Many people have asked where exactly FF-1’s results stand in relation to much better-funded efforts, such as the privately-funded Tri Alpha and General Fusion or the government-funded tokamaks. So we prepared these charts to summarize the present situation in the “fusion race.” The first chart compares the plasmas that each device creates, using a measure called n-tau-T. For net energy, we need three ingredients: enough temperature, T, to burn fusion fuels, enough time, tau, to confine the hot plasma, and enough density, n, to burn the fuel fast enough, since the burn rate increases as the square of density. Just multiply the three numbers together and you get n-tau-T the density-time-temperature product, a rough measure of how close the plasma is to the conditions needed for net energy.
Here, we plot the latest published results of various fusion experiments. Right now the best plasmas have been obtained with the new Chinese tokamak experiment, EAST, and the giant US laser facility NIF. In a second group, about a factor of ten lower, is the new German stellarator W7X, the JET tokamak in the UK and our own FF-1 in fifth place. Spread out a factor of hundreds to thousands below the second group are the other privately financed efforts, EMC2, Tri Alpha and General Fusion. These efforts are much better funded than FF-1 but at the moment have far cooler and less dense plasmas.
Another way to plot the same results is with the pressure-time product. Pressure is the product of density and temperature.
A better way to look at overall performance of these various devices is what is called ”wall-plug efficiency” —the ratio of the fusion output to the total energy put into the machine from the grid (the “wall plug.”) This combines how good the plasma is at producing fusion yield with how good the device is in getting energy into the plasma. For consistency we are comparing only results running with deuterium as a fuel, not the much more reactive deuterium-tritium mix.
Here the picture is different. The other private efforts drop out, as they don’t have measurable fusion yield from their machines (or in the case of EMC2 have not published any). NIF drops back to 4th place, because its lasers are extremely inefficient in converting input energy into plasma energy. FF-1 moves up to second place, nipping at the heels of JET, and EAST is in fifth. This is in part due to FF-1’s high efficiency in coupling electrical input into the plasmoid that produces the fusion.
Of course, if one is allocating resources, it also counts how much each research effort costs. In our view, all possible routes to fusion should be funded until one actually succeeds in producing a working generator. But it is worthwhile to see how much progress results from how much investment. In the chart below we just divide wall plug efficiency by the total cost of the projects to date to get “efficiency per billion dollars.” Here, we’re number 1. Since FF-1 has only cost $5 million since its inception, its efficiency per gigadollar is ten times that of EAST, a hundred times that of JET and a hundred thousand times that of NIF.
This is, to be sure, just a snapshot of the race to clean energy, one that can change radically in the future. Who knows? We might get to be first in all charts.