托卡马克^[1][2]（俄语：Токамак，罗马化：Tokamak）又译托克马克，或称环磁机，是一种利用磁约束来实现磁约束聚变的环性容器。达到稳定的等离子体均衡需要围绕环面移动的螺旋形状的磁力线。

托卡马克是磁约束装置的几种类型之一，并且是用于生产受控热核核聚变能中的一个最深入研究的候选类型。磁场被用于约束是因为等离子体冷却会使反应停止。而超导托卡马克可长时间约束等离子体。世界上第一个超导托卡马克为俄制的T-7（托卡马克7号）。另一种托卡马克的一种替代方案是仿星器。

托卡马克最初是由位于苏联莫斯科的库尔恰托夫研究所的物理学家伊戈尔·塔姆，安德烈·萨哈罗夫，和列夫·阿齐莫维齐等人在1950年代发明的。

Inertial Confinement Fusion: How to Make a Star

The idea for the National Ignition Facility (NIF) grew out of the decades-long effort to generate fusion burn and gain in the laboratory. Current nuclear power plants, which use fission, or the splitting of atoms to produce energy, have been pumping out electric power for more than 50 years. But achieving nuclear fusion burn and gain has not yet been demonstrated to be viable for electricity production. For fusion burn and gain to occur, a special fuel consisting of the hydrogen isotopes deuterium and tritium must first “ignite.” A primary goal for NIF is to achieve fusion ignition, in which the energy generated from the reaction outstrips the rate at which x-ray radiation losses and electron conduction cool the implosion.

All of the energy of NIF’s 192 beams is directed inside a gold cylinder called a hohlraum, which is about the size of a dime. A tiny capsule inside the hohlraum contains atoms of deuterium (hydrogen with one neutron) and tritium (hydrogen with two neutrons) that fuel the ignition process.

NIF was designed to produce extraordinarily high temperatures and pressures—tens of millions of degrees and pressures many billion times greater than Earth’s atmosphere. These conditions currently exist only in the cores of stars and planets and in nuclear weapons. In a star, strong gravitational pressure sustains the fusion of hydrogen atoms. The light and warmth that we enjoy from the sun, a star 93 million miles away, are reminders of how well the fusion process works and the immense energy it creates.

Replicating the extreme conditions that foster the fusion process has been one of the most demanding scientific challenges of the last half-century. Physicists have pursued a variety of approaches to achieve nuclear fusion in the laboratory and to harness this potential source of unlimited energy for future power plants.

See How ICF Works for a more detailed description of inertial confinement fusion.

Recipe for a Small Star

• Take a hollow, spherical plastic capsule about two millimeters in diameter (about the size of a small pea)
• Fill it with 150 micrograms (less than one-millionth of a pound) of a mixture of deuterium and tritium, the two heavy isotopes of hydrogen.
• Take a laser that for about 20 billionths of a second can generate 500 trillion watts—the equivalent of five million million 100-watt light bulbs.
• Focus all that laser power onto the surface of the capsule.
• Wait ten billionths of a second.
• Result: one miniature star.

In this process the capsule and its deuterium–tritium fuel will be compressed to a density 100 times that of solid lead, and heated to more than 100 million degrees Celsius—hotter than the center of the sun. These conditions are just those required to initiate thermonuclear fusion, the energy source of stars.

By following our recipe, we would make a miniature star that lasts for a tiny fraction of a second. During its brief lifetime, it will produce energy the way the stars and the sun do, by nuclear fusion. Our little star will produce ten to 100 times more energy than we used to ignite it.