LISA R&D activities at APC

1. LISA R&D activities at APC A status report Hubert Halloin

2. R&D activities at APC • Recent implication of APC in the LISA R&D (~ 1.5 year) : • LISA Pathfinder (Laser Modulator) : • Validation of test procedures ( Contraves) • Acquire experience for further experiments … • LISA : • Laser stabilization • Realization of a ‘LISA-representative’ laboratory LISA France – 02 February 2007

3. M. Abbès (electronics engineer) G. Auger (director of research) P. Binetruy (professor, director of the APC) H. Halloin (assistant professor) O. Jeannin (optical engineer) The LISA team @ APC • A. Petiteau (PhD student) • E. Plagnol (director of research) • P. Prat (electronics engineer, NPM for LISA Pathfinder) • E. de Vismes (electronics engineer) LISA France – 02 February 2007

4. LISA Optical Test Equipment • Centered on the interferometric signal reconstruction (excluding inertial masses) • “LISA-representative” test bench • What optical devices / electronics for the “best” signal extraction ? • Characterization of present techniques (laser, phasemeters, …) • Test facility for LISA instrumental developments. • Conformation to / interaction with LISA simulation • “Realistic” performance of signal reconstruction algorithms (TDI,…) • Supported by the French Space Agency (CNES) • In collaboration with : • A. Brillet (O.C.A) : Laser stabilization for Virgo • SYRTE : R&D in time/frequency standards and references LISA France – 02 February 2007

5. Development roadmap • 3 major steps : • Laser stabilization and characterization • Definition and development of a dedicated phasemeter • LISA test bench (3 lasers, variable propagation delays, realistic phasemeters,…) Short term ~1 year Long term ~5 years LISA France – 02 February 2007

6. Laser stabilization • Selected technique : saturated absorption on molecular iodine • Absolute reference (no long term drift, easier arm-locking ?). • Already tested and promising for LISA : successful experiments at Observatoire de la Côte d’Azur (Nice, France) and GSFC. • Financial support from the French space agency (CNES) • Collaboration with the OCA/ARTEMIS (A. Brillet) and the SYRTE • Ways of improvements : • Better thermal, mechanical and electronics stability • Improved feedback loop • Low pressure enclosure • Possible use of low pressure, non-saturated I2 cells at ~0°C, in collaboration with the BIPM (better thermal stability) • Main technical and performance concerns : • Overall frequency stability • Thermal and vibration control • Wave front quality of the IR beam after frequency doubling • I2 reactivity (in case of non saturated cells) LISA France – 02 February 2007

7. Laser 1 160 MHz λ=532nm AOM Laser 1 Feedback electronics λ=1064nm Iodine cell 20 MHz beat signal + laser noise Iodine cell Feedback electronics Laser 2 λ=1064nm Laser 2 AOM λ=532nm 80 MHz Laser stabilization : foreseen design • Current status : • Electronic cards development / realizations • Precise mechanical and optical design • Mounting to begin in Feb 2007 LISA France – 02 February 2007

8. LISA in the lab • « Representative » reconstruction of the interferometric signal : • Noise propagation delay (16 s !) • Spectral perturbations (Doppler, Sagnac, etc.) • GW simulation ? • Reconstruction algorithm(s) (TDI) : effective performance, comparison with numerical simulations. • Facility for methods and equipments tests : • Phasemeters • USO • TDI ranging • Arm locking • … … in the lab LISA … LISA France – 02 February 2007

9. Simulating the propagation delays • Global idea : • only the relative LF (<1Hz) phase noise + frequency shift has to be « propagated » • No need to delay the « full » phase data (i.e. carrier + phase noise) • Small information content (low frequency)  can be easily digitally delayed Measurements Doppler ~10-6 Hz LF laser phase noise <1 Hz HF laser phase noise >1 Hz (not of interest …) LISA France – 02 February 2007

10. LISA in the lab • 1st step : phase locking the lasers • Master laser reference noise • Null relative phase noise (modulo frequency offsets) • “Of the shelf” efficient techniques LISA France – 02 February 2007

11. LISA in the lab : first idea … May be laser 1, 2 or 3 Iodine stabilized Master laser Phase locking Laser 1 Phase locking Laser 2 locking  Laser 3locking LISA France – 02 February 2007

12. LISA in the lab • 1st step : phase locking the lasers • Master laser reference noise • Null relative phase noise (modulo frequency offsets) • “Of the shelf” efficient techniques • 2nd step : noise delays simulation • Use of AOM (frequency shifts) : • Low frequency noise can be easily digitally delayed • Possibility to simulate 1 year of data (Doppler, laser noise, GW ?) within hours LISA France – 02 February 2007

13. LISA in the lab : first idea … Master laser • Principle design, to be precised … • Continuity of precedent work (stabilization, -meter) + R&D (locking, delays) • Planned for 2008 … Phase locking Laser 1 AOM Phase locking Laser 2 locking  Laser 3locking L1 “delayed” Digital delays L1 “local” LF noise generator (statistically. representative) FM  Doppler shift PM  LF phase noise AOM 1216s Simulated delays of noise AOM 1316s     L2 local L3 local L2 delayed L3 delayed LISA France – 02 February 2007

14. Conclusions • Continuation of LISA Pathfinder activities • R&D on iodine stabilization : • Optical and electronics design started • Mounting to begin within a few weeks (on our new site …) • Strong support of the French space agency (CNES) • Collaboration with : • OCA / Artemis (A. Brillet) • SYRTE LISA France – 02 February 2007