LISA Benchtop Experiment at UF Guido Mueller University of Florida 21 st July 2005

01/08/2003 Gravitational Waves: Generated by huge accelerated masses such as black holes in a binary system Predicted by Einstein, never detected d

01/08/2003 Frequencies & Amplitudes Chirp Mass: Amplitude: GW Frequency Upper limit: h 0 ~ 2x kpc R f Hz M M NS 3/2 f < 3.2 kHz M NS M 3r S d 3/2 M= (M 1 M 2 ) (M 1 +M 2 ) 3/5 1/5 M ~ M S f ~ 10 Hz – 3 kHz M ~ 10 8 M S f ~ 0.1 mHz – 100 mHz

01/08/2003 History of a big fat wedding measure masses and spins of binary system detect normal modes of ringdown to identify final NS or BH. observe strong-field spacetime dynamics, spin flips and couplings…

01/08/2003 LISA: Joint NASA/ESA project Advanced LIGO LIGO: NSF project GW-Detectors

01/08/2003 Asymmetric Binaries Compact Star orbits MBH in center of galaxy Gravitational waves measure the multipole moments of the central object Tests No hair theorem (BH described by mass, spin, and charge) Survey of MBH population

01/08/2003 The Mission 3 spacecraft constellation S/C separated by 5x10 6 km Drag-free proof masses inside each S/C Earth-trailing solar orbit 5 year mission life 10pm/rHz-Sensitivity Launch 2014 LISA

01/08/2003 Spacecraft Problem 1: Environment will push/pull S/C by several m Free falling proof mass needs to be shielded Problems 2: Interferometry: pm-sensitivity over Gm distances

01/08/2003 The Challenges Technical Challenges: 1.How to build a gravitational reference sensor? Need a non-accelerated proof mass acceleration < 3x m/s -2 / rHz 2.How to do pm-Interferometry in LISA? Interferometry Measurement System (IMS) Post processing of data (subtract instrumental noise) Signal extraction (subtract known signals)

01/08/2003 GRS The Proof Mass: Gold Platinum alloy Cube (4cm) Will float inside S/C Housing: Electrodes for Position Read out Position Control Option: Optical readout Housing connected to Optical Bench and S/C

01/08/2003 GRS A few forces pushing the PM: Electro-magnetic Forces: Charges on PM and magnetic susceptibility couple to variable solar magnetic field Self gravity from S/C: S/C motion with respect to PM < 10nm/rHz Gas pressure noise: Gas hitting the PM from both sides: T < K/rHz Thermal photon pressure: Black Body Radiation from walls: T < K/rHz …

01/08/2003 LISA Interferometry Background: LISA-Signal: Phase of a laser field – Main detector: Phase meter Phase meter signal dominated by frequency noise – Laser frequency noise – Clock noise Non-stable working point – Doppler shifts – Arm flexing

01/08/2003 Laser frequency stabilization Current frequency noise at UF: 1 1mHz. Goal of 30Hz/rHz was met at AEI-Hanover and GSFC. Goal is still 9 orders of magnitude to high for a direct measurement! Pre-frequency stabilization using ultra-stable reference cavities

01/08/2003 LISA-Lab at GSFC: Reached 30Hz/rHz (original LISA Req.) Ira Thorpe, Rachel Parks, Jordan Camp, Paul McNamara, G.M. fm = Hz Laser Frequency Stab.

01/08/2003 LISA Interferometry Key Technologies to reduce frequency noise (FN): 1.Time Delay Interferometry (TDI) Measure same FN at different times and locations Time shift data sets Form appropriate linear combinations which cancel FN 2.Arm Locking Use LISA Interferometer arms as frequency reference Lock laser frequency on LISA arms Baseline: Combination of both to cancel 9 orders of magnitude noise!

01/08/2003 Experimental challenge: How to simulate 5 Gm (16 s) distance between S/C? Solution: Electronic Phase Delay (EPD) Delay only the laser phase (carrier frequency is meaningless)! 1.Beat laser against reference laser (Beat frequency < 25MHz) 2.Digitize Beat Signal 3.Store Beat signal for 16s 4.Regenerate Beat signal Transfer function same as LISA arm with LISA-like noise sin[ t+ 10 (t)]sin[ t- )+ 10 (t- )] LISA Benchtop at UF

01/08/2003 S 12 (t) = 20 (t- 21 )- 10 (t) S 21 (t) TDI test at UF S 23 (t) S 13 (t) S 32 (t) S 31 (t) S 12 (t)

01/08/2003 S 12 (t) –S 12 (t-2 13 )-S 13 (t)+S 13 (t-2 12 ) ~ GW S 21 (t)=0 TDI with Phase lock loop S 23 (t) S 13 (t) S 32 (t) S 31 (t)=0 S 12 (t)

01/08/2003 Armlocking Basic Idea: Lock laser frequency to LISA arm Far S/C: Transponder (phase locked laser) S(t) = (t-2 )- (t) = 0 ! Transfer function is zero at Fourier frequencies f N = N/ 2 Laser phase will change periodically with period of round trip time 2 Laser frequency noise suppressed at all frequencies except at f N = N/ 2

01/08/2003 S 13 (t) = GW S 21 (t)=0 TDI with Arm locking S 23 (t) S 13 (t) S 32 (t) S 31 (t)=0 S 12 (t)=0

01/08/2003 First Arm locking experiments First experimental tests of Arm locking with VCO at UF: Start-up transients:Noise suppression: Only 500ms delay here instead of 32s in LISA Laser phase changes with 500ms period

01/08/2003 Benchtop Experiment for LISA Research Plan at UF: Test TDI, data-reduction algorithms with realistic laser phase noise Test arm locking with realistic laser phase noise Add clock noise, bench motion, arm flexing, and Doppler shifts Start Mock-up data challenges Expand to two lasers per S/C Full Interferometer test before 2010 Development of data reduction and data analysis tools – Massive Downsampling – Subtraction of 1000s of known and unknown galactic binaries We will produce experimental data to test this

01/08/2003 The Crew at UF Rachel Cruz Ira Thorpe Alix Preston Rod Delgadillo Michael Hartmann Shawn Mitryk Gabriel Boothe Derek Kennedy Former Students: Guido Mueller Sergei Klimenko David Tanner Shannon Sankar Kim Lukas Mueller Movie