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ID Date Author Type Categoryup Subject
  13931   Fri Jun 8 00:36:54 2018 gautamUpdatePSLobserving the resonance signal corresponding to the injected frequency.

It isn't clear to me in the drawing where the Agilent is during this measurement. Over 40m of cabling, the loss of signal can be a few dB, and considering we don't have a whole lot of signal in the first place, it may be better to send the stronger RF signal (i.e. Marconi pickoff) over the long cable rather than the weak beat signal from the Transmission photodiode. 

  13932   Fri Jun 8 01:08:22 2018 johannesUpdatePSLFirst light of AUX at YEND

Among the things that we hadn't taken care of yesterday before beginning to look for transmission signals were the polarization of the AUX beam on the AS table and optimizing the PLL feedback. The AUX beam is s-polarized on the PSL table (choice due to availablility of mirrors), and I added a half waveplate in front of the fiber to match it's axes. I placed another half-waveplate at the fiber output and send the reflection port of a PBS cube onto a PDA1CS photodetector. By alternatingly turning the waveplates I minimized the reflected light, giving strongly p-polarized light on the AS table for best results when interfering with the IFO beam. I wiggled the fiber and found no strong dependency of the output polarization on fiber bending. Attachment 2 shows the current layout.

The beat signal between AUX and PSL table is at -20dBm, and I adjusted the PLL gain and PI-corner to get reliable locking behavior. I think it's a good idea to keep the AUX beam on the AS table blocked while it's not in use, and only unblock it when it is phaselocked to avoid a rogue beam with no fixed phase relation to the PSL in the IFO.I blocked the beam after completing this work today.

I used the signal chain that Keerthana, Koji, and I set up yesterday to look for mode flashed of the AUX light in the YARM using the RF beat with the PSL carrier in transmission. To align the AUX beam to the arm the following steps were performed:

  1. Using a spectrum analyzer to look at the RF power at the target frequency between frequency-shifted AUX beam and PSL carrier on AS110, align the beam using the mirror pair closest to the fiber coupler for maximum signal.
  2. Initiate a sweep of the PLL LO frequency sourced by the Marconi using GPIB scripts over about 1 FSR. A strong peak was visible at ~31.76 MHz offset frequency
  3. Tune and hold LO frequency (in this case at 48.2526 MHz) such that AUX beam resonates in the arm. Optimize alignment by maximizing RF signal on PD in transmission.

This was followed by a sweep over two full FSRs. Attachment #1 shows the trace recorded by the AG4395 using the max data hold setting during the sweep. Essentially the beat between AUX and PSL carrier traced out the arm's transmission curve. At minimum transmission there was still a ~82dB beat on the transmission PD visible.

The YEND QPD is currently blocked and sees no light.

  13981   Mon Jun 18 14:32:42 2018 gautamUpdatePSLOptics on AS table

Yesterday, I moved the following optics:

  1. Lens in front of AS110 PD.
  2. BS splitting light between AS110 and AS55.

After moving these components around a bit, I locked them down once I was happy that the beam was pretty well centered on both of them, and also on AS110 and AS55 (measured using O'scope with single bounce from one ITM, other optics misaligned).

The beam was close to clipping on the lens mentioned in #1, probably because this wasn't checked when the 90-10 BS was installed for the AUX laser. Furthermore, I believe we are losing more than 10% of the light due to this BS. The ASDC (which is derived from AS55 PD) level is down at ~110cts as the Michelson is fringing, while it used to be ~200 cts. I will update with a power measurement shortly. But I think we should move ahead with the plan to combine the beam into the IFO's AS mode as discussed at the meeting last week.


Unrelated to this work, but c1psl and c1iscaux were keyed. 


ASDC has something weird going on with it - my main goal yesterday was to calibrate the actuators of ITMX, ITMY and BS using the Michelson. But with the Michelson locked on a dark fringe, the ASDC level changed by up to 50 counts seemingly randomly (bright fringe was ~1000 cts, I had upped the whitening gain to +21dB), even though the CCD remained clearly dark throughout. Not sure if the problem is in the readout electronics or in the PD itself.

  13982   Mon Jun 18 15:59:17 2018 johannesUpdatePSLOptics on AS table
Quote:

Furthermore, I believe we are losing more than 10% of the light due to this BS. The ASDC (which is derived from AS55 PD) level is down at ~110cts as the Michelson is fringing, while it used to be ~200 cts. I will update with a power measurement shortly. But I think we should move ahead with the plan to combine the beam into the IFO's AS mode as discussed at the meeting last week.

Is the 10% specified for P-Pol or for UNP? I contacted CVI about beamsplitters, since their website doesn't list a BS1-1064-90-... option on the website. They say a R=90% beamsplitter would be a custom job. The closest stock item they got is BS1-1064-95-2025-45UNP specified at R=95% for UNPolarized beams. They were kind enough to sent me the measured transmission curves for a recent lot of these, which is attached was uploaded to the wiki [Elog Police K: NO PROPRIETARY DOCUMENTS ON THE ELOG, which is public. Put it on our wiki and put the link here]. The figure is not labeled, but according to the contact Red is S-Pol and Blue is P-Pol, which means that this one actually has R=~90% for P, pretty much what we want. We'll need to buy two of these to make the swap in the setup.

Back to your original point: There's only a BS1-1064-10-2025-45UNP on the website, so unless we got these as custom items, the R for P-Pol is probably NOT actually 10%, just somewhere between 0% and 20%

  13983   Mon Jun 18 16:57:54 2018 KojiUpdatePSLOptics on AS table

Of course, many (but no all) of the optics were custom-ordered back in ~2000.

  14006   Fri Jun 22 14:18:04 2018 SteveUpdatePSLOptics on AS table

 

Quote:
Quote:

Furthermore, I believe we are losing more than 10% of the light due to this BS. The ASDC (which is derived from AS55 PD) level is down at ~110cts as the Michelson is fringing, while it used to be ~200 cts. I will update with a power measurement shortly. But I think we should move ahead with the plan to combine the beam into the IFO's AS mode as discussed at the meeting last week.

Is the 10% specified for P-Pol or for UNP? I contacted CVI about beamsplitters, since their website doesn't list a BS1-1064-90-... option on the website. They say a R=90% beamsplitter would be a custom job. The closest stock item they got is BS1-1064-95-2025-45UNP specified at R=95% for UNPolarized beams. They were kind enough to sent me the measured transmission curves for a recent lot of these, which is attached was uploaded to the wiki [Elog Police K: NO PROPRIETARY DOCUMENTS ON THE ELOG, which is public. Put it on our wiki and put the link here]. The figure is not labeled, but according to the contact Red is S-Pol and Blue is P-Pol, which means that this one actually has R=~90% for P, pretty much what we want. We'll need to buy two of these to make the swap in the setup.

Back to your original point: There's only a BS1-1064-10-2025-45UNP on the website, so unless we got these as custom items, the R for P-Pol is probably NOT actually 10%, just somewhere between 0% and 20%

4  std cataloge item fused silica  BS1-1064-95-2025-45UNP 

ordered today. They will arrive no later than July 13, 2018

  14033   Fri Jun 29 18:16:32 2018 JonConfigurationPSLChanges to AUX Optical Layout on PSL Table

In order to use the 0th-order deflection beam from the AOM for cavity mode scans, I've coaligned this beam to the existing mode-matching/launch optics set up for the 1st-order beam.

Instead of being dumped, the 0th-order beam is now steered by two 45-degree mirrors into the existing beam path. The second mirror is on a flip mount so that we can quickly switch between 0th-order/1st-order injections. None of the existing optics were touched, so the 1st-order beam alignment should still be undisturbed.

Currently the 0th-order beam is being injected into the IFO. After attenuating so as to not exceed 100 mW incident on the fiber, approximately 50 mW of power reaches the AS table. That coupling efficiency is similar to what we have with the 1st-order beam. With the Y-arm cavity locked and the AUX PLL locked at RF offset = 47.60 MHz (an Y-arm FSR), I observed a -50 dBm beat note at Y-end transmission.

  14144   Tue Aug 7 23:06:30 2018 KojiUpdatePSLEOM measuement preparation

I was preparing for the aLIGO EOM measuement to be carried out tomorrow afternoon.

I did a few modifications to the PLL setup.

  • The freq mixier in the PLL setup was replaced with ZP3 (level 7) from ZAD-6
  • The PLL gain was reduced from 3.10 to 2.80 to prevent servo oscillation
  • The main PSL marconi is connected to the PLL mixier and providing fixed 200MHz 8dBm.
  • The main PSL modulation is off.

Tomorrow I am going to modulate the EOM with the AUX Marconi via an amplifier (probably)

Automated scripts (AGinit.py and AGmeas.py) are in /users/koji/scripts

I will revert the setup once the measurement is done tomorrow.

  14145   Wed Aug 8 20:56:11 2018 KojiUpdatePSLEOM measuement preparation

Rich and I worked on the EOM measurement. After the measurement, the setup was reverted to the nominal state

  • AUX PLL mixer was restored to ZAD-6
  • The PLL gain was restored to 3.10
  • The main PSL marconi is connected to the freq generator again. Using the beat note, I've confirmed that the modulations are applied on the beam.
  • The PSL HEPA was reduced from 100 to 30.
  14259   Wed Oct 17 09:31:24 2018 SteveUpdatePSLmain laser off

The main laser went off when PSL doors were opened-closed. It was turned back on and the PSL is locked.

  14276   Tue Nov 6 15:32:24 2018 SteveUpdatePSLMC_Transmitted

I tried to plot a long trend MC Transmitted today. I could not get farther than 2017 Aug 4

Quote:

The mode cleaner was misaligned probably due to the earthquake (the drop in the MC transmitted value slightly after utc 7:38:52 as seen in the second plot). The plots show PMC transmitted and MC sum signals from 10th june 07:10:08 UTC over a duration of 17 hrs. The PMC was realigned at about 4-4:15 pm today by rana. This can be seen in the first plot.

 

  14532   Wed Apr 10 23:37:59 2019 gautamUpdatePSLPSL fan is noisy

Attached is my phone recording of what it sounds like right now in the PSL enclosure - not good for frequency noise measurement! The culprit is the little PC fan that is hacked onto the back of the Innolight controller. 

  1. Is this necessary?
  2. If so, is it sufficient to replace this fan with one from our stock?
  14535   Thu Apr 11 11:42:10 2019 KojiUpdatePSLPSL fan is noisy

This thread: ELOG 10295

My interpretation of these ELOGs is that we did not have the replacement, and then I brought unknown fan from WB. At the same time, Steve ordered replacement fans which we found in the blue tower yesterday.
The next action is to replace the internal fan, I believe.

  14537   Thu Apr 11 12:21:01 2019 not KojiUpdatePSLPSL fan is noisy

I could probably install the new fan if we have one.  Can you do without the laser for a while?

Quote:

This thread: ELOG 10295

My interpretation of these ELOGs is that we did not have the replacement, and then I brought unknown fan from WB. At the same time, Steve ordered replacement fans which we found in the blue tower yesterday.
The next action is to replace the internal fan, I believe.

  14556   Fri Apr 19 14:06:36 2019 gautamUpdatePSLInnolight NPRO shutoff

When I got back from lunch just now, I noticed that the PMC TRANS and REFL cameras were showing no spots. I went onto the PSL table, and saw that the NPRO was in fact turned off. I turned it back on.

The laser was definitely ON when I left for lunch around 130pm, and this happend around 140pm. Anjali says no one was in the lab in between. None of the FEs are dead, suggesting there wasn't a labwide power outage, and the EX and EY NPROs were not affected. I had pulled out the diagnostics connector logged by Acromag, I'm restoring it now in the hope we can get some more info on what exactly happened if this is a recurring event. So FSS_RMTEMP isn't working from now on. Sooner we get the PSL Acromag crate together, the better...

  14560   Fri Apr 19 20:21:52 2019 gautamUpdatePSLInnolight NPRO shutoff

Happened again at ~730pm.

The NPRO diag channels don't really tell me what happened in a causal way, but the interlock channel seems suspicious. Why is the nominal value 0.04 V? From the manual, it looks like the TGUARD is an indication of deviations between the set temperature and actual diode laser temperature. Is it normal for it to be putting out 11V?

I'm not going to turn it on again right now while I ponder which of my hands I need to chop off.

Quote:
 

I'm restoring it now in the hope we can get some more info on what exactly happened if this is a recurring event.

  14566   Wed Apr 24 16:06:44 2019 gautamUpdatePSLInnolight NPRO shutoff

After discussing with Koji, I turned the NPRO back on again, at ~4PM local time. I first dialled the injection current down to 0A. Then powered the control unit state to "ON". Then I ramped up the power by turning the front panel dial. Lasing started at 0.5A, and I saw no abrupt swings in the power (I used PMC REFL as a monitor, there were some mode flashes which are the dips seen in the power, and the x-axis is in units of time not pump current). PMC was relocked and IMC autolocker locked the IMC almost immediately.

Now we wait and watch I guess.

  14570   Thu Apr 25 01:03:29 2019 gautamUpdatePSLMC trans is ~1000 cts (~7%) lower than usual

When dialing up the current, I went up to 2.01 A on the front panel display, which is what I remember it being. The label on the controller is from when the laser was still putting out 2W, and says the pump current should be 2.1 A. Anyhow, the MC transmission is ~7% lower now (14500 cts compared to the usual 15000-15500 cts), even after tweaking the PMC alignment to minimize PMC REFL. Potentially there is less power coming out of the NPRO. I will measure it at the window tomorrow with a power meter.

  14577   Thu Apr 25 17:31:56 2019 gautamUpdatePSLInnolight NPRO shutoff

NPRO shutoff at ~1517  local time today afternoon. Again, not many clues from the NPRO diagnostics channel, but to my eye, the D1_POW channel shows the first variation from the "steady state", followed by the other channels. This is ~0.1 sec before the other channels register some change, so I don't know how much we can trust the synchronizaiton of the EPICS data streams. I won't turn it on again for now. I did check that the little fan on the back of the NPRO controller is still rotating.

gautam 10am 4/29: I also added a longer term trend of these diagnostic channels, no clear trends suggesting a fault are visible. The y-axis units for all plots are in Volts, and the data is sampled at 16 Hz.

Quote:

Now we wait and watch I guess.

  14578   Thu Apr 25 18:14:42 2019 AnjaliUpdatePSLDoor broken

It is noticed that one of the doors (door # 2 ) of the PSL table is broken. Attachement #1 shows the image

  14580   Fri Apr 26 12:32:35 2019 JonUpdatePSLmodbusPSL service shut down

Gautam and I are removing the prototype Acromag chassis from the 1x4 rack to make room for the new c1susuax hardware. I shut down and disabled the modbusPSL service running on c1auxex, which serves the PSL diagnostic channels hosted by this chassis. The service will need to be restarted and reenabled once the chassis has been reinstalled elsewhere.

  14583   Mon Apr 29 16:25:22 2019 gautamUpdatePSLPSL turned on again

I turned the 2W NPRO back on again at ~4pm local time, dialing the injection current up from 0-2A in ~2 mins. I noticed today that the lasing only started at 1A, whereas just last week, it started lasing at 0.5A. After ~5 minutes of it being on, I measured 950 mW after the 11/55 MHz EOM on the PSL table. The power here was 1.06 W in January, so ~💯  mW lower now. 😮 

I found out today that the way the python FSS SLOW PID loop is scripted, if it runs into an EZCA error (due to the c1psl slow machine being dead), it doesn't handle this gracefully (it just gets stuck). I rebooted the crate for now and the MC autolcoker is running fine again. 

NPRO turned off again at ~8pm local time after Anjali was done with her data taking. I measured the power again, it was still 950mW, so at least the output power isn't degrading over 4 hours by an appreciable amount...

  14593   Fri May 3 12:51:58 2019 gautamUpdatePSLPSL turned on again

Per instructions from Coherent, I made the some changes to the NPRO settings. The value we were operating at is in the column labelled "Operating value", while that in the Innolight test datasheet is in the rightmost column. I changed the Xtal temp and pump current to the values Innolight tested them at (but not the diode temps as they were close and they require a screwdriver to adjust), and turned the laser on again at ~1245pm local time. The acromag channels are recording the diagnostic information.

update 2:30pm - looking at the trend, I saw that D2 TGuard channel was reporting 0V. This wasn't the case before. Suspecting a loose contact, I tightened the DSub connectors at the controller and Acromag box ends. Now it too reports ~10V, which according to the manual signals normal operation. So if one sees an abrupt change in this channel in the long trend since 1245pm, that's me re-seating the connector. According to the manual, an error state would be signalled by a negative voltage at this pin, up to -12V. Also, the Innolight manual says pin 13 of the diagnostics connector is indicating the "Interlock" state, but doesn't say what the "expected" voltage should be. The newer manual Coherent sent me has pin13 listed as "Do not use".

Setting Operating value Value Innolight tested at
Diode 1 temp [C] 20.74 21.98
Diode 2 temp [C] 21.31 23.01
Xtal temp [C] 29.39 25.00
Pump current [A] 2.05

2.10

  14595   Mon May 6 10:51:43 2019 gautamUpdatePSLPSL turned off again

As we have seen in the last few weeks, the laser turned itself off after a few hours of running. So bypassing the lab interlock system / reverting laser crystal temperature to the value from Innolight's test datasheet did not fix the problem.

I do not understand why the "Interlock" and "TGUARD" channels come revert to their values when the laser was lasing a few minutes after the shutoff. Is this just an artefact of the way the diagnostics is set up, or is this telling us something about what is causing the shutoff?

  14597   Wed May 8 19:04:20 2019 ranaUpdatePSLPSL turned on again
  1. Increased PSL HEPA Variac from 30 to 100% to get more airflow.
  2. All of the TEC setpoints seem cold to me, so I increased the laser crystal temperature to 30.6 C
  3. Adjusted the diode TEC setpoints individually to optimize the PMC REFL power (unlocked). DTEC A = 22.09 C, DTEC B = 21.04 C
  4. locked PMC at 1900 PT; let's see how long it lasts.

My hunch is that the TECs are working too hard and can't offload the heat onto the heat sinks. As the diode's degrade, more of the electrical power is converted to heat in the diodes rather than 808 nm photons. So hopefully the increased airflow will help.

I tried to increase the DTEC setpoints, but that seems to detune them too far from the laser absorption band, so that's not very efficient for us. IN any case, if we end up changin the laser temperature, we'll have to adjust the ALS lasers to match, and that will be annoying.

 

The office area was very cold and the HVAC air flow stronger than usual. I changed the setpoint on the thermostat near Steve's desk from 71 to 73F at 1830 today.

  14599   Thu May 9 19:50:04 2019 gautamUpdatePSLPSL turned off again

This time, it stayed on for ~24 hours. I am not going to turn it on again today as the crane inspection is tomorrow and we plan to keep the VEA a laser safe area for speedy crane inspection.

But what is the next step? If these diode temps maximize the power output of the NPRO, then it isn't a good idea to raise the TEC setpoint futher, so should I just turn it on again with the same settings?

I did not turn the HEPA down on the PSL enclosure. I also turned off the NPROs at EX and EY so now all the four 1064nm lasers in the VEA are turned OFF (for crane inspection).

Quote:

locked PMC at 1900 PT; let's see how long it lasts.

My hunch is that the TECs are working too hard and can't offload the heat onto the heat sinks. As the diode's degrade, more of the electrical power is converted to heat in the diodes rather than 808 nm photons. So hopefully the increased airflow will help

 
  14600   Thu May 9 22:26:39 2019 JonOmnistructurePSLSecond ADC added to PSL Acromag crate

This evening I added a second ADC module to the prototype Acromag chassis. This chassis can now read out all the PSL diagnostic channels.

I configured the second ADC identically to the first ("ADC0"), and assigned it IP address 192.168.113.122. I confirmed it is visible on the martian network.

There was an existing but unused DB-15 feedthrough which I used for ADC1 channels 1-7. The eighth channel I left unwired, but there are slots available in the neighboring DB-25 feedthough, if that channel is needed in the future. The channel wiring assignments are as follows.

ADC1 Channel DB-15 Feedthrough Pin
0+ 1
0- 9
1+ 2
1- 10
2+ 3
2- 11
3+ 4
3- 12
4+ 5
4- 13
5+ 6
5- 14
6+ 7
6- 15
7+ not connected
7- not connected

I tested all seven of these channels by applying a calibrated voltage source and measuring the response via the Windows Acromag software. All work and are correctly calibrated to better than 0.1%.

  14602   Fri May 10 15:18:04 2019 gautamUpdatePSLSome work on/around PSL table
  1. In anticipation of installing the new fan on the PSL, I disconencted the old fan and finally removed the bench power supply from the top shelf.
  2. Moved said bench supply to under the south-west corner of the PSL table.
  3. Installed temporary Acromag crate, now with two ADC cards, under the PSL table and hooked it up to the bench suppy (+15 VDC). Also ran an ethernet cable from 1X3 to the box on over head cable tray and connected it.
  4. Brought other end of 25-pin D-sub cable used to monitor the NPRO diagnostics channels from 1X4/1X5 to the PSL table. Rolled the excess length up and cable tied it, the excess is sitting on top of the PSL enclosure. Key parts of the setup are shown in Attachments #1-3. This is not an ideal setup and is only meant to get us through to the install of the new c1psl/c1ioo Acromag crate.
  5. Edited the modbus config file at /cvs/cds/caltech/target/c1psl2/npro_config.cmd to add Jon's new ADC card to the list.
  6. Edited EPICS database file at /cvs/cds/caltech/target/c1psl2/psl.db to add entries for the C1:PSL-FSS_RMTEMP and C1:PSL-PMC_PMCTRANSPD channels.
  7. Hooked up said channels to the physical ADC inputs via a DB15 cable and breakout board on the PSL table.
    CH0 --- FSS_RMTEMP (Pins 5/18 of the DB25 connector on the interface box to pins 1/9 of the Acromag DB15 connector)
    CH1 --- PMC TRANS (BNC cable from PD to pomona minigrabber to pins 2/10 of the Acromag DB15 connector)
    CH2-6 are unsued currently and are available via the DB15 breakout board shown in Attachment #3. CH7 is not connected at the time of writing
    The pin-out for the temperature sensor interface box may be found here. Restarted the modbus process. The channels are now being recorded, see Attachment #4, although checking the status of the modbus process, I get some error message, not sure what that's about.

So now we can monitor both the temperature of the enclosure (as reported by the sensor on the PSL table) and the NPRO diagnostics channels. The new fan for the controller has not been installed yet, due to us not having a good mounting solution for the new fans, all of which have a bigger footprint than the installed fan. But since the laser isn't running right now, this is probably okay.

modbusPSL.service - ModbusIOC Service via procServ
   Loaded: loaded (/etc/systemd/system/modbusPSL.service; disabled)
   Active:
active (running) since Fri 2019-05-10 13:17:54 PDT; 2h 13min ago
  Process: 8824 ExecStop=/bin/kill -9 ` cat /run/modbusPSL.pid`
(code=exited, status=1/FAILURE)
 Main PID: 8841 (procServ)
   CGroup: /system.slice/modbusPSL.service
           ├─8841 /usr/bin/procServ -f -L /home/controls/modbusPSL.log -p /run/modbusPSL.pid 8009 /cvs/cds/rtapps/epics-3.14.12.2_long/module...
           ├─8842 /cvs/cds/rtapps/epics-3.14.12.2_long/modules/modbus/bin/linux-x86_64/modbusApp /cvs/cds/caltech/target/c1psl2/npro_config.c...
           └─8870 caRepeater

May 10 13:17:54 c1auxex systemd[1]: Started ModbusIOC Service via procServ.

  14604   Sat May 11 11:48:54 2019 JonUpdatePSLSome work on/around PSL table

I took a look at the error being encountered by the modbusPSL service. The problem is that the /run/modbusPSL.pid file is not being generated by procServ, even though the -p flag controlling this is correctly set. I don't know the reason for this, but it was also a problem on c1vac and c1susaux. The solution is to remove the custom kill command (ExecStop=...) and just allow systemd to stop it via its default internal kill method.

modbusPSL.service - ModbusIOC Service via procServ
   Loaded: loaded (/etc/systemd/system/modbusPSL.service; disabled)
   Active:
active (running) since Fri 2019-05-10 13:17:54 PDT; 2h 13min ago
  Process: 8824 ExecStop=/bin/kill -9 ` cat /run/modbusPSL.pid`
(code=exited, status=1/FAILURE)
 Main PID: 8841 (procServ)
   CGroup: /system.slice/modbusPSL.service
           ├─8841 /usr/bin/procServ -f -L /home/controls/modbusPSL.log -p /run/modbusPSL.pid 8009 /cvs/cds/rtapps/epics-3.14.12.2_long/module...
           ├─8842 /cvs/cds/rtapps/epics-3.14.12.2_long/modules/modbus/bin/linux-x86_64/modbusApp /cvs/cds/caltech/target/c1psl2/npro_config.c...
           └─8870 caRepeater

May 10 13:17:54 c1auxex systemd[1]: Started ModbusIOC Service via procServ.

  14605   Mon May 13 10:45:38 2019 gautamUpdatePSLPSL turned ON again

I used some double-sided tape to attach a San Ace 60 9S0612H4011 to the Innolight controller (Attachment #1). This particular fan is rated to run with up to 13.8V, but I'm using a +15V Sorensen output - at best, this shortens the lifespan of the fan, but I don't have a better solution for now. Then I turned the laser on again (~1040 local time), using the same settings Rana configured earlier in this thread. PMC was locked, and the IMC also could be locked but I closed the shutter for now while the laser frequency/intensity stabilizes after startup. The purpose is to facilitate completion of the pre-vent alignment checklist in prep for the planned vent tomorrow. PMC Trans reports 0.63 after alignment was optimized, which is ~15% lower than in Oct 2016.

  14609   Wed May 15 10:56:47 2019 gautamUpdatePSLPSL turned ON again

To test the hypothesis that the fan replacement had any effect on the NPRO shutoff phenomena, I turned the HEPA on the PSL table down to the nominal 30% setting at ~10am.

Tomorrow I will revert the laser crystal temperature to whatever the nominal value was. If the NPRO runs in that configuration (i.e. the only change from March 2019 are the diode TEC setpoints and the new fan on the back of the controller), then hurray.

  14662   Tue Jun 11 00:00:15 2019 MilindHowToPSLSteps to lock the PMC

Today, Rana had me key the PSL crate.

  1. Locating the rack: the crate is 1X1. This link provides details of the locations and functions of the racks.
  2. Keying the crate: the key is located at the bottom of the rack (in this case). Keying it requires one to turn the key through 90 degrees (anti clockwise facing the rack) and back to to the original position.

Locking the PMC:

  1. Accessing the medm screen for the PMC: open a new terminal and use the command sitemap. This should open up the sitemap medm screen. Click on the PSL button and then select C1PSL_PMC from the dropdown that is produced. This opens up a medm screen similar to that in Attachment #1.
  2. The correct toggling: The keying of the crate sometimes scrambles the settings on the medm screen. Rana and I performed extensive toggling of the buttons and concluded that the combination in Attachment #1 ought to be the correct one.
  3. Locking the PMC: The state of the PMC was deduced by observing CH01 on monitor 7. When not locked, there is no observable bright spot. At this point the "Input Offset (V)" slider is set to zero and the "Servo Gain Adjust (dB)" slider is set to minimum. To obtain lock, complete step 2 and then move the "DC Output Adjust (V)"  slider (at the bottom left on the screen) around rapidly while looking for a bright spot. On observing such a spot on the monitor, release the slider and quickly increase the "Servo Gain Adjust (dB)" slider to around 15 dB. Higher gain values produce a bright spot on CH02 as well which vanishes (almost) on decreasing the gain to the aforementioned value.
  14817   Tue Jul 30 09:13:31 2019 gautamUpdatePSLc1psl keyed, Agilent setup cleared
  1. IMC would not lock. c1psl EPICS channels were unresponsive. I keyed the crate and went through the usual burtrestore/PMC-relocking dance.
  2. While at 1X2, I decided to take this opportunity to clean up the AG4395 setup that has been setup there unused for several weeks now.
    • Unplugged the active probe connected via BNC-T connector to the mixer IF output.
    • Noticed that the active probe (S/N 2850J01450) did not have it's power connection connected. According to the manual, this is bad. I don't know if the probe is damaged or not.
    • Moved the AG4395 cart out of the way so that there is a little more room around 1X1/1X2.
  15004   Thu Oct 31 10:44:40 2019 gautamUpdatePSLPMC re-locked

PMC got unlocked at ~4am. I re-locked it. Also tweaked the input pointing into the cavity. The misalignment was mostly in pitch.

There was also a loud buzzing in the control room due to the audio cable being improperly seated in the mixer. I re-seated it.

  15005   Sat Nov 2 16:36:55 2019 YehonathanUpdatePSLUp to date sketch of the 1x1 and 1x2 Eurocrates

I reproduced Gautam's sketch of the 1x1 and 1x2 Eurocrates into a pdf image that contains links to the appropriate DCCs in the legend (see attachement).

  15006   Sat Nov 2 17:08:34 2019 YehonathanUpdatePSLUp to date sketch of the 1x1 and 1x2 Eurocrates

Thanks. Please update this wiki page too.

https://wiki-40m.ligo.caltech.edu/Electronics/ElectronicsRacks#A1X1

  15008   Mon Nov 4 13:26:04 2019 YehonathanUpdatePSLUp to date sketch of the 1x1 and 1x2 Eurocrates

Done.

Quote:

Thanks. Please update this wiki page too.

https://wiki-40m.ligo.caltech.edu/Electronics/ElectronicsRacks#A1X1

  15011   Mon Nov 4 19:02:25 2019 YehonathanUpdatePSLMapping the PSL electronics

I created a spreadsheet (Attached) by taking Koji's c1psl sheet from slow_channel_list and filtering out the channels that do not need an Acromag. I added in the QPD channels that are relevant to the PSL from the c1iool0 sheet.

I began mapping the PSL related Eurocrates connectors to their respective VME channels starting with the PMC electronics.

I am confused about the TTFSS interface (D040423): While it is a Eurocrate card, in the schematics it seems to have 50 pin connectors.

I found old wiring schematics that might help with identifying the channels once the connector issue is clarified.

 

 

  15017   Wed Nov 6 19:26:57 2019 gautamUpdatePSLSome PSL cable admin

Koji and I taked about cleaning up some of the flaky cable situation on the PSL table a while ago. The changes were implemented and are documented in Attachment #1. Now the Pomona box between the Thorlabs HV Driver and the NPRO head is sitting on the PSL table (sandwiched between some teflon pieces I found in cabinet S4 along the south arm), and the cables between these two devices are better strain relieved. I turned off the Thorlabs HV supply while working on the PMC table. The IMC could be locked after this work. Probably won't solve the long standing FSS mysteries but probably can't hurt.

Unrelated to this work: I also removed a Bias tee that was just hanging out on top of the FSS electronics, which was used for the modeSpec project.

  15087   Mon Dec 9 19:19:04 2019 YehonathanUpdatePSLAOM first order beam alignment

{Yehonathan, Rana}

In order to setup a ringdown measurement with perfect extinction we need to align the first order beam from the AOM to the PMC instead of the zeroth order.

We connected a signal generator to the AOM driver and applied some offset voltage. We spot the first order mode and align it to the PMC. The achieved transmitted power is roughly as it was before this procedure.

Along the way few changes has been made in the PSL table:

1. Some dangling BNCs were removed.

2. Laser on the south east side of the PSL table was turned off.

3. DC power supplies were removed (Attachment 1 & 2). The rubber legs on the first one are sticky and leave black residue.

4. The beam block that orginally blocked the AOM high order modes was raised to block the zeroth order mode (Attachment 3).

5. The unterminated BNC T junction (Attachment 4 - before picture). from the PMC mixer to the PMC servo was removed.

However, we are currently unable to lock the PMC on high gain. When the gain is too high the PZT voltage goes straight to max and the lock is lost.

  15089   Tue Dec 10 01:24:17 2019 YehonathanUpdatePSLAOM first order beam alignment

 

However, we are currently unable to lock the PMC on high gain. When the gain is too high the PZT voltage goes straight to max and the lock is lost.

Just realized that the diffracted beam is frequency shifted by 80MHz. It would shift the PZT position in the PMC lock acquisition, wouldn't it?

  15090   Tue Dec 10 13:26:46 2019 YehonathanUpdatePSLAOM first order beam alignment

nvm the PZT can scan over many GHz.

Quote:

 

However, we are currently unable to lock the PMC on high gain. When the gain is too high the PZT voltage goes straight to max and the lock is lost.

Just realized that the diffracted beam is frequency shifted by 80MHz. It would shift the PZT position in the PMC lock acquisition, wouldn't it?

 

  15091   Tue Dec 10 15:17:17 2019 YehonathanUpdatePSLPMC is locked

{Jon, Yehonathan}

We burt-restored the PSL and the PMC locked immediately.

The PMC is now locked on the AOM first order mode.

  15092   Tue Dec 10 18:27:22 2019 YehonathanUpdatePSLPMC is locked

{Yehonathan, Jon}

We are able to lock the PMC on the TEM00 mode of the deflected beam.

However when we turn off the driving voltage to the AOM and back on the lock is not restored. It get stuck on some higher order mode.

There are plethora of modes present when the PZT is scanned, which makes us believe the cavity is misaligned.

 

To lock again on the TEM00 mode again we disconnect the loop (FP Test point 1), find a TEM00 mode using the DC output adjust and close the loop again.

 

  15093   Wed Dec 11 15:01:57 2019 JonSummaryPSLPMC cavity ringdown measurement

[Jon, Yehonathan]

We carried out a set of cavity ringdown measurements of the PMC. The 1/e decay time scale is found to be 35.2 +/- 2.4 (systematic) μs. The statistical error is negligible compared to the systematic error, which is taken as the maximum absolute deviation of any measurement from the average value.

To make the measurement, we injected the first order deflection beam of an 80 MHz AOM, then extinguished it quickly by cutting the voltage offset to the AOM driver provided by an RF function generator. A 100 MHz oscilloscope configured to trigger on the falling voltage offset was used to sample the cavity in transmission as sensed by a PDA55. We found the detector noise of the DC-coupled output of the 35.5 MHz REFL PD to be too high for a reflection-side measurement.

Further loss analysis is forthcoming.

  15094   Wed Dec 11 15:29:17 2019 YehonathanUpdatePSLPMC is locked

Make sure to measure the power drop of the beam downstream of the AOM but before the PMC. Need to plot both together to make sure the chop time is much shorter than the 1/e time.

  15096   Thu Dec 12 19:20:43 2019 YehonathanUpdatePSLPMC cavity ringdown measurement

{Yehonathan, Rana, Jon}

To check whether we laser is being shut fast enough for the ringdown measurement we put a PD55 in the path that leads to the beat note setup. The beam is picked off from the back steering mirror after AOM and before the PMC.

@Shruti the PD is now blocking the beam to your setup.

As before, we drive the AOM to deflect the beam. The deflected beam is coupled to the PMC cavity. We lock the PMC and then shut the beam by turning off the output of the function generator that provides voltage to the AOM driver.

We measure the transmitted light of the PMC together with the light that is picked off before the PMC. In Attachment 1, the purple trace is the PMC transmission, the green trace is the peaked-off beam and the yellow trace is the function generator signal.

Rana was pointing out that the PDs, the function generator and the scope were not carefully impedance matched, which could lead to erroneous measurements. He also mentioned that the backscattered beam was too bright which might indicate that the PMC is oscillating. To remedy this we lowered the gain of the PMC lock to ~8.

We repeat the measurement after setting all the components to 50ohm (attachment 2). We then realize that the BNC T junction connected on the function generator is splitting the signal between the 50ohm AOM driver and 1Mohm oscilloscope channel which causes distortions as can be seen. We remove the T junction and get a much cleaner measurement (see next elog).

 

It seems like either the shutting speed or the PDs are only slightly faster than the PMC. I also check the AOM driver RF output fall time doing the same kind of measurement (attachment 3).

We suspect the PDs' bandwidth is to blame (although they are quoted to have 10MHz bandwidth).

In any case, this is fast enough for the IMC and arm cavities whose lifetime should be much longer than the PMC.

I will post an elog with some numbers tomorrow.

  15097   Fri Dec 13 12:28:43 2019 YehonathanUpdatePSLPMC cavity ringdown measurement

I grab the data we recorded yesterday from the scope and plot it in normalized units (remove noise level and divide by maximum). See attachment.

It can be seen that the measured ringdown time is ~ 17us while the shut-off time is ~12us.

I plan to model the PD+AOM as a lowpass filter with an RC time constant of 12us and undo its filtering action on the PMC trans ringdown measurement to get the actual ringdown time.

Is this acceptable?

 

  15098   Mon Dec 16 18:19:42 2019 shrutiUpdatePSLPMC cavity ringdown measurement : beat-note disruption

I have removed the PD55 + ND filter attached to it (see Attachment) and placed it next to the oscilloscope, after disconnecting its output and power supply. The post is still in place.

I did see the beat after that.

Quote:

{Yehonathan, Rana, Jon}

To check whether we laser is being shut fast enough for the ringdown measurement we put a PD55 in the path that leads to the beat note setup. The beam is picked off from the back steering mirror after AOM and before the PMC.

@Shruti the PD is now blocking the beam to your setup.

 

  15099   Tue Dec 17 00:23:28 2019 YehonathanUpdatePSLMapping the PSL electronics

I added to the PSL wiring list the ioo channels and the laser shutter (See attached pdf for an updated list).

The total channel numbers for now:

ai 57
ao 13
bi 1
bo 36

I counted each mbbo as 1 bo but I am not sure that's correct.

Still need to allocate Acromags.

ELOG V3.1.3-