Got the go head from IMC folks and SEI. Locked up the HAM3 HEPI. The largest displacement see from unlocked to locked condition is 300 cts or 0.0005". The runout of the vertical shift is only 140cts so max tilting of the table is only a couple urads. I see a similar change in the yaw position. In conclusion, alignment should be very little affected.
late entry for wed afternoon restarts
h1peml0 was restarted to test the Id revision string substitution when the mdl file is committed to SVN.
h1ascimc model was changed to remove the WFS A,B WHITEN GAIN parts as these channels are now controlled by the Beckhoff slow controls system.
DAQ was restarted because of the ASC IMC change, it then used the modified ini files for the BSC HEPI systems. So h1hpiitmy and h1hpietmy models were restarted to load the latest code from Vincent.
We went in chamber this AM, locked up the ISI and did a level check with the Optical Level. The run out 0.2mm over the 1.5M Optical Table gives a level of 133urad. The numbers would suggest though that we are at the limits of the Optical Table Flatness. That is, the SE and NW corners of the Optical Table are low and the opposite corners are high. SUS is going in now to confirm no rubbing to insure the YAW evaluation is not suspect. ***The ISI Remains Locked***
At 9:22:13 UTC Jan. 24, the models on the h1seih23 computer stopped running. All models reported ADC timeout. Checked I/O chassis, power switch was on but found no indication of life. The I/O chassis refuses to power up, even after disconnecting the DC power and reconnecting. Suspect I/O chassis power supply is bad. h1seih23 is powered off for now.
Praxair arrived at 8:00 to make a delivery to MX.
Forgot this what with the BSC1 work. Yesterday between ~10M & Noon, I locked down the SW HEPI Foot and leveled the two L4Cs. This concludes the L4C leveling on the HAM. When done, after releasing the Foot, the largest change to the Inductive Position Sensor readings was ~400 cts or ~0.0007". This was a horizontal. I doubt it will be noticeable. SEI would like to lock up this HEPI. Since there is no HEPI operation at this point, the unlocked HEPI shows resonances that would nominally be suppressed. With approval, SEI will lock this today. WHAM3 remains locked but there are still three corners to level there which will mean it will be unlocked, again, when the IMC crew can tolerate the mild disruption.
All The repaired LSC RFPD has been re-installed on IOT2, and we could relock the IMC easily. We measured the OLTF of the fast loop: we have a 60 kHz UGF and 40 degrees of phase margin (measured with the 730 kHz notch ). Details will follow.
The first picture shows a comparison of the OLTF with and without the notch. At 60 kHz we lose 7 degrees of phase with the notch in. The second picture shows where the notch box is, and the third picture shows the MEDM screens with the standard gain settings.
Attached are plots of dust counts > .3 microns and > .5 microns in particles per cubic foot from approximately 5 PM Jan. 22 to 5 PM Jan. 23. Also attached are plots of the modes to show when they were running/acquiring data. Dust monitor 10 in the H1 PSL enclosure is still indicating a calibration failure.
We checked the grounding of WFS and LSC cables to the table.
Disconnected the cable from the DC interface and checked if the ground pin on the cable was connected to the ground pin of the DC interface, and they were not.
Then we went to the table, disconnected the WFS cable from the feedthrough panel of the table, connected a DB15 cable to the feedthrough and locally supplied +-18V from a power supply.
No oscillation was observed, but none of the channels in WFSA was responding to the light. For WFSB, segment 1 and 2 (pin4-12 and pin3-11) were good, positive output of the segment 3 (pin2) was dead but the negative output (pin 10) was fine, and the segment4 (pin1-9) was dead.
We removed the heads from the table and opened them to find that:
For WFSA, in 3 segments AD8599 (U1 in D1101614, that's the dual opamp for the differential output stage) was blown up, and the remaining one segment had a fried AD8597 (U2, that's the trans impedance amp before the differential stage).
For WFSB, only one segment had what seems to be a fried AD8597.
Pictures will be posted by Lisa or Giacomo.
We don't know how these things were broken.
Don't do this:
I repeatedly connected the positive output of the differential output stage to the core of the BNC and the negative to the sheild, and connected it to an oscilloscope. This means that the negative output is short-circuited to the mains ground. It was also connected to the DC ground of the demod board as the same scope was connected to the single ended monitor output of the demod board.
This doesn't explain why the opamps were burnt (the absolute maximum rating of the opamp, AD8599, for short circuit is specified as "indefinite"), but it's simply a bad practice so don't do it.
Keita K., Giacomo C., Richard M., Filiberto C., Kiwamu I.
The resonant RF PD [1][2] that has been used for the length sensing of the IMC, was found to have two broken amps on the circuit board. This PD is the one which showed a sudden big offset in the DC signal as reported in [3]. We further investigated and fixed it. After fixing we tested the DC path and no big offset was observed, which is good.
Symptom
The differential output was insane. The positive pin showed -2.2 V and the negative one showed -0.8 V with respect to the ground when no light is on the diode, resulting in an offset of -1.4 V in total. Though this number is not really what we got yesterday [3], the symptom remains the same --- a big offset and somehow magically the PD responds to light.
The repair
We removed the PD from the IOT2L table and brought it to the EE shop to have a close look. It seemed that
(1) one of two amplifiers for the differential output (U3 : at the very last stage of the DC path) seemed blown, resulting in such unbalance at the outputs.
(2) the trans-impedance amplifier (U2) was not closing the feedback loop at all. In the same trans-impedance loop there was a current buffer (U5) and this was also suspicious initially.
Filiberto replaced U3 and U2 with a new AD8672 and OP27 respectively. After the repair, it started working OK. We have tested the DC path by illuminating the diode with a visible laser pointer. It responded to the light, which tells us not only the DC path is OK but also the diode is still alive. Note that U2 was an AD8675 before the repair and interestingly it looked it had been replaced once as the foot prints were clearly dirtier than everyone else.
[1] D1101124-v6
[2] SN:1203396
[3] LHO alog #5219
Apparatus- Each HAM6 support tube bellows bagged (hermetically sealed) to encompass the large conflat joint and bellow's convolutions but not the small conflat joint -> 3/8" i.d. x 5' long exhaust tube (penetrating bottom of bag) -> Supply of helium to the top of the bag -> Applied 90 seconds of helium pressurization/flow per bag such that each bag remained inflated (like a balloon) and with confirmed/noticeable flow out of the exhaust tube -> Leak detector backing HAM6 turbo via series combo of (4) each 1.5" x 3' flex hoses HAM6 volume = ~7,500L Net pump speed for helium > 500 L/sec Indicated helium baseline at start of testing < 1 x 10-10 torr*L/sec Results- SW bellows and big CF joint -> OK NW bellows and big CF joint -> OK SE bellows and big CF joint -> OK NE bellows and big CF joint -> inconclusive -> large signal response -> need to reverse order of testing and pressurize this bag with air while applying low flow of helium the corresponding small conflat to rule it out then test bellows convolutions separate from the big conflat joint Will continue tomorrow
Kyle, Gerardo ~1055 hrs. local -> Connected and restarted HAM3 turbo backing pump and resumed pumping HAM2-HAM3 volume. ~1630 hrs. local -> 3.0 x 10-6 torr @ turbo inlet
After SUS made sure everything was clear and not biasing the measurements, IAS gave us direction. We moved the ITMy HEPI down 1.3mm, & 0.8mm North and tried to do no Yaw. After this we locked the ISI and looked at the level of the Optical Table. We saw a runout of 0.019" on the Optical Table. We did a tilt correction, down on the SE corner and up on the NW of ~0.2mm each. This put our runout on the Optical Table measurements at 0.12mm. Then, wouldn't ya know it, IAS says we have to Yaw 577urad CW. So we turned the HEPI Springs 1/2turn each for CW yaw and that got us under 100urad. Have to say after doing that I do want to confirm the Optical Table is still level.
On the 15th I started a purge on one of the oldest, and least purged ISIs we have. The LN2 boil-off straight from the dewar was measuring ~ -40 td°C, while ambient air was ~ -5 td°C. This unit was taking longer than usual to dry out and wasn't reaching as low of levels as other containers had in the past. I think revisiting Assy. 1 soon would be helpful.
Installed four vertical actuators and four horizontal actuators with the help of Apollo today.
