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ID Date Author Type Category Subject
8637   Fri May 24 02:12:50 2013 AnnalisaUpdate40m upgradingETMY - Mode Matching for green

Mode Matching calculation for green beam - Yarm

After measuring the beam radius out from the Faraday for the green, I made the calculation to match the green beam mode with the IR mode inside the arm.

The beam waist after the Faraday is elliptical, and I found the following value for the waist:

w0x = 3.55e-5 m @ z0x = -0.042 m

w0y = 2.44e-5 m @ z0y = -0.036 m

(the origin of the z axis is the output of the Faraday, so the waist is inside the Faraday itself)

I did the calculation using a la mode, using as beam waist and its position the following values:

w0 = sqrt(w0x*w0y) = 2.943e-5 m @ z0 = (z0x+z0y)/2 = -0.039 m

The results are shown in the attached plots.

Focal length (m)             position (m)

lens1            0.125                                0.1416

lens2            0.100                                0.5225

L                    1.000                                1.5748 (fixed lens used to focus transmitted beam)

As the first plot shows, the green beam size on the ETMY is about 6mm. My concern is that it could be too big.

The third plot shows the X and Y section of the beam. It is strongly elliptical, but nevertheless the coupling factor calculated with Koji's formula  gives C=0.936 for the astigmatic beam, and C=0.985 for the non astigmatic beam, so it seems to be still ok.

Attachment 1: ModeMatchingGreen.jpg
Attachment 2: ModeMatchingGreenZoom.jpg
Attachment 3: XYpath.jpg
8639   Fri May 24 12:50:25 2013 AnnalisaUpdate40m upgradingETMY - Mode Matching for green

 Quote: I got confused. Is the mode calculation in the cavity correct? Are you sure the wavelength in the code is 532nm? The first plot says "the waist radius at ITMY is 2.15mm". This number is already very close to the waist size of the cavity mode (2.1mm@ITM, 3.7mm@ETM), but the spot radius at ETMY is 6mm. They are inconsistent.

Jenne and I just realized that a la mode has 1064e-9 m as default value. I'll change it and make the calculation again.

8645   Sat May 25 02:03:48 2013 AnnalisaUpdate40m upgradingETMY - Mode Matching for green - new calculation

Mode matching calculation for green - Yarm

I did again the mode matching calculation. The previous one was using 1064nm as wavelength, so it was wrong.

The seed beam waist and its position are the same as in elog 8637. The new results are shown in the attached graphs.

I got the following values for focal lengths and positions of the two Mode Matching lenses:

Focal length (m)             Distance from the Faraday output (m)

lens1            0.125                                                  0.1829

lens2           -0.200                                                  0.4398

L                   1.000                                                  1.4986 (fixed)

The position of the lens L has changed because the path lengh has been slightly  reduced.

The Coupling factor for he astigmatic beam is C = 0.959 (it is C = 0.9974 if we consider the beam as non astigmatic).

I put the lenses and aligned the beam up to the shutter, which has been moved from its initial position because the beam size on it was too large.

TO DO

The green beam needs to be aligned and sent into the arm cavity.

Polarization has to be checked.

Many beams still have to be dumped, both in IR and Green paths.

Attachment 1: ModeMatchingGreenNEW.jpg
Attachment 2: ModeMatchingGreenZoomNEW.jpg
Attachment 3: XYpathNEW.jpg
Attachment 4: photo1.JPG
Attachment 5: photo2.JPG
8646   Mon May 27 21:38:53 2013 AnnalisaUpdate40m upgradingETMY - Beam Dumps

I put many razor dumps along the IR/green path. The rejected beam from the IR Faraday needs to be dumped (about 1.5 mW). I used all the new razor blade I had, so I need one more for that beam.

The IR reflection of the Harmonic separator right after the doubler needs to be dumped in a better way. At the moment there is a black screen, but we need something suitable to dump more than 300 mW.

After the second steering mirror along the green beam path there is a very small transmission (about 6 uW), which is difficult to dump because there is no space enough. Can it be dumped with a black screen?

The Oplev has a lot of reflection hitting the central BS (The BS for the transmitted beam). It is very difficult to dump them without intercepting the main beam path. Maybe we have to slightly change the Oplev beam angle to avoid so many reflections.

8652   Tue May 28 22:11:23 2013 AnnalisaUpdate40m upgradingETMY - Yarm shutter cable

For some strange reason the Yarm shutter cable runs up to the POY table, where it is connected to another cable going to the rack. It has to be put off from the table, at least. It would be better to have only one cable going directly to the rack.

I roughly aligned the green into the Yarm and I've seen the green beam flashing on the PSL table, but the mode matching is not so good and I get an higher order mode, so I'm going to fix the mode matching tomorrow.

8660   Thu May 30 20:45:53 2013 AnnalisaUpdateendtable upgradeETMY - oplev

Quote:

 Quote: Temporary oplev in place. The spot on the qpd is still big. My two lens solution did not work. I will finalize optical component position of the oplev after the the arm transmitted and green beam optics in place. They have priority.

Oplev spot size on qpd ~ 1 mm

PS: I realized it later that the returning beam is going through a lens for TRY. This is a nono.

This beam path will be relayed again as the TRY, green beam and IP-ang get there place.

Oplev is disabled. I removed one of the steering mirrors because it was on the green beam  path.

8662   Fri May 31 11:15:01 2013 AnnalisaUpdateendtable upgradeETMY - Mode Matching for green - new calculation

Since the beam waist after the Faraday had changed since the last time I measured it (maybe alignment changed a bit), I made a new mode matching calculation for green. I attached the results.

I'm going to align the beam into the Yarm.

RXA: JPG images deleted - replace with PDF please.

8671   Tue Jun 4 16:04:34 2013 AnnalisaUpdateLSCALS-TRY_OUT needs anti-whitening

 Quote: After working some more on the EY table, we are getting some TEM00 flashes for the Y arm green. We have had to raise the height of one of the MM lenses to prevent clipping. We used a function generator to apply a ~300 mV 10 Hz triangle wave to scan the laser frequency while aligning. We tried to use the C1:ALS-TRY_OUT channel to help us in our alignment but there are a couple problems: 1) It seems that there is an uncompensated whitening filter before the ADC - Annalisa is making a compensation filter now. 2) The data delay is too much to use this for fast alignment. We might need to get a coax cable down there or mount a wired ethernet computer on the wall. 3) We need to make DQ channels for the TRY and TRX OUT. We need long term data of these, not just test points.

I made the anti-whitening filter for the C1:ALS-TRY_OUT channel. But then I forgot to make an ELOG because I am bad.

8672   Tue Jun 4 17:28:09 2013 AnnalisaUpdateLSCC1:ALS-TRY_OUT filter and green progress

[Annalisa, Gautam, Rana]

I made the anti-whitening filter for the C1:ALS-TRY_OUT channel.

zpk [[150],[15],1] Hz

Now we can look at the picks of this signal to align the green into the cavity.

We already had some 00 flash, but a better alignment has to be done.

TO DO:

- put the shutter along the beam path

- check the polarization (we have a new PBS for visible)

Attachment 1: green.JPG
8674   Tue Jun 4 21:50:23 2013 AnnalisaUpdateLSCC1:ALS-TRY_OUT filter and green progress

[Annalisa, Gautam]

The green beam alignment has been improved, so we see much more 00 bright flashing. We checked the polarization and the Ygreen shutter is back in place.

A mirror is already in place to steer the rejected beam from the green Faraday into a PD, tomorrow morning we'll put a lens and the PD to take the signal for PDH locking.

8679   Wed Jun 5 14:43:42 2013 AnnalisaUpdateLSCALS-TRY_OUT DQ channels

 Quote: After working some more on the EY table, we are getting some TEM00 flashes for the Y arm green. We have had to raise the height of one of the MM lenses to prevent clipping. We used a function generator to apply a ~300 mV 10 Hz triangle wave to scan the laser frequency while aligning. We tried to use the C1:ALS-TRY_OUT channel to help us in our alignment but there are a couple problems: 1) It seems that there is an uncompensated whitening filter before the ADC - Annalisa is making a compensation filter now. 2) The data delay is too much to use this for fast alignment. We might need to get a coax cable down there or mount a wired ethernet computer on the wall. 3) We need to make DQ channels for the TRY and TRX OUT. We need long term data of these, not just test points.

[Jenne, Annalisa]

DQ channels have been created in the C1ALS model for TRX and TRY. They are called TRX_OUT and TRY_OUT and the sampling rate is 2048 Hz.

8680   Wed Jun 5 15:03:42 2013 AnnalisaUpdateLSCC1:ALS-TRY_OUT filter and green progress

 Quote: The rejected beam from this Faraday comes out at a tiny, tiny angle and so its tough to pick it off without clipping the main beam. Some care must be taken in setting this up - Steve may have some good ideas on what kind of mount can be placed so close to the beam. Why did we ever order this terrible Faraday? Let's never get a Faraday with a tiny angle between the beams again.

The rejected beam from the Faraday is steered with a mirror into the PDA32A PD  and a 75mm fl lens is used to focus the beam into it.

The main beam is a few millimeters away from the mirror mount (maybe 2mm), and I think it should be fine as long as the main beam is not supposed to move.

8691   Sat Jun 8 00:24:11 2013 AnnalisaUpdateGreen LockingY arm locked with green but bad mode matching

[Annalisa, Nic]

After connecting the PD with the reflection from the arm  to the PDH box, theY  arm has been locked on the 01 mode.  Maximizing the alignment, we obtained a 00 mode locking, but we couldn't maximize the power.

The size of the reflected beam was different with respect to the size of the incoming beam, so probably a bad mode matching was one of the issues.

Moreover, the reflected beam is very low power. We need to figure out why it is so (bad alignment? related to mode matching?)

After measuring better all the distances, I did a new mode matching calculation. I put the lenses after measuring the beam waist, so the size of the beam on the lenses was the same as expected from the calculation. Nevertheless, the beam size on the beam splitter looks bigger than expected, and also in this case green flashes into the cavity at some HOM (again 01).

I also tried to lock again the cavity and maximize the alignment, but I didn't get any improvement with respect to the previous mode matching.

8692   Mon Jun 10 21:39:26 2013 AnnalisaUpdateGreen LockingY arm locked with green but bad mode matching

Still no good locking!

After making the reflected beam size closer to the injected one, I maximized alignment. I locked again in 00 mode, but I couldn't maximize the power.

I just realized that maybe I'm not using the correct radius of curvature for the ETMY in the simulation. Tomorrow I will start checking from that.

8695   Wed Jun 12 01:56:58 2013 AnnalisaUpdateGreen LockingY arm locked with green but bad mode matching

For the mode matching calculation I was using the ETMY focal length that I found on Kiwamu's plot on the wiki page.

Taking into account also the substrate, the focal length turns out to be

fl = ((n-1)*(1/R1 - 1/R2 + (n-1)d/(nR1R2)))^(-1) = -125.81 m

with n = 1.46071 (refraction index of fused silica at 532nm)

R1 = 5625 m (radius of curvature of the first surface)

R2 = 57.37 m (radius of curvature of the second surface)

d = 25mm (thickness)

The value of the focal length is sligthly different from the one I was using before in the calculation, but maybe it is enough to change the coupling.

The mode matching solution I found is very sensitive to the lenses position.

The beam waist position can vary up to 20m varying by 1cm the first lens position, while it is slightly less sensitive to the second lens displacement.

As shown in the picture, along the green beam path there is also a 1m focal length lens. It's position is fixed, because it is along the IR transmetted beam path also. I tried to get a better solution without it, but I found that the waist position was still strongly dependent on one of the two lenses position, so it would not solve the problem to remove this lens.

I think that the main issue of this mode matching is related to the "space contraints", because the two lenses' positions can vary in a very small space, even though the green beam path on the table is quite long.

Eventually, I put the MM lenses found from this last simulation on the table, and it seems to work, since I've seen very strong 00 flashes. Unfortunately, while trying to maximize the alignment I broke it  and I have to do it again, but I feel confident!

Attachment 1: waistVaryingLensPos.pdf
Attachment 2: green.JPG
Attachment 3: ModeMatchingY.pdf
8696   Wed Jun 12 22:48:10 2013 AnnalisaUpdateGreen LockingY arm locked with green but bad mode matching

After restoring alignment I could see again strong 00 flashes (about 250-300 counts on ALS-TRY). So I locked the arm with IR and after enabling the PDH servo for the green locking, I also locked the green on the Y arm in 00 mode. Then I moved the two mode matching lenses to maximize the power into the 00 mode, but I didn't reach more than 30-35 counts.

Green power injected into the Y arm                    0.680mW

Green power reflected back                                  0.090mW

Green power transmitted on the PSL                  few uW

I would expect more power on the PSL table (maybe 10x more).

8699   Thu Jun 13 10:57:36 2013 AnnalisaUpdateGreen LockingY arm locked with green but bad mode matching
> > Hmmm.  You seem to be saying that more light is reflected than is injected. Is this a units problem? Or was some IR on the power meter during the 'reflected' measurement?
> > We should look at it with fresh eyes in the morning.
>
> Also, if you have been measuring the power of green refl at the rejection port of the green faraday, the polarization of the light entering the green faraday should be checked once again to make sure that you are measuring
> only the reflected power from the arm cavity.

Sorry Sorrry Sorry!!
It was 0.090 mW, I just forgot a zero!!!
Sorry!
8704   Thu Jun 13 23:28:40 2013 AnnalisaUpdateGreen LockingY arm locked with green but bad mode matching

Quote:

 Quote: After restoring alignment I could see again strong 00 flashes (about 250-300 counts on ALS-TRY). So I locked the arm with IR and after enabling the PDH servo for the green locking, I also locked the green on the Y arm in 00 mode. Then I moved the two mode matching lenses to maximize the power into the 00 mode, but I didn't reach more than 30-35 counts. Green power injected into the Y arm                    0.680mW Green power reflected back                                  0.090mW Green power transmitted on the PSL                  few uW I would expect more power on the PSL table (maybe 10x more).

Is this reflection measured with the cavity locked or unlocked?

So what's the actual designed reflectivity of the ETM for green? No one seems to be able to give me a straight answer about this.

Looking at the reflected beam when the beam is misaligned makes it look like it's << 0.9. Is that expected given the coating spec?

You say the cavity scan goes as high as 300cts but you can only lock to 30cts, are you locked on the sideband?

-The reflection is measured when the cavity is unlocked. I measured it with the power meter in front of the PD, so I interrupted the PDH loop.

- From the specs of ETM we have:

T(S1,HR,532nm)=5.0%+/-3% (+/-1% target),  R(S2,AR,532nm)<1000ppm

It means that I should have about 600-550 uW in reflection, but I don't. I can say that there are many losses, and maybe some power is clipping inside the Faraday. Nonetheless, the reflected beam looks less strong than the injected one, so most of the losses should be on the ETM table.

(- The reflected power is 0.090 mW, I just wrote it wrong yesterday, sorry!)

- The last question is actually very interesting. Maybe I was locking on the sideband when I locked to 30 cts, but if it is the case I cannot really explain why today I locked on the carrier (I locked the cavity to about 200-250 cts), and everything I changed was the PD gain and the amplitude on signal generator connected to the PDH box. It seems like there should be some sign flip somewhere, but I need to think about.

8715   Mon Jun 17 23:53:03 2013 AnnalisaUpdateGreen LockingY arm locked on green!!

## Y arm locked on green carrier in 00 mode!

It locked at almost 280 cts, and the transmitted power on the PSL table is  about 40 uW.

To make it lock on the carrier I had to flip the sign of the error signal in the PDH loop, so I put a phase shifter (a Pomona box with a 23 uF capacitor) right before the LO input of the PDH box (on the model of the X arm).

Tomorrow I will put more details about the power budget and the phase shifter transfer function.

8734   Thu Jun 20 17:47:44 2013 AnnalisaConfigurationSUSETMY oplev servo

[Jenne, Annalisa]

The ETMY Oplev servo didn't work properly, when it was activated the ETMY moved too much.

We measured the oplev TF for Pitch and Yaw and it turned out that the gain was too low by a factor 3, so we increased the gain from -.250 to -.750 on both.

We also locked the Y arm and we could see that the mirror's oscillations are actually suppressed.

8749   Tue Jun 25 23:49:04 2013 AnnalisaUpdateSUSETMY Oplev

I had some problem with the Oplev Servo today. I was working at the mode matching fine tuning and I left the Oplev servo enabled while aligning.

When I opened the Yend table lids, the Oplev beam started moving on the QPD and the Oplev servo didn't help in stopping the mirror movement, but it increased it.

So, the mirror was oscillating at a frequency of a few Hz

Koji suggested that maybe the shaking is due to the air conditioning moving the beam, so the servo tries to feed back the signal to the mirror, even if the mirror doesn't actually move.

I also measured the transfer function for the Oplev, but it didn't show any strange behavior.

8751   Wed Jun 26 00:15:51 2013 AnnalisaUpdateGreen LockingETMY - green locking and beat note setup

[Koji, Annalisa]

Alignment improving

• The alignment of the green beam injected into the Yarm has been improved, and when the green laser is locked on the cavity in 00 mode we moved from 500 cnts to almost  650 cnts in transmission on the PSL table. Now we have about 70 uW transmitted.
• Since the beam size on the GRTY PD was too big, I put a lens to focus it better.

Beat note setup

• The Ybeat RFmon was connected back to the power splitter that Yuta put and Manasa temporarily removed (as described in elog 8666), so that now we are using again the SUM port to monitor the beat signal.

TO DO

• Align better the beams on the BeatPD, in order to get a stronger beat note
• Calibrate the ALS screen to tune remotely the laser temperature
• Find the beat note!

8768   Thu Jun 27 17:41:08 2013 AnnalisaUpdateGreen LockingETMY -beat note found!

Y arm beat note found!

Procedure

• Arm lock on IR to align the mirrors
• Green Laser locked on the arm
• Green Transmission on the PSL and PSL green beam aligned into the BeatPD: they have been aligned both in the near field (looking at the beam on the camera) and in the far field (removing the DC PD and looking at the two beams on the wall)
• Checked the PSL temperature and, following the plot of the beat note measurement between "Alberto" laser and PSL reported in elog 8396, I got an idea of the range of temperature where the beat note could be found (I used the values of the second curve)
• Scanned the Y-green laser temperature using the slow servo on the ALS command window

Data

• PSL temperature = 31.58°C
• PSL slow servo temperature offset = 0
• "Alberto" laser temperature = 40.35 °C (ADJ = 0)
• Thermal output offset on the ALS screen = -11140
• Beat note frequency = 22 MHz
• Beat note amplitude = -31.7 dBm

The green transmission on the PSL reads about 500 cts, and the transmitted power is about 50 uW.

(the second peak on the screen in the picture is the 29 MHz of the MC)

Attachment 1: beat_note.JPG
8792   Wed Jul 3 01:49:46 2013 AnnalisaUpdateGreen LockingALS servo configuration

[Koji, Annalisa, Manasa]

Today we worked on the ALS servo stabilization for the Y arm.

First step: find the beat note

The beat note was found following the usual steps:

• Y arm cavity locked on IR to have a good alignment
• Y arm cavity locked on green (eventually unlocked on IR)
• beat note alignment maximized on the PSL table

Beat note amplitude = -27 dBm @ 50 MHz

PSL temperature = 31.54 degC

Laser Offset on the slow servo2 = -11011

In the GREEN HORNET we did the following changes for the Y arm:

Input Signal Conditioning

On the C1ALS-BEATY_FINE  screen the same antiwhitening filters of the C1ALS-BEATX_FINE have been reproduced. At moment, only the FM3 [10:1] is enabled.

On the C1ALS-BEATY_FINE_PHASE screen the gain was set at 3600, since the amplitude of the Q signal after the Phase rotator (BEATY_FINE_Q_ERR) was about 30. To set this value we made a proportion with respect to a previous optimized value, where the amplitude was 100 and the gain was set to 1200.

DOF filters

In order to stabilize the beat frequency, we started enabling the FM5 [1000:1] filter in the C1ALS_YARM panel, and then we started increasing the gain first in small steps (0.1), in order to understand which sign the gain should have without kicking the mirror.

We measured the Power Spectrum of the C1:ALS-BEATY_FINE_PHASE_OUT in-loop signal while varying the gain of the C1ALS_YARM servo filter.

Eventually, we enabled the following filters:

FM2 [0:1]

FM3 [1:5]

FM4 [1:50]

FM5 [1000:1]

FM6 [RG3.2]

FM7 [RG16.5]

Gain = -30.

Koji expects the UGF of the loop to be around 100-ish Hz, and he also expected the small bump around 300-400 Hz.

Then we realized that the channel we were measuring was not calibrated in unit of Hz, so we took again the measurement looking at the channel C1:ALS-BEATY_FINE_PHASE_OUT_HZ. In this case, we didn't observe any bump. Maybe the beat frequency was slightly changed from the previous measurement and the all servo shape was also different. The final value of the gain was set at -8.

The Y axis unit is missing (bad me!). It's in deg/sqrt(Hz) for the first plot and Hz/sqrt(Hz) for the second one.

Attachment 1: ALS
Attachment 2: ALS_calibrated
8793   Wed Jul 3 03:06:29 2013 AnnalisaUpdateGreen LockingALS servo configuration

I realized that I cannot open the attached plots. I'll fix them tomorrow.

8819   Wed Jul 10 02:28:04 2013 AnnalisaUpdateGreen LockingBeat notes lost!

[Manasa, Jenne, Annalisa]

I was going to find the beat note to start the cavity scan, but I couldn't.

These are the steps I followed:

• locked the arm with IR to reduce the arm swinging
• locked the green on the arm
• started changing the green temperature setting the offset from the slow servo2 in the ALS. The PSL slow actuator ADJ was always set approximately to zero, and the PSL temperature was checked in order to set the auxiliary laser temperature where the beat was expected (as in the plot)

After spanning the temperature by approximately 4degC, we started be suspicious that I couldn't find the beat in the range of temperature where it was supposed to be found, and we started making several trials:

• PD output disconnected from the beatbox and connected to the cable running to the Control Room
• Checked that the cable going to the Control Room was working by sending a signal with the Marconi (the cable was working)
• Put back the amplifier that had been previously removed
• PD DC output checked with the oscilloscope
• Spectrum analyzer connected to the PD output without passing trough the cable

The same trials were done also for the X arm, but we didn't succeed in finding the beat for the X neither.

8821   Wed Jul 10 11:44:02 2013 AnnalisaUpdateGreen LockingY beat note found!

I found the beat note for the Y arm. Nothing was changed with respect to yesterday night, but the beat is back!

8831   Thu Jul 11 14:38:38 2013 AnnalisaUpdateGreen LockingY arm cavity scan

Yesterday I did a cavity scan with IR while holding the Yarm with green.

ALS servo tuning:

• C1ALS-BEATY_FINE_PHASE

The gain of the loop is set such that BEATY_FINE_Q_ERR x GAIN = 120k. This is a kind of "empirical low" in order to have the UGF around 1kHz.

• C1ALS_YARM

Start with FM5 [1000:1] enabled, determine the sign of the gain increasing it in small steps and making sure that the mirror doesn't get a kick. Then gradually raise it while looking at the BEATY_PHASE_OUT power spectrum.

Enable FM7 [RG16.5], FM6 [RG3.2], FM3 [1:5], FM2[0:1], FM10 [40:7].

Plot 1 shows the power spectrum of BEATY_PHASE_OUT (calibrated in Hz).

1. blue curve - ALS disabled
2. green curve - in loop measurement, ALS enabled and servo tuned as described above
3. grey curve - RMS of the in loop measurement
4. red curve - out of loop measurement (arm locked with IR)
5. pink curve -  RMS of the out of loop measurement

Offset setting and cavity scan

The C1ALS_OFFSETTER2 was used to set an offset for ALS scan.

• LPF30m enabled
• Ramp time set to 150s
• Offset set to 1500 (approximately 3 FSR in this interval)

Many scans have been done to find the optimal offset conditions, I only attached one (Plot 2).

I also misaligned the END mirror in pitch to enhance the HOMs peaks, but it turned out that it was not enough, because I didn't see a very big difference between the "aligned" and the "slightly misaligned" measurements (Plot 3).

NEXT STEPS

Increase the cavity misalignment both in pitch and in yaw and repeat the measurement.

Attachment 1: IRlocked_res_mot_0710.pdf
Attachment 2: ArmScanN5.png
Attachment 3: CavityScanETMYmis
8842   Sat Jul 13 03:27:20 2013 AnnalisaUpdateGreen LockingY arm caity scan

I started doing a scan of the Y arm cavity with IR with ALS enabled.

ALS servo tuning:

The servo tuning procedure is basically the same as described in elog 8831.

This time I had a stronger beat note(-14 dBm instead of -24 dBm of the last measurement) thanks to a better alignment.

Plot1 shows the Power spectrum of the BEATY_PHASE_OUT. The RMS is smaller by a factor of 2 (400Hz), corresponding to a residual motion of about 25 pm.

Offset setting avity scan

In order to give an offset linearly growing in time, I used the ezcastep script instead of giving the offset in OFFSETTER2. If the ramp time is long enough, it is not necessary to enable the 30mHz filter.

To span 2 FSR, I started from an offset of 450 and I gave a maximum value of 1600 with a delay of 0.2s between two consecutive steps.

Cavity scan

I did a first scan with the cavity well aligned, basically to know the position of the 00 peaks and choose the best offset range (Plot2)

Then I misaligned the TT2, first in PITCH and yhen in YAW, in order to enhance the HOMs. (Plot3 and Plot4)

More investigation and measurements needed.

Attachment 1: PowerSpectrum0712
Attachment 2: ScanCavityAligned.pdf
Attachment 3: ScanCavityMisPitch.pdf
Attachment 4: ScanCavityMisYaw.pdf
8844   Sun Jul 14 18:19:00 2013 AnnalisaUpdateGreen LockingArm cavity scan

Yesterday evening Nic and me were in the lab. The Mode Cleaner was unlocked, but after many attempt we could fix it and we did many scans of the Y arm cavity.

Today I was not able to keep the MC locked. Koji helped me remotely, and eventually the MC locked back, but after half an hour of measurements I had to stop.

I made some more scan of the Y arm though. I also tried to do the same for the X arm, but the MC unlocked before the measurement was finished. I'll try to come back in the night.

8886   Mon Jul 22 03:09:51 2013 AnnalisaUpdateGreen LockingY Arm cavity scan

Yesterday and today I was in the lab doing many cavity scan.

First I did many measurement with the cavity aligned in order to get the position of the 00 modes, then I misaligned the beam in many different ways to enhance the higher order modes.

In particular, I first misaligned the mode cleaner to make the beam clipping into the Faraday. To do this, I set to 0 the WFS gain, but I left the autolocker still enabled. In this way, the autolocker couldn't bring the mirrors back to the aligned position.

Then I misaligned also the TT2 to get even more HOMs.

Eventually, Rana came and we misaligned TT1 to clip the beam, and using TT2 we aligned back the beam to the arm.

To increase the SNR, we changed the gain of the TRY PD, setting it to 20dB (which corresponds to a factor 100 in digital scale)

I attached one scan that I did with Rana on Sunday night. I could not upload a better resolution image because the file size was too big, but here's the path to find all of the scans:

../users/annalisa/sweep/Yarm

There are many folders, one per each day I measured. In each folder there are measurements relative to aligned cavity, Pitch and Yaw misalignment.

RXA EDIT:

The PDA520 used for TRY was set to 0 dB analog gain. This corresponds to ~500 counts out of 32768. The change to 20 dB actually increases the gain by 100. This makes the single arm lock saturate at ~25000 counts (obviously in analog before the ADC). The right setting for our usual running is probably 10 dB.

For the IMC WFS, we had disabled the turn on in the autolocker to use the IMC to steer the beam in the FI, but that was a flop (not enough range, not enough lever arm). In the end, I think we didn't get any clipping.

8910   Tue Jul 23 19:37:08 2013 AnnalisaUpdateendtable upgradeEnd table picture

 Quote: The spot on the IPANG QPD was checked. The spot is higher than the center and South side of the lens. Some photos are found below. The spot on the IPANG steering mirrors in the ETMY chamber was also checked. It is clipped at the top of the steering mirror. (See attachment 4) So basically the spot is about 1" above the center of the mirror.

After the vent, the IPang spot position on the steering mirrors on the Yend table moved approximately by 1 inch down.

Inside the chamber, the spot position is in the center of the steering mirror. (difficult to take a picture because the PSL beam power has been reduced)

Attachment 1: IMG950073.jpg
Attachment 2: IMG950072.jpg
8930   Sun Jul 28 19:39:04 2013 AnnalisaUpdateendtable upgradePicture

Yend table picture updated on the wiki page

8931   Sun Jul 28 20:13:41 2013 AnnalisaUpdateGreen LockingY Phase tracker calibration

I did a calibration measurement for the Y part of the BeatBox using a Marconi. This is in order to get a more accurate calibration for the arm cavity scan measurement.

The calibration factor I found is:

C1:ALS-BEATX_FINE_PHASE_OUT   50.801 +/- 0.009 deg/MHz

Procedure

During my cavity scan measurement, I had recorded the beat frequency and amplitude from the Spectrum Analyzer at each zero crossing.

I connected the Marconi to the RF in of the Y part of the BeatBox, and I set the Marconi carrier frequency at one of this zero-crossing frequency that I had recorded, while I set the amplitude in way to have on the spectrum analyzer the same beat amplitude that I read during the measurements or, equivalently, in order to have C1:ALS_BEATY_FINE_Q of the order of 1200 (which is the same value I had during my measurements).

I started with

• Carrier frequency = 80.2 MHz
• Amplitude = -3dBm

Then I monitored the C1:ALS_BEATY_FINE_I on the oscilloscope and I adjusted the carrier frequency so that I had zero signal on the oscilloscope. Eventually the frequency corresponding to the zero crossing was 79.989 MHz.

I resetted the phase (clear history in the BEATY_FINE_PHASE panel) and I started changing the frequency by steps of 0.2 MHz, and I spanned about 70 MHz (from 32 to 102 MHz).

Resutls

The calibration coefficient I found is not so different from the one that Yuta measured (elog 8199).

Here are the fit parameters:

y = a + bx

a = -4239.7 +/- 0.6 deg

b = 50.801 +/- 0.009 deg/MHz

Attachment 1: YbeatBox_Calibration.pdf
14041   Fri Jul 6 12:12:09 2018 AnnalisaConfigurationThermal CompensationThermal compensation setup

I tried to put together a rudimentary heater setup.

As a heating element, I used the soldering iron tip heated up to ~800°C.

To make a reflector, I used the small basket which holds the cork of champains battles (see figure 1), and I covered it with alumnum foil. Of course, it cannot be really considered as a parabolic reflector, but it's something close (see figure 2).

Then, I put a ZnSe 1 inch lens, 3.5 inch FL (borrowed from TCS lab) right after the reflector, in order to collect as much as possible the radiation and focus it onto an image (figure 3). In principle, if the heat is collimated by the reflector, the lens should focus it in a pretty small image. Finally, in order to see the image, I put a screen and a small piece of packaging sponge (because it shouldn't diffuse too much), and I tried to see the projected pattern with a thermal camera (also borrowed from Aidan). However, putting the screen in the lens focal plane didn't really give a sharp image, maybe because the reflector is not exactly parabolic and the heater not in its focus. However, light is still focused on the focal plane, although the image appears still blurred. Perahps I should find a better material (with less dispersion) to project the thermal image onto. (figure 4)

Finally, I measured the transmitted power with a broadband power meter, which resulted to be around 10mW in the focal plane.

Attachment 1: IMG_1887.jpg
Attachment 2: IMG_1884.jpg
Attachment 3: IMG_1883.jpg
Attachment 4: IR20180706_0358_labels.png
14043   Sat Jul 7 19:50:38 2018 AnnalisaConfigurationThermal CompensationStudy about the Thermal projection setup and its effect on the cavity

I made some simulation to study the change that the heater setup can induce on the Radius of Curvature of the ETM.

## Heat pattern

First, I used a non-sequential ray tracing software (Zemax) to calculate the heat pattern. I made a CAD of the elliptical reflector and I put a radiative element inside it (similar to the rod-heater 30mm long, 3.8mm diameter that we ordered), placing it in such a way that the heater tip is as close as possible to the ellipse first focus. (figure 1)

Then, by putting a screen at the second focus of the ellipse (where we suppose to place the mirror HR surface), I could find the projected heat pattern, as shown in figure 2 and 3 (section). Notice that the scale is in INCH, even if the label says mm. As you can see, the heat pattern is pretty broad, but still enough to induce a RoC change.

Mirror deformation

In order to compute the mirror deformation induced by this kind of pattern, I used this map produced with Zemax as absorption map in COMSOL. I considered ~1W total power absorbed by the mirror (just to have a unitary number).

The mirror temperature and deformation maps induced by this heat pattern are shown in figures 4 and 5.

RoC change evaluation

Then I had to evaluate the RoC change. In particular, I did it by fitting the Radius of Curvature over a circle of radius:

$r = w_{00} * \sqrt{n}$

where $w_{00}$ is the waist of tha Gaussian mode on the ETMY (5mm) and n is the mode order. This is a way to approximately know which is the Radius of Curvature as "seen" by each HOM, and is shown in figure 6 (the RoC of the cold mirror is set to be 57.37m). Of course, besides being very tiny, the difference in RoC strongly depends on the heat pattern.

Gouy phase variation

Considering this absorbed power, the cavity Gouy phase variation between hot and cold state is roughly 15kHz (I leave to the SURFs the details of the calculation).

So the still unaswered questions are:

- which is the minimum variation we are able to resolve with our measurement

- how much heating power do we expect to be projected onto the mirror surface (I'll make another entry on that)

Attachment 1: reflector.png
Attachment 2: heat_pattern_-_f2.png
Attachment 3: heat_pattern_-_f2_-_cross_section.png
Attachment 4: ETMtemperature.png
Attachment 5: ETMdeformation.png
Attachment 6: RoC_variation.png
14050   Tue Jul 10 23:44:23 2018 AnnalisaConfigurationThermal CompensationHeater setup assembly

[Annalisa, Koji]

Today both the heater and the reflector were delivered, and we set down the setup to make some first test.

The schematic is the usual: the rod heater (30mm long, 3.8 mm diameter) is set inside the elliptical reflector, as close as possible to the first focus. In the second focus we put the power meter in order to measure the radiated power. The broadband power meter wavelength calibration has been set at 4µm: indeed, the heater emits all over the spectrum with the Black Body radiation distribution, and the broadband power meter measures all of them, but only starting from 4µm they will be actually absorbed my the mirror, that's why that calibration was chosen.

We measured the cold resistance of the heater, and it was about 3.5 Ohm. The heater was powered with the BK precision DC power supply 1735, and we took measurements at different input current.

 Current [A] Voltage [V] Measured radiated power [mW] Resistance [Ohm] 0.5 2.2 20 4.4 0.8 6 120 7.5 1 11 400 11 1.2 18 970 15

We also aimed at measuring the heater temperature at each step, but the Fluke thermal camera is sensitive up to 300°C and also the FLIR seems to have a very limited temperature range (150°C?). We thought about using a thermocouple, but we tested its response and it seems definitely too slow.

Some pictures of the setup are shown in figures 1 and 6.

Then we put an absorbing screen in the suspension mount to see the heat pattern, in such a way to get an idea of the heat spot position and size on the ETMY. (figure 2)

The projected pattern is shown in figures 3-4-5

The optimal position of the heater which minimizes the heat beam spot seems when the heater inserted by 2/3 in the reflector (1/3 out). However, this is just a qualitative evaluation.

Finally, two more pictures showing the DB connector on the flange and the in-vacuum cables.

### Steve: how are you going to protect the magnets ?

Attachment 1: IMG_1992.jpg
Attachment 2: IMG_2002.jpg
Attachment 3: IR20180710_0364a.png
Attachment 4: IR20180710_0368.png
Attachment 5: IR20180710_0360.png
Attachment 6: IMG_1993.jpg
Attachment 7: IMG_5322.JPG
Attachment 8: IMG_5321.JPG
14071   Fri Jul 13 23:39:46 2018 AnnalisaConfigurationThermal CompensationThermal compensation setup - power supply

[Annalisa, Rana]

In order to power the heater setup to be installed in the ETMY chamber, we took the Sorensen DSC33-33E power supply from the Xend rack which was supposed to power the heater for the seismometer setup.

We modified the J3 connector behind in such a way to allow a remote control (unsoldered pins 9 and 8).

Now pins 9 and 12 need to be connected to a BNC cable running to the EPICS.

RXA update: the Sorensen's have the capability to be controlled by an external current source, voltage source, or resistive load. We have configured it so that 0-5V moves the output from 0-33 V. There is also the possibility to make it a current source and have the output current (rather than voltage) follow the control voltage. This might be useful since out heater resistance is changing with temperature.

Attachment 1: IMG_2012.jpg
Attachment 2: IMG_2013.jpg
Attachment 3: 20180713_213818.jpg
14081   Wed Jul 18 03:14:48 2018 AnnalisaUpdateGeneralVent 80 recovery

[Gautam, Johannes, Koji, Annalisa]

Tonight we increased the power of the PSL laser and we achieved the lock of both arms with high power.

The AUX beam alignment to the Y arm was recovered and the PLL restored (using the Marconi as LO).

We made a quick measurement of the phase noise and the results will be posted tomorrow.

The beam on the PSL has been blocked, as well as the AUX beam on the AS table. The Marconi has been switched off.

gautam:

1. Before turning up PSL power, I placed a block in front of MC refl to avoid any PD burning. Replaced HR Y1 2" optic with the usual 10% reflective BS to direct MC REFL to the locking PD.
2. Waveplate was rotated back to 180 deg (original position before the vent). After optimizing PMC transmission, I measured 1.05 W going into the IMC (pre-vent value was 1.07 W, prolly within power meter absolute accuracy).
3. IMC autolocker restored to usual high power version on megatron.
4. There seems to be some kind of vacuum interlock in effect that prevents me from opening the PSL shutter via EPICS - I had to toggle the position on the shutter controller under the table. After tonight's work, I returned the controller to the NC state, to avoid any further interference with this interlock code that may prevent pumping in the AM.
5. PLL gain was re-adjusted to achieve maximum stability (judged by eye) of the beat-note in lock triggered on the Marconi LO signal. Alignment onto the NF beatPD was also tweaked to squeeze out as much beat as possible.
6. The main objective tonight was to send AUX beam in, recover transmission beat, scan the AUX frequency, and resolve some peaks (MAX HOLD scanning technique, magnitude only for now, no phase info). Thanks to JE's expert fiber alignment and beatnote maximization, we achieved this . Annalisa will post a plot tmr.
7. For unknown reasons, the Y arm ASS does not maximize TRY. So we are in the unfortunate situation of neither arm having a working ASS servo. To be worked on later.
8801   Thu Jul 4 01:09:33 2013 Annalisa, KojiUpdateLSCPRMI locked with REFL165

Summary:

- The new REFL165 PD was installed on the AP table
- The REFL165I/Q signals are now showing sensible and robust PRCL/MICH signals
- PRMIsb was locked only with these REFL165 signals

Details:

- Installation of the REFL165 PD

We prepared the REFL165 PD for the 4" optical height. The actual issue was the power supply for the PD.
We soldered wires between the PD and the RF PD interface break-out board. Then the PD interface
cable for the old REFL165 (iLIGO style) was connected.

At the REFL port, most of the light is rejected by the first beam splitter (R=90%?). We attenuated the beam by a factor of 10
using an ND filter. The new PD showed the DC output of ~10V. This corresponds to the photocurrent of 5mA.
(cf. the shot-noise intercept current is ~1mA)

The output of the REFL165 PD was checked with the RF spectrum analyzer. It was a bit surprising but we had a forest of
RF signals betwen 11MHz and 178MHz.
We tried to use a high-pass filter with fc=100MHz (SPH-100) but still the rejection
was not enough. We ended up with using SPH-150 (fc=150MHz).

- Whitening / Demodulation phase

Then we connected the RF output to the SMA cable to the LSC rack. We immediately saw the nice signals from REFL165I/Q
channels, namely sensible structure of pendulum resonances (1/3/16Hz peaks) and floor level.

The whitening level was changed from 21dB to 45dB (max). The DC offsets in the I/Q channels (of the order of 2000~4000)
were removed by the ./LSC/LSCoffset script.

Firstly we locked the PRMI with the usual signals (REFL33I and AS55Q).
The demodulation phase was roughtly tuned (1deg precision) such that the Q phase signal is minimized,
assuming most of the signal is coming from PRCL. Our choise is 74deg.

In this configuration, PRCL shows same quality of signal as our prefered PRCL (i.e. REFL33I) in the amplitude and the sign.

- Locking

We switched to the REFL165 signal by handing off at the input matrix. The input matrix element for REFL165_I was gradually
increasded up to 0.8 while the element for REFL33I was gradually reduced to 0. We did the same for REFL165_Q with the element of 0.2.

Now we tried locking with REFL165I/Q from the beginning. Once the alignment is adjusted, the lock was immediately obtained
only with REFL165I/Q.
Today we did not adjusted the ASC stuff (OPLEVs and PRM ASC) so the lock was not long (<1min). Particularly
ITMX poiting kept drifting and it made the lock difficult. We should check the oplev setup carefully.

- LSC summary

PRCL
Signal source: REFL165I (74deg) / Whitening gain 45dB
Normalization sqrt(POP110I x 0.1) / Trigger POP110I 100up 3down
Servo: input matrix 0.80 -> PRCL Servo FM3/4/5 Always ON G=+2.50
Actuator: output matrix 1.00 -> PRM

MICH
Signal source: REFL165Q (74deg) / Whitening gain 45dB
Normalization sqrt(POP110I x 10.0) / Trigger POP110I 100up 3down
Servo: input matrix 0.20 -> MICH Servo FM4/5 Always On G=-40
Actuator output matrix -1.00 -> ITMX / +1.00 -> ITMY

To Do:

- Refine the PRM asc servo (AC coupled)
- Align oplevs
- ITMX oplev is drifting quickly (~1min time scale)

Attachment 1: 130703_PRMI.pdf
Attachment 2: Screenshot.png
14062   Fri Jul 13 00:15:13 2018 Annalisa, TerraConfigurationAUXY arm cavity scan

[Annalisa, Terra, Koji, Gautam]

Summary: We find a configuration for arm scans which significantly reduces phase noise. We run several arm scans and we were able to resolve several HOM peaks; analysis to come.

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

As first, we made a measurement with the already established setup and, as Jon already pointed out, we found lots of phase noise. We hypothesized that it could either come from the PLL or from the motion of the optics between the AUX injection point (AS port) and the Y arm.

• We first characterized the PLL loop phase noise by comparing the beat signal against the Agilent reference signal, and we found that the beat had lots of phase noise with respect to the reference. Decreasing the PLL gain, we got rid of the phase noise in the beat signal.
• Next, for the optical path length induced phase noise, we took the transfer function between TransMon and REFL signal rather than TransMon and Agilent reference signal. This takes advatage of the fact that the TransMon and REFL both see optical path length phase noise, which therefore gets canceled out in the transfer function.

In this configuration, we were able to do arm scans where the phase variation at each peak was pretty clear and well defined. We took several 10MHz scan, we also zoomed around some specific HOM peak, and we were able to resolve some frequency split.

We add some pictures of the setup and of the scan.

The data are saved in users/OLD/annalisa/Yscans. More analysis and plots will follow tomorrow.

Attachment 1: IMG_6492.JPG
Attachment 2: IMG_6494.JPG
14078   Tue Jul 17 17:37:46 2018 Annalisa, TerraConfigurationThermal CompensationHeaters installation

## Summary

We installed two heaters setup on the ETMY bench in order to try inducing some radius of curvature change and therefore HOMs frequency shift.

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

We installed two heaters setup.

Elliptic reflector setup (H1): heater put in the focus of the elliptical reflector: this will make a heat pattern as descirbed in the elogs #14043 and #14050.

Lenses setup (H2): heater put in a cylndrical reflector (made up with aluminum foil) 1'' diameter, and 2 ZnSe lenses telescope, composed by a 1.5'' and a 1'' diameter respectively, both 3.5'' focal length. The telescope is designed in such a way to focus the heat map on the mirror HR surface. For this latter the schematic was supposed to be the following:

This setup will project on the mirror a heat pattern like this:

which is very convenient if we want to see a different radius of curvature for different HOMs. However, the power that we are supposed to have absorbed by the mirror with this setup is very low (order of 40-ish mW with 18V, 1.2A) which is probably not enough to see an effect. Moreover, mostly for space reasons (post base too big), the distances were not fully kept, and we ended up with the following setup:

In this configuration we won't probably have a perfect focusing of the heat pattern on the mirror.

## In vacuum connections

See Koji's elog #14077 for the final pin connection details. In summary, in vacuum the pins are:

13 to 8 --> cable bunch 0

7 to 2 --> cable bunch 2

25 to 20 --> cable bunch 1

19 to 14 --> cable bunch 3

where Elliptic reflector setup (H1) is connected to cables 0 and 1, and the lenses setup is connected to cables 2 and 3.

## Installed setup

This is the installed setup as seen from above:

Attachment 5: IMG_5380.JPG
14086   Thu Jul 19 04:44:09 2018 Annalisa, TerraSummaryThermal Compensationfrequency shift observed with heating!

Annalisa, Gautum, Koji, Terra

Summary: with the reflector setup, we measured a frequency shift of the first and second order modes! First looks of shifts show 1st HOM shift ~-10 kHz, 2nd HOM shift ~-18 kHz (carrier ~4 kHz). We saw no shift with the cylinder/lenses set up.

- - - - -

Tonight we modified the cavity scan setup: the LO is provided by the Marconi which, at the same time, is also used to scan the AUX laser frequency instead of the Agilent. In order to get rid of the free running noise between Marconi and Agilent, the Marconi frequency was scanned and, point by point, the Agilent center frequency was changed accordingly. In order to speed up the process, the whole procedure was automated. The script is called AGfast.py and can be found in /users/annalisa/postVent.

One thing that helped in improving the data quality of the phase information was to set the Agilent IF bandwidth @1kHz. Not yet clear why, but it was better than having a lower bandwidth. To be further investigated.

With this setup, we made some coarse scan of the full FSR and then we "zoomed" around the main peaks in order to increase the resolution and get a more precise information about the peak frequency.

Here are the frequency ranges that we scanned:

• carrier - central frequency: 31.73MHz; range: [31.68MHz - 31.78MHz]
• HOM1 - central frequency: 32.88MHz; range: [32.84MHz - 32.93MHz]
• HOM2 - central frequency: 34.03MHz; range: [33.95MHz - 34.06MHz]
• HOM3 - central frequency: 35.18MHz; range: [35.09MHz - 35.25MHz]

We powered the heater of the lenses setup @4:55 am at 14.4V and 0.9A. Then we slightly increased the power @5:05am and the final "hot state" configuration is with heater powered at 16V and 0.9A.

With this setup we couldn't see any frequency shift

Then, at around 6:30 am we turned on the reflector setup and we measured a frequency shift of the first and second order modes. First scans show 1st HOM shift ~10 kHz, 2nd HOM shift ~18 kHz. First attachment shows carrier hot/cold, second attachment shows HOM2 hot/cold. We started to get plauged by high seismic noise. Heaters turned off at 7:45 am. Lots of scans and actual analysis to go.

gautam: about the questionable plotting -

• 10 faint (alpha~0.3) lines are individual measurements with the reflector doing its heating. (AG4395A, 0 span, single frequency measurements plotted together).
• charcoal line, labelled mean, is the mean of the 10 above lines.
• bright green ("Reference") is the mean of a coarse scan (cold ETM) overlaid for comparison.
• "cold" - self explanatory.

My personal favourite plot is Attachment #3, which is a 5 MHz scan (cold) to identify positions of the various peaks. The power of including phase information in the analysis is clear. The second FSR on the right edge of the plot is not as prominent as the first is because the arm transmission was degrading throughout the measurement. For future measurements, we should consider locking the IMC length to the arm cavity - this would eliminate such alignment drifts, and maybe also make the PLL control signal RMS smaller.

Attachment 1: scanning_fine_2018-07-19-07-32-08_parsed.pdf
Attachment 2: scanning_fine_2018-07-19-06-57-47_parsed.pdf
Attachment 3: Yscan_scanning_parsed_2am.txt.pdf
13703   Mon Mar 26 10:15:20 2018 ArijitUpdateIOOPMC and IMC re-locked

[Gautam, Arijit]

PMC and IMC re-aligned and re-locked. Both cavities are staying locked. Arm cavities are also locked.

13788   Wed Apr 25 17:44:39 2018 ArnoldUpdatePEMPEM Anti-Alias wiring

12621   Wed Nov 16 17:07:12 2016 AshleyUpdateGeneralPreliminary Microphone Data

I am currently looking at the acoustic noise around both arms to see if there are any frequencies from machinery around the lab that stand out and to see what we can remove/change.

• Attachment 1 is a picture of the microphone and suspension system (bungee cords) that hangs from the cable trays to isolate it from vibrations.
• To record data, I used both the microphone (attachment 1) attach it its preamp connected to a spectrum analyzer in order get a graph of power spectral density, recording from 0-10k Hz and 10-100kHz. I started recording data at the furthest end of the x arm and worked towards the center taking measurements every couple of feet (ten rungs on the cable tray).
• The second attachment is the first 5 psd I got from the furthest end of the x arm going 10 rungs on the cable tray closer each measurement.
• Going forward, I am going to take more measurements with greater resolution at the lower frequencies from 0-200 and stepping up from there by factors of 2.

Attachment 1: first_PSD_12kHz.pdf
12738   Thu Jan 19 10:21:54 2017 AshleyUpdateGeneralPreliminary Microphone Data

Brief Summary: I am currently looking at the acoustic noise around both arms to see if there are any frequencies from machinery around the lab that stand out and to see what we can remove/change. I am using a Bluebird microphone suspended with surgical tubing from the cable trays to isolate it from vibrations. I am also using a preamp and the SR875 spectrum analyzer taking 6 sets of data every 1.5 meters (0 to 200Hz, 200Hz to 400Hz, 400z to 800Hz, 800Hz to 3200Hz, 3.2kHz to 12kHz, 12kHz to 100kHz).

·                Attachment 1 is a PSD of the first 3 measurements (from 0 to 12kHz) that I took every 1.5 meters along the x arm with the preamp and spectrum analyzer

·                Attachment 2 is a blrms color map of the first 6 sets of data I took (from 2.4m to 9.9m)

·                Attachmetn 3 is a picture of the microphone set up with the surgical tubing

Problems that occurred: settings on the preamp made the first set of data I took significantly smaller than the data I took with the 0dB button off and the last problem I had was the spectrum analyzer reading only from -50 to -50 dBVpk

Attachment 1: xend_psd.png
Attachment 2: xblrms.png
Attachment 3: IMG_3734.JPG
12826   Mon Feb 13 17:39:45 2017 AshleyUpdateGeneralPreliminary Microphone Data Update
• Problems that have occurred since my last post: All of the sudden, I was getting very strange data that was very quiet and did not match the previous input range of my last locations (see attachment). After resoldering the custom bnc connection cables with Lydia, which were in disrepair, and checking almost everything we could think of, we found that the gain dial on the preamp was turned all the down. Immediately after it was fixed, the data returned to expected values (based on neighboring locations and data taken at the last location before the problem occurred).
• Updates: Since my last post, I have created a normalized blrms color map in addition to the one I already have. Additionally, I have started working on plotting the color maps next to a labeled, to-scale drawing of the lab, but have yet to complete it.
• Attachment 1: comparison of the psds
• Attachment 2: blrms color map
• Attachment 3: normalized color map
 Quote: Brief Summary: I am currently looking at the acoustic noise around both arms to see if there are any frequencies from machinery around the lab that stand out and to see what we can remove/change. I am using a Bluebird microphone suspended with surgical tubing from the cable trays to isolate it from vibrations. I am also using a preamp and the SR875 spectrum analyzer taking 6 sets of data every 1.5 meters (0 to 200Hz, 200Hz to 400Hz, 400z to 800Hz, 800Hz to 3200Hz, 3.2kHz to 12kHz, 12kHz to 100kHz).   ·                Attachment 1 is a PSD of the first 3 measurements (from 0 to 12kHz) that I took every 1.5 meters along the x arm with the preamp and spectrum analyzer ·                Attachment 2 is a blrms color map of the first 6 sets of data I took (from 2.4m to 9.9m)  ·                Attachmetn 3 is a picture of the microphone set up with the surgical tubing  Problems that occurred: settings on the preamp made the first set of data I took significantly smaller than the data I took with the 0dB button off and the last problem I had was the spectrum analyzer reading only from -50 to -50 dBVpk

Attachment 1: figure_1.png
Attachment 2: x_and_y_blrms_03.png
Attachment 3: xblrms_median.png
7589   Mon Oct 22 20:44:49 2012 AyakaUpdateAdaptive Filteringmicrophone noise

I will do some experiments on acoustic noise canceling during my stay.
Now I am planning to cancel acoustic noise from PMC and see how the acoustic noise work and how we should place microphones.

First, I measured the noise in microphones and its circuit.

-blue, green, red, solid lines; microphone signals
-blue, green, red, dashed lines; un-coherent noise in signals
-yellow, black, solid lines; circuit noise (signal input is open, not connected to the microphones)

We can see the acoustic signal above 1 Hz, and the circuit does not seem to limit its sensitivity. But I do not know why yellow and black is so different. I will check it tomorrow.

7596   Tue Oct 23 10:24:42 2012 AyakaUpdateAdaptive Filteringmicrophone noise

Quote:

 Quote: I will do some experiments on acoustic noise canceling during my stay. Now I am planning to cancel acoustic noise from PMC and see how the acoustic noise work and how we should place microphones.a First, I measured the noise in microphones and its circuit. -blue, green, red, solid lines; microphone signals -blue, green, red, dashed lines; un-coherent noise in signals -yellow, black, solid lines; circuit noise (signal input is open, not connected to the microphones) We can see the acoustic signal above 1 Hz, and the circuit does not seem to limit its sensitivity. But I do not know why yellow and black is so different. I will check it tomorrow.

Hi, Ayaka.  It would be good if you could give a little bit more detail about this plot:

• What exactly are the "signals"?  Are you making a sound somehow?  If so, what is producing the sound?  What is it's spectrum?
• Are the blue/green/red traces from three different microphones?
• Coherence usually implies a comparison between two signals.  Is something being compared in the dashed traces?
• Are the yellow and black traces from different amplifiers?
• What are the units of the Y axis?

Sorry for my poor explanation.

I measured this by the same way as you measured the instrumental noise of seismometers.
I put the three microphones at the same place so that the three can hear the same sound. I did not make any sounds, just put them in the lab.
The signals from microphones are all amplified by the circuit.
And I took the correlations of each signals and two others and got the noise (dashed lines) by subtracting the correlated signal from the original signal.

So,
-The signal is the acoustic sound in the lab, amplified by the circuit.
-Three lines are from three different microphones.
-Dashed lines are subtraction of coherent signal from the original.
-Yellow and black lines are from different amplifiers in the same circuit box. The circuit has 6 channels.
-I did not calibrate the signals I got by DTT since I do not know the calibration factor now. It is just the number I got from the real time system.

ELOG V3.1.3-