Ushiba, Chen Dan, Yasui, Tomaru, Akutsu; related to 17220 and 17428.
Abstract
Re-aligned GreenX with the recently lowered PR3 and the green beam reached the Xend (ETMX as well as TMSX). A steering mirro in front of the GigE camera for GreenX in TMSX was adjusted so that the beam image could be seen around the center of the display. We did not need to touch GrDCPD in TMSX so much, as the beam light was nicely illumiting the PD already.
Background
Long time has passed from the last time we installed the PR2 mid-size baffles and re-aligned the GreenX (17866). After the height measurement of relevant mirrors (18562), recently PR3 was lowered (see a series of works starting from 18572). Finally today the PR3 target was tuned to the lowered height as well (18896). So, we can start the final round of the GreenX alignment for closing the IXC and EXC chambers for O4.
The most upstream: PR2 and POP
We started with checking the status of the GreenX beam spots on several relevant mirrors on the POP table and in the PR2 chamber, including the invac POP-POM. Due to the already installed mid-size baffle for PR2 AR, it was hard to see the mirror surface of the invac POP-POM, we somehow judged the current positions would be sufficiently nice, or has been unchanged since the last time. Also, with putting the PR2 HR target, we were able to see the GreenX was shooting at the center of the target (Fig. 1; taken with a laser-safety goggle, maybe OD2 for 532 nm), so we judged the most upstream part would be ready for the following works.
Centering at PR3
Using the PR3 HR target that was tuned by Hirata-san and Yano-san (18896), and with adjsuting picomotors on the invac POP-POM, the GreenX beam was aligned to illuminate at the PR3 HR center (P: 1100 steps, Y: 400 steps) (Before the work: Fig. 2; the result of the work: Figs. 3 and 4.) The procedure today was:
- Attached the target
- Actuated the pico on the invac POP-POM in pitch to guide the beam to the pitch center of the target.
- Detached the target
- Swept PR3 to find the GreenX at the TMSX GrPD/GigE cam as usual, then found it.
- Attached the target again
- Actuated the pico on the invac POP-POM in yaw to guide the beam to the yaw center of the target.
- Detached the target
- Found the beam at the TMSX GrPD immediately without sweeping so much.
We anticipated that
- Certain off-loading in the PR3 suspension
- Certain re-adjustment of the oplev QPD because the PR3 tilt would make the oplev beam went out of the linear range of the QPD
but none of them was needed luckly!
Then we closed the opening part around the PR3 chamber. Also we asked to close the opening part between the PR2 and BS chambers to Uchiyama-san (and Sawada-san and Takahashi.M-san) so that the GreenX spot dancing at TMSX gige camera could be reduced as much as possible.
Tuning at the Xend: EXC and TMXS (TRX)
Then we went the the X-end together with some equipments (laser levels, legs...) required for measuring the height of ETMX.
In EXC, we leared the ETMX mirror height today was about 2.3 mm lower than the "reference", which is chamber-duct central line. More details (difficulties) around these would be reported separetely later. Anyway, we determined our mind to do fine tuning of PR3 as follows:
- In pitch: let the beam seen as a "round shape"as possible (for Tomaru-san's eyeballs); in this case, the beam came throught about 10 mm lower than the "reference" mentioned above, and this might be due to that it seemed the GV window close to the EXA chamber might be slightly off-centered; note that 10 mm / 3 km is only about 3 urad at PR3. Of course we could have matched the beam pitch (vertical displace) to the "reference", but today we selected to match to the "GV window", as we will try to make it resonated through the GV window.
- In yaw: as much as centered.
Then finally we came to the TMSX optical bench. And adjusted a steering mirror in front of Gr GigE camera so that the beam shape can be shown in the center of the display. Also I touched a steering mirror in front of the GrDCPD but learned that the beam would be well-included in this PD'saperature, so I did not touch it so much for now.
Next step
- Need to check the height relation between the GreenX beam vs optics in IXC, EXC, IXA, and EXA, and adjust in a "nice" way accordingly.
- See the flash!
