The top plot shows a sweep from 10 kHz to 5 MHz of the ratio of the voltage output of the PD detecting power from the NPRO laser beam and the RF source voltage (the magnitude of the complex transfer function). The black trace was taken with the laser beam blocked. For runs 2 and 3 I changed the laser temperature set point by 10 mK and 100 mK respectively to see if there was a significant change in the AM response. The bottom plots shows runs 2 and 3 compared to run 1 plotted in dB (to be explicit, i'm plotting 10 times the base 10 log of the magnitude of the ratio of two complex transfer functions). Changing the temperature seems to have only a minor effect on the output except at around 450kHz, where the response has a large peak in run 1 and much smaller peaks in runs 2 and 3.
The traces in the top plot consist of 16 averages taken with a 300Hz IF bandwidth, 15 dBm source power (attenuated with a 6 dB attenuator) and with 20dB attenuation of the input power from the PD.
Next I'm going to probe a narrow band region where the response is low (2.0MHz or 2.4MHz perhaps) and choose a bandwidth for the dither frequency for the PDH locking.
I've finished using the network analyzer to characterize find a dither frequency for driving the PZT to use in my PDH locking. I found a region in which the amplitude response of the PZT is low: The dip is centered at 2.418 MHz. Changing the NPRO laser temperature by 100mK has no significant effect on the transfer function in that region. I will post plots tomorrow.
I'm finished with the network analyzer. It is unplugged, and the cart is still near the PSL table. (I'll roll it back tomorrow when it won't disturb interferometer locking).
I closed the shutter on the NPRO at the end of the night.
Tomorrow I plan to put together the fast locking setup. I'll drive the PZT at 2.418 MHz. More details to come tomorrow.
I ended up choosing a different dither frequency for driving the NPRO PZT: 230 kHz, because the phase modulation response in that region is higher according to other data taken on an NPRO laser (see this entry). At 230 there is a dip in the AM response of the PZT.
I am driving the PZT at 230 kHz and 13 dBm using a function generator. I am then monitoring the RF output of a PD that is detecting light reflected off the cavity. (The dither frequency was below the RF cutoff frequency of the PD, but it was appearing in the "DC output", so I am actually taking the "DC output" of the PD, which has my RF signal in it, blocking the real DC part of it with a DC block, and then mixing the signal with the 230kHz sine wave being sent to the PZT.
I am monitoring the mixer output on an oscilloscope, as well as the transmission through the cavity. I am sweeping the laser temperature using a lock in as a function generator sending out a sine wave at 0.2 V and 5 mHz. When there is a peak in the transmission, the error signal coming from the mixer passes through zero.
My next step is to find or build a low pass filter with a pole somewhere less than 100 kHz to cut out the unwanted higher frequency signal so that I have a demodulated error signal that I can use to lock the laser to the cavity.
DMass and I locked the NPRO laser (Model M126-1064-700, S/N 238) on the AP table to the reference cavity on the PSL table using the PDH locking setup shown in the block diagram below (the part with the blue background):
A Marconi IFR 2023A signal generator outputs a sine wave at 230 kHz and 13 dBm, which is split. One output of the splitter drives the laser PZT while the other is sent to a 7dBm mixer. Also sent to the mixer is the output of a photodiode that is detecting the reflected power from off the cavity. (A DC block is used so that only RF signal from the PD is sent to the mixer). The output of the mixer goes through an SR560 low-noise preamp, which is set to act as a low pass filter with a gain of 5 and a pole at 30 kHz. That error signal is then sent to the –B port of the LB1005 PDH servo, which has the following settings: PI corner at 10kHz, LF gain limit of 50 dB, and gain of 2.7 (1.74 corresponds to a decade, so the signal is multiplied by 35). The output signal from the LB1005 is added to the 230 kHz dither using another SR560 preamp, and the sum of the signals drive the PZT.
I am monitoring the transmission through the cavity on a digital oscilloscope (not shown in the diagram) and with a camera connected to a TV monitor. I sweep the NPRO laser temperature set point manually until the 0,0 mode of the carrier frequency resonates in the cavity and is visible on the monitor. Then I close the loop and turn on the integrator on the LB1005.
The laser locks to the cavity both when the error signal is sent into the A port and when it is sent into the –B port of the PDH servo. I determined that –B is the right sign by comparing the transmission through the cavity on the oscilloscope for both ways.
When using the A port, the transmission when it was locked swept from ~50 to ~200 mV (over ~10 second intervals) but had large high frequency fluctuations of around +/- 50 mV. Looking at the error signal on the oscilloscope as well, the RMS fluctuations of the error signal were at best ~40 mV peak to peak, which was at a gain of 2.9 on the LB1005.
Using the –B port yielded a transmission that swept from 50 to 250 mV but had smaller high frequency fluctuations of around +/- 20 mV. The error signal RMS was at best 10mV peak to peak, which was at a gain of 2.7. (Although over the course of 10 minutes the gain for which the error signal RMS was smallest would drift up or down by ~0.1).
The open loop error signal peak-to-peak voltage was 180 mV, which is more than an order of magnitude larger than the RMS error signal fluctuations when the loop is closed, indicating that it is staying in the range in which the response is linear.
In the above plot the transmission signal is offset by 0.1 V for clarity.
Below is the closed loop error signal. The inset plot shows the signal viewed over a 1.6 ms time period. You can see ~60 microsecond fluctuations in the signal (~17 kHz)
The system remained locked for ~45 minutes, and may have stayed locked for much longer, but I stopped it by opening the loop and turning off the function generator. Below is a picture of the transmitted light showing up on a monitor, the electronics I'm using, and a semi-ridiculous mess of wires.
I determined that it’s not dangerous to leave the system locked and leave for a while. The maximum voltage that the SR560 will output to the PZT is 10Vpp. This means that it will not drive the PZT at more than +/-5 V DC. At low modulation rates, the PZT can take a voltage on the order of 30 Vpp, according to the Lightwave Series 125-126 user’s manual, so the control signal will not push the PZT too hard such that it’s harmful to the laser.
To aid Jenny's valiant attempt to finish her SURF project, I did some things with the front end system over the last couple days, largely tricking Jamie into doing things for me lest I ruin the 40m RCG system. Several tribulations have been omitted.
We stole a channel in the frontend, in the proccess:
Below are some plots from dataviewer of temperature-step data taken over the past 32 hours. (They show minute trends). I am looking at the thermal coupling from the can surrounding the reference cavity on the PSL table to the cavity itself, and trying to measure the cavity temperature response via the control signal sent to heat the NPRO laser, which is locked to the cavity.
I stepped the temperature set point from 35 to 36 deg. C for the can at 12:30am last night. Then I waited to see the cavity temperature change and the slow actuator (laser heater: TMP_OUTPUT) follow that change.
I was a bit worried about the oscillations that were occuring in the TMP_OUTPUT signal even long after this temperature step was made, but I figured that they were simply room-temperature changes propagating into the cavity, since they seemed to have a similar pattern to the room-temperature variations, and since it is clear that the out-of-loop temperature sensor on the can (RCTEMP) experiences variations, even when the in-loop sensors are recording no variation.
At 8:46pm tonight I stepped the temperature down 2 degrees to 34 deg. C. The step had a clear effect on TMP_OUTPUT. The voltage to the heater dropped and eventually railed at its lowest output. I'm worried that the loop is unstable, although I haven't ruled out other possibilities, such as that a 2 deg. C temperature step is too large for the loop. I will investigate further in the morning.
The lock was lost when I came in around noon today to check on it. The slow actuator was still railing.
1) I got lock back for a few minutes, by varying the laser temperature set point manually. TMP_OUTPUT was still reading -30000 cts (minimum allowed) and the transmission was not as high as it had been.
2) I toggled the second filter button off. The TMP_OUTPUT started rising up to ~2000 cts. I then toggled the second filter back on, and TMP_OUTPUT jumped the positive maximum number of counts allowed.
3) I lost the lock again. I turned off the digital output to the slow actuator.
4) I have so far failed at getting the lock back. My main problem is that when the BNC cable to the slow port is plugged in, even when I'm not sending anything to that port, it makes it so that changing the temperature set point manually has almost no effect on the transmission (it looks as though changing the setpoint is not actually changing the temperature, because the monitor shows the same higher order mode even when with +-degree temperature setpoint changes).
I am trying again to measure a temperature step response on the reference cavity on the PSL table.
I have been working to relock the NPRO to the cavity. I unblocked the laser beam, reassembled the setup described in my previous elog entry: 5202. I then did the following:
1) Monitored error signal (from LB1005 PDH servo), transmitted signal, and control signal sent to drive PZT on oscilloscope.
2) With loop open, swept through 0,0-mode resonance, saw a peak in the transmission, saw an accompanying error signal similar to the signal shown in 5202.
3) Tried to lock. Swept the gain on the LB1005 and could not find a gain that would make it lock. Tried changing the PI-corner freq. from 10 kHz to 30 kHz and back and still could not lock.
4) Noticed that the open loop error signal displayed on the scope was DC-offset from zero. Changed the offset to zero the error signal.
5) Tried to lock again and succeeded.
6) Noticed that upon closing the loop, the error signal became offset from zero again. Turning on the integrator on the LB1005 increased DC-offset.
7) Reduced the gain on the SR560 being used as a low pass filter from 5 to 1. Readjusted the open loop error signal offset on the LB1005.
8) Closed the loop and locked. Closing the loop then caused a much smaller DC change in the signal than I had seen with the larger gain (now around 3mV). RMS fluctuations in error signal are now 1 mV (well within the linear region of the error signal).
9) Noticed transmission has a strange distorted harmonic oscillation in it a 1MHz. (Modulation freq is 230kHz, so it's not that). Checked reflected signal and also saw a strange oscillation--in a sawtooth-like pattern.
I intend to
1) Post oscilloscope traces here showing transmitted and reflected signal when locked.
2) Look upstream to see if the sawtooth-like oscillation is in the laser beam before it enters the cavity:
3) At some point, try to close the slow digital loop, perhaps readjusting the gain.
4) Try to measure a temperature step response.
I decided to go forward and try to close the digital loop in spite of the unexplained oscillations in the transmission.
1) Plugged the 20dB attenuator into the slow port on the laser drive. This pushed the laser out of lock and, for some reason, made the laser temperature stop responding to sweeping the set point manually with the knob.
2) Plugged the output from the digital system into the slow port (with the attenuator still in place).
3) Displayed the beam seen by the camera on a monitor in the control room
4) Stepped the laser temperature using MEDM until finding the 0,1 mode. Locked to that mode.
5) Closed the digital loop (input to slow laser drive attenuated 20dB attenuator). Gain 0.010
6) Loop appeared stable for 30 minutes, then temperature began shooting off. I opened the loop, cleared history, reduced the gain to 0.008, and started it again. Loop appears stable after 15 minutes of watching. I'm going to leave it for a few hours, then come back to check on it and, if it's stable, step the can temperature.
After finishing my last elog entry, I monitored the digital loop's error signal (the control signal for the fast loop) and the output to the laser heater remotely, (from West Bridge), using dataviewer. The ref cav surrounding can temperature was set to 36 degrees C.
With the loop closed and a gain of 0.008, after seeing the output voltage to the laser heater (TMP_OUTPUT) remain fairly constant and the error signal (TMP_INMON) stay close to zero for ~3 hours, I tried to step the temperature. (This was at 2am last night). I was working remotely from West Bridge. To step the temperature I used the following command:
ezcawrite C1:PSL-FSS_RCPID_SETPOINT 35.5
Rather than change the can temperature to 35.5 C, it outputted:
It had set the setpoint to 0 degrees C, which was essentially turning the heater off. I tried resetting it back to 36 and had no luck. I tried changing the syntax slightly.: ezcawrite C1:PSL-FSS_RCPID_SETPOINT=36 and ezcawrite C1:PSL-FSS_RCPID_SETPOINT (36). No success.
I ran over to the 40m and changed the temperature back to 36 manually. The in-loop temp sensor had decreased to 31.5 degrees C before I was able to step the setpoint back up. The system seems to have recovered from this large impulse though, and the laser has remained locked.
(5 hours of minute-trend data)
From left to right:
Top: Out-of-loop can temp sensor; Voltage sent to heat can
Middle: signal sent to heat the laser (TMP_OUTPUT); room temp
Bottom: Error signal for slow loop (sampled control signal from fast loop); In-loop can temp sensor
At 9:30 this morning (7 and a half hours after accidentally setting the setpoint to zero), I came in to the 40m. TMP_OUTPUT was still decreasing but was slowing somewhat, so I decided to step the can temperature up half a decree to 36.5 C.
TMP_OUTPUT responded to the step, but it is also oscillating slowly with room-temperature changes, and these oscillations are on the same order as the step response. The oscillations look like the room-temp oscilations, but inverted. (TMP_OUTPUT reaches maxima when RMTEMP reaches minima). Oddly, there does not appear to be much of a time delay between the room temperature and TMP_OUTPUT signals. I would expect a time delay since there's a time constant for a room-temperature change to propagate into the cavity. Perhaps the laser itself is susceptible to room-temperature changes and those propagate into the laser cavity on a much faster time scale. I don't know the thermal coupling of ambient temperature changes into the laser.
(24-hours of second-trend data)
--If the system can handle it, do a larger temperature step (3 degrees, say), so that I can more clearly distinguish the oscillations with room temp from the step response.
--Insulate the cavity with foam (will in principle make the temperature over the can surrounding the ref cav more uniform and less affected by room temperature changes).
--Insulate the laser? Is this possible?
--Leave the system as is and, as a first approximation, fit the room-temp data to a sine wave and subtract it off somehow from my data to just see the step response.
--Don't bother with steps and just try to get the transfer function from out-of-loop temperature (RCTEMP, which is affected by temperature noise from the room) to TMP_OUTPUT via taking the Fourier transforms of both signals.
I'm flying out tomorrow morning, so I'll either need to figure out how to step the temperature set point of the can remotely, successfully, or I'll need someone to manually enter in the temperature steps for me in the control room.
c1psl has got frozen during our ezcaread/write business.
After the target was rebooted and we lost the previous setting as there was no burt snapshot for the slow targets since Dec 13, 2010.
It seems that burtrestore is essential for the bootstrapping of the MC servo, as the auto locker script refers the locking parameters
from the PSL setting values (C1PSL_SETTINGS_SET.adl).
Jenne is working on the recovery of the snap-shotting for the slow targets.
[Kiwamu Suresh Koji]
Some main parameters of the PSL has been recovered using Dataviewer and some screen snapshots, as seen in the screenshots below.
Relocked the PMC. MC came back immediately.
In the previous measurement, the PDA 255 had most probably saturated at DC, since the maximum ouput voltage of PDA255 is 5V when it is driving a 50 Ohm load. It has a bandwidth of 0 to 50MHz and so can be reliably used to measure only the 11 MHz AM peak. In this band it has a conversion efficiency of 7000 V per Watt (optical power at 1064nm). [Conversion efficiency: From the data sheet we get 0.7 A/W of photo-current at 1064nm and 10^4 V/A of transimpedance] The transimpedance at 55 MHz is not given in the data sheet. Even if PDA255 is driving a high impedance load, at high incident power levels the bandwidth will be reduced due to finite gain x bandwidth product of the opamps involved, so the conversion efficiency at 11 MHz would not be equal to that at DC.
So Koji repeated the measurement with a lower incident light level:
V_DC = 1.07 V with 50 Ohm termination on the multimeter.
Peak height at 11 MHz on the spectrum analyzer (50 Ohm input termination) = -48.54 dBm
a) RF_Power at 11 MHz : -48.45 dBm = 1.4 x 10^(-8) W
b) RF_Power = [(V_rms)^2] / 50_ohm ==> V_rms = 8.4 x 10^(-4) V
c) Optical Power at 11 MHz: [V_rms / 7000] = 1.2 x 10^(-7) W
d) Optical Power at DC = [V_DC / 7000] = 1.46 x 10^(-4) W
e) Intensity ratio: I_AM / I_c = 7.9 x 10^(-4) . AM:Carrier amplitude ratio is half of the intensity ratio = 4.0 x 10^(-4)
f) PM amplitude ratio from Mirko's measurement is 0.2
g) The PM to AM amplitude ratio is 506
As the AM peak is highly dependent upon the drifting EOM position in yaw, it is quite likely that a higher PM/AM ratio could occur. But this measurement shows how small it could get if the current situation is allowed to continue.
[Mirko / Kiwamu]
We have reviewed the AM issue and confirmed the ratio of AM vs. PM had been about 6 x103.
The ratio sounds reasonably big, but in reality we still have some amount of offsets in the LSC demod signals.
Next week, Mirko will estimate the effect from a mismatch in the MC absolute length and the modulation frequency.
Please correct us if something is wrong in the calculations.
According to the measurement done by Keiko (#5502):
DC = 5.2 V
AM @ 11 and 55 MHz = - 56 dBm = 0.35 mV (in 50 Ohm system)
Therefore the intensity modulation is 0.35 mV / 5.2 V = 6.7 x 10-5
Since the AM index is half of the intensity modulation index, our AM index is now about 3.4 x 10-5
According to Mirko's OSA measurement, the PM index have been about 0.2.
As a result, PM/AM = 6 x 103
* DC power = 5.2V which is assumed to be 0.74mW according to the PDA255 manual.
*AM_f1 and AM_f2 power = -55.9 dBm = 2.5 * 10^(-9) W.
Correction: Koji noted that Mirko actually reports a PM modulation index of 0.17 for the 11 MHz sideband (elog: http://nodus.ligo.caltech.edu:8080/40m/5462. This means
f) the amplitude ratio of the PM side-band to carrier is half of that = 0.084
g) the PM to AM amplitude ratio as 0.084 / [4.0 x 10^(-4)] = 209.
The steering mirrors for PMC were aligned. The transmission went up from 0.779 to 0.852.
I just relocked the PMC. I don't know why it was unlocked.
In order to move the emergency shut off switch in room 103 I had to turn off the 2 W Innolight laser. This job will take an hour.
It is back on.
Ben and Sam came over to fix one of the east side sliding door sensor that had to be moved from the inside to outside on the enclosure.
We turned off the 2w Innolight for 20minutes. The power is back on, the PMC and MC locked itself immediately.
This moring I centered the IOO Angle QPD. The IOO Pos QPD was not centered. The existing layout does not allow the beam centering of the Pos qpd without misaligning the MC
input. We have to add an aditional steering mirror. I will do that tomorrow morning.
I added the steering mirror for Pos and centered both qpds
C1:IOO-QPD_ANG_VERT beam movement in 1 degree C temp change in 3 hrs
I was measuring things to see how big my adapter plate needs to be, and I decided that we'd had enough days of the HEPA being on full blast, so I turned it down to 50, from 100. I think it's been on full since Katrin was working on the Y-green beat a week or so ago.
8:50PM HEPA@100% for the test
9:20-35PM HEPA level varies from 0%-50%
9:35PM HEPA@40% and left it running at this level
Nov18 1:40 AM HEPA@80% for a work around the PSL table (by KI)
Nov18 4:35 AM HEPA@40% (by KI)
I left the HEPA at the 50% level @5AM, Nov 24
PMC trans was only ~0.79, where it should be ~0.84 something. The MC was also not stellar.
I aligned the beam to the PMC, and am now getting PMC trans 0.837 .
Then I aligned the PSL zigzag to the MC, and got MC Refl down to ~0.6 .
I then aligned the WFS to the unlocked MC, and the MC Trans QPD to the locked MC.
Things seem good. MC axis is still in a good place, since we get good michelson fringes at the AS port.
I have realigned the steering mirrors for PMC because the transmitted light had been at ~ 0.741
After the alignment it went back to ~ 0.850.
I found the PSL laser has been off for four hours. Nobody seemed to know why.
I just turned it on and it is now providing about 10% lower power compared with one before the shutdown.
Let's keep the eyes on the power if it can recover as the housing gets warm.
It appears that the old PSL fast channels never made it into the new DAQ system. We need to figure out what to do with them.
A D990155 DAQ Interface card in far right of the 1X1 PSL EuroCard ("VME") crate is supposed output various PMC/FSS/ISS fast channels, which would then connect to the 1U "lemo breakout" ADC interface chassis. Some connections are made from the DAQ interface card to the lemo breakout, but they are not used in any RTS model, so they're not being recorded anywhere.
An old elog entry from Rana listing the various PSL DAQ channels should be used as reference, to figure out which channels are coming out, and which we should be recording.
The new ALS channels will need some of these DAQ channels, so we need to figure out which ones we're going to use, and clear out the rest.
I realigned the steering mirrors for the PMC. The trans value went up from 0.79 to 0.83.
The misalignment was largely in the pitch direction.
We removed the curved mirror behind the AOM (ROC=0.3m) on PSL table. The mirror is now in PSL lab. See PSL:905 for more detail.
We have aligned PMC, the WFS are not working yet.
I was interested what whitening filter do we have between MC servo and ADC. The shape is in the figure below, SR provided 1 V white noise. Before the whitening filter MC_F is measured in Volts with SR and ADC (for ADC the shape is calculated using the whitening filter form):
I also wondered if FSS or PZT servo can add noise to the mode cleaner length signal and what is their gain. It should be big, as the laser's calibration is ~1 MHz/V => to account for seismic noise of 10^-6 m at 1 Hz, the voltage given to the laser should be ~ 1 V. And it is indeed the case. The gain is ~1000. I measured the coherence between MC_F and the laser fast input. It is 1 in the range measured (0.05 - 100 Hz). FSS and PZT do not add significant noise.
Unfortunately, after the measurement when I unplugged BNS connector from the laser, I misaligned PMC. For several hours I adjusted the mirrors but could not significantly improve transmitted signal. I'll return to this issue tomorrow.
I suspect that it was just unlocked when you had disconnected the cable.
There is not reflection now. It seems that it is now misaligned after the alignment work.
So what you need is "align while scanning PZT -> lock -> align".
No, no, it was unlocked after I connected the cable back. The beam was even not on the PMC. I'll try PZT -> lock -> align.
No matter how you connect/disconnect, touching the laser may cause the PMC unlocked.
At least, I don't see the PMC reflection on the PD.
This means that the beam towards the PMC is largely misaligned.
If you are not sure what is misaligned, stop touching the table.
Close the shutter of the laser on the laser housing and leave the optics as they are.
Koji was right that I misaligned everything during the alignment work. I assumed that PMC should autolock and when I saw that it did not, I thought the laser is misaligned.
What we did:
1. Aligned mirrors to get the beam on the PD PMC REFL and PMCR camera. The PSL-PMC_RFPDDC was ~800 mV.
2. We disabled PMC servo, switching it to test position and changed "DC output adjust" by 0.01 in a loop
ezcawrite "C1:PSL-PMC_RAMP" -4.50
ezcastep "C1:PSL-PMC_RAMP" "+0.01,450" -s "0.1"
ezcawrite "C1:PSL-PMC_RAMP" 0.0
ezcastep -s "0.1" -- "C1:PSL-PMC_RAMP" "-0.01,450"
3. While the script was running we adjusted the position of the beam on the far PMC mirror looking at an IR viewer. The goal is to align two steering mirrors to catch some resonances. We monitored them on the oscilloscope and on the PMCT camera.
4. We locked PMC and aligned steering mirrors.
The ref cavity ion pump was running at 7.7kV instead of 5kV
This Digitel SPC-1 20 l/s ion pump should be running at 5kV
I noticed that the ion pump was turned off.
It was turned ON. It showed 0.00 microA at 5kV The current display is not sensitive enough. There must be some small outgassing or leak. It adds up if we stop pumping.
We want to keep the reference cavity in pristine condition. It required the ion pump running all times.
Nice PSL summaries from LHO:
The PMC was unlocked earlier this morning, for ~20min, presumably from the rocks next door. I relocked it.
Then, a few min ago, the PMC suddenly decided that it wouldn't lock with a transmission greater than ~0.7 . I found that the laser temp adjust on the FSS screen was at -1.9ish. I put it back to zero, and now the PMC locks happily again. I think we got into a PSL mode-hopping temperature region on accident.
Jenne, Den, Rana
The PMC transmission has been varying a lot and the MC seems unstable. Superstitious people might blame this on the El-nino or the alignment with Sagitarius, but we are ostensibly scientists.
WE found that the PMC EPICS values had not been toggled since the reboot and so the RF phase and Amplitude were totally wrong (we should replace this with a fixed oscillator box as we did with FSS).
Also, the NPRO SLOW slider was at -2 V which made the mode going into the PMC funny (although the mode was OK this morning before I started playing with the PMC sliders).
Before adjustment, there was a strong correlation between the seismic motions and the PMC reflection. This means that the PMC gain was low and it couldn't stay locked. Now, after fixing the RF and upping the gain slider it looks more stable. Let's watch it for a few days to see if there's an improvement in the trends.
The 10-minute trend of the lat 400 days shows that nothing has changed much this year; its been equally bad for a long while.
PMC transmission is oscillating in the range 0.5 - 0.85. PMC PZT voltage is 1-2 V.
FSS slow controls was -2.5 V. I adjusted it to 0 and PMC stabilized. PMC PZT voltage is 128, transmission is 0.845.
But most probably, slow control will drift again.
I added a subblock to the IOO model, and gave it a top_names of PSL, so the channels show up as C1:PSL-......
So far, there are just 2 channels acquired, C1:PSL-FSS_MIXER and C1:PSL-FSS_FAST, since those were already connected to the ADC. Those signals are both on the DAQ OUT of the FSS board in the rack. They are DQ channels now too.
So far, there are just 2 channels acquired, C1:PSL-FSS_MIXER and C1:PSL-FSS_FAST, since those were already connected to the ADC. Those signals are both on the DAQ OUT of the FSS board in the rack. They are DQ channels now too.
So there was a problem with the channel name C1:PSL-FSS_FAST, which conflicts with an existing slow channel. This was causing daqd to fail to start (shockingly, with an appropriate error message!). I renamed the channel to be C1:PSL-FSS_NPRO until we come up with something better.
After the change everthing worked and fb came back.
The PMC was locking right the way, but it's transmission would not go up. Finally I get it back up by moving the "sticky" DC Gain slider up and down a few times.
The FSS was -2.9, and the PMC won't lock happily unless you bring this back to 0. The symptom that this is happening is that the PMC reflection camera is totally saturated, but the PMC still looks like it's locked on 00.
The FSS Slow DC servo was turned off.
As MCL stabilizes the MC_F (Fast PZT), we no longer need to use the laser temp to do so.
In other word, if you like to turn off the MCL servo for some reason, we need to turn it on in order to keep the MC locked.