Transcript Diapositiva 1 - ego

Automatic Alignment
Noise Improvement
M. Mantovani, H. Heitmann, J. Marque, P. Ruggi
20-22 July 2006 Maddalena Mantovani
Automatic Alignment Status
Present Configuration
6 loops under Drift Control (low bandwidth) and 4 under AA (full bandwidth)
~10h of stable lock
tx
PR
BS
NI
NE
WI
WE
ty
PR
BS
NI
NE
WI
WE
DC AA LC (DC signals)
20-22 July 2006 Maddalena Mantovani
Automatic Alignment Status C7
During C7 10 loops
of AA system (full
bandwidth) were
engaged
Control noise
The 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
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 Ndimensional 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
% 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;
• optimization criterion
20-22 July 2006 Maddalena Mantovani
AA Filter Optimization
Comparison filter
Optimized filter
Optimization criterion
20-22 July 2006 Maddalena Mantovani
AA Filter Optimization
100
Tx
100
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).
20-22 July 2006 Maddalena Mantovani
Noise Propagation during C7
Estimated 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 shotnoise 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
20-22 July 2006 Maddalena Mantovani