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.

Filter by
Sorted by
Tagged with
9
votes
4answers
2k views

Tokamaks and the reason they are still not efficient

I'm curious about why tokamaks are inefficient as generators. In laymans terms, what is the main reason(s) tokamaks still cannot be used as generators? My limited understanding of tokamaks tells me ...
9
votes
3answers
2k views

Can the High beta fusion reactor work?

Are the claims made about the http://en.wikipedia.org/wiki/High_beta_fusion_reactor realistic? Can such a small fusion reactor really work?
9
votes
3answers
1k views

Nuclear fusion : ion vs atom fusion cross section?

I've read critique on ITER project (in Russian), and one of points was that cross section of ion-ion fusion is much lower than ion-atom and atom-atom, and that's the reason why it likely to not work. ...
9
votes
0answers
774 views

What is the theoretical efficiency of fusion?

What is the theoretical limit of the amount of energy that can be extracted from a fusion reaction? I am not talking about the practical efficiency of a reactor, but rather what fraction of the mass-...
8
votes
5answers
2k views

What new breakthrough energy technologies are close to being realized? [closed]

Energy production is one of the burning issues for humankind. There has been some talk about future energy technologies including Fusion, Anti-matter annihilation and Zero-point-energy (from most to ...
8
votes
3answers
14k views

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.
8
votes
2answers
2k views

What elements can be created in the fusion process of different types of stars?

As I understand it fusion inside a sun can produce heavier and heavier elements until some sort of "nucleus size limit" is reached. As far as I understand, the limit is thought to be reached with the ...
8
votes
1answer
334 views

Triple-alpha reaction rate

I'm trying to find a general equation for the fusion rate of the triple alpha process. I found this equation: The rate of energy generated by this process as a power law in $T$, centered around $10^...
8
votes
2answers
398 views

What is the difference between the KDEMO and DEMO projects?

I'm writing a paper on the future of fusion technology and I can't seem to find the difference between Europe's DEMO experiment and Korea's KDEMO except for the fact that they are both planned to ...
8
votes
1answer
173 views

What happens to Hydrogen-Boron plasma at 3 billion Kelvin?

A recent popular report states (beware, I believe it is not peer reviewed and this slightly smells like a PR stunt) that a private company TriAlpha has made some notable progress towards Hydrogen-...
7
votes
1answer
9k views

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 ...
7
votes
3answers
3k views

Why doesn't helium start to fuse while there is still hydrogen fuel?

In all the descriptions of the stellar life cycle it seems as though helium doesn't start being fused until all (most?) of the hydrogen is gone. Is this true? Why is this? It seems counter intuitive....
7
votes
4answers
8k views

How do you build a nuclear reactor in your garage?

When I came across this link earlier today, I was astounded. Nuclear reactors are immensely complex devices that took scientists years to develop, and are usually housed in huge facilities. The link ...
6
votes
7answers
6k views

As neutrons are more massive than protons, does the Sun increase its mass while fusioning elements?

Where is the mass coming from when neutrons are produced from protons in the Sun? If a positron is made, will it possibly annihilate with an nearby electron?
6
votes
4answers
4k views

How much of the energy from 1 megaton H Bomb explosion could we capture to do useful work?

The world is full of nuclear warheads being stockpiled. Controlled fusion power seems a long way away. Could we put these warheads to better use by exploding them in a controlled way and capturing ...
6
votes
2answers
7k views

Fusion: Why deuterium and tritium?

I would like to know why scientists try to use deuterium and tritium for fusion and not just the ordinary isotope of Hydrogen ${}^1H$?
6
votes
6answers
2k views

Is there any inherent danger in operating a Thermonuclear Reactor?

Nuclear fusion research appears to promise sustainable, practically unlimited energy, and according to ITER it will be a perfectly safe, non-polluting source of energy. My question is if there are ...
6
votes
2answers
1k views

How much faster is the fusion we make on earth compared to the fusion that happens in the sun?

I have come across many websites that states that the proton-proton fusion which is the dominant type of fusion that powers the suns, is extremely slow and that is why the sun is still burning to that ...
6
votes
1answer
458 views

Is nuclear fusion via underwater vacuum possible?

An under water explosion creates a bubble which quickly collapses on itself. The action takes less that 1/100 of a second for bubbles less than a foot across. This creates a point of extremely ...
6
votes
2answers
2k views

What is a simple mathematical model of a star?

I had a discussion at work regarding a recent fusion experiment in China that resulted in temperatures five times hotter than the Sun. Someone mentioned that no one can know the temperature of the Sun....
6
votes
4answers
881 views

Why can't we harness the energy from neutron + protium = deuteron reaction? [closed]

The answer to this physics se question, established that 2.2Mev (Mega electron volts) of energy is emitted as a gamma ray photon when the hydrogen atom nucleus oka protium absorbs a slow moving free ...
6
votes
1answer
218 views

Recent news about Tokamak

I first heard about the Tokamak in highschool 10 years ago and was wondering how far the technology has come since then. Can it sustain a reaction for more than a few seconds? Are these devices ...
6
votes
2answers
99 views

Is there a distinct size limit between planet and star?

This question was inspired by: This recent article about an exoplanet "10 times the size of Jupiter" Prof. David Taylor's website about the "Life and Death of Stars" (in particular, the first page's ...
6
votes
1answer
292 views

How large should an optically large fusion reactor be?

This is just theoretical consideration. I expect that size of the reactor would be impractical to build on Earth, but I'm interested how much. EDIT: perhaps it could be good for some huge spacecraft ...
6
votes
2answers
593 views

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. ...
6
votes
4answers
1k views

Why do stars undergo nuclear fusion?

This might sound silly. But we always talk about nuclear fusion in stars and I have always wondered why this process happens at all. Is it inevitable for fusion to happen at the temperature and ...
5
votes
3answers
9k views

Why doesn't fusion contradict the 1st law of thermodynamics?

I was reading up on the 1st law of thermodynamics for my Chemistry exam and I was wondering why doesn't fusion contradict the 1st law of thermodynamics? The 1st law states that The energy of an ...
5
votes
4answers
895 views

Help fill in my understanding of the Polywell fusion reactor

Polywell is a proposed new type of fusion reactor, which is designed to use magnetic fields to overcome the problems with the Elmore-Tuck-Watson fusor. I'm trying to understand exactly how it works. ...
5
votes
4answers
315 views

Does the weak force have an attractive/repulsive force observable in everyday life like the other forces?

After the correct comments, this question is not here to compare gravity's and EM's long range forces' energetics and amplitudes to microscopic scattering amplitudes of such forces as weak and strong. ...
5
votes
2answers
284 views

Is there evidence of gas ever forming a black hole without being a star first?

Here's my general understanding of how gas particles form a black hole: 1) Gravity pushes gas particles together. 2) These fast particles create heat (from friction due to them rubbing together?). ...
5
votes
3answers
8k views

Light formed by the sun?

This is an extract from the astrophysics chapter in my book: Hydrogen atoms fuse to form helium. At the same time, lots of of gamma photons and neutrinos are produced. The photons take thousands ...
5
votes
3answers
3k views

Complete list of nuclear fusion reactions

Could anyone suggest good source of all fusion reactions and their cross section vs energy graphs, including ones which were ruled out for nuclear fusion reactors (i.e. including endothermic and ...
5
votes
1answer
1k views

How would the explosion from a Pure Fusion Bomb differ from the explosion from a Fission Nuclear Bomb?

Suppose we have the technology to create high enough temperatures and pressures inside a confined space to fuse together deuterium and tritium, and create a Pure Fusion Bomb. How would the explosion ...
5
votes
2answers
111 views

Why do later fusion stages in a star last shorter?

When most of the hydrogen in the core of a massive star has fused to form helium, the next fusion stages (helium, carbon, neon, oxygen, ...) produce less and less energy in a single fusion reaction. ...
5
votes
2answers
1k views

Why do fusion cross sections drop after a certain temperature?

The title sums everything up. The fusion cross section increases up to a certain temperature due to collisions and the increased probability of tunneling through the coulomb barrier. But why does the ...
5
votes
1answer
820 views

PP Chain and CNO cycle relationship

At what temperature would the energy generation rates of the PP-Chain and CNO cycles be roughly equivalent? The dependences are so vastly different that I am wondering how and by what equations they ...
5
votes
1answer
494 views

What types of fusion reactions happened in population III stars?

I have read that, in smaller stars, such as our Sun, the fusion reaction that takes place is a proton-proton chain, or PP chain for short. From what I have learned, in larger stars, a different ...
5
votes
1answer
2k views

What does the Coulomb barrier really mean?

I realize I'm trying to get a simple answer on a complicated subject, but here goes anyway. I've done some research and I understand (well, mostly) about how Vc is the amount of energy required to get ...
5
votes
1answer
2k views

Can we generate infinite energy by successive fission and fusion reactions?

Fission divides one Helium atom into two Hydrogen (Deuterium) atoms. And fusion, once again, puts together those two Hydrogen atoms into one Helium atom. In both reactions, overall output energy is ...
5
votes
1answer
619 views

Free neutrons in the sun's core?

In the standard description of proton-proton fusion, the first step of the interaction proceeds through the unbound diproton $\rm^2He$: $$ \begin{aligned} \rm p + p &\to \rm {}^2He^* \\ \rm ^2He^* ...
5
votes
1answer
213 views

What is a quasi-axisymmetric stellarator?

I know that a tokamak is a donut shape fusion confinement device with an axisymmetric magnetic field configuration. The stellarator is similar but its field configuration is non-axisymmetric. I've ...
4
votes
5answers
10k views

How much iron would I have to shoot into the Sun to blow it up?

My understanding--though it's from a Science Channel show so I'm not sure if it is correct--is that there is a fusion reaction happening in the center of the sun. Atomic nuclei are being created and ...
4
votes
2answers
14k views

What is the lowest possible theoretical temperature that nuclear fusion can occur at?

I am not talking about the pseudo-science of so called cold fusion I am interested in what temperature you can get away with to produce fusion reaction. I was thinking in terms of micro-fusion or at ...
4
votes
2answers
2k views

Why nuclear fusion deliver energy instead of taking? [duplicate]

In nuclear physics, when you break eg. a nucleus of Uranium, some neutrons are liberated, and the original atom degrades to a lighter element. The energy that was used to keep these subatomic ...
4
votes
3answers
1k views

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 ...
4
votes
2answers
2k views

Is the E-cat by Andrea Rossi et al. for real?

Does this thing really do what they say? http://www.youtube.com/watch?v=EhvD4KuAEmo If it does, it looks like this will probably be the biggest breakthrough in science ever :)
4
votes
3answers
399 views

Whats the next step after commercial fusion reactors? [closed]

I'm trying to write some science fiction where they've had nuclear fusion working for quite sometime, interplanetary travel is no problem, and they're debating making the next step to a radical new, ...
4
votes
1answer
432 views

Was the Strontium-90 found in Godzilla's footprints a by-product of nuclear fusion?

In the movie Godzilla at one point the scientists discover a residue of Strontium-90 in Godzilla's footprint. In the ensuing report to the Diet a scientist announces that this is evidence that ...
4
votes
4answers
12k views

How is energy extracted from fusion?

I understand that combining deuterium and tritium will form helium and a neutron. There are three methods to do this (1) tokamak (2) lasers and (3) cold fusion. I would like to know after helium is ...
4
votes
2answers
81 views

Why does the sun have the Fe?

I read the information about 'Abundance in the sun for the elements'. There are a lot of elements in the Sun. I thought 'how is it possible to exist Fe, Au, and so on in the Sun ?', but I couldn't ...

1
2
3 4 5
10