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Questions tagged [neutrons]

The neutron is a subatomic particle, with no net electric charge and a mass slightly larger than that of a proton. It is a fermion of spin $\frac 1 2$; a hadron, that is it interacts strongly; and a nucleon, that is a crucial component of atomic nuclei.

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What if proton is heavier than neutron? [closed]

What really happens to the atom if proton gets heavier than a neutron. I've heard that proton emits radiation. Plz explain
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Is the Hamiltonian generated by the external magnetic field in the neutron interferometry experiment like "potential energy"?

I believe that the Hamiltonian generated by the external magnetic field in the neutron interferometry experiment effectively leads to an increase in the neutron's potential energy. Why is this ...
오성현's user avatar
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Free Neutron Decay

I've read that free neutrons can decay into hydrogen, but it's rare because the energy from the decay usually sends the electrons away, unable to bind with the protons. But if trillions of free ...
mdswartz's user avatar
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Neutron diffusion equation cylinder question

Hi there I was wondering if anyone could help me with how to approach this problem that I have. I'm looking to find the neutron flux outside of a cylindrical container which is made of steel, however ...
sp444cegirl's user avatar
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Neutron Dose Rate to Activity Calculation

This is a completely hypothetical question but say I have an unknown radioactive source inside a steel box, given the dimensions of the volumetric source and the container, the neutron dose rate 1m ...
sp444cegirl's user avatar
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Do neutrons have a higher entropy than protons?

Since free neutrons want to undergo beta decay into a proton while protons are relatively stable does that mean that neutrons have higher entropy than protons?
Oreoluwa Matilukuro's user avatar
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Is free neutron decay due to "running out" of something or just by chance?

When a free neutron (as an example) decays is that due perhaps to expending energy or is it because neutrons have some internal state which changes and sometimes that change results in decay? In the ...
releseabe's user avatar
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What is known about the isotope distribution of neutronium decay?

Sometimes it is known to happen. For example, neutron star mergers might result in unstable neutronium droplets which lose the enormous pressure that makes them stable. A "nucleon" of $10^{...
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Neutron Beta Decay Spectrum

Beta decay is generally displayed as below with a fairly significant intensity of electrons emitted with KE ~ 0. In this case, all the energy of the decay is given to the neutrino and the momentum is ...
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How does pion exchange cause protons and neutrons to be attracted to each other? [duplicate]

I read that neutron and protons are attracted through exchanging pions between each other. However, as far as I understand, they are just exchanging a meson, not any force carriers. What causes them ...
thingthingthing123's user avatar
4 votes
2 answers
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How do neutron stars overcome neutron degeneracy?

In a white dwarf, the star is prevented from collapsing due to the Pauli exclusion principle. If the star is heavy enough, the protons in the star will capture electrons, forming neutrons and ...
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Neutron double differential capture cross section

Can one define what is the double differential capture cross section for a neutron, and how one would construct an experiment to calculate the double differential cross section as a function of energy ...
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Is it possible to produce a focused, high-intensity neutron beam?

Since neutrons are uncharged, exceptionally hard to control, my understanding is that particle accelerators can never directly produce a beam of neutrons. Instead, they need to accelerate some charged ...
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How does a photon "cheat" its way past a neutron?

I learnt here Is a neutron deflected sideways by a laser beam? that a photon beam has no influence on the motion of a free neutron in the first and second approximation. Now I'm interested in what ...
HolgerFiedler's user avatar
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1 answer
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Is a neutron deflected sideways by a laser beam?

Is a freely moving neutron deflected sideways when a laser beam is directed at it from the side? It would be great if the question could be considered from the two points of view that the laser beam ...
HolgerFiedler'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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1 answer
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Where can I find accurate visual representations of atomic nucleus nucleons wave probability functions like I see for electron atomic orbitals?

Note the Wikipedia article for 'Atomic nucleus' was awkward here because first they depict the old concept with protons and neutrons as a bunch of spheres touching each other and in the sub-text ...
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How to use point-kinetics approximation to go from diffusion to point kinetics?

I understand that we get to point kinetics by neglecting spatial dependence in the diffusion equation, but I'm somewhat stuck on the details here. Robert E. Masterson's Introduction to Nuclear Reactor ...
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3 answers
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Does free neutron decay create a hydrogen atom?

When a free neutron decays, it is transformed into a proton, an electron, and a neutrino. Does this electron begin to "orbit" the proton, forming a hydrogen atom? Or does the electron run ...
Robert Goddard-Wright's user avatar
2 votes
1 answer
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Sensitivity of different elements to neutron activation analysis

When I look at Ortec AN34 Experiment 17, I see that the last page shows relative sensitivity to Neutron activation by weight for different elements. For example, the analysis of Fluorine is shown as ...
user192428's user avatar
1 vote
2 answers
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Is a neutron the mixture of a proton and an electron?

Is a neutron a combination of a proton and an electron either by mass and/or charge?
ChiquiFranklin's user avatar
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How does QED describe the electromagnetic scattering between two neutral fermions?

Fermions with no electric charge may carry magnetic moments e.g., the neutron. Since particles with magnetic magnetic moments interact, they're expected to scatter off each other electromagnetically. ...
Solidification's user avatar
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What is the significance of the Strong interaction between a pair of Neutrons?

When we are introduced to the Strong Nuclear force, we are told that it prevents the nucleus from flying apart because of the electric repulsion between protons. But there is no such repulsion between ...
Deepak Joshi'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
550 views

The difference between neutron and proton separation energy of a nucleus

For a given nucleus, why does the value of the neutron separation energy $S_n$ differ from the value of the proton separation energy $S_p$? One of the reasons that is immediately obvious is that the ...
Solidification's user avatar
5 votes
3 answers
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Can the neutrons in a nuclear reactor be collimated?

N.B. I am not a physicist. My layman's understanding of a nuclear reactor is essentially that neutrons are doing one of 4 things at any given time in the reaction chamber: Flying freely around. ...
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For Fermi's CP-1 experiments, why didn't they use much smaller slugs of natural uranium?

The Chicago Pile experiments used natural uranium slugs that were ~1.5 inches in diameter. The slugs were surrounded by graphite to slow down the naturally occurring neutrons to be able to affect ...
Young Jun Lee's user avatar
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1 answer
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Why do some nuclei decay by Neutron Emission?

Alright so I am confused somewhat about Neutron Heavy Nuclei not decaying, or more specifically why it is that Neutron Heavy Nuclei sometimes decay by emitting Neutrons. Someone has already answered ...
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Is this Why a Neutron can Decay Into a Proton, Electron and Electron Antineutrino?

A neutron is udd, then an u-anti-u starts to exist close to the neutron. Then the one d and u change places forming an uud (proton) and anti-ud which decays to an electron and electron-antineutrino. ...
Willem Esterhuyse's user avatar
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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
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3 answers
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Do electrons define the element? [closed]

In a nuclear reaction, protons and neutrons are exchanged and the resulting elements have a number of different protons and neutrons that uniquely define the element that we are studying. However, can ...
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How is the Neutron capture cross section of Xenon-135 so high?

Xenon-135 has a Neutron capture cross section of 2-3 million barns, this is equivalent in area to a disk with a radius of 8-10pm. The cross sectional area of a Uranium nucleus is roughly 1 barn. The ...
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Potential yields of Np-237 using a synchotron

U238 releases a neutron when it is exposed to photons of around 11 MeV, and the resulting U237 promptly decays into the fissile Np237. In such a situation, what equations can I use to relate the ...
Young Jun Lee's user avatar
-1 votes
1 answer
74 views

$\beta^{+}$ and $\beta^{-}$ decay processes

We know that electron cannot exist inside the nucleus for various reasons like its energy, angular momentum violation and etc. But these $\beta^{+}$ and $\beta^{-}$ processes occurs inside the nuclei ...
Anshul Sharma's user avatar
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Has Anti-beta decay been observed?

I am looking for references or resources regarding the transition of an anti-neutron through weak decay, into an anti-proton, positron, and electron-neutrino. Have such studies been conducted or ...
4 votes
1 answer
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Why the Fermi's energies of the proton, neutron and electron are related in this way in a neutron star?

I'm referring to this answer made by ProfRob about why neutrons are stable against beta decay in neutron stars. I've partially understood the answer: when the Fermi's momentum of the electron $p_f = (...
nervousdog's user avatar
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1 answer
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Refractive index of EM waves travelling though a gas of neutral particles

From what I have read and seen online. The explanation of why there is a net reduction in the speed of EM waves through a medium is due to the interference with the oscillating EM fields produced by ...
Jacob Daniels's user avatar
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In a fission reaction mass is converted to energy my students are asking where the mass is taken from - do the nucleons have less mass afterwards? [duplicate]

I am teaching year 11 Physics for the first time. In a fission reaction mass is converted to energy my students are asking where the mass is taken from - do the nucleons have less mass afterwards?
Diatom's user avatar
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-3 votes
1 answer
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Spallation neutron sources + wakefield particle accelerator + U-238 for generation of Pu-239 [closed]

I am looking to combine the principles of spallation neutron sources, wakefield particle accelerators, and neutron absorption to enable anybody to create large amounts of plutonium using relatively ...
Young Jun Lee's user avatar
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2 answers
58 views

Can Neutron Activation Analysis differ isotopes?

I know to carry out an NAA analysis, the specimen is placed into a suitable irradiation facility and bombarded with neutrons. This creates artificial radioisotopes of the elements present. Following ...
Carinha logo ali's user avatar
0 votes
1 answer
140 views

Is it possible to collide two neutrons? [closed]

If it is possible to collide two neutrons, how is it so? What particle accelerator or pre-collision processes are necessary and what results can be expected? If the products of neutron-neutron ...
Ayman Fayaz's user avatar
5 votes
1 answer
987 views

Is an electron more stable than a proton/neutron?

Is an electron more stable than a proton/neutron under extreme temperature/pressure conditions, like several 100 millions K?
Christian Speth's user avatar
0 votes
1 answer
19 views

Stacking of magnetic moments in a polarised neutron beam

Neutrons are particles that have a half spin and a magnetic moment. if you polarise a beam of neutrons so that they all align with spin +1/2 will the combined neutron beam have an overall magnetic ...
Moiz khokhar's user avatar
0 votes
1 answer
268 views

How electron, proton and neutron have mass numbers

As far as I know, the mass number of an atom means the amount of protons and neutrons it has. For example, the mass number of Sodium (Na) is 23 since it has 11 protons and 12 neutrons. Then how ...
Shaidozzaman Araf's user avatar
8 votes
2 answers
280 views

Why are nuclei with large numbers of neutrons only stable with correspondingly large numbers of protons? [duplicate]

Large numbers of protons need to be separated by neutrons, otherwise they repel.... But why do nuclei with large of numbers of neutrons only remain stable with a relatively, correspondingly large ...
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Fast neutron scattering in a neutron cloud

Will a 200 MeV neutron emitted into a neutron cloud undergo similar scattering interactions as one that is emitted into a water moderator with the resulting decreases in energy?
John Clayton's user avatar
1 vote
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Doppler broadening and Voigt profile

The shape of an isolated neutron resonance at incident neutron energy, $E_{R}$, can to first-order be represented by the single-level Breit-Wigner (SLBW) formalism, which is equivalent to a Lorentzian ...
unclearnuclear's user avatar
34 votes
4 answers
6k views

Why is water a good neutron absorber?

I've seen this question asked multiple times, and the answer is never detailed. I initially assumed that either hydrogen or oxygen had relatively large neutron absorption cross sections, however that ...
ryani42's user avatar
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1 vote
1 answer
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Can sub-uranic elements produce a nuclear explosion if they are exposed to an extreme neutron flux? [closed]

I believe that the gun-type nuclear bomb dropped on Japan used a neutron flux generator to help its uranium go critical. I also believe that while sub-uranic elements can undergo fission, they always ...
Thomas Brannan's user avatar
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2 answers
162 views

Neutron star vs. Islands of stability

"Neutron stars" are said to be almost entirely composed of neutrons. The islands of stability principle recognizes an upper limit to the number of neutrons that can be introduced to an atom. ...
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