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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19
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4answers
2k views

Does 60kg of fusion fuel produce as much energy as 400 kilotonnes of coal?

Several people, including Fusion for Energy have posted this infographic: To meet the energy needs of a city of 1 million people one would need: Either 250,000 tonnes of oil Or 400,000 ...
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2answers
151 views

Distinguishing an underground Hydrogen bomb test from a fission bomb explosion

A related question is Hydrogen bomb radiation output, but my question is based on the seismograph data (or any other data) possibly producing a distinctive pattern. Is it possible to tell the ...
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1answer
60 views

Stellar Ignition and Neutrino Energy

My question has to do with the following two pieces of information: When Fusion Ignites and a star is born, according to the Proton-Proton Chain, a positron and a neutrino are released when one ...
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0answers
50 views

How fusion reactor could be operated on space craft? [closed]

Considering that space craft uses engines only during acceleration and deceleration, how fusion reactor will be operated? For example: it will be started / stopped for each maneuver will be working ...
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2answers
120 views

Has a nuclear explosive ever been detonated by another nuclear explosive? That is, a “secondary nuclear explosion” [closed]

So the question is this: Even though thermonuclear explosives(those with 2++ stages) are complex devices that require symmetrical compression in order to detonate(the fission stage). If, say, a ...
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1answer
80 views

Could CPA lasers be used to produce a Pure Fusion Weapon?

In particular, has there been any experimental testing of using the Chirped Pulse Amplification (CPA) technique to ignite a fusion pellet in the first place. If so, have any of the experiments yielded ...
0
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1answer
155 views

High temperatures in Nuclear Fusion

So, during nuclear fusion, hydrogen-1 nuclei fuse with hydrogen-2 nuclei. Given that these nuclei are both positively charged, that means that they repel, and thus have a positive Coulomb Potential.($...
2
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1answer
168 views

Can efficiency of fusor be improved by scaling up?

Fusors are very inefficient, among other reasons because the ions have to be decelerated and accelerated every time they fly out of the fusor, while radiating the energy out. However, what if we could ...
16
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1answer
2k views

Can nuclear fusion alone account for the energy output from type 1a supernova?

Unlike other supernova, which can vary in their size, Type Ia supernova are all about the same size. This is due to the fact that they are caused when a white dwarf star gains enough mass from its ...
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2answers
2k views

How exactly is fusion possible?

It is a very dumb question but, I once read that fusion was possible when the wavefunction that describes the position of a particle overlaps with the wavefunction of other particle, but I think I don'...
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0answers
19 views

How to calculate the life expectancy / fusion rateof a star? [duplicate]

If I have the mass (and if needed, the atomic mixture) of a star before it forms, is there some mathematical way to calculate how fast the star will burn through its contents and die?
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2answers
378 views

Why does fusion use mass for energy?

I have the basic idea: for small nuclei the mass of product is less than the mass of the individual pieces, this mass is released as energy via $E=mc^2$. But why do nuclei use the mass for energy? ...
98
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4answers
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Would a pin head heated to 15 million degrees Celsius kill everyone in a 1000 mile radius?

The YouTube video How Hot Can it Get? contains, at the 2:33 mark, the following claim: A pin head heated to 15 million degrees will kill everyone in a 1000 miles radius. On what basis can this ...
3
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1answer
70 views

What is the shortest duration fusion reaction?

In a tokamak fusion reactor fusing hydrogen nuclei what is the shortest duration experiment that successfully fused nuclei. Is there a database with fusion reactions and their duration.
2
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1answer
136 views

How long does it take for fusion to occur in a tokamak?

Once the plasma is in the tokamak reactor how long does it take until fusion starts to begin? I found that it must reach 150000000 degrees so, how long does it take for the plasma to reach this ...
2
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1answer
3k views

How many times does plasma do a full loop tokamak before fusion?

From this photo I assume the plasma is also moving in a loop through the reactor due to it being a charged particle. I have been trying to find a speed at which it does this but couldn't and neither ...
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4answers
1k views

Where does mass deficit energy go?

I get the idea (at least, as much as a layperson can) that a helium nuclei has less mass than the sum of its parts. That mass deficit is turned into energy. At this stage I feel like I've heard two ...
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0answers
61 views

Can air plasma ions in a fusor fuse?

I know that hydrogen ions will fuse in a fusor but what about air ions? Can air plasma ions in a fusor fuse? https://en.wikipedia.org/wiki/Fusor, if so, under what cicumstances, and how would I ...
3
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1answer
324 views

How to calculate the bremsstrahlung limit in the fusion triple product diagram?

The fusion triple product is a commonly used figure of merit to quantify the progress in fusion research, it is the product of plasma density $n$, temperature $T$ and energy confinement time $\tau_E$....
3
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2answers
145 views

At what rate do I need to accelerate for my car to become a fusion reactor?

I was sitting on the bus on my way home, and this popped into my mind. As a car accelerates, the air pressure at the back of the car increases as air is pushed back due to inertia. This pressure will ...
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2answers
102 views

Fusion reactor with lasers and magnets

Both magnetic and laser fusion reactor work to a point, but what would happen if you had magnets and then lasers to heat up the pelts and/or plasma? And what would be the best the best way to achieve ...
-3
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1answer
301 views

Could south poles of magnets repel hydrogen plasma? [closed]

In a fusion reactor there is magnetic confinement so their must be some interaction. So if you put a bar magnet (for simplicity's sake) in hydrogen plasma what would happen. I am only in high school ...
41
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3answers
11k views

What stops us from creating a nuclear fusion reactor as we already have the hydrogen bomb working on the same principle of fusion?

I have been out of physics for some time now since my childhood, so please bear with me if the question below feels too novice. I grew up with the understanding that the nuclear fusion reaction is ...
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2answers
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Why is D-T fusion easier than T-T?

At a very basic level, fusion can occur when the electrostatic repulsion between nuclei is overcome and they approach close enough for the strong force to come into play. Thus, the easiest reactions ...
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1answer
218 views

What causes instabilities in tokamaks?

As far as I know, almost all kinds of instabilities are suppressed in a tokamak. The only problem I see is that the poloidal field diminishes as we move further out from the plasma. This ...
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1answer
763 views

Is net-positive fusion power generation impossible on Earth?

I recently ran across a rather interesting claim: the Coulomb Barrier equation states that the kinetic energy required to cause nuclei to fuse is greater than the thermal energy released by fusion ...
3
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1answer
296 views

Is there any significant difference between a tokamak and a spherical tokamak?

The title question is quite self-explanatory. Despite the fact that Spherical tokamaks are more spherical in shape, what else differentiates the ST from the conventional tokamak. I've heard that ST's ...
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1answer
70 views

Would $^3_2\mathrm{He}$ and $^3_1\mathrm{H}$-based fusion require different fusion reactors?

At school I have learned that there are two very similar fusion reactions, which physicists (and science fiction authors) hope can be used as an energy source: $$^2_1\mathrm{H}+^3_1\mathrm{H} \...
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1answer
91 views

What causes the glow in fusor experiments?

In short: Is the glow produced during nuclear fusion in a fusor the same as the glow (Cherenkov radiation) produced in nuclear fission? In nuclear fission Cherenkov radiation is formed by high-energy ...
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0answers
130 views

What changes does Lockheed's fusion concept have which makes it better than magnetic mirrors?

Magnetic mirrors were thought to be a viable solution for fusion power. But then, we found out that most of the plasma would simply escape. Is this right? So, then we realized that this method might ...
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2answers
547 views

What makes a fusion reaction an “explosion”?

The Lawrence Livermore National Laboratory just put out a bunch of movies of atomic bomb detonations. How does the nuclear reaction generate the destructive shockwave that can be seen? If it just ...
3
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1answer
539 views

Can heavy elements be fused? [duplicate]

Yes, I know, in stars, fusion occurs up to Iron(-56); but, I want to know if fusion past this nucleus can happen at all. If so, the daughter element would move to the right of the peak and its ...
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131 views

what is the nuclear cross section dependent on?

I understand that the nuclear cross section determines the probability of fusion taking place. When I was talking to my friend he said that the cross section doesn't depend on anything but the ...
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2answers
822 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 ...
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0answers
54 views

Why is the nuclear cross section for fusion so small?

Recently, I have learn't about the Gamows factor, and I have plotted it. Then I realized that the probability of Deuterium and tritium fusing at a temperature of 150 million kelvin when they collide, ...
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1answer
124 views

Do elastic collisions occur if a part of the plasma is heated to fusion conditions?

Consider you have a plasma, and then you use a laser to heat it so that the part of the plasma that the laser went through is heated to 150 million degrees. The rest of the plasma temperature is not ...
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0answers
93 views

What is wrong with particle acceleration based fusion? [duplicate]

Recently, I was thinking about fusion and this thought struck my mind. In tokamaks, the plasma is heated to extremely high temperatures in order to supply enough energy to the ions for them to fuse. ...
2
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1answer
206 views

What prevents high Beta plasma confinement and how to overcome it?

In order to confine a plasma, the plasma pressure is supposed to be lower than the magnetic pressure. The ratio of the plasma pressure to the magnetic pressure is called beta . Theoretically, the ...
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1answer
139 views

How large is the collision cross section compared to nuclear cross section in tokamaks or other fusion reactors?

Most Fusion reactors, and the leading ones like JET, use high temp. plasma and confine it. So, the plasma would approximate the Maxwell- Boltzmann distribution. This means that only a small portion of ...
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2answers
863 views

So a particle accelerator is the same thing as fusion?

I am doing a science project on Fusion and I need to know if a particle accelerator is the same thing as fusion.
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1answer
570 views

Energy release with hydrogen fusion

$$H_1^2 + H_1^2 \rightarrow He^4_2+ \text{energy}$$ How can energy be released, if the left hand side of this equation has less mass/energy than the right? $\text{BE}_H \approx 1 \text{MeV}\\ \text{...
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0answers
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In the middle of depletion layer of reverse biased p-n junction is the electric field almost zero?

My textbook states: Due to reverse biasing the width of the depletion region increases and current flowing through the diode is almost zero. In this case electric field is almost zero at the ...
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1answer
44 views

Why should we equate the formula for translational kinetic energy of monoatomic molecule with $P$ to find $T$?

In the nuclear fusion reaction, $$ H_1^2 + H_1^3 \rightarrow He_2^4 + n_0^1$$ suppose I have been given the repulsive potential energy (say $P$) between the two nuclei. I need to find the ...
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1answer
367 views

Coronal heating problem -How deep does it go?

On the top of the list of problems in solar physics we find the coronal heating problem. The Corona is the outer plasma atmosphere of the Sun, with a temperature of 1-5 millions of degrees Kelvin, ...
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1answer
82 views

Fusion inside a planet with high concentration of radioactive elements?

If an Earth-sized or larger planet had sufficiently large amounts of radium, thorium or uranium, couldn't the resulting fission trigger periodic fusion of hydrogen? I'm thinking of fission happening ...
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1answer
209 views

Hydrogen fusion in the Sun-neutrino

One of the ways nuclear fusion happens in the sun is deuterium and tritium fusion which forms a Helium-4 atom and a neutrino. What flavor of neutrino is created - a tau, muon, or electron neutrino?
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1answer
85 views

Could there be a rocky star, made from silicon, oxygen, etc?

Rocky in terms that it will have mostly silicon and oxygen composition, just like terrestrial planets. But not because it runs out of hydrogen and helium, rather it should start it's life by fusing ...
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1answer
186 views

Tunneling for hydrogen fusion

So I'm trying to find a rough estimate of the temperature required for Hydrogen to turn into Helium through quantum tunneling. In the lecture we were presented with the following: $$\frac{p^{2}}{2\mu}=...
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1answer
129 views

How do we know which lighter elements fuse to form heavier elements?

Formation of lighter elements is fairly straightforward: He + He + He = C-12. However for each heavier element (heavier than Fe in particular), is there exactly one combination of (two lighter) ...
3
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1answer
310 views

Learning resources for computational plasma physics

I'd like to try implementing a "simple" simulation of nuclear fusion (http://en.wikipedia.org/wiki/Nuclear_fuel_cycle) process taking place inside an idealized reactor. Are there any good resources (...