aLIGO LHO Logbook

H1 ISC

camilla.compton@LIGO.ORG - posted 13:57, Tuesday 13 May 2025 (84375)

ISC Alignment Work, Day 9 in HAM1 (May 13th): Beam dumps placed and final checks complete

Betsy, Jenne, Camilla

Day 1: 84193, Day 2: 84228, Day 3: 84230 and 84239, Day 4: 84274, Day 5: 84292, Day 6: 84314, Day 7: 84334, Day 8: 84361

This morning we finished our last laser hazard tasks in HAM1 mainly at 20W in, did some final checks and went back to laser safe.

POP LSC Pico: This pico was too close ot the edge of its range so I turned the mirror mount so there was range and realigned onto the center of the POP LSC diode.

Beamdumps: Photos of all beamdumps will be placed in 84321, will also make an updated map to show where the new beamdumps are located.

With both ITMs and PRM aligned the POP flashes were brighter (thanks Elenna) and we were able to check the beam was aligned onto BD1 and BD2.

We placed BD6a and BD6bwith BD6a between M14 and HW1 which is further upstream that Keita placed it last time 63595. We actually had this dump catching to ghost beams coming off HW1 (one round and the other a more unusual clipped shape), there was no clipping of HW1.

We found the ghost beams that BD7 and BD9 were catching, one was already caught by BD8 and we placed BD7 on the -Y side of the SLED to catch the other.

We found a lot of ghost beams, mainly from Betsy using a combination of IR viewer on the card and curtains. Extra beams found:

Two secondary off the REFL BDV1 that are ghost beams from the intal M7/M1/M17 optics transmitted through M1 but too close to block well before the beam divertor. As our low noise state is with this BDV1 closed, we changed the size of the places in BD5 to catch all three beams (main + 2 ghost). Note that these beams when reflected off M1 are blocked by BD7 and BD8.
There as also a beam being defected very low from ASC REFL B and bouncing off the ISI table, Betsy added a beamdump without post to catch this on the -Y side of the SLED. NO beam like this off the other ASC diodes.
Betsy and Jenne could a faint beam and disc on the +Y septum door but we couldn't understand where these were coming from.

Final Checks: We checked ndscope for all LSC and ASC diodes while blocking and unblocking the beam to check there was signal on all. Yesterday Elenna and I removed all of the temporary metal name tags and this morning I checked that there were no thumb knobs left on any optics. As it doesn't make sense for PM1 to be misaligned, we suggest having misaligned offsets of (0,0) for this, although if we really wanted, a setting of (1500,1500) would ge the beam off the diodes.

Have lots of component photos that will be attached later.