Fusion News: Science Insider – Fusion “Breakthrough” at NIF? Uh, Not Really …
The BBC story reported that during one experiment last month, “the amount of energy released through the fusion reaction exceeded the amount of energy being absorbed by the fuel – the first time this had been achieved at any fusion facility in the world.” This prompted a rush of even more effusive headlines proclaiming the “fusion breakthrough.” As no doubt NIF’s press officers would have told reporters, the experiment in question certainly shows important progress, but it is not the breakthrough everyone is hoping for.
“It is a good experiment,” says Michael Campbell, a former director of NIF who now works for Logos Technologies in Fairfax, Virginia. “From a science standpoint, the target worked well enough for alpha particles to heat some of the fuel.” But Campbell is concerned about overhyping each step in what is bound to be a long haul toward fusion as an energy source. The energy yield in last month’s experiment is still a very long way from ignition, the goal—enshrined in NIF’s name—that the facility was expected to reach a year ago. NIF is now partway through a 3-year campaign to nail down why it is struggling to reach that goal. “It’s a science-based program now. They are trying to identify some of the obstacles to getting to ignition,” Campbell says.
One requirement for ignition is that energy output should exceed the energy input from the laser, i.e., that gain (output divided by input) should be greater than 1. NIF’s laser input of 1.8 MJ is roughly the same as the kinetic energy of a 2-tonne truck traveling at 160 km/h (100 miles/h). The output of the reaction—14 kJ—is equivalent to the kinetic energy of a baseball traveling at half that speed. Numerically speaking, the gain is 0.0077. The experiment “is a good and necessary step, but there is a long way to go before you have energy for mankind,” Campbell says.
