[kTanaka, Hirose]
We measured beam profile and power budget around REFL WFS for REFL WFS f3 design.
Beam profile around REFLWFS
We placed the pickoff mirror at the 4th hole (0.01m) in front of PZT2 and measured the beam profile from the 10th hole from the pickoff mirror.
The distance from Lens2 (f=2000mm) to the pickoff mirror was 1.6m.
From fitting results from beam profile data,(Text file)
The result for the beam waist position is around 0.4 m from the pickoff mirror. This result is consistent with the focusing distance of the Lens2.(FIG1)
It is also consistent with Terrence's results, as the beam waist size and location are almost the same.
#The following ND filters are fitted to the beam profiler
- With ND-2 (e-2) of DataRay in 10-14th hole.
- With ND-4 (e-4) of DataRay in 15th- mass
| fitting result: waist | fitting result: distance from pickoff mirror | |
| lab x | 0.22mm | 447.66mm |
| lab y | 0.23mm | 485.66mm |
Power budget around REFLWFS
This time the IMC transmitted power was about 1.3 W and was done with PRM direct reflection (LOCK_aqedition). The results are similar to the calculations at each point.
The WFSHWP angle on the MEDM screen was 260 deg. More than 90% of the power was discarded by the HWP. Even if the REFLWFS power is reduced in the future by placing the BS after the shutter for f3 WFS, the power can be adjusted by HWP.
The power meter used in this project is currently charging on a table near IMCREFL.(FIG2)
| FIG3 | Position | measurement result | calculations |
| ① | Between the iris and the beam sampler | 1.08W | (IMC trans power)*(PRM reflectance :0.9)*(IFI transmittance:0.94) |
| ② | BS2 refl | 211.5mW | ①*(Beam sampler refl: 0.9)*(BS2 trans: 0.2?) |
| ③ | Before WFSHWP | 0.750W | ①*(Beam sampler refl: 0.9)*(BS2 trans: 0.8?) |
| ④ | In front of TFP（After WFSHWP） | 0.760W | ＝③ |
| ⑤ | In front of shatter | 58.3mW | Power is dumped by the HWP from ④ |
| ⑥ | PZT1 refl | 22.2mW | ④*(PZT1 refl: 0.4) |
| ⑦ | PZT1 trans | 36.3mW | ④*(PZT1 trans: 0.4) |
others
- The HWP1 cord for the RFPD seemed to be hanging down and blocking the BS2 transmission light, so the cord was bundled in the upper rack.(FIG4)
- We are considering moving the shutter for the WFS-f3 about 5 holes (0.12 m) in the z-direction to the PYD-20 in the future.
The connected cords seem to be long enough to move it. The power supply for the shutter near pico1 could also be moved to the rack above the REFL table.
(FIG5)
