I took some steps to reduce the coupling of 60 Hz harmonics in noise measurement. The box was transferred to the floor instead of on top of another instrument. Measurement was immediately converted into single-ended using SR560 in battery mode with a gain of 10. All of the setups was covered in aluminum foil to increase isolation.

Spectrum measurement details

• Boards were powered by sorenson power supplies with +/- 18V DC.
• 36 Ohm load was connected to coil output port.
• Signal was taken out using clips from V2+, V2- and GND.
• Signal was first sent to SR560 in A-B mode with a gain of 10 in battery mode.
• The board along with SR560s were covered in aluminum foil to reduce 60Hz harmonics.
• The output from 50Ohm port was sent to SR785 and read with floating ground.
• Instrument noise was measured by shorting the clips with each other.
• Transfer function of measurement setup was measured and divided by final output.
• Measurements were taken with file D1100687_SP.yml and D1100687_SP_LF.yml.
• D1100117_S2100027_Voltage_Noise_Spectrum.pdf and D1100117_S2100028_Voltage_Noise_Spectrum.pdf shows the measured voltage noise spectrum at the output monitors when loaded with 36 Ohms.
• D1100117_S2100027_Current_Noise_Spectrum.pdf and D1100117_S2100028_Current_Noise_Spectrum.pdf shows the esitmate current noise through the coil calculated by dividing the measured voltage noise by 2436 Ohms.

Ran HDMI to the new tv mounted on the north wall of control room.

I have been trying a couple of HDR algorithms, all of them seem to give very different results. I don't know how suitable these algorithms are for our purpose, because they are more concerned with final display. I'm attaching the HDR image I got by modifying Jigyasa's code a bit (this image has been be modified further to make it suitable for displaying). Here, I'm trying compare the plots of images that look similar. The HDR image has a dynamic ratio of 700:1

PS: 300us_image.png file actually looks very similar to HDR image on my laptop (might be an issue with elog editor?). So I'm attaching its .tiff version also to avoid any confusion.

I captured a few images of the beam spot on ETMX at 5ms, 10ms, 14ms, 50ms, 100ms, 500ms, 1000ms exposure and ran them through my python script for HDR images. Here's what I obtained. 
The resulting image is an improvement over the highly saturated images at say, 500ms and 1 second exposures. 
Additionally, I also included a colormapped version of the image. 

i wonder how 'HDR' these images really are. is there a quantitative way to check that we are really getting more bits? also, how many bits does the PNG format allow for monochrome images? i worry that these elog images are already lossy.

HEPA filter was running at 90% of max. I reduced it to 20%. Acoustic noise moved down

The range of MCL oscillations has also decreased but fluctuations in the frequency range 10-100 are still present.

MCL is much more stable now.

15:30
- PSL HEPA was running at 33% and is now at 100%
- South End HEPA was not on and is now running
- Yarm Portable HEPA was not running and is now running at max speed: the power was taken beneath the ITMY table. It is better to unplug it when one uses the IFO.
- Yend Portable HEPA was not running and is now running (presumably) at max speed

Particle Levels: (Not sure about the unit. The convention here is to multiply x10 of the reading)

Before running the HEPAs at their maximum
9/10/2020 15:30 / 0.3um 292180 / 0.5um 14420
(cf 9/5/2020 / 0.3um 94990 / 0.5um 6210)
==>
After running the HEPAs at their maximum
The number gradually went down and now became constant at about half of the initial values
9/10/2020 19:30 / 0.3um 124400 / 0.5um 7410

The AC cord from the PSL HEPA variac to the junction box was replaced.
Now the HEPA is running at 70%

Showed up at the 40m at 7pm

Preparation

• Closed the PSL shutter.
• Closed the innolight shutter
• Turned off the HEPA mains switch
• Checked the HEPA fan rating: 115V 4.5A.
• Brought the thickest power cord from the wall stock: the rating is 125V 15A. This should sufficiently hold two HEPAs.

Cable Replacing

• Rechecked the wire connection. The new cord has green/black/white wires. And the colors agree with the color of the wires in the junction box.
• Removed the existing cord.
• Attached the new cord.
• Checked the variac AC plug. The terminals in the plug look normal and the AC plug looked sufficiently rigid.
• Checked the connection again. = OK

Testing

• Turned on the HEPA mains switch
• VairAC turned to 70%
• Checked the air flow - The HEPA fans are sucking the air = OK

Closing the work

• Closed the junction box.
• Cleaned up the roof
• Opend the innolight shutter
• Opened the PSL shutter
• Locked the PMC
• Locked the IMC  - found the transmission was ~80% of the pre-work due to misalignment of the PMC
• Aligned the PMC - this recovered the IMC REFL of ~5.2 when the IMC was unlocked

Leaving the 40m at 9:30pm

Memo: 40m wiring/Mask/Camera/Red Pitaya/Particle Counter

I think the PSL HEPA (both 2 units) are not running. The switches were on. And the variac was changed from 60% to 0%~100% a few times but no success.
I have no troubleshooting power anymore today. The main HEPA switch was turned off.

From the last failure, I had ordered 2 extra capacitors (they are placed on top of the PSL enclosure above where the capacitors would normally be installed). If the new capacitors lasted < 6months, may be symptomatic of some deeper problem though, e.g. the HEPA fans themselves need replacing. We don't really have a good diagnostic of when the failure happened I guess as we don't have any channel recording the state of the fans.

Gautam reported that the PSL HEPA stopped running (ELOG 15592). So I came in today and started troubleshooting.

It looks like that the AC power reaches the motors. However, both motors do not run. It looks like the problem exists in the capacitors, the motors, or both.
Parts specs can be found in the next ELOG.

Attachment 1 is the connection diagram of the HEPA. The AC power is distributed by the breaker panel. The PSL HEPA is assigned to use M22 breaker (Attachment 2). I checked the breaker switch and it was (and is) ON. The power goes to the junction box above the enclosure (Attachment 3). A couple of wires goes to the HEPA switch (right above the enclosure light switch) and the output goes to the variac. The inside of the junction box looked like this (Attachment 4).

By the way, the wires were just twisted and screwed into a metal threaded (but isolated) caps (Attachment 5). Is this legit? Shouldn't we use stronger crimping? Anyway, there was nothing wrong with the caps w.r.t the connection for now.

I could easily trace the power up to the variac. The variac output was just fine (Attachment 6). The cord goes from the variac to the junction box (and then HEPAs) looked scorched. The connection from the plug to HEPAs was still OK, but this should be eventually replaced. Right now the cable was unplugged after the following tests for the safety reason.

The junction box for each HEPA unit was opened to check the voltage. The supply voltage came to the junction boxes and it was just fine. In Attachments 8 & 9, the voltages look low but this is because I just turned the variac only a little.

At the (main) junction box, the resistances of the HEPAs were checked with the Fluke. As the HEPA units are connected to the AC in parallel, the resistances were individually checked as follows.

The coils were not disconnected (... I wonder if the wiring of South HEPA was flipped? But this is not the main issue right now.)
 

By removing the pre-filters, the motors were inspected Attachments 10 & 11. At least the north HEPA motor was warm, indicating there was some current before. A capacitor was connected per motor. When the variac was tuned up a bit, one side of the capacitor could see the voltage. I could not judge which has the issue between the capacitor and the motor.

Dimensions / Specs

- HEPA unit dimentions
- HEPA unit manufacturer
- Motor
- Capacitor

[Koji, Suresh]

    We investigated the effect of airflow from the HEPA filters on the PSL beam fluctuation and the resultant noise injected into the WFS loops.   The hint that the WFS are injecting PSL beam jitter into MC mirror motion lies in the MC2_TRANS_PIT and YAW signal's power spectrum shown here.  First, in the blue trace, which shows the spectrum when the WFS loops are off, we see that the WFS1 and WFS2 error signals have a different shape from that of MC2_TRANS.  Since WFS are affected by the PSL beam jitter while the MC2_TRANS_QPD is not, the WFS spectrum contain excess noise, while the MC2_TRANS signals show only the mirror motion.  Next, upon switching on the WFS1 and WFS2 loops, we notice that the MC2_TRANS  spectra acquire the same shape as the WFS spectra.  This shows that the excess noise from the beam jitter has been injected into the MC2 motion, and shows up in the MC2_TRANS spectra.

   To confirm these conclusions we repeated the above measurement with the HEPA fans at 0% (Blue trace), 20% (Red), 30% (Brown) and  100% (Green).   The plots are shown below.  We can see that there is no difference between 0 and 20% levels but beam jitter is visible at 30% HEPA level.  The WFS loops were ON during this time and we can can see the PSL noise injected in to MC2 motion (Green).

The HEPA filter fans are now at 20%.  How can we be sure that they are really working at 20%, since we cannot see any difference between 0 and 20%?

Now that we have this quiet situation, we also investigated the effect (or lack thereof) of switching on the MC2_TRANS loops.  The figure below shows the spectra with all the loops turned off (Blue), with the WFS1 and WFS2  loops turned on (Green)  and with everything turned on (Red).   With the current output matrix, which is the same simple one as the one in this elog, we see some low frequency suppression.  But it also seems to add some noise into the other WFS loops.  I am not sure of this result, due the long duration of this measurement, the seimic noise level may have changed over the course of this measurement.

As they are not doing any good just now.  I have turned them off by setting the gain in MC2_TRANS PIT and YAW to zero.

[JV, GV]

The HEPAs work again. After running the HEPAs for ~1 hour, I checked the particle count on the PSL table - the meter registered 0 for both 0.3 um and 0.5 um. So I decided to turn the NPRO back on, at ~1730 local time. The PMC and IMC were readily locke, so the basic interferometer functionality is returned, and we can now go ahead with (i) vent prep (ii) air BHD tests and (iii) IMC debuggin as was discussed on the call today. The earth is shaking, but nothing serious so far, I will resume alignment of the interferometer later in the evening when hopefully things have calmed down a bit more...

Procedure:

1. Turned off mains switch on the NW corner of the PSL enclosure. Then, disconnected the power cables from mains to Variac and from Variac to HEPAs. Made sure both HEPAs were set to "OFF".
2. With confidence that no AC power was reaching the motors, I removed the pre-filters, and removed the old startup capacitors. These don't have a polarity, but I marked the cable that was connected to the left terminal of the capacitor when the cap is viewed with the label facing you, in the interest of changing as few things as possible.
3. The two new capacitors were measured with the LCR meter - the meter registered ~7.5 uF, as expected. Unsurprisingly, the old capacitors that were removed didn't register any reading on the LCR meter. The terminals weren't shorted, but I don't know what the failure mode for this kind of capacitor is.
4. The two new capacitors were installed. Then, I tested the system by undoing all the changes in bullet #1. We found that the Variac needs to be set to 100% for the motors to startup.
5. The motor speed was found to vary as the Variac dial was turned. FWIW, at the "nominal" setting of 33% on the Variac (when we run the interferometer), I could see both fan blades were turning, but the flow was low enough that you couldn't hear any wind (at least, neither Jordan nor I could).
6. Turned off the mains agian, and cleaned up - restored the insulating rubber sleeve on the capacitor leads, and re-installed the pre-filters on the HEPA blowers. Then we turned both blowers back on. 

Note that the many other issues Koji noted in the preceeding elog (e.g. flaky wiring) have not been addressed.

Flow measurements:

Chub kindly provided us with an electronic anemometer. With the meter held directly against the HEPA filter inside the enclosure, we measured ~700 cfm of airflow on each of the two HEPAs, with the Variac set to 100% and the HEPAs themselves set to "High". With the Variac at 50%, the flow drops to ~160 cfm. At the nominal setting of 33%, the meter didn't register any flow. I don't know what the spec'd flow rate is for this combination of blower + filter, but Jordan says similar units in Downs register ~1500 cfm at the "High" setting. The two protable (similarly sized) HEPA units in the 40m, one at ITMY and one at ETMY, register ~900 cfm and ~1100 cfm respectively, when set to high. So we may want to revisit what the "nominal" HEPA setting should be, in case the filters have become clogged over time. 

Some photos of the HEPA blowers with the pre-filters off and the capacitors switched out may be found here.

it would be a good idea for us to have an auto-reminder to have us check the flow of all the HEPAs in the lab and elog it once a year so that we can replace filters and pre-filters appropriately.

I set up a simple HEPA filter dryer to dry your clean room garment before  you can put it away into your storage box.

Our lab is dusty ! This is  specially important when we are vented. Please wipe things daily and cover item with foils .... etc.

[Koji, Suresh]

8:50PM HEPA@100% for the test

8:55PM HEPA@0%

9:20-35PM HEPA level varies from 0%-50%

9:35PM HEPA@40% and left it running at this level

Nov18 1:40 AM HEPA@80% for a work around the PSL table (by KI)

Nov18 4:35 AM HEPA@40% (by KI)

I will upload some plots later - but in summary, I set the HEPA speed to ~40%. I used (i)IMC transmission RIN, (ii) Arm cavity transmission RIN and (iii) ALS beat noise as 3 diagnostics, to see how noise in various frequency bands for these signals change as a function of the HEPA speed. The MC2T RIN shows elevated noise between 1-10Hz at even the lowest speed I tried, ~20% of the max on each blower. The elevated noise extended to ~50-70 Hz for HEPA speeds >40% of the maximum, and the arm cavity RIN and ALS signals also start to become noisy for speeds >60% of the maximum. So I think 40% is a fine speed to run at - for squeezing measurement we may have to turn off the HEPA for 10mins but for the usual single arm / PRMI / DRMI locking, this should be just fine. For the elevated ALS noise - I'm not sure if the coupling is happening over the top of the enclosure where the fiber bringing light from EX comes close to the HEPA filters, or if it is happening inside the PSL enclosure itself, near the beat mouth - but anyways, at the 40% speed, I don't see any effect on the ALS noise.

I checked with a particle counter at the SW corner of the PSL table (which is the furthest away we can be on the table from the HEPA blowers) after leaving the blowers on for ~30mins and it registered 0 for both 0.3um and 0.5um sized particles (if the blowers are off, the respective numbers are 43 and 9 but I forgot what the units were, and I believe they have to be multiplied by 10). 

I have not yet marked the speed control units yet in case there is some other HEPA science that needs to be done before deciding what is the correct setting. But I think I can get the PRFPMI lock without much issue with this lower speed, which is what I will try later today evening.

I believe that there is an internal setting for the minimum flow, so the flow is not linear ("0%" is not zero), but we should mark this flow speed once you find this is sufficiently low for the locking too.

The PSL was too hot, so I turned on the south HEPA on the PSL. The north one was on and the south one was off (or so slow as to be inaudible and no vibration, unlike the north one). Lets watch the trend over the weekend and see if the temperature comes down and if the PMC / WFS variations get less. Fri May 14 17:46:26 2021

Looks like the fan lowered the temperature as expected. Need to get a few more days of data to see if its stabilized, or if that's just a fluke.

The vertical line at 00:00 UTC May 18 is about when I turned the fans up/on.

Fluke. Temp fluctuations are as usual, but the overall temperature is still lower. We ought to put some temperature sensors at the X & Y ends to see what's happening there too.

I was measuring things to see how big my adapter plate needs to be, and I decided that we'd had enough days of the HEPA being on full blast, so I turned it down to 50, from 100.  I think it's been on full since Katrin was working on the Y-green beat a week or so ago.

The PSL HEPA was off. It was turned on and it is running at 30VAC now.

I left the HEPA at the 50% level @5AM, Nov 24

Zach found the HEPA switch on the PSL table OFF.  He turned them on.

The HEPA filters on the PSL enclosure are no longer running. I tried cycling the power switch on the NW corner of the enclosure, and also turned the dial on the Variac down to zero and back up to maximum, no effect. Judging by the indicator LED on it, the power is making it to the Variac - bypassing the Variac and directly connecting the HEPA to the AC power seems to have no effect either.

I can't be sure, but I'm almost certain I heard them running at max speed an hour ago while I was walking around inside the VEA. Probably any damage that can happen has already been done, but I dialled down the Innolight injection current, and closed its shutter till the issue can be resolved.

I turned the HEPAs back down to ~50.

This is an option to isolate the vacuum chamber from the dusty 40m lab: 4x8 HEPA unit or Air Curtain

It does not limit crane operations. Here is some  science based approach to air filters

Lets put horizontal and vertical witness plates next to our arm cavity TMs just before pumpdown.

Stephanie has needed the doors to the PSL open all day, and still has them open, so I just turned the HEPAs on high. 

• Save your file /cvs/cds/advLigo/src/epics/simLink/tpt.mdl
  
• go to /cvs/cds/advLIGO on the TPT machine
  
• do make clean-tpt tpt install-tpt
  
• do rm /cvs/cds/caltech/chans/daq/C2TPT.ini (this step is needed because the DAQ install code isn't quite right at the time of this writing.
  
• do make install-daq-tpt
  
• run starttpt to restart the tpt computer.
  

In case anyone is curious how I got the numbers for the effective radius of curvature of the flipped TT mirrors, I include the code below.  Now you can calculate at home!

Here's the calculation for the effective RoC of a flipped SR2 with nominal un-flipped HR RoC of -600:

>> [Mt, Ms] = TTflipped(600, 5);
>> M2Reff('t', Mt, 5)

ans =

  412.9652

>>

1) Goto http://localhost:631/
2) Click on "Add Printer"
3) Choose HP JetDirect
4) Use the correct address (socket://131.215.115.220:9100)
5) Choose HP and the 5550 postscript driver as the options
6) Try to only print useful stuff and not kill too many trees.

To check the basolute frequency stability of the old monochrome HP 8591E RF Spectrum analyzer that we're using for the ALS beat readout, I hooked its 10 MHz reference output (from its rear panel) into the A channel of the SRS SR620 frequency counter. The SR620 is locked to the FS 720 Rubidium clock via the 10 MHz connections in their rear panels.

So, we can assume that this is a good absolute readout. It reads 9.999860.7 +/- 0.3 Hz. So its 139.1-139.4 Hz lower than 10 MHz. The +/- 0.3 is just a slow drift that I see over the course of 10 minutes.

So, let's say that the analyzer is low by 10 ppm, so the arm length estimates are short by ~0.4 mm. A negligible correction, so there's no need to use atomic clocks to measure our arm lengths.

I've wheeled the old HP audio frequency signal analyzer into the control room to debug the GPIB/python interface. The wireless setup was getting more than 80% packet loss in the office area.

I also noticed that we have multiple and competing copies of the netgpib package installed. Kiwamu is going to merge them soon. Pleae only use the official location:

scripts/general/netgpibdata/

which is also the SVN working copy. Committ all changes periodicallty so that we can share the updated versions between sites.

www.avalontest.com has fixed the 25MHz oscillation.  Contact: Jim Burnham 760-536-0191

Actually, NOT FIXED.

Eric Gustafson is handling the old HP4291A rehabilitation. Tarac picked both units up today.

March of 2008 Tucker Electronics failed to fix it's intermittent ~25MHz 0.5V oscillation at the swept sine output

See 40m-elog id:398 on 3-24-2008 by Rob Ward

The script for running continuous scans on HP 8591E spectrum analyzer is located at scripts/general/netgpibdata/HP8591E_contdScan.py

Give the file HP8591E_param.yml as an argument when running the script. This contains the sweep parameters: Start and stop frequencies along with the place where the plot is stored as a PDF.

The default PDF is located on the Desktop and is named HP8591E_View.pdf     Open this using okular and then run the script.  (Okular pdf viewer automatically reloads the PDF as and when a new one is created)

What the script does:

1) Set the start and stop frequencies as given in the .yml file

2) Take a data trace and plot it in a PDF.

3) Repeat taking traces and update the PDF. Untill Ctrl+C is pressed (PDF refresh rate: approximately every 3 seconds )

4) Exit smoothly after the keyboard interrupt.

Other details:

This spectrum analyzer is connected to a GPIB - Ethernet controller that is configured as santuzza.martian (192.168.113.109)

I have currently stolen the wireless modem from the spectrum analyzer inside the lab (vanna.martian) and using it for this one. *poker face*

To improve:

Get the plot to show where the two biggest peaks are located. Currently it recognizes only the biggest one.

Possibly have makers on the two peaks.

PFA a sample pdf

Updated script does the following:

1) Gets the highest 2 peaks

2) Puts a marker on the peaks. Now it looks very similar to the spectrum analyzer display.

3) The refresh rate is still 3 seconds. It might become better if the analyzer was hooked up to a wired martian LAN port rather than the wireless module I am using now.

PFA a sample pdf

There was no such script in the directory when I looked today, but I found one called HP8591E. Of course, it didn't run because it hadn't been tested from the scripts directory and pointed to some /users/nichin/ stuff.

I modified a couple of lines and then committed it and the default .YML parameter file to the SVN. It runs and produces plots continuously from the scripts directory.

*** also, as you can see, we have mostly recovered the green beat amplitudes after yesterday's FLL attack on the ALS ***