Participants: Enzo, Hatoya (with the help of Fujii-san)
We have been trying to adjust the distances between the magnetic damper (MD) ring and the copper ring of the standard filter (SF) to study the decay times and frequencies of the torsion modes of the suspension. The nominal position of the magnets of the MD is (3.5 mm??) away from the copper ring of the SF and so far, we have obtained results for when the position of the MD is at [-0.5, 0, 0.5, 1, 2, 3, 4, 5] mm from its nominal position. To adjust the MD height (with respect to the SF copper ring) we had to move the 3 screws that support the MD itself.
We have been trying to adjust the distances between the magnetic damper (MD) ring and the copper ring of the standard filter (SF) to study the decay times and frequencies of the torsion modes of the suspension. The nominal position of the magnets of the MD is (3.5 mm??) away from the copper ring of the SF and so far, we have obtained results for when the position of the MD is at [-0.5, 0, 0.5, 1, 2, 3, 4, 5] mm from its nominal position. To adjust the MD height (with respect to the SF copper ring) we had to move the 3 screws that support the MD itself.
Previously, we had been exciting the IP by giving it impulses of excitation, but this produces excitation to too many modes of the suspension so we decided to excite the yaw DoF of the Inverted Pendulum (IP) at the Preisolator level only at the frequency of the torsion mode natural frequency. This was done by applying excitations of 0.05 [Hz] sinusoidal waves with amplitudes of 1500~2200, overall gain of: 1 and ramp time: 3 s (parameters used in 'awggui') and measuring the yaw motions (as well as the Pitch motions to see if there is any cross-coupling) of the TM.
I will later upload my documentation which will include the heights of the adjusted screws as well as the number of counts Enzo had to apply an offset to the Pitch and Yaw on the Intermediate Mass (IM) in order to make sure that the laser beam was hitting the centre of the QPD monitor. I have also created a program for calculating the decay times of the torsion mode for different heights. All of our measurements (time series data of the decay times, pdf of the decay time graph, time series data of the spectra graph, and the pdf of the spectra graphs) are saved under my folder in KAGRA Dropbox (Kagra/Subsystems/Dropbox/Type-B/Hatoya). The names of the files are not organized so I am currently trying to optimize the conventions for my filenames.
We will have f2f meeting tomorrow, so we plan to continue our measurement on next week Monday if possible to measure the decay time of the torsion mode when the distance between the MD and the Cu Ring is -1 [mm].