a gravitational wave interferometer at 5ghz l. piccirillo, g. pisano – jodrell bank a.m.cruise –...

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 10-4 – 10-2 Hz – Advanced LIGO 102 – 5×103 Hz

• Emerging science cases- new technology– Microwave Frequencies 108 – 1010 Hz– IR and Optical Frequencies 1012 – 1015 Hz

First Detections?

Gravitational Wave Frequency Ranges

Cardiff - 12 Jul 2011 2Lucio 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 PiccirilloCardiff - 12 Jul 2011 3Lucio 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,

3

228

c

LGBSpin states of g, B and

Detector Possibilities

B is magnetic field, L is path length


• Cross Section is small due to G/c3 factor but this is per incoming graviton

• Flux of gravitons is large due to c2/G factor

• Signal Power is

22 2 1

16 gwgw

cPhoton Flux h

G

2 2 2 2 2

0

1

8EMW gwP B L K h cSin

What are the fluxes ?


Conversion GW e.m waves

Inverse-Gertsenshtein effect


• 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


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 anglesCardiff - 12 Jul 2011 8Lucio Piccirillo - AMALDI 9 & NRDA

New instrument concept

Conversion volume

g – waves e.m.- waves

Collectionpart

Detectionpart

single-mode RF

Magnets & waveguideWaveguide

taper

Cryo LNA

Correlator


Collection part

Single-modeoutput

Conversion volume

Collection part

Finite-element e.m. modelling (HFSS)

MagnetsStandard single mode waveguide

Tall waveguide

Plane-waves / modesfrom different

directions in input


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…


Angular-acceptance: Modes mismatch

Incident radiation from different directions

Variable response with angle and frequency

5.00 GHz5.25 GHz


GW Correlation Receiver

Correlator

• Sensitivity increase• Narrower beam in the z direction• …


20 K

LIA

LIA

900LPF

LPF

PS1

PS2

LO 7GHz

BPF

BPF

VideoAmp.

VideoAmp.

PS waveform generator

IN1

IN2

Cryo LNAC-band (5 GHz)

RC cos

RC sin

Re Im

USB (LO + Si)(12 GHz)

LSB (LO - Si)(2 GHz)

LO (7 GHz)

Signal Si

(5 GHz)

LPF BPF

IF1

IF2

Correlation receiver circuitry


X

s s

antennab

)cos(2 tVV ])(cos[1 gtVV

2/])2cos()[cos(21 gg tVV

2/)]/2cos([2/])cos([ 2121 cVVVVR gc sb

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 receiverB’ham/M’cr GW prototype experiment

cg /sb


Synthesizing beams…

Transit of a point-like source


Sensitivity ( Provisional )


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 (Tmin = 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 synthesisCardiff - 12 Jul 2011 18Lucio 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


Thank you!

Questions?

• We generate the ‘sine’ pattern by inserting a 90 degree phase shift in one of the signal paths.

X

s s

antennab

cg /sb

)cos(2 tVV ])(cos[1 gtVV

2/])2sin()[sin(21 gg tVV

2/)]/2sin([2/])sin([ 2121 cVVVVR gs sb

multiply

average

90o

Making a SIN correlator


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).

iSC AeiRRV

C

S

SC

R

R

RRA

1

22

tan

dsIiRRV ciSC e /2)()( sbb

Define the Complex Visibility


• 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.

dcIRC )/2cos()( sbs

Correlation receiverB’ham/M’cr GW frequency detector


a gravitational wave interferometer at 5ghz l. piccirillo, g. pisano – jodrell bank a.m.cruise –...

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