20-22 July 2006 Maddalena Mantovani
Automatic AlignmentNoise Improvement
M. Mantovani, H. Heitmann, J. Marque, P. Ruggi
20-22 July 2006 Maddalena Mantovani
Automatic Alignment Status
tx PR BS NI NE WI WE
ty PR BS NI NE WI WE
Present Configuration6 loops under Drift Control (low bandwidth) and 4 under AA (full bandwidth)
DC AA LC (DC signals)
~10h of stable lock
20-22 July 2006 Maddalena Mantovani
Control noiseThe AA control noise dominates the sensitivity up to ~100 Hz.
To reduce the noise:• improve the decoupling of the AA control loop (improve the Matrix)• improve the electronic noise• reduce the re-injection of the control noise by improving the roll-off
Automatic Alignment Status C7
During C7 10 loops of AA system (full bandwidth) were
engaged
20-22 July 2006 Maddalena Mantovani
AA Filter Optimization
Developed a Matlab script to optimize the AA control filters
• the script optimizes the total open loop transfer function of the AA control loop (mechanical filter and control filter) by acting on the AA filter with an N-dimensional scan (on the zero/pole frequencies and on the quality factors) with a scan rate of ~2.3 msec/config.
Input:• gain margin and maximum overshoot required for the new filter• mechanical TF and the AA filter TF to optimize• vectors of poles/zeros with Q factors to add
• optimization criterion
% POLES:F = [logspace(log10(6),log10(10),10)];Q = [logspace(log10(0.5),log10(4),3)] ;pz(line,1:length(F)) = F; line=line+1;pz(line,1:length(Q)) = Q; line=line+1;
20-22 July 2006 Maddalena Mantovani
AA Filter Optimization
Optimization criterionOptimized filterComparison filter
20-22 July 2006 Maddalena Mantovani
AA Filter Optimization
Tx Ty
These filters have a better cut-off above the u.g.f. in order to reduce the noise re-injection, moreover there are simpler and lighter with respect to the old ones (due to a series of historical features removed and optimized).
100 100
20-22 July 2006 Maddalena Mantovani
Noise Propagation during C7Estimated centering of 10mm.
The electronic noise dominate the dark fringe
signal up to ~90Hz
20-22 July 2006 Maddalena Mantovani
Noise Propagation (Opt configuration C7 filters)
Estimated centering of 1mm.
We have optimized the power impinging on the quadrant diodes in order to be shot-noise limited.
The electronic noise dominates the
sensitivity up to 30Hz
20-22 July 2006 Maddalena Mantovani
Noise Propagation (Opt configuration Opt filters)
Estimated centering of 1mm.
We have optimized the power impinging on the quadrant diodes in order to be shot-noise limited.
The electronic noise does not dominate
the dark fringe.
20-22 July 2006 Maddalena Mantovani
Conclusions
The sensitivity at low frequencies is completely dominated by the alignment control noise.
It has to be reduce by:• improving the signal decoupling• improving the control filters• improving the electronic noise
Developed a matlab script to optimize the control filters
The alignment electronic noise can be reduced below the Virgo design sensitivity