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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64 views

In fusion inside stars (sun) or very hot gasses, how do the electrons get bound and what about tritons and $D$-$T$ vs $D$-$D$ fusion?

Most texts I've read focus on just the nuclei to begin with, but eventually start talking about Helium (or other) atoms and isotopes. A few aspects aren't clear to me and I'd be grateful for some ...
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How does protium-protium fusion work?

How does protium-protium fusion work? As far as I know, a proton turns into a neutron by emitting a positron. How does that work? Shouldn't a proton be slightly heavier than a neutron? This seems to ...
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If binding energy (from mass defect) is essentially the strong nuclear force maintaining the nucleus, why is it released?

I am aware that during nuclear fusion for light elements and nuclear fission for heavy elements, the resultant elements have less mass than the original reacting elements (ie the mass defect) because ...
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Why do tokamaks need to operate in pulsed mode?

The plasma current is normally induced by a transformer coil in the plasma. A Tokamak therefore does not operate continuously, but in pulsed mode like the transformer. https://www.ipp.mpg.de/1766212/...
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Do Efimov states contribute to fusion reactions other than the triple-alpha process?

An Efimov state is a three-body quantum state in which each two-body subsystem is unbound, but the system as a whole is bound because of the large s-wave scattering length. Intuitively, one can ...
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14 views

Why aren't Flux Compression Generators used in ICF or Z-Pinch experiments?

Inertial confinement fusion requires high pulsed power concentrated in a small area. This can be done with lasers, or it can be done with a Z-Pinch, which converts pulsed electricity into pulsed x-...
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110 views

Reactivity in nuclear fusion

In nuclear fusion, the graph of reactivity is shown as below. How can we explain that by increasing the temperature after a certain value, the reactivity decreases?
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What is the origin of elements heavier than iron?

In all the discussions about how the heavy elements in the universe are forged in the guts of stars and especially during a star's death, I usually hear that once the star begins fusing lighter atoms ...
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Why do helium fuse in the Sun?

Initially there are lots of hydrogen atoms and trace elements in the Sun. Despite insufficient energy for the hydrogen to fuse in the core, quantum tunneling saved the day and invoke proton-proton ...
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What is the relationship between binding energy, energy released, and mass defect? [duplicate]

Im learning about fission/fusion and cant get mass defect, binding energy, and energy released to fit together in my head. The three are all equal in magnitude if I understand it correctly? When, for ...
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Nuclear fusion scaling with reactor size

Thinking about the physics of thermonuclear fusion, I have always had an intuitive sense that making fusion feasible is matter of reactor size. In other words I feel like: If the fusion reactor is ...
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Speculative: What would happen if towers with supermagnets would be built around an experimental tokamak?

It is a speculative question from an amateur. I am interested in an expert reply carved-out for a non-expert As I'm avidly observing ITER developments and I'm a great fan of the project (as a child I ...
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On Nucleus-Nucleus potential for fusion reaction of light nuclei

Its know that in nuclear fusion reactions, the nucleus-nucleus potential cannot be simply given by; $V(r)=\frac{kZ_pZ_t}{r} for, r>\frac{kZ_pZ_t}{E}$ $V(r)=-U_0 , or, \frac{-U_0}{1+e^{\frac{a-r}{b}...
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Is the 300 second sustained fusion goal set by KSTAR a threshold for net positive energy product of fusion?

KSTAR recently broke a record in fusion technology by maintaining its heat for 20 seconds with a stated goalof reaching 300 seconds. Why 300? Does 300 get us to the point of net positive energy ...
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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. ...
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What's wrong with using protium catalytically in a fusion reactor?

P-D fusion results in 3He, then D-3He results in a P+D+D turning into P+4He. Isn't that net energy positive at a relatively low temperature without too many neutrons? Some D+D side products will ...
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Why is hydrogen-boron called a fusion reaction?

As we know, we usually call fusion such a reaction in which two light nuclei make a heavier one and release energy. For fission, a heavy nucleus breaks into light ones. My question is, in proton-boron ...
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30 views

Radiative Heat Transfer In Nuclear Fusion

Given the extremely high plasma temperatures that are required to sustain a nuclear fusion reaction in a device such as a tokamak reactor, how can such high temperatures be maintained in the presence ...
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156 views

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

Formation of lighter elements is fairly straightforward: $^4$He + $^4$He + $^4$He = $^{12}$C. However for each heavier element (heavier than Fe in particular), is there exactly one combination of (...
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How many times do solar protons repeatedly fuse and fission before they form deuteron

In the proton-proton chain reaction in the Sun, the first step is $$p + p \rightarrow \; ^2_2{\rm He} .$$ After this, the most likely thing to happen next is that the reverse reaction occurs: the $^...
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What would happen if you tried to use oil as fuel in a fusion reactor? [closed]

At first, this question seemed silly, but there might be some sense to it. OpenAI's GPT algorithm suggested to me that using oil in fusion technology could be a breakthrough. I thought about it for ...
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How much of ITER Tokamak's input power could be eliminated in a future commercial fusion reactor? [closed]

The ITER Tokamak is designed to produce 500 MW of thermal output from 330 MW of input power, ignoring electric conversion efficiency. The heaters require 150 MW (to heat input plasma by 50 MW), the ...
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Another way for production of positive fusion

I am wondering why energy positive fusion cannot be produced in the following manner. Large tank of hydrogen pressurized to such a high a level it would push the limits of current technology. ...
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Outside grid for fusor

I, for a while now, wanted to build a little Farnsworth desk fusor. Nothing too powerful, simply a small "desk lamp" if you will. As the fusor needs 2 grids, I was wondering, if it might be ...
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How is hydrogen stored in hydrogen bombs?

Fusion bombs obviously fuse hydrogen atoms, using the pressure from a fission bomb. But how much hydrogen does it contain, and how is it stored? AFAIK hydrogen easily drops its electron and escapes as ...
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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 ${}^1H$?
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I Need the Z-Machine's Circuit Diagram

Where can I find a copy of the circuit diagram for Sandia Lab's Z-Machine, or indeed for any pulse forming network that outperforms the ordinary Marx bank (if such a thing exists)? Google has let me ...
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Is the Marx Bank Still the Gold Standard?

Is the Marx bank still the fastest pulse forming network for generating high magnetic fields at large scale, or is there another design that outperforms it?
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Magnetic Lens Size required to ignite a Fusion burn

What are the dimensions and/or mass of the amount of permanent magnets( NdFeB) required to magnetically focus cosmic rays such that instead of 1 muon per square centimeter per minute hitting the ...
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What if Jupiter or the Sun was made of rock, like Earth and Mars, rather than gas?

Jupiter is a "gas giant". If it was (significantly) bigger the pressure from gravitation would ignite a fusion process and it would become a star, which is basically what happened to the sun....
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Nuclear reactions in stars: tunneling?

Energy production in stars occurs mainly when a nucleus absorbs a proton or fuses with another nucleus. Some examples: (i) $\rm{p}(\rm{p},\rm{e}^+\nu)\rm{d}~$ and $~\rm{d}(\rm{p},\gamma)^3\rm{He}~$ ...
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Can fusors be used to turn Uranium 238 into Plutonium 239?

Since a Farnsworth–Hirsch fusor is apparently a good fast neutron source that is simple enough to build at home, why can't it be used by rogue states or even terrorists to turn non fissile U-238, ...
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Do we have energy-positive fusion reactors?

This is something I have been wondering about for a long time. I know modern fusion reactors are far from being commercially viable, and probably just as far from going net positive. Still, has there ...
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Are there papers or experiments that point to non-fusion sources of solar neutrinos?

I've read that nuclear fusion is what generates such large quantities of solar neutrinos. Also saw that it was recently experimentally confirmed that two types/energies of neutrinos are generated in ...
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Energy from fusion beyond iron peak

In the diagram of nuclear binding energy per nucleon Eb/A (vertical axis) and mass number A (horizontal axis), Fe-56 has one of the highest values. Many authors state that nuclear fusion can only ...
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Why does fusion stop at iron when nickel is most tightly bound?

My understanding is that stellar fusion naturally stops at iron because it is energetically unfavourable to grow the nucleus further. But iron is only the third most tightly-bound nucleus, nickel is ...
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Why does nuclear fusion not occur with nuclei with a nucleon number higher than 56? Please tell me if I am correct

Please tell me if my assumption is correct. So nuclear fusion does not occur with nuclei (with a nucleon number higher than 56) because the binding energy of the product nucleus is lower than the ...
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What is box shape in ion beam drivers for ICF?

What is the meaning of box shape in the ion beam pulses? i mean in plasma we say the ion beam irradiating the capsule is box shaped. what does it mean?
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What is the difference between ion beam and laser?

What is the difference between laser beams and ion beams, especially in inertial confinement fusion? In inertial fusion, we use lasers as well as ion beams for driving the reaction. What is the ...
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162 views

How does the Sun generate its energy?

We all know that the sun generates its energy from nuclear fusion in the core. The electromagnetic radiation produced slowly travels upwards, while constantly being absorbed and re-emitted by the ...
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54 views

How to calculate the released energy in a fusion reaction knowing the mass of the reactants?

this the reaction formula:$H^2_1 + H^3_1 ->He^4_2 + n^1_0$ (idk how to put the numbers in the left) and I have the released energy of one reaction $E_r=2,8.10^{-12}J$, How to calculate the released ...
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Where is mass defect in nuclear fusion? [duplicate]

The hydrogen is one proton and the helium is two protons and two neutrons. Neutron is a little heavier than the proton. But there is something strange. Where is the mass defection? As a result, the ...
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Nuclear Fusion: What is the cause of transport? (Plasma leakage)

Context: I've been reading about The Hairy Ball Theorem which shows that the ideal shape for magnetic confinement fusion has to be a torus. Given that tokamaks use toroidal magnetic fields, I assumed ...
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Would a highly degenerate cosmic neutrino background affect fusion reactions that proceed via the weak interaction?

This might seem like a really strange question, but here's my reasoning. A proton-proton fusion reaction proceeds in two steps: \begin{align*} p + p + \text{1.25 MeV} &\rightarrow {}^2_2\mathrm{He}...
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Why is there more lead and mercury in the universe than gold?

I am watching a Science Channel program on the collapse of massive stars and it got me wondering... What is the distribution of heavier than iron elements in the universe. (It is my understanding ...
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Requirements for hydrogen fusion

What are the requirements for hydrogen atoms to go through fusion? Is it a ratio of heat to pressure or are there specific heat and pressure values that must be met (per atom or per mole?) Are there ...
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Fusion vs. Fission

I understand why fission generates large amounts of energy when the nucleus is split, but then why does fusion generate such large amounts of energy. If fission releases energy when some mass is lost ...
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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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Could you know in advance specifically when a star will go supernova?

I've been thinking about star trek 2009 and star trek Picard in which they happen to talk about a sun inside a fictional solar system which goes supernova destroying a particularly important planet to ...
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Is there anything quantum mechanical related to Fusion/Fission? ( Instead of special relativity)

Fusion/Fission is always accompanied by the special relativity relationship of $E=mc^2$. Yet there are atoms that are undergoing change, and that should be in the realm of Quantum Mechanics. Maybe in ...

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