Reply To: Nuplex.

[BSFusion]

Jo…, the links you posted are irrelevent. Prosperetti’s theory, pertaining to how stable single bubble sonoluminescence occurs, has been discredited; high speed cameras have recorded the phenomena and show that no liquid jets are present. In addition, BSF does not rely on stable oscilating bubbles, after one big acoustic squeeze, the fuel is laser-heated (~1,000,000 K) and then compressed using Andrei Sakharov’s notion of ionization compression.

“The high compression of a small bubble of fluid is similar to the explosive compression of a pellet of material by laser beams, one of the methods proposed for creating nuclear fusion, which has not been very successful. Prosperetti and others think that it is impossible for a bubble to maintain a perfectly spherical shape as it compresses, with either the laser or acoustic compression method, ruling out the high temperatures required for nuclear fusion.”

AFAIK, NIF scientists are still predicting ignition by 2013, and, contrary to predictions which claim a converging shock is always unstable, H. B. Chen of IBM T. J. Watson Research Center, in an article titled “The Rayleigh-Taylor and Imploding Shock Wave Instabilities in the Spherical Pinch”, found that the growth rate of perturbations was not exponential and that spherically imploding shock waves are relatively stable near the collapse phase of the shocks.

The initial stage of bubble collapse is slow and isothermal, during which the energy deposited in the bubble interior is readily transferred to the surrounding liquid via thermal conduction. As the speed of collapse increases the interior of the bubble undergoes compressional heating and becomes increasingly adiabatic due to the rapidity of the bubble collapse.

Sonoluminescence is now a well understood phenomena, unrelated to fusion. The spectrum of light emitted by a sonoluminescent bubble is extremely well fit to the spectrum of a blackbody. When a bubble is heated through adiabatic compression, the radiation of electrons (ie. a bremsstrahlung plasma) becomes thermally equilibrated in the opaque medium at the bubbles perimeter such that only the blackbody surface emission is observed for strongly driven bubbles.

In Journal of Fluid Mechanics 1998 “Analysis of Rayleigh-Plesset dynamics for sonoluminescing bubbles,” it was suggested that the ideal fluid for creating a violently collapsing but surface-stable bubble should have a low surface tension and a high viscosity… other suggestions capable of up-scaling the collapse intensity would be to use lower driving frequencies and/or larger ambient pressures at the same Pdriver / Pambient. BSF already incorporates several of these suggestions into its physical design, and its operational methods can incorporate the rest. In addition, because of the high ambient temperature inside of a BSF reactor, higher post-compression temperatures should be possible. Taken altogether, it should be easy to create a luminous burst of sufficient strength to trigger the necessary outgoing laser cascade.

Recent experiments conducted by the University of Illinois at Urbana-Champaign indicate temperatures of at least 20,000 K, in an oscillating bubble, but higher temperatures could be achieved, if the bubble was not required to be trapped and oscillating, by one powerful squeeze. In this method of Single Cavitation Bubble Luminescence (SCBL) the number of emitted photons per flash and the pulse duration are both much greater than in Single Bubble Sonoluminescence (SBSL). Another advantage of SCBL over SBSL is that SCBL bubbles can be about a thousand times bigger (radius = ~3 mm) and take a hundred times longer (~100 microseconds) to collapse. Under low driving pressure, the presence of a noble gas in the bubble was found to be crucial for producing stable high-intensity light emissions. Without the noble gas, there was a low temperature ceiling, of about 6000 K, most likely the result of molecular disassociation, H2 + energy -> 2H, inside the bubble. It takes energy to break bonds, and the noble gases have none. Under driving pressures from 1.9 to 3.1 bar, the observed emission temperature ranges from 6200 K to 9500 K. The temperature also increases if monatomic gasses are dissolved inside the bubble, such that higher temperatures are achieved by heavier Nobel gasses.