Quote:
Originally Posted by xelasnave
Thinking casually about the prospect of creating a fusion power plant it occurred to me that the thing missing, that is plentiful on the Sun is gravity.
To replicate that energy (required for containment) I expect that is where the magnets come in...and so to power those magnets I expect the Sun does not have that issue as it has 'free' gravity...sorry about my clumsy explanation...do you see what I am trying to "say"?
Alex
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Thanks Alex,
In addition to that, in order to to provide hydrogen atoms enough energy to
overcome repulsion between the protons, fusion requires extremely high
temperatures, over 100 million degrees Celsius (10keV).
So the challenge on Earth is to engineer a vessel that contain this
extremely hot plasma. That is where the 'tokamak' comes in.
It uses powerful magnetic fields to confine the plasma in the shape of
a torus, lest it touch the walls of the machine.
By definition, these extremely hot, high energy ions and electrons in the
plasma have correspondingly high velocities. If they aren't confined, they
rapidly cool. It transpires that the geometry of circulating them with a
toroidal solenoid is a geometrically convenient shape that exploits the
geometry of magnetic fields.
Tokamaks aren't the only type of fusion plasma magnetic containment
devices, but after decades of experimentation it is the one those in the
field bet on giving the best chance of success in the experimental ITER
device.
Stars are self-contained fusion reactions that are free-standing in
space holding their plasma together with gravity. The gravity creates
a inward force and the energy from fusion and outward force in a balancing
act. If the star is sufficiently large, as it fuses heavier and heavier
elements together advancing up through the periodic table, it will
eventually undergo gravitational collapse.
Plans are already underway for the successor machines based on the
outcomes of ITER referred to as DEMO (short for Demonstration Power
Plant). 15% larger than ITER, they are being designed to deliver
2 gigawatts of fusion power on a continuous basis and the goal is to
have them in operation around 2050.