Energy researchers seek new directions after Alcator C-mod decommissioned

After 23 years of service, Alcator C-mod, MIT’s nuclear fusion reactor, was decommissioned on Sept. 30, 2016.

The reactor achieved record-breaking plasma pressures a day prior, thus yielding promising results for the future of fusion energy on its very last day of operation.

Earl Marmar, senior research scientist at MIT and head of the Alcator C-mod project, presented the results at the International Atomic Energy Agency Fusion Energy Conference in Kyoto, Japan this Monday.

Nuclear fusion requires great pressure and temperature in order to overcome the repulsion between positively-charged nuclei. Alcator C-mod is a tokamak, a reactor that uses a cage of magnetic fields to confine plasma twice as hot as the sun’s core. The scientists behind Alcator C-mod chose to use stronger magnetic fields to increase pressure and energy yield instead of increasing the size of the reactor itself.

On Sept. 30, the pressure inside Alcator C-mod reached over 2 atmospheres, or 15 percent higher than the previous record in 2005 and about 70 percent higher than pressures achieved by any non-Alcator device.

The results “validate the high-field approach,” Martin Greenwald, the deputy director of the MIT Plasma Science and Fusion Center (PSFC), said in an interview with The Tech. “In a sense, the plasma pressure translates directly to the fusion power density…  it demonstrates that we’re on the right track.”

Despite being slated for shutdown in 2013, funding for Alcator C-mod was extended in 2014 and 2015. The U.S. Department of Energy allocated over $22 million to the MIT tokamak as part of its 2015 Fusion Budget, but also stipulated that “fiscal year 2016 will be the final year of funding for Alcator C-Mod.”

The C-mod team had already been planning to end their experiments when they received initial news of funding cuts in 2012.

“We wanted to look beyond Alcator C-mod in any case,” Greenwald said. “It happened sooner than we wanted, but the machine did run for 23 years… In the end, it’s pushing us in the direction we want to go.”

DOE funds for fusion energy research will now go toward the construction of the multilaterally-funded International Thermonuclear Experimental Reactor (ITER) in Saint-Paul-lès-Durance, France. ITER is set to begin operations in 2027.

ITER has been many years in the making, but its construction has been delayed by frequent setbacks and financial difficulties. ITER is many hundreds of times larger than the MIT tokamak, but C-mod’s recent breakthrough showed that fusion can also be feasible in a small reactor.

“The argument is that by using higher field technology, we can build machines smaller and faster. We want fusion soon enough to make a difference,” Greenwald said. “That’s one of the worrisome things about ITER. It’s not just large, it’s taking a long time.”

With over 100 professors, students, scientists, engineers, and technicians participating in the project when it ended, the decommissioning of Alcator C-mod marks the end of MIT’s largest experiment at the time. The PSFC website states that Alcator C-mod has produced “a wealth of new and important results since the experiment began operation in 1993.”

The PSFC itself will remain in operation. Nuclear Engineering professor Anne White clarified that research, including Undergraduate Research Opportunities, will continue. Plans have been made to shift the focus of research toward improving superconducting and magnetic technology.

“You know, these machines, they come and go. You build them; you do research; they shut down,” Greenwald said. Although the PSFC is seeking federal funding for new experiments, he added, it is also exploring the idea of private funding, partially through the MIT Energy Initiative.

Despite the closing of its fusion counterpart, the MIT fission reactor (MITR) remains operational.

This Thursday, Oct. 20, at 1 p.m., the Alcator C-mod team will hold an Ask Me Anything (AMA) session at to answer questions about the recent record, the decommissioning, or fusion and reactor operation in general.