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ID Date Author Typedown Category Subject
  2759   Sat Apr 3 11:35:47 2010 ranaConfigurationPSLReference Cavity PD Noise Spectrum

The units on this plot are completely bogus - we know that the thermal noise from the resonant part of the circuit is just V = sqrt(4*k*T*Z) ~ 3nV/rHz. Then the gain of the MAX4107 stage is 10. The output resistor is 50 Ohms, which forms a divide by 2 with the input impedance of the spectrum analyzer and so the bump in the dark noise should only be 15 nV/rHz and not microVolts.

Quote:

[Rana, Alberto]

This evening we measured the noise spectrum of the reference cavity PD used in the FSS loop. From that we estimated the transimpedance and found that the PD is shot-noise limited. We also found a big AM oscillation in correspondence of the FSS modulation sideband which we later attenuated at least in part.

This plot shows the spectrum noise from the RF output of the photodetector.

  2760   Sat Apr 3 16:07:40 2010 AlbertoConfigurationPSLReference Cavity PD Noise Spectrum

 I was aware of a problem on those units since I acquired the data. Then it wasn't totally clear to me which were the units of the data as downloaded from the Agilent 4395A, and, in part, still isn't.

It's clear that the data was in units of spectrum, an not spectral density: in between the two there is a division by the bandwidth (100KHz, in this case). Correcting for that, one gets the following plot for the FSS PD:

2010-03-29_FSS_PD_shotnoise_and_darknoise.png

Although the reason why I was hesitating to elog this other plot is that it looks like there's still a discrepancy of about 0.5dBm between what one reads on the display of the spectrum analyzer and the data values downloaded from it.

However I well know that, I should have just posted it, including my reserves about that possible offset (as I'm doing now).

Quote:

The units on this plot are completely bogus - we know that the thermal noise from the resonant part of the circuit is just V = sqrt(4*k*T*Z) ~ 3nV/rHz. Then the gain of the MAX4107 stage is 10. The output resistor is 50 Ohms, which forms a divide by 2 with the input impedance of the spectrum analyzer and so the bump in the dark noise should only be 15 nV/rHz and not microVolts.

Quote:

[Rana, Alberto]

This evening we measured the noise spectrum of the reference cavity PD used in the FSS loop. From that we estimated the transimpedance and found that the PD is shot-noise limited. We also found a big AM oscillation in correspondence of the FSS modulation sideband which we later attenuated at least in part.

This plot shows the spectrum noise from the RF output of the photodetector.

  2789   Mon Apr 12 16:20:05 2010 AlbertoConfiguration40m UpgradingREFL55 improved
During the commissioning of the AS55 PD, I learned how to get a much better rejection of the 11MHz modulation.
So I went back to REFL55 and I modified it using the same strategy. (Basically I added another notch to the circuit).
After a few days of continuous back and forth between modeling, measuring, soldering, tuning I got a much better transfer function.

All the details and data will be included in the wiki page (and so also the results for AS55). Here I just show the comparison of the transfer functions that I measured and that I modeled.

I applied an approximate calibration to the data so that all the measurements would refer to the transfer function of Vout / PD Photocurrent. Here's how they look like. (also the calibration will be explained in the wiki)

2010-04-12_REFL55_TF_model_to_meas_comparison.png.

The ratio between the amplitude of the 55Mhz modulation over the 11MHz is ~ 90dB

The electronics TF doesn't provide a faithful reproduction of the optical response.

  2805   Mon Apr 19 05:54:50 2010 ranaConfigurationPSLRC Temperature Servo Turned OFF temporarily

In order to measure the transfer function of the RC cavity's foam, I've turned off the servo so that the room temperature noise can excite it.

The attached plot shows a step response test from 2 weeks ago. Servo is nominally still working fine.

Attachment 1: Untitled.png
Untitled.png
  2808   Mon Apr 19 13:23:03 2010 josephbConfigurationComputersyum update fixed on control room machines

I went to Ottavia, and tried running yum update.  It was having dependancy issues with mjpegtools, which was a rpmforge provided package.  In order to get it to update, I moved the rpmforge priority above (a lower number) that of epel ( epel -> 20 from 10, rpmforge -> 10 to 20).  This resolved the problem and the updates proceeded (all 434 of them). yum update on Ottavia now reports nothing needs to be done.

I went to Rosalba and found rpmfusion repositories enabled.  The only one of the 3 repositories in each file enabled was the first one.

I then added priority listing to all the repositories on Rosalba.  I set CentOS-Base and related to priority=1.  I set CentOS-Media.repo priority to 1 (although it is disabled - just to head off future problems). I set all epel related to priorities to 20. I set all rpmforge related priorities to 10.  I set all rpmfusion related priorities to 30, and left the first repo in rpmfusion-free-updates and rpmfusion-nonfree-updates were enabled.  All other rpmfusion testing repositories were disabled by me.

I then had to by hand downgrade expat to expat-1.95.8-8.3.el5_4.2.x86_64 (the rpmforge version).  I also removed and reinstalled x264.x86_64.  Lastly I removed and reinstalled lyx. yum update was then run and completed successfully.

I installed yum-priorities on Allegra and made all CentOS-Base repositories priority 1. I similarly made the still disabled CentOS-Media priority 1.  I made all epel related repos priority 20.  I made all lscsoft repos priority=50 (not sure why its on Allegra and none of the other ones).  I made all rpmforge priorities 10.  I then ran "yum update" which updated 416 packages.

 

So basically all the Centos control room machines are now using the following order for repositories:

CentOS-Base > rpmforge > epel > (rpmfusion - rosalba only) > lscsoft (allegra only)

I'm not sure if rpmfusion and lscsoft are necessary, but I've left them for now.  This should mean "yum update" will have far fewer problems in the future.

 

  2849   Tue Apr 27 11:16:13 2010 josephbConfigurationCDSWiki page with CDS .mdl names, shared memory allocation

I've added a new page in the wiki which describes the current naming scheme for the .mdl model files used for the real time code generator.  Note, that these model names do not necessarily have to be the names of the channels contained within.  Its still possible to make all suspension related channels start with C1:SUS- for example.  I'm also allocating 1024 8 byte channels for shared memory address space for each controller and each simulated plant.

The wiki page is here

Name suggestions, other front end models that are needed long term (HEPI is listed for example, even though we don't have it here, since in the long run we'd like to port the simulated plant work to the sites) are all welcome.

  2873   Mon May 3 17:49:41 2010 ranaConfigurationPSLRC Temperature Servo Turned OFF temporarily

Quote:

In order to measure the transfer function of the RC cavity's foam, I've turned off the servo so that the room temperature noise can excite it.

The attached plot shows a step response test from 2 weeks ago. Servo is nominally still working fine.

 I've just now re-enabled the temperature control of the reference cavity can. Trend of the last 8 days is attached.

Attachment 1: rct.png
rct.png
  2875   Tue May 4 02:28:38 2010 ranaConfigurationPSLRC Temperature Servo Turned OFF temporarily

 

 My attempt to passively measure the transfer function of the foam failed fantastically.

As it turns out, the room temperature fluctuations inside the PSL box reach the 1 mK/rHz noise floor of the  AD590 (or maybe the ADC) at ~1-2 mHz. Everything at higher frequencies is noise.

So to see what the foam is doing we will have to do something smarter - we need a volunteer to disable the RC temperature servo from the EPICS screen and then cycle the PSL table lights every hour in the morning.

We'll then use our knowledge of the Laplace transform to get the TF from the step responses.

  2876   Tue May 4 06:32:58 2010 albertoConfigurationPSLRC Temperature Servo Turned OFF temporarily

Quote:

 

 My attempt to passively measure the transfer function of the foam failed fantastically.

As it turns out, the room temperature fluctuations inside the PSL box reach the 1 mK/rHz noise floor of the  AD590 (or maybe the ADC) at ~1-2 mHz. Everything at higher frequencies is noise.

So to see what the foam is doing we will have to do something smarter - we need a volunteer to disable the RC temperature servo from the EPICS screen and then cycle the PSL table lights every hour in the morning.

We'll then use our knowledge of the Laplace transform to get the TF from the step responses.

 more detailed instructions needed....

  2881   Wed May 5 02:37:55 2010 ranaConfigurationPSLRC Temperature Servo Turned OFF temporarily

Quote:

 more detailed instructions needed....

I showed Kiwamu and Alberto how to turn the lights on and off in the PSL. This is why Caltech is such a fine institution: most schools would have TAs delivering this kind of optics instruction.

We've turned off the RC temperature stabilization and the lights will supply the quasi-random heat input to the table and the cavity. Alberto and Kiwamu will be turning the lights on and off at random times.

The attached plot is the spectrum of temperature fluctuations of the room and the vacuum can with no stabilization from this weekend. I think the rolloff above 10 mHz is kind of fake - I had the .SMOO parameter set to 0.99 for both of these channels. I've just now set the .SMOO to 0 for both channels, so we should now see the true ADC or sensor noise level. It should be ~1 mK/rHz.

Attachment 1: Picture_7.png
Picture_7.png
  2901   Sun May 9 20:02:23 2010 ranaConfigurationSUSSUS filters deleted again to reduce CPU load on c1susvme2 again

On Friday, I deleted a bunch of filters from the c1susvme2 optics' screens (MC1,2,3 + SRM) so as to reduce the CPU load and keep it from going bonkers.

This first plot shows the CPU trend over the last 40 days and 40 nights. As you can see the CPU_LOAD has dropped by 1 us since I did the deleting.

40.png400.png

In the second plot (on the right) you can see the same trend but over 400 days and nights. Of course, we hope that we throw this away soon, but until then it will be nice to have the suspensions be working more often.

  2922   Wed May 12 12:32:04 2010 josephbConfigurationCDSModified /etc/rc.d/rc.local on megatron

I modified the /etc/rc.d/rc.local file on megatron removing a bunch of the old test module names and added the new lsc and lsp modules, as well as a couple planned suspension models and plants, to shared memory so that they'll work.  Basically I'm trying to move forward into the era of working on the actual model we're going to use in the long term as opposed to continually tweaking "test" models.

The last line in the file is now: /usr/bin/setup_shmem.rtl lsc lsp spy scy spx scx sus sup&

I removed mdp mdc mon mem grc grp aaa tst tmt.

  2923   Wed May 12 12:58:26 2010 josephbConfigurationCDSSetup fb to handle lsc, lsp models on megatron

I modified /cvs/cds/caltech/target/fb and changed the line "set controller_dcu=10" to "set controller_dcu=13" (where 13 is the lsc dcu_id number).

I also changed the set gds_server line from having 10 and 11 to 13 and 14 (lsc and lsp).

The file /cvs/cds/caltech/fb/master was modified to use C1LSC.ini and C1LSP.ini, as well as tpchn_C2.par (LSC) and tpchn_C3.par (LSP)

testpoint.par in /cvs/cds/caltech/target/gds/param was modified to use C-node1 and C-node2 (1 less then the gds_node_id for lsc and lsp respectively).

Note all the values of gds_node_id, dcu_id, and so forth are recorded at http://lhocds.ligo-wa.caltech.edu:8000/40m/Electronics/Existing_RCG_DCUID_and_gds_ids

  2938   Mon May 17 02:10:10 2010 KojiConfigurationIOOHow to lock / align the MC

Let me remind you how to lock and align the IMC

To lock

1. Open the doors for the IMC/OMC chambers. Open the manual shutter of the PSL just in front of the optical window

2. Run scripts/MC/mcloopson

3. Set the MC length path gain 0.3 / Set the MC total gain "+20"

4. If you want to avoid excitation of the mirrors by air turbulence, put a big plastic film and put three posters on the top and both the sides on the floor to block the wind go into the chamber.

To shut down

1. Run scripts/MC/mcloopsoff

2. Close the manual shutter, Remove the wind blockers, and the light door of the chambers

To align the MC

1. Tweak MC2 and MC3 to get maximum transmittion and/or minimum reflection.

  2939   Mon May 17 10:57:16 2010 steveConfigurationSUSdamping restored to ETMYs

ETMY-south sus damping was restored

  2943   Tue May 18 11:54:29 2010 steveConfigurationSAFETYpsl mechanical shutter is not working

As we learned yesterday, the PSL laser power out put mechanical shutter is not working in the remote mode. It only works in local manual mode.

Do not rely on the MEDM screen monitor readout! The position is only changing on the monitor. The main beam must be blocked before the output periscope.

  2947   Tue May 18 15:09:02 2010 steveConfigurationSAFETYPSL output shutter in order again

Quote:

As we learned yesterday, the PSL laser power out put mechanical shutter is not working in the remote mode. It only works in local manual mode.

Do not rely on the MEDM screen monitor readout! The position is only changing on the monitor. The main beam must be blocked before the output periscope.

Ben found the Sorenson 5V ps off. It was turned off since our last scheduled power outage. I wonder what else is running on 5V in the PSL? This power supply should be on the

"alarm handler"  list to avoid future repeat of this condition. However a real safety switch would have confirming position sensors of the shutter open or closed. Is there such thing at the sites?

  2957   Thu May 20 12:34:46 2010 kiwamuConfiguration40m Upgradingoptical breadboards with legs

Yesterday Steve and I revived two legs to mount some optical breadboards outside of the end table.

These legs had been used as oplev's mounts many years ago, but now they are served for 40m upgrading. These are really nice.

By putting them on the side of the end table, a mirror mounted on the top of the leg can reflect the beam outside of the end table.

Once we pick off the green beam from the end table to its outside, the green beam can propagate through the 40m walkway along the Y-arm.

So that we can measure the beam profile as it propagates.

These legs are also going to be used during mode matching of the vacuum optics.

Attachment 1: leg1_small.png
leg1_small.png
Attachment 2: leg2_small.png
leg2_small.png
  2965   Fri May 21 08:28:29 2010 steveConfigurationVACTP3 turned off

Quote:

[Jenne, Kiwamu, and Steve via phone]

Around 9:30pm, Kiwamu and I came back from dinner, and were getting ready to begin the beam scan measurements.  I noticed that one of the vacuum pumps was being very loud.  Kiwamu noted that it is the fore pump for TP3's turbo, which he and Steve replaced in January (elog 2538).  We had not noticed these noises before leaving for dinner, around 8pm.

We called Steve at home, and he could hear the noise through the phone. He said that even though it was really loud, since it was reading 3.3mTorr (on the display of the controller, in the vacuum rack just above head-height) which is close to the nominal value, it should be fine to leave.  He will check it out in the morning.  If it had been reading at or above ~1Torr, that's indicative of it being really bad, and we would have needed to shut it off.

For future reference, in case we need to turn it off, Steve said to use the following procedure:

1. Close VM3, to isolate the RGA, which is what this pump is currently (while we're at atmosphere) pumping on.  I don't know if there are other things which would need to be shut at this stage, if we were at vacuum nominal.

2. Close VM5, which is right in front of TP3, so TP3's pump is just pumping on itself.

3. Push the "Stop" button on the Turbo controller for TP3, in the vacuum rack, about waist level.  Turning off the turbo will also turn off the fore pump.

UPDATE, 1am: The controller in the rack is reading 3.1mTorr, so the pump, while still noisy, still seems to be working.

 The foreline pressure of TP3 is 2.9 mTorr  The drypump is loosing it's bearing and it is very noisy.

V3, V5 closed and TP3 small turbo controller off. This turned off the noisy forepump that has to be replaced.

RGA is running at cc4 2e-6 Torr

The RGA was turned off at cc4 1e-5 Torr

  2970   Fri May 21 16:37:35 2010 steveConfigurationVACtp3's drypump replaced

Bob replaced the tipseal in an other drypump and I swapped it in. TP3 turbo is running again, it's foreline pressure is 40 mTorr. The RGA is still off

  2972   Mon May 24 07:53:57 2010 steveConfigurationPEMair cond. just turned ON

IFO room temp 27.5C , Please remember to turn AC back on !

Attachment 1: acoff.jpg
acoff.jpg
  2980   Tue May 25 09:12:46 2010 kiwamuConfigurationGreen Lockingeffect from air conditioner

We should completely turn off the air conditioner when working on green locking.

Even if green beams propagates inside of chambers, the air conditioner does affect the spatial jitter of the beam. 

The attached picture was taken when Steve and I were seeing how the green beam jittered. 

At that time the beam was injected from the end table and going through inside of the ETM, the ITM and the BS camber.

Eventually it came out from the camber and hit the wall outside of the chamber. It was obvious, we could see the jittering when the air cond. was ON.

Attachment 1: green_spot.png
green_spot.png
  2996   Wed May 26 22:22:03 2010 AlbertoConfiguration40m UpgradingArm cavity length

The second sideband is resonant in the arms for a cavity length of 37.9299m.

The nearest antiresonant arm lengths for f2 (55MHz) are 36.5753m and 39.2845m.

If we don't touch the ITMs, and we use the room we still have now on the end tables, we can get to 37.5m.

This is how the power spectrum at REFL would look like for perfect antiresonance:

reflRFpowerVsArmLength_3658m.png

And this is how it looks like for 37.5m:

reflRFpowerVsArmLength_3750m.png

Or, god forbid, we change the modulation frequencies...

  3015   Sun May 30 15:33:21 2010 AlbertoConfigurationIOOmode cleaner and air conditioning

The mode cleaner is locked and the air conditioning is full on. So the the air conditioning doesn't seem to be so important for the lock to hold.

  3016   Sun May 30 15:36:22 2010 AlbertoConfigurationPSLIMC periscope shutter

Two days ago I opened the PSL shutter by switching the switch on the shutter driver. That caused the shutter's switch on the medm screen to work in reversed mode: open meant closed and closed meant open.

I fixed that. Now the medm screen switch state is correct.

  3023   Tue Jun 1 06:30:38 2010 KojiConfiguration40m Upgradingeffect of the arm length

I checked the effect of the arm length to the reflectance of the f2(=5*f1) sidebands.

Conclusion: If we choose L_arm = 38.4 [m], it looks sufficiently being away from the resonance
We may want to incorporate small change of the recycling cavity lengths so that we can compensate the phase deviation from -180deg.


f1 of 11.065399MHz is assumed. The carrier is assumed to be locked at the resonance.

Attachment 1: (Left) Amplitude reflectance of the arm cavity at f2 a a function of L_arm. (Right) Phase
Horizontal axis: Arm length in meter, Vertical Magnitude and Phase of the reflectance

At L=37.93 [m], f2 sidebands become resonant to the arm cavity. Otherwise, the beam will not be resonant.

Attachment 2: close-up at around 5 f1 frequency.
The phase deviation from the true anti resonance is ~0.7deg. This can be compensated by both PRC and SRC lengths.

Attachment 1: arm_cavity1.png
arm_cavity1.png
Attachment 2: arm_cavity2.png
arm_cavity2.png
Attachment 3: arm_cavity.nb.zip
  3081   Wed Jun 16 18:12:16 2010 nancyConfigurationComputers40MARS

i added my laptop's mac address to teh martian at port 13 today.

 

  3083   Wed Jun 16 18:44:07 2010 AlbertoConfigurationComputers40MARS

Quote:

i added my laptop's mac address to teh martian at port 13 today.

 

No personal laptop is allowed to the martian network. Only access to the General Computing Side is permitted.

Please disconnect it.

  3109   Wed Jun 23 18:05:00 2010 KojiConfigurationPSLFSS SLOWDC should be ~-4.0

FSS SLOWDC slider is at around 0.

Please someone relock this at ~-4.0 to exploit some last juice of the fruit.

See this entry for the details of the operating point.

 

Attachment 1: C1PSL_FSS.png
C1PSL_FSS.png
  3110   Wed Jun 23 23:08:30 2010 ranaConfigurationPSLFSS SLOWDC should be ~-4.0

 

  3133   Tue Jun 29 11:48:17 2010 JenneConfigurationSAFETYBack in LASER HAZARD mode.

[Steve, Kiwamu, Jenne]

The 40m is now back in Laser Hazard mode.  Safety glasses are required for entry into the LVEA / IFO room.

  3135   Tue Jun 29 14:16:35 2010 KojiConfigurationSAFETYBack in LASER HAZARD mode.

The insects and the laser trouble... Strange coincidences with LHO surprised me, but now I have been relieved.

Quote:

[Steve, Kiwamu, Jenne]

The 40m is now back in Laser Hazard mode.  Safety glasses are required for entry into the LVEA / IFO room.

 

  3151   Wed Jun 30 23:03:46 2010 ranaConfigurationIOOPower into MC restored to max

Kiwamu, Nancy, and I restored the power into the MC today:

  1. Changed the 2" dia. mirror ahead of the MC REFL RFPD back to the old R=10% mirror.
  2. Since the MC axis has changed, we had to redo the alignment of the optics in that area. Nearly all optics had to move by 1-2 cm.
  3. 2 of the main mounts there had the wrong handedness (e.g. the U100-A-LH instead of RH). We rotated them to some level of reasonableness.
  4. Tuned the penultimate waveplate on the PSL (ahead of the PBS) to maximize the transmission to the MC and to minimize the power in the PBS reject beam.
  5. MC_REFL DC  =1.8 V.
  6. Beams aligned on WFS.
  7. MC mirrors alignment tweaked to maximize transmission. IN the morning we will check the whole A2L centering again. If its OK, fine. Otherwise, we'll restore the bias values and align the PSL beam to the MC via the persicope.
  8. waveplates and PBS in the PSL were NOT removed.
  9. MC TRANS camera and QPD have to be recentered after we are happy with the MC axis.
  10. MC REFL camera has to be restored.
  11. WFS measurements will commence after the SURF reports are submitted.

We found many dis-assembled Allen Key sets. Do not do this! Return tools to their proper places or else you are just wasting everyone's time!

 

  3152   Thu Jul 1 10:26:34 2010 steveConfigurationVACpd68 at vacuum normal state

Slow pump down _pd68 has reached the vacuum normal state.  CC4_Rga region is pumped now. The RGA is still off.

Precondition to this pump down:                                                                                                                                                                                                                                                           129 days at atm,                                                                                                                                                                                                                                                                                         ITMs replaced. MMT, oplev and other components were removed from BSC, ITMCs. New MMT mirrors are in.                                                                                                             IOO_access_connector was out. The end chambers were not opened.

 

Attachment 1: pd68slow2d.jpg
pd68slow2d.jpg
Attachment 2: pem134d.jpg
pem134d.jpg
  3170   Wed Jul 7 17:18:57 2010 AlbertoConfigurationElectronicsStochmon and LSC AM Stabilizer Decomissioned
Today I disconnected and removed the Stochmon box from the 1Y2 rack.
I also removed the amplifiers that were sitting on the PSL table, next to the RF AM PD, that were connected to the Stochmon. I pulled back the RG cable and the power cables that went from the PSL table to the 1Y1 and 1Y2 racks.
The power cable, all rolled up, is now sitting on the floor, inside the 1Y1 rack and one of its end is still connected to the power of the rack. We'd like to turn off the entire rack in order to safely remove it. But since the laser driver is there too, we should do it the first time we have to turn off the rack for some other reason.

I also removed two of the AM stabilizers from the 1Y2 rack. The other one, which is currently running th MC modulations, is still in the rack, and there it is going to remain together with its distribution box.

I stored both AM stabilizers and the Stochmon box inside the RF cabinet down the East arm.

  3173   Wed Jul 7 22:52:38 2010 rana, nancyConfigurationIOObad length control offset for the MC

Rana found out that a connection was bad in the shown place, due to which the MEDM screen was showing bad offset for length control.

Basically, the offset slider value would not go into the system because of that bad connection, and was locking the mode cleaner at the wrong location.

Attachment 1: P7070251.jpg
P7070251.jpg
Attachment 2: Screenshot.png
Screenshot.png
  3178   Thu Jul 8 15:19:27 2010 josephb, kojiConfigurationComputersAdded Zonet camera to IP table on linux1

We gave the Zonet camera the IP 192.168.113.26 and the name Zonet1.

We did this by modifying the /var/named/chroot/var/named/113.168.192.in-addr.arpa.zone and martian.zone files on linux1 as root.

  3191   Mon Jul 12 02:21:01 2010 KojiConfigurationASCResurrection of MC WFS

I have resurrected the MC WFS on Friday night.
I have uncommented the WFS part of the MC autolocker.
The WFS total gain was empirically set to 0.1 such that the loops have no instability.

The loops somewhat worked through the weekend although they seemed to have the drift of the operating points
in accordance with the WFS spot.

  3206   Tue Jul 13 13:56:29 2010 GopalConfigurationOptic StacksVitol Material Properties

Viton flouroelastomers have somewhat variable material properties. The following parameters are being used for eigenfrequency analysis.

Young's Modulus: 72,500-87,000 psi (cite: http://www.row-inc.com/pfa.html) *Accurate for PFAs

Poisson's Ratio: 0.48-0.50 (cite: http://www.engineeringtoolbox.com/poissons-ratio-d_1224.html) *Accurate for rubber

Density: 1800 kg/m^3 (cite: http://physics.nist.gov/cgi-bin/Star/compos.pl?matno=275)

  3222   Wed Jul 14 19:00:56 2010 GopalConfigurationOptic StacksVitol Material Properties, REVISED

Quote:

Viton flouroelastomers have somewhat variable material properties. The following parameters are being used for eigenfrequency analysis.

Young's Modulus: 72,500-87,000 psi (cite: http://www.row-inc.com/pfa.html) *Accurate for PFAs

Poisson's Ratio: 0.48-0.50 (cite: http://www.engineeringtoolbox.com/poissons-ratio-d_1224.html) *Accurate for rubber

Density: 1800 kg/m^3 (cite: http://physics.nist.gov/cgi-bin/Star/compos.pl?matno=275)

 The Young's Modulus for PFA turned out to be orders of magnitude greater than for Viton. The revised values produced much more accurate results:

Young's Modulus for Viton-75: 1950 psi or 6.6 MPa

(Courtesy Row, Inc. and Steve Vass)

This website contains other details: http://www.row-inc.com/viton.html

  3227   Thu Jul 15 12:21:08 2010 AlbertoConfigurationLSCPRC and SRC length adjustements

Lately I've been trying to calculate the corrections to the recycling cavity lengths that would compensate for the phase that the sidebands will pick up from the arms in the upgraded interferometer.

To do that calculation , I tried two quite different ways, although equivalent in principle. They both use the optickle model of the 40m, but the calculation is made differently.

In the first way, I looked directly at the phases of the field: phase of [input field] / [reflected field], phase of [input field at PRM] / [transmitted field at SRM].

In the second way I looked at the demodulation phases of the LSC signals.

The first way is much simpler, especially from a computational point of view. It is the first I tried several weeks ago, but then I had abandoned because back then I thought it wasn't the correct way.

Anyway, both ways gave me the same results for the PRC length.
For the SRC length, the first way has given me a clear outcome. On the other hand, the second way has produced a less clear result.

According to these results, these would be the proposed adjustements to the cavity lengths:
dl(PRC) = -0.0266 m; dl(SRC) = 0.0612 m

I) 1st Way
a) case of arms ideal length (33.86 m)

sidebandPhaseRotation_73433447384.png sidebandPhaseRotation_73433447590.png


b) case arm length = 38.40 m

PRC

 sidebandPhaseRotation_73433447960.png zoom -> sidebandPhaseRotation_73433448864.png

SRC

sidebandPhaseRotation_73433445372.png zoom -> sidebandPhaseRotation_73433449354.png


II) 2nd Way
a) case of arms ideal length (33.86 m)

 demodPhaseVsRecCavLengths_73432637363.png


b) case arm length = 38.40 m

demodPhaseVsRecCavLengths_73433237349.png

  3228   Thu Jul 15 15:57:10 2010 KojiConfigurationLSCPRC and SRC length adjustements

Tell me whether it is correct or not. Otherwise I won't be able to sleep tonight.

Quote:

According to these results, these would be the proposed adjustements to the cavity lengths:
dl(PRC) = -0.0266 m; dl(SRC) = 0.612 m

  3229   Thu Jul 15 16:16:51 2010 AlbertoConfigurationLSCPRC and SRC length adjustements

Quote:

Tell me whether it is correct or not. Otherwise I won't be able to sleep tonight.

Quote:

According to these results, these would be the proposed adjustements to the cavity lengths:
dl(PRC) = -0.0266 m; dl(SRC) = 0.612 m

 Sorry. I was in a rush to go to the LIGO "all hands" meetings when I posted that elog entry, that I forgot a zero in the SRC length value. The correct values are:

dl(PRC) = -0.0266 m; dl(SRC) = 0.0612 m

The cavity absolute lengths are then:

L(PRC) = 0.5/2/f1*c - 0.0266 = 6.7466 m

L(SRC) = c/f2 + 0.0612 = 5.4798 m

where c is the speed of light; f1 = 11065399 Hz; f2 = 55326995 Hz

  3239   Fri Jul 16 16:12:31 2010 AlbertoConfigurationComputersc1susvme1/2 rebooted

Today I noticed that the FE SYNC counters of c1susvme1/2 on the RFM network screen were stuck at 16384. I tried to reboot the machines to fix the problem but it didn't work.

The BS watchdog tripped off when I did that, because I had forgotten to disable it. I had to wait for a few minutes before it settled down again.

Later I also re-locked the mode cleaner. But before I could do it, Rana had to reduce the MC_L offset for me.

  3242   Sun Jul 18 20:50:03 2010 ranaConfigurationIOOMC TRANS optics changed

To make the beam on the MC trans camera bigger, I removed the lens + ND filter that was in that path.

The camera was getting the transmission through a BS1-33 (33% reflector). The reflection went to the TRANS QPD. I changed

the R=33% into an HR mirror (Y1-45P) so now the camera has a nice beam. The QPD was now saturating so I put a ND06 into that path

so now the TRANS_SUM is ~4.5-5 V when the MC is aligned.

The MC was also misaligned and failing to lock all weekend (why??) so I aligned the MC mirrors to get it to acquire again. Since we want to

collect MC seismic data, please make sure the MC is locked and running after finishing with your various MC or PSL work (this means YOU).

  3248   Tue Jul 20 08:04:31 2010 steveConfigurationVACslow vent has started

The PSL shutter was closed. The beam path  blocked two places. High voltage power supplies to IOO and OMC PZT were checked to be off. Oplevs are off. 

The south arm green cavity was misaligned yesterday

We would like to keep the vent speed at 1 torr / min. I'm venting with N2 now up to 25 PSI. We have 3 cylinder  of instrument grade air inside the lab. Additional supply will arrive later. It can be as late as 1pm

  3252   Tue Jul 20 17:38:16 2010 GopalConfigurationOptic StacksStack Type Clarifications

Some clarification is warranted regarding the different shapes of stacks. Corrections are appreciated:

1) The single-leg stack that I just completed should function as a working model for the IO, OO, and MC1/3. Rana commented, however, that the current dimensions are slightly off for MC1/3 (which makes sense since I could only find drawings for the IOC). If anyone knows the whereabouts of similar drawings for MC1/3, I'd much appreciate it.

2) A triple-leg stack can model the BS, ITMX, and ITMY chambers. I don't have exact dimensions for these, but I can make decent approximations from to-scale stack drawings. I'll probably work on a model for this style next, since at least I have some information regarding this version.

3) The MC2 chamber has its own stack model, about which I haven't found any drawings in the binders. I can't start on MC2C at all until I find such drawings.

  3261   Wed Jul 21 17:41:17 2010 GopalConfigurationOptic StacksPictures of Stacks

Now that venting is complete, this is a request for anyone who opens any chamber:

1) Please notify me immediately so I can take pictures of the stacks in that chamber.

2) If I'm not around, please take a few pictures for me. I'm most interested in the shape, number of layers, size, and damper arrangements of each stack.

This is most important for the MC1/MC3 chamber, MC2 chamber, and BS/ITMX/ITMY chambers.

Thanks!

  3331   Fri Jul 30 09:55:34 2010 steveConfigurationVACslow pumpdown has started

Bob and Steve closed BS chamber with the help of the manual Genie lift and the pump down started. The PSL shutter was closed and manual block was placed in the beam path. High voltage power supplies were checked to be off.

Pumping speed ~ 1 Torr/min was achieved at  1/8 of a turn opened roughing valve RV1

Attachment 1: slowpd5hr.jpg
slowpd5hr.jpg
  3332   Fri Jul 30 12:46:38 2010 KojiConfiguration40m UpgradingBS chamber status
Attachment 1: BS_layout_Jul_29_2010.png
BS_layout_Jul_29_2010.png
ELOG V3.1.3-