We engaged the HV driver to the output port PZTs, hoping to mitigate the AS port clipping. Basically, the range of the PZT is not enough to make the beam look clean. Also, our observation suggested there are possible multiple clipping in the chamber. We need another vent to make the things clearly right. Eric came in the lab and preparing the IFO for it.
1. Before the test, the test masses have been aligned with the dither servo.
2. We looked at the beam shape on the AS camera with a single bounce beam. We confirmed that the beam is hard-clipped at the upper and left sides of the beam on the video display. This clipping is not happening outside of the chamber.
3. We brought an HV power supply to the short OMC rack. There is a power supply cable with two spades. The red and black wires are +150V and GND respectively.
4. The voltage of +/-10V was applied on each of the four PZT drive inputs. We found that the motion of the beam on the camera is tiny and in any case, we could not improve the beam shape.
5. We wondered that if we are observing ANY improvement of the clipping. For this purpose, we aligned AS110 sensor every time we gave the misalignment with the PZTs. Basically, we are at the alignment to have the best power we can get. We thought this was weird.
6. Then we moved the AS port spot with the ITMX. We could clearly make the spot more round. However, this reduced the power at the AS port reduced by ~15%. When the beam was further clipped, the power went down again. Basically, the initial alignment gave us the max power we could get. As the max power was given with the clipped beam, we get confused and feel safer to check the situation with the chambers open.
During this investigation, we moved the AS port opitcs and the AS camera. So they are not too precise reference of the alignment. The PZT HV setup has been removed.