CTN was raided today afternoon between 2 pm and 3 pm by 40m tribes. They have taken away precious Acromag units which are a very scarce resource these days. Following units were taken (Attachment 1):
3 rack mount units were affected:
CTN Slow Controls chassis:
PMC Servo Card Chassis:
All these units are stored in the flowbench side wire rack (see attachment 4).
I took the transfer function of North FSS side to see how much suppression we are doing. I took the transfer function by sending source signal to EXC port in common path and measuring transfer function as Source/OUT2 in AG4395a. The open loop transfer function is related to this by GOL = 1 - G2 (Source/OUT2) . Here G2 is the gain for source signal at the summing stage in common amplifier board which is -392/1.2e3 = -0.3267.
I have included an expected suppressed frequency noise plot assuming 104/f Hz/rtHz frequency noise of free running NPRO. We need to suppress much more in 100Hz-1kHz to be able to see Brownian noise.
I have also measured crossover frequency between PZT and EOM actuation. It came to around 26KHz which is not bad. We just need to increase FAST GAIN a lot more and COM gan little bit so that crossover remains the same while we get a lot of suppression in 100Hz-1kHz range. I'll look into the source of glitched causing our EOM to become unstable when increasing the feedback gains.
Code and Data
Edit Mon Jul 22 18:55:22 2019 by anchal
The gain values given in the plots are wrong. Correct values are unknown,
We measured EOM's transfer function again. The result is unexpected, it is flat from ~ 100k to 1MHz, instead of going up with frequency.
The setup is shown in this entry , but this time we used an RF summing box modified by Raphael. It does not have 50 ohms or resonant at 35.5MHz, but it's not worse than what we used before.
The TF is measured from three points,see fig 1 below.
figure 1: schematic for TF measurement. The excitation is split by a power spiltter, one is sent to EOM via RF summing box, another one is used for reference. The response is chosen from three points, OUT1, OUT2 and MIXER out. Since we have no direct access to the mixer out in the circuit, we split the signal and use an external mixer for mixer out measurement. This external mixer allows us to measure the response without seeing effects (extra poles, bandwidth) from other electronic components in the circuit.
We tried measuring the TF from three different points because we want to check which part of the circuit causes extra phase lag in the TF. The first time we took the measurements, the TFs from each points had different phase lag ( up to 52 degree), but when we remeasured again, the phases from three points actually did not vary that much, except the 180 degree phase flip. We have not yet determined what cause this problem, so we have to keep this in mind just in case.
The data will be fit, and used in Simulink model.
After the TF is measured, we will continue to work on the new layout and start removing all the optics and clean the table.
The data and code for plotting are attached below.
RCAV is locked, I have not optimized the mode matching yet, the coupling efficiency is ~ 67%.
This new setup has a double passed AOM. The frequency is shifted by 160 MHz.
I will try to optimize the mode matching tomorrow, then I can check the loop performance that it works as before.
I optimized mode matching for RCAV. The coupling is ~75%. I also minimized RFAM from the 35.5MHz EOM.
For RCAV mode matching, I moved only two lenses in front of RCAV (R=51.5 and 20.6 mm) to optimize the mode matching.
I have not tried moving other lenses or the mirror behind AOM yet, because I think 75% is enough for now.
The reflected beam will cause the shot noise level to be higher, but it should not be critical for our current situation.
I recalculated the mode matching so that the spot radius in AOMs is 100 um. Now the visibility of RCAV is 90%.
From the previous mode matching calculation, the spot radius in AOM is 220 um. This was too large for ISOMET AOM and caused beam distortion. The AOM was designed for much smaller spot radius (50 - 110 um). So I recalculated to make the spot radius inside the AOM to be 100 um. This spotsize is small enough for ISOMET and not too small for Crystal Tech AOM.
Rise time is 35 ns (28.5MHz) for 100 um radius in ISOMET AOM, diffraction eff ~80%. This should be sufficient for our less than 1MHz bandwidth loop.
For the new layout, I have to remove the Faraday isolator behind the EOM for another lens. I'll try to intall it back later.
I put most optics on ACAV path. I have not tried to lock the cavity yet. I'll install ACAV RFPD next.
I think I'm seeing a similar problem that y'all were when I use my heater circuit (which is I believe the same as your heater circuit, it's the one Kira and Kevin are using at the 40m). Our temperature readout circuits might be slightly different.
Basically when I have the heater on the board as my readout op amps, I get up to a few tenths of a volt jump in my temperature readout; however, even after moving this circuit to a different board and using a separate power supply, I'm getting about a millivolt shift. This is not good for <1K control. I'm also well within the limits of my power supplies, have voltage regulatorsbefore the OP amps, etc... I will try swapping out the OP amp as you did, but thought it was a pretty weird problem.
After some extensive testing, the circuit appears to be working as expected. The only exception is the affect the temperature control circuit has on all other electronics connected to the +24V kepco power supply. The model number on our electronics rack is ATE 36-3M, and is a Size "B" Quarter Rack model, rated for "Approx 100 watts" of power, with max DC voltage of 36V and max current of 3 amps, according to Table 1.1 of the manual. Our current readings on the power supply show between 1 and 2.5 amps at 24 volts, with the current depending on the 0 to 1.5 amps the vaccan heater draws. So our max power output from the power supply is 60 watts, well within the power limits.
I spent this afternoon tracing out all the connections to and from all the chassis in the CTN lab.
We currently have 19 power supplies in use. Take a moment and think about that.
I ordered the following Acromag units for a new slow controls test setup. The idea is to replace the Sun workstation running the VME slow controls.
Keith Thorne has already used some code to interface to these controls at the site:
As for Modbus, that package relies on the ASYN package, also for EPICS"
If you want it all put together for you, you can find some pre-built stuff at
ready to install at /ligo/apps/ubuntu12
source code ready to be built
- This has all the LIGO patches for macros, long variable names, etc. detail in
The Windows XP workstation in the lab died last week. After booting up to the "Windows XP" screen it reported a hardware problem. The subsequent reboot got to the BiOS and reported a corrupted memory problem. I'm going to pull the hard drive and replace the computer.
I've started removing a lot of the miscellaneous hardware from the lab (old pieces of Bosch framing, sheets of acrylic/plastic, etc). Some has gone into the ATF - we'll have to decide whether to keep it permanently or not. Right now, like Indiana Jones and the Last Crusade, I'm trying to see if there truly exists some space in this lab - or if it is a myth propagated though the ages.
Aidan rebooted the Sun machine and VME. It took a while to get the EPICS channels to work again. The following seemed to work:
Reboot Sun machine.
Reboot the VME crate by depressing the reboot button on the top of the crate.
Log into VME (psl1) at 10.0.0.2 from the Sun machine.
Check the existence of various channels with dbpr "C3:PSL-RCAV_RCPID_SETPOINT"
On the Sun, cd to /usr1/epics/psl/scripts and run "perl rcav_PID_2012_06_15.pl"
Confirmed that PID values started updating on the Sun screen.
Aidan also added a sitemap (~/sitemap.adl), see attached image, for the CTN lab. Aidan added an alias to /home/controls/.bashrc
The alias is:
alias sitemap="medm -x /home/controls/sitemap.adl"
I've been trying to lock the laser to the PMC since we adjusted the Faraday. It's basically badly out of alignment now. I can only see very higher order modes flash when I scan the cavity.
The problem, currently, is that the Faraday is too high and we don't have enough mirrors to control the beam going through it. I'm going to install a second mirror in a bow-tie configuration tomorrow and realign the beam through the Faraday, 21.5MHz EOM and, hopefully, the PMC.
I also spent a lot of today tracing out the control loop for the laser slow control. Once I have all the control loops understood, I'm going to draw a diagram for the Wiki.
P.S. Found out that the PSL PMC Servo board is D980352. I've updated the Electronics page on the Wiki to indicate this...
I set up an Acromag slow controls based on the procedure that Keith wrote in T1400200. It's really pretty easy. It took an hour and 15 minutes from installing Ubuntu on a machine to having a functioning ADC channel from the Acromag unit. I haven't yet set up a DAC unit - this will require some tweaking of some of the EPICS parameters. Once I've done that I'll upload a complete procedure to the Wiki.
This is relatively promising for supporting/replacing VME slow channels.
I configured the Acromag XT1541 DAC to run with EPICS. This was a touch trickier than the ADC as there is a subtlety with the channel configuration in the EPICS database. The bottom line is that now I can change the value in an EPICS channel and a multimeter attached to the unit will show a corresponding change in voltage.
The attached files (ioctest2.cmd and IOCTEST2.db) are used to access the first output channel, OUT00, on the unit. Now that I've got the thing working I can debug the calibration. Once that's sorted I'll summarize the set-up procedure on a Wiki page with glorious detail for future reference.
The following command line is used to open the modbus EPICS server.
The ioctest1 files are for the ADC unit.
I'm practicing the procedure of aligning the PMC. The input beam isn't great (I might be clipping a little on the Faraday). I'm mostly trying to get the hang of aligning into the cavity again as it's been a while.
My technique, so far, is to adjust the alignment, in yaw, of the third mirror before the cavity and then sweep the final mirror before the cavity slowly in yaw. I'm looking for flashes of transmission on the trans-camera. The goal is to keep tweaking until the order of the transitted mode is reduced to a few or zero. I should probably be sweeping the PZT at the same time.
I'm going to adjust the alignment through the FI tomorrow - just as soon as I get my hands on a couple more mirrors.
I cleaned the table with the computers and removed one of the monitors. I installed the Acromag units to the rack, powered them up and got them onto the network. They are:
XT1221 unit: 10.0.0.42
XT1521 unit: 10.0.0.41
I've pinged them successfully from other machines. I have an Ubuntu machine that I borrowed from the TCS lab to interface to them. I'll set up the EPICS control on Monday. In addition to adding the DC transmission channels to Acromag, we should be able to start migrating the PID controls away from the VME crates to these new units.
Like the title says ...
If I try running DAQD per https://nodus.ligo.caltech.edu:30889/ATFWiki/doku.php?id=main:experiments:psl:add_channel_for_daq_in_fb2
then it fails and the log file reveals that this is when it tries to write a GWF file to the trend folder. Manually trying to write anything to this location results in a "disk full" message.
The trusty df command yields the following.
[controls@fb2 frames]$ df
Filesystem 1K-blocks Used Available Use% Mounted on
232477448 125679200 94798608 58% /
/dev/sda1 101086 25961 69906 28% /boot
tmpfs 1029664 0 1029664 0% /dev/shm
/dev/sdc1 240362656 205728852 34633804 86% /frames/full
/dev/sdd1 307663800 307663800 0 100% /frames/trend
Summary of installation of new hardware:
I managed to figure out the modbusDrv configuration settings to get the binary output of the Acromag working. I've updated the Wiki page to reflect this. I've wired the XT1541 DAC, BIO Acromag unit to the T1EN and T2EN channels on the TTFSS box but I still can't get remote control of it yet for some reason. When the PDH loop is closed and I switch the TTFSS box to REMOTE, the loop stays closed regardless of what I do to the binary outputs in EPICS.
I've worked out how to get the binary IO to work with the TTFSS box so that we can activate switches in that unit. It wasn't working in the setup yesterday because of physics. Actually - there is a 10K pulldown resistor in the Acromag unit that attaches the output to ground. The actual circuit looks like this:
VCC (5V) --- (4.99K) --- T1EN -----|-----DIO0 ----(6.2V if DOUT set to 1)---- (10K) ------ | GND
......... TTFSS...................................| ..............................ACROMAG ...............................................|
T1EN is measured by the switch-chip (SN74HCT157D, chip U3 in D040423) to determine whether it should be open or closed. We need to bring T1EN below 0.8V to get the TTL logic to work.
If DOUT is set to 1, then DIO0 and T1EN become the excitation voltage, 6.2V, and the switch circuit reads high. If DOUT is set to 0, the excitation voltage is removed and we just end up with a voltage divider and around 3.33V at T1EN - which does not register as low.
We can get around this by adding a smaller resistor, say 810 Ohms, in parallel to the 10K, to lower the effective resistance of the pull-down resistor to 750 Ohms. The maximum current the Acromag unit will have to supply is 6.2V/750 Ohms = 8.4mA.
So that's what I did. Now, when I switch DOUT to 1, I see 6.2V at T1EN and when I switch DOUT to 0, I see 0.669V at T1EN. The TTFSS box registers these as two different states and I can lock and unlock the PDH loop from EPICS.
Volts (requested) to Counts
C = a1*V_req + a2
a1 = 3003.5 counts/Volt
a2 = -20.8285 counts
Entered counts (in +ve and -ve amounts) and measured the resulting voltage across the output. I'm not sure how stable this calibration is.
After two straight days of trying to get iPython notebooks to run on my Mac and two different Ubuntu installations, I gave up in frustration and rewrote the simpler parts of Evan's noise budget code into MATLAB. The following Noise Budget (without any BeatNote measurement from the lab) represents an estimate of the current noise in the system.
Clearly, with the ISS OFF, we are hugely dominated by intensity noise. We will investigate if this is the reason that we can't lower the FM deviation on the Marconi below 300kHz/V.
Removed a few old computers from the diagram (35W laser, old OPC server, PSL Workstation, HWS workstation). Added a few new ones (OPC server in TCS lab, New workstation in PSL lab, Acromag control box in PSL lab).
Here's the drawing for the shield. https://dcc.ligo.org/LIGO-D1500403
We have raised the table by ~ 16" and the enclosure around the table by about 13".
I've ordered a 4U rack mount kit with DIN rail for mounting the Acromag stuff. It's open on the top and bottom but is quite deep. I've made up a front panel for this kit which will connect to the slow controls with 8 analog inputs, 8 analog outputs, 4 binary inputs/outputs, 2x 25 pin connectors for connecting to the FSS boards and a 15 pin connector for connecting to the ion pump current supply.
With the (intentional) demise of the VME crate, the slow controls for the laser were brought back online today. So far, only the controls for the laser temperature are running. However, if you run the LASER SLOW MEDM screen, the channels C3:PSL-ACAV_SLOWOUT and C3:PSL-RCAV_SLOWOUT are now active.
To achieve this: I did the following:
1. Restored FB2 to the local network to allow for GUI interface to EPICS.
2. On the computer running the MODBUS IOC (10.0.0.33), I created some channels in the DB that are "ai" channels with the names C3:PSL-A(R)CAV_SLOWOUT. There are some CALC channels that use these as inputs to convert to counts and then the output is sent to the approrpiate DAC register on the acromag unit via the modbus protocol.
3. So now any computer running EPICS on the local network can interact with the SLOWOUT channels
We connected BNCs up between the Acromag terminals and the SLOW IN BNC inputs on the front panel of the two NPRO controllers and double-checked that a requested voltage actually yields that voltage at the NPRO controller.
I showed Andrew Wade the CTN lab and gave him a safety walkthrough. We also went over the safe operating procedure for turning on the laser.
I have a set of two Wenzel OCXO added to the electronics chassis, courtesy of the gentry from the Cryo Lab. The chassis has outputs for 36MHz and 37MHz.
We can use these temporarily and exchange the oscillators in future when we select a new sideband wavelengh.
These are the RTDs we use in aLIGO TCS
I've ordered a few of these Kapton heaters to fit the new shields: https://dcc.ligo.org/DocDB/0122/D1500403/002/D1500403-v2.PDF
Here's the RH driver PCB for aLIGO:
It uses this power amp: https://www.digchip.com/datasheets/download_datasheet.php?id=508953&part-number=LM12CLK
The heater driver in the old design (iLIGO PSL) is this horrible programmable power supply with high output noise (see measurement of 40m PSL heater).
What we want instead is something that takes in +/- 10 V and drives a DC current (not PWM) into our heaters (which are ~50-100 Ohms). A BUF634 is almost good enough; it can do 200 mA at 10 V. Is there a BUF634 equivalent which can do more like 500 mA? Otherwise we can just use a opamp + transistor.
What is being used for the ring heaters at the LIGO sites?
I'm working with Jamie to get a frame builder running in the ATF & CTN for these temp/pres/humidity channels to be stored on. There's no
long term storage right now.
I modeled the PMC in COMSOL. The lowest order body mode is around 13.9kHz. This means we want a UGF for the PMC control loop around 13.9kHz/4 ~3.5kHz.
The results have been added to the Wiki page: https://nodus.ligo.caltech.edu:30889/ATFWiki/doku.php?id=main:experiments:psl:pmc
I picked up one of the following linear lab power supplies for the TCS Lab. They can output 30V, 3A. They also have accept an analog input to control the output voltage (or current). It's the sort of thing that should be useful for quick heater driver tests.
I've pulled the old PMC driver board from the VIM crate architecture and inserted it into a chassis (D1700003). The interface has been reconfigured to insert directly into two Acromag units that are inside the chassis (see attached photo). It still needs a back panel.
So far, the DAC connections (loop gain control and locking point control) are wokring. The binary outputs are not properly switching between 0V and 5V - I'll need to double-check what circuit the Acromag 1541 is expecting to be attached.
Also, I've added a new EPICS database file for these channels (attached).
[Aidan, Gabriele, Eric]
We turned off and covered the clean flow bench by the west wall. We also removed the items from off the top on the half closest to that wall. We removed all the cables hanging below the pipe and lay them on the floor.
I showed Andrew how to set up the slow controls. We got the previous 3 ADC channels back up.
I had Facilities come and replace the dead light tube in the CTN lab antechamber. It's nice and bright in there right now.
We've noticed that the floor is pretty dusty - so we're implementing twice weekly mopping sessions starting tomorrow.
Both lasers have been locked to the cavities for 24 hours. The slow control of the frequency is handed off to the PID loop. Antonio and I observed strange behaviour on the DC value of the cavity transmission.
As Evan had noted before, there are two polarizations that will resonate and they're about 3MHz apart (if I remember correctly). We can see these on the DC photodiodes on transmission (the ISS PD and the RF DC output). One peak is large and the other much smaller. However, when we have large transmission onto the RF photodiode we have small transmission onto the ISS PD and vice versa. It's likely we have a pick-off optic with strong polarization selectivity.
We couldn't find the beat yesterday or Thursday.
We now have DC transmission channels in the frames. I'll post the details soon, but here's a plot that shows the transmission through the cavity on the RF_DC channel and the ACAV ISS DC as we slowly ramp the ACAV_SLOWOUT (temperature control) at a rate of 5E-5V/s.
Note the strange shape of the transmission peaks.
The wide view allows us to see the cavity transmit the upper and lower sidebands. Look carefully at the TRANS_RF_DC curve.
We swept the temperature of the ACAV laser and monitored the transmission through the cavity. In the attached image, the TEM00 modes (separated by 3GHz or 1 FSR) are located at C3:PSL-ACAV_SLOWOUT values of 0.5344V and 1.379V. There is a TEM20 mode at 1.52V.
We tried locking the PLL today but failed. Looking at the beat note on the network analyzer revealed some 70/140kHz harmonics. We thought this might be what is preventing us from locking.
Rana suggested that these are from the switching power supplies (which switch at 70kHz). If so, this may be a red-herring. It's possible we're not trying with high enough gain settings ...
The large peak that is offset by about 50kHz is from the Marconi ... we can make it move around by changing the Marconi frequency.
We finally got the temperature sensors broadcasting to EPICS channels again - well, in part anyway. There are a lot of configuration issues to work out (refresh rate, saving to frames, license for OPC server, battery monitors, data precision). But at least we can now see a temperature sensor channel in EPICS that corresponds to a live measurement. The configuration to get the data from the remote unit to EPICS is shown in the attached block diagram.
More details can be found here: