More framing work for the diode and chiller rooms. The ceiling joists have been added. No construction work tomorrow, but on Thursday they will start cutting into the LVEA drywall. The North crane is still tied up.
Dust counts are again low. A trend of the last 10 hours is included.
We continued inspection and wipe down in BSC-7. Three additional instances of the mystery substance were found and removed: these areas were also FTIR sampled. The flooring was removed and covered (just in case we need it for something after re-installing the dome) with C-3 and placed in a cleanroom. With the floor removed, we were able to get half of the chamber bottom wiped down and FTIR samples taken. The C-3 cover on the dome was removed in preparation for work tomorrow. Carolyn worked on paperwork for the FTIR samples and on modifying the spreadsheets for record-keeping in prep for BSC-8.
Changed prefilters for AHU1 and 2
(Corey, Hugh, Vincent)
Checked Level of the Optics Table and also took shots of the top of Stage0 (where the Alignment Pin cut-outs are). Optical Level was used for level-checking.
While working around the table, removed the Alignment Pin Washers for Stages1-2 & Stages0-1 (thought it would be a good idea to not leave these loose items on floated stages). There is a photo (which needs to be rotated clockwise 90deg) of where these washers are located. The Stage1-2 Washer is a little tough to retrieve, but it was pulled out with the use of a small allen wrench.
Took opportunity to pull lots of lingering hardware and tools which were "stored" on Stage0.
Vincent wanted to check the big masses (Leg Elements) on top of the Keel (Stage2) for any possible vibrations. Sure enough, the smaller (~200lb) masses on top of the bigger masses did have some observable gaps underneath them. [tried to snap some camera-phone photos to illustrate this].
The DAQ system for the Oplev Mid-y test has encountered an unexpected shutdown. The DAQ card and electronics have been brought back to the corner station for troubleshooting and will be put back 'online' as soon as possible. Our stand-alone system had been running for almost a week without interruptions. The last successful data log was taken around 16:07:02 (PDT) on 7-25-2011.
We completed the 2nd wipe down of the upper sections of BSC-7. Work was slowed by the discovery of a mystery substance (Jodi calls it goopies, Mike L. calls it snot: see pix below) found during inspection. It required special attention to remove as it was very tightly adhered to the chamber, in some cases appearing to be baked on. It seems likely that this material was left over from iLIGO install. We will continue to investigate. We ended the day by taking eight FTIR samples.
Framework for the chiller and diode rooms is being laid down. The North crane is temporarily tagged out, as it is supporting the make-up air ducting for the acoustic enclosure.
No dusty work, a trend of the last 10 hours is attached.
Today drove all M0 and R0 Top OSEM Basis Channels with a Uniform White Noise TF from 0.1Hz to 50Hz with the De-Whitening Filters disabled, first with Binary I/O LP Disabled and then with the Binary I/O LP Enabled. Then drove each M0 and R0 Top OSEM Basis Channel with a Uniform White Noise TF from 10Hz to 50Hz at twice the amplitude with the De-Whitening Filters Disabled, first with the Binary I/O LP Disabled and then with the Binary I/O LP Enabled. Overlaid the 10Hz to 50Hz data on the plots. Results Below.
The crew re-installed the BSC flooring and worked on the second wipe-down starting from the collar section. Cheryl got TCS fit check taken care of just after lunch and then wipe-down continued. The upper section was completed before end of shift. We also continued to move equipment from BSC-7 to BSC-8 as time permitted.
Summary: With a lowest resonance of 35 Hz, the new pier avoided the 4-pole motor region at 30 Hz. Reducing payload at the top could at most increase the resonance by 10% to 38 Hz. We examined the motion of the new leaning optical lever pylon that is grouted to the floor at MY for testing (see photo). A breadboard and translation stage for the photodiode at the top of the pylon appear larger than necessary, weighing about 15.7 kg, so we investigated the maximum gain possible from using lighter equipment by measuring without this load. We also measured with and without the 15 kg dummy photon calibrator. The figures show accelerometer spectra from near the top of the pylon for the nominal and modified configurations, as well as corresponding spectra for the floor below the pylon. The peak at just below 30 Hz is on the ground and likely produced by a four-pole motor. It is good that the peak for the nominal configuration mostly avoids 30 Hz because such peaks occur at all stations. The transient peak on the ground at 34 Hz is atypical and of unknown source. The lowest resonant frequencies are tabulated below:Equipment on pylon Lowest frequency (Hz) Diode assembly and photon calibrator (nominal).....34.9 Diode assembly only................................................36.4 Photon calibrator only...............................................38.1 Nothing on pylon.......................................................38.1We were a little surprised that the lowest frequencies for the pylon alone and for the pylon with the mock photon calibrator in place were virtually the same. We added various masses at different levels and found that mass at the level just above the photon calibrator (see photo, the mock photon calibrator is at the level where the caution tape attaches) moved the peak at 42 Hz, but had little effect on the lowest peak at 38.1 Hz. On the other hand, moving the same mass to the top of the pylon did move the peak at 38.1 Hz down. Thus, without stiffening the upper stage of the pylon, a lighter diode assembly could, at most, raise the lowest resonance from 34.9 to 38.1, about 10%. Robert Schofield and Gregorio Tellez
- Mid-Columbia Forklift arrives for RodneyH - Lots of kids on site for a tour...Riverton residents join them - Drilling by H2-PSL begins at ~1:20pm - Richard, Keita working on syncing OMC and LSC, AWG reboots involved - Fred leads tour for UW students into LVEA - Laser Hazard at ~4:30pm - ICC by BSC7
Dumped unpumped IP11 volume into Y-end turbo, energized IP11, isolated and shut down MTP and QDP80 Closed X-mid purge air valve
Continuing investigation of the Binary I/O TF when LP Filter is OFF versus ON. I ran a 0.001Hz resolution transfer function in order to get "prettier" plots that would track better to the modeled TF line.(Attachment 1) Also ran a TF with the DeWhitening Filter 'OFF' and stronger drive strength from 10Hz to 50Hz. (Attachment 2)
Anchor points for hanging the H2 PSL chiller in the new chiller room were drilled into the concrete today. No dust spikes were recorded. A trend of the last 10 hours is included.
HAM 7 had the chocks removed by Apollo on Thursday, allowing the support tubes to be adjusted. The crossbeam was slipped in between the two chambers and is now resting on the table secured to the opposite crossbeam. The housings have been moved onto the piers and the adaptor plates and weldments attached and will soon be ready to attach the crossbeams.
I've been running into problems with the bottom clamp where the threaded holes that support the clamp sleeve were not tapped deep enough. I may end up having to remove a lot of heli-coils and re-tapping the holes since other methods (such as attempting to tap the heli-coil) have ended up in many broken taps.
The crew spent the morning staging for the next chamber cleaning (BSC-8) while waiting for an overnight shipment of 99.9% isopropanol. The compressor trailer was moved from the LEA to the southwest corner of the LVEA, clean air hose was run to BSC-8, and the air drill assembly area was relocated to the HAM 6 bay. BSC-7 chamber floor wipe-down was completed but inspection showed some re-deposition and/or re-oxidation on the two mid-sections closest to the door so we will re-install the flooring tomorrow, wipe down upper sections again as required and re-inspect the support tubes for fibers. A cleanroom was moved over the BSC-7 dome in preparation for cleaning.
I took TFs today driving at OSEMOUTF and reading at OSEMINF in two states: Binary I/O LP ON and Binary I/O LP OFF. Further compensation for other electronics will need to be included to be conclusive, but this is a good start that shows the expected pole at 1Hz and the expected zero at 10Hz. ~sus/trunk/QUAD/H2/ITMY/SAGM0/Results/ ~sus/trunk/QUAD/H2/ITMY/SAGR0/Results/
Transition to laser safe Cleaning of bake oven room Gregario at MY Work permit for removal of HAM 7 support tube chocks King Soft Water to service well Service of data tape robot BSC7 chamber cleaning Tour led by Dale Trend of > .5 micron particle counts for LVEA, LABS, MX attached
12:30 – Patrick to replace PSL Dust monitor 2:00 – Christina, Terry S., and crew out to clean on and around the BSC 7 chamber. 3:00 – site-wide safety meeting.
Terry and Christina cleaned around HAM-7 (not BSC-7), I think.
By Mark, for Robert, Richard, Betsy, Jeff and Andres. Per the earlier report # 979, we found that the ITMy (Quad #2) BOSEMs had open light counts of opposite sign (positive) and somewhat larger magnitude (8 of 12 clipped at 32767 by the ADC) compared to earlier measurements on the staging building test stand (X1). We also noticed that the counts for the 4 OSEMs that weren't off-scale didn't seem well-correlated with the X1 values, as would be expected from a simple difference in gains. This led us to wonder if the X1 open light counts hadn't been suspiciously consistent, considering that the 50 BOSEMs that were characterised in detail in T0900496-v4 were evenly distributed in open light current over the full acceptable range of 45-80 µA, whereas the 12 values for the Quad #2 BOSEMs were tightly clustered between 30985 and 31555. We therefore asked Stuart Aston for the open light current measurements for all BOSEMs and made scatter plots against the open light counts recorded at X1 (E1000186-v15) and H2 (Robert's notes). See attached. Sure enough, in plot "X1 vs UK", there is no correlation between the two sets of measurements, even though the X1 data was formerly thought to be good. To make the cause clearer, the same data is replotted in "X1 vs UK (1:1 aspect)" with the aspect ratio forced to an equivalent value of 1:1 considering the different units, and the X1 data is compressed into a narrow band. This suggests saturation at some point in the electronics chain earlier than the ADC. Similarly, in "H2 vs X1" most of the H2 values are railed at 32767 suggesting saturation of the ADC, but the rest are in a narrow range just short of that and don't correlate with the X1 values. This suggests (i) we have saturation of an analog circuit earlier than the ADC as for X1 and (ii) the variation from channel to channel is all about the circuits that are saturating and not at all about the BOSEM that is connected. Therefore we need to set up a measurement where a flag is wound through a BOSEM in a calibrated fashion and the signal is monitored at each point in the chain to discover where the saturation is. (Richard is betting that the signal will already be too large at the output of the satellite amp and that that is where the gain will have to be reduced.) Richard has a dirty BOSEM #005 borrowed from the TipTilters that we can use. This will also be a good opportunity to measure the response of a BOSEM with a new-style flag.
J. Kissel, P. Fritschel, Mark Barton, for the SUS team --------------- This story has been sent around via email to relevant suspensions people, but I want to stick it here where the complete story will be held for future reference. --------------- The Problem After walking through the schematics involved, Peter and I have traced the problem of the saturating OSEMs. (1) The output impedance of one leg of the satellite amplifier is 160k V/A (as confirmed by Vern, and is evident from the schematic, D0901284-v1, defined by RX02 in each of the four channels of the box). (2) The BOSEMs' photo current can be as large as 80e-6 amps, (See distribution provided by Stuart, now posted to T0900496-v4) (3) The gain of the Anti-Aliasing chassis, D070081-v5 is +1. (4) The ADC, a General Standards 16AI64SSA card, with each channel have a range of +/- 10 Vpp, or | Vmax | = 10 V (see Data Sheet), receives one leg of the differential signal coming in from the satellite amplifier. See attachement 1 for a schematic of the M0/R0 QUAD electronics, which is a portion of version two of T1100378 I'm working on. So, from this, it is clear why we have saturations: 80e-6 [A] * 160e3 [V/A] = 12.8 V input > 10 V allowed. The Proposed Solution Assuming we're to make modifications to the entire lot of aLIGO satellite amps for the 1.7 kHz oscillation modifications anyways (replacing the inductors LX01 with 100 ohm resistors, removing the 100pF cap CX07 and replace both AD797s IC552 with OP27s), would be to change the output impedance to 120k V/A, such that 80e-6 [A] * 120e3 [V/A] = 9.6 V input < 10 V allowed. (The other choice would be to only use OSEMs with 60e-6 amps, but Stuart's distribution (T0900496) shows that the majority of the OSEMs show open light current above 60e-6 amps.) Justification of Proposed Solution and An Explanation of the Safety Margin (i.e. why 120k V/A is OK): The counts as measured by the ADC are the differential voltage between the two legs of the differential driver. Hence, BOSEM #638 (now installed as H2SUSITMY's M0 F2 BOSEM) would yield 57.39e-6 A * 160e3 V/A = 9.182 V on *one* leg of the differential output of the sat amp, which is what's fed into *one* pin of the differential ADC. The other leg of the differential driver / ADC pin would receive -9.182 V, making the differential voltage measured 2 * 9.182 = 18.364 V (Here in lies the (my) prior confusion between saying the "gain" of the sat amp is 160e3 V/A vs. 320e3 V/A -- because the input to the sat amp is single ended, and is split via a differential driver and we measure the signal differentially, the "gain" of the sat amp could be treated as though Differential Voltage OUT / Single Ended Current IN is 160e3*2 = 320e3 Ohms, *but* each leg of the driver (which is what a given pin on the ADC would see) does not see the factor of two.) On the 16-bit ADCs, which have a 40 Vpp differential swing over 2^16 cts, this would mean that the count value seen at the input of the digital filters is 18.364 V * 2^16 cts / 40 V = 30088 cts. Now, we cannot in anyway assume that the photo current from this guy has stayed exactly 57.3900000e-6 A. From the above eLOG entry, H2 SUS ITMY's M0 F2 has a open light value of 30840 cts, implying an open light current of 30840 cts * (40 V / 2^16 ct) * (1/2 * 1/160e3 A/V) = 58.82e-6 A, a (58.82 - 57.39) / 57.39 = 2% change. Using the data from T0900496, If we include a safety margin of 2%, then only 1 (one) of the 700 BOSEMs would exceed the 32000 ct saturation limit, if we converted to a transimpedance of 120 V/A: threshold = 32000 cts * (40 V / 2^16 ct) * (1/2 V/V) * (1/120e3 A/V) = 81.38e-6 A margin = 0.02 safeTreshold = threshold - margin * threshold = 79.75e-6 A find(T0900496 > safeThresh) = 1 (at 79.96e-6 A) Even if we have a safety margin of 5%, that would only exclude 37 of the 700. Further -- bare in mind that this is merely to measure the open light current such that we might operate in the mid range of the LED. It is by no means a show stopper if a few of the OSEMs exceed the 32k limit by 5%. Not a show stopper, once we replace the gain resistor Further Details explaining the difference between test stands and the production electronics (from Peter): Looking at the circuits a little more carefully, the problem is that the opamps in the satellite amp (OP2177) do not have adequate current drive capability when connected to the v1 (non-buffered) AA filters. The OP2177 is spec'd at a current drive of +/-10 ma, and with the v1 AA, it's driving close to 500 ohms, so it's well in its non-linear region when being asked to put out ~10 V. On the other hand, the small-signal gain in the two cases is actually the same. So we really shouldn't be using the v1-AA units with the sat amps. The whole story points out why we went to buffered inputs and outputs with v2+ on the AAs ... The ADC Downsampling filter Note that the only piece of DC Gain in the puzzle we have yet to included in the above analysis is the down-sampling filter from the native ADC sampling rate 65k Hz to the model's rate of 16k Hz. This *used* to have some small non-unity gain at DC (at the 5% level), but I have confirmed on the MIT system here that in RCG 2.3 (which is the same as at the sites, also confirmed) that this bug has been fixed, and the DC Gain is now unity to within 0.6% see second attachment for transfer function between a 65k test point in the IOP model (M1:IOP-HAMX_MADC3_TP_CH0) and the corresponding channel in the suspension model (M1:SUS-MCTS_M1_OSEMINF_T3_IN1)
