Post on 03-Jan-2016
LISA
http://www.esa.int/science/lisa October 3, 2005
LISALaser InterferometerSpace Antenna
Gravitational Physics ProgramTechnical implications
Jo van den BrandNIKHEF – Staff Meeting, January 2006
LISA
VIRGO & Lisa – Technical activities
Linear alignment of Virgo– Keep mirrors and input beam aligned
Monolithic suspension of Virgo mirrors – Reduce thermal noise
Recycling mirror for Virgo+– Improve mirror suspension
Lisa electronics– Drag-free control readout
LISA
Linear alignment of VIRGO interferometer
N
W
EOM
Phase modulation of input beam
Demodulation of photodiode signals at different output beams
– => longitudinal error signals
Quadrant diodes in output beams
– => Alignment information
– (differential wavefront sensing)
Anderson-Giordano technique
– 2 quadrant diodes after arm cavities
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
– Continue support for alignment electronics
– Make new modules / spare modules
– Continue development for new requirements
LISA
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
dem
odul
ator
phas
e sh
ifte
r
Quadrant diode box
Manpower estimate ~ 3FTEfrom electronics group
LISA
Virgo – local control of mirrors
Local control of mirrorsPresent accuracy about 1 micronFeedback systems induce noisePossible application for RASNIC
LISA
VIRGO Optical Scheme
Laser 20 W
Input Mode Cleaner (144 m)
Power
Recycling
3 km long Fabry-Perot
Cavities
Output Mode
Cleaner (4 cm)
LISA
Mirror suspension
High quality fused silica mirrors
• 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
LISA
Fused silica fibers
Bonded to mirror
Reduce thermal noise
Needed for Virgo+
Realized by GEO600
Silicate (Hydroxy- Catalysis) Bonding
Weld
Monolithic suspension
LISA
Input mode cleaner
Mode cleaner cavity: filters laser noise, select TEM00 mode
refbeaminbeam outbeam
Input beam Transm. beam Refl. beam
LISA
LISA - drag free control
SRON Test equipment for position sensor read-
out 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
LISA key technology
Test-mass position sensing: Capacitive sensing.
Drag-Free control.
FEEP micro-Newton thrusters. NIKHEF and SRON developASICS for electronic readoutof all LISA signalsLow noise, high resolution ADCsNIKHEF 2 – 3 ASIC designers+ 2 FTE support
LISA
Summary
Linear alignment of Virgo– 3 FTE electronics
Monolithic suspension of Virgo mirrors – 2 FTE EA
Recycling mirror for Virgo+– 2 FTE EA
Lisa electronics– 2 – 3 ASICS designers– 2 FTE support