First thing’s first: fusion is NOT fission. They both produce large amounts of energy, but fission splits heavy atoms while fusion combines lighter atoms. Fusion produces much less radioactive waste and unlike fission, a huge uncontrolled release of energy is virtually impossible.  But while fission is already used to generate electricity, fusion energy is an alternative energy source of the future. Scientists from all over the world, including some at our own Princeton Plasma Physics Lab, continue to pursue the perfect fusion reactor for the sole reason that if achieved, this energy source would be unparalleled in its potential for energy generation using raw materials harvested from water.


How a Tokamak works.

The basic idea for fusion is to shove together different types (or isotopes) of the very light hydrogen atom, called deuterium and tritium, producing a huge amount of energy.  But if atoms are tiny, how can it be that hard to push them together? The problem is that these atoms have centers (nuclei) that repel each other in normal conditions and like sworn enemies, cannot stand each other.  But when the heat is turned up at the party of a fusion reactor (to 100 million C, which is 6 times hotter than the inside of the Sun), these atoms start dancing faster and faster. Suddenly, the atoms are overcome by the heat of the moment, move past their initial repulsion, and hug it out. In other words, they collide head-on at high speeds and ultimately, fuse.  These collisions create colossal amounts of heat, which can then be harvested to produce commercial energy. Another plus? Deuterium, the main source of fuel, can be readily extracted from saltwater.The surface water on Earth alone can produce 10 million million tons of deuterium – good for a couple million years of energy.

The surface water on Earth alone can produce 10 million million tons of deuterium – good for a couple million years of energy.

But here’s the problem: while it’s not too hard to heat the fusion reactors to the required temperature, it’s a lot harder to sustain that temperature because particles that hit the walls cool the reactor down.  Currently, fusion can be sustained for short bursts of time, but it needs to be constantly re-ignited.  Scientists have tried to overcome this issue with creative reactor designs. A notable one is to crowd this reaction into a donut-shaped cage, called a Tokamak, and use magnetic fields to constrain the particles so that they won’t strike the walls.  Other tricks scientists are studying include neutral-beam injection, radio-frequency heating, and using a different shape like a stellarator. But experts agree that the limiting step for future progress is simple: money.  Since the beginning of fusion research, the amount of funding scientists estimated it would take to make a successful fusion reactor has never been fully raised.  With a lack of resources, there’s only so much scientists can do to build what is essentially a more efficient sun in a metal donut.


About The Author

Cissy Chen

Hi all! I’m Cissy, the current President of Innovation. I study computer science with interests in applied math as well. I like doing math puzzles, reading/writing poetry (I like to try at least), and playing piano. I’m also a big fan of green tea, oversized sweaters, and most other cuddly things. Come say hi at our board office hours or email me (cissyc@) if you ever want to get in touch! I’m excited to get to know all of our awesome staff members. :)