Nuclear fusion has been powering our sun for the past 4.5 billion years. Unlike fission — the process that powers our current nuclear facilities — fusion generates energy by fusing the nuclei of lighter atoms into heavier ones, and produces no long-term radioactive waste.

Imagine if we manage to replicate and miniaturize the process taking place in the core of stars. This would not only provide us a low-cost, clean and virtually limitless source of energy, it would also end our unsustainable reliance on polluting fossil fuels.

On Friday, researchers at the Massachusetts Institute of Technology’s Plasma Science and Fusion Center announced that they had achieved a key milestone — one that brings us closer than ever before to viable fusion reactors. The MIT team at the Alcator C-Mod tokamak nuclear fusion reactor set a new world record for plasma pressure at 2.05 atmospheres — 15 percent higher than the previous C-Mod record of 1.77 atmospheres set in 2005.

“This is a remarkable achievement that highlights the highly successful Alcator C-Mod program at MIT,” Dale Meade, former deputy director at the Princeton Plasma Physics Laboratory, who was not directly involved in the experiments, said in a statement. “The record plasma pressure validates the high-magnetic-field approach as an attractive path to practical fusion energy.”

For fusion to take place, there are two key factors that need to be kept at an optimum level — temperature and pressure. The plasma containing the nuclei, whose natural tendency is to repel each other, should be extremely hot — several times hotter than the sun’s core — and should be subjected to high pressures of more than 2 atmospheres.

The rate of fusion reactions quadruples every time the pressure is doubled — a factor that makes achieving optimum pressure key to creating a cost-effective and efficient fusion reactor.

In order to create and stabilize this dense and superhot plasma, C-Mod’s high-intensity magnetic field can create magnetic fields of up to 8 tesla, or 160,000 times the Earth’s magnetic field. In this particular experiment, the plasma produced 300 trillion fusion reactions per second and was contained through a 5.7 tesla magnetic field.

Alcator C-Mod is a tokamak — a doughnut-shaped device that can contain high-energy, plasma produced using relatively low and inexpensive magnetic fields. Another tokamak currently under construction in France — the International Thermonuclear Experimental Reactor — may achieve a plasma pressure of 2.6 atmospheres once operational, topping the MIT record.

“Compact, high-field tokamaks provide another exciting opportunity for accelerating fusion energy development, so that it’s available soon enough to make a difference to problems like climate change and the future of clean energy — goals I think we all share,” Dennis Whyte, the head of the department of nuclear science and engineering at MIT, said in the statement.