YuefanGuo - 10:53, Thursday 19 October 2017 (572)
Situation of the cavity and local control
Since the local control of PR and BS mirror are not enough to bring the beam back to the right height, so yesterday we tried to move the picomotor of PR mirror.
Before moving anything we did the coil check again one by one, each of them has response to the noise and the amplitude of the motion is similar. Then we tried to adjust the picomotor in order to put the beam back at the reference we put outside the BS chamber, which is the transmission of BS mirror. Of course after moving the picomotor we should put the PSD signal back to zero, then when we tried to close the loop, we found even we put the offset as the value when the mirror is free, the correction signal is around 5 or 6(should be around zero). This means we cannot control the PR mirror anymore.
We tried to go on,by changing the local control offset, we were able to sent the beam to end and saw it on the CCD camera. Then as usual the next step should be align the reflection of the input mirror to the injection beam. But we cannot see the reflection as the nearest window of the bench, so we check the reflection beam on the 2 inch mirror to align it. Yaw of the reflection looks fine, so we only tried to adjust the pitch, the range we can move of the pitch is between -3.5 to 4. This is the normal range, but with this range we are not able to bring back the beam at the good position.The possible reason should be the beam was not well aligned, so with the PR picomotor and BS local control, we tried to align the beam better, at the same time looking at the beam at the end for not losing it. But then we reach the limit of BS local control, we are not far from well-aligned. Actually during our adjustment, the BS range was slightly get smaller, which is very strange.
V
In the attachment, it is the test we did to each magnet, when we sent a sine wave with amplitude 1V and frequency 1Hz, the motion of pitch and yaw.
The next step we are going to do :
1. check the open loop transfer function of two mirrors
2. try to bring back the beam on the BS mirror to the right height, which means we can receive the whole round beam with the two inch mirror we put at the back side of the BS mirror, and got the reflection of it outside the window.
Before moving anything we did the coil check again one by one, each of them has response to the noise and the amplitude of the motion is similar. Then we tried to adjust the picomotor in order to put the beam back at the reference we put outside the BS chamber, which is the transmission of BS mirror. Of course after moving the picomotor we should put the PSD signal back to zero, then when we tried to close the loop, we found even we put the offset as the value when the mirror is free, the correction signal is around 5 or 6(should be around zero). This means we cannot control the PR mirror anymore.
We tried to go on,by changing the local control offset, we were able to sent the beam to end and saw it on the CCD camera. Then as usual the next step should be align the reflection of the input mirror to the injection beam. But we cannot see the reflection as the nearest window of the bench, so we check the reflection beam on the 2 inch mirror to align it. Yaw of the reflection looks fine, so we only tried to adjust the pitch, the range we can move of the pitch is between -3.5 to 4. This is the normal range, but with this range we are not able to bring back the beam at the good position.The possible reason should be the beam was not well aligned, so with the PR picomotor and BS local control, we tried to align the beam better, at the same time looking at the beam at the end for not losing it. But then we reach the limit of BS local control, we are not far from well-aligned. Actually during our adjustment, the BS range was slightly get smaller, which is very strange.
V
In the attachment, it is the test we did to each magnet, when we sent a sine wave with amplitude 1V and frequency 1Hz, the motion of pitch and yaw.
The next step we are going to do :
1. check the open loop transfer function of two mirrors
2. try to bring back the beam on the BS mirror to the right height, which means we can receive the whole round beam with the two inch mirror we put at the back side of the BS mirror, and got the reflection of it outside the window.
Non-image files attached to this report
