LISA October 3, 2005 LISA Laser Interferometer Space Antenna Gravitational Physics Program Technical implications Jo van den Brand NIKHEF – 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 Can have 1 normal diode and 2 quadrant diodes at each output port Detection

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 – Continue support for alignment electronics – Make new modules / spare modules – Continue development for new requirements

LISA Developments  Present developments – More modules needed –Installation of 9 th quadrant diode (maybe 10 th ) –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 demodulator phase shifter 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 Laser 20 W Input Mode Cleaner (144 m) Power Recycling 3 km long Fabry-Perot Cavities Output Mode Cleaner (4 cm)

LISA Virgo – inside the central building

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 Input beam Transm. beamRefl. 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 develop ASICS for electronic readout of all LISA signals Low noise, high resolution ADCs NIKHEF 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

LISA Optimized alignment noise budget Maximized power Optimized mirror centering (0.2 mm)

LISA Scheme of LA electronics ADC noise Preamp. noise Shot noise Low-pass filter AC: Gain 200 DC: Gain 1 diff. sig. non-diff.sig. Non-optimal treatment of DC signals dominated by ADC noise (but were not foreseen as error signals) VME QD box