What is a tokamak and how does it work?

In one line

The rule

A tokamak is a device that uses magnetic fields to confine plasma in a toroidal (doughnut-shaped) chamber for controlled nuclear fusion.

There is no single formula for a tokamak, but the main idea is:

• Magnetic force keeps charged particles moving in circles: F = q(v × B)
• Where F is the force, q is the charge, v is the speed, and B is the magnetic field.

Let's understand it simply

Imagine you want to make energy the way the Sun does—by smashing tiny particles together so they join and release a lot of energy. This is called nuclear fusion. But to do this on Earth, you need to heat gas to over 100 million degrees! At this temperature, the gas turns into plasma (a soup of free-moving electrons and nuclei).

Now, if you put this plasma in a normal container, it would melt everything. So, how do you hold it? Like how a cricket ball can be spun in the air using your hand, a tokamak uses strong magnets to hold and spin the plasma in a ring, without touching the walls. The shape is like a doughnut (a ring, or a tyre).

How it works

1. Plasma Creation: Hydrogen gas is pumped into the tokamak and heated until it becomes plasma (very hot, charged gas).
2. Toroidal Magnetic Field: Big coils around the ring create a magnetic field going around the doughnut (toroidal direction).
3. Poloidal Magnetic Field: Electric current is sent through the plasma itself, making another magnetic field that goes the short way around the ring (like a belt).
4. Magnetic Confinement: The two magnetic fields combine to twist and hold the plasma in the middle, away from the walls.
5. Heating: The plasma is heated even more using microwaves, particle beams, or by the current itself.
6. Fusion Reaction: When the plasma is hot and dense enough, hydrogen nuclei crash together and fuse, releasing energy (mostly as fast-moving particles and heat).

The story behind it

The tokamak was invented in the 1950s by Soviet scientists Igor Tamm and Andrei Sakharov, in Russia. They wanted to find a way to make controlled fusion, so we could have a nearly endless supply of clean energy. The word "tokamak" comes from Russian words meaning "toroidal chamber with magnetic coils."

One memorable detail: When the first tokamak results were shown in the 1960s, Western scientists did not believe them at first, because the results were so much better than other machines. But after visiting and checking, they agreed it worked!

Where you see it in real life

• ITER (France): The world's largest tokamak, being built by many countries, aims to show fusion can make more energy than it uses.
• EAST (China): A tokamak that has held plasma at over 100 million degrees for several seconds.
• K-STAR (South Korea): Another advanced tokamak, called the "Korean artificial sun."
• India's SST-1 (Gujarat): India's own tokamak, used for research and training.
• JET (UK): The Joint European Torus, which set records for fusion power.
• Medical research: The strong magnets in tokamaks are similar to those in MRI machines.

Why it matters

• Clean energy: Fusion makes no greenhouse gases and little radioactive waste—much safer than burning coal or nuclear fission.
• Unlimited fuel: The fuel (hydrogen isotopes) is found in water and is nearly unlimited.
• No meltdown risk: If something goes wrong, the plasma cools and stops—no big disaster.
• Future jobs: Engineers, physicists, and technicians will be needed to run and improve these machines.

Worked example

Let's see how a tokamak keeps plasma away from the wall:

Given: A plasma particle with charge q = 1.6 × 10⁻¹⁹ C, speed v = 1 × 10⁶ m/s, magnetic field B = 5 T
Step 1: Write the rule      F = q × v × B
Step 2: Put in the numbers  F = 1.6 × 10⁻¹⁹ × 1 × 10⁶ × 5
Step 3: Calculate           F = 8 × 10⁻¹³ N
Step 4: This tiny force bends the particle's path, keeping it in a circle inside the tokamak.

Common mistakes

• Thinking the plasma touches the walls: It does not—the magnetic field keeps it floating in the middle.
• Confusing fusion with fission: Fusion joins small atoms (like hydrogen), fission splits big atoms (like uranium).
• Believing fusion is already used for power: We are still testing; no power plants use tokamaks yet.
• Assuming magnets alone heat the plasma: Extra heating (like microwaves) is needed to reach fusion temperatures.

Remember it

A tokamak is a magnetic doughnut that holds super-hot plasma so we can try to make energy like the Sun.