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  #21  
Old 08-10-2021, 01:55 PM
gary
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Originally Posted by xelasnave View Post
What I find curious is why it is a few light elements that give off energy and yet with heavier elements energy is required..could they be wrong about light elements giving off energy in fusion? Why the difference?
alex
Hi Alex,

In order to fuse the nuclei, you have to overcome the repulsive force
of the protons. Lighter elements can be more readily fused because there is less
protons and therefore less electrostatic repulsive force. It transpires
for these lighter elements when you fuse them you get an net energy gain.
That is, the energy it produces once you manage to fuse them is greater
than the amount of energy you had to put into getting them to fuse.
Once you get to iron it takes more energy to fuse them than you get out.

Best example is stars.

Tried and tested here on Earth in the form of thermonuclear bombs.
Bikini isn't just famous for skimpy two-piece beachwear.
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  #22  
Old 09-10-2021, 07:49 AM
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Originally Posted by gary View Post
Hi Alex,

In order to fuse the nuclei, you have to overcome the repulsive force
of the protons. Lighter elements can be more readily fused because there is less
protons and therefore less electrostatic repulsive force. It transpires
for these lighter elements when you fuse them you get an net energy gain.
That is, the energy it produces once you manage to fuse them is greater
than the amount of energy you had to put into getting them to fuse.
Once you get to iron it takes more energy to fuse them than you get out.

Best example is stars.

Tried and tested here on Earth in the form of thermonuclear bombs.
Bikini isn't just famous for skimpy two-piece beachwear.
Thank you Gary you have understood what I was trying to identify and now that you have explained it I really do not know why I could not have worked that out for myself as it is so obvious... right under my nose yet I did not jerry.

The stars yes which made me hesitant to even ask if they could be mistaken because if they were a new explanation for the Suns energy production would have been needed...I think I was really just trying to find out why the difference between light and heavy elements...

And again the existence of the hydrogen bomb and where it gets its extra clout would need a different explanation..

I expect very few people think of Bikini Atol but a lot think about the swim wear.

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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  #23  
Old 11-10-2021, 12:48 PM
gary
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Originally Posted by xelasnave View Post
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
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.
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  #24  
Old 12-10-2021, 03:29 AM
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Thanks Gary
Alex
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