Workshop on Stellar Intensity Interferometry January January 29 29- -30 30, , 2009 2009, Salt Lake City , Salt Lake City New tools for intensity interferometry New tools for intensity interferometry
First experiment in intensity interferometry � Hanbury-Brown & Twiss 1954 Twiss 1954 � Correlate detectors’ currents � 2 nd order correlation � Measures only| γ 12 | � Measures only| γ 12 | Jodrell Bank 1958 J d ll B k 1958 � Optical accuracy c / Δ f Narrabri 1969-74 ~ 30 cm � Insensitive to atmosphere, optics p , p 2 New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry Erez Ribak Salt Lake City 2009
What has changed in the world since 1974? Amplitude interferometry, for one (and a big one, at that) But also • Telescopes: bigger phased panels adaptive optics Telescopes: bigger, phased panels, adaptive optics • Electronics: the transform from analogue to digital • Optics: modulators, fibres, materials • Detectors • Computers • Data analysis: phase retrieval, speckle methods y p , p All of these were used by amplitude interferometry Can we gain from them in intensity interferometry? Which are unique to intensity interferometry? Whi h i t i t it i t f t ? 3 New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry Erez Ribak Salt Lake City 2009
Advances in technology Light collectors are better, cheaper Photomultipliers out, avalanche photodiode arrays in … but analogue technology still has wider band width … but analogue technology still has wider band width Correlators up to10 9 bits /s in the radio, Č erenkov … but analogue technology still has wider band width New other tools • Non-imaging light concentrators • Long-haul fibre optics (single- and multimode) g p ( g ) • Other optical paraphernalia: spectrometers, correlators • Global positioning systems • Correlators on computer clusters (digital again) C l t t l t (di it l i ) 4 New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry Erez Ribak Salt Lake City 2009
Advances in performance: technology A Ofir thesis b ν = electronic bandwidth α = quantum efficiency Σ = system efficiency Σ = system efficiency m = optical channels b ν → 1GHz, α → 0.8, Σ → 0.8, m =1 4.99 4 99 NSII performance: 0 m star, 1 hr, SNR=27 b ν = 100MHz, α = 0.2, Σ = 0.2, m = 1 4.91 5 telescopes New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry Erez Ribak Salt Lake City 2009
Advances in theory • More correlations (Fontana 1983) M l ti (F t 1983) • Higher order correlations Source • Parallel spectral detectors • Correlators on computer clusters Square Law D 1 D 2 D 3 D k D n • Triple correlation Detectors • Adds phase information A 1 A 2 A 3 … A k … A n Amplifiers • Proposed by Gamo (1963) … … τ 1 τ 2 τ 3 τ k τ n Delays • Demonstrated in lab (Sato 1978) • Applied in speckle interferometry Applied in speckle interferometry M M Multiplier (Weigelt, Lohmann 1980s) • Use zero sheets in the Fourier domain I Integrator • 1-d polynomials (Bates 1984) 1 d polynomials (Bates 1984) • Cauchy-Riemann equations R Recorder (Holmes 2008) 6 New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry Erez Ribak Salt Lake City 2009
Advances in performance: high-order correlations A Ofir thesis Nonuplets Septuplets Octuplets N =99 N =71 N =85 Sextuplets N =57 Q Quintuplets p most improvement most improvement N =43 for sharp-contrast objects (high V ) Quadruplets N =29 Triplets Triplets T i l t N =15 N =54 Triplets N =210 Triplets Triplets N =3335 Scaling from NSII performance (<1972) 7 New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry Erez Ribak Salt Lake City 2009
Laboratory experiment • Blue LEDs Bl LED • Sheltered light path, light baffles • Telescopes: Fresnel lenses a few meters away • Fast photomultipliers at Fresnel foci p p LED spectrum LED spectrum Fresnel collector F l ll Lipson and Spektor (work in progress) 8 New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry Erez Ribak Salt Lake City 2009
Laboratory communication and correlation • Fast electronics using current technologies (e.g. optical coupler) • Employing RF gain/phase detector as phase difference element • Analogue function g • Slight frequency deterioration • Up to 2.7 GHz 9 New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry Erez Ribak Salt Lake City 2009
Implemenetation • Phase difference element Ph diff l • Wide frequency range: 0.1 → 1GHz (local radio stations → PMT limit) • Unfortunately device requires frequency to find phase • Used only to work at zero phase difference (zero delay) y p ( y) • First successful results obtained • With signal, noise level rises as expected • Higher correlation no signal with signal 10 New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry Erez Ribak Salt Lake City 2009
Space Formation flight Formation flight k k x source � Calculation of orbits requiring minimal fuel k y y � Proper Fourier coverage P F i � Simple collectors k x � UV-blue coverage � Data handling k y � Transmit photon events � Space/ground correlators � Space/ground correlators source k x source k y O b ts ou e cove age Orbits Fourier coverage Klein, Guellman, Lipson, 2007 Klein, Guellman, Lipson, 2007 11 New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Erez Ribak Salt Lake City 2009
Antarctica � Medium (~20m) collectors: bigger would resolve objects M di ( 20 ) ll bi ld l bj � Can be used for coronagraphy (resolve star, not planet) � Many base lines: simultaneity not so important for closure, but… � Many ( n> 50) collectors: improvement in SNR ~ n 1.1 for high γ � UV-Vis: complement amplitude interferometry in IR Presented at 2nd ARENA Workshop on Interferometry 2008 Presented at 2nd ARENA Workshop on Interferometry, 2008 12 New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry Erez Ribak Salt Lake City 2009
Setting up array observatories λ surface, diameter array no. of focal signal lunar in- synergy delay area elements position handling terference accuracy µ m µ m m km Č erenkov 0.3-1 100 5-25 1×1 10-100 below cross- high IceCube detection focus correlate radio 500+ 100 5-25 1×1 10-100 focus, cross- low IceCube interferometry interferometry chopper chopper correlate correlate intensity 0.3-1 100 5-25 1×1 10-100 focus cross- high - interferometry correlate amplitude li d 0 7 10 0.7-10 0 1 0.1 0 5 0.5 or 1×1 1 1 5 20 5-20 f focus, i interfere f l low - interferometry 8-10+AO chopper optically • All values are negotiable • The first three arrays share many parameters • Some optics can be shared, electronics less so • Planning and designing a common array is essential for funding 13 Presented at 2nd ARENA Workshop on Interferometry, 2008 New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry Erez Ribak Salt Lake City 2009
Sharing collectors with Č erenkov detectors • Focal plane camera is an array of photomultiplier detectors F l l i f h l i li d • Spot size (PSF) is relatively large, for parabolic collectors or Davies-Cotton • Addition of nearby detector signals encouraged • Better still: use cross detectors for spectral dispersion p p 14 New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry Erez Ribak Salt Lake City 2009
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