Signal photon flux and background noise in a coupling electromagnetic detecting system for high-frequency gravitational waves
Fangyu Li · Nan Yang · Zhenyun Fang · Robert M. L. Baker · Gary V. Stephenson · Hao Wen
Abstract and summary · read the original at the source
In one page
A gravitational wave crossing a strong magnetic field turns partly into light. That is the Gertsenshtein effect, and it is the oldest idea for catching gravitational waves with electronics rather than mirrors. Fangyu Li’s group at Chongqing University, with Robert Baker and Gary Stephenson, work out what a detector built on it would actually see around five gigahertz, the band where relic waves from the early universe are expected to peak. Their scheme is not the plain conversion, which they show is hopelessly faint on its own: they add a Gaussian microwave beam for the passing wave to beat against, so the signal grows in proportion to the wave’s amplitude instead of its square. The careful part is the noise. Signal photons and background photons spread differently across the apparatus, and there is one surface — the beam’s own symmetry plane — where the background transverse flux vanishes while the signal peaks. Focus that with fractal membranes and, they estimate, hours of counting would show it.
Why it matters hereChapter 10 says electromagnetism and gravity couple through fields and phase rather than through mass, and this paper is that coupling written as an instrument budget: how many photons, against how much background, on which surface, for how long. Chapter 11 wants a bench where the two meet under laboratory control, and a three-tesla magnet with a ten-watt beam is one. The same group’s later alternating-magnet scheme is on this site at /library/stm-949ba88682, and the twenty-five-author survey of the whole megahertz-to-gigahertz band is at /library/stm-96e41ddb23.
What it claims
01A detecting scheme based only on the pure inverse Gertsenshtein effect would not be useful for detecting high-frequency gravitational waves in the microwave band under laboratory conditions: for a field of 10 tesla over a path of 10 metres the converted power is of order ten to the minus forty watts, which is about seven times ten to the minus seventeen photons per second.Section II, Detecting scheme based on the inverse Gertsenshtein effect, Equations 7 and 8
Published and peer-reviewed02The electromagnetic detecting scheme proposed by the China and US high-frequency gravitational wave groups is based on the composite effect of the synchro-resonance effect and the inverse Gertsenshtein effect, in which the key parameter is the first-order perturbative photon flux and not the second-order flux.Abstract; Section IV, opening
Designed, not yet built03The distinguishable signal is the transverse first-order perturbative photon flux, which reaches its maximum at the longitudinal symmetrical surface of the Gaussian beam — exactly the surface where the transverse background photon flux vanishes identically, a fundamental characteristic of Gaussian beams — so the signal-to-noise ratio depends strongly on which receiving surface is used and can be optimised by choosing it.Section IV, Equations 45 and 46 and the two numbered points following them
Designed, not yet built04With typical parameters of a static magnetic field of 3 tesla, an interaction length of 6 metres, a 10 watt Gaussian beam at 5 gigahertz and a receiving surface of about one hundredth of a square metre, the requisite minimal accumulation time of the signal in the background noise fluctuation would be of order one thousand to one hundred thousand seconds for wave amplitudes between ten to the minus twenty-six and ten to the minus thirty at one hertz bandwidth.Section IV, numerical estimation, Equations 60 to 65; Section V, Brief summary
Designed, not yet built05The photon flux focused by the fractal membranes or other equivalent microwave lenses is not only the transverse first-order perturbative flux but the total transverse photon flux, and the two have different signal-to-noise ratios at different receiving surfaces, so the focusing optics and the choice of surface are part of the measurement rather than an afterthought.Abstract; Section IV, discussion of the fractal membranes
Designed, not yet built06Relic gravitational waves expected from quintessential inflationary models and from some string cosmology scenarios peak in the gigahertz band with root-mean-square dimensionless amplitudes of about ten to the minus thirty to ten to the minus thirty-four, which is why the microwave band is the one worth instrumenting.Section I, Introduction, reason 1; Table 1, Some possible HFGW sources and relevant parameters
Published and peer-reviewed
Read it · abstract
Abstract
A coupling system between Gaussian type-microwave photon flux, static magnetic field and fractal membranes (or other equivalent microwave lenses) can be used to detect high-frequency gravitational waves (HFGWs) in the microwave band. We study the signal photon flux, background photon flux and the requisite minimal accumulation time of the signal in the coupling system. Unlike pure inverse Gertsenshtein effect (G-effect) caused by the HFGWs in the GHz band, the electromagnetic (EM) detecting scheme (EDS) proposed by China and the US HFGW groups is based on the composite effect of the synchro-resonance effect and the inverse G-effect. Key parameters in the scheme include first-order perturbative photon flux (PPF) and not the second-order PPF; the distinguishable signal is the transverse first-order PPF and not the longitudinal PPF; the photon flux focused by the fractal membranes or other equivalent microwave lenses is not only the transverse first-order PPF but the total transverse photon flux, and these photon fluxes have different signal-to-noise ratios at the different receiving surfaces. Theoretical analysis and numerical estimation show that the requisite minimal accumulation time of the signal at the special receiving surfaces and in the background noise fluctuation would be about ten cubed to ten to the fifth seconds for the typical laboratory condition and parameters of h r.m.s. of about ten to the minus twenty-six to ten to the minus thirty at 5 GHz with bandwidth about 1 Hz. In addition, we review the inverse G-effect in the EM detection of the HFGWs, and it is shown that the EM detecting scheme based only on the pure inverse G-effect in the laboratory condition would not be useful to detect HFGWs in the microwave band.
The way in
https://doi.org/10.1103/PhysRevD.80.064013Published as Physical Review D 80, 064013 (2009) by Fangyu Li, Nan Yang, Zhenyun Fang and Hao Wen of the Department of Physics at Chongqing University, with Robert M. L. Baker Jr. of GravWave LLC and Gary V. Stephenson of Seculine Consulting. The revised manuscript is free to read on arXiv as 0909.4118, but that posting carries arXiv’s non-exclusive distribution licence rather than a Creative Commons licence, and the journal version is under the APS default licence, so this page holds the summary, the claims and the authors’ own abstract and sends the reader to the source.
How to cite it
Fangyu Li, Nan Yang, Zhenyun Fang, Robert M. L. Baker, Gary V. Stephenson, Hao Wen (2009) Signal photon flux and background noise in a coupling electromagnetic detecting system for high-frequency gravitational waves. doi:10.1103/PhysRevD.80.064013
Where it sits in the curriculum
Scalar waves and the field behind the fieldsGravity control and superconductorsThe metric, warp drives and wormholes