AAWSAP DIRD, High-Frequency Gravitational Wave Communications, April 2010

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DDl.4.3 Selection of appropriate microwave absorbing material at around 10GHz;
design of the interior baffles around the Gaussian beam, and a "tunnel" between
fractal-membrane reflectors and receivers (Baker, Stephenson and Li, 2008). A
computer program for ray tracing of the PPF and the BFF will be developed and utilized
for the baffle design. An analysis will be made of the latest technology reported by
Chan et al. (2006), Landy et al. (2008), and Yang et al. (2008), and these will be
compared with those available from established suppliers of current technology high
performance microwave absorbing materials including ARC Technologies, Inc. (San
Diego, California), Millimeter Wave Technology Inc. (Passaic, New Jersey), Cuming
Microwave (Avon, Massachusetts), and many others.
DDl.5 Detection Receivers
Design of the microwave receivers (for the PPF) at each end of the detector
containment vessel, tunable around 10GHz: G.V. Stephenson (TSC), Dr. R.C. Woods
(LSU) + graduate student, Dr. R. M L Baker (TSC). Three possibilities have already
been identified for the technology to be used here, and specifications will be developed
for each option found suitable for use in the final design so as to enable a final choice to
be made.
DDl.5.1 Off-the-shelf microwave horn plus HEMT receiver: if tens to hundreds of
photons per sample are available then standard microwave horns may be used, coupled
to high electron mobility transistor (HEMT) amplifiers. This task will include a sensitivity
analysis of this receiver type to determine the suitability of this approach, and a
conceptual design will be developed using off-the-shelf components. Now highly
developed, HEMT technology has previously been found reliable enough to use in the
receivers for differential microwave radiometers (DMRs) flown in the NASA cosmic
Background Explorer (COBE) satellite mission.
DDl.5.2 Rydberg-Cavity Receiver as developed at Kyoto University (Yamamoto et
al., 2000): Rydberg atoms are excited atoms with one or more electrons that have a
much higher principal quantum number than ground state, usually conditioned via laser
pumping. The low binding energy of the excited electrons leads to very low
photoionization energy; therefore, Rydberg atoms are sensitive to low-energy
microwave photons, and allow a microwave device somewhat analogous to a
conventional photomultiplier tube to be constructed. When a microwave photon strikes
a high cross-section Rydberg atom, it causes the electron to be ejected and the atom is
ionized. If a large electric field is established within the container, the electron is
accelerated, causing cascading impact ionization. The advantage of this receiver is that
it is sensitive to low-energy single-photon events, and has very good time resolution .
The disadvantage is its cost and complexity. This task will include a conceptual design
of an alternative Rydberg atom receiver apparatus suitable for the PPF arising from
HFRGW, and will also include a sensitivity calculation of the proposed apparatus.
DDl.5.3 Circuit QED microwave receiver as developed at Yale University (Schuster
et al.,2007): a third option will also be explored, the Circuit QED microwave photon
receiver. A resonant co-planar waveguide, containing a Cooper Pair Box (CPB) in the
center and delineated by Josephson junctions, define a photo-sensitive area in the
center of the cavity. The cavity qubit energy levels shift when the cavity encounters a
microwave photon. The advantage of this type of receiver is that it is very sensitive to
individual photons and can integrate multiple photons over time. It has the
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