On Apr. 23, 2021. Cont'd from 16549, 16550. Refs 15970 , 15986, 16008.
Abstract
As a serise of works to be done just before closing the MCF and MCE chambers, re-located beam dumps in MCF, and re-check the beam position on MCe.
Beam dump relocation
Before starting this work, assuming I would increase the input power to IMC, I shut the resonant optical axis of IMC, and detached the polycarbonate plate from the IMC_REFL flange. Also confirmed that the beam entered the water-cooled power meter.
| Names in 15970 | Names in JGW-E2112790 | Power w/ 100W (assumed) injection | Description |
| R | MCF_GB0? nameless? | 100 uW | Visible with P-pol 30mW. Displaced from the main laser beam path. Possible to ignore this? This is matter of threshold setting. |
| K, L | MCF_GB5, 6 | 100 mW | Need the IMC_REFL viewport window to see these ghost beams. Would be ok with KG5 glass, also as displaced from the main laser beam path. Moved from the original position 446 to the planned position in JGW-T2012114-v1, now this is re-located closer to the MCi suspension. If possible, check after re-installing the IMC_REFL viewport window. Figs. 1, 4, and 5. |
| N | MCF_GB1 | 30 mW | Visible with P-pol 30mW. Would be ok with KG5 glass, also as displaced from the main laser beam path. Figs. 1 and 2. |
| J | MCF_GB2 | 30 mW | Visible with P-pol 30mW. Would be ok with KG5 glass. Moved from the original position 446 to the planned position in JGW-T2012114-v1, now this is re-located closer to the IMC_REFL viewport window. Figs. 1 and 3. |
| a | MCF_GB3 | 30 mW | Invisible with P-pol 30mW and 330mW. Started visible with P-pol 600mW with making the vacuum chamber dark (ref: 1W input in 15970). Relocated the beam dump so that the beam dump was separated better from the main beam.Worry: slightly close to the main beam. Should be replaced with SiC??-> maybe no need... Fig. 6. See also the separation from the main beam transmitted from MCo and the beam dump in Fig. 9. |
| f | MCF_GB7 | 18 uW | Visible with P-pol 30mW. Anyway it is blocked by a black shield on the MCo suspension. This might be the left spot of the 2nd figure of 14200. |
| MCE_GB1,2 | 1mW | Invisible without IMC lock, without the MCE_TRANS viewport. Well, ignore now...? In the end, I did not have beam dumps in MCE. |
Note: By the way, the water cooled power meter is very easy to move... it is better to reconsider the fixing way.
Discussion on the no-dump ghost beams: GB "R" and MCE_GB1,2 are ghost beams without beam dumps. From the viewpoit of safety, I guess no need to dump these. From the viewpoint of performance as a GW detector, we will see the result soon, hopefully.
Beam position on MCe
As reported in 16549, the beam height in MCF seemed lower a few mm. This day I also confirmed this might be the case also in MCE (Figs. 7 and 8; centering would be very ok.). Anyway, this time, I would like to leave things as is. Hmmm... the relatively unstable steering mirror is in PSL room?
