The goal of the activity was to check the relative position of the NI RH center (i.e. the NI mirror center) and the NI CH center, continuing the activity started in 56633.
In preparation for the shift, at 14:22 UTC the NI DASes were blocked on the bench by flip mirrors and the ITF was realigned on green, after the work performed during the morning shift.
At 16.25 UTC Fabio set the ITF in N arm locked, W arm misaligned.
After checking the HWS DET illumination, at 16.26 UTC an HWS DET acquisition started and at 16.36 UTC the NI RH was switched ON @ 15 W.
After almost 1 hour the NI RH induced curvature center starts to stabilize: results are shown in table 1 and fig.1. The NI RH was switched OFF at 18.14 UTC.
| NI RH (03/08) | NI RH (04/08) | difference | |
| X [m] | (0.0003 +- 0.005) | (0.023 +- 0.015) | 23 mm |
| Y [m] | (-0.008 +- 0.004) | (-0.007 +- 0.002) | 1 mm |
The NI RH center position changed by around 23 mm along the horizontal direction: it could be justified by the intervention of the morning shift (56654), during which the position of the meniscus lens (through which also the HWS DET SLED beam passed) was changed. It could be worth considering a realignment of HWS DET SLED beam on top of NI TM.
At 20.06 UTC a new HWS DET acquisition was started and at 20.15 UTC the NI CH was switched ON at high power. The induced curvature became immediately evident and soon after the center stabilized: the comparison results between NI CH and RH centers are shown in table 2 and fig.2. At 20.27 UTC the NI CH was switched OFF.
| NI RH (05/08) | NI CH (05/08) | difference | |
| X [m] | (0.023 +- 0.015) | (-0.0066 +- 0.0019) | 29 mm |
| Y [m] | (-0.007 +- 0.002) | (-0.003 +- 0.002) | 4 mm |
Still a slight mis-centering along horizontal direction was present. I performed an horizontal movement to recover this mis-alignement: it should be checked in a next shift.
At the end of the shift, the NI DASes actuators were switched ON again ( 21.22 UTC), at the powers left from last shift (56650) to compensate for the NI CP cold lens, and the ITF was left locked on IR.
