Sound velocity measurements by x-ray shadowgraph technique for melting phenomena at ultrahigh-pressure regime.

Developments in measuring sound velocity of matter under ultrahigh pressure are described. We employed a time-resolved x-ray shadowgraph technique to measure the sound velocity of shock-compressed diamond and iron foils at around melt. The sound velocity significantly dropped at melting, a behavior that has been difficult to clarify by conventional measurements by subtracting particle velocity from shock velocity (u(s) - u(p)). In addition to sound velocity, other important parameters were also obtained simultaneously.

Experimental evidence of impact ignition: 100-fold increase of neutron yield by impactor collision.

We performed integrated experiments on impact ignition, in which a portion of a deuterated polystyrene (CD) shell was accelerated to about 600 km/s and was collided with precompressed CD fuel. The kinetic energy of the impactor was efficiently converted into thermal energy generating a temperature of about 1.6 keV. We achieved a two-order-of-magnitude increase in the neutron yield by optimizing the timing of the impact collision, demonstrating the high potential of impact ignition for fusion energy production.

Streaked x-ray backlighting with twin-slit imager for study of density profile and trajectory of low-density foam target filled with deuterium liquid.

Low-density plastic foam filled with liquid deuterium is one of the candidates for inertial fusion target. Density profile and trajectory of 527 nm laser-irradiated planer foam-deuterium target in the acceleration phase were observed with streaked side-on x-ray backlighting. An x-ray imager employing twin slits coupled to an x-ray streak camera was used to simultaneously observe three images of the target: self-emission from the target, x-ray backlighter profile, and the backlit target. The experimentally obtained density profile and trajectory were in good agreement with predictions by one-dimensional hydrodynamic simulation code ILESTA-1D.

Comprehensive diagnosis of growth rates of the ablative Rayleigh-Taylor instability.

The growth rate of the ablative Rayleigh-Taylor instability is approximated by gamma = square root[kg/(1 + kL)] - beta km/rho(a), where k is the perturbation wave number, g the gravity, L the density scale length, m the mass ablation rate, and rho(a) the peak target density. The coefficient beta was evaluated for the first time by measuring all quantities of this formula except for L, which was taken from the simulation. Although the experimental value of beta = 1.2+/-0.7 at short perturbation wavelengths is in reasonably good agreement with the theoretical prediction of beta = 1.7, it is found to be larger than the prediction at long wavelengths.

Ablative Rayleigh-Taylor instability at short wavelengths observed with moiré interferometry.

One of the most important quantities to be measured for better understanding of the ablative Rayleigh-Taylor (RT) instability is the growth rate in the short wavelength region at which the RT instability is significantly reduced. The short wavelength ( 4.7-12 microm) RT growth rates for direct-drive targets were measured for the first time by utilizing the innovated moiré interferometry [M. Matsuoka et al., Rev. Sci. Instrum. 70, 637 (1999)]. These growth rates were reasonably well reproduced by the simulation that solves the Fokker-Planck equation for nonlocal heat transport.

100 million refugees. The world stabilizes through population stability.

PIP: Global change has come about due to shifts in the business cycle, a new undeveloped paradigm to replace the Cold War, and a stabilization of expansion and development of modern industrial society. Japan has been transfixed with its own internal domestic affairs, but will feel the consequences of the Industrial Age nearing its end. Industrialization had relied on unlimited resources from the natural environment and the belief that a free-market economy would automatically lead to orderliness and a state of economic equilibrium. Population control has been an issue that has slid over the years as a priority status. In 1800, the population in developed countries was 4 times the population in developing countries; the reverse is becoming true. Mass migration was an unusual phenomena and not the problem it is today. There is a gap between population and productive capacity. Developed countries believed in humanitarian aid for refugees and impoverished peoples, but the numbers were unanticipated. There is no shame for war or civil unrest to drive boat people and hugh numbers to another country. The notion of nation state has changed. The boat people from Cuba were a beginning example of how governments were unconcerned about the loss of population. Afghanistan in 1979 was another example of refugees fleeing civil war. Iraq bombed the Kurds until there was no choice but to leave. Turkey was required to use troops to drive the Kurds back into Iraq. To increase aid indefinitely, or to send out more refugees than it takes in, or to use military forces to kill the invading refugees are not acceptable. An international framework with consensus from developed and developing countries is needed for dealing with mass migrations. Conventions adopted would have to be recognized as in each countries self-interest; disregard of the regulations would have to reflect significant disadvantages to a nation. Several issues are discussed as key in such a global framework: assuring productivity for all by absorbing some refugees, and developing new training programs for the private sector at home, and assuring development aid (technology, capital, markets). A self perpetuating cycle of growth and expansion must be set in motion. Infrastructure development must be replaced with stable employment in the home country.^ieng