1. Fusion: Basic Principles, Current Progress and ITER Plans
MODIFIED FROM:
Mohamed Abdou
Distinguished Professor, Mechanical and Aerospace Engineering Department
Director, Center for Energy Science and Technology Advanced Research (CESTAR)
Director, Fusion Science and Technology Center
University of California Los Angeles (UCLA)
Plenary Talk presented at the 9th International Cairo Conference on Energy and Environment

2. What is Nuclear Fusion?
Nuclear Fusion is the energy-producing process taking place in the core of the Sun and stars
The core temperature of the Sun is about 15 million °C. At these temperatures hydrogen nuclei fuse to give Helium and Energy. The energy sustains life on Earth via sunlight

3. Energy Released by Nuclear Reactions
Light nuclei (hydrogen, helium) release energy when they fuse (Nuclear Fusion)
The product nuclei weigh less than the parent nuclei
Heavy nuclei (Uranium) release energy when they split (Nuclear Fission)
The product nuclei weigh less than the original nucleus

4. Energy Released by Nuclear Fusion and Fission
Fusion reactions release much higher energies than Fission reactions

5. Fusion Reactions
Deuterium – from water (0.02% of all hydrogen is heavy hydrogen or deuterium)
Tritium – from lithium (a light metal common in the Earth’s crust)
Deuterium + Lithium → Helium + Energy
This fusion cycle (which has the fastest reaction rate) is of interest for Energy Production

6. Plasmas
A Plasma is an ionised gas. A mixture of positive ions and negative electrons with overall charge neutrality
Plasmas constitute the 4th state of matter, obtained at temperatures in excess of 100,000 degrees
Plasmas conduct electricity and heat

7. Self-Sustaining or ‘Ignited’ Plasmas
Deuterium – tritium fusion reaction:
D + T → 4He + n + Energy
The 4He nuclei (‘a’ particles) carry about 20% of the energy and stay in the plasma. The other 80% is carried away by the neutrons and can be used to generate steam.
Plasmas become Self-sustaining or Ignited when there is enough a power to balance losses from the plasma
In stars plasma particles (including a’s) are confined mainly by gravity and high plasma densities achieved
On Earth:
hot dense plasmas can be confined in Magnetic fields (Magnetic Confinement Fusion)
superdense plasmas can be obtained by imploding solid deuterium-tritium pellets (Inertial Confinement Fusion)

8. Fusion in the Sun
Hydrogen fuses to form helium and 2 positrons and lots of energy.

9. Further fusion makes heavier elements (but not heavier than iron in our sun – it’s too small…)
Once Fe (iron) is reached, no more fusion can occur in stars up to about 5 – 10 times the size of our sun.

10. Larger Elements Than Iron
There are lots of elements heavier than iron.
These are formed in supernovae.
Supernovae occur in extremely large stars Generally speaking, they implode and then explode, sending these larger molecules across the universe.
Later, gravity pulls them back together in large masses which can eventually become solar systems.

11. So, how do billions of atoms of one element get back together after being scattered across the universe?

12. The answer is gravity first, then density.
By gravitational pull all of the elements come back to together in large masses (planetary nebulae which eventually become planets – take astronomy for the details.
In hot molten rock (which was present for developing planets), denser atoms sink to the center, less dense atoms stay near the surface.
Just as if you place oil and water in a container, the water ends up with the other water, and the oil with the other oil.

13. Core is Mostly Iron
So, if the core is mostly iron and gold is more dense than iron, where is most of the gold on Earth?
If gold is there, how have we found it in the crust?
The answer is meteorites.