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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Nuclear fusion by Z-pinch without Marx generator?
The Marx generator was invented by Erwin Marx in 1924 (1). This electric generator is an assembly of capacitors and spark-gaps. The capacitors charged in parallel and are discharged in serie. This ...
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How does the second stage of a fusion bomb create and maintain the needed pressure?
My understanding of the second stage of a thermonuclear bomb is as follows:
X-rays from the first stage compress the "tamper", thereby igniting the fission sparkplug, and that the resulting ...
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Why do most MRI machines and fusion reactors use helium-cooled superconducting magnets instead of cheaper, higher-temperature nitrogen-cooled ones?
I am always hearing about the high (and increasing) costs of helium, as well as the difficulty of handling it....
Are there no high(ish) temperature superconductors that can create a strong enough ...
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Why are nuclear fusion reactors difficult?
The first fission bomb was created in 1944, and the first fission reactor in 1951 (and actually productive one in 1954). This delay seems possible to explain by there being a larger amount of initial ...
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What "changes" in the quantum state of bound nucleons that cause that system to have mass defect?
The electric field in an excited hydrogen atom is non-zero over a bigger volume than the electric field in a ground-state hydrogen atom. The energy associated with this extra electric field must be ...
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Derivation of pressure balance equation for a toroidal geometry [closed]
Derivation of pressure balance equation in toroidal geometry
$$
\boxed{
\frac{\mathrm{d}p}{\mathrm{d}r} + \frac{\mathrm{d}}{\mathrm{d}r} \left( \frac{B_{\phi}^2}{2\mu_0} \right) + \frac{B_{\theta}}{\...
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Exchange interaction and nuclear fusion
Most texts about nuclear fusion say that the reason it is so hard to get protons to fuse is the strong Coulombic repulsion between them. However, it seems to me that at close distances, protons should ...
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Why does deuterium fusing with a proton produce a gamma ray?
For the pp chain, the second process is listed as the d(p,γ) 3He reaction: D + p --> 3He + gamma ray.
I cannot find an explanation why a gamma ray is created in this process. Can anyone explain why ...
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Would an intersecting plasma in a fusion reactor increase yield due to the collision of particles in the plasma?
It seems to me that having a plasma “stream” in a tokamak that intersected itself would increase the number of collisions happening between particles. Is this feasible or is it negligible in the face ...
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How is the branching ratio defined for nuclear reactions?
The Wikipedia page for candidate nuclear reactions for terrestrial fusion power notes that the D + D and He-3 + T reactions can proceed through either of two alternative routes; for example:
(2i) D ...
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Is the universe getting hotter? Brighter?
Due to their fusion processes every star is radiating massive amounts of photons and (to a lesser extent) neutrinos. Are all of these getting absorbed in matter over time, warming it, or is the total ...
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What would the nucleus of a water planet be like?
If we have a planet made out of water, would it be all solid? What about the nucleus? Would it depend on the size of the planet?
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Is the energy of matter (via $E=mc^2$) actually available to do work?
If energy is functionally defined as the capacity to do work, then in what sense does mass offer a lot of energy (via $E=mc^2$). Most people responses I've seen to similar questions state “there’s a ...
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It is possible to combine two heavy elements into one?
Is it possible to combine say two uranium atoms into very heavy new element? Periodic table ends around 115 today, but can it go forever technically?
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How can the binding energy per nucleon graph be useful if you can't compare "all" products with "all" reactants?
How can the binding energy per nucleon (BEN) graph be useful if one can't compare "all" products with "all" reactants?
Take the fission process of Uranium to Thorium:
$${}^{238}U \...
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What does thermal (non-)equilbirum mean in the context of a fusion reactor (such as the Helion reactor)?
A while ago, there was a question here asking about the impact of Todd Rider's thesis about various fundamental limitations to fusion reactor efficiecy. That question was mainly concerned with why ...
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Mass per nucleon graph
I am a high school student and am struggling with understanding the significance of the mass per nucleon graph.
What does this graph show with regard to nuclear reactions? (y-axis: M/A, x-axis:A) I ...
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How do the atoms and electrons move around space when the solar core presses them into a dense plasma? [closed]
It takes a lot of intelligence to compute the center of the sun. As far as I imagine, it's compressed by the hand of gravity and high energy fusion radiation wants to escape one way or the other. ...
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Are there any calculations that "backup" magnetized inertial fusion by steam pistons?
Piston driven MTF can generate fusion. General Fusion has released data on the plasma confinement that they do in their machines, so there is no doubt to the feasibility of the approach.
Nonetheless, ...
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Neutronization process
How can I find the neutronization density for cold hydrogen plasma?
Does it happen within the fusion process of protons and electrons which yields neutrons and neutrino?
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NIF Ignition Achievement
Although the National Ignition Facility achieving positive energy output is hailed as an achievement in fusion energy, I am curious whether their configuration could ever be adapted to produce ...
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Which proportions of deuterium and tritium did the National Ignition Facility's hohlraum contain?
The National Ignition fusion recently announced the achievement of nuclear fusion "ignition", i.e. more energy released from a sample undergoing nuclear fusion reactions than was directly ...
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Rough estimation/calculation of the efficiency of a fusion reactor [closed]
Where are the losses during the reaction. In the creating of the electromagnetic field? The heat released by the fast moving neutron? or something else?
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How do X-rays cause fusion?
I have watched the news of the recent fusion experiments and had a question.
I understand that X-rays will make the electrons break away from the atom, because the electons absorb energy.
All of the ...
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Where is the 2.05 MJ input energy measured? (referring to the recent experiment at the National Ignition Facility (NIF))
The recent fusion experiment at the National Ignition Facility delivered "2.05 megajoules (MJ) of energy to the target, resulting in 3.15 MJ of fusion energy output." But where exactly is ...
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Are there any "nano" or "micro" fusion reactors that can produce really small electric energy currents around 5 volts? [closed]
If there was such a thing, I probably would've heard of, but when I try to research about that on google, I can only see the fusion reactors meant to generate energy on the scale of supplying cities, ...
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Would a fusion reactor using Helium-3 get some of its energy from fusing it with free neutrons?
I know that He-3-based fusion is supposed to be aneutronic, but aren't there still some free neutrons? Would this make a noticeable difference in heat/energy produced?
Also, couldn't helium-3 be ...
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What enabled ignition at the NIF?
The National Ignition Facility
achieved breakeven on December 5th,
obtaining more than 3 MJ from an
input of 2.05 MJ.
What have they been doing differently,
starting this summer?
Laser shots this year ...
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Open problems in nuclear fusion [closed]
I'm starting to learn about the nuclear fusion and wonder what are (if any) the major open theoretical/computational problems in this field? Ideally something related to the properties of quantum mamy-...
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How was the recent $\rm 59 MJ$ JET fusion record (Dec 2021) different from previous records?
Did they simply induce a stronger current (meaning more heat) in the plasma? Did they manage to compress the plasma more? Or did they change DT pressure or something else?
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Meaning of Lawson criterion
Does Lawson criterion mean the same as the minimum value of triple fusion product? If not, could you please explain what each of them are?
Wikipedia page on Lawson criterion
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Nuclear fusion reactors and neutrons
The majority of energy produced by nuclear fusion is harnessed by neutrons or protons that split out from the product.
Given the dominant fusion method today is Deuterium + Tritium which produces He ...
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Why can't relativistic beams facilitate fusion?
From this SE post, I see that the Coulomb force between two charged particles moving at relativistic speeds is balanced by the Lorentz force, and the overall force between the particles limits to zero ...
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Neil de Grasse Tyson on Nukes and Radiation - What the Heck Is He Talking About?
Last week Neil de Grasse Tyson was on Bill Maher's show and the topic of nuclear weapons came up.
Tyson said, "modern nukes don't have the radiation problem.... They're a different kind of weapon ...
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Does a fission bomb end up causing fusion of ambient elements or remain parts of the bomb itself?
Given the heat and pressure, is there some reason why a relatively small amount of atoms of various elements in the atmosphere or soil or in the metals used to make to bomb itself do not fuse?
I do ...
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Enthalpy of fusion - water [closed]
Trying to solve:
$$l = \frac{Q(\text{melt})}{m(\text{ice})}$$
$$Q(\text{melting of water}) = Q(\text{heating of
ice}) - Q(\text{cooling of water})$$
$$l \times m(\text{ice}) = c \times m(\text{...
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What physical properties make fusion of iron unlike lighter nuclei in main sequence stars?
I understand that after fusing lighter nuclei, a main sequence star will either stop fusing or the fusion does not release enough energy to continue the sequence.
What physical properties make iron ...
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Why will nuclear fusion ever be energy net-positive?
Question from a layman:
In nuclear fission, you don't do all the work to split each nuclei every time. You set things up in a clever way so there is a chain reaction. Previously split nuclei cause ...
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Lightning produces antimatter -- does an h-bomb?
When I search on this, I get hits for antimatter weapons but I am wondering if very energetic events like an h-bomb or a fission weapon are know to produce antimatter? If so, could it be produced in a ...
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If muons had long enough half lives, could muon-catalyzed p-p fusion be viable?
I was reading about muon-catalyzed fusion and how the "alpha sticking problem" is a major barrier to viability, but when you fuse two protons together you get deuterium instead, which still ...
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What's the lifespan of Deuterium and Helium-3 in the Sun?
What's the lifespan of Deuterium and Helium-3 in the sun?
How long on average, the Deuterium and Helium-3 atoms last in the Sun's core?
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How big would a star made of pure deuterium have to be to start fusion?
$D$-$D$ fusion happens much more easily than proton-proton fusion, so I imagine a star made of pure deuterium could be much smaller and still have fusion. Are precise size limits known? How does ...
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Is a nuclear detonation wave on a gas giant like Jupiter possible?
I've seen papers doing detailed calculations showing that it's not possible to create a propagating nuclear detonation in Earth's atmosphere or oceans, e.g., this paper. Is it known whether it's ...
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Maximum theoretical $\text{D-T}$ energy output in proposed First Light Fusion (FLF) fuel pellet
I recently stumbled into Youtube videos diving into the science behind First Light Fusion's (FLF) goal of creating an inertial confinement fusion (ICF) fuel pellet by leveraging the phenomenon of ...
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If someone dropped a conventional bomb on a stellerator, what would happen?
Let's say we have a stellarator outputting a steady 200 GW of electrical power. If someone dropped a conventional bomb / explosive / shell on it that was just enough to breach plasma containment, how ...
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What is the role of permanent magnets on a Tokamak reactor?
Maybe I'm wrong, but to my understand, electromagnets can only be made with a conductive coil and a ferromagnetic piece, not permanent magnets.
I first thought that electromagnets where the only ...
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How much energy from neutrinos does a Helium flash create?
How much energy from neutrinos is given of by a solar mass star when it undergoes a Helium flash?
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Can fusional nuclear compression theoretically be achieved with a unidirectional compressive force?
In other words, is it theoretically possible to get an energy-profittable nuclear fusion reaction by simply slamming compressive force into some nuclei from a single laser compressing from one ...
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Amount of atoms in 1000kg of Deuterium per Britannica [closed]
I was recently attempting to calculate the amount of energy released in fusion reactions, and began using as a reference the Britannica article Energy released in fusion reactions. Within that ...
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Why don't deuterons produce a helium-4 nucleus when they fuse?
I would expect two deuterium nuclei to fuse straight into a single helium-4 nucleus, because that's by far the most stable way to arrange 2 protons and 2 neutrons. But instead, any two fusing ...
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