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ID Date Authorup Type Category Subject
  10164   Wed Jul 9 16:33:05 2014 manasaUpdatePSLPMC ringdown setup

Quote:

Quote:

I moved stuff on the PSL table to accommodate the PMC ringdown setup.

I used the beam that leaks from the steering mirror at the PMC transmission that was dumped to a razor blade dump. I installed a Y1 to steer the beam to the ringdown PD. Power in the beam 75mW. 

 I am guessing that 75 mW will burn / destroy any Thorlabs PD. I hope that mW is supposed to be uW.

 It was ~7.5mW and measured ~2V at the PD output (given its range 0-5V ) on the oscilloscope . So PD is safe !

  10168   Wed Jul 9 21:05:31 2014 manasaUpdateGeneralAOM and PSL Ringdown

After the fits, here are the numbers!

Component Measured Expected
AOM 85.1 ns 200 ns (spec sheet) 
PMC 164.6 ns  Finesse/(2*pi*FSR)  = 163.4 ns

* We have a huge difference to the AOM switching time that was measured. The spec sheet mentions acoustic velocity in the material to be 4.2 mm/us and the well matched diameter in the AOM to be 1100 um. This would give a switching time ~ 200 ns. We could probably be having a much smaller beam size in the AOM for the measured switching time.

* The PMC  parameters that I had been referring to from the wiki were actually wrong and which was the reason for the mismatch that I was finding. I modified the wiki according to the found references to the actual measurement here: PMC parameters The measured values now and then match pretty well.

* Since the AOM does not change the power of the output beam by very much, what we see is actually a step response. Also, we have a lot of noise in the data obtained at the PD. 

RXA: some more comments...

  1. The fact that the AOM can only modulate the power by a tiny bit means that it is very mis-aligned or that the driver is broken.
  2. You need to take into account the AOM step time in the calculation of the PMC step time. Its not a step response if the input step is not a step, but a exponential.
  3. I wouldn't trust that old John Miller entry for the PMC Finesse. As you can see from his elog, even he didn't trust it.
  4. As we were discussing before, making a little step is not the same as a full ringdown. cf. G000413 and T900007

 

  10171   Thu Jul 10 00:38:20 2014 manasaUpdateGeneralAOM and PSL Ringdown

Quote:

RXA: some more comments...

  1. The fact that the AOM can only modulate the power by a tiny bit means that it is very mis-aligned or that the driver is broken.
  2. You need to take into account the AOM step time in the calculation of the PMC step time. Its not a step response if the input step is not a step, but a exponential.
  3. I wouldn't trust that old John Miller entry for the PMC Finesse. As you can see from his elog, even he didn't trust it.
  4. As we were discussing before, making a little step is not the same as a full ringdown. cf. G000413 and T900007

 

I think we should revisit the AOM alignment because the last time it was aligned, PMC trans dropped from 0.84 to 0.15 (a little more than 80%) for 0-1V modulation input to the AOM driver [elog]. The drop in power right now is ~10-15% only.

I could not find any elogs of AOM alignment touchups after Oct 2012.
But can the ISS team throw some light on the status of AOM when they were installing the ISS servo before we decide on touching the AOM alignment? [elog

  10203   Tue Jul 15 17:34:01 2014 manasaUpdatePSLproposing AOM re-alignment

I am going to tweak the alignment of the beam into the AOM (before the PMC) tomorrow morning. If anybody has any objections to this, please raise a red flag.

Proposed alignment procedure:

1. Reduce PSL power to say 10% 

2.  Since the AOM is not on any sort of a mechanical stage, I will have to just play around carefully until I see a maximum power rejection into first order.

I am assuming that moving the AOM is not going to affect the input pointing because all these activities are happening before the PMC. So as long as I have the output beam from the AOM aligned to the PMC at the end, everyone should be happy.

  10219   Wed Jul 16 19:38:37 2014 manasaSummaryPSLAOM alignment issues and removed from beam path

AOM removed from the beampath and PMC relocked. 

AOM alignment:

1. Measured the initial power after PMC as 1.30W and reduced it down to 130mW.
2. Checked the power in the AOM zero order transmission before touching it. For 0-1V modulation input, the power dropped from 125uW to 98.3uW.
3. Steered the mirror right before the AOM to increase AOM zero order transmission and then carefully moved the AOM around to obtain maximum power attenuation. I repeated this a few times and the maximum attenuation that I could obtain was 125uW to 89.2uW (~30% attenuation).
Although this is not the right way to align the AOM, we do not have much options with the current setup as there is not enough separation between the zero order and first order beams and the AOM is on a fixed rigid mount.
4. I tried to dump the first order beam from the AOM and it wasn't satisfactory as well. There is barely any separation between the zero order and first order beams.

PMC relocking:

1. SInce the alignment to the PMC was disturbed by moving the AOM and the steering mirror in front of it, the PMC alignment was lost.
2. I could not relock the PMC at low power or high power. Rana had to come to rescue and fixed the alignment so that we could see flashes of PMC on the trans camera (This was done by aligning refl beam to the PMC REFL PD while giving a triangular ramp to the PMC PZT voltage).
Also I should not have tried to lock the PMC at high power as I could have been steering the beam at high power to the edges of the PMC mirrors that way and burning stuff easily.
3. Before fine tuning the alignment, I decided to remove the AOM from the beam path as there needs some work done on it to make it useful.
4. I removed the AOM from the beam path and relocked the PMC. 
5. PMC is relocked with 0.79 counts in TRANS and I measured the power after PMC 1.30W

Attachment: picture showing AOM removed from the beampath.

  10470   Mon Sep 8 12:11:36 2014 manasaUpdateComputer Scripts / Programspreparing vac system to reboot

Quote:

FYI: in that rack, the +15V pulls ~0.5 A more than -15V usually. I think this is due to some RF amplifiers which are powered by this (e.g. the AOM that Manasa set up). The Sorensen's can source ~30A in principle, so we should make sure to set the current limit appropriately so as to not overheat them when there is a short.

Was this power supply not fused for all of its connections? I remember that this was connected to at least one un-fused connection in the past year.

 +15V supply powers the following (from what I see):

1. PMC and MC boards on the rack.

2. RF amplifiers on the rack for the beat signals from the green beat PDs.

3. Beatbox itself.

The beatbox was the one that had an un-fused connection last year. I re-did it properly to go through a fuse quite sometime ago.

I dont see any other un-fused connections now from the +15V supply right now.
 

P.S. AOM driver takes a 0 to +28V power supply and not connected to the +15V

  10531   Wed Sep 24 11:02:38 2014 manasaUpdateLSCMoving SRM

I looked at the CAD layout and it seems like we will clearly be clipping POY if we move SRM by 7.5cm. Since POY is not visible at low power, we cannot be sure about the clipping.

We should have a plan B before we move everything. I suggest we move a combination of SRM and SR2 to get the desired SRC length.
Moving SR2 will require extra effort to walk the beam unclipped through all the 6 output steering mirrors that follow; but there will be little room for error if we use irides to propagate the beam through the first 4 mirrors that are in the BS and ITMY chamber.

  10567   Mon Oct 6 10:04:58 2014 manasaUpdateGeneralUnexpected power shutdown

We had a unexpected power shutdown for 5 sec at ~ 9:15 AM.

Chiara had to be powered up and am in the process of getting everything else back up again.

Steve checked the vacuum and everything looks fine with the vacuum system.

  10569   Mon Oct 6 10:28:18 2014 manasaUpdateGeneralUnexpected power shutdown

Quote:

We had a unexpected power shutdown for 5 sec at ~ 9:15 AM.

Chiara had to be powered up and am in the process of getting everything else back up again.

Steve checked the vacuum and everything looks fine with the vacuum system.

 The last time we had a power failure IFO recovery elog

  10573   Mon Oct 6 18:15:12 2014 manasaUpdateGeneralUnexpected power shutdown: end green alignment

After Q brought back the IR, I went to check the green situation.

1. The end lasers had to be turned ON. 
2. The heaters for the doubler crystals had to be enabled. The heaters are at the set values.
3. The X arm PZTs for the steering mirrors had to be powered up (Set voltage 100V and current 6.7mA)
4. I aligned the green to the already IR-aligned arms.

Green PSL alignment has to be done after Q finishes his work on the MC WFS.

  10575   Tue Oct 7 10:09:07 2014 manasaUpdateGeneralChiara not responding

Chiara doesn't seem to be responding and I guess something happened 7 hrs ago.

I tried to hook up chiara to a monitor to reboot or atleast look for error messages; but it is not even detecting the external monitor (Tried changing monitors and vga cables; still see nothing).

I tried to ssh into it and only received errors :
NFS lookup failed for server XXX.XXX.XXX.XXX : error 5 (RPC: Timed out)
ssh: chiara: host/servname not known

Steve had the vacuum checked and everything seems fine with the status of the vacuum system atleast.

  10586   Thu Oct 9 10:52:37 2014 manasaUpdateGeneralPower outage II & recovery

Post 30-40min unexpected power outage this morning, Steve checked the status of the vacuum and I powered up Chiara.

I brought back the FE machines and keyed all the crates to bring back the slow machines but for the vac computers.

c1vac1 is not responding as of now. All other computers have come back and are alive.

  10610   Wed Oct 15 17:09:49 2014 manasaUpdateGeneralDiode laser test preparation

[EricG, manasa]

The He-Ne laser oplev setup was swapped with a fiber-coupled diode laser from W Bridge. The laser module and its power supply are sitting on a bench in the east side of the SP table. 

  10629   Tue Oct 21 18:40:46 2014 manasaUpdateGeneralEnd laser fiber setup

 [Manasa, Diego]

This is our first time touching tables for Frequency Offset Locking. 

The goal was to couple the 1064nm that leaks after the SHG crystal and couple it into the fiber before we run it along the length of the arm. 

The fiber has been mounted at the end but there is no light coupled into the fiber as yet.

In the process, the following were done:

1. ETMY oplev servo disabled. This was enabled after the work.
2. NPRO laser power was reduced so that nothing gets burnt accidently while putting things on the table. This was also reset after the work.

The arms could be locked to green and IR after the work. So I am hoping today's work will not affect locking.

  10638   Fri Oct 24 10:08:24 2014 manasaUpdateGeneralY AUX laser - fiber coupled

The Y end aux laser light leaking after the doubling crystal has been coupled into the 70m long PM fiber. 

Input power = 250mW;  Output after 70m = 20mW

The poor efficiency is partially due to the ellipticity of the beam itself and partially due to the compromise I had to make using a single lens to couple the light into the fiber (given the limitations in space). But 20mW should be more than sufficient for a beat note setup.

Light propagates as follows after the doubling crystal:

Doubler ---> Harmonic Separator (45deg) ---> Lens (f=12.5cm) --> Steering mirror (Y1) --> Fiber collimator ( Thor labs CFC-2X-C) --> FIber end

I will update photos of the setup shortly.

I have left the 70m fiber in its spool sitting at the Y end and blocked the light before the last Y1 steering mirror in the above setup. So it should be safe.

Other:

Through the course of the work, I disabled the ETMY oplev and enabled it before closing the enclosure. I also reduced the AUX laser power and brought it back up after the work.
I did a check to see if the arms are locking in both IR and green and they did.
 

  10640   Mon Oct 27 12:17:46 2014 manasaUpdateGeneralY AUX laser coupling telescope design

Since I obtained a poor coupling efficiency from the earlier setup, I went back to calculate the coupling efficiency of the current setup.

For the current setup, I took the average of the x and y waist of the input beam and calculated the distance at which the input beam diameter would match the (fiber +collimator) beam diameter.

Average waist = 40.2um @-3.3mm from face of doubling crystal

(Fiber PM980 + Collimator f=2.0mm) beam waist = 205um

Distance(z) at which the input beam waist is 205um = 11.9cm

The closest available lens was f = 12.5cm. So I used it to couple the input beam by placing it at z ~12.5cm on a micrometer stage.

Since this gave only 10% coupling, I went back to calculate (using 'a la mode') the best possible coupling that can be obtained taking into consideration the ellipticity of the beam.

The maximum obtainable coupling (mode overlap) is 14.5%  which is still poor.

 

Redesign

Taking into account the ellipticity of the input beam, the available lenses and the space restrictions (lens can be placed only between z= 8 to 28cm), I calculated the best possible coupling efficiency (using 'a la mode').

The maximum possible mode overlap that can be obtained is 58.6% (matlab code and plot attached)

>>auxmode

modematching = 0.58632 

Optimized Path Component List:

    label    z (m)     type    parameters         

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

    L1       0.0923    lens    focalLength: 0.0750

 

  10645   Tue Oct 28 11:45:21 2014 manasaUpdateSUSETMX - observation

I looked at what are the situations that make ETMX lose alignment.

This is not occur all that often this morning; less than 10 times in may be the last 4 hours of poking the X arm. I found that the bad behavior of ETMX also exists in certain other cases apart from the case when we enable LSC.

(I) Even the MISALIGN and RESTORE scripts for the suspensions make the suspension behave bad. The RESTORE script while in the process of  bringing back the suspension to the place where it was, kicks it to some place else sometimes (even with LSC disabled)

(II) The suspension also gets kicked while realigning ETMX manually using sliders at 10^-3 (pace of 2-3 steps at a time).

I am suspecting something wrong right at the coil inputs and gains of the suspension.

Also, I recollect that  we haven't done a check on the X arm LSC limiters and filters ramping times like it was done for the Y arm ( Elog 9877 ). We should do this check to be sure that we are not seeing a mixed puddle of problems from 2 sources.

  10650   Wed Oct 29 11:45:11 2014 manasaUpdateGeneralY AUX laser - fiber coupled (52%)

Quote:

Redesign

Taking into account the ellipticity of the input beam, the available lenses and the space restrictions (lens can be placed only between z= 8 to 28cm), I calculated the best possible coupling efficiency (using 'a la mode').

The maximum possible mode overlap that can be obtained is 58.6% (matlab code and plot attached)

>>auxmode

modematching = 0.58632 

Optimized Path Component List:

    label    z (m)     type    parameters         

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

    L1       0.0923    lens    focalLength: 0.0750

 

I used the above configuration and was able to obtain ~52% coupling.

Input power = 250mW
Output power with absorptive ND 1.0 = 13 mW

I used the absorptive ND filter before the lens to keep the coupled output power within the range of fiber power meter and also avoid scattering of enormous amount of uncoupled light all over the table.

I have attached the screenshot of the out of loop ALS noise before opening the table (BLUE) and after closing down (MAGENTA). The beat note frequency and amplitude before and after were (14.4MHz/-9.3dBm) and (20.9MHz/-10 dBm).

  10651   Wed Oct 29 18:07:28 2014 manasaUpdateGeneralDiode laser test preparation

I ran 3 BNC cables from the SP table to 1X7 rack so that we can have 16 bit channels for the Ontrak PD that will be used to test oplev lasers. The BNC cables are plugged to the Ch 29, 30 & 31 that were already created for this purpose (elog 10488)

  10657   Fri Oct 31 11:46:15 2014 manasaUpdate Rattling HEPA : Eventually stops

The PSL HEPA stopped working while it was running at 80%. I have closed the PSL enclosure.

Steve is working to fix this.

  10666   Tue Nov 4 14:46:00 2014 manasaUpdateGreen LockingMissing beatnotes

Summary: Cannot find beatnotes between the arms and PSL.

I wanted to measure the ALS out of loop noise before putting stuff on the PSL table for frequency offset locking.

But I was not able to find the beat notes between the arms and PSL green. All I could find while scanning through the end laser temperatures is the beatnote between the X and Y green.

EricQ says that he spent some time yesterday and could not find the beatnotes as well.

Debugging and still could not find:

1. Checked the FSS slow actuator. This was close to zero ~0.003

2. Checked the green alignment on the PSL table. Everything seems fine.

3. Checked the actual PSL laser temperature. It was 31.28deg and not very far from when it was last set at 31.33deg elog.

4. Also checked the end laser temperatures. Both the lasers are ~40deg (where I could see the beatnote between the arms). Based on the plot here and  here , we are very much in the regime where there should be a beatnote between the PSL and the arms.

  10670   Wed Nov 5 11:37:29 2014 manasaUpdateGeneralLight from Y end reaches PSL table

[Steve, Diego, Manasa]

Since the beatnotes have disappeared, I am taking this as a chance to put the FOL setup together hoping it might help us find them.

Two 70m long fibers now run along the length of the Y arm and reach the PSL table.

The fibers are running through armaflex insulating tubes on the cable racks. The excess length ~6m sits in its spool on the top of the PSL table enclosure.

Both the fibers were tested OK using the fiber fault locator. We had to remove the coupled end of the fiber from the mount and put it back in the process. So there is only 8mW of end laser power at the PSL table after this activity as opposed to ~13mW.  This will be recovered with some alignment tweaking.

After the activity I found that the ETMY wouldn't damp. I traced the problem to the ETMY SUS model not running in c1iscey. Restarting the models in c1iscey solved the problem.

 

  10671   Wed Nov 5 17:50:29 2014 manasaUpdateGeneralPSL and AUXY beatnote in IR found

Found the IR beatnote between PSL and Y end laser.

Since our goal was to find the beatnote ASAP to recover ALS, I ignored the fine details in alignment. I will revisit the setup to make some improvements in the near future.

1. Coupled the PSL IR beam leaking after the doubler into the fiber. We have only 10% coupling into the fiber at the PSL table right now (6mw); but this will be improved once I get a suitable translation stage for the telescope.

2. PSL IR --> PM980 fiber --->50-50 fiber beam splitter ---> 50-50 fiber beam combiner
  AUX Y ---> PM980 fiber ---> 50-50 fiber beam combiner

The output port of the fiber beam combiner is connected to the fiber coupled broadband RF PD.

3. The RF output of the PD when connected to a spectrum analyzer shows a beatnote of -50dBm. The small amplitude of the beatnote is due to the laser power being attenuated before coupling into the fiber to keep the PD safe.

Attached is photo of how the setup is put on the PSL table. We will put all the stuff in a box once the X setup is also in place.

  10702   Wed Nov 12 15:14:09 2014 manasaUpdateGeneralX end AUX laser fiber setup

 I looked at the endtable for possible space to setup optics in order to couple the X end laser into a PM fiber.

Attached is the layout of where the setup will go and what are the existing stuff that will be moved.

ETMXtable.png

  10715   Fri Nov 14 11:07:59 2014 manasaUpdateCDSNot able to run models on FE machines

Quote:

PRM, SRM and the ENDs are kicking up.  Computers are down.  PMC slider is stuck at low voltage.

Still not able to resolve the issue.

Except for c1lsc, the models are not running on any of the FE machines . I can ssh into all the machines but could not restart the models on the FE using the usual rtcds restart <modelname>

Something happened around 4AM (inferring from the Striptool on the wall) and the models have not been running since then.

 

  10730   Fri Nov 21 11:41:24 2014 manasaUpdateGeneralX end fiber insulated and on cable tray

Quote:

Quote:

[Steve, Diego, Manasa]

Since the beatnotes have disappeared, I am taking this as a chance to put the FOL setup together hoping it might help us find them.

Two 70m long fibers now run along the length of the Y arm and reach the PSL table.

The fibers are running through armaflex insulating tubes on the cable racks. The excess length ~6m sits in its spool on the top of the PSL table enclosure.

Both the fibers were tested OK using the fiber fault locator. We had to remove the coupled end of the fiber from the mount and put it back in the process. So there is only 8mW of end laser power at the PSL table after this activity as opposed to ~13mW.  This will be recovered with some alignment tweaking.

After the activity I found that the ETMY wouldn't damp. I traced the problem to the ETMY SUS model not running in c1iscey. Restarting the models in c1iscey solved the problem.

 

 AP Armaflex  tube 7/8" ID X 1" wall insulation for the long fiber in wall mounted cable trays installed yesterday.

The 6 ft long sections are not glued. Cable tied into the tray pressed against one an other, so they are air tight. This will allow us adding more fibers later.

 Atm2: Fiber PSL ends  protection added on Friday.

 

[Steve, Manasa] 

Two 70m long fibers are now running through armaflex insulating tubes along the X arm on the cable racks. The excess length of the fiber sits in its spool on top of the PSL enclosure. 

Fibers were checked after this with the fiber fault locator (red laser) and found OK.

  10760   Sun Dec 7 13:11:57 2014 manasaSummaryGeneralFrequency Offset Locking - To Do List

Attached is the timeline for Frequency Offset Locking related activities. All activities will be done mostly in morning and early afternoon hours.

  10765   Mon Dec 8 15:54:39 2014 manasaSummaryGeneralDec 8 - Check Frequency Counter module

Quote:

Attached is the timeline for Frequency Offset Locking related activities. All activities will be done mostly in morning and early afternoon hours.

[Diego, Manasa]

We looked into the configuration and settings that the frequency counters (FC) and Domenica (the R pi to which the FCs talk to) were left at . After poking around for a few hours, we were able to readout the FC output and see it on StripTool as well.

We have made a list of modifications that should be done on Domenica and to the readout scripts to make the FC module automated and user-friendly.

I will prepare a user manual that will go on the wiki once these changes are made.

 

  10767   Tue Dec 9 00:30:27 2014 manasaSummaryGeneralDec 9 - Elaborate to do list

Quote:

Attached is the timeline for Frequency Offset Locking related activities. All activities will be done mostly in morning and early afternoon hours.

Elaborate to do list:

1. The FC module should be mounted on the IOO rack. Domenica has to be powered up appropriately to the rack power supply.

2. The fiber chassis needs to be built. This will hold all the fiber components and will sit inside the PSL enclosure.
Fiber connectors and fiber couplers need to be installed in the chassis. Attached is the cartoon sketch of layout in the chassis.

3. User guide for FC module (work in progress)

  10771   Tue Dec 9 16:07:16 2014 manasaSummaryGeneralDec 9 - FC module and fiber chassis

Quote:

Quote:

Attached is the timeline for Frequency Offset Locking related activities. All activities will be done mostly in morning and early afternoon hours.

Elaborate to do list:

1. The FC module should be mounted on the IOO rack. Domenica has to be powered up appropriately to the rack power supply.

2. The fiber chassis needs to be built. This will hold all the fiber components and will sit inside the PSL enclosure.
Fiber connectors and fiber couplers need to be installed in the chassis. Attached is the cartoon sketch of layout in the chassis.

3. User guide for FC module (work in progress)

1. FC module has been mounted on the IOO rack. The module gets it AC supply from the powerstrip already installed on the back side of the rack.

FCmodule.png

2. The fiber chassis has not been put together completely. We have still not received the front and back panels for the chassis; which is keeping me on hold. Diego is almost done with his housekeeping on Domenica. He will post an elog with all the details.

3. User guide for FC module (work in progress)

  10775   Wed Dec 10 16:12:29 2014 manasaSummaryGeneralDec 10 - PSL table

Quote:

Attached is the timeline for Frequency Offset Locking related activities. All activities will be done mostly in morning and early afternoon hours.

I was working around the PSL table today.

I wanted to modify the telescope that couples PSL light into the fiber; now that I have the translation stages for the lenses. I could not finish it as the locking work started earlier than usual this afternoon. I measured the out of loop noise for ALS error signals before I opened the PSL enclosure. X and Y beat notes were at -18dBm at 49.3MHz and -29.56dBm at 62.2MHz for this measurement. DTT data can be found in /users/manasa/data/141210/ALSoutLoop.xml; so there is reference to go back to in case of any damage done due to the work on the PSL table.

Also, I received the front and back panels for the Fiber chassis and put it together. Find photos (front panel and inside) of chassis in attachment. This will go inside the PSL enclosure tomorrow.

FiberMod_front.jpg    FOL_fiber.jpg

 

  10777   Thu Dec 11 09:11:18 2014 manasaUpdatePSLPSL FSS Slow actuator

I am not sure if people have been noticing it lately; but the slow actuator on the PSL FSS has been railing up quite often these days. I found it at >0.8 and as high as 1.5 on certain occasions before resetting it to nominal zero.

It could be because the PMC alignment needs to be tweaked. The night crew should consider doing this before starting to lock.

  10778   Thu Dec 11 10:08:10 2014 manasaUpdateGeneralIFO update

Status of IFO:

1. The X end slow computer is down. ETMX sliders and buttons on the ETMX suspension screens have gone white. I have disabled the ETMX oplev because it is largely misaligned in yaw. I am not poking it and leaving it as is for the time being.

2. The Y arm green alignment had drifted and GTRY was down to 0.15 . I tweaked the alignment using the last two steering mirrors and brought GTRY to 0.7 which gives a beat note of -14dBm.

  10780   Thu Dec 11 12:50:12 2014 manasaSummaryGeneralPSL table optical layout

 I assembled the telescope to couple PSL light into the fiber. The maximum coupling that I could obtain was 10mW out of 65mW (~15%).

I was expecting to achieve 80-90% coupling from my design estimates. It makes me wonder if the beam waist measurements made by Harry during summer were correct in the first place. I would like to go back and check the beam waist at the PSL table.

Also, we need a pair of 8m (~25 feet) long SMA cables to carry the RF signal from the beat PD on the PSL table to frequency counter module on the IOO rack.

Steve says that we had a spool of SMA cable and it was borrowed by someone a few months ago. Any updates on either who is holding it or if it has been used up already would help.


The X end slow computer was down this morning. So I used only the Y arm ALS to record the noise level for reference. DTT data for ALSY out of loop noise before opening PSL enclosure is saved in /users/manasa/data/141211/ALSYoutLoop.xml

  10787   Thu Dec 11 23:34:06 2014 manasaSummaryGeneralPSL table optical layout

Quote:

 I assembled the telescope to couple PSL light into the fiber. The maximum coupling that I could obtain was 10mW out of 65mW (~15%).

I was expecting to achieve 80-90% coupling from my design estimates. It makes me wonder if the beam waist measurements made by Harry during summer were correct in the first place. I would like to go back and check the beam waist at the PSL table.

Also, we need a pair of 8m (~25 feet) long SMA cables to carry the RF signal from the beat PD on the PSL table to frequency counter module on the IOO rack.

Steve says that we had a spool of SMA cable and it was borrowed by someone a few months ago. Any updates on either who is holding it or if it has been used up already would help.


The X end slow computer was down this morning. So I used only the Y arm ALS to record the noise level for reference. DTT data for ALSY out of loop noise before opening PSL enclosure is saved in /users/manasa/data/141211/ALSYoutLoop.xml

 I missed to elog this earlier. I have temporarily removed the DC photodiode for GTRY to install the fiber holder on the PSL table. So GTRY will not be seeing anything right now.

 

  10791   Fri Dec 12 14:38:39 2014 manasaSummaryGeneralFrequency Offset Locking - To Do List (Revised)

Unfortunately the order placed for beam samplers last week did not go through. These will be used at the X and Y end tables to dump the unwanted light appropriately. Since they will not be here until Tuesday, I revised the timeline for FOL related activities accordingly.

  10792   Fri Dec 12 15:19:04 2014 manasaSummaryGeneralDec 12 - PSL table

Quote:

Unfortunately the order placed for beam samplers last week did not go through. These will be used at the X and Y end tables to dump the unwanted light appropriately. Since they will not be here until Tuesday, I revised the timeline for FOL related activities accordingly.

I was working on the PSL table today. 

Since the rejected 1064nm light after the SHG crystal is not easily reachable to measure beam widths close to the waist, I put a lens f=300mm and measured the beam size around its focus. I used this data and redesigned the telescope using 'a la mode'.

I used a beam splitter to attenuate the beam directed towards the fiber. The reflected beam from BS has been dumped (I need to find a better beam dump than what is being used right now. 

I have only ~200uW at the input of the fiber coupler after the BS and 86uW at the output of the fiber (43% coupling)

I moved the GTRY DC photodiode and the lens in front of it to make space for the fiber coupler mount.

The layout on the PSL table right now is as shown below.

PSLtoFiber.png 

I have also put the fiber chassis inside the PSL enclosure on the rack. I moved the coherent spectrum analyser controller that is not being used to make space on the rack.

PSLfiberChassis.png

 
  10808   Wed Dec 17 11:57:56 2014 manasaSummaryGeneralY arm optical layout

I was working around the PSL table and Y endtable today.

I modified the Y arm optical layout that couples the 1064nm light leaking from the SHG crystal into the fiber for frequency offset locking.

The ND filter that was used to attenuate the power coupled into the fiber has been replaced with a beam sampler (Thor labs BSF-10C). The reflected power after this optic is ~1.3mW and the trasmitted power has been dumped to a razor blade beam dump (~210mW).

Since we have a spare fiber running from the Y end  to the PSL table, I installed an FC/APC fiber connector on the PSL table to connect them and monitored the output power at the Y end itself. After setting up, I have ~620uW of Y arm light on the PSL table (~48% coupling).

During the course of the alignment, I lowered the power of the Y end NPRO and disengaged the ETMY oplev. These were reset after I closed the end table.

Attached is the out of loop noise measurement of the Y arm ALS error signal before (ref plots) and after.

 

  10831   Mon Dec 22 17:06:14 2014 manasaUpdateGeneralX end AUX laser fiber setup

Quote:

 I looked at the endtable for possible space to setup optics in order to couple the X end laser into a PM fiber.

Attached is the layout of where the setup will go and what are the existing stuff that will be moved.

ETMXtable.png

Since we will not be doing any major locking, I am taking this chance to move things on the X end table and install the fiber coupler.

The first steering mirror shown in the earlier elog will be a Y1 (HR mirror) and the second one will be a beam sampler (similar to the one installed at the Y endtable for the fiber setup). 

 

Configuration:

Doubler --> Y1 ---> Lens (f=12.5cm) ---> Beam sampler --->Fiber coupler

The fiber coupler mount will be installed in the green region to the right of the TRX camera. 

This work will involve moving around the TRX camera and the optic that brings the trans image on it.

Let me know if this work should not be done tomorrow morning for any reason.

  10834   Tue Dec 23 13:18:37 2014 manasaUpdateGeneralX end AUX laser fiber setup

Quote:

 

Since we will not be doing any major locking, I am taking this chance to move things on the X end table and install the fiber coupler.

The first steering mirror shown in the earlier elog will be a Y1 (HR mirror) and the second one will be a beam sampler (similar to the one installed at the Y endtable for the fiber setup). 

Configuration:

Doubler --> Y1 ---> Lens (f=12.5cm) ---> Beam sampler --->Fiber coupler

The fiber coupler mount will be installed in the green region to the right of the TRX camera. 

This work will involve moving around the TRX camera and the optic that brings the trans image on it.

Let me know if this work should not be done tomorrow morning for any reason.

I was working around the X endtable and PSL table today.

1. Y1 mirror, beam sampler and the fiber coupler have been installed.

2. Removed TRX camera temporarily. The camera will be put back on the table once we have the filter for 532nm that can go with it.

3. Removed an old fiber mount that was not being used from the table. 

4. Lowered the current for X end NPRO while working and put it back up at 2A before closing.

5. The fibers running from the X end to the PSL table are connected at an FC/APC connector on the PSL table. 

6. Found the HEPA left on high (probably from yesterday's work around the PSL table). I have brought it back down and left it that way.

I have not installed the coupling lens as yet owing to the space restrictions - not enough space for footprint of the lens. I have to revisit the telescope design again.

  10867   Wed Jan 7 12:15:17 2015 manasaUpdateGeneralNew RF cables

I was working around the PSL table this morning.

1. I have fibers running from the Y end and the PSL table to the Optical Fiber Module for Frequency Offset Locking. 

Y+PSL out power is ~200uW. From the transimpedance and responsivity specs of the RFPD (ThorLabs FPD310), we expect ~100uW or -10dBm RF power. I have not hooked up the RF output to a spectrum analyser to confirm this as yet.

2. Also, Steve and I ran RF cables (LMR-195A) from the PSL table to the FC module on the IOO rack.

 

  10873   Wed Jan 7 19:49:09 2015 manasaUpdateGeneralX end space issues

I have attached a photo of the ETMX table. The path of the 1064nm light rejected after the doubler and the green light are indicated for reference.

The fiber mount can only be mounted in the green space shown in the picture.

Calculating lens solutions for coupling the 1064nm light rejected after the doubler into the fiber, a lens of f=12.5cm should be placed at z=15.31cm (measured from the waist in the doubler crystal) gives the best ~80% coupling. This falls in the blue region where there is not enough space to mount a lens

The region marked in orange has enough room for a lens; but the lens solutions give a coupling <10% which means there will be light scattering everywhere.

I am open to any suggestions on how to go about this.

ETMXspace.png

  10883   Fri Jan 9 14:01:17 2015 manasaUpdateGeneralAUX Y + PSL beat note at 1064nm

I worked around the PSL table today.

The Y+PSL output from the optical fiber module for FOL was fed to the input of the Thorlabs FPD310
200uW of incident light on the RFPD gave an RF signal of -70dBm as measured on a spectrum analyzer.

I swapped the beam splitter along the PSL path so that the incident power on the RFPD is ~1.5mW (Maximum incident power that the PD can tolerate is ~2mW).
This RF signal generated was - 43dBm which is still small for the input to the frequency counter module.

I checked this with a function generator and found that the frequency counter requires around -25 to -30 dBm at the input.

I plan to use the Minicircuits ZFL-1000ln that is on the IOO rack but not being used (This was used for green beatnote amplification but is not required/used anymore) to amplify the RF signal to the frequency counter.
If anyone has any objections to using this amplifier for the frequency counter, let me know.

 

  10884   Fri Jan 9 14:13:02 2015 manasaUpdateGeneralALS noise at ~30Hz

Before starting to move things around the PSL table, I measured the ALS out of loop noise for reference. The noise spectrum showed excess noise around 30Hz.  The traces in blue were taken before I went in and those in red were taken after my work.

I also looked at the power spectrum of LSC-TRY_OUT to see if the noise is from the IR lock itself and there was nothing suspicious with it. 

Since the green transmission was 50% lower than the usual, I touched the steering mirrors for green at the Y end table to get a better transmission and beat signal. The noise still hasn't disappeared. 

I am not sure if this could be from our neigbors who have been running rock experiments since morning. We should check back to see if this noise disappears once they shut down.

DTT xml files are available in directory /users/manasa/data/150109/

  10893   Tue Jan 13 10:28:02 2015 manasaUpdateGeneralAUX Y + PSL beat note at 1064nm
Quote:
 

I plan to use the Minicircuits ZFL-1000ln that is on the IOO rack but not being used (This was used for green beatnote amplification but is not required/used anymore) to amplify the RF signal to the frequency counter.
If anyone has any objections to using this amplifier for the frequency counter, let me know.

The above mentioned amplifier has been used to amplify the input to the frequency counter. The frequency counter is now getting an input that it can read.

I have done an edit to the ALS medm screen and the PSL and AUX Y laser beat frequency is now readable.

  10895   Tue Jan 13 14:01:20 2015 manasaUpdateGeneralAUX Y + PSL beat note at 1064nm: needs work
Quote:

I'm super excited about this new frequency readback, but I'm not sure that it's reliable yet.  Without touching any settings, the readback is currently saying 78.6MHz, and is changing slightly (as is the FSS Slow Temp), so something is working.  However, the beatnote as measured on the spectrum analyzer is 158.2MHz.  So, either the calibration or the tracking or something isn't quite finished being tuned yet.

It's going to be super awesome when we have this though!!

As Jenne pointed out, this is still not fully tuned. 

For example, I found today that the frequency counter requires more power at the input >= -20dBm to measure frequency inputs < 40 MHz. Since the RFPD gives ~ -40dBm at its output, the ~20dB gain amplifier will not be enough to measure low frequencies in case the beat power at the PD drops (which is very much possible when the alignment drifts or things move around on the PSL table).  So I am shopping for an RF amplifier with higher gain to replace the current one. In the meantime, I will test the PID loop for set point frequency > 40MHz.

I have also observed the frequency difference between the measured frequencies on FC and the spectrum analyzer. I am not sure where this comes from as yet. 

At this point, the FC readout is only reliable enough to find a beatnote that is lost on the spectrum analyzer.

  10918   Sat Jan 17 15:07:28 2015 manasaUpdateGeneralBeat note frequency discrepancy

I was around the PSL table and the X end table today.

X end table:

I was at the X end table making some distance measurements for the telescope to the fiber coupler. I have NOT moved anything as yet.

PSL table:

I wanted to get some data to look at the beat note frequency discrepancy between the green and IR. 

I tried making measurements using the spectrum analyzer at the PSL table but the MC was getting unlocked quite often with PSL enclosure open and HEPA on high. 

So I switched off the power supplies to the RFPDs (3 of them) on the PSL table and disconnected the Xmon input to the adder (at the IOO rack) which brings the green beat note signals to the conrol room. I connected the fiber RFPD output to the adder and took a bunch of measurements of the green and IR beat notes from the spectrum analyzer in the control room. I have NOT undone this setup assuming there are no locking plans for tonight and I will come back tomorrow. 

If anyone is planning to do some locking in the meantime, you can undo the connections keeping in mind to turn off the power to the RFPDs before you do so.

P.S. I walked in this morning to PSL FSS slow actuator at 0.89 and brought it down to zero before making measurements.
I also touched the steering mirrors that are part of the Y green beat note alignment while looking at the amplitude of the RF signal on the spectrum analyzer.

  10919   Mon Jan 19 11:03:32 2015 manasaUpdateGeneralRF connections to adder

RF connections to the beat note adder on the IOO rack have been undone and it should be good to proceed with any locking attempts.

Quote:

I was around the PSL table and the X end table today.

X end table:

I was at the X end table making some distance measurements for the telescope to the fiber coupler. I have NOT moved anything as yet.

PSL table:

I wanted to get some data to look at the beat note frequency discrepancy between the green and IR. 

I tried making measurements using the spectrum analyzer at the PSL table but the MC was getting unlocked quite often with PSL enclosure open and HEPA on high. 

So I switched off the power supplies to the RFPDs (3 of them) on the PSL table and disconnected the Xmon input to the adder (at the IOO rack) which brings the green beat note signals to the conrol room. I connected the fiber RFPD output to the adder and took a bunch of measurements of the green and IR beat notes from the spectrum analyzer in the control room. I have NOT undone this setup assuming there are no locking plans for tonight and I will come back tomorrow. 

If anyone is planning to do some locking in the meantime, you can undo the connections keeping in mind to turn off the power to the RFPDs before you do so.

P.S. I walked in this morning to PSL FSS slow actuator at 0.89 and brought it down to zero before making measurements.
I also touched the steering mirrors that are part of the Y green beat note alignment while looking at the amplitude of the RF signal on the spectrum analyzer.

 

  10954   Thu Jan 29 09:50:47 2015 manasaUpdateElectronicsIOO rack amplifier panel

The RF amplifier panel on the IOO rack (Attachment 1) will be used to also hold the RF amplfiers for the frequency counters. The amplifiers mounted on it right now are getting +15 (orange wire) and GND (black wire) from the rack power supply (Attachment 2).

Proposed plan to install RF amplifiers:

1. Disconnect the D sub connector that powers the amplifiers and pull out the panel. The rack power supplies will NOT be shut down for this. 

2. Mount the RF amplifiers with bypass capacitors. There will be 4 amplifiers ZFL-500LN mounted on the same panel (2 for each frequency counter).

3. While putting back the panel on the IOO rack, we will need to shut down the +15V and -15V sources to connect the amplifiers to the rack power supply.

I will do this over this weekend so that we dont lose any locking time. If anybody has any concerns, let me know

  10955   Thu Jan 29 10:14:21 2015 manasaUpdateGeneralX end space issues

It is certain that we have space issues at the X end that has been preventing us from sticking in a lens to couple light into the fiber. 

The only way out is to install a platform on the table where we can mount the lens. I have attached the a photo of how things look like at the X end (attachment 1) and also a drawing of the platform that which can hold the lens (attachment 2). Additional support to the raised platform will be added depending on how much space we can clear up on the table by moving the clamping forks of the doubler.
Steve and I have been able to gather parts that can be put together into something similar to what is shown in the drawing. 

Proposed modifications to the X end table:

1. The side panels of the table enclosure will come out while putting in the new platform.

2. The clamping forks for the doubling crystal will be moved.

Let me know of any concerns about the proposed solution. 

ELOG V3.1.3-