Transcript Calva update

Calva update
M1
L1
Cavity 1
M2
L2
M3
Cavity 2
Main
Laser
Aux. Laser
Nicolas Leroy for the CALVA group
(LAL, ESPCI, LAPP, LMA)
Infrastructure/Mechanics
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Both clean rooms built
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All vacuum system installed and tested
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3 vacuum tanks and 50m+5m long tubes
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Residual pressure : ~ 6 10-7 mbar
Optics
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Mephisto lasers (1064 and 1319 nm) installed in
final position
All 3 mirrors are installed in the vacuum tanks
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Coated by LMA
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1 long 50m cavity, finesse 620
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1 long 5m recycling cavity, finesse 15
Local controls installed on the long cavity
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Last mirror will be very soon equipped
Beam size matching for the cavities have been
retuned
Software and electronics
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Electronic:
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Digital : used Annecy's system (tolm, ADCs, ...)
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Analogic : home made (coil drivers, DAC, ...)
Software:
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Used Virgo software
Only some adds to take into account different
optical scheme and specific parts
First tests
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We have start we the high finesse cavity in 5m
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Tests electronics, software and controls
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Mirrors free then under local controls
Reflection
Transmission
First locks
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First lock on 1319 nm (DC transmission signal)
δL ~ 3nm
Reflection
Transmission
First locks
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Then move to 1064 nm – δL ~ 100 pm
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Not lot of force needed for the transition
Reflection
Transmission
Present status
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Since we move to the 50m cavity
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Problem with lock acquisition
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We are able to lock on 1319 nm
No more lock on 1064 nm
Simulation studies show that the frequency noise of
the 1064 nm is at the limit
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Usual noise ie 104/f Hz/sqrt(Hz)
Only changing the frequency noise shape between
10/20 Hz and 100 Hz will be enough
Using Laurent Derome measurments (PhD thesis) and
Romain Gouaty tests (logbook entry 28709), the Virgo
OMC could be enough to act as reference
Edwige kindly give us one of the spare to perform some
tests – currently under installation
CALVA Simulation and Lock Acquisition
Simulation of a double cavity in Siesta
A new Siesta module have been developed to simulate the CALVA layout
 Field propagation in two cavities "a la OPcavity"
 Quasi-static and full dynamic methods have been implemented
 2 lasers (or more) can be propagated simultaneously
Lock Acquisition procedure
We started to study different locking scenarios
which are to be tested on the CALVA platform
For example:
1/ lock the long cavity with a tilted recycling mirror
1319nm2/ tilt back the recycling mirror
3/ lock the recycling cavity
4/ move the locking point to catch the main resonance
Transmitted power
1319nm
5/ lock the long cavity
1064nm6/ move the locking point to lock the
recycling cavity
7/ lock the recycling cavity
1064nm
s
Calva and Advanced Virgo
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Fabien made some simulations to study the
lock acquisition of the 3-km cavities with a
finesse of 450 (VIR-0656A-10)
Conditions:
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Same algorithm for locking than for Virgo
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Limitation on actuation current
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Let the cavity free (10s) before locking
Tests:
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Seismic noise – speed from 1.5um/s to 6 um/s
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Delays in control loops
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Force limitation
Calva and Advanced Virgo
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Ground motion:
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Only very large motions make problem
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Delay : no problem observed up to 1ms
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Force limitation : 5mN/A is still acceptable
Conclusions
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Calva is ready to achieve its first goal : study a
new lock acquisition method on a Virgo-like
setup
Still some technical problems, soon behind us
CALVA is not required with the current foreseen
finesse for arm locking
However it could still be interesting when we
will have signal recycling
Start to think on new physics subject :
Laguerre-Gauss beams, deformable mirrors , ...