Reply To: Nuplex.

[BSFusion]

Jo…,

Continuing where I left off with my last post… In BSF, when the amplified blackbody radiation returns, it must either be reflected or absorbed at the bubbles periphery, since it cannot penetrate beyond the critical depth, which for hot, dense DT is only a fraction of a millimeter. The laser’s heat and pressure quickly create a powerful shockwave, capable of ionizing everything in its path. Light cannot penetrate beyond the highly ionized leading edge of this shockwave, so the absorption sight for any subsequent laser energy would have to travel outward with the shockwave. Complicating the situation further, an explosive phase transformation is expected to occur in the coolant that surrounds the fuel. The reason for this is that the central focus-point of the reactor gets very hot and the rate of spontaneous nucleation increases exponentially with temperature. It is known that the frequency of spontaneous nucleation is about 0.1 s^-1 cm^-3 at the temperature near 0.89 Tc (critical temperature), but increases to 1021 s^-1 cm^-3 at 0.91 Tc. This indicates that a rapidly heated liquid could possess considerable stability with respect to spontaneous nucleation up to 0.89 Tc, with an avalanche-like onset of spontaneous nucleation of the entire high temperature liquid layer at about 0.91 Tc. Therefore, at a temperature of about 0.9 Tc, homogenous nucleation, or explosive phase transformation occurs. This idea of explosive phase transformation has been applied to the process of laser glass cutting, which uses a 10.6 m m wavelength CO2 laser since glass is opaque in the mid-infrared region of the spectrum. These lasers can deposit, through partial transmission and absorption, a large fraction (90%) of their energy.

LASERS, by A. Siegman, says:

“…If the amplification along a long thin cylinder of inverted atoms is sufficiently large, for example, this can produce an output beam from each end of the laser medium which can be quite bright, powerful, and moderately directional, with a fair amount of spatial (but usually not temporal) coherence. This radiation may become strong enough to produce significant saturation along the gain medium, and to extract the major portion of the inversion energy into the directional beams. The inverted medium thus acts as a “mirrorless laser,” with output characteristics that are intermediate between a truly coherent laser oscillator and a completely incoherent thermal source.”

BSF depends on amplified blackbody emission ABE, which is more intense and localized than amplified spontaneous emissions ASE. The ABE from a high-temperature sonoluminescent bubble will quickly reach saturation (see figure 18), unlike ASE. In addition, because a medium’s saturation fluence goes down (due to thermal line broadening) with increased temperature BSF’s hot laser medium will diminish the amplification of ASE relative to ABE.

Spherical phase coherency of the laser should not be a problem for BSF. The reason I say this is that, the size of a sonoluminescent bubble is large (~1 cm dia.) compared to the predominant laser wavelengths (~1.06 +/- 0.005 micron for Nd3+), so, even when two waves (located near the desired absorption point) are temporally or directionally out of phase, it is likely that they will constructively interfere within a short distance, and this, in turn, might cause electrons in the vicinity to absorb their energy. The absorption band of laser energy at the start of a BSF implosion is expected to be about 0.4 mm thick, mostly coolant at the outer perimeter of the bubble, which gets heated to a temperature of around 90 eV. At this temperature most of the elements in the coolant will be ionized to the 4th level, and it is the expansion of this highly ionized coolant that drives the bubbles compression. Most of the pressure used to compress the fuel comes from the extra particles (electrons), since, at a given temperature, all particles acquire the same kinetic energy. In addition, since the acoustical pressures in the vicinity of the bubble would be extremely high, and since there is no vacuum for the fuel to squirt out into, I see no reason why BSF targets could not be imploded non-symmetrically.

[0085] An observation worthy of attention, is the fact that, because of spherical geometry, a ray of light inside the sphere has its path confined, bouncing on a single plane that it cannot leave. That plane is determined by the ray’s origin, the first point of reflection, and the sphere’s center. A close examination reveals that if a ray of light passes close to the center it will return after two reflections, revisiting the same approximate location. This observation appears prominently in the simulation results (figure 11), which show an unexpectedly high two-reflection reabsorption rate. This (high two-reflection reabsorption rate) improves the sphere’s overall energy retention ability, allowing off-center target ignition. Also, since there is extra leeway to position the fuel, a less stringent control system is required.