With a lot of money and a lot of good scientists working on a project with =
a lot of incentive to succeed-it is not surprising
that outstanding results can happen.
Take a look at the high-tech monolithic folded pendulum 'seismometer' =
that has been developed by
an Italian team trying to be the first to see gravitational waves. A rece=
nt paper (June 2012) describing their instrument is online:
"Low Frequency - High Sensitivity Horizontal Inertial
Sensor based on Folded Pendulum",
Fausto Acernese, Rosario De Rosa, Gerardo Giordano, Rocco
Romano, Silvia Vilasi, Fabrizio Barone
http://iopscience.iop.org/1742-6596/363/1/012001
Their figure 6 illustrates the outstanding broadband performance of the ins=
trument, when using the interferometric sensor.
I was also pleased to see their Figure 4, which shows that the ultimate lim=
iting performance of their instrument (operating in vacuum) will be determi=
ned by internal friction.
How can I conclude this? Because the quality factor is proportional to the=
square of its (tunable) eigenfrequency. My career has been devoted to st=
udies of nonlinear
damping of mechanical oscillators, and this feature (quadratic dependence o=
f Q on frequency) was first noted by Gunar Streckeisen in his studies of a =
LaCoste type spring vertical seismograph. For a 'synopsis' providing some =
details, look at the following page
http://www.iris.edu/stations/seisWorkshop04/PDF/tahoeI1.pdf
We have recently engaged here on the list-serve in spirited discussions of =
mechanical versus electronic considerations, relative to differing views on=
what limits the ultimate performance of a seismometer. You will find in t=
his paper an expressed opinion on the matter by these scientists, by the st=
atement that reads:
" the force feed-back configuration (accelerometer) was an obliged choic=
e, with the consequent
limitations in band and sensitivity due to the control electronic noise". =
(talking about a previous folded pendulum configuration that used feedback)=
.
And then later, you find the following comment: ".......(no force feed-=
back control) has the great advantage
that no limitations to the band and sensitivity are introduced by the contr=
ol electronics, so
that the quality of the instrument depends mainly on a careful and optimize=
d mechanical
design".
Randall
With a lot of mo=
ney and a lot of good scientists working on a project with a lot of incenti=
ve to succeed—it is not surprising
that outstanding results can happen.
&n=
bsp; Take a look at the high-tech monolithic folded pendu=
lum ‘seismometer’ that has been developed by
an Italian team trying to be the first to see gravitationa=
l waves. A recent paper (June 2012) describing their instrument=
is online:
“Low Frequency - High Sensitivity Horizontal I=
nertial
Sensor based on =
Folded Pendulum”,
=
Fausto Acernese, Rosario De Rosa, Gerardo Giordano, Rocco
Romano, Silvia Vilasi, Fabrizio Barone
http://iopscience.iop.org/1742-6596/363/1/012001
Their figure 6 illustrates the outstanding broad=
band performance of the instrument, when using the interferometric sensor.<=
o:p>
I was also pleased to see their Figure 4, whi=
ch shows that the ultimate limiting performance of their instrument (operat=
ing in vacuum) will be determined by internal friction.
How can I conclude this? Because the qu=
ality factor is proportional to the square of its (tunable) eigenfrequency.=
My career has been devoted to studies of nonlinear
damping of mechanical oscillators, an=
d this feature (quadratic dependence of Q on frequency) was first noted by =
Gunar Streckeisen in his studies of a LaCoste type spring vertical seismogr=
aph. For a ‘synopsis’ providing some details, look at the=
following page
http://www.ir=
is.edu/stations/seisWorkshop04/PDF/tahoeI1.pdf =
We have recently engaged here on the list-serve in spirited discussio=
ns of mechanical versus electronic considerations, relative to differing vi=
ews on what limits the ultimate performance of a seismometer. You wil=
l find in this paper an expressed opinion on the matter by these scientists=
, by the statement that reads:
“ =
the force feed-back configuration (accelerometer) was an obliged choice, w=
ith the consequent
limitations in band and sensitivity due to the control =
electronic noise”. (talking about a previous folded pendulum co=
nfiguration that used feedback).
=
And then later, you find the following comment:&=
nbsp; “…….(no force feed-back control) =
has the great advantage
that no limitations =
to the band and sensitivity are introduced by the control electronics, so
that the quality of the instrument depends ma=
inly on a careful and optimized mechanical
design”.
Randall=
<=
/p>
<=
/span>
=
&n=
bsp;