Today I tested the circuitry within the QPD to make sure I had put it back together correctly. The output was able to detect when a laser pointer was shone on different quadrants of the QPD when hooked up to the oscilloscope, so fixing the QPD worked!
Following this, I spent awhile understanding what was going on with the circuit reading from the QPD. I concluded that the opamp on the QPD circuit acted as a low pass filter, with corner frequency of about 17 kHz, which serves our purposes (we are only interested in frequencies below 1 kHz). I diagrammed the circuit that I plan to build to give pitch and yaw (attached). It will be necessary to make small modifications to the circuitry already built (removing some resistors), which I have started on.
Next time, I will construct the circuit that adds/subtracts signals on a breadboard and test it with the QPD circuit that is already built.
We replaced the dead photodiode on MC REFL PD with a new one (GAP 2000). We measured the frequency response of the PD and tuned the resonant frequency using inductor L5 (in the circuit diagram) to be 29.575MHz - over an average of 10 measurements.
Riju is measuring the characteristics of the PD and will be posting an elog in detail.
We turned IFO power back to 1.25W by removing the attenuator and forgot that the Y1 mirror before the REFL PD must be replaced with BS 10% before getting to full power. The PD is dead and now we are in the process of fixing it. Forgive us for all our sins!
On the other note, we have changed the mech shutter mode from N.O back to N.C. So the shutter now works as usual from the medm screen.
IFO P1 pressure is 1 mTorr. It is ready for high power light.
The Maglev took over the pumping at 500 mTorr
Pump down is restarted after 10.5 hrs stop overnight.
[Rana, Yuta, Koji]
21:05 at the pressure of 10torr
V3 closed. RV1 manually closed. RPs were turned off. And the bellows between RV1 and the rughing pumps are disconnected.
We have aligned the Y-arm to lock in green. The green beams at the PSL table were clipping at the attenuation optics we installed for the vent (HWP-PBS-HWP). We had to move the polarization changing wave plate to get the green beam on the steering mirror. We installed the GRNT camera on the PSL table and aligned the arms to get TEM00 flashing. Green TRX PD was then installed and the trans power was brought to a maximum of 210uW.
We will use this to align the IR to the arm when we are back in full power tomorrow.
This plot shows the trend of the OL during the past several hours of roughing pumping.
The big steps at the start of the pump down is NOT due to the pumping, but is instead the "recentering" that Yuta did. Looks like he was unable to find zero on the ETMY.
Some of the rest of the drift is probably just the usual diurnal variation, but there does seem to be some relation to the pumping trend. I guess that the shift of ~0.3 in the ITMX and ITMY pitch is real and pressure related.
We need to figure out how to put the OL calibration factor into the SUS-OL screens.
We are pumping down with RP1 & RP3 oily roughing pumps at 3 Torr/min speed. The butterfly valve was just removed.
The PSL shutter is open to vacuum at ~100 mW 1064 nm. The inter lock should close it at ~5 mTorr.
Rana will shut down pumping tonight.
He will close V3 from screen, close RV1 valve with torque wheel, turn off roughing pumps and disconnect hose between RV1 and roughing pumps.
I will restart pumping early morning tomorrow.
[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.
[Steve, Manasa, Jenne, Sendhil, Evan, Yuta]
We put heavy doors on ITMX/ITMY/BS chamber and started pumping down from annulus.
What we did:
1. Replaced POP55 with AS55 back, because it was not broken.
2. Centered on AS55, REFL55, REFL11, POPDC PD.
3. Tried to lock PRMI, but I couldn't lock even MI stably for more than 1 min. I believe this is because it was noisy this morning. But I checked again that REFL/POP/AS beams are coming out without clipping and we have some error signals.
4. Noticed AS beam has less range in left (on AS camera), so we tweaked OM4 a little to make more room.
6. Took pictures inside ITMX and BS chambers
7. Put heavy doors on ITMX/ITMY/BS chambers.
8. Started pumping down annulus.
9. Recentered IPANG/IPPOS and oplevs on their QPDs.
POP, REFL, AS:
c1iscex is dead again. Red lights, no "breathing" on the FE status screen.
The c1iscex machine itself wasn't dead, the models were just not running. Here are the last messages in dmesg:
[130432.926002] c1spx: ADC TIMEOUT 0 7060 20 7124
[130432.926002] c1scx: ADC TIMEOUT 0 7060 20 7124
[130433.941008] c1x01: timeout 0 1000000
[130433.941008] c1x01: exiting from fe_code()
I'm guessing maybe the timing signal was lost, so the ADC stopped clocking. Since the ADC clock is the everything clock, all the "fe" code (ie. models) aborted. Not sure what would have caused it.
I restarted all the models ("rtcds restart all") and everything came up fine. Obviously we should keep our eyes on things, and note if anything strange was happening if this happens again.
Yuta retrieved the IR card that had fallen to the bottom of the IOO chamber, just before we put on the access connector yesterday. The clean "pickle picker" long grabber tool worked wonders.
I have found two great FET input chips that rival the storied, discontinued AD743. In some ways, they are even better. These parts are the OPA140 and the OPA827.
Below is a plot of the input-referred voltage noise of the two op amps with Rsource = 0, along with several others for comparison. The smooth traces are LISO models. The LT1128 and AD797 are BJT-input parts, so their voltage noise is naturally better. However, the performance you see here for the FET parts is the same you would expect for very large source impedances, due to their extremely low current noise by comparison. I have included the BJTs so that you can see what their performance is like in an absolute sense. I have also included a "measured" trace of the LT1128, since in practice their low-frequency noise can be quite higher than the spec (see, for example, Rana's evaluation of the Busby Box). The ADA4627 is another part I was looking into before, the LT1012 is a less-than-great FET chip, and the AD797 a less-than-great BJT.
As you can see, the OPA140 actually outperforms the AD743 at low frequencies, though it is ~2x worse at high frequencies. The OPA827 comes close to the AD743 at high frequencies, but is a bit worse at low ones. Both the OPA140 and OPA827 have the same low-frequency RMS spec, so I was hoping it would be a better all-around part, but, unfortunately, it seems not to be.
The TI chips also have a few more things on the AD743:
These characteristics make both parts exceptionally well suited for very-high source impedance applications, such as very-low-frequency AC-coupling preamplifiers or ultra-low-noise current sources.
(Apologies---the SR785 I was using had some annoying non-stationary peaks coming in. I verified that they did not affect the broadband floor).
I'm not sure about the OMC situation at 40m. I think there are no direct beam reflected back into IFO from OMC path. There must be some backscatter, but we have to open OMC chamber again to put a beam dump.
I don't think we want to put one in OMC path for this pump-down, but we can put a beam dump to dump reflected beam from mis-aligned SRM tomorrow, if available.
Is the beam going towards the OMC going to cause backscatter because of uncontrolled OMC or can we park that beam somewhere dark?
Blue ones are the ones we checked yesterday.
Green ones are the ones we checked today.
Red ones are the ones we couldn't check.
We noticed mis-centering on green optics and partial clipping of higher order modes, but we did not touch any green optics in-vac. This is because green beam from Y end and X end has different spot positions on the green optics after periscopes. We confirmed that direct green beam from ends are not clipped.
I believe we have checked everything important. Any other concerns?
Currently, SRM is misaligned in pitch so that SRM reflected beam hits on the top edge of SR3 (not on the mirror, but on the cage holding the mirror).
We also confirmed that SRM oplev beam is coming out from the chamber unclipped, and centered on QPD when SRM is "aligned".
Please confirm the SRM OL beam is not too bad and also find where the mis-aligned SRM puts its beam. WE want to be sure that there is not too much unwanted scattering from SRM into the PRFPMI.
After aligning IFO and putting the access connector on, we also centered IPANG/IPPOS and all oplevs (except SRM).
To avoid clipping of PRM/BS oplevs, we re-arranged oplev steering mirrors on BS table.
What we did:
1. Checked IPANG comes out unclipped after putting on the access connector.
2. Centered IPANG on its QPD.
3. Checked oplevs beams for ITMX/ITMY centered on in-vac mirrors, and centered them on their QPDs.
4. Checked IPPOS beam is centered on the mirrors inside BS chamber, and centered IPPOS on its QPD.
5. Tweaked oplev mirrors on BS chamber to make PRM/BS oplev beam unclipped and centered on mirrors, and centered them on their QPDs. To avoid clipping of oplev beams in BS table, we re-arranged oplev steering mirrors on BS table (outside the vaccum).
QPD values, IFO_ALIGN/MC_ALIGN screens, OSEM values attached.
- IR incident beam and IFO aligned
- X/Y end green coming out to PSL table (in higher order modes)
- IPANG/IPPOS available
- All oplevs available
- AS/REFL/POP cameras ready
- access connector, ETMX/ETMY heavy doors on
- ITMX/ITMX/BS heavy doors are not on
- AS/REFL/POP PDs not centered
- POX/POY/TRX/TRY not aligned
- AS beam coming out of the OMC chamber low by ~ 1 beam diameter (my bad)
- Align AS/REFL/POP PD and lock PRMI
- Take pictures of ITMX/ITMY/BS stacks
- Put heavy doors on ITMX/ITMY/BS chambers
- Start pumping down
Manasa and I are trying to get the AS beam onto the AS camera with a focusing lens. Currently, the mirror immediately preceding the camera has been removed and the camera and lens are sitting directly behind the BS.
[Yuta, Manasa, Sendhil, Jenne, Steve, Jamie, Koji, Evan]
The interferometer is well-aligned, and ready for pump-down. The access connector is in place, as are the ETM heavy doors. We will do ITM and BS doors tomorrow, then begin pumping.
Before we redid the ITM pointing, I confirmed that I could see both POX and POY on their respective tables, on a camera, unclipped. I should check again quickly now that the ITM pointing has been finalized.
We went back to the arms, to perfect the ITM pointing. Input beam was already centered at ETMY. ETMY was pointing so that beam reflected to ITMY. ITMY was adjusted a few (less than 4?) steps of 1e-3 size, to make reflected beam hit center of ETMY.
BS was already pointing so beam hit center of ETMX. ETMX was pointing to hit center of ITMX. ITMX was adjusted a few (less than 4 again?) steps of 1e-3 size to make reflected beam hit center of ETMX.
Checked centering on AS path. AS beam comes out of the vacuum a little low, but this wasn't discovered until after the access connector was in place. We could adjust PZT3 (last AS mirror on BS table that sends beam over to OMC table), but we don't want to do this since we won't be able to re-confirm centering on the 3 mirrors on the OMC table.
Green beams (first Y, then X) were aligned using out-of-vac steering mirrors until beams were flashing in their respective arm cavities. Green Y is a little close to the edge of the bottom periscope mirror, on the "up" periscope. Since there is no steering between the arm and this periscope, fixing it would require moving the periscope. We leave this to the next vent, when we finally install the BS table extension. We were flashing a higher order yaw mode (5ish nodes) for the Y arm, and the very edge of the higher order mode on one side was a little bit clipped after reflecting off the steering mirror on the OMC table. This is happening because that mirror is in the mount backwards (so we have access to the knobs). We are confident that the straight-through beam is well centered on that mirror, so once we get it aligned to TEM00, there will be no clipping. We then did the X arm green, which was flashing a pitch higher order mode (again 5ish nodes). The very edge of the higher order mode is clipping a little bit on the top mirror of the "down" periscope on the IMC table, but again the straight through beam is okay, and we're confident that the TEM00 mode will make it unclipped. We could have touched some steering mirrors on the BS table, but since this was once upon a time well aligned, we don't want to futz with it.
Corner oplevs are all centered on their QPDs. (The ETM oplevs were centered a few days ago).
Access connector and ETM doors are on.
The last 3 vertex doors will go on tomorrow when Steve gets in, and then we'll start pumping.
There are no in-vac PZTs that need to be turned on (we've been using the output steering PZTs as non-energized fixed mirrors for some time), so we can lock at our leisure tomorrow afternoon.
I have updated the vacuum checklist for in vacuum alignment. Please take a look (https://wiki-40m.ligo.caltech.edu/vent/checklist) and see if I missed anything. My goal was to make it incredibly step-by-step so there can be no mistakes.
After in-vac alignment work last night, PRC is flashing brighter than PRMI alignment last week.
My hypothesis is that "we aligned PRM to junk MI fringe last week". Possibly, we used MI fringe caused by AR reflection of ITMs, or MI fringe reflected from SRM.
PRC flashing last week (youtube, elog #8085, elog #8091)
PRC flashing this time (Lens in-front of AS camera was taken out)
My hypothesis can explain:
- why we had dimmer POP last week (flash in half-PRC was way brighter even when we had more attenuators (youtube))
- why I thought AS55 is broken (AS was too dim)
Be careful of junk beams.
I attached clipping/centering checklist for the alignment.
Blue ones are the ones we checked today. Red ones should be checked tomorrow. Circles indicate centering on the optics, rectangles indicate clipping check, and arrows indicate retro-reflecting or bounces.
We found mis-centering on MMT1, PR2 and SR3 tonight (by ~0.5 beam diameter). They are also indicated.
I think we don't want to touch MMT1 and PR2 anymore, because they change input beam pointing.
I'm a little bit concerned about high beam on SR3, because we had PRC flashing in vertical higher order modes. We also see ETMX slider values high in pitch (~ 5.4).
Also, the diameter of ETMX reflected beam on ITMX looked larger and dimmer than ITMX transmitted beam, which doesn't seem reasonable.
Wednesday, Feb 20:
- tweak TT1/TT2 and PRM so PRC flashes
- re-check Yarm/Xarm bounces
- center beam on all AS optics, starting from SR2
- make sure REFL and AS is clear
- check if TRY/TRX are coming out from the ends
- check beam centering on mirrors in IMC/OMC chamber as far as you can reach
- inject green from both ends
- make sure green beams are not clipped by mirrors on BS chamber, IMC/OMC chamber
- re-center all oplevs, with no clipping
- check all OSEM values
- take pictures of flipped PR2 and input TTs (and everything)
- close all heavy doors and put the access connector back
Thursday, Feb 21:
- make sure we can lock PRMI
- start pumping down when Steve arrives
[Yuta, Sendhil, Jamie, Jenne, Rana]
1. After the MC centering, we tried to align the IFO using IPPOS and IPANG as reference. This did not recover the alignment perfectly. We were clipping at the BS aperture. Using TTs, we centered the beam at BS and PRM.
2. Using TTs, the beam was centered at ITMY and ETMY.
3. IPPOS and IPANG mirrors in-vacuum were aligned and were centered at the out-of-vacuum optics.
4. We checked the centering of the beam on optics in the BS and ITMY chamber. (Yuta will make an elog with the layout)
5. We retro-reflected ITMY at the BS and aligned ETMY such that we saw a couple of bounces in the arm cavity.
6. Using BS, the beam was steered to go through the center of ITMX and ETMX.
7. At this point we were able to see the MI fringes at the AS port.
8. We made fine alignments to the ITMX such that we saw MI reflected at the Farday.
9. We retro-reflected ITMX and aligned ETMX to see the beam bounce at the ITMX.
10. We aligned PRM such that PRC flashes. But we were not happy with the flashes (they were in higher order modes). We suspect that minor tuning of the input pointing might be necessary.
11. We closed for the day
[Jenne, Manasa, Yuta]
Since we levelled IMC stack, we had to center beam spots on MC mirrors again.
We did this by steering PSL mirror in yaw (about same amount but opposite direction to what we did in elog #8077)
Residual beam tilt compared with a line through MC1 and 3 actuator nodes is ~ 15 mrad, mainly in yaw.
I finished working out the circuit and figured out where the broken connections were. This is diagrammed in my notebook (will draw up more nicely and include in future elog post). Within the QPD circuitry, it seems like there are already opamps which regulate the circuit. I need to discuss the final diagram further with Eric.
I rewired the circuit inside the QPD box, which took awhile because it was difficult to solder the wires to such small locations without having multiple wires touch. This is completed, and on Friday I will begin to make the circuit to add/subtract signals to give pitch and yaw.
After spending a good deal of time learning how to use the SR785, I was able to characterize my prototype circuit. The transfer function from a swept sine measurement looks very similar to the theoretically calculated transfer function (both of which are attached). The frequency response of the circuit was considered over the range 10 Hz - 10 kHz, which contains the eventual working range of the ISS (at least to my knowledge).
Note that OP27 op-amps were used instead of the high-speed AD829 op-amps that will be implemented in the actual design. This was done as a result of the limitations and inherent noise characteristics of the breadboard on which the prototype was built.
Unfortunately, I saved the wrong dataset (i.e. phase of the transfer function, not magnitude) and thus the presented function here is image generated by the SR785.
RXA: One must learn to use the python-GPIB interface to not lose data in the future.
c1iscex is back up. It is communicating with it's IO chassis, and all of it's models (c1x01, c1scx, c1spx) are running again.
The problem was that the IO chassis had no connection to the computer. The One Stop card in the IO chassis, which is the PCIe bridge from the front-end machine and the IO chassis, was showing four red lights instead of the dozen or so green lights that it usually shows. Upon closer inspection, the card appeared to be complaining that it had no connection to the host card in the front-end machine. Un-illuminated lights on the host card seemed to be pointing to the same thing.
There are two connector slots on the expansion card, presumably for a daisy chain situation. Looking at other IO chassis in the lab I determined that the cable from the front-end machine was plugged into the wrong slot in the One Stop card. wtf.
Did someone unplug the cable connecting c1iscex to it's IO chassis, and then replug it in in the wrong slot? A human must have done this.
In order to address the issue of low MC1 OSEM voltages, Yuta and I looked at the IMC table levelling. Looking with the bubble level, Yuta confirmed that the table was indeed out of level in the direction that would cause MC1 to move closer to it's cage, and therefore lower it's OSEM voltages. Looking at the trends, it looks like the table was not well levelled after TT1 installation. We should have been more careful, and we should have looked at the MC1/3 voltages after levelling.
Yuta moved weights around on the table to recover level with the bubble level. Unfortunately this did not bring us back to good MC1 voltages. We speculate that the table was maybe not perfectly level to begin with. We decided to try to recover the MC1 OSEM voltages, rather than go solely with the bubble level, since we believe that the MC suspensions should be a good reference. Yuta then moved weights around until we got the MC1/3 voltages back into an acceptable range. The voltages are still not perfect, but I believe that they're acceptable.
The result is that, according to the bubble level, the IMC table is low towards MC2. We are measuring spot positions now. If the spot positions look ok, then I think we can live with this amount of skew. Otherwise, we'll have to physically adjust the MC1 OSEMS.
See TT DB25 pin swapping elog#7869
[Steve, Yuta, Koji]
The ETMX heavy door was removed.
I didn't use LED flash light. We learned from the past (elog #7355). I checked that POP55 and REFL55/165/33/11 are clearly responding to flash flight, but I didn't expect that much difference in DC gain.
I wonder why we could align AS beam to AS55 in Feb 8 (elog #8030), but not in Feb 15 (elog #8091). I will check during the pump down.
10010 Ohm for POP55 vs 50 Ohm for AS55 (cf. http://nodus.ligo.caltech.edu:8080/40m/4763)
I wonder if you used an LED flash light, which emits no IR.
I wonder if you used an LED flash light, which emits no IR.
These are things need to be done for demonstrating PRFPMI using ALS.
All of these should be done before March 8!
- Fix c1iscex -JAMIE (done Feb 19: elog #8109)
- Is ASS and A2L working? -JENNE
- Are all whitening filters for PDs toggling correctly? -JENNE, JAMIE
- Adjust I/Q rotation angles for error signals -JENNE, YUTA
- Adjust filters -JENNE, YUTA
- Coil balancing for BS (and ITMs/ETMs) -YUTA
PRC characterization in PRMI:
- Measure PR2 loss from flipping -MANASA
- Measure mode matching ratio -JENNE, YUTA
- Measure finesse, PR gain -JENNE, YUTA
- Calibrate PRM and/or ITM oplevs -MANASA, YUTA
- Measure g-factor by tilting PRM or ITMs -JAMIE, YUTA
- Calculate expected mode matching ratio and g-factor -JAMIE
- Calculate expected finesse, PR gain -JENNE
- Align aux laser into AS port? -ANNALISA?
- What's the end green situation? Optical layout changed? Laser temperature in CDS? -MANASA
- What's the PSL green situation? Green trans cameras/PD? -JENNE, MANASA
- Make ALS handing off to DARM/CARM LSC script -JENNE, YUTA
- Demonstrate FPMI using ALS -JENNE, YUTA
- Phase tracker characterization -YUTA, KOJI
- Measure mode matching between PRC and arms -JENNE, YUTA
- Measure PR gain -JENNE, YUTA
- Calculate expected finesse, PR gain -JENNE
- Update optical layout CAD after PR2 flipping -JAMIE, MANASA
- AS55 situation? -YUTA
- Look into PMC drift -JENNE, MANASA
- Measure RFAM contribution to error signals -YUTA
Please fix, add or update if you notice anything.
I thought AS55 is broken because it was not responding to the AS beam nor flashlight in DC. What's the DC gain difference between AS55 and POP55 (or REFL55)?
I undertook the investigation of the AS55 PD. I found the PD is not broken.
We aligned IPPOS, IPANG and all OPLEVs (except for ETMX and SRM).
1. First aligned the IPPOS by tweeking the steering mirrors inside the BS chamber.
2. Aligned the IPANG by tweeking the steering mirrors inside the BS chamber and ETMY chamber.
3. Aligned the OPLEVS for the BS and PRM was done by tweeking the steering mirrors inside the BS chamber and checked that OPLEV beams were not clipped.
4. Centred the OPLEV beams for the ITMY and ETMY.
5. For the OPLEV of ITMX the alignment was done by tweeking the steering mirrors inside the ITMX chamber.
I tested the PD on the PD test bench and it works just fine.
I attatched the characterization result as there has been no detailed investigation of this PD as far as I remember.
The transimpedance gain at 55MHz is 420Ohm, and the shotnoise intercept current is 4.3mA.
We will start preparing for pumping down. Main goal for this is to demonstrate PRFPMI using ALS.
Here are to-dos before we pump down.
Feb 18 eveing
- check input beam and Y arm alignment again
- IPPOS/IPANG alignment
- check all oplevs
Feb 19 morning
- open ETMX chamber heavy door
- align BS to X end
- adjust OSEM values (added by YM)
- center beam on all AS optics
- make sure AS/REFL is clear
- take picture of flipped PR2 (added by YM)
- make sure green is not clipped by new PRM oplev mirrors (added by YM)
- center all oplevs
Feb 19 afternoon - Feb 20 morning
- close PSL shutter
- close all heavy doors and put the access connector back
- start pumping down
Feb 20 evening
- start aligning IFO
Crontab: The bug of data only plotting until 5PM is being investigated. The crontab's final call to the summary page generator was at 5PM. This means that the data plots were not being generated after 5PM, so clearly they never contained data from after 5PM. In fact, the original crontab reads:
0 11,5,11,17 * * * /users/public_html/40m-summary/bin/c1_summary_page.sh 2>&1
I'm not exactly sure what inspired these entries. The 11,5,11,17 entries are supposed to be the hours at which the program is run. Why is it run twice at 11? I assume it was just a typo or something.
The final call time was changed to 11:59PM in an attempt to plot the entire day's data, but this method didn't appear to work because the program would still be running past midnight, which was apparently inhibiting its functionality (most likely, the day change was affecting how the data is fetched). The best solution is probably to just wait until the next day, then call the summary page generator on the previous day's data. This will be implemented soon.
Calendars: Although the calendar tabs on the left side of the page were fixed, the calendars displayed at: https://nodus.ligo.caltech.edu:30889/40m-summary/calendar/ appear to still have squished together text. The calendar is being fetched from https://nodus.ligo.caltech.edu:30889/40m-summary/calendar/calendar.html and displayed in the page. This error is peculiar because the URL from which the calendar is being fetched does NOT have squished together text, but the resulting calendar at 40m-summary/calendar/ will not display spaces between the text. This issue is still being investigated.
I have uploaded ARBCAV v3.0 to the SVN. The major change in this release, as I mentioned, is the input/output handling. The input and output are now contained in a single 'model' structure. To define the cavity, you fill in the substructure 'model.in' (e.g., model.in.T = [0.01 10e-6 0.01]; etc.) and call the function as:
model = arbcav(model);
Note: the old syntax is maintained as legacy for back-compatibility, and the function automatically creates a ".in" substructure in the output, so that the user can still use the single-line calling, which can be convenient. Then, any individual parameter can be changed by changing the appropriate field, and the function can be rerun using the new, simpler syntax from then on.
The function then somewhat intelligently decides what to compute based on what information you give it. Using a simple option string as a second argument, you can choose what you want plotted (or not) when you call. Alternatively, you can program the desired functionality into a sub-substructure 'model.in.funct'.
The outputs are created as substructures of the output object. Here is an example:
>> th = 0.5*acos(266/271) *180 /pi;
OMC.in.theta = [-th -th th th];
OMC.in.L = [0.266 0.284 0.275 0.271];
OMC.in.RoC = [1e10 2 1e10 2];
OMC.in.lambda = 1064e-9;
OMC.in.T = 1e-6 * [8368 25 8297 33];
OMC.in.f_mod = 24.5e6;
in: [1x1 struct]
>> OMC = arbcav(OMC,'noplot')
Warning: No loss given--assuming lossless mirrors
> In arbcav at 274
in: [1x1 struct]
df: [1000x1 double]
coefs: [1000x4 double]
HOM: [1x1 struct]
f: [1x1 struct]
pwr: [1x1 struct]
carr: [15x15 double]
SBp: [15x15 double]
SBm: [15x15 double]
Some other notes:
I have added lots of information to the help header, so check there for more details. As always, your feedback is greatly appreciated.
I will check out the AS55 situation tomorrow. Just put it on my desk.
MC Autolocker was disabled - I enabled it.
For the F2P.py, you should look at how we did this with the script written 8 years ago in csh. There we stored the initial values in a file (so they don't get blow away if someone does CTRL-C). Your python script should have a trap for SIGINT so that it dies gracefully by restoring the initial values. In order to have the smooth value adjustment, you must first set the TRAMP field for all the coil gains to 2 and then switch. Make sure that the lockin ignores the first few seconds of data after making this switch or else it will be hugely biased by this transient.
For the PRM OL use as a F2A reference, you also have to take into account that the OL beam is hitting the PRM surface at non-normal incidence. IF it is a large angle, there will be a systematic error in the setting of the F2Y values.
It is my pleasure to announce that the first lock of PR2 flipped PRMI was succeeded.
POP looks very nice. TEM00 and not wobbling.
We need more I/Q phase and gain/filter adjustment and characterization soon.
Some more details:
MICH error signal: AS55_Q_ERR (using POP55 PD; phase rotation angle 70 deg)
PRCL error signal: REFL11_I_ERR (phase rotation angle 80 deg)
MICH feedback: BS (MICH_GAIN = -60)
PRCL feedback: PRM (PRCL_GAIN = -0.5)
I measured openloop transfer function of the phase tracking loop for the first characterization of phase tracker.
What is phase tracker:
See elog #6832.
For ALS, we use delay-line frequency discriminator, but it has trade-off between sensitivity and linear range. We solved this trade-off by tacking the phase of I/Q signals.
Figure below is the current diagram of the frequency discriminator using phase tracker.
OLTF of phase tracking loop:
Below. UGF at 1.2 kHz, phase margin 63 deg for both BEATX and BEATY. Phase delay can be clearly explained by 61 usec delay. This delay is 1 step in 16 KHz system.
Note that UGF depends on the amplitude of the RF input. I think this should be fixed by calculating the amplitude from I/Q signals.
BEAT(X|Y)_PHASE_GAIN were set to 300, and I put -3dBm 100 MHz RF signal to the beatbox during the measurement.
Other measurements needed:
- Linear range: By sweeping the RF input frequency and see sensitivity dependence.
- Bandwidth: By measuring transfer function from the modulation frequency of the RF input to phase tracker output.
- Maximum sensitivity: Sensitivity dependence on delay-line length (see PSL_Lab #825).
- Noise: Lock oscillator frequency with phase tracker and measure out-of-loop frequency noise with phase tracker.
- Sensitivity to amplitude fluctuation: Modulate RF input amplitude and measure the sensitivity.
PRM coil gains and f2a filters are adjusted for PRMI work.
It seems like UR/LL coil gains were ~10 % larger than others, and f2a filters changed by few %.
What I did:
1. Tried to lock PRMI but when I turn on PRCL lock, PRM reflection looked like it tends to go up and left in REFL camera (last night).
2. So, I set up PRM oplev back, by steering PRM oplev mirrors on the BS table (last night).
3. Turned PRM oplev sero on, f2a filters off, and ran
> /opt/rtcds/caltech/c1/scripts/SUS/F2P_LOCKIN.py -o PRM
I had to fix F2P_LOCKIN.py because it assumed some OUTPUT buttons in LOCKIN1 filters to be ON.
Also, I had to restore filters in LOCKIN1 (8.5 Hz bandpass filter etc.) because their names were changed. To do this, I copied filters needed from /opt/rtcds/caltech/c1/chans/filter_archive/c1sus/C1SUS_110916_162512.txt, renamed LOCKIN1_(I|Q|SIG) with LOCKIN1_DEMOD_(I|Q|SIG), and pasted to the current filter bank file. I checked that they look OK with foton after editing the file.
This measurement takes about 30 minutes. I ran several times to check consistency. There was ~ 0.1 % standard deviation for the measurement results.
4. By putting measured coupling coefficients and PRM pendulum frequency (f0=0.993 Hz) to /opt/rtcds/caltech/c1/scripts/SUS/F2Pcalc.py, I got new f2a filters.
5. Overwrote f2a filters in C1:SUS-PRM_TO_COIL_(1-4)_1 FM1 with new ones, and turned new f2a filters on.
Below is the DC gain adjustment result from F2P_LOCKIN.py;
multiplier factors are :
UL = 1.141525
UR = 0.879997
LR = 1.117484
LL = 0.860995
Set C1:SUS-PRM_ULCOIL_GAIN to 1.04990177238
Set C1:SUS-PRM_URCOIL_GAIN to -0.983396190716
Set C1:SUS-PRM_LRCOIL_GAIN to 0.954304254663
Set C1:SUS-PRM_LLCOIL_GAIN to -0.971356852259
So, UR/LL coil gains somehow got ~10 % larger than other two since last coil balancing.
Measured coupling coefficients from F2P_LOCKIN.py were
- measured coupling coefficients are :
P2P(POS=>PIT) = 0.014993
P2Y(POS=>YAW) = 0.001363
New f2a filters are plotted below. They look fairly different compared with previous ones.
We need better F2P_LOCKIN.py:
Some one should make F2P_LOCKIN.py better. The main problem is the sudden gain change when starting diagonalization at low frequency. It sometimes trips off the watchdog.
Some elogs related:
Kiwamu made f2a filters in Sep 2011: elog #5417
Koji adjusting DC gains in Jan 2013: elog #7969
> /opt/rtcds/caltech/c1/scripts/SUS/F2P_LOCKIN.py -o PRM
- measured coupling coefficients are :
P2P(POS=>PIT) = 0.014993
P2Y(POS=>YAW) = 0.001363
I temporarily replaced AS55 PD with PD labeled "POP55(POY55)".
I think POP55 is working because I could lock MI with this PD using AS55_Q_ERR as an error signal. I rotated I/Q phase (C1:LSC-AS55_PHASE_R) to 70 deg by minimizing ASDC during MI lock.
POP55 PD was freely sitting on the ITMX table.
I will leave AS55 PD at free space of the AP table. Someone, please look into it.
We set up POP camera and POPDC PD, and centered REFL PDs.
We also tried to center AS55 PD, but AS55 seems to be broken.
What we did:
1. POP path alignment:
Shot green laser pointer from ITMX table at where POPDC PD was sitting and centered green beam at optics in the POP path. Steered POPM1/M2 mirrors in the ITMX chamber to make green laser overlap with the PRM-PR2 beam as far as I can reach from ITMX chamber. We removed some ND filters and a BS for attenuating POP beam because POP power was somehow so low. Currently, POP is pick-off of the beam which goes from PRM to PR2.
2. POP camera and PD:
We first used camera to find the beam at where POPDC PD was sitting because it is much easier to find focused beam. Put an iris in front of the camera, and put POP DC behind it. Steered a mirror in front of PD to maximize DC output.
3. REFL PDs:
Steered mirrors in the REFL path to center the beam and maximized DC outputs, as usual.
AS55 was not responding very much to the flashlight nor AS beam. C1:LSC-ASDC_OUT looked funny. By swapping the ribbon cables of AS55, REFL55, and REFL165, I confirmed that AS55 PD itself is broken. Not the ribbon cable nor PD circuit at LSC rack. I don't know what happened. AS55 was working on Feb 8 (elog #8030).
We aligned PRMI coarsely. POP(right above) looks much better than before. REFL (left below) still looks elliptic, but ellipticity differs with the position on the camera. Some astigmatism is happening somewhere. AS (right below) looks pretty nice with MI aligned.
1. Fix AS55? Or replace it with POP55 PD, which is currently unused.
2. Confirm we are getting the right error signals or not, and lock PRMI.
I took better pictures of the circuits of the QPD and spent a couple of hours with a multimeter trying to figure out how all the connections worked. I will continue to do so and analyze the circuits over the weekend to try to understand what is going on. I also have an old SURF report that Eric sent me that is similar to the design I was planning to use to sum the pitch and yaw signals. I will try and look at this over the weekend.