With Hirata-san.
See pictures in album PR3 Remedying Work.
Summary
We shook the suspension using the Trump method three times. Pitch changed by 0.5 mrad, 1.1 mrad and -1 mrad measured with an oplev. This is a significant improvement with respect to the previous condition in which pitch got to change by 17 mrad at least one time upon the same procedure. The Trump method is quite brusque. The question is, how will the suspension behave under the less violent procedures used during normal usage? We have never tried the Trump procedure on a suspension known to be healthy; we don't know whether pitch would change and by how much.
Details
- We secured the RM with the stop screws from below and locked the mirror to the RM.
- We adjusted the tilt of the coil bodies in the RM in order to make the gap bigger between the magnets standoffs and the closest parts of the coil bodies. (See before and after pictures in the album.)
- Then we released the mirror and the RM and locked the IRM close to its hanging-free position so the IM was hanging free.
- We brought V1 OSEM into measuring range.
- We released the IRM.
- We measured TFs for IM-P, T anbd R. They showed a healthy system.
- For the sake of safety of the magnet standoffs, we set the stop screws in the RM very close to the mirror. This is specially important in PR3 because, after tightening the inner locating clamps, the position of the mirror with respect to the RM changed, rendering the magnet standoffs a bit off the centre.
- We set up an oplev with the laser level and a ruler.
- We shook the payload from the BF as Donald Trump did to solve any problem. See notebook notes in the album. We did three rounds:
- The initial pitch of the mirror was -3.6 mrad, veru close to our aim of -3 mrad.
- According to the oplev, during the first round of shaking, pitch changed by +0.5 mrad and, according to the OSEMs, the change was about 140 mrad.
- During the second round, pitch changed by 1.1 mrad measured by the oplev and , accprding to the OSEMs, by 160 urad.
- During the 3rd and final round, the oplev measured a change in of -1 mrad. The OSEMs measured -160 urad.
- Measurements of IM TFs show the system is healthy.