Why don't Tokamaks blow up whenever they lose confinement?

[nlieb]

I haven't been able to find an answer to this anywhere. Suppose there's a quench in a coil at a tokamak and confinement is lost. I understand that there is no longer anything keeping the fusion going, but it seems to me that the plasma should still have enough inertia that, however momentarily, fusion would continue occurring, and the whole thing would go off like an h-bomb. Obviously this doesn't happen. Why?

 

[jedishrfu]

The plasma hasn't reached fusion density yet when the containment is lost hence it doesn't fuse. It is resisting being compressed to that density and squirts out of the containing magnetic field.

 

[raining Pete]

Hi there,

That's a really interesting question! From my understanding, a quench in a tokamak coil means that the magnetic field that is responsible for confining the plasma has suddenly collapsed. This results in the plasma expanding and losing its density and temperature, which are essential for fusion reactions to occur.

Even though the plasma may have some inertia, it's not enough to sustain fusion reactions without the strong magnetic field. Additionally, the plasma is also losing its energy through radiation and collisions with the walls of the tokamak, further preventing it from sustaining fusion.

So while there may be a brief moment of fusion occurring, it quickly dissipates due to the loss of confinement and other factors. It's important for tokamaks to have reliable and robust magnetic fields to prevent these quenches and maintain stable fusion reactions.

I hope that helps answer your question!