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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Neutron capture calculation

So, the problem state is: Neutron beam radiates sample A with initial number of atoms $N_0$. With neutron capture nuclei (cores) of A are transitioning to nuclei B (they are just one neutron richer ...
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Ultra Cold Neutrons in a Bottle Question

If you take a large amount of ultracold neutrons and confine them in a bottle would they then decay into protons and then fuse because they are so tightly condensed that the protons, once neutrons, ...
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Is this a radioactive meteorite? [closed]

Can a neutron beam emission from a strong naturally-occurring radioisotope deflect a small sewing needle hung by a thread an inch from the source? I have someone reporting to me of such a thing ...
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Polonium 210 degradation

From what I read online - Polonium 210 is the isotope used as the neutron initiator in nuclear weapons. But the half-life of this element 138 days. This raises questions: how do substantial ...
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Direction of neutron scattering

When neutrons interact with matter scattering, what direction to they scatter? Is it random, or some probability distribution of directions? I'm trying to understand why neutron reflectors reflect ...
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Why don't we coat the pressure vessels of nuclear reactors in boron to reduce neutron embrittlement?

Neutron embrittlement is a big problem in reactor design, as high energy neutrons cause lattice defects in materials like steel by slamming into iron nuclei. This limits the lifetime of the reactor, ...
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Why neutrons production is falling along beam axis in proton/nucleus collisions?

I'm studying a case where I simulate a protons beam (~70 MeV) on a spherical target composed of light nuclei such as carbon and oxygen. I'm looking for the angular distribution of neutrons produced by ...
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Neutron capture gamma energy

I have the atom 113Cd which captures a neutron and becomes 114Cd. This 114Cd goes from being exited to its base by emitting gamma rays. How can I calculate the Energy of those gamma rays? I can ignore ...
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How can you determine how much neutron shielding is necessary for a given neutron source?

Trying to make a fusor at home and I was wondering if there is an industry standard or perhaps an equation to determine how and what type of neutron shielding is necessary to protect against the high ...
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What came first, neutrons or electrons? [closed]

I wonder if electrons were first (at an early stage of the cosmos) embedded into neutrons, making it easier to understand why they would fit so well with protons later, or if the genesis of electrons ...
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Limit to number of neutrons in nucleus [duplicate]

As far as I understand the number of protons in a nucleus is limited because Coulomb forces grow faster with the number of protons than the nuclear force. So alpha/cluster decay limits the size in ...
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What is the escape velocity of a neutron particle (not neutron star)

I'm not sure if this question makes sense (if not maybe you can explain why) But if the neutron has mass and have a size, then it should have a escape velocity in the "surface" right? I know the ...
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Neutron decay discrepancy

I have been reading the article Neutron Lifetime Puzzle Deepens, but No Dark Matter Seen on the present methods of measuring the life span of neutrons The bottle method measures a mean lifespan which ...
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What happens to the electron when a neutron knocks off a proton from hydrogen atom?

In recoil proton scintillators, the hydrogen acts as a neutron converter to produce protons when a neutron strikes a H atom. But what happens to the electron in H atom? Where does it go? Does it ...
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Polarisation inside neutron

What happens to a neutron when it is placed in an electric field? Does polarisation take place inside the neutron (As it consists of charged quarks) in a similar way as that of neutral atom?
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Can neutronic emissions be used as a power source?

The free neutron will degrade to a proton electron and anti neutrino in about 15 minutes. Assuming you could slow a beam of free neutrons sufficiently to keep the size of the reactor manageable: Is ...
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How is mass of neutron compared with proton when it is inside the nucleus? [closed]

The mass of free neutron is around 0.1% more than the mass of proton. When it is bound inside the nucleus, neutron mass is less compared to its mass in free state. The question is how much mass it ...
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Strong force and radioactivity [duplicate]

Why does adding more neutrons to an atom unstabilise it? Won’t adding more neutrons increase the strong force and thus knit the nucleus more tightly? Or is it because it’s being added in a particular ...
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Why does a scintillator need to be fast decaying?

I have two scintillators, say, one with a decay time of 1 ns vs. one with 100 ns. All other parameters like light yield, size of crystal, electronics used, source emission rate, are the same for both. ...
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Minimum energy of proton converting into a neutron

I'm given the isotope sodium 22 (which is positron emitter) and I'm stuck with calculating the minimum energy that a proton needs to convert into a neutron and a positron. It got to do with $E=MC^2$ ...
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Scintillator decay time=1000 nsec,does that mean dead time is really high?

What I'm really confused about is, say my scintillator is really slow, and has a decay time of about 1000 nsec. Does that mean, if one neutron is being read by the electronics, for that particular ...
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Why does this quiz question say that protons and electrons do not combine to form neutrons?

I read this somewhere: Where are the protons and electrons in a neutron star? When the neutron star forms, most of the protons and electrons combine together to form neutrons. But on a true/false ...
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Where is the missing energy in the Debye-Waller effect?

X-ray/neutron scattering from crystals and liquids is well-described by the scattering theory to give the (dynamic) structure factor which is a function of momentum and energy: $$S(\mathbf{k},\omega)=...
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What is the effect of isospin on the proton or neutron alone, i.e. not in a doublet?

So I start with a proton $p$. I extend my "physical" space by means of the internal degree of freedom of isospin, so that I know write $p$ in a higher dimensional space: $$ p = \left( \begin{array}{...
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Can a neutron decay into a proton + muon (+ muon-neutrino)

Can a neutron, if it has enough kinetic energy, decay like: $ \hspace{0.3cm} n \rightarrow p + \mu^- + \bar{\nu}_\mu $ I assume it's not allowed since it's not on the possible decay modes on the ...
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What is the upper limit for the size of an atom? [duplicate]

I read an article saying an Israeli scientist had discovered the heaviest nucleus with 122 protons and 170 neutrons, and found it in a sample of purified thorium, and I would like to know if there are ...
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Stability in Nuclear Shell Model

As far as I understand , a particular sub-shell is filled with either protons or neutrons, $2*(2l+1)$ number of them, and never both together since protons and neutrons fill up levels separately in ...
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Would Newton law of gravity be the same between two neutrons at smaller distance? [closed]

Imagine 2 neutrons placed at some distance apart, they should only gravitationally attract each other according to Newton law of gravity. Theoretically the law should work at smaller distance until ...
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formation of atomic nuclei from nucleons

What holds the nucleus together? In a nucleus there are several protons, all of which are positive. Why don't they push themselves apart? It turns out that in nuclei there are, in addition to ...
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Why is neutron slightly heavier than the proton? [duplicate]

With latest knowledge of QCD, is there any explanation for why the neutron is slightly heavier than the proton? Can it be boiled down to a simple formula?
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How do you move a neutron? [duplicate]

An electron can be moved using magnetic field so how about neutron? What really happens at quantum level when you physically move it and what fundamental force is involved? For this question let's ...
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Is a nucleus a collection of quarks or a collection of neutrons and protons? [duplicate]

I do not much about particle physics. But people say that neutron and proton are composed of quarks, and in turn a nucleus is composed of neutrons and protons. Therefore, the question is, is this ...
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Wildly Inconsistent Answers Re: A Teaspoon of Neutron Star versus the Giza Pyramid

I'm experiencing a mild fit of nerd-rage here and I'm hoping someone can help. I was watching a documentary and it made a claim I've heard a few times before: that a teaspoon of material from a ...
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Why exactly is Neutronium-4 unstable and how to explain Marqués' experimental results?

Wikipedia states: A tetraneutron is a hypothetical stable cluster of four neutrons. The existence of this cluster of particles is not supported by current models of nuclear forces. There is some ...
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What is the measured decay rate of antineutrons? / What is the measured mean lifetime of antineutrons?

Please do not post any "answers" dealing with predicted/theoretical estimates. The question specifically asks for measured / experimental evidence.
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Heating effect of fast neutrons in Fast Breeder Reactors

Do fast neutrons play effective(meaningful) role in heating up the water in Fast Breeder Reactors? If so, how much do they?
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ultracold neutron captured inside fullerene molecule

I wonder if one could capture an ultracold neutron (energy below 180 neV) inside an equally cold C60 molecule to obtain a composite molecule n@C60. It is known that neutrons with this very low ...
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Do neutrons that undergo diffraction lose or gain energy? And how much and in what form?

Neutrons that undergo diffraction change direction ... is there a change in the kinetic energy of that neutron? If so, how is that manifested?
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What would happen to a room full of neutrons?

Suppose you had a room full of neutrons at standard pressure and temperature. Would it be just like a room full of hydrogen?
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In a quantum state, Maximum how many protons & neutrons can exist?

This is in reference to the statement I have read in a book i.e., " each quantum state can contain at the most two protons (with opposite spin) & two neutrons (again with opposite spin)". So what ...
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Unstable vs. stable nuclei plotted on a graph

The enclosed graph shows the number of Protons on the x-axis (Z), and the number of Neutrons on the y-axis for all elements (N). Stable combinations are marked by black squares, whereas unstable ones ...
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Could anyone explain how energy and momentum are conserved when an isolated neutron decays into a beta-minus particle?

I am not able to get to a reasonable explanation as to how momentum and energy are conserved when an electron, a proton, and a neutrino are created.
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What happens if a neutron flies towards a nucleus?

Rutherford experiment shows that alpha-particles when they fly towards metal foil sometimes (in minority of cases) can bounce. An explanation proposed was that atoms in fact have positively charged ...
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Enrico Fermi and neutron interactions

Enrico Fermi and his team were studying neutron absorption and the subsequent gamma ray emissions, in the 1930’s era. They calculated, based on the size of the nucleus and the speed of the neutron, ...
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Neutron reflectivity/X-ray reflectivity vs critical angle

I am trying to write a code that calculates Neutron/X-ray reflectivity profile of a multilayered system using Parrat algorithm. I am wondering what to do for $Q$ values below the critical $Q$ edge (...
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Why do we not use cold neutrons in nuclear reactors?

Typical nuclear reactors use neutrons in the $10^{-2}$ eV range (thermal neutrons) which corresponds to a fission cross section of a few hundred barns. What stops us from using a super-cold moderator, ...
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Which elements or isotopes can be analyzed by Neutron activation analysis (NAA)?

Some sources name only a handful, but that might refer to the use of optical film. Others state more than 70. I would like to know which elemets or isotopes can be detectet/imaged by NAA.
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How are exchange terms in phenomenological nuclear potentials related to the exchange of nuclear force carrirer particles?

Consider a proton-neutron system. Phenomenlogical nucleon-nucleon potentials contain exchange forces terms (Majorana, Bartlett and Heisenberg terms), which are linked to the symmetry of the state w.r....
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What happens to the chlorine in epichlorohydrin when a two-part epoxy is air-cured?

Where does the chlorine go? Does it evaporate as a by-product or does it remain in the epoxy? I'm using a two-part resin and hardener and curing them at room temp. The resin is bisphenol-A-...
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Spallation Neutron Source design

The Spallation Neutron Source (all details taken from this link) is described as firing a 1 GeV proton beam into a mercury target. As this makes the proton beam relativistic, a cyclotron cannot be ...