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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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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? [on hold]

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 ...
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Making a particle accelerator with nanomaterials

In typical particle accelerators, protons are sped up by the electric field. From what I've read, neutrons can also be accelerated, by first accelerating protons and somehow converting them into ...
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What happens when a neutron star loses enough mass to go under Chandrasekhar limit?

Say if a blackhole passes very close by a neutron star at high speed fly-by and eats half of the neutron star. What happens to the other half? Does it blow up in size as the electroweak force pushes ...
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Even-odd nuclei and nuclear fission

"By adding a neutron to $U^{235}_{92}$ an even-even nucleus is obtained. The binding energy increases in the process, so the energy gained in the process is greater." I'm confused, if the binding ...
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What is an Anderson-Braun neutron counter?

I found this type of tool reading an article ("A neutron monitor with silver activation") but surfing the internet I can not find an explanation of what it is and how it works. It's probably a basic ...
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What is cosmic ray albedo neutron decay (CRAND)?

I need a small description of what is cosmic ray albedo neutron decay (CRAND), where it comes from and what effects they have?
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Creating isotopes by shooting neutrons into an unstable nucleus [closed]

I've been doing a lot of amateur research lately (youtube videos) on particle physics and find it all really interesting. I'm also a crazy alien conspiracy theorist who believes in the whole "Bob ...
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Nuclear stability [duplicate]

Why does increasing the number of neutrons in a nucleus make it more unstable? I know that adding more protons increases electrostatic repulsion, therefore the nucleus is more unstable, but as ...
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1answer
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Understanding $\beta$ Decay Transition Classifications

I'm currently trying to understand the allowed transitions of Beta Decay through conservation of momentum and parity. I'm currently confused on how multiple types are allowed for the same decay in ...
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How do you calibrate a proton-recoil scintillation fast neutron detector?

I have a proton recoil scintillator, but gamma sources like Cs-137, Co-60 don't seem to have linear calibration for the device. Are there other ways of calibrating this device? I'm trying to detect ...
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Can gravity give neutrons a longer lifespan? [duplicate]

Isolated neutrons have a lifespan of about one minute yet neutrons in a neutron star can have the lifespan of the neutron star itself and not decay into proton and electron. Is the intense gravity ...
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2answers
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Why is a nuclei with too many neutrons unstable? [duplicate]

I understand that a nuclei with too many protons is unstable as the electromagnetic repulsion becomes too strong to be balanced by the strong nuclear force. However in the case of there being too ...
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What is the reason for the shift in balance between neutrons and protons in the early universe?

In the book of The First Three Minutes by Weinberg, on pages 106-107, it is stated that SECOND FRAME. The temperature of the universe is 30,000 million degrees Kelvin [...] The nuclear particle ...
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Why doesn't hydrogen have a neutron?

Why doesn't hydrogen have a neutron?
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Do neutrons exhibit momentary small charges due to the movement of its quarks?

So in a similar way to electrons moving in atoms, causing induced dipole-dipole interactions, can neutrons momentarily attract or repel?
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What is the force carrier for neutrons in fission?

Say I have a neutron capture event, leading to a fission reaction in which a few neutrons are expelled. These neutrons inherit a certain momentum from this fission reaction. How do these neutrons ...