bubba.gateley@LIGO.ORG - posted 09:02, Monday 17 August 2015 (20594)
LTS Container Trends
10 day trends for LTS containers
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10 day trends for LTS containers
Late last week we had one of the two compressors quit on the AAON unit at the staging building. See FRS 3455. This unit is designed to supplement the original 12 T Carrier chiller which also has one of the two condenser fan motors beginning to show signs of failure. See FRS 3451. The failed compressor has been disconnected and the AAON is operating at 50% capacity which should be enough to assist the main unit enough to keep the staging building cool especially during the somewhat cooler temperatures. The faulty parts have now been ordered and hopefully arrive before any additional triple digit temperatures.
LVEA: Laser Hazard IFO: UnLocked Observation Bit: Commissioning All Times in UTC 07:00 Take over from Ed M. 07:00 Commissioners working on IFO 09:11 Locked at Nominal_Low_Noise – Commissioning on going 11:09 Lock Loss – Commissioning activities 11:30 Dust counts at End-Y high 12:01 Locked at Nominal_Low_Noise – Commissioning on going 15:00 Turn over to Travis 15:04 Lockloss -
The attached pdf contains current Stage-1 and Stage-2 NB model performance of ITMY chamber for X,Y,Z and RZ dof. Fig 1- ST1 ITMY X Low frequency near microseism model performance is limited by the ground blend filter (HEPI L4C+IPS) 1-5Hz frequency band is limited by GND-STS passing through the sensor correction path 5Hz and above (upto 10Hz say) is limited by Stage-2 back reaction Below microseism model does not match with actual performance. (May be because of some tilt coupling?? But it looks like actual measurement is limited by the sensor noises (T240/CPS) via isolation filter. - Not sure about it) Fig 2- ST2 ITMY X Instead of T240 BLND OUT, I have used T240 BLND IN as the input (stage-1 displacement) to the ST-2 model. Though the model and measured GS13 are in agreement above blend frequency (250mHz), the shape between 1-3Hz are not same. The model output looks more like the input signal T240 BLND IN. May be a better input noise model will work better. Since the stage-2 model performance above ~1Hz is highly dependent on stage-1 displacement, we can san say that the Stage-2 back reaction on stage-1 can have effect on the final performance of the model. Fig 3 - ST1 ITMY Y Most of the features and model performance are same as X dof. Fig 4 - ST2 ITMY Y Though this one is same as ST2 ITMY X only thing I have noticed here is the actual IFO ST1 performance is better than ST2 between ~ 300-500 mHz. Fig 5- ST1 ITMY Z ST-1 model performance matches the actual measurement at almost all the frequency range of interest. The conclusions derived for ground model and Stage-2 back reaction hold here too. Fig 6- ST2 ITMY Z Unlike X and Y dof, the model performance between 60 to 250 mHz is quite good (I am still trying to figure out why this sort of discrepancy exists between these dofs ???) At the same time the mismatch between model and actual performance above 5Hz is noticeable. Model is over estimating the actual performance here (though the model has already included stage-2 back reaction in Stage-1) Fig 7- ST1 ITMY RZ Apart from the limitations of the model due to ground noise at low frequencies, the performance of this stage is mostly limited by CPS sensor noise via BLEND+ISO path. Fig 8- ST1 ITMY RZ Please DO NOT go through this figure. Still need to sort out the problems. Same sort of features can be seen in almost all the BSC chambers except BS where the stage-2 controllers are not in use.
T240 and GS13 sensor noise floors are added to the seismic noise budget plots.
Have been seeing high dust counts at End-Y during evening ops shift. The counts are not that far off the normal values for End-Y, but there is no apparent cause for the spikes. Will continue to monitor.
Darkhan, Jenne, Stefan, Evan
Upon revisiting the shape of the DARM loop, we found that we had 4 dB of gain peaking from 10 Hz to 50 Hz.
That seems a bit too strong for our taste, so we took a look at the DARM suscomp filter that we've been using for the past few months. Aside from the low-frequency (<2 Hz) suspension resonance compensation and the high-frequency (>900 Hz) inversion rolloff, there is a single pole at 200 Hz.
This serves us well when locking DIFF, but in full, low-noise lock it costs us phase (not least because we also have the effect of the 350 Hz RSE pole).
Anyway, there is now a filter installed in EY L3 lock with a zero at 200 Hz and a pole at 1000 Hz in order to push this pole up to higher frequency. This gives us a modest improvement in phase margin at the DARM ugf (34° to 46°). The DARM ugf is 40 Hz or so (more or less the same as before). The EY ESD has about 16000 ct rms, mostly accumulated around 1 kHz (magenta/orange in the attached spectra show the before/after).
[In the longer term, we should just roll p/z pair into the suscomp filter, so that it rises like f essentially from 1 Hz to 1 kHz. Then put a 200 Hz pole / 1000 Hz zero pair in EX L3 lock, so as not to disturb the DIFF loop shape. However, I've put what we have so far into the guardian and it works fine.]
Darkhan and I retuned the DARM OLTF template in order to not saturate with this new loop shape. The attachment shows the before (blue) and after (red), along with the closed-loop gain and loop suppression. There's still moderate gain peaking below 20 Hz.
Also attached is new pcal sweep measurement.
Attached is a screen snapshot of the ETMy L3 LOCK filter bank and the corresponding CAL-CS_DARM_FE_ETMY_L3 bank, now showing the new filter. There are still differences between the banks...
Evan, Stefan, Evan will make a more detailed log entry with actual measurements, but here are the highlights: - We beat the 45Mhz signal from the installed and the spare harmonic generators. - the first odd thing was that straight out of the harmonic generators, the 45Mhz signals were out of phase by about 170deg, even though the 9MHz inputs were nicely in phase... - We phased the two signals to be exactly in phase an stuck them into a mixer: 0.415V - We phased the. To be exactly 90deg apart: no DC signal, and ~ 220nV/rtHz of flat broadband noise. - this gives 5.3e-7 rad/rtHz between the two signals. - Assuming equal and non-coherent contributions, the phase noise of one box is thus: 3.75e-7 rad/rtHz - If we assume that the oscillator phase noise has the same coupling as the oscillator amplitude noise (9e-2mA/RIN), we would expect 3.4e-8mA/rtHz. Thats's pretty close to what we see on ODC_DCPD_SUM.
Data attached: two amplitude noise measurements, two phase noise measurements. One set taken sending equal drive levels into the mixer, and another set taken with the rf attenuated by 5 dB.
We had noticed last week that the refl 45 WFS were phased incorrectly, and tonight Jenne and I rephased them by moving PR3 100 counts in pitch. This only affects the PRC2 loop. We've locked and engaged the ASC several times since then, and this seems fine.
While we did improve the phasing and tuned it to within 5 degrees, I is only about 9 dB higher than Q for PR3 motion. We will need a different phasing strategy, where we phase 45 to minimize the signal from chard in one quadrature if we want to distinguish between PR3 motion and CHARD.
CThe first two attached screenshots are the phases before we started, except that for REFL A the phase of the first quadrant was -165 not -145. The following 2 screenshots were the phases we rephased. For the time being we have reverted.
Earlier tonight, we rephased the REFL 45 WFS to be maximally sensitive to PR3 motion, but I think that instead, we should phase them to be minimally sensitive to CHARD motion.
Jenne and I spent some time making SDF green before the enigneering run starts in the morning.
The main things that are still showing diffs are HAM1 HPI, some violin mode damping settings on ITMY, and many diffs in CALCS.
While we were doing this we noticed a potentially nasty trick that SDF does. We chose some channels that should be not monitored from the list of DIFFs, and right as I was about to CONFIRM, the IFO lost lock. A new diff showed up on the top of the list, and the channels I had intended to not mon were moved down the list, but the yellow squares stayed in the same place. It would have been verry easy to miss this and apply the action to the wrong channels. Jenne is putting this in bugzilla.
The OMC_LOCK guardian now has the states ADD_WHITENING and REMOVE_WHITENING, which do what they say on the tin. If you have one stage of whitening on, running ADD_WHITENING will turn on one more stage, etc.
They are not connected to the rest of the graph at all, so you'll have to run them manually.
They are intended to be compatible with full lock, so they can be run at any time (so long as you don't end up saturating the DCPD ADCs, of course).
ALL TIMES IN UTC
Arrived to find IFO beginning lock sequence after TJ did some PRMI alignment to help DRMI. It seems previous lock segments were on the average of about half a hour
23:09 DRMI locked.
23:10 Robert in the LVEA
23:15 Guardian hung on an OMC error. (no light on QPD)
23:37 noticed HEPI L4 WD SATURATION MONITOR for ITMX is at 43820cts. WD limit is set to 30000(safe)(max is 122880). WIll reset at next opportunity.
23:29 Dick and Wayne in the optics lab
23:30 Robert out of the LVEA
23:48 reset ITMX HEPI WD accumulator.
00:10 DRMI taking in excess of 16 minutes. No environmental noise observed. Tried PRMI lost lock. restored slider values back 1 hour. Re-Aligned SRM DRMI locked 1 minute later.
00:29 Wayne out of optics lab.
01:02 Stefan out to CER
01:16 Dick out
-1:20 Guardian ISC_LOCK in Error at Engage ASC Part 2. Stefan cleared error
LOCK LOG:
23:23 Locked at NLN
23:47 Lockloss at ENGAGE_ISS_SECOND_LOOP
DRMI ~ 13 minutes to lock
23:49 Began sequence
DRMI taking over 16 minutes.
00:20 PRMI align
00:48 Locked at NOMINAL_LOW_NOISE
0:48 Lockloss . Gabriele trying to fine tune OMC
00:49 Began Sequence
01:07 Lockloss @ ENGAGE_ASC_PART3
01:08 Began Sequence
01:29 Locked at NOMINAL_LOW_NOISE
00:00 IFO still locked. 70mpc
Evening Summary:
IFO locking in half hour segments. DRMI was taking a rather long time locking. Visiting PRMI may have improved it slightly.
Stefan and Evan have been taking measurements and tuning for the last 5.5 hour lock.
IFO still locked at shift change @ ~70-72mpc.
Sheila, Evan
Running the dc-coupled oplev servo on SR3 for long periods of time seems to be causing us grief (LHO#20519).
As an alternative, we are trying out a cage servo which feeds the witness sensor in pitch back to M2:
ezcaservo -r H1:SUS-SR3_M3_WIT_PMON -g -300 -s
The step response of this loop has a time constant of 30 s or so.
Jenne and I put this cage servo into a new guardian, called SR3_CAGE_SERVO. One hick up in this process was the fact that the gain setting that works for ezcaservo is opposite to the one that works for cdsutils.servo
This guardian is managed by the ISC_DRMI guardian, which doesn't turn it off but does make sure that it is turned on after DRMI locks. There are states to run the servo, turn it off, and to clear the history (clear offset). We've added this guardian to the list of guardians in IFO guardian. (That is the guardian who checks that the state of other guardians), and set the nominal state to CAGE_SERVO_RUNNING.
We've also added it to the ISC guardian overview screen.
If misaligning SR3, this servo needs to be off. The guardian will go to CAGE_SERVO_OFF if SR3 is misaligned.
Did you guys add this new node to the overview screen? Please let me know when you add new nodes. All nodes have to be tracked in the infrastructure, so we need to know all nodes that are running and are being depended upon by other nodes.
I alrady noticed yesterday that the DARM noise at the periscope peaks (200-400 Hz) was high at the beginning of the lock and then reduced over time.
The first attached plot shows a BLRMS of DARM around those peaks, starting right after reaching the low noise state. There is a clear reduction of the noise over time. The second plot shows that on a similar time scale, the OMC alignment output signal changed, mostly ANG_Y.
This seems to confirm the idea that input beam jitter at the periscope peaks is converted into intensity noise by an OMC misalignment, which changes over time.
To confirm this, I move the OMC angular loops during full lock, adding offsets of few tens of counts to the POS and ANG loops. The third plot shows the steps in the control signals. I was able to reduce the BLRMS by adding an offset of -40 to the ANG_Y loop. The fourth plot compares the DARM spectrum with (red) and without (blue) the ANG_Y offset. I should have increased the offset more. Unfortunately, I noticed that the output was hitting the limit of 300 and I stupidly increased it to 1000: but since the loop was integrating, I broke the lock since I suddenly increased the output from -300 to -1000.
However, the experiment confirms that the noise at the periscope peaks changes in amplitude with the OMC alignment, which is not optimal.
I am not 100% sure what value Gabriele meant to leave, but I have accepted in SDF (Sheila and I are in process of clearing a bunch of diffs in SDF) the value of -30 for ANG_Y for the OMC. I'll check with Gabriele about what value he meant to leave (his alog seems to indicate -40, but we found it at -30).
Since we're using the QPD loops to align the OMC, it's probably better to record any change in the alignment in the QPD offsets. I forget the channel names at the moment, but these are the offsets in the OMC QPD channels (not the same channels in the ASC models). If the offsets are stored in the ANG and POS loops, they will have to be turned off if/when we switch to the dither alignment. If they are recorded in the QPD filter banks it is one less thing to think about.
To summarize the OMC alignment: the QPD offsets have been tuned so the OMC is well-aligned in the low power state. In this state, the dither error signals should be zero. We know that as the power is increased, the QPD offsets are no longer a good alignment, especially in pitch -- this is according to the dither error signals. We suspect the misalignment is due to some junk light that shifts the nominal alignment position on the QPDs. Unfortunately, the misalignment is large enough that engaging the dither loops in the high power state saturates the drive to the OMC SUS. This is why we have stuck with the QPD alignment for now...we should find a solution before O1 that allows us to use the dither loops. The last time the alignment scheme had any attention was in late May.
Needless to say, do remember to check the drives to the OMC SUS OSEMs when changing the alignment settings, they may saturate!
The offsets I left (-30) is better than 0, but not the optimal one yet. It's better to check the OMC alignment again
After the PSL temperature adventure on monday afternoon, it seems as though the PMC alignment shifted. We now get less transmitted power, although the sum of refl and trans has not changed much.
In looking at the data around the period of the temperature excursion, all the power monitoring photodiodes indicate a change in power monitored. The ones located before the pre-modecleaner return to their previous values. The ISS photodiodes after the pre-modecleaner return to their previous values however the transmission and reflection signals are lower than before. The pre-modecleaner reflected spot doesn't look substantially different, however the pre-modecleaner heater output did not return to its previous level. It has remained at an elevated level since the temperature excursion. The coefficient of thermal expansion for aluminium is approximately 22 microns per degK. The attached plot suggests the body of the pre-modecleaner changed by 0.5 degK and stayed at the higher temperature. It should be noted that the pre-modecleaner heater did its job and relieved the PZT high voltage. In doing so the length of the spacer is different and this may be the cause of any mis-alignment. The plot also shows the Laser Room temperature. It might be worth trying reducing (presumably reducing, might also be increasing) the heater offset to bring the pre-modecleaner temperature back down to 304.5 degK from its current value of 305.0 degK to see if this peaks the power transmitted by the pre-modecleaner.
Attached is the output of the quadrant photodiode in the ISS photodiode box with the corresponding temperature measurement. Clearly a change in the beam position is indicated, with the vertical not returning to its previous value. The horizontal seems to track the room temperature.
