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ID Date Author Type Category Subjectup
  1111   Wed Mar 6 21:56:12 2013 taraDailyProgressVacuumnote on feedthrough

Feedthrough channel (as seen from the connector outside of the chamber)

1-6: heater on cavity#98 : 85.4 Ohm

3-7: Temp sensor on cavity #98

 

4-8: heater on cavity#99: 156 Ohtm

5-9: Temp sensor on cavity#99

 

  1822   Sat Mar 4 17:01:00 2017 yinziDailyProgressTempCtrlnpn transistor buffer and metal piece measurements

So I put together a little test circuit to test out a NPN BJT buffer circuit with a TIP122 transistor and an OP27 op amp. Power voltages are ~ +-14V, just used the positive rail as V+ for the transistor.

(diagram from https://www.allaboutcircuits.com/technical-articles/how-to-buffer-an-op-amp-output-for-higher-current-part-1/)

I verified that the op amp functioned alone in a buffer configuration.

Putting the BJT in the loop added a (negative) offset, though:

WIth a 51ohm load, inputs of 1.5Vpp and 2Vpp respectively:

WIth a 910 ohm load, with inputs of 1.5Vpp and 2Vpp respectively:


I realized afterwards that this circuit theoretically shouldn't be able to go below ground. I'm surprised that the output is basically offset so that the entire output signal is below ground. I guess I will test it again with the input signal being entirely positive, but I'm not sure if this is even related. 
 

Side note: also made measurements of the metal slab (including the tape that is currently around it) to do some calculations later:

34.5mm by 61.5mm (basically flat in the third dimension, plus it's crinkly from tape so hard to measure consistently)

  1824   Thu Mar 9 15:02:46 2017 awadeDailyProgressTempCtrlnpn transistor buffer and metal piece measurements

What exactly is the offset? Is there some threshold voltage the BJT requires before it starts conducting, maybe one should expect a ~0.7 V difference between the op-amp output and the load voltage? There should be some opamp configuration where can you can bias the feed back to the -ve pin of the op-amp: this is commonly done for op amps running with single sided supply.

Is it possible to make use fo the full +/- 15 V range? 

Also, want to use a FET on the output BJT, it has lower noise and better thermal stability. 

 

Quote:

So I put together a little test circuit to test out a NPN BJT buffer circuit with a TIP122 transistor and an OP27 op amp. Power voltages are ~ +-14V, just used the positive rail as V+ for the transistor.

 

 

  438   Mon Dec 20 22:52:55 2010 ranaHowToPMCnuts

 The RefCav pole is 37 kHz, not 37 MHz.

To minimize the RFAM, you just look at the PMC REFL PD with the PMC unlocked and adjust the waveplate to minimize the peak. Before doing this, make sure that there is no signal on the PD with the light blocked.

  439   Thu Dec 23 22:26:14 2010 ranaHowToPMCnuts

Ah right, that's embarassing. I'll try that.

Quote:

 The RefCav pole is 37 kHz, not 37 MHz.

To minimize the RFAM, you just look at the PMC REFL PD with the PMC unlocked and adjust the waveplate to minimize the peak. Before doing this, make sure that there is no signal on the PD with the light blocked.

 

  67   Wed Feb 17 15:40:04 2010 FrankLaserLaserold 100mW NPRO

does anyone know the typical operating current for the 100mW lightwave laser model ? (M126N-1064-100) It's typically ~1.1A for the 200mW model. I've set up everything and it starts to lase around 0.44A, so at least its not dead but i don't know how high up i can go. My guess is that it is something around 0.8A but i have no datasheet which tells me...

  18   Sat Nov 21 17:27:32 2009 FrankMiscRefCavold Minco heaters

found four old Minco heaters (model HR5494-106) (from 1995) .  This type with 106 Ohms is not in their system anymore.
But corresponding to their data the maximum current for this type of heater is about 7.5A. So driving this heater with 24V would give us 5.4W of heating power beeing well below the limit. Using the standard power supply for heating refcavs we can get even more power. Due to the age (14years!) the adhesive back is not sticky anymore so i will use aluminum tape for first tests.

Model
HR5494 
Silicone Rubber heater :
4.00" x 8.00"
(101.60 mm x 203.20 mm)
Heater Shape
Effective Area : 30.3 in2
(195.484 cm2)
 
Lead Gauge : AWG 24
 
Max. current : 7.5 Amps
 
Configure this model in Kapton
Application Information Actual Current : 0.21 Amps
Operating Temperature : °C   Heat Output at Volts
Resistance in Ohms
378 1.52 Watts 0.05 W/in2 (0.0078 W/cm2)
189 3.05 Watts 0.1 W/in2 (0.0155 W/cm2)
114 5.05 Watts 0.17 W/in2 (0.0264 W/cm2)
55.1 10.45 Watts 0.34 W/in2 (0.0527 W/cm2)
37.6 15.32 Watts 0.51 W/in2 (0.0791 W/cm2)
26.3 21.9 Watts 0.72 W/in2 (0.1116 W/cm2)
13.1 43.97 Watts 1.45 W/in2 (0.2248 W/cm2)
Leadwire Length
Units Inches    Centimeters
Up to 12" included in price. Over 12", up to 80" add $3.00
Heater Backing - Based on Operating Temperature (see above)
Type Temperature Maximum Allowable
Watt Density
A No Backing -45 to 235° C    
    Installation options for unbacked heaters
    #20 Stretch Tape -45 to 200° C   1545.3 W (51 W/in2)
    #6 RTV -45 to 235° C   887.4 W (29.3 W/in2)
    Factory Vulcanized -45 to 235° C   1656.4 W (54.7 W/in2)
B #12 PSA -45 to 177° C   1292.4 W (42.7 W/in2)
D 0.003" Aluminum Foil Backing -45 to 235° C    
E Foil with Acrylic PSA -45 to 150° C   1100.4 W (36.3 W/in2)
F Foil with #12 PSA -45 to 204° C   1100.4 W (36.3 W/in2)
UL Component Recognition
Check to have heater marked for UL component recognition
Part Number (as configured):   HR5494R114L12B
  241   Wed Jul 28 22:11:11 2010 FrankNotesDAQold channel connections - blocks TB2 and TB4

- personal notes -

current cross-connect connections

PMC_RFPDDC:
block TB4
1 - LO
2 - HI
connected to ?

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

FSS_RFPD_DC:
block TB2
1 - LO
2 - HI
connected to J2-3113A  43/44 (CH21)

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

FSS_RCTRANSPD:
block TB2
5 - LO
6 - HI
connected to J2-3113A  53/54 (CH26)

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

PMC_TRANSPD:
block TB4
3 - LO
4 - HI
connected to J3-3113A   (CH34) (?)

 

 

  242   Wed Jul 28 22:12:41 2010 FrankNotesDAQold connections - J4 / J5

- personal notes -

VMIC3123 (16bit)

J-4:

12/25 : FSS_RMTEMP

6/19 : FSS_MINCOMEAS

 

J-5:

2/14 : FSS_RCTEMP

  90   Tue Mar 23 00:26:43 2010 Frank, TaraMiscRefCavongoing work

over the weekend we baked the two AR-coated windows for the new chamber.  Bob doesn't need the oven the next couple of days so i restarted the baking again and will continue to bake the remaining parts the next couple of days. We also set up peters old vacuum pump. We got lots of stuff from 40m and cleaned all parts today. The pump is now running and pumping the whole system including the hose to the chamber. We also wrapped some heaters around the parts and started heating the stuff to make it a bit cleaner as no one knows for what the parts have been used before. They all looked pretty clean and wiping everything didn't show any obvious contamination. We can't bake it to high as some parts are viton sealed.

The new, insulated feet should be finished by wed or so. Tomorrow we start cutting the remaining foam to size and glue the parts together. I ordered the remaining heaters, one is already attached to the chamber and it fits good except that the sticky back is not sticky enough to hold it in place. The bending force is too high, so i added some aluminum tape which holds it in place now (the corners didn't want to stick). We have plenty of space for temp sensors and we will add several AD590 and a couple of platinum sensors. If we find out that the AD590 is not good enough we can easily switch to the other sensors. We should discuss how many we want and especially where. My guess is that we should add some more on this first prototype to get a feeling for the gradients or so. We can then reduce the amount on the second chamber if we want. The platinum sensors are cheap. Typically one is about $8-10 each, but  I bought a pack of 100 directly from the manufacturer and so its about $1 each only.

  1106   Wed Feb 27 10:16:09 2013 koji, taraDailyProgressVacuumopening vac chamber

We opened the vacuum chamber and brought the stack with the 8" cavities out to the clean bench. New 1.45" cavities are under preparation to go in the chamber.

The 8" cavities and the double seismic isolation stack were removed from the chamber. The connector had to be removed from the inside of the mini flange for the feedthrough [add pic]. We replaced the top seismic stack along with 8" cavities and their mounts, with the new stack/new mount for the shorter cavities. We reuse the bottom stack.

Next is to modify the wiring for heaters and temp sensors. Currently, the connector is wired for 3 sensors and 1 heaters (for 9-pin connector). Soldering at the 9-pin connector seems to be a tough job. Koji suggested that I remove one of the temp sensor at its legs, not at the connector end. Then connect the unoccupied cables to the heating wire.

  1108   Sun Mar 3 22:08:26 2013 taraDailyProgressVacuumopening vac chamber

 I found all necessary parts for the heater (crimp connectors, heating wire). I'll bake all parts once all the wiring is ready

 

 IMG_2255.JPGIMG_2258.JPG

fig1: left Dsub connector for the cable, Right, heater(yellowish wire around the tube) is connected to wiring cable with crimp connectors.

download.jpg

fig2: crimp connector( vacuum compatible material). I need to borrow the suitable crimp tool from Down, see PSL:775

heater.png

fig3: above, previous wiring (one heater,3 sensors), below current wiring (two heaters, two sensors)

  602   Wed May 18 20:51:35 2011 taraDailyProgressopticoptic layout for new fss setup

I planned the layout for new fss setup.

The new setup has 1) both cavities placed in the same vacuum chamber, 2) two AOMs used in both RCAV and ACAV paths, 3) more compact beat path.

 In the layout, I assumed that

  • Two cavities in the chamber are 3 inches apart.
  • Two AOMs are of the same model, have the same setup
  • There is no change of plan for the layout between PMC and the laser

This is just a plan, no mode matching has been calculated yet.

I am concerned  that the mode matching lens might block the beam in ACAV path where the incoming beam and reflected beam cross, but this can be adjust later.

The outer foam box will be smaller, but it should have enough space to keep some electronics inside like we have now.

I should find two similar sets of beam splitters/ mirrors for beams in the beat path behind the cavity. So the pick up beams from two cavities can have same power.

Right now the power going into two PDs for RCTRANSPD are not the same because the splitter are not the similar.

Note that we might install a platform  behind the cavities so that we don't need the periscopes to lower the beam, and get rid of their associated mechanical peaks.

fss_layout_2011_05_18.png

  603   Thu May 19 11:32:46 2011 taraDailyProgressopticoptic layout for new fss setup

I added more details on the layout, and necessary half wave plates in the beam path.

fss_2011_05_18.png

  614   Tue Jun 14 23:07:03 2011 taraDailyProgressopticoptic layout for new fss setup

The mode matching for new FSS is calculated. The plan is shown below.

 

Note for the setup:

1) the spotsize in the AOM is 200um, the specsheet says 550 um (I might have to correct this).

2) Two AOMs are of the same model.

3) For mode matching to the AOM in acav path, I used only a single lens.

4) focal lengths of the lenses are in mm, We have to order the one with * (f = 57.4 mm)

5) Both cavities are 1" apart (3" from center to center)

6) Mistake in the drawing: the x2 QWPs just before the beams enter the vacuum chamber should be placed before the periscopes, not after.

2aom_fss.png

  628   Mon Jul 18 02:20:01 2011 taraDailyProgressopticoptic layout for new fss setup

  The new mode matching for optics in front of the cavities is done.  The rest (for beat measurement) will be finished soon.

A few changes in this layout are:

1) spotsize for AOM is 500 um, as specified by the datasheet.

2) Mirrors behind the AOMs will be changed to R= 2.0 m instead of 0.3 m.

3) Spot size in the 35.5 MHz EOM is ~300um which is good for the model.

4) More mirrors (for steering the beam) for the AOMs are added.

 

I'm a bit worried about using f=57.4mm lenses because they are quite sensitive when we have to move the lenses around, but the space is very limited this time.

I'll let Raphael double check my calculation so he can learn how to do mode matching.

2aom_fss_2011-07-15.png

 

 

  629   Mon Jul 18 11:41:22 2011 ranaDailyProgressopticoptic layout for new fss setup

There's no need to use such a large spot size on either the AOM or the EOM.

When using high power this could be an issue, but you can use a beam radius of more like 100-200 microns for the AOM to get fast response time.

  631   Wed Jul 20 15:54:21 2011 taraDailyProgressopticoptic layout for new fss setup

  I edited the layout so that the spots in both AOMs are 200 um. I'll list what optics we might have to buy.

 

Most of the optics are already used on the table. I need to find:

  •  a lens with f = 343.6 m (plcx R =154.5mm)
  •  one more curve mirror with R = 0.3m for the second AOM.
  • aom adaptor plate (need to submit this to the work shop to have it done
  • periscope sets for both ACAV and RCAV (we need 4 in total, but we have only 2 sets)
  • second VCO

The optics on ACAV path have been removed, I left the optics on RCAV path for now because Raphael might want to remeasure EOM TF.

Once the measurement is done, all optics will be removed. We will clean the table, clean the optics before put them back on the table.

 

 

 

2011_07_20_layout.png

  632   Wed Jul 20 23:00:30 2011 FrankDailyProgressopticoptic layout for new fss setup

the lens and mirror are in the ATF, a second VCO is in the left cabinet.

 

 

  1050   Tue Sep 18 02:35:56 2012 taraDailyProgressRefCavoptical contact practicing

I got the mirror blanks for optical contact practicing. I tried to contact them together, but I have not succeeded yet.

 The mirrors are not transparent on the back, but we can still see the fringe due to the gap between the two surfaces clearly with just room light, see the picture below. I might not clean it well enough. I'll try to do it again later.

IMG_1764.jpg

  388   Wed Nov 10 20:04:13 2010 taraSummaryPMCoptical gain vs Vrf for side bands

 I checked that the optical gain in PMC loop increases as the power in the sideband increases. The result is 10.7 dB/V.

 

This measurement is for checking how much gain (in optical path) will we get from changing power in the side bands.

The excitation is sent to EXT DC channel on PMC. Reference signal is at HV mon, response is picked up at Mix mon.

This TF includes PZT and OPT paths, PZT TF should remain the same independent from the side band power.

 

I vary the RF voltage, and adjust the gain slider for maximum stability.  The gain setup should not matter

in the TF part we are measuring as long as the loop is stable.

 

I measured the gain at 3 different frequencies, 290.8 Hz, 1.035 kHz, 5.09 kHz where the TF look reasonable and smooth.

(The loop UGF is ~ 500-900 Hz, Thus the data at 1k and 5 kHz are nicer than that of 290 Hz)

 the slopes from each fit are

 

290 Hz 10.3 dB/V
1.035 kHz 10.72 dB/V
5.09 kHz 10.84 dB/V

 

The results are fairly linear in our region (RF between 4.8 to 5.9 V). The gain slider for this voltage range is between 13 - 20 dB.

At higher RF voltage, PMC_RCTRANSPD starts to drop significantly.

At lower RF voltage, the gain is too low.

 

This means we can increase the gain in OPT TF up to 10 dB by adjusting RF voltage (increase side band power)

Attachment 1: dBvsV.png
dBvsV.png
  726   Tue Nov 8 18:51:38 2011 taraDailyProgressopticoptics for RFAM

I added mirrors to pick up stray beams just before the cavities. These beams will be used for monitoring RFAM.

    I arranged the optics so that stray beams at the beam splitters (just in front of the cavities) could be used. The power of the beam is ~ 9 uW, but it can be increased by changing the polarization of the input beam later.

     Two photodiodes are needed, I haven't checked yet if I still have some spare PDs left.

     Then the signal from PD will be demodulated with 35.5 MHz signal (modulation frequency). The cable length + PD position will be adjusted so that the phase is the same as the PDH signal.

IMG_2186_ACAV.jpg

IMG_2187_RCAV.jpg

 

  739   Tue Nov 29 01:50:40 2011 taraDailyProgressopticoptics for RFAM

I made some minor adjustment to the optics layout so that the reflected beam at the PBS before the cavity can be used to measure RFAM. Now RCAV's beam can be picked up for RFAM measurement.

    The PBS just before RCAV was moved Eastward a bit so that the reflected beams from both PBSs are not blocked. I removed mirrors with soft mounts and use only rigid 1" posts only. 

    I used a spare 35.5MHz RFPD for the pickup beam from RCAV path (in red). The power cable for RFPD was made and checked. It works properly. There is a spare new focus 1811 RFPD, but the connector is broken, the pins are bent. I'll try to fix this and use it for ACAV's RFAM pickup.

RFPD_setup.jpg

     The AC signal from RFPD will be demodulated with 35.5 MHz signal which is split from the LO signal for ACAV PDH's lock. I have not adjusted the phase by trying different cable lengths yet. This will be done later.

     There is one thing I'm a bit concerned with. The RF signal from the RFPD has DC level ~ 120 mV, I'm not sure if it's unusual or not. I'll check with another RFPD.


  1484   Mon Aug 25 03:56:17 2014 taraHowToNoiseBudgetoptimization for ETM with a-Si/SiO2 coatings

 I used optimization codes for ETM. The optimization reduce the PSD of Brownian noise by ~ 3/4 (in units of [m^2/Hz]) from QWL structure.

 Since we have not had all the material parameters for aSi:H at 120K with 1550nm, the optimization here is for room temperature with 1550 nm (for Brownian noise only). 

 opt2_aSi.png

opt2_RT.png

fig1: optical thickness for ETM with minimized BR noise. The transmission is 5.4 ppm and the reflected phase is ~ 179 degree.

Parameters/configuration used in the optimization:

  • T = 300 K   (room temp)
  • wavelength = 1550 nm;
  • Si substrate, n = 3.5;
  • Low index material : fused silica, loss = 0.4e-4, n = 1.444;
  • High index material: aSi:H, loss = 1e-6, n = 3.48; 
  • The coating has SiO2 cap (air-coating surface) for protection
  • Spot radius = 6 cm.
  •  This optimization is only for Brownian noise, we can do another optimization once the thermo-optical properties are known (thermal expansion, dn/dT)

It is remarkable that 5ppm transmission can be achieved with just 17 layers of coatings due to the largely different values between nL and nH. This makes the total thickness down to ~ 3 um.

BR noise from the optimized coating is  3.3x 10^-42 [m^2/Hz] at 100 Hz. This is converted to the strain of ~ 5x10^-25 [1/sqrt Hz] for 4 km interferometer. 

Note: for QWL structure, with 14 layers + half wave cap of SiO2 (total of 15 layers), the transmission is ~5.2 ppm and the coating Brownian noise is 4.2x10^-42 [m^2 /Hz]. So the optimization reduced the PSD of BR noise by ~ 25%. 

  1486   Wed Aug 27 03:21:53 2014 ranaSummaryopticoptimization for ETM with a-Si/SiO2 coatings

 I filled in more values for a-Si at 120 K into the wiki that Matt Abernathy set up. Then I ran the optimization code for Brownian noise only:

 aSi_120_Layers_60000.pdf

The above plot shows the comparison between the optimized aLIGO coating (silica:tantala at 300K) v. the a-Si coating at 120 K.

 aSi_R_60000.pdf

Then, finally, I compared the TO and Brownian noise of the two designs using the plotTO120.m script:

 aSi_120_TOnoise_60000.pdf

The dashed curves are silica:tantala and the solid lines are a-Si:silica. The Brownian noise improvement is a factor of ~6. A factor of ~1.6 comes from the temperature and the remaining factor of ~3.9 comes from the low loss and the lower number of layers.

I think this is not yet the global optimum, but just what I got with a couple hours of fmincon. On the next iteration, we should make sure that we minimize the sensitvity to coating thickness variations. As it turns out, there was no need to do the thermo optic cancellation since the thermo-elastic is so low and the thermo-refractive is below the Brownian almost at all frequencies.

  832   Thu Feb 16 23:27:50 2012 Frank, TaraNotesBEAToptimized cable-delay setup sensitivity

Started characterizing the cable-delay setup with the right length of cable (134ft of RG58 for 160MHZ). After checking the change in sensitivity with load impedance i've changed the load to 500 Ohms (instead of the usual 50 Ohms). I think an additional low-impedance path for the 2f has to be put in parallel later (to have proper 50Ohms @ 2f) to not get it reflected at the input of the low-pass filter back into the IF port of the mixer. (see first schematic).

mixer_termination-01.png

 

However, the following simple setup has been used for the measurements:

cable-delay_v5.png

 

I've measured the output signal vs different LO power levels while keeping the RF signal strength constant (8.29dBm) to find out the optimum signal strength in terms of size (not noise at this point!).
The following plots show the result:

  • The peak mixer output signal (for pi phase shift) increases with LO power
  • at the same time the slope around the zero-crossing shows a maximum around the specified LO power value (13dBm) - update: had a typo in vertical units, now correct - plot itself was correct

LO_power.png LO_power2.png

[discussion]

  826   Tue Feb 14 21:21:19 2012 FrankDailyProgressBEAToptimum cable length for delay line & comparison with LP-filter

now as we know that the optimum loss of the delay line is 8.68dB we can calculate the optimum cable length.

optimum_cable_length.png

optimum length for 160MHz are:

  • RG58C/U :    40.9m (134.2ft),     delay= 205.74ns      $0.30/ft
  • RG142B/U :  52.88m (173.5ft),    delay= 251.17ns      $2.25/ft
  • RG316 :        24.86m (81.6ft),     delay=120.81ns       $1.05/ft
  • RG405 :        30.68m (100.6ft),   delay=146.97ns       $6.00/ft
  • LMR-240 :     84.94m (278.7ft),   delay=337.20ns       $0.72/ft
  • LMR-400 :   166.56m (546.5ft),   delay=652.92ns       $0.90/ft

cables which introduce more delay for the same amount (8.68dB) of loss are better.

Now, we compare the minicircuits low-pass filter SLP-200 (datasheet) with the cables.

  • Insertion loss @150MHz is 0.4dB
  • group delay ~6ns

so we could add 22 filters for an optimum total delay/loss ratio. Total group delay would be 132ns.
If we compare now with the delays we get from the cables we see that even the simple RG58 gives us 50% more delay for the same loss ( and the price for the cable is the same as a single filter).
Using RG142 instead we get almost a factor of 2 more sensitivity and even more using lower loss cables.

So i don't see an advantage using those LP filters instead of cables.

 

  1586   Thu Oct 8 22:48:36 2015 ranaSummaryNoiseBudgetorder the heat shields

If you can't install python, you can run it all in the Sage Math Cloud for free.

Also, please post the final design for the heat shields which you've sent out for fab.

  48   Thu Feb 4 20:13:53 2010 FrankLaserLaseroutput coupler to acav changed

exchanged the old mirror (T330-HR, T331-AR) by a simple Y1-1025-45P to get more power.

measured laser power : 7.17W
downstream of the new output coupler : 134.6mW

added waveplates & pbs to make the power adjustable. current power through the EOM is 8mW which gives about 4.33V on the RF-PD (Thorlabs PDA10CS, 0dB-setting, 17MHz)

  1403   Mon Feb 3 23:56:07 2014 taraPhotosopticpacking mirror

 I"m packing the mirrors so that they are ready to be shipped to G. Cole. The mirrors are packed properly, see picasa.

  892   Thu Mar 29 18:50:51 2012 taraNotesNoiseBudgetparameters for coating brownian noise calculation

I make a list of parameters found in literature. This will be used for estimate the coating Brownian noise level and its error.

 SiO2 loss:

  • 1 +/- 0.2 x10-4  (Crooks et. al. 2006)
  •  0.4 +/- 0.3 x10-4 (Crooks et. al 2004)
  • 0.5 +/- 0.3 x 10-4 ( Penn et al. 2003)

Ta2O5 loss:

  • 3.8 +/- 0.2 x10-4  (Crooks et. al. 2006)
  • 4.2 +/- 0.4 x10-4  (Crooks et. al 2004)
  • 4.4 +/- 0.2 x 10-4  ( Penn et al. 2003)

 * the values reported by Crooks etal in 2006, are supposed to be more accurate than the results in 2004, because of the better estimation of energy stored in the coatings and the corrected thermoelastic contribution. They mention that the Poisson's ratio has small effect on the level of the estimated thermal noise.

The numbers from Penn et al are extracted from the multilayer coating ringdown measurement. Since they measure the ring down of the coating which has both materials. The values depend on Young's moduli of the materials as well. They use Ysio2= 72 GPa/ YTa2O5 = 140GPa. Thermoelastic loss is not taken into account.

 

The values for Young moduli are usually measured directly with nanoindentation technique.

 SiO2, Young modulus (Thin film)

  • 72 GPa (used in Penn et al 2003)

Ta2O5, Young modulus (Thin film)

  • 140+/-14 GPa  (Alcala et al, 2002, nano indentation,stacks.iop.org/Nano/13/451)
  • 140 GPa (Martin PJ et. al.,1993 Mechanical and optical properties of thin films of tantalum oxide deposited
    by ion-assisted deposition Thin Films: Stresses and Mechanical Properties IV, Mater. Res. Soc. Symp. Proc.). This source is not available by caltech connect. This source is cited in the paper by Penn et al, 2003.
  • 144+/- 42 GPa (Crooks et al 2006, this assumes that Young's modulus of SiO2 is 72 GPa)

                      

SiO2, Poisson's ratio:

  • 0.17: (Bamber, et al,2001), but they use SiO2 for calibration and assume that its Young's modulus and Poisson's ratio in thin film form are known.

 Ta2O5, Poisson's ratio

  • 0.23 (assume that it is the same as in bulk, Crooks, 2006)

The uncertainties in Poisson's ratios of the materials have small effect on the coating noise level. For examples, the 10% increase of SiO2's, and Ta2O5 Poisson's ratios, causes the thermal noise to increase by 0.09%, and 0.06%, respectively.  

list of all materials' properties,here.

  895   Mon Apr 2 22:33:21 2012 taraNotesNoiseBudgetparameters for coating brownian noise calculation

Coating Brownian noise with uncertainty (worst & best case scenarios)

 nb_with_uncertainty.png

I use the parameters found in the literature for coating Brownian noise calculation. 

The upper limit ( high noise level)  has

  • loss (silica) =1.2 e-4,
  • loss (tantala)= 4.6e-4,
  • Young's modulus (Tantala)= 186 GPa

The lower limit (low noise level) has

  • loss (silica) = 0.1 e-4;
  • loss(tantala) =3.6 e-4;
  • Young's modulus (Tantala) = 102 GPa

The rest of the parameters are their nominal values. The max/min values are ~ 18% from the average level. @ 100 Hz, the average noise level is 4.097 mHz/rtHz. The upper limit is 4.815mHz/rtHz, the lower limit is 3.324 mHz/rtHz.

Quote:

I make a list of parameters found in literature. This will be used for estimate the coating Brownian noise level and its error.

 SiO2 loss:

  • 1 +/- 0.2 x10-4  (Crooks et. al. 2006)
  •  0.4 +/- 0.3 x10-4 (Crooks et. al 2004)
  • 0.5 +/- 0.3 x 10-4 ( Penn et al. 2003)

Ta2O5 loss:

  • 3.8 +/- 0.2 x10-4  (Crooks et. al. 2006)
  • 4.2 +/- 0.4 x10-4  (Crooks et. al 2004)
  • 4.4 +/- 0.2 x 10-4  ( Penn et al. 2003)

 * the values reported by Crooks etal in 2006, are supposed to be more accurate than the results in 2004, because of the better estimation of energy stored in the coatings and the corrected thermoelastic contribution. They mention that the Poisson's ratio has small effect on the level of the estimated thermal noise.

The numbers from Penn et al are extracted from the multilayer coating ringdown measurement. Since they measure the ring down of the coating which has both materials. The values depend on Young's moduli of the materials as well. They use Ysio2= 72 GPa/ YTa2O5 = 140GPa. Thermoelastic loss is not taken into account.

 

The values for Young moduli are usually measured directly with nanoindentation technique.

 SiO2, Young modulus (Thin film)

  • 72 GPa (used in Penn et al 2003)

Ta2O5, Young modulus (Thin film)

  • 140+/-14 GPa  (Alcala et al, 2002, nano indentation,stacks.iop.org/Nano/13/451)
  • 140 GPa (Martin PJ et. al.,1993 Mechanical and optical properties of thin films of tantalum oxide deposited
    by ion-assisted deposition Thin Films: Stresses and Mechanical Properties IV, Mater. Res. Soc. Symp. Proc.). This source is not available by caltech connect. This source is cited in the paper by Penn et al, 2003.
  • 144+/- 42 GPa (Crooks et al 2006, this assumes that Young's modulus of SiO2 is 72 GPa)

                      

SiO2, Poisson's ratio:

  • 0.17: (Bamber, et al,2001), but they use SiO2 for calibration and assume that its Young's modulus and Poisson's ratio in thin film form are known.

 Ta2O5, Poisson's ratio

  • 0.23 (assume that it is the same as in bulk, Crooks, 2006)

The uncertainties in Poisson's ratios of the materials have small effect on the coating noise level. For examples, the 10% increase of SiO2's, and Ta2O5 Poisson's ratios, causes the thermal noise to increase by 0.09%, and 0.06%, respectively.  

list of all materials' properties,here.

 

  649   Wed Aug 3 18:06:32 2011 RaphaelDailyProgressElectronics Equipmentpdrf progress

Hey,

I measured the optical transfer function with more points (again after the floppy didn't properly save the data from yesterday) and I made some shot noise measurements (after finding out that the shot noise measurements I made yesterday weren't as good as I thought they were). Matlab is acting stupid on me right now, so I will post the plots tomorrow.

  820   Sun Feb 12 12:21:09 2012 FrankDailyProgressBEATpeak hunting

Did a little bit of peak hunting to clear our frequency span of interest from those massive mechanical resonances we currently have. After replacing the combining beam splitter mount we got rid of the 1.4kHz peak already. Yesterday i've focused on the mounts within the beat setup, but not the periscope, as we already know that this is very unstable and we will take care of that soon. I didn't want to replace things, just know where which stuff comes from.

I've found (only) one mirror mount which is currently clearly visible in our noise spectrum . Tapping the other mounts or damping the front plate or springs does not change the spectrum (at least i don't see any changes). Tapping (even slightly) is very difficult anyway as you also excite all the mounts surrounding your DUT, especially the periscopes and your whole spectrum changes and it's hard to figure out which is your primary resonance you are looking for. So i prefer damping it with a large piece of rubber and than compare it with a spectrum taken before with a reasonable.amount of averages.

Anyway, i found only one mirror mount (out of six) which i could clearly identify in our current noise spectrum. It's one of the mirrors right in front of the combining beam splitter.
Below a comparison before and after damping the front plate of the mirror mount. Resonance frequency is 544Hz. I have to check but i think we can replace this one with a non-adjustable turning mirror.

We still don't know where the 1.1KHz stuff is coming from.

 peak_reduction.pngmirrordamping.jpg

  835   Thu Feb 23 13:40:00 2012 Koji, FrankDailyProgressNoiseBudgetperformance of tuned experiment

- incoming -

We did optimize the alignment, power levels etc and tweeked almost every knob of the system to get an idea where we have to look for the current limit in sensitivity. Didn't find anything dominant. A lot of already known things can limit if you intentionally make it worse / misalign things, but once optimized they are below the current measured noise performance.  Detail later.

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

Tue Feb 28 21:28:53 2012 

Beat measurement after optimization, floated table.

beat_2012_02_22.pngbeat_zoom.png

     The beat noise is roughly a factor of 2 above the coating noise at 130 Hz. This gives us a good reason to change the springs for the seismic stack in order to get better sensitivity at lower frequency, as it is getting closer to the coating noise at lower frequency.  At 2kHz and above, the noise spectrum's feature is similar to the noise budget, but with some offset. We might miss a few other flat noise sources( noise from RFPD, electronics) that we have to add into the noise budget. Most of the mechanical peaks around 100 - 1kHz are probably from the mirror mounts.

  502   Wed Feb 16 21:29:17 2011 taraNotes perl script for SLOWDC PID control added

A perl script/ an medm screen are created for SLOWDC PID control. The gain is not optimized yet. Some debugging might be needed.

The script for SLOW_PID.pl is similar to rcav_PID_2011_01_25.pl. I just changed the channel names for SLOWDC.

The process is C3:PSL-FSS_FAST

The actuator is C3:PSL-FSS_SLOWDC

Setpoint is C3:PSL-FSS_SLOWPID_SETPOINT (set to 0)

and other parameters follow the form of C3:PSL-FSS_SLOWPID_...

 

The perl scripts can be executed on the sun machine, but the result is abnormal. I tried to adjust P gain,

but for either signs I chose for Kp, SLOWDC seems to rail, instead of being steady at a certain value.

I'll check this later, for now it's not very important, since another loop for SLOWDC is also working, and

we can lock the cavity for a long time without SLOWDC feedback.

 

note for thermal PID

      RCAV   ACAV

P        -0.9         -0.9

I       -0.006      -0.0028

D       0                0

  512   Thu Feb 24 15:47:10 2011 FrankHowToComputersperl script parameters for both loops inconsistent

after rebooting both crates i found that the perl script parameters for both loops are inconsistent with what's documented in the elog here.

Tara, can you plz check what the right numbers are. The numbers in the startup script are totally different from the values you posted.

  515   Thu Feb 24 23:02:30 2011 taraHowToComputersperl script parameters for both loops inconsistent

Yes, I changed the numbers to see the response and haven't logged

or changed the values in the start up file yet. Will do that.   

       RCAV   ACAV

KP  -0.7      -0.85

KI   -0.007   -0.0035

set  35.03    37.1

Quote:

after rebooting both crates i found that the perl script parameters for both loops are inconsistent with what's documented in the elog here.

Tara, can you plz check what the right numbers are. The numbers in the startup script are totally different from the values you posted.

 

  871   Wed Mar 7 00:43:05 2012 FrankHowToNoiseBudgetphase noise and other things

VERY IMPORTANT ! (HAS TO BE MEASURED NEXT BEFORE ANYTHING ELSE):

  • phase noise of Marconi locked to Rb-clock for input ranges 100Hz to 10kHz - current level in NB is too high below 1kHz
  • projection of RF-AM contribution from both EOMs - we know that we are close to that if we are slightly misaligned
  • proper RIN coupling - we know that it does not dominate at the moment as we can change optical power levels without seeing an effect, but we don't know when it does
  • Acoustic coupling estimation - do we need acoustic shields for cavity readout or beat?

seismic is not important at the moment as it will change end of the week anyway

  169   Sun Jun 20 02:17:06 2010 ranaElectronicsRefCavphase noise of IFR + Rubidium

see this entry

  823   Mon Feb 13 13:42:43 2012 FrankNotesBEATphase/group delay for RG58 (and other cables)

measured the delay for the old cable (RG58):  dPhi=180deg, df=600KHz 

1.67ns/ft                (value from datasheet:  1.53ns/ft)

 

typical values for other cables using the following dielectric materials:

Dielectric Type                           Time Delay (ns/ft)
Solid Polyethylene (PE)               1.54
Foam Polyethylene (FE)              1.27
Foam Polystyrene (FS)                1.12
Air Space Polyethylene (ASP)     1.15-1.21
Solid Teflon (ST)                           1.46
Air Space Teflon (AST)                 1.13-1.20

  1011   Mon Jul 2 19:01:18 2012 SarahDailyProgressPDphotodiodes behind cavities

 Tara and I put another photodiode behind ACAV, so that now there are two photodiodes behind each cavity.This is necessary because one is needed for monitoring and another is needed as a detector for feedback. The following image shows the setup of the second pd behind ACAV, note that there are no beam steering mirrors for alignment:

 

 2012_07_02.JPG

Now we have to think of a sensible solution for wiring all of the cables (8 in total)

  1012   Mon Jul 2 23:44:59 2012 taraNotesPDphotodiodes behind cavities

After installing the second pd behind ACVA, I tried to re-measure RIN behind ACAV and RCAV again. The measured RIN from ACAV and RCAV are about the same as we measured before.

 

    I was having problem with the measured RIN after we installed the second PD for ACAV. It turned out that the beam was not dumped properly. The measurement was done after I realigned the beam to ACAV/RCAV and centered the beam on the PD. I'll use the coupling we measured in PSL:1008 to add the contribution from RIN in ACAV to beat noise (assuming no common mode rejection).

 RIN.png

 

 

  805   Sat Jan 28 02:41:45 2012 FrankPhotosopticphotos of cavity input optics

just for reference which part is/was where for later...

IMG009.jpg IMG010.jpg

IMG011.jpg IMG012.jpg

  1384   Thu Nov 7 05:08:13 2013 taraDailyProgressNoiseBudgetphotothermal noise in SiO2/Ta2O5

I add the photo thermal noise effect in the noise budget. With ISS, photothermal noise should be sufficiently small.

 

What I did

  • Measure beat
  • Measure RIN after ACAV and RCAV
  • Measure TF between TRANSPD and beat, compare the result with Farsi's calculation to determine the absorption (8ppm, with Finesse = 1e4) [add more details]
  • Apply the measured RIN to Farsi calculation to get the conversion from RIN to frequency noise ( I did not use the measured TF because I have not measured the whole range yet, and the calculation matches the measurement quite well).

beat_2013_11_07.png

Comment about the beat

  • At DC -30 Hz, the noise seems to be a combination of photothermal noise, and seismic induced scattered light. Air spring might not help as much as I thought.
  • Above 2kHz, it's not clear if it is gain limited on ACAV loop or not, but this is likely. We can check by measure the PSD of the error signal and convert it to frequency noise.
  • Frequency stabilization of ACAV is significantly inferior than that of RCAV. I don't know if it is the result from PMC or not. More investigation is needed.

Note about RIN measurement

  • RIN (measured behind the cavities) depends considerably on the TTFSS gain, luckily, at optimum gain level, RIN is pushed down enough.
  • RIN from ACAV is almost a factor of 10 worse than that of RCAV @ the optimum gain setting
  • There might be coupling from BB EOM to RIN (due to the mismatches E field between the EOM and the beam). This may explains why RIN is getting worse if common gain is increased a bit before the loop oscillate. Will check that.

 

Note about loss angles: For  SiO2 and Ta2O5 loss angles = 1e-4 and 7.5e-4 (a factor of 3 above the regular number), the noise budget matches the measurement well. I'll see if it is the same for the data from 8" cavities or not.

Attachment 2: beat_2013_11_07.fig
  1388   Wed Nov 20 18:19:01 2013 taraDailyProgressNoiseBudgetphotothermal noise in SiO2/Ta2O5

I compared our beat measurement with results from Numata2003 and TNI. They agree well. I'm quite certain that we reach Brownian thermal noise from coatings.

 

 To make sure that what we measure is real Coating Brownian noise (It could be something else, i.e thermal noise in the support, spacer , or optical bond), we should compare our result to previous measurements to make sure that the numbers agree.

 Numata etal and TNI reported coating thermal noise measurement from suspended cavities (no spacer). They adjusted loss in the coatings to fit the measurement.  Phi coatings as reported in Numata is 4e-4 while TNI gives phi perp = phi_para = 2.7e-4.  Both agree with our result, see the plot below.  This means that our result is comparable with what they measured. It should be an evidence to support that we see real coating thermal noise, not contribution from something else (spacer, optical bond between the mirrors and the spacer).

beat_compare.png

Another evidence is from our previous measurement from 8" cavity.

  • The measurement also agrees with Numata's 2003 result, with phi coatings = 4e-4, see PSL:1018.
  • And the signal scales correctly with a factor of ~ 9 (from shorter cavity, and from smaller spotsize^2), seeT1200057. Had it been noise from optical bonding/ spacer (independent from spotsize), the scale factor would have been 8/1.45 ~ 5.5. The scale from substrate Brownian will also be different because of 1/w_spot dependent. Thermoelastic/ thermoopitc will have different slope.

So It is clear that our beat measurements from both 8" and 1.45" cavities are coating Brownian noise limited (around 50Hz-1kHz).

 

Attachment 2: beat_compare.fig
  529   Wed Mar 2 23:20:49 2011 FrankDailyProgressSeismicpiezo shaker updated - TF measurement started

Koji and i updated the shaker today. We replaced the short multilayer piezoelectric actuator (10mm) by a longer one (20mm) from the NEC TOKIN’s we have. (datasheet)
The pzt is glued to a brass disk, about 2" diameter and clamped between the side of the table and the steel frame around it using a aluminum base on the other side. (will add photo later).

We use a modified PMC servo card as a HV piezo driver. The modified schematic can be found below.
We added a 1kOhm resistor in the output which forms a ~100Hz low-pass with the 1.5uF capacitance of the PZT.

We get a good SNR ratio for TF measurements even when using white noise as the source. doing some low-frequency TF measurement over night.
WiIl also try a swept-sine measurement if required, but takes too long at low frequencies.

We also tried to build a simple loop using two stanford preamps to suppress the horizontal seismic motion of the table but couldn't see any improvement. Will wait for the measured TF to design the right loop.

 

HV amplifier schematic (modified PMC servo):

HV-amp_modified_D980352-A.pdf

  1040   Mon Aug 27 14:24:06 2012 taraNotesScheduleplan for upgraded thermal noise probe experiment

 

 The 1.45" cavities have arrived. So I think it is a good time I layout the plan for the next phase of the experiment:

IMG_1579.JPG

 

To Do:

  • Design optic layout for 2-laser setup
  • Try assemble the cavities with our SiO2/Ta2O5 mirrors
  • modify seismic stack / design for holding the cavities
  • getting AlAs/GaAs coating on the substrates
  • find substrate with AdvLIGO coating
  • Choose resonant frequency for 2nd PMC, and 2nd cavity

 

2_laser_setup.png

fig2: proposed new setup with 2 laser sources

Since we want to upgrade the current setup to 2-laser setup, we need to find:

  • another NPRO
  • another PMC
  • broad band EOM, and two resonant EOMs (one for locking PMC, one for locking to the cavity)
  • RFPD, servo, oscillator for locking 2nd PMC to NPRO
  • RFPD for 2nd cavity (with the correct resonant frequency)
  • second oscillator for locking NPRO to the cavity (we can reuse the marconi for AOM)
  • another servo for PMC (I think there is one spare that we used for driving a PZT, I'll check)
  482   Tue Feb 8 13:50:01 2011 FrankNotesRefCavplz no more temp servo tuning - want to take data

by tuning the servo Tara unlocked both cavities and they are out of range right now, so plz no more temp servo tuning until further notice

  287   Tue Aug 17 15:57:11 2010 FrankNotesBEATpower on beat PD

- personal notes -

New Focus PD:

power from ACAV: 0.958mW
power from RCAV: 0.967mW

DC-OUT: 1.94V
AC-OUT: 1.27Vpp @160MHz in 50R

ELOG V3.1.3-