Spatial resolution in photoacoustic and thermoacoustic tomography is ultrasound transducer (detector) bandwidth limited. For a circular scanning geometry the axial (radial) resolution is not affected by the detector aperture, but the tangential (lateral) resolution is highly dependent on the aperture size, and it is also spatially varying (depending on the location relative to the scanning cent...

A cascade thermoacoustic engine is described, consisting of one standing-wave stage plus two traveling-wave stages in series. Most of the acoustic power is produced in the efficient traveling-wave stages. The straight-line series configuration is easy to build and allows no Gedeon streaming. The engine delivers up to 2 kW of acoustic power, with an efficiency (the ratio of acoustic power to hea...

Heat exchangers are of key importance in overall performance and commercialization of thermoacoustic devices. The main goal in designing efficient thermoacoustic heat exchangers (TAHXs) is the achievement of the required heat transfer rate in conjunction with low acoustic energy dissipation. A numerical investigation is performed to examine the effects of geometry on both the viscous and therma...

The goal of this study was twofold. First, modelling strategies were proposed to characterize the dynamics driving the thermoacoustic instabilities in a swirl-stabilized premixed burner. Secondly, this model was used to synthesize controllers in order to apply active control strategies to suppress this phenomenon. An experimental combustor model based on acoustic properties of the combustion ch...

Quantum technology promises revolutionizing applications in information processing, communications, sensing and modelling. However, efficient on-demand cooling of the functional quantum degrees of freedom remains challenging in many solid-state implementations, such as superconducting circuits. Here we demonstrate direct cooling of a superconducting resonator mode using voltage-controllable ele...

Please cite this article in press as: Burton JC doi:10.1016/j.cryogenics.2011.03.001 We have designed and constructed a continuously operating He cryostat with windows for laser ablation and spectroscopy. A two-stage pulse-tube refrigerator cools two platforms to base temperatures of approximately 40 K and 4 K respectively. The platforms are equipped with heat exchangers that cool separate stre...

Thermoacoustic instabilities can arise in systems where unsteady heat release is favorably coupled with acoustic pressure oscillations. A modified Rijke tube with segments having different sections is found to have lower threshold levels of heat addition rate needed for exciting the fundamental acoustic mode of the tube. Experiments indicate that about 115 W of heating power is required to prod...

There is a large promise for thermophones in high power sonar arrays, flexible loudspeakers and noise cancellation devices. The freestanding aerogel-like carbon nanotube sheet as a thermoacoustic (TA) heat source demonstrates so far the best performance. However, the limited accessibility of large size free standing carbon nanotube sheets and other even more exotic materials published recently,...

We developed a novel concept of using a negative acoustic lens to increase the acceptance angle of an unfocused large-area ultrasonic transducer (detector), leading to more than twofold improvement of the tangential resolution in both thermoacoustic and photoacoustic tomography. In both thermoacoustic and photoacoustic tomography, for a given transducer bandwidth, the aperture size of the detec...

A new acoustical sensing system for the nuclear power industry has been developed at The Pennsylvania State University in collaboration with Idaho National Laboratories. This sensor uses the high temperatures of nuclear fuel to convert a nuclear fuel rod into a standing-wave thermoacoustic engine. When a standing wave is generated, the sound wave within the fuel rod will be propagated, by acous...