I made the signal box as described in eLog 7210. It adds the geophone signal and an external signal.
It has six switches, for x, y, and z signals from both an external and local (geophone) source. The x signals add if both x switches are flipped down (and the same for the other directions). For example, if you want to feed in only an external signal in the x direction, flip down the external x direction switch (it's labeled on the box), leaving all others flipped up.
The x, y, and z outputs are wired to the pins from the preamplifier that go to the high voltage board. These I disconnected from the preamplifier by cutting at their base (there are spare connectors if this wants to be undone, or, a wire can just be soldered from the pin to its old spot on the board). The power (plus/minus) and ground are wired to the respective pins from the geophone preamplifier (naturally, the STACIS must be turned on for the box to work since the box shares its power source). Below, the front (switches and geophone/external inputs) and back (power, ground, outputs) of the box are shown:
The preamplifier can plug into its regular connectors- the x,y,and z signals will all be redirected to the signal box with these modifications. The box sits outside the STACIS, there is room to feed the wires out from underneath the STACIS platform.
NOTE: The geophone z switch is a little different than the others, just make sure it's flipped all the way down if you want that signal to be seen in the z output.
I found this entry in the old 40m ilog which describes the STACIS performance. It shows that even though the STACIS is bad for the differential arm motion below 3 Hz. It has quite a big and positive effect at 10-30 Hz. The OSEMs show a bigger effect than what the single arm does. I think this is because the single arm is limited by the MC frequency noise above 10 Hz.
We should figure out how to turn on the STACIS but set the lower UGF to be ~5 Hz.
LIGO GC notified us that nodus had SSL2.0 and SSL3.0 enabled. This has been disabled now.
The details are described on 40m wiki.
Koji's design of the SS 2" mirror holder with flexure spring optic retainer like Polaris-K1 has been ordered. We are getting just one to see it's effect on the hysteresis.
Kiwamu and Koji
- Checked the SRM/PRM balancing after the gluing.
- The mirrors were removed from the suspensions for baking.
- Bob is going to bake them next week.
The SRM qpd cable was removed from the BS-table. It's path was changed from 1x4 to ITMY-table following the inner cable tray.
Laser diode oplev SRM is working. Qpd matrix values were reset like others.
In 0.44mW, returning 0.1mW, -500 counts.
[Jenne, Kiwamu, Rana, Eric Gustafson]
The SRM and PRM have been re-hung, and are ready for installation into the chambers. Once we put the OSEMs in, we may have to check the rotation about the Z-axis. That was not confirmed today (which we could do with the microscope on micrometer, or by checking the centering of the magnets in the OSEMs).
Also, Eric and Rana inspected the Tip Tilt magnets, and took a few that they did their best to destroy, and they weren't able to chip the magnets. There was concern that several of the magnets showed up with the coatings chipped all over the place. However, since Rana and Eric did their worst, and didn't put any new chips in, we'll just use the ones that don't have chips in them. Rana confiscated all the ones with obvious bad chips, so we'll check the strengths of the other magnets using a gaussmeter, and choose sets of 4 that are well matched.
Eric, photographer extraordinaire, will send along the pictures he took, and we'll post them to Picasa.
[Kiwamu, Suresh] This is a belated elog entry from last Friday night + Saturday morning!
We shifted the SRM tower across the beam and away from the door by about 5mm.
After the input beam from MC was aligned to the Y-arm, Kiwamu noticed that the AS beam was being clipped and that the correction had to start from SRM onwards as the beam had become offcentered on the SRM. So we shifted the SRM tower by about 5mm away from the door and transverse to the beam and rotated it by a few degrees to center the OSEM offsets. After this we aligned all optics along the AS beam path to extract the AS beam from the chamber. We then aligned each optic in the vertex so that their beams overlap at the AS port with the reflection from ITMY. Then we aligned BS to center the beam on ETMX and then looked for flashes from the Y arm.
At this point Kiwamu checked and found that the input beam from the MC had shifted. It was landing on the ITMY about 5mm below the center. And (inexplicably) it was still centered on ETMY! The Y- green which traced the cavity axis (since this was still flashing) was not coincident with the IR beam. So all the work we did in aligning the AS beam and the vertex optics work was lost..... and had to be done again.
Sorry Kiwamu, I realized too late that you were freeswigging. Hopefully 4 hrs was enough.
We realized that the SRM sensors are connected to the readout but just sitting on the BS in vacuum table with no magnets and therefore no shadows in them. We swapped the inputs to the SRM and PRM satellite boxes to use the higher transimpedance gain of the PRM side sensor. The attached plot shows the current spectrum in this configuration. The PD readback voltage was 9.5 V. Since this is close to the rail we put a slightly higher voltage into the AA of this channel to test that we can read out more ADC counts to make sure we are not saturating. The margin was 15800 vs 15400 counts with p-p of 5 counts on the dataviewer 1 second trend. We returned all cables to nominal configuration.
The calibration from A to m is 59 uA/1 mm.
IF I believe this calibration and IF I believe that the noise is the same with no magnet in there, then its almost 1 nm/rHz @ 1 Hz.
I am guessing that Jenne's calculation will show that this is an unacceptably high level of OSEM sensor noise, OAF-wise.
The SRM oplevs were found to be oscillating because of a small phase margin.
I reduced the gains to the half of them. The peak which Steve found today maybe due to this oscillation.
The SRM bounce peak 18.33 Hz. Suresh helped me to retune filter through Foton, but we failed to remove it.
The sum vs. pitch and yaw signals for the SRM QPD weren't making sense to me - centering on the PD lowered the sum, etc. So, I had a look at the SRM oplev setup.
The beam going in to the chamber looked fine, but the beam coming out was weird, like it was being clipped, or diffracted off of a sharp edge. The beam was spread out in yaw over almost 1cm as seen by eye. I looked into the vacuum window, and the beam was sitting on the edge of one of the in-vac steering optics. So, I adjusted the yaw of the beam-launching optic on the out of vac table so that I was roughly centered on both of the in-vac SRM steering mirrors. This required moving the first out of vac mirror for the SRM oplev path on the way to the QPD to move a small amount to one side, since the beam was near-ish the edge of the optic. I then centered the beam on the oplev (I had the SRM roughly aligned already).
Now the SRM oplev makes more sense to me. I have turned on FMs 1, 2, 5, 9 to match ITMY's loop shape. I have set the gains to -10 for pitch and +10 for yaw, to make the upper UGF about 6 Hz.
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".
Same measurements for SRM pitch (as previously done for yaw in entry 5460) are complete. The QPD is back in the path and aligned. I will be doing the same measurements for ITMY now though, so please ask before activating the SRM or ITMY oplev servos, as I may be blocking the beam.
The SRM oplev beam is clipping.
I checked the dark and bright noise of the SRM oplev QPD. The SRM QPD has a rather high dark level for SUM of 478 counts. The dark noise for the SRM QPD looked a little high in the plot against the bright noise (see first attachment), so I plotted the dark noise with the ITMY QPD dark noise (see second attachment). It seems that the SRM QPD has a much higher dark noise level than the ITMY! In case anyone is wondering, to make these traces I record the data from the pitch and yaw test points, then multiply by the SUM (to correct for the fact that the test point signal has already been divided by SUM). I will check the individual quadrants of the SRM QPD to see if one in particular is very noisy. If so, we/I should probably fix it.
I made the first measurements towards oplev calibration measurements: calibrating the oplevs in SRM YAW. The measurements seemed fine, I had a range of between -1.5 and 1.5 in SRM DC alignment before clipping on mirrors on the oplev bench became a problem. This seemed to be plenty to get a decent fit for the spot position against DC alignment value - see attached plot. The fitted gradient was -420um oplev yaw count. I calculated oplev yaw values as UL+LL-UR-LR. Pitch next.
The following optics were kicked:
Wed Oct 19 04:22:53 PDT 2011
By looking at a longer data stretch for the SRM (6 hours instead of just one), we were able to get enough extra resolution to make fits to the very close POS and SIDE peaks. This allowed us to do the matrix inversion. The result is that SRM looks pretty good, and agrees with what was measured previously:
pit yaw pos side butt
UL 0.869 0.975 1.140 -0.253 1.085
UR 1.028 -1.025 1.083 -0.128 -1.063
LR -0.972 -0.993 0.860 -0.080 0.834
LL -1.131 1.007 0.917 -0.205 -1.018
SD 0.106 0.064 3.188 1.000 -0.011
We have looked a little more at the SRM situation. We aligned the SRM, and then aligned the oplev, so that we had a convenient monitor of the optic's motion.
When we use the _COMM channels, which are the usual ones on the IFO_ALIGN screen, the pitch slider makes pitch motion, but the yaw slider makes the oplev spot move ~45degrees from horizontal.
However, when we use the bias channels that are in the front end model, parallel to the ASC path, pitch moves pitch, and yaw moves pure yaw.
So, we conclude that the SRM coils are fine, and there is something funny going on with the slow part of the actuation.
Koji restarted the slow computer susaux, and burt restored it, but that did not fix the situation. We went inside and looked at all of the ribbon cable connections, and pushed them all in, but that also has not fixed things.
We have been looking at D010001-b, the coil driver board, and we think that's where the summing resistor network between the slow bias slider, and the coil outputs from the fast model exists. (It's not 100% clear, but we're confident that that's what is going on).
Tomorrow, we will pull the SRM's coil driver board, and see if any of the components in the slow slider path, before the summing point, look burned / broken / bad.
I've added marked-up schematics + high-res photographs of the SRM coil driver board and dewhitening board to the 40m DCC Document tree (D1700217 and D1700218).
In the attached marked-up schematics, I've also added the proposed changes which Rana and I discussed earlier today. For the thick-film -> thin-film resistor switching, I will try and make a quick LISO model to see if we can get away with replacing just a few rather than re-stuff the whole board.
Another change I think should be made, but I forgot to include on the markups: On the dewhitening board, we should probably replace the decoupling capacitors C41 and C52 with equivalent value electrolytic caps (they are currently tantalum caps which I think are susceptible to fail by shorting input to output).
I've made the LISO models for the dewhitening board and coil driver boards I pulled out.
Attached is a plot of the current noise in the current configuration (i.e. dewhitening board just has a gain x3 stage, and then propagated through the coil driver path), with the top 3 noise contributions: The op-amps (op3 and op5) are the LT1125s on the coil driver board in the bias path, while "R12" is the Johnson noise from the 1k input resistace to the OP27 in the signal path.
Assuming the OSEMs have an actuation gain of 0.016 N/A (so 0.064 N/A for 4 OSEMs), the current noise of ~1e-10 A/rtHz translates to a displacement noise of ~3e-15m/rtHz at ~100Hz (assuming a mirror mass of 0.25kg).
I have NOT included the noise from the LM6321 current buffers as I couldn't find anything about their noise characteristics in the datasheet. LISO files used to generate this plot are attached.
After the DRMI measurements on Friday, SRY cavity was locked in order to compare ITMY and SRM actuators.
SRY cavity was locked with AS55Q -> SRM servo with gain of +10?
(My memory is fading. I tried +50 and noticed it was saturated at the limiter. So I thought it was 10)
Then the transfer functions between SRM->AS55Q TF and ITMY->AS55Q TF were measured.
The ratio between two transfer functions was obtained as seen in the second attachment.
The average at f<100Hz was 4.07 +/- 0.15. Therefore the calibration is ... as you can find below
SRM = (19.0 +/- 0.7) x 10 -9/ f2
PRM: (19.6 +/- 0.3) x 10 -9 / f2 m/counts
BS = (20.7 +/- 0.1) x 10 -9 / f2 m/counts
ITMX = (4.70 +/- 0.02) x 10 -9/ f2 m/counts
ITMY = (4.66 +/- 0.02) x 10 -9/ f2 m/counts
I helped the vacuum installation work in the evening.
- Three steering mirrors after the SRM (OM1-OM3) were installed on the table. OM1 and OM2 were aligned.
OM3 is in-place but not aligned to the OM4 (PZT).
- The ITMY oplev setup was disintegrated. The SRM/ITMY oplev beams were prepared.
- The SRM oplev mirrors were placed on the table and aligned.
- The ITMY oplev mirrors were placed on the table but not in-place.
The SRM Oplev injection and detection paths interfere heavily with the POY11. Due to the limited optical access, I suggest we try steering POYM1 YAW and adapting the RFPD path accordingly.
After agreement from Yuta/Anchal, I moved POYM1 yaw to clear the aforementioned path, and Ian restored the POY11 RFPD path. The demodulation phase might need to be corrected afterwards, before any lockign attempts.
[Zach and Kiwamu]
We worked on some more vacuum businesses. Today we finished did the following works:
- alignment of the POX mirrors
- alignment of the POP1 and POP2 mirrors
- installation of OSEMs onto SRM
- alignment of the SRM tower
(alignment of POP mirrors)
Since a beam on the POP path was quite too weak to see even by IR viewers, we used a He-Ne laser to imitate the real beam instead.
We injected the He-Ne beam from an optical bench to the chamber, and made it go through the PRM and PR2 by using some steering mirrors.
The pin assignment was flipped in a way of mirror image due to the extension cables which cause a mirroring.
So we made mirroring connectors to flipp them back to the correct pin assignment, and plugged the mirroring connectors in between the feedthrough of the BS chamber and the SRM satellite box.
This is a picture showing how they are connected now.
I just realized that Gautam set this test up and turned damping off......He will explane the details
Cheater cables for SRM sus tied up. They were dangling aimlessly on the floor.
Kiwamu removed the 18.3 Hz ocsillation by turning down the oplev servo gain.
Since ETMX seems to have been on good behavior lately, we tried to fire the IFO back up.
We had a fair amount of trouble locking the DRMI with the arms held off resonance. For reasons yet to be understood, we discovered that the SRCL OLG looks totally bananas. It isn't possible to hold the DRMI for very long with this shape, obviously.
With the arms misaligned and the DRMI locked on 1F, the loop shape is totally normal. I haven't yet tried 3F locking with the arms misaligned, but this is a logical next step; I just need to look up the old demod angles used for this, since it wasn't quickly possible with the 3F demod angles that are currently set for the DRFPMI.
I have modified the ASS model to also have an ASS for SRCL. The input options are POPDC, POP110, AS110. I suppose I could/should have included ASDC.
Screens are modified / made. I haven't finished setting the servo gains and oscillator amplitudes, and all that jazz yet.
Using the parameters that Koji had in elog 9116, I was able to get nice long DRMI locks (several on a ~10 minute time scale).
I tried some pseudo-ANDing for the triggers, to no avail. I was trying to have the trigger matrix row for the SRCL loop have 1*POP22 and 0.02*AS110, where the 0.02 is to scale AS110 so that it has a similar amplitude to POP22. I then set threshold levels to ~250 for up, and 100 for down (I tried several different values for the up threshold). I was watching the TRIG_MON_FAST channels for both PRCL and SRCL, and I wasn't able to get SRCL to be triggered only at the same times as PRCL using this technique. Since we can get the DRMI to lock, perhaps my AND logic for the triggers is a low priority, but I think we'll need something like that if we want real logic.
In this morning, we have disconnected SR785 which was in front of 1X2 rack, to measure a Hall sensor noise.
After a while, we put back SR785 and re-connected as it has been.
After a while, we put back SR785 and re-connected as it has been.
But the display setup might have been changed a little bit.
But the display setup might have been changed a little bit.
The unit was repaired and returned to the 40m. Now, with a DMM, I measure a DC offset value that is ~1% of the AC signal amplitude. I measured the TF of a simple 1/20 voltage divider and it looks fine. In FFT mode, the high frequency noise floor levels out around 5-7nV/rtHz when the input is terminated in 50 ohms.
I will upload the repair documents to the wiki.
The "source" output of the SR785 has a DC offset of -6.66 V. I couldn't make this up.
SN 46,795 of 2003 is back.
I'm working near 1X5 and there is an SR785 adjacent to the electronics rack with some cabling running along the floor. I plan to continue in the evening so please leave the setup as is.
During the course of this work, I noticed the +15V Sorensen in 1X6 has 6.8 A of current draw, while Steve's February2018 label says the current draw is 8.6A. Is this just a typo?
Steve: It was most likely my mistake. Tag is corrected to 6.8A
I'm still in the process of electronics characterization, so the SR785 is still hooked up. MC3 coil driver signal is broken out to measure the output voltage going to the coil (via Gainx100 SR560 Preamp), but MC is locked.
In preparation for later today evening. The TT alignment wasn't visibly disturbed.
A poor lonely SR785 was found this morning roaming around in the lab in evident violation of the fundamental rule which requires all the equipment on carts to be brought back inside the lab right after use.
The people and the professors related to the case should take immediate action to repair for their misdeed.