This entry described the realignment of the suspension after the pump down. I still need to measure transfer functions in order to assess the health of the system.
Temperature: T = 24.5 ºC (24 ºC requested).
Inverted pendulum
Positions of IP LVDTs and stepper motors before and after pump down:
- H1: -3,742 µm ⇒ -3,903 µm ; 85,000 steps ⇒ 220,000 steps
- H2: -2,298 µm ⇒ -2,320 µm ; -45,000 steps ⇒ -40,000 steps
- H3: -3,038 µm ⇒ -2,934 µm ; 0 steps ⇒ -140,000 step
- See entry 7783.
Bottom filter
The FR was not enoug to put the keystone to zero. Using the coil-magnet actuator was necessary.
The position of the LVDT and of the stepper motor before and after this exercise were:
- LVDT: -750 µm ⇒ 4 µm with 5000 counts of actuation.
- Motor #0: 98,000 steps ⇒ -286,000 steps.
The stepper motor is at its maximum. The movement of the keystone when using the FR around this position is not predictable or straightforward.
Standard Filter F1
The FR is not operational. The position of the LVDT before and after this exercise was:
LVDT: -1,250 µm ⇒ -885 µm with 1000 counts of coil-magnet actuation.
I didn't want to use more actuation right now. This value may change.
Top filter F0
Accoding to entry 7900, when the F1 keystone is at -532 µm the F0 keystone should be at -731 µm in order to have the optic at the correct height. This means that when F1 is at -852 µm F0 must be at -411 µm:
F0 LVDT = ( 852 µm - 532 µm ) - 731 µm = -411 µm.
The position of the LVDT and of the stepper motor before and after this exercise were:
- LVDT: -1,485 µm ⇒ -422 µm (aim -411 µm).
- Motor #2: -500,000 steps ⇒ 1,275,000 steps. (See entry 7758.)
Intermediate Mass
I used the IM pico-motors to adjust its orientation. Before and after this exercise:
- IM Yaw: 1,993 µrad ⇒ 0 µrad.
- IM Roll: 95 µrad ⇒ 0 µrad.
Oplev
I didn't move the F0 yaw mechanism neither the IM pitch pico-motor. I'll let the alignemnt team do it according to their needs. Now they are sufficiently close to zero:
- Pitch: 35 µrad
- Yaw: -28 µrad
Required positions of the GAS filters
- BF: Zero. We need the IM vertical OSEMs to be in the right place. We need coil-magnet actuation (~5000 counts) because the FR is not enough.
- F1: -852 µm. The FR is not operational, therefore, we need to use the coil-magnet actuator (~10,000 counts). The position may be reviewed if the temperature ever becomes stable.
- F0: -411 µm. Currently it's very close to this position (-425 µm), therefore, it's suitable to use the coil-magnet actuator. The position may be reviewed if the temperature ever becomes stable.