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ID Date Author Type Categoryup Subject
  2829   Wed Apr 21 22:11:48 2010 ranaUpdatePSLInnolight 2W Vertical Beam Profile

Back in Gainesville in 1997, I learned how to do this using the chopper wheel. We had to make the assumption that the wheel's blade was moving horizontally during the time of the chop.

One advantage is that the repetitive slices reduces the random errors by a lot - you can trigger the scope and average. Another advantage is that you can download the average scope trace using USB, floppy, or ethernet instead of pencil and paper.

But, I never analyzed it in enough detail to see if there was some kind of nasty systematic error.

  2830   Wed Apr 21 23:35:37 2010 KojiUpdatePSLInnolight 2W Vertical Beam Profile

Good fit. I assumed sqrt(x) is a typo of sqrt(2).

Quote:

Koji and Kevin measured the vertical beam profile of the Innolight 2W laser at one point.

This data was taken with the laser crystal temperature at 25.04°C and the injection current at 2.092A.

The distance from the razor blade to the flat black face on the front of the laser was 13.2cm.

The data was fit to the function y(x)=a*erf(sqrt(x)*(x-x0)/w)+b with the following results.

Reduced chi squared = 14.07

x0 = (1.964 +-  0.002) mm

w = (0.216 +- 0.004) mm

a = (3.39 +- 0.03) V

b = (3.46 +- 0.03) V

 

  2834   Thu Apr 22 21:42:24 2010 AlbertoUpdatePSLInnolight 2W Vertical Beam Profile

 

 What kind of fit did you use? How are the uncertainties in the parameters obtained?

  2837   Sat Apr 24 15:05:41 2010 KevinUpdatePSL2W Vertical Beam Profile

The vertical beam profile of the Innolight 2W laser was measured at eight points along the axis of the laser.

These measurements were made with the laser crystal temperature at 25.04°C and the injection current at 2.091A. z is the distance from the razor blade to the flat black face of the front of the laser.

The voltage from a photodiode was measured for the razor at a number of heights. Except for the first two points, one scan was made with the razor moving down and a second scan was made with the razor moving up. This data was fit to

y = a*erf(sqrt(2)*(x-x0)/w) + b with the following results:

z(cm) (±0.1cm) w(mm) chi^2/ndf
3.9 0.085 ± 0.006 77.09
6.4 0.130 ± 0.004 12.93
8.8 down 0.145 ± 0.008 66.57
8.8 up 0.147 ± 0.008 18.47
11.6 down 0.194 ± 0.010 64.16
11,6 up 0.214 ± 0.009 27.23
14.2 down 0.177 ± 0.008 49.95
14.2 up 0.183 ± 0.007 29.85
16.6 down 0.205 ± 0.006 18.35
16.2 up 0.203 ± 0.007 17.16
19.2 down 0.225 ± 0.007 18.92
19.2 up 0.238 ± 0.011 25.56
21.7 down 0.292 ± 0.006 11.30
21.7 up 0.307 ± 0.008 11.85

The values for w and its uncertainty were estimated with a weighted average between the two scans for the last six points and all eight points were fit to

w = w0*sqrt(1+(z-z0)2/zR2) with the following results:

chi^2/ndf = 17.88

w0 = (0.07 ± 0.13) mm

z0 = (-27 ± 121) mm

zR = (65 ± 93) mm

It looks like all of the data points were made in the linear region so it is hard to estimate these parameters with reasonable uncertainty.

  2838   Sat Apr 24 15:50:47 2010 KojiUpdatePSLre: 2W Vertical Beam Profile

1. The vertical axis should start from zero. The horizontal axis should be extended so that it includes the waist. See Zach's plot http://nodus.ligo.caltech.edu:8080/40m/2818

2. Even if you are measuring only the linear region, you can guess w0 and z0, in principle. w0 is determined by the divergence angle (pi w0/lambda) and z0 is determined by the linear profile and w0. Indeed your data have some fluctuation from the linear line. That could cause the fitting prescision to be worse.

3. Probably the biggest reason of the bad fitting would be that you are fitting with three parameters (w0, z0, zR) instead of two (w0, z0). Use the relation ship zR= pi w0^2/lambda.

  2846   Mon Apr 26 16:51:37 2010 KevinUpdatePSLre: 2W Vertical Beam Profile

I tried Koji's suggestions for improving the fit to the vertical beam profile; however, I could not improve the uncertainties in the fit parameters.

I started retaking the data today with the same laser settings used last time and noticed that the photodiode was saturating. We were using an ND 4.0 neutral density filter on the photodiode. Koji and I noticed that the coating on the filter was reduced in the center and added an additional ND 0.6 filter to the photodiode. This seemed to fix the photodiode saturation.

I think that the photodiode was also saturating to a lesser extent when I took the last set of data. I will take another vertical beam profile tomorrow.

[Edit by KA: Metallic coating started being evaporated and the ND filters reduced their attenuation. We decided to use absorptive one as the first incident filter, and put a thinner one behind. This looked fine.]

  2847   Mon Apr 26 17:34:31 2010 KojiUpdatePSLre: 2W Vertical Beam Profile

Give me the plot of the fit, otherwise I am not convinced.

Quote:

I tried Koji's suggestions for improving the fit to the vertical beam profile; however, I could not improve the uncertainties in the fit parameters.

  2851   Tue Apr 27 15:29:16 2010 KevinUpdatePSLre: 2W Vertical Beam Profile

I thought that the micrometer I was using to move the razor through the laser beam was metric; however, it is actually english.

After discovering this mistake, I converted my previous measurements to centimeters and fit the data to

w = sqrt(w0^2+lambda^2*(z-z0)^2/(pi*w0)^2) with the following results:

reduced chi squared = 14.94

z0 = (-4.2 ± 1.9) cm

w0 = (0.013 ± 0.001) cm

  2857   Wed Apr 28 14:22:36 2010 KevinUpdatePSLre: 2W Vertical Beam Profile

I used the Mathematica CurveFit package that we use in Ph6/7 to make the fits for the beam profile data. I wrote two functions that use CurveFit shown in the attachment to make the fits to the error function and square root.

  2859   Wed Apr 28 16:15:02 2010 KevinUpdatePSLAccelerometer Calibration

Koji, Steve, and Kevin looked into calibrating the Wilcoxon accelerometers. Once calibrated, the accelerometers will be used to monitor the motion of the PSL table.

We want to use the shaker to shake each accelerometer and monitor the motion with an OSEM. We will make a plate to attach an accelerometer to the shaker. A flag will also be mounted on this plate.The OSEM will be mounted on the table next to the shaker and positioned so that the flag can block the LED light as the plate moves up and down. We will then measure the motion of the accelerometer as it is shaken from the OSEM signal. The OSEM signal will be calibrated by keeping the plate and the flag still and moving the OSEM down along the flag a known distance with a micrometer.

  2873   Mon May 3 17:49:41 2010 ranaConfigurationPSLRC Temperature Servo Turned OFF temporarily

Quote:

In order to measure the transfer function of the RC cavity's foam, I've turned off the servo so that the room temperature noise can excite it.

The attached plot shows a step response test from 2 weeks ago. Servo is nominally still working fine.

 I've just now re-enabled the temperature control of the reference cavity can. Trend of the last 8 days is attached.

  2875   Tue May 4 02:28:38 2010 ranaConfigurationPSLRC Temperature Servo Turned OFF temporarily

 

 My attempt to passively measure the transfer function of the foam failed fantastically.

As it turns out, the room temperature fluctuations inside the PSL box reach the 1 mK/rHz noise floor of the  AD590 (or maybe the ADC) at ~1-2 mHz. Everything at higher frequencies is noise.

So to see what the foam is doing we will have to do something smarter - we need a volunteer to disable the RC temperature servo from the EPICS screen and then cycle the PSL table lights every hour in the morning.

We'll then use our knowledge of the Laplace transform to get the TF from the step responses.

  2876   Tue May 4 06:32:58 2010 albertoConfigurationPSLRC Temperature Servo Turned OFF temporarily

Quote:

 

 My attempt to passively measure the transfer function of the foam failed fantastically.

As it turns out, the room temperature fluctuations inside the PSL box reach the 1 mK/rHz noise floor of the  AD590 (or maybe the ADC) at ~1-2 mHz. Everything at higher frequencies is noise.

So to see what the foam is doing we will have to do something smarter - we need a volunteer to disable the RC temperature servo from the EPICS screen and then cycle the PSL table lights every hour in the morning.

We'll then use our knowledge of the Laplace transform to get the TF from the step responses.

 more detailed instructions needed....

  2881   Wed May 5 02:37:55 2010 ranaConfigurationPSLRC Temperature Servo Turned OFF temporarily

Quote:

 more detailed instructions needed....

I showed Kiwamu and Alberto how to turn the lights on and off in the PSL. This is why Caltech is such a fine institution: most schools would have TAs delivering this kind of optics instruction.

We've turned off the RC temperature stabilization and the lights will supply the quasi-random heat input to the table and the cavity. Alberto and Kiwamu will be turning the lights on and off at random times.

The attached plot is the spectrum of temperature fluctuations of the room and the vacuum can with no stabilization from this weekend. I think the rolloff above 10 mHz is kind of fake - I had the .SMOO parameter set to 0.99 for both of these channels. I've just now set the .SMOO to 0 for both channels, so we should now see the true ADC or sensor noise level. It should be ~1 mK/rHz.

  2883   Wed May 5 16:58:21 2010 KojiUpdatePSL2W hooked up to the interlock service

Ben, Steve, and Koji

Ben came to the 40m and hooked up a cable to the main interlock service.
We have tested the interlock and confirmed it's working.

[Now the laser is approved to be used by persons who signed in the SOP.]

The RC, PMC, and MZ were unlocked during the interlock maneuver.
Now they are relocked.

  2898   Fri May 7 21:55:59 2010 kiwamuUpdatePSLremove Mach-Zehnder

[Koji, Kiwamu]

The Mach-Zehnder on the PSL table was removed.

A path for 166 MHz modulation in the Mach-Zehnder (MZ) was completely removed, the setup for another path remains the same as before.

Also the photo detector and the CCD for the PMC transmittion were moved to behind the PZT mirror of PMC. 

 


Before removing them, we put an aperture in front of the PD for MC REFL so that we can recover the alignment toward MC by using the aperture.

After the removal we tried to re-align the EOM which imposes the sideband of 29MHz for MC.

We eventually got good alignment of 97% transmissivity at the EOM ( the power of the incident beam is 1.193W and trans was 1.160W )

And then we aligned the beam going to MC by guiding the reflected beam to the aperture we put. This was done by using the steering mirrors on the periscope on the corner of the PSL table.

Now MC got locked and is successfully resonating with TEM00.

  2976   Mon May 24 16:34:22 2010 KevinUpdatePSLND Filters for 2W Beam Profile

I tried to measure the beam profile of the 2W laser today but ran into problems with the ND filters. With the measurements I made a few weeks ago, I used a reflective ND 4.0 filter on the PD. The PD started to saturate and Koji and I noticed that a lot of the metallic coating on the filter had been burnt off. Koji told me to use an absorptive ND 4.0 filter in front of a reflective ND 0.6 filter. I tried this today but noticed that a few holes were being burned into the absorptive filter and that the coating on the reflective filter behind it was also being burned off in spots. I don't think we wanted to use a polarizing beam splitter to reduce the power before the PD but I didn't want to ruin any more filters.

  3014   Sun May 30 13:26:07 2010 rana, kiwamuUpdatePSLnew HIGH-LOW value for PMC_TRANS

We changed the HIGH/LOW values of the PMC_TRANS.

The edited file was updated on the svn.


Since the PMC_TRANSPD was replaced behind the pzt mirror (see the entry), its nominal value were reduced to something like ~1V from the previous value of ~2V.

In the medm screen C1PSL_PMC.adl the PMC_TRAN always indicated red because the value were low compared with the previous one.

We went to /cvs/cds/caltech/target/c1psl, then edited psl.db

- Here are the new parameters we set up in the file.

grecord(ai,"C1:PSL-PMC_PMCTRANSPD")
{

  field(LOW,"0.98")
  field(LOLO,"0.93")
  field(HIGH,"1.15")
  field(HIHI,"1.3")

}

- - - -

These values are based on ~4days trend of the PMC_TRAN.

Then we manually updated those numbers by using ezcawrite in order not to reboot C1PSL.

So now it nicely indicates green in the medm screen.

  3016   Sun May 30 15:36:22 2010 AlbertoConfigurationPSLIMC periscope shutter

Two days ago I opened the PSL shutter by switching the switch on the shutter driver. That caused the shutter's switch on the medm screen to work in reversed mode: open meant closed and closed meant open.

I fixed that. Now the medm screen switch state is correct.

  3028   Tue Jun 1 20:40:03 2010 KojiUpdatePSLnew HIGH-LOW value for PMC_TRANS

The alarm had kept crying. I reduced the LOW to be 0.90 and the LOLO to be 0.85 both in psl.db and with ezcawrite.

Quote:

We changed the HIGH/LOW values of the PMC_TRANS.

The edited file was updated on the svn.


Since the PMC_TRANSPD was replaced behind the pzt mirror (see the entry), its nominal value were reduced to something like ~1V from the previous value of ~2V.

In the medm screen C1PSL_PMC.adl the PMC_TRAN always indicated red because the value were low compared with the previous one.

We went to /cvs/cds/caltech/target/c1psl, then edited psl.db

- Here are the new parameters we set up in the file.

grecord(ai,"C1:PSL-PMC_PMCTRANSPD")
{

  field(LOW,"0.98")
  field(LOLO,"0.93")
  field(HIGH,"1.15")
  field(HIHI,"1.3")

}

- - - -

These values are based on ~4days trend of the PMC_TRAN.

Then we manually updated those numbers by using ezcawrite in order not to reboot C1PSL.

So now it nicely indicates green in the medm screen.

 

  3030   Wed Jun 2 03:24:22 2010 KevinUpdatePSL2W Beam Profile

[Rana, Kiwamu, Kevin]

The Innolight 2W beam profile was measured with the beam scan. A W2-IF-1025-C-1064-45P window was used to reflect a small amount of the main beam. A 5101 VIS mirror was used to direct just the beam reflected from the front surface of the W2 down the table (the beam reflected from the back surface of the W2 hit the optic mount for the mirror). A razor blade beam dump was used to stop the main transmitted beam from the W2. The distance from the laser was measured from the front black face of the laser to the front face of the beam scan (this distance is not the beam path length but was the easiest and most accurate distance to measure). The vertical and horizontal beam widths were measured at 13.5% of the maximum intensity (each measurement was averaged over 100 samples). These widths were divided by 2 to get the vertical and horizontal radii.

The mirror was tilted so that the beam was close to parallel to the table. (The center of the beam fell by approximately 2.1 mm over the 474 mm that the measurement was made in).

The measurement was taken with an injection current of 2.004 A and a laser crystal temperature of 25.04°C.

This data was fit to w = sqrt(w0^2+lambda^2*(x-x0)^2/(pi*w0)^2) with lambda = 1064nm with the following results

For the horizontal beam profile:

reduced chi^2 = 4.0

x0 = (-138 ± 3) mm

w0 = (113.0 ± 0.7) µm

For the vertical beam profile:

reduced chi^2 = 14.9

x0 = (-125 ± 4) mm

w0 = (124.0 ± 1.0) µm

In the following plots, the blue curve is the fit to the vertical beam radius, the purple curve is the fit to the horizontal beam radius, * denotes a data point from the vertical data, and + denotes a data point from the horizontal data.

  3032   Wed Jun 2 04:27:02 2010 KojiUpdatePSL2W Beam Profile

This is what I already told to Kevin and Rana:

A direct output beam is one of the most difficult measurements for the mode profiling.
I worried about the thermal lensing.

Since most of the laser power goes through the substrate (BK7) of the W2 window, it may induce thermal deformation on the mirror surface.
An UV fused silica window may save the effect as the thermal expansion coefficient is 0.55e-6/K while BK7 has 7.5e-6.

In addition to the thermal deformation issue, the pick-off setup disables us to measure the beam widths near the laser aperture.

I rather prefer to persist on the razor blade then use the pick off between the blade and the PD.

I also confess that the description above came only from my knowledge, and not from any scientific confirmation including any calculation.
If we can confirm the evidence (or no evidence) of the lensing, it is a great addition to my experience.

Quote:

[Rana, Kiwamu, Kevin]

The Innolight 2W beam profile was measured with the beam scan. A W2-IF-1025-C-1064-45P window was used to reflect a small amount of the main beam. A 5101 VIS mirror was used to direct just the beam reflected from the front surface of the W2 down the table (the beam reflected from the back surface of the W2 hit the optic mount for the mirror). A razor blade beam dump was used to stop the main transmitted beam from the W2. The distance from the laser was measured from the front black face of the laser to the front face of the beam scan (this distance is not the beam path length but was the easiest and most accurate distance to measure). The vertical and horizontal beam widths were measured at 13.5% of the maximum intensity (each measurement was averaged over 100 samples). These widths were divided by 2 to get the vertical and horizontal radii.

The mirror was tilted so that the beam was close to parallel to the table. (The center of the beam fell by approximately 2.1 mm over the 474 mm that the measurement was made in).

The measurement was taken with an injection current of 2.004 A and a laser crystal temperature of 25.04°C.

This data was fit to w = sqrt(w0^2+lambda^2*(x-x0)^2/(pi*w0)^2) with lambda = 1064nm with the following results

For the horizontal beam profile:

reduced chi^2 = 4.0

x0 = (-138 ± 3) mm

w0 = (113.0 ± 0.7) µm

For the vertical beam profile:

reduced chi^2 = 14.9

x0 = (-125 ± 4) mm

w0 = (124.0 ± 1.0) µm

In the following plots, the blue curve is the fit to the vertical beam radius, the purple curve is the fit to the horizontal beam radius, * denotes a data point from the vertical data, and + denotes a data point from the horizontal data.

 

  3040   Wed Jun 2 22:25:39 2010 KevinUpdatePSLLow Power 2W Beam Profile

Koji is worried about thermal lensing introducing errors to the measurement of the 2W beam profile so I measured the profile at a lower power.

I used the same setup and methods used to measure the profile at 2W (see entry). This measurement was taken with an injection current of 1.202 A and a laser crystal temperature of 25.05° C. This corresponds to approximately 600 mW (see power measurement).

The data was fit to  w = sqrt(w0^2+lambda^2*(x-x0)^2/(pi*w0)^2) with the following results

For the horizontal beam profile:

reduced chi^2 = 2.7

x0 = (-203 ± 3) mm

w0 = (151.3 ± 1.0) µm

For the vertical beam profile:

reduced chi^2 = 6.8

x0 = (-223 ± 6) mm

w0 = (167.5 ± 2.2) µm

In the following plots, the blue curve is the fit to the vertical beam radius, the purple curve is the fit to the horizontal beam radius, * denotes a data point from the vertical data, and + denotes a data point from the horizontal data.

The differences between the beam radii for the low power and high power measurements are

Δw0_horizontal = (38.3 ± 1.2) µm

Δw0_vertical = (43.5 ± 2.4) µm

Thus, the two measurements are not consistent. To determine if the thermal lensing is in the laser itself or due to reflection from the W2 and mirror, we should measure the beam profile again at 2W with a razor blade just before the W2 and a photodiode to measure the intensity of the reflection off of the front surface. If this measurement is consistent with the measurement made with the beam scan, this would suggest that the thermal lensing is in the laser itself and that there are no effects due to reflection from the W2 and mirror. If the measurement is not consistent, we should do the same measurement at low power to compare with the measurement described in this entry.


  3041   Wed Jun 2 22:58:04 2010 KevinUpdatePSL2W Second Reflected Beam Profile

[Koji, Kevin]

The profile of the Innolight 2W was previously measured by measuring the reflected beam from the front surface of a W2 window (see entry). To investigate thermal effects, Rana suggested also measuring the profile of the beam reflected from the back surface of the W2.

I used the same setup and methods as were used in the first measurement. The mirror was moved so that only the beam reflected from the back surface of the W2 was reflected from the mirror. This beam was reflected from both the front of the mirror and the back of the mirror. An extra beam dump was positioned to block the reflection from the back of the mirror.

This measurement was made with 2.004 A injection current and 25.04°C laser crystal temperature.

The data was fit to w = sqrt(w0^2+lambda^2*(x-x0)^2/(pi*w0)^2) with the following results

For the horizontal beam profile:

reduced chi^2 = 5.1

x0 = (-186 ± 6) mm

w0 = (125.8 ± 1.4) µm

For the vertical beam profile:

reduced chi^2 = 14.4

x0 = (-202 ± 11) mm

w0 = (132.5 ± 2.7) µm

In the following plots, the blue curve is the fit to the vertical beam radius, the purple curve is the fit to the horizontal beam radius, * denotes a data point from the vertical data, and + denotes a data point from the horizontal data.

The differences between the beam radii for the beam reflected from the front surface and the beam reflected from the back surface are

Δw0_horizontal = (12.8 ± 1.6) µm

Δw0_vertical = (8.5 ± 2.9) µm

So the two measurements are not consistent. This suggests that the passage through the W2 altered the profile of the beam.

  3042   Thu Jun 3 00:47:17 2010 KevinUpdatePSL2W Beam Profile of Second Reflected Beam

[Koji, Kevin]

The profile of the Innolight 2W was previously measured by measuring the reflected beam from the front surface of a W2 window (see entry). To investigate thermal effects, Rana suggested also measuring the profile of the beam reflected from the back surface of the W2.

I used the same setup and methods as were used in the first measurement. The mirror was moved so that only the beam reflected from the back surface of the W2 was reflected from the mirror. This beam was reflected from both the front of the mirror and the back of the mirror. An extra beam dump was positioned to block the reflection from the back of the mirror.

This measurement was made with 2.004 A injection current and 25.04°C laser crystal temperature.

The data was fit to w = sqrt(w0^2+lambda^2*(x-x0)^2/(pi*w0)^2) with the following results

For the horizontal beam profile:

reduced chi^2 = 5.1

x0 = (-186 ± 6) mm

w0 = (125.8 ± 1.4) µm


For the vertical beam profile:

reduced chi^2 = 14.4

x0 = (-202 ± 11) mm

w0 = (132.5 ± 2.7) µm


In the following plots, the blue curve is the fit to the vertical beam radius, the purple curve is the fit to the horizontal beam radius, * denotes a data point from the vertical data, and + denotes a data point from the horizontal data.

  3109   Wed Jun 23 18:05:00 2010 KojiConfigurationPSLFSS SLOWDC should be ~-4.0

FSS SLOWDC slider is at around 0.

Please someone relock this at ~-4.0 to exploit some last juice of the fruit.

See this entry for the details of the operating point.

 

  3110   Wed Jun 23 23:08:30 2010 ranaConfigurationPSLFSS SLOWDC should be ~-4.0

 

  3163   Wed Jul 7 00:15:29 2010 tara,RanaSummaryPSLpower spectral density from RefCav transmitted beam

I measured the RC transmitted light signals here at the 40m. I made all connections through the PSL patch panel.

Other than two steering mirrors in front of the periscope, and the steering mirror for the RFPD which were used to steer

the beam into the cavity and the RFPD respectively, no optics are adjusted.

We re-aligned the beam into the cavity (the DC level increased from 2 V to 3.83V) (Fig2) (We could not recover the power back to what it was 90 days ago)

and the reflected beam to the center of the RFPD.

 

I measured the spectral density of the signal of the transmitted beam behind RefCav in both time and frequency domain.

This will be compared with the result from PSL lab later, so I can see how stable the signal should be.

I did not convert Vrms/rtHz to Hz/rtHz because I only look at the relative intensity of the transmitted beam which will be compared to the setup at PSL lab. 

 

 

 We care about this power fluctuation because we plan to measure

 photo refractive noise on the cavity's mirros

(this is the noise caused by dn/dT in the coatings and the substrate,

the absorption from fluctuating power on the coating/mirror changes

the temperature which eventually changes the effective length of the cavity as seen by the laser.)

      

      The plan is to modulate the power of the beam going into the cavity,

the absorption from ac part will induce frequency noise which we want to see.

Since the transmitted power of the cavity is proportional to the power inside the cavity.

 Fluctuations  from other factors, for example, gain setting,  will limit our measurement. 

That's why we are concerned about the stability of the transmitted beam and made this measurement.


 

  3164   Wed Jul 7 10:42:29 2010 KojiSummaryPSLpower spectral density from RefCav transmitted beam

How do you calibrate this to Hz/rtHz?

Quote:

I measured the RC transmitted light signals here at the 40m. I made all connections through the PSL patch panel. No optics/PD were touched.

I measured the spectral density of the signal of the transmitted beam behind RefCav in both time and frequency domain.

This will be compared with the result from PSL lab later, so I can see how stable the signal should be.

We re-aligned the beam into the cavity (the DC level increased from 2 V to 3.83V)

and the reflected beam to the center of the RFPD.

 

 

  3189   Fri Jul 9 20:16:19 2010 ranaSummaryPSLThings I did to the PSL today: Refcav, PMC, cameras, etc.

I re-aligned the beam into the PMC. I got basically no improvement. So I instead changed the .LOW setting so that PMCTRANS would no longer go yellow and make the donkey sound.

I did the same for the MOPA's AMPMON because its decayed state is now nominal.

 

Steve and I removed the thermal insulation from around the reference cavity vacuum chamber. It wasn't really any good anyways.

Here are the denuded photos:

 

Steve and I are now planning to replace the foam with some good foam, but before that we will wrap the RC chamber with copper sheets like you would wrap a filet mignon with applewood bacon.

This should reduce the thermal gradients across the can. We will then mount the sensors directly to the copper sheet using thermal epoxy. We will also use copper to cover most of this hugely

oversized window flange - we only need a ~1" hole to get the 0.3 mm beam out of there.

 

My hope is that all of this will improve the temperature stability of this cavity. Right now the daily frequency fluctuations of the NPRO (locked to the RC) are ~100 MHz. This implies

that the cavity dT = (100 MHz) / (299792458 / 1064e-9) / (5e-7) = 1 deg.    That's sad....

 

I also changed the RC_REFL cam to manual gain from AGC. I cranked it to max gain so that we can see the REFL image better.

  3190   Sun Jul 11 20:11:48 2010 ranaSummaryPSLRC trend after the insulation removal

rc.png

 

  3196   Mon Jul 12 14:22:36 2010 JenneSummaryPSLThings I did to the PSL today: Refcav, PMC, cameras, etc.

Quote:

I re-aligned the beam into the PMC. I got basically no improvement. So I instead changed the .LOW setting so that PMCTRANS would no longer go yellow and make the donkey sound.

I did the same for the MOPA's AMPMON because its decayed state is now nominal.

[Jenne, Chip]

The alarm was still going, because the LOLO setting was higher than the LOW, which is a little bit silly.  So we changed the .LOLO setting to 0.80 (the LOW was set to 0.82)

We also changed psl.db to reflect these values, so that they'll be in there the next time c1psl gets rebooted.

  3210   Tue Jul 13 21:04:49 2010 tara,ranaSummaryPSLTransfer function of FSS servo

 I measured FSS's open loop transfer function.

For FSS servo schematic, see D040105-B.  

4395A's source out is connected to Test point 2 on the patch panel.

Test Point 2 is enabled by FSS medm screen.

"A" channel is connected to In1, on the patch panel.

"R" channel is connected to In2, on the patch panel.

the plot shows signal from A/R.

Note that the magnitude has not been corrected for the impedance match yet.

So the real UGF will be different from the plot.

 

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

4395A setup

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

network analyzer mode

frequency span 1k - 10MHz

Intermediate frequency bandwidth 100Hz

Attenuator: 0 for both channels

Source out power: -30 dBm

sweep log frequency

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

medm screen setup

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

TP2: enabled

Common gain -4.8 dB

Fast Gain 16 dB

  3232   Thu Jul 15 19:27:04 2010 ranaSummaryPSLRC trend after the insulation removal

Untitled.png

As you can see, there was not much (if any) worsening of the laser frequency fluctuation from removing the RefCav insulation. The plots below are zooomed in:

a.pngb.png

I have used the same peak-to-peak scale so that its easy to compare the fluctuations before (LEFT) and after (RIGHT).

As you can clearly see, the laser frequency moves just as much now (the SLOW_DC) as it did before when it had the insulation. Only now the apparent (i.e. fake) RC temperature fluctuations are much larger. So this sensor is fairly useless as configured.

  3240   Fri Jul 16 20:25:52 2010 MeganUpdatePSLReference Cavity Insulation

Rana and I

1) took the temperature sensors off the reference cavity;

2) wrapped copper foil around the cavity (during which I learned it is REALLY easy to cut hands with the foil);

3) wrapped electrical tape around the power terminals of the temperature sensors (color-coded, too! Red for the out of loop sensor, Blue for the first one, Brown for the second, Gray for the third, and Violet for the fourth. Yes, we went with an alphabetical coding system, excluding the out of loop sensor);

4) re-wrapped the thermal blanket heater;

5) covered the ends of the cavities with copper, ensuring that the beam can enter and exit;

6) took pretty pictures for your enjoyment!

We will see if this helps the temperature stabilization of the reference cavity.

 

DSC_2271.JPG

The end of the reference cavity, with a lovely square around the beam.

 

DSC_2266.JPG

The entire, well-wrapped reference cavity!

  3241   Fri Jul 16 23:53:27 2010 RanaUpdatePSLReference Cavity Insulation

From the trend, it seems that the Reference Cavity's temperature servo is working fine with the new copper foil. I was unable to find the insulating foam anywhere, but that's OK. We'll just get Frank to make us a new insulation with his special yellow stuff.

The copper foil that Steve got is just the right thickness for making it easy to form around the vacuum can, but we just have to have the patience to wrap ~5-10 more layers on there. We also have to get a new heater jacket; this one barely fits around the outside of the copper wrap. The one we have now seems to have a good heating wire pattern, but I don't know where we can buy these.

I also turned the HEPA's Variac back down to the nominal value of 20. Please remember to turn it back up to 100 before working on the PSL.

  3260   Wed Jul 21 15:43:38 2010 MeganSummaryPSLCopper Layer Thickness on the Reference Cavity

Using the equation for thermal resistance

Rthermal = L/(k*A)

where k is the thermal conductivity of a material, L is the length, and A is the surface area through which the heat passes, I could find the thermal resistance of the copper and stainless steel on the reference cavity. To reduce temperature gradients across the vacuum chamber, the thermal resistance of the copper must be the same or less than that of the stainless steel. Since the copper is directly on top of the stainless steel, the length and width will be the same for both, just the thickness will be different (for ease of calculation, I assumed flat, rectangular strips of the metal). Assuming we wish to have a thermal resistance of the copper n times less than that of the stainless steel, we have

RCu = RSS/n

or

L/(kCu*w*tCu) = L/(kSS*w*tSS*n)

so that

tCu/tSS = n*kSS/kCu

We know that kSS = 401 W/m*K and KCu = 16 W/m*K, so

tCu/tSS = 0.0399*n

By using the drawings for the short reference cavity vacuum chamber (the only one I could find drawings for online) I found a thickness of the walls of 0.12 in or 0.3048 cm. So for the same thermal resistance in both metals, the copper must be 0.0122 cm thick and for a thermal resistance 10 times less, it must be 0.122 cm thick. So we will have to keep wrapping the copper on the vacuum chamber!

  3268   Thu Jul 22 14:07:20 2010 kiwamuUpdatePSLPSL front end machine

It looks like something wrong happened around the PSL front end.  One of the PSL channel, C1:PSL-PMC_LOCALC, got crazy. 

We found it by the donkey alarm 10 minutes ago.

The attached picture is a screen shot of the PMC medm screen.

The value of C1:PSL-PMC_LOCALC ( middle left on the picture ) shows wired characters. It returns "nan" when we do ezcaread.

Joe went to the rack and powered off / on the crate, but it still remains the same. It might be an analog issue (?)

  3269   Thu Jul 22 15:59:29 2010 AlbertoUpdatePSLPSL front end machine

Quote:

It looks like something wrong happened around the PSL front end.  One of the PSL channel, C1:PSL-PMC_LOCALC, got crazy. 

We found it by the donkey alarm 10 minutes ago.

The attached picture is a screen shot of the PMC medm screen.

The value of C1:PSL-PMC_LOCALC ( middle left on the picture ) shows wired characters. It returns "nan" when we do ezcaread.

Joe went to the rack and powered off / on the crate, but it still remains the same. It might be an analog issue (?)

The problem seems to be a software one.

In any case, Kiwamu and I looked at the at the PMC crystal board and demod board, in search of a possible bad connection. We found a weak connection of the RG cable going into the PD input of the demod board. The cable was bent and almost broken.

I replaced the SMA connector of the cable with a new one that I soldered in situ. Then I made sure that the connection was good and didn't have any short due to the soldering.

  3270   Thu Jul 22 18:18:54 2010 AlbertoUpdatePSLProblem Solved

Quote:

Quote:

It looks like something wrong happened around the PSL front end.  One of the PSL channel, C1:PSL-PMC_LOCALC, got crazy. 

We found it by the donkey alarm 10 minutes ago.

The attached picture is a screen shot of the PMC medm screen.

The value of C1:PSL-PMC_LOCALC ( middle left on the picture ) shows wired characters. It returns "nan" when we do ezcaread.

Joe went to the rack and powered off / on the crate, but it still remains the same. It might be an analog issue (?)

The problem seems to be a software one.

In any case, Kiwamu and I looked at the at the PMC crystal board and demod board, in search of a possible bad connection. We found a weak connection of the RG cable going into the PD input of the demod board. The cable was bent and almost broken.

I replaced the SMA connector of the cable with a new one that I soldered in situ. Then I made sure that the connection was good and didn't have any short due to the soldering.

[Alberto, Koji]

By looking at the reference pictures of the rack in the wiki, it turned out that the Sorensen which provides the 10V to the 1Y1 rack was on halt (red light on). It had been like that since 1.30pm today. It might have probably got disabled by a short somewhere or inadvertently by someone working nearby it.

Turning it off and on reset it. The crazy LO calibrated amplitude on the PMC screen got fixed.

Then it was again possible to lock PMC and FSS.

We also had to burtrestore the PSL computer becasue of the several reboots done on it today.

  3271   Fri Jul 23 00:13:11 2010 ranaUpdatePSLProblem NOT REALLY Solved

So...who was working around the PSL rack this morning and afternoon? Looks like there was some VCO phase noise work at the bottom of

the rack as well as some disconnecting of the Guralp cables from that rack. Who did which when and who needs to be punished?

  3272   Fri Jul 23 08:15:59 2010 steveUpdatePSLref cavity ion pump

The ref cavity ion pump was running at 7.7kV instead of 5kV

This Digitel SPC-1 20 l/s ion pump should be running at 5kV

  3280   Fri Jul 23 16:02:16 2010 RanaUpdatePSLReference Cavity Insulation

This is the trend so far with the copper foil wrapping. According to Megan's calculation, we need ~1 mm of foil and the thickness of each layer is 0.002" (1/20th of a mm), so we need ~20 layers. We have ~5 layers so far.

As you can see the out-of-loop temperature sensor (RCTEMP) is much better than before. We need another week to tell how well the frequency is doing -

the recent spate of power cycles / reboots of the PSL have interrupted the trend smoothness so far.

  3282   Fri Jul 23 21:14:29 2010 RanaUpdatePSLReference Cavity Insulation

I wrapped another ~3 layers onto there. It occurs to me now that we could just get some 2mm thick copper plates made to fit over the stainless steel can.

They don't have to completely cover it, just mostly. I also took the copper circles that Steve had made and marked them with the correct beam height

and put them on Steve's desk. We need a 1" dia. hole cut into these on Monday.

To compensate for the cooling during my work, I've set the heater for max heating for 1 hour and then to engage the temperature servo.

I also noticed the HEPA VARIAC on the PSL was set to 100. Please set it back to 20 after completing your PSL work so that it doesn't disturb the RC temperature..

  3346   Sun Aug 1 21:40:27 2010 ranaSummaryPSLFSS: SLOWDC response

I bet you thought that the NPRO slow actuator response could be well represented by a pole at ~0.1 Hz? Well, that's just what they want you to believe.

I attach the response measured in FSS-FAST (with no feedback to the SLOW actuator) when the SLOW is given a step. As you may remember from

kindergarten, the response of a single pole low pass should just be an exponential. Clearly, there's more here than 1 pole.

 I also inserted a factor of 0.01 in the FSSSlowServo code so I could make the gain sliders have reasonable values (they used to all be ~1e-3). The SVN and the MEDM snapshot are updated.

  3364   Thu Aug 5 00:17:41 2010 KojiUpdatePSLPSL preparation work

We start the work on the cables at around the PSL table.

Aug 5th 10am-4pm?: (Kiwamu, Alberto, Koji)
- Removal of the unused cables around the PSL table and the control room
- Removal of the cable ties on the PSL frame

- Removal of the big nuts at the side of the PSL table

Aug 6th 10am-4pm?: (Kiwamu, Alberto, Koji, Jenne (~noon) )
- Labeling of the cables
- Planning of the disconnection

Aug 9th  9am-5pm: (Steve, Jenne, Alberto, Koji)
- Shutting down of the PSL
- Disconnection of the cables
- Draining of the cooling water
- Removal of the accelerometers
- Removal of the PSL chamber
- Sealing of the table with the plastic sheets

  3369   Thu Aug 5 17:59:23 2010 KojiUpdatePSLCable removal from the control room

[Alberto, Kiwamu, and Koji]

We removed the BNC cables from the control room.
The work was as hard as the one I had when I swept a 300m tunnel with a vacuum...

If we could remove the video cables, that would be a real epoch.

We found that the cabling behind the AP table is still quite ugly....grurrrh

  3370   Thu Aug 5 22:36:11 2010 KojiUpdatePSLPSL preparation work

PSL preparation work

Aug 5th 10am-4pm?: (Kiwamu, Alberto, Koji)

  • Removing the unused cables around the PSL table and the control room

Aug 6th 10am-4pm?: (Kiwamu (ex. noon-2pm), Alberto, Koji, Jenne ('till noon) )

  • Labeling the cables to be disconnected / making the records ==> All
  • Removals
    • the big nuts at the side of the PSL table ==> Steve
    • the cable ties on the PSL frame ==> Easy
    • Innolight 2W ==> Kiwamu
    • the green pickoff optics at the edge, if necessary ==> Kiwamu talking with Steve
    • Optics on the shelf ==> Jenne / Koji
    • Oscilloscopes on the shelf ==> Jenne / Koji
    • CCD camera connections (optional, as far as not critical for the operation)
  • Put poles on the table (for the plastic sheet) ==> Alberto / Koji

Aug 9th  9am-5pm: (Steve, Jenne, Alberto, Koji)

  • Disconnecting the cables ==> All
  • Shutting down the PSL ==> Steve/Koji
    • Draining the cooling water  ==> Steve
  • Removals
    • The accelerometers ==> Jenne
    • the PSL chamber ==> Steve
    • Periscopes ==> Alberto
  • Sealing of the table with the plastic sheets

 

  • The chiller is planned to go to MIT

 

  3371   Fri Aug 6 08:09:15 2010 steveUpdatePSLPSL preparation work

Quote:

PSL preparation work

Aug 5th 10am-4pm?: (Kiwamu, Alberto, Koji)

  • Removing the unused cables around the PSL table and the control room

Aug 6th 10am-4pm?: (Kiwamu (ex. noon-2pm), Alberto, Koji, Jenne ('till noon) )

  • Labeling the cables to be disconnected / making the records ==> All
  • Removals
    • the big nuts at the side of the PSL table ==> Steve
    • the cable ties on the PSL frame ==> Easy
    • Innolight 2W ==> Kiwamu
    • the green pickoff optics at the edge, if necessary ==> Kiwamu talking with Steve
    • Optics on the shelf ==> Jenne / Koji
    • Oscilloscopes on the shelf ==> Jenne / Koji
    • CCD camera connections (optional, as far as not critical for the operation)
  • Put poles on the table (for the plastic sheet) ==> Alberto / Koji

Aug 9th  9am-5pm: (Steve, Jenne, Alberto, Koji)

  • Disconnecting the cables ==> All
  • Shutting down the PSL ==> Steve/Koji
    • Draining the cooling water  ==> Steve
  • Removals
    • The accelerometers ==> Jenne
    • the PSL chamber ==> Steve
    • Periscopes ==> Alberto
  • Sealing of the table with the plastic sheets

 

  • The chiller is planned to go to MIT

 

Monday, August 9

 We should move the reference cavity too. Will this cavity be pumped while relocated?

Check and insure that attached and cut-free cables of PSL have enough room to tolerate the raising of the enclosure by 6"

I had second thoughts about the power line to the OMC. Koji was right, we should disconnect them from the power supplies.

The PSL enclosure doors on the north side will have to be removed some times to move exiting and entering ports.

 

  3381   Fri Aug 6 20:00:03 2010 KojiUpdatePSLPSL preparation work

PSL preparation work report

Aug 6th 10am-5pm: (Steve, Jenne, Alberto, Kiwamu, Koji)

- We labeled the cables to be disconnected

  • These will be disconnected in order to isolate the PSL table and the frame (housing) from the other part of the lab.
  • Upon the labeling we made the list and the map of the cables to be removed.
  • On Monday we disconnect those cables one by one accoding to the list.

- The following stuffs have been removed from the PSL table

  • The big nuts at the side of the PSL table
  • The cable ties on the PSL frame
  • Innolight 2W
  • The green pickoff optics at the edge
  • The optics on the shelf
  • The oscilloscopes on the shelf

- The OMC power supply cable was visited.

  • The connections to the power supply were removed. There are two HV outputs.

- We put thick and long optical poles

  • They are placed at the edge of the table so that we can put the plastic sheets on the table without touching the optics.

Plan on Monday

Aug 9th  9am-5pm: (Steve, Jenne, Alberto, Koji)

  • Disconnecting the cables ==> All
  • Shutting down the PSL ==> Steve/Koji
    • Draining the cooling water  ==> Steve
  • Removals
    • The accelerometers ==> Jenne
    • The reference cavity chamber ==> Steve
    • The small periscope ==> Alberto
  • Sealing of the table with the plastic sheets
  • The chiller is planned to go to MIT 

 

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