aidan.brooks@LIGO.ORG - posted 16:20, Friday 22 June 2012 (3240)
Hartmann sensor imaging of ETM
I've put a loose foil cover over the illuminator at EY, where John took the Lexan out yesterday. The official dust cover for the lexan slit that we do have, D0902791-v1, doesn't fit tightly over the slit, so flops back and forth leaving a gap, so not an improvement. That part is on -v2 (D0902791-v2), which I believe will fit tightly, and modifying -v1 would be a good short-term fix. However, the better plan is to beef up the dust cover into a part that fits into the slit, and thus holds itself in place, which can then be secured with a couple screws. In the mean time, I was uncomfortable leaving the slit uncovered, and folded a piece of foil to prevent something small, like a screw, from falling through the slit and hitting the viewport. I called John and talked it over, so he's aware of the very temporary solution.
Attached is an RGA scan of the Y-end taken this morning (RGA parameters are not optimized for current conditions but, rather, are left unchanged from initial scans for comparison purposes). I changed the programmed pump current value at which point IP11 "steps" from 7000V to 5000V from 5x10-4 amps to 1.5x10-3 amps. Prior to this change the pump current was 1.4x10-3 amps @ ~8.5x10-8 torr. The result is that IP11 is now at 5000V.
[Stuart A, Betsy B, Deepak K, Andres R, G2] After taking an initial set of M1-M1 transfer functions earlier in the week on PR2 (HSTS), it was observed by Jeff B that somehow a magnet had become detached from the M2 mass (see LHO aLog entry 3157). Thanks to the efforts of the assembly team, this magnet was rapidly re-attached and left to cure for a period of 24 hrs. PR2 was re-suspended yesterday, and a small pitch offset corrected. AOSEMs were then adjusted to their final operating positions and aligned. The canopy/cover was fitted over PR2. Following this re-work, it was prudent to take another M1-M1 transfer function with damping loops OFF for all degrees of freedom, which can be found below (see 2012-06-21_1700_X1SUSPR2_M1_ALL_TFs.pdf). Damping loops were then turned ON and a further complete set of M1-M1 transfer functions taken overnight. All the transfer functions obtained have now been plotted against all other HSTS suspensions previously measured on both LLO and LHO test-stands (see allhstss_2012-06-22_AllHSTS_ALL_ZOOMED_TFs.pdf). n.b. Yellow trace = X1 PR2 M1 (2012−06−21_1700) with damping loops OFF Purple trace = X1 PR2 M1 (2012−06−21_2120) with damping loops ON The transfers functions obtained again demonstrate good agreement with the model and the spread of all HSTS measurements obtained thus far. Power spectra have been taken with damping loops both ON and OFF for each stage (012-06-22_0800_X1SUSPR2_M*_ALL_Spectra.pdf). Power spectra plots, with both damping ON and OFF have been produced, which compare LHO PR2 and LHO MC2 measurements (allhstss_2012-06-22_ALL_Spectra_Don.pdf and allhstss_2012-06-22_ALL_Spectra_Doff.pdf). In addition, power spectra for specific degrees of freedom (L, P and Y) can be more conveniently compared across multiple stages (M1, M2 and M3) of the same suspension in the final plots found below (allhstss_2012-06-22_X1SUSPR2_M1M2M3_Spectra_ALL_Don.pdf). A BURT snapshot has been taken of the current functioning environment "20120622_x1sushxts27_PR2.snap", which has been stored in the following directory:- opt/rtcds3/tst/x1/cds_user_apps/trunk/sus/x1/burtfiles. This BURT snapshot directory has also been tidied to remove old or incomplete snapshots. All of the above data, plots, scripts, and snapshots have been committed to the SUS svn as of this entry. This should now provide sufficient measurements to complete Phase 1b testing of the PR2 suspension and allow it to progress to Phase 2 (chamber-side) testing.
The M3 stage watchdog was observed to be perpetually tripping and could not be reset. This is due to watchdogs being triggered for the OPELV_RMS and OPLEV_SUM, which are not visible/settable in the medm screens. To rectify this I have manually set the following:- caput X1:SUS-HXTS_M3_WD_OPLEV_RMS_MAX 5 caput X1:SUS-HXTS_M3_WD_OPLEV_SUM_MIN -10 For now, this prevents the watchdog from tripping.
These results look excellent. The only thing that concerns me (where the level of concern (from 1 = "it's awesome. no worries" to 10 = "OMG take it apart and rebuild it") is a 5.5) is the cross-coupling I see in the individual comparison with the model, i.e. in 2012-06-21_1700_X1SUSPR2_M1_ALL_TFs.pdf. In there, I see cross-coupling between degrees of freedom which we don't normally expect to be there: 1st Yaw Mode (@ 1.09 Hz) into T and L 2nd Yaw Mode (@ 2.04 Hz) into T and L 2nd Roll/Pitch Mode (@ 1.51 Hz) into Y 2nd Vert or 3rd Long Mode (@ 2.80 Hz) into Y I'm not terribly concerned, because -- as usual -- the cross coupling is reduced to barely visible with damping loops ON. But, it's something to watch out for with this guy as he progresses through the testing (i.e. we'll look with more scrutiny after the optic is swapped). To refresh one's memory -- the reason why we care: (1) When the model doesn't match measurements, we can't trust the model to accurately predict other transfer functions which we can't normally measure (2) If the transfer functions (which are representative of the "plant" upon which we design control loops) are *different* between suspensions by some (as-yet-to-be-quantified) significant amount, then it will make copying and pasting control systems more difficult and time consuming to design. I think with this suspension, and all others, we're doing fine in both these departments -- but again, we won't really know until we start locking some cavities and really try to push the SUS's to their limit.
Elli, Rana. We connected a low-pass filter to the common mode servo input, to simulate the feedback response of the green laser inside the cavity. The transfer function of this loop confirmed the location of the pole and zero of the first boost filter. We removed common mode servo B and will change out some of the boost filter components in order to improve the servo transfer function.
Final inspection was completed by 10:00 am and doors were back in place by 11:00 am. Tooling was prepared for transfer to Xend. FTIR kit will be sent off on Monday.
Image files have thumbnails, but PDFs do not. For multipage PDFs, the thumbnail could be just the first page.
This PDF shows that the RMS of the PD signals is dominated by 60 Hz + harmonics as we suspected. Unfortunately, it looks like we would have to notch out many, many harmonics to appreciably reduce the RMS. Perhaps we should use a low pass in combo with some comb filters?
In order to reduce the noise in the channel, I added a Comb filter into the CS_CHAN_NN filter banks to knock down the first 8 harmonics. Also added a 2nd order Butterworth low pass at 11 Hz to get rid of the HF harmonics. The RMS was reduced by 100x.
Restarted the rotating lissajous search pattern on the ALS table PZTs, but still now blips seen in the baffle PD times series...
Dust alarm levels at EY for location 1 were set to:
0.3: minor 20000 major 100000
0.5: minor 10000 major 50000
[Aidan, Thomas, Elli] Following some strange behavior in the Hartmann sensor signals, we checked the layout of the telescope on the ALS table and found that the lenses were out of position. The target and measured distances are show in the following table.
| Distance | Target | Measured |
| F0 to F1 | 614 mm | 675. mm |
| F1 to F2 | 1313 mm | 1232. mm |
| F2 to HWS | 1338 mm | 1530. mm |
We adjusted the positions of the lenses until they matched the target distances.
Separately, I calculated the tolerance of the conjugate plane of the ETM near the HWS to the position of these lenses. The ratio of the displacement of the conjugate plane to variation in the distances between optics is ~14x for F0-to-F1 and ~ 0.02x for F1-to-F2. As such, we placed lens F1 on a translation stage oriented along the optical axis. This will give us fine control over the position of the image plane of the ETM near the HWS.
The beam now looks much more uniform and Gaussian on the HWS. The beam size is 11% smaller than the expected beam size of 1.58mm (see attached plot).
We removed the Hartmann plate from the sensor last night and left a version of the code running that measured the beam position on the CCD. Watching this in real-time we could see the beam wandering around as Keita and Rana swung the TMS telescope around.
- One Arm Test Begins: Gate valves opened, and the laser has been sent down the arm. If you find the beam, let Keita or Rana know ASAP. - Safety discussion: If the work involves manipulating components in the beam path, including viewport covers and gate valves, the LSO must be notified. In addition, all viewport covers must bare a warning that removal requires approval by the LSO. - BSC8: Transfer functions today. Discussions at morning meeting about coordinating cleaning with measurements. Decision was to hold off on cleaning until this is resolved. Also, GV-6 was opened. In addition to Illuminator lights, Rana and Keita were using a flashlight to locate the green laser beam. - BSC6: HEPI transfer functions. Richard installed cameras yesterday and set up the Illuminator lights. The cameras are still being worked on, as the analog feed from EndY is not great.GV-17 was opened. - HAM5: ICC ongoing. - HAM2: ISI - Electronics work. - HAM3: ISI - Richard doing cable-pulling prior to entry - ISCT4 is cleaned and ready to be moved to Betsy's spot. - H1 PSL: Michael worked on the software and network connections. - MidX everything out, grout beginning next week. - EndX prep beginning. - Craning: Moving doors in the LVEA (HAM5 and HAM6), crane in staging building (Corey). - LSB HVAC work to begin Friday morning. - Pickup+Delivery of cardboard recycling. - Riverside High School visited in the morning.
Excellent Summary for your final Operator log. :) We'll miss 'em!
We set up a CCD camera looking at ITMY and the entire baffle and some more, sent a green beam from EY, modulated its angle by using PZTs, and found nothing on the camera. No luck with the baffle diode, either.
It seems like the beam is not getting to the corner station at all.
One (or more) of three things should be true:
Tomorrow we should use HEPI and/or ISI to move everything by a milli radian or so in YAW.
The reason why I think we're already wiggling enough is because, when we wiggle MCL PZTs, I can see on the CCD camera monitoring ETMY that the motion is so big the beam falls off of the primary. It's not impossible that this is all in translation and not in angle, but we used both PZTs that are placed at different Gouy phase positions and we didn't see anything at IY.
As a side note, 1/20 angle reduction only applies to the tilt upstream of TMS telescope (e.g. PZT on the ALS table).
For the rotatoin of TMS itself, it should be 19/20 or 21/20. However, we (Rana and I) felt as if TMS rotation is not producing enough beam rotation. We should calibrate the TMS angle to know how much we're actually tilting it by measuring the displacement of the retro reflected beam on the ALS table.
Also, we need to keep the optical axis fixed to the TMS even during the alignment, which (among other things) means that the TMS angle and the ALS beam angle on the ALS table should always be moved by the same amount. Elli and Thomas are working on the QPD servo for this.
Some details on the sensitivity of the search:
* For the ETMY camera, we are only a few meters from the TM. The iris is opened up as far as it can go and still stay nearly focused on the mirror (as seen w/ illuminator on).
* For the ITMY camera, we are ~30m away at the spool position. A large maglight flashlight injected from there can easily be seen on the baffle, the chamber, and the optic.
* The light from the flashlight shows up as ~10000 cts on the baffling photodiodes (mounted near the ITM). Wiggling the green beam from the end produces no signal as seen on the camera and if it produces any signal on the baffle PDs, it must be below the noise level of ~50 cts-rms. Given that the flashlight puts out ~500-1000 lumens, how big of a signal should the green beam make if its the right size?
* Assuming that we inject ~10 mW into the ETMY and that it has a transmission of ~1.5% for 532 nm, we should get ~100 uW of light at ITMY. By comparison, when we hunted for the iLIGO beams, we were injecting ~100 mW at the PRM and ~50-100 uW would get through to the ETM before lock (in the single arm config). The silicon CCDs should pick up the green light much better than the IR, so we should be seeing some beam on the chamber walls, etc. We were injecting non-integer frequency sine waves simultaneously into both pitch and yaw for the PZT, so I think its unlikely that we were unluckily sitting in some dark space.
* We need an SEI & SUS expert to inspect the HEPI/ISI & the ETMY angle biases to ensure that they are pointed in the right direction as determined by the IAS.
Video of the swinging beam on the ITM (left) and ETM (right)
Images of the ETMY as seen from the spool cam: illuminator on (left) and off (right)
I calculated roughly what the intensity of light should be on the baffle PDs. Rana's 500 lumen flashlight was emitting around 10W of light. I assumed this was filling an area roughly 1m in diameter - this yields an intensity of 13W/m^2. The corresponding intensity for the green beam at the ITM (assuming 100uW is transmitted through the ETM and the beam radius is ~5cm at the ITM) is about 12mW/m^2. So the response of the PDs to the green beam should be ~1000x less than the response to the flashlight.
On behalf of Gerardo and Danny:
Both ears were silicate bonded to the LLO ITM (ITM-08) this week. The mass has been stowed back in it's cake tin and await shipment out to LLO.
(GMoreno, DSellers, BBland, GMorenoJr.)
ITM08 ears were bonded succesfully, ears with SN 59 and SN 64 were used.
SN 59 was used for side S3, and SN 64 for side S4.
After setting the mass on the base of cake tin, a full inspection of ears and mass was performed, no problems found.
Attached are photos of ears on ITM08. Also a photo of the mass as I was putting it away in its cake tin, ready for shipping.
One of the GS13s of HAM-ISI unit #6 (Pod #94) appeared to be defective this week (see aLog 3183).
Greg and I opened it this morning. Two flexures were broken.
One can see wear on the non-broken side of D0901319-v4, s/n199 (Pic. 3,4). The pattern is very similar to what Jim reported in the SEI Log a few months ago.
We also found a small flexure debris. This debris was identified as being part of D0901318-v3 s/n 124 (see black line on pic. 5).
The pod was tested at reception on a leveled surface. Nothing abnormal could be seen on its response at that time. It was then installed in the ISI. No major event was reported (drop/shock/…). Spectra were taken with the ISI tilted and the pod appeared defective. Any spectra, even with the ISI leveled showed it defective after that.
As it already happened, it is possible that the shocks, endured by the instrument during its shipment, damaged the flexures. In these conditions, tilting the pod back and forth to install it, and/or tilting the ISI for testing purposes, could have lead to the breakage.
We have shockwatch data for this shipment. Greg will post it later on.
This shipping log was less eventful, especially as the threshold had been set higher, than the previous LHO-LLO. A big difference in this shipment was the large vertical shocks whereas the previous one had seen mostly horizontal. 3 of the 4 events also happened in Louisiana going by the time stamps.
It appears that pod #94 was already shiped back to LLO in March to be reworked after a pre-amp issue. see alog #2369.
Nothing was noticed on its flexures then. If the flexures were not changed at LLO, they saw at least 3 Livingston-Hanford trips .
In his aLog, Greg also mention a similar issue experienced on Pod #71: Working at reception. Stopped working afterwards. Opened and broken flexure found.
DCC document Q1100073 sensor issues tracking was updated.
I went through the history/time-series/spectra available for the Pod #94 (H1).
06/05 the batch of GS13s the Pod #94 belongs to, is sent from LLO.
06/12 Pod #94, and all the pods of that batch, are huddle tested OK (Plot 1). None of their spectra show partiicularities (H2 channel corresponds to the horizontal GS13 #58 which was already in the ISI).
06/13 Pod #94 is installed in HAM-ISI Unit #6 with the Pod #66(H) from the same batch. Interfaces chassis are turned ON. All instruments are tested OK (Plot 2).
06/14 Plot.3 shows that Pod #94 was functional, with no particularities on its spectra, until the interfaces chassis were turned OFF around 3.45 PM
06/19 Interfaces chassis are turned back ON around 10am. Pod #94 appears defective right away (Plot 4). It seems like the flexure breakage happened during the re-installation of the GS13s, even though no major event was reported (shock, drop, ...).
I can not notice any feature on spectra/time series that would have warned us of upcoming flexure breakages.
While talking about it at today's SEI call, we agreed on gently tilting the GS13s back and forth before huddle testing them at reception, so we can discard the GS13s with flexures that are about to break.
