aLIGO LHO Logbook

H1 SUS

betsy.weaver@LIGO.ORG - posted 17:59, Tuesday 19 December 2017 - last comment - 16:23, Wednesday 20 December 2017(39827)

BSC 1 2 3 Chamber closeout work today

Today, Travis and I worked to closeout BSC 3 to finish out the set of chambers needing doors put on. We:

Pulled FC from CPX-AR, which needed a second paint job since there was some small bits left in the center of the optic from the first pull. The second paint-and-dry was successful. The usual N2ionizing blow was used
Painted and pulled FC on the ITMX-HR which came off clean. The surface looked good considering we were inspecting with laser goggles on (same for the CP above).
Ran a few TFs - discovered major rubbing somewhere. A few hours of troubleshooting later and we finally found the ring heater structure cable pushing on the main chain UIM. That alleviated and the TFs all look great.
For whatever reason, the ITMX needs ~+300 bias to get back on the oplev. Not sure what that means, but at least we're still on the slider.
Jim unlocked the ISI - his TFs look good.
Added witness wafers and 1" optics where they should be: 1 vert on QUAD, 1 horiz under QUAD, 1 horiz under ACB in tube.
WIped floor and surfaces many times throughout the day.
Finished full round of high res TFs with Travis and Kissel - will post in coming days.
Shopped around for all subsystem signoffs to put doors on. Waiting for Kissel, but all looks good.

Comments related to this report

jeffrey.kissel@LIGO.ORG - 16:23, Wednesday 20 December 2017 (39850)DetChar

Link

I attach a screenshot of the pitch transfer function during the Ring Heater cable rubbing. I also include illustrative drawings and pictures of the rubbing site.

In words -- the ring heater cables (CBL7 and CBL 8 of D1001517), exiting the QUAD lower structure, should be sandwiched between the two inner face plates (aka "figure eights", D060462). On this ITM, it is not, and for the first time, it escaped far enough out of its designated path that it started to lightly interfere with the bottom of the main chain's UIM base plate (D060376).

Attachments:
First -- (from D0901346) A side view of the full solidworks assembly of the quad. The face plates are the long vertical blue things that extend the length of the lower structure. The two in the middle are the inner face plates.

Second -- (from D1001838)An isolated view of the test-mass-side's inner face plate, with the fully assembled ring heater and cabling system.

Third -- (from G1100850) Another view of the test-mass-side's inner face plate, with the fully assembled ring heater and cabling system.

Fourth -- (from D0901346) A screenshot of the QUAD's solidworks eDrawing assembly, where I've hidden enough to show the ring heater cables, and made the face plates transparent. Naturally, the eDrawing is buggy, and the ring heater cables are displaced from where they're designed to be, and are actually interfering with the *reaction* chain's UIM base plate, but you get the point.

Fifth -- a picture Betsy / Travis took of the offending cable rubbing against the *main* chain UIM base plate.

Sixth -- (from D1001517) A screenshot of just the cable assembly to show what "CBL7" and "CBL8" are.

Seventh -- A screenshot of the Pitch transfer function. Blue and Black are nominal, normal transfer functions. Red was while this rubbing was happening. As expected from the modes shapes of the middle-frequency pitch modes nominally at 1.33 Hz, 1.59 Hz, and 1.98 Hz, that had so clearly shifted, we knew that something was (wrong / rubbing) (in / around) the middle masses -- the PUM / UIM.

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