Questions and Answers on Nuclear Fusion

I try to keep questions submitted by groups as the are. Unclear or trivial questions are not replied. Reply has not been proof read.

Q
Muon catalyzed fusion
There has been a little research in Muon Catalyzed Fusion but it has not been considered a very plausible possibility for commercial fusion power. Do you think the Muon Catalyzed Fusion is a credible possibility? Do you think that with other technologies, it could be the way for us to obtain commercial fusion power? If so, why do you think that Muon Catalyzed Fusion has not been researched further?
A
Muon catalyzed fusion will not have much benefit because muon is very unstable and the technology will be very expensive.

Q
Neon plasma
How are the plasma contained in neon lights?
A
Neon plasma has low temperature, and they are contained in glass tubes.

Q
Plasma and fusion
Why isn't there nuclear fusion taking place in cold plasma?
What is plasma leakage and how does this occur?
Why does the removal of the formed nuclei from the plasma help to maintain a high efficiency of fusion?
A
Ion speed is too slow in cold plasma to make nuclei to approach each other at fusion distance.
Plasma leakage loses energy, and the plasma cools and leaks out of the confinement.
Remove nuclei increases the efficiency of collision leading to fusion. Collison with fusion product nuclei will not lead to fusion.

Q
Fusion for energy supply
Do you believe that in the future nuclear fusion will be used to satisfy more of the world's energy needs than nuclear fission? If so, how far into the future do you predict this will occur?

How close in the future do we see ourselves utilizing nuclear fusion in energy production?
A
To achieve chain fusion to contineously supply has a long way to go. Unless breakthrough come soon, 30-50 years is still a speculation.

Q
Tokamak
What is the structure of a Tokamak torus and what properties make it superior to other torroids?
A
The Tokamak has the shape of a torus as described in the lectures. I think the magnetic field of the D-shape coil makes a difference compared to the UK and US designs.

Q

What is a white dwarf? How long does it take to generate the different energies in stars and which reaction is responsible for this reaction? Fusion or Fission?
A
White dwarf is a stage of the life of a star. The surface temperature is lower than that of a star, and light intensity from a white dwarf is also low. The time for each stage of the life of stars depends on the mass.

The White Dwarf Coorperation gives this definition:

A white dwarf is a type of star that contains about as much matter as the Sun, but packed into a size comparable to the Earth. The majority of white dwarfs are thought to be made mostly of carbon and oxygen.
In stars like the Sun, the inward pull of gravity is balanced by the outward push of the high-temperature hydrogen in the center fusing into helium and releasing energy in the process. There is no nuclear fusion in a white dwarf. Instead, the force that opposes gravity is called "electron degeneracy pressure".

Q
Cold fusion
Why is cold fusion possible? If cold fusion were to be realized, what products would we see? Would that be an environmentally friendly electricity source?

S. Pons and M. Fleischmann announced excess heat was generated when they electrolyzed heavy water. The heat has melted their electrodes and they attributed the heat to fusion. What are their reasoning to conclude this is a fusion reaction?
Cold fusion refers to fusion reactions taking place at room temperature rather than at some millions of degrees. If cold fusion is possible, what are some feasible factors or conditions that would cause such reaction?
A
Cold fusion may be possible. The fact that it's not observed does not mean impossible. On the other hand, cold fusion has not been confirmed yet. Since cold fusion has not been confirmed, we have to keep an open mind for its product. The product may be 4He or 3He. for D + D fusion. For others, I will not speculate.

Pons and Fleischmann believed in conservation of energy. Since there is no other source of energy, they suggested fusion. There are other explanations, but not conclusive due to lack of evidence.

Discovery is part of science, and explanation is offered usually after the discovery. At this point, I really do not want to speculate on factors affecting cold fusion.

Q
Fusion temperature
On page 283, it says that to achieve controlled thermonuclear reaction, the temperature must be of 100,000,000 K or higher. However, on page 282, it says that deuteron-triton reaction only requires an ignition temperature of 40,000,000K. Our question is: which one is the lowest temperature required to achieve controlled thermonuclear fusion?
A
Fusion temperature is not a definite number, because the fusion probability is higher at higher temperature. Ignition temperature may not be able to sustain a chain reaction to continue the fusion process. Thus, some estimates are given. To achieve controlled fusion requires technology to maintain the plasma at higher temperature than simply start seeing fusion reaction.

Q
Fusion reactor
What is the efficiency current fusion reactors?
A
There is no fusion reactor to produce energy yet. So the efficiency is negative. Fusion research reactors consume much energy, but produce non. Break-even fusion experiments may claim a efficiency of 0%, because these consume as much as it produces.

Q

2X + 3T = 4He + n + 17.6 What is X in the above equation?
A
X is apparently D for deuterium.

Q
Fusion and environment
If a Fusion reactor could ever be feasible created, would it be safe and environmentally sound, or would it offer the same risks as a fission reactor?
A
There is certainly risk in fusion reactors. The structure becomes radioactive. Is there a technology that is really environmentally sound, not really. However, the media and the public often dreamed of fusion as the perfect technology for energy production.

Q
Particl beam fusion
It would seem as though inertial confinement fusion reactions would be relatively straight forward to provide a continuous supply of fuel to through the addition of a continuous, focused plasma stream. Why can't the use of particle beams be substituted for laser energy once the fusion reaction has been initiated? Would they not provide both a source of fuel, and if injected with proper geometry and velocity, also provide the necessary confinement to sustain the reaction as well?
A
This question is well phrased and thoughtfull.

Particles have to travel in vacume but not laser beams. Early investigation of fusion uses particle beams to strike at frozen target. Therefore, the tehcnology of particle-collision fusion is already known. I guess the number of fusion by particle accelerator is still small, and the amount of energy harvested is limited. Since a lot of energy is still required to accelerate the particles, making it economical is still very difficult.