40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
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ID Date Author Type Category Subject
13829   Thu May 10 08:45:16 2018 SteveUpdateGeneral4.5M eq. Cabazon, CA

20180508 4:49am Cabazon earth quake 4.5M at 79 miles away.  ETMX is in load cell measurment condition.

 Quote: There was an earthquake, all watchdogs were tripped, ITMX was stuck, and c1psl was dead so MCautolocker was stuck. Watchdogs were reset (except ETMX which remains shutdown until we finish with the stack weight measurement), ITMX was unstuck using the usual jiggling technique, and the c1psl crate was keyed.

Attachment 1: Cabazon4.5m79m.png
Attachment 2: 4.5Meq.png
13828   Wed May 9 19:51:07 2018 gautamUpdateGeneralInput beam misaligned

As suspected - the problem was with the TTs. I tested the TT signal chain by driving a low frequency sine wave using AWG and looking at the signal on an o'scope. But I saw nothing, neither at the AI board monitor point, nor at the actual coil driver mon point. I decided to look at the IOP testpoints for the DAC channels, to see if the signals were going through okay on the digital side. But the IOP channels were flatlined, as viewed on dataviewer (see Attachment #1). This despite the fact that the DAC output monitor screen in the model itself was showing some sensible numbers, again see Attachment #1.

Looking at the CDS overview screen, there were no red flags. But there was a red indicator sneakily hidden away in the IOP model's CDS status screen, the "DAC" field in the state word is red. As Attachment #2 shows, a change in the state word is correlated with the time ASDC went to 0.

Note that there are also no errors on the c1lsc frontend itself, judging by dmesg. I want to do a model restart, but (i) this will likely require reboots of all vertex FEs and (ii) I want to know if any CDS experts want to sniff for clues to what's going on before a model restart wipes out some secret logfiles. I'm a little confused that the rtcds isn't throwing up any errors and causing models to crash if the values are not being written to the registers of the DAC. It may also be that the DAC card itself is dead . To re-iterate, all the EPICS readbacks were suggesting that I am injecting a signal right up to the IOP.

Quoting from the runtime diagnostics note:

NOTE: As V2.7, if this error is detected, the IOP will output zero values to all DAC modules, as a protective measure. Only method to clear this is to restart the IOP and all applications on that computer
Attachment 1: DACweirdness.png
Attachment 2: DACerror.png
13827   Wed May 9 17:30:04 2018 gautamUpdateGeneralInput beam misaligned

There is no beam going into the IFO at the moment. There was definitely a spot on the AS camera after I restored the suspensions yesterday, as you can see from the ASDC level in Attachment #1. But at around 2pm Pacific yesterday, the ASDC level has gone to 0. I suspect the TTs. There is no beam on the REFL camera either when PRM is aligned, and PRM's DC alignment is good as judged by Oplev.

Normally, I am able to recover the beam by scanning the TTs around with some low frequency sine waves, but not today. We don't have any readback (Oplev/OSEM) of the TT alignment, and the DC bias values havent jumped abnormally around the time this happened, judging by the OUT16 monitor points (see Attachment #2). The IMC was also locked at the time when this abrupt drop in ASDC level happened. Unfortunately, we don't have a camera on the Faraday so I don't know where the misalignment is happening, but the beam is certainly not making it to the BS. All the SOS optics (e.g. BS, ITMX and ITMY) are well aligned as judged by Oplev.

Being debugged now...

Attachment 1: InputBeamGone.png
Attachment 2: TTpointing.png
13826   Tue May 8 11:41:16 2018 gautamUpdateGeneralIFO maintenance

There was an earthquake, all watchdogs were tripped, ITMX was stuck, and c1psl was dead so MCautolocker was stuck.

Watchdogs were reset (except ETMX which remains shutdown until we finish with the stack weight measurement), ITMX was unstuck using the usual jiggling technique, and the c1psl crate was keyed.

Attachment 1: ITMX_stuck.png
13825   Tue May 8 10:24:10 2018 KiraSummaryPEMplan for this week

Here are a few things I will be working on:

• Design PCB boards for the heater circuit and temperature sensor circuits [by wednesday]
• Order the front panel I've designed for the seismometer block [today]
• [next week?] install the new Acromag when it comes
13824   Tue May 8 00:40:51 2018 gautamConfigurationALSBeathMouth pulled out of PSL table

Summary:

I did some more BeatMouth characterization. My primary objective was to do a power budget. Specifically, to measure the insertion loss of the mating sleeves and of the fiber beam splitters. All power numbers quoted in this elog are measured with the fiber power meter. Main takeaways:

• Measured insertion loss of all mating sleeves, which are ADAFCPMB2, are in agreement with the < 1dB spec. 1 dB in power is ~20%.
• But there is large variance in the above number, between different supposedly identical connectors.
• Measured insertion loss from input port to coupled ports of the fiber beamsplitters are slightly larger than spec (~3.5dB), when measured after mating the fiber beamsplitter (which has Hi1060 flex fiber) and PM980 fiber (which is what brings light to the BeatMouth).
• But measured insertion loss when mating is between Hi1060 flex fiber ends is more in line with the expected value of ~3.5dB.
• Isolation of fiber beam splitters seems to match the spec of >55dB.

Results:

• I used the fiber bringing 416uW of IR light from EY for this test.
• Insertion loss was measured by injecting the fiber light at one port and measuring the transmitted power at various other ports.
• In order to couple the fiber power meter across a single mating sleeve, I used a short (~1m) patch cable from newport (F-SY-C-1FCA). Technically, this is single mode fiber with the correct type of connector, FC/APC, but is not PM.
• See Attachment #2 for the labeling of the connectors which is how I refer to them in the table below.
• Lest there be confusion, I use the definition of insertion loss  $\mathrm{Insertion ~loss [dB] }=10\mathrm{log_{10}}(\frac{P_{in}}{P_{out}})$.
Mating Sleeve # Insertion loss [dB]
1 0.38
2 0.65
3 0.71
4 0.43
5 0.95
6 0.79
7 0.5

Remarks / Questions:

1. Is there any way to systematically reduce the insertion loss? Like getting a better mating part?
2. Question for the fiber experts: How do we deal with the unused port of the beam-splitters? Right now, they are just capped. But as you can see in Attachment #1, the caps certainly don't block all the light. What are the implications of back-scattered light into the fiber on the ALS noise? I guess the beamsplitter itself has the spec'd 55dB directivity, so do we not care about this?
Attachment 1: IMG_6986.JPG
Attachment 2: IMG_6987.JPG
13823   Mon May 7 20:01:14 2018 RorpheusUpdateGeneralUse anti-dewhitening + show CARMA/DARMA

example of plots illustrating DAC range / saturation

13822   Mon May 7 16:23:06 2018 gautamUpdateGeneralDARM actuation estimate

Summary:

Using the Wiener Filter estimate of the DARM disturbance we will have to cancel, I computed how the control signal would look like for a few scenarios. Our DACs are 16-bit, +/-10V (i.e. +/-32,768cts-pk, or ~23,000cts RMS). We need to consider the shape of the de-whitening filter to conclude whether it is feasible to increase the series resistance by x10 or not.

Some details:

Note that in this first computation, I have not considered

• Actuation range required by other loops (e.g. local damping, Oplev etc).
• At some point, I need to add the 2P/c radiation pressure disturbance as well.
• The control signal is calculated assuming we are actuating equally on both ETMs (but with opposite phase).
• RMS computation is done from 30 Hz downwards, as above 30 Hz, I think the estimate from the previous elog is not true seismic displacement.
• De-whitening filters (or digital whitening), which will be required to suppress DAC noise at 100Hz.
• DARM loop shape, specifically low-pass to avoid sensing noise injection. In this calculation, I just used the pendulum transfer function.

While doing this calculation, I have accounted for the fact that right now, the analog de-whitening filters in the ETM drive chain have a x3 gain which we will remove. Actually this is an assumption, I have not yet measured a transfer function, maybe I'll do one channel at EY to confirm. Also, the actuator gains themselves need to be confirmed.

As I was looking at the coil driver schematic more closely, I realized that there are actually two separate series resistances, one for the fast controls path, and another for the DC bias voltage from the slow ADCs. So I think we have been underestimating the Johnson noise of the coil drivers by sqrt(2). I've also attached screenshots of the IFOalign and MCalign screens. The two  ITMs and ETMX have pitch DC bias values that are compatible with a x10 increase of the series resistance. But even so, we will have ~3pA/rtHz per coil from the two resistances.

gautam 8pm May8: Seems like I had confirmed the x3 gain in the EX de-whitening board when Johannes and I were investigating the AI board offset.

Attachment 1: darmProj.pdf
Attachment 2: 37.png
Attachment 3: MCalign_20180507.png
13821   Mon May 7 15:27:28 2018 gautamUpdateSUSStack measurement expectation

[steve,gautam]

We tried to estimate what the load cell measurement should yield. Here is the weight breakdown (fudge factor for Al table is to try and account for tapped holes):

### Dim in inches

Table 1.22 0.08 2700.00 240.07 0.85 Dia=48", thickness=3"
Stack leg 0.36 0.13 8000.00 100.85 9 Dia=14", thickness=5"
Base plate 1.37 0.05 8000.00 600.18 1 Dia=60",thickness=2"
Base rods 0.10 1.83 8000.00 118.55 2 Dia=4", length=6ft
Stuff on table       100.00
Blue beams       100.00

Total [kg]       2149.01
Total [lbs]       4835.28

• Steve pointed out that there is some material removed from the stack legs for stability (hollows into which the viton springs fit). These countersinks have dimensions of diameter=2", height=1.75". So if we assume each leg has 10% less mass, the total weight becomes ~4600lbs.
• I think we will need to use one more load cell (i.e. total 4) for this measurement (we have more load cells, just need to setup one more controller).
• Steve is looking into acquiring some low profile jacks to deal with the fact that we only have limited travel range on the overall stack height because of the bellows.
• A useful document, from which we pulled some numbers (which also look reasonable using estimated dimensions and density calculations): P952005
Attachment 1: 40m_TMstack.JPG
13820   Mon May 7 11:46:07 2018 gautamUpdatePEMFW parameter update

As part of investigation into this issue, Jonathan Hanks pointed out that the "minute trends" being recorded by our system were actually only being recorded every 120 seconds (a.k.a. 2 minutes). He had fixed the appropriate line in the parameter file, but had not restarted the FW processes. I had restarted it on Friday. (but failed to elog it !)

To check if this made any difference, I pulled 1 hour of "minute trend" data for the PSL table temperature channel from ~1 hour ago, and compared the number of datapoints against a 1 hour minute trend time series from 2 May. I've put the display with # of datapoints (for an identical length of time) from before [left] and after [right] the restart next to the plots in Attachment #1. Seems like we are getting minute trends written every 60 seconds now, as it should be .

The unavailability of trends from nodus is a separate issue for which JH has suggested another fix, to be elogged separately.

 Quote: for whatever reason, I am unable to get minute or second trends from nodus for any channels (IMC, PEM, etc) since the reboot. has there been some more recent FB failure or is this still a bug since last years FB catastrophe?
Attachment 1: FWreboot.png
13819   Sat May 5 22:32:07 2018 KojiUpdatePSLModulation depth measurement for the 3IFO aLIGO EOM

The 3IFO EOM was formerly tuned as the H2 EOM, so the resonant frequencies are different from the nominal aLIGO ones.

PORT1: 8.628MHz / 101 +/- 6 mrad_pk/V_pk
PORT2: 24.082MHz / 41.2 +/- 0.7 mrad_pk/V_pk
PORT3: 43.332MHz / 62.2 +/- 4 mrad_pk/V_pk

9MHz modulation is about x2.4 better than the one installed at LHO.
24MHz modulation is about x14 better. (This is OK as the new 24MHz is not configured to be resonant.)
45MHz modulation is about x1.4 better.

13818   Sat May 5 20:30:21 2018 KojiUpdatePSLModulation depth measurement for the 3IFO aLIGO EOM and aftermath

Caution: Because of this work and my negligence, the RF output of the main Marconi for the IFO modulation is probably off. The amplifier (freq gen. box) was turned on. Therefore, we need to turn the Marconi on for the IFO locking.

I worked on my EOM m easurement using the beat setup. As there was the aux injection electronics, I performed my measurement having tried not to disturb the aux setup. The aux Marconi, the splitted PD output, and an open channel of the oscilloscope were used for my purpose. I have brought the RF spectrum analyzer from the control room. I think I have restored all the electronics back as before. I have re-aligned the beat setup after the EOM removed. Note that the aux NPRO, which had been on, was turned off to save the remaining life of the laser diode.

13817   Fri May 4 21:17:57 2018 gautamConfigurationALSBeathMouth pulled out of PSL table

I have been puzzled about the beat note level we get out of the BeatMouth for some time.

• The beat PD used is the Menlo FPD310.
• But the version we have is an obsolete version of the product, for which a manual is hard to find.
• Hence, I don't know the transimpedance/electrical characteristics of this PD.
• The optical damage threshold of the PD is quoted as 2mW, which is a number I have been careful not to exceed.
• But I've felt that the beat amplitude level we get out of this PD is far too low considering the amount of DC optical power (as measured with a fiber power meter) incident on the PD.
• After some emailing and online hunting, I've gathered some numbers for the PD which are now on the wiki.
• The fiber beam splitters we use inside the BeatMouth don't have PM fibers. There are 3 such splitters inside the BeatMouth. So the overlap efficiency on the PD is unknown.
• But even so, the beat levels I was seeing were too low.

I have pulled the box out in order to re-characterize the DC power levels incident on the PD, and also to change the gain setting on the PD to the lower gain which is more compatible with the level of optical power we have going into the BeatMouth. The modern catalog for the FPD310 (see wiki) suggests that the maximum output voltage swing of the PD is 1Vpp driving a 50ohm load. With 50% overlapping efficiency between the PSL and AUX beams, and 400 uW of optical power from each beam, I expect an output of 0.5Vpp. Even with perfect overlap, I expect 0.8Vpp. So these numbers seem reasonable.

I also plan to check the scaling of electrical beat amplitude to optical power for a couple of levels to see that these scale as expected...

13816   Fri May 4 19:06:28 2018 ranaConfigurationElectronicsAUX-PSL PLL Implementation & Characterization

this doesn't make much sense to me; the phase to frequency conversion (mixer-demod to PZT ) should give us a 1/f loop as Johannes mentioned in the meeting. That doesn't agree with your loop shape.

How about give us some more details of the setup including photos and signal/power levels? And maybe measure the LB1005 TF by itself to find out what's wrong with the loop.

13815   Fri May 4 18:59:39 2018 gautamUpdateSUSStack measurement ongoing

[SV,KA,RXA,GV]

The stack weight measurement is going on at EX. ETMX watchdog is shutdown. Area is off limits over the weekend until the test is finished.

Not related to this work, but the dog clamps used on the EX table have to be re-positioned such that the clamping force is better distributed. The 2" beam splitter mount used to pick off a portion of the EX NPRO beam to the fiber has to be rotated. Also, there was a M6.9 EQ in Hawaii while we were doing this work it seems..

13814   Fri May 4 13:24:56 2018 Jon RichardsonConfigurationElectronicsAUX-PSL PLL Implementation & Characterization

Attached are final details of the phase-locked loop (PLL) implementation we'll use for slaving the AUX 700 mW NPRO laser to the PSL.

The first image is a schematic of the electronics used to create the analog loop. They are curently housed on an analyzer cart beside the PSL table. If this setup is made permanent, we will move them to a location inside the PSL table enclosure.

The second image is the measured transfer function of the closed loop. It achieves approximately 20 dB of noise suppression at low frequencies, with a UGF of 50 kHz. In this configuration, locks were observed to hold for 10s of minutes.

Attachment 1: PLL_Schematic.pdf
Attachment 2: PLL_AUX-PSL_40m.pdf
13813   Thu May 3 20:29:39 2018 gautamConfigurationElectronicsPSL-Aux. Laser Phase-Locked Loop

Some notes about the setup and work at the PSL table today, Jon can add to / correct me.

• All equipment for the phase locking now sit on a cart that is on the west side of the MC beam tube, near ITMX chamber.
• Cables have been routed through the space between the PSL enclosure and the optical table.
• HEPA was turned up for this work, now it has been turned down to the nominal level of 30%.
• Alignment into the PMC had degraded a bit - I tweaked it and now MC transmission is up at ~15600 which is a number I am used to. We still don't have a PMC transmission monitor since the slow ADC failure.
13812   Thu May 3 12:19:13 2018 gautamUpdateCDSslow machine bootfest

Reboot for c1susaux and c1iscaux today. ITMX precautions were followed. Reboots went smoothly.

IMC is shuttered while Jon does PLL characterization...

Now relocked.

13811   Thu May 3 12:10:12 2018 gautamConfigurationGeneralAS port laser injection

I think we need AS55 for locking the configuration Jon suggested - AS55 I and Q were used to lock the SRMI previously, and so I'd like to start from those settings but perhaps there is a way to do this with AS110 I and Q as well.

 Quote: What signals are needed for the Guoy phase measurement? Is AS 110 sufficient, or do we need AS55?

13810   Thu May 3 10:40:43 2018 johannesConfigurationGeneralAS port laser injection

Instead of trying to couple the fiber output into the interferometer, I'm doing the reverse and maximize the amount of interferometer light going into the fiber. I set up the mode-matching solution shown in attachment #1 and started tweaking the lens positions. Attachment #2 shows the setup on the AS table. After the initial placement I kept moving the lenses in the green arrow directions and got more and more light into the fiber.

When I stopped this work yesterday I measured 86% of the AS port light coming out the other fiber end, and I have not yet reached a turning point with moving the lenses, so it's possible I can tickle out a little more than that.

It occured to me though that I may have been a little hasty with the placement of the mirror that in attachment #2 redirects the beam which would ordinarily go to AS55. For my arm ringdown measurements this doesn't matter, I could actually place it even before the 50/50 beamsplitter that sends light onto AS110 and double the amount of light going into the IFO. What signals are needed for the Guoy phase measurement? Is AS 110 sufficient, or do we need AS55?

Attachment 1: mm_solution_AStable.png
Attachment 2: AStable_beampath.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.

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.

13808   Thu May 3 00:42:38 2018 KevinUpdatePonderSqueezeCoil driver contribution to squeezing noise budget

In light of the discussion at today's meeting, Guantanamo and I looked at how the series resistance for the test mass coil drivers limits the amount of squeezing we could detect.

The parameters used for the following calculations are:

• 4.5 kΩ series resistance for the ETM's (this was 10 kΩ in the previous calculations, so these numbers are a bit worse); 15 kΩ for the ITM's
• 100 ppm transmissivity on the folding mirrors giving a PRC gain of 40
• PD quantum efficiency of 0.88

Since we need to operate very close to signal recycling, instead of the current signal extraction setup, we will need to change the macroscopic length of the SRC. This will change the mode matching requirements such that the current SRM does not have the correct radius of curvature. One solution is to use the spare PRM which has the correct radius of curvature but a transmissivity of 0.05 instead of 0.1. So using this spare PRM for the SRM and changing the length of the SRC to be the same as the PRC we can get

• 0.63 dBvac of squeezing at 205 Hz for 1 W incident on the back of PRM
• 1.12 dBvac of squeezing at 255 Hz for 5 W incident on the back of PRM

This lower transmissivity for the SRM also reduces the achievable squeezing from the current transmissivity of 0.1. For an SRM with a transmissivity of 0.15 (which is roughly the optimal) we can get

• 1 dBvac of squeezing at 205 Hz for 1 W incident on the back of PRM
• 1.7 dBvac of squeezing at 255 Hz for 5 W incident on the back of PRM

The minimum achievable squeezing moves up from around 205 Hz at 1 W to 255 Hz at 5 W because the extra power increases the radiation pressure at lower frequencies.

13807   Wed May 2 21:39:33 2018 gautamConfigurationALSIR ALS for EY

The new K6XS mounts I ordered have arrived. I want to install one of them at the Y-end. I can't find a picture of the current layout but it exists as there is a hardcopy affixed to the ETMY chamber door, Steve, can we dig this up and put it in the wiki? In any case, the current beam going into the fiber is the pickoff from the post-SHG harmonic separator. I'd like to change the layout a bit, and use a pickoff before the doubling oven, but looking at the optical table, this seems like a pretty involved task and would probably require large scale optical hardware rearrangement. In any case, the MM of the green beam into the Y-arm is <50%, so I would like to redo that as well. Does anyone know of a measurement of the mode from the Lightwave NPRO that is installed at EY? I think Annalisa is the one who installed this stuff, but I can't find an actual NPRO mode measurement in her elog thread.

Found it: elog4874, elog8436. I updated the laser inventory page to link the lasers in use to the most recent mode measurements I could find on the elog. I guess ideally we should also link the AM/PM response measurements.

------------------------------------------------------------------------------------------------------

as of 3-31-2016

The oplev path was optimized with AR coated lenses and new He/Ne laser Jan 24, 2017

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 4: DSC01009.JPG
Attachment 5: jack_screw.jpg
Attachment 6: ETMX_NW_foot_STACIS.pdf
13805   Tue May 1 19:37:50 2018 gautamUpdateGeneralDARM actuation estimate

Here is an updated plot - the main difference is that I have added a trace that is the frequency domain wiener filter subtraction of the coherent power between the L_X and L_Y time series. I tried reproducing the calculation with the time domain wiener filter subtraction as well, using half of the time series (i.e. 5 mins) to train the wiener filter (with L_X as target and L_Y as witness), but I don't get any subtraction above 5 Hz on the half of the data that is a test data set. Probably I am not doing the pre-filtering correctly - I downsampled the signal to 1 kHz, weighted it by low passing the signal above 40 Hz and trained the Wiener filter on the resulting time series. But this frequency domain Wiener filter subtraction should be at least a lower bound on DARM - indeed, it is slightly lower everywhere than simply taking the time domain subtraction of the two data streams.

To do:

• Re-measure calibration numbers used.
• Redo calculation once the numbers have been verified.

Putting a slightly cleaned up version of this plot in now - I'm only including the coherence-inferred DARM estimate now instead of the straight up time domain subtraction. So this is likely to be an underestimate. At low (<10 Hz) frequencies, the time domain computation lines up fairly well, but I suspect that I am getting huge amounts of spectral leakage (see Attachment #2) in the way I compute the spectrum using scipy's filtering routine (once the Wiener filter has been computed). Note that Attachment #2, I didn't break up the data into a training/testing set as in this case, we just care about the one-off offline performance in order to get an estimate of DARM.

The python version of the wiener filter generating code only supports [b,a] output of the digital filter, an sos filter might give better results. Need to figure out the least painful way of implementing the low-noise digital filtering in python...

Attachment 1: darmEst.pdf
Attachment 2: darmEst_time.pdf
13804   Tue May 1 15:23:18 2018 KiraUpdatePEMnew ADC channel setup issue

[Kira, Johannes]

I connected up the channels for the ADC Acromag a while back and we were planning to install it today so that we could set up a new channel for the out of loop sensor. Unfortunately, the Acromag seems to be broken. We connected up a precision 10V voltage to one of the channels, but the Acromag read out ~7V and it kept fluctuating. Even after calibration, we still got the same result. When enabling the legacy support, we got ~11V. But when we measured the voltage at the screw terminals with a multimeter and it showed 10V, so the issue is not with the wiring. All of the channels have this same issue. We will be ordering more Acromags soon, so hopefully we'll be able to set up the channel soon. I've attached a picture of the Acromag along with the front panel with the channels labeled

Attachment 1: IMG_20180501_152014.jpg
13803   Tue May 1 11:15:19 2018 KiraUpdatePEMPID Quixote

I added an out of loop sensor to the can by placing the lab temperature sensor inside the can. I'm not sure which channel is logging this temperature though. I also noticed that the StripTool still had the old misspelled name for the temperature readout so I fixed that as well.

I've attached a picture of the setup.

 Quote: Increased the Integral gain (from -1 to -4) on the EX temperature controller. This didn't work a few weeks ago, but now with the added P gain, it seems stable. Daily temperature swings are now ~3x smaller. Notes for Kira on what we need to do tomorrow (Friday): add the MEDM screen EPICS values to the DAQ so that we can plot those trends DONE add the out-of-loop sensor to the EX can reboot the AUX-EX so we can pick up the new channels and the fixed spelling of the old channels DONE Re-install EX seismometer and hook up seismometer channels to PEM DAQ so we can start testing its performance. For those who are flabbergasted by the way I calibrated the TEMP_MON channel from volts to deg C, here's how: XMgrace->Data->Transformations->Geometric Transforms... use the 'scale' and 'translate' fields to change the slope and offset for calibration in the obvious ways

Attachment 1: IMG_20180501_154826.jpg
13802   Tue May 1 08:04:13 2018 Jon RichardsonConfigurationElectronicsPSL-Aux. Laser Phase-Locked Loop

[Jon, Gautam, Johannes]

Summary: In support of making a proof-of-concept RF measurement of the SRC Gouy phase, we've implemented a PLL of the aux. 700mW NPRO laser frequency to the PSL. The lock was demonstrated to hold for minutes time scales, at which point the slow (currently uncontrolled) thermal drift of the aux. laser appears to exceed the PZT dynamic range. New (temporary) hardware is set up on an analyzer cart beside the PSL launch table.

Next steps:

- Characterize PLL stability and noise performance (transfer functions).

- Align and mode-match aux. beam from the AS table into the interferometer.

- With the IFO locked in a signal-recycled Michelson configuration, inject broadband (swept) AM sidebands via the aux. laser AOM. Coherently measure the reflection of the driven AM from the SRC.

- Experiment with methods of creating higher-order modes (partially occluding the beam vs. misaligning into, e.g., the output Faraday isolator). The goal is identify a viable techinque that is also possible at the sites, where the squeezer laser serves as the aux. laser.

The full measurement idea is sketched in the attached PDF.

Attachment 1: IMG_2553.jpg
Attachment 4: src_gouy_phase_v3.pdf
13801   Mon Apr 30 23:13:12 2018 KevinUpdateComputer Scripts / ProgramsDataViewer leapseconds

I was trying to plot trends (min, 10 min, and hour) in DataViewer and got the following error message

Connecting.... done
mjd = 58235
Opening leapsecs.dat
Open of leapsecs.dat failed

thoough the plots showed up fine after. Do we need to fix something with the leapsecs.dat file?

13800   Mon Apr 30 15:36:18 2018 KiraUpdatePEMfinal setup sketch

I've attached a sketch of how the panel will be mounted. We should make a small rectangular box that would raise the panel from the block by 1 cm or so to allow the cables to fit into the hole in the block without getting bent. It also has to be airtight so maybe having a thin layer of rubber between the mount and block would be good.

Attachment 1: mount.png
13799   Sun Apr 29 22:53:06 2018 gautamUpdateGeneralDARM actuation estimate

Motivation:

We'd like to know how much actuation is required on the ETMs to lock the DARM degree of freedom. The "disturbance" we are trying to cancel is the seismic driven length fluctuation of the arm cavity. In order to try and estimate what the actuation required will be, we can use data from POX/POY locks. I'd collected some data on Friday which I looked at today. Here are the results.

Method:

• I collected the error and control signals for both arm cavities while they were locked to the PSL.
• Knowing the POX/POY sensing response and the actuator transfer functions, we can back out the free running displacements of the two arm cavities.
• I used numbers from the cal filters which may not be accurate (although POX sensing response which was recently measured).
• But the spectra computed using this method seem reasonable, and the X and Y arm asds line up around 1 Hz (albeit on a log scale).
• In this context, $L_X$ is really a proxy for $|f_X - f_{MC}|$ and similarly for L_Y so I think the algebra works out correctly.
• I didn't include any of the violin mode/AA/AI filters in this calculation.
• Having calculated the arm cavity displacements, I computed "DARM" as L_y- L_x and then plotted its asd.
• For good measure, I also added the quadrature sum of 4 optics' displacement noise as per the 40m GWINC model - there seems to be a pretty large discrepancy, not sure why.

If this approach looks legit, I will compute the control signal that is required to stabilize this level of disturbance using the DARM control loop, and see what is the maximum permissible series resistance we can use in order to realize this stabilization. We can then compare various scenarios like different whitening schemes, with/without Barry puck etc, and look at coil driver noise levels for each of them.

Attachment 1: darmEst.pdf
13798   Fri Apr 27 18:42:02 2018 ranaUpdatePEMnew Seis temp chans

for whatever reason, I am unable to get minute or second trends from nodus for any channels (IMC, PEM, etc) since the reboot. has there been some more recent FB failure or is this still a bug since last years FB catastrophe?

13797   Fri Apr 27 16:55:31 2018 gautamUpdateGeneralEY area access blocked

Steve was calibrating the load cells at the EY table with the crane - we didn't get through the full procedure today, so the area near the EY table is kind of obstructed. The 100kg donut is resting on the floor on the North side of the EY table and is still connected to the crane. There are stopper plates underneath the donut, and it is still connected to the crane. Steve has placed cones around the area too. The crane has been turned off.

13796   Fri Apr 27 01:36:02 2018 gautamConfigurationALSIR ALS noise performance

Summary:

My goal was to do some further characterization of the IR ALS system tonight. With POX as an OOL sensor, I measured an RMS displacement noise of  8 pm with the arm under ALS control. I calculated the CARM linewidth to be 77 Hz (=10.3 pm) for the 40m parameters, assuming 30ppm arm loss. Fuurthermore, this number is 3x better than the 24 pm RMS quoted in the Izumi et. al. paper. Of course I am quoting the best results from my efforts tonight. Conclusions:

1. [Attachment #1] --- With XARM locked using POX, the ALS beat noise (i.e. Phase Tracker output noise) lines up well with the reference we have been using for some time now (and indeed, is better in some places).
2. [Attachment #2] --- With the arm locked on ALS and POX as an OOL sensor, I measured performance comparable to this measurement we did sometime last year. Anomalies in this measurement and the one above were what precipitated the IMC noise investigation.
3. [Attachment #3] --- The above two attachments are not the whole story. During the day, I get significantly worse performance (so much so that I couldn't even do the handoff to ALS control). But in 5 minutes of measurement, the ALS noise seems quite stationary.
4. [Attachment #4] --- This is really the same as Attachment #2, but I wanted to overlay some vlines. Maybe this is a clue to some 60 Hz / ground loop issues, but the RMS has significant contribution from these harmonics. Tmrw, I will add the old measurement overlaid to this plot (and for what its worth, the Izumi et. al. spectrum as well).
5. [Attachment #5] --- With the arm under ALS control, I was able to maintain the lock for a solid hour (and more as I write up this elog). Somehow inkscape screwed up the fonts, but main point here is that TRX is stable to within 10% throughout the observation time.

Since the stability and noise seemed quite good, I decided to collect some arm scan data to give to our modeSpec SURFs to practice fitting (which is the short dip in TRX in Attachment #4). Although after the discussion with Rana today, I think it may be that we want to do this measurement in reflection and not transmission, and look for a zero crossing in the PDH signal. In any case, I was able to scan 7 FSRs without any issues. I will upload the data to some git repo. GPS start time is 1208850775, sweep was 3mins long.

I think the next step here is to noise-budget this curve. At least the DFD noises

Attachment 1: 2018_04_BeatMouth_POX.pdf
Attachment 2: 2018_04_BeatMouth.pdf
Attachment 3: ALSSpecgram.pdf
Attachment 4: ALS_ASD.pdf
Attachment 5: ALSstab.pdf
13795   Thu Apr 26 23:00:42 2018 ranaUpdatePEMnew Seis temp chans

After fixing the spelling of the EX temperature readback, I also added all of the MEDM sliders to the C0EDCU.ini file (making sure to add an even number of channels). Restarted FB (after installing telnet on rossa):

telnet fb 8083

> shutdown

preferred method of posting DataViewer images: print as a SVG image (since its vectorized). Then from the command line do:

inkscape steven.svg --export-pdf=vass.pdf

Attachment 1: chans.pdf
13794   Thu Apr 26 20:22:21 2018 KevinUpdatePEMADC common mode rejection with new seismometer connections

Yesterday I wired the outputs from the seismometers directly to the ADC input bypassing the old AA board circuit as is described in this elog. The old circuit converted the single-ended output from the seismometers to a differential signal. Today I looked at whether 60 Hz noise is worse going directly into the ADC due to the loss of the common mode rejection previously provided by the conversion to differential signals.

I split the output from the BS Z seismometer to the new board and to an SR785. On the SR785 I measured the difference between the inner and outer conductors of the seismometer output, i.e. A-B with A the center conductor and B the outer conductor, with grounded input. At the same time I took a DTT spectrum of C1:PEM-SEIS_BS_Z_IN1. Both spectra were taken with 1 Hz bandwidth and 25 averages. The setup is shown in attachment 1.

The spectra are shown in attachment 2. The DTT spectrum was converted from counts to volts by multiplying by 2 * 10 V/32768 cts where the extra factor of 2 is from converting from single-ended to differential input. If there was common 60 Hz noise that the ADC was picking up we would expect to see less noise at 60 Hz in the SR785 spectrum measured directly at the output from the seismometer since that was a differential measurement. Since both spectra have the same 60 Hz noise, this noise is differential.

Attachment 1: setup.pdf
Attachment 2: seismometerASD.pdf
13793   Thu Apr 26 19:46:26 2018 ranaUpdatePEMPID Quixote

Increased the Integral gain (from -1 to -4) on the EX temperature controller. This didn't work a few weeks ago, but now with the added P gain, it seems stable. Daily temperature swings are now ~3x smaller.

Notes for Kira on what we need to do tomorrow (Friday):

1. add the MEDM screen EPICS values to the DAQ so that we can plot those trends DONE
2. add the out-of-loop sensor to the EX can
3. reboot the AUX-EX so we can pick up the new channels and the fixed spelling of the old channels DONE
4. Re-install EX seismometer and hook up seismometer channels to PEM DAQ so we can start testing its performance.

For those who are flabbergasted by the way I calibrated the TEMP_MON channel from volts to deg C, here's how:

XMgrace->Data->Transformations->Geometric Transforms...

use the 'scale' and 'translate' fields to change the slope and offset for calibration in the obvious ways

Attachment 1: dv.pdf
13792   Thu Apr 26 18:58:21 2018 BruceConfigurationALSNew look EX Fiber coupling - pol stability

13791   Thu Apr 26 11:24:50 2018 gautamConfigurationALSNew look EX Fiber coupling - pol stability

Here is a first look at the overnight stability. For the temperature, I used the calibration I found in the old psl database file, seems to give sensible results. It's only 15 hours of data plotted, so we don't see the full 24 hour temperature swing, but I think it is safe to say that for the EX fiber, the dominant cause of the "waveplate effect" is not in fact temperature drift. The polarization extinction is still better than 10dB in the entire period of observation though... I'm going to push ahead with a beat spectrum measurement, though there is room for improvement in the input coupling alignment to fiber special axes.

The apparent increase in these plots towards the end of the 15 hour period is because the lights on the PSL table were switched on.

Annoyingly, it seems like the PSL NPRO channels (which I have hijacked to do this test) do not have minute trend data directly accessible from NDS2. Not sure whether this is an NDS2 problem, or something missing in the way the channels are setup with Acromag. Probably the former, as I am able to generate minute trend plots with dataviewer. I forget whether this is the same as the infamous minute trend problem. Second trend data is available though, and is what I used to make these plots...

Attachment 1: polStab.pdf
13790   Thu Apr 26 09:35:49 2018 KevinUpdatePEMPEM Anti-Alias wiring

I wired all 32 channels going to the AA board directly to the ADC as described in the previous log. However, instead of using the old AA board and bypassing the whole circuit, I just used a breakout board as is shown in the first attachment. I put the board back in the rack and reconnected all of the cables.

The seismic BLRMs appear to be working again. A PSD of the BS seismometers is shown in attachment 2. Tomorrow I'll look at how much the ADC alone is suppressing the common mode 60 Hz noise on each of the channels.

Steve: 5 of ADC DAC In Line Test Boards [ D060124 ] ordered. They should be here within 10 days.

Attachment 1: board.jpg
Attachment 2: SeismometerPSD.pdf
13789   Wed Apr 25 19:09:37 2018 gautamConfigurationALSNew look EX Fiber coupling

Summary:

I implemented most of the things outlined in my previous elog. Implementing the a la mode solution after including all lenses, I managed to achieve >90% mode-matching into the fiber. Power monitor PD has not been re-installed yet, neither has the bracket I removed. The polarization monitoring setup on the PSL table has now been hooked up to the EX fiber, let's see how it does overnight. All quoted power measurements in this elog were made with the Ophir power meter (filter off).

Details:

Attachment #1 shows the implemented MM solution. I did not include the PBS substrate in the calculation, maybe that will help a little.

Attachment #2 shows the new layout. The beam is a little low on the PBS and HWP - I will swap these out to mounts with slightly lower height, that should improve the situation a little. There is no evidence of clipping, and the beam clears all edges by at least 3 beam diameters.

Attachments #3 and #4 show the EX fiber before and after cleaning respectively. Seems like the cleaning was successful.

Attachment #5 shows the beam incident on the coupler with on an IR card. This beam only goes through a QWP, lens, BS and 45 degree steering mirror, so I'm not sure what's responsible for the large halo around the main beam. There is significant power in the halo too - I measured 25mW right before the coupler, but if I use an iris to try and cut off the halo, the power is measured to be ~19mW.

Alignment Procedure:

• Connect spare fiber such that I can monitor coupled power (minus fiber losses and joint loss) at EX table.
• Use Fluke fault analyzer to align input and collimator modes coarsely.
• Monitored coupled power continuously using Fiber Power Meter (although MM calculations were made with Ophir, this was more convenient for "Live" viewing).
• Tweaked one available steering mirror and K6XS axes to maximize coupled power.
• Tweaked lens positions slightly to see if significant improvement could be made.
• After optimizing, I measured 17.1mW coming out of the EX fiber at the PSL table. As mentioned earlier, the input power is tricky to measure given the large amount of junk light around the main mode. But I measured 18.6 mW after the iris. So this is ~95%. In any case, safe to say that we are waaaay better than the previous situation of 380uW out of 1.9mW.
• Added PBS and HWP to cut the incident power to 1.6mW. I measured 1.2mW on the PSL table. Probably adding the PBS screwed up the MM a bit, to be tweaked tomorrow.
• I had moved the Green shutter a bit during this work - as a result, the Green REFL was not making it back to the REFL PD. I remedied this, and EX Green TEM00 mode was locked to the arm. GTRX of ~0.4 was recovered, which is around the number I'm used to seeing.
Attachment 1: EX_fiber_MM.pdf
Attachment 2: IMG_6977.JPG
Attachment 3: IMG_6972.JPG
Attachment 4: IMG_6974.JPG
Attachment 5: IMG_6976.JPG
13788   Wed Apr 25 17:44:39 2018 ArnoldUpdatePEMPEM Anti-Alias wiring

13787   Tue Apr 24 21:19:08 2018 KevinUpdatePEMSeismometer BLRMs

In the ongoing attempt to recover the seismometer BLRMS, I removed the AA board from the rack and modified the BS seismometer Z channel. The BS_Z BLRMs seem to be recovered after this modification.

I removed the three resistors from the output of the circuit and wired the input and from the seismometer directly to the input to the ADC. The modified schematic is shown in attachment 1. Attachments 2 and 3 show the top and bottom of the modified board. The board is doing nothing now other than serving as a connector for this channel.

I put the board back in the rack and injected a 2 Vpp signal into the BS_Z channel and saw +/- 1600 cts in C1PEM-SEIS_BS_Z. I then plugged the seismometer back into the board and took the spectrum shown in attachment 4. This shows the working Z channel giving a reasonable seismic spectrum. Note that X and Y are not modified yet.

If there are no objections, I will modify all the other channels on the board in the same way tomorrow.

Attachment 1: modified_schematic.pdf
Attachment 2: top.jpg
Attachment 3: bottom.jpg
Attachment 4: BS_Seis_PSD.pdf
13786   Tue Apr 24 18:54:15 2018 gautamConfigurationALSProposed changes to EX fiber coupling

I started working on the EX table. Work is ongoing so I will finish this up later in the evening, but in case anyone is wondering why there is no green light...

1. EX laser shutter was closed.
2. Disconnected EX input to the beat mouth at the PSL table in order to avoid accidentally frying the PDs.
3. Prepared new optomechanics hardware
• To my surprise, I found a bubble-wrapped K6XS mount (the one with locking screws for all DoFs) on the SP table. No idea where this came from or who brought it here, or how long it has been here, but I decided to use it nevertheless.
• Prepared f = 200mm and f = -200mm lenses on traveling mounts (Thorlabs DT12, lenses are also Thorlabs, AR1064).
• Made a slight translation of the beam path towards the north to facilitate going through the center of the mounted lenses.
• Temporarily removed a beam dump from next to the final steering mirror before the Green REFL PD, and also removed one of the brackets between the enclosure and the table for ease of laying out components. These will be replaced later.
4. Installed this hardware on the PSL table, roughly aligned beam path.
• Beam now goes through the center of all lenses and is hitting the collimator roughly in the center.

To do in the eve:

1. Clean fiber and connect it to the collimator.
2. Optimize mode-matching as best as possible.
3. Attenuate power using PBS and HWP so as to not damage the BeatMouth PD (Pthresh = 2mW). These are also required to make the polarizations of the EX coupled light (S-pol) and PSL (P-pol) go along the same axis of the PM fiber.
4. Re-install temporarily removed beam dump and bracket on EX table.
5. Re-install EX power monitoring PD.
6. Measure beat frequency spectrum.
 Quote: Motivation: I want to make another measurement of the out-of-loop ALS beat noise, with improved MM into both the PSL and EX fibers and also better polarization control. For this, I want to make a few changes at the EX table.  Barring objections, I will start working on these changes later today.

gautam 1245am: Fiber cleaning was done - I'll upload pics tomorrow, but it seems like the fiber was in need of a good cleaning. I did some initial mode-matching attempts, but peaked at 10% MM. Koji suggested not going for the final precisely tunable lens mounting solution while trying to perfect the MM. So I'll use easier to move mounts for the initial tuning and then swap out the DT12s once I have achieved good MM. Note that without any attenuation optics in place, 24.81mW of power is incident on the collimator. In order to facilitate easy debugging, I have connected the spare fiber from PSL to EX at the PSL table to the main EX fiber - this allows me to continuously monitor the power coupled into the fiber at the EX table while I tweak lens positions and alignment. After a bit of struggle, I noticed I had neglected a f=150mm lens in my earlier calculation - I've now included it again, and happily, there seems to be a solution which yields the theoretical 100% MM efficiency. I'll work on implementing this tomorrow..

13785   Tue Apr 24 15:59:23 2018 SteveUpdateWiki AP table layout 20180328
 Quote: ETMX table layout uploaded with beam paths to the wiki.

The pdf file is uploaded into the wiki.

Attachment 1: DSC00668AP20180328.png
13784   Tue Apr 24 11:31:59 2018 gautamConfigurationALSProposed changes to EX fiber coupling

Motivation: I want to make another measurement of the out-of-loop ALS beat noise, with improved MM into both the PSL and EX fibers and also better polarization control. For this, I want to make a few changes at the EX table.

1. Replace existing fiber collimator with one of the recently acquired F220-APC-1064 collimators.
• This gives an output mode of diameter 2.4mm with a beam divergence angle of 0.032 degrees (all numbers theoretical - I will measure these eventually but we need a beam path of ~5m length in order to get a good measurement of this collimated beam).
• I believe it will be easier to achieve good mode matching into this mode rather than with the existing collimator.
• Unfortunately, the mount is still going to be K6X and not K6XS.
2. Improve mode-matching into fiber.
• I used my measurement of the Innolight NPRO mode from 2016, a list of available lenses, and some measured distances to calculate a solution that gives theoretical 100% overlap with the collimator mode, that has beam diameter 2.4mm, located 80cm from the NPRO shutter head location (see Attachment #1).
• The required movement of components is schematically illustrated in Attachment #2.
• One of the required lens positions is close to the bracket holding the enclosure to the table, but I think the solution is still workable (the table is pretty crowded so I didn't bother too much with trying to find alternative solutions as all of them are likely to require optics placed close to existing ones and I'd like to avoid messing with the main green beam paths.
• I will attempt to implement this and see how much mode matching we actually end up getting.
3. Install a PBS + HWP combo in the EX fiber coupling path.
• This is for better polarization control.
• Also gives us more control over how much light is coupled into the fiber in a better way than with the ND filters in current path.
4. Clean EX fiber tip.
5. Dump a leakage IR beam from the harmonic separator post doubling oven, which is currently just hitting the enclosure. It looks pretty low power but I didn't measure it.
6. Re-install EX power monitoring PD.

Barring objections, I will start working on these changes later today.

Attachment 1: EX_fiber_MM.pdf
Attachment 2: EX_fiber_changes.png
13783   Tue Apr 24 10:10:43 2018 gautamUpdateComputer Scripts / ProgramsParticle swarm hyper parameter optimization

I'm copying and pasting Nikhil's email here as he was unable to login to the elog (but should now be able to in order to reply to any comments, and add more details about this test, motivation, methodology etc).

I did some post-processing after running the grid search. The following steps were carried out:

1) Selected those sets whose cost fun were less than a specific threshold (here 10000)

2) Next task was to see if the parameters of these good solutions had some pattern

3) I used a dimensionality reduction technique called t-SNE to project the 6 dimensional parameter space to 2 dim (for better visualization )

4) Made a scatter plot of these (see fig )

5) Used K-Means to find the clusters in this data

6) MarkerSize & Color reflect the cost fun. Bigger the marker size means better the solution.

7) Visual inspection implied cluster 5 had the best ranking points & more than any other cluster

8) These points had the following Parameter set: Workers {20,40}, SwarmSize {500}, MaxIter {500}, Self Adjustment {1}, Social Adjustment {1}, Tolerance {1e-3,1e-8}

     See fig: for the box plot

9) It looks like is a particular set of values rather than individual values that gives the best results.

Attachment 1: ClusterFminScaled.png
Attachment 2: ClusterID_5.png
13782   Tue Apr 24 09:10:20 2018 KiraUpdatePEMfinal setup sketch

I've attached the final sketch for the panel on the granite block.

Attachment 1: EX-can-panel_1.pdf
13781   Tue Apr 24 08:36:47 2018 johannesConfigurationGeneralAux Laser LD dying? (AS port laser injection)

In September 2017 I measured ~150mW output power, which was already kind of low. What are the chances of getting this one repaired? Steve, can you please check the serial number? It's probably too old like the other ones.

 Quote: I suspect that the LD of the aux laser is dying. - The max power we obtain from this laser (700mW NPRO) is 33mW. Yes, 33mW. (See attachment 1)

13780   Mon Apr 23 20:06:35 2018 ranaUpdatePEMPID tune

This shows a step response of the EX seis temp control with K_I = -1 and K_P = -0.1. The time constants for both heatup and cooldown are ~2 hours.

I'm not so sure if the PID code itself makes sense though:

  # The basic finite-difference PID approximation   e[0] = (p-s)   print("Error signal = {}" .format(e[0])) 

  # These are the main equations of the PID Process   u[0] = u[1]   u[0] = u[0] + Kp * (e[0] - e[1])   u[0] = u[0] + Ki * (e[0])   u[0] = u[0] + Kd * (e[0] - 2*e[1] + e[2])

Seems like the Proportional term uses the difference (or derivative) of the error signal. This makes it more likely to pick up some high frequency noise; maybe we should low pass this signal somewhat, or at least implement a running average.

Since we still don't have an out of loop sensor or a PSL room temperature monitor or a particle counter in the frames, I've disabled the PID loop to see how much the can temperature varies with no feedback. Please leave it this way for a few days.

Attachment 1: HeaterTest.png
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