Questions tagged [fusion]

The fusion tag is used for questions about nuclear fusion, both the basic process at a physical level and it's use as a potential energy source.

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p+n reaction in nuclear fission reactors

There is a recent question (Proton - neutron fusion?) about the possibility of the fusion reaction $p+n$. According to @dmckee's answer, the reaction is possible, but not useful for fusion power ...
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Proton - neutron fusion?

In reviewing some problems in an elementary book, I ran across a reference to the reaction $p+n\rightarrow d$ + "energy". Is that possible? I don't see any reason why not, but I don't find any ...
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Why is hydrogen or helium used in nuclear fusion?

I am not a Physics student. Just out of own interest, I'm studying about fission and fusion reactions. Where I found in fusion, the scientist are using either hydrogen isotope or helium-3 as fuel (...
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Can Hydrogen Fusion via CNO Cycle Occur in First Generation Stars

CNO cycle requires the presence of carbon, nitrogen and oxygen to undergo hydrogen fusion. Does this mean that for first generation stars, no matter how big they are, can't undergo hydrogen fusion by ...
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Dangers of controlled fusion temperatures

I've been looking for an answer to this question for some time, and I apologize in advance for my lack of general knowledge on the subject matter. I can't wrap my head around how we can have ...
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Why can't two hydrogen atoms be slowly “pressed together” (fused to form helium) with some advanced device (not collided at high speed)?

I apologize for my lack of physics knowledge, and I won't be gaining much any time soon, since I'm focusing mostly on work and physical exercise. I can't help but wonder about this: Questions: ...
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Nuclear Fusion with extremely high pressure and low temperature

Theoretically, if we just create a high pressure with low (room 20C) temperature, at some point nuclear fusion can be started. Is there any research on this topic, how high should be this pressure ...
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A question about fusion and fission

https://www.youtube.com/watch?v=yTkojROg-t8 1) Watch till 0:20 "Then the binding energy is the amount of energy that takes to completely separate them" But the gravitational force between 2 masses ...
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198 views

How do stars survive their own gravitational pull?

I read that stars burn hydrogen and helium to fight against gravity. How does burning something help against gravity?
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Why is there a mass defect in nuclear fusion? [duplicate]

So I'm currently trying to wrap my head around nuclear fusion, but there is something that keeps bugging me: I've read in many places that when two hydrogen atoms combine, the resulting helium atom ...
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1answer
726 views

Why do only red dwarf stars have convective currents?

Stellar models indicate that red dwarfs less than 0.35 M☉ are fully convective.[3] Hence the helium produced by the thermonuclear fusion of hydrogen is constantly remixed throughout the star, avoiding ...
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How long does a positron last in the Sun's core?

Kicking off of this question, I have a short follow-up. The fusion of hydrogen into helium in the Sun's core requires the emission of two positrons per final helium nucleus, because we start off with ...
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How does our sun create positrons in it?

How does our sun create positrons? And does the sun emit said positrons after their creation? I read that the sun creates positrons at it's center but I couldn't find how they form. Is it a ...
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How are our enzymes able to perform quantum tunnelling?

The hydrogen protons undergo quantum tunnelling in the the sun to fuse into helium, but are only able to do so as they are under immense heat and pressure and the protons and electrons get separated. ...
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How much more mass would Jupiter have to accrete to start fusion? [duplicate]

How long would it take? Is it likely in the life of our sun?
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398 views

Does fusion continue to happen as a star collapses into a black hole (beyond our view)?

I know that we can't actually see a black hole form, because of time dilation, and we would see a frozen image just before the final collapse past the event horizon, slowly redshifting to nothing... ...
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In a fusion reactor like Tokamak, how is fuel injected without destroying the fuel injector? [closed]

Plasma temperatures in a tokamak are around 100 million C. Presumably for a power plant that will run for a long period of time, fuel will have to be injected and "burnt" products will have to be ...
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Why is Helium an anomaly on the binding energy curve?

So I'm failing to understand why helium is anomalous on the binding energy curve. I know it includes concepts such as pairing, shell correction, and the liquid drop model. However, these were simply ...
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How can matter be squeezed extremely dense [duplicate]

I'm fairly new to physics and currently reading A Brief History of Time by Stephen Hawking. Hawking is talking about black holes being the size of a few miles containing the mass of multiple times the ...
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Simulation of plasma in tokamak

I am reading some papers on numerical algorithms for simulation of plasma in the context of nuclear fusion in a tokamak. I am getting a little lost as there is a huge number of references, and it is ...
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3answers
101 views

Can we observe solar p-p fusion reaction somehow on Earth?

What are the properties of proton+proton fusion reaction $p + p → 2H + e^+ + ν_e + 0.42 MeV$ making it hard to replicate on Earth? If we aim beam of protons to a can of water, won't we observe ...
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What is the role of plasma in nuclear fusion energy production?

I read that confined plasma in electromagnetic field uses in TOKAMAK nuclear fusion reaction. But I don't know what is the main role of plasma in fusion reaction. Is it use for producing energy ...
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1answer
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Physics needed for a quite well understanding of nuclear bomb [closed]

I am an undergraduate student in physics and mathematics and one of my early dreams in physics was to understand the way nuclear weapons work. Is there a book which deals with the physics and the ...
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How much of fusion energy is positron-electron annihilation?

Stellar fusion involves protons becoming neutrons, which means ejecting a positron. Positrons annihilate electrons. This must deliver some energy in stellar fusion. But how much of the energy from ...
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Does nuclear fusion of light nuclei occur in fire or boiling water?

At the temperature range of ordinary fire or maybe even ordinary boiling water, is the Coulomb potential between light atomic nuclei occasionally overcome to give way to fusion? Basically, how are ...
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5answers
3k views

Could we use nuclear bombs to generate electricity? [closed]

it seems the biggest problem with fusion power is confinement. on the other hand, we developed a fusion bomb in just a few years. i was wondering if it could be economically viable to use nuclear ...
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Why only light nuclei are able to undergo nuclear fusion not heavy nuclei?

Is it because of the binding energy or the binding energy per nuclei . I am having trouble with this whole binding energy and nuclear fusion concept.
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How much energy does proton - carbon 12 fusion produce?

Page 25 of this document from the California Institute of Technology says that proton-carbon 12 fusion releases 7.54 MeV, while Wikipedia says it releases 1.95 MeV. Which one is correct?
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What would keep a hypothetical fusion reactor from “igniting the atmosphere”? [duplicate]

So in the early days of Nuclear fission, there was a concern about the resulting energy igniting the atmosphere in a ball of fire and world-wide death which is awesome terrifying awesomely terrifying. ...
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So how much fuel does a hypothetical fusion plant need?

Reading about potential fusion plants it's easy to get the impression that we have nearly infinite access to the fuels required. But looking aside form how much we have available, I am interested in ...
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1answer
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Why is a stellarator-type nuclear fusion reactor so oddly-shaped?

My first impression: It's a mess. Why is it shaped like that? I can't find any info about its shape other than it's a special arrangement of magnetic coils.
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Why did they start Wendelstein 7-X With Helium?

Just saw the first Hydrogen plasma at the Wendelstein reactor. I haven't found anywhere that gives a good explanation as to why they first used a Helium plasma - can anyone shed any light?
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How much iron would result of fusing a human body?

While discussing nonsense plots, a friend and I ran into the question of what would happen to a human enclosed perfectly with an enormous amount of energy, Antimatter or fusion level energy. It was a ...
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Temperature of fusion in the Sun vs. fusion in controlled experiments on Earth

I recently learned that hydrogen fusion (i.e., hydrogen to helium) experiments on Earth have been successful at temperatures in excess of 100,000,000 degrees Celsius. However, I also learned that ...
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Is neutron-neutron fusion viable?

Do I get unusual baryon maybe like pentaquark or just a pair of conjoined twin that is very unstable?
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486 views

Why do people say nuclear fusion is 50 years away? [closed]

This '50 years' number is floating around media pretty consistently, even the ITER road map claims that the first commercial reactor will happen post-2050. But why is that? I understand that there is ...
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Could atmospheric muons be used to catalyze nuclear fusion?

https://en.wikipedia.org/wiki/Muon-catalyzed_fusion I read above that some work as been done investigating whether muons could be used to catalyze fusion of deuterium and tritium. Apparently they can ...
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Usage of rare earth barium copper oxide (ReBCo) superconductors (for fusion reactors)

Recently, scientist from MIT have proposed a new design for a compact fusion reactor, see for example this ArXiV paper. I do not want to discuss the physics of their reactor but am more interested in ...
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Could anyone explain to me how the products of nuclear fusion/fission are predicted? [duplicate]

I have an idea of how quantum mechanics work, but I know too little to understand which products are a result of certain reactions like bombarding a certain atom with neutrons or just by natural decay....
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1answer
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Can a spheromak propagate in vacuum?

I recently learned about (and am now fascinated by) spheromaks. I am no expert on plasma physics, but as I understand they are analogous to propagating toroidal vortices (smoke rings), but with plasma ...
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Why can't electrostatically accelerated deuterium beams neutralized by electrons produce net energy fusion? [duplicate]

I was looking through the various nuclear fusion approaches and it struck me that they all suffered from one of two problems. Either they wasted a lot of energy trying to accelerate fusion fuel to the ...
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2answers
720 views

Why does the core of a low mass star contract after reaching electron degeneracy?

I am learning about the lives and deaths of stars with a solar mass of 0.4-2. What I understand is that once the star stops hydrogen fusion after using up all its hydrogen, the star leaves the main ...
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Reason why stars do not produce elements heavier than iron

In his book "Origins", Neil deGrasse Tyson says that "if you seek to split iron nuclei apart, you must them with additional energy. On the other hand, if you combine iron atoms they will also absorb ...
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Fusing Hydrogen with lightning

I've been reading about fusion recently (Specifically Deuterium fusion) and a friend of mine asked me if it was possible to fuse two Deuterium atoms with a lightning strike? Now this question has a ...
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In a nuclear reaction, where does the energy go?

Lets say two hydrogen fuse together, where does the energy released go? Is it carried away as momentum imparted on the helium atom? Is it carried away in neutrinos? Is it carried away as gamma rays? ...
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Mass loss for Fusion energy? [closed]

I am thinking how you can estimate the mass loss of the fusion energy for 1 kWh. I think you cannot use Einstein's $E=mc^2$ to calculate the mass loss in the fusion reaction of the Sun. How can you ...
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In what ways does the sun output energy?

I'm curious about the energy output of the sun, and how it breaks down. What fraction is from EM radiation, solar wind, neutrinos, et cetera? How does energy output vary over the EM spectrum? I was ...
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Using nuclear devices to terraform Mars: Elon Musk's nuclear proposal? [closed]

Elon Musk has recently suggested Using nuclear devices to terraform Mars. In the past, comet related ideas were mooted, but Musk seems, to me anyway, to be a man in a hurry and perhaps his idea has ...
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How does fusion work in the Sun if neutrons have more mass than protons?

According to my textbook, the next result of the fusion reactions in the Sun is: 4H -> He + neutrinos + gamma photons However, if hydrogen atoms are basically a proton and helium atoms are 2 protons ...
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How can the magnetic field of a tokamak or stellatron hold against the outwards plasma pressure?

I understand that magnetic containment structures like tokamaks generate a toroidal magnetic field in which the plasma particles move in helices around the field lines, because of the Lorentz force. A ...