I have installed a dust monitor at end X. The RS485 loop there is not currently working, so it is powered from a power strip and connected directly to the Comtrol.
Walking Plates were prepared for fit check: welds were spot-treated with pickling solution, ink/stamps were removed, and then the sections were pressure washed. Bubba and I went down to Y-end and oriented cleanrooms preliminary to locating the mechanical test stand. Doug visited Y-end later and was satisfied with the location of the test stand cleanroom. Cryo-Baffle parts were uncrated and moved under the cleanroom at H1 PSL bay. Apollo started the process of dismantling and removing the BSC cleanroom skeleton from Y-mid. It will be transported to the LVEA and placed over BSC-4 so we can continue the fit check of Work Platforms and Walking Plates (which requires the dome off) with all the major components in place.
No in-chamber work today as no tools were available. Mark L. and Mick worked on tooling all day and have three air drills ready for tomorrow. They also marked up the air drill cleaning procedure as they worked. I worked on refining the design of the new C-3 support tube covers sent by the vendor (too short, does not unzip all the way, shock cord only accessible from inside) and will follow-up tomorrow with e-mail and pix. I spent a little time out around BSC-7 doing some general clean-up/re-organization and visited with Michael L. about ICC needs while I'm on vacation (starting day after tomorrow).
HAM10 HEPI crossbeams (scheduled, unknown status) layout and drilling for HEPI and test stand piers at end Y (scheduled, unknown status) move clean room from mid Y to LVEA bsc8 (scheduled, unknown status) assembly of laser safety wall in east bay of LVEA (complete) optical lever test at mid Y belt replacements on air compressor for end Y instrument air all lasers manually killed when RM, BS, ITMX and ITMY trip from 7.7 earthquake in Kermadec Islands Region, optics damped and laser power restored delivery for Apollo fire department on site Control Solutions Northwest to visit Ski tours in LVEA for MSP teachers Dani transitioned the LVEA to laser safe
This lovely new studio sits at the scenic end of the LVEA East Bay, and is conveniently HAM6-adjacent. The interior is spacious enough to allow for two optical tables (and accessories!), and the craftsman-like work on the walls assures the concerned resident that unwanted lasers will not be getting out or in. It has one single door on the south face and a large double door on the west, to allow the transfer of larger furniture. A great find! (Cash-only deposit, no physicists. Other terms and conditions apply.)
Oplev laser was turned-off @ 2:40 pm in order to allow the Apollo crew to remove the cleanroom from MY.
Replaced the belt at Y end compressor. This accounts for the step drop in pressure.
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)
The alarm level settings for the dust monitors were lost during the last power outage and will need to be reset.
- GregorioT and RolfM to MY for optical lever pier studies
- ~0935 LVEA being transitioned to laser safe by Keita
- Jodi's crew in BSC7 for ICC, done at 1520.
- Cyrus to EY to work on racks
- Filiberto going to racks on Y-arm
- JeffB and AndreasR out to test-stand in LVEA to check for bad cable
- Catering delivery for MSP group at ~1050
- UniFirst makes delivery in the morning
- Patrick brings dust monitor to MX
- Keita and Jim to LVEA to remove trapeze from HAM5, done at 1515
- MSP group on site, touring with Fred
- 1520 - Patrick leaves for MX and EX to do work on dust monitors
- 1600-1700 - Many deliveries from UPS, FedEx, etc., for DanielS, HughR, etc. Thanks to Hugh, TerryG, and JodiF for helping out late!
- 1650 - LVEA back in laser hazard
- Patrick fixed KVM switch for Control Room projector computers so they are now available for tours. Please promptly report issues to him.
- NergisM, KeitaK, and SheilaD ("The Squeezers") will be entering HAM4 via HAM5 this evening
I have put a dust monitor at mid X.
First article walking plates arrived from Apollo for the fit check. We (John, Bubba, myself) discussed cleaning requirements for the fit check and which BSC/cleanroom to use for the fit check. We tentatively agreed that we will use BSC-4 and will look at the possibility of moving the cleanroom skeleton from Mid-Y to the corner as LVEA BSC cleanrooms are either in use (BSC-7) or effectively trapped. Brian O'Reilly was in touch with questions/concerns about the work platforms. Hugh expressed concern about the fact that the work platforms were touching the HEPI crossbeams. He and Bubba discussed possible solutions (some kind of bracing system that uses the BSC as a stabilizing influence on the work platform?). Richard, Ken, and I discussed possible locations for Y-end VEA cable trays given the constraints of install tooling (E-module, spiral staircase, garbing/staging cleanrooms, etc).
Turbos valved-out and spun down.
Crew: Mark L., Mick, Carolyn
Mark and Mick prepared tooling ("5 of 6" and "4 of 6")and then ran start of the day checks. John W. came out at my invitation and 'bunnied-up" to go into BSC-7 to assess the quality of the brushing so far and give us some idea of "good enough". John is generally satisfied with the cleaning, agrees that the round brush gives a smoother finish, and thinks that the sections cleaned with the cup brush are probably OK as-is. Mick took an FTIR at section M-9 and then Mark started cleaning that section. Two minutes into the run, "5 of 6" seized due to a small bearing failure. (Fortunately, extra bearings and end plates arrived Friday!)"4 of 6" was then put to work. Mark took pix of the iLIGO dust barrier for Bubba. The brushing of the three remaining mid-section areas was completed with "4 of 6". The guys also hand-worked various areas that the air drill cannot reach (close to the support tubes and fins). Dome and door covers were replaced and end of day checks run. Mark and Mick spent time late this afternoon dis-assembling and cleaning new drills and bearings.
Since a number of the 227b dust monitors have been alarming with "sensor fail" recently, I've started trying to get the external pump in the mechanical room running again, so that I can use some of the ones that have their internal pumps removed. I had stopped my previous attempts when the pump seemed to be running too hot. So far I have only been able to replace the dust monitor at the H1 PSL (location 10). After going back and forth between the LVEA and the mechanical room to adjust the valve on the pump and check the flow rate at that dust monitor, I got a reading of ~.1 cfm. However, the flow measured at the dust monitor in the H1 electronics racks (location 8) was less than .1 cfm. I do not know why the flows differ and I have left that dust monitor turned off. The flow rate the H1 PSL dust monitor should probably be rechecked. These are the only two currently connected to the external pump. Since I wanted to make sure that there wasn't some unused connection that was not blocked, I traced the hose out in the LVEA as much as I could. Since it was unused, I disconnected and plugged the connection on the hose manifold that led to the previous locations of ISCT 10 and the H2 electronic racks. I have also removed the flow meter from the hose next to the pump in the mechanical room, since I do not trust its readings, and therefore thought there might as well be a clear line there for now. I have also replaced the exhaust filter on the vacuum pump with a tee. The pump seems to be running alright at this point. The valve on the vacuum pump is set so that the gauge reads 350 mmHg VAC.
The fit check of the work platform continued around BSC-4 today. The hand-rails were in place and Dale Ingram used the platform to advantage while filming the BSC ISI flight. I sent work platform pictures off to Brian O'Reilly so that he could send back questions. John and Bubba both plan some careful measuring on Tuesday, 05 July, as HEPI actuators and the chamber cleanroom must be taken into account to determine if changes are needed. Randy and crew worked on the relocation of many items in the West Bay to provide better passage around the test stands and their cleanrooms. Two ion pumps were moved to the termination slab, two HAM doors were moved over by HAM-11/12 along with the rectangular 4-point spreader-bar. Once space was cleared, they picked the Fiber Welding cleanroom and placed it to the west of the Test Stand 2 cleanroom. Just as the ISI was exiting the Staging Building, Test Stand 3 arrived from MCE. It was delivered to Y-end and unloaded by Mark Dodson and Slim. Some parts were placed in the first airlock and some were placed in the second airlock. While I was at Y-end for a brief inspection of the parts (uneventful but I'll take a closer look on Tuesday), Mark, Slim, and I talked about reorganizing things a bit (moving the refrigerator out of the entry way, where to put the two tan cabinets, could cleanroom parts be consolidated and stored) I looked at the Type A (Test Stand) and B (Work Space) cleanrooms that Dave, Nicole and Kevin have been working on. The Type B nests very nicely under the Type A which is good news.
The chamber cleaning crew (Mark Layne, Chris, with Carolyn as recorder) was in BSC-7 this morning, and using the indomitable "5 of 6" air drill, cleaned eight more sections. They also touched up around several fins. 46.59% of BSC-7 has now been cleaned. Mick worked on the other five drills throughout the morning and made a couple of modifications. Tyler Guidry worked on fabricating the first of our chuck replacements. Mark and I went back into chamber after lunch to fit check the prototype bellows vacuum attachment (too thick, suction vents on ID rather than on OD, handle overly long for application). We also examined the quality of the finish left by the large rounded brush vs various cup brushes and tried to determine a path forward for the lower part of the chamber (when to remove the flooring, do we need some flooring in place to remove dome cover, safety implications of partial flooring, etc). I took a few pix for documentation, then we replaced the dome cover and door cover. Mick performed the end of day checks and blow-outs. Mick and Mark moved the compressor trailer back into the LEA and Mark ran a few test with a drill that Mick had modified earlier in the day.
(Adrian, Bubba, Corey, Dale, Fabrice, Greg, Jeff, Mitch, Sebastian, Vincent, and many others who've helped with the building of this assembly over the last few months/years!)
Bright and early (7am!), the SEI crew began the task of removing LHO's BSCISI#1 Assembly. Before the actual move, lots of activity commenced to get the task going (i.e. gathering lifting hardware & installing, clearing out space for the move, disconnecting cables, etc.). Once everything was ready to go, the team & the job went like clockwork. The Assembly was lifted and lowered on to Storage Container platform.
The Storage Container we used for this move is for a HAM ISI Assembly, and was retrofitted for the BSC. One item which couldn't be fixed was top of the enclosure (it is too small for the behemoth known as the BSC ISI!). So we used several C3 Covers to cover the Assembly, and then used plastic wrapping to cover the gap between the covers and the platform. Once we were happy the system was sealed up, it was rolled out a few feet with our large mechanized pallet jack. For the next move, Bubba and "Big Red" (the large capacity forklift) took over and carried our heavy load up the hill and over to the LVEA.
The Assembly was then rolled into the LVEA via the big pallet jack and placed in a spot for pick up with the main crane (here the Assembly was partially unwrapped to regain access to the lifting gear; it was then lifted off the Platform). The system was lifted and traveled over a few beamtubes and made its way to the waiting Test Stand in the LVEA's West Bay.
A minor issue was noticed here: we did not have correct studs for the Test Stand! The retrofit plate used on the Platform used coarse-threaded rods to capture the ISI. We should have used fine-thread, because fine-threaded rods/bolts are used for all of our Test Stands and the actual Support Tubes. Since we had a load in the air and it was not in a cleanroom, we decided to lower the Assembly on the Test Stand without the threaded rods in place. (as I type, correct threaded rods have been found and the team is now re-lifting the Assembly, installing rods, and dropping the ISI on these rods on the Test Stand).
All of this activity went pretty smoothly, and was done well before lunch!
I've attached a few photos from this activity (via my phone) to this entry. I also took quite a few videos with my phone, but since they are too big for the ALog, I uploaded them to ResourceSpace. They are located here:
Our cinematographer Dale also took tons of photos and videos as well, and I'm sure his work will be posted soon as well.
::::: Note: So from about April 11th, we went from having parts in the kitchen-----> Today June 30th, where we had an Assembly on the Table! :::::
... and Unit #2 was floated in the staging building later in the afternoon!
Here are some of Dale's "Best Of" shots from the BSCISI#1 move from last week:
https://ligoimages.mit.edu/?c=634