>Does that mean that deuterium-tritium reactions need less energy for the reaction to start?
Yes and no.
Focusing on energy "needed to start" misses the key physics and related engineering issue.
When two fusion reactants (such as deuterium and tritium) collide, that vast majority of the time they do not fuse. Instead they scatter off of each other. This is true even if they have enough energy to fuse. The reactants only occasionally fuse when they collide. The specific reactivity is a measure of how often they fuse.
While the scattering collisions conserve energy, they lead to thermal conduction. Without some sort of thermal insulation, a fusion-ing plasma will cool off quickly and fizzle due to this collision induced thermal conduction. In fusion we call this insulation (energy) confinement.
So the key issue for engineering an economical fusion power plant is not providing enough heat to the fuel we can do this, but instead it's about building a good enough insulator to keep the plasma warm.
The more reactive the plasma, the more leaky the our insulator can be. It turns out the deuterium-tritium has the highest reactivity of all fusion fuels.
>Is that because tritium is less stable than the other isotopes?
It's complicated, but I'd argue is has more to do with He-4 being a very stable isotope. There are other factors, such a a relatively low coulomb barrier compared to high-Z reactants.
UWwolfman t1_iz0py64 wrote
Reply to comment by DoubleDot7 in Why not use hydrogen and deuterium in fusion reaction rather than tritium and deuterium? by Curious_user4445
>Does that mean that deuterium-tritium reactions need less energy for the reaction to start?
Yes and no.
Focusing on energy "needed to start" misses the key physics and related engineering issue.
When two fusion reactants (such as deuterium and tritium) collide, that vast majority of the time they do not fuse. Instead they scatter off of each other. This is true even if they have enough energy to fuse. The reactants only occasionally fuse when they collide. The specific reactivity is a measure of how often they fuse.
While the scattering collisions conserve energy, they lead to thermal conduction. Without some sort of thermal insulation, a fusion-ing plasma will cool off quickly and fizzle due to this collision induced thermal conduction. In fusion we call this insulation (energy) confinement.
So the key issue for engineering an economical fusion power plant is not providing enough heat to the fuel we can do this, but instead it's about building a good enough insulator to keep the plasma warm.
The more reactive the plasma, the more leaky the our insulator can be. It turns out the deuterium-tritium has the highest reactivity of all fusion fuels.
>Is that because tritium is less stable than the other isotopes?
It's complicated, but I'd argue is has more to do with He-4 being a very stable isotope. There are other factors, such a a relatively low coulomb barrier compared to high-Z reactants.