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ID Dateup Author Type Category Subject
  13542   Fri Jan 12 18:22:09 2018 gautamConfigurationComputerssendmail troubles on nodus

Okay I will port awade's python mailer stuff for this purpose.

gautam 14Jan2018 1730: Python mailer has been implemented: see here for the files. On shared drive, the files are at /opt/rtcds/caltech/c1/scripts/general/pizza/pythonMailer/

gautam 11Feb2018 1730: The python mailer had never once worked successfully in automatically sending the message. I realized this may be because I had put the script on the root user's crontab, but had setup the authentication keyring with the password for the mailer on the controls user. So I have now setup a controls user crontab, which for now just runs the pizza mailing. let's see if this works next Sunday...

Quote:

I personally don't like the idea of having sendmail (or something similar like postfix) on a personal server as it requires a lot of maintenance cost (like security update, configuration, etc). If we can use external mail service (like gmail) via gmail API on python, that would easy our worry, I thought.

 

  13543   Fri Jan 12 19:15:34 2018 johannesUpdateDAQetmx slow daq chassis

Steve and I removed c1auxex from 1X9 today to make space for the DAQ chassis. Steve installed rails for mounting. To install the box I had to remove all cabling, for which I used the usual precautions (disconnect satellite box etc.)

On reconnect c1auxex2 didn't initialize the physical EPICS channels (the 'actual' acromag channels), apparently it had trouble communicating. A reboot fixed this. It's possible that this is because of the direct cable connection without a network switch that exists
between the Acromags and c1auxex. The EPICS server was started automatically on reboot.

Currently the channel defaults need to be loaded manually after every EPICS server script restart with burt. I'm looking for a good way to automate this, but the only compiled burt binaries for x86 (that we can in principle run on c1auxex2 itself) on the martian network are from EPICS version 3.14.10 and throw a missing shared object error. Could be that simply some path variable is missing.

The burt binaries are not distributed by the lscsoft or cdssoft packages, so alternatively we would need to compile it ourselves for x86 or get it working with the older epics version.

  13544   Fri Jan 12 20:35:34 2018 Udit KhandelwalSummaryGeneral2018/01/12 Summary
  1. 40m Lab CAD
    1. Worked further on positioning vacuum tubes and chambers in the building.
    2. Next step would be to find some drawings for optical table positions and vibration isolation stack. Need help with this! 
  2. Tip Tilt Suspension (D070172)
    1. Increased the length of side arms. The overall height of D070172 assembly matches that of D960001.
    2. The files are present in dropbox in [40mShare] > [40m_cad_models] > [TT - Tip Tilt Suspension]
  13545   Sat Jan 13 02:36:51 2018 ranaConfigurationComputerssendmail troubles on nodus

I think sendmail is required on nodus since that's how the dokuwiki works. That's why the dokuwiki was trying to send an email to Umakant.

  13546   Sat Jan 13 03:20:55 2018 KojiConfigurationComputerssendmail troubles on nodus

I know it, and I don't like it. DokuWiki seems to allow us to use an external server for notification emails. That would be the way to go.

  13547   Mon Jan 15 11:53:57 2018 gautamUpdateIOOMCautolocker getting stuck

Looks like this problem presisted over the weekend - Attachment #1 is the wall StripTool trace for PSL diagnostics, seems like the control signal to the NPRO PZT and FSS EOM were all over the place, and saturated for the most part.

I traced down the problem to an unresponsive c1iool0. So looks like for the IMC autolocker to work properly (on the software end), we need c1psl, c1iool0 and megatron to all be running smoothly. c1psl controls the FSS box gains through EPICS channels, c1iool0 controls the MC servo board gains through EPICS channels, and megatron runs the various scripts to setup the gains for either lock acquisition or in lock states. In this specific case, the autolocker was being foiled because the mcdown script wasn't running properly - it was unable to set the EPICS channel C1:IOO-MC_VCO_GAIN to its lock acquisition value of -15dB, and was stuck at its in-lock value of +7dB. Curiously, the other EPICS channels on c1iool0 seemed readable and were reset by mcdown. Anyways, keying the c1iool0 crate seems to have fixed the probelm.

Quote:

I've noticed this a couple of times today - when the autolocker runs the mcdown script, sometimes it doesn't seem to actually change the various gain sliders on the PSL FSS. There is no handshaking built in to the autolocker at the moment. So the autolocker thinks that the settings are correct for lock re-acquisition, but they are not. The PCdrive signal is often railing, as is the PZT signal. The autolocker just gets stuck waiting to re-acquire lock. This has happened today ~3 times, and each time, the Autolocker has tried to re-acquire lock unsuccessfully for ~1hour.

Perhaps I'll add a line or two to check that the signal levels are indicative of mcdown being successfully executed.

 

  13548   Mon Jan 15 17:36:03 2018 gautamHowToOptical LeversOplev calibration

Summary:

I checked the calibration of the Oplevs for both ITMs, both ETMs and the BS. The table below summarizes the old and new cts->urad conversion factors, as well as the factor describing the scaling applied. Attachment #1 is a zip file of the fits performed to calculate these calibration factors (GPS times of the sweeps are in the titles of these plots). Attachment #2 is the spectra of the various Oplev error signals (open loop, so a measure of seismic induced angular motion for a given optic, and DoF) after the correction. Loop TF measurements post calibration factor update and loop gain adjustment to be uploaded tomorrow.

Optic, DoF Old calib [urad/ct] New Calib [urad/ct] Correction Factor [new/old]
ETMX, Pitch 200 175 0.88
ETMX, Yaw 222 175 0.79
ITMX, Pitch 122 134 1.1
ITMX, Yaw 147 146 1
BS, Pitch 130 136 1.05
BS, Yaw 170 176 1.04
ITMY, Pitch 239 254 1.06
ITMY, Yaw 226 220 0.97
ETMY, Pitch 140 164 1.17
ETMY, Yaw 143 169 1.18

Motivation:

We'd like for the Oplev calibration to be a reliable readback of the optic alignment. For example, a calibrated Oplev would be a useful diagnostic to analyze the drifting (?) ETMX.

Details:

  1. I locked and dither aligned the individual arms.
  2. I then used a 60 second ramp time to misalign <optic> in {ITMX, ITMY, BS, ETMX, ETMY} one at a time, and looked at the appropriate arm cavity transmission while the misalignment was applied. The amplitude of the misalignment was chosen such that in the maximally misaligned state, the arm cavity was still locked to a TEM00 mode, with arm transmission ~40% of the value when the cavity transmission was maximized using the dither alignment servos. The CDS ramp is not exactly linear, it looks more like a sigmoid near the start and end, but I don't think that really matters for these fits.
  3. I used the script OLcalibFactor.py (located at /opt/rtcds/caltech/c1/scripts/OL) to fit the data and extract calibration factors. This script downloads the arm cavity transmission and the OL error signal during the misalignment period, and fits a Gaussian profile to the data (X=oplev error signal, Y=arm transmission). Using geometry and mode overlap considerations, we can back out the misalignment in physical units (urad).

Comments:

  1. For the most part, the correction was small, of the order of a few percent. The largest corrections were for the ETMs. I believe the last person to do Oplev calibration for the TMs was Yutaro in Dec 2015, and since then, we have certainly changed the HeNes at the X and Y ends (but not for the ITMs), so this seems consistent.
  2. From attachment #2, most of the 1Hz resonances line up quite well (around 1-3urad/rtHz), so gives me some confidence in this calibration.
  3. I haven't done a careful error analysis yet - but the fits are good to the eye, and the residuals look randomly distributed for the most part. I've assumed precision to the level of 1 urad/ct in setting the new calibration factors.
  4. I think the misalignment period of 60 seconds is sufficiently long that the disturbance applied to the Oplev loop is well below the lower loop UGF of ~0.2Hz, and so the in loop Oplev error signal is a good proxy for the angular (mis)alignment of the optic. So no loop correction factor was applied.
  5. I've not yet calibrated the PRM and SRM oplevs.

Now that the ETMX calibration has been updated, let's keep an eye out for a wandering ETMX.

  13549   Tue Jan 16 11:05:51 2018 gautamUpdatePSL PSL shelf - AOM power connection interrupted

While moving the RefCav to facilitate the PSL shelf install, I bumped the power cable to the AOM driver. I will re-solder it in the evening after the shelf installation. PMC and IMC have been re-locked. Judging by the PMC refl camera image, I may also have bumped the camera as the REFL spot is now a little shifted. The fact that the IMC re-locked readily suggests that the input pointing can't have changed significantly because of the RefCav move.

 

  13550   Tue Jan 16 16:18:47 2018 SteveUpdatePSLnew PSL shelf in place

[ Johannes, Rana, Mark and Steve ]

On the second trial the shelf was installed. Plastic cover removed. South end door put back on and 2W Inno turned on.

Shelf 10 " below the existing one:   92" x 30" x 3/4" melamine (or MDF) covered with white Formica.  200 lbs it's max load. Working distance to top of the table 18"

Quote:

While moving the RefCav to facilitate the PSL shelf install, I bumped the power cable to the AOM driver. I will re-solder it in the evening after the shelf installation. PMC and IMC have been re-locked. Judging by the PMC refl camera image, I may also have bumped the camera as the REFL spot is now a little shifted. The fact that the IMC re-locked readily suggests that the input pointing can't have changed significantly because of the RefCav move.

 

 

  13551   Tue Jan 16 21:46:02 2018 gautamUpdatePSL PSL shelf - AOM power connection interrupted

Johannes informed me that he touched up the PMC REFL camera alignment. I am holding off on re-soldering the AOM driver power as I could use another pair of hands getting the power cable disentangled and removed from the 1X2 rack rails, so that I can bring it out to the lab and solder it back on.

Is anyone aware of a more robust connector solution for the type of power pins we have on the AOM driver?

Quote:

While moving the RefCav to facilitate the PSL shelf install, I bumped the power cable to the AOM driver. I will re-solder it in the evening after the shelf installation. PMC and IMC have been re-locked. Judging by the PMC refl camera image, I may also have bumped the camera as the REFL spot is now a little shifted. The fact that the IMC re-locked readily suggests that the input pointing can't have changed significantly because of the RefCav move.

 

 

  13552   Tue Jan 16 21:50:53 2018 gautamUpdateALSFiber ALS assay

With Johannes' help, I re-installed the box in the LSC electronics rack. In the end, I couldn't find a good solution to thermally insulate the inside of the box with foam - the 2U box is already pretty crowded with ~100m of cabling inside of it. So I just removed all the haphazardly placed foam and closed the box up for now. We can evaluate if thermal stability of the delay line is limiting us anywhere we care about and then think about what to do in this respect. This box is actually rather heavy with ~100m of cabling inside, and is right now mounted just by using the ears on the front - probably should try and implement a more robust mounting solution for the box with some rails for it to sit on.

I then restored all the cabling - but now, the delayed part of the split RF beat signal goes to the "RF in" input of the demod board, and the non-delayed part goes to the back-panel "LO" input. I also re-did the cabling at the PSL table, to connect the two ZHL3-A amplifier inputs to the IR beat PDs in the BeatMouth instead of the green BBPDs.

I didn't measure any power levels today, my plan was to try and get a quick ALS error signal spectrum - but looks like there is too much beat signal power available at the moment, the ADC inputs for both arm beat signals are overflowing often. The flat gain on the AS165 (=ALS X) and POP55 (=ALS Y) channels have been set to 0dB, but still the input signals seem way too large. The signals on the control room spectrum analyzer come from the "RF mon" ports on the demod board, and are marked as -23dBm. I looked at these peak heights with the end green beams locked to the arm cavities, as per the proposed new ALS scheme. Not sure how much cable loss we have from the LSC rack to the network analyzer, but assuming 3dB (which is the Google value for 100ft of RG58), and reading off the peak heights from the control room analyzer, I figure that we have ~0dBm of RF signal in the X arm. => I would expect ~3dBm of signal to the LO input. Both these numbers seem well within range of what the demod board is designed to handle so I'm not sure why we are saturating.

Note that the nominal (differential) I and Q demodulated outputs from the demod board come out of a backplane connector - but we seem to be using the front panel (single-ended) "MON" channels to acquire these signals. I also need to update my Fiber ALS diagram to indicate the power loss in cabling from the PSL table to the LSC electronics rack, expect it to be a couple of dB.

 

Quote:

After labeling cables I would disconnect, I pulled the box out of the LSC rack. Attachment #1 is a picture of the insides of the box - looks like it is indeed just two lengths of cabling. There was also some foam haphazardly stuck around inside - presumably an attempt at insulation/isolation.

Since I have the box out, I plan to measure the delay in each path, and also the signal attenuation. I'll also try and neaten the foam padding arrangement - Steve was showing me some foam we have, I'll use that. If anyone has comments on other changes that should be made / additional tests that should be done, please let me know.

20180111_2200: I'm running some TF measurements on the delay line box with the Agilent in the control room area (script running in tmux sesh on pianosa). Results will be uploaded later.

 

 

  13553   Wed Jan 17 14:32:51 2018 gautamUpdateDAQAcromag checks
  1. I take back what I said about the OSEM PD mon at the meeting - there does seem to be to be some overall calibration factor (Attachment #1) that has scaled the OSEM PD readback channels, by a factor of (20000/2^15), which Johannes informs me is some strange feature of the ADC, which he will explain in a subsequent post.
  2. The coil redback fields on the MEDM screen have a "30Hz HPF" text field below them - I believe this is misleading. Judging by the schematic, we are monitoring, on the backplane (which is what these channels are reading back from), the coil to the voltage with a gain of 0.5. We can reconfirm by checking the ETMX coil driver board, after which we should remove the misleading label on the MEDM screens.
Quote:

Some suggestions of checks to run, based on the rightmost colum in the wiring diagram here - I guess some of these have been done already, just noting them here so that results can be posted.

  1. Oplev quadrant slow readouts should match their fast DAQ counterparts.
  2. Confirm that EX Transmon QPD whitening/gain switching are working as expected, and that quadrant spectra have the correct shape.
  3. Watchdog tripping under different conditions.
  4. Coil driver slow readbacks make sense - we should also confirm which of the slow readbacks we are monitoring (there are multiple on the SOS coil driver board) and update the MEDM screen accordingly.
  5. Confirm that shadow sensor PD whitening is working by looking at spectra.
  6. Confirm de-whitening switching capability - both to engage and disengage - maybe the procedure here can be repeated.
  7. Monitor DC alignment of ETMX - we've seen the optic wander around (as judged by the Oplev QPD spot position) while sitting in the control room, would be useful to rule out that this is because of the DC bias voltage stability (it probably isn't).
  8. Confirm that burt snapshot recording is working as expected - this is not just for c1auxex, but for all channels, since, as Johannes pointed out, the 2018 directory was totally missing and hence no snapshots were being made.
  9. Confirm that systemd restarts IOC processes when the machine currently called c1auxex2 gets restarted for whatever reason.

 

 

 

  13554   Wed Jan 17 22:44:14 2018 johannesUpdateDAQAcromag checks

This happened because there are multiple ways to scale the raw value of an EPICS channel to the desired output range. In the CryoLab I was using one way, but the EPICS records I copied from c1auxex were doing it differently. Basically this:

DTYP  - Data type -
LINR "NO CONVERSION" vs "LINEAR"
RVAL Raw value
EGUF Engineering units full scale
EGUL Engineering units low
ASLO Manual scaling factor
AOFF Manual offset
VAL Value

If the "LINR" field is set to "LINEAR", the fields EGUF and EGUL are used to convert the raw value to the channel value VAL. To use them, one needs to enter the voltages that return the maximum and minimum values expected for the given data type. It used to be +10V and -10V, respectively, and was copied that way but that doesn't work with the data type required for the Acromag units. For -some- reason, while the the ADC range is -10V to +10V, this corresponds to values -20000 to +20000, while for the DAC channels it's -30000 to +30000. I had observed this before when setting up the DAQ in the CryoLab, but there we were using "NO CONVERSION", which skips the EGUF and EGUL fields, and used the ASLO and AOFF for manual scaling to get it right. When I mixed the records from there with the old ones from c1auxex this got lost in translation. Gautam and I confirmed by eye that this indeed explains the different levels well. This means that the VMon channelsfor the coils are also showing the wrong voltages, which will be corrected, but the readback still definitely works and confirms that the enable switches do their job.

Quote:
  1. I take back what I said about the OSEM PD mon at the meeting - there does seem to be to be some overall calibration factor (Attachment #1) that has scaled the OSEM PD readback channels, by a factor of (20000/2^15), which Johannes informs me is some strange feature of the ADC, which he will explain in a subsequent post.

 

  13555   Wed Jan 17 23:36:12 2018 johannesConfigurationGeneralAS port laser injection

Status of the AS-port auxiliary laser injection

  • Auxiliary laser with AOM setup exists, first order diffracted beam is coupled into fiber that leads to the AS table.
  • There is a post-PMC picked-off beam available that is currently just dumped (see picture). I want to use it for a beat note with the auxiliary laser pre-AOM so we can phaselock the lasers and then fast-switch the phaselocked light on and off.
  • I was going to use the ET3010 PD for the beat note unless someone else has plans for it.
  • I obtained a fixed triple-aspheric-lens collimator which is supposed to have a very small M^2 value for the collimation on the AS table. I still have the PSL-lab beam profiler and will measure its output mode.
  • Second attached picture shows the space on the AS table that we have for mode-matching into the IFO. Need to figure out the desired mode and how to merge the beams best.
  13557   Thu Jan 18 00:35:00 2018 gautamUpdateALSFiber ALS assay

Summary:

I am facing two problems:

  1. The X arm beat seems to be broadband noisier than the Y arm beat - see Attachment #1. The Y-axis calibration is uncertain, but at least the Y beat has the same profile as the reference traces, which are for the green beat from a time when we had ALS running. There is also a rather huge ~5kHz peak, which I confirmed isn't present in the PDH error/control signal spectra (with SR785).
  2. The Y-arm beat amplitude, at times, "breathes" in amplitude (as judged by control room analyzer). Attachment #2 is a time-lapse of this behaviour (left beat is X arm beat, right peak is the Y arm peak) - I caught only part of it, the the beat note basically vanishes into the control room noise floor and then comes back up to almost the same level as the X beat. The scale is 10dB/div. During this time, the green (and IR for that matter) stay stably locked to the arm - you'll have to take my word for it as I have no way to sync my video with StripTool Traces, but I was watching the DC transmission levels the whole time. The whole process happens over a few (1< \tau <5) minutes - I didn't time it exactly. I can't really say this behaviour is periodic either - after the level comes back up, it sometimes stays at a given level almost indefinitely.

More details:

  • Spent some time today trying to figure out losses in various parts of the signal chain, to make sure I wasn't in danger of saturating RF amplifiers. Cabling from PSL table -> LSC rack results in ~2dB loss.
  • I will upload the updated schematic of the Beat-Mouth based ALS - I didn't get a chance to re-measure the optical powers into the Beat Mouth, as someone had left the Fiber Power Meter unplugged, and it had lost all of its charge angry.
  • The Demod boards have a nice "RF/LO power monitor" available at the backplane of the chassis - we should hook these channels up to the DAQ for long term monitoring.
    • The schematic claims "120mV/dBm" into 50ohms at these monitoring pins.
    • I measured the signal levels with a DMM (Teed with 50ohm), but couldn't really make the numbers jive - converting the measured backplane voltage into dBm of input power gives me an inferred power level that is ~5dBm higher than the actual measured power levels (measured with Agilent analyzer in Spectrum Analyzer mode).
  • Looking at the time series of the ALS I and Q inputs, the signals are large, but we are well clear of saturating our 16-bit ADCs.
  • In the brief periods when both beats were stable in amplitude (as judged by control room analyzer), the output of the Q quadrature of the phase tracker servo was ~12,000 cts - the number I am familiar with for the green days is ~2000cts - so naively, I would say we have ~6x the RF beat power from the Beat Mouth compared to green ALS.
  • I didn't characterize the conversion efficiency of the demod boards so I don't have a V (IF)/V (RF) number at the moment.
  • I confirmed that the various peaks seen in the X arm beat spectrum aren't seen in the control signal of the EX Green PDH, by looking at the spectrum on an SR785 (it is also supposedly recorded in the DAQ system, but I can't find the channel and the cable is labelled "GCX-PZT_OUT", which doesn't match any of our current channels).
    Note to self from the future: the relevant channels are: C1:ALS-X_ERR_MON_IN1 (green PDH error signal with x10 gain from an SR560) and C1:ALS-X_SLOW_SERVO_IN1 (green PDH control signal from monitor point - I believe this is DC coupled as this is the error signal to the slow EX laser PZT temp control). I've changed the cable labels at the X end to reflect this reality. At some point I will calibrate these to Hz.
  • The control room analyzer signals come from the "RF mon" outputs on the demod board, which supposedly couple the RF input with gain of -23dBm. These are then routed reverse through a power splitter to combine the X and Y signals, which is then plugged into the HP analyzer. The problem is not local to this path, as during the "breathing" of the Y beat RF amplitude, I can see the Q output of the phase tracker also breathing.

Next steps (that I can think of, ideas welcome!):

  1. For Problem #1 - usual debugging tactic of switching X and Y electronics paths to see if the problem lies in the light or in the electronics. If it is in the electronics, we can swap around at various points in the signal chain to try and isolate the problematic component.
  2. For Problem #2 - hook up the backplane monitor channels to monitor RF amplitudes over time and see if the drifts are correlated with other channels.
  3. There is evidence of some acoustic peaks, which are possibly originating from the fibers - need to track these down, but I think for a first pass to try and get the red ALS going, we shouldn't be bothered by these.

 

 

  13558   Fri Jan 19 11:13:21 2018 gautamUpdateCDSslow machine bootfest

c1psl, c1susaux, and c1auxey today

Quote:

MC autolocker got stuck (judging by wall StripTool traces, it has been this way for ~7 hours) because c1psl was unresponsive so I power cycled it. Now MC is locked.

 

  13559   Fri Jan 19 11:34:21 2018 gautamUpdateALSFiber ALS assay

I swapped the inputs to the ZHL-3A at the PSL table - so now the X beat RF signals from the beat mouth are going through what was previously the Y arm ALS electronics. From Attachment #1, you can see that the Y arm beat is now noisier than the X. The ~5kHz peak has also vanished.

So I will pursue this strategy of switching to try and isolate where the problem lies...


Somebody had forgotten to turn the HEPA variac on the PSL table downsad. It was set at 70. I set it at 20, and there is already a huge difference in the ALS spectra

Quote:
 
  1. For Problem #1 - usual debugging tactic of switching X and Y electronics paths to see if the problem lies in the light or in the electronics. If it is in the electronics, we can swap around at various points in the signal chain to try and isolate the problematic component.
  13560   Fri Jan 19 15:22:19 2018 Udit KhandelwalSummaryGeneral40m CAD update 2018/01/19

40m CAD Project

  1. All parts will be now named according to the numbering system in this excel sheet: LIGO 40m Parts List in dropbox folder [40mShare] > [40m_cad_models] > [40m Lab CAD]
  2. I've placed optical tables in the chambers at 34.82" from the bottom for now. This was chosen by aligning the centre of test mass of SOS assembly (D960001) with that of vacuum tube (Steve however pointed out last week they might not necessarily be concentric).

  13561   Fri Jan 19 20:59:07 2018 Udit KhandelwalUpdateGeneralSolidworks Rendering

Rendered the SOS assembly (D960001) with correct materials and all and it looks very nice. Will extend this to the building cad later.

  13562   Fri Jan 19 23:04:11 2018 gautamUpdateALSFiber ALS assay

[rana, kevin, udit, gautam]

quick notes of some discussions we had today:

  1. Earlier in the day, Udit and I measured (with a 20dB coupler and AG4395) ~20dBm of RF beat power at input to power splitter (just before delay line box) at the LSC rack. This means that we have ~17dBm going into the LO input of the demod board. The AP1053 can only really handle a max of 16dBm at the input. After discussion with Rana, I put a 3dB attenuator at the input to the power splitter so as to preserve the LO/RF ratio in the demod circuit.
  2. Need to make a detailed optical and RF power budget for both arms.
  3. The demod circuit board is configured to have gain of x100 post demod (conversion loss of the mixer is ~-8dB). This works well for the PDH cavity locking type of demod scheme, where the loop squishes the error signal in lock, so most of the time, the RF signal is tiny, and so a gain of x100 is good. For ALS, the application needs are rather different. So we lowered the gain of the "Audio IF amplifier" stage of the circuit from x100 to x10, by effecting the resistor swaps 10ohms->50ohms, 1kohm->500ohms (more details about this later).
  4. There is some subtlety regarding the usage of the whitening interface boards - I need to look at the circuit again and understand this better, but Rana advised against running with the whitening gain at low values. Point #3 above should have helped with this regard.
  5. I wanted to test the new signal chain (with 3dB attenuation and modified IF gain) but ETMX is not happy now, and is making it impossible to keep the X arm locked. Will try again tomorrow.
  6. Eventually: need to measure the mode of the fiber, and up the MM efficiency to at least 80%, which should be doable without using any fancy lenses/collimators.
  7. Udit and I felt that the back panel RF power monitor wasn't working as expected - I will re-investigate this when I have the board out again to make the IF gain change permanent with the right footprint SMD resistors.

RXA: 0805 size SMD thin film resistors have been ordered from Mouser, to be shipped on Monday. **note that these thin film resistors are black; i.e. it is NOT true that all black SMD resistors are thick film**

  13563   Sat Jan 20 01:20:37 2018 gautamUpdateElectronicsWhitening filter D990694

We use D990694 in various places. Today, Rana alerted me to an important consideration to be kept in mind when we use this board, which I found quite interesting. I still don't understand the problem at the BJT level, but I think one can appreciate the problem without going to the transistor design of the LT1125. I'm attaching an annotated schematic of the whitening section in question. If the following assumptions are valid, then I think my picture is valid.

  1. The switch used to bypass the various whitening gain stages, namely the ADG333ABR, has infinite impedance in the "OFF" state, such that when the 24dB gain stage is bypassed, U28A (or in general one of the 4 quad op-amps) is forced to drive it's output voltage across 1.0665 kohms of resistance.
  2. The individual LT1125 Op Amps can drive a maximum of 30mA of current.

Then, as one can see in the attached schematic, when we set the gain of any input to <24dB, we must ensure that the input voltage is less than approximately 2V. Otherwise, by asking too much of the first stage op-amp in the quad IC LT1125, we may be messign around with all the 4 op amps in the quad! Even the 0dB setting is not immune to this problem, as it uses one of the 4 op amps.

I don't think the usual rules of calculating the gain of a non-inverting amplifier (G = 1 + Rf/Ri) remain valid even when the op-amp is forced to drive more output current than it can, and I don't have a way to quantify the possible interference between the 4 op amps in the quad - but does this seem like a valid conclusion? If so, we must check signal levels of various LSC signals. AS55 signals currently have the 0dB gain setting - I had turned this down from 6dB some months ago, because it seemed like the ADC was saturating at the 6dB gain setting, which suggests that the input voltage is ceratinly > 2V, and AS55_Q is what is used for MICH control in the DRMI. All of my noise budgeting work over the last few months used this setting, I wonder if they are all invalid surprise


Now that I think about this a bit more - this problem shouldn't be significant for the usual LSC degrees of freedom when in lock, as the huge DC gain of the loop should squish large DC values of the error signals, and so there shouldn't be any danger of overloading the LT1125. But I don't know if we are being hurt by this effect when flashing through resonances, when the PDH horn-to-horn voltage can be quite high (which is in principle a good thing?). I don't know if there is any "hysterisis" effect where the overloaded quad IC has some relaxation time before it returns to normal operation, and if we are being limited in our ability to catch lock because if this effect. 

The concerns remain valid for th ALS demodulated error signals though, for which the signals will remain large throughout.

  13564   Sat Jan 20 15:57:11 2018 ranaUpdateElectronicsWhitening filter D990694

this is the note from Hartmut Grote on this topic from 2004

  13565   Sun Jan 21 13:11:25 2018 johannesUpdateDAQAcromag checks

After some research: -the- reason for the reduced +/- 20,000 swing in raw values is a default setting for having support for legacy devices enabled when using the acromag proprietary i2o peer-to-peer protocol. So this is doubly unnecessary because a) we don't have any legacy devices at all and b) we're using pure modbus/TCP and no i2o. To change the setting I have to connect via the USB configuration utility. In addition, I want to understand the averaging feature of the acromag units better, which is also configured via USB, and lets one set a fixed amount of samples to be averaged before updating the read-register value. The documentation says that the 8 channels are multiplexed into a single ADC, and that new input data is available after 10 ms for each channel, suggesting a sampling rate of 100 Hz per channel and that the multiplexing happens faster, but is not super-clear about this, so I want to test it in the cryo lab first before unleashing it onto c1auxex2.

Furthermore, the standard timing options for updating epics records are 10s, 5s, 2s, 1s, 0.5s, 0,2s, and 0.1s. On the previous c1auxex, the monitoring channels were set to 0.1s, but that clashes with the 16 Hz global EPICS rate, resulting in partial double-sampling. One can manually provide the option 0.0625s for 16Hz update rate. I will test this and how it deals with the averaging in the cryolab too.

  13566   Mon Jan 22 12:48:48 2018 KojiSummaryGeneralBeat setup for aLIGO EOM test

I'm planning to construct a beat setup between the PSL and AUX beams. I am going to make it in the area shown in a blue square in the attached photo. This does not disturb Johannes' and PSL setups. The beams are obtained from the PBS reflection of the PSL and the dumped beam of the aux path (0th or 1st order beam of the AOM).

  13567   Mon Jan 22 20:54:58 2018 KojiSummaryGeneralAUX-PSL beat setup

The beat setup has been made on the PSL table. The BS and the PD were setup. The beat was found at 29.42degC and 50.58degC for the PSL and AUX crystal temperatures, respectively.
We are ready for the EOM test. I have instruments stacked around the PSL table. Please leave them as they are for a while. If you need to move them, please contact with me. Thanks.


A picked-off PSL after the main modulator was used as the PSL beam. This was already introduced close to the setup thanks to the previous 3f cancellation test ELOG 11029. The AUX beam was obtained from the transmission of 90% mirror. Both paths have S polarization. The beams are combined with a S-pol 50% BS. The combined beam is detected by a new focus 1GHz PD.

The PSL crystal temp (actual) was 50.58degC. The AUX crystal temp was swept upward and the string beat was found at 50.58degC. After a bit of alignment, the beat strength was -18dBm (at 700V/A RF transimpedance of NF1611) .

  13568   Tue Jan 23 01:33:23 2018 gautamUpdateElectronicsWhitening filter D990694

After discussing with Koji, we looked at the aLIGO incarnation of this board. Interestingly, it too has a similar topology of 4 switchable gain stages with gains of 24, 12, 6 and 3dB. The main differences are that they use single Op27 ICs instead of the quad LT1125s, and also, they use a different combination of feedback resistors to realize the various gains. 

We considered upping the feedback resistance (R15, R143) on the 24dB gain stage of our boards from (1k, 66.5ohms) to (3k, 200ohms) as on the aLIGO boards - but this doesn't really help? Because KCL demands that the same current flow in R15 and R143, and so the output Vsat of the op amp and its max current driving capabilities in combination determine if the inverting input can follow the non inverting input?

As Hartmut points out in his note, he was able to access the full range of ADC voltages when the gain was set to 3dB, despite the fact that the LT1125 was still getting internally saturated. Operating with minimum 24dB whitening gain doesn't really solve the problem either because the problem just gets shifted to the next gain stage in the chain, and we still have saturation. I also don't have a feeling for how much differential voltage these LT1125s can sustain before they are damaged - I guess the planned THD check will reveal if they are okay or not.

It seems to me like the only way to truly fix this problem of one stage saturating and screwing up the others is to use single Op27s (or equivalent) in place of the quad LT1125s. The aLIGO design also has a series resistance to the non-inverting input - this can help prevent current overdraw from the previous stage (due to a lowered input impedance of the OpAmp - but I wonder how low this can go?).

Quote:

this is the note from Hartmut Grote on this topic from 2004

 

  13569   Tue Jan 23 01:56:18 2018 gautamUpdateElectronicsTeledyne AP1053

I have acquired 5 pieces of the Teledyne AP1053 from Koji - these are now at the 40m. I will determine an appropriate location for storage of these and update. We are also looking to acquire 5 more of these. The combination of high power output (26dBm), low gain (10dB), and low noise figure (1.5dB) are quite uncommon in an amplifier and so these should be used only when such properties are required simultaneously.

*Steve informs me that these amps have been stored in the RF cabinet E6 along the east arm.

Steve's note: Teledyne rf amp product selection guide

                   Teledyne rf low noise amp guide

 

  13570   Tue Jan 23 16:02:05 2018 SteveConfigurationSEIload cells

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

Quote:

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

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

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

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

 

  13571   Wed Jan 24 00:33:31 2018 gautamUpdateALSFiber ALS assay

I did some work on the PSL table today. Main motivations were to get a pickoff for the BeatMouth PSL beam before any RF modulations are imposed on it, and to improve the mode-matching into the fiber. Currently, we use the IR light reflected by the post doubling oven harmonic separator. This has the PMC modulation sideband on it, and also some green leakage. 

So I picked off ~8.5mW of PSL light from the first PBS (pre Faraday rotator), out of the ~40 mW available here, using a BS-80-1064-S. I dumped the 80% reflected light into the large beam dump that was previously being used to dump this PBS reflection. Initially, I used a R=10% BS for S-pol that I found on the SP table, but Koji tipped me off on the fact that these produce multiple reflected beams, so I changed strategy to use the R=80% BS instead.

The transmitted 20% is routed to the West edge of the PSL table via 2 1" Y1-1037-45S optics, towards the rough vicinity of the fiber coupler. For now it is just dumped, tomorrow I will work on the mode matching. We may want to cut the power further - ideally, we want ~2.5mW of power in the fiber - this is then divided by 4 inside the beat mouth before reaching the beat PD, and with other losses, I expect ~500mW of PSL power and comparable AUX light, we will have a strong >0dBm beat.

Attachment #1 is a picture of my modifications. For this work, I

  • Closed PSL shutter, turned HEPA up 
  • Moved HP GHz spec analyzer to the side for ease of access to the table.
  • Moved several optics that look to me as to have once been part of the RefCav setup - I don't think this would have been a useful alignment reference in any case as we moved the RefCav in a non-deterministic way for the PSL secondary shelf install.
  • Used one 1" 45 deg S-pol optic from the optics cabinet - remaining optics were scavenged from PSL table and SP table.
  • Removed an SMA cable connected to an EOM, whose other end wasn't connected to anything.
  • Turned HEPA back down, IMC locks fine now.

 

  13572   Wed Jan 24 00:48:47 2018 gautamUpdateElectronicsWhitening filter D990694

I plan to do some characterization of this problem. The plan is to use THD as a metric for whether we are having hidden saturations. Pg 9 of the LT1125 datasheet tells us what fraction of THD to expect. I will use one of the several unused DAC channels available at the LSC rack to drive a 100Hz sine wave into one of the inputs of the whitening chassis, and measure the THD up to a reasonable harmonic number (will probably be set by the ADC noise) for (i) various whitening gain settings and (ii) various input signal amplitudes.

The motivation is to attempt to quantify the problem better:

  1. How bad is it to have one or more of the OpAmps in the quad IC either saturated to its voltage rails, or max output current?
  2. Can we reproduce Hartmut's observations?
  3. Are the OpAmps already irreversibly damaged because of extended abuse?

Then we can decide what, if anything, to do about this issue.

  13573   Wed Jan 24 00:58:59 2018 gautamUpdateALSX Green PDH modulation depth

On Friday, while Udit and I were doing some characterization of the EX+PSL IR beat at the LSC rack, I noticed that there were sidebands around the main beat peak at 20dBm lower level. These were offset from the main peak by ~200kHz - I didn't do a careful characterization but because of the symmetric nature of these sidebands and the fact that they appeared with the same offset from the main peak for various values of the central beat frequency, I hypothesize that these are from the modulation sidebands we use for PDH locking the EX laser to the arm cavity. So we can estimate the modulation depth from the relative powers of the main beat peak and the ~200kHz offset sidebands.

Since the IR light is used for the beat and we directly couple it to the fiber to make the beat, there is no green or IR cavity pole involved here. 20dBm in power means \frac{\beta^2}{4} \approx 10^{\frac{-20}{10}} \approx 0.01. And so the modulation depth, \beta \approx 0.2 \mathrm{rad}. I will do a more careful meaurement of this, but this method of measuring the modulation depth can give us a precise estimate - for what it's worth, this number is in the same ballpark as the measurement I quote in elog12105.

What is the implication of having these sidebands on our ALS noise? I need to think about this, effectively the phase noise of the SR function generators we use to do the phase modulation of the EX laser is getting imprinted on the ALS noise? Is this hurting us in any frequency range that matters?

 

  13574   Wed Jan 24 10:45:14 2018 gautamUpdateALSFiber ALS assay

I was looking into the physics of polarization maintaining fibers, and then I was trying to remember whether the fibers we use are actually polarization maintaining. Looking up the photos I put in the elog of the fibers when I cleaned them some months ago, at least the short length of fiber attached to the PD doesn't show any stress elements that I did see in the Thorlabs fibers. I'm pretty sure the fiber beam splitters also don't have any stress elements (see Attached photo). So at least ~1m of fiber length before the PD sensing element is probably not PM - just something to keep in mind when thinking about mode overlap and how much beat we actually get.  

 

  13575   Wed Jan 24 13:55:04 2018 KiraSummaryPEMSeismometer can insulation test

Gautam and I set up the insulated seismometer can in the lab today. I had previously wired up the two heaters I placed onto the sides of the can in parallel to get a total resistance of 12.5 ohms and then I wrapped the whole can in 3 layers of insulation (k-factor 0.25). We placed it on a large sheet of insulation as to not crush the wires leading out the bottom of the can. I stuck on one of my AD590 sensors to the inside of the can onto the copper lining using duct tape, though this is only a temporary solution. In the future, it would be nice to have some sort of thermal clamp to secure the sensor to the can. To provide power to the heater circuit board and the temperature sensor board, we got a powerstrip and plugged in two power supplies and a function generator into it. The heater circuit (attachment 3) is powered by one of the power supplies and the function generator, while the temperature sensor (attachment 5) is stuck to the side of the can and is powered by the second power supply. The heater circuit's MOSFET (IRF640, attachment 4) is placed on a metal block and sandwiched between two more to make sure it doesn't move around. The temperature sensor is connected by a long BNC cable to the channels in attachment 6.


gautam: we plugged the BNC output of Kira's temperature sensor circuit to J7 on the AA input chassis in 1X2 - this corresponds to ADC1 input 12 in c1ioo. I then made a "PEM" namespace block inside the c1als model, and placed a single CDS filter module inside it (this can be used for calibration purposes). The filter module is named "C1:PEM-SEIS_EX_TEMP", and has the usual CDSfilt channels available. I DQ'ed the output of the filter module (@256 Hz, probably too high, but I'm holding off on a recompile for now). Recompilation and model restart of c1als went smoothly. 

2 bench power supplies are being used for this test, we can think of a more permanent solution later.

**25 Jan noon: Added another filter module, "C1:PEM-SEIS_EX_TEMP", to which Kira is hooking up a second temperature sensor, which will serve as a monitor of the "Ambient" lab temperature. Added DQ channel for the output of this filter module, fixed sampling to 32Hz. Compile and restart went smooth.

  13576   Wed Jan 24 18:12:31 2018 johannesUpdateDAQETMX auxiliary DAQ work

I replaced the two remaining D-Sub M/M cables that still had gender-changers with M/F cables today, completing the mechanical and wiring work on the ETMX rack. All backplane adapter boards were secured to a cross-strut of the crate using zip ties. This was necessary because the adapter boards don't fit the crate with their panels attached ( the ETMX eurocrate is the only one with slightly different dimensions from all the others), and the we can't mount them to the strut using the panels. This won't be an issue on any of the other crates.

   

   

In other news:

I disabled the legacy support in the three Acromag ADC units and set the input averaging to 10 samples via the USB configuration utility. The documentation is unfortunately a little sparse about what this actually means. The manual states that "fresh input data is available to the network every 10ms", so the sampling rate is for sure faster than 100Hz. Since the IOC updates its channels every .1 seconds I assume that an averaging value of 10 to reduce the input noise is safe. The maximum value the configuration tool permits is 200. I tried this using the CryoLab DAQ and set all input channels to 200 and used StripTool to look at the time series of a slow oscillation (.1Hz) with a large amplitude (16Vpp) and looked for missed data points, indicating too long wait times for channels updates. There was no such qualitative difference between 1 sample, 10 samples, and 200 samples, so even pushing the averaging value to max seemed okay. I went with the conservative value of 10 for the ETMX DAQ, but we can likely increase this if noise on the slow inputs becomes an issue.

The input scaling of the ADC channels has been corrected. I changed the conversion method in the EPICS records from manual using the ASLO and AOFF fields to using engineering units via EGUF and EGUL. This required a little attention. The Acromags scale the dynamic input range of +/- 10V to +/- 30,000 raw value, but the EPICS IOC interprets the data type as ranging from -32767 to +32768, so the EGUF and EGUL fields must be set to -10.923 and +10.923 to achieve proper scaling. I also changed the SCAN field on all ADC channels to 0.1 seconds. This has been done for all ADC and DAC channel records.

  13578   Wed Jan 24 19:17:06 2018 johannesUpdateDAQc1auxex2 startup behavior

I compiled the burt binaries on c1auxex2 which took a little fiddling with dependencies and paths but nothing too major. The complete local epics folder (/opt/epics/) which contains the base epics binaries, modbus and burt for 32-bit linux has been copied to the shared drive at /opt/rtapps/epics-3.15.5. They belong to the most recent stable release. This was so we can now automatically call burt after the IOC initialization on c1auxex2 to restore the backed-up channel values.

I also copied the database definition and modbus instruction files to /cvs/cds/caltech/target/c1auxex2, from where they are now being read upon IOC initialization. This is an excerpt of the service file:

#ExecStart=/usr/bin/procServ -f -L /home/controls/modbusIOC/modbusIOC.log -p /run/modbusioc.pid 8008 /opt/epics/modules/modbus/bin/linux-x86/modbusApp /cvs/cds/caltech/target/c1auxex2/ETMXaux2.cmd   <-- Contains logging to file, see note 1)
ExecStart=/usr/bin/procServ -f -p /run/modbusioc.pid 8008 /opt/epics/modules/modbus/bin/linux-x86/modbusApp /cvs/cds/caltech/target/c1auxex2/ETMXaux2.cmd <-- Initializes the EPICS IOC with Modbus support
ExecStop=/bin/kill -9 ` cat /run/modbusioc.pid` <-- Kills the detached process by its process ID
ExecStartPost=/bin/bash -c "/opt/epics/extensions/bin/linux-x86/burtwb -f /opt/rtcds/caltech/c1/burt/autoburt/latest/c1auxex.snap" <-- Restores general channel values
ExecStartPost=/bin/bash -c "/opt/epics/extensions/bin/linux-x86/burtwb -f /opt/rtcds/caltech/c1/medm/MISC/ifoalign/burt/ETMX.snap" <-- Restores PIT and YAW values from align MEDM screen
ExecStartPost=/bin/bash -c ". /home/controls/modbusIOC/ETMXaux2.sh" <-- Enables writing to PIT and YAW DAC channels, see note 2)

Note 1) I removed the logging to file for now because I noticed that if there are Acromag communication issues the logfile tends to grow in size VERY fast. In the cryo lab is had gotten to over 70GB just over the winter break. I don't think it's absolutely necessary to have it, and if diagnostics are needed we can easily uncomment it temporarily.

Note 2) I modified the static EPICS records of the four OSEM bias adjust channels so they won't start updating as soon as the IOC starts up (and before the channel defaults are restored by burt). This was done by setting the OMSL (output mode select) field from "closed_loop" to "supervisory". Sample record:

record(ao,"C1:SUS-ETMX_ULBiasAdj")
{
        field(DESC,"Bias Adjust for ETMX UL Coil Output")
        field(DTYP,"asynInt32")
        field(OUT, "@asynMask(C1AUXEX_XT1541A_DAC, 0, -16)MODBUS_DATA")
        field(SCAN,".1 second")
        field(OMSL,"supervisory")  <-- Used to be "closed_loop"
        field(DOL, "C1:SUS-ETMX_ULBiasSet  PP")
        field(PREC,"3")
        field(EGUF,"10.923")
        field(EGUL,"-10.923")
        field(EGU, "Volts")
        field(LINR,"LINEAR")
        field(DRVH,"10")
        field(DRVL,"-10")
        field(HOPR,"10")
        field(LOPR,"-10")
}

Now, on reboort/IOC re-initialization the physical DAC channels are performing a one-time readback of the last stored value in the Acromag's register, then idle until the last StartPost statement executes the script ETMXaux.sh, which changes their OMSL field back to "closed_loop". This causes them to start updating their output from the calc records defined in their DOL field (which have by then recovered their default values curtesy of burt). The result is a smooth transition from idling to the controlled state with no sudden or large offset changes. yes

  13580   Wed Jan 24 23:13:30 2018 johannesUpdateDAQc1auxex2 startup behavior
Quote:

The result is a smooth transition from idling to the controlled state with no sudden or large offset changes. yes

[Gautam, Johannes]

While checking how smooth the transition is we still noticed significant motion of ETMX by looking at the locked green laser and OpLevs. We found that this motion was not caused by interruption of the slow offset adjust, but rather the Watchdog being re-initialized to its OFF state, which cuts the fast channels OFF. On other optics this is observed too, but not as severe. The cause is a rather large offset on the LR coil coming from the fast DAQ, which was reported as 50mV by the slow readback channel (while other readback values are <10mV). It is present even when turning the output of the CDS model OFF, but vanishes when the watchdog is triggered. This helped us trace it to an offset of the DAC output itself: it is present at the output of the AI board but vanishes when the DAC is disconnected. The actual offset is ~40mV, as opposed to other channels on the same board, which ahve offsets in the range 3-7mV.

While we can compensate for this offset in software - it made us  wonder if the DAC channel is somehow busted and if that's what causing the 'wandering' of ETMX that we have been observing recently. There are two free DAC channels on the AI chassis that has the side coil and the green temperature control signals. We could re-route the LR signal through a different DAC channel to fix this.

gautam: 40mV offset at the AI board output gets multiplied by 3 in the dewhitening board, so there is a 120mV DC offset going to the coil (measured at dewhite board output with DMM). The offset itself isn't hurting us, but the fact that it is several times larger than other channels led us to wonder if it could be drifting around as well. From my SOS pitch balancing forays, in my head I have the number 30mrad as being the full range of the OSEM actuation - so if the offset swings by 120mV, that's ~150urad of motion, which is quite large, and is of the order of magnitude I'm used to seeing ETMX move around by.

  13581   Thu Jan 25 08:27:25 2018 SteveUpdatePEMearthquakes

M4 local earthquake at 10:10 UTC    There is no sign of damage.

....here is an other one.........M5.8 Ferndale, CA at 16:40 UTC

 

  13582   Thu Jan 25 12:41:18 2018 KiraUpdatePEMSeismometer can insulation test

We started the actual heating test today and it seems to be working so far. Hoping to heat it to about 40C. We also set up another temperature sensor to measure the lab temperature and connected it to J7, bottom.

Quote:

Gautam and I set up the insulated seismometer can in the lab today. I had previously wired up the two heaters I placed onto the sides of the can in parallel to get a total resistance of 12.5 ohms and then I wrapped the whole can in 3 layers of insulation (k-factor 0.25). We placed it on a large sheet of insulation as to not crush the wires leading out the bottom of the can. I stuck on one of my AD590 sensors to the inside of the can onto the copper lining using duct tape, though this is only a temporary solution. In the future, it would be nice to have some sort of thermal clamp to secure the sensor to the can. To provide power to the heater circuit board and the temperature sensor board, we got a powerstrip and plugged in two power supplies and a function generator into it. The heater circuit (attachment 3) is powered by one of the power supplies and the function generator, while the temperature sensor (attachment 5) is stuck to the side of the can and is powered by the second power supply. The heater circuit's MOSFET (IRF640, attachment 4) is placed on a metal block and sandwiched between two more to make sure it doesn't move around. The temperature sensor is connected by a long BNC cable to the channels in attachment 6.


gautam: we plugged the BNC output of Kira's temperature sensor circuit to J7 on the AA input chassis in 1X2 - this corresponds to ADC1 input 12 in c1ioo. I then made a "PEM" namespace block inside the c1als model, and placed a single CDS filter module inside it (this can be used for calibration purposes). The filter module is named "C1:PEM-SEIS_EX_TEMP", and has the usual CDSfilt channels available. I DQ'ed the output of the filter module (@256 Hz, probably too high, but I'm holding off on a recompile for now). Recompilation and model restart of c1als went smoothly. 

2 bench power supplies are being used for this test, we can think of a more permanent solution later.

**25 Jan noon: Added another filter module, "C1:PEM-SEIS_EX_TEMP", to which Kira is hooking up a second temperature sensor, which will serve as a monitor of the "Ambient" lab temperature. Added DQ channel for the output of this filter module, fixed sampling to 32Hz. Compile and restart went smooth.

 

  13583   Thu Jan 25 13:18:41 2018 gautamUpdateALSFiber ALS assay

I was looking at this a little more closely. As I understand it, the purpose of the audio differential IF amplifier is:

  1. To provide desired amplification at DC-audio frequencies
  2. To low pass the 2f component of the mixer output

Attachment #1 shows, the changes to the TF of this stage as a result of changing R19->50ohm, R17->500ohm. For the ALS application, we expect the beat signal to be in the range 20-100MHz, so the 2f frequency component of the mixer output will be between 40-200MHz, where the proposed change preserves >50dB attenuation. The Q of the ~500kHz resonance because of the series LCR at the input is increased as a result of reducing R17, so we have slightly more gain there. 

At the meeting yesterday, Koji suggested incorporating some whitening in the preamp itself, but I don't see a non-hacky way to use the existing PCB footprint and just replace components to get whitening at audio frequencies. I'm going to try and measure the spectrum of the I and Q demodulated outputs with the actual beat signal to see if the lack of whitening is going to limit the ALS noise in some frequency band of interest.

Does this look okay?

Quote:

The demod circuit board is configured to have gain of x100 post demod (conversion loss of the mixer is ~-8dB). This works well for the PDH cavity locking type of demod scheme, where the loop squishes the error signal in lock, so most of the time, the RF signal is tiny, and so a gain of x100 is good. For ALS, the application needs are rather different. So we lowered the gain of the "Audio IF amplifier" stage of the circuit from x100 to x10, by effecting the resistor swaps 10ohms->50ohms, 1kohm->500ohms (more details about this later).

  13584   Thu Jan 25 14:58:20 2018 KiraUpdatePEMSeismometer can insulation test

After almost 3 hours the temperature rose by about 3.5C. Seems a bit slow, but we can drive it more if necssary. The heating curve itself is exponentiial, which is a good sign.

Quote:

We started the actual heating test today and it seems to be working so far. Hoping to heat it to about 40C. We also set up another temperature sensor to measure the lab temperature and connected it to J7, bottom.

 

  13585   Thu Jan 25 16:39:09 2018 KiraUpdatePEMSeismometer can insulation test

The final temperature reached in about 4.5 hours is 30.5C, while the starting temperature is about 24C. I can't seem to screenshot the data for some reason.

Also, I will calibrate the lab temperature sensor to Celcius in the near future so that we would have a working sensor inside the lab.

Quote:

After almost 3 hours the temperature rose by about 3.5C. Seems a bit slow, but we can drive it more if necssary. The heating curve itself is exponentiial, which is a good sign.

Quote:

We started the actual heating test today and it seems to be working so far. Hoping to heat it to about 40C. We also set up another temperature sensor to measure the lab temperature and connected it to J7, bottom.

 

 

  13586   Thu Jan 25 23:59:14 2018 gautamUpdateALSFiber ALS assay

I tried to couple the PSL pickoff into the fiber today for several hours, but got nowhere really, achieved a maximum coupling efficiency of ~10%. TBC tomorrow... Work done yesterday and today:

  • I changed the collimator from the fixed focal length but adjustable lens position CFC-2X-C to the truly fixed F220-APC-1064 recommended by johannes.
  • Used a pair of irises to level the beam out at 4" with two steering mirrors.
  • Used a connector on the PSL table to couple the EX laser light to the PSL fiber - then measured the mode using the beam-scanner (beam is ~300uW) 
  • Measured the mode of the PSL pickoff beam, also using the beam scanner. 
  • Per specs on the Thorlabs website, the F220-APC-1064 has a divergence angle of 0.032 degrees. So expected waist is ~1200um, and the Rayleigh range is ~4.3m, so this is not a very easy beam to measure and fit. I may be thinking about this wrong?
  • Measured beam 1/e^2 dia over ~0.65m, and found it to be fairly constant around 1800um (so waist of 900um) - beam is also pretty symmetric in x and y directions, but I didn't attempt an M^2 measurement.
  • The pickoff from the PSL also did not yield a very clean beam profile measurement, even though I measured over ~1m z-propagation distance. Nevertheless, this looked more like a Gaussian beam, and I confirmed the fitted waist size/location approximately by placing the beam profiler at the predicted waist location and checking the spot size.
  • Used jammt to calculate a candidate mode-matching solution - the best option seemed to be to use a combination of a f=150mm and f=-75mm lens in front of the collimator. 
  • Despite my best efforts, I couldn't get more than ~500uW of light coupled into the fiber - out of the 8mW available, this is a paltry 12.5% sad
  • Because the mode coming out of the fiber is relatively large, and because I have tons of space available on the PSL table, this shouldn't be a hard mode-matching problem, should be doable without any fast lenses - perhaps I'm doing something stupid and not realizing it. I'm giving up for tonight and will try a fresh assault tomorrow. 
  13587   Fri Jan 26 20:03:09 2018 gautamUpdateALSFiber ALS assay

I think part of the problem was that the rejected beam from the PBS was not really very Gaussian - looking at the spot on the beam profiler, I saw at least 3 local maxima in the intensity profile. So I'm now switching strategies to use a leakage beam from one of the PMC input steering optics- this isn't ideal as it already has the PMC modulation sideband on it, and this field won't be attenuated by the PMC transmission - but at least we can use a pre-doubler pickoff. This beam looks beautifully Gaussian with the beam profiler. Pics to follow shortly...

Quote:

I tried to couple the PSL pickoff into the fiber today for several hours, but got nowhere really, achieved a maximum coupling efficiency of ~10%. TBC tomorrow... Work done yesterday and today

 

  13588   Tue Jan 30 10:22:20 2018 SteveUpdateVACRGA scan at day 175

pd80b rga scan at 175 day.  IFO pressure 7.3e-6 Torr-it

Condition: vacuum normal, annuloses not pumped. Rga turned on yesterday.

The rga was not on since last poweroutage Jan 2, 2018 It is warming up and outgassing Atm2

  13589   Wed Jan 31 15:27:55 2018 gautamUpdateSUSSUS MEDM master screens updated

I've often gotten confused by the labeling on the SUS MEDM screens about the coil "Vmon" fields - they're labelled as "30 Hz HPF", and indeed this is one of the many readbacks available on the coil driver board. But the actual EPICS channel that is being displayed in this field is from the "EPICS VMON" monitor point on the coil driver board. It has a gain of 1/2, so the actual voltage going to the coil is twice the channel value. Today, I fixed the SUS master screen to avoid this confusion - new labeling is shown in Attachment #1.

  13590   Wed Jan 31 15:29:44 2018 johannesUpdateDAQPSL acromag server moved from megatron to c1auxex2

I moved the epics IOC server process for the single Acromag ADC that monitors the PSL signals from megatron to c1auxex2.

First, I disabled the legacy support on all channels as explained in elog 13565. Then I copied the files npro_config.cmd and NPRO.db from /opt/rtcds/caltech/c1/scripts/Acromag to /cvs/cds/caltech/target/c1psl2/ following the pattern of the old Motorola machines and the new c1auxex2. I had to make some edits for correct paths and expanded the epics records to the standard we're using for ETMX.

I then added a service to systemd on c1auxex2 that runs the epics IOC for the Acromag PSL channels: /etc/systemd/system/modbusPSL.service. No more tmux on megatron.

Running two IOCs on a signle machine at the same time did not produce any errors and seems fine so far.

  13591   Wed Jan 31 15:45:22 2018 gautamUpdateALSFiber ALS assay

Attachment #1 shows the current situation of the PSL table IR pickoff. It isn't the greatest photo but it's hard to get a good one of this setup. Now there is no need to open the Green PSL shutter for there to be an IR beat note.

  • The key to improving the mode-matching was to abandon my "measurements" of the input mode and the mode from the collimator.
  • The best I could do with these measurements was ~25% coupling, whereas now I have ~78%yes (all powers measured with Ophir power meter).
  • Focusing was done using two f=300mm lenses (see attachment).
  • By moving the second (closer to collimator) lens through ~1inch of its current position, I was able to see a clear maximum of the coupled power.
  • By moving the second lens by ~5mm, and touching up the alignment, I couldn't see any improvement.

All this lead me to conclude that I have reached at least some sort of local maximum. The AR coating of the lens has ~0.5% reflection at 8 degrees AOI according to spec, and EricG mentioned today that the fiber itself probably has ~4% reflection at the interface due to there not being any special AR coating. There is also the fact that the mode of the collimator isn't exactly Gaussian. Anyways I think this is a big improvement from what was the situation before, and I am moving on to debugging the ALS electronics.

There is 3.65mW of power coupled into the fiber - our fiber coupled PDs have a damage threshold of 2mW, and this 3.65mW does get split by 4 before reaching the PDs, but good to keep this number in mind. For a quick measurement of the PMC and X end PDH modulation depth measurements, I used an ND=0.5 filter in the beam path.

 

  13592   Wed Jan 31 15:46:05 2018 SteveUpdatesafetycrane inspection

Annual crane inspection with load tests is scheduled for Monday, Feb 5, 2018 from 8 to 11:30am

Konecranes rescheduled this appointment to: Monday, Feb 12, 2018

  13593   Wed Jan 31 16:29:42 2018 gautamUpdateALSModulation depths

I used the Beat Mouth to make a quick measurement of the PMC and EX modulation depths. They are, respectively, 60mrad and 90mrad. See Attachments #1 and #2 for spectra from the beat photodiode outputs, monitored using the Agilent analyzer, 16 averages, IF bandwidth set to resolve peaks offset from the main beat frequency peak by 33.5MHz for the PMC and by ~230kHz for the EX green PDH.

For this work, I had to re-align the IFO so as to lock the arms to IR. c1susaux was unresponsive and had to be power-cycled. As mentioned in the earlier elog, to avoid saturating the Fiber Coupled beat PDs, I placed a ND=0.5 filter in the fiber collimator path, such that the coupled power was ~1mW, which is well inside the safe regime.

For the EX modulation depth, I could have gotten multiple estimates of the modulation depth using the higher order products that are visible in the spectrum, but I didn't.

  13594   Wed Jan 31 16:33:53 2018 gautamUpdateALSALS electronics at LSC rack

[steve, gautam]

We installed some rails to mount the 2U chassis containing ~100m of delay line cabling, and the 1U chassis containing the FET demodulators for the ALS signals in the LSC rack. This has made it MUCH easier for a single person to work there and remove/reinstall these chassis. The delay line box has 100m of cable inside it, and so was rather heavy (~8kg) - previously, it was being supported only by a pair of brackets on the front, so the new arrangement is much more robustyes. Steve is looking into acquiring plastic spacers of the appropriate width, so that we can secure the units to the rack using usual rack mount screws (but the material of the newly installed rails and the screw heads holding them in place necessitate this plastic spacer). 

Delay line box has been re-installed, demodulator chassis has been removed by me for characterization. Steve will put up photos once the units are re-installed.

For this work, I had to disconnect a bunch of cabling, but only those connected to ALS. All cables were labelled, and I will re-connect them once I am done with the demod chassis.

Quote:
 

Anyways I think this is a big improvement from what was the situation before, and I am moving on to debugging the ALS electronics.

 

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