External heating

The ways energy is put into a plasma from outside: driving a current through it, which heats it the way current heats a kettle element (ohmic heating); firing beams of fast neutral atoms into it (neutral-beam injection); or beaming in radio waves or microwaves tuned to the ions or the electrons. In laser fusion the laser plays this role. The heating power that reaches the plasma is the denominator of plasma gain. The electricity these systems draw is larger, because none of them is perfectly efficient, and only engineering and wall-plug gain count it. Sources also differ on whether they count power injected or power absorbed, which is one reason one JET shot from 1997 is quoted as both 0.63 and 0.67.

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concept:plasma-heating

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