[Jenne, Raji (before dinner)]
We put the beam attenuation optics in place. Before putting any optics down, I centered the IOO QPDs, then adjusted the HWPs and PBS such that we remained centered on those QPDs.
Now, I'm about to unblock the beam and let ~100mW into the vacuum so I can lock the MC. Steve and Manasa were putting on the light access connector when I left earlier, so I'm excited to use it!
Aluminum foil replaced by sheet metal on Enclosure and AP table.
In order to calibrate MC_F signal, I need to know the calibration value from thorlab's PZT driver to laser frequency.
The calibration value should be ~ 15MHz/V (the PZT driver has 15 gain, and the laser has the calibration value of ~ 1MHz/V according to the laser spec sheet), but I want to confirm it.
This can be measured by sweeping the input voltage of the PZT driver and see the transmission signal from unlocked PMC.
1. Response of PMC transmission when the signal is inputted to laser PZT
I inputted 0.2 Hz triangular wave with 5Vamp and 2.5V offset into the PZT driver and see the transmission signal from PMC. After the PZT driver and before the laser, there is an analog low pass filter but its cut off frequency is 1 Hz so I did not take it into consideration.
(TEK00000.CSV, TEK00001.CSV in the zip file)
I could not the side-band resonances. I guess it was because the generated signal is not big enough (but still the maximum range of the signal generator.)
Therefore, in order to calibrate the input voltage to the frequency, I need to know finesse or FWHM frequency.
2. Responce of PMC transmission when the voltage of PZT on the PMC is swept
In order to measure the finesse and FWHM frequency, I also swept the PMC PZT voltage with the DC offset slider at the FSS.adl and tried to measure the finesse of PMC. (reference: elog #904)
(PMC-PZTcal_121203.xml in the zip file)
The result of fitting:
V_FSR (the PZT voltage difference between the 2 resonances) ~ 63 +/- 7 V (= 731MHz (given))
V_FWHM (the PZT voltage to sweep FWHM) ~ 0.32 +/- 0.04 V (~ 3.7 MHz)
Finesse ~ 200 +/- 30
However, this finesse value is much smaller than the value on the Wiki, 800. (Manasa showed me.)
V_FSR is comparable to the result Rana got at the referenced elog. But I am not sure about the V_FWHM because it is hard to figure out how large the PZT voltage changed from the template file (PMC-PZTcal.xml).
Are those mode wrong? But if so, where is the correct mode resonances? I think they should be visible...
3. Calibration value
When I know the FWHM frequency, I can calibrate the input on the PZT driver into laser frequency.
The results are:
if I take the finesse of 800 and FSR of 731 MHz (the values on the Wiki): ~5.0 MHz/V
if I take the finesse of 200 and FSR of 731 MHz (the measured value): ~20.0 MHz/V
Actually, the measured value is closer to the value calculated from the spec sheet.
Hmm... Does anyone find falses in my measurement?
If not, the finesse can be 4 times smaller than the value which was 5 years ago?
If you can't find the PMC sidebands in the transmission, its because the SNR is too small.
It may be a better idea to look at the PMC error signal, since the DC signal there is suppressed by the demodulation.
In order to have less unknown, you can calibrate the PMC PZT separately. Lock the PMC and take a transfer function from either the NPRO PZT input or the FSS AOM VCO input to the PMC control signal. The VCO is better, since the calibration should be much better known, but I am not sure what the current setup of the 40m PSL is, so I don't know if the FSS is normally locked.
Since you know the NPRO PZT or VCO actuation coefficients, you can assume the PMC loop (where the OL gain is high enough) is correcting for the frequency fluctuations. So, simply multiply the known coefficient by the transfer function to get the PMC PZT gain.
Then, you can re-do your PMC PZT sweep measurement and be confident of the calibration. The FSR must be right, so you can get the finesse with confidence.
Hmm... Does anyone find falses in my measurement?
If not, the finesse can be 4 times smaller than the value which was 5 years ago?
I found that MC got unstable this morning. This is caused by the drift of PMC. The transmission of PMC was going down and eventually unlocked PMC.
We adjusted 'Slow Actuator Adjust' in FSS and now the PMC is locked with transmission of ~ 0.735.
Also we aligned the MC to be locked. Now it is locked with transmission of ~ 0.5 with WFS and MCL on.
Ayaka pointed out that the PMC has too low unity gain frequency. We checked the history of "C1:PSL-PMC_GAIN"
and found that the gain was minimum from the Friday night. It was returned to nominal gain of 10.
The PMC screen had the gain status indicator always red. This was because C1:PSL-STAT_PMC_NOM_GAIN was 2 instead of 10.
This was fixed by the following command.
ezcawrite C1:PSL-STAT_PMC_NOM_GAIN 10
This will be recorded by the snapshot in an hour.
Another annoying false alerm on the PMC screen was the PMC transmission monitor.
In order to fix this, the following commands were executed.
ezcawrite C1:PSL-PMC_PMCTRANSPD.LOLO 0.75
ezcawrite C1:PSL-PMC_PMCTRANSPD.LOW 0.8
ezcawrite C1:PSL-PMC_PMCTRANSPD.HIGH 0.9
ezcawrite C1:PSL-PMC_PMCTRANSPD.HIHI 0.95
Also the corresponding EPICS database (/cvs/cds/caltech/target/c1psl/psl.db) has been updated accordingly.
I calibrated MC_F signal into Hz/rtHz unit using the transfer function from MC_F to PMC feedback signal.
Here is the diagram:
n_mcf is MC_F signal we can get at dtt. I measured n_pmc/n'_mcf using SR.
Other information I used:
G_out = 2.49/123.49 (see the document D980352-E01-C)
Fout has 1 pole at 10 Hz (see the document D980352-E01-C)
A_pzt = 371e+6/63 [Hz/V] (see elog)
F_wt has 1 pole at 100 Hz and 1 zero at 10 Hz.
Then, calibration transfer function of H is fitted as 1e+9/f [Hz/V]:
Then, the calibrated spectrum of MC_F is below:
This calibration have about 20 % error.
Compared to the spectrum in Jenne's paper (elog), above 20 Hz it seems to be laser frequency noise. But now we have extra unknown noise below 10 Hz.
Note: calibration value of laser's PZT is ~ 1MHz/V. This is reasonable compared to the data sheet of the laser. (This is calculated by combining result of H and transfer function of the circuit box1 and FSS.)
Wednesday night, there was ~0.4 V on the PMC transmission PD. I adjusted the steering mirrors into the PMC and got the transmission up to 0.81 V.
The PMC PZT voltage slider seemed sticky. First it would not do anything, than after moving slider back an forth a few times, it had a range of 60V and later it had full range and it locked
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 looked at PMCR camera on the MC1 tv, and tweaked up the beam going into the PMC - it only needed a little bit of pitch.
Yuta and I measured the MC spots, determined (consistent with my measurements this morning) that they were only off in yaw. We touched the 2nd steering mirror in the zigzag on the PSL table in yaw a small amount (top of knob away from me), realigned the MC, and things were good. The plot is zoomed in to show only measurements taken today. 2 in the morning, before anything in the IFO room was touched. 1 this afternoon after tweaking PMC. 1st attempt at PSL beam tweaking was successful, 2nd measurement confirms it wasn't a fluke.
[Steve, Jenne, Yuta, Manasa]
We have kept the laser ON at low power through the pump down process. As we pumped down, at around 400torr, we found that the PSL mech shutter closed. Steve explained that it was due to an interlock with a pressure gauge. To keep the IFO running, we switched the shutter from N.C (normally close) to N.O (normally open). This should be undone after the pumpdown.
In the process of figuring out, we reset the shutter and switched it ON and OFF a couple of times.
1. Filter module (FM1) on PRCL and MICH show significant delay while enabling and disabling.
2. I tried to fix PMC alignment (PMC trans was 0.76). I was not able to get PMC trans more than 0.79.
PMC has been this way since yesterday.
3. MICH is still bright when locked (ASDC_OUT reads 0.08 for dark and 2.0 for bright). We suspect it is because of the AS55_I error offset that persists even after running LSCoffsets script.
4. PRMI shows some dither at 3Hz when locked.
PMC is fixed with 0.84 in transmission. It was misaligned in pitch (fixing this increased PMC_trans to 0.822 from 0.773) and Koji also touched the wave plate and polarizer (changed PMC_trans to 0.845).
Last night I measured the modulation depth of the MC incident beam.
The beam is taken from one of the PO beam at the wedge plate before the IMC.
After removing the knife edge to dump this beam, the beam is sent to the west side
of the PSL table and put into the OSA cavity.
[The beam dump was returned after the measurement.]
I had some confusion and after all I use the OSA labeled as AS OSA rather than the one on the PSL table.
[The AS OSA was returned to the AP table.]
The transmission was detected by PDA255 and filtered by ITHACO 1201 preamp with G=10, no HPF, 30kHz LPF.
It was confirmed that the peak amplitudes are not reduced by the LPF filter. The resulting time series
was recorded by an oscilloscope.
Three measurements have been taken. The 11MHz peaks are offset by the carrier peak. They appropriately
removed. The ratio of the sideband and carrier peaks is converted to the modulation depth using the following formula.
P_sb / P_ca = [J1(m)/J0(m)]^2
The modulation depth for the 11MHz: 0.190 +/- 0.003
The modulation depth for the 55MHz: 0.2564 +/- 0.0003
The three scans showed very similar numbers. That's why the statistical error is such small.
I don't think the systematic error is not such good.
This number is much different form the previous meaurement by Mirko.
http://nodus.ligo.caltech.edu:8080/40m/5519 m=0.14 (11MHz) & 0.17 (55MHz)
but the measured voltages and the modulatio depths are inconsistent.
http://nodus.ligo.caltech.edu:8080/40m/5462 m=0.17 (11MHz) & 0.19 (55MHz)
Probably the modulation depths should be checked by the IMC again.
However, it is certain that the 55MHz modulation exists, and even larger than the 11MHz one.
The next is to confirm that the modulation frequency is matched with the IMC FSR.
It is to make sure that the modulation is transmitted to the main IFO without attenuation.
The PMC locked manually. MC grabbed lock instantaniously
Note: The TRY PD isn't installed and normalized properly yet, so the IFO OVERVIEW screen indicates lock for the Yarm constantly, which is not true. Hopefully in the next day or so the screen will be back to telling the truth.
Also, the LSC Locking was left ENABLED (presumably over the weekend). This is not so good. It can kick optics around, so we should all take a look when we walk through the control room, and if no one is locking, please disable the LSC master switch.
The MC seemed to be losing lock recently quite a bit. I noticed that the PC Drive RMS signal was red.
This means that the high frequency drive to the Pockels cell was too high by a factor of 2-3 and sometimes saturating and breaking the lock.
I fiddled with the gains on the FSS screen until this value went down. It looks like there is some kind of high Q oscillation; it takes a couple minutes for the PC Drive RMS to settle to its new position after changing the gains.
The attached trend plot show the last 2 hours. The mean is now back to ~1 V and seems OK. We should really examine the FSS or MC error point spectra with the RF analyzer while exploring this gain space.
Today Rana pointed out that our FSS slow servo is malfunctioning. It has been for a while that our laser temperature control voltage drifted from 0 to 10.
I looked at FSSSlowServo script that runs at op340m and controls the servo. Script disables the servo when MC transmission is less then FSS_LOCKEDLEVEL. But his value was set to 0.2 probably till reference cavity time.
This means that slow servo was not disabled when MC was unlocked. I changed this value to 7000.
Also I increased integral gain from 0.0350 to 0.215 such that fast control is always in the range 4.5 - 5.5
PMC aligned. C1:PSL-PMC-PMCTRANSPD improved from 0.72ish to 0.835ish.
I'm just now realizing that the PMC has also not been locked since noon today, and doesn't seem to be responding to anything right now.
wtf is going on here?
Rana showed up and diagnosed the problem as a railed FSS SLOW output. The SLOW Monitor about was showing ~6V, which is apparently a bad mode-hoppy place for the NPRO. Reducing the SLOW output brought things back into a good range which allowed the PMC to lock again.
In attempting to diagnose the problem I noticed that there is -100 mV DC coming out of the PMC RFPD RF output. This is not good, probably indicating a problem, and was what I thought was the PMC lock issue for a while. Need to look at the PMC RFPD RF output.
All of these changes were committed to the SVN.
To allow Annalisa to work on the Y-green alignment as I work with the X-green, the part of the PSL green beam that goes to the Y-green beat PD has been blocked with an iris.
Rana and I connected the PMC_trans output to the BNC connector board on the west end of the PSL table (the channel is labeled). I took a few spectra off of PMC_trans and the SR785 was connected directly to the PMC_trans output for about an hour.
Data will follow.
The PMC was locked on an LG 10 mode (or something like it), for at least the last 8 hours. I relocked it on the regular 00 mode, and it's fine now.
Also, in CDS news, I did an mxstream restart (the RCG upgrade is supposed to make this not an issue anymore...), and did a "diag reset" afterwards, and all of the IPC errors except for one in the LSC model have gone away (OAF is still not running....on my to-do list, but not super high priority).
After relocking the PMC at a good voltage, Steve and I re-aligned the beam into the PMC by walking the last two steering mirrors. After maximizing the power, we also aligned the reflected beam by maximizing the PMC_REFL_DC with the unlocked beam.
Transmission is back to 0.84 V. We need Valera mode matching maintenance to get higher I guess. Maybe we can get a little toaster to keep the PMC PZT more in the middle of its range?
PSL temperature changed
The beat note of Xarm looked somehow strange before (elog). It should be the highest when the green transmission power is highest, in other words when the end green PDH locks with a TEM00 mode. But it was not like that. When the end PDH locked with other modes (GTRX: below 0.3), the beat note was higher than TEM00 mode (GTRX: around 0.5).
We guessed that end green laser was somewhere around the point where there were 2 stable TEM00 modes . In order to move away from this unstable region of the end laser, we changed PSL temperature to obtain beat note at a different green laser frequency where we do not have any of the weird modes oscillating.
We changed the PSL temperature from 31.63 degree to 31.33 degree. We measured the in-loop noise of ALS loop and I attached it. There is not big difference in Yarm, but the Xarm in-loop noise become better in high frequency region. We think before the xend green laser was in a not-so-good state and the laser had more frequency noise then.
After change PSL temperature, Xarm ALS is so stable. Actually Xarm is being locked right now and it is locked for more than 50 minutes!!
Although the Xarm ALS is so stable, Yarm ALS is not stable right now. It lost lock by ~5min. We don't know what is the reason, so we will try to fix it tomorrow.
I have just turned on the PSL Innolight laser. The laser shut down with unknown reason a day ago.
The PMC was unlocked for a little over an hour. I relocked it, and the MC locked itself. Today, it looks like PMC yaw alignment is bad, and maybe pitch isn't so good either. Transmission is 0.77
I wonder what's drifting between the laser and the PMC? And why is it getting worse lately?
The PMC refl is bad in pitch today, and the transmission is only 0.76, rather than our usual 0.83ish.
I did a quick, rough tweak-up of the alignment, and now we're at 0.825 in transmission.
The PMC transmission continuously degrades. In order to see what is really drifting the laser output after PBS was sampled as shown.
I went to re-align the beam into the PMC just now. I also tapped all the components between the laser and the PMC; nothing seems suspicious or loose.
The only problem was that someone (probably Steve or Valera) had closed down the iris just downstream of the AOM to ~1-2 mm diameter. This is much too tight! Don't leave irises closed down after aligning. An iris is not to b used as a beam dump. Getting it within a factor of 5-10 of the beam size will certainly make extra noise from clipping/scattering. After opening the iris, the reflected beam onto the PMC REFL camera is notably changed.
Not sure if this will have any effect on our worsening transmission drift, but let's see over the weekend.
I took pictures of this clipping as well as the beam position on Steve's new Retro Position Sensor, but I can't find the cable for the Olympus 570UZ. Steve, please buy a couple more USB data cables of this particular kind so that we don't have to hunt so much if one of the cryo (?) people borrows a cable.
Attachment shows PMC power levels before and after alignment. After alignment, you can see spikes from where I was tapping the mounts in the beamline. We ought to replace the U-100 mount ahead of the AOM with a Polanski
EDIT: Cryo team returns cable - receives punishments. Picture added.
While looking at the PMC REFL beam for the AOM diffracted beam, we noticed that although only one beam exists between the PMC and the first steering mirror, there are two afterwards and they both go to the PMC REFL RFPD!!! This is madness. We only want one beam on our PDH diode.
The reason that we have two beams is that that first steering mirrors is actually a (W1-PW-1025-UV-1064-45P) non-wedged window with an AR coating on only one side. So two beams come out of it. There is a terrible and floppy and illegal anodized aluminum dump close to this beam which *someone* probably intended to use as a "scraper" to get rid of one of the beams.
Black anodized aluminum is a horrible beam dump material at 1064 - its about as grey as Steve's chair. And its so soft that it scatters light back into the PMC and makes more acoustic noise. And it is mounted so poorly (only one screw) that it can easily be bumped and twist and miss the beam. Punchline: only use anodized aluminum dumps for stray light around cameras or for HeNe for OL. Its NOT allowed anywhere where we care about interferometry of NIR beams.
It was also set to dump the dimmer beam. On Monday, we should order ~5 W1 and get them with a wedge of 1-2 deg. Then we use a black glass dump for the dim beam and orient the bright one to hit the REFL camera and the PMC REFL PD.
For the weekend, I have adjusted the crappy grey aluminum flapper to catch the bright beam so that the PMC REFL image no longer shows the interference fringe of two beams. Lets see how the PMC drifts over the next 3 days.
I was working on the electronics bench and what sounded like a huge truck rolled by outside. I didn't notice anything until now, but It looks like something became misaligned when the truck passed by (~6:45-6:50 pm). I can hear a lot of noise coming out of the control room speakers and pretty much all of the IOO plots on the wall have sharp discontinuities.
I haven't been moving around much for the past 2 hours so I don't think it was me, but I thought it was worth noting.
The PMC auto locker is not set to acquire error message made me lock PMC manually. Arms locked instantly: TRY 0.9 V and TRX 0.65 V
Back in 2009, Jenne replaced the PMC board mixer with a Level 13 one. Today I noticed that the LO level on the PMC screen was showing a LO level of ~5-10 dBm and fluctuating a lot. I think that it is related to the well known failure of the Mini-Circuits ERA-5SM amplifier which is on the D000419-A schematic (PMC Frequency Reference Card). The Hanford one was dying for 12 years and we found it in late 2008. If we don't have any in the blue bin, we should ask Steve to order 10 of them.
The attached trend shows 2000 days of hour trend of the PMC LODET channel. The big break in 2009 is when Jenne changed the mixer and then attenuated the input by 3 dB. The slow decay since then is the dying amplifier I guess.
Since the LOCALC channel was not in the trend, I added it to the C0EDCU file tonight and restarted the FB DAQD process. Its now in the dataviewer list.
I went out and took out the 3 dB attenuator between the LO card and the PMC Mixer. The LO monitor now reads 14.9 dBm (??!!). The SRA-3MH mixer data sheet claims that the mixer works fine with an LO between 10 and 16 dBm, so I'll leave it as is. After we get the ERA-5, lets fix the LODET monitor by upping its gain and recalibrating the channel.
PSL NPRO shut down again today for reasons unknown. I was working near the IOO rack and noticed there was no light at both the refl and trans PMC cameras. Jenne and I checked the PSL and found the 'OFF' red switch on the laser driver lit up. Switching ON the green button brought the laser back. PMC and MC autolocked after this.
This is a 10-minute trend of the last 60 days of the pointing of the PSL beam.
The main fluctuation seems to be at the ~30 day time scale (not 24 hour) and its all in the vertical direction; the horizontal drift is ~10x less (as long as we believe there is no calibration error).
So what's causing all of this vertical shift? And why is there not just as much horizontal??
I went to the PSL table to re-align the input pointing to the IMC. After trying to optimize the pointing into the PMC and not succeeding I also then touched the wrong mirror and messed up our IOO QPD reference pointing.
The IMC is locking again, but I'll have to fix the pointing on Monday.
I'm not sure which pointing Rana wanted to fix today, but here's a measurement of the MC spots. They actually look pretty good. There is some room for improvement, but not a lot, so I'm leaving it alone for now, while I play with other things in the IFO.
spot positions in mm (MC1,2,3 pit MC1,2,3 yaw):
[0.63368182839757914, 1.3004245778952557, 0.33621668795755993, -1.5585578137597658, -3.1344594013487286, -1.0533063060089816]
IOO QPDs tested in dark, lighted and open PSL enclosure. The created temperature change 0.03 C has effect on monitoring in pitch.
Atm1, all lights off 10 min, PSL enclosure lights on 10 min, all lights off 15 min, open door # 11 at north east corner of enclosure ( HEPA filters are running at 30V ) for 10 min, closed-dark enclosure 15 min
dark 10, lighted 10, dark 15, open-dark 10 and closed-dark 15 minutes
Atm2, Pitch drift of 24 hours does not recover
I looked at IOO QPDs again. QPD_POS was clamped by one screw. Dog clamp was added on the unclamped side.
QPD_ANG chassis has no isolation to optical table..._POS has. QPD_ANG base was tightened also.
Both QPDs moved a little bit but I did not centered them. The spot sizes are 2-3 mm They should be smaller.
How ever, we still can not explane the pitch movement of the IOO beam
Razor beam dumps were labeled at the AP table.
The 40m roof was cleaned from leafs this morning.
IOO pointing is drifting in pitch. I'd like to use a QPD instead of the paper target to see if the Innolite output is stable. The idea is to move temporarily IOO-QPD_POS to this location
Three good days of IOO pointing: Friday, Sat and Sun What was changed? May be the clamping on Friday?
IOO vertical changes recovering as tempeture. IP is clipping at plastic enclosure of ETMY
NOTE: ANTS at the PSL optical table. I will mop with chemicals tomorrow if we see more.
I do like to move IOO-QPD_POS temporarily to see that the feedback has anything to do with with the pointing.
GariLyn is using our green light on the west side of the PSL table. The green PDA36As were moved and the HEPA turned up to 60V
The 2W Innolight was off for 4 hours.
CVI broadband AR coating was measured at the PSL-enclosure table around 9-10am today. The 2W Innolight first PBS S polarization beam was used with an other 1/2 wave plate and PBS.
W2-PW1-1004-C-633-1064-0 This 0.045" thick window has 0.7- 0.8 % reflected beam on each sides at 5 degrees of incidence, P polarization.
The specification is R avg <0.5 % per surface at 0 degree
Rana wants The device would be useless with such a high R, but R 0.1% is OK so I will get V coating.
CVI V-AR coating at 1064 nm, 0 degree, catalog item is R< 0.25% on each sides,
R <0.1 % is custom at much higher prices.
This custom order should go with other orders that has similar need.
From CVI: 5-6-2014
I checked the trace info on the W2-PW1-1004-C-633-1064-0, BBAR coated window that you received. It is side 1, 0.42%R & side 2, 0.53%R @ 1064nm. And with the shift, I’m not too surprised you ended up with 0.7%. A V coat would start with <0.25% (and more typically coming in at ~0.1%) per surface. As far as stock options, I have a 1”dia x 4mmT, fused silica window that is recorded as side 1, R=0.09 and Side 2, R=0.08% @ 1064. Is this too think or will it work for you?