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ID Date Author Type Category Subjectup
  44   Wed Feb 3 13:05:26 2010 FrankLaserRefCavbeam pointing @ refvac

measured the beam pointing caused by driving the AOM frequency modulation input. data is uncalibrated so far, just a screenshot of the dataviewer. PDHOUT is the VCO input signal...

pointing.jpg

  844   Sun Feb 26 17:40:43 2012 taraDailyProgressopticbeam realignment after new seismic stack installation

I'm trying to re-align the beams to the cavities. Due to the new RTV springs for the seismic stack, the cavities' natural axes shift by ~1/4 " with respect to the previous position.

     I had to adjusted the height of the top mirror of the periscope before I could align and lock RCAV (visibility ~ 95%) again. The pictures below show the position of the current beam. With the previous setup, the beam position was almost at the center of the holes. Now, for RCAV, the axis shifts closer to the edge. RCAV might yaw with respect to the previous position. Left picture shows the incoming beam position, Right picture shows the outgoing beam position.

IMG_0374.jpgIMG_0373.JPG

      For ACAV, however, it seems that the position changes a lot and the beam clips on the outer edge of the top mirror before I can even find TEM00. I think I'll have to add a spacer between the mirror mount and the vertical plate in order to re align the beam.

     I think we can keep the stack position as it is for now, if I can lock both cavities and the transmitted beams can be adjusted on the breadboard for beat path. We might also have to increase the hole size on the insulation cap as well depending on where the beam position of ACAV will be.

 

  845   Mon Feb 27 10:56:43 2012 taraDailyProgressopticbeam realignment after new seismic stack installation

I realigned ACAV and found TEM00, but now the transmitted beam is completely missed the opening on the insulation, it is off from the center by ~ 1 cm.

  819   Fri Feb 10 23:47:22 2012 Tara, FrankDailyProgressBEATbeam splitter mount replaced

we replaced the mount for the combining beam splitter in the beat setup as it caused a large, broadband peak in the spectrum around 1.4kHz. The new mount is one of the old, fixed turning mirror blocks they used in initial LIGO at LLO as far as i know. After replacing the mount the peak is entirely gone. I've used two springs instead of one to increase the pressure.  We could not determine the resonance frequency of the new mount. Tapping the mount excites only known mechanical resonances from the surrounding mirror mounts. Tara posted a plot for comparison before and after replacing that mount (see here). He also has prepared a nice plot combined with a drawing which mount corresponds to which resonance we see in the spectrum. We will use this to start reducing (or even eliminating) those resonances starting with the most dominant ones close to 1kHz

Attached a copy of the drawing.

SCAN1623_000.pdf

 

  1321   Mon Sep 2 03:38:27 2013 taraDailyProgressNoiseBudgetbeat

It's a quiet night, so I went down the lab to measure the beat signal. We are getting close. I think I have to review my noise budget calculation and estimate the error in the measurement carefully.

So after a few things Evan and I did a few days ago:

  1. rotate the stack to get rid off the reflected beam from the window
  2. fix the insulation so the beam is not clipped on the opening.
  3. add more modulation depth to RCAV path with the EOM driver (tuned to 14.75MHz)
  4. Minimize some RFAM, by rotating the half wave plate in front of the sideband EOM

Then I measured the beat signal.

We reduce some noise from scattered light at frequency below 100 Hz, we are limited by some white noise at high frequency ~ above 1 kHz.

beat_2013_09_02.png

fig1: measurement vs noise budget

zoom_beat_2013_09_02.png

fig2: zoom in. The slope of the measured signal agrees well with the slope of thermal noise.

ToDo

  • Estimate/measure shot noise PD noise and electronic noise in the setup. See if they match up with the measurement.
  • Review the noise budget calculation. Looking at the slope of the signal around 1kHz, I think the calculated brownian noise is lower than what it should be.
  • noise hunting, seems like scattered light at frequency below 100Hz. There are many mechanical peaks, and harmonic lines at higher frequency.
  • add the contribution from RIN induced TO noise in the nb.
Attachment 1: zoom_beat_2013_09_02.png
zoom_beat_2013_09_02.png
Attachment 3: nb_short_cav.fig
  1327   Sat Sep 7 04:29:32 2013 taraDailyProgressNoiseBudgetbeat

Short note from tonight measurement:

1) scattered bump from dc to 100Hz is mostly from seismic. It is worse during the day. It gets smaller at around 3-4 am. Unless we have a better seismic isolation, we might not be able to see anything below 100Hz.

2) RIN shape from RCAV changes, reasons still unknown. (DC level 0.7 V)

3) I might see the effect from RIN induced TO noise at frequency ~ 1-3 kHz. (compare RIN and beat).

I'll get into details tomorrow.

  507   Tue Feb 22 21:57:02 2011 frank, taraDailyProgressBEATbeat

Today, we found out that at high frequency, the limiting noise source is probably electronics noise might be from the Universal PDH box.

 

We tweaking the setup parameters, FSS gain, UPDH gain, sideband power, laser power to see what will change the beat noise.

We learned that

 

1) The current setup is not FSS gain limit, because we adjust the gain, but the beat noise remains the same,

and the range of the gain we can adjust is quite high, between 5 - 30 dB.

 

2) By adjusting side band power, the noise level changes.

However, when we added gain to compensate for the lower side band power, the noise does not go back to original level.

This is weird. We adjusted decrease 35.5 MHz sideband power, and noise level goes up. Increasing gain in FSS and ACAV loop does not change it back.

 

3) The peaks around acoustic frequency (mechanical peaks)can be suppressed by increasing PDH gain, but the flat level changes.

The noise level calculated from input referred noise sitll does not match with the beat noise, but they are close.

beat_2011_02_22.png

Now the beat noise is not limited by LO phase noise.From the flat shape of the noise, we think that it might be the electronic noise

from the PDH box.

 

To do next: increase the error signal slope for ACAV path. Now it is very small ~23 mV.

  509   Wed Feb 23 01:47:15 2011 frankDailyProgressBEATbeat

you have to be a bit more precisely fro points 2 and 3, e.g. no one knows what you mean as "PDH" gain as you have two loops using the PDH technique.

Some comments:

  • For Point 1: What does it mean "and the range of the gain we can adjust is quite high, between 5 - 30 dB" ? From you description it could be that the gain adjustment is limited by loosing lock below gain of 5dB or lower, but you can actually change it from -20 to 30dB without loosing lock. Forgot to mention that the noise does not stay the same if you change the gain below that value. If you lower it below a threshold you see that you don't have enough gain to suppress the laser noise. Only for gains above ~5dB or so you have enough gain and so for the setting we typically use we are not gain limited.
  • For point 2: You forgot to describe what happens when you change the optical power . Reducing the sideband power causing a higher noise floor and not be able to bring it back by increasing the gain is not surprising, e.g. the power is so low that the shot noise level limits you. Then you can't win with more gain. You have to calculate that level and compatre it before you can make a statement.
     
  • For point  3: Describe a bit more detailed what you changed, no one understands it. Which noise projection did you use, PDH box terminated or with photodetector? That's a huge difference. The noise of the box can be well below and you are still limited by electronic noise from the detection! You should work on that block diagram with all the parts and individual noise sources to get a better picture of what's going on and which noise couples in which way.

 

  560   Fri Apr 1 01:58:25 2011 taraNotesBEATbeat and UPDH gain on ACAV loop

I checked electronic noise, of the UPDH box while tuning its gain, to understand why the beat signal gets higher when the gain on UPDH increases.

  I still don't understand ACAV loop's behavior, but it is not the current limiting noise source, either RCAV loop or PLL is.

Right now, the beat signal at high frequency is limited by an unknown source(s). But by changing the gain of the UPDH which is used

for locking the beam to ACAV, the beat signal gets higher, before the oscillation in the loop occur.

I would expect the loop to become unstable first, so the beat gets worse, but this is not the case. So I measured

error signal, Vout to VCO, TF of the UPDH, noise of the UPDH, and varied the gain.

 This UPDH has knob to adjust its gain. The dial reads from 0 to 10.

 

I check that the beat signal does not change when the gain of the UPDH is changed from 0 to 1.5, then it starts to get higher, broadband at high frequency, 200Hz and above.

So I varied the gain and recording the following(I made sure that the loop is still stable, no oscillation in ACAV_RCTRANSPD)

beat_gain.png

1)Above, beat measurement

 

err_gain.png

2)Above, error signal, during closed loop

 

 

 act_gain.png

3) actuator signal to VCO, during closed loop

 

UPDHnoise.png

4)noise of the UPDH box, 50ohm terminated input,

 

TFUPDH.png

5) TF between input and output(UPDH TF)

 

ifr_gain.png

6) so from, 4 and 5 I can compute the input referred noise of the box. The result is unexpected. The input referred noise is getting lower

as the gain increases. With the error signal slope of 0.11 MHz/V the input referred noise is still lower than the beat (~ 10^-1 Hz/rtHz.)

So the input referred noise of the UPDH that changes with gain might not be the limiting noise.

 

However, when I project the noise from error point to beat noise with the slope of the error signal being 0.11 MHz/V.

The noise when the gain is 1 and 1.5 are lower than the beat. However, when the gain is 3.2 and 4 where the beat is getting higher,

the noise projection match the beat signal.

This means that

1) the noise projection factor I get this time is correct,

2) the limiting noise at gain 1.5 (usual setup) is not from ACAV loop.

3) UPDH will be the limiting noise source very soon. Since at gain 1.5, it is only a factor of 2 lower than the current beat.

beat_err.png

So the next thing is to check if the limiting noise source comes from RCAV loop or from PLL loop.

 

 

* note: the phase shift dial on UPDH box is probably broken. I could not change the error signal with it.

 I'll have to think over about what causes this.

  564   Mon Apr 4 19:48:51 2011 taraNotesBEATbeat and UPDH gain on ACAV loop

I check the noise projection from RCAV's error signal. It is still lower than the beat frequency. So the limiting noise source is not from RCAV loop.

From previous entry, I measured the slope of the error signal for RCAV loop. The value is 0.275 MHz/V. So I can calculate the frequency noise level from RCAV loop by measureing the noise at the error point, then multiplying the noise by the slope of the error signal.

rcav_errnoise.png

The noise level is about 2*10^-2 Hz/rtHz which is lower than the current beat noise (~0.1 Hz/rtHz).

Since the beat signal contains all noise from RCAV ACAV, and PLL loop, and I verified that the noise contributions from RCAV and ACAV loop are smaller than the measured noise. The limiting noise must come from the readout part.

So the next thing to look into is the noise in PLL loop.

  565   Tue Apr 5 22:32:08 2011 taraNotesBEATbeat and UPDH gain on ACAV loop

 I made sure that the gain setup for ACAV's servo was not too high and caused instability in the loop. The beat was not improved.

Previously from this entry, we see that noise at the error point, ACAV loop, increases with the ACAV servo gain.In general, it should decrease, since larger signal from actuator can suppress more noise. Frank told me that it might start oscillating somewhere and should check that the gain setting we use still make sense (increase gain, lower noise at error point,) so I added more data from gain 0(minimum) and 0.5 to show that the noise is actually going down as gain increase at these gain setup, and the beat signal still remain the same.

 

errnoise.png

 Above, noise at error point during close loop operation.

noise_prj_beat.png

Above, noise at error point projection to frequency noise. From gain 0 to 1.5 noises at error point still lie below the measured beat.

 

Since the error signal measured above might not be very clear, I repeated the experiment by adding a 20 dB attenuator at the UPDH input to make sure that the signal from the mixer is not too large and cause any osscilation. However, there is no improvement in beat measurement. I think the PLL readout part is the most suspicious one right now.

  1231   Tue Jul 9 19:35:20 2013 taraDailyProgressopticbeat board is back

I installed the beat board back behind the cavities. I still have not finished aligning both beams to the 1811.

  • Note about ACAV ( this path has PMC on it): After new mode matching with more visibility (from 80% to 95%), I can increase more gain and the error noise is getting lower. However, there is a problem with the beam reflected from the window of the tank. It overlaps with the main beam and cannot be blocked. I think this is the reason why we cannot suppress the error noise down to what we had before. I still need to convert the error noise back to frequency noise to see if it is below the estimated coating noise or not. If not, we have to reopen the chamber and tilt the cavity a bit. Rcav does not have this problem, the back reflection is away from the main beam and can be dump properly.
  • Note about RCAV: Erica and I plan to finish the EOM driver test tomorrow. After that I'll use it to drive the broadband EOM for locking RCAV to the cavity. The plan is to use one marconi to drive two EOM at the same frequency (14.75 MHz). We use a 4-way splitter for 2 EOM and 2 demodulations. I don't know how using same frequency for EOM will turn out (cross talk problem), but I want to see the first beat measurement within this week.
  • Note about beat setup: Evan calculated the mode matcing for beat setup, but I had to modify it. The first lenses were moved out of the board and mounted between the vacuum tank and the board due to space limitation. This might add some extra resonant peaks in the beat setup due to the long posts for lenses. The spot diameter on the PD is about 130um, which should be fine because 1811's diameter is ~300 um.
  73   Mon Feb 22 18:58:23 2010 Tara ChalermsongsakLaserRefCavbeat frequency between transmitted beams

 Today  we finally see the beat between transmited beams from Ref Cavity and A Cavity.  Now we are trying to use a local oscillator [IFR2023b] to demodulate the signal.

The beat signal will be fed to a low pass amplifier and  sent to IFR2023 as external  frequency modulation.

Attachment 1: 02.TIF
02.TIF
  858   Fri Mar 2 23:37:36 2012 taraDailyProgressBEATbeat is back

 Beat signal is back now, but we have not measured the spectrum yet since the temperature is still drifting fast (10kHz/ min). We plan to measure it tomorrow afternoon.

    The optics for RCAV are aligned. The visibility is ~95% without adjusting the lenses for mode-matching. I do not redo the mode match yet because we probably have to move the chamber for installing the air springs very soon. For ACAV, the beam is aligned, with visibility only ~ 80%. I also adjusted the cable length for PDH locking so that the error signal looks symmetric (Frank added the 4-ch splitter for demodulating RFAM, so the phase shift changed a bit.  All reflected beams  are properly blocked with razor blade blocks.

    The beat frequency is ~ 188MHz instead of the nominal value of 160 MHz because the temperature is not settled at the set point yet. It takes longer than before because of the copper shields around the cavities.  We expect it to be stable by tomorrow afternoon.

  860   Sat Mar 3 14:53:51 2012 ZachDailyProgressBEATbeat is back

Quote:

We expect it to be stable by tomorrow afternoon.

 What about my dance party?! 

disco.png

  861   Sat Mar 3 17:50:45 2012 taraDailyProgressBEATbeat is back

NO!! no dance party for you because you didn't return our label maker.

Quote:

Quote:

We expect it to be stable by tomorrow afternoon.

 What about my dance party?! 

disco.png

 

  862   Sat Mar 3 18:07:15 2012 ZachDailyProgressBEATbeat is back

And I stole one of your air dusters :-)

There used to be TWO label makers in the ATF---one of which looked like that one. What ever happened to those?!

Quote:

NO!! no dance party for you because you didn't return our label maker.

 

 

 

  863   Sun Mar 4 00:45:26 2012 frank, taraDailyProgressBEATbeat is back

Beat is back.

The beat signal( with the new softer springs) is measured and compared with the previous result (unfloated table). 

several notes about this measurement:

  • The resonant peaks from the stack show up as expected at 10, and 35Hz.
  • I have not added the contribution from seismic in the nb yet since TF between beat signal and seismic is not measured. We will measure that once the temperature settles.
  • Beat noise at high frequency  and  PLL readout noise do not match. This is probably because the gain setup on PLL changes and the readout noise changes with the gain, see psl:816 .
  • The table is not floated. If we float the table,seismic noise at frequency above 3-4Hz along with acoustic noise around100- 1kHz should decrease, and we might have a good chance to measure thermal noise around 100 Hz.
  • In loop noise for RCAV is around 50nV/rtHz instead of 10 (we could go down to this level before, see psl:855). The gain on TTFSS loop cannot be increased to what it was before (Common/Fast=920/850)We are checking what are the problems.
  • A quick measurement for ACAV in loop noise gives flat noise floor of ~40nV/rtHz. The slope from ACAV's error signal is 52kHz/V. Thus, the frequency noise floor from ACAV is ~ 2mHz/rtHz. Although it is higher than the designed value  (smaller than shot noise level), it is certainly not the current limiting noise source. 

 

beat_2012_02_03.png

  864   Mon Mar 5 16:29:50 2012 frank, taraDailyProgressBEATbeat is back

As mentioned in the previous entry that the in loop noise is higher than before. We investigate what might be the causes. We suspect that mode hopping or relaxation oscillation might be the case, but they are not.

The loop gain for TTFSS cannot be increased up to the usual setup, one thing we notice is that the signal from error point is quite large ( the input range selected on SR785 cannot go down below -30 dBVpk, it used to be -48 or -50 dBVpk)and oscillating at 200kHz. So we are also looking for what causes the oscillation at this specific frequency as well.

1)Checking for mode hopping:      Mode hopping might produce unexpected behavior of the laser. We want to make sure that the   usual SLOW_DC value is not close to where mode hop occurs.

 method: scan PMC and look at the signal from reflected power. The dip from transmitted TEM00 should become shallower when  mode hop occurs because some of the power is lost to other TEM00 mode.

 result: we are no where near mode hopping. The SLOW_DC coarse knob can be adjusted between 200 - 700 easily without seeing mode hopping. The usual set value is around 500 +/-20.

 

2) Relaxation oscillation: (cf siegman, laser, ch 25)

   Since we are looking for what cause the oscillation at 200kHz, relaxation oscillation is a possible candidate. We use a PDA10CS to measure the spectrum of the laser power. We use the beam reflected from the first Faraday isolator just after the NPRO. A broad peak at 462 kHz is observed, so this is unlikely to cause the oscillation.

relax.JPG

fig1: relaxation oscillation is measued (green) with the frequncy at 462kHz. The yellow line is the noise floor of the PD.

    To sum up, we are looking into what degrade the performance on RCAV loop. We ruled out two possibilities which are laser mode hopping and relaxation oscillation.

  870   Tue Mar 6 20:48:47 2012 frank, taraDailyProgressBEATbeat is back

After debugging the RCAV loop, we measured the beat signal again.  We still cannot reach coating thermal noise, the noise floor now seems to be mostly seismic related.

 

beat_2012_02_22.png

 Fig1: Beat measurement, grey trace shows the beat measurement from 2012-02-22, floated table. After that we changed the springs on seismic stack. Blue is the beat signal, unfloated table, and Pink is the beat signal with floated table.

 

     The new beat signal has more mechanical peaks around 300 Hz - 1kHz than the old one does. This is probably because I do not properly damp a few mirrors. The input range used in today's measurement is 2kHz. It does not change between 1 or 2kHz input range, so we probably sits on other technical noise sources.

     In conclusion, with the new springs, we can reduce seismic noise in 5Hz- 100Hz bandwidth (see grey and pink traces in the plot). Next step, we will work on damping mechanical peaks in the signal properly, and adding air spring for the vacuum chamber.

    Note: The setup was optimized for unfloated table. The blue trace was measured after we optimized everything, from polarization to beam alignment, both before and after the cavities. When I floated the table, the beam was barely aligned and could not be locked. I realigned the beam with periscopes, and adjusted the beam alignment on beat RFPD before measuring the pink trace.

  674   Mon Sep 12 01:21:14 2011 taraDailyProgressBEATbeat layout

New beat layout, both paths travel with the same distance before combining at the beam splitter. I'll try if this layout work tomorrow.

I'm a bit worried that the CCD cameras might not fit on the table. 

Attachment 1: beat_2011_09_12.png
beat_2011_09_12.png
  677   Tue Sep 13 20:54:11 2011 taraDailyProgressBEATbeat layout

 

 Beat path was setup. Beat RFPD sees the signal around 125 MHz. Beat measurement will be done tomorrow after ACAV is locked.

  678   Wed Sep 14 19:17:19 2011 frank, paul, taraDailyProgressBEATbeat layout

 Beat signal from double cavities in the same chamber was measured. At DC to 100Hz, it seems to be dominated by seismic. Above 100 Hz, the frequency's laser noise is the limiting source. The setup has yet to be optimized. This is for a quick check to see how beat signal changes with the new seismic isolation setup.

      I measured beat signal after Paul and Frank locked ACAV. At frequency above 100 Hz, beat signal changes with RCAV's gain setup. Error signal from RCAV's mixer out matches the shape of the beat signal ( I did not do the  calibration with error signal slope, just observed the displays on SR785). However, at low frequency (DC - 100 Hz), the beat signal does not change with anything, RCAV gain, ACAV gain, PLL gain, so I'm quite certain that it's the real signal we see here.

beat_2011_09_14.png

Tuning range on PLL loop was 10kHz, the calibration is 7kHz/V. A peak close to 7 Hz might come from the beam line transverse mode of the stack.

At DC - 10 Hz, the noise is lower than before. This might be the result from common mode suppression. However, the two spacers are not identical. They have significantly different holes' sizes. This may explain why the seismic cancellation is not that good at higher frequency.

Snapshot_2011-09-14_19-39-37.png

We might have to suspend the whole vacuum chamber to win against seismic.

  449   Thu Jan 20 11:32:40 2011 taraPhotosBEATbeat layout with 3" height

The picture is posted on the board outside the lab as well.

Attachment 1: beat.jpg
beat.jpg
  1393   Tue Dec 31 19:33:47 2013 taraSummaryNoiseBudgetbeat measurement

I got a chance to measure beat measurement. The noise budget is updated and contains all dominant noise traces.

 

== Beat measurement ==

beat_2013_12_24.png

1) at DC to 10Hz, the contribution is mostly from RIN driven Photothermal noise and a bit of seismic noise, a small peaks around 10Hz is probably from the stack, not the cavity sagging. The hump from DC to ~ 50Hz disappear when it is quiet. I think it is mostly scattered light associated with the seismic noise, not displacement noise due to the vibration.

2) 10Hz to 1kHz is pretty much Coating Brownian noise.

3) At 1kHz and above, it is PLL readout noise and residual frequency noise from the laser, where the gain cannot suppress enough noise. This is mostly from ACAV. The residual frequency noise = free running noise / (1+ OLGTF). The measurement of the open loop gain is explained below.

 

==TTFSS Loop characterization==

The OLG TF of TTFSS is measured up to 10MHz and compared with the calculation. The schematic explaning how TTFSS actuates on the laser is shown below.

TTFSS.png

The freqeuncy discriminator can be measured from the slope of the error signal (from Common out1) while scanning the laser. For RCAV Dv = 1/ (194 kHz/V) and 1/(164kHz/V) for ACAV. with 1mW input power.

The adjustable gain stage can be tuned by turning the dial knob. At 400, gain=1, and the gain changes by 10dB with every 250click.

The PZT actuator has a gain of  4.5MHz/V (measured), and the EOM actuator is 15mRad/V (or 15mHz/f  Hz/V) (taken from the spec sheet).

OLG measurement is taken:  RCAV OLG is measured and plotted against the theoretical approximation, see the below figure.

RCAV_OLG.png

above: RCAV OLG TF. Note: The calculation and the measurement do not include the integrator with corner frequency at 4.6kHz.

 

There are some problems with ACAV loop and I could not increase the gain up as much as it used to be and the UGF is around only 200kHz , but the measurement matches the calculation. Right now RCAV servo has a better loop performance.

ACAV_OLGTF.png

 The calculated OLG TF trace(green) should go down at 1MHz or above because of the opamps' bandwidth. I used ideal Op Amps in the simulation because I don't have some op amps in my liso library. I'll see if I can fix it.

  506   Mon Feb 21 20:15:14 2011 frank, taraDailyProgressBEATbeat measurement b/w cable delay and PLL

Today we compared beat noise measured from phase lock loop(PLL) and cable delay technique (CD.)

The results do not agree well. Eventhough we can get the calibration factor correctly, CD is not working yet.

 

We want to use CD instead of PLL because CD has no phase noise added to the signal which is the limiting

source for PLL at high frequency.

One drawback is that to get the calibration factor for CD. It has to be done every time with each measurement

as the calibration factor varies with the carrier frequency of the beat, cables used for the measurement, but it's not that hard.

 

We use CD to measure the phase noise of IFR2023b used for PLL, its phase noise was measured and added in the noise budget.

The result at 100kHz input range from CD agrees well with the previous measurement, we can see the feature of the phase noise nicely.

 phasenoise_by_CD.png

 This ensures that we got the CD calibration [Hz/V] correctly.

 

Then we switch to a 500 ft cable for better resolution and measure the phase noise of the LO again.

The results from 100 kHz input range are similar.

However, for phase noise at 10kHz input range (with lower phase noise,) CD cannot measure it properly by either short or long cables.

there is no phase noise's feature at high frequency like the previous result measured by SR785, note that

CD's noise floor is still lower than LO phase noise.

500ftCD.png

With that in mind, we measured beat noise by PLL(10kHz input range) and CD (500ft +2w amplifier).

We also injected a 1.092 kHz peak, generated by a func generator through a speaker on the table, to compare for the calibration.

1)If we use our regular calibrations for PLL and CD, the noise looks like this

beat_CD_PLL.png

 

 

2)If we match the 1.092 kHz peaks in both plot (I use a regular calibration for PLL). The result looks like this

matchpeak.png

And the coherence between PLL and CD is quite low (we have to think about it if the two signal should be coherence or not)

 

coherence.png

We will figure out what happen with the cable delay tech.

 

To sum up, we

1) make sure that we get the calibration factor correct for 500 ft cable setup with 2W amplifier,

by measuring ifr2023B phase noise at 100kHz range and compare it to the previous result.

 

2) are not certain why the LO phase noise and beat results are not similar at 10 kHz range

 

3) trust signal from PLL more than CD, since the beat noise from CD changed

(while PLL gave the similar result)when we adjusted the equipment, and we could not find out why.

Attachment 1: phasenoise_by_CD.png
phasenoise_by_CD.png
  966   Fri May 18 03:56:22 2012 taraDailyProgressBEATbeat measurement update

The beat signal is getting better at lower frequency, there is no obvious scattering bump around 80 Hz anymore. It is possible that the previous legs + leveling valves were bad and caused extra vibration.

After legs and leveling valves replacement,  the beat signal has better stability at low frequency. There is no bump due to scattered light around 80 Hz anymore. Plus, acoustic coupling (400-600Hz)f is significantly reduce without any improvement on the acoustic shield. Thus, it is very likely that acoustic coupling is related to legs' isolation performance.,Wrong statement, see PSL:970.(Mon May 21 21:13:11 2012 )

 Mechanical peaks around 25-50 Hz are probably from horizontal, or tip/tilt motion of the seismic stacks.

beat_2012_05_18.png

fig1: beat measurement. floated table, floated air spring. 1mW input power for each cavity, 1kHz input range on PLL.

 The result around 80-200 Hz has slope  f^(-0.5). Alas the span is only ~100 Hz bandwidth, with hideous unidentified peaks around 240 Hz. Otherwise we can be more certain that we reach thermal noise of something even though it is ~ a factor of 1.5 above the upper limit.

zoom.png

fig2: close up plot of the above figure, around 80-300 Hz. The measurement result is about a factor of 1.5 above the upper estimated level.

compare.png

fig3: comparison with f^-0.5 line (cyan).

 

 

  967   Fri May 18 18:44:38 2012 taraDailyProgressBEATbeat measurement update

I'm trying to fix the mechanical peaks in the beat signal. The work is still in progress.

There are several mechanical peaks around our most sensitive band (60 Hz - 600 Hz). It is important that we damp these to improve the beat signal. 

One of unidentified peaks are around 240 Hz , which might be originated inside the vacuum chamber. I tried tapping the chamber, and saw the peaks went up, but I could not pinpoint to where(stack/heat shield/ cavity motion) exactly.

There are peaks around 500Hz that come from QWPs behind the cavities. I checked their components individually to pinpoint where was the part that produced 500 Hz peak.  Each QWP was mounted on a rotatable square mount that are screwed down to a solid aluminum block.

  1. I inserted a sheet of rubber between the two mounts to damp any possible motion from the structure, but there was no improvement.
  2. I replaced the Al block with a steel 1" post.-> The peaks still there. So,
  3. I replaced the rotatable square mounts to the circular desing, on a steel post, and made sure that the QWPs were secured. -> The peaks still there
  4. I tilted the wave plates a little bit to prevent any possible back reflection, still no improvements.

It might be the motion of the plate itself. If this is the case, we have to have a better acoustic insulation box. The current one for the beat path has to many holes.

  1009   Sat Jun 30 05:01:04 2012 taraDailyProgressBEATbeat measurement with 2mW input power

I changed the power input from 1mW to 2mW for both cavities and measure the beat signal. From the measured results, there is no difference between the beat signal at different power input levels. This means that the current signal is unlikely to be sitting on shot noise or electronic noise that depend on power level.

 

     With the current laser (500mW), we can increase the power to both cavities up to 2mW. With higher input power, shot noise and electronics noise can be brought down. Even though the noise budget suggests that we are not limited by shot noise and electronic noise, I think it is a good idea to verify it . If we are limited by the shot noise due to low input power or electronic noise due to low frequency discriminator gain, we can see the change if we increase the power.

==setup==

  1. The power into both cavities are increase to 2mW.
  2. For RCAV, common/fast gain are 630/750.
  3. For ACAV I used an ND filter to reduce the power incident on RFPD. I chose the one that reduce the power roughly in half.

==results and comments==

     beat_2012_06_29_3.png

I plot the beat measurement with  1mW (black) and 2mW(pink) power together to show that there is no apparent improvement. Note that the noise budget is corrected for 2mW input power for both cavities. (I have not include the noise due to power fluctuation yet, I'll add that soon). 

 The slope around 50 Hz to 200 Hz is strongly go with 1/f^0.5 which is the slope of Brownian noise. However, it is ~ a factor of 1.2 above the upper limit of our estimation. I will check with Peter if he still has some information about the coating or not, and also the parameters in the noise budget calculation (for example, the loss in SiO2 for spacer, substrate to see if the values I use are sensible or not.

  353   Fri Sep 10 12:22:04 2010 taraDailyProgressBEATbeat noise measurement

Plot from yesterday measurement. The new result is in red.

The data is measured from the feedback signal in PLL loop. Its UGF is about 53 KHz.

The data is calibrated to Hz/ rt Hz unit by a factor of 71.3 kHz/ volt.

Attachment 1: new_beat.png
new_beat.png
  391   Thu Nov 11 22:50:14 2010 taraDailyProgressBEATbeat noise measurement

I measured the beat note signal from two different setup (f modulation) and plot the result below

 

We want to see where our beat signal is, and compare it to the noise budget, and improve the sensitivity.

I'm using the same noise budget for now, because

my noise model from RIN has not been finished yet. I'll try to finish it soon.

 

For beat measurement, I measured the feedback signal of the PLL loop,

since the UGF of the loop, which is 53 kHz, covers the region of our interest.

 

I used two frequency span on marconi, 20 kHz and 100 kHz.

I checked the calibration for each frequency spans which are 14.31 kHz/V and 70.8 kHz/V respectively.

The results are the same at low f to ~ 200 Hz, at higher f, 20 kHz span(brown line) has better sensitivity.

 

*b100 and b20 in the data.mat files are the result of beat at fmod 100kHz and 20 kHz in the format of

frequency, V/rtHz , f / rtHz

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

Setting

 

PMC

power input: 16mW

V_RF: 5.7 V

Phase ADj: 2.23 V

Gain: 13 dB

 

RCAV

power input: 2.86 mW

V_RF: 10

Phase ADJ: 4.2 V

Common gain: 18.9 dB

Fast Gain: 20 dB

 

ACAV

power input: 2.0 mW

Attachment 1: psl_refcav_sio2_300K.png
psl_refcav_sio2_300K.png
Attachment 2: data.mat
  1693   Sat Jul 30 19:08:08 2016 Antonio and AndrewDailyProgressBEATbeat note work and PLL

Summary

  • Today we have worked reying to improve the beat note signal in its amplitude.
  • We also connected all the parts for the PLL loop and tryied to lock the PLL but we did not succeded;
  • We noticed at some pint a noise at the input of the sr560 which pheraps prevents the PLL lock


    Conclusions

           We need to improve the lock of the cavities in order to get a more stable signal and solve the origin
           of the noise at the input of the sr560 in order to lock the PLL.

 

  574   Mon Apr 11 18:20:02 2011 taraDailyProgressBEATbeat setup is back

The optics behind RCAV for beat measurement are re-installed, with the new periscope. I'm waiting for the temperature to settle.

 

The periscope behind RCAV was removed when we opened the chamber and took out the cavity. Now everything is back in place  

The new periscope is installed. The bottom mirror is still on the same mount we have used before(fig1), but the top part is removed, so it should be less sensitive to seismic compared to what it was before (fig2).

 

I removed the hose between the RCAV chamber and the turbo pump since the valve and the turbo were turned off. Then I closed the insulation box.

The yellow foam insulation on RCAV was fixed. I melted it a bit to make sure that no part of the beam is blocked by the insulation.

 

000_0019.jpg

fig1: new periscope setup

 000_0020.jpg

 fig2) previous periscope

  286   Tue Aug 17 14:52:57 2010 FrankPhotos beat setup panorama picture incl beams

beat_panorama_small_with_beams3.jpg

  290   Wed Aug 18 03:15:20 2010 ranaPhotos beat setup panorama picture incl beams

The panorama is a good idea. We should make it a mandatory step whenever we make any change to the setup.

The asymmetry in the paths of the transmitted beams is dis-satisfying though. I would have tried to just take the transmitted beam and interfere them via short path lengths and no lenses. The cavity eigenmodes of each cavity should already be matched to ~1%. If the path length from the cavities to the BS can be made equal, the overlap should also be good. In general, it is hard to make a low phase noise setup with a long path length.

To ensure low backscatter from the transmission RFPDs back into the cavity, the beat signal PD should be placed slightly ahead of the focus of the final lens.

And since the Z=40 kOhms for the 1811, the light power from each cavity should be made ~200 mV / 40000 ~ 5 uW. I know its tiny, but otherwise the 1811 is not going to be very linear. And the RF signal going into a level 13 mixer ought to be less than 300 mVrms.

The better option is to use a RFPD with only ~1 kOhm of RF transimpedance...

  291   Wed Aug 18 12:19:17 2010 FrankPhotos beat setup panorama picture incl beams

i know the the asymmetry is not nice but we made the first beat setup symmetric and suffered a lot from the (former) little space behind the cavities.
Also one of the cavities is tilted and so the beam height is about .5in different.
Now as me moved both cavities a bit further away from the end of the table we should re-think about changing it to a symmetric setup. I think it's a good idea.
Anyway, shouldn't we just see all the resonances of the mounts in the spectrum, not a broadband noise hump? or do you expect lots of scatter from all the unnecessary optics?

you are right with the power, i reduced it by a factor of 10 and 100 but no change in noise spectrum (almost absolutely the same). But if i reduce the power some pickup of the 35.5MHz shows up in the signal (which is tiny), which i didn't see before. But it's ground loop related as you can change it by connecting/disconnecting some more channels to the scope e.g.. About the gain: i didn't measure the TIA gain of the PD, but the manual says 24e3 in the text, and 40e3 in the table at the end. Which one is right?

Another problem is that the bandwidth is only 125MHz, but we are looking at 160MHz. That shouldn't be much of a problem, only the noise of the PD increases and we are more sensitive to changes in the TF of the PD due to almost anything like power fluctuations, power supply fluctuations, temperature etc... So that probably the best argument right now to add the second AOM to reduce the beat frequency to something we can handle much better

Quote:

The panorama is a good idea. We should make it a mandatory step whenever we make any change to the setup.

The asymmetry in the paths of the transmitted beams is dis-satisfying though. I would have tried to just take the transmitted beam and interfere them via short path lengths and no lenses. The cavity eigenmodes of each cavity should already be matched to ~1%. If the path length from the cavities to the BS can be made equal, the overlap should also be good. In general, it is hard to make a low phase noise setup with a long path length.

To ensure low backscatter from the transmission RFPDs back into the cavity, the beat signal PD should be placed slightly ahead of the focus of the final lens.

And since the Z=40 kOhms for the 1811, the light power from each cavity should be made ~200 mV / 40000 ~ 5 uW. I know its tiny, but otherwise the 1811 is not going to be very linear. And the RF signal going into a level 13 mixer ought to be less than 300 mVrms.

The better option is to use a RFPD with only ~1 kOhm of RF transimpedance...

 

  459   Mon Jan 31 20:24:45 2011 frank, taraNotesBEATbeat signal down to 12.5 mHz

This morning I was able to measure the beat noise down to 12.5 mHz. So I plot it together with the noise budget here.

We also added channel for frequency counter,C3:PSL-FSS_FREQCOUNT which will allows longer data acquisition time for lower frequency.

Then we will be able to see the temperature effect at lower frequency(~ 10 mHz.)

 

Fig1: beat signal at 12.5 mHz to 10 Hz

 

We are also working on PID thermal control for refcav.

Perl script for PID thermal control won't work on Solaris because it doesnt have ezcaread/write command, we will get that from op40m machine at the 40m.

(We can't run Perl script on Linux because it complains that it fails to read / write data from C3:PSL-FSS_HEATER.)

 

Attachment 1: beat_2011_01_30_lowf.png
beat_2011_01_30_lowf.png
  463   Tue Feb 1 22:22:46 2011 frank, taraNotesBEATbeat signal down to 12.5 mHz

We measured beat noise from the frequency counter(FC) instead of the feedback from PLL. The result is plotted below

 

We switch to use the FC because we hope it will allow us to measure the signal down to lower frequency (~10 mHz) which is not quite possible

for PLL because of its small input frequency range for the acceptable phase noise level.

 

The FC can measure the relative frequency from the chosen center frequency and give a voltage output (from 0 to 8 V.)

For example if we set the center frequency to be 160 MHz, with 1MHz/V gain, signals at 156 MHz and 164 MHz will correspond to 0 V and 8 V respectively.

Since the LIGO VCO range is ~ 10 MHz, we tried measuring the signal with 500 kHz/V setup which is equal to 4 MHz range. However the noise is too high,

so we have to choose a new gain setup, and  20kHz/V setup is still acceptable for our signal compared to the signal from PLL.

 (It turns out that data from 50kHz/V is too noisy)

Attachment 1:

Blue and Green show the beat noise measurements from PLL and FC. They agree well. The gain for FC is set to 2kHz/V.

When the temperature became more stable, the data could be acquired to down to ~ 3mHz (red).

 

We used AC coupling for FFT measurement, so the TF for AC coupling is measured. There is a 160 mHZ high pass, and the data is corrected accordingly.

Attachment2:

Time series for ACAV's temperature, RCAV's temperature, VCO mon, and Frequency count Vout during the FFT measurement.

 

Attachment3: show TF measurement for AC highpass and fit with 160mHz high pass.

The plot is flipped because chA is AC couple and ChB is DC couple during the measurement, and

The output is B/A.

Quote:

This morning I was able to measure the beat noise down to 12.5 mHz. So I plot it together with the noise budget here.

We also added channel for frequency counter,C3:PSL-FSS_FREQCOUNT which will allows longer data acquisition time for lower frequency.

Then we will be able to see the temperature effect at lower frequency(~ 10 mHz.)

 

Fig1: beat signal at 12.5 mHz to 10 Hz

 

We are also working on PID thermal control for refcav.

Perl script for PID thermal control won't work on Solaris because it doesnt have ezcaread/write command, we will get that from op40m machine at the 40m.

(We can't run Perl script on Linux because it complains that it fails to read / write data from C3:PSL-FSS_HEATER.)

 

 

Attachment 1: PLL_FC_good.png
PLL_FC_good.png
Attachment 2: 2011_02_01_log3.png
2011_02_01_log3.png
Attachment 3: ac_highpass.png
ac_highpass.png
Attachment 4: 2011_02_01_dat.mat
Attachment 5: code_2011_02_01.m
load 2011_02_01_dat.mat

fc=fc_20kHz_22db_gd;
%correct for 160 mHz high pass
fc(:,3)=fc(:,2).* sqrt( (1 + (0.16./fc(:,1)).^2 ));

loglog(fc_2kHzv(:,1),fc_2kHzv(:,2)*2e3,...
        beat5Hz(:,1),beat5Hz(:,2)*71e3,...
        t2kHzv(:,1),t2kHzv(:,2)*2e3,...
... 5 more lines ...
  415   Wed Dec 1 22:07:05 2010 taraDailyProgressBEATbeat vs Power Input

I measured the beat signal from 3 different power input levels, the signal goes down with the power mostly at higher frequency.

When HEPA filters above the table are off, the noise also goes down, this might suggest that we still have scattering light problem.

 

 We are hunting for the noise source for our experiment. We want to see if our setup is limited by intensity noise or not

so, we try to change the power level and see the beat signal.

 

 I used 3 levels of power (measured after PMC) to be 10 mW (original value), 20 mW , 2mW, (the settings are listed below.)

The reason that the level at 10 mW decreases from previous beat msmt is that the gain for FSS and AOM loops are optimized

PDH box for AOM loop is also modified (R12, 1k -> 10k), the power into both cavities are adjusted to be about the same.

 The noise level at 10 and 20 mW are almost the same except a hill at 60 kHz on 20mW, and

  the noise from 2mW setup is lower than other settings at high frequency, starting ~ 20kHz.

 

 At 1 mW, I can't lock the PMC (the transmitted beam on the PD is so faint), so I increase to 2 mW to make locking easier.

At 2mW power, the range for feedback signal for PLL loop becomes smaller.

If it exceeds approximately +/- 50 mV [3.5kHz], the lock loses, but I still keep the frequency range at 100kHz.

I tried to increase the gain on SR560 which is a servo for PLL loop, but

the beat signal was worse at high frequency, starting at 2kHz.  Fortunately, the temperature drift at night (~10mV/min)is much smaller than

the drift during the day(~5mV/sec), so I can wait long enough to measure the beat at low frequency, with the gain level of 1, as usual.

 

At 2mW setting, I have the HEPA filter on and off in comparison. The noise level decreases a bit when the fan off, this might suggest that

scattering light is still a problem.

 

Even though the noise from beat measurement change with the power, the amplitude does not go with the power change.

i.e, the noise in the beat note does not go up with the same factor of the power change.

So the setup is not limited by intensity noise.  

 

setting for the measurement ["-" means the same as previous value]

                                      10 mW              20 mW             2mW

PMC: common gain         16 dB                 -                     30dB                       

PMC:RF                            5.7V                 -                       -

FSS:FAST gain               18.5 dB              -                      -

FSS:common                  22 dB               18 dB             20dB   

FSS:RF                           10 V                  -                      -

PDH for AOM:GAIN        4.45 (knob)       3.2                 7.0

Pin RCAV/ACAV            2.1/2.1 mW        4.8/3.9 mW    0.4/0.4 mW

Attachment 1: beat_2010_12_01.png
beat_2010_12_01.png
Attachment 2: 2010_12_01.zip
  882   Mon Mar 12 23:31:38 2012 frank, taraDailyProgressBEATbeat with floated table, air spring.

We measured beat signal with the upgraded seismic isolation system. It seems that we are sitting on some scattering noise source at low frequency.

 

      Most of the mirrors mount in beat path, are damped with rubber cones. A lead block is put on the board for beat setup to damp down any resonant peaks. With air springs and floated table, seismic noise is significantly reduced. From the shape of the bump around 70 Hz, we suspect that it is the scattering noise. That will be investigated further.

beat_2012_03_12.png

Fig1:  In grey: beat signal after softer RTV springs were used. In pink: beat signal with air spring, unfloated table. In blue: beat signal with air spring, floated table.

  878   Sat Mar 10 18:42:42 2012 taraDailyProgressBEATbeat- with air spring isolation

 Beat measurement with new air springs is measured with unfloated table (the N2 supply is empty). Good improvement can be seen at frequency above 20Hz.

beat_2012_03_10.png

The data is compared with beat signal before the air springs, unfloated table on 2012_03_03.  Once we float the table we should see no seismic/mechanical peaks around 100Hz. Then effects from RFAM/RIN couplings might reveal themselves.

Note about the setup:

  • Power into both cavities are ~ 1mW (I also adjust the power for beams to RFAM measurement PDs to be ~0.8 mW).
  • I replace the plastic legs for RCAV RFPD, so that the height is 3 inch, the reflected beam is dumped properly.
  • The measured Marconi frequency noise from Marconi in this nb is not updated yet. I'll update that soon.
Attachment 1: beat_2012_03_10.png
beat_2012_03_10.png
  1808   Tue Jan 10 16:40:28 2017 yinziDailyProgressTempCtrlbeginning integration on temperature control

We did some more hardware integration for the temperature control loop yesterday. We first added a new input channel and a new output channel in the “IOCTEST_BIO_generic.db” file to correspond with one temperature measurement and one control output. We hooked up the driver circuit and confirmed that we could control the output signal from the computer GUI. We also hooked up the RTD sensor and corresponding measurement circuit and confirmed that we could get measurements that made sense. Pictures of the hardware are shown below:

Driver circuit board:

Sensor and measurement circuit:

 

I then made a couple of software updates to accommodate temperature control:

1. I edited the following GUI to have to appropriate indicators and controls. I left out the control channels that do not have corresponding hardware channels yet to avoid possible confusion. All (? at least most) of the soft channels are mapped.

 

2. I made a copy of the “IOCTEST_BIO_generic.db” file, “IOCTEST_BIO_generic_20170109_edit.db” and added in all of the soft channels. I also renamed the hardware output channel to follow a more specific naming convention (HEATERN, and later HEATERS and HEATERV (if that’s okay), as opposed to just HEATER1, 2, 3). Once the channels are more finalized, they’ll be put into a separate post for reference.

I also routed the inputs and outputs of the driver circuit to the connectors on the front. A separate post will be made with the pin assignments for reference.

 

  184   Tue Jun 29 14:59:52 2010 FrankNotesNoiseBudgetbetter list of emissivity coefficients

source : http://www.omega.com/temperature/z/pdf/z088-089.pdf

emission_coefficients.pdf

  51   Fri Feb 5 20:37:06 2010 Tara ChalermsongsakLaserRefCavbetter pointing alignment

 After adjusting the mirror for reflecting beam back to the AOM, the QPD signal shows the better alignment. Before the voltage different readout is about 1.2 V, now it's reduced to ~500 mV.

We'll try to add a translational stage for the mirror for better alignment.

  2533   Thu Feb 13 18:00:30 2020 anchalDailyProgressscatterblocked NF1811 with hex beam dump

I have blocked the unused output port of the beam splitter before our beatnote detector with a hex beam dump at (13, 19). This was being used for broadband detector NF1811. We don't need it now.

  934   Tue Apr 24 22:07:10 2012 taraNotesLaserborrow NPRO from TNI

I borrow an NPRO from TNI. The model is similar to what we have, but I think the maximum power is 500mW (what we have is 100mW). I'll check the beam waist position tomorrow.

     Since we might switch to 2-laser setup, it is a good idea to have the second one ready. I checked a few companies for 1064 laser diode, but I could not find the information about how to control the frequency and its performance on the webpages. So I asked Eric Black and got the laser from TNI. Plus, the TTFSS is proved to be sufficient to suppress NPRO free running noise below coating noise level, the NPRO laser should be good for our setup.  We might need to think about preparing the rest of the equipments (resonant EOM for 2nd PMC, resonant and Broadband for refcav, PMC, and the servo circuits). For now, if the borrowed laser works fine and has more power, we might just switch it with the current one to gain more power.

 

IMG_0818.jpg

  936   Wed Apr 25 10:13:55 2012 FrankNotesLaserborrow NPRO from TNI

Don't forget to write an SOP for that laser before using it. A few things changed recently if you want to use the old SOP as an template. The hazard zone and emergency laser shutdown procedures, table layout etc. have slightly changed since the 10W laser has been moved. The map outside the lab is also not up-to-date anymore. The main kill switch at the door is still active but the second one which was attached to the 10W laser is gone now, but also not required for the NPRO. The required OD for safety glasses has to be recalculated for the document, but the ones we have are all good. The rest of the old SOP should be the same.

You also have to redo the mode matching to the PMC as the beam waist changes if you switch to the higher power laser.

For a two-laser setup we don't have all the parts at the moment to do so. There is no EOM for the PMC nor the refcav sidebands, no servo for the PMC, and no PMC. We don't have all parts to build a new PMC, especially no PZTs. Mirrors exist, spacer parts too but have to be assembled and we have to ask P.K. if we can have them, but shouldn't be a problem.

Quote:

I borrow an NPRO from TNI. The model is similar to what we have, but I think the maximum power is 500mW (what we have is 100mW). I'll check the beam waist position tomorrow.

     Since we might switch to 2-laser setup, it is a good idea to have the second one ready. I checked a few companies for 1064 laser diode, but I could not find the information about how to control the frequency and its performance on the webpages. So I asked Eric Black and got the laser from TNI. Plus, the TTFSS is proved to be sufficient to suppress NPRO free running noise below coating noise level, the NPRO laser should be good for our setup.  We might need to think about preparing the rest of the equipments (resonant EOM for 2nd PMC, resonant and Broadband for refcav, PMC, and the servo circuits). For now, if the borrowed laser works fine and has more power, we might just switch it with the current one to gain more power.

 

IMG_0818.jpg

 

  939   Wed Apr 25 15:15:03 2012 taraNotesLaserborrow NPRO from TNI

Duly noted, I'll write the sop for this one and put it on svn and wiki.

Quote:

Don't forget to write an SOP for that laser before using it. A few things changed recently if you want to use the old SOP as an template. The hazard zone and emergency laser shutdown procedures, table layout etc. have slightly changed since the 10W laser has been moved. The map outside the lab is also not up-to-date anymore. The main kill switch at the door is still active but the second one which was attached to the 10W laser is gone now, but also not required for the NPRO. The required OD for safety glasses has to be recalculated for the document, but the ones we have are all good. The rest of the old SOP should be the same.

You also have to redo the mode matching to the PMC as the beam waist changes if you switch to the higher power laser.

For a two-laser setup we don't have all the parts at the moment to do so. There is no EOM for the PMC nor the refcav sidebands, no servo for the PMC, and no PMC. We don't have all parts to build a new PMC, especially no PZTs. Mirrors exist, spacer parts too but have to be assembled and we have to ask P.K. if we can have them, but shouldn't be a problem.

 

 

 

  68   Thu Feb 18 15:07:39 2010 FrankMiscLaserboth IR viewers missing

so please bring it back - we are waiting for it and can't go on without those... For the future: if you take it, bring it back and don't wait until someone is missing it...

  338   Thu Sep 2 17:11:39 2010 taraNotesRefCavboth cavites locked

ACAV_TEMPAVG still adjusting it self to 37.2 (SETPT)  three overshoots in the last 8 hrs (+/-0.01 C)

 

                     ACAV                   RCAV

SETPT             37.2                  35

TEMPAVG    37.215               35.005

SLOWDC       N/A            -0.10932

VCOMON              1.11 V

 

*RCAV_TEMPAVG is very noisy compared to ACAV_TEMPAVG

ELOG V3.1.3-