shoshana.apple@LIGO.ORG - posted 15:54, Monday 12 May 2025 - last comment - 15:04, Friday 16 May 2025(84366)
BRS ETMY Mass Adjuster Install
[Shoshana, Michael] We've started preparing to install the BRS mass adjuster to the End-Y BRS. The plan is to follow the same procedure/same parts as the End-X install outlined in LIGO-T2400043 and SEI log 1886 (https://alog.ligo-la.caltech.edu/SEI/index.php?callRep=1886). We've taken apart the BRS and discovered that doesn't match the designs on the DCC. How the parts are arranged blocks access to where the pico-motor mount should attach, but we think we have a work around that should work. The electronics/wiring of the BRS is as expected and we've finished all the wiring for the pico-motor so that it should attach to the feed through. Assuming all goes well we plan on installing the mass adjuster parts and begin testin.
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[Shoshana, Michael] We've managed to get all of the hardware/parts installed in and we've closed up the BRS chamber. We had to add an inch of shims beneath to motor mount in order to get it to fit/align properly, but otherwise there were only minor complications during installation. We've tested the pico-motor and the mass adjuster using the pico-motor driver that we brought from UW and both seem to work fine. For in air balancing, we left the new mass adjuster centered to increase range for future adjustments for when the BRS is pumped down and running, and tried to just stick to moving masses that are inaccessible when the BRS chamber is pumped down. We unfortunately reached the maximum range with the internal masses and had to slightly move the manual mass adjustment system (what is currently used to adjust the center of mass) from center, but that might be returned to center after we re-balance it when it's pumped down. Right now the resonance frequency looks to be around ~7mHz (around 130 second period) which is about the same as it was before Mass Adjuster installation, but we'll check again after the chamber has been pumped down. Tomorrow we'll finish all of the wiring and electronics to hook up the pico-motor to the LIGO system. The plan is to pump down the BRS chamber tomorrow and re-balance and test the pico-motor some more. The reference pattern has a higher intensity than expected and we aren't sure why. Right now our best guess is that the light source drifted slightly, and we'll look into it more tomorrow.
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EPO tag for BRS pics
[Shoshana, Michael] Pumped down the BRS chamber overnight and started the ion pump this morning and got it down to 1.9e-6 Torr before we left end End-X. We also wired up the picomotor to the LIGO picomotor controller system. It is hooked up to the 7th channel X-direction and we tested it out and were able to hear it spinning for both directions. The BRS's thermal insulation was reapplied the box closed and the temperature sensors and heating plate were all re-attached and plugged back in. The reference beam's intensity has gone down to be closer to normal somehow, so it doesn't seem to be anything to worry about We might go back to End-Y one more time tomorrow to clean up the wiring and do a final check of the vacuum pressure. We waited for the temperature to equilibrate a bit before balancing because we were hoping that as the temperature rises it would drift back to center, but we ended up using the mass adjuster to try and balance it. It looks like the + - wires for the damping were switched, meaning when the damping was on it would ring up the BRS. Fixed by changing a line in the BRS code[IF H1_ISI_GND_BRS_ETMY_CAPDRIVE>=0] by switching the [>=0] to [<=0] and switching [H1_ISI_GND_BRS_ETMY_CAPOUTL] and [H1_ISI_GND_BRS_ETMY_CAPOUTR], and [H1_ISI_GND_BRS_ETMY_RELAYL] and [H1_ISI_GND_BRS_ETMY_RELAYR] FROM THE END-X INSTALL: Coupling/decoupling move: 1.25k steps Maximum: +-140k steps Be careful: +-100k steps NOTE: MOVING PICOMOTOR +(POSITIVE) DIRECTION TRANSLATES TO MOVING THE BRS UP TOTAL MOVEMENT TODAY:+21k steps
Centered both ETMY and ETMX BRSs. For ETMX net movement was +2200 steps, for ETMY net movement was -3200 steps. For ETMX we saw that the DRIFTMON was moved by about ~3.27 counts per step, and ~2.3 counts per step for ETMY
Cleaned everything up for the ETMY BRS and relabeled all the wires. The final reading that we saw for the ion pump was 9.9e-7 Torr (186uA, 6950V) which seems about right. We left some extra mass adjuster parts with Jim just in case.
Shoshana, Michael
We took tilt subtraction spectra as a final life check of the BRSs. Both BRSs appear to be in good working order and doing their jobs well.
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