Hi there fusion enthusiast.
In most fusion reactions, there are actually several working methods, you start with cold fuel and then heat to crazy temperatures. It takes so much heat or voltage to start the reaction and much of the heat are lost and neutrons when they appear.
Wouldn’t it be a good idea to surround the reaction place with fuel. The reaction take place in a narrow volume and that volume gets very hot after a time and if it’s D-D or D-T reaction it throw out lots of neutrons to. The plasma/fuel that surrounds the volume also get hotter and maybe absorbs neutrons also. It doesn’t get so hot as the reaction volume and the further away you go the cooler it gets. After a while the reaction device use very hot plasma as fuel and a little cooler plasma takes it place when a portion of plasma has react. Say if the nearest plasma is 80 milj kelvin and 100 milj kelvin is needed for reaction there is not much voltage or energy needed for ignition.
Everything could be kept in a big cylinder, probably with magnets on outside to keep the plasma from the walls. A cylinder must be the simplest shape to elaborate with magnetic and electrical fields. There would be a great temperature gradient from 100 milj Kelvin, se above, in the narrow core to just about 10 000 Kelvin at outer part of the plasma. Must of all, radiation and neutrons would be absorb and used as a heat source. Heating the plasma and gradually rise it’s temperature, that’s are about to ignite sooner or later.
Do you get anything out of it then? Of course. First of all take the reactant products out. Could you use them as a direct electric source good, do so. Probably you can take out some of the hot plasma to use, without cooling the process to much. If not it cold get hotter and hotter to know what happens. You could use next hottest plasma in a heater or in a gas turbine or you could maybe in use it in a reversed accelerator to make electricity.
If anyone think I invented a Perpetum Mobile calm down. It’s just a more effective approach I hope. It can’t get more heat than the reactions give – what it takes to ignite. Also it’s a why to keep the reactions going without risk that it blows out. By the way one advantage of the Tokamak is that the plasma in there get kind of reheated after a while.
A few comments:
1) the notion of pre-heating the fuel a pinch device is being tried right now at Sandia National Lab. It is call MagLif.
2) The neutrons from fusion, D-D or D-T, are such high energy that they will pass through a plasma of sustainable volume. Even ITER cannot contain its neutrons and it is many times larger than a pinch. The same is true for a NIF fuel pellet that is extremely dense but small.
3) Preheating a plasma in a pinch is not a positive attribute. You want cold fuel to start with. If the fuel is hot, it is difficult to compress to even higher temperatures as radiation becomes an important loss mechanism. Even pre-heating at MagLif is only 100 eV at most. Pre-heating is also an energy intensive process. It might cost more than it benefits.
Comments on comments
1. What I mean with preheating is very different from what MagLif do. I mean that the core volume leak heat to the surrounding volume. Maybe hard to describe without a drawing, but I don’t give that now. Much better to leak heat passively then make electricity with losses and then heat the fuel.
2. The neutrons are annoying, but if they leak some heat to the fuel around it’s of some use, no matter how that happens. I’m not sure yet how they work, but if they hit an nuclei a big part of there energy should be transferred. I see them as small very hot and fast objects, why they should radiate a lot on their way out of the cylinder. Maybe a few of them even gets absorb by deuterium but that’s quite rare. Am I wrong, well frankly I’m not sure, but even if the heat from them can’t preheat the fuel other reaction products definitely can.
3. If a pinch process is best or another I have not decide. The important is to use some of the excess heat for the reaction. You could of coarse use electricity solely to every reaction period, but that has big drawbacks I mean. Efficiency is not yet enough in any method used so far. Should you really do a energy-balance from fuel to light in your light bulb, no method is even near to give an excess energy. Using heat directly in the process is at least twice as god as using electricity from the grid. In longer or more continues process like the Tokamak the cooling is so great it’s more or less blow out the reaction. Not good at all.
4. The way of preheating I suggest, gives small losses. You can almost see it as an insulated volume. In such a volume the temperature gradually decrees from the worm core to the colder surface. I can also mention an example. I was working with a sandbox that was about 1000 K in the core and 400 K at surface. The paint shop pumped in fumes from the paint shop into the sandbox to burn the fumes. They contained a lot of flammable and poison substances but also much air. To much to burn the substances, but in the box they burned well. It was very important to keep the heat in the box and preheat the fumes to run the burning. That’s quite similar to what I mean with preheat the fuel.