alberto.stochino@LIGO.ORG - posted 14:06, Thursday 12 July 2012 - last comment - 09:45, Thursday 19 July 2012(3420)
TMS ISC Table Stability
I measured the TMS ISC table angular and lateral stability when the end station VEA was quiet last night.
I found the table displacement to be around 5-10 um rms laterally and 1-3 urad rms in angle over 100s. The motion thus appears to be within the requirements: 100 um and 1 urad, respectively.
See attached plots. The bump below 1 Hz is probably due to the table's roll mode. A peak shows up at about 8 Hz due to the table enclosure: opening the table's doors reduced its amplitude.
The measurement was done with the PZT loops closed. These loops use the TMS green QPD error signals and have a UGF of about 8 Hz. I then calibrated the PZT control signals according to the manufacturer's specs and used the ABCD matrix of the beam path from the PZT onwards on the ALS table (see attached drawings for the optical details). Fianlly I compensated for the loop gain.
Initially the spectrum looked mostly flat up to 10 Hz, masking any features of the TMS table motion. After checking for several causes, eventually turning off the HEPA filters in the ALS table as Bram suggested, solved the problem. The airflow due to the HEPA filters was shaking the PZTs and the other optics on the table. This shouldn't be a problem during science mode, when the filters are meant to stay off. The plot attached shows a comaprison of the PZT control signal spectra with the HEPA filters ON (reference traces) and OFF.
Data and matlab code code are in the svn: /svn/cdsutils/trunk/ALS/TMS_stability
I found the table displacement to be around 5-10 um rms laterally and 1-3 urad rms in angle over 100s. The motion thus appear to be within the requirements: 100 um and 1 urad, respectively. See attached plots.
The bump below 1 Hz is probably due to the table's roll mode. A peak shows up at about 8 Hz due to the table enclosure: opening the table doors reduced the amplitude.
The measurement was done with the PZT loops closed. These loops use the TMS green QPD error signals and have a UGF of about 8 Hz. I then calibrated the PZT control signals according to the manufacturer's specs and used the ABCD matrix of the beam path from the PZT onwards on the ALS table (see attached drawings for the optical details).
Initially the spectrum looked mostly flat up to 10 Hz, masking any features of the TMS table motion. After checking for several causes, eventually turning off the HEPA filters in the ALS table as Bram suggested, solved the problem. The intense airflow due to the filters was shaking the PZT and the other optics on the table. This shouldn't be a problem during science mode, when the filters are off.
I measured the TMS table angular and lateral stability when the end station VEA was quiet.
I found the table displacement to be around 5-10 um rms laterally and 1-3 urad rms in angle over 100s. The motion thus appear to be within the requirements: 100 um and 1 urad, respectively. See attached plots.
The bump below 1 Hz is probably due to the table's roll mode. A peak shows up at about 8 Hz due to the table enclosure: opening the table doors reduced the amplitude.
The measurement was done with the PZT loops closed. These loops use the TMS green QPD error signals and have a UGF of about 8 Hz. I then calibrated the PZT control signals according to the manufacturer's specs and used the ABCD matrix of the beam path from the PZT onwards on the ALS table (see attached drawings for the optical details).
Initially the spectrum looked mostly flat up to 10 Hz, masking any features of the TMS table motion. After checking for several causes, eventually turning off the HEPA filters in the ALS table as Bram suggested, solved the problem. The intense airflow due to the filters was shaking the PZT and the other optics on the table. This shouldn't be a problem during science mode, when the filters are off.
I measured the TMS table angular and lateral stability when the end station VEA was quiet.
I found the table displacement to be around 5-10 um rms laterally and 1-3 urad rms in angle over 100s. The motion thus appear to be within the requirements: 100 um and 1 urad, respectively. See attached plots.
The bump below 1 Hz is probably due to the table's roll mode. A peak shows up at about 8 Hz due to the table enclosure: opening the table doors reduced the amplitude.
The measurement was done with the PZT loops closed. These loops use the TMS green QPD error signals and have a UGF of about 8 Hz. I then calibrated the PZT control signals according to the manufacturer's specs and used the ABCD matrix of the beam path from the PZT onwards on the ALS table (see attached drawings for the optical details).
Initially the spectrum looked mostly flat up to 10 Hz, masking any features of the TMS table motion. After checking for several causes, eventually turning off the HEPA filters in the ALS table as Bram suggested, solved the problem. The intense airflow due to the filters was shaking the PZT and the other optics on the table. This shouldn't be a problem during science mode, when the filters are off.
I measured the TMS table angular and lateral stability when the end station VEA was quiet.
I found the table displacement to be around 5-10 um rms laterally and 1-3 urad rms in angle over 100s. The motion thus appear to be within the requirements: 100 um and 1 urad, respectively. See attached plots.
The bump below 1 Hz is probably due to the table's roll mode. A peak shows up at about 8 Hz due to the table enclosure: opening the table doors reduced the amplitude.
The measurement was done with the PZT loops closed. These loops use the TMS green QPD error signals and have a UGF of about 8 Hz. I then calibrated the PZT control signals according to the manufacturer's specs and used the ABCD matrix of the beam path from the PZT onwards on the ALS table (see attached drawings for the optical details).
Initially the spectrum looked mostly flat up to 10 Hz, masking any features of the TMS table motion. After checking for several causes, eventually turning off the HEPA filters in the ALS table as Bram suggested, solved the problem. The intense airflow due to the filters was shaking the PZT and the other optics on the table. This shouldn't be a problem during science mode, when the filters are off.
I measured the TMS table angular and lateral stability when the end station VEA was quiet.
I found the table displacement to be around 5-10 um rms laterally and 1-3 urad rms in angle over 100s. The motion thus appear to be within the requirements: 100 um and 1 urad, respectively. See attached plots.
The bump below 1 Hz is probably due to the table's roll mode. A peak shows up at about 8 Hz due to the table enclosure: opening the table doors reduced the amplitude.
The measurement was done with the PZT loops closed. These loops use the TMS green QPD error signals and have a UGF of about 8 Hz. I then calibrated the PZT control signals according to the manufacturer's specs and used the ABCD matrix of the beam path from the PZT onwards on the ALS table (see attached drawings for the optical details).
Initially the spectrum looked mostly flat up to 10 Hz, masking any features of the TMS table motion. After checking for several causes, eventually turning off the HEPA filters in the ALS table as Bram suggested, solved the problem. The intense airflow due to the filters was shaking the PZT and the other optics on the table. This shouldn't be a problem during science mode, when the filters are off.
Initially the spectrum looked mostly flat up to 10 Hz, masking any features of the TMS table motion. After checking for several causes, eventually turning off the HEPA filters in the ALS table as Bram suggested, solved the problem. The intense airflow due to the filters was shaking the PZT and the other optics on the table. This shouldn't be a problem during science mode, when the filters are off.Initially the spectrum looked mostly flat up to 10 Hz, masking any features of the TMS table motion. After checking for several causes, eventually turning off the HEPA filters in the ALS table as Bram suggested, solved the problem. The intense airflow due to the filters was shaking the PZT and the other optics on the table. This shouldn't be a problem during science mode, when the filters are off.
Non-image files attached to this report
Comments related to this report
These are the close loop plots of the same measurements.
Non-image files attached to this comment
As Keita noted, the HEPA-off curves show a large bump at around 100mHz which which goes above spectra with the HEPA on. It's not clear why.