Since last Friday we found out when we sent the beam to the end, the shape of the beam is very bad, much worse than the beam shape we saw at the beginning of last week, both the green and the infrared, the beam both are large and long in the horizontal direction. Last Friday we tried to align the beam to the center of both the suspension mirrors, but the situation did not become better, so we tried to move the 2inch mirror a little bit by the picomotor, and found out to one direction the beam gets better but not very obvious, it seems we did not have enough range of that picomotor, so we decided to move 2inch mirror by hand.
Yesterday before we start to move the 2inch, we checked the beam shape at different place of the beam path with beam profiler,the beam seems circular, although at some place the beam is fluctuated very quickly, but during the fluctuation there are some moments that the beam is round. Then we tried to adjust the beam more center on the lens of green beam, and finally we had to adjust from the very beginning, we aligned all the component to let the beam go straight and checked each time we put back a component,almost circular everywhere,(except there seems have some dust on one of the component of green, so when the beam reached the window, there is one line shape shadow on the top of the beam, we tried to clean all the component with gas, but cannot remove that) after everything was done, the beam shape at the 290m target did not get any better. So then we can focus on the two vacuum chamber.
We tried to push or pull the 2 inch mirror by hand and align the green beam to see it on the target, although the beam shape is still strange but at some point the beam is much smaller than the other place, and except the main beam there is another small beam on the side of it which is quiet good shape, maybe we can find out where it comes. Then when we cut the green and tried to see the infrared, the infrared is almost what we want to see, a small beam with almost circular shape, so this means with moving the 2 inch mirror, we can get the situation better. Today we are going to find a good position of that mirror to get a better green beam.
When we tried to move the BS yaw picomotor yesterday, it does not work with the computer command again, it is better to change the picomotor before we close the chamber.