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
98
votes
4answers
33k views

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
votes
1answer
80 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
votes
1answer
168 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
votes
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 ...
0
votes
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 ...
1
vote
0answers
66 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
votes
1answer
406 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
votes
2answers
146 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 ...
-1
votes
2answers
120 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
votes
1answer
333 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 ...
42
votes
3answers
12k 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 ...
18
votes
2answers
2k views

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 ...
0
votes
1answer
238 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 ...
-1
votes
1answer
788 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
votes
1answer
346 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 ...
2
votes
1answer
72 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} \...
0
votes
1answer
97 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 ...
0
votes
0answers
157 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 ...
0
votes
2answers
597 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
votes
1answer
588 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 ...
0
votes
0answers
135 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 ...
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 ...
0
votes
0answers
57 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, ...
1
vote
1answer
128 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 ...
2
votes
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
votes
1answer
216 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 ...
1
vote
1answer
145 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 ...
-3
votes
2answers
987 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.
0
votes
1answer
582 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{...
1
vote
0answers
2k views

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 ...
0
votes
1answer
45 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 ...
-1
votes
1answer
392 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, ...
0
votes
1answer
86 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 ...
-4
votes
1answer
211 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?
3
votes
1answer
94 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 ...
1
vote
1answer
190 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}=...
1
vote
1answer
139 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
votes
1answer
336 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 (...
-5
votes
1answer
102 views

Is the following scheme real?

Nuclear fusion in a liquid Electrolytic Environment The main necessary to consider the formula of the nuclear reaction, the following This is the nucleus of the helium fusion reactions ...
1
vote
0answers
100 views

Flyback transformer for fusor?

I've always wanted to construct a farnsworth nuclear fusor. I recently ordered a 3-6 volt to 400,000 volt flyback transformer, and was wondering if that could be used in a fusor setup
2
votes
1answer
216 views

Nuclear Fusion Fuels

I have seen some possible fuels for nuclear fusion. My questions are: Are there other fuels available even theoretically or the list of candidates is limited? What are the requirements that a "...
4
votes
1answer
431 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 ...
1
vote
0answers
71 views

Would a charged particle moving through a carbon nanotube experience no or negligible bremsstrahlung?

The context here is for beam-target fusion. The supposition is that it would actually possible to achieve breakeven with an accelerator-based system and cold targets based solely on a modest ...
1
vote
1answer
81 views

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 ...
11
votes
3answers
2k views

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 ...
4
votes
2answers
3k views

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 (...
1
vote
2answers
399 views

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 ...
3
votes
2answers
58 views

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 ...
2
votes
3answers
2k views

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: ...
10
votes
2answers
4k views

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 ...

1
3 4
5
6 7
10