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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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Hollow Conical Shell Z-pinch Lithium Penning Gas For $^6Li$ + $^2H$ => $^4He2$ Fusion?

It occurred to me that boiling $^6Li$ as the thermal step in a Z-pinch device, given lithium's low first-ionization energy, might be a better way of creating homogeneous ions for the subsequent ...
James Bowery's user avatar
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Is there any formula for calculating the temperature required for nuclear fusion for a specific pressure?

From what I have gathered through my research I've come to the conclusion that the temperature required for nuclear fusion decreases with increasing pressure; this seems intuitive enough. However, I ...
2 ADITYA KRISH DEB XII SCIENCE's user avatar
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Can you create fusion through scattering?

Could you scatter deuteron molecules (D-D) at high energies into some heavy metal target such that at the time of impact the bond in the deuteron molecule is compressed to such a degree that fusion is ...
EigenDragon16's user avatar
-8 votes
1 answer
65 views

Is cold fusion the only avenue for fusion reactors? [closed]

To my understanding, cold fusion proposes a solution to usable fusion reactions by finding a way to fuse nuclei at room or near-room temperatures. However, I also understand that improving energy in ...
yolo's user avatar
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Can electrons or protons due to fusion reduce in their individual mass?

It's a ridiculous question, but that's why I am asking it after getting confused over a paragraph about nuclear fusion in my textbook. The total mass of a stable nucleus is slightly less than the ...
HBP's user avatar
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On the units of NRT-dpa electronic losses formula (Lindhard)

I'm trying to convert the PKA energy into damage energy following equation (5) of the NRT-dpa model article. In Fig. 1 you have an example of what you should get. Let's take $E=40keV$ (PKA), therefore ...
Abel Gutiérrez's user avatar
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2 answers
47 views

Relationship between gravitational force and fusion energy in stars [duplicate]

From what I understand, stars like our Sun constantly have a gravitational force on their surface due to their mass, which is balanced out by the fusion reactions taking place in the core of the Sun. ...
Waev's user avatar
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1 answer
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Finding the cross section for the proton-proton fusion reaction

I have been looking at the cross section $(\sigma)$ for the proton-proton collision in plasma. From what I have researched, the cross section cannot be found experimentally so it must be found through ...
Waev's user avatar
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2 answers
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Can Muon Catalyzed Fusion work in a Plasma?

From what I understand, muon catalyzed fusion works by injecting muons into the deuterium and tritium, which then they replace the electron shared between the hydrogen isotopes in a molecule, making ...
Barry Allen 's user avatar
3 votes
1 answer
64 views

Can X-rays compress plasma for fusion?

I know in ICF fusion, generally lasers are used to generate X-rays inside a holhraum to compress a duetirium tritium fuel pellet until it generates fusion reactions. I was wondering if the same ...
Barry Allen 's user avatar
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Artificial Nucleosynthesis

Is it possible to artificially turn hydrogen into helium, let's say, and then go from helium to lithium and so on? I know that fusion reactors do that by fusing deuterium and tritium. Could this be a ...
Aaa's user avatar
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What is magnetic shear?

Can someone please summarise to me what exactly magnetic shear is? I know shear as $\tau=F/A$, and intuitively interpret is as, eg, a force on an object and the friction response being shear forces. ...
matrixender's user avatar
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3 answers
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Question about the use of the term 'mode' vs 'instability' in fusion experiments

I am currently trying to get to grips with MHD instabilities in fusion experiments, and I am confused at to why instabilities are sometimes referred to as modes? To my understanding, a 'mode' is a ...
matrixender's user avatar
2 votes
3 answers
78 views

Does the definition of "energy produced" by the LLNL's NIF fusion experiment include the energy delivered?

A figure in a 23 Nov 2023 article on Optics.org shows that more energy was produced than delivered. That is, the area or the red region seems to represent the energy produced. But a similar figure in ...
phil1008's user avatar
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Muonic Hydrogen Dissociation

Is the dissociation energy of a muonic molecular hydrogen ion the same as an ordinary molecular hydrogen ion? Would the cross-section for dissociation be the same as an ordinary molecular hydrogen ion?...
S.T. Zweig's user avatar
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1 answer
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Fusion in the sun for 4 hydrogen to Helium-4. How is the energy produced

So please correct me if I am wrong but: First 2 proton’s (each with an electron) fuse together, The mass stays the same so no energy is produced? Then 1 of the protons turns into a neutron with a ...
Bobbie Space's user avatar
1 vote
1 answer
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Why does a Tokomak work on low pressure? In most other places high pressure seems to be required for fusion

In a star gravity creates the pressure, and fusion reactions create the temperature for fusion. In a thermonuclear bomb the fissile shell around the core exploding inwards create the temperature and ...
Luke Campbell's user avatar
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What mass fraction of a main sequence star produces energy?

Only some fraction of the total mass of a main sequence star produces energy in the star's centre through the pp-chains, or in heavy stars, the CNO-cycle. My question is about the mass fraction where ...
gamma1954's user avatar
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Muon-catalyzed fusion: muon number

I recently read a paper "Meson-catalyzed fusion in ultradense plasmas" (it is behind a paywall: only subscribers to Physical Reviews E can read it) that claims that muon-catalyzed fusion in ...
S.T. Zweig's user avatar
0 votes
1 answer
88 views

Efficient way to convert hydrogen atoms to neutrons?

Can a hydrogen atom be converted to a neutron with a sufficiently high energy photon? Or perhaps via a pair of photons having total energy of about 800 keV? One photon would have an energy of say ...
Mike J's user avatar
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1 answer
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High-energy neutron multiplier

Are there any materials that can function as efficient high-energy neutron multipliers? I have read about the utilization of Beryllium and Lead as neutron multipliers, but they seem to only be ...
S.T. Zweig's user avatar
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0 answers
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Green's function for a Hirsch-Farnsworth fusor

I'm writing a proposal for building a Hirsch-Farnsworth fusor at my university using a vacuum chamber, deuterium, and high voltage power. A loop of wire inside the chamber is set at a negative voltage ...
Tyler Mark's user avatar
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0 answers
127 views

Ideal ignition temperature for a D-T plasma fusion reaction

I've been trying to calculate the ideal ignition temperature for a 50-50% Deuterium-Tritium (D-T) reaction. In the literature this value is $4.4$keV and I'm getting $5.2$keV. Here's how I'm carrying ...
kid_a's user avatar
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Are there spectra that "prove" that measured energy excesses came purely from deuterium-tritium fusion reactions at the NIF during ignition events?

More energy was produced than was supplied by ultraviolet (UV) lasers (creating x-rays in the gold chamber wall to compress the spherical hollow capsule creating a dense, high-temperature, high-...
Alden Park's user avatar
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0 answers
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HB11 fusion Engine

Looking for a way to achieve torch ship performance (https://www.projectrho.com/public_html/rocket/torchships.php#torchdrive) Without strapping my reactor/engine to the outside of my ship. The main ...
Michael Ferrell's user avatar
6 votes
2 answers
2k views

During fusion, how does mass turn into energy?

This is my (flawed) understanding of how fusion basically works: Let's assume that a fusion reaction has a net gain in energy. First, there is an input amount of kinetic energy to get the two light ...
Edward Chen's user avatar
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0 answers
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Power from CNO Cycle Fusion

There are all sorts of projects trying to get power from fusion reactions. The best known and funded are the Tokamaks, big expensive crush Deuterium and Tritium (He3 sometimes) plasmas and spew ...
MongoTheGeek's user avatar
0 votes
1 answer
59 views

How is volume defined and measured in nuclear physics, in particular regarding the Sun’s core? [closed]

The Sun’s core is, from the micro/quantum perspective (from what I've read) the constantly moving phenomena of nuclear fusion (as the Earth is mostly the constantly moving phenomena of stable atoms ...
lars706's user avatar
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In a tokamak, is there a density-dependent limit on plasma current?

In a tokamak, the kink limit places an upper bound on the magnitude of the plasma current. For example, Parisi and Ball (2019) write this limit as (p. 246) $$I\lesssim\frac{1}{q}\frac{2\pi}{\mu_0}\...
SapereAude's user avatar
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Could lithium deuteride sustain a "cold" chain reaction?

When Lithium 6 absorbs a neutron (thermal or not) it reacts forming an alpha particle and a tritium. The formed tritium has an average kinetic energy of 2.5 MeV. That kinetic energy is way higher than ...
Peter S.'s user avatar
1 vote
1 answer
61 views

Why lasers are used in inertial nuclear fusion?

Why in inertial fusion are used laser rays but not, for example, merely focused light? Is there a problem with precision of focusing or power density?
Nonexistent user's user avatar
2 votes
1 answer
85 views

Confusion about energy conservation for fusion and fission (binding energy and $Q$-value)

In a nuclear reaction, a system consisting of a nucleus or nuclei lose mass, and this mass gets turned into energy, which is quantified by $E=mc^{2}$. But I'm conceptually confused. According to ...
beancurdedward's user avatar
1 vote
0 answers
25 views

Improved estimate of density of free neutrons in solar core

In an answer to this question: Free neutrons in the sun's core? I made a very rough attempt to estimate the density of free neutrons in the solar core. There is some non-zero rate for production ...
Andrew Steane's user avatar
1 vote
1 answer
227 views

Why does the Nuclear fusion rate decrease with temperature after a point?

According to here the Fusion rate for D-T peaks at a little under 1E9 Kelvin and decreases afterwards. Why is this? Why does the rate stop increasing?
blademan9999's user avatar
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1 vote
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How do protons fuse in the sun?

I know that Nucelar fusion in the sun requires quantum tunneling to occur, as otherwise the Sun's core wouldn't be hot enough to overcome the Fusion barrier. However while the 2nd and further stage of ...
blademan9999's user avatar
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0 votes
2 answers
113 views

What’s the lightest you could make a "star" if you made it out of different materials?

What’s the lightest you could make a "star" if you made it out of different materials? How large would the "star" be? For example according to here https://astronomy.stackexchange....
blademan9999's user avatar
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1 vote
0 answers
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Determing for particle density of many particle species in plasma

For quasi-neutrality plasma of many species, the relation of electron density and ion density said that \begin{equation} n_{\text{e}} = \sum_{s}Z_{\text{i},s}n_{\text{i},s}, \end{equation} where $n_{\...
nirama_xox's user avatar
0 votes
1 answer
116 views

What’s the minimum mass required for a star to burn helium?

What’s the minimum mass required for a star to burn helium? I’ve liked online but I’ve gotten inconsistent answers.
blademan9999's user avatar
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0 votes
1 answer
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What are some practical problems with static electrical confinement of plasma?

Plasma and fusion physics experts, help me with this one: Suppose we have a D-T plasma with net positive electrical charge inside a positively charged metal sphere. As the containment sphere's net ...
wdsky's user avatar
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0 votes
1 answer
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How Should the True Energy Gain of the NIF's "Scientific Breakeven" Fusion Experiment be Calculated?

According to this article "LLNL’s experiment surpassed the fusion threshold by delivering 2.05 megajoules (MJ) of energy to the target, resulting in 3.15 MJ of fusion energy output." It isn'...
phil1008's user avatar
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1 vote
0 answers
55 views

Theoretical calculation for deuterium tritium fusion

How would a deuterium-tritium fusion feynmann diagram look like in terms of QHD (i.e meson exchange like eta,pi,sigma,omega,...)? I couldn't find anything online whilst this would be quite an ...
nemo's user avatar
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-1 votes
3 answers
214 views

Why it is not possible to reach the sun if we are able to create plasma? [closed]

if we are able to create plasma in isolated environment possessing temperature much more than temperature of sun then why are we not able to create something that can go to the sun?
Mohammad Sameer's user avatar
0 votes
1 answer
101 views

How does an electron absorb the energy released during inelastic collision between a neutron and the nucleus of a hydrogen atom?

In atomic collisions,does the neutron fuse with the proton of hydrogen and release a photon which is absorbed by the electron which then gets excited to higher energy state? Or do the neutron and ...
Pranstein's user avatar
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1 answer
213 views

Is there an intuitive picture for quasi-isodynamic versus quasi-axisymmetric versus quasi-helically symmetric flow in stellarators?

I recently read a paper in which Alan Boozer says, The W7-X stellarator was made quasi-isodynamic rather than quasi-symmetric in order to minimize the parallel currents as well as the ripple-trapped ...
SapereAude's user avatar
1 vote
1 answer
40 views

Are there any research mentioning the principle of tornados or maelstroms in plasma physics related to fusion?

There are many different ideas and concepts related to design of fusion reactors and handling plasma confinement, but what about designing one around the principles of a maelstrom or a tornado? Is ...
Andreas Zita's user avatar
0 votes
1 answer
106 views

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 ...
Daumic's user avatar
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0 votes
2 answers
155 views

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 ...
user56834's user avatar
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3 votes
2 answers
337 views

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 ...
Kurt Hikes's user avatar
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23 votes
15 answers
9k views

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 ...
user56834's user avatar
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1 vote
2 answers
91 views

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 ...
TheJeran's user avatar
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