A Gravitational Wave Interferometer at 5GHz L. Piccirillo, G. Pisano – Jodrell Bank A.M.Cruise – Birmingham

Strong science cases- well understood technology –Pulsar timing ~10 -8 Hz –LISA/DECIGO – Hz –Advanced LIGO 10 2 – 5×10 3 Hz Emerging science cases- new technology –Microwave Frequencies 10 8 – Hz –IR and Optical Frequencies – Hz First Detections? Gravitational Wave Frequency Ranges Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

Early Universe –Garcia-Bellido, Easther, Copeland, Leblond, etc Kaluza-Klein modes from Black Holes in 5-D gravity –Seahra, Clarkson and Maartens, Clarkson and Seahra EM-GW mode conversion in magnetised plasmas –Servin and Brodin Possible Sources at Very High Frequencies ?  See poster by Cruise, Pisano and Piccirillo Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

Laser interferometers lose sensitivity as increases Use Graviton to Photon conversion in B Field De Logi and Mickelson (1977) Cross section for g Graviton, g Virtual Photon ( Static Magnetic Field, B) Photon, Spin states of g, B and Detector Possibilities B is magnetic field, L is path length Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

Cross Section  is small due to G/c 3 factor but this is per incoming graviton Flux of gravitons is large due to c 2 /G factor Signal Power is What are the fluxes ? Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

Conversion GW  e.m waves Inverse-Gertsenshtein effect Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

Need smart transducer GW  EMW  waveguides  LNA  detection With EMW’s. we can use standard interferometric techniques Correlation receiver for a single baseline GW detector Conversion GW  e.m waves Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

Instrument angular-acceptance/beam First tests at Birmingham create EMW’s completely inside single mode waveguide- simple geometry New detector requires GW-EMW conversion outside modified waveguide and at many angles Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

New instrument concept Conversion volume g – waves   e.m. - waves Collection part Detection part  single-mode RF Magnets & waveguide Waveguide taper Cryo LNA Correlator Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

Collection part Single-mode output Conversion volume Collection part Finite-element e.m. modelling (HFSS) Magnets Standard single mode waveguide Tall waveguide Plane-waves / modes from different directions in input Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

New Detector Partial list of problems: –Conversion plane-wave  waveguide modes –Waves from different directions  Mismatch with the main waveguide mode –Gradient of e.m. intensity along conversion volume –Magnetic field projection effects –Difference in waveguide phase-velocity –Multiple reflections inside the waveguide structure –Etc… Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

Angular-acceptance: Modes mismatch Incident radiation from different directions Variable response with angle and frequency 5.00 GHz 5.25 GHz Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

GW Correlation Receiver Correlator Sensitivity increase Narrower beam in the z direction … Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

20 K LIA 90 0 LPF PS1 PS2 LO 7GHz BPF Video Amp. Video Amp. PS waveform generator IN1 IN2 Cryo LNA C-band (5 GHz) R C cos R C sin Re Im USB (LO + S i ) (12 GHz) LSB (LO - S i ) (2 GHz) LO (7 GHz) Signal S i (5 GHz) LPF BPF IF1 IF2 Correlation receiver circuitry Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

X ss antenna b multiply average A small (but finite) frequency width, and no motion. Consider radiation from a small solid angle d , from direction s. Cosine output Correlation receiver B’ham/M’cr GW prototype experiment Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

Synthesizing beams… Transit of a point-like source Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

Sensitivity ( Provisional ) Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

Ideas for the (not so distant) future Amplifier is the low noise element (HEMT is state of the art) Amplifiers have an intrinsic noise limit (T min = hν/k) due to uncertainty principle Bolometric detectors (thermal detectors) are classical detectors and not limited by quantum mechanics Bolometric interferometry (adding interferometry) can improve the minimum noise by a substantial factor (at least 1 order of magnitude)  Bolometric interferometry will allow to explore the 10 GHz – 1 THz GW region with aperture synthesis Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

Conclusion In addition to the obvious sources at LIGO and LISA frequencies there may be GW radiation at microwave although the sources are speculative The prototype detectors using the graviton to photon conversion are relatively cheap to build The Jodrell – Birmingham collaboration is studying the design a single baseline interferometer operating at 5GHz. The aim is to design and build an aperture synthesis array for Microwave Frequencies GWs The detector will locate sources in the sky Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

Thank you! Questions?

We generate the ‘sine’ pattern by inserting a 90 degree phase shift in one of the signal paths. X ss antenna b multiply average 90 o Making a SIN correlator Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

We now define a complex function, V, to be the complex sum of the two independent correlator outputs: where This gives us a relationship between the source brightness, and the response of an interferometer: This expression can be inverted to recover I(s) from V(b). Define the Complex Visibility Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA

Formally identical to single baseline radio interferometer Stable, low-noise solution Re-use existing radio hardware at Jodrell Bank Multiply the two GW detector outputs The averaged signal is independent of the time t, but is dependent on the lag,  g – a function of direction – and hence on the distribution of the brightness. To determine the dependence of the response over an extended object, we integrate over solid angle. Correlation receiver B’ham/M’cr GW frequency detector Cardiff - 12 Jul Lucio Piccirillo - AMALDI 9 & NRDA