Physical Insights

An independent scientist’s observations on society, technology, energy, science and the environment. “Modern science has been a voyage into the unknown, with a lesson in humility waiting at every stop. Many passengers would rather have stayed home.” – Carl Sagan

A brief point about nuclear fusion devices.

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It’s a common misconception that controlled nuclear fusion in a device like a magnetic confinement reactor such as ITER requires you to heat the material up to a temperature of hundreds of millions of degrees.

That’s a little bit of a subtle issue, and in the context of the everyday, familiar notion of temperature, it’s kind of complicated. It’s a plasma temperature, an ion temperature. The Lawson product is minimised for a plasma temperature of 25 keV, for deuterium-tritium fusion, so that’s the optimum plasma temperature of the DT plasma in the reactor. Having such a plasma at such an effective temperature doesn’t really compare to materials being heated up in our familiar everyday experience.

In a colour TV, for example, (The CRT kind, not the newfangled kinds) the electrons are accelerated across a potential of approximately 25 kV – the electrons are accelerated to an energy of 25 keV, corresponding to a effective “temperature” of 290 million K. But clearly the TV tube isn’t heated up to a temperature of 290 million K in the conventionally familiar sense.

Written by Luke Weston

October 28, 2008 at 4:55 pm

Posted in fusion, physics

Tagged with ,

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