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ID Date Authorup Type Category Subject
  12784   Wed Feb 1 16:45:56 2017 LydiaUpdateIMCRF AM stabilizer box Modification Plan

Here's what I'm planning to do to the RF AM stabilizer box. I'm going to take out several of the components along the path to the EOM (comments in green), including the dead ERA-4 and ERA-5 amplifiers, the variable attenuator which is controlled by a switch that can't be accessed outside the box, and the feedback path from the daughter board servo. I'm arranging things so that the output of the HELA-10 does not exceed the maximum output power. 

I wasn't quite as sure what to do about the path to the ASC box (comments in blue). I talked with Gautam and he said this gets split equally between several singals, one of which goes to the LO of the demod board which expects -10 dBm and currently gets -12 dBm (can go up to -8 by turning switch). So maybe we don't actually want the signal to be anywhere near +27 dBm at the output. The plans for the box are here, it looks like +27 in will end up with +10 at each output, which is way more than what's currently coming out. But maybe this needs to be increased to match the other path? 

Also we haven't measured the actual response of the variable attenuator U4 for various switch positions; it's the same model as the one I'm removing from the EOM path and that one had slightly different behavior for different switch positions than what the spec sheet says. Same goes for the HELA-10 units along this path: what is their actual gain? So perhaps these should be measured and then a single attenuator should be chosen to get the right output signal level. Alternatively it could just be left alone, if it is at an OK level right now. Advice on what to do here would be appreciated.  

I'll work on the EOM path tonight and wait for feedback on the rest of it. 

EDIT: Gautam pointed out that there's some insertion loss from the components I'll be removing that hasn't been accounted for. Also the plans have been updated to reflect that I'm replacing AT5 with a 1dB attenuator (from 6 dB). 

  12786   Wed Feb 1 23:13:30 2017 LydiaUpdateIMCRF AM stabilizer box Modification Plan

I made some of the changes. Gautam and I will finish tomorrow. 

While I was soldering the sharpest tip of the soldering iron (the one whose power supply shows the temperature) stopped working and I switched to a different one. Not sure how to fix this. 

Do we want to replace all of the removed ERA's with 50 Ohm resistors, or just the one along the spare output path? I shorted one of them with a piece of wire and left all the others open. 

I couldn't get one of the attenuators off (AT1, at beginning of ASC path). In trying I messed up the solder pad. Part of the connecting trace on the PCB board is exposed so we should be able to fix it. 

  12801   Sun Feb 5 21:56:50 2017 LydiaUpdateIMC29.5 MHz stabilizer box replacement

Since the "stablizer box" doesn't really need to stabilize, it just needs to amplify, I decided to replace it with an off the shelf amplifier we already had, ZHL-2. I worked on getting it set up today, but didn't connect anything so that people have a chance to give some feedback. 

  • The gain we expect is 18 dB, and the maximum output with 1dB of compression is 29 dBm. To avoid compression, I'm aiming for ~26 dBm output, so ~8 dBm input. We measured the output of the source to be 12.8 dBm before, so I attached a 5dB attenuator to the input side of the amplifier. 
  • Across the 24V power input and the ground pin, I soldered a 100 uF, 50V electrolytic capacitor and a .27 uF, 50V metal film capacitor. Note that unlike the other similar amplifiers we have, the ground and +24 pins are separated (see image on datasheet). I wasn't sure if that changed what to do so I just found comparable caps to the ones that were there on another model. 
  • I twisted and soldered wires to the +24 and ground, making sure they were long enough to reach the clips where the power from the Sorensens gets split up. I placed the amplifer in the rack on top of the RF distribution box and ziptied the power cable in place. 
  • I connected a splitter to the output of the amplifier. Should I use a 10dB coupler instead, to maximize the power to the EOM?

So, I think the remaining thing to do is to connect the splitter to ASC out and to the line to the EOM, the +24V supply to the amplifier, and the 29.5 MHz input to the attenuator. I wanted to wait on this to get confiration that the setup is OK. Eventually we can put all of this in a box. 

Also, I noticed that in the clear cabinet with the Sorensens next to this rack, the +24 V unit is not supplying any voltage and has a red light that says "OVP." 

  12807   Tue Feb 7 12:01:10 2017 LydiaUpdateIMC29.5 MHz stabilizer box replacement

I tested the amplifier with the Agilent network analyzer and measured 19.5 dB of gain between 29 and 30 mHz. The phase only changed by 1 degree over this same 1 MHz span. Since everything seems to be in order I'll hook it up this afternoon, unless there are any objections

  12809   Tue Feb 7 17:00:55 2017 LydiaUpdateIMC29.5 MHz stabilizer box replacement

I set everything up and connected it as shown on the block diagram attached to the previous entry, with the exception of the DC power. This is becuase there is no place open to connect to on the DIN rail where the DC power is distributed, so the +24V power will have to be shut off to the other equipment in 1X1 before we can connect the amplifier. (The amplifier is in 1X2, but the DC power distribution was more accessible in 1X1.) I also added 3 new +24 V clips with fuses despite needing only one, so next time we need to connect something new it's not such a hassle. 

The RF distribution box where the 29.5 MHz signal originates should not be turned on until the amplifer has DC power. Since we may have a power interruption tomorrow, the plan is to wait until things are shut down in preparation, and then shut off anyhting else necessary before connecting the new clips on the rail to the existing ones. 

  12817   Fri Feb 10 11:41:43 2017 LydiaUpdateIMC29.5 MHz stabilizer box replacement

To install the replacement amplifier, I did the following:

  • Mounted the amplifier in a 2U chassis, with a metal plate between the amplifier and the bottom of the box. The plate is separated from the box and the amplifier with 2 sets of Nylon screws. I did it this way to make use of the holes that were already in the chassis bottom and just drill holes into a plate instead. 
  • Cannibalized mounting brackets and back panel from old ALS Beatbox. The back panel has an on/off switch and a 3W3 feedthrough for power. 
  • Made a power cable to reach from the 1X1 fuse blocks to the back panel of my box. Goes up through the top of the rack and then back down. 
  • Installed the chassis in the rack. The lid is currently off and there is no front panel yet. 
  • Changed the +5dB attenuator to +30 to be able to check things first before supplying a way stronger signal. 
  • Installed 4 new +24 V fuse blocks on the adjacent rack (1X1). 
    • Put the new fuses on the DIN rail and wired them together. Connected the new power cable to one of them. 
    • Blocked PMC transmission and made sure all RF sources in 1X1 and 1X2 were turned off
    • Turned off the + 24 V and -24 V Sorensens, trying to keep them fairly balanced as I turned them to 0. 
    • At this point Rana suggested I turn off the other DC power supplies in the rack, which I did.
    • Connected the new fuse blocks to the existing +24 V ones. Note that they are not contiguous but they follow the color code and will be labeled. 
    • I'm only using one of the new +24 outputs, but I made more for future use to minimize the number of times we have to turn the power off. 
  • Connected the output of the amplifier to the EOM, and the coupled signal to the distribution box (which splits it and sends it to the demod boards). 
  • Turned on the power switch and checked that the amplifier was in fact getting 24 V. 
  • Connected the input from the 29.5 MHz source and measured the power coming from the amplifier. I measured -12 dBm instead of the expected ~0 dBm, but Gautam was able to see the expected power later, so maybe something just wasn't connected right.
  • Double checked the power coming into the amplifier, which was consistent with earlier measurements at about 12.8 dBm. 

 

Still to be done:

  • Label/relabel several things (fuse blocks, back panel, etc) 
  • Current label on +24 Sorensen needs to be updated
  • Order front panel and install
  • Install power indicator lights on front and back 
  • Readjust gains (analog and digital) to use full signal output and measure (hopefully) improved WFS performance
  • Insert bi-directional coupler and measure modulation depth and reflections from EOM
  12827   Mon Feb 13 19:44:55 2017 LydiaUpdateIMCFront panel for 29.5 MHz amplifier box

I made a tentative front panel design for the newly installed amplifier box. I used this chassis diagram to place the holes for attaching it. I just made the dimensions match the front of the chassis rather than extending out to the sides since the front panel doesn't need to screw into the rack; the chassis is mounted already with separate brackets. For the connector holes I used a caliper to measure the feedthroughs I'm planning to use and added ~.2 mm to every dimension for clearance, because the front panel designer didn't have their dimensions built in. Please let me know if I should do something else. 

The input and coupled output will be SMA connectors since they are only going to the units directly above and below this one. The main output to the EOM is the larger connector with better shielded cables. I also included a hole for a power indicator LED. 

EDIT: I added countersinks for 4-40 screws on all the screw clearance holes. 

Johannes, if you're going to be putting a front panel order in soon, please include this one. 

Also, Steve, I found a caliper in the drawer with a dead battery and the screws to access it were in bad shape- can this be fixed? 

 

  12832   Wed Feb 15 22:21:12 2017 LydiaUpdateDAQpanels and pcbs

This is already how it's hooked up. The hole on the from that says +24 V is for an indicator light.

Quote:

The amplifier unit should use the three pin dsub connectors (3w3?) that we use on many of the other units for DC power, and preferably go through the back panel. You can leave out the negative pin, since you just need +24 and ground.

 

  12861   Wed Mar 1 21:15:40 2017 LydiaUpdateIMCFront panel for 29.5 MHz amplifier box


I installed the front panel today. While I had the box out I also replaced the fast decoupling capacitor witha 0.1 uF ceramic one. I made SMA cables to connect to the feedthroughs and amplifier, trying to keep the total lengths as close as possible to the cables that were there before to avoid destroying the demod phases Gautam had found. I didn't put in indicator lights in the interest of getting the mode cleaner operational again ASAP. 

I turned the RF sources back on and opened the PSL shutter. MC REFL was dark on the camera; people were taking pictures of the PD face today so I assume it just needs to be realigned before the mode cleaner can be locked again. 

I've attached a schematic for what's in the box, and labeled the box with a reference to this elog. 

  12865   Thu Mar 2 20:32:18 2017 LydiaUpdateIMCFront panel for 29.5 MHz amplifier box

[gautam, lydia]

I pulled out the box and found the problem: the +24 V input to the amplifier was soldered messily and shorted to ground. So I resoldered it and tested the box on the bench (drove with Marconi and checked that the gain was correct on scope). This also blew the fuse where the +24 power is distributed, so I replaced it. The box is reinstalled and the mode cleaner is locking again with the WFS turned on.

Since I tried to keep the cable lengths the same, the demod phases shouldn't have changed significantly since the amplifier was first installed. Gautam and I checked this on a scope and made sure the PDH signals were all in the I quadrature. In the I vs. Q plot, we did also see large loops presumably corresponding to higher order mode flashes.

Quote:

Walking over to the 1X1, I noticed that the +24V Sorensen that should be pushing 2.9A of current when our new 29.5MHz amplifier is running, was displaying 2.4A. This suggests the amplifier is not being powered. I toggled the power switch at the back and noticed no difference in either the MC locking behaviour or the current draw from the Sorensen.

 

 

  12713   Fri Jan 13 14:33:00 2017 MAX (not Rana)UpdateSummary PagesDecember outage

PEM config file was also lacking a section named "summary", which is necessary for all parent tabs; this has now been solved. I have deactivated the MEDM pages because Praful's screencap script seemed to be broken (I should have logged this, I apologize).

Quote:

Pages still not working: PEM and MEDM blank.

  • Committed existing MEDM grabbing scripts to SVN. Ran the cron job on megatron by hand. It grabs PNG files, but somehow its not getting into the summary pages.
  • Changed the MEDM grabbing scripts to use '/usr/bin/env'.
  • GW summary log files were numbering in the many thousands, so I moved everything over 320 days old into the OLD/ sub-directory using 'find . -type f -mtime +320 -exec mv {} OLD/ \;' (the semi-colon is needed)
  • Did apt-get upgrade on Megatron.
  • pinged Max
  • Stared at GWsumm docs to see if there's a clue about what (if anything) is wrong with the .ini file.

 

  5760   Fri Oct 28 20:39:19 2011 MIrkoUpdateLSCRFAM monitor in place. ( Uncalibrated ) EPICS troubles

{Suresh, Jamie, Mirko]

We adapted the Stochmon box to include LP filters at 1.8Hz behind the RMS parts.
Then measured the RMS signals for different RF signal levels at 11.0.65, 29.5, 55.325MHz provided by a RF freq. generator.
As you can see in the data below the suppression of the BP filters of neighboring frequencies is only 35-35dB in power (see also manufacturer specs).

We therefor want to substract crosstalk, by calculating it out. We decided to use C-code in CDS. No computer crashing this time :)

We however ran into the problem that the RMS signal channels are acquired by the slow (EPICS) maschine c1iool0. Channels are (C1:IOO-RFAMPD_33MHZ , -"-133MHZ, -"-166MHZ) and we could not access those in the CDS c1ioo model. Using the EpicsIn block we got an CA.Exception stating that the variable was hosted on multiple servers. We then tried to use the EzcaRead to access the variables. Got an compile error, about the compiler not beeing able to connect all parts. It seems that the EzcaRead left behind a "ghost" part in the model (something with M1:SYS-FOO_BAR which is the default naming of the EzcaRead block) even after we deleted that block. We toyed around with the /opt/rtcds/caltech/c1/chans/daq/C1EDU_IOO.ini  and  /cvs/cds/caltech/target/c1iool0/ioo.db  files. We tried to uncomment the "old" (33,133,166) channels there to get rid of the conflict, but that didn't work.

We want to write the outputs to C1:IOO-RFAMPD_11MHZ , -"-29MHZ, -"-55MHZ EPICS channels.

We had to get the model back from the svn to get it running again.

  5810   Fri Nov 4 14:18:24 2011 MIrkoUpdateAdaptive FilteringCoherence between seismometers and MC length

Looking into the coherence between the seismometers and IMC length (MC_F):

FIrst with the seismometers only AC filtered at around 0.003 Hz and AA30Hz:
Coherence_without_compensation.pngWith_Pend_compensation.mat

Ignore the increase in coherence at very low frequencies. That is an artefact.

Then with an additional filter single complex pole @1Hz Q=1000 (giving 20dB per decade in attenuation above 1Hz) , only for GUR1X:
Coherence_with_compensation.png

  5928   Thu Nov 17 17:03:28 2011 MIrkoUpdateIOOMC noise projection

Another go at the noise projection from MC1-3 pit/yaw to MC length. This time injecting into the MC autoalignment FB (e.g. C1:IOO-WFS1_PIT_EXC ).

LTPDA is working now, but still the NDS server is not so cooperative.

Summary: Alignment fluctuations of the MC mirrors don't significantly contribute to MC length changes up to at least 3.5Hz. Especially they can't explain the lack of coherence between seismometers and MC length below 1Hz that we worry about for the OAF.

At high frequencies >= 10Hz you can see angle to length coupling as is evident in Sureshes spot position measurements.

Whiteish noise injection:

Injection from 0.1-20Hz.Filtered by the servo filters and zp:[1],[1] , Gain = 1 @ 2Hz

 MCLengthToAngleCouplingNoiseProjection.png

Look at the coherence plots for the quality of the measurement:

Coherence_WFS1pit.png

Coherence_WFS2pit.png

 

Coherence_WFS1yaw.png

 Coherence_WFS2yaw.png

Injection details:

DOF      Amplitude[counts]        UTC Time (duration always 4mins)
WFS1p  70                               22:28
WFS1y  55                               22:03
WFS2p  70                               22:13
WFS2y  70                               22:18
None      -                                 22:23

Fixed sine injections:

To get some better SNR at low frequencies I did a fixed sine noise injection at 0.3Hz. See attached files.

DOF      Amplitude[counts]        UTC Time (duration always 4mins)    Lower limit of SNR MC length via mirror misalignment
WFS1p  4                                  00:05                                                29.3
WFS1y  4                                  00:14                                                22.0
WFS2p  4                                  00:19                                                18.5
WFS2y  4                                  00:25                                                18.0

  7090   Mon Aug 6 11:07:06 2012 ManasaUpdate40m UpgradingOptical layout updated

ACAD files of the 40m optical layout have been updated as per the vent in Aug 2011.

Files are available at the 40m svn docs-->Upgrade12-->Opt_Layout2011.

 

  7122   Wed Aug 8 19:54:06 2012 ManasaConfigurationIOOMC trans optics configured

Jan and I wanted to measure the ringdown at the IMC. Since the QPD at the MC trans is not fast enough for ringdown measurements, we decided to install a pickoff to include a faster PD while not disturbing much of the current MC trans configuration. The initial configuration had very little space to accommodate the pickoff. So the collimating lens along with the QPD were moved 2 inches closer to the incoming beam. A 50-50 BS was put in front of the QPD and the steering mirror was moved behind to reflect MC trans output to the new PD. The current configuration is shown below with the MC autolocker threshold mentioned in Jenne's elog

Pic1.png

The hunt for a faster PD wasn't satisfactory and we found a couple of PDs that were good for measurements actually didn't work after installing them. The one currently installed is also not satisfactorily fast enough for ringdown measurements. We'll hunt for faster PDs at Bridge tomorrow and replace PDA400. Also the IMC unlocked from time to time....may be we were noisy and didn't master the 'interferometer walk' very well.

 

 

  7125   Wed Aug 8 20:51:56 2012 ManasaUpdate40m UpgradingOptical layout updated

Quote:

ACAD files of the 40m optical layout have been updated as per the vent in Aug 2011.

Files are available at the 40m svn docs-->Upgrade12-->Opt_Layout2011.

 

 To ease the pain of hunting files, optical layout ACAD files have been moved to a new directory 40M_Optical Layout in the repository. Relevant files from directories Upgrade12 and upgrade 08 will be moved to "40M_Optical Layout" very soon and eventually these old directories will be removed. 

  7127   Wed Aug 8 22:17:43 2012 ManasaConfigurationIOOMC trans optics configured

Quote:

  The PDA255 is a good ringdown detector - Steve can find one in the 40m if you ask him nicely.

 We found a PDA255 but it doesn't seem to work. I am not sure if that is one you are mentioning...but I'll ask Steve tomorrow!

  7140   Fri Aug 10 09:54:51 2012 ManasaConfigurationIOOMC trans optics configured

Quote:

Quote:

  The PDA255 is a good ringdown detector - Steve can find one in the 40m if you ask him nicely.

 We found a PDA255 but it doesn't seem to work. I am not sure if that is one you are mentioning...but I'll ask Steve tomorrow!

 I double checked the PDA255 found at the 40m and it is broken/bad. Also there was no success hunting PDs at Bridge. So the MC trans is still in the same configuration. Nothing has changed. I'll try doing ringdown measurements with PDA400 today.

  7144   Fri Aug 10 15:05:52 2012 ManasaConfigurationIOOMC trans optics configured

Quote:

Quote:

Quote:

Quote:

  The PDA255 is a good ringdown detector - Steve can find one in the 40m if you ask him nicely.

 We found a PDA255 but it doesn't seem to work. I am not sure if that is one you are mentioning...but I'll ask Steve tomorrow!

 I double checked the PDA255 found at the 40m and it is broken/bad. Also there was no success hunting PDs at Bridge. So the MC trans is still in the same configuration. Nothing has changed. I'll try doing ringdown measurements with PDA400 today.

Can you explain more what "broken/bad" means?  Is there no signal?  Is it noisy?  Glitch?  etc.

 The PD saturates the oscilloscope just by switching on the power; with no real signal at all. But Steve helped locating a PD that is not being used at the AP table. So I will check it and replace the current one if it works!

  7159   Mon Aug 13 12:17:41 2012 ManasaConfigurationIOOPD from AP table removed

The PD (pda255) at the AP table, close to the MC refl , which Steve mentioned to be not in use, has been removed from the table for testing.

  7164   Mon Aug 13 19:29:10 2012 ManasaSummary Ringdown measurements

I tried to make ringdown measurements at the IMC using the DC falling edge as the trigger. Input to the MC was switched off by changing the polarity of the MC servo. But it does not seem to give the needed data as there seem to be several DC falling edges as soon as the polarity is switched. We should think about a better trigger or try to setup data recording from the oscilloscope seamlessly.

Also an ethernet cable has been connected to the router from the oscilloscope at the MC trans, but has not been set up to record data yet.

  7200   Wed Aug 15 20:53:48 2012 ManasaUpdateIOORingdown measurements

Quote:

Quote:

While I thought that the bumps observed at the end of the ringdown might be because of the cavity trying to lock itself, Jan commented that they have always existed in these measurements and their source is not known yet.

What I meant to say was that in all ringdown measurements that we observed today, the bumps were consistently part the ringdown, and that I have no explanation for the bumps. It should also be mentioned that fitting the bumpy part of the ringdown instead (we used the clean first 10us), the ringdown time is about twice as high. In either case, the ringdown time is significantly smaller than we have seen in documents about previous measurements.

We (basically I) also made one error when producing the plots. The yaxis label of the semi-logarithmic plot should be log(...), not log10(...).

 I thought about  why we do not find any bumps beyond the exponential fall. Could it be because we neglected fluctuations of voltage in the negative direction and plotted the absolute values?

  7205   Thu Aug 16 16:44:55 2012 ManasaConfigurationIOOPD from AP table removed

Quote:

The PD (pda255) at the AP table, close to the MC refl , which Steve mentioned to be not in use, has been removed from the table for testing.

 The PD installed at MC trans to make ringdown measurements has been replaced with the above PDA255. 

  7206   Thu Aug 16 17:28:51 2012 ManasaConfigurationIOOMC trans optics configured

Quote:

Quote:

Quote:

Quote:

Quote:

  The PDA255 is a good ringdown detector - Steve can find one in the 40m if you ask him nicely.

 We found a PDA255 but it doesn't seem to work. I am not sure if that is one you are mentioning...but I'll ask Steve tomorrow!

 I double checked the PDA255 found at the 40m and it is broken/bad. Also there was no success hunting PDs at Bridge. So the MC trans is still in the same configuration. Nothing has changed. I'll try doing ringdown measurements with PDA400 today.

Can you explain more what "broken/bad" means?  Is there no signal?  Is it noisy?  Glitch?  etc.

 The PD saturates the oscilloscope just by switching on the power; with no real signal at all. But Steve helped locating a PD that is not being used at the AP table. So I will check it and replace the current one if it works!

Koji opened up the PD and found that the screw connecting the PD to the pole was doing an additional job as well; connecting the power cable to the PD output in the inside. The PD is now fixed! Yippie...we have two PDA255 s at 40m now!!

  7222   Fri Aug 17 18:49:55 2012 ManasaUpdate40m UpgradingOptical layout updated

Quote:

Quote:

ACAD files of the 40m optical layout have been updated as per the vent in Aug 2011.

Files are available at the 40m svn docs-->Upgrade12-->Opt_Layout2011.

 

 To ease the pain of hunting files, optical layout ACAD files have been moved to a new directory 40M_Optical Layout in the repository. Relevant files from directories Upgrade12 and upgrade 08 will be moved to "40M_Optical Layout" very soon and eventually these old directories will be removed. 

Changes mentioned by Koji and Steve have been updated to the files (except for the cable connector which have been added but whose part number has to be found to match accurately with the current layout). The file in the directory should now match the current setup after the last vent Aug 2011.

Let me know if you find any mismatch between the current setup and the layout.

Plans about new installations/reconfiguration during the new vent will be carried out in a separate file.

  7245   Tue Aug 21 18:23:58 2012 ManasaUpdate40m UpgradingETMX table layout

Optical layout of the current endtable at ETMX has been updated in the svn repository (directory: 40M_Optical Layout). This layout will help in redesigning the table for the proposed replacement.

Some part numbers of mounts/optics are missing and will be updated once I find them. If you find anything wrong with the layout, do let me know.

 

  7256   Thu Aug 23 12:17:39 2012 ManasaUpdate IMC Ringdown

The ringdown measurements are in progress. But it seems that the MC mirrors are getting kicked everytime the cavity is unlocked by either changing the frequency at the MC servo or by shutting down the input to the MC. This means what we've been observing is not the ringdown of the IMC alone. Attached are MC sus sensor data and the observed ringdown on the oscilloscope.  I think we need to find a way to unlock the cavity without the mirrors getting kicked....in which case we should think about including an AOM or using a fast shutter before the IMC.

P.S. The origin of the ripples at the end of the ringdown still are of unknown origin. As of now, I don't think it is because of the mirrors moving but something else that should figured out.

  7260   Thu Aug 23 17:51:25 2012 ManasaUpdate IMC Ringdown

Quote:

 

 It is HIGHLY unlikely that the IMC mirrors are having any effect on the ringdown. The ringdowns take ~20 usec to happen. The mirrors are 0.25 kg and you can calculate that its very hard to get enough force to move them any appreciable distance in that time.

The huge kick observed in the MC sus sensors seem to last for ~10usec; almost matching the observed ringdown decay time. We should find a way to record the ringdown and the MC sus sensor data simultaneously to know when the mirrors are exactly moving during the measurement process. It could also be that the moving mirrors were responsible for the ripples observed later during the ringdown as well.

* How fast do the WFS respond to the frequency switching (time taken by WFS to turn off)? I think this information will help in narrowing down the many possible explanations to a few.

  7330   Fri Aug 31 17:44:21 2012 ManasaUpdateRingdownData

Quote:

Ok, so the whole idea that mirror motion can explain the ripples is nonsense. At least, when you think off the ringdown with "pump off". The phase shifts that I tried to estimate from longitudinal and tilt mirror motion are defined against a non-existing reference. So I guess that I have to click on the link that Koji posted...

Just to mention, for the tilt phase shift (yes, there is one, but the exact expression has two more factors in the equation I posted), it does not matter, which mirror tilts. So even for a lower bound on the ripple time, my equation was incorrect. It should have the sum over all three initial tilt angles not only the two "shooting into the long arms" of the MC.

Quote:

Laser frequency shift = longitudinal motion of the mirrors

Ringing: http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-20-24-2463

Quote:

Hmm. I don't know what ringing really is. Ok, let's assume it has to do with the pump... I don't see how the pump laser could produce these ripples. They have large amplitudes and so I always suspected something happening to the intracavity field. Therefore I was looking for effects that would change resonance conditions of the intracavity field during ringdown. Tilt motion seemed to be one explanation to me, but it may be a bit too slow (not sure yet). Longitudinal mirror motion is certainly too slow. What else could there be?

 

 

It is essential we take a look at the ringdown data for all measurements made so far to figure out what must be done to track the source of these notorious ripples. I've attached the plot for the same showing the decay time to be the same in all cases. About the ripples; it seems unlikely to both Jan and me that the ripples are some electronic noise because the ripples do not follow any common pattern or time constant. We have discussed with Koji about monitoring the frequency shift, the input power to the MC and also try other methods of shutting down the pump to track their source as the next steps.

 

cum_plot.png 

  7336   Tue Sep 4 13:44:17 2012 ManasaUpdateGeneralThe Plan

Quote:

We need a plan for the rest of the week.  I want to be closing the heavy doors on Friday at the latest.  Please add to / comment on this list!

 

Tues

* Lock MICH to get BS, ITMs aligned well

* Check if beam is hitting center of ITMs. 

* Check for clipping around BS

     - Use Watek in-vac to look at beam at all 4 BS ports - make sure no clipping going into BS, after BS in the michelson, or the AS port

* Try to get arms to flash??

* Prepare glass beam dumps??

Wed

* IPPOS / IPANG - make sure beam gets out of chambers (this may require opening ETMY)

* Jan take photos of ETMX scattering setup

* Manasa take in-vac photos of all tables, for table layouts

* Install glass beam dumps?

* If ETMY open, install glass baffle

* ????

Thurs

* ????

* Check table levelling one last time on all tables. 

Fri

* Close all heavy doors.  (Access connector, ITMX, ITMY, BS, ETMX, ETMY? )

* Start at ~10am?

Mon (if not Fri)

* Start pumping

Wed

* Jan/Manasa - Measure transmission of viewport at ETMX

 

 

 

 

 

  7354   Thu Sep 6 19:21:58 2012 ManasaConfiguration40m UpgradingBaffle problem

For the current baffle (dia. 40mm) centered along the beamline place at 1.77" from the test mass, the baffle will allow ~8.6mm visibility on the camera from the center of the test mass (in case of ETMY).

*assuming the pick off mirror is placed at the edge of the tunnel

  7359   Fri Sep 7 11:58:12 2012 ManasaConfiguration40m UpgradingBaffle problem

Quote:

The required diameter for the baffle if it sits on the cage at 1.77" from the test masses: the current baffle (dia. 40mm) centered along the beamline, will allow ~8.6mm visibility from the center of the test mass (in case of ETMY).

*assuming the pick off mirror is placed at the edge of the tunnel

Estimations of the visibility region (r1 on the test mass) with baffle (aperture size 40mm).

The baffle is installed on the cage at 1.125" from the test mass (distance changed from the previous elog after a double check).

The 40mm aperture is in no way going to help get clear view of the ITMs; 

  7361   Fri Sep 7 13:01:53 2012 ManasaConfiguration40m UpgradingBaffle problem

Quote:

Quote:

The required diameter for the baffle if it sits on the cage at 1.77" from the test masses: the current baffle (dia. 40mm) centered along the beamline, will allow ~8.6mm visibility from the center of the test mass (in case of ETMY).

*assuming the pick off mirror is placed at the edge of the tunnel

Estimations of the visibility region (r1 on the test mass) with baffle (aperture size 40mm).

The baffle is installed on the cage at 1.125" from the test mass (distance changed from the previous elog after a double check).

The 40mm aperture is in no way going to help get clear view of the ITMs; 

Required baffle diameter to have a visibility region r1 = 3 times the beam diameter

Picture1.png

  7403   Tue Sep 18 20:32:42 2012 ManasaConfigurationPSLAOM installation

 {Jan, Manasa}

We tried towards calibrating the RF driver of the AOM. We decided to use the normal power supply for both the driver control voltage and the ALC voltage.  But we could not figure out the type of the ALC port to find a compatible mating connector...it did not match with SMA, SMB or SMP. Finally I wrote to the company and got to know it is a filtered feed through. Now that we know how to control the ALC voltage, we will try looking at the signal for varying ALC voltage and see how that goes. 

But when we tried to see the 2W RF signal through the RF scope, with ALC open, we found that the RF signal was distorted and did not measure 80MHz.  It was lame that we did not get a snapshot 

P.S. The AOM has been left disconnected from the RF driver. 

  7409   Wed Sep 19 11:39:37 2012 ManasaConfigurationPSLAOM installation

Quote:

 {Jan, Manasa}

We tried towards calibrating the RF driver of the AOM. We decided to use the normal power supply for both the driver control voltage and the ALC voltage.  But we could not figure out the type of the ALC port to find a compatible mating connector...it did not match with SMA, SMB or SMP. Finally I wrote to the company and got to know it is a filtered feed through. Now that we know how to control the ALC voltage, we will try looking at the signal for varying ALC voltage and see how that goes. 

But when we tried to see the 2W RF signal through the RF scope, with ALC open, we found that the RF signal was distorted and did not measure 80MHz.  It was lame that we did not get a snapshot 

P.S. The AOM has been left disconnected from the RF driver. 

 {Jan, Manasa}

We started again to calibrate the RF driver. We connected the ALC to the power supply and observed the output RF power on the scope. The RF power did change with ALC voltage, but the RF signal still seems not to be operating at 80MHz 

There is some kind of additional disturbance to the waveform at 80MHz (the frequency of just the waveform with tall peaks or small peaks alone). We made sure we get a snapshot this time!! I am not sure if it will be safe to feed this RF signal to the AOM as such

ALC_25.png

  7411   Wed Sep 19 15:41:27 2012 ManasaConfigurationPSLAOM installation

 

 AOM driver has been removed from the PSL table for testing. However the AOM is still inside; so there should be no problems with the alignment. 

  7416   Thu Sep 20 01:29:04 2012 ManasaConfigurationPSLAOM installation

Quote:

Mannasa and Unni and I looked at the RF driver for the AOM. It was fine.

With the ALC input left unconnected, with the power supply set to +28V, it was drawing 0.56 A.

By adjusting the modulation input we were able to get 1.1 Vrms into the scope (terminated at 50 Ohms) after going through 2 10dB attenuators. 11 Vrms into 50 Ohms is 33.8 dBm ~ 2W.

The RF power trimpot on the front of the driver is now adjusted so that -0.31 to 0.69 V takes the driver output from off to 2W output at 80 MHz.

 

The previous distorted signal that Jan and Manasa saw was at a level of ~100 mVrms, which is ~0.5 mW of power. At this tiny drive level, the internal amplifier is not linear and is mostly putting out a signal at ~160 MHz.

 

We checked by putting a square wave into the modulation input that the RF power from the driver would indeed shut off with a time scale of ~20 ns. Manasa will add a picture to this entry. We are ready now to calibrate the transmitted power of the AOM v. the modulation input voltage and then to measure the step time of the AOM.

Remember: do NOT believe the spec sheet of whatever PD you are using. All commercial PDs are slower than they advertise. In order to measure a <1 us step time you must use a PD with a >50 MHz 'bandwidth'.

  7417   Thu Sep 20 08:34:46 2012 ManasaUpdateGeneralDRMI aligned again, but with good arms

Quote:

[Jenne, Manasa]

Using the alignment of the PZTs and BS from pre-dinner, where the beam was hitting the center of both ETMs, we aligned the DRMI.  The beam was off on the SRM in yaw by ~half a beam diameter, so I undid Koji's movement of SR2 from a week ago.  I loosened the SR2 dog clamps, touched it gently on the base to do a little bit of angle, then re-clamped it.  Once again, Steve's new brass centering target was awesome, since it was on the SRM while I was moving SR2. 

We approximately recentered the beam on the AS camera, although it didn't need much once we got the beam out of the vacuum, by centering it on all of the output AS path mirrors.

We also got IPPOS out of the vacuum.  Manasa was in the process of centering the QPD when the laptop died from too long being unplugged, so we leave that for tomorrow.

Left to do:

REFL path.  REFL is not coming out of the vacuum, and with the light access connector I can't reach any of the REFL steering mirrors, since they're in the center of the IOO table.

IPANG.  Should be easy.

POP, POX, POY.  Need to the the camera-on-a-stick back down to the corner (from ETMY) and point it at the pickoff mirrors to ensure that beam is getting out of the vacuum.

 Steve!! The light access connector got more ripped during the work last night...we've just taped it back. We might need  to figure out a better way to do this than just cutting through the cover.

  7419   Thu Sep 20 11:39:40 2012 ManasaUpdateGeneralDRMI aligned again, but with good arms

 

 QPD at IPPOS has been centered by removing the filter at the QPD.

So we need to remember to check back on AS camera path and the IPPOS as well in addition to the usual MCrefl path.

P.S. We would be happy to have a new laptop in the lab to replace "Belladonna"!

  7425   Fri Sep 21 12:12:56 2012 ManasaConfigurationPSLAOM installation

    {Jan, Manasa}

We installed the AOM driver back on the PSL table this morning. To calibrate the AOM RF output we connected a 1V dc to the modulation input of the driver and we are convinced with the setup.

Before we direct the rf signal to the AOM, in order to check its diffraction efficiency, we would like to setup an rf PD at the AOM output. We think we have place for a filter and PD after the AOM (replacing a beam dump) and would like to confirm the position before we actually install them. The layout is the picture below showing sweet spots for the new pd to sit. If you think it may disturb the system in any way, let us know!

PSL.png

  7449   Thu Sep 27 19:03:06 2012 ManasaUpdate40m UpgradingNew ETMX layout - Version 1.0

 I am working towards redesigning the endtables. I've attached the first version of the layout. As per Steve's comment I've tried to leave a 2" empty space on all sides of the table. It still has to be updated with the whole 40m layout to be more precise about the pickoff and the ingoing beam directions.

  7462   Tue Oct 2 14:20:33 2012 ManasaConfigurationIOOPDA255 not working

The PDA255 that Koji repaired is still not alright. It seems to be saturating again. I've left it in the PD cabinet where it is marked 'PDA 255'. I've asked Steve to order a fast PD at 150MHz, PDA10A because we don't seem to have any at the 40m.

  7464   Tue Oct 2 16:15:22 2012 ManasaConfigurationPSLAOM installation

Quote:

    {Jan, Manasa}

We installed the AOM driver back on the PSL table this morning. To calibrate the AOM RF output we connected a 1V dc to the modulation input of the driver and we are convinced with the setup.

Before we direct the rf signal to the AOM, in order to check its diffraction efficiency, we would like to setup an rf PD at the AOM output. We think we have place for a filter and PD after the AOM (replacing a beam dump) and would like to confirm the position before we actually install them. The layout is the picture below showing sweet spots for the new pd to sit. If you think it may disturb the system in any way, let us know!

 

The rf PD and filter have been installed at the earlier proposed spot on the PSL table.  

psl_aom.png

  7470   Wed Oct 3 16:26:58 2012 ManasaUpdatePEMants on the PSL table

I spotted around 4 within 30 minutes working at the PSL table even after the deathly spray. They seem to be running down from the cables on the oscilloscope rack to the table and the optics.

  7471   Wed Oct 3 16:52:16 2012 ManasaConfigurationPSLAOM installation

{Jan, Manasa}

We set start to check the performance of the AOM on the PSL table. The AOM driver spits out ~1.5W rf at 80MHz for 1V DC at its modulation input. In order to align the AOM, we reduced the input power to the AOM to ~10% using the QWP between the PBS and the laser. We touched the steering mirror before the AOM...but did not succeed in getting any appreciable first order deflection. We then released the AOM mount and moved it a few microns in and out until we obtained a significant change in power along the zero-order beam from 400mV to 100mV when the rf power was changed from 0 to ~1.5W (by changing modulation input from 0 to 1V).  The AOM was clamped at this alignment and the QWP was rotated to give maximum input power. 

During the course of aligning the AOM, the PMC unlocked and was restored after the alignment. 

All went well without having to make any emergency calls to anyone

We will now have to think about switching the AOM on and off for ringdown measurements. This could be done by either using a high-power rf switch or by switching the modulation DC input between 0 and 1V; whichever will be more comfortable to take many many ringdown measurements.

 

  7479   Thu Oct 4 17:54:59 2012 ManasaConfigurationPSLAOM installation

Quote:

After the AOM work the beam wasn't well aligned to the PMC. The PMC REFL CCD shows large misalignment in yaw.

 {Jan, Manasa, Den}

We wanted to align the PMC and followed Koji's procedure detailed to us by mail. We touched the 2 steering mirrors in front of the PMC for alignment.

- Stand in front of the PMC.
- Find an oscillosocpe on the shelf in the PSL enclosure.
- This has two signals connected. One is the PMC refl dc.
  The other is the PMC trans dc.
- Minimize the refl. Maximize the trans.
- You have the CRT monitor on the MC chamber.
- Project the image of the PMC refl CCD.
  This should show some what symmetric image like an LG mode.
- Use the dataviewer to see how C1:PSL-PMC_PMCTRANSPD is recovered.

We were able to obtain 0.7 at PMC trans; but the PMC was never really stable dropped from 0.7 to 0 abruptly from time to time.

Jenne and Jamie also find that the PMC is behaving very weird 

Summary: Problem unresolved 

 

  7481   Thu Oct 4 20:57:43 2012 ManasaConfigurationPSLAOM installation

Quote:

Quote:

Jenne and Jamie also find that the PMC is behaving very weird 

 Can someone detail what "weird" means? Is it singing old songs from Guns & Roses?

 It isn't singing Jan..it's dancing between 0.7 to 0 and we are not able to figure out whose the DJ ; there seems to be something else that is controlling the PMC as there is no coordination between what we do (tweaking the mirrors) and what we observe (the PD signals).

  7494   Fri Oct 5 18:08:17 2012 ManasaConfigurationPSLAOM installation

Quote:

Do more investigation to understand what is causing the power reduction.

Is the alignment inadequate? Check the in-lock ccd image.

Is the incident power reduced? (by what?) Use dataviewer.

Is the AOM doing something? Is it active? Then how much power is it eating?

BY THE WAY, how the deflected beam is dumped?
If you don't have anything for blocking the 1st order beam, you have to expect Steve coming to you.

The PMC has been aligned and is all happy happy 

I have installed an  iris to dump the higher order beams deflected by the AOM. After installing the iris, I found that the PMC trans dropped to 0.58V and the PMC misaligned in pitch. So I've touched the 2 steering mirrors before the PMC. Now it is satisfactorily locked with PMC trans at 0.84.

I have also checked the alignment with AOM switched on. PMC trans drops to 0.15 with AOM on and comes back to 0.84 when AOM is switched off without losing lock .

  7600   Tue Oct 23 17:41:20 2012 ManasaUpdateAlignmentPower supply at OMC removed

Quote:

Manasa and Raji hooked up HV power supplies to the PZTs and set them to the middle of their ranges (75 V).

 [Raji, Manasa]

The high-voltage power supply from the OMC was removed to replace one of the PZT power supplies. The power supply terminals were connected to the rear connection ports as per instructions from the manual (TB1 panel: port 3 - (-)OUT and port7 - (+)OUT). They were both switched  on and set to deliver (75V) to the PZTs.

 

ELOG V3.1.3-