Matt called to report a chilled water temperature alarm at ENDX.
I was able to start the second chilled water pump which in turn enabled the second chiller. Water temperatures are now falling. We'll investigate the tripped chiller on Monday.
We were lucky yesterday when we connected the REFL DC to the Tabletop Interface Box on the EY ISC table. The signal arrived in digital land in H2:ISC-ALS_EY_PDH_DC as expected. None of the other 3 DC signals work (IR_PWR, GR_PWR and BB_PWR). I connected BB DC to the TTIF box Ch4, and found that it arrives at the concentrator in the field rack (D1102045 #36, on cable 73), but I didn't continue tracking the problem beyond that.
The EY ISI was also tripped. I reset it, so we have damping, but I don't know the secret handshakes for turning on the isolation, so we will live without.
I added an offset to the input of the ST!-ISO_RZ filter bank, turned off the Cont_1 filter, and set the output gain to 200. This results in essentially no alignment bias for ETMY and TMSY. Of course, the isolation won't work like this, but I couldn't find any other way to bias the alignment of the ISI. SEI team: please make this right!
It isn't obvious to me how to reset this watchdog. Has this system ever been made to work? For the moment we are "floating on oil".
I guess it should have been obvious that with the ISI tripped I couldn't reset HEPI. Maybe we should make the screen say that... btw, the HEPI screens remind me of carnival signs (blocky, with offensively bright colors). We can do better.
Some time this week, somebody changed PEM corner station model, and as a result it seems like one of the baffle diode channels, H2:PEM-CS_CHAN_30, is gone. The channel doesn't exist any more.
Please give us the baffle diode back. You don't have to revert the model back, all we need is another PEM channel (e.g. H2:PEM-CS_CHAN_26) and we'll fix our MEDM screen.
We're done with Faraday replacement. We might have to tune the optical paths on the ALS table a bit, but basically we're done.
We don't see any serious clipping in the PDH error signal, the arm locks, and the alignment is already reasonable (50% reflection visibility).
Now that we can do things without worrying too much about the clipping on the Faraday, we quickly tested to change the cavity length by pushing on the ETM while maintaining the PDH lock, and it worked. We were able to (manually) relieve VCO tuning signal by merely giving an offset to the ETM TEST L filter. We'll implement (or Matt has already implemented) a fully featured low frequency feed back to the ETM.
We haven't tuned WFS demod phase yet.
OPC database (database for variables used in Beckhoff world) seems to have been "reset" some time between Thursday and Friday afternoon. PDH settings, PLL settings and laser temperature control seemed to be gone. On Friday afternoon we recovered it manually (because we don't have an equivalent of burt restore for OPC). At least we thought we did.
We were able to lock to 00 mode, which was really tiny, and we were able to lock to some off-axis higher order modes, which were much brighter than the 00 mode. So we naturally thought that there was a massive alignment problem caused by either Faraday swap or SUS/SEI change in TMS, ETM and/or ITM.
We spent ridiculously long hours doing many things, we even started over from the baffle diode to center the input pointing on the ITM, and the 00 mode coupling was still orders of magnitude worse than before.
Finally it came to my mind that no matter what we did we're still in a close proximity of our old alignment, and that maybe we're locked to the 00 mode SB because I got the polarity of the CM board B wrong. I flipped the polarity and voila!
But at that point it was already late in the evening and I had to give up jogging with one of my kids.
Making the ETM off-load work was trickier than expected. Apparently the Fast Monitor channel does not montior the fast output on this CM board. (It may be AC coupled.) I cabled in the signal that we are sending to the VCO and then closing the loop was easy.
(It is running at the time of the entry.)
hmmm... AC coupled in a complicated way: the PDH and PHASE signals are swapped. The cables appear to match the drawing, so maybe the problem is in the model. Anyway, all cables are in their original places, and I've gone with a software "fix".
Just a heads up, I'll be starting some measurements using ETMY nowish (2pm ET, July 7th 2012) which should last for 2 to 3 hours. I will post when I finish, and then results and analysis will be to come. I'll be launching DTT measurements from cdsws1. For those who are interested (though I think I emailed everyone who might be): Matt Evans and I, before I left last friday (June 29) had thought we'd stumbled on something interesting regarding cross-coupling vs. excess cavity motion while measuring the open loop gain transfer functions of the damping loops. See LHO aLOG 3312. Specifically the 4th page of the L and P sets of plots showing that, with the damping loops open, the cross-coupling from L to P is *huge*, where it's not huge in P to L. But, as I mention in the log, the right thing to do is to measure the open loop gain with the loops closed (i.e. IN1/IN2), and take a look at the results. These are the measurements I'll be taking now.
These measurements are finished (as of 3pm PT).
As a first step to making the L1 and L2 sensors useful, I brought the reaction chain damping up to speed. It now matches the main chain on both the ITM and ETM. I also spent some time playing with M0 gains and filters, but without any definitive success. Some directions to explore:
I'll poke at the first of these today.
In the process I added a new filter for L damping: 0.43HzBoost2. It just adds a little more gain around 0.43Hz, which flattens more the peak there. It does what it should, but had little effect on the motion seen at the L1 and L2 levels.
Attached are plots of dust counts > .5 microns in particles per cubic foot.
So the week has been spent trying to get the chamberside testing area up and running. Satellite amplifiers were put in place, field cables run and the MC2 suspension (which currently sits on the table in the testing area) was all connected up. The models/medm screens (which were ported over from LLO I believe) for the MC2 suspension has all the matrices, filters, etc filled in as well as I have used the values from log entry 3125, to put in the correct offset and gains. I made a burtbackup using Joe B's, makeSafeBackup script and this has been put into the SVN
The BOSEMs were centered (in and out around the magnet, not up and down and side to side, this can be done after the optic is in) so that the speedo indicators now all stand straight up at a half open light count value. The aOSEMs are still pulled back, and can probably do so until after the optic has been put in
I did however notice that the open light readings of the MC3-LR aOSEM (S/N 188) was quite different to log report 3125. After first checking that this S/N OSEM was indeed in this location I remeasured the open light voltage of this particular OSEM using tdsavg 10 H1:SUS-MC2_M3_OSEMINF_LR_IN1. This gave an open light value of 19455.2 counts. I modified the offset and gain in the medm screen appropriately (I can't remember if I made a new burt backup of this or not. I am pretty sure I did, but cant be certain. Be aware of this if you need to Burt restore this model).
A dtt template of the channels used for a pitch TF measurement was brought over from LLO, and the channel names renamed appropriately. However when a TF was attempted to run the error message came back "Unable to select test points". A long period of time has been spent on the phone Tuesday and Thursday with Joe B at LLO and Dave Barker here at LHO trying to resolve this (and other software problems have run into especially in terms of permissions.........thanks very much to the two of them for their patience) and the usual suspects of looking that had correct ADC channels connected , INI files were as they should be, etc and various other things tried (including a DAQ restart) we were unable to fix the problem.I have copied and pasted below a couple of extracts of emails sent between the three of us giving what I believe is the latest on the unable to select test points problem:
The "Unable to select test points" message seems to be related to the excitation channel. Providing no excitation channels allows data to be taken with diaggui. Similarly opening up awggui and trying to even select the H1:SUS-MC2_M1_TEST_P_EXC channel brings up an error message "Cannot connect to channel".
and then the latest from David Barker
Looking at the network switch configuration (which does the UDP broadcast forwarding to the front ends), the environment variables and the GDS parameter files; all look correct for an H1 system. But when I run diag it always finds the H2 awgtpman systems and not H1 so I'm wondering if it is hard coded somewhere.
So the problem still exists but is being looked into. I believe (but dont hold me to this), that once this problem is fixed I should be good to go to start taking TF's on the suspensions chamberside
This was before we replaced the ALS Faraday today.
I tilted the beam by the PIT and YAW offset sliders of the TMS table. Then I used Keita's calibration of the sliders from counts to radians (see aLOG entry 3244) to estimate the actual beam tilt.
I swept the beam over the ITMY PD2 baffle PD. The beam was centered on this PD when the offsets were:
PIT -79500, YAW +49041
Initial values were:
PIT -60691, YAW +56641
Sampling a Gaussian beam in X or Y with a PD of finite radius r0, produces and intensity profile defined by the function attached below: xc is the beam center location, and w the beam radius.
I measured the beam radius by fitting the data from the PD scan with this function. Assuming that the ITMY baffle PDs are Perkin Elmer YAG-444AH (although a document by Mike Smith says that they're YAG-444-4AH QPD), then r0=16.3/2mm and the resulting radii are:
The beam is astigmatic and not well matched to the cavity mode.
We are going to improve the mode matching soon.
We replaced the green Faraday due to clipping problem.
We've already aligned the injection path (i.e. the beam goes to the TMS and the QPDs are centered) but we need to work on the PDH and WFS path tomorrow.
Before/After picture
First picture is the beam with the original Faraday. You can easily see some really ugly lines. According to Alberto and Dan, this gets uglier when the beam is centered in the Faraday, so it was aligned closer to the Faraday edge. Combined with large TM motion, this caused a serious clipping problem.
The second picture is with the new Faraday taken at the same position. No apparent ugliness here. If you look closely you can tell that there's some funny stuff still there at the top (it would become more apparent in the far field), but this is much better than before. We expect that the clipping problem will be gone, though the large TM motion is still a problem on its own.
Turns out that segment 1 and 2 of the legacy WFS DC interface for WFS1 are not working. When we injected some offset using a break out board, these segments didn't show anything in the output. It's not the WFS head, it's the interface.
Pulled the board to investigate in the lab.
Two op-amps in the interface board were broken. WFS1-Anode 1-U2 (OP27) and WFS1-Anode 2-U3 (AD8672) were removed and replaced, resolving the issues observed yesterday. The board is now functional and can be returned to the end station. According to Richard McCarthy, the board should be replaced after we're done with the one-arm test.
Having figured out how to reset the HEPI watchdog, I moved the RZ bias to HEPI. In the process I discovered that the HEPI DC Biases have no ramps or filters, so they are pretty disruptive. This lead me to use the ISC YAW filter offset (mislabeled V). Here I discovered that the HEPI ISC paths are not in the order speciied on the screen, so I have to send my offset to RX to get RZ. Furthermore, we seem to still have the "poor choice of calibration units" problem, since the offset needed to make 14k counts on the H sensors was greater than 106.
The ISI settings are now as before. Note: we have no isolation on either ISI just damping.