[Corey, Betsy, Fil, Peter, Calum, Stefan, Koji]
Summary
- The ISC portion of the HAM6 vent work has been completed.
- Shield isolation of the in-vacuum cables was confirmed.
- The fast shutter was reinstalled on the table after some modifications.
=> Ready for the SEI mass balancing and other exiting procedures. OMC PZT HV is still on. Remeber to turn it off before pumping down.
Some details
- Shield isolation: It is always confusing to check the shiels isolation on HAM6 because of several reasons.
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All the OMC cables (OMC DCPDs, OMC QPDs, and OMC PZT) are sharing their shield on the OMC breadboard. Therefore one needs to remove the related three DB25 cables from the flange when the shield shorting is checked for them.
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The beam diverters connects the shields of their cables shorted to the ISI table. Therefore the shorting needs to be checked with the beam diverter disconnected at the mighty mouse connectors. When the test is done, the connectors need to be restored and the function of the beam diverters should be checked again.
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The picomotors don't short the shields on the table. Check them as usual.
We initially had several cables shorting to the chamber but all of them but one happened at the slack of the cables right inside of the flange. The last one happened on the DB25 cable before it climb up to the vertical wall of the ISI.
- The fast shutter modification / reinstallation
(Photos are supposed to come later.)
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The new bobbin came in for replacing the moving part of the shutter.
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The wire stays were modified to have the bobbin wires more relaxed. Also it should allow us to have more clearance of the wires from the beam towards OM1.
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To allow this modification, the direction of a coil wire (shorter, negative, lower slot) in the terminal block was flipped (Corey's attachment 1).
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The shutter was placed on the ISI table. Then we found that clearance of the wire is in fact poor. We bent one of the wire clamps (Corey's attachment 2: The clamp at the right side of the shutter) and also adjusted the wire length to have 8~9mm clearance from the beam now. (Corey's attachment 3: The clearance does not look great in the photo but in reality the beam is clearly away from the wire.)
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The shutter function was tested with the shutter test controller. No HV was used during the test.
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The beam alignment from the shutter to the gold coated tube was checked. The beam is on the tube but close to the top edge of the tube aperture when the shutter mirror wobbles. We believe this does not create any issue even if the beam falls off from the dump as there is nothing sensitive behind the tube beam dump.
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Related to the entry LHO ALOG 28958, we found the shutter height was too low. The distance between the top of the shutter mirror and the beam was ~9mm. The nominal distance is 6mm. We adjusted the height of the shutter to have the nominal height. (Corey's attachment 4)
Photos From Yesterday's Fast Shutter Work
Photos are on Resourcespace here:
https://ligoimages.mit.edu/?c=1705
Cable Grounding Check
(Corey, Fil, Koji)
Documents of interest:
We went through as many of the ISC/SUS cables as we could, which is mainly all the DB25 connectors (most were on a single flange, D6). The non D6 cables [i.e. SUS OMC & WFS Heads] were checked at the CDS rack (east of HAM6) & the SUS rack (south west of HAM6). We did not check the RF WFS cables at D5 (not sure how to make check on these connectors, and Koji was worried about disconnecting the connectors since it could make things worse. We also did not check SEI since those cables were not touched and are nicely clamped & out of the way.
Some notes:
OMC Cables (D6: F1, F2, & F3): These cables all go to a harness on the OMC breadboard. Their sheilds are all tied to each other. Since we checked these cables at the flange, You must disconnect all three cables at the same time. Then you can do the ground loop check (otherwise, if you do one at a time, you will trick yourself into seeing ground loops, but this is because their sheilds are all connected).
For the Picomotor cables, I thought Koji said we should disconnect the cable from the picomotor and then check for grounding, but I can't remember if that is really necessary.
Bird's Nest!: We found some shorts. When one finds a short, the job is to go in chamber and then "wiggle" the cable in question until you no longer see the short. I believe we were able to do this in-chamber right next to the D6 flange. This is where there is a "bird's nest" of ISC cables (unfortunate...I reckon we could clean this up by carefully clamping ISC cables down to HAM6's Stage0.).
At any rate, whenver one fixes a cable with a ground loop, one must then re-check all cables! This is because all these cables are in this "bird's nest". And if you remedied one by moving it around, you don't know whether you made things worse for a neighboring cable in the "nest".
At the end of the day, we were happy with our ground loop checks for these cables.
OH, a To Do Item:
At the D6 Flange, it was easier for Fil to plug/unplug cables when he removed some protective bars were removed from the flange protector. At the nearest convenience, those bars should get re-installed.
Re the To Do Item--removal of the 'protective bars' aka strain relief, to make it easier to unplug cables. These should be replaced and returned to relieving strain by the remover. There is plenty of instances where this has not been done and I expect is the SOP, sadly. The job is always so much easier if you don't have to return to it later, after you've remembered it.
> For the Picomotor cables, I thought Koji said we should disconnect the cable from the picomotor and then check for grounding,
> but I can't remember if that is really necessary.
No. It turned out that the picomotors have no shields at the mighty mouse connectors and have no shorting the the table.
HAM6 CC wafer placement - it is now back in the same place as the last one was pulled from.