Researchers at the National Ignition Facility (NIF) who collaborated with the Department of Energy's Lawrence Livermore National Laboratory, report that there is at least one significant obstacle to overcome before achieving the highly stable, precisely directed implosion required for ignition, but they have met many of the demanding challenges leading up to that goal.
To reach ignition, the NIF focuses 192 laser beams simultaneously in billionth-of-a-second pulses inside a cryogenically cooled hohlraum - a hollow cylinder the size of a pencil eraser.
Within the hohlraum is a ball-bearing-size capsule containing two hydrogen isotopes, deuterium and tritium (D-T). The unified lasers deliver 1.8 megajoules of energy and 500 terawatts of power-1,000 times more than the United States uses at any one moment-to the hohlraum creating an "X-ray oven" which implodes the D-T capsule to temperatures and pressures similar to those found at the center of the sun.
John Edwards, NIF associate director for inertial confinement fusion and high-energy-density science, said what they want to do is use the X-rays to blast away the outer layer of the capsule in a very controlled manner, so that the D-T pellet is compressed to just the right conditions to initiate the fusion reaction.
He said that in their arcticle they reported that the NIF has met many of the requirements believed necessary to achieve ignition-sufficient X-ray intensity in the hohlraum, accurate energy delivery to the target and desired levels of compression-but that at least one major hurdle remains to be overcome, the premature breaking apart of the capsule.
The new study has been published in the journal Physics of Plasmas.
--ANI (Posted on 26-09-2013)