Earlier this month, Lawrence Livermore National Laboratory (LLNL) announced to the world that they had achieved a record 1.3 MJ yield from a fusion experiment at their National Ignition Facility (NIF). Yet what does this mean, exactly? As their press release notes, the main advancement of these results will go towards the US’s nuclear weapons arsenal.

This pertains specifically to the US’s nuclear fusion weapons, which LLNL along with Los Alamos National Laboratory (LANL) and other facilities are involved in the research and maintenance of. This traces back to the NIF’s roots in the 1990s, when the stockpile stewardship program was set up as an alternative to nuclear weapons testing. Much of this research involves examining how today’s nuclear weapons degrade over time, and ways to modernize the existing arsenal.

In light of this, one may wonder what the impact of these experimental findings from the NIF are beyond merely ensuring that the principle of MAD remains intact. To answer that question, we have to take a look at inertial confinement fusion (ICF), which is the technology at the core of the NIF’s experiments.

Everything Is Better With Lasers

ICF is one of the two main branches of fusion research, the other being magnetic confinement fusion (MCF) which includes today’s tokamaks and stellarators. Much like with the initial optimism in MCF and the crushing disappointment when Z-pinch fusion turned out to be unworkable, ICF has had its own share of disappointments. Although it was initially regarded to be a practical way to produce power from fusion, it soon turned out that the power requirements to initiate (ignite) fusion were much higher than estimated, and far less easy to achieve.

MCF found a second life in the form of tokamak and stellarator research, which were more complicated, but promised solving the Z-pinch issues, in particular the plasma instabilities. ICF got a fresh start with the invention of powerful lasers, which might be powerful enough to heat fuel and initiate fusion. This process involves subjecting a sphere of fuel uniformly either directly to laser energy (direct drive), or indirectly (indirect drive).

LLNL has been involved in ICF since the 1950s, but only in the 1970s with the advent of more powerful lasers could the first high-power experiments take place. These included the Shiva laser in 1978 and the Nova laser starting in 1984. Both of these laser systems failed to achieve ignition and only got middling results, mostly due to variations in the laser beam’s irradiation.

Despite a funding crunch for fusion research in the …read more

Source:: Hackaday