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ID Date Author Type Categoryup Subject
  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.

Attachment 1: profile_2nd.png
profile_2nd.png
  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.

 

Attachment 1: C1PSL_FSS.png
C1PSL_FSS.png
  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.


 

Attachment 1: RIN_rftrans.png
RIN_rftrans.png
Attachment 2: tara.png
tara.png
  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

Attachment 1: TF_FSS_ser.png
TF_FSS_ser.png
  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 (?)

Attachment 1: PSL-PMC2010-07-22.png
PSL-PMC2010-07-22.png
  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.

Attachment 1: Untitled.png
Untitled.png
  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.

Attachment 1: Untitled.png
Untitled.png
  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

Attachment 1: IMG_2684.jpg
IMG_2684.jpg
  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 

 

Attachment 1: PSL_cable_map.pdf
PSL_cable_map.pdf PSL_cable_map.pdf
  3383   Sat Aug 7 11:07:44 2010 KojiConfigurationPSLMC kept locked / PMC control gain reduced to +13dB

Jenne asked us to keep th MC locked and let the seismometers happy through this weekend.
Note that the work at the control room and the desks are no problem as far as you are quiet.

Nancy told Jenne and me that she finished the work and reverted the WFS to the old state at 4:30AM.
She could not make the elog as it has been crashed.

MC and old MC WFS looks working as usual.

From 6:40AM to 9:40AM the oscillation of the PMC looks present.

At 10:30AM I reduced the gain of the PMC from +15dB to +13dB.

  3391   Tue Aug 10 05:56:07 2010 KojiUpdatePSLPSL Table Lifting Preparation

Work on Aug 9th

Steve, Jenne, Koji, Alberto, Aidan, Jan, Sharmila, Katherine

From 9am to 6pm

  • Shutting down the PSL after the 90885 hours of service
  • Removals
    • The accelerometers
    • The reference cavity chamber
    • The periscopes were left so far
  • The cables between the PSL table and the outside have been disconnected
    • Listed items on Friday
    • Some unlisted items recorded and disconnected
    • Drained the cooling water from the chiller lines
    • Pulled out the chiller connections at the control room as well as the chiller control cables (temp sens & RS232C)
  • Sealed the PSL table with plastic sheets
    • Put antistatic films to the table (they are supported by the long optical poles)
    • Used capton tapes to fix the films on to the table
    • Put the white huge plastic sheet to cover the table at once
    • Some spaces at the edge of the tables are left flat such that the C-clamps can be attached
  • Sealed the AP and the ITMY tables by capton tapes

Some photos are attached in this entry. All of the photos found in the picasa album (click the slideshow)

Attachment 1: IMG_2686.jpg
IMG_2686.jpg
Attachment 2: IMG_2691.jpg
IMG_2691.jpg
Attachment 3: IMG_2692.jpg
IMG_2692.jpg
Attachment 4: IMG_2711.jpg
IMG_2711.jpg
  3451   Fri Aug 20 17:46:30 2010 ranaUpdatePSL40m PSL Upgrade Layout v0.3

http://lhocds.ligo-wa.caltech.edu:8000/40m/PSL/LayoutUpgrade

P-pol = purple

S-pol = red

The .graffle file for this is in the 40m SVN's omnigraffle dir/

  3463   Tue Aug 24 12:03:57 2010 ranaUpdatePSLPSL Upgrade: Mode Matching from PMC to IMC

I used the free software called 'ABCD' for Mac to construct this mode matching solution for going from the PMC to the IMC.

After getting it close by eye, I plugged the initial guess into Matlab and let it optimize the distances. I then plugged this into 'ABCD'

to get the exact solution. ABCD doesn't actually optimize anything; it just makes a nice table and graphically plots the solution.

  • The first waist between the first lens (f = +200 mm) and the second lens (f = -150 mm) is where the triple mod EOM goes. I have not accounted for the index (1.75) of the KTP.
  • The third lens we need is a f = +400 mm lens. I have put the lenses in the new layout drawing at the positions indicated in the Omnigraffle drawing. Each grid square corresponds to 1 inch.

The part numbers for these lenses are:

PLCX-25.4-103.0-UV-1064
PLCC-25.4-77.3-UV-1064
PLCX-25.4-206.0-UV-1064
40mPSL.pngScreen_shot_2010-08-24_at_6.07.43_PM.png
  3469   Wed Aug 25 15:32:52 2010 ranaUpdatePSLPSL Upgrade: Mode Matching from PMC to IMC

In a manner similar to the now classic 'Mode Matching from PMC to IMC' entry, I have calculated the lenses and positions needed to match the 2W NPRO beam into the PMC.

The added complication is that we also want to have a reasonable beam size to get into the Faraday and the AOM. It seems that this should be possible using one lens.

After the beam comes out of the AOM, there's another lens to match to the PMC. Its possible to do this with more lenses, but this is just an effort to minimize the number

of surfaces in the beam.

40mPSL.pngScreen_shot_2010-08-25_at_6.26.23_PM.png

 

  3470   Wed Aug 25 15:42:01 2010 JenneUpdatePSLPSL Upgrade: Mode Matching from PMC to IMC

Thoughts on where to take the pickoff for the SHG for the PSL-green?  We discussed today at the meeting the possibility of putting a 90/10 beam splitter right after the PMC, so that the green team would get somewhere between 100-200mW. 

Quote:

40mPSL.png

 

 

  3482   Fri Aug 27 22:09:37 2010 JenneUpdatePSLThe beginnings of the new PSL

[Rana, Jenne]

Like a new phoenix, the 40m PSL is in the process of being reborn...

phoenix.jpg

We cleared many old optics and components (including Alberto's favorite periscope) off of the north end of the PSL table.  Some optics are stored on the SP table, others on the shelf inside the PSL enclosure.

The new Innolight 2W NPRO is on the table, the PMC has been moved, and the main path of the laser has been sketched out using steering mirrors. Since we still don't have a beam, we're roughly placing all of our optics, and we'll finalize the alignment after turning on the laser.

Using a leveled HeNe, I checked the height of optics we should use to match the height of optics in the chambers by shining the light at the first steering mirror in the chamber, and ensuring that the beam hit the center of that optic .  Since the new PSL table height is identical to the AP table, it's not a surprise that from now on we will be using a 4" beam height on the PSL table, rather than the old PSL 3" beam height.

On the to-do list is to make a plate with 4 through holes to raise the PMC up by 1 inch, and to make an adapter plate (or come up with another plan) for mounting the AOM that goes directly after the NPRO/Faraday, among many other things.  We also still need to make some space for the RefCav to be put in its new place on the table, and then install it with Steve's help.   

  3483   Sat Aug 28 01:02:31 2010 ranaUpdatePSLThe beginnings of the new PSL

In fact, many of the mounts need to be adapted to 4": the beefy steering mirrors going into the PMC, the PMC RFPD, the ISS AOM, the Faraday between the NPRO and the AOM, the NPRO itself, the ISS PDs.

Also for the FSS: the 21.5 MHz EOM, the PBS, the AOM, the refcav periscope, and the RFPD.

Its obvious, in retrospect, that we would have to do this, but it somehow didn't occur to me until actually trying to put things on the table...

The NPRO itself is already tapped with 3 (metric) M3 holes. It also has 4 (un-tapped) holes at its 4 corners which look like they are for feet. Anyone have a mount design for the Innolight NPRO already?

We also started labeling the table with the new coordinate system. In this system, the NE corner is the origin. The screw hole which is most NE is 1,1. The numbering increases in the south (+X) direction and goes negative in the west (-Y) direction.

  3487   Mon Aug 30 13:57:25 2010 KojiSummaryPSLPSL table vibrational performance after the upgrade

Jenne and Koji

Last week Jenne has put the accelerometers on and under the PSL table immediately after the plastic sheets were removed.

So I took the same measurement as I did on 9th Aug.

Here is the comparison of the vibrational performance of the table before and after the modification.

Basically the table is now stiffer and more damped than it was before.
We don't find any eminent structure below (at least) 70Hz.

This result is obtained despite elevating of the table.

1) Attachment 1

For the horizontal comparison (top),  it is clearly seen that the large resonant peak at 20Hz was eliminated.
At least the new resonances went up to 70-90Hz region. Y is basically equivalent to X.

For the vertical comparison (bottom), it is clearly seen that the resonant peaks at around 50 & 70Hz were eliminated. 
At least no new resonance is seen.

2) Attachment 2

All-in-one plot for the measurement --- spectra, coherences, transfer functions --- after the upgrade. I put the same plot for the one before the upgrade.

Attachment 1: PEM_100830_SPE.pdf
PEM_100830_SPE.pdf
Attachment 2: PEM_100830.pdf
PEM_100830.pdf PEM_100830.pdf
  3488   Mon Aug 30 18:22:00 2010 ranaSummaryPSLPSL Enclosure is UNSTABLE

The lifting and resetting of the BLUE PSL enclosure has made it unstable somehow. When I push on it a little it rocks back and forth a lot.

Steve, please look into what's happening and stiffen it if you can. Its too unstable right now.

  3491   Mon Aug 30 23:21:36 2010 ranaHowToPSL2W NPRO Mount designed with emachineshop.com software

To test out this website - emachineshop.com, Jenne and I are designing some of the mounts for the new beam height.

LaserMount.png

It took me a few hours to figure out how to do it, but the software is easy enough for simple stuff. This is a brass mount with M4 clearance holes which are countersunk and a lip so that it can be dogged down to the table.

  3500   Tue Aug 31 19:46:00 2010 ranaUpdatePSLPSL upgrade update
  1. Steve is handling the mount height increase for the PMC and RC steering mirrors, as well as a mount (non-steerable) for the ISS' AOM.
  2. Rana is working on the laser mount.
  3. Jenne is drawing and getting the PMC mount made.
  4. We got the lenses from CVI for the mode matching, but not the metric screws for the laser mounting. I am tempted to tap holes in the laser base.
  3502   Wed Sep 1 08:28:43 2010 KojiUpdatePSLPSL upgrade update

Quote:
  1. We got the lenses from CVI for the mode matching, but not the metric screws for the laser mounting. I am tempted to tap holes in the laser base.

I am feeling that it is ok to carefully make new holes and threads as far as the holes do not penetrate the plate.
The thickness of the plate can be measured by the four holes at the corners.

 

  3503   Wed Sep 1 08:36:59 2010 KojiHowToPSL2W NPRO Mount designed with emachineshop.com software

1. I can not see whether the attaching surface is flat or not.
It should have ~1mm step to avoid "the legs" of the laser at the four corners.
Otherwise we will have ~0.5mm space between the block and the laser
and will squish this gap by the screws => cause the deformation of the block and the laser.

2. The countersinks for the M4 screws can be much deeper so that we can use the existing M4 screws.
In any case, the long M4 screws are not rigid and also not common.

Quote:

To test out this website - emachineshop.com, Jenne and I are designing some of the mounts for the new beam height.

LaserMount.png

It took me a few hours to figure out how to do it, but the software is easy enough for simple stuff. This is a brass mount with M4 clearance holes which are countersunk and a lip so that it can be dogged down to the table.

 

  3511   Thu Sep 2 01:44:13 2010 JenneUpdatePSLPSL beam hitting the PMC!

[Rana, Jenne]

More PSL progress. 

The new laser was raised to a 4 inch beam height using basically the most randomly thrown together method possible.  (It'll work just fine for aligning things, but we seriously need to get a nice block made.)  The PMC and the nice Osamu-mirror mount to go into the PMC also have temporary risers, so we'll need to replace them with the real deal as soon as we get things back from the shop.

So far we've got (1) the lens after the laser, (2) a Half Wave Plate (no quarter wave plate yet), (3) steering mirror that will go after the EOM, (4) 2 steering mirrors to get into the PMC, in addition to all of the stuff that we did the other day.  With all of this stuff we've got the beam hitting the 1st PMC mirror. We still don't have the EOM and AOM in the beam path however.

To get the rough alignment that we did, we turned on the new 2W NPRO, operating at the minimum power we could see on a card.  We turned it off after use, so it is still off.  Steve, we left the cable for the interlock sitting on the PSL table on the NW corner....can you please hook it up tomorrow?  Also, after the interlock is installed we should go back to regular running laser hazard mode. 

 

 

  3519   Fri Sep 3 06:55:42 2010 ranaUpdatePSLPSL beam hitting the PMC!

NPRO

Koji and I inspected and photographed the laser after opening up its case. I then drilled the clearance holes in the 4 corners and tapped holes for 1/4-20. I was careful to tap with the laser sideways, to avoid shavings getting into the laser and suctioned out as much of the pieces as I could. The laser is now mounted on some bad 1/4-20 based NewFocus style pedestals. The riser block can now be made with 1/4-20 through holes and the laser will sit on its for corner feet. We'll make the base aluminum to avoid differential CTE based stress in the laser base.

We checked the level of the laser. With the new mounting the beam is level to within ~1 mrad and has a 4" beam height.

 

Faraday

I've mounted the Faraday Rotator from the old MOPA. It has 8-32 mounting holes (who's shafts are curiously not parallel). We need an aluminum block of the proper height (2 3/4" ??) to make a permanent solution.

I've also mounted the thin-film polarizer. This works well, but it also needs a block machined to get the mounting to be less Mickey Mouse.

 

Pockel Cell for phase correction and 35.5 MHz PMC modulation

The EOM is mounted as before on the angle bracket to align it for P-pol light. The beam now goes cleanly through there. No further mounting hardware required.

 

Lenses

The 2 lenses in the 'mode matching telescope' between the laser and the PMC are in place, but not placed with any accuracy.

 

By sheer luck, I saw the PMC flashing in the TEM27 mode without any alignment from me. Next step is to get the lens positions tuned and then do the beam scan on the beam going towards the PMC to verify the approximate mode matching. This is all crude, but I just want to get the beam going into the vacuum as fast as possible.

  3523   Fri Sep 3 23:42:34 2010 JenneUpdatePSLPSL update of the day

Rana and I were poking around on the PSL table today, getting a few more items raised to the correct height.

I checked the polarization state of the new NPRO by using a HWP to minimize the transmission through a PBS cube, and then compared the power transmitted through the cube vs. reflected.  When the NPRO current was 0.772 \pm 0.001 (as read on the LCD), the transmission through the cube was 1.44mW, while the reflected was 10.53mW.  The reading of the Ophir power meter with no incident light was 0.03mW.  This factor of 10 means that the NPRO beam is ~10% circularly polarized and ~90% linearly polarized.  In order to improve the beam, we need a Quarter Wave Plate, which it turns out we don't have.  We need a QWP!

After that, using the linearly polarized part of my beam (maximizing the transmission through the PBS by rotating my HWP by 45deg), I tried to tune the angle of the polarizers that Rana pulled out of the MOPA.  I think I'm confused / too tired, because I can only get the polarizer to reflect a bunch of light, and I can't get it to pass any significant amount of light through, no matter where in its actuation range I put it (It's on a rotation stage with a few degrees of range).  It should just be a Brewster's Angle thing, and since I already have P-pol coming through the BS cube, this shouldn't be so hard.....

In any case, it may not be useful to do the final fine tuning of these polarizers until they are in their final places.  The hacky stack of mounts that I have has some slop in the position / alignment of the base of the polarizer, so no matter what we'll have to redo the tuning after the mounts are finalized.

  3525   Mon Sep 6 01:46:58 2010 ranaUpdatePSLPSL update of the day

To bypass the polarizer issue, I just used cubes. One I took from the FSS-Refcav path and the other from the power control part of the old MOPA, just downstream of the MOPA's periscope.

We'll swab these out with the thin-film polarizers after we get the mounts made.

With the cubes in, I also installed the Faraday + its 1/2-wave plate. The transmission looks good and we're getting into the PMC and its flashing a TEM00 mode sometimes. I set up a signal generator to drive the SLOW actuator by 1 FSR at 0.1 Hz.

I have set up a PMC transmission camera and transPD so that its easy to align. The flashing mode already allows us to align most of the rest of the table (except FSS).

Our next step should be to run the cables for locking the PMC:

  1. RF cables to the PMC_REFL
  2. Dsub for the PMC RFPD
  3. HV cable between the PMC servo board and the PMC PZT (why is this not RED? we have to make sure to abide by the cabling color code).
  4. RF cable from 35.5 MHz Frequency Reference card to the PMC EOM via the RF summing box on the table.

On Tuesday, we need to make sure that all of our mounts' drawings are in the cue for the shop. I'll put the list of mounts onto the PSL upgrade wiki page.

We also have to come up with a plan for wiring some of the 2W NPRO's channels into the cross-connect so that we can have some laser channels recorded by EPICS.

  3542   Wed Sep 8 00:01:07 2010 rana, valeraUpdatePSLPMC update

We ran the cables for the PMC: The RF cable for the 35.5 MHz drive was cheap and so we swapped the 29.5 MHz cable for it.

There now remain 1 RG-174 cable to drive the FSS PC (21.5 MHz) and 3 Heliax for the Kiwamu Tri-Mod EOM (11, 29.5, and 55 MHz).

We also changed the BLACK HV drive cable for the RED one (previously used for the MZ). All HV cables MUST be RED.

The BLACK cable is now used for the PMC_REFL DC.

The Heliax cables are routed onto the table - it remains a Alberto/Kiwamu job to strain relieve them and attach them to the TriMod box and EOM in the morning.

The PMC is locked and we did some partially bootless alignment and mode-matching. It locks easily on a TEM00 mode (with very poor visibility), but the

rest of the beam train can now be aligned while Valera does the PMC matching mambo.   

 

  3543   Wed Sep 8 09:50:13 2010 ranaUpdatePSLPSL update

Also, Kiwamu has modified the layout drawing to add the green PLL stuff. This has collapsed the reference cavity's wave function placing it close to its original position.

WE (maybe Valera and Steve) can now put the reference cavity back on the table.

  3544   Wed Sep 8 11:46:53 2010 kiwamuUpdatePSLupdate of the layout

I put some green stuff on the layout drawing.

I continue to refine the positions of these stuff.

 

Notes :

 1. I flipped the reference cavity. So now the cavity is sitting on the left hand side of the layout.

  2. I removed the ISS stuf. We should think about where ISS should be.

Quote:

Also, Kiwamu has modified the layout drawing to add the green PLL stuff. This has collapsed the reference cavity's wave function placing it close to its original position.

WE (maybe Valera and Steve) can now put the reference cavity back on the table.

 

Attachment 1: 40mPSL.png
40mPSL.png
  3548   Thu Sep 9 05:58:04 2010 kiwamuUpdatePSLmode matching from PMC to IMC

 I started mode matching of the beam going to IMC. The work is still going on.

According to Rana's calculation (see here), I put the first lens (f=200mm) in between two steering mirrors after PMC.

The distance from PMC to the first lens was adjusted by using a metal ruler.  So I believe the accuracy is something like 1mm.

I aligned the beam path going through the broadband EOM and the mode matching lenses.

 

  I could find the optimum position for the second lens  (f=-150mm) by sliding the position of the lens and measuring the mode after it.

But the optimum position looked a bit far from the EOM. It's off by about 3-4 inch from the designed position.

Somehow I feel that the beam before the second lens goes with a smaller divergence angle than that of designed.

So tomorrow I am going to restart the work from checking the mode before the second lens.

Maybe at first I should measure the mode without going through the EOM because it changes the waist position and makes the system not straightforward.

  3556   Fri Sep 10 02:35:30 2010 rana, kiwamu, valera, taraConfigurationPSLupdate

Over the last couple nights we got the beam into the FSS path and all the way to the IMC and out onto the AP table.

Tara and Valera have calculated a mode-matching solution for the reference cavity. It utilizes only a single lens between the AOM and the reference cavity. Valera and Steve will move the reference cavity into place in the morning.

We noticed that the layout was too tight on the end going into the MC and so we adjusted the angle of the final zig-zag. This will put the final mode-matching lens in between the final steering mirrors (which is generally undesirable) but the lens in this case is only f=400 mm. In addition, this lens may provide some more decoupling between the steering mirrors.

The whole layout has to be a little adjusted because of a calculation mistake I made in the mode-matching. I used only the nominal focal lengths from the CVI catalog and not the effective one. For the UV-grade fused silica lenses, the effective focal length is actually 20-30% longer. Today we measured that the "f=200 mm" lens we got is actually f = 238 mm. The BK7 lenses are much closer to the nominal.

We also replaced the Klinger mount ahead of the PMC with a Polanski style so that we could get the PMC REFL beam out without hitting the mount. Valera will continue to refine this section on the weekend.

Tomorrow, we will lock the MC using feedback only to the NPRO. The 0-150 V piezo driver is on the PSL table ready for action.

I also got a LCD video monitor from Frank and hooked it up on the PSL table. If we like this kind of thing, we can get many of them. They are pretty cheap. It would be handy to have 3-4 of them on the PSL and one on every of the ISC tables. They take the standard video for input and need +12V for power. Right now the one in there is looking at the PMC transmission.

The Omnigraffle layout as of tonight is attached.

Attachment 1: 40mPSL.pdf
40mPSL.pdf
  3558   Sat Sep 11 22:42:07 2010 valeraUpdatePSLPSL update

- The PMC REFL PD was moved from the temporary location to the one called for by the PSL layout (picture attached). The leakage beams were dumped.

- The FSS reference cavity was aligned using temporary periscope and scanned using NPRO temperature sweep. The amplitude of the sweep (sine wave 0.03 Hz) was set such that the PMC control voltage was going about 100 V p-p with. With rough alignment the visibility was as high as 50% - it will be better when the cavity is locked and better aligned but not better than 80% expected from the mode astigmatism that Tara and I measured on Thursday. The astigmatism appear to come from the FSS AOM as it depends on the AOM drive. We reduced the drive control voltage from 5 V to 4V beyond that the diffraction efficiency went below 50%. The FSS REFL PD was set up for this measurement as shown in the attached picture. There is also a camera in transmission not shown in the picture.

Attachment 1: DSC_2502.JPG
DSC_2502.JPG
Attachment 2: DSC_2505.JPG
DSC_2505.JPG
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