this post was submitted on 19 Feb 2025
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I didn't see any mention of the output in the article. 22MW injected, but does anyone know if the reaction was actually generating a positive output?
No magnetic confinement fusion reactor in existence has ever generated a positive output. The current record belongs to JET, with a Q factor of 0.67. This record was set in 1997.
The biggest reason we haven't had a record break for a long time is money. The most favourable reaction for fusion is generally a D-T (Deuterium-Tritium) reaction. However, Tritium is incredibly expensive. So, most reactors run the much cheaper D-D reaction, which generates lower output. This is okay because current research reactors are mostly doing research on specific components of an eventual commercial reactor, and are not aiming for highest possible power output.
The main purpose of WEST is to do research on diverter components for ITER. ITER itself is expected to reach Q ≥ 10, but won't have any energy harvesting components. The goal is to add that to its successor, DEMO.
Inertial confinement fusion (using lasers) has produced higher records, but they generally exclude the energy used to produce the laser from the calculation. NIF has generated 3.15MJ of fusion output by delivering 2.05MJ of energy to it with a laser, nominally a Q = 1.54. however, creating the laser that delivered the power took about 300MJ.
I wasn't aware of that distinction about the energy for the laser to generate the heat energy within the reaction not being factored into the Q value, very interesting, thank you! Would that energy for the laser still be required in a "stable reaction" continuously, or would it be something that would "trail off"?
In my experience the community will usually distinguished between "scientific Q" and "wall plug Q" when discussing fusion power gain. Scientific is simply the ratio of power in vs power out, whereas wall plug includes all the power required to support scientific Q. Obviously the difference isn't always clearly delineated or reported when talking to journalists...