Download Gravitational physics program

LISA
Laser Interferometer
Space Antenna
Gravitational Physics Program
Technical implications
Jo van den Brand
NIKHEF – Staff Meeting, January 2006
http://www.esa.int/science/lisa
LISA
October 3, 2005
VIRGO & Lisa – Technical activities

Linear alignment of Virgo
–

Monolithic suspension of Virgo mirrors
–

Improve mirror suspension
Lisa electronics
–
LISA
Reduce thermal noise
Recycling mirror for Virgo+
–

Keep mirrors and input beam aligned
Drag-free control readout
Linear alignment of VIRGO interferometer
 Phase modulation of input beam
W
 Demodulation of photodiode
N
signals at different output beams
–
=> longitudinal error signals
 Quadrant diodes in output beams
–
=> Alignment information
–
(differential wavefront sensing)
 Anderson-Giordano technique
–
EOM
LISA
2 quadrant diodes after arm cavities
Detection
Can have 1 normal diode
and 2 quadrant diodes at
each output port
LISA
Linear alignment setup
LISA
Present Virgo noise budget
Control noise
LISA
Present situation
 Frascati group is leaving Virgo
–
Since 01/2006
 Frascati’s responsibilities
–
Original design of alignment system
– Strategy, optics, prototype experiments, …
–
Design & realization of electronics
 Problem
LISA
–
Continue support for alignment electronics
–
Make new modules / spare modules
–
Continue development for new requirements
Developments
 Present developments
–
More modules needed
– Installation of 9th quadrant diode (maybe 10th)
– Spares needed
–
New Annecy local oscillator boards, compatible with alignment
– Phase shifters for standard photodiodes

Possible developments
–
Substitute Si diodes with InGaAs diodes
– Better quantum efficiency
– Lower bias voltage
– => higher power capability
 lower noise

Reduction of electronics noise
 Better preamplifier: 5 pA/rtHz -> 1.6 pA/rtHz (?)
 DC signals: pre-amplification / pre-shaping
–
Fast quadrant centering system
– (Napoli is working on that)
– LA noise limits sensibility (especially at low frequencies)
LISA
QD electronics
Quadrant diode box
Manpower estimate ~ 3FTE
from electronics group
LISA
Virgo – local control of mirrors
Local control of mirrors
Present accuracy about 1 micron
Feedback systems induce noise
Possible application for RASNIC
LISA
VIRGO Optical Scheme
Input Mode Cleaner (144 m)
3 km long Fabry-Perot
Cavities
Laser 20 W
Power
Recycling
Output Mode
Cleaner (4 cm)
LISA
Virgo – inside the central building
LISA
Mirror suspension
High quality fused silica mirrors
LISA
•
35 cm diameter, 10 cm thickness, 21 kg mass
•
Substrate losses ~1 ppm
•
Coating losses <5 ppm
•
Surface deformation ~l/100
Superattenuators
Possible contributions:

Virgo+ will use
monolythic suspension

Input-mode cleaner
suspension
Monolithic suspension
 Fused silica fibers
 Bonded to mirror
 Reduce thermal noise
 Needed for Virgo+
 Realized by GEO600
Weld
Silicate
(HydroxyCatalysis)
Bonding
LISA
Input mode cleaner
 Mode cleaner cavity: filters
laser noise, select TEM00
mode
Input beam
inbeam
LISA
Transm. beam
outbeam
Refl. beam
refbeam
LISA - drag free control
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LISA
SRON
Test equipment for position sensor readout electronics in on-ground tests of the
satellite system
Simulation software modules of the
position sensors, used in system
simulations
TNO-TPD
Test equipment of the Laser Optical Bench
Decaging Mechanism (TBC)
Bradford Engineering
Cold Gas propulsion (TBC)
LISA key technology
LISA

Test-mass position sensing:
Capacitive sensing.

Drag-Free control.

FEEP micro-Newton thrusters.
NIKHEF and SRON develop
ASICS for electronic readout
of all LISA signals
Low noise, high resolution ADCs
NIKHEF 2 – 3 ASIC designers
+ 2 FTE support
Summary

Linear alignment of Virgo
–

Monolithic suspension of Virgo mirrors
–

2 FTE EA
Lisa electronics
–
–
LISA
2 FTE EA
Recycling mirror for Virgo+
–

3 FTE electronics
2 – 3 ASICS designers
2 FTE support
Optimized alignment noise budget
Maximized power
Optimized mirror centering
(0.2 mm)
LISA
Scheme of LA electronics
Low-pass filter
AC: Gain 200
diff. sig.
Shot noise
Preamp. noise
QD box
non-diff.sig. DC: Gain 1
Non-optimal treatment of DC signals
dominated by ADC noise
(but were not foreseen as error signals)
LISA
VME
ADC noise