Borja
I just came back from a quick visit to End-X (UTC 2014-08-27 00:25:00).
I took some pictures (see attached) at the feedthrough wiring for the ESD at BSC9 (ETMX chamber). I compare it with the ones I took a while back at ETMY (see attached).
There is an obvious difference, the red insulating tape at ETMY wiring which does not show at ETMX. The wire which has the insulating tape carries VBIAS to the ESD at ETMY. The reason for the insulation is that the coax cable's shield is cut off because the corresponding coax cable inside the chamber has the known issue of having the shield connected to the center lead. This problem is non existen at ETMX.
This is another big difference between both masses which may be related to the more stable results on the charge measurements observed at ETMX.
We need to fix the shielding in any event. The shield now acts as a large capacitance coupling of the electrode to the chamber and will inevitably cause cross talk and noise in later operations.
7:58 – Checked the Crystal Chiller water level (Maintenance)- Operator 8:15 - 8:30 Morning Meeting 8:25 – SPRAGUE on site 8:47 - Pulling cables all around the LVEA – Aaron/Ed 8:48 – Heading into H2 PSL enclosure in LVEA – Peter 9:15 – Cameras installation in LVEA – Filiberto 9:22 – Heading into the LVEA to work on SR3 Optical levers – Jason 9:44 – Back from LVEA – Peter 9:45 – Getting 3IFO(Quad#8)ready to be moved to its storage location – Jeff B. 10:04 – Working on ASC model – Dave 10:12 – Returned from LVEA – Jeff B. 10:22 - Reset HEPI overflow counters for HAM2, HAM3, HAM4, HAM5, ITMX, and ITMY (Maintenance) – Operator 11:43 – Back from the LVEA – Aaron/Ed 12:41 – Heading to End X (Cleaning) – Chris 13:37 – Heading to End Y (Cleaning) – Karen 13:46 - Heading to End Y to work on Low frequency microphone – Sudarshan 14:14 – Returning from End Y – Karen 14:18 – Back from End X – Chris 15:01 – Heading into the LVEA – Jason 15:07 – Working at End Y (Valves operation) - Kyle
Gerardo has just torqued down the bolts for HAM6 viewports. We're done with H1 in-chamber installation (for the current configuration)!
Congrats everyone!
At request of Borja
Thanks a lot Kyle for the very quick response.
S. Karki, Dave Barker Troubleshooting low freq Mic at ENDY and CS: 1. The power to the DAQ (sitting on top of each microphone) was reset by pugging off the power supply cable and plugging it back in. 2. The signal cable were switched to a known working channel. Both resulted in no difference to the signal output suggesting that the microphone itself could have been damaged. The signal from the mic seemed to have stopped since the last power glitch.
Switching from the currently used CS microphone to the extra one sitting on the floor solved the problem, suggesting that microphone is bad.
Removed the Ring Heater Assembly from the ITMy quad structure going into 3IFO storage. Before starting I noticed the lower ring heater assembly had a crack in the glass former. Not sure when the break happened, but this one also displayed a lot of movement inside the ring heater shield. The pictures show how the former has pushed pretty far out of position. The ring heater cables were also removed. This includes the "antlers" (D1001755) but not the plate (D1002420) which the earthquake stop is attached to. The assemblies removed were: ASSY-D1001895-V5 #001 (lower ring heater, broken) ASSY-D1001517-V7 #612 (cable assembly) ASSY-D1001838-V6 #005 (upper ring heater)
That should read ITMx (not y) and ASSY-D1001838-V6 #002 (upper ring heater) not #005. typos.
Note, when the 40kg optics are installed and removed from the QUAD lower structures that these ring heaters are mounted to, there is some torquing of the structure (and therefore the RH). Possibly this adds to these failure modes.
One more fix. The lower ring heater should be: ASSY-D100195-108 Made a mistake with a V5 and V6 part.
This last occurred at EndY 5 Aug but it wasn't restarted until 11 August. So barely 24 hours later it dropped out again. 14 August was the power outage and it appears no restart attempt was made at EndY. EndX is running at this time. Borja is taking data at the moment and asks the optic not be disturbed. This restart will require a trip to the EndY MR.
Dave just reminded me of the power glitch at 2355utc 12 August and this is when the pump stopped. I can see that EndX also saw the glitch but appears to ride it out and was quickly restarted after the power outage. All assumptions as I've found no logs about HEPI restarts before or after the power outage.
Filiberto, Kiwamu (WP4816)
We have installed three analog cameras that are going to monitor the signal-recycling mirrors (i.e. SR2, SR3 and SRM) on HAM4 and HAM5. We put a good TV lens on each of them and adjusted the aperture and focus.
The detailed location of the cameras are described in the viewport final design document (page 54 and 55 in DCC-T1000746-v7) and we followed it.
no restarts reported.
Maintenance: Reset HEPI overflow counters for HAM2, HAM3, HAM4, HAM5, ITMX, and ITMY
Attendees: Gerardo, Filiberto, Keita, Koji, Kiwamu, Jim, Jeff B, Ed, Peter, Justin, Aaron, etc … Today's Tasks: • Viewports installation on HAM6 – Gerardo • Running power cables for illuminators and analog cameras in LVEA – Filiberto • SR3 Optical Lever work continues in LVEA - Jason • Cameras installation on SR2, SR3, and SRM (LVEA) - Filiberto • Dust monitor work in LVEA – Jeff B • ISC table to be moved (LVEA) – Keita • Cable pulling all around the LVEA – Aaron • Moving 3IFO (Quad#8) to its proper location in LVEA – Jeff B
The performance of the intensity stabilisation servo (ISS) will not be measured this week due to some problems with the servo. I am not sure what the cause of the problems are but the servo has problems locking. The diffracted power as indicated in the MEDM screen, switches between two states, regardless of whether the servo is attempts to lock in either automatic or manual mode. The relative power noise measurement is close to the reference measurement. It is slightly better below 10 Hz and slightly better above ~5 kHz. Both are well within the requirement for the laser. Both the control and error signals in the frequency noise measurement are better than the reference measurement. The error signal looks strange below about 60 Hz with a number of steps present. The beam pointing measurement is not as good as the last one performed on August 12th, with the 1x and 1y error signals being a factor of 3 higher. The control signal in both cases is about the same as the previous measurement. The power incident on the reflection photodiode is about the same. The mode scan does not look all that different from the previous two scan measurements. The relative peak heights look the same to the eye. The higher mode content has increased by 2%, with the higher order mode power increasing by 0.2%. The cavity finesse is the same within the errors.
I checked the Crystal Chiller this morning. The water level was fine.
Borja
Yesterday's results in ETMX although positive from aLIGO operation point of view (no charging mechanism was observed based on green light and ion pump) however it was discouraging from the point of view of providing answers to the big charge changes that were observed in ETMY. If the ion pump was not charging the mass then what was doing it? Is this unexplained behaviour in ETMY charge changes casting a shadow over the charge measurements methodology? Fortunately a new set of measurements in ETMY that were taken during the experiments at ETMX confirms that the measurement method is reliable and it also tells us what is charging ETMY. For a period of 62 hours 6 charge measurements were taken on ETMY, for all these measurements the ion pump gate valve was closed. The results are remarkable in their consistency and stationarity of the charge values for all quadrants and for both orientations (pitch and yaw) within no more than 20Volts (less depending on the quadrant and orientation). The charge values agree with the last measurement taken just before closing the ion pump gate valve.
The amount of measurements make it impractical to show a summary table like in my previous aLog so this time I go for a more friendly graphical display. As always attached are the measurement documents and the standard VBIAS vs normalised deflection plots comparing each measurement with the ion pump gate valve closed with the first one, and the first one with the one previous to closing the valve.
So what is different between X and Y regarding the charging effect of the ion pump? mainly 3 differences:
1) The Earth magnetic field
2) The pressure being different by an order of magnitude. The pressure in end-X is 2.7e-7 torr while in end-Y is 4.8e-8 torr. A higher preasure will reduce movement of the ions, but at the same time the higher the pressure the more charge is emitted by the ion pump (see attached document "charged_particle_emiss_ion_pumps.pdf").
3) Both ion pumps were costume made to the same specifications. They are made of 50 smaller ion pumps so maybe the way these were configured is different for each final ion pump.
Next I show the summary plots of all measurements taken so far both for ETMX and ETMY. Each mass has 2 set of plots; Veff and slope of normalised deflection vs VBIAS. Each set of plot is divided in 2 subplots, one per deflection orientation (pitch and yaw).
ETMX:
ETMY:
The numbers in the plots represent the major changes that took place at the time of the measurements. These are summarised next:
1) 1st ionizer discharge.
2) 2nd ionizer discharge.
3) Wire swap to right configuration: BIAS going through the ESD LP filter box.
4) Wire swap to wrong configuration: LL quadrant driver going through the ESD LP filter box.
5) Wire swap to right configuration and Final: BIAS going through the ESD LP filter box.
I'm not sure if this plays a roll in this study, but for the record the ETMx, ITMx, and ITMy test masses and reaction masses had the long ~9 minute deionozation blow off before chamber close out earlier this month. The ETMy and it's reaction mass did not because it was not opened for this vent. The ETMy only had the quick ~1-2 minute blow off when the First Contact was pulled from it's surfaces earlier in the year. As well, the ERMy FC was pulled many weeks before the ETMy FC was pulled, so these short deionization blow offs were also widely separated in time.
Keita and Kiwamu
In order to investigate the large cross coupling issue in OMs (alog 13575 by Dan), we checked the OM driver electronics.
We found that the OM1 and OM2 coil driver Vmon are not properly functioning. However, this does not explain the cross coupling that Koji and Dan experienced.
Anyway, these two coil driver chassis (S1200614 and S1200612) need to be swapped at some point.
(some details)
When we started looking at the OM screens, we immediately noticed the LL voltage monitor of OM1 and OM2 displaying anomalously high voltage while the zero DAC voltage were requested. OM1_LL showed approximately 23000 cnts and OM2_LL showed approximately -23300 cnts. Even so, these channels were still sensitive to the bias we sent through the DAC -- we could change the readout values by changing the biases. But they did not go to the other sign in the readout voltages.
We then went to the electronics room to check out the analog circuits. Looking at DB9s' signals for the Vmons by inserting a 9-pin breakout board, indeed we saw LLs exhibiting a funny voltage. LL of both OM1 and OM2 were at -14 V when the zero DAC voltage were requested. Then we went to the AS port rack to check if this is also the case for the actual drive signals. However the drive signals looked healthy on both OM1 and OM2. We checked this by looking at the signals at the input of the satellite amplifiers. All the signals could swing from -22 to 22 V as we changed the DAC voltages.
We are concluding that the Vmon part is not properly functioning in the OM1 and OM2 coil drivers. But, since the actual drives are healthy, this issue is independent of the cross coupling issue.
By the way, the OM3 coild driver looked healthy and its Vmon looked fine. So we did not check them.
I investigated this and found that S1200614 had an OP27 IC in the -Vmon CH2 that was railed. The IC was replaced and the chassis seems fully functional once again. The other chassis (S1200612) will be addressed tomorrow morning. I'm going to assume the same is true of that one as well. I will let you know when the repair is complete and please let me know if you have further issues with these two.
yesterday we noticed that ITMX has been tripping, it seems to happen within a minute or so of becoming fully isolated. HEPI seems to have position loops running, there is no feedback from ISC to the suspension or HEPI. The last few trips have been just stage 2, actuator trips. It looks like something is ringing up.
The stage 2 blends were on Tbetter expect RZ, which was on Tcrappy for the two trips plotted in the first screenshot attached. I've tried setting stage 2 blends to start, this also caused a trip which is the second attached screenshot.
Now I have set the guardian to isolated_damped, so that stage 1 is isolated and stage 2 is damped. So far its not tripped.
For the last 20 minutes or so, stage 2 has been isolated level 1 with no problems.
It seems that the level 3 controllers for X are the problem. It was fine with stage 2 on level one controllers, and it stayed isolated with all DOFs other than X at level 3. It tripped even when I used no boost for X.
From looking at the trends it seems as though the ITMX ISI hasn't really been isolated since the first week of june. Jeff suggests that the problem could be that the plant has changed durring the vent, and now the controllers designed before the vent aren't stable (for X). Here is a screen shot of a spectrum just before one of these trips. The problem seems to be at 147 Hz. The filter is also plotted here, with the cursor at 147 Hz.
Hugh also reported a problem on August 8th, at 320 Hz. (alog 13294 )
It looks like this loop needs some TLC. For now I'm leaving the guardian at ISOLATED_DAMPED, but it can be semi isolated by going to the command scripts, and turning on the level three controller for all DOFs except X.
I worked on these loops a bit this morning. I ended up adding a notch in the ST2 X isolation loop at 147, and now everything turns on. I wouldn't say everything is happy, as the drives are still quite high, so it would be good to get an in-vac tf and re-visit the loop design. It's been running for the last 20 minutes or so. Will talk to commissioners about a convenient time to do further work on this.
