The new dolphin eventually helps us. But the installation is an invasive change to the existing system and should be done at the installation stage of the 40m BHD.

That's great news we won't have to worry about a new timing fanout for the two new machines, c1bhd and c1sus2. And there's no plan to change Dolphin IPC drivers. The plan is only to install the same (older) version of the driver on the two new machines and plug into free slots in the existing switch.

Problem:

We had timing problems across the front ends.

Solution:

Noticing that the 1PPS reference was not blinking on the Master Timing Distribution box.  It was supposed to be getting a signal from the c0dcu1 VME crate computer, but this was not happening.

We disconnected the timing signal going into c0dcu1, coming from c0daqctrl, and connected the 1PPS directly from c0daqctrl to the Ref In for the Master Timing distribution box (blue box with lots of fibers coming out of it in 1X5).

We now have agreement in timing between front ends.

After several reboots we now have working RFM again, along with computers who agree on the current GPS time along with the frame builder.

Status:

RFM is back and testpoints should be happy.

We still don't have a working binary output for the X end.  I may need to get a replacement backplane with more than 4 slots if the 1st slot of this board has the same problem as the large boards.

I have burt restored the c1ioo, c1mcs, c1rms, c1sus, and c1scx processes, and optics look to be damped.

[J Hanks (remote), koji, gautam]

Summary:

The problem stems from the way GPS timing signals are handled by the FEs and FB. We effected a partial fix:

• Now, old frame data is no longer being overwritten
• For the channels that are indeed being recorded now, the correct time stamp is being applied so they can be found in /frames by looking for the appropriate gpstime.

Details:

• The usual FE/FB power cycling did not fix the problem.
• The gps time used by FB and associated RT processes may be found by using  cat /proc/gps (i.e. this is different from the system time found by using date, or gpstime).
• This was off by 2 years.
• The way this worked up till now was by adding a fixed offset to this time.
  • This offset can be found as a line saying set symm_gps_offset=31622382 in daqdrc.fw (for example)
  • There were similar lines in daqdrc.rcv and daqdrc.dc - however, they were not all the same offset! We couldn't figure out why.
  • All these files live in /opt/rtcds/caltech/c1/target/daqd/.

Changes effected:

1. First, we tried changing the offset in the daqdrc.fw file only.
   • Incremented it by 24*60*60*365 = number of seconds in a year with no leap seconds/days.
   • This did not fix the problem.
2. So J Hanks decided to rebuild the Spectracom driver - these commands may not be comprehensive, but I think I got everything).
   • The relevant file is spectracomGPS.c (made a copy of /usr/src/symmetricom-3.3~rc1, called symmetricom-3.3~rc1-patched, this file is in /usr/src/symmetricom-3.3~rc1-patched/include/drv)
   • Added the following lines:
     /* 2018 had no leap seconds or leap days, so adjust for that */
            pHardware->gpsOffset += 31536000;
   • re-built and installed the modified symmetricom driver.
   • Checked that cat /proc/gps now yields the correct time.
   • Reset the gps time offsets in daqdrc.fw, daqdrc.rcv and daqdrc.dc to 0
   • With these steps, the frames were being written to /frames with the correct timestamp.
3. Next, we checked the timing on the FEs
   • Basically, J Hanks rebuilt the version of the symmetricom driver that is used by the rtcds models to mimic the changes made for FB.
   • This did the trick for c1lsc and c1ioo - cat /proc/gps now returns the correct time on those FEs.
   • However, c1sus remains problematic (it initially reported a GPS time from 2 years ago, and even after the re-installed driver, is 4 days behind) - he suspects that this is because c1sus is the only FE with a Symmetricom/Spectracom card installed in the I/O chassis. So c1sus reports a gpstime that is ~4 days behind the "correct" gpstime.
   • He is going to check with Rolf/other CDS experts to figure out if it's okay for us to simply remove the card and run the models, or if we need to take other steps.
   • As part of this work, the c1x02 IOP model was recompiled, re-installed and re-started.

The realtime models were not restarted (although all the vertex FEs are running) - we can regroup next week and decide what is the correct course of action.

Summary:

The gps time mismatch between /proc/gps and gpstime seems to be resolved. However, the 0x4000 DC errors still persist. It is not clear to me why.

Details:

On the phone with J Hanks on Friday, he reminded me that c1sus seems to be the only machine with an IRIG-B timing card installed. I can't find the elog but I remembered that Jamie, ericq and I had done this work in 2016 (?), and I also remembered Jamie saying it wasn't working exactly as expected. Since the DAQ was working fine before this card was installed, and since there are no problems with the recording of channels from the other four FE machines without this card installed, I decided to simply pull out the card from the expansion chassis. The card has been stored in the CDS/FE cabinet along the Y arm for now. There was also a cable that interfaces to the card which brings over the 1pps from the GPS unit, which has also been stored in the CDS/FE cabinet.

This seems to have resolved the mismatch between the gpstime reported by cat /proc/gps and the gpstime commands - Attachment #1 (the <1 second mismatch is presumably due to the deadtime between commands). However, the 0x4000 DC errors still persist. I'll try the full power cycle of FEs and FB which has fixed this kind of error in the past, but apart from that, I'm out of ideas.

Update 1215:

Following the instructions in this elog did not fix the problem. The problem seems to be with the daqd_fw service, which reports the following:

Update 1530:

The frame-writer error was tracked down to a C0EDCU issue. Jon told me that the Hornet CC1 pressure gauge channel was renamed to . C1:Vac-CC1_pressure, and I made the change in the C0EDCU file. However, it returns a value of 9990000000.0, which the frame writer is not happy about... Keeping the old channel name makes the frame-writer run again (although the actual data is bunk).

Update 1755:

J Hanks suggested adding a 1 second offset to the daqdrc config files. This has now fixed the 0x4000 errors, and we are back to the "nominal" RTCDS status screen now - Attachment #2.

I started a GPS timing monitor script, /opt/rtcds/caltech/c1/Git/40m/scripts/cds/tempusTimingMon/tempusTimingMon.py, which runs inside a docker container on optimus. It accesses the GPS receiver (EndRun Tempus LX) status via pysnmp, and creates the following epics channels with pcaspy:

• C1:DAQ-GPS_TFOM “The Time Figure of Merit (TFOM) value ranges from 3 to 9 and indicates the current estimate of the worst case time error. It is a logarithmic scale, with each increment indicating a tenfold increase in the worst case time error boundaries.” (nominally 3, corresponding to 100 nsec)
• C1:DAQ-GPS_STATE “Current GPS signal processor state. One of 0, 1 or 2, with 0 being the acquisition state and 2 the fully locked on state.”
• C1:DAQ-GPS_SATS “Current number of GPS satellites being tracked.”
• C1:DAQ-GPS_DAC “Current 16 bit, Voltage Controlled TCXO DAC value. Typical range is 20000 to 40000, where more positive numbers have the effect of raising the TCXO frequency.”
• C1:DAQ-GPS_SNR “The current average carrier to noise ratio of all tracked satellites, in units of dB. Values less than 35 indicate weak signal conditions.”

Attached is a 1-day trend of the above channels, along with the IRIG-B timing offsets from the IOPs. No big timing excursions or slippages were seen yet, although the c1sus IOP (FEC-20) timing seems to be hopping around by one IOP sample time (15 µsec).

While recovering from the power outage, I took the opportunity to try having the timing system trigger on the rising edge of the 1 PPS signal from the GPS receiver (rather than the falling edge, as it had been doing since before the CDS upgrade). This was done in order to eliminate a timing offset between the clock used by the ADCs and the IRIG-B timestamps from the Spectracom boards. It was successful in that regard, and cleared the timing errors seen in the IOP statewords on most of the front ends.

The two exceptions were c1lsc and c1sus, where something is broken with the DuoTone readbacks. The attached plot shows the DuoTone signal in the last channel of ADC 0 on c1x01 (working normally) vs c1x02 and c1x04 (busted).

However, this change apparently also had some unexplained effect on the way the c1sbr model runs. There were frequent CPU time overruns and IPC errors. So on Sunday afternoon I reverted to the falling-edge trigger. This caused the timing errors to return, but allowed c1sbr to run normally.

Located in /opt/rtcds/caltech/c1/userapps/release/cds/common/scripts

Script 1: Diagreset.sh
Hits the diag reset buttons on the models on c1lsc and c1sus computers.

Script 2: Burtrest.sh
Restores the burt files from "today" 4am. Use a text editor if you want to change the times.

[Jenne, Kyung Ha]

We successfully suspended the 4 eddy current dampers for the first Tip Tilt.  We had some lessons learned, including how to carefully get an allen wrench in between the dampers to do up some of the screws, and how to be careful not to bend the wire while tightening the screws.  More tomorrow...

 We also wrote down the serial numbers (top center of each TT, inscribed by hand) for what tip tilt is installed where.  I then went through the elog to determine which TT was suspended with what kind of wire (thick or thin).  Summary: all installed tip tilts have thick wire, 0.0036" diameter.

As noted in elog 3295, we had found that there was similar hysteresis whether we used the thick or the thin wire, so we had decided not to go back and re-suspend every optic.

Also, since we will redo the pitch balance tomorrow with the new hardware tomorrow, I think we should put in the new LaserOptik mirrors at the same time.  We have not yet gotten phase maps of them, but we might as well do this rebalancing once, rather than twice.

Jamie and I spent some time with tip tilt SN001 this afternoon.  This was installed as SR3, so I was going to put a new LaserOptik mirror in there.  I accidentally snapped one of the wires (I forgot how strong the magnets are - one zipped from the mirror holder and captured the wire).  Jamie and I put the new LaserOptik mirror in, with the wedge correct, but we need to re-resuspend it with the 0.0036" wire tomorrow.  We'll also keep working on re-pitch aligning the other optics.

PR2 needs to be put back as a G&H, and we need to put a LaserOptik mirror into PR3.

 We resuspended SN001 this morning with 0.0036" wire.  We did as Koji suggested, and flipped the wire clamp so the suspension point is a little higher, so we'll see if that helps.  We put LaserOptik mirror SN1 into this TT001.

We put the G&H mirror back into TT004, which is PR2.  We also put a LaserOptik mirror (SN5) into TT005, which is SR3.

Jamie is working on re-pitch aligning TT004 and TT005 (we already did 001), then we can re-install them in the vacuum system later this afternoon.

 The tip tilts have all been pitch-adjusted now, and they have all been put back onto the tables, with the same serial numbers in the same places as we took them out.  Jamie also re-leveled the BS table.

Raji and I will align things after I finish measuring the MC spot positions.

I have made a preliminary sketch of the cabling involved in connecting the Tip-tilt coil drivers.   This is a preliminary document. 

2 questions (so far) regarding your diagram / doc:

We are using 3 of the feed-throughs on the BS chamber, and 1 on the OMC chamber, even though we have 2 TTs on the BS table, 1 on the OMC table, and 1 on the IMC table? Just wanted to check.

Does your list / table at the bottom include all of the cables we already have, as well as the ones we need?  (Or maybe we just have nothing so far, so this is a moot question).

 The scheme currently is to run a 25pin Kapton strip cable from BS to IMC table inside the chamber.  However we cannot do the same for the OMC table since it will cross the bellows which we often remove.  So we need to supply the one tip-tilt on the OMC table from outside.  I could not spot a spare unused feedthough on the OMC chamber.  We will have to swap one of the blank flanges for one with a few feed throughs.

We do not have any of the cables.   So everything listed has to be arranged for.   The pics are from the existing coil driver system on the SUS machine.

Arnaud and I moved one of the two spare TT suspensions from the south clean cabinet to the bake lab clean room. The main purpose was to inspect the contents of the packaging. According to the label, this suspension was cleaned to Class A standards, so we tried to be clean while handling it (frocks, gloves, masks etc). We found that the foil wrapping contained one suspension cage, with what looked like all the parts in a semi-assembled state. There were no OSEMs or electronics together with the suspension cage. Pictures were taken and uploaded to gPhoto. Arnaud is going to plan his tests, so in the meantime, this unit has been stored in Cabinet #6 in the bake lab cleanroom.

Recent History

The lower blades which I had given to the Physics Workshop for making a vacuum relief hole (using a sinker-EDM process) came back about ten days ago.   Merih Eken <meken@caltech.edu>,  the supervisor at the Physics Dept workshop, handled this matter for us.  The blades were sent to a local EDM machineshop and returned in about three working days ( a weekend intervened). 

Bob cleaned and handed them over to me yesterday evening.  

Current status

Today I have reassembled the four tip-tilts.  I have repacked them in clean bags (double bagged) shifted them to Clean Optics Cabinet (near the ETMX chamber).  The four tip-tilts are in the bottom-most shelf in the cabinet.  There are also some tip-tilt spares in a separate envelope.

Note:  The mirror holder is now held tightly by the eddy current dampers.  This was done for safety of the wires during transportation from LHO.  The eddy current damper in the front of the mirror has to be retracted to allow the mirror holder to swing free.  It has be to about 1mm away from the suspended mirror holder

Work Remaining

1) We need to install the quadrapus cables.  The connector placement on the BOSEM side will have some issues.  It is best to loosen the BOSEM seating as well as the connector seating screws and then push the cable connector into place.  Caution:  when the connector seating screws on the BOSEM are loosened the flexible ckt could be damaged by the loose connector.

2) Insert the mirrors into the mirror holders and balance the suspension such that the mirror's hang vertical and do not have a large yaw offset.

3) Adjust the wire suspension point height so that the flags are in the center of the BOSEM aperture.  Else they will strike against the

4) We need to adjust the position of the BOSEMs such that the shadow sensor signals are at 50%.  This ensures that all the magnets hang at an appropriate distance from their respective coils.

5) To do (3) we need to set up a shadow sensor read-out set-up for one tip-tilt (four sensors)

Final Summary of changes to mirror holder in Tip-Tilt holder.

Determining minimum range for Side Clamp:

1. The initial distance b/w wire-release point and mirror assembly COM = 0.265 mm

2. But this distance is assuming that wire-release point is at mid-point of clamp. So I'm settling on a range of +/- 1mm. The screenshots below confirm range of ~1mm between (1) side screw & protrusion and (2) clamp screw and clamp.

Determining length of tilt-weight assembly rod at the bottom to get 20mRad range

The tilt-weight assembly is made from following Mcmaster parts:
Rod   - 95412A864 18-8 SS  #2-56 Threaded Rod
Nuts  - 91855A103 18-8 SS #2-56 Acorn Cap Nut

Since the weights are fixed, only rod length can be changed to get the angle range.

So a range of 1 mm between nut's inner face and mirror-holder face should be enough. Since holder is 12 mm thick, rod length = 12mm + 2 x 1mm + 2 x (nut length) = 12 + 2 + 9.6 = 23.6 mm = 0.93 inch. So a 1" rod from Mcmaster will be fine.

Here are some tasks that I want someone to work on during my absence.

1. Y-arm alignment for IR

 Basically we gradually have to move onto the Y-arm locking at some point.

Prior to it we need to align the Y arm for IR. Probably we have to touch PZT1 and PZT2.

It would be very nice if the X-arm alignment also gets improved together with this work. 

2. Temperature feedback with a digital control for X end PDH lock

  Need a temperature feedback not with an analog way but with a digital way because we want to put an offset and the feedback signal at the same time (#4198).

 Right now the temperature control input of the laser is connected to a slow DAC (#3850).

Probably we should plug the feedback signal from the PDH box to the fast ADC (i.e. c1iscex), and then connect a fast DAC to the laser temperature.

This entry maybe helpful.

3. Calibration of optical gain for IR arm locking

 In order to evaluate the performance of the green locking, one of the key points is the IR PDH signal.

Because it tells us how much the motion of the X arm is suppressed at IR when the green lock is engaged.

To get this information in m/sqrtHz, we need to know the optical gain.

4. MC servo characterization and PSL frequency noise measurement

 SInce the green beat note tells us the frequency difference between the MC and the arm in the current configuration, we should know how the MC servo is.

Along with this work, I need someone to measure the PSL frequency noise, when it is locked to the MC over the frequency range from 0.01Hz to 1kHz.

5. PLL characterization 

 Solve this issue (#4195) and make it reliable.

1) Fixup REFL165: remove ND filters, get box for PD, dump diode reflections, put less light on diode, change DC transimpedance (?), max power dissipation on BBPD < 0.5 W w/ 25 V bias. Perhaps replace OP27 with TLE2027.

2) Make plan for fixing fiber layout up and down the arms. Need tubing for the whole run. Don't make it cheesy. Two fibers per arm.

3) Fix LSC model to allow user switching of whitening. Get back to working on AutoLock scripts (not Guardian).

4) Manasa, Q, Jenne, tune Oplev servos Tuesday morning/afternoon.

5) Reconnect the other seismometers (Steve, Jenne). For real.

6) Balance PRMI coils at high frequency.

This is just a listing of  CDS problems I still notice today:

1. MC2-MCL button was left ON due to BURT failure. This, of course, screws up our Green locking investigations because of the unintended feedback. Please fix the BURT/button issue.

2. The GCV - FB0 status is RED. I guess this means there's something wrong? Its really a bad idea to have a bunch of whited out or falsely red indicators. No one will ever use these or trust these in the future.
3. MC1/2/3 Lockins are all white. Also, the MODE switches for the dewhitening are all white.
4. Is the MC SIDE coil dewhitening filter synced with anything? It doesn't seem to switch anything. Maybe the dewhite indicators at the top right of the SUS screens can be made to show the state of the binary output instead of just the digital filter
5. MC WFS is all still broken. We need a volunteer to take this on - align beams, replace diodes, fix code/screens.

  I am concentrating on the RF system just now and will be attending to the RF PDs one by one.  Also plan to work on some of the simpler CDS problems when I overlap with Joe.  Will be available for helping out with the beam alignment.

1. ETMX cannot load his filter coefficients. Even if I change the file, the load button doesn't work. I tried changing the lockin filters but they won't load.
2. The ETMX filter modules appear to have 2048 for some of the modules and 16384 for some of the others. How come the make script doesn't make them all 16384?
3. There are a bunch of kill/start scripts in the scripts/ directory instead of in the scripts/FE/ directory. Did this get reverted after a new code exchange?
4. I tried restarting the code using c1startscx, but that doesn't work correctly. It cannot find the burtrb and burtwb files even though they are in the normal path.
5. Kiwamu was using a bunch of cockamamie filters I found.
6. I can't get any minute trend data. I tried on rossa, rosalba, and op440m.

inline cdsToggle /opt/rtcds/caltech/c1/userapps/release/cds/common/src/cdsToggle.c

void cdsToggle(double *in, int inSize, double *out, int outSize){
  static double x = 0;
  static double y = 0;

  if (*in != y){
    y = *in;
    if (y == 1){
      x = (x == 1) ? 0 : 1;
      *out = x;
    }
  }
}

The toilet tank in the big bathroom stopped refilling. I contacted PPService@caltech.edu and put up an "Out of Order sign".

a plumber came in yesterday and fixed the issue.

 Required arm length = 37.7974 +/- 0.02 [m]

This is a preliminary result of the estimation of the Arm length tolerance.

Figure.2  A sensing matrix of the 40-m DRFPMI while changing the position of ETMX/Y by \sigma = 2 cm.

wow. This Monte-Carlo matrix is one of the most advanced optical modeling things I have ever seen. We never had this for any of the interferometers before.

Keiko, Kiwamu

We noticed that we have used wrong code for MICH degree of freedom for both of the ELOG entries on this topic (cavity lengths tolerance search). It will be modified and posted soon.

 Keiko, Kiwamu

Length tolerance of the vertex part is about 5 mm.

Sorry for my procrastinating update on this topic. In my last post, I reported that the length tolerance of the vertex ifo would be 2mm, based on Kiwamu's code on CVS. Then we noticed that the MICH degrees of freedom was wrong in the code. I modified the code and ran again. You can find the modified codes on CVS (40m folder, analyzeDRMITolerance3f.m and DRMITolerance.m)

In this code, the arm lengths were kept to be ideal while some length offsets of random gaussian distribution were added on PRCL, SRCL and MICH lengths. The iteration was 1000 times for each sigma of the random gaussian distribution. The resulting sensing matrix is shown as histogram. Also, a histogram of the demodulation phase separation between MICH and SRCL is plotted by this code, as these two length degrees of freedom will be obtained by one channel separated by the demodulation phase. We check this separation because you want to make sure that the random length offsets does not make the separation of these two signals close.

The result is a bit different from the previous post, in the better way! The length tolerance is about 5 mm for the vertex ifo. Fig.1 shows the sensing matrix. Although signal levels are changed by the random offsets, only few orders of magnitude is changed in each degrees of freedom. Fig.2 shows that the signal separation between MICH and SRCL at  POP55 varies from  55 to 120 degrees, which may be OK. If you have 1cm sigma, it varies from 50 degrees to 150 degrees.

Fig. 1 Histgram of the sensing matrix including 3f channels, when sigma is 5mm. Please note that the x-axis is in long 10.

 Fig. 2 Histogram of the demodulation phase difference between MICH and SRCL, when sigma is 5 mm. To obtain the two signals independently, 90 is ideal. With the random offsets, the demodulation phase difference varies from 55 degrees to 120 degrees.

My next step is to run the similar code for LLO. 

I wanted to check the script archive to see some old settings. I found that the script archive inflated to huge volume (~1TB).
The size of the common NFS volume (/cvs/cds) is 3TB. So it is really significant.

- The scripts living in /opt/rtcds/caltech/c1/scripts are archived daily in /cvs/cds/caltech/scripts_archive as bz2 files. This is done by crontab of megatron (see https://wiki-40m.ligo.caltech.edu/Computers_and_Scripts/CRON)

- In fact, the script folder (say old script folder) /opt/rtcds/caltech/c1/scripts has the size of 10GB. And we have the compressed copy of thi s everyday.

- This large script folder is due to a couple of huge files/folders listed below

• (scripts)/MEDMtab is 5.3GB / This is probably related to the web MEDM view (on nodus) but I don't think the web page is not updated. (i.e. the images are unused)
• (scripts)/MC/logs/AutoLocker.log 2.9GB / This is just the accumulated MC autolocker log.
• (scripts)/GigE 780M / This does not look like scripts but source and object files
• (scripts)/Admin/n2Check.log 224M / This is important but increases every minute.
• (scripts)/ZI 316MB / Zurich Instrument installation. This should not be here.

Here I propose some changes.
For the script archive

• We can remove most of the scripts for the past (say ~2019). We leave an archive file per month.
• For the scripts in 2020, we leave a weekly archive.
• For 2021 and 2022, we leave all the archive files.

For the existing large files/folders

• MEDMtab: the stored files are redundant with the burt snapshots. Remove the image files. Also, we want to move the image-saving location.
• Autolocker.log: simply zap it
• n2Check.log: we should move the saving location
• GigE /ZI: they need a new home where the daily copy is not taken.

As a result of the following work, the file volume of /cvs/cds was reduced from 3.2TB to 2.2TB, and /opt/rtcds/caltech/c1/scripts was reduced from 10GB to 1.5GB

/cvs/cds/caltech/scripts_archive was cleaned up. Now the archive files are reduced to have:

• every month 1st day from 2005 to 2018/12
• every ten days (1, 11, 21) for 2019 and 2020
• everyday for 2021 and 2022

(scripts)/MEDMtab/image was deleted. I can be restore back from one of the script_archive files.

(scripts)/MC/logs/AutoLocker.log was just deleted and refreshed. For the past settings, we can refer autoburt snapshots or script_archive files.

(scripts)/Admin/n2Check.log

• It turned out that the frequency of the check was reduced to once per 10min on Sep 9th, 2021 (unelogged activity).
• The volume of the text since then was not much volume. So I deleted the lines before this date. And the file size is <7MB now.

(scripts)/ZI was moved to /cvs/cds/apps

/opt/rtcds/caltech/c1/burt/autoburt/snapshots

• 2018, 2019, 2020 snapshots were archived in tar.gz.
• These snapshots were then deleted

I noticed (while relocking the MC after Jamie and I zeroed the LSC offsets) that the MC refl power was 4.8 V.  Usually we should be ~4.2, so I closed the PSL shutter and went in to measure the power.  We were injecting ~125mW or a little more.  I had adjusted the power the other day, and through yesterday, it looked fine, but overnight it looks like it drifted up.

I took the 5565 RFM card out of the IOVME machine to so I could put it in the new IO chassis that will be replacing it.  It is no longer on the RFM network.  This doesn't affect the slow channels associated with the auxilliary crate.

I took away the fiber collimator and the collimator mount from the air BHD setup [Attachment 1 (before removal), 2 (after removal)]

The removed collimator is shown in Attachment 3 and will be used for mode-matching telescope for the OMCs.
 

 Nick and I measured the reflected power of the green light in locked and unlocked. I'm working on the calculation of the mode matching. Tonight, I'll be posted my calculation I'm still working on it.

JCD:  Andres forgot to mention that they closed the PSL shutter, so that they could look at the green light that is reflected off the harmonic separator toward the IR trans path.  Also, the Xarm (and the Yarm) were aligned to IR using the ASS, and then ASX was used to align the green beam to the cavity.

I cleaned up around the 40 m lab. All the Laser Safety Glasses have been picked up and placed on the rack at the entrance.

Some miscellaneous BNC Connector cables have been arranged and organized along the wall parallel to the Y-Tunnel.

Nitrogen tanks have been swapped out. Current tank is at 1200 psi and the other is at 1850 psi.

The tool box has been organized with each tool in its specified area.

Whoa! Thanks!

For the last week, I have been attempting to determine the mirror stack transfer function which relates mechanical mirror response to a given ground-motion drive. The idea is to model the stacks in COMSOL and ultimately apply mechanical tests for manual calculation.

Procuring the correct drawings to base my 3D models off of was no simple task. There are two binders full of a random assortment of drawings, and some of them are associated with the smaller chambers, while others are appropriate for the main chamber, which is what we're interested in right now. For future workers, I suggest checking that your drawings are appropriate for the task at hand with other people before wasting time beginning the painstaking process of CAD design in COMSOL.

The drawings that I ultimately decided to use are attached below. They detail four layers of stacks, each which arrange 15, 12, 8, and 5 (going from bottom to top) Viton damping springs in an orderly fashion. The numbers have been chosen to keep the load per spring as constant as possible, in order for all springs to oscillate with as close a resonant frequency to each other as possible.

After making some minor simplifications, I have finished modeling the top stack:

After triangular meshing, before my many failed attempts at mechanical testing:

Both the Viton and steel portions have been given their material properties, and so I should be (theoretically ) ready to perform some eigenfrequency calculations on this simplified system. If my predictions are correct, these eigenfrequencies shouldn’t be too far of the eigenfrequencies of the 4-layer stacked system, because of the layout of the springs. I’ve tried doing mechanical tests on the top stack alone, but there hasn’t been much progress yet on this end, mostly because of some boundary value exceptions that COMSOL keeps throwing at me.

In the next couple weeks or so, I plan to extend this model to combine all four layers into one completed stack, along with a simple steel base and mirror platform. I also plan to figure out how to make eigenfrequency and transfer function measurements.

Lastly, to anyone who is experienced with COMSOL, I am facing two major roadblocks and could really use your help:

1) How to import one model into another, merge models together, or copy and paste the same model over and over.

2) Understanding and debugging run-time errors during mechanical testing.

If you have any idea how to attack either of these issues, please talk to me! Thanks!

[Mirko, Jenne]

We tried to run an extended version of Matt's LMS adaptive filter c-code. We got the extension to compile separately in gcc first. Then after some tweaking of the code we could make-install c1oaf with the c-code.

This killed c1lsc (the FE computer running c1oaf). Not responding to ssh or even pings. We replaced the bad c-code with harmless code, then reset c1lsc via the hardware button. While looking for c1lsc we discovered the problem with c1iscy network card (see previous entry).

After c1lsc reboot, restart of the FB, and a BURT restore not ok yet

 We had lots of trouble damping the Vertex Suspensions after this craziness.  A symptom was that even if all of the damping servos on an optic were OFF, and I turned the watchdog on (LSC is disabled, so no OAF siganls, no LSC signals), there were signals going to the coils. 

We did a reboot of the c1sus computer, did another BURT restore, and the optics started damping happily.   Burt restore, at least for c1susepics and c1mcsepics, seems to not be happening automatically.  I thought it was supposed to happen when the model was restarted?

Things now appear to be normal again.

[Koji, Jenne]

Steve pointed this out to me today, and Koji and I just took a look at it together:  The total power coming out of the MOPA box is constant, about 2.7W.  However, the NPRO power (as measured by 126MOPA_126MON) has decreased from where we left it last night.  It's an exponential decay, and Koji and I aren't sure what is causing it.  This may be some misalignment on the PD which actually measures 126MON or something though, because 126MOPA_LMON, which measures the NPRO power inside the NPRO box (that's how it looks on the MEDM screen at least...) has stayed constant.  I'm hesitant to be sure that it's a misalignment issue since the decay is gradual, rather than a jump. 

Koji and I are going to keep an eye on the 126MON value.  Perhaps on Monday we'll take a look at maybe aligning the beam onto this PD, and look at the impedance of both this PD, and the AMPMON PD to see why the reading on the DMM changed last night when we had the DAQ cable T-ed in, and not T-ed in. 

 This experiment deals with measuring the total harmonic distortion (THD) contribution of mixers in a circuit.

(a circuit diagram is attached) where:

Mixer: ZFM-3-S+ at +7dBm

Attenuator: VAT-7+, at +7dB

Low-pass filter: SLP-1.9+, which is set to DC-1.9MHz

The total harmonic distortion can be calculated by the equation: 

where Vn represents the voltage of the signal at a certain harmonic n.

In this experiment, only the voltages of the first three harmonics were measured, with the first harmonic at 400Hz, the second at 800Hz, and the third at 1.2kHz. The corresponding voltages were read off the spectrum analyzer after it had time averaged 16 measurements. (picture of the general shape of the spectrum analyzer output is attached)

(results for this mixer's particular configuration are on the pdf attached)

There really isn't that much correlation between the modulations and the resulting THD.

We won't know how good these numbers are until more experiments on other mixers are done, so they can be compared. Since the rest of the mixers are relatively high levels (+17dBm, +23dBm in comparison to this experiment's +7dBm), an RF amplifier will need to be hooked up first to do any further measurements.

[Koji Gautam]

We talked about touch interface of medm. We realized that android (and iOS) has vnc clients. I just installed VNC viewer on my phone and connected to my mac. Typing is tricky but I managed to get into pianosa, then launched sitemap. We could unlock/lock the IMC by screen touch!

Basically we can connect to one of the laptops (or control machines) from a tablet (either android or ipad). It'd be better to put both in a same network. It'd be great if we have a tablet case with a keyboard so that we can type without blocking the screen.

I gave some of the data analysts a look around because they asked and nothing was currently going on in the 40m. Nothing was changed.