTACISthe resurrection of STACIS -surf

There is a small wood cabinet under the south end flow bench, labeled STACIS.

Unit is complete with extension cards and cables.

Attachment 1: IMG_1364.JPG
IMG_1364.JPG
  6882   Wed Jun 27 14:18:30 2012 Yaakov SummarySTACISFirst week summary

The beginning of my first week was spent at various orientations and safety meetings, some for general SURF and some more specific to LIGO and the lab. In between these I started  work.

Jenne and I took out the spare STACIS and took it apart, taking out the circuit boards. I've spent some time looking through the boards and sketching various parts of the board in trying to understand the exact function without any useful technical diagrams (STACIS supplied us only with a picture of the board without components, not all that helpful). I think I now at least understand the basic block diagram of the circuitry: the STACIS geophone signal goes through a preamplifier and filters (the semi-circular board), and converts it into a signal for the PZT stacks. This signal then goes through a high voltage amplifer, and then goes to the five PZTs (3 in the z, one each in the x and y direction). The unit I am looking at has an extension board, which allows us to tap into the signal going into the preamp and the one leaving it. This should allow us to input our own signal instead of the geophone signal, and thereby drive the PZTs ourselves.

My next step, once I get a resistor to replace a burnt one on the high voltage amplifier, is to take a transfer function of the STACIS and see if it is possible to drive the PZT stacks with the cables from the extension board. If that does not work, I'll have to keep tracing the circuit to determine where to input our own signal.

  6905   Mon Jul 2 23:08:38 2012 YaakovUpdateSTACISTurning on STACIS

This past Friday I swapped out a burnt resistor on the spare STACIS unit I'm working with and powered it up. Here's the setup:

stacy1.JPG

And here's what happened:

X an Y directions: When I switched from open to closed loop (making the internal geophones provide feedback), the STACIS started making a loud noise- it seemed like it was oscillating uncontrollably.

Z direction: The same thing happened in z until I added some weight to the top of the STACIS- then it quieted down, and seemed to work okay. The geophone signal dropped considerably compared to the open loop signal, which is expected if the feedback is working.

Then I tried driving the PZTs with a signal from the SR785 network analyzer. With an amplitude of tens of mV and frequencies from around .1 to 200 Hz, I could see the accelerometers I mounted on top of the STACIS definitely register motion, which means I was successfully driving the PZTs.

 

Below are transfer functions of the STACIS as I drove the PZTs from .1 to 100 Hz at 10 mV. The top graph is open loop, the second is closed loop. These were measured with the internal geophones.

In the bottom graph, "A" is closed loop and "B" is open loop, where the transfer functions were taken with the accelerometers instead of the geophones.

geo_open.GIF

 

 geo_closed.GIF

SCRN0005.GIF

Attachment 2: geo_closed.GIF
geo_closed.GIF
  6908   Tue Jul 3 18:58:14 2012 YaakovUpdateSTACISMore transfer functions and netGPIB status

I'm still having issues with the STACIS oscillating uncontrollably with the slightest extra vibration, but with some more added weight both x and z direction are stable if you don't disturb the setup.

I took more transfer functions of the STACIS. In the last data I took Jenne pointed out that the geophone signals were not correlated well with the driving signal, so I increased the amplitude of the driving signal and am looking in x and y too instead of just z. 

Details of the driving signal: 25 mV, swept sine from 0.1 to 100 Hz from the SR785. 

NOTE: The data below was all transferred from the SR785 using netGPIB, which works fine, if anyone was interested in using it.

Open loop in the y direction, taken with the y geophone (magnitude on top, phase on bottom):

geo_open_y.png

Open loop in the x direction, taken with the x geophone (with some extra weight to try to make the closed loop more stable):

 geo_open_x.png

Open loop in the x direction, taken with accelerometer instead of geophone:

accel_open_x.png

  6963   Wed Jul 11 14:27:29 2012 YaakovSummarySTACISCurrent STACIS Status

The X and Y directions in the STACIS still both oscillate uncontrollably in closed loop, so I'll be doing my testing in Z for now. If I need to use the other axes I'll lower their gain with the pots and add weight to the STACIS platform to try to make it more stable.

Measurements I've taken for Z:

--Open loop gain, taken by driving the PZTs with a swept sine signal and measuring with both internal geophones and external accelerometers. These measurements look a lot like the plots supplied by the STACIS manufacturer, with a resonance at 15-16 Hz (X and Y also look good). Figure below was taken with geophones:

geo_open_z2.png

--Open loop gain, where the input is ambient seismic noise measured by one set of accelerometers on the floor and one set on top of the STACIS:

 ambient_open_z.png

--Closed loop gain, where the input is ambient seismic noise, and feedback is supplied by the geophones (like normal STACIS operation). There's a definite drop in the transfer function, as expected:

ambient_closed_z_geoFeed.png

--Open and closed loop transfer functions superimposed (the higher one is open):

openVclosed.GIF

I am currently working on using the less-noisy accelerometers to provide feedback instead of the geophones. I have found the right point before the extension board to input the accelerometer signal which is NOT the same as the Signal IN/OUT cables- those are at the end of the board, after amplifying and filtering. I want the accelerometer signal to go through the same circuitry as the geophone signal so that the noise of the sensors themselves can be compared.

Problem: Coherence isn't great between the accelerometer sets at low frequencies, which leads to a not very smooth transfer function. I might try using the shaker, because the larger motion may lead to better coherence between the accelerometers on top of the STACIS and at its base.

 

 

Attachment 1: geo_open_z.png
geo_open_z.png
  6969   Thu Jul 12 15:43:07 2012 YaakovUpdateSTACISNew input point, using accelerometers for feedback

 Here's a picture of where I am now inputting signals into the STACIS with the accelerometers (the orange and blue wires): 

new_input.JPG

I know this is the right point because I could see the geophone signal from these points . By inputting a swept sine signal into this point, I was able to take a transfer function of this first amplifier/filtering circuit board, which will be useful if I need to make my own filter for the STACIS:

cBoard_tFunction.png

I have unplugged the geophones and am inputting a signal from an accelerometer into this point. The accelerometers output a different signal than the geophones, so I am trying to modify the accelerometer signal to be closer to the geophone one. I've lowered the gain on all the pots for the z axis and put in several BNC attenuators to lower the accelerometer signal amplitude.

At the moment, using the accelerometers as feedback makes the platform vibration worse, which will hopefully be solved by some more attenuation or filtering of the accelerometer signal.

  6988   Wed Jul 18 13:53:34 2012 YaakovUpdateSTACISWeekly update

I have been working on substituting the internal geophones in the STACIS with accelerometers, and this week specifically I have been trying to modify the accelerometer signal so the STACIS PZTs respond properly.

The major problem was that the high signal amplitude caused the STACIS to oscillate uncontrollably, so I lowered all of the pots (for the z direction) and placed several BNC attenuators before the accelerometer signal enters the first amplifier board. The accelerometers now successfully provide feedback without making the STACIS unstable, as shown by this transfer function (the higher and flatter line is open loop, the lower is closed loop with accelerometers providing feedback):

really_accelFeed.GIF

The next step is to optimize the accelerometer feedback so it provides good isolation from 0.1 to 3 Hz, a span that the geophones introduced a lot of noise into. The accelerometers definitely don't introduce as much noise in that region, but don't seem to be doing much isolation either. I will also make some more quantitative plots of the platform motion (using the calibration value for the Wilcoxon accelerometers in the velocity setting with a gain of 1).

Some random discoveries I made this week which are relevant for STACIS testing:

1) Placing weight on the STACIS platform improves stability, but NOT if several blocks are placed on top of each other (they rub against each other, causing lots of vibrations).

2) The accelerometer that is providing feedback must be VERY securely fastened to the STACIS platform; even with three clamps there was extra motion that caused instability. Luckily, there's a convenient steel flange Steve showed me which has a hole that perfectly accommodates the accelerometer and doubles as a weight for the platform. Here is said flange, clamped to the STACIS platform with the accelerometer sitting in the center:

flange.JPG

 3) Using the shaker next to the STACIS (all on one platform) improves coherence between the base and platform accelerometers above around 10 Hz, but does nothing lower than that, which unfortunately is the region I'm most concerned with.

  7027   Wed Jul 25 12:00:21 2012 YaakovUpdateSTACISWeekly update

The past few days I've been working on making a noise budget for the STACIS that incorporates all the different noises that might be contributing.

The noises I am concentrating on are accelerometer noise, geophone noise, electrical noise, and ground noise. Noise from the PZT stacks themselves should be tiny according to various PZT spec sheets, but I haven't actually found a value for it (they all just say it's negligible), so I'll keep it in mind as a potential contributor.

Here's how I am determining accelerometer noise: I take two vertical accelerometers side by side, sitting on a granite block and covered in a foam box, and take the time series of both. Then I take the difference of the time series and calculate the PSD of that, which with the calibration factor of the accelerometers (the V/m/s sensitivity) I am able to find the noise in m/s/rtHz. The noise agreed with the accelerometer specs I found at low frequencies but was higher than expected at high frequencies, so I'm still investigating. If I can't find an obvious problem with my measurements I'll try the three-corner hat method (as per Jenne's recommendation), which would allow me to determine the noises of the independent accelereometers.

I tried a similar method for the geophone noise, but the value I came up with was actually higher than the accelerometer noise, which seems very fishy. I realized that the geophones were still connected to the STACIS circuitry when I took the measurements ,which was probably part of the problem. So this morning I disconnected the STACIS entirely and am looking at just the geophone signals which should give a more accurate noise estimate.

Once I have all the noises characterized, the next step is seeing how those noises affect the closed loop performance of the STACIS. I've been working on a block model that incorporates the different noises and transfer functions involved, and when I have the noises characterized I can test a prediction about how a certain noise affects the platform motion.

 

  7040   Thu Jul 26 16:08:59 2012 YaakovUpdateSTACISNoise plot update

I have a tentative noise plot for the STACIS that includes accelerometer noise, geophone noise, and platform motion with the STACIS off. (Accelerometer noise was measured for the VEL and NONE setting, which are settings on the accelerometer box which make the accelerometer signal correspond to velocity and acceleration, respectively. ) I'm focusing on sensor noise because this is the variable I am looking at changing, and knowing how the sensor noise translates into STACIS platform motion is therefore important.

stacy_noise.bmp

stacy_noise.fig

The accelerometer and geophone noise I determined as described in my last eLog (http://nodus.ligo.caltech.edu:8080/40m/7027) Along the way I found out several things of importance:

1) Horizontal geophones are ONLY horizontal geophones. This is obvious in retrospect, because the springs supporting the magnet inside must be oriented based on vertical/horizontal operation.

2) The geophones in the STACIS are GS-11D (geospace), with a sensitivity of 32 V/m/s (compared to about 3.9 V/m/s for the accelerometers in VEL setting).

3) The accelerometers have different V/m/s sensitivities. I noticed the voltage output of one was consistently higher than the other, leading to very high noise estimates, but then Jenne showed me the actual calibration factors of the individual accelerometers which differed by as much as 0.4 V/m/s (a few percent difference). Taking this into account made the noise plots much more reasonable, but variations in calibration could still create some error.

The accelerometer noise agrees fairly well with the specs on the Wilcoxon page (http://www.wilcoxon.com/prodpdf/731A-P31%2098079a1.pdf). The geophone noise seems surprisingly low; it is even better than the geophone below about 4 Hz. 

To see how this noise translates into actual platform motion, I took PSDs of the STACIS while it was off, on with accelerometer feedback, and on with geophone feedback (the "off" PSD is in the above noise plot). Using this data I'm working on estimating a transfer function that shows how the sensor noise translates to motion so I can come up with a sensor noise budget.

feedbacks.bmp

feedbacks.fig

This shows that the geophones are actually doing a better job of isolating than the accelerometers, which is not surprising if the noise plot is accurate and the geophones are actually lower noise. It must be noted, though, that the noise plot was for the horizontal geophones whereas the plot above is for the vertical axis which may have a different noise level. Also, the vertical have some extra isolation by being enclosed in a metal stack with rubber padding at its base.

The problem with the STACIS in the past was the differential motion it introduced. I think this might be because the horizontal isolation was not uniform for each chamber. This means that even what would be symmetric motion (no differential length change) would be translated to differential motion because one end is more fixed than the other. Having accelerometers or better-padded geophones (maybe like the vertical geophones) in the STACIS ought to help with this by making the horizontal isolation more consistent and thus reducing differential motion. So the key may not be the geophone noise as much as varying geophone sensitivities or variation in how well they're mounted in the STACIS. I can test this by swapping out the horizontal geophones with other spares, changing the tightness of the mount, and seeing if either of these changes the horizontal isolation significantly, since these are factors that may differ from unit to unit.

I will also compare horizontal closed loop response with geophone vs. accelerometer feedback to see if the geophones are only doing a good job in the above plot because of their extra padding (the vertical stack).

  7053   Mon Jul 30 17:24:45 2012 YaakovUpdateSTACISRevised sensor noise plot; dead PZT

The geophone noise in my last eLog was taken before any amplification of the signal, but what really matters is the noise after amplification, since it is this signal that the PZTs are driven by. The noise goes on to be amplified about 1000x before the geophone signal gets to the PZTs.

To obtain a more relevant noise plot, I multiplied the geophone noise by 1,000, the approximate gain of the amplification stage for the geophones (called the "compensator board", the semicircular board that sits toward the top of the STACIS). Below is a plot (sensor_noise.fig) that shows the noise for the geophones after amplification and the accelerometer noise (with accelerometers set with a gain of 100x, their highest).

sensor_noise.bmp

The actual signal from both these sensors has the right magnitude to drive the PZTs (whereas it was much too small in my last plot, where I looked at the sensors before any gain)- this means that for these sensors, both of which are outputting signals that are ready to provide feedback to the STACIS, the accelerometer noise is significantly lower than the geophone noise. This is good news, because it means that there could be a real advantage to using the accelerometers instead of the geophones.

In the process of investigating further advantages of the accelerometers, I believe I killed one of the horizontal PZTs in the spare STACIS (the eBay one). The story: I had that axis in closed loop, and I saw the STACIS shudder, heard a noise, and there was a faint acrid smell. I shut the STACIS off and took out the high voltage card at the base but couldn't find any visible signs of damage (like the current-limiting resistors which burn when a PZT shorts, acc. to old STACIS records). I then tried driving the PZTs with a sine wave, and there was no response in that axis (the other axes looked fine), which leads me to believe I either did unseen damage to the high voltage amplifier (for the y-axis) or killed the PZT itself.

Attachment 1: sensor_noise.bmp
ELOG V3.1.3-