Leak tested Chevron Baffle nipple @ IP12 location (X-end)

Helium leak tested nipple-to-GV 16.5" joint as well as nipple welds with background of 2 x 10-9 torr*L/sec -> OK.  Currently there is a zero-length reducer with a 1 1/2" valve installed in place of the nominal 2500 L/sec ion pump which has been removed and is being refurbished.  

Shift Transition - Day

TITLE: 04/19 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Planned Engineering
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    Wind: 14mph Gusts, 9mph 5min avg
    Primary useism: 0.07 μm/s
    Secondary useism: 0.19 μm/s
QUICK SUMMARY:

Front end laser error message

Noticed the "NPRO switchoff during run" error flagged this morning.  The front end laser was still running,
seemingly without problems.  First time I've ever seen this error message under these circumstances.  Every
other time, the NPRO was clearly off.

IFO Aligned to new PSL pointing, OMC loops closed and mode scanned

Dan Brown, Alexei, Sheila, Nutsinee, Terry, TVo

After lunch we were able to get the PSL beam after the new PMC was installed and aligned,  Sheila adjusted the FSS gain to stabilize the loop and the IMC locked pretty easily after that.  We moved the mode cleaner optics pretty close to the alignment from February 8th when we had the X-arm peak.  Then we adjusted PR2 and PRM to flash PRX and MICH as well and got the beam down to HAM6.  The AS_A and AS_B centering loops converged pretty quickly and we offloaded the loop's control signal to the OM1 and OM2 alignment sliders.  We also closed the OMC_ASC loops and roughly offloaded to the OM3 and OMC alignment sliders.  

Before, when I closed the OMC angular loops, I didn't actually turn the integrators. But when I tried this time, it would push the beams off the QPD so after some hunting around I narrowed down the error to  a change in the phasing.  But I'm not sure where it came from.  Anyway, I added a negative sign in the POS_X gain filter bank and that seemed to make the loops converge nicely.  Not only that, the TEM01 mode in our new OMC mode scan was smushed down significantly, so we can get a more accurate mode-matching estimate.

Attachments:

• Alignment sliders
• OMC Mode Scan DTT Template
• OMC Mode Scan Data

Electric field meter spectra with and without shielding, and RC decay time

[Craig Niko Georgia]

Conclusions:

    - We have taken electric field spectra with the foil door off, foil door on, and a foil house built around the EFM. Spectra coming soon.
    - We also applied a DC voltage to the calibration plates and looked at the decay time at the output of the EFM, which should give us a confirmation of the EFM resistor (should be 1 TOhm)


We went back to end-X to take more electric field meter (EFM) data. We wanted to find out whether the low frequency slope shown in our previous log post is due to sensor noise or fields within the chamber. We were also interested in confirming the dependence of the 60 Hz and 30 Hz peaks on the presence of the foil door. We made a foil house for the EFM which attached to the rod, and were careful not to ground the sensor plates (picture 1). The soft door cover was on for all these measurements. These three spectra will be posted shortly.

We also used a voltage calibrator to apply a DC voltage to the calibration plates, and measure the decay time of the voltage out of the EFM. The reason we checked this was to confirm the 1e12 Ohm resistor. The time constant of the RC circuit formed by the capacitance of the calibration-sensor plate (~7.6 pF), and the 1e12 Ohm resistor should be 7.6 seconds.
    - Note that we were using larger spacers between the sensor plates and calibration plates as we (embarrassingly) lost track of the old ones, and so cleaned up and used the spacers from the first EFM, the capacitances were measured to be 7.8 pF from calibration plate to +X sensor plate, and 7.5 pF from calibration plate to -X sensor plate.
    - We applied 3V DC continously to the calibration plates.
    - The decay is shown in the 2nd photo, the two traces are the positive and negative x outputs (generally we do a differential measurement, this is not a very fancy scope). The decay time looks to me to be about 12 seconds (though it’s hard to tell since I can’t tell when exactly the voltage was applied, Crag can correct me here...), so perhaps our resistance is larger than expected.
 

Here are the results from the measurements Georgia described.

A couple of notes:
1) Our overall EFM noise is lower today than yesterday.
2) The EFM ambient electric field noise below 100 Hz still follows f^{-1.5}.  It seems like it is sensor noise, but the LT Spice model disagrees.
3) Our different foil configurations did not affect the overall noise floor, only the height of the 60 Hz line and some (probably acoustic) resonances.
4) The estimated displacement noise in plot 2 relies on many assumptions (zero charge on test mass, true measurement of ambient electric fields near the test mass, correct calibration from volts to electric field) and is posted for discussion purposes.

Some differences from my last ambient electric field post alog 41483:
1) Included Rich's LT Spice model of the EFM circuit noise.
2) Updated the calibration from calibration volts to electric field.  Estimated |E/V_Cal| ~ 38.9 (V/m)/V, based on the series capacitance between the calibration plate and the sensor plate (~11 pF), and the sensor plate to the grounded EFM body cube (~19 pF).  This explains the increased EFM noise from alog 41483.  Before I used |E/V_Cal| ~ 5 (V/m)/V, which I now believe is incorrect.

EDIT: After some notes from Sheila and Aaron Buikema, Plot 2 as it is is definitely untrustworthy.  It relies on the force coupling F = q E, where E is the ambient electric field and q is the charge on the test mass.  If the total charge on the test mass is 0, then F = 0, even with the ESD bias inducing a polarization on the test mass.

Reading the results of the RC decay experiment and the observation of a ~12 second time constant instead of the anticipated 7.6 seconds, I think the more likely conclusion is that the capacitance is larger than anticipated.  In an ideal world, the 10^12 ohm resistor has a 10% tolerance from the manufacturer.  Poor cleaning could certainly decrease the value of the resistor, but it seems unlikely that the resistor would be almost 60% higher in resistance.

I wonder if the assumed capacitances are accurate?  Was the 3V stimulus removed such that the calibration plate was no longer attached to the voltage source, or was the voltage stepped from 3V to 0V leaving the source still attached?  I have a picoammeter here at Caltech and I will try to establish the accuracy of the resistors.

Leak checked new 12" CFF joint on turbo side of new 10" valve at X-end

O-ring valve isolating Turbo Header from turbo fore line leaked so I had to run the QDP80 in addition to the leak detector during testing today -> shut down both this evening. 

 

Correct.  No leaks detected around this new joint.  

PZT Driver Chassis Issue Resolved

Tuesday night, about 8:30PM pacific time the PZT driver power supply for HAM6 and Squeezer tripped.  After checking the cabling and trying to restart the power supply, we determined that the PZT driver likely had a bad component.  The spare is still at Caltech, so we pulled the chassis from the rack and in the lab everything checked out ok (no bad components).  We discovered that the label on the power supply which indicated 100V at 2mA was incorrect.  With the addition of the squeezer, this supply is required to provide 110V and up to 100mA.  This label has been updated along with the correct procedure to bring the power supply back up from glitching.  This closes WP7439.

Nutsinee, Terry, Marc, Fil, Daniel

Fiber pulling update

I am working toward pulling more fibers to fill in some gaps in our fiber grouping scheme.  This has been slow going so far due to Windows updates (I promised Ryan that I would keep up to date on these in exchange for the ability to have the computer connected to the network).  So far I have spent ~1.5 days on Windows updates that apparently need to be done consecutively or the installation fails, and some Labview updates.  

Shift Summary - Day

TITLE: 04/18 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY:
LOG:

15:22 Untripped OM and SEI WDs in HAM6

15:28 Robert out to LVEA for equipment

15:46 Karen to Y arm stations for cleaning

15:48 APS on site

15:53 TvO out to LVEA to retrieve a laptop

16:00 Jason out to PSL

16:20 Jeff B out to LVEA

16:50 N and Terry out to HAM6

16:51 Verbal Alarms restarted_ crashed

16:53 Hugh out to LVEA to do property inventory

17:19 Marc to CER mez to check HV squeezer HV supply

17:24 Mark and Tyler back from EX

17:38 Jeff B back

17:42 Vac team out to MY

18:01 Hugh back

18:33 Marc out to floor to replace squeezer PZT supply

18:35 Hugh to EX for inventory

18:20 Dave B at EX for a SUSAUX computer reboot

18:50 Dave back

19:26 Marc back

19:28 Hugh back

19:49 Rick, Peter, and Jason out of the PSL

20:33 Ken out to the LVEA to breech the outside door for an electrical installation

20:35 Jonathan to restart FW0

20:37 Travis to EX to take pictures of weld mirrors

20:43 Ken back

20:44 Marc out to LVEA

20:45 Georgia, Craig, and Niko to EX to work in-chamber - EFM

20:49 N out to HAM6 table area

20:50 Hugh out to HAM6

20:55 Travis back

20:56 Corey out to LVEA- installing panel on squeezer table

20:57 Dave to MX to restart PEMMX

21:04 Cheryl out to the optics lab

21:23 Cheryl back

21:36 Corey back

21:39 Hugh back

21:41 Dave back to MX to try again

21:42 Tyler ad Mark out to LVEA - large equipment access area

21:48 N back

22:00 Site Weekly

 

SQZ Table Panels Installed

Completed installation of the (qty2) SQZ Table Enclosure rear panels (with duct nozzle).  Mark & Mark & Tyler cut these out for us after the Squeezer Team gave us finalized beam locations.  

CP4 gas N2 heater

Yesterday Ken D. with K&N Electric and Richard M. installed the new 28 A, 480 VAC variable transformer at MY to bypass the problematic SCR and power the GN2 heater. Today Kyle, Gerardo and I turned it on. We first flowed unheated, vaporized GN2 and let the temperature settle (~20C) and then ramped the variac to 40% power, until the temperature stabilized to ~85C. After lunch I increased it to 45% power and will wait till it stabilizes and will continue that trend until we reach 160C. The GN2 flow fluctuates between 20-60 scfhx100 with one full turn on draw valve. We may need to increase flow over time as the vaporizer cools down and the Dewar level decreases. The exhaust temperature is currently 65C.

IP12 valve + baffle installed

Mark D., Tyler G.

The Apollo crew installed a new 12" gate valve on IP12 port at end-X, along with chevron baffle and an adapter cap until a rebuilt ion pump returns from vendor (after pump down and perhaps after some commissioning). The baffle and cap were torqued on the valve at floor level and then the crane was used to carry the valve and torque the beam tube side flange. 

Prior, I assembled the baffle louvers with Gerardo in the VPW lab and then "top gunned" it at EX. All 12 bolts are torqued. Baffle nipple/housing is SN006. Chevron baffle assembly is SN004. We will leak check next.

 

OPO to OMC mode matching

Dan Brown, TVo

In alog 41504 we looked at the mode matching of the OPO beam to the OMC whilst varying an adjustable lens. With the lens positioned closest to the OPO we got the best (estimated) matching of ~80%. We wanted to know if moving the lens even closer would improve on this. The Finesse models suggest that moving the lens closer doesn't help and actually reduces the modematching (down to ~60%) as the waist gets too small, ~80% is about as good as it gets with the current setup.

Next we want to look at adjusting the lens closest to the OPO and perhaps trying different lens options in the model.

Details

The largest uncertainties we have are the lengths between all the optics. The model updates were mostly a combination of measurements and inferred lengths (from Solidworks models), I've tried to keep track of where these have come from in the LHO file. We we're able to get a reasonable agreement for the propagation of the OPO beam to the OMC for the "close" and "middle" positions on the translatable lens stage near the OPO, as can be seen in figure. The farthest position has a lot of astigmatism compared to the other two, so we're not sure if that's comparable to what the model predicts too much. To narrow down the beam shapes better, Nutsinee and Terry took another beamscan between ZM1 and HAM5. This allowed us to get a much better idea of the beam shape heading towards the SRM. There were also measurements taken from OMC REFL, seen in figure around 7.25m which appear very astigmatic. The model does not currently replicate this large astigmatism but the average of the two seem to roughly agree.

The notebook with the code and measured data for all this is in: https://git.ligo.org/IFOsim/Finesse_playground/blob/8370d9bb0c0b01b7e79d6565d831ec33e598f728/daniel_brown/LHO/OPO_to_OMC_beamscan_matching.html

The LHO parameters used can be found in: https://git.ligo.org/IFOsim/Finesse_playground/blob/8370d9bb0c0b01b7e79d6565d831ec33e598f728/daniel_brown/LHO/LHO.py

Further Electric Field Meter Prototype Characterization and Rough Displacement Noise Estimate

Craig, Niko, Georgia

Today Georgia, Niko, and I went down to Xend to take more careful measurements of the Electric Field Meter (EFM) Prototype built by Rich, Calum, and Luis.  

We drove the ISI to check if we could see the electric fields above our EFM noise floor.  We drove the ISI both vertically and horizontally until the watchdog tripped, but never saw a signal in the EFM.  This is surprising, since Rai's prototype was sensitive to ISI driving in the Y chamber.

We measured a calibration TF for both the positive X EFM sensor plate and negative X EFM sensor plate (Plot 1),
the common mode rejection from the X sensor plates (Plot 2),
and an ambient electric field ASD in the X-end chamber (Plot 3).  

Finally, I roughly estimated the ETMX displacement noise we might expect from ambient electric fields given our usual ESD setup. (Plot 4)  
The details of the calculation made to get plots 3 and 4 are in a jupyter notebook on git.ligo.org.

At 100 Hz I estimate around 10^{-22} m/rtHz displacement noise, far below our noise floor.  However, I'm getting a stronger frequency dependence than we perhaps anticipated: our measured electric field falls like f^{-1.5}, until it runs into what is probably the EFM circuit noise floor at 200 Hz.  This gives an overall displacement frequency dependence of f^{-3.5}.

Pictures are courtesy of Niko and Georgia who did all the in-chamber work today.  

Things to do:
1) Get capacitance measurement between calibration plates for a better volts to electric field TF.
2) Understand and create a noise model of the EFM circuitry.  This will probably help explain the strong frequency dependence we're seeing with some low frequency pole.

I ran a noise simulation of the ungrounded-plate noise spectra.  The attached image shows what would be expected from the 10^12 ohm resistance filtered by the approximately 20pF capacitance of the sense plate to the body (including amplifier input capacity).  The results at 100Hz confirm the ~200nV/rtHz associated with the asymptote of the intrinsic electronics noise of the device as seen when the sense plates are grounded.

In my estimate, I assumed that charge on the test mass is zero and the ambient electric fields at the EFM are the same as those at the test mass.
My concern is that we are just looking at EFM sensor noise and not really ambient electric fields.  It seems like we are seeing ambient electric fields below 200 Hz with a frequency dependence of f^{-1.5}.  
Many assumptions went into the estimated displacement noise, I wouldn't trust it to better than an order of magnitude.

Output beam study, clipping?

Aidan, Daniel V-H., TVo, Dan B., Terra

This is the initial analysis of the HAM6 output beam scan we did last week. Attached is the overall picture, in the style of LLO's beam study.

Measurements are done in HAM6 during single bounce configuration (no TCS) either directly in beam or using pickoff. Data is then fit by varying input beam parameters and, to some degree, OM optical/path length parameters. These are compared against the original output beam design. (There is a caveats to this, see below.) Since there was large astigmatism, what I show is beam fit prioritized to fit vertical measurements. [R,w] directly after SRM for design and vertical fits shown in plot. X-axis distances are in meters from SRM.

Main points:

•  we find up to 20% astigmatism coming into HAM6 
  • Finesse modeling for the single bounce beam parameters using the up-to-date design configuration shows about 3% astigmatism coming out of the SRM
  • table-top check of beam profiler gives 2-3% variation between vertical and horizontal, even when tilting scanner various ways with respect to incoming beam (NanoScan NS-SI/9/5 scanning slit profiler)
• looking at just the vertical beam, fit mismatch from OMC is ~5%
• we find similar shifts in OM placements (towards SRM) as LLO compared to original design; the distance between the edge of the ISI and OM1 & OM1 to OM2 was measured in situ. We find the latter agrees with up-to-date Zemax distance.

Caveat/to do: the design beam includes a 50km ITM lens, so I need to subtract that for more meaningful comparison; in the works.

For reference, the parameters used are:

• SRM to OM1: 3.4 m (Zemax gives 3.454 and I tweaked this slightly for fit), OM1 to OM2: 1.39 m (Zemax and in situ measurement)
• OM1 S: 1/4.6, OM2 S: 1/(1.7)

 

SDF snapshots taken Monday Morning between 8:20AM and 8:40AM Pacific Time (15:20-15:40UTC)

I took snapshots of every SDF screen that had diffs when I arrived Monday, in response to Dave's alog that said a number of our front end computers might freeze at any time.  I've renamed the snapshots to have the format (screen/system name)_SDF, and if I included more than one screen/system in the snapshot then the name is in the format (screen/system name)_(screen/system name)_(screen/system name)_SDF.  This morning, in preparation for reboots on Thursday,  JeffK is accepting some values, for example TRAMP times that have changed, and TVo is looking at some SDF screens to accept changes that reflect commissioning modifications that should be kept.  At this time, Tuesday at 9:20PT, we have 56 SDF screens that show diffs.