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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5
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2answers
271 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?). ...
8
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1answer
289 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^...
19
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3answers
4k views

How do fusion reactors deal with blackbody radiation?

The plasma of the ITER reactor is planned to be at 150 million K. Using the Stefan-Boltzmann law, setting the surface area as $1000\,\mathrm{m}^2$ (the plasma volume is $840\,\mathrm{m}^{3}$ so this ...
4
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1answer
158 views

What does 'high-beta' mean for a fusion reactor?

I see the term 'high-beta' a lot, but cannot find a definition. When I type it into Google, I mostly see results about a Lockheed Martin fusion reactor project.....
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1answer
55 views

Are there processes other than fusion which can create very heavy elements? [closed]

Have there been hypothesized processes other than nuclear fusion which could possibly create heavy elements? For example these incredibly powerful particle accelerators we are continuously building ...
1
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1answer
54 views

How to generate plasma above 10^6 K without using neutral beam injection.

I want to make a model Tokamak fusion reactor to experiment with and toy around. I am willing to sink some money into its construction, but I cannot afford a neutral beam injector to heat the plasma. ...
9
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3answers
335 views

Magnetic confinement in a tokamak

I have a question about why exactly the twisting of the field lines in a Tokamak solves the magnetic confinement issue. My understanding is that the magnetic confinement issue arises in the toroidal ...
3
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3answers
112 views

Why electron/ion beams are not prefered over lasers as driver for inertial confinement fusion?

Most of hi-end ICF research facilities, and proposals for future powerplant or space-ship propulsion use lasers as driver. Problems with lasers intense lasers needed (e.g. NdYAG 3rd harmonic ...
3
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1answer
125 views

Minimum size of a “water star”

So I had this weird idea the other day. We know that stars form from simple matter (dust, gasses, etc) forming a gravity well, attracting to each other, until the amount of mass and density in the ...
2
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1answer
49 views

Filling a flux surface in a tokamak or stellarator

Assume you have a magnetic confinement device like a tokamak or a stellarator. Let's assume further a configuration with closed magnetic field lines resulting in typical flux surfaces. If you now ...
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2answers
144 views

Energy from nuclear fusion? [closed]

Upon doing research on tge nuclear fusion reactors people build at home, Ive always heard that I will be using more energy than I make. So how could I change that and make energy off of the reactor?
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1answer
127 views

Could we create an artificial sun? [closed]

based on dyson spheres.. imagine we construct an sphere of high radius R , then we fill the sphere with hydrogen, if the sphere is huge and the hydrogen is too then the gravity will make the ...
3
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1answer
153 views

Is a dipole fusion reactor feasible?

It is well known that the earth's dipole-like magnetic field is able to confine charged particles to paths that spiral along the field lines. That's why we have auroras and the Van Allen radiation ...
2
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1answer
113 views

Nuclear fusion difficulties

What is it that make nuclear fusion so difficult at low temperatures? There is plasma existing at low temperatures, so what does it make for fusion to be so difficult to reach at ambient temperatures?
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2answers
251 views

Can you combine protium and tritium to produce Helium-4?

Can you combine protium and tritium to produce Helium-4? I think they're a perfect match like a piece of puzzle since tritium just need another proton and electron to make a stable helium-4 atom. Also,...
4
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1answer
173 views

Why is energy emitted when nucleons come together?

In terms of nuclear fusion, why exactly does the coming-together of nucleons result in a net gain of energy (at least until iron)?
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3answers
270 views

How does gravity cause nuclear fusion in stars?

I am a bit confused regarding the nuclear fusion that occurs during star formation. For example, suppose there is a huge hydrogen cloud. It gets more mass and therefore pulls in more and more hydrogen,...
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0answers
55 views

Why does hydrogen fuse in a star? [duplicate]

I have only had basic classroom experience with physics but I have done a lot of research on my own and I am wondering why a newly formed star or any planetary body composed purely of hydrogen will ...
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3answers
65 views

Are the magnets in tokamaks variable in strength?

For example, if the plasma inside is beginning to terminate and collide with the walls of the confinement vessel, can the magnets account for this and realign the plasma?
1
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1answer
177 views

Why is deuterium and tritium used in fusion reactions rather than two deuterium? [duplicate]

Sorry if this question has been asked to death, but it doesn't make sense to me why we use a extremely rare isotope of hydrogen even though we have a much more abundant isotope. I am somewhat new to ...
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1answer
188 views

Why Hydrogen bomb is called “Thermonuclear Bomb”?

Why do we call Hydrogen bomb as "Thermonuclear Bomb" ?
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2answers
171 views

What would happen if you detonated a nuclear bomb inside a tank of liquid hydrogen?

Say you had a large bomb - take the 50 megaton Tsar Bomba. You then proceed to place it in the center of a spherical tank containing liquid hydrogen, and then detonate it. Could you start a fusion ...
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1answer
115 views

Nuclear fusion/fission vs. magnetic characteristics of Iron

Is the fact that Iron is attracted to magnets in any way related to the fact that it is also the element occupying the singular periodic table position where the chains of nuclear fission and fusion ...
0
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1answer
62 views

How dense could an Earth-sized planet be before beginning to undergo fusion?

I'm trying to figure out the maximum possible density for an earth-sized planet before it would become an earth-sized star. To try to figure this out, I found a reference star, VB 10, known for being ...
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1answer
224 views

Kinetic energy required for a fusion event

This question is given in my textbook: Consider the radius of both deuterium and tritium to be $2.0 fm$. What is the kinetic energy needed to overcome the coulomb repulsion between the two nuclei? ...
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1answer
523 views

Ohmic heating in a fusion plasma

In a microscopic classic picture, ohmic heating occurs due to collisions. Let's start with the simplest case: a cooper wire and a battery that induces a current. Electrons start flowing and the energy ...
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2answers
56 views

Could focused sunlight ignite a pellet of lithium deuteride?

This is a basic question, but it something I have been wondering ever since I learned about inertially confined fusion. In the ICF reactor configurations I am aware of, the drivers that are used to ...
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1answer
470 views

Energy needed to overcome the coulomb barrier

I am in my first year of college and doing an EPQ type project on nuclear fusion and am wondering about Coulomb's Law. I am looking into the force experienced by a particle due to the Coulomb force ...
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2answers
156 views

Can the fusion and fission of a group of atoms occur infinitely? [closed]

Is it possible to split a nucleus and put it back together? If so, is it feasible to do it an indefinite number of times, i.e. without them wearing out or failing to stick together once again?
3
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1answer
158 views

Is the Dynomak concept physically sound?

I recently stumpled upon this article: Inside the Dynomak: A Fusion Technology Cheaper Than Coal Is the Dynomak concept physically sound? What kind of challenges could it run into? Can it make ...
2
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1answer
575 views

Why does resistance decrease as the temperature increase in plasma?

I am writing about Ohmic heating as a heating method for fusion for a class in school. But I wonder why the resistance decreases as the temperature increases in the plasma? This seems odd because ...
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1answer
54 views

Ion acoustic waves in a deuterium plasma?

Has anyone ever experimented with inducing ion acoustic waves in a deuterium plasma? Perhaps to observe the phenomenon of Landau damping? Or to heat the plasma for fusion reactions to occur? And, ...
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1answer
46 views

Calculating the energy produced in watts in Alcator C-Mod

I calculated the energy in joules that a deuterium-tritium fusion reaction releases and found 2.81829046e-12J. I then read on some MIT articles that the Alcator C-...
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3answers
195 views

Nuclear Fusion Reaction [closed]

My question is about the energy released in a nuclear fusion reaction, consider: $\mathrm{{^{2}_1H}} \ + \ \mathrm{{^{2}_1H}} \ \rightarrow \ \mathrm{{^{3}_2He} \ + \ n \ + \ 3.27 \ MeV} $ ...
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2answers
162 views

How ready is the current fusion reaction technology for the mass production of electricity?

Could you give a clear summary statement about the maturity of the controlled fusion reaction technology and its readiness for the mass production of electricity? There are many articles on internet ...
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3answers
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Nuclear Fusion: Why is spherical magnetic confinement not used instead of tokamaks in nuclear fusion?

In nuclear fusion, the goal is to create and sustain (usually with magnetic fields) a high-temperature and high-pressure environment enough to output more energy than put in. Tokamaks (donut shape) ...
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1answer
48 views

Can stellar nucleosynthesis processes other than deuterium-lithium, i.e., oxygen-burning, take place in a reactor?

It is known that gravitational confinement and supernovae facilitate the synthesis of heavy nuclides; and, that magnetic confinement is thought to facilitate the deuterium-lithium fusion in human-...
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1answer
131 views

Were the 1st generation stars low or high-mass stars?

I have been taught that the first stars to be "born" could not use the CNO cycle to fuse Hydrogen into Helium as there were no elements heavier than Helium and a bit of Lithium to use in those ...
6
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2answers
94 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 ...
4
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2answers
1k 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 ...
5
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3answers
779 views

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

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 ...
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2answers
59 views

Could we create our own mini star?

If NASA were to work together with other space programs, could we accomplish the task of creating a mini star in the future. It wouldn't be huge, under a mile in diameter. We could make a core of ...
18
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1answer
1k views

Why all the orifices, protuberances, hinged/bolted panels, etc. on a stellarator?

My question was inspired by this one - in particular the image it has (also shown here): Why does the external casing of the Stellarator (in particular, the Wendelstein 7-X shown in the above image) ...
8
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0answers
702 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-...
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1answer
127 views

Why is there a difference in measured binding energy vs formula for binding energy? [closed]

I have a question about calculating the energy release from a fusion reaction. With parameters I have been supplied the liquid drop model semi-empirical binding energy formula gives the wrong answer. ...
0
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1answer
63 views

Proof of actual collisions in beam collision fusion?

An enormous number of experiments have been done over the years where the experimenters collide nuclei from a particle accelerator with a target. Typically nuclear reactions take place with a very low ...
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2answers
203 views

Ways to make a star go supernova? [closed]

Asking for a fictional storyline. Say a type iii civilisation on kardashev scale want to make a star go supernova. Then what are the possible ways to achieve this? The said star being massive ...
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1answer
44 views

Logic behind Coulomb explosion fusion?

Many experiments seem to have been done where the experimental setup consists of an extremely short, but intense laser pulse, impinging on e.g. deuterated plastic of some sort or some "jet" of nano ...
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1answer
896 views

What is the critical electron density in a plasma?

In the article Ion Acceleration and D-D Nuclear Fusion in Laser-Generated Plasma from Advanced Deuterated Polyethylene by Lorenzo Torrisi, the author mentions a critical electron density on page 17057....
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1answer
106 views

Can a fusion bomb make electricity? [closed]

Would blast energy remove a single piece of pre-cut earth above an underground explosive? Could you then break apart the piece of earth and lower it back into the cavity as a way of generating power? ...