Study Cautiously Optimistic on Inertial Confinement Fusion

Breck Hitz

A Jason committee, working under a charter from the US National Nuclear Security Administration, has surveyed the inertial confinement fusion program at the National Ignition Facility at Lawrence Livermore National Laboratory in Livermore, Calif. In a report published in June, it concludes that all the critical technologies required for successful ignition experiments are likely to be in place by 2010.

In inertial confinement fusion, hydrogen nuclei are held in place by their own inertia while the energy to initiate fusion is supplied by a huge laser. Ignition occurs when the energy generated by the fusion reaction exceeds that supplied by the laser. The National Ignition Facility is the nation's leading research facility on the technology.

Although fundamentally optimistic, the Jason report is couched in cautious language. It notes that the success of initial attempts to achieve ignition in 2010 is "possible" but "unlikely." One potential problem is the relatively low laser energy (1 MJ) planned for the experiments. Nonetheless, according to the report, the National Ignition Facility has a "reasonable roadmap for progress toward ignition after the initial attempts," as the laser energy is ramped up to 1.8 MJ and other technologies advance.

In evaluating the program, the committee focused on progress in target fabrication and the associated cryogenic systems, and it assumed that the laser technology itself would be successful. In particular, it endorsed the choice of a beryllium fuel capsule shell, given anticipated advances in the technology. The greatest uncertainties, the committee found, are associated with the low laser energies planned for the initial experiments and with the possibility of deleterious laser-plasma interactions and/or implosion asymmetry. It recommended that computational analysis be significantly expanded to study these phenomena more thoroughly.

The committee is organized by the Jason Program Office of Mitre Corp. in McLean, Va. The program's mission is to conduct scientific and technical research and analysis in support of the US national security community with funding from the US government.