Exterior view of the Ignitor fusion reactor, whose core will be built in Italy and external housing built outside Moscow, where it will be installed.Image courtesy of Bruno Coppi
MIT-led Ignitor reactor could be the world’s first to reach fusion ignition and perhaps paving the way for eventual power production. Fusion ignition is the point where a fusion reaction becomes self-sustaining instead of requiring a constant input of energy. This reactor is a tokomak variant. It is several times smaller than ITER but with a stronger magnetic field.
Hasinger goes further in his scepticism of the IGNITOR reactor by questioning the feasibility of the whole project. Hasinger says that the IGNITOR team’s plan to heat the plasma mostly with a current, a process known as ohmic heating, will not work. ITER complements ohmic heating with two other methods of plasma heating — neutral-beam injection and electromagnetic waves. “We studied the possibility of a high-field ignition machine and came to the conclusion that relying on ohmic plasma heating has a very narrow corridor for success,” he says.
But Coppi refutes the criticism, saying that ohmic heating has been shown to heat plasma to higher temperatures than expected, and points out that IGNITOR has an alternative heating method known as ion-cyclotron resonant heating
According to a 2003 ENEA estimate, at least an additional €226 million will be needed to build IGNITOR, although neither Italy nor Russia have yet officially committed any funds to the project. Coppi claims that the costs will be lower. He hopes to have the machine built and working within 3–5 years and to have the first results immediately afterwards.
The concept for the new reactor builds on decades of experience with MIT’s Alcator fusion research program, also initiated by Coppi, which in its present version (called Alcator C-Mod) has the highest magnetic field and highest plasma pressure (two of the most important measures of performance in magnetic fusion) of any fusion reactor, and is the largest university-based fusion reactor in the world.
Ignitor would be about twice the size of Alcator C-Mod, with a main donut-shaped chamber 1.3 meters across, and have an even stronger magnetic field. It will be much smaller and less expensive than the major international fusion project called ITER (with a chamber 6.2 meters across), currently under construction in France. Though originally designed to achieve ignition, the ITER reactor has been scaled back and is now not expected to reach that milestone.