J. Driggers, K. Izumi, S. Dwyer, J. Kissel, V. Adya, T. Shaffer

We've been able to find green alignment quite easily. Yes!!

However, once we were able to get ALS X well aligned and locked, with Green WFS and ITM camera alignment systems ON -- the ALS X Beckhoff state machine turned into a blinking MEDM light show. The arm would remain locked, with good alignment, the ALSX guardian would go into fault.

The obvious symptoms were several momentary errors on the (from the ALS Overview Screen) Beckhoff screens for PDH, Fiber PLL, and VCO that each complained of each other.
We started with slow calculated attempts of trying to disable various parts of the state machine, e.g. 
    - using H1:ALS-X_FIBR_LOCK_LOGIC_FORCE to force the fiber PLL lock, or 
    - by hitting reset (H1:ALS-X_VCO_CONTROLS_CLEARINT) on the H1:ALS-X_VCO_TUNEOFS to reset the frequency finding servo.
we then degraded to a bit of button mashing, after which the state machine would just restore everything to what it was before we started.

Finally, Sheila showed us how to dig down an alternate path for finding errors via the sitemap > SYS > EtherCAT overview and follow the error messages from there. However the screens only show explanatory text when there are errors present, which makes tracing a momentary error frustrating at best. Our path down this rabbit hole was
    sitemap >
        SYS >
            EtherCAT overview > ECAT_CUST_SYSTEM.adl
                X-End PLC2 (because it showed a text "ALS-X; ISC-EX") > H1_X1PLC2.adl
                    Als (which had no text) > H1ALS_X1_PLC2.adl
                        X (had no text) > H1ALS_X1_PLC2_X.adl
                            Potential BUG: On this screen the "Lock" and "Refl" were showing constant errors but "Laser" ended up being the problem
                            Laser (maybe showed only momentary text) > H1ALS_X1PLC2_X_LASER.adl
                                Head > H1ALS_X1_PLC2_X_LASER_HEAD.adl
                                    After careful scrutiny of this screen we found that the ALS-X laser diode 2's powr monitor
                                        H1:ALS-X_LASER_HEAD_LASERDIODE2POWERMONITOR
                                    was bouncing between 2.038 and 2.039, with is just hovering along the edge of the user defined tolerance of
                                        H1:ALS-X_LASER_HEAD_LASERDIODEPOWERTOLERANCE == 0.2
                                    from the user-defined nominal
                                        H1:ALS-X_LASER_HEAD_LASERDIODEPOWERNOMINAL == 1.842
                                    After increasing the threshold on deviations from the nominal from 0.2 to 0.5, the entire state machine became happy and normal.

This is a problem we'd never seen before, but upon further inspection while writing this log (because we found it hard to believe that laser diodes would produce *more* power than before), I took a look at the 15 day trend of this laser power vs. the X VEA temperature (as measured by the PCAL Receiver's Temperature Sensor), and indeed, the laser power follows it nicely. We should be prepared for the HVAC upgrade to be impacting a lot more than just suspension alignments (LHO aLOG 36331).

Lesson Learned The state machine for the ALS system is really hard to debug when there are momentary errors. 
    - We should change the beckhoff error reporting to be latching
    - We should change these automatically generated screens to *always* display text, so that one can navigate around them with comfort
    - There may actually be a bug in the reporting system

As Jeff posted last night, we've been working on doing Z tilt decoupling on the ISI's like Hugh and Krishna did back in 2014 (!) for the HEPIs in alog 15726. I followed a similar procedure to Hugh, getting tf's (with Jeff's help) driving in Z,RX and RY and dividing the Z to X/Y tfs by the RY/RX to X/Y tfs to get  the magnitude of the Z to RX/RY coupling. The calculated coefficients are then writtent into the Z->RX/RY cps2cart matrix elements. I still need to get the BS RY drive data and I need to do some close-out transfer functions to evaluate how good the decoupling is. Additionally, it looks like ETMY didn't need tilt decoupling in either dof, and ITMX & ETMX RX were also good.

The two attached plots are the ETMX & ITMX before and after Z drive to X transfer functions. These plots show the reduction in the magnitude of the coupling from Z to X, which implies that the magnitude of the Z to RY coupling has been reduced.

I've added all of my measurement data to the seismic svn at /ligo/svncommon/SeiSVN/seismic/BSC-ISI/H1/Common/Data/ Z_RX_RY_decouple, but its a couple hundred of megabytes of data.

(This concludes WP #6644) 

Kyle

RGA scans were taken this morning followed by the spinning down of the Vertex, YBM and XBM MTPs (main turbo pumps), isolating the scroll fore line and stopping the scroll pumps, "burping" GV5 and GV7's gate annulus volumes into the adjacent ion-pumped annulus volumes and then opening GV5 and GV7.  

Note:  

GV5's gate separated without a fuss but approximately 3/4 of the way into its "open" stroke it came to a halt with a "clunk" confirmed by a stoppage of audible displaced air out of the electro-pneumatic selector manifold .  I assumed that it was at the mechanical stop but CDS was indicating a "yellow" field.  After a minute or so of contemplation, and on its own, it resumed stroking to the mechanical stop.  GV5 has always been worrisome but seems to be getting worse with use.  GV7 behaved weird as well in that the gate seemed to separate as usual and CDS transitioned to "yellow" but the adjacent vacuum pressures indicated no gate separation.  With additional increase in pneumatic air pressure the vacuum pressures finally responded but the displaced air out of the electro-pneumatic selector manifold was barely audible during the stroking.  Even with 55 psi applied, it took noticeably longer than normal for it to open.  This is consistent with the "dribble' of displaced air.  I did note that the red light showing which side of the piston the instrument-air was being applied to was not illuminated.  I don't know if this is a new problem or if the bulb has been burned out for a while????  

Starting CP3 fill. LLCV enabled. LLCV set to manual control. LLCV set to 50% open. Fill completed in 27 seconds. TC B did not register fill. LLCV set back to 19.0% open.
Starting CP4 fill. LLCV enabled. LLCV set to manual control. LLCV set to 70% open. Fill completed in 1620 seconds. LLCV set back to 37.0% open.

J. Kissel, K. Izumi, (A. Brooks by phone)

We had restored the ITM ring heater settings, but failed to see any measured current. After calling Aidan, he told us to check the drivers in the CER. We found they were OFF. We've turned the drivers back ON and restored the settings. ITMs are now being toasted as normal.

As I suspected, one of the accumulators, a supply side at the chamber, was found to have zero pressure.  Additionally, it would take no gas.  I replaced the Schrader Valve Stem and then it would take a charge and appeared to hold charge.  Nothing obvious on the stem but for 20¢, I'm not investigating further.

This is a pretty good case for the frequent HEPI fluid level check being an indicator of the accumulators' state of charge.  As I reported in 36356, the level was down by 7/16" while running.  While stopped, the level increased by only 4 or 5/16" when recharged.  Additionally, this accumulator was on the supply side which run at a higher charge, 69psi.  Had it been a return side accumulator which run at 35psi, this loss might not have been apparent.  However, I'd argue that the return side accumulators are marginal in their benefit.  Further, the much greater fluid volume in the corner station system might absorb the charge loss in a single accumulator without revealing that loss at the reservoir.

Bottom line, verify as best you can that the Schrader valve is sealing after the charge check and closely monitor the fluid levels for otherwise unexplained reasons of fluid level change.

Closing WP 6655 and FRS 8192.

Vern S. asked that I post these scans so as to make them available for review to all who are interested prior to opening GV5 and GV7.  So, here they are. 

h0rgacs_SEM_analog_05242017a is a scan of the combined Vertex+YBM+XBM volumes while they are being pumped via IPs1-6.  Note that, for this scan, I am running 1mA filament current and 1300V SEM voltage.  For scan h0rgacs_SEM_05242017b I reverted the settings back the Quadera default of 2mA filament current and 1500V SEM voltage.  I think that the scans that Chandra R. had taken prior to this vent exercise had used the as found Quadera default settings.  As such, if you are comparing "before" to "after" scans, you will want to use h0rgacs_SEM_05242017b.

J. Kissel

In prep for IFO recovery, I've restored the end station ESD configurations to their nominal low noise configuration and confirmed they are functional.

FAMIS 8037

Signals currently look reasonable.

Took a couple of shots of the existing PZT mount at the base of the IO periscope.

    I also checked the beam on the iris that is seen in the photos.  To me it looked
like the beam was clipped on the right hand side of the beam (~3 o'clock) as you look
from the PZT mount down the length of the table.  So either the beam moved or the iris
was not placed correctly.

    We should definitely check this more rigorously before we swap the mount out.

The laser was shutdown to accommodate fixing the leak in the air bleed circuit
(WP 6654).

    Upon restoration the flow rate to head 3 didn't quite come back to where it
was, and is a tad lower.  We will be watching this over the next few hours.  Nothing
appeared to be in the flow sensor body or hindering the turbine.



JeffB / Peter

Daniel, Kiwamu per WP6650,

We made two major changes to IOO today as follows.

• The IMC locking RFPD (36322) was replaced by the one with the correct resonant frequency.
• A new modulation path for 118 MHz was added to the existing 24 MHz modulation path via a power combiner.

After these tasks, we have confirmed that the IMC could still lock with an UGF of 50 kHz (which had been 54-ish kHz before we made changes today, approximately corresponding to a 1 dB loss in the sensing system). Tomorrow, we will try to measure the modulation index for 118 MHz using the Michelson fringes.

[IMC length RFPD]

The old unit (S1203263) was replaced by the one with the correct resonant circuit (S1203775). I have repeated the same measurement as yesterday with the AM laser (36322) to check out the response of the new RFPD. The first attached figure shows comparison of the new and old RFPD responses. The magnitude at 24 MHz was found to be lower than that with the old one by half a dB. So the response is virtually unchanged at 24 MHz. The raw data is attached as well.

I made sure about the alignment of the beam onto the RFPD by touching the 2" steering mirror in front of it. I also made sure that the reflection from the RFPD was dumped properly with a razor blade.

[Addition of 118 MHz modulation]

We newly installed two IFR function generators in an ISC rack in the CER. One of them provide us with the modulation rf source at 118 MHz while the other does for the demodulation at 72 MHz or whatever frequency we desire. The 118 MHz generator was then hooked up to an RF amplifier, ZHL-1-2W, and then to the patch panel which transfers it to the ISC field racks by the PSL. Then, the 118 MHz signals is combined with the existing 24 MHz modulation signal via a power combiner, MECA 2-way combiner. As it turned out that the power combiner gave us a relatively high insertion loss of ~3 dB, we decided to increase the rf power for 24 MHz as a compensation. We increased it by installing another MECA 2-way combiner and let it do the coherent sum. So in total we have installed two 2-way combiner in series as seen in the attached picture.

We also studied rf losses for 118 MHz and found extra frequency dependent losses in the cable that connects the field and remote racks. The cable loss for 118 MHz was found to be higher than that for 24 MHz by a couple of dB. In the end, we measured an rf power of 30 dBm for 118 MHz at the output of the last power combiner, which we think is reasonably high and not too high for causing serious problems with the EOM. Note that we tried inserting a balun which turned out to be as lossy as 3-4 dB. So we decided not to use a balun for 118 MHz. We are thinking of installing a DC block instead.

As this setup messed up the rf phase, we then re-adjusted the delay of the delay line unit for 24 MHz, by flipping 1 and 2 nsec switches. This gave us almost the same UGF of 50 kHz when the IMC was locked with a 2 W input and with the new RFPD in use. Good.